In the production of automotive taillights, the lens in polycarbonate (PC) or polymethyl methacrylate (PMMA) is joined to a housing in acrylonitrile-butadiene-styrene (ABS). Heated tool welding is the most frequently employed method for this. One of the types of damage that can occur is stress cracking. Apart from impairing appearance, stress cracking also leads to the penetration of moisture. Different direct and indirect methods for establishing stress are to be applied to a rectangular specimen and an industrial component in order to assess the influence of the process parameters that prevail during heated tool welding on stress cracking. It is clear that the different investigation methods reflect the action of the process parameters of heated tool temperature and heating time in the same way. The lowest possible heated tool temperature and / or heating time should thus be aimed at in order to join amorphous thermoplastics with a low level of stress. Further investigations shows that joining parts that have been briefly pre-heated or are still hot from injection molding can reduce susceptibility to stress cracking and thus provide an alternative to subsequent annealing, which is a highly cost - intensive process on account of the high tirne and energy outlay involved. The methods presented, however, differ clearly in respect of the time outlay they involve and their practical serviceability. It would thus only appear worthwhile employing FE analysis at the component design stage, in order to permit an estimate of the influence of ribs and notches on the development of inherent stresses. When photoelastic strain analysis is employed, it is not possible to assess complex 3D parts, which means that only the drilled hole method and the wetting test are available for practical use. Preference is to be given to the wetting test on account of the lower time outlay and its easier handling.
Influence of process parameters on the phenomenon of stress cracking in hot plate welded tail lights
Einfluss der Verfahrensparameter auf die Spannungsrißbildung in heizplattengeschweißten Rückleuchten
2001
6 Seiten, 10 Bilder, 8 Quellen
Aufsatz (Konferenz)
Englisch
Influence of Process Parameters on the Phenomenon of Stress Cracking in Hot Plate Welded Tail Lights
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