Cohesive Zone Model Characterization of the Adhesive Hysol EA-9394

Abstract

The cohesive zone model approach is attractive for the analysis of failure of adhesively bonded structures. While the numerical implementation of cohesive elements has been well established, there remains a lack of cohesive material data. The present paper contributes to efforts to fill this void. An investigation of crack growth in the widely used structural adhesive Hysol EA-9394 is presented, and the adhesive is characterized by a cohesive zone law. Crack growth experiments were performed on specimens consisting of aluminum adherends bonded by use of the adhesive. Measurements of the surface topography leading reconstruction of fracture processes indicate that plastic deformation is absent during fracture. Thus, the cohesive zone law can directly be determined from the energy release rate and the material separation measured at the initial crack tip. The cohesive zone law is then applied in finite element model to predict crack growth. The predicted strain fields during crack growth are well matched to those obtained by digital image correlation measurements. An independent set of crack growth experiments was performed, and finite element models based on the cohesive law were used to predict the outcome of these experiments. Again good agreement between simulation and experiment was obtained. The results give confidence that the cohesive zone model parameters are transferable to the analysis of structures bonded with the adhesive Hysol EA-9394 in general. A comparison of the cohesive zone law for Hysol EA-9394 demonstrates that this adhesive possesses high strength and moderate toughness. Limits to the transferability regime are discussed.     

Strength Degradation of Adhesively Bonded Single-Lap Joints in a Cyclic-Temperature Environment Using a Cohesive Zone Model

Adhesively bonded joints are widely used in automotive industry. Adhesively bonded joints permit to have more uniform stress distributions, join complex shapes, and reduce the weight of the structures. The requirement to reduce the weight of automobiles is also increasing the application of composites. In this article, CFRP (carbon fiber-reinforced plastics) composite was used in experimental tests. In many cases, adverse environments cause non-negligible degradation in joints mechanical performance. So a combined experimental–numerical approach was developed to characterize the effect of cyclic-temperature environment on adhesively bonded joints. Experimental tests were carried out on single-lap joints with CFRP and steel adherend in a cyclic-temperature environment. A cohesive zone model was taken into consideration to predict the results observed during the experimental tests and an environmental degradation model was developed. Scanning electron microscopy was utilized to investigate the fracture surfaces.     

Modelling the Environmental Degradation of the Interface in Adhesively Bonded Joints using a Cohesive Zone Approach

The use of a cohesive zone model (CZM) to predict the long-term durability of adhesively bonded structures exposed to humid environments has been investigated. The joints were exposed to high relative humidity (RH) environments and immersion in both tap and deionised water for up to a year before quasi-static testing to failure. Both stressed and unstressed conditions during aging were considered. The degradation was faster for the stressed joints and for those joints immersed in the more corrosive environments. Two mechanisms were suggested to explain this behaviour: cathodic delamination and stress-enhanced degradation. In the model, the cohesive zone parameters determine the residual strength of the joints. The degradation of these parameters was, in the first instance, related directly to the moisture concentration. The model was then extended to include degradation due to stress and more corrosive environments. Good correlation between the numerical modelling and the experimental results was obtained.     

Modelling the Environmental Degradation of the Interface in Adhesively Bonded Joints using a Cohesive Zone Approach

The use of a cohesive zone model (CZM) to predict the long-term durability of adhesively bonded structures exposed to humid environments has been investigated. The joints were exposed to high relative humidity (RH) environments and immersion in both tap and deionised water for up to a year before quasi-static testing to failure. Both stressed and unstressed conditions during aging were considered. The degradation was faster for the stressed joints and for those joints immersed in the more corrosive environments. Two mechanisms were suggested to explain this behaviour: cathodic delamination and stress-enhanced degradation. In the model, the cohesive zone parameters determine the residual strength of the joints. The degradation of these parameters was, in the first instance, related directly to the moisture concentration. The model was then extended to include degradation due to stress and more corrosive environments. Good correlation between the numerical modelling and the experimental results was obtained.     

Fatigue Analysis of Adhesive Joints Under Vibration Loading

Adhesively bonded joints have been used extensively for many structural applications. However, one disadvantage usually limiting the service life of adhesive joints is the relatively low strength for peel loading, especially under dynamic cyclic loading such as impulsive or vibrational forces. Moreover, accurately predicting the fatigue life of bonded joints is still quite challenging. In this study, a combined experimental–numerical approach was developed to characterize the effect of the cyclic-vibration-peel (CVP) loading on adhesively bonded joints. A damage factor is introduced into the traction-separation response of the cohesive zone model (CZM) and a finite element damage model is developed to evaluate the degradation process in the adhesive layer. With this model, the adhesive layer stress states before and after being exposed to various CVP loading cycles are investigated, which reveals that the fatigue effect of the CVP loading starts first in the regions close to the edges of the adhesive layer. A good correlation is achieved when comparing the simulation results to the experimental data, which verifies the feasibility of using the proposed model to predict the fatigue life of adhesively bonded joints under the CVP type of loading.     

Strength Prediction of Adhesively Bonded Single Lap Joints Under Salt Spray Environment Using a Cohesive Zone Model

The aim of this research was to develop an experimental–numerical approach to characterize the effect of salt spray environment on adhesively bonded joints and predict the degradation in joint strength. Experiments were conducted on bulk adhesive specimens and single lap joints (SLJs) under salt spray condition and the corresponding experimental results were reported. The environment degradation factor, Deg, was incorporated into a bilinear cohesive zone model (CZM) to simulate the degradation process of the joints. The degraded CZM parameters, determined from static tests on bulk adhesive, were imported into the CZM using an approximate moisture concentration gradient approach. The reduction in residual strength of SLJ under salt spray environment was successfully predicted through comparing the experimental and numerical results.     

O形环膨胀节的设计与有限元分析

介绍了O形环膨胀节的结构设计 ,并对已运行的两台换热器上的膨胀节进行了有限元法分析 ,为进一步搞好膨胀节安全可靠的设计奠定了基础     

Finite Element Modeling of Particle Adhesion: A Surface Energy Formalism

The adhesion of particles is modeled with finite element analysis using an energy approach comparable with that used in the JKR formalism. The strain energy of a cylindrically symmetric system, comprising a particle adhering to a surface with a fixed contact size, is computed as a function of contact size and then added to an energy term that is linearly proportional to the contact patch area. These computations also include contributions from the potential energy of a body force comparable with that which might be applied by a centrifuge. The results show regions of stability (adhesion) where a local energy minimum exists and regions of release where separation of the particle from the surface leads to a continuous decrease in the energy of the system. The effect of the deformation of the particle is included implicitly as a result of the FEM which provides details of the strains and stresses within the system. Discussion concentrates on the physical meaning of the behaviors and the significance of JKR-like theories that use an effective surface energy to represent electrostatic and van der Waals contributions to the adhesion. Modeling the effects of surface roughness of particles and the plastic deformation of particles through an effective surface energy is considered.     

Finite Element Modeling of Particle Adhesion: A Surface Energy Formalism

The adhesion of particles is modeled with finite element analysis using an energy approach comparable with that used in the JKR formalism. The strain energy of a cylindrically symmetric system, comprising a particle adhering to a surface with a fixed contact size, is computed as a function of contact size and then added to an energy term that is linearly proportional to the contact patch area. These computations also include contributions from the potential energy of a body force comparable with that which might be applied by a centrifuge. The results show regions of stability (adhesion) where a local energy minimum exists and regions of release where separation of the particle from the surface leads to a continuous decrease in the energy of the system. The effect of the deformation of the particle is included implicitly as a result of the FEM which provides details of the strains and stresses within the system. Discussion concentrates on the physical meaning of the behaviors and the significance of JKR-like theories that use an effective surface energy to represent electrostatic and van der Waals contributions to the adhesion. Modeling the effects of surface roughness of particles and the plastic deformation of particles through an effective surface energy is considered.     

压力容器装配体结构的Patran局部有限元分析

利用MSC.PatranNastran有限元软件,为压力容器装配体结构建立了三维实体几何模型,并对该局部装配结构进行了有限元分析,阐明各部位的力学作用,得出装配体应力和位移的分布规律,为实际的后续分析提供了安全技术保证和数据支持。     

Strength prediction of single- and double-lap joints by standard and extended finite element modelling

The structural integrity of multi-component structures is usually determined by the strength and durability of their unions. Adhesive bonding is often chosen over welding, riveting and bolting, due to the reduction of stress concentrations, reduced weight penalty and easy manufacturing, amongst other issues. In the past decades, the Finite Element Method (FEM) has been used for the simulation and strength prediction of bonded structures, by strength of materials or fracture mechanics-based criteria. Cohesive-zone models (CZMs) have already proved to be an effective tool in modelling damage growth, surpassing a few limitations of the aforementioned techniques. Despite this fact, they still suffer from the restriction of damage growth only at predefined growth paths. The eXtended Finite Element Method (XFEM) is a recent improvement of the FEM, developed to allow the growth of discontinuities within bulk solids along an arbitrary path, by enriching degrees of freedom with special displacement functions, thus overcoming the main restriction of CZMs. These two techniques were tested to simulate adhesively bonded single- and double-lap joints. The comparative evaluation of the two methods showed their capabilities and/or limitations for this specific purpose.     

一种新型航空轮胎—双刚圈轮胎

飞机滑跑阶段航空轮胎在高充气压力、高负荷、大变形条件下与路面相对滑动过程中,摩擦剧烈、生热迅速,对航空轮胎的耐磨性、耐热性、承载等性能提出了更严苛的要求。本文基于4617R20型航空轮胎和耐磨、耐冲击、散热性能优越的“双刚圈”轮胎,采用ABAQUS软件研究分析其静载工况下的径向、横向、纵向、扭转刚度以及以280KM/h 为初始水平速度的制动过程中轮胎的胎面受力及接地性能。分析结果表明：“双刚圈”轮胎的径向刚度比传统轮胎提高约60%,纵向刚度略有下降;胎面等效应力、法向、纵向接触压力分布规律均明显优于传统轮胎;综合轮胎承载能力、接地性能、制动性能,“双刚圈”轮胎均优于传统轮胎,其中C型轮胎综合性能最优越;     

复合材料气瓶有限元应力应变分析

本文利用ANSYS大型有限元程序建立了复合材料气瓶（金属内衬）的有限元模型,建模中将纤维缠绕层作为复合材料层合板处理,考虑了封头处缠绕层厚度及缠绕角沿子午线不断变化的情况。针对建立的模型进行了气瓶在几个工况点下的变形分析,通过在30MPa压力、45MPa压力下的位移分析和试验测量对比,分析和试验结果分别为6．25MPa和5．86MPa、8．48MPa和7．69MPa,误差分别为9．3％、9．O％,均在10％以内。利用最大应变准则预测了气瓶的爆破压力约为66MPa。两次爆破试验中,测得的爆破压力分别为65MPa和68MPa。结果表明,建模与分析方法县诈确的．     

有限元分析在快开盲板筒体设计中的应用

利用有限元软件对快开盲板筒体结构进行仿真模拟,得到了应力分布云图和位移分布图,并采用JB4732对其进行了强度刚度分析。所得结论对今后快开盲板筒体结构设计具有指导作用。     

内伸入式接管焊接接头应力的有限元分析

本文应用Ansys有限元应力分析软件,根据钢制化工容器结构设计规定(HG20583-1998),分别建立内部施焊和外部施焊的内伸入式接管与壳体间焊接接头的模型,分析焊接接头处应力分布的情况,并对焊接接头处的应力进行对比。对比结果表明:a类焊接接头所受应力最大;c类焊接接头应力相对较小;b类焊接接头受力效果最好。若可以对焊缝的坡口连接拐点附近进行优化,可以大大的减小应力水平,改善焊缝的受力情况。     

有限元分析在ABS控制面板模具设计中的应用

通过对丙烯腈-丁二烯-苯乙烯塑料(ABS)控制面板制件进行模流分析,即对模具进行冷却水道系统设计,可以提高模具的生产效率,避免发生翘曲变形等问题,还可以尽早发现ABS控制面板模具的质量问题,同时优化模具结构,减少塑料模具修复次数。选取咖啡机ABS控制面板为例,对其模板进行模流分析,进而对冷却水道系统设计和控制面板模具的强度和刚度进行分析。实验结果表明,选择冷却水孔尺寸为?10 mm,采用外进内出的进出水口设置,并且向水孔位置进行适量移动调整,经过冷却、充填、保压、翘曲模拟分析,冷却均匀性效果达到最好,最大变形量达到最小为0.648 9 mm,冷却时间为12.97 s,模具温度为55.81℃。使用ANSYS软件对矩形型方孔与组合式圆孔进行模板的强度与刚度分析,并通过对比计算理论值与ANSYS分析值,验证ANSYS分析结果的精确性。在矩形型方孔中,最大应力值为101.613 MPa,最大变形量为0.005 962 mm。在组合式圆孔中,最大应力值为131.434 MPa,最大变形量为0.045 398 mm。     

Behavior and failure of adhesive bonds in pin fin heat sinks using cohesive zone model

Adhesive bonding is a versatile material joining method that tends to distribute the load over the bonded area and provide more flexibility in selecting the base material without worrying about the joining process and its effects. To improve the performance of heat sinks, polymer composite pin fin are used to improve the thermal conductivity. Adhesives are usually used in bonding composite fins to their metal base plate. In this work we provide a methodology for estimating the fatigue life of the adhesive joint. A thermo-mechanical cohesive zone model (CZM) is used at the interfaces to measure the softening of the bond under thermal cyclic loading which in turn decreases the critical stress for failure. A summary of the fatigue crack initiation (FCI) life prediction model is presented before a qualitative study is performed to estimate the effect of convection environment on the life and behavior of the adhesive bond.     

玻璃钢筋混凝土的有限元计算与试验

钢筋混凝土广泛应用于土木工程领域，但其结构耐久性因钢筋本身的锈蚀成为现今急待解决的问题。人们一直在寻找对钢筋混凝土进行改良的途径，用玻璃钢筋代替普通钢筋是解决这一问题的一个有效的方法，为此进行了试验和ANSYS有限元分析，结果证明此法具有可行性。     

Influence of Acrylic Adhesive Viscosity and Surface Roughness on the Properties of Adhesive Joint

In adhesion, the wetting process depends on three fundamental factors: the surface topography of the adherend, the viscosity of the adhesive, and the surface energy of both. The aim of this paper is to study the influence of viscosity and surface roughness on the wetting and their effect on the bond strength. For this purpose, an acrylic adhesive with different viscosities was synthesized and some properties, such as viscosity and surface tension, were studied before adhesive curing took place. Furthermore, the contact angle and the lap-shear strength were analyzed using aluminum adherends with two different roughnesses. Scanning electron microscopy was used to determine the effect of the viscosity and the roughness on the joint interface. The results showed that the adhesive exhibits an optimal value of viscosity. Below this value, at low viscosities, the low neoprene content produces poor bond strength due to the reduced toughness of the adhesive. Additionally, it also produces a high shrinkage during curing, which leads to the apparition of residual stresses that weakens the interfacial strength. However, once the optimum value, an increase in the viscosity produces a negative effect on the joint strength as a result of an important decrease in the wettability.     

计及胎面花纹的子午线轮胎接地性能有限元分析

采用Abaqus软件建立带有部分胎面花纹的三维轮胎有限元模型,模拟研究不同工况下子午线轮胎的接地性能.研究结果表明：轮胎在静负荷和自由滚动工况下应力分布相似,沿轮胎中分面基本对称,最大应力在胎肩部位;在驱动工况下,高应力区向轮胎前进的反方向扩展,制动工况与此相反;在斜坡路面的应力分布与自由滚动时相似,但最大应力有所提高;侧偏滚动工况下的应力主要分布在轮胎的中分面及与侧偏方向相同的一侧,应力值明显提高.