本文選題：非線性超聲　切入點(diǎn)：多晶純銅　出處：《華東理工大學(xué)》2017年碩士論文

【摘要】：及早地準(zhǔn)確定量和定位結(jié)構(gòu)損傷對(duì)于確保設(shè)備的長(zhǎng)周期安全服役和生產(chǎn)安全至關(guān)重要。近期研究表明,非線性超聲對(duì)結(jié)構(gòu)損傷早期的微納尺度演化如位錯(cuò)和第二相析出等均可敏感地響應(yīng),然而對(duì)于微納尺度下的缺陷如何與非線性超聲的相互作用和動(dòng)力學(xué)機(jī)制尚不清晰。本文從實(shí)驗(yàn)角度出發(fā),以多晶純銅、PMMA和304奧氏體不銹鋼等典型材料為對(duì)象,開展拉伸載荷下不同程度微觀損傷對(duì)超聲非線性影響的實(shí)驗(yàn)研究,進(jìn)而建立微觀結(jié)構(gòu)演化、損傷與非線性超聲信號(hào)的關(guān)聯(lián)。主要的研究工作和結(jié)論如下:(1)開展了不同熱處理參數(shù)下多晶純銅的拉伸塑性損傷對(duì)超聲非線性參量影響的實(shí)驗(yàn)研究。結(jié)果表明多晶銅中拉伸塑性損傷與超聲非線性參量的變化密切相關(guān),通過系統(tǒng)定量分析多晶純銅的位錯(cuò)組織演化與超聲非線性參量之間的響應(yīng)關(guān)系,建立了微觀位錯(cuò)對(duì)超聲非線性參量影響的規(guī)律。(2)系統(tǒng)分析了多晶純銅、PMMA和304奧氏體不銹鋼三種典型材料微觀組織演化對(duì)非線性超聲信號(hào)影響的差異。研究表明,PMMA材料拉伸過程中并不產(chǎn)生微觀位錯(cuò)等缺陷,因此對(duì)非線性超聲信號(hào)幾乎沒有影響;相比而言,多晶銅和304不銹鋼產(chǎn)生了明顯的不同形式的位錯(cuò)組織演化和馬氏體相變,對(duì)超聲非線性信號(hào)產(chǎn)生了顯著的影響。(3)基于多晶銅拉伸損傷與超聲非線性參量的實(shí)驗(yàn)數(shù)據(jù),建立了位錯(cuò)弦模型的參數(shù)修正。研究表明:多晶純銅塑性損傷過程中由位錯(cuò)結(jié)構(gòu)演化引起的超聲非線性參量與位錯(cuò)密度1.2次方、位錯(cuò)弦長(zhǎng)度的4.45次方和內(nèi)應(yīng)力成正比例關(guān)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.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG115.52

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