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1.
The stress corrosion cracking (SCC) growth kinetics for a cold worked 316L stainless steel was continuously monitored in high purity water at different temperatures and dissolved oxygen (DO) levels under a K (or Kmax) of 30 MPa m0.5. The total SCC test time was more than 8000 h to make sure the steady state crack growth rate under each test condition could be reached. Crack growth rate (CGR) increases with increasing temperature in the range 110-288 °C. A typical intergranular-cracking mode is identified. Depending on the previous test condition, especially the temperature, three kinds of crack growth kinetics, i.e., increasing with testing time then becoming steady, being constant during the whole period, or decreasing with test time then becoming steady, are identified and discussed. Time-dependent and testing history-dependent crack growth modes were confirmed in two series of tests in 2 ppm DO and 7.5 ppm DO pure water. The apparent activation energies are calculated and compared with other data in different environments under different applied loading levels for understanding the cracking mechanism.  相似文献
2.
Tungsten and tungsten alloys show the typical change in fracture behavior from brittle at low temperatures to ductile at high temperatures. In order to improve the understanding of the effect of microstructure the fracture toughness of pure tungsten, potassium doped tungsten, tungsten with 1 wt.% La2O3 and tungsten rhenium alloys were investigated by means of 3-point bending, double cantilever beam and compact tension specimens. All these materials show the expected increase in fracture toughness with increasing temperature. The experiments demonstrate that grain size, texture, chemical composition, grain boundary segregation and dislocation density seem to have a large effect on fracture toughness below the DBTT. These influences can be seen in the fracture behavior and morphology, where two kinds of fracture occur: on the one hand transgranular and on the other hand intergranular fracture. Therefore, techniques like electron backscatter diffraction (EBSD), Auger electron spectroscopy (AES) and X-ray line profile analysis were used to improve the understanding of the parameters influencing fracture toughness.  相似文献
3.
在热轧地下卷取机牌坊式转向夹送辊设计过程中,针对下夹送辊的辊径大小、上辊压下力大小难确定的问题,本文参照热轧卷筒最小直径的计算方法,确定下辊的最小直径;把带钢的夹送过程假设成轧制过程和弯曲过程的合成,按轧制理论计算的轧制力其值等于夹紧力值;把带钢弯曲简化成悬臂梁,并用矫直弹塑性理论进行建模,计算的上辊弯曲力值等于压下力值,并用实例验证上辊压下力大小的合理性。  相似文献
4.
采用电沉积法在Ni基体上制备Cu膜。悬臂梁法在线测量沉积Cu膜后的Ni基片挠度,由测得的挠度值计算出Cu膜内的平均内应力和分布内应力。结果表明,Cu膜内的平均内应力和分布内应力均随膜厚的增加而急剧减小。膜内的界面应力很大,而生长应力很小。基于改进的Thomas-Feimi-Dirac-Cheng(TFDC)电子理论,对由于界面电子密度调整而引起的Cu膜内平均内应力作出了初步估算。结果表明,理论估算结果与实验结果较接近。这说明理论计算模型具有较高的准确性。  相似文献
5.
周之  刘冰 《无损检测》2014,(1):11-14
为了对悬臂梁缺口形式的损伤程度进行评估,以缺口深度为衡量标准,将径向基网络与传统的结构损伤检测相结合,运用有限元方法以及MATLAB软件对一种低碳钢材料的悬臂梁损伤进行了损伤模拟,并对径向基神经网络进行了训练,以相关试验数据对该方法进行了验证,证明了其可行性,为进一步实现飞行器的结构健康监测打下了基础,具有一定的指导意义。  相似文献
6.
基于压电效应,设计了一种包含悬臂梁、压电片、磁铁和驱动马达的新型压电系统,通过对其发电性能的优化分析,将该系统应用于自行车警示灯装置中,并作为自主供电系统.首先利用ANSYS对压电悬臂梁进行结构应力和动力学分析,探讨尺寸变化对发电性能的影响,进一步利用圆盘的转动和磁力的作用使压电悬臂梁弯曲变形并增加其振幅,研究了磁铁不同间距、马达转速对输出电压的影响,并进行了电路分析实验.结果表明:将该压电系统装配在自行车上,车轮转速240 r/min,磁铁间距为15 mm时,可输出4.42 V电压,LED灯能保持稳定点亮状态,作为自行车夜间警示灯使用具有较好的效果.  相似文献
7.
根据已有的热式MEMS气体微流量传感器芯片的各部分热敏电阻热串扰现象严重,造成很大的测量误差,改进设计了一种MEMS热式流量传感器,将加热电阻和上下游测温电阻采用悬臂梁隔离结构,并相互隔离,有效的避免了热膜流量传感器各部分热敏电阻间相互热串扰现象.基于改进的MEMS热式流量传感器,设计了流量传感器的测试系统,包括恒温差电路、桥式测量电路及放大、滤波电路,所采集的流量信号经过滤波放大后输入AD模块进行模数转换,最后经过单片机处理,利用单片机与计算机串口通信功能,在不同流速下打印出不同的电压值;通过Matlab对所测出的数据进行拟合,完成对传感器性能的检测.测量结果表明:在一定的流量范围内,该流量传感器具有测量精度高、响应速率快、输出信号平滑等特点,能够广泛应用于工业、医疗领域的流量测量.  相似文献
8.
采用飞秒激光器制备了纯Ni微悬臂梁试样,研究了它的腐蚀与腐蚀疲劳性能.结果表明,宏试样表面出现明显的局部腐蚀特征,微试样表面主要表现为全面腐蚀特征;载荷幅和介质中Cl-的含量对试样的疲劳寿命有显著的影响;试样在疲劳断裂前的最大载荷逐渐降低.  相似文献
9.
Young’s modulus and Poisson’s ratio for thermal spray coatings are needed to evaluate properties and characteristics of thermal spray coatings such as residual stresses, fracture toughness, and fatigue crack growth rates. It is difficult to evaluate Young’s modulus and Poisson’s ratio of thermal spray coatings be-cause coatings are usually thin and attached to a thicker and much stiffer substrate. Under loading, the substrate restricts the coating from deforming. Since coatings are used while bonded to a substrate, it is desirable to have a procedure to evaluate Young’s modulus and Poisson’s ratio in situ. The cantilever beam method to evaluate the Young’s modulus and Poisson’s ratio of thermal spray coat-ings is presented. The method uses strain gages located on the coating and substrate surfaces. A series of increasing loads is applied to the end of the cantilever beam. The moment at the gaged section is calcu-lated. Using a laminated plate bending theory, the Young’s modulus and Poisson’s ratio are inferred based on a least squares fit of the equilibrium equations. The method is verified by comparing predicted values of Young’s modulus and Poisson’s ratio with reference values from a three-dimensional finite ele-ment analysis of the thermal spray coated cantilever beam. The sensitivity of the method is examined with respect to the accuracy of measured quantities such as strain gage readings, specimen dimensions, ap-plied bending moment, and substrate mechanical properties. The method is applied to evaluate the Young’s modulus and Poisson’s ratio of four thermal spray coatings of industrial importance.  相似文献
10.
研究了时效制度对Al-Zn-Mg-Cu合金(LC4)双悬臂梁(DCB)试样的残余应力分布及其对应力强度因子、腐蚀开裂行为的影响。结果表明,轴向残余拉应力可以引起试样弯曲成弓形,相当于DCB试样附加一应力强度因子K1R,K1R随时效温度提高而减小。在自然时效状态K_(1R)约10MPa·m ̄(1/2),120℃时效时态K_(1R)约7.5MPa·m ̄(1/2)时,无外加载荷均可产生严重的腐蚀开裂现象,且具有沿晶断裂特征并呈特殊的长舌形区。160℃时效状态未出现腐蚀开裂现象,对其原因进行了讨论。  相似文献
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