• Korean Journal of Metals and Materials
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• v.46 no.9
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• pp.545-553
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• 2008

Dynamic deformation behavior of ultra-fine-grained pure coppers fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four copper specimens using a torsional Kolsky bar, and then the test data were analyzed by their microstructures and tensile properties. The 1-pass ECAP'ed specimen consisted of fine dislocation cell structures elongated along the ECAP direction, which were changed to very fine, equiaxed subgrains of 300~400 nm in size as the pass number increased. The dynamic torsional test results indicated that maximum shear stress increased with increasing ECAP pass number. Adiabatic shear bands were not found at the gage center of the dynamically deformed torsional specimen of the 1- or 4-pass ECAP'ed specimen, while some weak bands were observed in the 8-pass ECAP'ed specimen. These findings suggested that the grain refinement according to the ECAP was very effective in strengthening of pure coppers, and that ECAP'ed coppers could be used without serious reduction in fracture resistance under dynamic torsional loading as adiabatic shear bands were hardly formed.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.5-14
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• 1999

The necessity of six axis force-torque sensors is well recognized in the fields of automatic fine assembly, deburring polishing, and automatic fish processing using robotic manipulators. The paper proposes a simple and compact elastic structure of the force-torque sensor which senses externally applied three force and three torque components. Rough surface strain distribution of the elastic structure is examined analytically, and then more accurate surface strain are obtained from finite element analysis. The compliance matrix which is a linear relationship between force components and strain measurements is obtained for the proposed sensor. Some basic principles of measuring 3 force and torque components are also presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.3
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• pp.94-104
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• 1994

In order to improve engine performance and its reliability it is very important to find the friction force between piston-ring assembly and cylinder wall in engine operating conditions. A new system was developed for the piston-ring assembly friction force measurement. This system had a relatively high fundamental frequency at 884 Hz and a fine resolution of 0.5N in friction force measurement. Comparing with existing floating liner systems this systems required small installation space and at the same time alleviated the system noise problem induced by the thrust and slap impulse forces.