硬球押し込みによる多軸残留応力場の応力腐食割れ試験法への適用性評価

摘要

A multi-axis stress field is indispensable for quick and quantitative evaluation of stress corrosion cracking for constructional materials and weld joints of existing industrial plants. The applicability of multi-axis residual stress field formed by pushing of a hard sphere ball made of WC into stress corrosion cracking tests was evaluated. The Brinell type hard sphere ball was stuffed into small flat-plate of type 304SS. The residual stress and displacement around the indentation were measured using an X-ray diffraction method and a displacement meter. Numerical analysis by the finite element method was conducted in order to compare with the experimental results. The numerical analysis was comparatively in agreement with the experimental results. A hard sphere ball diameter, a specimen holder hole diameter, specimen thickness, and an indentation depth were selected by numerical analysis to optimize the residual stress of specimen. The stress corrosion cracking test in chloride solution was performed using the specimen with optical residual stress condition. It is confirmed that the multi-axis residual stress field was useful in quick and quantitative stress corrosion cracking test by comparing the initiation of cracks with the distribution of residual stress obtained by numerical analysis.%石油化学工業や原子炉施設等の構造材ゃ機能材として使用されているステンレス鋼の高経年化事象の多くは，応力腐食割れ(Stress Corrosion Cracking:SCC)であり，稼働率の低下や有用資源の喪失の主要因となっている.それの防止対策，耐SCC合金の開発には，機構解明と迅速定量的なSCCの評価試験法の高度化が不可欠となる.