For Joining Technology of Glass Fiber Reinforced Polyamide: Screws and Inserts
Joining properties of thread forming screws, hot-embedded brass-inserts and ultrasonic-embedded plastic-inserts in glass fiber static and dynamic load.
Based on the exceptional engagement of the thread flanks, direct fastening joints achieve the highest specific pull-out-strength. The investigated thread geometries did not vary significantly. The long term behaviour of fastenings with plastic parts is affected by a loss of the pre-stressing force. Relaxations compared to the initial pre-stressing force down to 60-70% at 23° C and 10-20% at 80° C are expected.
Under dynamic load, the failure of the direct fastening joints is influenced by the screw strength and not by the material properties of the plastic part. The dynamic load limit is between 30% (not pre-stressed) and 40% (pre-stressed) of the static pull-out force.
Due to the notch geometry of dynamic loaded fastenings with brass-inserts, the danger of crack formation is not sufficiently accounted for with the existing design criterias. The advantage of the plastic-inserts is the reduction of such notch effects, which is achieved by using welded joining technology.
A disadvantage of the plastic-insert in respect of its long term behaviour is the fact that its metric thread geometry is not designed tailored to plastics.
Fatigue and deterioration under dynamic load were reliably determined by the hysteresis measurement method, whereby the damping in particular reacted quite sensitively.Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Joining technology, Plastic fastenings, thread forming screws, inserts, glass fiber reinforced polyamide, prestressing force, relaxation, hysteresis measurement, static load, dynamic load, load limits, fatigue behaviour
Institute / chair: Technischen Fakultät der Universität Erlangen-Nürnberg
Technical consultant for expert services: Prof. Dr.-Ing. Dr. h.c. Gottfried W. Ehrenstein (Betreuer), Prof. Dr.-Ing. Klaus Feldmann,
Publication year: 1999
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de
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