• Steel and Composite Structures
• /
• v.22 no.5
• /
• pp.1193-1214
• /
• 2016

In this paper, the 3D stress state and inter-laminar stresses in a rotating thin laminated cylinder shell are studied. The thickness of the cylinder is supposed to be thin and it is made of laminated composite material and can have general layer stacking. The governing equations of the cylindrical shell are obtained by employing the Layerwise theory (LWT). The effect of rotation is considered as rotational body force which is induced due to the rotation of the cylinder about its axis. The Layerwise theory (LWT), is used to discrete the partial differential equations of the problem to ordinary ones, in terms of the displacements of the mathematical layers. By applying the Free boundary conditions the solution of the governing equations is completed and the stress state, the inter-laminar stresses, and the edge effect in the rotating cylindrical shells are investigated in the numerical results. To verify the results, LWT solution is compared with the results of the FEM solution and good agreements are achieved. The inter-laminar normal and shear stresses in rotating cylinder are studied and effects of layer stacking and angular velocity is investigated in the numerical results.

• Computers and Concrete
• /
• v.20 no.5
• /
• pp.529-537
• /
• 2017

Excessively elevated temperature can lead to cracks in prestressed concrete (PC) continuous bridge with box girder on the pier top at cement hydration age. This paper presents a case study for evaluating the behavior of PC box girder during the early hydration age using a two-stage computational model, in the form of computer program ANSYS, namely, 3-D temperature evaluation and determination of mechanical response in PC box girders. A numerical model considering time-dependent wind speed and ambient temperature in ANSYS for tracing the thermal and mechanical response of box girder is developed. The predicted results were compared to show good agreement with the measured data from the PC box girder of the Zhaoshi Bridge in China. Then, based on the validated numerical model three parameters were incorporated to analyze the evolution of the temperature and stress within box girder caused by cement hydration heat. The results of case study indicate that the wind speed can change the degradation history of temperature and stress and reduce peak value of them. The initial casting temperature of concrete is the most significant parameter which controls cracking of PC box girder on pier top at cement hydration age. Increasing the curing temperature is detrimental to prevent cracking.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.7
• /
• pp.1131-1138
• /
• 2001

This paper concerns the crashworthiness of the widely used vehicle structure, the spot welded hat and double hat shaped section members, which are excellent on the point of the energy absorbing capacity and low production cost. The target of this paper is to analyze the energy absorption capacity of the structure against the front-end collision, and to obtain useful information for designing stage. Changing the spot weld pitches on the flanges, the hat and double hat shaped section members were tested on the axial collapse loads in impact velocities of 4.72m/sec, 6.54m/sec, 7.19m/sec and 7.27m/sec. To efficiently review the collapse characteristics of these sections, the simulation have been carried out using explicit FEM package, LS-DYNA3D. The solutions are compared with results from the impact collapse experiments.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.396-401
• /
• 2008

The disc-pad brake system is an important part of automobile safety system. During braking, the kinetic energy and potential energies of a moving vehicle are converted into the thermal energy through frictional heat between the brake disc and the pads. Most of the thermal energy dissipated through the brake disc. The temperature could be exceed the critical value for a given material, which leads to undesirable effects, such as the brake fade, premature wear, brake fluid vaporization, bearing failure, thermal cracks, and thermallyexcited vibration. The object of the present study is to investigate temperature field and temperature variation of brake disc and pad during single brake. The brake disc is decelerated at the initial speed with constant acceleration, until the disc comes to stop. The pad-disc brake assembly is built by 3D model with the appropriate boundary condition. In the simulation process, the mechanical loads are applied to the thermomechanical coupling analysis in order to simulate the process of heat produced by friction.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.491-496
• /
• 2008

A HEV-relay plays a significant role as a mechanical switch which determines the operation of a gasoline engine or an electric motor in a hybrid electric vehicle (HEV). The HEV-relay has critical two problems in the operating process. First, the unstable current can occur in the operating process of the HEV-relay due to the severe bounce between moving and fixed electrode. Second, noises occur due to impact between electrodes in HEV-relay. In this research, spring properties such as stiffness and initial compression force, and electrode shape are designed to reduce the bounce time and noises caused by impact between moving and fixed electrode. The operating process of HEV-relay is simulated using LS-DYNA3D as explicit finite element code. The optimum spring properties are determined using the response surface method (RSM) as the design methodology, and the electrode shape is newly designed through the modifying the stiffness of moving and fixed electrode.

• Geomechanics and Engineering
• /
• v.14 no.1
• /
• pp.43-50
• /
• 2018

Applicability of constructing piled raft foundations on soft clay has been given attention in recent years. Lack of sufficient stiffness for soil and thus excessive settlements to allow higher contribution of piles is the major concern in this regard. This paper presents a numerical investigation of performance of piled-raft foundations on soft clay with focusing on a case study. A 3D FEM numerical model is developed using ABAQUS. The model was calibrated by comparing physical and numerical modeling results of other researchers. Then the possibility of using piled-raft system in construction of foundation for a water storage tank in Sarbandar, Iran is assessed. Soil strength parameters in the numerical model were calibrated using the instrumentation data of a heavily instrumented preloading project at the construction site. The results indicate that choosing the proper combination of length and spacing for piles can lead to acceptable differential and total settlements while a high percentage of total bearing capacity of piles can be mobilized, which is an efficient solution for the project. Overall, the construction of piled-rafts on soft clays is promising as long as the total settlement of the structure is not imposing restrictions such as the common 25 mm allowable settlement. But instead, if higher allowable settlements are adopted, for example in the case of rigid steel tanks, the method shall be applicable with considerable cost savings.

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.778-782
• /
• 2000

Deep drawing and ironing are the major process used today in manufacturing of battery case used in cellular phone and IMT-2000 from aluminum. The same technology is utilized in manufacturing of steel or aluminum rectangular cans for components of medical instrument, portable PC, walkman and so on. Most of these processes require multi-stage ironing following the deep drawing and redrawing processes. The practical aspects of this technology are well known and gained through extensive experiment and production know-how. However, the fundamental aspects of theses processes are relatively less known. Thus, it is expected that process simulations using FEM techniques would provide additional detailed information that could be utilized to improve the process condition. This paper illustrates the application of process modeling to deep drawing and redrawing operations with the cellular phone and IMT-2000. A commercially avaliable finite element code LS-DYNA3D was used to simulate deep drawing and redrawing operations.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.34 no.1
• /
• pp.10-17
• /
• 2014

A 3D model based on the finite element method (FEM) was built to simulate the infrared thermography (IRT) inspection process. Thermal contrast is an important parameter in IRT and was proven to be a function of defect parameters. Parametric studies were conducted on internal defects with different depths, thicknesses, and orientations. Thermal contrast evolution profiles with respect to the time of the defect and host material were obtained through numerical simulation. The thermal contrast decreased with defect depth and slightly increased with defect thickness. Different orientations of thin defects were detected with IRT, but doing so for thick defects was difficult. These thermal contrast variations with the defect depth, thickness, and orientation can help in optimizing the experimental process and interpretation of data from IRT.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.515-518
• /
• 2005

In this paper, we report on our theoretical study on the effect of surface anchoring. Molecular dynamics as well as optical characteristics of PVA cell are computer-simulated with 3D-FEM numerical solver, TechWiz $LCD^{(R)}$. Although simulation parameters are the same except for the consideration of surface anchoring, the simulation reveals that optical transmittance is improved by more than 8% for the weak anchoring case with comparison to the strong anchoring case. Moreover, capacitance between pixel and common electrode is 7% lower for the strong anchoring than that for the weak anchoring. This implies that there exists an appreciable difference between the strong anchoring case and the weak anchoring case. It is very important to take the effect of surface anchoring into account in order to figure out the optical characteristics of an LCD cell more accurately.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.783-784
• /
• 2006

In case of a difference exist between the experimental value and estimated value of back-emf, there can be a difference of turn number or residual flux density of permanent maget of the motor. In order to presume the turn number, the average length for each coil is used to calculate the resistance. However in producing the motor, doc to the tension of coil, the outer diameter of coil becomes smaller, and then the resistance estimated by average length for each coil is not correct. Therefore in this paper, through the comparison of experiment value and estimated value of inductance, a method of presuming the turn number and PM's residual flux density of an IPM motor is presented. The inductance of IPM motor changes with the rotor position, therefore the rotor part is taken out and then the inductance in open circuit condition is measured. In the analytical calculation, 3D FEM(Finite Element Method) is used, which can consider the leakage flux of end turns in frinzing effect.