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面向再制造铁磁性构件损伤程度的磁记忆/超声综合无损评估

Metal Magnetic Memory and Ultrasonic Complex Method for Damage Degree Evaluation of Used Ferromagnetic Component Before Remanufacturing

【作者】 石常亮

【导师】 徐滨士; 何鹏; 董世运;

【作者基本信息】 哈尔滨工业大学 , 材料加工工程, 2011, 博士

【摘要】 随着社会的飞速发展和人口的迅猛增多,土地、能源和矿产的缺乏将会日益严重,因此,保护地球环境、节约可用能源和保持社会可持续发展变得尤为重要。再制造工程是以产品全寿命周期理论为指导,以提升废旧产品性能为目标,以优质、节能、高效、环保为准则,以先进的表面工程技术和产业化生产为手段,修复、改造废旧产品的一系列技术措施或工程活动的总称。再制造工程符合社会发展的需求,它以其特有优势,受到世界各国的广泛关注。随之而来,再制造工程需要解决的问题也越来越多。其中,如何保障再制造产品质量、增强用户对使用再制造产品的信心是重中之重,直接关系到再制造工程技术的推广应用。本课题以无损评估再制造铁磁性毛坯剩余寿命、保障再制造产品质量为研究目的,以金属磁记忆检测方法和超声检测方法为研究对象,通过大量静载和疲劳拉伸试验,研究金属磁记忆信号随载荷、循环次数和应力集中程度的变化规律,提取金属磁记忆信号表征疲劳损伤程度的关键参量。在此基础上,结合断裂力学理论,建立了综合采用金属磁记忆信号和超声波信号表征疲劳寿命的预测模型。在理论联系实际的基础上,综合采用金属磁记忆和超声波检测方法对再制造曲轴毛坯进行无损评估,研发相关检测装置,为无损检测技术在再制造质量评估中的应用奠定基础。主要研究成果如下:通过静载拉伸试验和拉-拉疲劳试验,研究了磁记忆信号与加载载荷的变化规律、磁记忆信号随载荷循环次数的变化规律以及应力集中系数对磁记忆信号的影响,提取磁记忆信号表征疲劳损伤程度的特征参量。研究了表面裂纹、应力集中程度、检测方向和提离高度对磁记忆信号的影响,用以指导磁记忆检测的工程应用。通过摩擦磨损试验,研究了试件磨损程度对磁记忆信号的影响,结果表明:磨损程度对磁记忆信号有显著影响,磁记忆信号表征磨损程度的关键参量为磁异变峰,磁记忆信号能较准确地表征试样表面磨损区域的大小和位置,并能定性评估试样表面磨损程度。在大量试验数据基础上,建立了静载拉伸和拉-拉疲劳时磁记忆信号随载荷和循环次数变化的数值拟合模型,并结合大量试验,验证了磁记忆信号和超声信号为特征参量表征疲劳裂纹萌生寿命和疲劳裂纹扩展寿命的预测模型的适用性。以再制造曲轴毛坯为研究对象,进行仿真模拟和失效分析,明确其受力状态、危险区域和失效原因,并根据分析结果,采用金属磁记忆检测技术检测旧曲轴表面裂纹和应力集中,评估旧曲轴的疲劳损伤程度;采用超声检测技术检测旧曲轴内部缺陷。根据再制造曲轴毛坯的材质和结构特征,设计了曲面单晶双斜探头和曲轴超声检测的专用检测装置,制定了探头校准方法,规范了曲轴超声检测步骤,解决了曲轴超声检测的定位和定量问题。规范了再制造曲轴毛坯的金属磁记忆检测方法。根据实际检测结果,提取了磁记忆信号表征曲轴疲劳损伤程度的关键参量——磁示应力集中系数KM,并利用KM将曲轴分为三个损伤等级,确定了表征斯泰尔发动机曲轴疲劳损伤的KM的阈值。以此为基础,综合采用金属磁记忆和超声波检测方法对再制造曲轴毛坯的再制造性进行评价。

【Abstract】 With the rapid society and population growth, the lack of land, energy and mineral resources will become more and more serious, therefore, it becomes more and more important for environmental protection, energy conservation and society sustained development. Remanufacturing engineering is a generic terms of all techniques and engineering activity to maintain and rebuild worn products, which takes the productive whole life as direction, takes the upgrade of the perfomance of worn products as goal, takes the good quality, high efficiency, energy saving, environment protecting as rule, and takes the advanced surface engineering techniques and industrializing process as measures. Remanufacturing engineering is fit for the development of society, which is widely recognized. Then, more and more issues come out from remanufacturing engineering. How to ensure product quality and upgrade the consumer confidence are the most important, related with the application of remanufacturing engineering.Taking nondestructive evaluation on residual life of remanufacturing core and quality ensurence of remanufacturing product as goal, and taking metal magnetic memory testing and ultrasonic testing as subject, in this research, the regularity of metal magnetic memory signals, which changed with loads, cycles and stress concentration, were studied, and the key parameter characterizing fatigue damage was found by static tension test and fatigue tensile test. Meanwhile, the fatigue life evaluating models characterized by metal magnetic memory signals and ultrasonic signals were gived, combined with fracture mechanics. In practical application, metal magnetic memory testing and ultrasonic testing were used to evaluate the worn crankshaft before remanufacturing, and nondestructive testing clamping fixture was designed. Some of main experimental results and conclusions are shown as follow.By static tension tests and fatigue tensile tests, the regularity of magnetic memory signals, changed with applied load, fatigue cycles and stress concentration factor, were investigated, and the key parameter between magnetic memory signals and fatigue damage was extracted. The influences of surface cracking, stress concentration, testing direction and lift-off height on magnetic memory signals were studied for the application of metal magnetic memory testing. The regularity of magnetic memory signals, influenced by friction wear, was studied. The results showed that magnetic memory signals were obviously affected by friction wear, and the key parameter between magnetic memory signals and friction wear was abnormal magnetic peak, which could quantitatively detect the size and site of friction area, and qualitatively estimate the degree of wear.The numerical models of magnetic memory signals, changed with applied load in static tension test and fatigue cycles in fatigue tensile test, were fitted based on test data. The simple models of fatigue life evaluation were constructed, which were characterized by magnetic memory signals and ultrasonic signals.Taking the worn crankshaft before remanufacturing as subject investigated, the simulation and failure analysis of crankshaft were done to confirm the stress distribution, risk area and failure reason. According to the results, metal magnetic memory testing was used to detect the surface cracking and stress concentration, and ultrasonic testing was used to detect the flaws in the crankshaft.Curved double angle beam probe was applied to detect the crankshaft because of the special construction of crankshaft. The calibrating method of probe was designed, and the testing procedure of worn crankshaft was confirmed. The special clamping fixture for ultrasonic testing on crankshaft was designed, and the problems of locating testing and quantitative testing were solved.Metal magnetic memory testing method of worn crankshaft before remanufacturing was confirmed for application. The key parameter KM, which was magnetic stress concentration factor, was extracted from the practical data, and used to estimate the degree of fatigue damage as three grades. The key value of KM for Stir engine crankshaft was confirmed in practical application. Finally, the quality of worn crankshaft before remanufacturing was estimated by metal magnetic memory testing and ultrasonic testing.

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