Clinching process for joining dissimilar materials: state of the art

Clinching is a method for mechanically joining sheet metal of different thickness and properties in which the two plates to be joined undergo plastic deformation. The clinching process is established by connection or joining using simple tools: a punch and a die. This method has different characteristics compared to thermal joining methods, such as spot welding, including low purchase and operating costs, little preparatory work, safe and environmentally friendly, interesting mechanical properties, reproducibility, and durability. In this article, a brief review of traditional joining methods for dissimilar materials and the clinching process are illustrated in greater detail. In addition, the article looks to guide researchers for future work by identifying weaknesses of the current processes as well as a potential for valuable contributions in the field of clinching

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

Nondestructive evaluation of welded joints using digital image correlation

This paper demonstrates a novel approach in which the digital image correlation technique is used as a nondestructive testing tool for the inspection of welded joints. In this approach, the joint is loaded with the maximum load that it is expected to encounter during actual operation (i.e., the design load) and two images are recorded, one before and one after applying the load. Artificially made defects of different types and sizes were introduced along the welding line of a butt-welded joint. The results of this study show that this approach can be used for detecting different types of welding defects; however, it cannot distinguish between the different types of defects. The results also show that the minimum detectable defect size depends on the type of the defect. The minimum detectable defect size using this approach was found to be smaller than the maximum acceptable defect length according to the American Petroleum Institute acceptance criteria for most of the defect types investigated here. Also, results of a selected group of samples are compared to the results obtained using the well-established and widely used radiographic imaging technique, for reference purposes

Numerical investigation of springback in mechanical clinching process

In this work, a numerical investigation was conducted to study the springback phenomena in the mechanical clinching process. The springback values were calculated using finite element simulations and it was found that these values depend strongly on the strength of the materials. A Taguchi optimization method was used to determine the optimal parameters affecting springback. However, in the case of materials with low tensile strength, determining parameters affecting springback becomes difficult. Implicit and explicit simulations of clinching joints using the springback analysis show that the distance between the joint sheets becomes almost zero after stress recovery

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

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