There are two groups of destructive test methods for welded thermoplastic joints: the short- term tests and the long-term tests. The short-term tests are used to obtain information about the short-term behaviour of welded joints. The most applied test methods are the bending tests and the tensile tests. Additional information about welded joints from short-term tests can be obtained by more severe test conditions (e. g. lower test temperatures and/or waisted tensile test specimens). The short-term tests are widely used in connection with the qualification of welders. The long-term tests (creep rupture tests) give information about the long-term fracture of welded joints. For butt welded pipes the long-term tensile creep rupture test is applied up to a wall thickness of 70 mm. The long-term creep rupture tests on welded polyolefins can be accelerated using aqueous solutions of detergents as test media. A further method of reducing the testing times is to use elevated temperatures.
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