Method for joining two objects and corresponding joining element

A method for joining a first and a second object with the aid of a joining element comprising at least in the region of a distal end and a proximal end a material having thermoplastic properties, the method comprising the steps of:

• providing a recess between the two objects to be joined,
• positioning the joining element into the recess such that its distal end is in contact with a recess bottom face in the first object, that its proximal end is in contact with a recess bottom face in the second object and that there is a gap between the two objects,
• positioning the first object against a non vibrating support and positioning an element capable of being excited to vibrate mechanically against the second object,
• forcing the excitable element and the support towards each other in a direction to compress the joining element between its proximal and distal ends and to close the gap, while exciting the excitable element to vibrate mechanically, thereby liquefying at least part of the material having thermoplastic properties, there, where the joining element ends are pressed against the recess bottom faces and allowing the liquefied material to infiltrate into pores of the recess surfaces or unevennesses or openings provided in the recess surfaces, such anchoring the joining element ends in the objects,
• wherein for achieving suitably similar anchorage qualities at the two joining element ends, the distal end of the joining element is different from the proximal end and/or the recess bottom face in the first object is different from the recess bottom face in the second object, wherein the differences are design differences or material differences.