Tension test. Kompetenzzentrum Bauteilsimulation: SimBau

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Tension test

The tensile test is part of conventional materials testing. As a standard test procedure, it gives relevant information about the yield stress R_p0,2and the tensile strength R_m. The evaluation of the test results as stress-strain curves is used as input for elastic-plastic FEM-simulations.

With the development of micro-mechanical material models describing ductile failure of metallic materials improved measurement techniques were developed in order to gather additional information about damage and failure. The picture shows a test set-up with a camera to measure the necking of a round bar specimen.

The need to characterise smaller components, and the requirements to resolve severe property gradients, e.g., in welded joints, have led to the development of smaller and smaller specimens. Now, IWM is able to fabricate specimens with diameters as small as 1 mm and test them in a temperature range of about -180°C to 600°C.

Besides round specimens flat specimens are utilized especially in the automotive industry. Since the measurement of necking is not possible with flat specimens, the experiments must be supplemented by numerical simulations to determine damage mechanics parameters.

Round and flat specimens used for impact testing

Applications for the transportation industry (crash) also call for dynamic test in order to determine the strain rate sensitivity of the material properties. The sketch shows schematically the arrangement used in a drop weight tower. The movement of the impacting hammer is converted into a tensile load on the specimen. The deformation of the tensile specimen is measured by a high speed camera, local loads are determined from a strain gauge attached to the thicker part of the specimen.

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