Prediction of linear noise-load relationship for impact forming machines

INTRODUCTION NOlSE emitted during hot forming on a high-energy-rate-forming (HERF) machine bears a linear relationship with the magnitude of the forming load [ 1]. The existence of this linear correlation has been confirmed for a drop hammer [2] : though the slope and the intercept of the noise-load line differed from the H E R F case. It appears that for every hammer this noise-load relationship can be expected to be unique and independent of the process variables, i.e. input energy, billet size and properties, etc. A linear noise emission vs forming load variation, independent of the process variables, with a unique gradient and intercept for each hammer, could be used as a measure of the overall acoustic quality of the hammer structure. Such a criterion might prove in certain cases to be more meaningful than the conventional "sound power" criterion, especially when the prime concern is the avoidance of the operator's hearing damage. Furthermore, such a criterion would be easier to apply than that of the sound power. The present paper contains a theoretical analysis furnishing an explanation of the observed linear noise-load variation.