本文選題：軸類零件　切入點(diǎn)：疲勞　出處：《天津大學(xué)》2014年碩士論文

【摘要】：軸類零件在工程機(jī)械設(shè)備中廣泛應(yīng)用,作為支撐傳動(dòng)部件,在長(zhǎng)期循環(huán)載荷作用下,不可避免地會(huì)產(chǎn)生金屬疲勞,甚至使零件突然斷裂,造成災(zāi)難性事故,帶來巨大的人力、財(cái)力損失。45號(hào)鋼是軸類零件常用材料,可作為基礎(chǔ)研究對(duì)象,用于軸類零件疲勞檢測(cè)的研究。本文采用非線性超聲無損檢測(cè)技術(shù),利用超聲波在結(jié)構(gòu)中傳播時(shí)所表現(xiàn)出來的非線性特征——諧波滋生,經(jīng)分析計(jì)算,提取非線性系數(shù)β,進(jìn)行材料性能評(píng)估和疲勞程度檢測(cè),能夠?qū)S類零件進(jìn)行疲勞早期的診斷和評(píng)價(jià),預(yù)測(cè)其剩余使用壽命,從而發(fā)現(xiàn)潛在威脅,防范零件疲勞斷裂事故于未然。本課題目的是進(jìn)行材料疲勞早期的診斷與評(píng)價(jià),該階段試件并未產(chǎn)生裂紋等宏觀損傷或缺陷,而只是材料性能的退化。因此,論文采用超聲非線性最經(jīng)典的表現(xiàn)形式——高次諧波,對(duì)不同拉伸加載次數(shù)的45號(hào)鋼試件進(jìn)行表征。針對(duì)試件早期疲勞診斷的非線性超聲檢測(cè)方法,主要對(duì)以下四項(xiàng)關(guān)鍵技術(shù)進(jìn)行了研究:通過ABAQUS有限元分析,進(jìn)行試件拉伸變形仿真;以與激勵(lì)超聲波脈沖相同時(shí)間作用下的微小壓強(qiáng)載荷,模擬超聲波在試件中的傳播,可以實(shí)現(xiàn)精確跟蹤超聲應(yīng)力波傳播過程,并觀察其波形衰減、反射等規(guī)律的目的。搭建非線性超聲實(shí)驗(yàn)系統(tǒng),通過多次重復(fù)測(cè)量,確定系統(tǒng)穩(wěn)定性,并成功應(yīng)用實(shí)驗(yàn)系統(tǒng)進(jìn)行非線性超聲檢測(cè)實(shí)驗(yàn)。以A_2 vs.A_1~2數(shù)據(jù)點(diǎn)擬合直線的歸一化斜率值,作為等效相對(duì)非線性系數(shù),用于表征試件非線性特征,相當(dāng)于對(duì)試件多次測(cè)量所得非線性系數(shù)的平均,可增加實(shí)驗(yàn)結(jié)果準(zhǔn)確度和可靠性。以頻譜直接提取法與脈沖反轉(zhuǎn)提取法所得A_2 vs.A_1~2數(shù)據(jù)點(diǎn)擬合直線的歸一化斜率值,作為試件非線性特征,以基波幅值A(chǔ)_1歸一化系數(shù)作為超聲線性特征。通過三種方法進(jìn)行試件不同疲勞程度下測(cè)量結(jié)果的對(duì)比,說明只有采用脈沖反轉(zhuǎn)法得到的歸一化斜率值有增大趨勢(shì),可用于試件疲勞早期診斷與評(píng)估。
[Abstract]:Shaft parts are widely used in construction machinery and equipment, as supporting transmission parts, under the action of long-term cyclic load, metal fatigue will inevitably occur, and even parts will break suddenly, resulting in catastrophic accidents, and bringing huge manpower. Financial loss. 45 steel is a common material for shaft parts, which can be used as basic research object for fatigue testing of shaft parts. In this paper, nonlinear ultrasonic nondestructive testing technology is used. By using the nonlinear characteristic of ultrasonic wave propagating in the structure-harmonic breeding, the nonlinear coefficient 尾 is extracted through analysis and calculation, and the material performance evaluation and fatigue degree testing are carried out. It can diagnose and evaluate the shaft parts in the early stage of fatigue, predict their remaining service life, so as to find the potential threat and prevent the fatigue fracture accident of the parts. The purpose of this project is to diagnose and evaluate the material fatigue in the early stage. At this stage, the specimen does not produce macroscopic damage or defect, such as crack, but only the degradation of material properties. Therefore, the most classical expression of ultrasonic nonlinearity, high order harmonic, is adopted in this paper. The 45 steel specimens with different tensile loading times were characterized. The following four key techniques were studied: ABAQUS finite element analysis, the nonlinear ultrasonic testing method for early fatigue diagnosis of specimens. In order to simulate the tensile deformation of the specimen and simulate the propagation of the ultrasonic wave in the specimen under the same pressure load at the same time as the excited ultrasonic pulse, the ultrasonic stress wave propagation process can be tracked accurately and the wave attenuation can be observed. The purpose of this paper is to set up a nonlinear ultrasonic experimental system. The stability of the system is determined by repeated measurements, and the nonlinear ultrasonic testing experiment is carried out successfully by using the experimental system. The normalized slope value of the straight line is fitted with A-2 vs.A_1~2 data points. As an equivalent relative nonlinear coefficient, it is used to characterize the nonlinear characteristics of the specimen, which is equivalent to the average of the nonlinear coefficient obtained from multiple measurements of the specimen. The accuracy and reliability of the experimental results can be increased. The normalized slope value of the fitting line of A _ 2 vs.A_1~2 data points obtained from direct spectral extraction method and pulse inversion extraction method is regarded as the nonlinear feature of the specimen. The normalized coefficient of fundamental amplitude A _ 1 is taken as the ultrasonic linear characteristic. The comparison of the measured results under different fatigue degree by three methods shows that only the normalized slope obtained by the pulse inversion method has an increasing tendency. It can be used for early diagnosis and evaluation of fatigue of specimen.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TH133.2;TB559

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