基于疲劳竞争的废旧高强度钢零件可再制造性判断研究

At present, there is a lack of effective methods for predicting the giga-fatigue life and the remanufacturability judgment of high strength steel. Therefore, the competitive fatigue life prediction and the establishment of critical threshold model based on fatigue defect for high strength steel are the key problems in the remanufacturability judgement and residual fatigue life prediction for the high-strength steel remanufacturing cores..Project intends to carry out research from four aspects for high-strength steel remanufacturing cores as the studying object: “Coupling fatigue competition between surface defect and internal defect”, “Giga-fatigue life prediction” , “Remanufacturability judgement rule” and “Remanufacturability judgement method”: 1.Revealing the mechanism of fatigue competition between the surface fatigue defect and internal fatigue defect in giga-fatigue regime, establishing the fatigue competition model to realize the quantitative characterization of the fatigue competition; 2. Establishing the giga-fatigue life prediction model based on the fatigue competition;3Proposing the remanufacturability judgment rule based on fatigue competition; 4.Studying the remanufacturability judgment rule, proposing a new remanufacturability function based on fatigue competition, realizing the quantitative characterization of the remanufacturability judgment based on fatigue competition. The research results would have positive significance to enhance remanufacturability judgment capacity for the high-strength steel remanufacturing cores.

目前，缺乏针对高强度钢的超高周疲劳寿命预测与可再制造性判断的有效手段。基于疲劳竞争的高强度钢疲劳寿命预测与基于损伤的可再制造性判断模型的建立，是废旧高强度钢零件剩余寿命评估及可再制造性判断的关键科学问题。本项目以废旧高强度钢零件为研究对象，从“表面与内部耦合疲劳竞争”、“超高周疲劳寿命预测”、“可再制造性判断指标”及“可再制造性判断方法”四方面开展研究：1.高强度钢表面和内部竞争失效机理及模型研究，实现疲劳竞争失效定量表征；2.建立基于疲劳竞争的超高周疲劳寿命预测模型；3.提出基于疲劳竞争的可再制造性判断指标；4.研究疲劳竞争的可再制造性判断指标，提出基于疲劳竞争的可再制造度函数，实现基于疲劳竞争的可再制造性判断的定量表征。研究成果对于废旧高强度钢零件可再制造性判断具有重要意义。

高强度钢压气机叶片在长期服役过程中，受到交变载荷的作用，极易产生疲劳裂纹。针对叶片的微观裂纹，可直接开展再制造修复，而对于叶片的宏观裂纹，需对裂纹进行打磨清除，叶片表面进而形成表面缺口。目前，针对高强度钢的疲劳寿命预测与可再制造性判断缺乏有效手段，而且，再制造后零件的疲劳寿命预测尚缺少广泛认可的方法和理论模型，再制造前毛坯的剩余疲劳寿命预测及可再制造性判断就显得尤为重要，只有在叶片毛坯可再制造性判断的基础上，才能开展后续再制造修复。课题基于断裂力学，在不同表面粗糙度条件下，结合不同疲劳损伤的疲劳强度模型，揭示了高强度钢表面和内部疲劳失效竞争机理。分析叶片在不同损伤情况下疲劳失效的主要因素，提出表面与内部疲劳失效竞争模型。基于Inglis公式，在现有研究仅考虑缺口本身几何参数的基础上，引入厚度参数的影响，提出表面缺口叶片应力集中系数公式，为叶片裂纹打磨后应力集中的评估提供理论支撑。基于Neuber法则提出表面缺口应变公式，建立表面缺口叶片剩余疲劳寿命模型。提出了基于表面缺口的叶片可再制造性判断方法，为裂纹打磨尺寸的制定提供理论指导。