Figure 14 The values of energy absorption of different joints.
Related Figures (15)
Figure 2. The auxiliary process with a rivet. Figure |. The mechanical clinching process with extensible dies. After mechanical clinching process, an auxiliary pro- cess with a rivet can be performed on the clinched joint to increase the strength. The auxiliary process with a rivet is shown in Figure 2. A pair of flat dies is used in the auxiliary process to compress the Figure 3. The auxiliary process with a bumped die. After mechanical clinching process, an auxiliary pro- cess with a bumped die also can be performed on clinched joint to increase the strength. The auxilia process with a bumped die is shown in Figure 3. T surface of the top die is flat, and the surface of bottom die is bumped. The protrusion of the clinched joint is compressed by the flat die and bumped die. ne ry ne ne The bump of the bottom die is used to support ne Figure 4. The geometrical parameters of the extensible dies. A clinching machine produced by Express Company (Shenzhen, China) was used to perform the mechanical clinching process. The speed and displacement of the clinching equipment can be controlled easily. The exten- sible dies were produced by high strength steel. The geo- metrical parameters of the extensible dies are shown in Figure 4. The sliding sectors are used in the extensible dies to control the material flow uniformly. The sheets can be placed on the sliding sectors. The speed of the mechanical clinching was set to 0.5mm/s. When the bottom thickness of the joint was reduced to 1.3mm, Figure 7. The specimens: (a) the specimens used in tension-shearing strength tests and (b) the specimens used in cross-tensile strength tests. The tension-shearing strength tests and cross-tensile strength tests were used to evaluate the strength of the joint after auxiliary process. The tension-shearing strength tests and cross-tensile strength tests were con- ducted on an Instron 5982 tensile testing machine. The speed of the strength test was set to 2mm/min. Five specimens of each joint type were used for ten- sion-shearing strength test and cross-tensile strength test, respectively. The strength tests were controlled to stop when the joints were fractured and separated. As shown in Figure 7(a), the specimens used in tension- shearing strength tests were cross-shaped type. As shown in Figure 7(b), the specimens used in cross-tensile strength tests were lap-shear type. Figure 6. The geometrical parameters of the bumped die. Figure 5. The geometrical parameters of the rivet. In order to increase the strength of the clinched joint, an auxiliary process with a rivet was used to compress the protrusion of the joint. A hydraulic servo press with a maximum load of 160 kN was used in the aux- iliary process. The rivet was placed in the pit of the joint. Finite element simulation and orthogonal design were used to optimize the geometrical param- eters of the rivet in terms of cross-tension strength. The best combination of geometrical parameters of the reshaping rivet was gotten by simulating Table |. Tension-shearing strengths of the joints with differ- ent auxiliary processes. Table 2. Cross-tensile strengths of the joints with different auxiliary processes. Figure 8. The typical tension-shearing force—displacement curves of the joints. Figure 10. The failure mode of the joints: (a) failure mode in the tension-shearing tests and (b) failure mode in the cross- tensile test. Figure 9. The typical cross-tensile force—displacement curves of the joints. Figure Il. The neck thickness and interlock of the joint. Table 3. Neck thicknesses of the joints with different auxil- iary processes. Figure 13. The appearances of the joints: (a) clinched joint, (b) joint with a rivet, and (c) joint with a bumped die. Figure 12. The cross-sectional profiles of the joints: (a) clinched joint and joint with a rivet and (b) clinched joint and joint with a bumped die.
