Study of interference fit between steel and brass parts

Abstract

Interference fits are generally used in mechanical systems because they have low-cost production and their assembly parts are much smaller than other mechanical joints. Also, their geometric shapes and material properties allow technicians to actively determine how strong the fits are. In this study, let’s present research on interference fits between steel and brass assembly parts. The experimental processes were accomplished with five pairs of specimens to evaluate the behaviours of surface asperities under a high loading condition. Specifically, the specimen pair includes a C45 steel shaft and a C2680 brass hub, which have different surface roughness values (Ra). Let’s apply high-precision methods in measuring all dimensional parameters and employed axial load tests for distinctively inspecting the steel-brass interference fit performance. In every experiment, the measured responses are: 1) the surface roughness values (Ra) before and after loading cycles; 2) the axial load (Fa); 3) the relative displacement value or the real-time interface length in loading stages (l). The aim of this study is to propose a new relative interference value specifically between steel and brass assembly parts, which can help determine the interference loss value more accurately. It was not concluded that with the relative interference of 2.25 ‰ the load capability of steel-brass interference fits is extended. Besides, let’s narrow down the predictive loss coefficient (a) for steel-brass interference assemblies ranging from 1.1 to 2.1, which varies from widely used standards considering a=3. This result helps minimize inaccuracies in interference fit designs, calculations, and work capabilities.