Failure of road grader channel member

Abstract

The samples forwarded were inadequate for a complete appraisal of the reason for failure. The fracture samples were too small for the preparation of mechanical test specimens, and were heat affected by the flame cutting procedure. Microscopic examination was of little use, but visual examination of the specimens revealed a typically brittle fracture. Sections taken from another channel conformed chemically to the ASTM A7 specification, although the mechanical requirements of the specification were .not quite met. The material of the broken member was of a similar classification, but analysis of the samples showed a higher carbon content than for the channel sections. Impact tests on samples prepared from the channel section material showed a transition temperature of 70°F and a Charpy V-notch impact strength of 3 ft/lb at the service-failure temperature. The higher carbon content of the broken channel would accentuate the tendency to low temperature brittleness . The chemical and mechanical characteristics would combine to make this steel prone to brittle failure under the loading and temperature conditions which occurred.