CFD simulation of hydroforming complex aerospace sheet metal components 

MSM aerospace fabricators specialises in manufacturing complex formed sheet metal parts for the aerospace industry from tough materials such as Nickel alloys (Inconel 625 and Inconel 718) and Titanium (all of which are often referred to as memory materials due to their inherent desire to return to their original shape). In order to achieve these complex forms MSM has perfected the hydroforming (sometimes referred to as fluidforming) method of pressing; this being a cold forming process.

Because of the nature of these complex forms and materials a lot of this knowledge has been built up empirically over many years experience. Consequently there is generally a degree of uncertainty when taking on a new job and often the process (along with most other forming processes) can require a substantial amount of time and cost to develop. MSM has resolved this by adopting and tailoring a CFD (computational fluid dynamics) package which enables this process to be simulated and perfected prior to any metal being cut or tools being manufactured. This method predicts the outcome of the hydroforming process and effectively creates a virtual hydroforming process.This has proved to be a significant saving in not only cost but also in lead time from initial enquiry to supplying good, conforming components.

The following flow chart diagram compares the traditional method of developing the press forming process for a new componentwith MSM’s CFD simulation method for their hydroforming process:-

 

With the traditional method there can be a number of iterations of the “re-design---modify/re-cut---re-press---re-measure” cycle before the forming process can be fully proven and good parts made. This can be both expensive in having to re-make blanks and/or re-cut press tools plus the cost of setting up the press every time to form a new sample, as well as being very time consuming with it often taking weeks to complete.

With the MSM’s CFD simulation method the process can very quickly be optimised as these iterations can be done in much less time, in hours rather than weeks, and with no metal being cut whatsoever. Furthermore there’s much less risk of scrapping expensive sheet material and/or the press tools. This represents a significantly less expensive process development cost and a significantly quicker response time to new business.

The CFD system also produces a very high level of 3 dimensional analysis across the whole of the part and allows a greater understanding of how the material “flows” during the process. Using the example of a formed elbow type component made out of 1.2mm thick Inconel 718 and hydroformed in one operation at 4,200 psi to a depth of 38mm, the analysis is shown in the following figures:- 

Fig.1 shows the potential areas of cracking and wrinkling 

Fig.2 shows in detail how the part would form, prior to any modifications being made

Fig.3 shows the localised thickness of the formed part in all areas

Another advantage which MSM has found is that, working in conjunction with their customers' design engineers, they have used the system as a tool to assist in the initial design of the aircraft component. This optimises the component design to suit MSM’s hydroforming process prior to it being finalised, effectively being design for manufacture thereby creating a win-win situation for both the customer and MSM.

MSM’s CFD simulation system is equally as effective in predicting bulge forming of parts as well as hydroforming.

If you need more information or you would like us to get in touch to discuss a specific requirement please complete the contact us sheet.