This paper deals with introduction of testing equipments for the evaluation of dynamic tensile characteristics of auto-body steel sheets and the crashworthiness of auto-body members. The servo-hydraulic high speed material testing machine was developed for tensile tests at the intermediate strain rate to obtain the tensile material properties at the strain rate under 500/sec. The split Hopkinson bar apparatus using the elastic wave was developed for dynamic material characteristics at the high strain rate ranged from 1,000 to 10,000/sec. The servo-hydraulic high speed crash testing machine is the equipment for the evaluation of the collapse load and crashworthiness of auto-body members. High speed carrying truck crashes to specimen with the maximum velocity of 17 m/sec.

At the time when nanostructured materials (NSMs) are becoming a major focus of materials research, the attention of researchers is turning more to their mechanical performance. In contrast with conventional coarse grained materials, which are either strong or ductile, but rarely both at the same time, it is expected that with NSMs both high strength and ductility can be achieved and confirmed by several experimental studies. In spite of the significant interest and efforts in the mechanical properties of NSMs, deformation mechanisms during plastic deformation as well as elastic deformation are not well established yet. In this talk, the deformation mechanisms of NSMs under various grain sizes, temperatures and strain rates were investigated. It is based on recent modelling that appears to provide a conclusive description of the phenomenology and the mechanisms underlying the mechanical properties of NSMs. Based on the theoretical model that provides an adequate description of the grain size dependence of elasticity and plasticity covering all grain size range from coarse down to the nanoscale, the tensile deformation response of NSMs, especially focusing on the deformation mechanisms was investigated.

In order to measure the friction coefficient used in sheet metal forming analysis, a friction tester was manufactured and friction tests were performed in various forming conditions. Based on the friction coefficients measured, a mathematical friction model was constructed in terms of lubricant viscosity, blank holding force, punch velocity and sheet roughness. In addition, the effect of the number of forming parameters in the calculation of friction coefficient on the accuracy of sheet metal forming analysis was investigated by comparing the punch loads obtained from the FEM simulation, in which the friction coefficients were determined by a few parameters with the experimental measurement.

In this study, optimum processing condition of AZ31 Mg alloy was investigated utilizing processing map and constitutive equation considering microstructure evolution (dynamic recrystallization) during hot-working. A series of mechanical tests were conducted at various temperatures and strain rates to construct a processing map and to formulate the recrystallization kinetics and grain size relation. Dynamic recrystallization (DRX) was observed to occur revealing maximum intensity at a domain of $250^{\circ}C$ and 1/s. The effect of DRX kinetics on microstructure evolution was implemented in a commercial FEM code followed by remapping of the state variables. The volume fraction and grain size of deformed part were predicted using a modified FEM code and compared with those of actual hot forged one. A good agreement was observed between the experimental results and predicted ones.

The purpose of this study is to design the free forging tool for the high accuracy of the thrust shaft in marine engine. In order to do it, the principal factor controlling the uprightness of the flange part and the excessive margin and folding in middle part of thrust shaft after forging process was identified using FEA. Based on the results, the optimum shape of free forging tool and working method were proposed and verified through the mock-up and the actual product test.

Recrystallization behavior during ingot-breakdown process of Alloy 718 was investigated with finite element analysis and experimental approaches. In order to analyze microstructural changes during the cogging process of an Alloy 718 ingot, the side-pressing and heat treatment tests were performed at different temperatures and ram speed. From the side-pressing and heat treatment test results, it was found that microstructural changes during hot forging of Alloy 718 ingot greatly influenced on a close interaction between dynamic and static-recrystallization behaviors. A recrystallization model of Alloy 718 was used to predict the complex microstructural variation during continuous heating and forging processes of the cogging, and the predicted grain size and its distribution were compared with the actual cogged Alloy 718 billet.

The purpose of this study is to develop the optimum shape of blank for the crank throw of large marine engine in order to reduce manufacturing cost and forging defects. The effects of the curvature radius and the height of wing part of blank selected as design variables on the defects and machining margin of final products after forging process were investigated using FEA. Based on the results, the optimum shape for the blank of the crank throw was proposed and verified by experiment.

Large size forged parts usually were made by hot open die forging because of the die cost, high applied load and small manufacturing quantities. Cast ingots were used in open die forging and the ingots almost included the cavities in its inside. Therefore, one of the aims for forging processes is to close and remove the cavities. However, its criteria were well not defined since the studies have many difficulties to investigate the cavity behaviors because of its large size. In this study, the cavity closure behavior was investigated by experimental and FE analysis. The FEM analysis is performed to investigate the overlap defect of cast ingots during free forging stage. The measured flow stress data were used to simulate the forging process of cast ingot using the practical material properties. Also the analysis of cavity closure is performed by using the $DEFORM^{TM}$-3D. The calculated results of cavity closure behavior are compared with the measured results before and after forging, which are scanned by the X-ray scanner. From this result, the criteria for deformation amounts effect on the cavity closure can be investigated by the comparison between practical experiment and numerical analysis.

Computer simulation of microstructure evolution during hot forging process is of great interest in recent years. Recrystallization model and grain growth model which use a phenomenological approach were summarized. For the waspaloy, upsetting process and cogging process were simulated using $DEFORM^{TM}$ and the change in grain size were investigated in each deformation procedure.

The effect of process parameters on springback of AZ31B magnesium alloy sheet was investigated by performing 2D draw bending test at the elevated temperatures. And also the springback characteristics were studied different blank holding forces between 30 to 250 kgf. Springback was considerably reduced at higher temperatures than $200^{\circ}C$. The blank holding force in the range used, however, had little influence on springback in isothermal tests. For a given temperature, springback decreased with increasing blank holding force in non-isothermal tests.

Asymmetric rolling, where circumferential velocities of the upper and lower rolls differ, can be one method to change texture of magnesium alloy sheet by introducing shear deformation throughout the thickness of a sheet. In this study, the texture, microstructure and mechanical properties of AZ31 Mg sheets has been investigated during the symmetrical rolling procedure and the asymmetric rolling procedures of different roll speeds with different roll diameters. Texture of Mg alloy sheets were evaluated by using X-ray diffraction and ODFs were calculated using ADC method. The major texture of rolled specimens can be expressed by ND//(0001) fiber texture. The major fiber texture changed according to the rolling processes and such a slight difference of texture changes the formability of sheets. The mechanical properties were enhanced during asymmetrical rolling.

Unusual mechanical constitutive behavior of magnesium alloy sheets has been implemented into the finite element program ABAQUS via user material subroutine. For the verification purpose, the springback of AZ31B magnesium alloy sheet was measured using the unconstrained cylindrical bending test of Numisheet'2002. In addition to the developed constitutive models, the other two models based on isotropic constitutive equations with tensile and compressive properties were also considered. Preliminary comparisons have been made between simulated results by the finite element analysis and corresponding experiments and the newly proposed model showed enhanced prediction capability in springback prediction.

The forming characteristics of cup-rod combined extrusion process were investigated with process parameter change. Simultaneous forward rod extrusion and backward cup extrusion was conducted with magnesium alloy, AZ31B. Process parameters such as forward extrusion ratio, backward extrusion ratio, and working temperature were controlled in a specific region and the effects of the parameter change were examined. Surface crack was developed in a certain state of the process parameters combination. The crack-free forming limit of the alloy in the combined process was disclosed by the parameter study. The microstructures of the initial and extruded workpieces were observed.

Mg alloys have the highest specific strength which can be used industrial application. Since formability of Mg alloys is very limited, optimization of forming process is always needed for successful engineering application. In the present study. three different Mg alloys were used for hot forging processes and several process variables such as temperature and forging speed were investigated to improve forgeability of Mg alloys. To understand the effect of process variables in details, 2D-finite element analysis and forging experiment was performed. In the results, forging speed seems to be more important than forging temperature in hot forging of Mg alloys.

Cryogenic rolling combined with warm rolling has been found to be more effective than only cryogenic rolling procedure in improving the strength of a 5052 Al alloy. In this study, cryo-rolled 5052 Al alloys were aged at $175^{\circ}C$. Warm rolling was conducted after dipping plates into silicon oil bath. A notable increase of tensile strength is achieved by the precipitation during warm rolling. The mechanical behavior of this alloy was investigated by hardness and tensile tests. The microstructure was investigated by transmission electron microscopy. It was found that the cryogenic rolling combined with warm rolling was very effective in improving tensile strength.

Aluminum sheets were asymmetrically cold rolled without lubrication by using different roll velocities of upper and lower rolls in order to intensify the shear deformation. During asymmetrical cold rolling of aluminum sheets, a reduction per a rolling pass, initial sheet thickness, roll diameter, roll velocity ratio were varied to investigate the effect of rolling parameters. The formation of through thickness shear texture was related to the ratio of the contact length between the roll and sample($l_c$) to the sheet thickness(d). The strain states associated with asymmetrical rolling were investigated by the finite element method (FEM) simulation. FEM results indicated that the evolution of deformation texture in a thickness layer is strongly governed by integrated values of strain rates $\dot{\varepsilon}_{13}$ and $\dot{\varepsilon}_{11}$ along the streamline in the roll gap.

The evolution of texture and microstructure was tracked for a number of differently cold rolled aluminum sheet and through-thickness layers which were differentiated by different strain states upon preceding deformation. The results substantiate a correlation of deformation texture with the amount of shear applied during cold rolling.

Control of crown and flatness in plate rolling is important not only for enhancement of the structural precision of products, but also for improving the yield and rolling operation. In the heavy plate mill, there have been strong demands for upgrading plate crown and flatness. In order to satisfy these demands, it is essential to develop the high precision numerical models. This paper gives a general description of the crown and flatness preset control model, work roll bender system, simulation result for shape control.

Studies on ski-end shape control at the top end of rolling plate in heavy thick plate mill by using FEM analysis and measuring system have been performed. Plate shape behaviour at the top-end on rolling by the two different methods in finishing rolling process has been observed. One is to minimize the height of ski-end by using pass line based on the relational model between shape factor and pick-up and the other one is to prevent turn down problem caused by the impact between table roller and down bended plate on rolling by using roll speed difference. To minimize the height of ski-end, the prediction models based on the FEM analysis and measuring data was developed. The control method of ski - end shape on finishing rolling process was applied in actual mill and the height of ski-end was reduced by about 50% compared with conventional operation.

The microstructure with fine and uniform AGS(austenite grain size) along thickness direction over no recrystallization temperature is strongly required for production of the high strength steels. The previous AGS prediction only based on the average strain improves to find the rolling conditions for accomplishment of the fine grain, but cannot find those for uniform grain. In this paper, an integrated mathematical model for prediction of the strain distribution along thickness direction is developed by carrying out finite element simulation for a series of rolling conditions. Also, the AGS distribution after rough rolling is predicted by applying the proposed model with AGS prediction model.

A microlens array has been required to improve light conversion efficiency in image sensors. A microlens array can be usually fabricated by photoresist reflow, hot-embossing, micro injection molding, and UV-imprinting. Among these processes, a UV-imprinting, which is operated at room temperature with relatively low applied pressure, can be a desirable process to integrate microlens array on image sensors, because this process provides the components with low thermal expansion, enhanced stability, and low birefringence, furthermore, it is more suitable for mass production of high quality microlens array. In this study, to analyze the optical properties of the wafer scale microlens array integrated image sensor, another wafer scale simulated image sensor chip array was designed and fabricated. An aspherical square microlens was designed and integrated on a simulated image sensor chip array using a UV-imprinting process. Finally, the optical performances were measured and analyzed.

An aspheric microlens array to improve the properties of multi optical probes was designed and fabricated. To generate multi optical probes with good qualities, a microlens array with the minimum spherical aberration was designed by ray tracing. Using the reflow process, a master pattern of aspheric microlens array was made and finally with the ultraviolet-imprinting (UV-imprinting) method, the aspheric microlens array was replicated. The reflow condition was optimized to realize the master pattern of the microlens array with the designed aspheric shape. The intensity distribution of the optical probes at the focal plane showed a diffraction-limited shape.

It's important to measure quantitative properties about thermal-nano variation conduct of polymer for producing high quality components using NIL process. NanoScale indents can be used ad cells for molecular electronics and drug deliver, slots for integration into nanodevices, and defects for tailoring the structure and properties. In this study, it's to evaluate mechanical characteristic of polymer such as PMMA and PC at high temperature for manufacture of nano/micro size of polymer using indenter at high temperature. At high temperature mechanical properties of polymer have extreme variation. Because heating the polymer, it becomes softer than room temperature. In this case it is especially important to study for mechanical properties of polymer at high temperature.

In order to investigate the residual stress evolution during the leveling process of hot rolled high strength coils for cold forming, the in-plane residual stress of plate sampled at SPM, rough leveler and finish leveler were measured by cutting method. Residual stress was localized near the edge of plate. As the thickness of plate was increased, the region with residual stress was expanded. The gradient of residual stress within plate was reduced during the leveling process. But the residual stress itself was not removed at the ranges of tested conditions. From the measured residual stress distribution within the plate, camber of plate cut to small width was predicted exactly within error range of experiment.

The application of light weight materials, such as aluminum alloy, has been limited due of their poor formability. Especially, aluminum alloy tube has limited expansion capability at most 15% at room temperature. New manufacturing process, called hot air forming, is introduced to apply aluminum tube to the automotive suspension components which have complex shape and require high expansion ratio about 40%. The process is carried out at the elevated temperature above $500^{\circ}C$, so numerous material properties and process parameters related to the high temperature should be investigated and determined to get a sound product. In this study, the effect of thermal properties and forming parameters such as the temperature of tool, axial feeding and gas pressure are analyzed by using explicit finite element method.

The effects of annealing condition on the occurrence of the delamination in cold drawn hyper-eutectoid steel wires, were investigated. Annealing treatment was performed on cold drawn steel wires for temperature range of $425^{\circ}C\sim500^{\circ}C$ with the variation of annealing time from 30sec to 15min. The increase of annealing temperature and time would cause the decrease of tensile strength and the increase of ductility. However, the occurrence of the delamination, representing torsional ductility, showed the different way from the variation of ductility.

In this study, we focused on investigation of governing parameters affected on the fatigue properties in the hyper-eutectoid steel wires used for TBR tires. Steel wires are fabricated under different drawing strain from 3.36 to 3.80. Their diameters are 0.21 mm and 0.185mm, respectively. The fatigue properties was measured by hunter rotating beam tester, specially designed thin-sized steel wires. The results showed that the fatigue properites of steel wire, marked as A-1, were greater than the others, due to the low value of residual stress. In order to elucidate the variations of fatigue properties, the microstructure, surface defect and residual stress were observed and measured by useful analysis technique, such as TEM, 3D profiler and FIB.

It is very important that there are saving resource and energy in the future as well as in these day. Weight saving of structural parts, which are formed by extrusion, plays a key role in manufacturing field. Especially these aluminum parts used in the car need other processes to vary the cross section in the axial direction. Thus, applications of these parts are limited by high cost. if the cross section of the parts is variable by only extrusion, application of extruded aluminum parts will more increase. Therefore, a new CNC extruder which can control the section area of a car part was invented the nation's first. Using the extrusion machine, the experiment and FE analysis were performed during the varied section extrusion process.

In this study, hydroformability and mechanical properties of pre- and post- heat treated Al6061 tubes at different extrusion type were investigated. For the investigation, as-extruded, full annealed and T6-treated Al6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, uni-axial tensile test and free bulge test were performed at room temperature and $250^{\circ}C$. Also mechanical properties of hydroformed part at various pre- and post-heat treatments were estimated by tensile test. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube at $250^{\circ}C$. As for the heat treatment, hydroformability of full annealed tube is 25% higher than that of extruded tube. The tensile strength and elongation were more than 330MPa and 12%, respectively, when hydroformed part was post-T6 treated after hydroforming of pre- full annealed tube. However, hydroformed part using T6 pre treated tube represents high strength and low elongation, 8%. Therefore, the T6 treatment after hydroforming for as-extruded tube is cost-effective. Hydroformability of Al6061 tube showed similar value for both extrusion types. But flow stress of seam tube showed $20{\sim}50MPa$ lower value.

Compression tests were carried out to investigate morphologies of compressed specimen, deformation microstructure and stress-strain relation in high-nitrogen austenite stainless steel. Tests were performed under a wide range of temperature and, with true strain rates up to $\dot{\varepsilon}$ =0.05, 0.1, 0.5 and $1.0s^{-1}$. The activation energy of loading force was equal to plastic deformation energy within the temperature range of $900^{\circ}C$ to $1250^{\circ}C$. Dynamically recrystallized grain size decreased with an increasing strain rate and temperature. Flow stresses and deformation microstructures, were used to quantify the critical strain rate and recrystallized grain size. The grain size versus strain rate-temperature map obtained in the study was in good agreement with the deformation microstructures of compressed specimens.

The correlation between crystallization and deformation behavior in the supercooled liquid region (SLR) of a $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ bulk metallic glass (BMG) alloy is investigated by compression tests, differential scanning calorimetry (DSC), electron energy loss spectrometry (EELS) and high resolution transmission electron microscopy (HRTEM). In the SLR, This BMG alloy was strongly depended on the deformation temperature and the alloy exhibits important change in deformation behavior after a given time which is directly connected to the development of crystallization. Compressive stress impeded decomposition and consequently retarded forming of nano-crystal, which led to enlarge the homogeneous deformation region of the BMG alloy in SLR during compression test.

The effects of boron additions in steels have long been recognized as very important, mainly with respect to hardnability of heat treatable steels. The systematics of structure and properties of boron steels will then be illustrated in the context of low-alloy steels with carbon contents raging from 0.05 to 0.25% and boron contents 0-130 ppm. we investigated the effect of the microstructure and mechanical properties with heat treatment condition of the boron-treated(0.0013 ppm) low carbon(0.2 %C) low alloy steel. The specimens were austenitised for 5 and 10, 15 min at $880{\sim}940^{\circ}C$(with/without tempered at 150, 180 and $210^{\circ}C$ for the various periods of time from 60 min to 120 min) After heat treatment, mechanical properties were measured by tensile test and hardness test. For analysis of microstructure, Optical/SEM analysis and XRD were carried out.

Apply electromagnetic stirring system to making rheology slurry of Al7075. This experiment has important element which is the relation between solid fraction percent and melt temperature of Al7075. The rheology slurry of Al7075 eliminated liquid phase to include alloying element of copper and zinc by squeeze casting process. In result the most structure was composed entirely of globular primary $\alpha$. Used this material for this study. This study made a comparison of mechanical property according to heat treatment T6 at each melt temperature ($619^{\circ}C$ and $615^{\circ}C$). The microstructure and component are observed how heat treatment T6 weight with the mechanical property by SEM-EDS.

The austenite phase observed in low carbon HSLA steels is well known to be decomposed to various bainitic microstructures, such as granular bainite, acicular ferrite and bainitic ferrite during continuous cooling process. These bainitic microstructures have been usually identified by using either scanning electron microscope (SEM) or transmission electron microscope (TEM). However, SEM and TEM images do no exactly coincide, because of the quite different sample preparation method in SEM and TEM observations. These conventional analysis method is, thus, not suitable for characterization of the complex bainitic microstructure. In this study, focused ion beam (FIB) technique was applied to make site-specific TEM specimens and to identify the 3-dimensional grain morphologies of the bainitic microstructure. The morphological feature and grain boundary characteristics of each bainitic microstructure were exactly identified.

In order to investigate the evolution of strain states during screw rolling, the samples of pure copper rod were rolled in a three-roll screw rolling mill. Microstructure observations and hardness measurements were carried out for examining the deformation during screw rolling. In addition, the finite element method (FEM) was employed to calculate. The strain states reveal that the shear strain plays a dominant role in the deformation during screw rolling.

AAO(Anodic Aluminum Oxidation) method has been known that it is practically useful for the fabrication of nano-structures and makes it possible to fabricate the highly ordered nano masters on large surface and even on the 2.5 or 3D surface at low cost comparing to the expensive e-beam lithography or the conventional silicon processing. In this study, by using the multi-step anodizing and etching processes, highly ordered nano patterned master with concave shapes was fabricated. By varying the processing parameters, such as initial matter and chemical conditions; electrical and thermal conditions; time scheduling; and so on, the size and the pitch of the nano pattern can be controlled. Consequently, various alumina/aluminum nano structures can be easily available in any size and shape by optimized anodic oxidation in various aqueous acids. In order to replicate nano patterned master, the resulting good filled uniform nano molded structure through electro-forming process shows the validity of the fabricated nano pattern masters.

본 연구에서는 Anodic Aluminum Oxide(AAO)-Nano Template 제조 시 알루미늄의 결정방위가 AAO 미세공 형성에 미치는 영향을 연구하였다. 시료는 직경 20mm 두께 2mm의 (200), (220), (111) 세가지 알루미늄 단결정 시편을 사용 하였으며 이는 XRD 장비로 단결정임을 확인 하였다. 양극산화에 앞서 평활한 면을 얻기 위해 다이아몬드 콤파운드($1{\mu}m$)로 미세연마 하였으며 양극산화는 세가지 시편에 대해 모두 동일한 조건에서 2단계 양극산화까지 하였다. 결과는 주사전자현미경(FE-SEM)으로 제조된 AAO 표면의 세공형태와 단면을 모두 관찰 하였으며 그 결과 (200) 결정방위가 (220), (111) 결정 방위보다 세공 형태 균일도 및 단면 정열도와 직진성이 우수함을 관찰 할 수 있었다.

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

We simulated an electric upsetting process by the rigid-thermoviscoplastic finite element method. Several engineering assumptions were made to calculate the heat generation due to the electric resistance. The skin effect of the bar was taken into account for the heat generation. The approach was applied to simulate an artificial electric upsetting process for the exhaust valve of the ship engine.

We simulated a hot forging process for the spider with four legs and an enclosed die forging process for the spider with three legs using an intelligent forging simulator AFDEX 3D and compared the predictions with the experiments in terms of the deformed shape. The formation of characteristic lines was emphasized in the simulation to simulate the extruded legs with higher accuracy.

The forging process design and microstructure evolution for gas turbine disk of a Waspaloy is investigated in this study. Parameters related to deformation are die and preform geometry, and forging temperature of die and workpiece. Die and preform design are considered to reduce the forging load, and to avoid the forging defects. Blocker and finisher dies for multistage forging are designed and the initial billet geometry is determined. The control of hot forging parameters such as strain, strain rate and temperature also is important because the microstructure change in hot working affects the mechanical properties. The dynamic recrystallization evolution has been studied in the temperature range 900-$1200^{\circ}C$ and strain rate range 0.01-1.0s-1 using hot compression tests. Modeling equations are required represent the flow curve, recrystallized grain size, recrystallized volume fraction by various tests. In this study, we used to thermo-viscoplastic finite element modeling equation of DEFORM-2D to predict the microstructure change evolution during thermo-mechanical processing. The microstructure is updated during the entire thermal and deformation processes in forging.

We analyzed a sequence of multi-stage automatic cold forging processes composed of four axisymmetric processes followed by a non-axisymmetric process using rigid-plastic finite element based forging simulators. The forging sequence selected for an example involves a piercing process and a heading process accompanying folding or overlapping, which all make it difficult to simulate the processes. To reduce computational time and to enhance the solution reliability, only the non-symmetric process was analyzed by the three-dimensional approach after the axisymmetric processes were analyzed by the two-dimensional approach. It has been emphsized that this capability is very helpful in simulating the multi-stage automatic forging processes which are next to axisymmetric.

In this paper, we apply a three-dimensional rigid-plastic finite element method to simulate an unsteady-state roll forming process. A typical roll forming process is investigated from the standpoint of computer simulation and its realistic analysis model is proposed. The material is considered as bulk material and discretized into hexahedral finite elements. The presented approach is applied to simulating the roll forming process of straight stringer used for aircraft structure.

This study is concerned with working hardening of bending operation on hydroforming parts. Generally, hydroforming parts having the complicated shape of the automobile, require a 3-dimentional bending operation. This operation involves several variations in the tube which are the thickness, the mechanical characteristics, the hardness, the circumference etc., on original tube. So, we study those variations and the affect on the hydroforming operation and hydroforming parts. We used two methods, one of which was computer simulation and the other the actual test in the plant.

Coating of Hot-dip galvannealed steel consists of various Fe-Zn intermetallic compounds. Since the coating is hard and there for is very brittle, the surface of steel sheet is easy to be ruptured during second manufacturing processing. This is called as powdering. In addition, forming equipment might be polluted with debris by powdering. Therefore, various research have been carried out to prohibit powdering fur improving the quality of GA steel. This paper carried out finite element analysis combined with damage model which simulate the failure of local layer of hot-dip galvannealed steel surface during v-bending test. Since the mechanical property of intermetallic compound was unknown exactly, we used the properties calculated from measurements. The specimen was divided into substrate, coating layer and interface layer. Local failure at coating layer or interface layer was simulated when elemental strain reached a prescribed strain.

New forming technologies are being introduced to automotive manufacturing processes. Among them, a simultaneous forming is one of the innovative forming technologies to be able to reduce production time and cost. Several parts can be simultaneously manufactured by the process, while the conventional stamping demands the same number of die sets with the number of parts. In this study, the automotive rear floor side member was manufactured by the simultaneous forming. The position and the size of initial blank were determined by forming analyses and try-outs, and the blank movement during the forming was controlled by introducing the spotweld.

As one way of weight saving of the vehicle, 1-piece typed lower control arm has been developed using high strength hot rolled steel sheet. In order to overcome the edge splitting problem during edge flanging or burring process, HER (hole expansion ratio) value of steel sheet was primarily considered. The strength grade of steel sheet and the shape were optimized utilizing Taguchi method.

Due to their low density, high specific strength and electromagnetic interference shielding, magnesium alloy sheets are used increasingly more often in automotive, aerospace, and electronics industries. However, magnesium ally sheets should be usually formed at elevated temperature because of their poor formability at room temperature. For the use of magnesium alloy sheets for an industrial, their mechanical properties at elevated temperature and appropriate forming process conditions have to be developed. In this study, the warm deep drawing process of AZ31 sheets is studied numerically by non-isothermal simulation. The difference between the isothermal simulation results and the non-isothermal simulation results and the progress of warm forming are discussed.

Deep drawing of magnesium alloy sheet is conducted at elevated temperatures($200{\sim}300^{\circ}C$) to improve the press formability because of low formability at room temperature. Then magnesium alloy sheet formability is known to be very sensitive to the strain rate. In this paper, we conducted warm deep drawing tests of magnesium alloy AZ31 sheet for various punch velocities. We examined the forming velocity effect on the deep drawing formability and the correlation with the tensile test result.

A roller straightening process is a metal forming technique to improve the geometric quality of products such as straightness and flatness. The geometrical quality can be enhanced by eliminating unnecessary deformations produced during upstream manufacturing processes and minimizing any detrimental internal stress during the roller straightening process. The quality of steel cords can be achieved by the roller straightening depends the process parameters. Such process parameters are the roll intermesh, the roll pitch, the diameter of rolls, the number of rolls and the applied tension. This paper is concerned with the design optimization of the roller straightening process for steel cords with the aid of elasto-plastic finite element analysis. Effects of the process parameters on the straightness of the steel cord are investigated by the finite element analysis. Based on the analysis results, the optimization of the roller straightening process is performed by the response surface method. The roller straightening process using optimum design parameters is carried out in order to confirm the quality of the final products.

In the present investigation, the multi-stage warm drawing process was applied to the magnesium alloy AZ31 sheet to examine the feasibility of multi-stage forming process as a high formability product making process. For that purpose, a multi-stage drawing die system with heating module was developed, and the AZ31 sheets of different sizes were consecutively drawn by the multi-stage drawing die. The obtained drawn cups of AZ31 showed that the multi-stage drawing provided the better formability than the single stage drawing in terms of drawing depth without cup defects such as wrinkles or fractures. The sheet formability improvement by using the multi-stage drawing die system against the single stage was also analyzed in terms of the finite element analysis of material state variables evolution.

This study is concerned with deep drawability of magnesium sheets(AZ31B) at the warm conditions. Especially the dependency on forming speed has been investigated at the temperature of $200^{\circ}C$ and $300^{\circ}C$. Deep drawing test has been carried out at the temperature of $200^{\circ}C$ and $300^{\circ}C$. The die and blank holder are kept at test temperature by local heating and the punch is kept at room temperature by cooling technique. The magnesium sheets called AZ31B with the thickness of 0.5mm have been applied to deep drawing of circular cup. The drawability has been estimated at the conditions of forming speed (0.1, 1, 10 mm/sec). The results of deep drawing experiments show that the drawability is better at $300^{\circ}C$. Also the deep drawability is improved at the low speed(1mm/sec).

Since Mg alloy has many attractive advantages among the practically used metals, many researchers have been studied to develop useful process and material. The crystal structure of Magnesium was hexagonal close-packed, so its formability was poor at room temperature. But formability was improved in high temperature with increasing of slip planes, twins, dynamic recrystallization. In this study The formability of AZ31B magnesium sheet is estimated according to the variable temperatures, forming speed, thickness, blank holding force. The results of deep drawing experiences show that the formability is well at the range from 200 to $250^{\circ}C$, 20 to 60 mm/min forming speed and 2.5 to 3KN blank holding force.

In this paper, anisotropic tensile properties of the AZ31B Mg-alloy sheet are obtained with the tensile test at elevated temperatures. Change of microscopic structures and the hardness is inspected after the solution heat treatment process in order to confirm the micro-structural stability of the used sheet metal. Results obtained from tensile tests show that it is very difficult to apply the conventional modeling scheme with the assumption of strain hardening to the forming analysis of the magnesium alloy sheet which shows the strain-softening behavior at the elevated temperature.

Simulations of the thermally-induced residual stresses and birefringence in freely quenched plates of polycarbonate were performed by using the linear viscoelastic and photoviscoelastic constitutive equations for the mechanical and optical properties, respectively, and the first order rate equation for volume relaxation. The predictions for the birefringence showed good agreement with experimental measurements. Based on the simulation, the influences of various cooling conditions on the residual stress and birefringence in plates were investigated. The residual stress and birefringence increased with increasing initial temperature, decreasing coolant temperature and increasing heat transfer coefficient of coolants.

Cooling circuit of injection mold affects part quality and cycle time of injection molding process. Examination on mold cooling circuit is usually omitted in part design stage because cooling circuit is designed in the mold design stage. It is desirable to examine mold cooling circuit with respect to part quality in the part design stage. In order to make the examination process convenient and fast, cooling circuit design should be automated without intervention of skilled designer. In this study, optimization of cooling circuit design is automated with commercial softwares; Visual DOC and Moldflow MPI. Effect of initial value for optimization is examined for the optimization result.

Small injection molded articles such as lens and mobile product's parts are usually molded in multi-cavity mold. The problems occurred in multi-cavity molding are flow imbalance among the cavities. The flow imbalance affects on the dimensions and physical properties of molded articles. First of all, the origin of flow imbalance is geometrical imbalance of delivery system. However, even the geometry of delivery system is balanced well the cavity imbalance is being developed. This comes from the unsuitable operational conditions of injection molding. Among the operational conditions, injection speed is the most significant process variable affecting the filling imbalances in multi-cavity injection molding. In this study, experimental study of flow imbalance has been conducted for various injection speeds and materials. Also, the filling Imbalances were compared with CAE results. The dimensions and physical state of multi-cavity molded parts were examined. The results showed that the filling imbalances vary according to the injection speed and flow property of resins. Subsequently, the imbalanced filling and pressure distribution in the multi-cavity affect on the dimensions and physical states of molded parts.

Housing and insulation of electrical connectors are made of plastic resin by injection molding process. The metallic inner tube is easily deformed by high pressure during the injection process. In order to prevent deformation of the inner tube, it is desirable to simulate it by structural CAE analysis. However, it takes a long time to calculate the stress- of the part by commercially available injection molding CAE software with sufficient accuracy. In this study, structural analysis in conjunction with injection molding analysis is proposed to improve accuracy of the structural analysis. Pressure distribution on the inner tube is predicted by the injection molding CAE analysis, and then mapped onto the mesh of structural analysis by a mapping algorithm developed in this study. As a result reliable result is obtained in shorter time than the conventional method. The predicted deformation of the inner tube is compared with the actual part after experiment.

In family mold, defects are frequently occurred by an excessive packing the smaller volume cavity during molding. Although runner size could be optimized by CAE analysis or experimental data, the filling imbalance is hardly avoided in the actual injection molding process by various means. Before this study, we developed a variable-runner system for balancing the cavity-filling for three resins (ABS, LDPE, and PA66) in the family-mold, and examined the effect of cross-sectional area reduction of a runner in the system. In this study, we examined the conditions of the pressure and temperature in the system with a CAE analysis. We also analyzed the influence of the rheological characteristic of resins to the balancing-capability of the system in order to help mold designers easily adopt the variable-runner system to their design.

The effect of Ca addition on the microstructure evolution and deformation behavior of AZ31 magnesium alloy produced by hot extrusion was investigated. For this purpose, Ca was added into AZ31 melts to the level of 0.7 and 2.0 wt.% Ca. Then, AZ31 base alloy and Ca modified AZ31 alloys were extruded at $383^{\circ}C$. Ca added alloys showed finer grain size and increased hardness value rather than AZ31 base alloy. After isothermal hot compression, the shape of tested specimen exhibited a noticeable anisotropy due to the crystallographic texture effect. The ratio of major and minor axes of ovality was not directly related to test condition and Ca amount. Flow stress level increases with the increase of Ca addition at temperature below $300^{\circ}C$ because of fine microstructure. However, at high temperature and low strain rate region ($400^{\circ}C$ and $10^{-3}s^{-1}$), reverse tendency was observed since main deformation mechanism changes from dislocation slip to grain boundary sliding or diffusional process at high temperature.

In the recent years the using of low-density material such as high-strength Al alloy on the various industries is becoming light-weight. High strength and hollow Al alloy is good material for stiffness and recycling. Therefore the advanced manufacturing technology with Al alloy is continuously required in many industrial fields. In this study simplified hallow rectangular section of Al alloy is analyzed by FE analysis. Bending stress is affected punching and rotating of wing-die. The analysis of press bending is preformed at first. The elastic recovery value of component and stress distribution acting from the result of the bending angle of three types were obtained. The designed precesses were analyzed by the commercial FE code, Deform-3D. Forming dies for each process were designed and prototypes were manufactured by the verified forming process. Some of the important features of design parameters in the press bending were reviewed.

To prevent the damage of glass lens molds and deterioration of glass lenses using in progressive GMP process, a thermal stress and a deformation of the glass lens molds at forming temperature should be considered in the design step. In this study, as a fundamental study to develop a multi cavity mold used in an aspheric glass lens molding, a heat transfer and a thermal stress analysis were carried out for the case of one cavity glass lens mold used in progressive GMP process. Finally, using analysis results, we estimated the thermal stress in a glass lens mold and predicted a modified height of guide ring that determines the forming height of a glass lens.

The thixoforming process become important for forming automobile parts. But, the thixoforming process cannot still prevent to forming defects such as pores and shrinkage which reduce mechanical properties of automobile parts. Therefore, it is necessary to analyze the correlation between forming defects and mechanical properties. However, it is difficult to get data about relations between mechanical properties and forming defects in thixoformed aluminum alloy parts. In this study, three parts of aluminum thixoformed knuckle have been analyzed using tensile test and computer tomography(CT scan). Experimental results showed that the elongation properties of thixoformed aluminum parts were significantly dependent on size and number of forming defects.

The focus of this study is to estimate the stiffness factor of the separator plate of MCFC (Molten Carbonate Fuel Cell) at the elevated temperature. The process factors affecting the stiffness of the separator plate were chosen to determine the most important factor using the finite element analysis with the Taguchi method. The most influential factor, picked out by the ANOYA, turned out the pitch in the separator plate.

In this study, it is investigated that sheet characteristics of high strength steel sheets and effect of springback. High strength steel sheets has got attention in automobile industry of high strength and high formability. Springback is a common phenomenon in sheet metal forming, caused by the elastic recovery of the internal stresses after removal of the tooling. However, the information in deformation behavior of high strength steel sheets, including bending and sheet characteristics and springback, is not enough until now. In this research, the V-bending experiment and analysis have been done to obtain the information of springback of high strength steel sheets. Tensile test for high strength steel sheets was done to got tensile properties of elastic modulus and flow stress of the material. It analyzed springback according to the sheet characteristics with using roll-forming model. FE-Simulation used DEFORM-$3D^{TM}$.

In recent years, many researches on new storage media with high capacity and information are developing. For manufacture of optical storage with high capacity, the injection molding process is generally used. In order to increase the filling ratio of the injection molding structure, the injection molding process required for high injection pressure, packing pressure and temperature control of the mold. However, conventional injection molding process is difficult to increase the filling ratio using injection master with the range of several nanometers and high aspect ratio. In order to improve and increase filling ratio of nano-structure with high aspect ratio, the active temperature control of injection mold was used. Experimental conditions were used injection pressure, time and temperature. Consequently, by using the peltier device into injection mold, we carried out the efficient and active temperature control of mold at low cost.

Recently, magnesium alloys have been widely used in automotive, aerospace and electronic industries with the advantages such as lightweightness, high specific strength and stiffness. However, magnesium alloy has quite low formability at room temperature due to its hexagonal close-packed crystal structure. Warm deep drawing is one of the forming technologies to improve the formability of magnesium alloy sheet and the lubrication condition is an important process parameter in that. In this study, the drawing tests of AZ31 alloy sheet at elevated temperature for various kinds of lubricant were carried out and the effects of lubrication conditions on drawbility were investigated.

In roll forming process, a sheet metal is continuously progressively formed into a product with required cross-section and longitudinal shape, such as a circular tube with required diameter, wall-thickness and straightness, by passing through a series of forming rolls in arranged in tandem. In this process, each pair of forming rolls installed in a forming machine play a particular role in making up the required cross-section and longitudinal shape of the product. In recent years, that process is often applied to the bumper rail in the automotive industries. In this study, a optimal roll flower model and proper roll-pass sequence can be suggested by analyzing courcenter strain and longitudinal strain according to the roll-pass with FEM simulation. And also effects of the process parameters on the final shape formed by roll forming defects a evaluated.

Domestic automobile industries have been focusing their effort on development of exhaust manifolds using high temperature stainless steel. Exhaust manifolds fabricated with stainless steels can be categorized into tubular and cast ones. The former is usually manufactured by forming and welding process and the latter by vacuum casting process. In the present study, high temperature mechanical properties of 5 austenitic stainless steels, one was sand cast and the others vacuum cast, were investigated by performing a series of high temperature tensile tests and high temperature low cycle fatigue tests.

The temperature distribution of high speed tool steel wire/bar during high speed hot rolling procedures has been studied in this study. The tool steels wire/bar show severe temperature gradient during rolling procedures and the temperature of center part much higher than that of the surface. This temperature gradient accumulated after every rolling procedure and the center of rolled wire/bar could be remelt in a certain stage to cause inside defects. In the present study, the temperature distribution was simulated using finite element method and the processing parameters such as rolling speed, cooling condition, has been discussed to prevent the temperature increases of center wire/bar.

Precipitation characteristics of the Fe-36Ni based high strength Invar alloy for power transmission wire was investigated in this study. High strength can be obtained in this alloy through solution hardening, precipitation hardening and strain hardening by cold working. In the present study, ingots of Fe-36Ni based Invar alloys with the contents of C, Mo and V varied. Microstructure observations by OM, SEM, and TEM were carried out to validate the simulation results. BCC phase and $FeNi_3$ phase are also expected at lower temperatures below $500^{\circ}C$. Aging treatments were carried out at temperatures ranging from 400 to $900^{\circ}C$ for time intervals from 3 min to 100hrs. Peak aging condition was obtained as $400^{\circ}C$ and 1 hr. With temperature increased, peak strength was decreased abruptly. Microstructure observation was conducted by optical microscopy, scanning electron microscopy, and transmission electron microscopy.

A study on the texture and the formability after asymmetric rolled and subsequent heat-treated AA 1050 aluminum alloy sheets have been carried out. The specimens after the asymmetric rolling showed a very fine grain size, a decrease of <100>//ND, and an increase of <111>//ND textures. The change of plastic strain ratios has been investigated and it was found that they were higher than those of the initial Al sheet.

A study on the texture and the formability after frictional rolled and subsequent heat-treated AA 1050 aluminum alloy sheets have been carried out. The specimens after the frictional rolling showed a very fine grain size, a decrease of <100>//ND, and an increase of <111>//ND textures. The change of plastic strain ratios has been investigated and it was found that they were higher than those of the initial Al sheet.

The effect of frictional rolling and subsequent heat treatment was studied on the evolution of texture of AA 3003 Aluminum alloy. With frictional rolling without lubrication it is possible to obtain a larger friction between roll and sample which lead to the formation of uniform rolling texture in the whole thickness layers.

The effect of asymmetric rolling on the recrystallization texture of an AA 3003 Aluminum alloy was investigated by X-ray diffraction. It was found that the texture of asymmetrically rolled sheets prior to subsequent heat treatment promoted the formation of the <111>//ND textures, and remained after heat treatment at $275^{\circ}C$ during 20 min in salt bath condition.

Austenitic stainless steel is used as high temperature components such as gas turbine blade and disk because of its good thermal resistance. In the present investigation, tensile and low cycle fatigue(LCF) behavior of stainless steel for turbine disks was studied at wide temperature range $20^{\circ}C\;{\sim}\;750^{\circ}C$. In the tensile tests, it was shown that elastic modulus, yield strength, ultimate tensile strength decreased when temperature increased. The effect on fatigue failure of the parameters such as plastic strain amplitude, stress amplitude and plastic strain energy density was also investigated. Coffin-Manson and Morrow models were used to adjust experimental data and predict the fatigue life behavior at different mean strain values during cyclic loading of high temperature components.

We presented a special method of forging hollow shafts of hard-to-form material, which is composed of piercing with back pressing and hollow shaft extrusion. The presented method was applied to cold forging a bushing of an excavator. The finite element simulation technology was employed for developing the optimized process and the predictions were compared with the experiments. The method was also applied to an automotive part and was verified to be powerful for manufacturing the cold forged hollow shafts of the hard-to-form materials.

For modeling the non-periodic and randomly scattered powder particles, the quasi-random multi-particle array is introduced. The multi-scale process simulation, which enables to formulate a regression model with a response surface method, is performed by employing a homogenization method. The size of ${Al_2}{O_3}$ particle, amplitude of cyclic compaction pressure, and friction coefficient are considered as optimal process parameters. The optimal conditions of process parameters providing the highest relative density are finally found by using the grid search method.

Simulations of the buckling behavior of a single wall carbon nanotube(SWCNT) was carried out using molecular dynamics simulation. Molecular dynamics simulations were done with 1fs of time step. Tersoff's potential function was used as the interatomic potential function since it has been proved to be reliable to describe the C-C bonds in carbon nanotubes. Compressive force was applied by moving the top end of the nanotube at a constant velocity. Buckling behavior under compressive load was observed for (15,15) armchair SWCNTs with 2nm of diameter and 24.9nm of length. Buckling load and critical strain is obtained from the MD simulation. Deformation occurred on the top region of the CNT because of fast downward velocity.

Polycrystalline materials such as steels(BCC) and aluminum alloys(FCC) show the strain hardening and the strain rate hardening during the plastic deformation. The strain hardening is induced by deformation resistance of dislocation glide on some crystallographic systems and increase of the dislocation density on grain boundaries or inner grain. However, the phenomenon of the strain rate hardening is not demonstrated distinctly. In this paper, tensile tests for various strain rates are performed in the rage of $10^{-2}$ to $10^2s^{-1}$ then, specimens are extracted on the same strain position to investigate the microscopic behavior of deformed materials. The extracted specimen is investigated by using the electron backscattered diffraction(EBSD) and transmission electron microscopy(TEM) results which contain grain size, grain shape, aspect ratio and dislocation substructure.

Continuing improvements in integrated circuit chip density and functionality have mostly contributed toward a very large-scale integrated circuit(VLSI) and display device. In order to test (pass or fail) all of the high integrated semiconductor chip and display device, fine pitch probes are used. Fine pitch probes are manufactured by electroforming process of a Ni alloy in an electrolytic bath. In this paper, we expect that the electric field in bath with the Finite Element Method and applying the FEM result. So, we can obtained the probes that have high aspect ratio of 10 : 1

This paper deals with the dynamic tensile characteristics of the steel sheets for structural members of a train. Train accidents occurs rarely but lead to many casualties and economical loss. Therefore the safety of the train becomes important during the train crash. The dynamic tensile characteristics of the steel sheets are indispensable to analyze the structural crashworthiness. Current research reports the stress-strain curves, fracture elongation and strain rate sensitivities evaluated at the various strain rates especially for SUS304L-ST and SUS304L-LT steel sheets. The results include the difference in the dynamic tensile characteristics of both rolling and transverse directions. Dynamic tensile tests were performed at the strain rates ranging from 0.003/sec to 200/sec using High Speed Material Testing Machine. The materials tested in this research shows interesting behavior at the low strain rates. The strain hardening exponent decreases remarkably while the yield strength increases.

In nano-imprint lithography (NIL) process, which has shown to be a good method to fabricate polymeric patterns, several kinds of pattern defects due to thermal effects during polymer flow and mold release operation have been reported. A typical defect in NIL process with high aspect ratio and low resist thickness pattern is a resist fracture during the mold release operation. It seems due to interfacial adhesion between polymer and mold. However, in the present investigation, FEM simulation of NIL molding process was carried out to predict the defects of the polymer pattern and to optimize the process by FEA. The embossing operation in NIL process was investigated in detail by FEM. From the analytical results, it was found that the lateral flow of polymer resin and the applied pressure in the embossing operation induce the weld line and the drastic lateral strain at the edge of pattern. It was also shown that the low polymer-thickness result in the delamination of polymer from the substrate. It seems that the above phenomena cause the defects of the final polymer pattern. To reduce the defect, it is important to check the initial resin thickness.