Joining Of Dissimilar Materials Research Articles

The application of equivalent modeling of joints for bending simulation of hybrid aluminum/high strength steel thin-walled sections joined by clinching

Fuel economy and stringent environmental regulations have forced the automotive industry to adopt lightweight materials for car bodies. Utilization of multi-materials is an effective approach for lightweight design of the automotive body structure. Introducing such lightweighting solutions faces the automotive industry with challenges in terms of joining methods. Clinching is a cost-effective alternative of conventional spot welding which enables joining of similar and dissimilar materials by local plastic deformation. This study undertakes the experimental and numerical investigation of the bending energy absorption of a multi-material aluminum alloy Al 5052/SPFC 390 high strength steel clinched beam by means of a quasi-static three-point bending test. Connector elements with six degrees of freedom are employed as simplified equivalent models of the beam clinched joints in software ABAQUS. The elastic and plastic behaviors of the connector are calibrated using experimental shear lap and pull-out tests. The calibrated clinch joint model is then used in the bending test simulation of the hybrid clinched beam and the numerical results are validated with experiments. The simulations results are found to be in good agreement with experiments and it is shown that the employed equivalent model can successfully predict the bending behavior of the hybrid material clinched beam.

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.

Magnetic pulse welding of copper to steel tubes–Experimental investigation and process modelling

Abstract Magnetic pulse welding allows joining of metallic tubes by a short electromagnetic pulse and the resulting high strain rate impact and plastic deformation. Since melting of materials is avoided, magnetic pulse welding is an efficient method for joining of dissimilar materials. However, the process occurs very fast with little opportunity for real-time monitoring and control, which is also difficult due to the presence of a high amplitude electromagnetic field. A novel attempt is presented here to examine the underlying phenomena for magnetic pulse welding of copper flyer tubes to steel target tubes by computational process modeling and a focused experimental investigation. A coupled electromagnetic and mechanical finite-element model was created to compute the electromagnetic field and pressure distribution, and the progressive nature of flyer tube impact velocity on the target tube. The consequent progress of the angle of impact and contact length are examined for a range of standoff distances between the flyer and target tubes, the target tube wall thickness. The computed results are validated extensively with corresponding experimentally measured results. Overall, the coupled theoretical and experimental investigation provided a useful quantitative insight of magnetic pulse welding of copper and steel tubes, which is expected to help in the advancement of practical application of the process.

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.

Alleviation of Stress Concentration with Rivet-Like Joints Fabricated by Friction-Stir Forming

In this paper, the authors propose a design for the mechanical joining of dissimilar materials by employing rivet-like structures fabricated by friction-stir forming (FSF) considering the stress concentration on the joined material. The authors have utilized the FSF approach to generate rivet-like joints as follows. First, a substrate material (an aluminum alloy plate) was placed on a joined dissimilar-material plate containing prepared holes, i.e., a steel plate. Afterwards, these materials were placed on a die containing the cavity to fabricate the head of the rivet-like structure. FSF was then conducted to form the stems and heads of the rivet-like structure from the substrate material. Unlike conventional riveting, fastener was not considered necessary for the process; therefore, choosing different diameters of the prepared holes with multiple joints for the optimization of their structural design was easier. It is known that two auxiliary holes neighboring a main hole on either side reduce the stress concentration on the rim of the main hole. In this study, the authors applied the “round-hole-array design” on rivet-like joints fabricated by FSF. The authors examined the design of two smaller prepared holes with a commercial Finite element analysis (FEA) software for the rivet-like joint containing a 4 mm-diameter hole on a joined plate. To prove this, a 3 mm-thick A5083P-O aluminum alloy plate and a 0.7 mm-thick and 20 mm-wide SPCE steel plate was joined with the suggested design, and the strength and fracture of the joints were investigated using the tensile shear test. As a result, all joints were destroyed by the facture of the prepared holes, and it was confirmed that their strength was improved by the round-hole-array design.

On the Surface Quality of CFRTP/Steel Hybrid Structures Machined by AWJM

The joining of dissimilar materials in a hybrid structure is a line of research of great interest at present. Nevertheless, the machining of materials with different machinability requires specific processes capable of minimizing defectology in both materials and achieving a correct surface finish in terms of functional performance. In this article, abrasive water jet machining of a hybrid carbon fiber-reinforced thermoplastics (CFRTP)/Steel structure and the generated surface finish are studied. A parametric study in two stacking configurations (CFRTP/Steel and Steel/CFRTP) has been established in order to determine the range of cutting parameters that generates the lowest values in terms of arithmetic mean roughness (Ra) and maximum profile height (Rz). The percentage contribution of each cutting parameter has been identified through an ANOVA analysis for each material and stacking configuration. A combination of 420 MPa hydraulic pressure with an abrasive mass flow of 385 g/min and a travel speed of 50 mm/min offers the lowest Ra and Rz values in the CFRTP/Steel configuration. The stacking order is a determining factor, obtaining a better surface quality in a CFRTP/Steel stack. Finally, a series of contour diagrams relating surface quality to machining conditions have been obtained.

Interfacial microstructure characterization of aluminum/aluminum-lithium joints fabricated by magnetic pulse welding

Magnetic pulse welding (MPW) is a cost-effective solid-state welding technology, which is mainly used in the lap joining of similar and dissimilar materials. It has broad application prospects in aerospace, automotive and appliance industries. In this paper, the corrosion-resistant 5052 aluminum alloy (Al) and the high-strength 2A66 aluminum-lithium alloy (AlLi) were joined by MPW. The interface microstructure of Al/AlLi welded joints was characterized and analyzed by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the welding interface was composed of four zones: the molten zone with porous structure, the shear molten zone, the sine wave interface zone and the flat interface zone. It can be seen that the shear molten zone consisted of ultra-fine equiaxed grains, which were formed by the rapid melting and solidification of Al alloy at the interface. A fine grain layer was observed at the sine wave interface, and some precipitated phases disappeared inside the fine grains. These were caused by dynamic recrystallization and a certain temperature rise at the interface. The precipitated phases near the fine grain layer only deformed to a certain extent and did not dissolve. This showed that the grains outside the fine grain layer were only subjected to a certain impact without severe deformation and temperature rise, reflecting that the heat-affected zone (HAZ) of MPW was very narrow.

Physical and mechanical characterization of dissimilar laser welded joints of AISI 316/Cu/SMA using fiber laser technology

The present study explores an experimental investigation of dissimilar welding of austenitic stainless steel (AISI 316) with nitinol (NiTi) plates by inserting copper (Cu) as an interlayer using a fiber laser system. The presence of copper influences controlling the formation of brittle intermetallic compounds forming compounds of copper with iron, titanium, and nickel. The weldments are examined to understand the physical and mechanical properties of the joints. A micrograph study of welded joints shows a crack-free surface and reveals the nature of solidification in the weld zone. The analysis of pores in the weldment indicates the presence of 1.89%, 2.26%, and 6.32% of pores in the weld zone area of three different weldment samples, 1, 2, and 3, respectively, and the obtained porosity percentage was quite satisfactory. The insertion of copper helps in attaining the welded joints bearing a tensile strength of 219.74 MPa. The failure of the welded joint shows a mixed nature of fracture. This study suggests that the presence of an interlayer during joining of dissimilar materials provides stable, crack-free, and less brittle joints as compared to joining of dissimilar materials without an interlayer. The author of the article agrees to the retraction of the article effective JULY 12, 2021.

Rapid surface activation of carbon fibre reinforced PEEK and PPS composites by high-power UV-irradiation for the adhesive joining of dissimilar materials

Carbon fibre reinforced poly-etherether-ketone (PEEK) and poly-phenylene-sulfide (PPS) composites were rapidly surface-treated by high-power UV light, and then adhesively bonded to aluminium 2024-T3 and carbon fibre/epoxy composites. The results of a single lap-shear joint test demonstrated that a UV-treatment lasting for 5 s was sufficient to prevent joint failure occurring at the composite/adhesive interfaces in all cases, e.g. it increased the failure strength of the PPS composite/aluminium joints from 11.1 MPa to 37.5 MPa. Moreover, the composite/adhesive interfaces performed well upon an exposure of the joints to an environment of high humidity and temperature for 8 weeks. Additionally, an investigation lasting for 6 months showed no degradation of the surface functionalisation from UV-irradiation. Overall, this work highlights high-power UV-irradiation a very promising method for surface preparation of thermoplastic composites (TPCs) for adhesive joining, i.e. TPC adhesive joints with excellent structural integrity can be obtained by using this rapid, eco-friendly and low-cost surface-treatment method.

Rapid surface activation of carbon fibre reinforced PEEK and PPS T composites by high-power UV-irradiation for the adhesive joining of dissimilar materials

Rapid surface activation of carbon fibre reinforced PEEK and PPS T composites by high-power UV-irradiation for the adhesive joining of dissimilar materials

Model-based, multi-material topology optimization taking into account cost and manufacturability

Multi-material topology optimization has become a popular design optimization discipline since it allows to go a step further in topology optimization of the design of lightweight components and structures. However, it also presents additional challenges in terms of managing a higher complexity in the optimization problem, reliably estimating the manufacturing cost taking into account the cost of joining dissimilar materials, or assessing the manufacturability of the design. This paper proposes a set of methods that solve generic multi-material topology optimization problems, while including several novel aspects such as a comprehensive cost model, specific design rules for multi-material design, and model order reduction techniques to improve the computational efficiency. Two different examples, consisting of a sitting bench and a car cowling, have been solved in order to support the benefits of the approach.

Influence of Friction Stir Processing on Weld Temperature Distribution and Mechanical Properties of TIG-Welded Joint of AA6061 and AA7075

The joining of dissimilar materials is required in many engineering and defense applications, and the conventional fusion welding often results in defective welds. The friction stir welding has minimized the welding defects, but not completed. This work focuses on the effect of friction stir processing on TIG-welded joints with filler ER 5356 to improve the mechanical properties of TIG-welded joints. In this paper, the FSP tool pin rotates on an already welded joint by TIG welding to lower the welding load and improve the weld quality by adjusting the processing parameters of friction stir processing. After analyzing the mechanical properties of TIG + FSP-welded joint, computational fluid dynamics-based numerical model was developed to predict the temperature distribution and material flow during TIG + FSP of dissimilar aluminum alloys AA6061 and AA7075 by ANSYS fluent software. The minimum compressive residual stress 18 MPa, maximum tensile strength (281.1 MPa) and hardness (107 HV) were located at the nugget zone of the TIG + FSP weldment at tool rotation speed of 1300 rpm, traverse speed of 30 mm/min and tilt angle 2°. The predicted peak values of temperature at the weld region were calculated and the maximum temperature (505 °C) and maximum heat flux (2.93 × 106 w/m2) were observed at a tool rotation of 1300 rpm.

Modelling of intermetallic layers formation during solid-liquid joining of dissimilar metallic materials

Joining of dissimilar metallic materials gives rise to the production of components with improved properties. At the joint interface, the formation of brittle intermetallic layers might deteriorate the component application. Therefore, its formation and growth must be well understood and carefully controlled. Numerical simulations assist in the determination of processes parameters to obtain the desired bond characteristics. In solid-liquid joining processes, the melt movement plays an important role und must be accounted in the simulations. In this paper, a mathematical model at the continuum scale is used for the description of the interface formation during solid-liquid joining. The description of convection and advection of the molten alloy and the dissolution of the solid substrate are of interest. The substrate dissolution into the melt alters the local composition of the molten alloy, leading to precipitation of intermetallic compounds on the substrate surface during the solidification process. To account for these phenomena, convection heat transfer with phase transformation and diffusion and reaction at the solid-liquid interface are considered in the mathematical model that is based on conservation equations of mass, momentum, energy and species. The different scale problem is solved by applying a dynamic mesh refinement at the interface to accurately solve the intermetallic layer growth. The model was implemented in OpenFoam® and simulation results for the intermetallic layer thickness as a function of solid substrate temperature (Ts) for compound casting between initially liquid Al and a solid Cu substrate are presented. In general, for Ts initial value ranging from 400 to 700 °C while keeping the initial Al melt temperate at 750 °C, the intermetallic layers thickness increases as Ts increases.

A new strategy for high-strength joining of dissimilar materials

A new strategy that utilizes the multicomponent amorphous alloy as the filler metal to join the hard-to-weld dissimilar materials was proposed. The coexistence of multiple principal elements was envisaged to improve the role of mixing entropy and retard the atomic diffusion between the filler metal and base metals, inhibiting the formation of bulky directional intermetallic compounds. To give a theoretical analysis of the phase evolution of the joint and verify the feasibility of this strategy, vacuum brazing of TiAl- and Ni-based alloys with a high-entropy amorphous filler Ti20Zr20Hf20Cu20Ni20 as the filler metal was performed and the phase evolution was analyzed from the perspective of kinetics and thermodynamics. The experimental result showed that a circular solid solution phases firstly formed at high temperature, and fine phases were then precipitated from the solid solutions accompanied by a precipitation strengthening effect to the joint as the temperature decreased. The shear tests showed that a maximum shear strength of 319 MPa can be obtained, and the multiple principal elements filler metal proved to be a promising and feasible approach to solve the difficult joining of hard-to-weld dissimilar alloys.

Metallographic and Microstructure Analysis of Gas Tungsten Arc-Welded Bimetallic Copper-to-Stainless Steel Joints

The steel–copper dissimilar material joining is obtained by gas tungsten arc welding process at different current levels. High Ni-based filler material is used due to its compositional solubility into both Cu and SS aiming to achieve better joint consolidation. The joint is examined on the scale of tensile test, microstructural analysis, microhardness, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. The highest tensile strength of 179 MPa at 150 A current is obtained. On the other hand, defect-free joint of steel–copper at all the parametric conditions is achieved. The post-tensile fracture surface morphology showed a dimple-like structure; the microhardness levels are in the range of 103–228 Hv for fusion zone. The joint assessment indicated successful dissimilar material joining. However, the unmixed zone and partially melted region are identified near the SS/weld metal interface. The mentioned zones are the function of current levels, whereas the tensile property reported marginal variation in the values with the change in current levels. Moreover, defect-free sound joints can be obtained at exploited current levels.

Exploratory study on the effect of amplitude on ultrasonic spot welding of aerospace materials

The recent developments in aerospace materials to enhance the properties of strength to weight ratio led to the joining of dissimilar metals like aluminum to titanium alloys particularly applied in parts like fuselage of aeroplanes prefer better processes to join dissimilar metals with higher joint efficiency. The major issue in joining of dissimilar materials by fusion welding techniques is the rate at which the metals reaches its melting point and flow of material on melting. This can be overthrown by choosing solid state techniques over the conventional ones. The process of Ultrasonic spot-welding leads to be a better option as the joint produced utilizes lower energy than other solid-state techniques with higher productivity and better joint strength. The experiment was carried out with AA6061-T6 (75 × 25 × 1.5 mm) and Ti-6Al-4V (75 × 25 × 0.75 mm) in lap welded position. The experiment aimed at evaluating the effect of amplitude of welding with other parameters set constant. The samples joined with amplitude 90% of the power of machine exposed maximum load carrying capacity of 2.9 kN. The samples that failed exhibited ductile mode of fracture with the parent materials pull apart from each other. From the experimental results, the joints fabricated with lower welding amplitude resulted in joints with lower strength and with amplitude to the maximum capacity of machine resulted in joint with strength lower than the joint that were fabricated at optimum level.

Effect of Process Parameters in Pinless Friction Stir Spot Welding of Al 5754-Al 6061 Alloys

Joining of lightweight dissimilar materials by friction stir spot welding (FSSW) provides numerous advantages over conventional welding methods such as resistance spot welding and self-piercing rivets. However, the keyhole left behind by the tool is a major drawback in FSSW, as it acts as a stress concentration factor and initiates corrosion. In this paper, the keyhole is avoided in FSSW of Al 5754 and 6061 alloys using pinless tools. The process parameters such as tool rotational speed, plunging speed, dwell time, plunge depth, and shoulder diameter were optimized using response surface methodology with Box–Behnken design. The results showed that shoulder diameter was the most crucial factor that affected the joint strength. The micro-hardness analysis indicated the strengthening of the thermo-mechanically affected zone. SEM and EBSD techniques were employed to analyze the microstructure of the weld joint.

Influence of Friction Stir Welding Parameters on Mechanical Properties of dissimilar AA 7475 to AISI 304

Joining of dissimilar materials is difficult and challenging. Trend towards replacement of high density material (HDM) by low density material (LDM) is gaining importance in automotive industries. In the present work, friction stir welding (FSW) of high strength dissimilar materials i.e. aluminium alloy AA7475-T761 and stainless steel AISI 304 was conducted. The mechanical properties and microstructure of butt joint were investigated on using Taguchi L8 orthogonal array (OA). Different combinations of FSW parameters were used to obtain the maximum value of UTS. It was observed that most dominating parameter affecting UTS is tool rotational speed, contributing 42.19%, followed by traverse speed with 38.96% and shoulder diameter with 12.60%. The maximum UTS was observed 75.22% of base material AA 7475 (452MPa) under the optimum combination of parameters; tool rotational speed at 450 rpm, traverse speed 63 mm/min and shoulder diameter 14 mm. The microstructure of the resulted efficient joint shows appreciable variation in grain sizes in different zones and the micro hardness was found maximum in SZ on the retreating side.

Influence of the process temperature on the forming behaviour and the friction during bulk forming of high nitrogen steel

Due to the trend towards lightweight design in car body development mechanical joining technologies become increasingly important. These techniques allow for the joining of dissimilar materials and thus enable multi-material design, while thermic joining methods reach their limits. Semi-tubular self-piercing riveting is an important mechanical joining technology. The rivet production, however, is costly and time-consuming, as the process consists of several process steps including the heat treatment and coating of the rivets in order to achieve an adequate strength and corrosion resistance. The use of high nitrogen steel as rivet material leads to the possibility of reducing process steps and hence increasing the efficiency of the process. However, the high tool loads being expected due to the high strain hardening of the material are a major challenge during the rivet production. Thus, there is a need for appropriate forming strategies, such as the manufacturing of the rivets at elevated temperatures. Prior investigations led to the conclusion that forming already at 200 °C results in a distinct reduction of the yield strength. To create a deeper understanding of the forming behaviour of high nitrogen steel at elevated temperatures, compression tests were conducted in a temperature range between room temperature and 200 °C. The determined true stress – true strain curves are the basis for the further process and tool design of the rivet production. Another key factor for the rivet manufacturing at elevated temperatures is the influence of the process temperature on the tribological conditions. For this reason, ring compression tests at room temperature and 200 °C are carried out. The friction factors are determined on the basis of calibration curves resulting from the numerical analysis of the ring compression process. The investigations indicate that the friction factor at 200 °C is significantly higher compared to room temperature. This essential fact has to be taken into account for the process and tool design for the rivet production using high nitrogen steel.

On the evaluation of a critical distance approach for failure load prediction of adhesively bonded dissimilar materials

The validity of the critical longitudinal strain method (CLS) was proved for a wide range of adhesives and substrates employed in bonding similar substrates (same substrate thickness and material). However, the recent need of weight reduction yields a challenge of joining dissimilar materials, especially where composite laminates are bonded to metal substrates. Based on this industrial demand, the need of using a simple approach for failure load estimation of dissimilar adhesive joints is increasing. The aim of this work is to extend the CLS approach to be able to predict the failure load of adhesively bonded dissimilar single lap joints (SLJs). To achieve this, dissimilar SLJs with a brittle adhesive were manufactured and tested. On the other hand, experimental results of other researchers were also considered where composite substrates were bonded to metal adherends. Based on the results, it was found that by doing a minor modification, the already developed CLS method can be successfully applied to dissimilar SLJs. It is shown that the modified CLS method is able to predict the failure load of dissimilar SLJs with both brittle and ductile adhesives.