回転曲げ疲労破面のＸ線フラクトグラフィ

Abstract

X-ray fractography is a technique for estimating the loading conditions at fractures from the information obtained by X-ray stress analysis on fatigue fractured surfaces. This technique was applied to a rotating bending fatigue fractured surface. The specimens were actual size “Shinkansen (Bullet train)” axles bench tested at the Railway Technology Research Institute.The axles are 209 or 210mm in diameter, induction hardened 0.38% carbon steel (JIS S38C) with semi-elliptical artificial flaws. Fatigue fracture was caused mainly by rotating bending stress, and the effect of torsional stress was very slight. The residual stress at the fatigue fractured surface was tensile at the initial crack propagation region, increased to a tensile maximum value, then decreased to a compressive maximum value and increased again toward zero near the final fractured area.The results were compared to the residual stress distribution on fatigue fractured surfaces of CCT specimens under a tension-compression fatigue load of stress ratio R=-1. The general tendencies of residual stress distributions on both fatigue fractured surfaces agree well qualitatively.