| 摘要 |
A joint is produced in at least two overlapping workpieces (W1, W2) using a joining tool comprising a punch (16) reciprocally disposed in a cylinder. The workpieces (W1, W2) are disposed between the tool and a die (12) and the tool is used to apply a compressive force to deform the workpieces into a joint at a joining area between the tool and the die. Continuous ultra-sonic energy (A) is applied to at least one of the workpieces in the joining area for at least part of the time during production of the joint so as to increase the ductility of at least one of the workpieces in the joining area. This induces an acousto-plastic effect in the material being formed which temporarily reduces its strength so as to exhibit increased ductility. The joining method is used in self-piercing riveting and enables viable joints to be formed in high strength materials or thick sheets of material.
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