• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.10a
• /
• pp.128-131
• /
• 2004

Magnesium alloys are being extensively used in weight-saving applications and as a potential replacement for plastics in electronic and computer applications. Magnesium alloy has some good characteristics, EMI shielding property and high specific strength. Nevertheless their high brittleness make it uneasy to process the magnesium. Magnesium alloys are extruded like aluminium alloys. The present work was done to find a characteristic of magnesium alloy(AZ31) changing the extrusion ratio 8.5, 19.1, 49 respectly and changing the die half angle $30^{\circ},\;45^{\circ},\;60^{\circ}$. Here this present done by the hydrostatic extrusion in the hot condition, $310^{\circ}$. The higher the extrusion ratio goes, the higher the extrusion force goes.

• International Journal of Precision Engineering and Manufacturing
• /
• v.6 no.2
• /
• pp.26-33
• /
• 2005

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effect of process variables such as gap height, relative gap width and die comer radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.12
• /
• pp.168-175
• /
• 2003

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effects of process variables such as gap height, relative gap width and die corner radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.356-363
• /
• 2001

Piston seal is a device designed to prevent leakage in split connecctions or between relatively moving part. Contact force, critical pressure at which extrusion occurs, leakage rate, fluid film thickness and friction force have been analyzed for some design parameter such as clearance between cylinder wall piston, depth of rectangular groove and pressure of sealed hydraulic fluid. In this paper, we analyze displacement and stress of Wearing by finite element analysis to understand Contact Behaviour Characters.

• Journal of Powder Materials
• /
• v.2 no.1
• /
• pp.44-52
• /
• 1995

Effects of the extrusion temperature and die angle on the tensile properties of SiCIyAl composites in powder extrusion have been investigated. SiCP/Al composites were extruded at various extrusion temperatures (450, 500, $550^{\circ}C$) under the extrusion ratio of 25 : 1. The ram speed was maintained at 13 cm/min for all the extrusion conditions. The surface of the extruded rod appeared to be smooth without tearing at 450 and 50$0^{\circ}C$, whereas it was very rough due to tearing at $550^{\circ}C$. It was found that the tensile strength and elongation of the composites extruded at $500^{\circ}C$ are greater than those of composites extruded at $450^{\circ}C$ This is due to the easier plastic deformation of composite extruded at $500^{\circ}C$, compared with the composites extruded at $450^{\circ}C$. The effect of die angle was examined under 20=60, 120, $180^{\circ}$die angles at extrusion temperature of $500^{\circ}C$ under 25:1 extrusion ratio. The tensile strength of the composites extruded with 20=$60^{\circ}$approved to be higher than that of the composties extruded with 28 : 120 and $180^{\circ}$This is attributable to the higher extrusion pressure, which mixed composite powders could be densely consolidated at elevated temperatures, resulting from high friction force between billet and sliding surface of conical die.

• Transactions of Materials Processing
• /
• v.11 no.1
• /
• pp.84-89
• /
• 2002

This study is concerned with the analysis of the forming characteristics of radial-forward extrusion. Angle between radial and forward extrusion, gap height, and friction factor are considered as important design factors to affect forming characteristics in radial-forward extrusion. The rigid-plastic finite element method is adopted to analyze the effects of design factors on forming loads. The incremental rates of loads are nearly constant except the deformation zone from radial to forward extrusion. The smaller angle induces lesser force increment, therefore forming load increases as the angle increases. Maximum load also increases as gap-height decreases and friction factor increases.

• Steel and Composite Structures
• /
• v.18 no.2
• /
• pp.481-496
• /
• 2015

A Lead Extrusion Damper (LED) is experimentally studied under various frequencies and displacement amplitudes. Experimental results show that the force-displacement hysteresis loops of the LED are close to rectangular and the force-velocity hysteresis loops exhibit nonlinear hysteretic characteristic. Also, the LED can provide consistent energy dissipation without any stiffness degradation. Based on the experimental results, a mathematical model is then proposed to describe the effects of frequency and displacement on property of LED. It can be proved from the comparison between experimental and numerical results that the mathematical model can accurately describe the mechanical behavior of LED. Subsequently, the seismic responses of the Schwedler reticulated shell structure with LEDs are analyzed by ANSYS software, in which three different installation forms of LEDs are considered. It can be concluded that the LED can effectively reduce the displacement and acceleration responses of this type of structures.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.10a
• /
• pp.482-489
• /
• 2000

The cyclic extrusion damper, Lead Extrusion Damper, was invented by the W H Robinson in order to produce the isolated buildings and bridges the damping force. Recently, LED was applied to reduce the vibration of the tall building. In this study, to verify the dynamic characteristics of LED, the tests to find out the dependences on the velocity, displacement, repeated cycle, and temperature were performed at structural lab of Unison Industrial Co. Ltd. Through the result of the dynamic characteristics. we`ll define the design parameters and apply the appropriate parts.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.20 no.2
• /
• pp.173-178
• /
• 1991

The rheological properties of acorn crude starch gel and refined starch gel were investigated by puncture test, back-extrusion test and retrogradation test. Puncture test was a useful method to compare the different gel type and concentration, and to calculate the compression and shear coefficient. Maximum extrustion force and adhesiveness were also examined by performing back-extrustion test. The retrogradation rate was analysed by Avrami equation in retrogradation test.

• Journal of Korea Foundry Society
• /
• v.13 no.3
• /
• pp.248-258
• /
• 1993

A semi-solid alloy in which solid and liquid phase are co-existing is obtained by stirring of A17075 molten metal. A semi-solid alloy is dependent on the corresponding temperature within the solid-liquid range, and the process parameters should be controlled accurately to obtain the homogeneous semisolid alloy. The fabrication possibility of fiber-reinforced aluminum alloy containing $Al_2O_3$ short fibers with vigorous agitation of short fibers were obtained by control of stirring time, solid fraction and impeller speed in extrusion billet fabrication processes. The microstructure to extrusion billet fabricated by low pressure casting was investigated for fiber dispersion state. The relationship between the extrustion force and velocity at hot extrustion, the flow strain and extrusion ratio were theoretically described. The surface defects with lubricants and without lubricant after hot extrusion were investigated. The composites materials after hot extrusion were measured by vickers hardness with extrusion ratio. It has become clear that the secondary working such as hot extrusion was very useful to obtained improved the mechanical properties of metal matrix composites.