Clinching joints with an additional deformable rivet are modifications of the clinching joints. The clinch riveting (CR) joint is formed indirectly by a deformable rivet. The research included an analysis of CR joints’ forming process for aluminum alloy sheets made of AW 6082 in T6 state condition and AW 5754 in three different state conditions: H11, H22 and H24. As a result of forming the joint for various sheet arrangements, the highest value of blocking the upper sheet in the lower sheet (t_u) was obtained for the arrangements with two 5754-H24 aluminum alloy sheets. For such a large interlock parameter t_u, the greatest thinning of lower sheet (t_n) was obtained, which influenced the maximum tensile shear force and the joint failure mechanism. Based on the load-displacement diagrams obtained from the static shear test of lap joints, the total energy of failure and energy to achieve the maximum load capacity were calculated. The highest energy absorption to achieve the maximum load capacity, in the case of the same sheet materials, was obtained for the 5754-H11 aluminum alloy sheets. On the other hand, among the tested combinations, the highest value of energy absorption (for the joint maximum load capacity) was obtained for the sheet arrangement: top sheet AW 6082-T6 and the bottom AW 5754-H24. The highest value of the total energy up to fracture was obtained when the material of the top sheet was AW 6082-T6, and the bottom AW 5754-H22. For each sheet arrangement, a similar analysis of the joint strength parameters, interlock parameters and forming force were made.

In the publication, the results of an experimental analysis of joint formation by pressing of DX51D steel sheets with thickness of 1.5 (mm) with the use of a rigid punch and an additional deformable rivet of various shapes were presented. The influence of the use of a steel rivet with a diameter d = 5 (mm), similar to the dimensions of the forming punch in the case of the classic clinching variety on the interlock parameters was investigated. The used die was with a four movable segments—dedicated to connections made in the clinch-riveting technology by TOX^® PRESSOTECHNIK. In additional, experimental tests were made for joining sheets with a rivet of various shapes, i.e. with a through hole. Joints were formed and the correctness of the upper blockage in the lower sheet was observed on the joints cross-sections. The interlock parameters were measured for each joints samples. In order to compare the influence of using an additional rivet on interlock parameters and joints strength the traditional clinching joints were also made. The minimal thickness of the traditional clinching joint embossment for 2 sheets of 1.5 (mm) thickness for each was X = 0.75 (mm).

This paper presents the results of research on the impact of the use of different tools and the shape of the additional rivet, on the geometric quality of the joint, the energy consumption of the forming process, the distortion of the steel samples, and the load capacity of the joints. The tests were carried out for DX51D steel sheets with a thickness of 1.5 [mm] joined by using three different sets of tools. A steel rivet with a hardness of 400HV1 and various shapes was used for the tests. In addition to the full rivet, two types of rivet were used, the first with a through hole and the second with a depth of hole of 3 [mm]. The holes in the rivet had different diameters: 1.0, 1.5, 2.0 and 2.5 [mm]. The influence of changing the shape of the rivet (hole and its diameter) on the change in forming force and energy consumption of the joining process was analyzed. The lowest forming force was achieved for a rivet with a through hole and a hole diameter of 2.5 [mm]. The lowest joint forming force was obtained for the die with movable segments. For joints made with three tool arrangements and a series with a modified rivet, the amount of sheet metal deviation was analyzed. Of the three cases of arrangement of tools used to form the joint, the largest deviation of the sheets occurred at the clinch joint formed with a solid round die. In the case of a series of clinch-rivet joints with a modified rivet, the greatest deviation of the sheets occurred for the rivet with a hole of 1.5 [mm]. Changes in the geometric structure of the joint were also studied, and changes in the surface of the sheets in the joint area were observed. The highest value of the interlock in the joint was obtained when a solid rivet was used in the clinch-riveting technology. The strength of the joints was also identified in the lap shear test and the energy consumption at failure was determined. The use of a rivet increased the maximum load capacity to almost twice that of the clinch joint. Graphical abstract

This paper presents the possibility of forming a pressed joint between two 1.5 mm thick sheets made of HX340 steel. The joint was formed using an additional deformable steel rivet with a hardness of 400HV1. Different distances of rivet pressing below the initial surface of the upper sheet were chosen: 0, 0.15, 0.30, 0.45 and 0.60 (in mm). For the mentioned rivet-pressing distances, forming tests were performed using an “SKB” die with three die depths: 1.45, 1.60 and 1.75 (in mm). Observations and measurements of the characteristic geometric dimensions of the interlock were made. Furthermore, the strength of the clinch-riveted joints was analysed. Changing the depth of the die by 20%, i.e., from h_d = 1.45 mm to h_d = 1.75 mm for the same rivet press-in depth (o_f = 0%), resulted in a 12% reduction in the forming-force value. The maximum load capacity of the joint in the shear test decreased by 3.5% for the mentioned joint variant. The greater the rivet press-in depth used in the joint (o_f), the greater the value of the interlock size (t_u). Increasing the value of rivet-pressing depth below the initial surface of the upper sheet from 0 mm to 0.6 mm resulted in an increase in the size of the interlock (t_u) by 136% (for h_d = 1.45 mm), by 128% (for h_d = 1.60 mm) and by 85% (for h_d = 1.75 mm).