Rosenhain Centenary Conference - 1. Engineering requirements 1.5 Undercarriage material requirements

Abstract

The main basic engineering requirements for undercarriage materials are described: while magnesium, aluminium and titanium alloys still continue to play a useful part, the ultra high tensile steels are now the preferred choice for many major structural items. The high standard of material quality and subsequent processing control necessary to ensure the integrity of components produced from these steels are described, with specific reference to the 300M alloy. Comparable data on fracture toughness and stress corrosion are given: it is explained why a fracture-mechanics approach to material selection has only limited application and that service reliability is dependent primarily on the steps taken to avoid crack initiation. Despite efforts to improve the intrinsic properties of these steels, with particular emphasis on reducing subcritical crack growth of environmental origin, no worthwhile replacement for 300M has been found. It is concluded that the compromise between strength and brittleness has already been reached.