【摘要】：由于應(yīng)力腐蝕的影響因素較多,過程復(fù)雜,應(yīng)力腐蝕發(fā)生的內(nèi)在機(jī)理目前尚無統(tǒng)一的理論,因此對(duì)于材料在腐蝕環(huán)境和應(yīng)力共同作用下的壽命和可靠性還不能簡(jiǎn)單有效的評(píng)估。傳統(tǒng)的慢應(yīng)變速率法側(cè)重于研究材料的應(yīng)力-應(yīng)變曲線、斷口形貌等試驗(yàn)現(xiàn)象,對(duì)應(yīng)力腐蝕開裂(SCC)裂紋萌生擴(kuò)展的過程缺乏深入的研究。而原位(In-situ)測(cè)試技術(shù)能夠?qū)崟r(shí)的監(jiān)測(cè)試驗(yàn)過程中材料微觀結(jié)構(gòu)組織變化損傷的詳細(xì)過程,對(duì)應(yīng)力腐蝕機(jī)理的研究具有重要意義。本文結(jié)合原位測(cè)試技術(shù),設(shè)計(jì)了一臺(tái)慢應(yīng)變速率應(yīng)力腐蝕原位測(cè)試裝置,并在此基礎(chǔ)上針對(duì)典型材料進(jìn)行試驗(yàn)研究。本文在已有慢應(yīng)變速率應(yīng)力腐蝕測(cè)試方法理論的基礎(chǔ)上,設(shè)計(jì)了一臺(tái)小型化的臥式慢應(yīng)變速率應(yīng)力腐蝕原位測(cè)試裝置,測(cè)試裝置采用輕量化和緊湊化的設(shè)計(jì)使測(cè)試裝置便于移動(dòng),能夠與大多數(shù)光學(xué)顯微鏡兼容。相應(yīng)地,研制了與原位測(cè)試相適應(yīng)的腐蝕介質(zhì)池,同時(shí)發(fā)明了一種新的腐蝕介質(zhì)池密封方法,將一處動(dòng)密封轉(zhuǎn)變?yōu)閮商庫o密封,解決了矩形截面試樣動(dòng)密封困難的問題。另外,設(shè)計(jì)了滿足原位測(cè)試要求的非標(biāo)準(zhǔn)試樣。還對(duì)關(guān)鍵零部件進(jìn)行了仿真分析、計(jì)算校核,驗(yàn)證了測(cè)試裝置工作的可靠性。配套設(shè)計(jì)了伺服控制系統(tǒng)。對(duì)測(cè)試裝置進(jìn)行了性能測(cè)試分析。對(duì)精密傳感器進(jìn)行了標(biāo)定,驗(yàn)證了測(cè)試數(shù)據(jù)的準(zhǔn)確性。分析了采用間接方法測(cè)量試樣變形造成的系統(tǒng)誤差,提出了相應(yīng)的修正算法消除誤差。試驗(yàn)檢測(cè)了測(cè)試裝置拉伸速度的恒定性,分析了三種對(duì)拉伸速度造成影響的因素:試驗(yàn)發(fā)現(xiàn)機(jī)架剛度和傳動(dòng)鏈接觸剛度的不足對(duì)試樣彈性變形階段的拉伸速度有較大的減小,本文給出了檢測(cè)拉伸速度誤差的方法,并推導(dǎo)出了相應(yīng)的修正算法;分析了電磁干擾對(duì)拉伸速度造成的波動(dòng)影響;試驗(yàn)檢測(cè)了夾具可靠性對(duì)拉伸速度的影響。進(jìn)行了重復(fù)性測(cè)試試驗(yàn),驗(yàn)證了測(cè)試結(jié)果的可靠性。與標(biāo)準(zhǔn)商業(yè)化試驗(yàn)機(jī)進(jìn)行了試驗(yàn)結(jié)果對(duì)比,證明本文設(shè)計(jì)測(cè)試裝置的準(zhǔn)確性。試驗(yàn)驗(yàn)證了水浴加熱的性能,發(fā)現(xiàn)溫度穩(wěn)定性較好。在本文研制的測(cè)試裝置的基礎(chǔ)上,對(duì)典型材料進(jìn)行了應(yīng)力腐蝕試驗(yàn)研究。原位觀測(cè)了7075鋁在3.5%Na Cl溶液中應(yīng)力腐蝕開裂的過程,發(fā)現(xiàn)7075鋁在試驗(yàn)早期表面會(huì)產(chǎn)生點(diǎn)蝕坑,在應(yīng)力和腐蝕環(huán)境共同作用下,點(diǎn)蝕坑附近會(huì)萌生出裂紋,不同位置的裂紋擴(kuò)展連接到一起,最后導(dǎo)致試樣斷裂。研究了應(yīng)變速率對(duì)304不銹鋼應(yīng)力腐蝕的影響,發(fā)現(xiàn)應(yīng)變速率為3×10-6/s時(shí),304不銹鋼具有最大應(yīng)力腐蝕敏感性。本文研制的慢應(yīng)變速率應(yīng)力腐蝕原位測(cè)試裝置為應(yīng)力腐蝕的研究提供了新的手段,有利于應(yīng)力腐蝕機(jī)理的深入研究。本文進(jìn)行的一些設(shè)計(jì)、分析工作具有普遍借鑒意義。
[Abstract]:Because of the many influencing factors and complex process of stress corrosion, there is no unified theory on the internal mechanism of stress corrosion, so the life and reliability of materials under the combined action of corrosion environment and stress can not be evaluated simply and effectively. The traditional slow strain rate method focuses on the stress-strain curve and fracture morphology of the material, but lacks in-depth study on the process of crack initiation and propagation of stress corrosion cracking (SCC). In situ (In-situ) testing technology can monitor the detailed process of microstructure change and damage of materials in real time, which is of great significance to the study of stress corrosion mechanism. In this paper, a slow strain rate stress corrosion in situ testing device is designed based on in situ testing technology, and the experimental research on typical materials is carried out on the basis of this device. Based on the theory of slow strain rate stress corrosion test method, a miniaturized horizontal slow strain rate stress corrosion in situ testing device is designed in this paper. The device is lightweight and compact, which makes it easy to move and compatible with most optical microscopes. Accordingly, a corrosion medium pool suitable for in-situ test is developed, and a new sealing method of corrosion medium pool is invented, which converts one dynamic seal into two static seals, which solves the problem of difficult dynamic sealing of rectangular interviewing samples. In addition, non-standard samples were designed to meet the requirements of in-situ testing. The key parts are simulated and checked, and the reliability of the test device is verified. The servo control system is designed. The performance of the test device is tested and analyzed. The precision sensor is calibrated to verify the accuracy of the test data. The systematic error caused by indirect measurement of sample deformation is analyzed, and the corresponding correction algorithm is put forward to eliminate the error. The constant tensile speed of the test device is tested, and three factors affecting the tensile speed are analyzed. It is found that the deficiency of the frame stiffness and the contact stiffness of the transmission chain greatly reduces the tensile speed of the specimen in the elastic deformation stage. In this paper, the method of detecting the tensile velocity error is given, and the corresponding correction algorithm is deduced. The influence of electromagnetic interference on tensile velocity is analyzed, and the effect of fixture reliability on tensile speed is tested. The repeatability test was carried out to verify the reliability of the test results. The test results are compared with those of the standard commercial testing machine, which proves the accuracy of the design of the test device in this paper. The performance of water bath heating is verified by experiments, and it is found that the temperature stability is good. On the basis of the test device developed in this paper, the stress corrosion test of typical materials was carried out. The stress corrosion cracking process of 7075 aluminum in 3.5%Na Cl solution was observed in situ. It was found that 7075 aluminum would produce pitting pits on the surface at the early stage of the test, and cracks would occur near the pitting pits under the combined action of stress and corrosion environment. Cracks at different positions propagate and connect together, and finally lead to fracture of the specimen. The effect of strain rate on stress corrosion of 304 stainless steel was studied. it was found that 304 stainless steel had the maximum stress corrosion sensitivity when the strain rate was 3 脳 10 ~ (- 6) 鈮，

本文編號(hào)：2474507