慢应变速率应力腐蚀原位测试装置设计与试验研究
发布时间：2019-05-11 12:56
【摘要】：由于应力腐蚀的影响因素较多,过程复杂,应力腐蚀发生的内在机理目前尚无统一的理论,因此对于材料在腐蚀环境和应力共同作用下的寿命和可靠性还不能简单有效的评估。传统的慢应变速率法侧重于研究材料的应力-应变曲线、断口形貌等试验现象,对应力腐蚀开裂(SCC)裂纹萌生扩展的过程缺乏深入的研究。而原位(In-situ)测试技术能够实时的监测试验过程中材料微观结构组织变化损伤的详细过程,对应力腐蚀机理的研究具有重要意义。本文结合原位测试技术,设计了一台慢应变速率应力腐蚀原位测试装置,并在此基础上针对典型材料进行试验研究。本文在已有慢应变速率应力腐蚀测试方法理论的基础上,设计了一台小型化的卧式慢应变速率应力腐蚀原位测试装置,测试装置采用轻量化和紧凑化的设计使测试装置便于移动,能够与大多数光学显微镜兼容。相应地,研制了与原位测试相适应的腐蚀介质池,同时发明了一种新的腐蚀介质池密封方法,将一处动密封转变为两处静密封,解决了矩形截面试样动密封困难的问题。另外,设计了满足原位测试要求的非标准试样。还对关键零部件进行了仿真分析、计算校核,验证了测试装置工作的可靠性。配套设计了伺服控制系统。对测试装置进行了性能测试分析。对精密传感器进行了标定,验证了测试数据的准确性。分析了采用间接方法测量试样变形造成的系统误差,提出了相应的修正算法消除误差。试验检测了测试装置拉伸速度的恒定性,分析了三种对拉伸速度造成影响的因素:试验发现机架刚度和传动链接触刚度的不足对试样弹性变形阶段的拉伸速度有较大的减小,本文给出了检测拉伸速度误差的方法,并推导出了相应的修正算法;分析了电磁干扰对拉伸速度造成的波动影响;试验检测了夹具可靠性对拉伸速度的影响。进行了重复性测试试验,验证了测试结果的可靠性。与标准商业化试验机进行了试验结果对比,证明本文设计测试装置的准确性。试验验证了水浴加热的性能,发现温度稳定性较好。在本文研制的测试装置的基础上,对典型材料进行了应力腐蚀试验研究。原位观测了7075铝在3.5%Na Cl溶液中应力腐蚀开裂的过程,发现7075铝在试验早期表面会产生点蚀坑,在应力和腐蚀环境共同作用下,点蚀坑附近会萌生出裂纹,不同位置的裂纹扩展连接到一起,最后导致试样断裂。研究了应变速率对304不锈钢应力腐蚀的影响,发现应变速率为3×10-6/s时,304不锈钢具有最大应力腐蚀敏感性。本文研制的慢应变速率应力腐蚀原位测试装置为应力腐蚀的研究提供了新的手段,有利于应力腐蚀机理的深入研究。本文进行的一些设计、分析工作具有普遍借鉴意义。
[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，
本文编号：2474507
[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，
本文编号：2474507
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