共查询到20条相似文献,搜索用时 0 毫秒
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Frontiers of Mechanical Engineering - In this study, the micro curing residual stresses of carbon fiber-reinforced thermoset polymer (CFRP) composites are evaluated using a multiscale modeling... 相似文献
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Machining-induced residual stress distribution is strongly influenced by the machining process condition, tool geometry and workpiece material mechanical properties. The high temperature, large strain and high strain rate environment will promote the material micro-structural attribute changes. The material micro-structural attribute changes could directly affect the material mechanical properties. An analytical model is proposed for the residual stress prediction in the orthogonal turning by considering the material dynamical recrystallization induced grain growth effect. The grain size effect on the material flow stress behavior is included by adding a grain size dependent term into the traditional Johnson–Cook model. The Johnson–Mehl–Avrami–Kolmogorov model calculates the recrystallized volume fraction and grain size as a function strain, strain rate and time. The average grain size is calculated with a rule of mixture by volume. Then the modified Johnson–Cook model is embedded into a classic residual stress prediction model for the machining induced residual stress profile prediction on the machined workpiece surface. Experimental tests are conducted for the model validation. The predicted residual stress shows good approximation with the measurement in both the trend and magnitude of the residual stress. Also, the effects of cutting speed and feed rate on the residual stress profile are investigated. 相似文献
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Raman spectroscopy has proved to be a useful nondestructive technique for measuring residual stresses in semicondutors. The Raman microprobe is used to investigate the effects of machine parameters on residual stresses in single point diamond turned germanium (Ge). A profiling technique that provides a method of obtaining the residual stress information as a function of depth with depth resolutions of 10.0 nm is discussed. This method is used to analyze the asymmetrically broadened and shifted spectral features in the machined samples. Residual stresses are sampled across ductile feed cuts in (100) Ge wafers, which were single point diamond turned using various feed rates (12.5, 25 nm/rev), rake angles (0°, −10°, −30°), and clearance angles (6°, 16°). In general a region of plastically deformed material that shows slight compressive stresses exist near the surface of the diamond turned sample. The compressive surface stress increases to a maximum at a depth of ≈ 50 nm beneath the surface at which point the stress rapidly changes sign. The rapid sign change is indicative of the transition from plastic to elastic deformation. Deeper probe regions exhibit increasing tensile stresses, which reach a maximum and then relax to zero at greater depths in the sample. A related study of the stress field occurring around Vicker's hardness indents provides a link between theoretical and experimental stress profiles and demonstrates the accuracy of the micro-Raman profiling technique. 相似文献
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Mo/Si多层膜残余应力的研究 总被引:1,自引:3,他引:1
在极紫外光刻技术中,光学系统对多层膜光学元件表面面形精度有严格的要求,并且多层膜光学元件需要较高的反射率.由于多层膜中存在的内应力将改变光学元件的表面面形,因此在不减少反射率的前提下,一定要减少或补偿多层膜内的残余应力.论述了Mo/Si多层膜应力产生的原因和几种减少与补偿应力的技术,介绍应力的几种测量方法. 相似文献
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Zheng Yang Chang-Boo Kim Chongdu Cho 《International Journal of Mechanical Sciences》2010,52(6):836-846
The elastic stress and strain fields of a finite thickness plate containing a circular hole subjected to out-of-plane bending are systematically investigated using the finite element method. It is found that the stress and strain concentration factors of the finite thickness plate are different except at the notch root of the free surface even if the plate is in elasticity state. The through-thickness distributions of strain components are not linear with the distance from the mid-plane in the stress concentration region. The nonlinearity of these distributions is very severe near the free surface especially in thick plate. The Euler-Bernoulli hypothesis and Kane-Mindlin's plate theory may not be reasonable to be used in the stress concentration region especially near the free surface. The maximum stress and strain do not always occur on the free surface and their locations depend on the moment ratio and the plate thickness. The maximum stress and strain concentration factors occur on the free surface only in thin plates of small moment ratio. The differences between the maximum value and surface value of stress concentration factor increase with the plate thickness and the moment ratio. This relation of strain concentration factor is similar to the one of stress concentration factor. But the difference magnitude of stress concentration factor is larger than that of strain concentration factor in same plate. 相似文献
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Fretting fatigue tests for Ti–6Al–4 V alloy were conducted by use of the plate fatigue specimen with bolt-tightened shoe on both sides of the plate. It was clarified that the repeated bending stress at the contact area where fretting fatigue failure starts linearly decreased as stress over the contact area increased. Fretting fatigue crack starts from the pit where stress concentrate. The pit initiates when fretting debris were removed from the surface striation formed due to the contact slip movement. The fretting fatigue crack initiation mode was transgranular, while the fretting fatigue crack propagation mode was striation. 相似文献
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残余应力测试技术的进展与动向 总被引:6,自引:0,他引:6
针对几种常见的残余应力测试方法的研究进展与应用现状,指出了较为成熟的残余应力测试方法是盲孔法和X射线法,但盲孔法受限于对测试对象有损伤,X射线法受限于测试条件的苛刻,其它的残余应力测试方法在有效性、准确性和操作简便性等方面还不能很好地满足工业需求.而利用压痕法测量残余应力是一个值得关注的研究动向,在局部压载作用下,材料... 相似文献
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薄壁铝合金结构焊接应力变形数值模拟 总被引:1,自引:0,他引:1
实际结构焊接过程的三维数值模拟因为计算量大而往往难以进行。为了采用三维热弹塑性有限元方法对薄 壁铝合金结构的焊接过程进行数值模拟,提出了粘贴单元和混和单元两种网格划分技术相结合的单元划分方案进 行有限元建模,通过薄板对接模型试验验证了此方案的可行性,并研究了不同建模方案对计算效率的影响。将这 种单元划分方案应用到实际薄壁筒体结构焊接过程的数值模拟中,对焊接过程产生的残余应力和变形进行了成功 地预测。结果表明:对于薄壁构件,采用粘贴单元和混合单元相结合的单元划分方案可以在保证一定精度的前提 下,可大大减少有限元网格划分工作量,同时可降低计算规模,提高计算效率。 相似文献
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焊接残余应力的小孔法测试 总被引:1,自引:0,他引:1
应用小孔释放法对系列手弧焊接接头的焊接残余应力分布进行测试,讨论了焊接残余应力的分布规律及其相关影响因素,对加载法消除焊接残余应力的效果进行了初步的验证。结果表明,焊接接头的应力不均匀性和不确定性是影响钢制压力容器安全性的关键,采用加载法可以有效地改善这种非均匀应力分布状况。 相似文献
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Ann Bettina Richelsen 《International Journal of Mechanical Sciences》1997,39(11):1199-1211
Asymmetric plane strain plate rolling is analysed numerically by using an elastic-viscoplastic finite-element method. The asymmetric conditions are here due to different interface friction conditions of the two rolls. Two sets of different interface friction conditions are used. The influence of the degree of reduction on the curvature of the rolled plate and the corresponding distributions of the stress and strain are examined. For the rolling parameters considered, the curvature of the plate is found to be towards the roll with highest friction. The largest curvature is obtained for the biggest difference in interface friction conditions. The curvature shows a change from increasing to decreasing curvature with increasing reduction followed by a change in the distribution of the strain. 相似文献
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铝合金预拉伸板在成型过程中会产生较大的残余应力,在切削过程中毛坯的初始残余应力的释放对整体结构件的宏观变形有重要的影响。在弹塑性力学的基础上,综合运用Hypermesh和ABAQUS建立残余应力单因素作用下的三维铣削仿真加工变形场的有限元模型,利用生死单元技术模拟了材料的去除,分析了铝合金板材材料去除过程中残余应力释放引起的加工变形规律。并且运用Hypermesh提高了有限元前处理的速度,解决了复杂模型的残余应力加载困难与单元去除困难的问题。 相似文献
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弯曲残余应力对转子蠕变性能的影响研究 总被引:2,自引:0,他引:2
针对某600 MW火力发电机组高中压合缸汽轮机转子的中部弯曲进行分析,认为高温蠕变和残余应力的耦合作用是导致转子发生塑性永久变形的主要原因。首先按照转子结构图利用有限元软件ANSYS建立精细化的三维实体模型,并进行温度场和应力场的有限元分析。在此基础上对高中压转子进行热-固耦合分析,通过对转子材料蠕变试验数据进行处理,得到Norton蠕变模型参数,并在ANSYS中对转子的高温蠕变和残余应力进行有限元仿真。研究表明,单纯的高温蠕变不足以引起转子在启动过程中发生弯曲,耦合残余应力的作用后该高中压转子会在很短时间内发生弯曲值超标,选取Norton三参数模型和残余应力生成方法比较有效。该研究对高中压合缸转子中部弯曲原因分析具有借鉴和指导作用。 相似文献
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Residual stresses generated in cutting process have important influences on workpiece performance. The paper presents a method of theoretical analysis in order to explicate the formation mechanism of residual stresses in cutting. An important conclusion is drawn that the accumulated plastic strain is the main factor which determines the nature and the magnitude of surface residual stresses in the workpiece. On the basis of the analytical model for residual stress, a series of simulations for residual stress prediction during cutting AISI 1045 steel are implemented in order to obtain the influences of cutting speed, depth of cut and tool edge radius on surface residual stress in the workpiece. And these influences are explained from the perspective of formation mechanism of residual stress in cutting. The conclusions have good applicability and can be used to guide the parameters selection in actual production. 相似文献