INTERFACIAL FRACTURE TESTING OF DEPOSITED METAL LAYERS UNDER 4-POINT BENDING

In this work, a four-point bend test for determining interfacial fract ure resistance is applied to deposited metal layers. The motivating ap plication for this study is a layered manufacturing technique involvin g the successive deposition of molten metal. A four-point bend test fo r determining the interfacial fracture toughness of a two-layer bimate rial specimen has been considered in the literature. In this study, th is concept is extended and applied to both two-layer and three-layer d eposited metal specimens. A closed-form expression for a steady-state energy release rate (independent of crack length) is obtained for the three-layer specimen and is verified by finite element calculations. I n addition, finite element results are used to calculate a steady-stat e measure of mode mix. Experimental procedures for determining the int erfacial fracture toughness of deposited metal layers are described fo r both two-layer and three-layer specimens. Insight is given into spec imen design such that interfacial fracture occurs prior to large-scale yielding. Critical interfacial fracture parameters are presented for two deposited metal interfaces and the existence of varying toughness along deposited metal interfaces is discussed. Copyright (C) 1996 Else vier Science Ltd