本文選題：應(yīng)力集中　切入點(diǎn)：金屬磁記憶檢測　出處：《天津科技大學(xué)》2017年碩士論文

【摘要】：應(yīng)力集中一直是工程界普遍關(guān)注的問題。構(gòu)件存在應(yīng)力集中會(huì)造成其承載能力降低,嚴(yán)重時(shí)會(huì)使運(yùn)行中的承載構(gòu)件突然斷裂,導(dǎo)致災(zāi)難性事故的發(fā)生。因此,最好的解決辦法是可以對(duì)工作中的構(gòu)件進(jìn)行實(shí)時(shí)監(jiān)測,及時(shí)發(fā)現(xiàn)應(yīng)力集中及早期損傷,降低突發(fā)性事故的發(fā)生率。傳統(tǒng)的無損檢測技術(shù)雖然已經(jīng)在工程中得到了廣泛的應(yīng)用,但主要的檢測對(duì)象是構(gòu)件上已經(jīng)存在的缺陷,對(duì)于那些由于應(yīng)力集中等引起的早期損傷并不能檢測出來。金屬磁記憶檢測技術(shù)的出現(xiàn),使鐵磁構(gòu)件的早期診斷成為可能,該技術(shù)是利用地磁場環(huán)境,通過檢測構(gòu)件由于應(yīng)力集中引起的表面漏磁場變化來判斷損傷部位以及損傷程度。由于發(fā)展時(shí)間較短,該技術(shù)還不是很成熟,且檢測過程中受到的影響因素較多,目前只是作為判斷鐵磁構(gòu)件應(yīng)力集中位置的一種初步檢測方法,還需要其他檢測方法進(jìn)行復(fù)檢,且不能提供量化結(jié)果。在該技術(shù)中,常用的磁參數(shù)是自有漏磁場法向分量以及其在長度方向上的梯度值。在現(xiàn)階段大多數(shù)的實(shí)驗(yàn)研究中,主要是對(duì)試件表面應(yīng)力集中區(qū)域上所作的一些測量線進(jìn)行檢測并研究磁記憶信號(hào)變化情況,并通過法向磁記憶信號(hào)曲線過零點(diǎn)來判斷應(yīng)力集中位置,但一些實(shí)驗(yàn)研究也表明,通過此方法來判斷試件的應(yīng)力集中位置不是十分準(zhǔn)確。針對(duì)此問題,本文首先對(duì)不同直徑的中心小孔試件加載并進(jìn)行磁記憶檢測,研究試件表面小孔附近測量線上法向磁記憶信號(hào)變化過程,并進(jìn)行力學(xué)仿真分析磁記憶信號(hào)與應(yīng)力集中的關(guān)系;其次,分別對(duì)預(yù)制中心圓孔和兩半圓槽試件進(jìn)行磁記憶檢測,提出了通過法向磁記憶信號(hào)在兩個(gè)方向上的梯度來判斷試件應(yīng)力集中位置的方法,主要內(nèi)容和結(jié)論包括:(1)對(duì)一系列不同直徑中心小孔試件拉伸加載并進(jìn)行磁記憶檢測,觀察試件經(jīng)拉伸后法向磁記憶信號(hào)變化情況,并進(jìn)行力學(xué)仿真得到受載試件在不同拉伸載荷下,不同位置應(yīng)力集中系數(shù)相同而磁記憶信號(hào)過零點(diǎn)位置不同的現(xiàn)象,得出僅根據(jù)法向磁記憶信號(hào)過零點(diǎn)判斷受載試件應(yīng)力集中位置方法欠妥的結(jié)論。(2)在彈性階段內(nèi),對(duì)中心圓孔試件表面劃分網(wǎng)格后進(jìn)行拉伸,對(duì)不同載荷下試件表面上的網(wǎng)格點(diǎn)進(jìn)行磁記憶信號(hào)采集,提出了通過法向磁記憶信號(hào)在檢測平面長和寬兩個(gè)方向上的梯度來判斷試件應(yīng)力集中位置的方法。此外,利用COMSOL軟件對(duì)試件在彈性階段內(nèi)的受力情況進(jìn)行了仿真,發(fā)現(xiàn)應(yīng)力與法向磁記憶信號(hào)梯度成正比關(guān)系,得出可通過法向磁記憶信號(hào)在兩個(gè)方向上的梯度判斷受載試件的應(yīng)力集中位置。(3)對(duì)兩半圓槽試件加載并進(jìn)行磁記憶檢測,該實(shí)驗(yàn)與中心圓孔試樣的實(shí)驗(yàn)方法完全相同,進(jìn)一步驗(yàn)證了通過法向磁記憶信號(hào)在試件長和寬兩個(gè)方向上的梯度來判斷應(yīng)力集中位置方法的可行性。
[Abstract]:Stress concentration has always been a common concern in engineering circles.The stress concentration of the member will lead to the decrease of its bearing capacity, and when it is serious, it will suddenly break the bearing member in operation and lead to the occurrence of catastrophic accident.Therefore, the best solution is to monitor the components in real time, to find stress concentration and early damage in time, and to reduce the incidence of sudden accidents.Although the traditional nondestructive testing technology has been widely used in engineering, the main detection object is the existing defects on the components, which can not be detected for the early damage caused by stress concentration.The appearance of metal magnetic memory detection technology makes it possible for the early diagnosis of ferromagnetic components. The technique uses geomagnetic field environment to judge the damage location and damage degree by detecting the change of magnetic field leakage on the surface of the components due to stress concentration.Because of the short development time, the technology is not very mature, and there are many influencing factors in the testing process. At present, it is only a preliminary detection method to judge the stress concentration position of ferromagnetic components, and other detection methods are needed for re-examination.And can not provide quantitative results.In this technique, the commonly used magnetic parameters are the normal component of the self-leakage magnetic field and its gradient value in the length direction.In most of the experimental studies at present, some measuring lines in the stress concentration area of the specimen surface are detected and the changes of the magnetic memory signal are studied.The zero-crossing point of the normal magnetic memory signal curve is used to determine the stress concentration position, but some experimental studies also show that it is not very accurate to judge the stress concentration position of the specimen by this method.To solve this problem, this paper first loads the specimen with different diameter and carries on the magnetic memory detection, studies the change process of the normal magnetic memory signal on the measuring line near the small hole on the surface of the specimen.The relationship between the magnetic memory signal and the stress concentration is analyzed by mechanical simulation. Secondly, the magnetic memory test of the prefabricated central circular hole and the two semicircular groove specimens are carried out respectively.A method is proposed to determine the stress concentration position of the specimen by the gradient of the normal magnetic memory signal in two directions. The main contents and conclusions include: 1) tensile loading and magnetic memory detection of a series of specimens with different diameter center holes.The change of normal magnetic memory signal after tensile is observed, and mechanical simulation results show that the stress concentration coefficient is the same at different positions and the crossing position of magnetic memory signal is different under different tensile loads.It is concluded that only the zero crossing point of normal magnetic memory signal is used to determine the stress concentration position of loaded specimen. The conclusion is that in the elastic stage, the surface of the specimen with a central circular hole is meshed and stretched.The magnetic memory signal was collected from the grid points on the surface of the specimen under different loads. A method to determine the stress concentration position of the specimen was proposed by measuring the gradient of the normal magnetic memory signal in the direction of the length and width of the plane.In addition, the stress of the specimen during the elastic stage is simulated by COMSOL software. It is found that the stress is proportional to the gradient of the normal magnetic memory signal.It is concluded that the stress concentration position of loaded specimen can be determined by the gradient of normal magnetic memory signal in two directions) and the magnetic memory test can be carried out on two semicircular grooves. The experimental method is identical to that of the specimen with central circular hole.The feasibility of the method to determine the stress concentration position is further verified by the gradient of the normal magnetic memory signal in both the length and width directions of the specimen.
【學(xué)位授予單位】：天津科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG142.15

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本文編號(hào)：1722109