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Fatigue life enhancement of defective structures by bonded repairs
Wang, Q.Y.,Kawagoishi, N.,Chen, Q.,Pidaparti, R.M. Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.18 No.3
Defective metallic components and structures are being repaired with bonded composite patches to improve overall mechanical and fatigue properties. In this study, fatigue crack growth tests were conducted on pre-cracked 7075/T6 Aluminum substrates with and without bonded Boron/epoxy patches. A considerable increase in the fatigue life and a decrease in the stress intensity factor (SIF) were observed as the number of patch plies increased. The experimental results demonstrate that the patch configurations and patch thickness can enhance fatigue life by order of magnitude. Quantitative comparisons between analytical and experimental data were made, and the analytical model based on a modified Rose's analytical solution appears to best estimate the fatigue life.
Optical Technique to Measure Five-Degree-of-Freedom Error Motions for a High-Speed Microspindle
Hiroshi Murakami1,Norio Kawagoishi,Eiji Kondo,Akira Kodama 한국정밀공학회 2010 International Journal of Precision Engineering and Vol. No.
We present an optical technique to measure five-degree-of-freedom error motions of a high-speed microspindle. The measurement system consists of a rod lens, a ball lens, four divided laser beams, and multiple divided photodiodes. When the spindle rotates with its concomitant rotation errors, the rod and ball lenses, which are mounted to the chuck of the spindle, are displaced, and this displacement is measured using an optical technique. For this study, we decide the design parameters of the optical system using ray tracing, fabricate a prototype of the measurement system, and evaluate it experimentally. The results show that the measurement system has a resolution of 5 nm and can be used to evaluate high-speed microspindle rotation errors.
Tensile Properties and Fatigue Strength of Ultrafine Grained Pure Copper
Goto, Masahiro,Han, Seung Zeon,Kim, Sang Shik,Kawagoishi, Norio,Lim, Cha Yong Trans Tech Publications, Ltd. 2007 Key Engineering Materials Vol.353-358 No.3
<P>Oxygen-free copper was processed by equal channel angular pressing with different numbers of ECAP process cycles, NP. Tensile strength was increased with an increase in NP, but it tended to saturate after NP = 4. Conversely, elongation was dramatically decreased by first pressing, but it tended to saturate up to NP = 3, followed by slight increasing trend after NP = 4. Fatigue tests of specimens processed with NP = 4 and 8 were performed. The change in surface morphologies during fatigue was monitored successively. In addition to this, the change in surface hardness was measured. Significant decrease in surface hardness due to cyclic stresses was measured. The physical basis of fatigue damage of UFG copper was discussed based on the experimental results.</P>