Random Amplitude Fatigue Life of Electroformed Nickel Micro-Channel Heat Exchanger Coupons

Abstract

The use of micro-channel heat exchangers (MCHEX) with coolant flow passage diameters less than 1 mm has been proposed for heat flux, weight, or volume limited environments. This paper presents room temperature, random amplitude, ε − N (strain versus number of cycles to failure) curves for MCHEX coupons formed by electroplating nickel on a suitable form. These coupons are unique in two aspects; the microstructure formed by electroplating and the presence of holes as an integral part of the structure. The hole diameters range from approximately 10% to 50% to the specimen thickness. The fatigue life of electroformed nickel can be estimated from constant amplitude data using the formulation presented. The heat exchangers with channels parallel to the coupon direction have a lower fatigue life than the solid material.