中強度アルミニウム合金のじん性の評価方法

Abstract

A testing method has been investigated to evaluate quantitatively the toughness of medium-strength aluminum alloys using sheet-type specimens. In this method, toughness was evaluated by the balance of the following two values; the resistance to crack initiation and the resistance to crack propagation, which were obtained by the static tear test at room temperature.It was considered that notch strength was an index of the resistance to crack initiation. In this method, notch strength was defined by the maximum load in the load-deflection curve of the tear test. For the resistance to crack propagation, the slope of the load-deflection curve during crack propagation was considered as its index.In the load-deflection curve, the toughness values are expressed as follows:1) as an index of the resistance to crack initiationNotch strength: σmax=Pmax/A(kg/mm2)Pmax: the maximum load of a load-deflection curve (kg)A: net sectional area (sectional area at the notch) (mm2)2) as an index of the resistance to crack propagationUnit slope=U. S.=Actual slope/A(kg/mm/mm2)Actual slope is the slope of the load-actual deflection curve during crack propagation. (kg/mm)It was recognized that there existed correlations between σ0.2 and (σmax)2 and between (σmax)2 and the U. S. value for about twenty commercial aluminum alloys with no defects. The relation between (σMax)2 and σ0.2, which was considered to show the resistance to crack initiation, was linear in the whole range. The relation between (σmax)2 and the U. S. value, which showed the resistance to crack propagation, was linear only in some regions.