Artificial hip-joints must withstand both compressive loads and torsion loads.
To determine the optimum materials and alloys, these are tested with a special testing unit consisting of a 20 kN capacity Zwick materials testing machine plus a 500 Nm torsion drive.
The artificial hip-joint (here made of metal) is rotated on a support unit (torsion loading) and at the same time compression loading is applied.