For transfer path analysis (TPA) methods, the description of the source is essential. The possibilities of source characterization are as different as the TPA methods. For the classical methods, the source is considered in the installed state with feedback from the receiver structure, while for component-based TPA the source is described without feedback from the coupled structure. In addition to TPA, source characterization is also used in the product development process for evaluation or comparisons. Also in these cases, the source must be characterized without feedback from the test structure, which can generally be realized by measuring free velocities or blocked forces. Because of the need of external load to reach the components operating point, force measurements are often used.
However, the realization of a reactionless test setup for the measurement of forces poses some challenges. The paper presents a setup that can be used to perform a direct force measurement at a point in six degrees of freedom. The necessary boundary conditions to approximate the idealized blocked force assumption are discussed, the calculation of the blocked force in six degrees of freedom is presented, the structural dynamic response at a reference point is calculated and compared with operational measurements.