Two Case Studies: Renault and Daimler Apply New Tribology Friction Model!

OEM’s Show-casing TriboForm at the IDDRG 2019 Conference

On 3-7 June 2019, the 38th International Deep Drawing Research Group (IDDRG) conference was held in Enschede, the Netherlands. At the IDDRG, the leading sheet metal specialists and researchers from all over the world gathered for fruitful discussions on challenging technical topics in forming technology. One of the main sessions of the conference covered tribology in cold stamping simulations. In this session, two cases were presented, from Daimler and Renault, showing how tribology plays a key role in simulating and producing high quality parts. In this post, we reveal these two cases with a particular look at how these leading OEM companies apply TriboForm in their engineering processes to reduce production issues and reduce springback deviations.

Tribology Study 1: Front fender Mercedes-Benz Passenger Car

Figure 1: Front fender of a new Mercedes-Benz passenger car

In this case study, Daimler evaluated and combined TriboForm’s friction model in stamping simulations for the front fender of a new Mercedes-Benz passenger car with different drawbead models. As a result, they achieved an improved simulation accuracy of this part using TriboForm’s friction model applied to all considered draw-bead models. They found a reduction of variances, in terms of draw-in and strain between different drawbead models when applying TriboForm. Also, the best match with experimental results was achieved using 3D profile drawbeads with TriboForm’s friction model compared to using a constant friction coefficient.

Figure 2: Springback comparison between simulation results using a constant friction coefficient (left), TriboForm’s friction model (center) and a production part (right).

In addition, the draw-in and springback prediction of the front fender was evaluated in detail. The right image in Figure 2 shows the springback results of the front fender part after performing a first try-out without applying any specific optimizations. The amount of spring-back of the part was measured and compared with simulation results. As can clearly be seen, the simulation using TriboForm’s friction model increased the accuracy of spring-back prediction as compared to the simulation using the Coulomb constant friction coefficient. Also, draw-in was predicted more accurately compared to applying a constant friction coefficient. For more details, please see the conference paper.

You can download the full conference paper here.

Tribology Study 2: Trunk Lid Inner Part Renault Talisman

Figure 3: Tail-gate inner part of the Renault Talisman

In the second project, Renault Group, Tata Steel and TriboForm joined forces to examine the cause issues observed on a trunk lid inner part, which was facing wrinkles and splits in production. A comparison was made between simulation results using a constant friction coefficient and TriboForm’s friction model. It was found that that the production part had a smaller draw-in than the simulation had predicted using a constant friction coefficient. However, the prediction when using TriboForm’s friction model resulted in a simulated part with a draw-in that was much closer to the outer edge of the real part. Simulation of the strain levels using the constant friction coefficient did not correspond in terms of magnitude and critical locations with the production part. Results using TriboForm’s friction model showed the critical strain levels, successfully predicted at the exact location. Finally, a comparison between observed wrinkles in the produced part and simulation shows that both models could predict wrinkles as observed in production.

You can download the conference paper here.

Concluding remarks IDDRG 2019 Conference

The IDDRG 2019 conference was organized by the University of Twente and Tata Steel Europe, with AutoForm as main sponsor. With TriboForm being an AutoForm product and a spin-off company of the University of Twente, and with close R&D cooperation’s with Tata Steel, this was a great opportunity to show-case TriboForm at the IDDRG 2019 conference.

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