An Experimental Evaluation on Rate Sensitivity of Absorption Energy Evaluated by Measurement of J-integral in Austenitic Stainless Steel

Abstract

はじめに ・川端 敏之3) ・石 磊石 4) An Experimental Evaluation on Rate Sensitivity of Absorption Energy Evaluated by Measurement of J-integral in Austenitic Stainless SteelTakeshi Iwamoto, Shin-ya HasHImoto, Toshiyuki Kawabata and Leishi sHI Synopsis : Austenitic stainless steel is widely used in important industries since it has excellent mechanical and chemical properties such as anti-corrosion, high ductility and high strength. In the past, it was reported that its extremely high energy absorption can be measured by the Charpy impact test. The mechanism of its energy absorption characteristic is still unclear and its rate sensitivity has not been discussed. In the present study, a rate sensitivity of energy absorption characteristic of austenitic stainless steel will be discussed experimentally by measuring J-integral under 3-point bending condition for a wide range of displacement rate. In the experiment, the direct current potential difference method is employed for sensing an onset of a stable crack extension. As a result, the positive rate sensitivity on the energy absorption can be observed and high energy absorption can be achieved by the high ductility of the steel.

An Experimental Investigation on Rate Sensitivity of Fracture-Mechanical Characteristics in 304 Austenitic Stainless Steel under Bending Deformation

“…Deflection at the onset of crack extension in quasi-static test and impact test is 12.7 and 12.6 mm, respectively. The deflection in the quasi-static condition is larger than that of previous study 13) at the same normalized deflection rate. Figure 4 shows the normalized force-normalized deflection curve at the different normalized deflection rates.…”

“…As can be seen from this figure, the tendency of output voltage signals clearly changes when the crack begins extending and the onset point of crack extension is determined. Tendency of the change in the voltage is different from that in the investigation of Iwamoto et al 13) because of a difference in the size of specimen. Deflection at the onset of crack extension in quasi-static test and impact test is 12.7 and 12.6 mm, respectively.…”

“…7,11,12) To obtain this correlation at room temperature, an equation for the relationship between J-integral and normalized deformation rate should be given. In the recent research works by Iwamoto et al 13) and Shi et al,14) the rate sensitivity of fracture toughness in an austenite stainless steel is evaluated by bending tests carried out on relatively-small specimens. This might induce some errors for the evaluation of J-integral because the plane strain condition is not ensured for J-integral.…”

“…The deformation rate sensitivity of J-integral is discussed and compared with previous investigation. 13) Finally, discussions on energyabsorption characteristic and its rate sensitivity in austenitic stainless steel are made.…”

“…The output voltage is considered to relate directly to area of the crack extension, and the onset point of crack growth is defined by the point that the tendency of a change in the voltage. In this study, a different method with previous studies 13,14) is applied to evaluate J-integral by following ASTM E1820 19) as,…”