“…The high-strength sheet is used as the lower sheet, in which a hole is formed between the sheets, and the low strength sheet is used as the upper sheet. Figure 15 Various method of clinching process for difficult-to-form sheet (metal and composite) by using hole clinching: (a) Pre-punched hole clinching [125]; (b) Friction-assisted clinching [35]; (c) Multi-stage clinching with pre-hole on die-side [77]; (d) Single-stage shear-clinching [67,77,133]; (e) Clinching by local heating of composite [32]. …”
The clinching technology attracted increasing attention in recent years, but its application might be restricted due to the growing employment of materials that are difficult to join and hybrid structures involving different mechanical performance materials. Traditional clinching technology has limitations of strain rate sensitivity, ductility and damage fracture when applied to materials with high strength, low strain-to-failure and low plasticity. However, the ductility and formability of the material represent a limitation for the clinching process. The present study explored some concepts of clinching, such as hole, friction-assisted, laser-assisted, electro-hydraulic, electromagnetically assisted and hot assisted clinching, for the difficult-to-form sheets. The paper includes the description of the deformation mechanism of clinched joints and the analysis of clinched joint performance and applicability.
“…The high-strength sheet is used as the lower sheet, in which a hole is formed between the sheets, and the low strength sheet is used as the upper sheet. Figure 15 Various method of clinching process for difficult-to-form sheet (metal and composite) by using hole clinching: (a) Pre-punched hole clinching [125]; (b) Friction-assisted clinching [35]; (c) Multi-stage clinching with pre-hole on die-side [77]; (d) Single-stage shear-clinching [67,77,133]; (e) Clinching by local heating of composite [32]. …”
The clinching technology attracted increasing attention in recent years, but its application might be restricted due to the growing employment of materials that are difficult to join and hybrid structures involving different mechanical performance materials. Traditional clinching technology has limitations of strain rate sensitivity, ductility and damage fracture when applied to materials with high strength, low strain-to-failure and low plasticity. However, the ductility and formability of the material represent a limitation for the clinching process. The present study explored some concepts of clinching, such as hole, friction-assisted, laser-assisted, electro-hydraulic, electromagnetically assisted and hot assisted clinching, for the difficult-to-form sheets. The paper includes the description of the deformation mechanism of clinched joints and the analysis of clinched joint performance and applicability.
“…Tool size, tool shape, material performance, material combination, and process plan directly affect clinched joint quality. For the connection of different sheets, different process plans can be selected, or different tool combinations can be selected [15][16][17] . Lambiase [18] compared four tool types,namely, round split, round grooved, round flat, and rectangular shear.…”
The geometric size of the clinching tools determines the geometric size and strength of the clinched joint. This study establishes an orthogonal analysis experimental plan to examine how a group of geometric size of the tool affects the objective functions of a clinched joint, including its bottom thickness, necking thickness and interlocking thickness. Particularly, the study evaluates the effects of die radius, die depth, punch stroke, punch radius and punch fillet on the geometric size of the clinched joint. A multiple quadratic regression model is used to quantitatively analyze the contribution value of the feature parameters of the tool to the objective function. Furthermore, a multi-objective genetic algorithm based on the Pareto solution is used to solve the multiple quadratic regression model, and the optimal combination size of the tool is determined by comparing theoretical and simulation calculations. The optimal die radius is 4.6 mm, the die height is 1.10 mm, the punch stroke is 4.1 mm, the punch is 2.6 mm and the punch filled is 0.5mm. These parameters are used to manufacture a pair of tool for improving the clinched joint quality.
“…1) [6] besides the penetration of the material in the out-of-plane direction, the material flows radially outwards during the joining process due to the hemispherical outer punch [7], so that a strong bending of the ductile joining partner on the punch side occurs [8]. Han et al [9] indicated the modification of inner punch and blank holder is efficient in shear-clinching to decrease the out-of-plane bending further on the gap between the sheets and the global distortion. In addition, Hörhold [10] showed numerically that the outer punch radius and the friction conditions between the joining partners are decisive for the distortion as well.…”
Section: Intr Introduction Oductionmentioning
confidence: 99%
“…In addition, Hörhold [10] showed numerically that the outer punch radius and the friction conditions between the joining partners are decisive for the distortion as well. In general, these distortions can be determined experimentally using various optical measuring methods [9]. Numerically, the dimensional changing of joint partners in case of axial-symmetric joining can be estimated by means of two-dimensional modelling.…”
Three-dimensional modelling enables to determine the in-plane material flow in asymmetrical situation. Thus, the distortion of the sheets to be joined can be characterized more exactly. This study shows a method for building up a three-dimensional shear-clinching framework without damage criteria. In fact, the die-sided sheet in shear-clinching was designed as a pre-punched sheet and slugs. The material separation in the die-sided joining partner, which in two-dimensional simulation is often described by macro- and micromechanical fracture criteria, was realised in this study based on a defined contact condition. By means of a shear-cutting simulation, a correlation between the break angle and the separation stress was determined, which was used as a separation criterion in the shear-clinching simulation. The separation line was confirmed using post-particles. To validate this model, the results of the simulation using a quadratic single-point specimen were compared to the experiments with respect to the distortion of the joining partner. In general, the built three-dimensional framework provides for further tool developments with regard to the reduction of distortion in shear-clinching.
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