焊接缺陷对结构疲劳性能影响的模糊评判

本文应用模糊集理论进行了焊接缺陷对结构疲劳性能影响的模糊综合评判，评判时考虑了缺陷的类型、大小、在结构厚度上的位置和缺陷间的相互影响等因素对结构疲劳强度的影响，得到了缺陷对结构疲劳强度危害严重性的特征参量μＡ（Ｘ），评判结果与试验结果相一致。     

提高9.00-20载重斜交胎耐久性的几项措施

轮胎耐久性试验表明，胎肩鼓包和脱层是载重斜交胎最常见的质量缺陷。本文从工艺和产品结构设计方面分析了产生这种缺陷的原因，并提出了相应措施。     

提高9．00－20载重斜交胎耐久性的几项措施

轮胎耐久性试验表明，胎肩鼓包和脱层是载重斜交胎最常见的质量缺陷。本文从工艺和产品结构设计方面分析了产生这种缺陷的原因，并提出了相应措施．     

提高垫带耐用性能的探讨

针对轮胎垫带在使用中常出现局部从轮辋气门嘴孔槽处挤出的缺陷，分析了垫带胶配 方对这种质量缺陷的影响。     

花纹展开图中的点在世界坐标系中的位置

花纹展开图中的点在世界坐标系中的位置姚钟尧，林惠音（华南理工大学５１０６４１）轮胎总图也称花纹总图，是轮胎结构设计所要产生的核心图纸之一。这种图纸貌似机械零部件图，实际上两者的制图准则并不相同。机械图中的主视图、俯视图和侧视图三者的尺寸具有“长对正，...     

具有尺寸驱动功能的轮胎CAD系统

介绍了完全基于Windows系统平台并具有尺寸驱动功能的轮胎结构设计CAD系统（WTireCAD系统）的模块结构，设计界面，设计模块组成等，说明了该系统利用ObjectARX在AutoCAD环境下实现轮胎结构设计尺寸驱动功能的基本原理，展示了该设计系统的特点和新的设计环境。     

题录精选

题录精选１．国内外轮胎行业概况及浅议／／轮胎信息，［专刊１］，２７—４０（１９９５）（中文）２．有限元法在轮胎结构设计中的分析与应用Ｖ橡胶工业，４２［５］，３０４—３１５（１９９５）（中文）３．用计算机分析轮胎结构力学／／自勤车研究，［５〕，１—９（...     

猎迷预警机将装用邓禄普胎

邓禄普航空轮胎公司将向（海上巡逻甩的）猎迷（Nimrad）2000型预警机提供机上使用的全部轮胎。这种轮胎将以最先进的技术进行结构设计，以适应预警机有效载荷增大的需要。以高层级强力帘线制造而成的猎迷2000型预警机用邓禄普航空轮胎，旨在使航胎具有较高的性能和较长的使用寿命；在极高的气压、速度、负荷和温度条件下使用时，能经受冲击、变形和下沉的作用；还能有效地传递转向力和刹车力；并能经多次翻新后保持住轮胎结构的完整性。猎迷预警机将装用邓禄普胎@姚岐轩     

18－20低断面（斜交）沙漠轮胎

介绍了低断面（斜交）沙漠轮胎外胎、内胎、垫带的结构设计特点，进口沙漠轮胎剖析结果，国产沙漠轮胎的室内及实际使用结果，并对这些特点和试验结果进行了讨论。     

《缺陷汽车产品召回管理条例（征求意见稿）》发布轮胎缺陷责任方明确

日前，国务院法制办公室发布了关于《缺陷汽车产品召回管理条例（征求意见稿）》（下称《意见稿》）。《意见稿》明确规定：汽车产品出厂时随车装备的轮胎存在缺陷的，由汽车产品的生产者负责召回；未随车装备的轮胎存在缺陷的，由轮胎的生产者负责召回。     

Steady-State Mechanics of Delamination Cracking in Laminated Ceramic-Matrix Composites

A fracture mechanics delamination cracking model has been developed for brittle-matrix composite laminates. The near-tip mechanics is discussed in the context of material orthotropy and composite material inhomogeneities. A fracture mechanics framework based on the near-tip energy release rate and the associated phase angle Ψ has been adopted. In the case of steady-state delamination cracking in a prenotched cross-ply symmetric laminated beam, analytical expressions for the steady-state energy release rate, _ss, have been obtained for the combined applied loading of an axial force and a bending moment. Parameter studies assessing the effects on _ss of load coupling, crack location, and lamination morphology which includes the total number of layers, layer thickness, and material properties are presented. Thus, composite homogenization criteria with respect to the total number of layers placed along the beam height can be obtained for a wide range of material selection. The associated phase angle Ψ at the delamination crack tip is discussed in the context of existing solutions. The analysis has been developed based on a theory for structural laminates. The delamination model can be used in conjunction with experimental data obtained from model geometries to extract the mixed-mode transverse composite fracture toughness. Thus, conditions for stable delamination crack growth can be established and design criteria based on toughness for composite laminates and composite fasteners can be obtained.     

纵向花纹载重斜交轮胎受力分析及花纹沟底裂口改善措施

根据对载重斜交轮胎纵向花纹块的受力分析,采取改善轮胎轮廓设计、优化接地印痕形状和接地压力分布、改善花纹沟形状、减小花纹块曲折度、减小花纹深度和花纹块所占比率及合理设计花纹沟下部圆弧等措施,可以降低花纹沟底的应力集中和橡胶的应变幅度,提高胶料的耐疲劳寿命,进而改善花纹沟底裂口现象。     

Dynamic Fatigue of a Lithia-Alumina-Silica Glass-Ceramic

A dynamic fatigue study was performed on a Li₂O-Al₂O₃-SiO₂ glass-ceramic in order to assess its susceptibility to delayed failure. Fracture mechanics techniques were used to analyze the results for the purpose of making lifetime predictions for optical elements made from this material. The material has reasonably good resistance ( N = 20) to stress corrosion in ambient conditions. Analysis also indicated the elements should survive applied stresses incurred during grinding and polishing operations.     

胎肩厚度及胎体曲线对工程机械子午线轮胎力学性能的影响

采用数值仿真分析技术对18.00R25工程机械子午线轮胎进行结构优化,重点研究胎肩厚度及胎体曲线对轮胎力学性能的影响。针对不同胎肩厚度及胎肩部位胎体曲线,对充气后轮胎轮廓、接地印痕以及胎肩和胎圈部位受力等进行模拟,分析了不同设计方案轮胎从装配轮辋到充气、加载工况下的受力情况。结果表明:增大胎肩厚度可有效改善胎冠部位受力,提高轮胎的耐磨性能,同时可大大减小钢丝圈外包布处受力;使胎肩部位胎体曲线与胎肩部位轮廓曲线半径接近可以大大减小带束层端点部位应力集中现象。根据分析情况选择设计方案并进行产品试验,达到很好的预期目标。     

Flaw Characteristics in Dynamic Fatigue: The Influence of Residual Contact Stresses

The effect of residual contact stresses on the dynamic fatigue response of surfaces containing indentation-induced flaws is studied. Indentation fracture mechanics is used to analyze the growth of well-defined "median/radial" cracks in combined residual (elastic/plastic) contact and applied (uniform) tensile fields, and thence to determine strength characteristics. In this way a general formulation is obtained for the fatigue strength at constant stress rate. Experimental confirmation of the essential predictions of the theory is obtained from strength tests on Vickers-indented soda-lime glass disks in water environment. It is thereby implied that residual stresses can have a significant deleterious influence on the fatigue behavior of any brittle solid whose controlling flaws have a contact history. Such effects need to be considered in the design of structural ceramics, most notably where fracture-mechanics calibrations of crack-velocity parameters are used for lifetime predictions.     

子午线轮胎胎冠部橡胶结构数值模拟

本文针对12.00R20全钢丝载重子午线轮胎,基于组合模型技术建立了带复杂花纹的全局模型,基于子模型技术建立了胎冠部具有精细网格的接地区子模型,并验证其有效性。应用子模型精确模拟了静负荷工况下胎冠部橡胶结构的应力应变特征,并分析胎冠部5个危险区域的应力情况。结果表明,子午线轮胎的带束层端部（区域M）在使用中是最容易破坏的位置,由于材料及结构均存在突变,其应力集中和剪切变形在整个胎冠部位是最严重的。基于此,提出改进方法。     

Effect of notch size on the fatigue damage behaviour of toughened epoxy adhesive specimens

ABSTRACT

In the present work the influence of notch size on the fatigue damage behaviour of toughened epoxy adhesive specimens is investigated. Notched and un-notched bulk adhesive specimens were fatigue tested at room temperature under tension-tension cyclic loading at a stress ratio of 0.1. The investigation was based on the analysis of fatigue life (SN) and stiffness degradation curves, which were correlated with notch size and applied stress. Finite element analysis (FEA) was carried out in order to evaluate the notch-dependent stress concentrations. Fatigue results evidenced a reduction of lifespan with increased applied stress amplitude and a possible relationship between the inverse slope of SN curves and notch size. Most notched samples exhibited lower fatigue strength in comparison to un-notched, except in the low cycle fatigue range where un-notched and notched samples had similar fatigue strength. Stiffness degradation showed a correlation with applied stress, i.e. an increase in applied stress was accompanied by faster and stronger degradation. For higher loads, un-notched and 0.2 mm notch samples presented greater stiffness degradation prior to failure than other notched samples.     

全钢子午线轮胎疲劳破坏现象仿真与优化设计研究

基于有限元的轮胎疲劳寿命评价方法,建立295/80R22.5全钢子午线轮胎的有限元模型。使用ABAQUS隐式分析方法获得轮胎的应变、应力以及应变能密度等基本参数后,根据轮胎实际使用中的破坏情况选择影响疲劳寿命的评价指标。结果表明:高速耐久工况下,应选择应变能密度和帘线张力作为影响疲劳寿命的评价指标,而且适当增加带束胶厚度能有效提高轮胎的疲劳寿命;低速重载工况下,应当选择帘线和橡胶间的剪应力(层间剪应力)作为影响疲劳寿命的评价指标,且适当降低胎体帘布层和补强层的高度能有效提高轮胎的疲劳寿命。     

Arrest of Fatigue Cracks in Transformation-Toughened Ceramics

A theoretical model based on the theory of complex potentials and dislocation formalism is used to simulate fatigue crack growth in a transformation-toughened ceramic. The effective stress-intensity factor is calculated during crack growth, because it is believed to determine the crack-growth rate similar to the Paris-type growth law. For certain combinations of transformation strength and load, the effective stress-intensity factor decreases to zero, indicating crack arrest. A detailed parametric study of this phenomenon reveals that the applied load and minimum transformation strength parameter necessary to cause crack arrest are linearly related, independent of initial crack length. This suggests that a threshold stress similar to the endurance limit in the conventional stress/life (S/N) approach should be used instead of the threshold stress-intensity factor in the design of transformation-toughened ceramics against fatigue.     

A Fracture Mechanics Approach to Characterizing Cyclic Debonding of Varied Thickness Adhesive Joints to Electroprimed Steel Surfaces

Applications of adhesive bonding for automotive structures have been increasing in recent years due to improvements in the types of adhesives available and in improved knowledge of bonding procedures. Consequently, there exists a demand for design techniques to assess the influence of bondline thickness on adhesive joint strength. One design approach currently being used is based on limiting shear stresses in the adhesive while designing to eliminate peel stresses. Another design approach is based on fracture mechanics and accounts for shear and peel stresses and both static and fatigue modes of failure. The present study applies fracture mechanics to investigate the mixed-mode response of cracked-lap-shear (CLS) joints bonded with unprimed and electroprimed steel surfaces. Three bondline thicknesses equal to 0.254, 0.813, and 1.27 mm were evaluated for unprimed and primed bondlines. For the experimental portion of the study, debond growth rates (da/dN) were measured using a remote imaging system over a range of applied cyclic loads. Corresponding changes in the strain release rates (ΔG) were calculated, through finite element analyses, as a function of debond length and applied load level. The computations for ΔG applied a finite element formulation to determine both the peel component, ΔG_i, and the shear component, ΔG_ii. When computed ΔG values were plotted against the measured debond growth rates, da/dN, the results showed a power law relationship which characterizes the debond behavior of a given material system and bondline thickness.