Properties of inductively cured adhesive-bonded joints under cyclic loads

摘要

Within the framework of the presented project, investigations were conducted into the influence of fast inductive curing on the mechanical-technological properties of adhesive-bonded joints under cyclic loads. With reference to automobile practice, a distinction was made between fast curing in the inside and outside inductive fields. The investigations prove that inside field induction leads to a higher fatigue strength. In contrast with this, a fatigue strength which is significantly lower in part can be established after fast inductive curing in the outside field depending on the process parameters of the induction temperature and the induction variant. 1 Introduction Constantly rising raw material prices and increased environmental awareness are forcing the automobile manufacturers to consistently reduce the vehicle mass [1]. Lightweight material construction offers high potential for lowering the vehicle mass and consequently the emissions. For this purpose, higher-strength and ultrahigh-strength steels are being combined with aluminium alloys and composite materials in a mixed construction method to an increasing extent. Thanks to its large-area force transmission, adhesive bonding permits high exploitation of the material potential. This leads not only to a weight saving but also to an increase in the vehicle stiffness and to improved dynamics of vehicle movement. In any case, adhesives utilised in body shell construction generally only cure during the drying process of the cathodic electrodepos-ition painting (CEP). This results in the disadvantage that, when adhesive bonding technology is applied, the joining parts must frequently be fixed temporarily because of the times required for the curing of the adhesive [2]. As far as structural adhesive-bonded joints between steel and aluminium are concerned, this disadvantage is normally offset by using hybrid joints as a combination of adhesive bonding with spot welding or mechanical joining technology. However, these additional joining operations give rise to substantial extra costs. The actual geometry of the adhesive-bonded coat and the properties of the joint are altered as well [3]. Correspondingly, alternative fixing processes not only for heat-curing one-pack (1 P) adhesives but also for cold-curing two-pack (2P) reactive adhesives are of technological and economic interest.