Hybrid Fatigue Life Assessment considering Meso- and Macro-scale Cyclic Plasticity Analysis

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03489
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Naval and maritime engineering
• Research Institution: Osaka University
• Principal Investigator: Tsutsumi Seiichiro 大阪大学, 接合科学研究所, 准教授 (70344702)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 疲労 / 塑性 / 破壊 / 溶接 / 数値解析

Outline of Final Research Achievements

It is considered that fatigue life can be divided into two separate contributions: the crack initiation life and crack propagation life. The purpose of this research is to propose a methodology for predicting fatigue crack initiation and propagation life of weld joint using an unconventional elasto-plasticity model called the FSS model. The FSS model is based on the Subloading Surface theory, which was enriched by including the elastic boundary and cyclic damage concepts for the description of strain softening behavior within macroscopically elastic stress state. The model was used to investigate the inelastic response of the material under different cyclic loading conditions. In this study, finite element analysis was conducted to assess the fatigue crack initiation life and subsequently propagation life by extending the assessment method for fatigue crack initiation life by considering a cyclic plasticity accumulation during fatigue loading.

Free Research Field

plasticity

Academic Significance and Societal Importance of the Research Achievements

疲労に起因する損傷事例は数多く報告されており，そのうちの多くが溶接継手部に確認されている。そのため、これまでに鋼材および溶接継手の疲労寿命評価について数多くの有用な知見が示されている。しかし、溶接構造物の疲労に関する実験的検討では，一般にき裂の起点となる溶接止端部等の応力集中部は形状が複雑であり、溶接プロセスに伴い発生する残留応力も重畳することから各種影響因子を定量的に評価することは容易ではない。そこで本研究では、疲労損傷のメカニズムを反映した寿命評価手法を開発するものである。