• Transactions of Materials Processing
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• v.20 no.6
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• pp.420-426
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• 2011

Dent resistance is determined by both shape characteristics, i.e., local radius of curvature and sheet thickness, and material properties such as yield strength. This work presents results of a study on the effect of work hardening and bake hardening on dent resistance of aluminum alloy sheet parts by considering the forming condition and baking temperature.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.6
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• pp.95-103
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• 1998

Solutions of geotechnical engineering problems require calculation of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such calculation even for complicated problems. To get accurate results, realistic stress-strain relationships of soil are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. The nature of stress-path dependency, the principle that governs deformations in sand, and the use of Lade's single work-hardening model for predicting sand response for a variety of stress-paths have been investigated and are examined. The test results and the analyses presented show that under some conditions sand exhibits stress-path dependent behavior. The strains calculated from Lade's single work-hardening model are in reasonable agreement with those measured, but some discrepancies occur. The largest difference between measured and calculated strains occurs for proportional loading with increasing stresses and for stress-path directions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.317-320
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• 2005

The micro-alloying forging steels have been developed to save energy consumption during forging and subsequent heat treatment stages. The work hardening ability of micro-alloying forging steels is one of major hardening component while it gives severe die damage if the forging process design is poorly set up on the other hand. In the present study, it was tried to characterize three types of micro-alloying forging steels to understand the differences with the conventional low carbon steels used fur cold forging with a spherodizing heat treatment. After forging of a certain forging part with both micro-alloying forging steels and conventional low carbon steel, several mechanical tests were carried out.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.223-232
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• 2019

Since the actuators with small- scale structures may be exposed to external reciprocal actions lead to create undesirable loads causing instability, the buckling behaviors of them are interested to make reliable or accurate actions. Therefore, the purpose of this paper is to analyze plastic buckling behavior of the micro beam structures by adopting a Conventional Mechanism-based Strain Gradient plasticity (CMSG) theory. The effect of length scale on critical force is considered for three types of boundary conditions, i.e. the simply supported, cantilever and clamped - simply supported micro beams. For each case, the stability equations of the buckling are calculated to obtain related critical forces. The constitutive equation involves work hardening phenomenon through defining an index of multiple plastic hardening exponent. In addition, the Euler-Bernoulli hypothesis is used for kinematic of deflection. Corresponding to each length scale and index of the plastic work hardening, the critical forces are determined to compare them together.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.9_10
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• pp.1172-1177
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• 2003

Microcapsules were prepared by complex coacervation between gelatin and gum arabic. The object of this work is evaluation of the effect of jelly strength, hardening agent on the particle size distribution, surface morphology and DSC. It was found that the 300bloom jelly strength caused microcapsules' size larger. When the amount of hardening agent increased, the particle mean diameter was larger. The amount of hardening agent was determined to be 10m1 for getting suitable size to finish the fabric.

• Journal of Welding and Joining
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• v.22 no.4
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• pp.35-42
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• 2004

Contact tips are required to have a higher resistance to wear and thus to have an extended life time under the advanced GMAW welding process. Several requirements have been specified and employed by domestic industries for selecting their tips for such a purpose. However no attempt has been made to justify their requirements based on the experimental data of wear resistance or life time of contact tips. In this study, five different contact tips with three different compositions were employed for actual GMA welding up to 4 hours and were evaluated their wear resistance by measuring in every one hour the area of enlarged hole at the exit side. Experimental results clearly showed that the Cr-containing tips strengthened by precipitation hardening have much better resistance to wear than those made by work hardening. It was further noticed that Cr is an excellent alloying element for improving the wear resistance of contact tips only when it is in an properly aged condition. Initial hardness may play some role in the early stage of wear but not in the later stage of welding because the microstructure of tip changes significantly by the prolonged exposure to welding arc heat. Based on these results, critical review has been made on the current requirements employed by domestic industries. Of importance is that a new guideline has been confirmed to be more reasonable.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.266-278
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• 1995

The high strain-rate dynamic plastic behavior of Fe-X%Mn alloys was investigated. The strain rate did not have an effect when tested under quasi-static strain rates($2{\times}10^{-3}/sec$ and $2{\times}10^{-1}/sec$). However, the true stress increased at all strain levels when the strain rate increased to $6{\times}10^3/sec$. Based on the experimental results, an constitution equation to calculate the dynamic strength for strain rates over $10^4/sec$ was determined. The Fe-5%Mn alloy containing athermal ${\alpha}^{\prime}$ martensite initially did not show work hardening. The work hardening increased with Mn content showing a maximum at 20% Mn. The high work hardening of Fe-20%Mn and Fe-30%Mn alloys appears to be closely related not only to the initial amounts of ${\varepsilon}$ martensite but to the strain induced transformation (${\gamma}{\rightarrow}{\varepsilon}$ and ${\varepsilon}{\rightarrow}{\alpha}^{\prime}$) occurring during each stages of deformation.

• Geotechnical Engineering
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• v.8 no.2
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• pp.81-96
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• 1992

This paper dealt with the influence of experimental error generated inevitably during performing experiments on the granular soil behaviour analysis selecting Lade's Single Work-Hardening constitutive model. Several isotropic compression-expansion tests and a series of drained conventional triaxial tests with various confining pressures for Baekma river sands were performed and the values of parameters for the above model were determined using computer program developed for this study based on regression analysis. By finding the range of the upper and lower bound for deviator stress and volumetric strain versus axial strain dependant on the increase and decrease of the standard deviation from mean value of parameters, sensitivities of all the parameters were examined. Practical use of program to determine the parameters and capability to predict the behaviour of granular soil by Lade's Single Work -Hardening model verified.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.266-271
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• 2003

Safety diagnosis of various structural components and facilities is indispensable for preventing catastrophic failure of material by time-dependent and environment accelerating degradation. Also, this diagnosis of operating components should be done periodically for safe maintenance and economical repair. However, conventional standard methods for mechanical properties have the problems of bulky specimen, destructive procedure and complex procedure of specimen sampling. So, a non-destructive and simple mechanical testing method using small specimen is needed. Therefore, an advanced indentation technique was developed as a potential method for non-destructive testing of in-field structures. This technique measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation such as yield strength, tensile strength and work-hardening index. In this paper, we characterized the tensile properties including yield and tensile strengths of the V-modified Cr-Mo steels in petro-chemical and thermo-electrical plants. And also, the effects of hydrogen-assisted degradation of the V-modified Cr-Mo steels were analyzed in terms of work-hardening index and yield ratio.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1335-1342
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• 1988

In this paper, mechanical properties of mild steel plate which was pretreated by prestress and prestrain loading conditions were studied. The variation of the mechanical properties of the test materials is evaluated in the light of Taylor's work hardening theory. Through this experimental study, it is recognized that material showed unstable phenomena after cyclic loading and it will recover its stability after a certain period of time accompaning the increment of hardness and the yield strength of the material. Also, the strength of smooth specimen, the notch strength of notch specimen and propagation behavior of fatigue specimen which were subjected to prestress and prestrain reveal that the optimal conditions may occur in the first, the middle and the later half of stage II of Taylor's work hardening theory, respectively.