Phast results

Steel giant and metrology specialist team up to devise a speedy method of measuring accurately the strain within a pressed body panel. Stuart Nathan reports.

A combination of digital photography and measurement technologies could help form complex car panels more efficiently, according to steel manufacturer Corus.

Working with metrology specialist Geodelta, the company has developed a system known as PHAST (PHotogrammetric Automated STrain measurement system) which uses photogrammetry to measure accurately the strain within a pressed body panel.

Strain is produced when an object is deformed, and being able to measure it accurately is important for processes involving the forming of metals. For car makers, it’s an important parameter, as the percentage strain in a panel — how much it has been deformed from its original shape — can determine how it flows when it is pressed.

Traditional strain analysis methods allow only small areas of a pressed component to be measured, usually by examining how far pre-placed markers have moved apart. This makes the process for a large panel extremely time-consuming.

The Corus system, developed at the company’s R&D centre in IJmuiden, in the Netherlands, uses digital photography to take images of a pressed panel from up to 20 different positions. ‘The number depends on the part geometry,’ explained Hans Brouwer,

Corus RD
&T customer support engineer. ‘Each new image enhances the reliability of the determined results, and improves the accuracy of the co-ordinates of the surface points.’

The images are then fed into Geodelta’s software, which processes the data from the different angles to give an accurate model of the deformed piece. The system calculates the strain for the whole part, with an accuracy of plus or minus five per cent strain, within one to three hours.

These results, said Corus, can be used to make changes to the pressing tools to avoid subsequent production problems, such as thinning and splitting of the metal as it is pressed; it also helps the engineers improve the robustness of the pressing operation and reduce the amount of scrap metal produced.

PHAST has been under test at Ford’s plant in Genk, Belgium, where its portability has proved useful. Corus material engineers have been able to monitor and visualise material feasibility and strains on-site.

‘We now have the ability to discuss how to improve material performance with the Ford engineers while on-site, thus streamlining the process,’ said Brouwer.

As well as the ability to analyse large parts with complex shapes, such as car and van side-panels, PHAST also combines the strain analysis with materials knowledge, said Brouwer. ‘PHAST was originally developed to provide a rapid response to production press shop problems,’ he explained. ‘Additionally the system allows us to compare the performance of new grades of steel during a current vehicle’s lifecycle with the ability to introduce better performing grades, if robustness of the pressing process can be demonstrated to our customer.’