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1.
不锈钢和Ti基体上Cu,Ag,Ni膜中的内应力研究   总被引:3,自引:0,他引:3  
用电镀工艺在不锈钢基体上镀制了Cu,Ag,Ni膜的Ti基体上制备了Ni膜,并用悬臂梁法和X射法测量了膜中的残余应力。并基于改进的TFD模型,对任意膜厚下由界面电子转移引起的膜内应力作了理论估算。结果表明,理论估算所给出的膜内应力与实验测量值具有可比性,这说明理论计算模型具有较高的准确性和膜内残余应力主要由界面电子转移引起。  相似文献
2.
Analysis of free and forced vibration of a cracked cantilever beam   总被引:1,自引:0,他引:1  
Structures are weakened by cracks. When the crack size increases in course of time, the structure becomes weaker than its previous condition. Finally, the structure may breakdown due to a minute crack. Therefore, crack detection and classification is a very important issue. In this study, free and forced vibration analysis of a cracked beam were performed in order to identify the crack in a cantilever beam. Single- and two-edge cracks were evaluated. The study results suggest that free vibration analysis provides suitable information for the detection of single and two cracks, whereas forced vibration can detect only the single crack condition. However, dynamic response of the forced vibration better describes changes in crack depth and location than the free vibration in which the difference between natural frequencies corresponding to a change in crack depth and location only is a minor effect.  相似文献
3.
The Ni microcantilevers were fabricated by femtosecond laser. The corrosion behavior of the micro-sized Ni cantilever beams was studied by electrochemical noise and a newly developed fatigue testing method. The results show that the micro-sized specimens exhibit general corrosion behavior under the studied corrosion condition, whereas the ordinary-sized plates exhibit the localized corrosion behavior. The critical load amplitude of the micro-sized Ni specimens under corrosion fatigue status was determined to be 15 mN. The maximum bending loads, which were measured by fatigue tests, decrease gradually prior to final fracture. Corrosion fracture first occurs in the range of notch with a higher tensile bending stress, and exhibits clear evidence of trans-columnar fracture. The variation of maximum bending loads with time agrees with that creep deformation of the micro-sized Ni specimens can easily occur at room temperature, which implies that the micro-sized Ni specimens appear to have an improved resistance towards total crack as compared with the ordinary-sized Ni specimens.  相似文献
4.
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
5.
Double cantilever beam (DCB) specimens were used to research the stress corrosion cracking of T225NG titanium alloy in loop water of high temperature and high pressure. DCB specimens were forced pre-stress, put into high pressure ataoclave , and the stress corrosion and crack expansion of specimens were observed and measured in 500 h, 1 000 h and 2000 h respectively. The results show that small expansion occurred along the direction of pre-cracking. According to calculation, the speed of cracking expansion is lower than 10 -9 m/s in 500 h and the value of K ISCC /KI is higher than 0. 75, which proves that T225NG has an excellent corrosion resistance in loop water. The main reason is that there is an oxide film on the surface of specimens. According to the analysis of energy dispersive spectroscopy (EDS) and X-ray diffraction ( XRD ) , the oxide film consists of TiO2. Therefore, the oxide film at the crack tip impedes the hydrogen separating out from the cathode to penetrate into titanium alloy and resists hydrogen embrittlement.  相似文献
6.
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
7.
In order to compare the active damping (computer-controlled damping) via a control theory with the passive (material) damping, the vibration suppressing effect has been investigated by constructing a feedback control system. It consists of a cantilever beam (3×35×300 mm3), a sensor, an actuator and a feedback controller, which has been designed on the basis of the optimal regulator control theory. In a freely decaying vibration state, the active damping effect increases the vibration damping capacity (Q−1) from 0.011 to 0.157 (almost 14.3 times). On the other hand, in a resonant state, the active damping reduces the resonant amplitude to about 1/12. The active damping corresponds to about 6.8 times the maximum damping observed in the ferromagnetic metal SIA.  相似文献
8.
用悬臂梁法研究了不锈钢4Cr13基体上的Cu膜和Ag膜的平均残余应力和残余应力分布。结果表明,Cu膜和Ag膜的平均残余应力和分布残余应力随膜厚的增加而急剧减小。2种膜生长过程中界面应力很大,而生长应力很小。Cu膜在厚度较小时,残余应力值很大,超过了铜块材的断裂强度。  相似文献
9.
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
10.
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
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