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Abstract

This thesis examines the effects of some process variables on the performance and their relation with the various component forces during the spin-forging of cones from two sheet metals. Some of the theoretical methods available for the analysis of metal-forging problems have been used to determine the various forming forces involved in the process.

The spin-forging operation was performed on a robust centre lathe and cones were produced from commercially pure aluminium and 70/30 brass sheet. The experimental work performed to examine the various process variables can be classified to two groups:

(a) using a mandrel of constant cone angle,
(b) using mandrels with various cone angles.

The parameters examined with a mandrel of constant cone angle were the effect of speed, feed rate and fractional reduction in wall thickness of the formed conical workpiece on the component forces during the spin-forging operations.

The parameters examined with a mandrel adapter capable of accepting different conical heads were, the effect of cone semi-angle on the component forces and the speed and feed rate on the tangential component force at various cone semi-angles during the spin-forging operations.

This study enables a judicious choice of the process variables mentioned above to be made as far as the forming forces or the power is concerned for a particular application. It is shown that the three component forces in spin-forging vary inversely as the mandrel speed and the cone semi-angle but vary directly as the feed rate. It is also concluded that an optimum mandrel speed exists for a given cone angle at constant feed rate and it varies directly proportional to the cone semi-angle and increases with feed rate for the range of feed rate examined. It is further shown that the component forces are dependent on the final thickness of the formed workpiece and the condition of spin-forging.

Experimental values of the tangential component force as a function of the fractional reduction in thickness of the formed cones are compared with those predicted by the elementary theories and the uniform plastic deformation method.

Upperbound estimates for the tangential component force are presented assuming plane strain deformation and axisymmetric deformation assuming both plane and curved surfaces of velocity discontinuity. These theoretical predictions are compared with the experimental values for varying fractional reduction in thickness of the cones. The Upperbound estimate assuming plane strain deformation provides the best correlation with the experimental results.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TJ Mechanical engineering and machinery
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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