Significance evaluation of effect of operational changes in material on impact strength of various zones in leaf spring at low temperature

Abstract

Significance of the effect of structural changes in spring steel arising during operation in various zones of the leaf springs on zonal resistance of the steel to a brittle fracture at temperatures of a climatic range of a permafrost region is studied. Structural damage was determined at the temperatures of 20, –20 and –60 °C and impact strength of the different zones of the leaf spring failed during the operation was estimated. Features of a fine structure of fracture surfaces of Charpy specimens and micromechanisms of their failure are investigated. To determine variability of the impact strength in the zones of the spring, analysis of variance (ANOVA) of test data was carried out. It was found that at temperatures of 20 and –20 °C the effect of the zone damage of a material on the impact strength is insignificant, and at –60 °C the effect of the zonal damage on the resistance to the brittle fracture becomes significant. The fractographic features of the fine structure of the fracture surfaces at the various test temperatures are discussed. Results can be used in a prediction of a life time of elastic elements in vehicle suspension: it is necessary to take into account zoning of the operational damage of the steel under conditions of the low climatic temperatures.