Qualitest introduces our new advance Sample Specimen Preparation CNC machines known as QualiMill and QualiLathe.
A test specimen is the most important component of tensile testing for it determines the actual physical properties of the material being tested. The specimen must conform to exact physical dimensions and must be free of induced cold working or heat distortion. Qualified laboratory personnel and accurately calibrated tensile machines are important, but the ultimate test results are based on the quality and accuracy of the test specimen.
A highly skilled machinist, a precision milling machine and considerable hand finishing can achieve the required configurations of the test specimen. However, the slow milling cutter speeds create heavy chip loads and can induce severe internal distortion to the machined edges. The amount of induced cold working or heat distortion cannot be determined by visual or heat distortion cannot be determined by visual inspection, hence test results often produce erratic and inaccurate tensile properties.
Specimens of light gauge sheet must be blanked, sheared or die cut to the required tensile configuration. The basic principle of shearing causes severe deformation and distortion to the critical specimen edges and creates even greater variations and errors in the physical properties.
The ideal tensile specimen should duplicate the pure basic metal or plastic being tested with a total absence of tool marks, incipent cracks, induced stresses, internal deformation or heat distortion.