Prediction of linear noise-load relationship for impact forming machines

Abstract

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 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.