Development of a material testing machine with multi-dimensional loading capability

This paper presents a multi-dimensional loading material testing machine based on a hexapod parallel mechanism. We designed a model-based PID closed-loop control method using feedbacks from six uniaxial force sensors installed on limbs. Three simulations were proceeded to estimate the feasibility of this control method. Furthermore, we established two series of experiments, including multi-dimensional loading experiments and standard tension tests. The former experiment results demonstrate the multi-axial loading capacity since the actual multi-axial output wrench has the deviation less than 5% of the desired ones. The latter experiments reveal that the uniaxial tension test is not considerably influenced by the redundant degree of freedoms, because the tensile-test results are relatively identical to those results achieved by universal material testing machine. Both experimental results suggest that this proposed material testing machine are feasible to perform multi-dimensional material tests, as well as standard uniaxial tests.