Deviations during forging processes lead to workpiece failure when the forming limits of the
material are exceeded. In production processes an early detection of manufacturing faults is
preferred. The acoustic emission (AE) technique is examined with respect to its ability to
detect deviations in lubrication conditions and in the structural integrity of different
aluminum part geometries and alloys during forming. In a first step, an upsetting of varying
specimen shapes was performed in order to study correlations of occurring defects as well as
changing friction conditions with acoustic emission response. Afterwards, a cross joint was
forged and AE was analyzed. The results suggest that crack detection during forging is
feasible but limited by material ductility. In addition, it is shown that the characteristics of
the acoustic emission during forming strongly depend on the respective alloy. With respect
to faultless warm forging it is found that different stages are reflected in the AE signal,
facilitating the detection of process deviations