Abstract
Friction welding is a popular process for joining metal and polymer work pieces by rubbing them against each other. This way, friction heat is generated in a zone of the faying surfaces, thinner than 1 mm. After cooling down, the heated surfaces establish a tight and strong bond. To improve this joining process, a method is desirable allowing measuring generated temperature and shear stress in the zone between the joining work pieces. Unfortunately, this is a very difficult task because the welding zone cannot be accessed with a sensor without significantly altering the process and thereby the desired measurement results. This paper describes how shear stress and temperature change generated by rubbing polymer pieces in a friction welding machine have been measured between the faying surfaces by employing sensor foils from the piezoelectric and pyroelectric polymer polyvinylidene fluoride (PVDF). This way, heating and cooling rates, pressure rise of the pneumatic system, frequency rise of the starting machine, the duration of starting and stopping, the damping of the vibrations after the drive was stopped, and the stress generated by the pullback of the machine head have been measured. A careful characterization of the sensor was necessary to enable distinguishing the measured voltage due to straining, shearing and temperature change.
Highlights
Patents on friction welding were already filed in 1942 [1] and 1956 [2]
Shearing and can temperature change, from theseeach foils other need to bemeasurements characterized and carefully before foils employed theother workand described in this paper are called FDT1-028K and these The effects can sensor be distinguished fromfor each measurements can be evaluated
The polyethyleneterephthalate glycol (PETG) plates were rubbed over the polyvinylidene fluoride (PVDF) foil generating shear stress
Summary
Patents on friction welding were already filed in 1942 [1] and 1956 [2]. Friction welding is a joining process employed mainly for metals and for polymers [3,4,5,6,7,8,9,10,11,12,13]. The surfaces of the work pieces to be joined are mounted at an upper and a lower holder of a friction welding machine (cf Figure 1a). The upper or lower holder of the friction welding machine is moved in lateral direction generating shear and friction heat between the pieces to be joined. At the end of the process the relative movement of the work pieces needs to be stopped before cooling down has established a strong bond [14,15]. Way, influence of process parameters movement type circular friction welding. Curie of PVDF, investigations are limited to limited to parameters at which no weld is established even between polymer pieces.
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