Effect of Hardness on Creep Response of Strain Gage Based Force Transducer Using AISI 4340 Steel as Spring Material

摘要

Creep problem of spring materials plays an effective role on the performance of force transducers. Several heat treatments can be applied to spring materials in order to minimize creep response. The effect of heat treatment on creep properties of AISI 4340 steel was investigated in this study. The tensile specimens of AISI 4340 steel were austenitized and oil quenched, and then tempered to 35, 45 and 55 Rockwell-C hardness levels. After proper heat treatment and final machining of column type specimens, the preparation of tensile force transducers was completed by bonding special-class transducer strain-gages onto them and constructing necessary Wheatstone bridge circuits. Then all force transducers were loaded in a dead-weight force standard machine to measure the related creep response. It was observed that heat treatment (and the resulting martensitic structure) of the spring material had a major effect on the performance of the transducer, particularly where creep response was concerned. Since the minimization of creep problem had prime concern, best results could be achieved in transducers consisting the hardest spring material.