• Transactions of Materials Processing
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• v.5 no.4
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• pp.320-326
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• 1996

Based upon experimental observations the authors have shown in the previous studies that the orientations of orthotropy axes of anisotropic sheet metals are subjected to change during tensile loading at angles to the rolling direction. To predict the rotations of orthotropy axes under general plane stress conditions, a simple phenomenological model is proposed which accounts for the effect of work hardening. Predictions from the model are compared against the experiments for 0%, 3%, and 6% of 1st tensile prestrains in the rolling direction and 2nd tensile prestrains at 30$^{\circ}$, 45$^{\circ}$ and 60$^{\circ}$ to the 1st prestrains axis. The model showed good agreements with the experimental observations. A new interpretation of the experimental data is suggested regarding the rotations of orthotropy axes.

• Transactions of Materials Processing
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• v.25 no.5
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• pp.332-337
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• 2016

The automobile cowl cross bar which is a backbone frame part holding electrical and air conditioning components inside the cockpit module has been designed with more complex geometries recently due to demands of its enhanced functions and reduced weight of frame parts. The traditional manufacturing process using welding between tubes with different diameters shows several problems such as poor mechanical characteristics and appearance, etc. Therefore, in this study, one-piece manufacturing processes which can eliminate the welding process were developed by applying the rotary swaging process. CAE analyses were conducted to examine the feasibility of the process and prototypes were manufactured by using a rotary swaging machine with 4 split rotating dies and 12 head rollers. Bending tests of the manufactured prototypes confirmed that the rotary swaging process gives better mechanical properties comparing with the conventional processes.

• Transactions of Materials Processing
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• v.3 no.3
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• pp.320-334
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• 1994

A set of full size cold rolled steel sheets has been prestrained in the direction of rolling by uniform tensile elongation of 3% and 6%. Then mid-sized tensile specimens were cut from each of the full size sheets at 30, 45, 60 and 90 degrees to the rolling direction. The mid-sized tensile specimens were then prestrained again by uniform tensile elongation by 1%, 2%, 5%, 10% and 15%. finally, miniature tensile specimens were prepared from each of the mid-sized specimens at every 10 degrees to the specimen axis. From the tensile tests on miniature specimens material's hardening behavior under non-proportional loading has been investigated. There are a number of new observations which has not been known to the authors before current work. One of them is continuous reservation of orthoropic symmetry during tensile elongation of mid-sized specimens. Another is continuous rotations of orthotropy axes. Existing theories seem to fail to explain this observations. A new model is proposed in relation to the rotation of orthotropy axes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.117-121
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• 2005

In this paper, an approximate time-effective approach to rigid-plastic finite element method is presented with its solution scheme and a volume compensation method is proposed to simulate rotary forging processes. The applicability is examined by comparing the results obtained by the presented approach with those by the conventional approach. The approach is applied to simulation of a rotary forging process fur a wheel bearing assembly. The analyzed results are compared with the experimental results.

• Transactions of Materials Processing
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• v.7 no.6
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• pp.610-619
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• 1998

The superplastic blow forming technology has advantages of cost reduction and low material consumption. compared to the conventional sheet metal forming technology due to the capability of precisely forming with high elongation and low flow stress. however it has a disadvantage that its partial thickness distribution is non-uniform. A processing technology like diaphragm forming has been developed even though it is difficult to prepare materials for superplastic blow forming. in this study a hemisphere forming of sheet before superplastic forming. It was found that the rotary forming material was less in quantity of cavitation at pole than that of hemisphere part that was superplastic formed without rotary forming treatment. Also discussed are the critical strain which is closely related to cavity shape and size.

• Transactions of Materials Processing
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• v.32 no.6
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• pp.376-383
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• 2023

The torsion bar, which is a steering torque sensor, is mounted between the steering pinion and the input shaft in the IPA(input pinion assembly). Accurate torque measurement is important to improve the sense of operation, and the straightness of the torsion bar can affect torque measurement. In this study, the amount of bending was measured and the exact shape was analyzed regarding the bending phenomenon in the press-fitting process for torsion bars. The effect of alignment error was analyzed through finite element forming analysis. Process data analysis was conducted for the double-end press fit model. If there is an alignment error of about 10% of the serration tooth height, the indentation load is reduced by about 10%. If there is an alignment error, the torsion bar is rotated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.190-200
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• 1991

Certain structural components are exposed to high temperatures. At high temperature, under thermal and mechanical loading, metal components exhibit both creep and plastic behavior. The unified constitutive theory is to model both the time-dependent behavior(creep) and the time-independent behavior(plasticity) in one set of equations. Microscopically both creep and plasticity are controlled by the motion of dislocations. A finite element method is presented encorporating a unified constitutive model for the transient analysis of viscoplastic behavior of structures exposed to high temperature.

• Transactions of Materials Processing
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• v.5 no.2
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• pp.122-129
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• 1996

The main objective of the study is to offer some basic information in relation to optimal shape and dimensions of the rotating band through the development of three-dimensional finite element method for metal forming analysis of the rotating band whose primary function is to impart spin to the projectile. The three-dimensional metal forming analysis of the rotating band has perfor-med by using recurrent boundary conditions. Such design factors as the outside diameter the total length and the profile of the rotating band must be considered carefully in order to design an optimal rotating band. Above design factors can be determined from such available analysis results as the deformed shape and the deformation load. of the rotating band and the normal pressure of the rotating band on a projectile shell. The remeshings are needed to carry out plastic deformation analysis with severe deformation through which the complete process analysis gets possible. The results can be utilized effectively in determining the optimal shape and size of the rotating band.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1293-1298
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• 2010

In most power plants, wall thinning in carbon-steel pipes due to flow-accelerated corrosion is one of the major aging phenomena, and it reduces the load-carrying capacity of the piping system. Various types of wall-thinning defects were manufactured in real-scale elbows, and monotonic in-plane bending tests were performed under internal pressure to evaluate the failure behavior of the elbows. In this paper, the behavior of elastic and plastic limit leads of locally thinned elbows in a real-scale failure test is presented. The loads determined on the basis of TES (twice elastic slope) were considered to be the limit loads of locally thinned elbows so that the integrity of the thinned elbows could be maintained, even when a small amount of plastic deformation might have occurred.

• Journal of Korean Association for Spatial Structures
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• v.4 no.4 s.14
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• pp.55-63
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• 2004

Double angle connections are commonly used for the construction of the low-rise steel framed buildings. Several experimental tests lave been conducted to investigate the effect of the number of bolts on the rotational stiffness of a double angle connection. Several parameters are obtained by performing regression analysis. An analytical model has been introduced to calculate the initial stiffness of a double angle connection in this research.