金属胶接工艺设计专家系统

介绍了用Turbo—PROLOG说明性语言写成的金属胶接接头工艺设计专家系统。本系统对钢、铝及其合金、铜及其合金、不锈钢、钛及其合金、铸铁等同种或异种金属胶接接头的工艺设计，胶粘剂选择、胶接工艺参数的确定均可自动完成．     

金属胶接接头劈裂破坏的模型分析

对金属胶接接头劈裂强度测试方法和影响劈裂强度的主要因素的作用进行了分析与讨论。本文提出了金属胶接接头劈裂破坏模型，对完善劈裂强度测试方法提出了改进意见．     

胶接接头耐久性的综合研究

以AG—80/DDS、环氧—聚砜和环氧—丁腈结构胶为胶粘剂,45~#钢和LY_(12)—CZ铝合金为被粘材料,综合研究了胶接接头的耐久性。研究结果表明,除胶粘剂外,内外应力、温度、介质和被粘物的表面状态均是影响接头耐久性的重要因素。激光双折射法测定胶接接头内应力是较可行的新方法。     

金属胶接面上显微硬度分布的研究

本文通过测定正交拉和拉剪试样连续几次拉断后胶接面上的显微硬度分布,研究了胶接接头受载时应力的分布情况和断裂过程,结果表明被贴粘物表层存在着较大的显微硬度波动,确已发生了一定量的塑性变形,且某些区域存在着残余应力,同时也表明,试样受载时,正应力及剪应力的发布是不均匀的,如果所用过的试样不经处理,从新使用,当其受载时,粘接面上会继续发生性变形,且试样上正应力和剪应力的分布会变更加不均匀。     

受集中载荷作用的金属胶接接头应力分布研究

分析了金属胶接接头受集中载荷作用下应力分布的一般模型，指出了其局限性和不足。借助于金属试样表层的显微硬度测定及应变片电测法间接确定了胶接接头承受不同的载荷作用时接头上的实际应力分布，结果表明胶层中存在着较宽的分布拉伸应力。作者根据实验结果提出了金属胶接接头在集中载荷作用下肢层内应力分布的修正模型。     

剥离载荷作用下胶层内应力分布研究

讨论分析了现有的剥离力学模型,指出了其局限性与不足,建立了新的剥离力学模型以描述金属胶接接头的剥离载荷作用下胶层内的实际应分布情况,认为剥离试验中胶层中的压缩应力其实行不存在。     

聚四氟乙烯与金属胶接及其耐久性

本文叙述了聚四氟乙烯与金属胶接的方法,同时对影响其耐久性的部分因素进行了讨论,采取相应措施可获得耐久性已达十年的胶接接头。     

环氧结构胶固化工艺对胶接接头性能的影响

以XH-11环氧结构胶为研究对象,采用正交试验法进行多因素试验设计,研究了固化温度、固化时间、晾置时间、表面粗糙度等因素对金属胶接接头拉伸剪切强度和冲击强度的影响,得出了最佳固化条件,并通过数据统计分析得到影响因素为自变量的力学性能回归方程,为胶接接头的强度预测提供参考.     

热处理对Ni-P镀层内应力及结合强度的影响

采用薄片弯曲法和压痕法分别研究了热处理温度对化学镀镍层的内应力以及镀层与基体的结合强度的影响规律。结果表明 :镀层的内应力为拉应力 ;当热处理温度为 2 0 0℃时 ,内应力减小 ,镀层经过 30 0、4 0 0或 6 0 0℃热处理 ,内应力逐步增大。随热处理温度升高 ,镀层与基体的结合力增大     

胶接接头受劈裂载荷作用应力分布研究

对金属胶接接头劈裂试样承载后的应力分布情况进行了实测分析，结果表明胶层沿胶接面试样长度方向上受到分布较宽的拉伸力的作用，印证了作者所提出的胶接接头受劈裂载荷作用力学模型是符合实际的。     

A Method for the Stress Analysis of Lap Joints

A theory is presented for the adhesive stresses in single and double lap joints under tensile loading, while subjected to thermal stress. The formulation includes the effects of bending, shearing, stretching and hygrothermal deformation in both the adherend and adhesive. All boundary conditions, including shear stress free surfaces, are satisfied. The method is general and therefore applicable to a range of material properties and joint configurations including metal-to-metal, metal-to-CFRP or CFRP-to-CFRP. The solution is numerical and is based on an equilibrium finite element approach. Through the use of an iterative procedure, the solution has been extended to cater for non-linear adhesive materials.     

A Method for the Stress Analysis of Lap Joints

A theory is presented for the adhesive stresses in single and double lap joints under tensile loading, while subjected to thermal stress. The formulation includes the effects of bending, shearing, stretching and hygrothermal deformation in both the adherend and adhesive. All boundary conditions, including shear stress free surfaces, are satisfied. The method is general and therefore applicable to a range of material properties and joint configurations including metal-to-metal, metal-to-CFRP or CFRP-to-CFRP. The solution is numerical and is based on an equilibrium finite element approach. Through the use of an iterative procedure, the solution has been extended to cater for non-linear adhesive materials.     

Stress Analysis and Failure Properties of Carbon-Fibre-Reinforced-Plastic/Steel Double-Lap Joints

The present paper considers the strength of CFRP/steel double-lap joints loaded in tension. A detailed stress analysis has been conducted of the shear and transverse tensile stresses in the joint, using an elastic-plastic model for the rubber-modified epoxy adhesive. The results of this analysis have been combined with the measured properties of the materials forming the joint in order to predict quantitatively the failure strengths of the various joint designs studied. There was good agreement between the theoretically predicted and experimentally measured strengths. These studies have led to a highly efficient design being developed.     

Three-dimensional Finite Element Analysis of Stress Response in Adhesive Butt Joints Subjected to Impact Tensile Loads

The stress wave propagation and the stress distribution in adhesive butt joints of similar adherends subjected to impact loads are analyzed using a three-dimensional finite-element method (FEM). The code employed is DYNA3D. An impact load is applied to a joint by dropping a weight. An adherend of a joint is fixed and the other adherend to which a bar is connected is impacted by the weight. The height of the weight is changed. The effect of Young's modulus ratio between the adherends and the adhesive, the adhesive thickness and the geometry of T-shaped adherends on the stress wave propagation at the interfaces are examined. It is found that the maximum stress is caused at the interfaces of the adherend subjected to an impact load. In the case of a T-shaped adherend, it is seen that the maximum stress is caused near the center of the interfaces and that it increases as Young's modulus of the adherends increases. In the special case where the web length of the T-shaped adherends equals the interface length, it is seen that the singular stress occurs at the edge of the interfaces and it increases as Young's modulus of the adherends decreases. The maximum principal stress increases as the adherend thickness increases. In addition, the strain response of adhesive butt joints subjected to impact loads was measured using strain gauges. A fairly good agreement is found between the numerical and the measured results.     

Comparison Between Experimental and Theoretical Analysis of Stress Distribution in Adhesively-Bonded Joints: Tenon and Mortise Joints and Single-Lap Joints

We have studied the agreement between theoretical computations and experimental results of surface strains of bonded joints of two types: tenon and mortise, and single-lap joints, for different lengths of the lap. For instance, with the single-lap joint, we have tested four lengths of the overlap from 14 mm to 88 mm. Surface strains are measured by an extensometrical method with electrical gauges, when the specimen is loaded in uniaxial traction on a universal testing machine.

Experimental results and computations made by an improved method, such as the asymptotic expansions method, agree but only if the global traction load applied on the specimen is low, or if the overlap in respect with the others dimensions of the section of test specimen is long.

In these joints, effectively, stress fields are disrupted near the butts and become very difficult to compute. Actually, near the ends of the overlap, stresses can reach high limits with only low global load applied on the test specimen. With a short length of the overlap, linear behaviour disappears almost totally because of a strong interaction of the two perturbed fields. On the contrary, with a high length of overlap, stress fields become linear on the major part of the overlap, even with a high tensile load applied on the specimen. So, the length of the overlap has a great effect on the linear behaviour of the joint.     

Comparison Between Experimental and Theoretical Analysis of Stress Distribution in Adhesively-Bonded Joints: Tenon and Mortise Joints and Single-Lap Joints

We have studied the agreement between theoretical computations and experimental results of surface strains of bonded joints of two types: tenon and mortise, and single-lap joints, for different lengths of the lap. For instance, with the single-lap joint, we have tested four lengths of the overlap from 14 mm to 88 mm. Surface strains are measured by an extensometrical method with electrical gauges, when the specimen is loaded in uniaxial traction on a universal testing machine.

Experimental results and computations made by an improved method, such as the asymptotic expansions method, agree but only if the global traction load applied on the specimen is low, or if the overlap in respect with the others dimensions of the section of test specimen is long.

In these joints, effectively, stress fields are disrupted near the butts and become very difficult to compute. Actually, near the ends of the overlap, stresses can reach high limits with only low global load applied on the test specimen. With a short length of the overlap, linear behaviour disappears almost totally because of a strong interaction of the two perturbed fields. On the contrary, with a high length of overlap, stress fields become linear on the major part of the overlap, even with a high tensile load applied on the specimen. So, the length of the overlap has a great effect on the linear behaviour of the joint.     

Effect of Adhesive Stiffness and Thickness on Stress Distributions in Structural Finger Joints

Environmental, political, and socioeconomic actions over the past several years have resulted in a decreased wood supply at a time when there is an increased demand for forest products. This combination of increased demand and decreased supply has forced more emphasis on engineered wood products, a varied category usually connected with adhesively-bonded end joints, of which the most common type is the finger joint. This paper presents the results of a finite-element analysis of structural finger joints, and focuses primarily on the effect of adhesive stiffness and thickness on stress distribution patterns in finger joints. Results indicate that a flexible adhesive layer concentrates adherend longitudinal and radial stresses at the finger base, whereas a stiff adhesive layer minimizes adherend stresses but increases adhesive stress levels. Results also show that a thin adhesive layer concentrates longitudinal adherend stresses at the juncture of the finger tip and flexible finger base and concentrates radial stresses at all finger bases. However, these increased longitudinal and radial stresses are balanced by reduced adhesive shear stresses.