Analytical and experimental bond strength investigation of cold forged composite shafts

Composite cold forging denotes the simultaneous processing of hybrid raw parts by cold forging operations. The objective is the manufacturing of composite components by means of joining by plastic deformation. For lightweight purposes, composite shafts were produced by forward rod extrusion of backward extruded steel cups, into which an aluminum core has been inserted. The final composite shafts possess a wear-resistant outer steel sleeve and a light aluminum core. An analytical model has been developed to predict the strength of the force fit of composite shafts produced by cold forging. Push-out tests were conducted in order to experimentally determine the bond strength for the validation of the model. The analytically estimated bond strengths are in good accordance with the experimental values determined by push-out tests. The bond strength can be increased significantly by structuring the inner surface of the cups for the hybrid raw part to cause a form fit between steel sleeve and aluminum core after forward rod extrusion. Metallurgical bonds are not established between steel and aluminum in the investigated composite cold forged shafts.