STIFFENING EFFECT OF BOLT-ON TRANSDUCERS ON STRAIN MEASUREMENTS

Abstract

THE STRAIN OF A STRUCTURAL ELEMENT IS OFTEN MEASURED INDIRECTLY BY DETERMINING THE STRAIN OF A TRANSDUCER THAT IS SUPPOSED TO FOLLOW PERFECTLY, AND WITH NEGLIGIBLE INTERACTION, ITS DEFORMATION AROUND THE MOUNTING POINT. THIS ASSUMPTION IS NOT ALWAYS TRUE, DEPEND-ING ON THE STIFFNESS OF THE TRANSDUCER RELATIVE TO THE LOCAL STIFFNESS OF THE PIECE IT IS ATTACHED TO. THIS PAPER DEALS WITH THE PROBLEM OF EVALUATING THE INFLUENCE THAT A RELATIVELY RIGID TRANSDUCER (THE HBM SLB-700A WAS CHOSEN AS AN EXAMPLE) HAS ON THE STRAIN FIELD, STUDIED FROM BOTH THE THEORETICAL AND THE EXPERIMENTAL POINT OF VIEW. THE FINDINGS OF THE RESEARCH SHOW THAT, TO INTERPRET COR-RECTLY THE MEASUREMENTS OBTAINED FROM THIS KIND OF INSTRUMENTS, THE PERTURBATION THEY INDUCE TO THE STRAIN FIELD CANNOT BE DISRE-GARDED. A CORRECTIVE FACTOR OBTAINED NUMERICALLY BY MEANS OF THE FEM AND DISCUSSED IN THE PAPER CAN BE USED AS A FIRST APPROXIMA-TION TO EVALUATE THE TRUE STRAIN, STRESS, AND FORCES IN COMMON STRUCTURAL STEEL ELEMENTS.