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本文建立了复合材料胶接修理金属裂纹板的三板有限元模型;采用分析金属裂纹板裂纹尖端应力强度因子的方法,分析了残余热应力对复合材料修理金属裂纹板修理效果的影响。结果表明,残余热应力对单面修理结构的影响小于双面修理结构。残余热应力对单面修理结构的影响由于裂纹板宽度比值不同而不同。补片与母板的热膨胀系数相差越大,残余热应力对修补效果影响越大。 相似文献
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哈氏合金C276管道焊接残余应力与变形的有限元分析 总被引:1,自引:0,他引:1
针对哈氏合金C276焊接特点,运用有限元分析软件ABAQUS,对哈氏合金C276管道多道焊残余应力进行了有限元模拟。利用单元生死技术,模拟焊缝金属的形成;利用FORTRAN语言编写子程序DFLUX,实现了移动的高斯分布热源;考虑对流、传导、辐射以及高温下的材料性能,获得了残余应力和变形的分布规律。计算结果表明,在焊缝及热影响区,轴向拉应力对内壁裂纹的产生有主要的影响,环向拉应力对外壁裂纹的产生有主要的影响。线能量对温度和变形的影响较大,而对残余应力影响不大。 相似文献
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残余热应力会增大裂纹尖端的应力强度因子SIF,加快疲劳裂纹扩展速率,缩短修补结构的疲劳寿命。利用三维有限元方法,对含裂纹金属板复合材料胶接修补结构中的残余热应力进行了分析,利用虚拟裂纹闭合技术(VCCT)计算了修复结构裂纹尖端的SIF。并以SIF为判据,讨论了补片铺层方向、固化温度、胶层的材料参数对修复结构残余热应力的影响。结果表明,[0°/45°/-45°/90°]s的铺层方式可有效降低残余热应力引起的SIF;残余热应力引起的SIF随着固化温度的升高而线性增加;胶层的材料参数及胶层厚度对残余热应力引起的SIF影响不显著。 相似文献
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为了防止管子与管板连接处的应力腐蚀裂纹,需要找到一种产生较低残余应力的连接方法。液压胀接就是一种可取的方法。本文介绍为确定这些残余应力而进行的实验和理论工作。我们最感兴趣的是管子的胀接部分与非胀接部分之间的过渡区域。所用的测量技术是X光衍射试验、应力腐蚀裂纹试验和应变测量。应用了有限元分析。此外,对这种连接方式的拉力强度、长度变化等等也进行了研究。 相似文献
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通过以ABAQUS为平台,采用扩展有限元方法对钢结构钻孔止裂进行数值模拟,同时对循环载荷下止裂孔应力应变状态进行分析,对疲劳裂纹钻孔止裂处理机理进行了深入研究。研究表明,扩展有限元法分析疲劳裂纹扩展再生及钻孔止裂技术时不需要预先指定裂纹扩展方向,无须重新剖分网格,克服了常规有限元方法的弊端,为复杂形状裂纹问题提供了更优的解决方法;止裂孔减小了孔边应力集中部位的平均应力,延长了疲劳裂纹在止裂孔边的再生寿命;当止裂孔直径取为0.4倍疲劳裂纹长度时可以获得较好止裂效果,对钻孔止裂理论的研究具有一定参考意义。 相似文献
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新型裂纹釉的试制生产 总被引:1,自引:0,他引:1
1前言裂纹釉又名百圾碎,是祖国传统陶瓷艺术瑰宝之一,因纹路奇特而闻名于世。为使其在新世纪旧貌换新颜,更好更广泛地应用于陶瓷行业,笔者探索出一种简易实用的裂纹釉生产方法。2裂纹釉形成原理为生产出裂纹釉,必须了解裂纹釉的形成原理。裂纹的形成原理可以分成两种。原理一,是在开发釉料配方的过程中,有意增加碱性氧化物的含量,使釉的热膨胀系数大于坯的热膨胀系数,这样,在烧成的冷却过程中,由于坯釉之间收缩不一致,产生张应力,当张应力超过釉层所能承受的限度时,釉层就出现龟裂,从而形成裂纹釉。裂纹釉形成的另一种原理… 相似文献
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Al2O3-(W,Ti)C/Al2O3-TiC对称型叠层陶瓷的结构设计和力学性能 总被引:1,自引:1,他引:0
为提高陶瓷材料表面的硬度和韧性,热压烧结制备了Al2O3-(W,Ti)C/Al2O3-TiC对称型叠层陶瓷材料.研究了该叠层材料的层厚比和层数对材料表层的硬度、断裂韧性的影响.此外,通过压痕裂纹法的测量和有限元计算均可以得到叠层陶瓷材料表面层的残余应力值,两种方法获得的残余应力值符合得很好.通过有限元计算还可以得到叠层陶瓷材料不同层内的残余应力分布特征.对比实验表明:叠层陶瓷材料表面层较之相应单一材料而言,具有更高的硬度和断裂韧性.叠层陶瓷材料中残余压应力的存在,是叠层陶瓷材料表面层具有高硬度、高韧性的原因.而且通过改变叠层材料的层厚比和层数可改变叠层材料残余应力的分布. 相似文献
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The resistance of a hotel-china glaze to fracture by impact was improved by increasing the residual compressive stresses in the glaze. Increases in residual compressive stresses were developed, for laboratory convenience, by increasing the coefficient of expansion of the body by the incorporation of alumina in the body. 相似文献
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E. Bannier J. García-Ten J. Castellano V. Cantavella 《Journal of the European Ceramic Society》2013,33(3):493-501
Most industrial porcelain tiles suffer changes in their curvature after firing: such process is known as delayed curvature. One of the hypotheses used to explain this phenomenon is based on the relaxation of residual stresses by creep. In this study two types of industrial glazed porcelain tiles have been studied. One of them displayed delayed curvature after firing, whereas the other one presented a stable curvature. The main objective was to determine if the delayed curvatures were caused by the residual stresses generated during rapid industrial cooling. Both types of existing residual stresses (thermal stresses, caused by thermal gradients inside the tile during cooling, and body–glaze fit stresses, due to the thermal expansion mismatch between body and glaze) were measured, as well as related samples properties (elastic modulus, creep behaviour, thermal expansion). The results demonstrated that the residual stresses are not the main cause of the delayed curvature phenomenon. 相似文献
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古代龙泉青瓷的装饰风格独特,具体表现有:(一)无纹而饰的釉色之美;(二)片纹雅饰之美;(三)刀法如笔意,布局通画理。当代龙泉青瓷艺人传承传统青瓷的独特装饰风格,创新发展了更加丰富的青瓷装饰技法,而且更加强调发挥龙泉青瓷的厚釉类玉品质优势,把龙泉青瓷人造美玉的效果发挥到极致。 相似文献
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不同基体条件下Sm_2Zr_2O_7/YSZ热障涂层的残余应力 总被引:1,自引:0,他引:1
采用有限元法研究了基体条件对等离子喷涂Sm2Zr2O7/YSZ双陶瓷层热障涂层涂层的残余热应力,并与单一Sm2Zr2O7涂层进行了比较。计算结果表明,涂层的残余热应力随金属基体的热膨胀系数增加而增大,当基体厚度超过25mm后,径向应力不再变化,基体半径对涂层残余应力的影响可以忽略。Sm2Zr2O7/YSZ涂层的热应力明显小于单一的Sm2Zr2O7涂层,增加涂层的层数可缓解残余热应力。 相似文献
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This paper presents the numerical simulation of inducing residual stresses on equal channel angular pressed (ECAP) magnesium alloy by shot peening process. Mg-Al-Mn (AM) series magnesium alloy was ECAP processed up to 4 passes using route BC. Microstructures were analysed and grain size reduced from 100 µm for the as-received sample to 3 µm for ECAP 4 pass sample. Tensile test was carried out and maximum tensile strength was found in ECAP 2 pass sample and decreased with higher ECAP passes. Grain refinement was characterized by optical microscopy, electron backscatter diffraction analysis (EBSD) and X-ray diffraction (XRD). Material (tensile) behaviour of 2 pass sample was implemented for finite element modelling. A finite element method was used to estimate the intensity of residual stresses developed due to shot peening in ECAP processed AM80 alloy. Simulation was done with different boundary condition such as impact velocity, geometry of shot-peen media, angle of impact and multiple impacts. The results are presented and the relationship between process parameters and the intensity of residual stresses are discussed. Increase in velocity of shot peening media showed an increase in the magnitude of residual stresses. Change in geometry of shot media altered the contact area between target and shot media during impact which influenced the magnitude of residual stresses and coverage area. The magnitude of residual stresses varied with the angle of impact and the multiple repeated impacts showed that the effective depth of residual stresses increased with the number of impacts. 相似文献
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This paper investigates the influences of imperfect bonding between the fiber and matrix on thermal micro-residual stress fields in polymer matrix composites. For this purpose, a representative volume element consisting of a three-phase composite material subjected to a uniform temperature change is considered. Based on the energy method, a three-dimensional closed-form solution for micro-residual stresses is obtained. Besides, a finite element model is developed and the results are compared with the analytical solution. Both the energy method and finite element analysis show similar trend for thermal stress distribution along the fiber length, while due to the stress singularity, the interfacial shear stress from the finite element solution cannot satisfy the stress-free condition at the fiber end. The analysis shows that the magnitude of thermal stresses and their distribution mainly depend on the bonding efficiency parameter. An increase in thermal and elastic properties bonding efficiencies leads to a considerable decrease in composite axial and shear residual stresses, while the Poisson's ratio bonding efficiency does not affect the thermal stress fields. The interfacial radial residual stress distribution is approximately independent of the bonding conditions. Inefficient bonding may result in higher residual stresses in comparison with the perfect bonding condition. It means that in cases of low bonding efficiency conditions, the ability of composites to sustain and transmit load decreases drastically. Thermal stress concentration occurs at the vicinity of the fiber ends, although peak values depend on the bonding efficiency value. 相似文献