共查询到19条相似文献,搜索用时 183 毫秒
1.
目的 研究腐蚀环境中EA4T车轴钢疲劳性能,为车轴的腐蚀检测和使用寿命评估提供依据.方法 采用旋转弯曲疲劳试验机,在人造雨水模拟的腐蚀环境和空气环境中,对EA4T车轴钢试样进行疲劳试验,以获得不同环境下试样的疲劳S-N曲线、表面损伤以及裂纹扩展规律.然后对扩展裂纹进行概率统计,通过扫描电镜对疲劳失效的断口进行观察,并分析对比不同环境中裂纹扩展门槛值的变化.结果 空气环境中,试样的疲劳极限为355 MPa,而在腐蚀环境中,试样不存在疲劳极限,107循环周次对应的疲劳强度降低到245 MPa,相比空气环境中降低了31%.Gumbel分布统计与Weibull双参数分布统计相比,更适合描述EA4T车轴钢试样表面腐蚀裂纹长度随加载次数的变化.腐蚀环境中,疲劳裂纹萌生于表面腐蚀坑,并存在多个裂纹源.腐蚀环境显著降低了试样裂纹扩展门槛值,空气环境下,该值为6.29 MPa·m1/2,腐蚀环境下降低到4.1 MPa·m1/2.结论 腐蚀环境降低EA4T钢疲劳寿命的主要原因是,腐蚀环境降低了裂纹扩展门槛值,加快了裂纹萌生以及短裂纹扩展.而当裂纹达到一定长度时,腐蚀环境对裂纹扩展几乎没有影响. 相似文献
2.
3.
S690高强钢由于其良好的综合力学性能广泛用于海洋平台中. 海洋平台结构易产生腐蚀疲劳失效,海水腐蚀、循环载荷和结构本身的拘束水平对裂纹扩展有重要的影响. 通过空气中和海水环境中的S690高强钢疲劳裂纹扩展试验,结合显微断口分析,研究了拘束水平对S690高强钢腐蚀疲劳裂纹扩展行为的影响. 结果表明,在阳极溶解和氢致开裂的共同作用下,海水环境对S690高强钢疲劳裂纹扩展具有明显的加速作用. 同时随着裂纹的不断扩展,拘束水平对S690高强钢腐蚀疲劳裂纹的影响不断增加,且裂纹扩展速率与裂纹扩展前后的拘束水平增量和结构本身的拘束水平均密切相关. 相似文献
4.
5.
6.
本研究总结了应力腐蚀研究的5个经典理论:活性通路理论、钝化膜破坏理论、氢脆理论、腐蚀产物楔入模型和环境破裂三阶段理论。详细介绍了最为广泛接受的钝化膜破坏理论,在此基础上,从单一参数计算和应力腐蚀裂纹扩展模拟两个方面着重介绍了基于有限元方法对应力腐蚀裂纹扩展的研究方法和技术,单一参数计算可以满足获取应力腐蚀裂纹扩展预测模型关键参数,但是将裂纹尖端认为是一个点的假设存在不合理,应力腐蚀裂纹扩展模拟可以将载荷和环境因素综合考虑在内,但还仍然不能仿真出裂纹微观扩展现象。研究结合实践总结提出了应力腐蚀裂纹扩展模拟的工程技术方法,讨论了有限元技术在应力腐蚀研究方面不能实现微观物理过程、时间相关性等存在的问题,指出了基于应力腐蚀时间相关性的应力腐蚀裂纹扩展模拟研究是应力腐蚀破坏预防及预测研究工作的重点。 相似文献
7.
《中国有色金属学会会刊》2016,(11)
研究2024铝合金搅拌摩擦焊缝在空气、预腐蚀与3.5%盐水腐蚀液中的疲劳与裂纹扩展性能,并采用SEM对断口的近门槛区、稳定扩展区与瞬断区进行观测。结果表明,腐蚀环境对铝合金搅拌摩擦焊缝的寿命产生很大影响,焊缝的腐蚀疲劳寿命只有空气中的一半左右;焊缝的裂纹扩展速率比母材快,在腐蚀环境下,随着应力强度因子幅度的增大,母材与焊缝裂纹扩展速率的差距越来越大,但预腐蚀损伤对焊缝的裂纹扩展速率影响较小,只是降低了裂纹萌生寿命。 相似文献
8.
9.
10.
《热加工工艺》2021,50(7):18-22,26
对于深海油气输送结构,焊接产生的初始预应力会对其腐蚀疲劳性能产生影响。针对深海油气输送常用材料X65钢开展腐蚀疲劳裂纹扩展试验。分别从焊接热影响区和母材上制备了标准紧凑拉伸(CT)试样,利用直流电压降(DCPD)方法测量了疲劳裂纹扩展长度,对焊接试件的腐蚀疲劳性能进行了研究,并拟合出了两种试件在不同试验环境下的Paris常数C和m。试验结果表明:在0.2 Hz的加载频率下,腐蚀溶液可明显加快裂纹扩展速率,并使裂纹扩展阈值分别提高16.25%和13.75%。焊接试件在空气环境下拟合的C值和m值均要略高于母材试件,在腐蚀环境下其C值和m值要略低于母材试件。 相似文献
11.
A study has been made of corrosion fatigue in a 0.5Cr0.5Mo0.25V low alloy steel in a de-aerated distilled water environment at various test temperatures, using the change of specimen compliance with fatigue crack growth as a method of monitoring the crack length. The fatigue crack growth rates and fracture surfaces are compared with those obtained in a dry argon reference environment.The corrosion fatigue is shown to be controlled by a thermally activated process, with an apparent activaton energy independent of the crack tip stress intensity. The percentage of intergranular failure is correlated with the increase in the fatigue crack growth rate due to the aqueous environment. 相似文献
12.
预腐蚀疲劳寿命影响系数模型研究 总被引:1,自引:0,他引:1
针对腐蚀环境下飞机结构疲劳寿命评定问题,研究了恒幅应力水平下的地面停放预腐蚀影响系数C模型,根据统计分析推导出C曲线的关系式;疲劳试验数据分析结果建立了预腐蚀影响系数C模型.结果表明,随着腐蚀时间的增加,疲劳寿命影响系数C不断下降;同一时间下,应力水平S高,影响系数C大;应力水平S低,影响系数C小;在一定的腐蚀疲劳条件(时间、应力水平)下,可求出任一给定可靠度p时的Cp值和疲劳寿命预测值. 相似文献
13.
研究了TC21钛合金缺口试样在两种腐蚀环境(油箱积水、3.5%NaCl水溶液)与室温空气环境下的疲劳性能与断裂机理。并与光滑试样在室温空气环境下疲劳性能进行对比。结果表明,室温空气环境下,当两种试样疲劳寿命均达到5×105次循环时,缺口试样的循环应力值较光滑试样下降了52.7%;相同环境下随着应力水平降低,试样疲劳寿命增加;相同应力条件下,3.5% NaCl水溶液环境下试样疲劳寿命最低,油箱积水环境下次之,室温空气中TC21钛合金试样疲劳寿命最高;当应力较低时,差异更为显著。在腐蚀环境下,溶液中离子与金属原子发生电化学反应,加速了裂纹的萌生与扩展,3.5% NaCl水溶液中离子浓度较大,电化学反应更为剧烈 相似文献
14.
《中国有色金属学会会刊》2016,26(11):2830-2837
In this investigation, 2024 aluminium alloy plates were friction stir welded, a sequence of experiments was performed including fatigue and crack propagation tests in air, under pre-corrosion and in a 3.5% NaCl solution, in combination with fractography analyses of near-threshold region, Paris region and finial fracture region with the aid of scanning electron microscopy (SEM). Results showed that the corrosive environment caused a dramatical decrease in fatigue lives of FS welds, the corrosion fatigue lives of FS welds were almost a half of those of the as-welded specimens. The crack growth rates in FS welds were higher than their counterparts in base materials, under the corrosive environment, the crack growth rate differences between base materials and FS welds become increasingly apparent with the increase of stress intensity factor range ΔK, but the pre-corrosion process had little effect on the FS welds' crack propagation behavior except for shortening the crack initiation lives greatly. 相似文献
15.
H. Garbacz J.M. PouquetE. García-Lecina M. Díaz-FuentesP. Wieciński R.H. MartinT. Wierzchoń K.J. Kurzydlowski 《Surface & coatings technology》2011,205(19):4433-4440
In this research the microstructure and mechanical properties of Ti-Al intermetallic layers before and after exposure to corrosive environments have been evaluated. The intermetallic layers have been deposited on the Ti6Al2Cr2Mo titanium alloy by the duplex method. For this purpose, a coating of magnetron sputtered Al was deposited on titanium specimens. Subsequently, these sputtered titanium alloy substrates were treated under glow discharge conditions. The uncoated and coated samples were exposed to cyclic acidified synthetic sea water and an environment composed of 100% hydrogen sulphide. Exposure in those aggressive environments did not have an effect on the high surface microhardness of the Ti-Al layers. Furthermore, the surface treatment significantly increased the fatigue properties of the titanium alloy. 相似文献
16.
Z Khan 《Journal of Materials Engineering and Performance》1996,5(1):78-83
Fatigue behavior of aluminum alloy 5454- H32 was studied under laboratory air and 3 % NaCl solution environment using smooth
cylindrical and notched plate specimens. Presence of 3 % NaCl environment during fatigue loading drastically reduced alloy
fatigue life. The deleterious effect was pronounced in both types of specimens in the long- life regions, where the fatigue
lives were lowered by as much as a factor of 10. However, the sharply notched specimens showed only a modest reduction in
fatigue life in corrosive environment. The severe influence of the corrosive environment in the long- life (low- stress) regime
cannot be explained merely by the early initiation of the fatigue crack from surface pits; the environmental contribution
in the early crack growth regime must also be considered an important factor. Fracture surface studies revealed extensive
pitting and some secondary cracking in the crack initiation region. It was shown that lowered fatigue life in Al 5454- H32
occurs by early initiation of fatigue cracks from surface pits. In addition, a corrosion pitting and secondary cracking process
may be operative in the small crack growth region. This could have enhanced the early crack growth rate and thus contributed
to the lower fatigue life in the long- cycle region. 相似文献
17.
Current‐potential correlated noise measurement (CorrElNoise) – a new technique for the evaluation of electrochemical noise analysis A new method for electrochemical noise measurements is presented. In contrast to most conventional noise measurement techniques which require an electrode arrangement of three “identical” electrodes, the new method is able to work with a two electrode set‐up. As a consequence, the recorded noise response of current and potential in this two electrode system is strongly correlated. This method is denoted as correlated noise measurement technique (CorrElNoise), therefore. It is shown by examples using aluminum as well as stainless steel electrode systems in corrosive environment that the CorrElNoise technique is more sensitive than the conventional method. This was checked by variation of particular experimental parameters during the noise measurements. Compared with the conventional set‐up, the resulting changes in the noise spectra become more clearly recognisable using CorrElNoise. 相似文献
18.
减速机齿轮轴断裂分析 总被引:1,自引:0,他引:1
某型减速机齿轮轴的伞齿在使用的早期发生断裂。采用宏观、微观检验和化学成分检测等方法对失效的齿轮轴进行了分析。结果表明,伞齿断裂为接触疲劳断裂,主要是由于伞齿表层硬度偏低和工作环境存在腐蚀性介质所致。 相似文献
19.
腐蚀条件下新型胶体密封剂对典型飞机结构材料疲劳性能影响 总被引:1,自引:0,他引:1
针对飞机结构密封防水问题,研制了一种新型胶体密封剂。采用加速模拟环境方法,考核验证了这种胶体密封防水新技术的腐蚀防护性及其对典型飞机结构材料疲劳性能的影响。试验结果表明,与常规环境下原始疲劳寿命相比,随加速腐蚀周期增加,典型飞机结构材料疲劳寿命大幅度降低,而涂敷新型胶体密封剂后其疲劳寿命没有明显变化。新型胶体密封剂具有良好的密封防水、防腐功能,能够有效地抑制或减缓水分、腐蚀性介质的侵入,明显提高了典型飞机结构材料的抗环境腐蚀品质,适用于解决飞机结构密封防水问题。 相似文献