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N. Sinsamutpadung,E. Sasaki 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.3
This study aims to investigate the eff ects of strain rate on the low-cycle fatigue strength of steel welded joints. Load-carrying cruciform joints with diff erent material mismatch ratios were fabricated in order to observe the eff ects of material mismatching. A series of displacements that generate low-cycle fatigue damage were applied to the specimens. The experiment was conducted by fast cyclic loading and displacement control, using feedback from a displacement transducer. The feedback control algorithm was found to be critical. Thus, a non-linear feedback control algorithm, i.e., PID control, was implemented in the testing machine. An experimental setup capable of fast cyclic loading was developed. Fatigue life based on the load drop curve indicated that higher strain rates caused lower fatigue life. Failure behavior regarding the strain rate eff ects of steel welded joints was observed.
Amanov, A.,Sasaki, S.,Cho, I.S.,Suzuki, Y.,Kim, H.J.,Kim, D.E. Scientific and Technical Press ; Elsevier Science 2013 Materials & design Vol.47 No.-
In this work, the friction and wear behavior of Fe-Ni-Cr alloy specimens processed by direct metal laser sintering (DMLS) method was investigated by using a ball-on-disk reciprocating tribotester sliding against a hardened steel ball under dry sliding conditions. After DMLS, the specimens were further treated by hot isostatic pressing (HIP) in order to reduce the porosity and to increase the density. Subsequently, one of the specimens was subjected to high-frequency ultrasonic peening (HFUP) with the aim to enhance the tribological properties. The microstructural characterization was conducted using a scanning electron microscope (SEM) and an atomic force microscope (AFM). In addition, nano-scratch tests were carried out on the specimens using a nano-scratch testing (NST) system. The friction and nano-scratch tests results showed that the HFUP-treated specimen led to a reduction in friction coefficient and wear rate, and an increase in resistance to scratch compared to that of the HFUP-free specimen, which may be attributed to the increase in hardness and the formation of corrugated structure.
Mendis, C.L.,Jhawar, H.P.,Sasaki, T.T.,Oh-ishi, K.,Sivaprasad, K.,Fleury, E.,Hono, K. Elsevier Sequoia 2012 Materials science & engineering. properties, micro Vol.541 No.-
A high strength bulk nano-crystalline Al-1Fe-(0-1)Zr alloys were processed by mechanical alloying and spark plasma sintering. The high yield strength of ∼850MPa was achieved in an Al-1Fe-0.5Zr alloy with 19% strain in compression. The high strength was attributed to the nanosized Al-Fe grains and the dispersion of fine Al<SUB>6</SUB>Fe particles. High temperature compressive yield strength of 455MPa and elongation of 16.7% was achieved at 250<SUP>o</SUP>C.