电解槽端压板的结构改进及强度分析

结合200m~3/h、1.6MPa电解槽,对直接用厚钢板制造电解槽端压板结构作了整体有限元分析和应力强度评定,得到了安全而经济的端压板厚度。     

VCM回收液分离器大开孔结构的应力分析和强度评定

采用有限元方法对一台ＶＣＭ回收液分离器大开孔结构进行了计算，得到了接管部位的应力分布，并对应力结果进行了分类处理，最后按照分析设计原理进行了强度评定，为该结构的安全服役提供了必要的依据。     

双向应力对失效评定图的影响

文中通过弹塑性有限元方法探索了双向应力对失效评定曲线的影响，同时比较了弹塑性有限元建立的失效评定曲线与Ｒ６选择１曲线。从工程角度出发，单向应力条件下的Ｒ６选择１曲线可粗略地作为双向应力下含缺陷结构的失效评定方法，但更精确的评定必须考虑双向应力影响。文中同时还研究了双向应力对Ｊ积分守恒性及数值的影响。     

某微车缓冲块静态特性有限元分析与实验对比

为了研究设计的缓冲块承受的载荷是否满足悬架匹配要求,利用abaqus/standard建立缓冲块的有限元模型,根据硬度和缓冲块在上极限的压缩量,反求其支反力,研究设计的缓冲块是否符合设计要求,为缓冲块的设计提供一种指导方向,并通过实验进行实际模型的验证,从而缩短产品的开发周期,节约成本。     

偏置偏心开孔接管有限元应力分析、强度评定与修复

对高压汽包简体壁侧的偏置偏心开孔接管进行三维有限元应力分析计算,并按分析设计标准对接管应力进行强度评定,用按此计算合格的偏心开孔接管对汽包进行修复。经1年多的运行,结果表明此偏心开孔接管能满足安全生产的要求。     

内压容器壳体上矩形大开孔接管三维有限元分析与强度计算

运用三维有限元分析方法 ,对内压容器壳体上有内伸矩形大开孔接管和无内伸矩形大开孔接管结构进行应力分析 ,得到了接管部位的应力分布规律。对比两种结构的分析结果 ,并按照分析设计原理对两种结构进行了强度评定。结果表明 ,带有内伸接管结构的容器强度基本能满足安全要求 ,且比无内伸接管容器更安全     

涡旋压缩机动涡盘的应力及变形分析

通过对实际工况下动涡盘的受力分析 ,建立了有限元分析模型 ,对整个载荷循环过程进行应力和变形分析 ,并由此得到了涡旋压缩机动涡盘在实际工况时 ,惯性载荷、气体力载荷作用下的应力分布特点及变形规律 ,求得动涡盘最大应力位置和最大应力时的主轴转角     

进口设备局部凹坑缺陷有限元应力分析及安全性评估

介绍了设备局部凹坑缺陷的有限元应力分析方法及结果,并以应力分析设计为准则,对凹坑缺陷进行了安全性评估。     

The ball on three balls test for strength testing of brittle discs: stress distribution in the disc

Biaxial strength testing of brittle materials is claimed to have some benefits compared to uniaxial testing, e.g. the much simpler specimen preparation, the avoiding of tensile loaded edges, the similarity of the stress state to those from typical loading (e.g. during a thermal shock loading) and the fact, that biaxial stress states are more revealing of defects than uniaxial stress states. The experience of the past showed, that biaxial strength testing has its own problems, to avoid these led to the development of several variants. One of these variants, the ball on three balls test, seems to be extremely simple: a disc is supported by three balls and then axially loaded from the opposite side via a fourth ball. In this system small deviations from the requested geometry, especially some out of flatness of the disc, are mentioned to be tolerable, but the threefold bending symmetry makes an exact analytical assessment of the stress state in the loaded disc extremely difficult. A numerical approach has yet not been performed. In this paper a FE analysis of the stress state in a ball on three balls tested disc is performed. The stress field scales with the maximum principle stress, which occurs in the centre of the tensile surface. For this stress an analytical approximation (which has been fitted to the numerical results) is given, which accounts for the influence of all relevant geometrical and material parameters. The investigated range of parameters considers the values typical for testing of brittle materials.     

On the relationship between ceramic strength and the requirements for mechanical design

During the last fifty years the mechanical properties of ceramic materials have been greatly improved, their toughness and strength have been increased and the scatter of strength decreased. Adequate statistical design procedures for brittle materials exist but cracking and brittle fracture of ceramic components still occur very often.In this review the theory of brittle fracture and the underlying assumptions are critically discussed and the measurement procedures of strength are reviewed. It is shown that the strength of materials, the strength of specimens and the strength of components are often quite different properties. Three main factors are identified which – in order to avoid unexpected failure of components – have to be considered much more than in the past: (i) hidden stresses, i.e. stresses caused by thermal strain mismatch, by contact (for example in joints) and internal stresses, (ii) the quality of the component's surfaces and edges and (iii) proper handling of ceramic materials and components.It can clearly be stated that the mechanical properties of many ceramic materials are appropriate even for applications under severe loading conditions but bad or incomplete mechanical design, insufficient surface finish and mishandling are the main reasons for unexpected failure of ceramic components.     

椭圆封头水平接管部位应力分析和加强效果研究

针对椭圆封头水平接管部位的强度评定和加强效果研究,采用有限元法建立了接管部位的应力计算模型,运用ANASYS程序进行了应力计算,应用分析设计原理对接管部位的强度进行了强度评定,最后根据接管部位的应力分布特点,对接管部位的加强结构进行了设计。通过应力计算和强度分析可见,合理的加强后,接管部位的局部应力明显降低,加强效果显著,强度满足要求。     

Modified average stress criterion for open hole tension strength in presence of localised wrinkling

Abstract

This paper presents an analytical and experimental study to examine the behaviour of notched carbon/epoxy laminates containing out of plane fibre waviness defects. The open hole tension specimen geometry is modified to include carefully controlled waviness defects. The specimen is proposed to study the interaction between the notch and out of plane waviness. A new methodology using the modified average stress fracture criterion is developed for predicting the failure of notched composites containing localised waviness. The approach can be used to assess the quality of a given processing technique for the manufacturing of the composite system.     

内压容器筒体与大接管相贯区的应力强度评定

针对内压容器筒体开有大直径孔后会产生很高的应力集中这一问题,采用有限元方法计算了具有同一开孔率但有不同接管与筒体直径比的压力容器结构的应力分布,并在应力危险截面选择了5条应力处理线进行了应力强度评定。结果发现,5条应力处理线中处理线c的一次局部薄膜应力分量SⅡ最大;而一次应力加二次应力SⅣ的最大值则随t/T的大小体现在不同的处理线上,故SⅣ的评定应针对各处理线进行。在笔者的算例中,4种t/T结构中只有t/T=1.0的结构可满足应力分析设计准则要求。     

带大孔径接管锥壳变径段应力的数值计算和强度分析

针对带有大孔径接管锥壳变径段结构不连续应力和局部应力的计算与强度分析问题,根据其结构特点,选择研究对象,处理边界条件;应用有限元理论和方法,建立数值计算模型;采用ANSYS程序,进行网格划分和数值计算,获得变径段部位详尽的位移场和应力场;在应力分析的基础上,根据分析设计的思想对应力进行分类和强度评定。应力计算结果表明,变径段上多个部位产生了较高的局部应力,强度评价结果表明,锥壳变径段的强度满足要求。     

Finite element stress analysis and strength evaluation of epoxy-steel cylinders subjected to impact push-off loads

The stress wave propagations and stress distributions in epoxy-steel cylinders in which the outside surface of a solid cylinder (steel) is adhered to the inside surface of a hollow cylinder (epoxy resin) subjected to impact push-off loads were analyzed using the finite element method (FEM). The impact push-off loads were applied to epoxy-steel cylinders on a solid cylinder by dropping a weight. The FEM code employed was ANSYS/LS-DYNA. It was found that the maximum principal stress occurs at the upper edge of the interface, where the rupture initiates in epoxy-steel cylinders under the impact push-off loads. Besides, it was also found that the normal stress near the upper edge of the interface increases as the rigidity and the initial impact velocity increase; meanwhile it decreases as the diameter and the height of the solid cylinder increase. The strength of epoxy-steel cylinders increases as the rigidity of the solid cylinder increases, and the diameter and the height of the solid cylinder decrease. In addition, it was observed that the characteristics of the joints subjected to the impact push-off loads are opposite to those of the joints subjected to the static push-off loads. Furthermore, experiments were carried out to measure the strain response of epoxy-steel cylinders subjected to impact and static push-off loads. Fairly good agreements were observed between the numerical and the measured results.     

The ball on three balls test for strength testing of brittle discs: Part II: analysis of possible errors in the strength determination

Biaxial strength testing of brittle materials using the ball on three balls test (B3B test) is a useful tool for direct strength testing of disc specimens offering some advantages compared with the testing of bended beams: there are less problems with the alignment of the specimens in the fixture, in many cases the production of the specimens is easier, the area of maximum tensile stress amplitudes is far from the edges of the specimen (were often machining defects exist) and the testing procedure can easier be miniaturised. In a preceding paper, a proposal for a suitable testing set up was made, the stress fields in the disc specimens were analysed and first testing results were reported. A simple solution for the maximum tensile stress amplitude in the discs was given for a range of parameters concerning the geometry of the specimen, the supporting situation during the test and the material properties. In this paper, possible sources for deviations of this stress from the reported idealised solution (which would result in measuring errors) are discussed. For example, the not accounted influence of friction forces between the disc and the support balls, the influence of a possible buckling of the disc and the influence of geometric inaccuracies are analysed. It is shown, that the thickness of the disc is the most sensitive parameter determining the maximum tensile stress. Therefore it has to be determined with high accuracy.     

A new evaluation procedure for the butt-joint test of adhesive technology: Determination of the complete set of linear elastic constants

Simple analytical formulae have been reported in literature to extract basic elastic material properties of adhesives subjected to tensile loading. The assumptions and simplifications of classical evaluation procedures may result in a remarkable error depending on the investigated material combination. This work proposes a new evaluation procedure for the butt-joint test of adhesive technology. The main idea is to determine the deformed shape of the adhesive layer and to relate the deformation, i.e. contraction and elongation, to a unique set of Young's modulus and Poisson's ratio. A numerical parameter study for different combinations of adherend/adhesive materials and butt-joint geometries has been performed to investigate the influence of these parameters on the adhesive deformation. Comprehensive diagrams are derived which relate the deformation of the adhesive layer to the complete set of linear elastic constants.     

Corrugated board bonding defect visualization and characterization

Adhesive bonding of fluted medium to linerboard is a fundamental process in manufacturing of wood-fiber based corrugated combined board for packaging. The quality of bonds requires frequent testing since production speed and container box stacking capacity are affected. Several different testing techniques are investigated in this paper that complement the standard tests commonly used: bond tensile strength “pin adhesion” (Technical Association of the Pulp and Paper Industry (TAPPI) method T 821), visual qualitative inspection of adhesive distribution by iodine stained separated components (TAPPI method T 610), and examination of manually peeled separated boards. A specially prepared corrugated board sample set was made on a pilot corrugating machine producing a range of bonding defects associated with common inadvertent improper corrugating operating conditions. A thermoelastic stress analysis using infrared image processing applied to the produced samples demonstrates a patterned localization of strains that is associated with adhesive distribution and bond strength. Analysis of load-displacement data of the pin adhesion test indicates significant measurable changes in the elastic properties of the corrugated board structure corresponding to bond quality. The experimental results supported by Finite Element Analysis indicate that increased bond strength arises from an increased localized modulus attributable to a combination of adhesive penetration into the substrate and formation of covalent bonds. Infra-red imaging of back-lighted board samples provides a complementary convenient means to assess the glue distribution.     

3-D FEM stress analysis and strength evaluation of single-lap adhesive joints subjected to impact tensile loads

The stress wave propagations and interface stress distributions in the single-lap adhesive joint under impact tensile loads are analyzed using the three-dimensional finite element method (3D-FEM) taking into account the strain rate sensitive of the adhesive using Cowper–Symonds constitutive model. It is found that the rupture of the joint initiates near the middle area of the edges of the interfaces along the width direction. In addition, the effects of Young's modulus of the adherend, the overlap length and the thickness of the adhesive layer, and the initial impact velocity of the impacted mass on the stress wave propagations and the interface stress distributions are examined. The characteristics are compared with those of the joint under static loads, which show the different properties. Furthermore, experiments are also carried out for measuring the strain responses and the joint strength. A fairly good agreement is observed between the numerical and the measured results. The strength of the single-lap adhesive joint, which is described using impact energy, is obtained between 5.439 and 5.620 J for the present joint.