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针对油气田勘探中,复杂的钻井工况导致动密封工作性能极不稳定的问题,结合单金属密封结构和井底高压环境,利用有限元方法对单金属密封受压情况下的接触压力进行分析。用雷诺方程计算单金属动密封的泄漏率,以减小最大接触压力和泄漏率为优化目标,利用正交试验和F评价方法对单金属密封结构参数进行优化,得到密封结构参数对密封面接触压力和泄漏率的影响情况,并将每个水平数对应的优化目标计算结果分别取平均值,得到不同水平影响下接触压力和泄露率平均值的变化趋势,从而确定密封结构的最优水平值,并借助有限元仿真对优化前后的密封性能进行对比。最后根据优化前后的密封结构参数加工2套密封试件,进行密封实验。仿真分析和实验结果表明:高压工况下优化前的密封面内侧磨损严重,钻井液颗粒容易侵入密封面;而优化后密封面的最大接触压力有所降低,动密封面的最高温度和泄漏率明显降低。研究结果对改进单金属密封的工作性能、提高井下动密封的可靠性有重要的现实意义。 相似文献
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焊缝匹配影响焊接残余应力的研究 总被引:3,自引:0,他引:3
采用有限元法对相同温度场的焊缝与母材强度和线膨胀系数匹配影响焊接残余和的规律进行了数值模拟,计算结果表明:等强度等匹配的焊缝区纵向残余应力水平高达母材的屈服强度, 相似文献
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This paper discusses the laser-irradiated microjoints between glass and polyimide for applications in neural implants. To
facilitate bonding between them, a thin titanium film with a thickness of approximately 0.2 μm was deposited on glass wafers
using the physical vapor deposition (PVD) process. Two sets of samples were fabricated where the bonds were created using
diode and fiber lasers. The samples were subjected to tension using a microtester for bond strength measurements. The failure
strengths of the bonds generated using fiber laser are quite consistent, while a wide variation of failure strengths are observed
for the bonds generated with diode laser. Few untested samples were sectioned and the microstructures near the bond areas
were studied using an optical microscope. The images revealed the presence of a sharp crack in the glass substrate near the
bond generated with the diode laser. However, no such crack was observed in the samples made using fiber laser. To investigate
the reasons behind such discrepancy in bond quality further, uncoupled three-dimensional finite element analyses (FEA) were
conducted only for the samples created using diode laser. First, the transient heat diffusion-based FEA was conducted by using
the laser power intensity distribution as a time dependent heat source. This model calculates the temperature distribution
within the substrates as a function of time. Next, the structural model predicts the amount of residual stresses developed
in the joint system as it is cooled down to room temperature. The out-of-plane normal component of residual stresses was within
the failure strength range of glass that may have caused fracture initiation in the substrate. 相似文献
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In this study, the fatigue life of an automotive suspension component was analysed using finite element methods with regard to stamping and welding effects. Because automotive suspension components are produced by forming and welding sheet metal, there are various effects on the final product, such as uneven thickness distribution, residual stresses and weld notches. Manufacturing effects may change the mechanical performance of the automotive components; therefore, it is desirable to consider these effects in the early design stage. Residual stresses due to work hardening and thermal deformation were investigated through process simulation. The redistribution and relaxation of residual stresses in a component were investigated in fatigue life analysis under a cyclic loading condition. Various equivalent relaxation curves were investigated and one was selected after comparisons with test results. The fatigue simulation results were compared to the test results; a good correlation between the two was achieved for the residual stress effects in terms of life cycles and failure locations. The simulation results also show that welding produces more detrimental effects than stamping with regard to the fatigue life of a component. 相似文献
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The residual stresses induced when adhesively bonding patches to a 7085 alloy SENT (side edge notched tension) specimen in order to produce fatigue crack growth retardation have been investigated. Knowledge of the induced residual stresses is important as they affect the beneficial bridging effect of the strap. The strap materials studied were: Titanium, GLARE (fibre metal laminate), GFRP (glass fibre reinforced polymer) and CFRP (carbon fibre reinforced polymer). The residual stresses were measured using neutron diffraction and are compared with those predicated by FE (finite element) simulation. The measured and modelled residual stresses were in reasonable correlation. Tensile residual stresses were found close to the strap, whereas small compressive residual stresses were found on the un-bonded side. The residual stresses were induced due to the mismatch in the coefficient of thermal expansion (ΔCTE) between the SENT and the strap. The magnitude of the stresses induced by the bonded crack retarders depend both on the ΔCTE and the stiffness ratio between the reinforced structure and the strap. For the straps studied, the magnitude of the peak residual stresses found were in the following descending order: CFRP, titanium, GFRP and GLARE. 相似文献
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《Materials Science & Technology》2013,29(11):1030-1033
AbstractA method by which measured values of residual stresses in a component of complex shape may be corrected using the finite element is presented. The surface of the component is removed layer by layer and the residual stresses after removal of each layer are measured using X-ray diffraction; the correction factors are calculated using the finite element method, thereby obtaining the distribution of internal stresses in the complex component. In addition, methods of verifying the final values of the internal stresses are suggested. As examples, the distributions of the residual stresses, within several cross-sections of two types of heat treated shaft are calculated using the above method. Finally, the reliability of the results is discussed.MST/16 相似文献
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TAE‐KWANG SONG HONG‐RYUL BAE YUN‐JAE KIM KYUNG‐SOO LEE 《Fatigue & Fracture of Engineering Materials & Structures》2010,33(11):689-702
This paper presents finite element simulation results of residual stresses in dissimilar metal welds of a PWR pressurizer safety/relief nozzle. The present results are believed to be significant in two aspects. The first one is to consider the effect of the presence of similar metal welds on resulting residual stresses. The second one is the mitigation effect of the overlay welding thickness on residual stresses. After dissimilar metal welding, tensile residual stresses are present both at the inner surface and at the outer surface of dissimilar metal welds. Adjacent similar metal welding, however, decreases residual stresses to compressive ones at the inner surface of dissimilar metal welds, possibly due to the bending mechanism caused radial contraction of the weld. At the outer surface of dissimilar metal welds, similar metal welding increases residual stresses. Overlay welding further decreases residual stresses at the inner surface of dissimilar and similar metal welds, but increases slightly residual stresses at the outer surface. 相似文献
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Albert J. Shih Henry T. Y. Yang 《International journal for numerical methods in engineering》1993,36(9):1487-1507
The development and implementation of a finite element method for the simulation of plane-strain orthogonal metal cutting processes with continuous chip formation are presented. Experimental procedures for orthogonal metal cutting and measurement of distributions of residual stresses using the X-ray diffraction method are also presented. A four-node, eight degree-of-freedom, quadrilateral plane-strain finite element is formulated. The effects of elasticity, viscoplasticity, temperature, friction, strain-rate and large strain are included in this formulation. Some special techniques for the finite element simulation of metal cutting processes, such as element separation and mesh rezoning, are used to enhance the computational accuracy and efficiency. The orthogonal metal cutting experiment is set-up on a shaper, and the distributions of residual stresses of the annealed 1020 carbon steel sample are measured using the X-ray diffraction method. Under nominally the same cutting conditions as the experiment, the cutting processes are also simulated using the finite element method. Comparisons of the experimental and finite element results for the distributions of residual stresses indicate a fairly reasonable level of agreement. The versatility of the present finite element simulation method allows for displaying detailed results and knowledge generated by orthogonal metal cutting processes, such as the distribution of temperature, yield stress, effective stress, plastic strain, plastic strain-rate, hydrostatic stress, deformed configuration, etc. Such knowledge is useful to provide physical insights into the process as well as to better design the process for machining parts with improved performance. 相似文献
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Composite journal bearings are becoming popular for marine applications because they eliminate the possibility of seizure to steel journals, which is a drawback of white metal bearings. However, a reliable joining method for composite bearings to steel housings is required. In this work, hybrid composite journal bearings composed of carbon/phenolic and glass/epoxy laminated composites were manufactured with different stacking sequences and adhesively bonded to steel housings. The effect of deformations of the composite bearings due to thermal residual stresses on the adhesive joint performance was estimated with respect to stacking sequence by finite element method, and compared to the experimental results. From the measured and experimental results, it was found that the outward radial deformation of the composite bearings was beneficial to the adhesively bonded joint strength of the hybrid composite journal bearing. 相似文献
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低熔封接玻璃组成及其发展 总被引:25,自引:2,他引:23
综述了低熔封接玻璃的组成特点,给出了大量低熔玻璃组成实例,批出了低熔封接玻璃的封接低温化和无铅化发展方向,磷酸盐玻璃是首选组成之一。新的制备工艺和新的玻璃形成体系将对封接玻璃发展起着十分重要的作用。 相似文献
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Numerical and experimental investigations on the residual stresses of the butt-welded joints 总被引:5,自引:0,他引:5
Welding is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Localized heating during welding, followed by rapid cooling, can generate residual stresses in the weld and in the base metal. Estimating the magnitude and distribution of welding residual stresses is important. This study applies thermal elasto-plastic analysis, using finite element techniques, to analyze the thermomechanical behavior and evaluate the residual stresses in butt-welded joints. The residual stresses at the surface of the weldments were measured by X-ray diffraction. The results of finite element analysis were compared with experimental residual stress data to confirm the accuracy of the method. The aim is to present data that may confirm the validity of currently employed fabrication processes in welded structures and even improve them. 相似文献
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The drive towards rapid cure thermosetting composites requires a better understanding of the residual stresses that develop during curing. This study investigates the impact of residual stresses on the interlaminar shear strength of resin-infused epoxy/anhydride carbon-fibre laminates. The magnitude of the residual stress was varied by changing the initial injection cure temperature between 75 °C and 145 °C. The corresponding cycle times and the final glass transition temperature of the resin were also measured. The experimentally measured chemical shrinkage and thermal expansion properties of the resin after vitrification were used as inputs to a finite element analysis to calculate the peak residual stresses in the composite. An increase in the initial cure temperature from 85 to 135 °C resulted in an increase of 25% in the residual stress, which led to an experimentally measured reduction in the composite’s short beam shear strength of approximately 16% (8 MPa), in good agreement with model prediction. 相似文献
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Residual stresses and fracture mechanics analysis of a crack in welds of high strength steels 总被引:1,自引:0,他引:1
Kyong-Ho Chang 《Engineering Fracture Mechanics》2007,74(6):980-994
This study presented the characteristics of residual stresses in welds of high strength steels (POSTEN60, POSTEN80) whose tensile strengths were 600 MPa and 800 MPa, respectively. Three-dimensional thermal elastic-plastic analyses were conducted to investigate the characteristics of welding residual stresses in welds of high strength steels through the thermal and mechanical properties at high temperatures obtained from the elevated temperature tensile tests. A finite element analysis method which can calculate the J-integral for a crack in a residual stress field was developed to evaluate the J-integral for a centre crack when mechanical stresses were applied in conjunction with residual stresses.The results show that the volumetric changes associated with the austenite to martensite phase transformation during rapid cooling after welding of high strength steels significantly influence on the development of residual stresses in the weld fusion zone and heat-affected zone. For a centre crack in welds of high strength steels where only residual stresses are present, increased tensile strength of the steel, increased the J-integral values. The values of the J-integral for the case when mechanical stresses are applied in conjunction with residual stresses are larger than those for the case when only residual stresses are present. 相似文献
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A. Drai B. Bachir Bouiadjra M. Meddah M. Benguediab 《Computational Materials Science》2009,46(4):1119-1123
In this study, the finite element method is used to analyze the behavior of interface cracks in ceramic–metal assemblies under the effect of thermal residual stresses. These stresses are due to the elaboration process of the bimaterial junctions. The stress intensity factor is used as fracture criterion. The effects of the temperature of elaboration and the metal thickness on the variations of the thermal SIF are highlighted. The obtained results show that the mode of fracture under thermal residual stresses for all ceramic–metal couples is the mixed mode (opening + sliding). The mode II (the sliding mode) is the dominant mode. 相似文献
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Thermal Residual Stresses in W Fibers/Zr-based Metallic Glass Composites by High-energy Synchrotron X-ray Diffraction 总被引:1,自引:0,他引:1
Xinqiang Zhang Yunfei Xue Haifeng Zhang Huameng Fu Zhengbin Wang Zhihua Nie Lu Wang 《材料科学技术学报》2015,(2):159-163
Thermal residual stresses in W fibers/Zr-based metallic glass composites were measured by in situ high energy synchrotron X-ray diffraction(HEXRD). The W fibers for the composites were 300,500,and 700 m m in diameter,respectively. Coaxial cylinder model(CCM) and finite element model(FEM) were employed to simulate the distribution of thermal residual stress,respectively. HEXRD results showed that the selected diameters of W fiber had little influence on the value of thermal residual stresses in the present composites. Thermal residual stresses simulated by CCM and FEM were in good agreement with HEXRD measured results. In addition,FEM results exhibited that thermal residual stress concentrated on interface between the two phases and area where the two W fibers were the closest ones to each other. 相似文献
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《Composites Science and Technology》2007,67(7-8):1340-1347
This paper addresses prediction of the strength of tubular adhesive joints with composite adherends by combining thermal and mechanical analyses. A finite element analysis was used to calculate the residual thermal stresses generated by cooling down from the adhesive cure temperature, and a nonlinear analysis incorporating the nonlinear adhesive behavior was performed to accurately estimate the mechanical stresses in the adhesive. Joint failure was estimated by three failure criteria: interfacial failure, adhesive bulk failure, and adherend failure. The distributions of residual thermal stresses were investigated for various stacking angles. The effect of residual thermal stresses on joint strength was also taken into consideration. The results indicate that the residual thermal stresses, depending on the stacking angle, have a significant influence on the failure mode and strength of adhesive joints when a subsequent mechanical load is applied. Good agreement is also obtained between the predicted joint strength and the available experimental data. 相似文献