典型材料拉伸损伤对超声非线性响应影响的研究

发布时间：2018-03-25 23:47

本文选题：非线性超声　切入点：多晶纯铜　出处：《华东理工大学》2017年硕士论文

【摘要】：及早地准确定量和定位结构损伤对于确保设备的长周期安全服役和生产安全至关重要。近期研究表明,非线性超声对结构损伤早期的微纳尺度演化如位错和第二相析出等均可敏感地响应,然而对于微纳尺度下的缺陷如何与非线性超声的相互作用和动力学机制尚不清晰。本文从实验角度出发,以多晶纯铜、PMMA和304奥氏体不锈钢等典型材料为对象,开展拉伸载荷下不同程度微观损伤对超声非线性影响的实验研究,进而建立微观结构演化、损伤与非线性超声信号的关联。主要的研究工作和结论如下:(1)开展了不同热处理参数下多晶纯铜的拉伸塑性损伤对超声非线性参量影响的实验研究。结果表明多晶铜中拉伸塑性损伤与超声非线性参量的变化密切相关,通过系统定量分析多晶纯铜的位错组织演化与超声非线性参量之间的响应关系,建立了微观位错对超声非线性参量影响的规律。(2)系统分析了多晶纯铜、PMMA和304奥氏体不锈钢三种典型材料微观组织演化对非线性超声信号影响的差异。研究表明,PMMA材料拉伸过程中并不产生微观位错等缺陷,因此对非线性超声信号几乎没有影响;相比而言,多晶铜和304不锈钢产生了明显的不同形式的位错组织演化和马氏体相变,对超声非线性信号产生了显著的影响。(3)基于多晶铜拉伸损伤与超声非线性参量的实验数据,建立了位错弦模型的参数修正。研究表明:多晶纯铜塑性损伤过程中由位错结构演化引起的超声非线性参量与位错密度1.2次方、位错弦长度的4.45次方和内应力成正比例关系。
[Abstract]:Early and accurate quantification and location of structural damage is essential to ensure long-term safe service and safety in production of equipment. Recent studies have shown that. Nonlinear ultrasound can respond sensitively to micro- and nanoscale evolution such as dislocation and second phase precipitation in the early stage of structural damage. However, it is not clear how the defects in the micro- and nanoscale scale interact with nonlinear ultrasound. In this paper, the typical materials, such as polycrystalline pure copper (PMMA) and 304 austenitic stainless steel, are studied from the experimental point of view. An experimental study on the influence of different degrees of microdamage on ultrasonic nonlinearity under tensile loading was carried out, and the microstructure evolution was established. The relationship between damage and nonlinear ultrasonic signal. The main research work and conclusion are as follows: 1) the experimental study on the effect of tensile plastic damage on ultrasonic nonlinear parameters of polycrystalline pure copper under different heat treatment parameters has been carried out. The results show that there are many kinds of ultrasonic nonlinear parameters. Tensile plastic damage in crystalline copper is closely related to the change of ultrasonic nonlinear parameters. The response relationship between the dislocation structure evolution of polycrystalline pure copper and ultrasonic nonlinear parameters is analyzed systematically. The influence of micro dislocation on ultrasonic nonlinear parameters was established. The difference between microstructure evolution of polycrystalline pure copper (PMMA) and 304 austenitic stainless steel (304 austenitic stainless steel) on nonlinear ultrasonic signals was analyzed systematically. The results show that the microstructure of PMMA is different from that of polycrystalline pure copper and 304 austenitic stainless steel. In the tensile process of the material, there are no microdislocations and other defects, In contrast, polycrystalline copper and 304 stainless steel have different dislocation structure evolution and martensite transformation. Based on the experimental data of tensile damage and ultrasonic nonlinear parameters of polycrystalline copper, The parameter correction of dislocation string model is established. The results show that the ultrasonic nonlinear parameters caused by dislocation structure evolution are proportional to dislocation density 1.2, dislocation string length 4.45 and internal stress in the plastic damage process of polycrystalline pure copper.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115.52

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