• Physical Therapy Korea
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• v.13 no.4
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• pp.56-63
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• 2006

This study examined the effects of the abdominal drawing-in (ADI) maneuver using a pressure biofeedback on muscle recruitment pattern of erector spinae and hip extensors and anterior pelvic tilt during hip extension in the prone position. Fourteen able-bodied volunteers, who had no medical history of lower extremity or lumbar spine disease, were recruited for this study. The muscle onset time of erector spinae, gluteus maximus, and medial hamstring and angle of anterior pelvic tilt during hip extension in prone position were measured in two conditions: ADI maneuver condition and non-ADI maneuver condition. Muscle onset time was measured using a surface electromyography (EMG). Kinematic data for angle of anterior pelvic tilt were measured using a motion analysis system. The muscle onset time and angle of anterior pelvic tilt were compared using a paired t-test. The study showed that in ADI maneuver during hip extension in prone position, the muscle onset time for the erector spinae was delayed significantly by a mean of 43.20 ms (SD 43.12), and the onset time for the gluteus maximus preceded significantly by a mean of -4.83 ms (SD 14.10) compared to non-ADI maneuver condition (p<.05). The angle of anterior pelvic tilt was significantly lower in the ADI maneuver condition by a mean of 7.03 degrees (SD 2.59) compared to non-ADI maneuver condition (15.01 degrees) (p<.05). The findings of this study indicated that prone hip extension with the ADI maneuver was an effective method to recruit the gluteus maximus earlier than erector spinae and to decrease anterior pelvic tilting.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.27-30
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• 2004

Clad wire , which has the advantages of the high strength of a steel core and the electro-conductivity, corrosion resistance of a copper layer, is widely being used the telecommunications, electric-electronic and military technology industries, among others. It is important to obtain uniform coated rate when producing clad wires. Clad wire drawing process can be influenced on damage and coated rate of core and sleeve by process variables as semi-die angle and reduction in area. Therefore, in this study, the finite-element results established in previous study is used to analyze the effect of the various forming parameters, which included the semi-die angle, reduction in area etc. The coated rate will be predicted with observation copper coated rate variation according to total reduction in area and the optimal pass schedule will be set up through proper reduction in area and semi-die angle variation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.834-837
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• 2005

This study presents a study on the influence of process parameters(semi-die angle, die reduction, friction condition, and bearing length) in drawn wire on residual stresses were investigated using FE-analysis. In this study, semi-die angle and die reduction have a significant effect on the residual stresses at the surface of drawn wire. In the previous study, in order to reduce the residual stresses, several methods were suggested: addition of axial tension, application of skin pass, straightening in multi-roll straightener etc. In this study, it can be known that the concurrent application of skin pass with low die reduction and low semi-die angle at the final stage of drawing operation reduces dramatically the both axial and hoop residual stresses after drawing.

• Transactions of Materials Processing
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• v.7 no.2
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• pp.127-138
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• 1998

Process design of multi-step wire drawing process, conducted by means of finite element analysis and ANN(Artificial Neural Network) has been considered. The investigated problem involves the ade-quate selection of the drawing die angle and the correspondent reduction rate in the condition of desired initial and final diameter. Combinations of the process parameters which are used in finite ele-ment simulation are selected by using the orthogonal array. Also the orthogonal array. Also the orthogonal array and the results of finite element simulation which are related to the process energy are used as train data of ANN. In this study it is shown that the application of new technique using ANN and Othogonal array table to the process design of metal forming process is useful method.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.3
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• pp.249-256
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• 1983

The study is concerned with the analysis of sheet metal for the prediction of limit drawing ratio and forming load. The direct redrawing process is analyzed by using an equilibrium approach and strain increment theory both for non-workhardening material and for workhardening material. Computations are carried out numerically for the workhardening case. Limit drawing ratios are predicted for some chosen variables. The forming loads are also computed with respect to punch travel. Then the predicted loads are compared with the experimental results. For ordinary lubricated conditions, the comparison shows reasonable agreement between the theory and experimental observation. It is also shown that limit drawing ration can be increased by using a greater die angle and proper lubrication significantly reduces the punch load. Finally numerical results show that material of greater R-value and strain-hardening exponent(n)is better for direst redrawing of sheet metal.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.144-147
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• 1997

Process design of multi-step wire drawing process, conducted by means of finite element analysis and ANN(Artificial Neural Network), has been considered. The investigated problem involves the adequate selection of the drawing die angle and the correspondent reduction rate sequence in the condition of desired initial and final diameter. Combinations of the process parameters which are used in finite element simulation are selected by using orthogonal array. Also the orthogonal array and the results of finite element simulation which are related to the process energy are used as train data of ANN. In this study, it is shown that the new technique using ANN is useful method in application to the wide range of metal forming process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.3098-3107
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• 1994

The central burst defects, so-called chevroning, in wire drawing are analyzed by the rigid-plastic finite element method. The occurrence of central burst defects in wire drawing is estimated by the distribution of the hydrostatic pressure around the central part of the workpiece. It has been possible to obtain numerical boundaries which, in reduction in area vs. semicone angle plane, divide the safe and the danger zones, depending on friction factors and material properties. Based on the results of the analysis, it is suggested that the previous criterion derived from the upper bound analysis should be modified for better prediction of the defects. The back tension and the billet with a spherical hole on the central axis are also included in the analysis of the defects.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.46-49
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• 2003

Cu have been widely used as signal transmission materials for electrical electronic components owing to its high electrical conductivity. However, it's size have been limited to small ones due to its poor mechanical properties, Until now, strengthening of the copper at toy was obtained either by the solid solution and precipitation hardening by adding alloy elements or the work hardening by deformation process. Adding the at toy elements lead to reduction of electrical conductivity. In this aspect, if carbon nanofiber is used as reinforcement which have outstanding mechanical strength and electric conductivity, it is possible to develope Cu matrix nanocomposite having almost no loss of electric conductivity. It is expected to be innovative in electric conduct ing material market. The unidirectional alignment of carbon nanofiber is the most challenging task developing the copper matrix composites of high strength and electric conductivity In this study, the unidirectional alignment of carbon nanofibers which is used reinforced material are controlled by drawing process in order to manufacture the intermediary materials for the carbon nanofiber reinforced Cu matrix nanocomposite and align mechanism as well as optimized drawing process parameters are verified via experiments and numerical analysis. The materials used in this study were pure copper and the nanofibers of 150nm in diameter and of $10~20\mu\textrm{m}$ In length. The materials have been tested and the tensile strength was 75MPa with the elongation of 44% for the copper it is assumed that carbon nanofiber behave like porous elasto-plastic materials. Compaction test was conducted to obtain constitutive properties of carbon nanofiber. Optimal parameter for drawing process was obtained by experiments and numerical analysis considering the various drawing angles, reduction areas, friction coefficient, etc Lower reduction areas provides the less rupture of cu tube is not iced during the drawing process. Optimal die angle was between 5 degree and 12 degree. Relative density of carbon nanofiber embedded in the copper tube is higher as drawing diameter decrease and compressive residual stress is occurred in the copper tube. Carbon nanofibers are moved to the reverse drawing direct ion via shear force caused by deformation of the copper tube and alined to the drawing direction.

• Transactions of Materials Processing
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• v.27 no.3
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• pp.154-159
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• 2018

In the rectangular bar multi-stage drawing process, the cross-section dimensional accuracy of the rectangular bar varies depending on the aspect ratio and process conditions. It is very important to predict the dimensional error of the cross-section occurring in the multi-stage drawing process according to the aspect ratio of the rectangular bar and the half die angle of each pass. In this study, a process map for improving the dimensional accuracy according to the aspect ratio was derived in the drawing process of a rectangular bar. FE-simulation of the multi-stage shape drawing process was carried out with four types of rectangular bar. The results of the FE-simulation were trained to the nonlinear relationship between the shape parameters using an Artificial Neural Network (ANN), and the process maps were derived from them. The optimum half die angles were determined from the process maps on the dimensional accuracy. The validity of the suggested process map for aspect ratios 1.25~2:1 were verified through FE-simulation and experimentation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.195-199
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• 2001

The flow turning process, an incremental forming process, is a cost-effective forming method for axi-symmetric intricate parts to net shape. However, the flow turning process shows a fairly complicated deformation, it is very difficult to obtain satisfactory results. Therefore extensive experimental and analytical research has not been carried out. In this study, an fundamental experiment was conducted to improve productivity with process parameters such as tool path, angle of roller holder($\alpha$), feed rate(v ) and comer radius of forming roller(Rr). These factors were selected as variables in the experiment because they were most likely expected to have an effect on spring back. The clearance was controlled in order to achieve the precision product which is comparable to deep drawing one. And also thickness and diameter distributions of a multistage cup obtained by flow turning process were observed and compared with those of a commercial product produced by conventional deep drawing.