Development of a test procedure for establishing the mechanical properties of electro fusion and heated tool sleeve welds with mechanised torsional and linear shear tests (Part 2: The linear shear test)

摘要

In 2008, the Siiddeutsches Kunststoff-Zentrum (South German Plastics Centre) (SKZ), Wurzburg, in cooperation with WIDOS GmbH, Ditzingen, began to develop a testing device for establishing the mechanical properties of joints executed by means of sleeve welding with an incorporated heating element (HM) and heated tool sleeve welding (HD) with the mechanised shear test. The aims of this investigation were to generate a reproducible test procedure for HM and HD welds and to investigate this with regard to its utilisation suitability. The core statement of this research paper is that the mechanised torsional shear test is very suitable for detecting defects in HM-welded and HD-welded joints. In addition to frequent and, in part, obviously incorrect preparations (e.g. wrong insertion lengths of the pipe into the sleeve), it was even possible to detect defects which, with the naked eye or even with manual radial peeling and torsional shear tests, could not be recognised at all or only with very great difficulty and with a very great deal of experience, such as oil in the joining face, double welding etc. Initial pioneering evaluation algorithms were generated in addition to the designing and elaboration of the testing apparatus for the mechanised torsional shear test. On the basis of these algorithms, it is relatively simple to make comparative evaluations about defect-free welding (see Part 1: "The mecha- nised torsional shear test (TST)" in JOINING PLASTICS - FUGEN VON KUNSTSTOF-FEN 2/2010). However, since the comparative measuring methodology did not yet constitute the optimum, a new mechanised linear test procedure (the mechanised linear shear test, LST) which has not been specified in the technical code of DVS (German Welding Society, Dusseldorf) until now was developed and is presented below.