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RESEARCH ON NONDESTRUCTIVE MEASUREMENT OF FATIGUE DAMAGE

疲劳损伤无损测量研究

基本信息

批准号：
06452143
负责人：
SHOJI Tetsuo
金额：
$ 5.38万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1996
项目状态：
已结题

项目摘要

THE OBJECTIVE OF THIS PROJECT IS TO ESTABLISH A NONDESTRUCTIVE MEASUREMENT AND EVALUATION OF FATIGUE DAMAGE TO PREVENT FATIGUE FAILURES IN VARIOUS ENGINEERING STRUCTURES.FATIGUE DAMAGE PROCESSES CAN BE CATEGORIZED INTO THREE,ONE IS FATIGUE DAMAGE ACCUMULATION STAGE WHERE MICROSTRUCTURAL CHANGES WILL TAKE PROCESS WITHOUT ANY CRACK FORMATION,SECOND CRACK INITIATION AND SMALL CRACK GROWTH STAGE AND THIRD MACROSCOPIC CRACK GROWTH STAGE WHICH CAN BE INTERPRETED BY FRACTURE MECHANICS APPROACH.IN THIS PROJECTS,TWO NOVEL NONDESTRUCTIVE TECHNIQUES ARE PROPOSED FOR DETECTION OF DAMAGE ACCUMULATION AND CRACK INITIATION AND PROPAGATION ON NUCLEAR PRESSURE VESSEL STEELS,Ni-BASE SUPPER ALLOY AND SINTERED LOW ALLOY STEELS.FIRST PROPOSAL IS INDUCED CURRENT FOCUSING POTENTIAL DROP TECHNIQUE (HERE AFTER DENOTED AS ICFPD) AND SECOND IS ELECTROCHEMICAL METHOD.ICFPD HAS BEEN SUCCESSFULLY APPLIED FOR MONITORING OF FATIGUE DAMAGE PROCESSES AND CAN DETECT DAMAGE ACCUMULATION AS A DECREASE OF MEASURED POTENTIA … More L DUE TO REDUCTION OF MAGNETIC PERMEABILITY CORRESPONDING TO MICROSTRUCTURAL CHANGES BY FATIGUE.AFTER CRACK INITIATION,MEASURE POTENTIAL INCREASES AS EXPECTED FROM AN INCREASE IN CURRENT PATH DUE TO CRACKS.THIS KIND OF VARIATION OF MEASURED POTENTIAL CAN BE INTERPRETED BY A SIMPLE MODEL OF A COMBINATION OF DECREASE IN MAGNETIC PERMEABILITY OF MATERIALS AND INCREASE IN CURRENT PATH CAUSED BY CRACKS.SECOND ONE IS BY ELECTROCHEMICAL METHOD FOR A DETECTION OF FATIGUE DAMAGE ACCUMULATION.DAMAGE ACCUMULATION CAN BE CAUSED BY INCREASE IN DISLOCATION DENSITY AND RESULTANT FORMATION OF DISLOCATION CELL STRUCTURES.THIS METHOD IS BASED ON DETECTION OF THESE POSSIBLE ELECTROCHEMICALLY OR CHEMICALLY ACTIVE SITES BY A PROPER ELECTROLYTE AND POLARIZATION PROCEDURES.THE BEST ELECTROLYTES ARE SODIUM MOLYBDATE SOLUTION FOR PRESSURE VESSEL STEELS AND MIXTURE OF HCL,H2SO4, CUSO4 AND WATER FOR INCONEL 718, RESPECTIVELY.THESE RESULTS CAN PROVIDES A POTENTIAL PROCEDURE FOR NONDESTRUCTIVE EVALUATION OF FATIGUE DAMAGE IN THOSE OPERATING PLANTS SUCH AS NUCLEAR POWER PLANTS,CHEMICAL PLANTS AND AEROSPACE ENGINEERING COMPONENTS. Less

本课题的目的是建立一种无损的疲劳损伤测量与评估方法，以预防各种工程结构的疲劳失效，疲劳损伤过程可分为三个阶段，一是疲劳损伤累积阶段，在此阶段，微观结构发生变化，但没有裂纹形成，第二裂纹萌生和小裂纹扩展阶段和第三宏观裂纹扩展阶段，可以用断裂力学的方法来解释。本文提出了两种新的无损检测技术，用于核压力容器用钢的损伤累积和裂纹萌生与扩展的检测。镍基合金和烧结低合金钢.第一种方案是感应电流聚焦电位降技术（以下简称人发会议）ICFPD已成功地应用于疲劳损伤监测，并能检测损伤累积作为测量电位的降低 ...更多信息疲劳引起的微观结构变化导致磁导率降低。裂纹萌生后，测量由于裂纹引起的电流路径增加而引起的电位增加。这种被测电位的变化可以用材料磁导率降低和裂纹引起的电流路径增加的简单模型来解释。第二种是用电化学方法检测裂纹引起的电流路径增加。第三种是用电化学方法检测裂纹引起的电流路径增加。第四种是用电化学方法检测裂纹引起的电流路径增加。第五种是用电化学方法检测裂纹引起的电流路径增加。第六种是用电化学方法检测裂纹引起的电流路径增加。第七种是疲劳损伤累积。损伤累积可由位错密度增加和位错胞结构的不稳定形成引起。该方法基于通过适当的电解质和极化程序检测这些可能的电化学或化学活性位点。对于压力容器钢，最佳电解质是钼酸钠溶液;对于Inconel 718，最佳电解质是HCl、H2SO 4、H2O 4和水的混合物。这些结果可为核电站、化工厂和航空航天工程部件等在役设备的疲劳损伤的无损评定提供一种可能的方法。少