180°轴用双键槽样板的设计与使用探讨

论述180°键槽样板的设计方法及正确的使用方法.从不同角度不同使用情况下,分析了180°键槽样板使用时产生的测量误差的原因,并给出了正确的使用方法,并因此而降低了轴的加工成本.     

某转管武器双向环形弹簧缓冲器的设计

深入研究了武器缓冲问题,提出了使用双向环形弹簧缓冲器,建立并求解了缓冲运动的微分方程,并给出了缓冲器的具体设计流程,可为缓冲器的设计和使用提供参考。     

混凝土搅拌站的常见故障及解决方法

以中铁一局使用的混凝土搅拌站为研究对象,分析了目前使用过程中经常出现的故障问题,并提出了解决和排除故障的方法和措施,为高效使用混凝土搅拌站提供了参考。     

大同市农药经营市场状况与对策

对大同市农药使用现状和农药经营市场状况进行了调查,指出了当前农药使用、农药经营中存在的问题,并对今后的农药管理和使用提出了建议。     

浅谈压缩天然气汽车的安全性

就压缩天然气汽车的使用燃料、专用装置、使用环境等的特点和安全性进行了分析,并提出了提高天然气汽车使用安全性的一些措施。     

除草剂使用情况调查分析

近几年来由于除草剂连年使用单一的品种,致使除草效果不好。农民使用新型的除草剂或者加大用量又产生药害。本文对镇内今年使用除草剂情况进行调查,并剖析了除草剂不好使和产生药害的原因,总结了除草剂正确的使用方法,以提高的除草剂使用效果。     

挖掘机油缸密封选型设计

根据挖掘机的使用工况,对挖掘机油缸密封的选型作了分析,并通过实际装机使用试验,验证了所选用的密封结构能满足挖掘机的油缸使用要求。     

除草剂使用情况调查分析

近几年来由于除草剂连年使用单一的品种,致使除草效果不好。农民使用新型的除草剂或者加大用量又产生药害。本文对镇内今年使用除草剂情况进行调查,并剖析了除草剂不好使和产生药害的原因,总结了除草剂正确的使用方法,以提高的除草剂使用效果。     

变频器的常见误区及维护要点

阐述了变频器在使用中的常见误区,并给出了相应的解决方法,介绍了使用和维护变频器时应注意的事项。     

变频器的常见误区及维护要点

阐述了变频器在使用中的常见误区,并给出了相应的解决方法,介绍了使用和维护变频器时应注意的事项。     

Stress analysis in elastic joint structures

A new inverse problem approach is introduced to analyse the stresses in the overlap elastic joint structures consisting of two adherents and an adhesive interlayer. Displacements in the elements of a joint are expressed in terms of some initially unknown contact stresses by solving the boundary-value problem for each element considered separately. The contact stresses are calculated from the matching continuity conditions for the displacements. Contact tearing and shear stresses, three-dimensional stress distribution in the bulk of adhesive interlayer, and the maximum stress values are calculated for different ratios of thicknesses and material properties of the adherents and the adhesive interlayer. The present study represents a new alternative modelling approach to stress analysis in the elastic joint structures.     

Bending analysis of a laminated composite patch considering the free-edge effect using a stress-based equivalent single-layer composite model

The interlaminar stresses of a laminated composite patch, which is made up of reinforcing fibers (carbon/graphite) and epoxy matrix are analyzed using a stress-based equivalent single-layer model under a bending load. The composite patch is frequently used as reinforcement for a metallic adherend of mechanical/aerospace structures (i.e., aluminum alloy, etc) by attaching the film- or paste-type adhesive (i.e., epoxy, BMI, etc). To calculate the adhesive stresses transferred from the substrate, an interlayer model is introduced. The adhesive stresses are obtained by solving the equilibrium equations. The stress fields of the patch are determined by assuming certain stress functions. To satisfy the equilibrium state of the patch, the stress functions are divided into homogeneous and particular parts. The adhesive stresses act as prescribed stress boundary conditions of the laminated composite patch. The stress functions are substituted into a complementary virtual work principle, and from this, two coupled ordinary differential equations are obtained. General eigenvalue problems are derived to solve the coupled governing equations. To demonstrate the validity and efficiency of the proposed method, cross-ply, angle-ply and quasi-isotropic laminated composite patches are studied. From the observations made, the authors found that the stress function-based approach is suitable for solving the stress prescribed boundary value problem with accuracy and efficiency compared to a displacement-based approach such as the finite element method. The proposed method can be used as an efficient tool in the initial design stage of structural components when it is necessary to consider the free-edge effect.     

粘接点焊单搭接头的静力分析

建立了粘焊单搭接头的力学分析模型，得到了粘焊结构中粘接剂层内的剪应力和剥出应力分布，并由此确定了粘接层的人效判据。同时，对粘焊结构进行了数值分析，所得到的粘接剂层内的应力分布与理论值吻俣得较好，从而证实了所建理论模型的合理性。     

协调形变法消除小直径管道焊接应力方法的研究

由焊接残余应力带来的焊接接头应力腐蚀开裂问题，是石油化工行业广泛使用的输送管道的主要失效形式。很多情况下，改变接头的应力分布状态，是解决这一问题的有效方法。结合小直径管道的特点，文中提出一种新的消除应力方法——协调变形法，即在管道焊缝两侧压应力区制造温差，使该区产生一定的与焊缝区相协调的收缩变形。对比协调形变法消除小直径管道焊接残余应力的数值模拟结果和实验结果，分析协调形变法消除残余应力的机理。结果显示，数值模拟结果与实际情况一般都符合得较好，可以达到100％的消除应力效果(内表面轴向应力)。该方法使用简单、效果好，表明协调形变法是消除残余应力的有效方法，可以解决小直径管道由于消除应力难而产生的应力腐蚀问题。     

Pre-stressed adhesive strap joints for thick composite sandwich structures

A simple but effective design to improve the strength of thick adhesive composite strap joints is validated with experiment and finite element method. The strap joint under investigation, with a particular application to naval ship structures, consists of two thick woven E-glass/vinyl ester laminates joined together with two steel doublers. Longitudinal tensile loads are applied to the joints, resulting in large concentrated shear and peel stresses near the free edges of bondlines. The new design intends to reduce the adhesive peel stress by application of through-the-thickness compressive pre-stress along the bondline and thus leads to an increase of joint strength. Experiment results show that all the joint failures are delamination of the top layer of the laminated adherends. The test further confirms that joint strength increases significantly by applying the transverse pre-stress. Finite element analysis reveals that the pre-stress can effectively reduce the magnitude even reverse the sign of the peel stress in the adhesive layer and the adherends. Recessing the adhesive leading edge could magnify the pre-stress effect and reduce the adhesive peel stress, but would increase the shear stress. For those composite joints with low transverse interlaminar strength and susceptible to delamination, this simple design/technique can considerably improve their joint strength.     

考虑弯曲效应的混元胶接单搭接头应力模型

混元胶接接头是利用多种不同剪切弹性模量的胶层来传递被粘物载荷的单搭接头。它兼具胶层连续性连接和降低端头应力集中等优点,因此能充分利用被粘物材料性能(如复合材料)以提高接头强度。以典型双元胶接接头为对象,考虑加载作用线偏心引起的弯曲效应和胶层剥离正应力,建立被粘物为各向同性的线弹性双元胶接接头应力解析模型。理论模型中的胶层切应力、剥离正应力和上被粘物纵向正应力与精细有限元模型吻合得较好,证实了理论模型的正确性。参数研究中确定了影响混元胶层应力分布的关键耦合参数。     

光学玻璃退火应力生成的计算机辅助分析

本文提出了一个以有限元法为基础的光学玻璃退火应力计算模型。可以在微机上预测一定退火规程和工艺条件所确定的暂时应力和退火后的永久应力。最后按三维应力状态计算第二类光学均匀性和应力双折射。     

BT20钛合金热变形流变应力的预测模型

对现有的流变应力模型进行了分析,针对BT20钛合金流变应力的特性,提出了一个新的计算热变形条件下钛合金流变应力的模型.该模型考虑了温度和应变速率的影响,能描述热变形过程中加工硬化阶段和加工软化阶段的流变应力;并建立了峰值应变、峰值应力、稳态应力和变形参量之间关系的模型.结果表明:这些模型预测结果与试验结果吻合,具有较好的精度.     

TC4管状零件内壁加工残余应力计算及其有限元分析

针对残余应力对加工零件使用性能有严重影响以及TC4材料难以用X射线法进行残余应力测量的现状,提出了一种通过测量外壁应变来计算TC4管状零件内壁加工残余应力的方法。为验证该方法的正确性,在有限元软件中对模型内壁进行分层施加预定的随深度变化的残余应力,并用生死单元技术将内层单元逐层“杀死”来模拟实际实验中应力层被腐蚀的过程。根据外层不断变化的应变以及推导出的计算公式来计算内壁随深度变化的残余应力,并将计算得到的残余应力与之前所施加的应力进行对比,可发现该方法求得的残余应力值准确度较高,由此可以得出结论：该方法可用于测量实际零件的残余应力。     

一种考虑胶瘤的胶接简化有限元模型:应力与刚度分析

胶接接头中总存在胶瘤,由于建模复杂,胶接接头有限元分析中胶瘤常被忽略.但胶瘤能减少峰值应力,提高结构强度和刚度.为此,提出一种简化的胶接有限元模型,即用壳单元代表胶瘤,体单元代表被粘体和胶层,并用弹性理论建立壳单元等效厚度公式.以体单元精细模型结果作为对比的真实解,考察五种载荷工况下,单搭接头简化有限元模型的胶层应力和刚度.分析表明,壳单元等效厚度公式正确,胶接简化有限元模型精度高,可用于诸如汽车等大型结构中;用壳单元简单模型可定量分析胶瘤大小和形状对接头应力和总体刚度性能的影响.