Dissimilar Material Joints Research Articles

Laser surface pretreatment of metal for joints of metal and dissimilar materials

Joining technology of metal and dissimilar materials is attracting attention in various industrial fields. Especially in the automotive industry, the joining of metal and plastics is expected to be a key technology for weight reduction. A new joining technology of metal to plastics has been developed by laser surface pretreatment to metal. The pretreatment is done by a continuous wave (cw) single mode fiber laser. High energy density and high scanning speed are required for making characteristic surface shapes of metal that are suitable for joining. The characteristic shape is not just a simple corrugation, but has tunnel-like shapes, which is called as stitch anchor. In the present work, a laser beam of 10–30 μm in diameter is focused on the work piece. The intensity is more than 10 MW/cm2. To make stitch anchor, the laser beam is moved at more than 2 m/s using Galvano-mirrors. It is confirmed that the characteristic surface shape is not only good for metal-plastics joining, but also for metal-metal, metal-rubber, and metal-adhesive-metal joining.

Using Sealants for Gluing Dissimilar Materials

Data on gluing of various nonmetallic materials, as well as dissimilar materials with different TLEC values using Viksint U-2-28 and Viksint U-10-80 organosilicon sealants, as well as Elasil 137-175M organosilicon adhesive sealant, are given. It is shown that adhesive joints of dissimilar materials with different TLEC values could resist impact and pulse loads upon operation, while adhesive joints of nonmetallic materials operate under bending loads.

Effect of adhesive layer properties on the shear strength of single-lap structures of dissimilar materials based on the cohesive zone model

An analysis method for improving the shear strength for the single-lap joints of dissimilar materials based on the cohesive zone model (CZM) is presented in this paper. The shear-lag model is established for the single-lap joint, and the stress distribution of joints is derived on the basis of this model, which is verified by simulation. The bilinear CZM is constructed to simulate the fracture process of joints, and the influence of lap length and adhesive layer thickness on the stress distribution of adhesive layers is comprehensively analyzed through simulation. Therefore, the effects of different properties of adhesive layers on the bonded structure strength are discussed with experiments. Results show that the reasonable lap length and thickness in this work are, respectively, 20–22 and 0.4–0.6 mm. The research results will serve as a guide for the parameter design, fracture prediction, and performance optimization of bonded joints.

Effect of filler on strength characteristic of a dissimilar materials joint between surface-treated metal and rubber

Effect of filler on strength characteristic of a dissimilar materials joint between surface-treated metal and rubber

Superior Durability of Dissimilar Material Joint between Steel and Thermoplastic Resin with Roughened Electrodeposited Nickel Interlayer

Superior Durability of Dissimilar Material Joint between Steel and Thermoplastic Resin with Roughened Electrodeposited Nickel Interlayer

Thermo-mechanical stress analysis of dissimilar material joints using FEM

Abstract: This article presents numerical investigation of isotropic dissimilar material joints. Dissimilar material joints are broadly used in in various structures, including offshore, nuclear, electronic packaging, IC chip and spacecraft various fields of science and technology. In bi-material joints two different material are bonded with common interface region. High stress concentration occur at the interface of the joint under thermo-mechanical loadings due to the difference in the elastic properties and the thermal expansion coefficients of dissimilar materials. The stresses acting along the interface of dissimilar material joints are very important to determine whether the structure is reliable or not for operation. The main purpose of this research is to provide finite element solutions to predict the stress distribution at the interface of the joint based on the theory of elasticity. Keywords: Numerical Investigation, Dissimilar material joints, Stress concentration, Stress distributions, Theory of elasticity.

Analysis of tool wear and deformation in friction stir welding of unequal thickness dissimilar Al alloys

Friction stir welding between plates of unequal thickness, which are made from similar or dissimilar materials, finds wide range of applications in the aerospace and automotive sectors. Friction stir welding of plates made from dissimilar materials having unequal thicknesses is challenging. One of the major challenges is the control of rapid tool degradation which occurs during welding. This work reports a maiden study on tool degradation of high thickness ratio unequal thickness dissimilar material joints made between 6.3 mm thick AA2024-T3 and 2.5 mm thick AA7475-T7 plates. The degradation of friction stir welding tool made of T4 tool steel having tapered cylindrical pin and scrolled shoulder was analyzed. The geometry of tool (before and after welding) was compared; the degradation was categorized, characterized, and analyzed in the light of measured welding temperature, process forces, and process parameters. It was found that the pin undergoes significant degradation in the form of wear and deformation compared to the tool shoulder. The experimental results demonstrated that lower flow stresses caused by higher process temperature leads to lower tool wear and deformation, and vice versa. In addition to temperature and process forces, the surface tilt angle was found to significantly affect the pin deformation. The higher surface tilt angle caused an increase in tool wear and deformation.

Superior Durability of Dissimilar Material Joint between Steel and Thermoplastic Resin with Roughened Electrodeposited Nickel Interlayer

The durability of the dissimilar material joint between a steel coated with a roughened nickel plating‐film and a thermoplastic resin is assessed. The roughened nickel film is fabricated by electrodeposition using carbon nanotubes (CNTs) as the roughening agent and a polyphenylenesulfide (PPS) resin as the thermoplastic resin. The plated steel and PPS resin are joined by injection molding without adhesive. The bonding strength is determined by a tensile lap shear strength test during the durability tests that includes a high‐temperature and high‐humidity test (85 ± 2 °C, 85 ± 2% relative humidity; 0–2000 h) and a thermal shock test (−50 °C–150 °C; 0–1000 cycles). During the high‐temperature and high‐humidity test, the bonding samples maintain their initial bonding strength (>40 MPa) even after 2000 h. By contrast, during the thermal shock test, although the bonding strength gradually decreases with increasing number of cycles, it remains above 20 MPa even after 1000 cycles. The mechanism of the deterioration of the bonding strength during the thermal shock test is analyzed in detail. The present joining method, which uses a roughened plating film as an interlayer, offers a way to achieve not only high initial bonding strength but also bonding durability for dissimilar material joining between steels and resins.

Experimental measurement of mode-I fracture toughness of dissimilar material joints with thermal residual stresses

The current study presents a novel test method to experimentally cancel out the thermal stresses in dissimilar material joints. For the commonly used double cantilever beam test the presence of thermal stresses results in a significant mode mixity at the crack tip, which varies with applied load even if the elastic properties of the adherends are similar. This is particularly a challenge for fibre reinforced plastics bonded to metals due to the large difference in thermal expansion coefficients. The presence of mode-II loading is likely to provide a higher fracture energy from experiments than if tested under pure mode-I loading, which can lead to non-conservative results when using standard test methods. To overcome this challenge a novel test method inspired by the mixed mode bending test is developed. It is shown that the thermal stresses can be cancelled by applying initial constant loads during testing, and that the fracture toughness under pure mode-I loading can be obtained under specific conditions. The test method is validated by carrying out virtual compliance calibration experiments using cohesive zone finite element modelling. As the test method relies solely on analytical calculations and can be used with standard test equipment, it is relatively simple to apply in practice.

Experimental and numerical failure analyses of dissimilar material joints between aluminium and thermoplastic

In the automotive industries, joining of dissimilar materials has extensively attracted interest, because combinations of various lightweight materials in car bodies becomes more significant in order to achieve the most optimum design. On the other hand, several techniques for hybrid assembly have been continuously developed. In this work, aluminium sheets A5052 were joined with PBT-30GFR using two different methods, namely, hot pressing and adhesive bond. Then, resulted load carrying capacities were evaluated by means of single-lap joint (SLJ) specimens and occurred failure mechanisms were examined. Effects of surface treatments for aluminium samples on the strength of SLJ samples were also studied. Furthermore, FE simulations of single-lap shear tests were performed, in which cohesive zone (CZ) model was applied for representing the separation and subsequent failure behaviour of SLJ specimens. The parameters of the traction-separation law were individually determined for each joining techniques by mode-I and mode-II fracture toughness tests. Afterwards, force-displacement curves, maximum loads and failure occurrences of SLJ specimens with different overlap lengths were predicted. It was found that the proposed FE models and CZ parameters could correctly describe the experimental results of both joining methods.

A Study of Thermal Characteristics in DC Pulsed Gas Metal Arc Welded Joints of Dissimilar Materials (AA5052 - DP590 GA) by Numerical Analysis

A Study of Thermal Characteristics in DC Pulsed Gas Metal Arc Welded Joints of Dissimilar Materials (AA5052 - DP590 GA) by Numerical Analysis

Weldability and mechanical properties of IC10 single crystal and GH3039 superalloy dissimilar laser beam welding joint

The weldability and mechanical properties of IC10 single crystal and GH3039 superalloy dissimilar laser beam welded joint was investigated. The results showed that the dissimilar materials joint was obtained by laser beam welding. The crack sensitivity was reduced in dissimilar weldment. The tensile strength of the dissimilar welded joint is 602 MPa.

The Hybrid Joints between an FRP Panel and a Steel Panel through Tubular Reinforcements: A Methodology for Interlaminar Stress Calculations

The advantages of laminates in terms of the chemical properties and mechanical properties/weight relationship have motivated several applications of fiber-reinforced plastic (FRP) composites in naval constructions due to the reduction in structural weight. This weight advantage has motivated multiple investigations dedicated to dissimilar material joints. We present a methodology for the interlaminar stress calculations of a tubular hybrid joint between an FRP panel and a steel panel through tubular reinforcements. The proposed formulas allow the estimation of the shear and normal stresses on the adhesive, which are generated in the bonding angle of the tubular hybrid joint. The stresses generated at the adhesive bonding ends influence on the adherent’s adjacent layer. A failure criterion is shown to check the accomplishment of the resulting stresses in the adherent laminate. Finally, the proposed formulas are validated using the finite element method and compared with the obtained interlaminar stresses.

Creep-Relaxation Modeling of HDPE and Polyvinyl Chloride Bolted Flange Joints

AbstractSimilar to many polymer materials, high-density polyethylene (HDPE) and polyvinyl chloride (PVC) show a clear creep behavior, the rate of which is influenced by temperature, load, and time. Most bolted flange joints undergo relaxation under compression, which is caused by the creep of the material. However, the creep property of the two polymers is different under tension and compression loading. Since the sealing capacity of a flanged gasketed joint is impacted by the amount of relaxation that takes place, it is important to properly address and predict the relaxation behavior due to flange creep under compression and thereby reducing the chances of leakage failure of HDPE and PVC bolted flange joints. The main objective of this study is to analyze the compressive creep behavior of HDPE and PVC flanges under normal operating conditions. This is achieved by developing a respective creep model for the two materials, based on their short-term experimental creep test data. Both numerical and experimental simulations of the polymeric flange relaxation behavior are conducted on an NPS 3 class 150 bolted flange joint of dissimilar materials, where one of the flanges is made of HDPE or PVC material and the other one is made of steel SA105. The study also provides a clear picture on how the compression creep data of ring specimen may be utilized for predicating the flange bolt load relaxation over time at the operating temperatures.

A discrete element model simulation of structure and bonding at interfaces between cathode and cathode contact paste in solid oxide fuel cells

For the first time, the impacts of solid oxide fuel cell (SOFC) cathode/contact paste interface roughness on mechanical strength are quantified using a particle based numerical technique in micro-scale. This work identifies a potential new direction to develop high strength SOFC stack structures to enhance SOFC long-term durability with most commonly used material. To model the effect of different interface roughness values on the integrity of the dissimilar material joint as well as the fracture behavior of the bonded interface, a discrete element model (DEM) method is adapted due to many unique advantages. The model demonstrates that interfacial toughness increases with interfacial roughness and sintering temperatures. In particular, the roughened interface can increase ultimate mechanical strength to a factor of 2–3 compared with the smooth interface. Moreover, contact paste with higher stiffness properties can be beneficial in terms of delaying the onset of the initial interfacial damage at rough interfaces. The results also show that toughness decreases with increasing strength ratio between the interface and contact paste. It is expected that this study can provide guidance to improve SOFC cathode design with better mechanical strengths, which would benefit the mechanical integrity of the SOFC stack.

Diffusion Bonding and Transient Liquid Phase (TLP) Bonding of Type 304 and 316 Austenitic Stainless Steel—A Review of Similar and Dissimilar Material Joints

Similar and dissimilar material joints of AISI grade 304 (1.4301) and AISI grade 316 (1.4401) austenitic stainless steel by solid state diffusion bonding and transient liquid phase (TLP) bonding are of interest to academia and industry alike. Appropriate bonding parameters (bonding temperature, bonding time, and bonding pressure) as well as suitable surface treatments, bonding atmosphere (usually high vacuum or protective gas) and interlayers are paramount for successful bonding. The three main parameters (temperature, time, and pressure) are interconnected in a strong non-linear way making experimental data important. This work reviews the three main parameters used for solid state diffusion bonding, TLP bonding and to a smaller degree hot isostatic pressing (HIP) of AISI grade 304 and AISI grade 316 austenitic stainless steel to the aforementioned materials (similar joints) as well as other materials, namely commercially pure titanium, Ti-6A-4V, copper, zircaloy and other non-ferrous metals and ceramic materials (dissimilar joints).

Microstructure & mechanical properties of dissimilar material joints between T91 martensitic & S304H austenitic steels using different filler wires

The power generating sector uses combination of both ferritic steels, employed at temperatures below 635 °C and stainless steels at steam temperatures above 635 °C in a boiler. Considerable savings on cost is made by dissimilar metal welding of the economical steels replacing the expensive high alloy steels. The austenitic steels have the better stability of microstructures at high temperature and creep strength along with good corrosion resistance whereas ferritic steels have good thermal conductivity and mechanical properties. The austenitic steels are expensive as the contents of alloying element is high. Consequently, different steels are chosen from both service and economical point of view in a boiler as per the requirements, satisfying both performance parameters and savings.Until now, many previous studies have focused mainly on the individual properties of austenitic stainless steel (S304H/Super304H/ SA213 S30432) and martensitic steel (T91), however, there is almost no report about T91 and Super304H dissimilar materials joints with Semi-Automatic Gas Tungsten Arc Welding (SGTAW) process using three different filler wire. Therefore, in the present study, the Super304H and T91 was welded together using SGTAW process by using ERNiCrCoMo-1, ER90S-B9 and YT304H filler material. The dissimilar material welding was studied for mechanical properties and microstructure in this paper.

Microstructural and micromechanical assessment of aged ultra-fast sintered functionally graded iron/tungsten composites

Functionally graded (FG) iron/tungsten (Fe/W) composites are considered for stress-relieving interlayers in tungsten-steel joints, required in future fusion reactors. The macroscopic gradation of the two materials allows relaxation of thermally-induced stresses and hence extend the lifetime of the cyclic-loaded dissimilar materials joints. While many properties, e.g. thermal expansion and strength, of the as-manufactured Fe/W composites are promising with respect to the anticipated application, the temperature-induced microstructural changes and their effect on the material properties remain largely unexplored. Given that the thermodynamic system of FeW contains two types of intermetallic phases, understanding the microstructural changes in the FG Fe/W composites is crucial for long-term operation of fusion reactors.In the present work, the microstructure of ultra-fast sintered Fe/W composites containing 50 and 75 vol% tungsten is studied via electron microscopy (SEM) and X-ray diffraction (XRD) in as-manufactured and thermal aged conditions (300, 500, and 800 °C for up to 72 h). The hardness and modulus of selected composites are measured via nanoindentation, and the fracture toughness of the FeW interfaces is tested via notched micro-cantilever bending tests. The results from microstructural and micromechanical analyses are discussed, and the materials are evaluated for their application in fusion reactors based on the microstructure-to-property relationship.

Laser Welding of Dissimilar Materials Based on VT20 Titanium and V-1461 Aluminum Alloys

This paper describes the experimental study of strength characteristics and the microstructure of a permanent joint of dissimilar materials (VT20 titanium alloy and V-1461 aluminum alloy), obtained by laser butt welding. Optical and electron microscopy, X-ray spectral and phase analysis, and the transmission diffraction method with the help of synchrotron radiation are all used to investigate the properties of a weld. It is shown that the laser radiation offset relative to the contact surface of dissimilar materials significantly changes the microstructure and phase composition of the intermetallic interlayer formed between the materials welded, thereby affecting the strength of dissimilar welded joints.

Quantitative Weld Quality Acceptance Criteria: An Enabler for Structural Lightweighting and Additive Manufacturing

Most of the existing weld quality acceptance criteria stipulated in various codes and standards, as well as in recommended practices, are empirical in nature. Historically, these workmanship-based criterias have been adequate for quality control purposes in construction of welded structures. However, as the competition for achieving structural lightweighting intensifies, more quantitative quality acceptance (also known as fitness-for-purpose based) criteria are increasingly called for. This is because various new forms of discontinuities and joint configurations (e.g., dis-similar materials joints) cannot be readily related to existing acceptance criteria. Even if existing criteria can be made applicable, recent research findings have shown that existing criteria can be excessively conservative for some and unconservative for others when dealing with thin gauge and lightweight construction. A similar situation exists for additively manufactured metallic components, which can be viewed as “all weld metal” components containing randomly distributed discontinuities over the entire component volume. In this paper, some of the recent developments in quantitative weld quality acceptance criteria will be first highlighted, some of which are made possible by advanced fracture mechanics analysis techniques. Applications in structural lightweighting and additive manufacturing will then be demonstrated with some real-world examples. Finally, implications on a broader application of the methodologies presented for ensuring both structural integrity and cost-effectiveness in construction will be discussed in light of these developments.