# Quality Tests of Hybrid Joint-Clinching and Adhesive--Case Study
###### Abstract  
Inseparable joints are widely used in machine and vehicle construction. Hybrid joints include bonding with sheet metal clinching. This combination reduces costs as well as the time of production compared to welded joints. Tests on the samples made of DC01 sheets were carried out. A case study was conducted on four research series. For each series, the shear forces of the joint were measured. The first series consisted of adhesive bonding, and the second and third series consisted of hybrid bonding, during which the sheet metal clinching joint was developed immediately after the completion of adhesive application and after full joint formation. The last test series only includes sheet metal clinching. In the series where bonding was used, the homogeneity of the prepared joints was analysed using the ultrasonic echo technique. The shear strength of the bonded joints was 476 N, whereas the shear strength of sheet metal clinching was 965 N. For the hybrid joint, the average forces were 1085 N (for the specimens in which the lap joint was made after the joint was fully cured) and 1486 N (for the specimens in which the lap joints were made immediately after the adhesive was applied). It was discovered that the clinching of the steel sheets significantly increases the strength of the joint. The stabilisation of the joint causes better crosslinking conditions. This results in an increase in the strength of the hybrid joint. adhesion; ultrasound; strength; connection quality; sheet metal clinching 2022211782022211782022211782022211782022211782022211782022211782022211782022211782022211782022211782022211782022212117820222121178202221211782022212117820222121  
using ultrasonic testing [12; 13; 14] and fabrication [14] are well-known and commonly used in technical applications. The use of adhesive bonds results not only in reduced production costs but also in reduced vehicle mass, resulting in reduced combustion and exhaust gas emission into the atmosphere. Joining technologies in motor vehicles are being improved all the time. These works include such connections as welding [15; 16; 17], bonding [12; 13; 14; 15; 16; 17; 18], and welding and clinching [19; 20; 21; 22; 23]. Sheet metal clinching is carried out by a compression method, using small values of lateral forces on the die side and no adverse deformations near the joint [24; 25; 26; 27]. The joint may be oval in shape and consist of cup-shaped indentations on the die and punch side. The joint is purely plastic in nature without compromising the cohesion of the material. This method makes it possible to permanently join parts mainly of thin sheets and to achieve high static and dynamic joint strength. Sheet metal clinching consists of cold pressing the sheets to be joined with a round punch and a suitably shaped die. The result of this process is a connection in the form of a round point, which is not subject to further processing and is free of burrs and sharp edges (Figure 1). The deformation does not affect the surface of the materials to be joined. The technology of joining by compression allows joining metal sheets in such a way that in the area of their overlap--by means of plastic deformation (displacement, elongation, swelling)--fasteners are formed without the thermal loading of connected parts. The sheets involved in the joining can be of different thicknesses and materials. Spatial fasteners are formed in the area of the die and punch action of a given forming tool. The depth of clinching determines the nominal convexity of the fastener on the die side and the elongation of the cup wall on the punch side. The bottom thickness characterises the degree of swell as well as the strengthening of the material in the joint area. It is a dimension of the part and a parameter describing the joining process. The most widespread use of this type of sheet metal joining has found its application in electrotechnics and radiotechnics, as well as in the construction of instruments in precision mechanics.