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.

Claims

1. A method of shear forming a component from 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, the method comprising the steps of: (i) providing the metallic 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.

2. The method as claimed in claim 1, wherein the metallic sheet blank is formed by a rolling process, and step (ii) comprises the step of: (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, the second surface of the sheet blank remaining in an as-rolled condition.

3. The method as claimed in claim 1, wherein step (ii) comprises the step of: (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, and applying a surface modification process to the second surface of the sheet blank to reduce a surface roughness of the second surface to a second predetermined roughness value, the second predetermined roughness value being greater than the first predetermined roughness value.

4. The method as claimed in claim 1, wherein the surface modification process is selected from the group consisting of abrasive grinding, electrochemical grinding, electrolytic etching, electro-polishing, shot blasting, grit blasting, acid pickling, molten salt bath treatment, and etching.

5. The method as claimed in claim 1, wherein the sheet blank is formed from a material selected from the group comprising titanium alloys nickel-cobalt-based superalloys, stainless steels, and aluminium alloys.

6. The method as claimed in claim 1, wherein the first surface of the sheet blank has a first predetermined roughness value (Ra) of less than 3.0 m.

7. The method as claimed in claim 6, wherein the first surface of the sheet blank has a first predetermined roughness value (Ra) of less than 2.0 m.

8. The method as claimed in claim 6, wherein the first surface of the sheet blank has a first predetermined roughness value (Ra) of less than 1.0 m.

9. A computer program that, when read by a computer, causes performance of the method as claimed in claim 1.

10. A non-transitory computer readable storage medium comprising computer readable instructions that, when read by a computer, causes performance of the method as claimed in claim 1.

11. A signal comprising computer readable instructions that, when read by a computer, causes performance of the method as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] There now follows a description of an embodiment of the disclosure, by way of non-limiting example, with reference being made to the accompanying drawings in which:

[0035] FIG. 1 shows a schematic view of a shear forming apparatus for carrying out the method of the present disclosure, with the material blank held against the mandrel;

[0036] FIG. 2 shows the shear forming apparatus of FIG. 1 with the method of the present disclosure underway; and

[0037] FIG. 3 shows schematically the fatigue performance of shear formed articles formed by the method of the present disclosure together with articles formed by the method of the prior art.

[0038] It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

[0039] Referring to FIGS. 1 and 2, a shear forming apparatus that is capable of carrying out the method of the present disclosure is designated generally by the reference numeral 100.

[0040] The shear forming apparatus 100 comprises a mandrel 110 that can be rotated in a direction of rotation 112 by means of a rotary actuator 114. The mandrel 110 has a generally radially outwardly facing surface 118. This radially outwardly facing surface 118 is formed as an inverse of the desired surface profile of the finished article resulting from the shear forming process.

[0041] A pre-formed metallic sheet blank 120 is clamped against the distal end of the mandrel 110 by a clamping force 150. In this way the rotation 112 of the mandrel is transmitted to the sheet blank 120 that rotates co-operatively with the mandrel 110.

[0042] The sheet blank 120 is provided with a first surface 122 and an opposite second surface 124. In the present disclosure, the first surface 122 is subjected to a surface modification process prior to being clamped in position in the shear forming apparatus 100.

[0043] In one arrangement, the surface modification process is a surface grinding process. The surface grinding process serves two main purposes. Firstly, it enables a thickness 126 of the sheet blank 120 to be maintained to a pre-determined value. Secondly, it enables the surface roughness of the first surface 122 to be reduced to a first predetermined roughness value that is less than the surface roughness of the as-rolled surface.

[0044] In this embodiment, the surface roughness of the first surface 122 is reduced to a first predetermined roughness value of approximately 2.0 m. The surface roughness of the second surface is left in the as-rolled condition.

[0045] In other embodiments, the surface roughness of the second surface may also be subjected to a surface modification process to reduce a surface roughness of the second surface to a second predetermined roughness value, with the second predetermined roughness value being greater than the first predetermined roughness value. A controllable roller assembly 140 is provided to flow form the material of the sheet blank 120 against the radially outwardly facing surface 118 of the mandrel 110.

[0046] FIG. 1 shows the sheet blank 120 clamped against the mandrel 110 before the roller assembly 140 has started the flow forming of the sheet blank 120. FIG. 2 shows the shear forming process underway. The sheet blank 120 remains clamped against the mandrel 110 by the clamping force 150. The roller assembly 140 is part way through the process of flow forming the material of the sheet blank 120 against the radially outwardly facing surface 118 of the mandrel 110.

[0047] The shear forming process continues with the roller assembly 140 flow forming the sheet blank 120 against the radially outwardly facing surface 118 of the mandrel 110 until the component is fully formed.

[0048] In the embodiment of the present disclosure, the shear forming apparatus 100 is controlled by a computer 160. The computer 160 is provided with a computer program 162 that causes the computer 160 to control the shear forming apparatus 100 to carry out the method of the present disclosure. A computer readable storage medium 164 is provided that sends a signal 166 to the computer that causes the computer 160 to carry out the claimed method.

[0049] The technology of shear forming is well known to a skilled person and the control of the shear forming apparatus 100 is not herein discussed in further detail.

[0050] FIG. 3 illustrates schematically the fatigue performance of some examples of shear forming the same component but starting from sheet blanks 120 with different combinations of surface finish on opposing surfaces.

[0051] Sheet blanks 120 having three combinations of surface finish on opposing surfaces were used. Firstly, sheet blanks 120 having both surfaces finished by grinding. Secondly, sheet blanks 120 having one surface finished by grinding, with the ground surface clamped against the mandrel and the roller assembly 140 pressed against the as-rolled surface. Thirdly, sheet blanks 120 having one surface finished by grinding, with the as-rolled surface clamped against the mandrel and the roller assembly 140 pressed against the ground surface.

[0052] Although in production there are no controls over which surface is placed against the mandrel an intuitive situation would be to place the smoother ground side against the smooth surface of the mandrel with the roller assembly being pressed against the as-rolled surface. This arrangement would also give rise to the cosmetic benefit of improving the rougher as-rolled finish during the shear forming process as a result of the action of rollers. However, in reality this arrangement results in a decrease in fatigue performance. It is postulated that this decrease in fatigue performance is caused by the rollers interacting with the rough as-rolled surface to produce microstructural features from which fatigue initiates more readily.

[0053] As shown in FIG. 3 placing the as-rolled surface of the sheet blank against the mandrel, with the roller assembly pressing against the ground surface of the sheet blank, results in an increase in the fatigue performance of the formed component.

[0054] Various example embodiments of the invention are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the invention. Various changes may be made to the invention described and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the present invention. Further, as will be appreciated by those with skill in the art that each of the individual variations described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present inventions. All such modifications are intended to be within the scope of claims associated with this disclosure.

[0055] Example aspects of the invention, together with details regarding material selection and manufacture have been set forth above. As for other details of the present invention, these may be appreciated in connection with the above-referenced patents and publications as well as generally known or appreciated by those with skill in the art. The same may hold true with respect to method-based aspects of the invention in terms of additional acts as commonly or logically employed.

[0056] The breadth of the present invention is not to be limited to the examples provided and/or the subject specification, but rather only by the scope of claim language associated with this disclosure.