Forming method

Abstract

A method of shear forming a component comprises the steps of:(i) providing a pre-formed metallic sheet blank, the sheet blank having a first surface and an opposite second surface, the perpendicular separation between the first surface and the second surface defining a thickness of the sheet blank;(ii) applying a surface modification process to the first surface of the sheet blank to reduce a surface roughness of the first surface to a first predetermined roughness value;(iii) positioning the second surface of the sheet blank against a mandrel; and(iv) applying a roller to the first surface of the sheet blank in a shear forming operation to form the sheet blank into the component.

Description

CROSS-REFERENCE RELATED APPLICATIONS[0001]This disclosure claims the benefit of UK Patent Application No. GB 1702463.9, filed on 15 Feb. 2017, which is hereby incorporated herein in its entirety.FIELD OF THE DISCLOSURE[0002]The present disclosure relates to a method of shear forming and particularly, but not exclusively, to a method of shear forming components for a gas turbine engine.BACKGROUND OF THE DISCLOSURE[0003]Shear forming has been used to produce conical parts from sheet and plate material for many years. Shear forming is a cold forming technology whereby a flat metal plate blank (or ‘pre-form’) is mounted onto a rotating mandrel (typically having a conical surface profile) and the material is made to flow against and up the mandrel by the action of one or more rollers. The final wall thickness is achieved by controlling the gap between the roller and the mandrel so the material is displaced axially, and generally parallel to the axis of rotation.[0004]Sheet material used ...

AI Technical Summary

Benefits of technology

The present patent provides a method for shear forming a component from a pre-formed metallic sheet blank by applying a surface modification process to the first surface of the sheet blank to reduce surface roughness, positioning the second surface of the sheet blank against a mandrel, and applying a roller to the first surface of the sheet blank in a shear forming operation to form the sheet blank into the component. The method results in improved fatigue properties of the shear formed article compared to articles formed without the surface modification process. The surface modification process can be applied by abrasive grinding, electrochemical grinding, electrolytic etching, electro-polishing, shot blasting, grit blasting, acid pickling, molten salt bath treatment, or etching. The sheet blank can be formed from titanium alloys, nickel-cobalt-based superalloys, stainless steels, or aluminium alloys. The first surface of the sheet blank can have a roughness value of less than 3.0 μm, preferably less than 2.0 μm, or even less than 1.0 μm. The computer program can control the shear forming apparatus, and the method can be performed using a computer or a separate storage medium.

Problems solved by technology

This has led to a situation whereby grinding on both sides of the sheet is often stipulated prior to shear forming, which substantially increases the cost of the shear forming process.

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