Clinch Joints Research Articles

EXPERIMENTAL STUDY ON DP600 CLINCHED JOINTS

Clinching is an effective joining technique for lightweight sheet materials that are difficult or impossible to weld. Clinching is a relatively new technology in which two to three sheet metal parts are joined together by a process of local plastic deformation without the use of any additional components with the application of a special tool. In this study, an experimental investigation of clinch joints was performed. A non-standardized technique was used to determine the optimal joint geometry for further experiments. The used material type was DP600 (dual-phase, advanced high strength steel).

Mechanical Clinching of Titanium and Aluminum-Lithium Sheet Materials

This paper deals with the join-ability of extensible die mechanical clinching in titanium and aluminium-lithium sheet materials. Latest developments in extensible die mechanical clinching processes for sheet materials are reviewed. Clinching process tests were carried out for the dissimilar alloy sheets combinations. To increase the join-ability, TA1 sheets were heated to 700 °C by an oxyacetylene flame gun. The temperature was controlled by an infrared thermometer. Tensile-shear tests were carried out to characterize the mechanical properties of the clinched joints. The quality assessment and failure mode of clinched joints were studied. Results showed that clinched joints of titanium and aluminium-lithium have very good join-ability and load-bearing capacity. It can be inferred from the energy absorption analyse results that the clinch joints failed with neck fracture mode can absorb more energy than that of the clinch joints failed with button separation mode.

Fatigue Analysis of Swept Friction Stir Clinch Joints between Aluminum and Steel Sheets

Fatigue Analysis of Swept Friction Stir Clinch Joints between Aluminum and Steel Sheets

Analyzing alternatives for green logistics in an Indian automotive organization: A case study

Green logistics is an important aspect of production system in today’s world. It combines various efforts to quantify and control the environmental effect of production activities in an enterprise. This research is intended to emphasize upon the ways by which organizations can accomplish positive ecological effects simply by modifying their logistics practices. This paper presents a case study of an Indian automobile company by analyzing alternatives for green practices along with organizational objectives. It is imperative to focus on the green practices in context of Indian automobile sector as the volume of vehicles in India has increased considerably during last few decades. Accordingly, this paper attempts to improve the performance for sustainable adaptation of green practices of an Indian company by selecting the best alternative obtained from the use of Analytical Hierarchy Process to analyze alternatives for green practices in the assembly and packaging processes. Alternatives have been evaluated on the basis of three criteria i.e. green efficiency, factor of safety and ease of operation. The study revealed that clinch joint is the most appropriate alternative for assembly operation while carbon positive packaging material is the best alternative for packaging.

Numerical modeling of mechanical behavior of clinch connections at breaking out and shearing

This article describes an approach to constructing the defining relationships between increment of true stresses and true deformations, with considering the contact interaction of elastoplastic deformed bodies among each other. Within the framework of finite element method, solving these problems in case of “breaking out” and “shearing” in the clinch joint, the stress fields in the zone of the clinch connection are defined, and recommendations are given for realizing the process of their creation.

Finite Element Analysis of Mechanical Clinching Process

In this study numerical simulation of the mechanical clinching process is performed by using the FEA software. Clinching is mechanical joining process, performed with simple tools like punch, die and a blank holder. A 2D axisymmetric model is generated for clinching tools and sheets by using LS-DYNA software. The geometry of the clinching tools affects the strength and quality of the final clinch joint. Mechanical clinching is high speed cold forming process, thus, process simulation is difficult task. Load verses displacement graphs are plotted and validation study carried out with experimental results. Parametrical study is performed to acquire best possible results for good mechanical interlock of two aluminium sheets.

Numerical Investigation of Clinch Connection Manufacturing Process

In the framework of the finite element method, an approach to the solution for the contact interaction problems for elastoplastic deformable bodies with considering friction in the contact zone is implemented. The geometrically nonlinear approach to the description deformation based on the definitive relationship between the increment of true stresses and deformations, a static statement is given for elastoplastic problems in three-dimensional structures, which have complex geometry. The algorithm of the solution is drawn based on "modified Lagrangian approach" to describe the motion. The problem of body deformation of steel sheets which involve clinch connection, and sample in under punch has been solved, also the distribution of residual stresses in the zone of the clinch joint has been determined.

Low Fatigue Strength of Clinch Joints

Low Fatigue Strength of Clinch Joints

Mechanical properties of the two-steps clinched joint with a clinch-rivet

In the present study, mechanical properties of the two-steps clinched joint with a clinch-rivet were investigated. The two-steps clinching method includes two steps, mechanical clinching and upsetting with a clinch-rivet. The protrusion of the joint was upset to reduce the protrusion height with different upsetting forces. This method contributed to increase the strength and reduce the protrusion height of the clinched joint. Extensible dies were used to perform the mechanical clinching process, and a pair of flat dies was used to perform the upsetting process. AL6061 sheets were used to carry out the experiment. The upsetting forces were set to 25, 30, 35, 40 and 45kN respectively to generate different two-steps clinched joints. Forming force, geometrical parameters, material flow and mechanical properties of the two-steps clinched joint were investigated by an experimental method. According to the achieved results, the cross-tension and tension-shearing strengths of the two-steps clinched joints with different upsetting forces were all higher than those of the conventional clinched joint. The strength of the two-steps clinched joint with an upsetting force of 35kN was the highest of all. The average cross-tension strength of the two-steps clinched joints with an upsetting force of 35kN was increased by 25% compared with the conventional clinched joints, while the average tension-shearing strength of the two-steps clinched joints was increased by 128%. The two-steps clinched joint could absorb more energy than the conventional clinched joint in the failure process. The two-steps clinching method was proved to be effective and reliable.

Durability of hybrid clinch-bonded steel/aluminum joints in salt spray environment

In this work, hybrid aluminum alloy/steel joints by combining clinching and bonding processes were realized. Furthermore, we investigated how the presence of an adhesive interlayer can influence the performance of hybrid joints when exposed in salt spray environment up to 15 weeks of ageing. The durability of steel/aluminum joints is a well-known problem, in particular for steel-reinforced aluminum frames, in aggressive environmental conditions. The aluminum alloy/steel joints were made by interposing an adhesive layer (modified silane (MS) polymer) and clinching before the polymerization has taken place. A proper design of experiment has been carried out, followed by the ANOVA of the results. The experimental results of long-term ageing tests (ASTM B 117) evidenced that the corrosion degradation phenomena influenced significantly the mechanical performance of the hybrid joints. By comparison with the pure mechanical clinching joints, in the same configurations studied in a previous work, the shear load trends are similar. The presence of the flexible adhesive layer gave a significant advantage on resistance to a corrosive attack but little influences the mechanical strength.

Multi objective optimization of clinching joints quality using Grey-based Taguchi method

Clinching joint quality and functionality may have undesirable features because of the choice of the forming process parameters. In fact, there are different factors controlling the mechanical connection strength such as the tools’ geometry and the joint final shape. This paper presents the implementation of the Taguchi-based Grey optimization of the mechanical clinching with fixed dies for dissimilar materials (Aluminum alloy 7075 and Mild Steel) to derive the optimal process parameters combination that leads to a high strength connection subjected to multiple characteristics, namely, the bottom thickness, the interlock length, and the neck thickness of the joint. LS-DYNA explicit and implicit finite element (FE) software was used to simulate the process in order to evaluate the joint strength by loading the sheets vertically. Taguchi’s L27 orthogonal array design and the notion of signal-to-noise (S/N) ratio were utilized to obtain the objective function. Analysis of variance (ANOVA) showed the importance of factors on overall output. The output of the study provided the optimal geometrical parameters of the punch, die, and blank holder. Indeed, the die groove height, die diameter, punch diameter, punch corner radius, and clearance between punch and blank holder were found to be the most influential parameters on the bottom and neck thicknesses. In addition, the output indicated that when bottom thickness or neck thickness increased, the interlock decreased.

Investigation on the corrosion and mechanical behavior of thin film batch galvanized thick plate components in clinch joints

Clinching is well known as an efficient joining technology but is mainly focused on thin-sheet applications. New potentials are seen in applications such as steelwork structures or commercial vehicles, which are characterized by the use of thick-sheet components. In this context, the effectiveness of coatings for these components needs clarification, since these have to fulfill high requirements on corrosion protection as well as on the deformation during the clinching process. The present study reports on investigations regarding the performance of a thin film zinc layer which could be applied in a batch hot dip galvanizing process. The clinch joint quality of such thin film galvanized 5-mm-thick sheet material out of mild steel S235 is visually inspected and compared to classical batch galvanized samples. The influence of the thin zinc layer on the mechanical load bearing behavior is investigated in shear and tensile testing. Further, corrosion testing after clinching is done to investigate the performance of the coating in a highly deformed condition. As a result, the inspection of the clinch joints show that on the thin film batch galvanized thick-sheet components proper clinch points can be carried out without any negative effect on the zinc layer in terms of cracking or peeling off. Subsequent corrosion tests prove the resistance of the deformed zinc coating. The thicker zinc layer, which is applied in classical batch galvanizing process, is not able to withstand the forming process and fails under corrosive loading. The mechanical load bearing behavior of the clinched components with the thin film zinc layer is tested with good results under shear and tension load, showing a significantly lower variance of test results in comparison to an uncoated material.

Recent and future development of the application of finite element analysis in clinching process

Clinching is a mechanical joining method using a simple toolset consisting of a punch, a die, and a blank holder. The shapes of these tools are the most important parameters that control the final geometry of the clinch joints and consequently the strength and quality of the latter. In order to save time and cost, these geometric parameters could be optimized by the use of finite element simulation. This paper reviews the published research related to the finite element modeling of the clinching process. In this study, a critical review of the latter had been carried out from different perspectives. The findings about difficulties facing the simulations of different clinching processes, the optimization of the process parameters, and the strength, joinability, and the quality of the joint were highlighted. In addition, future development, investigation, and more research are still needed to minimize problems and expenses in the industrial practical application of clinching.

FEA-Based Optimisation of a Clinching Process with a Closed Single-Part Die Aimed at Damage Minimization in CR240BH-AlSi10MnMg Joints

The paper presents results of FEA-based optimisation of the tool design of a clinching process with a closed single-part die. The studied materials are the bake-hardening steel CR240BH, 1.5 mm thick, on the punch side and the die-cast aluminium alloy AlSi10MnMg, 2.95 mm thick, on the die side. The optimisation was aimed at suppression of cracks that appear at the bottom of the clinch joint in AlSi10MnMg in the case of using conventional tool designs. By varying geometry parameters of the tools it was possible to reduce crack probability, though along with slightly worse, but still acceptable geometry parameters of the clinch joint.

Finite Element Modeling of Clinching Process for Joining Dissimilar Materials

Clinching is one of the important new joining techniques, in which two plate metal parts are locally plastically deformed by mechanical interlock. Clinching is a mechanical joining method by using simple tools that consist of a punch, a die, and a blank-holder. The shapes of these tools are the most important parameters that control the final geometry of the clinch joints which in turn strongly affect the strength and quality of the final joint. In this study, finite element simulations are carried out to investigate some of the difficulties regarding the optimization of the process parameters, and major expected geometric parameters that will influence the strength, joinability, and the quality of the joint.

Mechanical properties of extensible die clinched joints in titanium sheet materials

Abstract The mechanical properties of extensible die clinched joints in titanium sheet materials were investigated in this paper. Tensile–shear tests were carried out to characterize the mechanical properties of different clinched joints made of the similar titanium sheets and the dissimilar metal sheets combinations. The normal hypothesis tests were performed to examine the rationality of the test data. The load-bearing capacity, energy absorption and failure modes of different titanium sheets clinched joints were studied. Results showed that almost all titanium sheets clinched joints failed in the neck fracture mode. Results also showed that the load-bearing capacity and energy absorption of clinch joints with titanium as upper sheets are higher than that of the clinched joints with titanium as lower sheets.

FEA-based optimisation of a clinching process with an open multiple-part die aimed at damage minimisation in CR240BH-AlSi10MnMg joints

The paper presents results of a FEA-based tool design optimisation for a clinching process with an open multiple-part die. The studied materials are the bake-hardening steel CR240BH (1.5 mm) on the punch side and the die-cast aluminium alloy AlSi10MnMg (2.95 mm) on the die side. The objective of the optimisation was to minimise probability of cracks that appear at the outer circumference of the bottom of the clinch joint in AlSi10MnMg. In the framework of the optimisation, it was possible to minimise crack probability by varying geometrical parameters of the tools though at the cost of slightly worse but still tolerable geometrical parameters of the clinch joint.

Fatigue behaviour of clinched joints in a steel sheet

AbstractClinch joining has been used in sheet metal work owing to its simplicity and because it facilitates the joining dissimilar metal sheets. In this study, monotonic and fatigue tests were conducted using coach‐peel and cross‐tension type specimens to evaluate the fatigue strength of clinch joints in a cold‐rolled mild steel sheet. The monotonic experimental results reveal that the coach‐peel specimen exhibits the lowest monotonic strength among the three specimen configurations. The coach‐peel and cross‐tension specimen geometries exhibit very low fatigue ratios, compared with the tensile‐shear specimen. The maximum von Mises and principal stresses at the fatigue endurance limit are much higher than the engineering tensile strengths of the steel sheet used to determine the three specimen geometries. Compared with the effective stress and maximum principal stress, the Smith–Watson–Topper fatigue parameter can be used for an appropriate prediction of the current experimental fatigue life. With regard to the coach‐peel specimen geometry, all samples exhibit pull‐out failure mode in the fatigue testing range. However, for the cross‐tension specimen geometry, mixed (pull‐out and interface) and interface failure modes occurred, depending on the number of cycles to failure.

Fatigue analyses of self-piercing rivets and clinch joints in lap-shear specimens of aluminum sheets

Fatigue behavior of self-piercing rivets (SPRs) and clinch joints in lap-shear specimens of 6111-T4 aluminum sheets with different thicknesses was investigated. Lap-shear specimens with SRPs and clinch joints were tested under quasi-static and cyclic loading conditions. Micrographs showed different failure modes of SPRs and clinch joints under different loading conditions. Dominant fatigue cracks were identified. The structural stress model from Tran and Pan’s recent works was adopted. The structural stress solutions at the crack initiation locations and the stress-life data of aluminum 6111-T4 were adopted to estimate fatigue lives. The fatigue life estimations show good agreement with the experimental results.

Effect of aluminum pre-straining on strength of clinched galvanized SAE1004 steel-to-AA6111-T4 aluminum

Normally, the sheet metal may be pressed or stamped prior to mechanical clinching. The pre-strain from the pressing or stamping may have an influence on the quality of the clinched joints. To understand how the pre-strained sheets materials affect the joint quality, we conducted the study to understand the effect of pre-straining aluminum on the static strength of the clinched aluminum-to-steel joint. The section parameters (i.e. undercut, neck thickness, and bottom thickness) and joint strength were measured. It was found that the work hardening resulting from pre-straining decreased the ductility of aluminum AA6111-T4 and induced some ductile damage on the clinched aluminum workpieces. A 5% pre-strain on AA6111-T4 caused a significant decrease (about 20%) in joint strength. Though the bottom thickness is a good indicator for detecting the strength variation for the clinched as-received and pre-strained aluminum–steel joints, it barely detected the effect of ductile damage in the pre-strained aluminum on the joint strength. The application of the similar “X” parameter (i.e., bottom thickness of the clinched joint) from the as-received aluminum to monitor the quality of the clinched steel-pre-strained aluminum joint resulted in overestimates of the joint strength. Therefore, the optimum clinching tools and process variables for clinching of the pre-strained AA6111-T4-to-steel cannot be derived from the experiments using the as-received aluminum workpieces. To obtain the desired strength of the joints made with dissimilar materials, it is important to achieve a good balance between the undercut and neck thickness by optimizing the clinching tools and process parameters. The variation of electrical resistance of the joints during the clinching process can differentiate the difference of the damage between the as-received and pre-strained clinched joints. Therefore, a method of monitoring the variation of electrical resistance is proposed to inspect the quality of the clinched steel-to-pre-strained aluminum joints.