三种高强度钢的包辛格系数及其特性

提出按单层超高压自增强圆筒弹-塑性交界面半径实测值确定高强度钢包辛格系数的方法;基于有关试验数据,分析了三种高强度钢的包辛格系数及其特性。研究表明:(1)高强度钢的包辛格系数大小与钢材的种类密切相关;相同钢材包辛格系数的大小与其屈强比的大小基本无关。(2)45CrNiMoVA钢的包辛格系数为0.873 5,精密度为0.041 6;40Cr钢的包辛格系数为0.817 1,精密度为0.097 9;33CrNi3MoA钢的包辛格系数为0.817 1,精密度为0.094 9。     

包辛格效应对单层圆筒自增强的影响

本文分析认为,材料拉伸和压缩屈服极限不一致的包辛格效应,对单层圆筒自增强的影响是不可忽视的,并用包辛格系数对Mises屈服准则进行了修正,导出了单层圆筒自增强预应力和最佳自增强半径表达式。经有关试验数据和工程实例验证,本文表达式可用于工程设计。     

单层自增强圆筒的反向屈服限制条件

为防止单层厚壁圆筒自增强处理后发生反向屈服,导致自增强效果下降,分析了包辛格效应对单层厚壁圆筒反向屈服限制条件的影响。     

自增强容器反向屈服限制条件的讨论

为了防止厚壁容器自增强处理后发生反向屈服，造成自增强效果下降，本文分析了包辛格效应对自增强容器反向屈服限制条件的影响。     

基于双剪强度理论的弯管塑性极限载荷计算与有限元分析

根据对弯管在受内压作用下的应力分布特点,应用双剪强度理论推导出求解弯管极限载荷的一般公式,并用基于Mises和Tresca这两种准则的有限元方法以及Goodall公式法计算的结果进行了比较,得到了弯管系数m和包辛格系数a对极限载荷的影响规律,为双剪强度理论在工程中计算弯管的极限载荷的应用提供理论上的参考.     

最佳自增强圆筒的反向屈服限制条件

工程材料拉伸和压缩屈服极限不一致的包辛格效应，对单层自增强圆筒的反向屈服限制条件有较大影响。本文定量分析了这种影响，导出了由工程材料制成的单层最佳自增强圆筒的反向屈服限制条件。     

单层自增强圆筒反向屈服限制条件的讨论

该文在考虑到包辛格效应的前提下,提出了自增强压力的控制范围,旨在防止自增强处理中由于较大的压缩应力带来的反向屈服造成容器承载能力的下降。     

Bauschinger效应对单层圆筒自增强影响的初步分析

本文分析认为：工程材料拉伸屈服极限与压缩屈服极限不一致的Ｂａｕｓｃｈｉｎｇｅｒ效应,对单层圆筒自增强的影响是不可忽 ,在用包辛格系统对Ｍｉｓｅｓ屈服准则进行修正的基础上,导出了单层圆筒残应力和最佳自增强半径表达式。经有关实验数据验证,本文表达式精度高,可用于工程设计。     

轮胎胶料热物性参数对温度场的影响研究

研究轮胎胶料热物性参数对温度场的影响。结果表明:橡胶材料的热物性参数对轮胎温度场影响显著,胎圈处的软三角胶、纤维包布和型胶及耐磨胶的热扩散系数和导热系数对最高温度和温度偏差均有较大影响;胎肩部位胎面胶的导热系数对最高温度影响最大,胎肩垫胶的热扩散系数对温度偏差的影响最大。依据分析结果对胎圈和胎肩部位胶料的热物性参数进行优化设计,为胶料配方改善提供了参考。     

HFW系列管线管的力学性能控制技术

高频电阻焊（HFW）管线钢管生产过程中,钢卷弯曲变形成钢管,由于存在加工硬化和包辛格效应的交互作用,制管后钢管的力学性能较钢卷有所变化。因此,需要掌握制管过程中的力学性能变化,从而得到钢卷的力学性能控制要求,生产出满足要求的HFW管线钢管。通过分析B,X42,X46及X52钢级的HFW管线管生产过程中的力学性能变化,形成了从钢卷到钢管之间的力学性能控制技术,对于实现HFW高频焊管的全流程质量控制具有一定的实用价值。     

Experimental and numerical investigations of crack face adhesive bonding effect on the mixed-mode fracture strength of PMMA

Experimental and numerical investigations have been conducted to evaluate the effect of adhesive bonding of crack surfaces on the mixed-mode (I and II) fracture strength and effective stress intensity geometry/loading factor of a plate with an edge crack. The experimental tests were carried out on five batches of simple edge crack and specimens in which adhesive bonding was used on crack faces at different distances from the crack tip. The cracked specimens made from poly methyl-methacrylate rectangular plates. The specimens’ fracture strength was obtained by employing a tensile testing machine at different loading angles using a modified Arcan fixture. In the numerical part, finite element simulations were used to model the test specimens and thereby establishing their stress intensity geometry/loading factors. The results show that the adhesive bonding of the crack surfaces has a significant effect on reducing the equivalent mixed-mode stress intensity factor for all loading angles. The bonded specimens show considerable fracture force enhancement compared to the simple edge crack specimens.     

Study on the effect of inclusion shape on crack-inclusion interaction using digital gradient sensing method

The effect of inclusion shape on the mode I stress intensity factor of the matrix crack interaction with a rigid inclusion was studied experimentally using digital gradient sensing (DGS) method. First, the noncontact optical measurement system of DGS was built up, and the specimens with different shapes of inclusion ahead of matrix crack were performed using transparent epoxy resin. Then, the angular deflection contour at the crack tip with different shapes of inclusions was obtained, and the stress intensity factors were extracted from the stress gradient filed based on least square fitting. Finally, a numerical simulation was conducted on the same problem using ABAQUS, and the stress intensity factors computed from FEM were compared with the experimental results. The results show that the stress intensity factors extracted from the stress gradient filed are agreed well with the numerical and theoretical results.     

玻璃应力对玻璃强度的影响

介绍了玻璃的应力与玻璃强度之间的关系,并讨论了几种不同类型的应力对玻璃强度的影响。     

Numerical analysis to study the effect of through thickness reinforcement with different stitch orientations on open-hole laminates

The effect of through thickness reinforced open-hole laminates was analysed in terms of laminate behaviour under in-plane tensile loading based on continuum mechanics. Stitches around the notch were oriented in the longitudinal and transverse directions. To obtain the macroscopic damage and the local stress–strain constitutive behaviour, laminates were modelled on a lamina-wise basis. Interfaces between lamina and stitch yarns were assumed to be perfectly glued and modelled by the contact capability. Discretisation procedures using the principle of virtual work were applied in addition to discretisation of the contact traction. Progressive failure analysis with Puck’s failure criteria was conducted to characterise the failure behaviour of the laminate. In both cases, damage was initiated by a matrix crack in the perpendicular direction of the loading axis on the notch. The longitudinally stitched laminate showed a 14.29% higher strength compared to the transversely stitched laminate by suppressing damage propagation. The results obtained using this finite element technique was consistent with the experimental results.     

鞍座包角和宽度对双支座卧式容器筒体应力分布影响的研究

通过有限元软件ANSYS建立双支座卧式容器的有限元模型,考察了鞍座包角和宽度对附近筒体环向峰值应力分布的影响,得出了最大的环向拉应力和压缩应力随着鞍座宽度的增加而减少,随着鞍座包角的增大而变小的规律,并且利用有限元计算的结果和统计学的方法分别拟合了它们对环向峰值应力的影响系数。     

钢纤维增强水泥基复合材料增韧机理研究

钢纤维可有效阻碍水泥基材料中微裂缝的产生和发展,提高其抗裂能力。基于Eshebly等效夹杂理论和最大周向应力准则,获得了平面应力条件下无限大薄板中裂缝与钢纤维相互作用的应力强度因子(SIF)解,推导了掺入纤维后的Ⅰ-Ⅱ复合型断裂裂缝尖端最大应力表达式。根据掺入钢纤维前后裂缝尖端最大应力比,分析了钢纤维方向、位置和弹性模量对增韧效果的影响。结果表明,钢纤维通过改变裂缝尖端应变场,影响应力强度因子,从而降低尖端最大应力。当钢纤维方向与裂缝方向垂直时,裂缝尖端最大应力比最小,定向后钢纤维的增韧效果最明显。钢纤维的增韧效果主要受纤维方向影响,而受纤维弹性模量的影响小。     

Measurement of AC conductivity and dielectric properties of flexible conductive styrene–butadiene rubber‐carbon black composites

Flexible conductive polymer composites were prepared using styrene–butadiene rubber (SBR) as a matrix and conductive carbon black as filler. The filler loading was varied from 10 to 60 phr. The effect of frequency, filler loading, temperature, and applied pressure on the AC conductivity, permittivity, and loss factor of the composites was studied. The AC conductivity of low and high loaded composites was found to be frequency dependent and independent respectively. The permittivity and the loss factor were continuously decreasing with increasing frequency. The increase in filler loading increased the AC conductivity, dielectric constant, and loss factor of the composites. Increase in temperature imposed increase in conductivity and permittivity of the composites. With increasing applied pressure the properties showed exponential increase. The effect of time under a constant compressive stress was studied and dielectric relaxation times were evaluated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 986–995, 2007     

Improved one-dimensional beam model for unbalanced composite single-lap joint

An analytical nonlinear solution was provided for unbalanced composite single-lap joint (CSLJ) using an improved one-dimensional beam model, which incorporated the effect of bending–tension coupling. The bending–tension coupling stiffness was introduced to characterize the coupling bending and tension behavior induced by the un-symmetric stacking sequence of composite laminates. The governing differential equations captured the bending–tension coupling behavior and the geometrically nonlinear features were constructed based on the displacement compatibility conditions of flexible interface. The transverse deformation in overlap region, edge moment factors and adhesive stress distributions for the unbalanced CSLJ with inflexible, intermediate flexibility and flexible adhesive can be determined by the present one-dimensional beam model. The accuracy of the present model was validated by the comparison with nonlinear finite element model. The effect of bending–tension coupling on edge moment factors and peak values of adhesive stresses was shed light on with the present model.     

Fatigue life prediction method for central hole of needled ceramic matrix composite

Based on the consideration of matrix porosity and representative volume element of needled structure, the macroscopic elastic constants of needled C/SiC ceramic matrix composite and the stress concentration factor of the hole-edge were calculated by the finite element method first. Then, based on the fatigue test data of the smooth and central hole specimens, the fatigue notch factors corresponding to different stress levels were obtained. In view of the different characteristics of the fatigue notch factor obtained under different limit lives, the relationship between the fatigue notch and stress concentration factors was established, and the influence of nominal stress on the fatigue notch factor was also considered. Based on this, a fatigue life prediction method for central hole of needled C/SiC composite was proposed. The proposed method can predict the fatigue life of central hole by using the S–N curve of smooth specimen and the stress concentration factor of central hole specimen. The comparison between predicted and experimental lives showed that the proposed method can better predict the fatigue life of central hole specimen for needled C/SiC composite.     

基于DIC的BFRC受压损伤特性及本构模型研究

采用数字图像相关(DIC)技术对玄武岩纤维混凝土(BFRC)受压过程中试件表面应变场进行计算,分析了试件表面水平应变云图变化情况,得到了BFRC受压损伤演化规律;通过对水平应变场统计分析,利用应变场标准差统计指标定义损伤演化因子,得到不同纤维掺量下BFRC损伤演化曲线;同时,基于应变等效原理及损伤演化因子,推导出BFRC单轴受压损伤本构模型,通过对比试验与模型曲线,发现两者吻合较好,该模型在峰值应变之前可有效描述BFRC单轴受压下损伤演化过程;对比曲线发现玄武岩纤维可有效提高混凝土峰值应力及峰值应变,提高其变形能力,并具有延缓损伤作用.