How Finite Element simulation can support you in your material choice?

How Finite Element simulation can support you in your material choice?

25 Jun, 2021

    How Finite Element simulation can support you in your material choice?

    25 Jun, 2021

      Case of study: polymers used in push-in of a backpack buckle

       

      Material modelling is a key point for a realistic simulation. A good material model has to predict accurately material behaviours under different loading conditions.

      Most products can be dimensioned based on linear elastic models with a stress limit, and the optimization of such products can be performed with basic simulation tools; However, these tools are not relevant when the mechanical test case involves large deformations, contacts between the different parts of the product, and materials that exhibit non-linear behaviours.

      For instance, polymers can be highly non-linear and predicting their behaviour through simulation guides the designer in choosing the right grade according to the specifications:

      Let’s consider the push-in of a backpack buckle: this is a complex case to model because of the sudden energy release at the end of the clipping phase that can cause non-convergence of the solution. Let’s say that the designer has the choice between two POM (Polyoxymethylene) and wants the push-in force to be below 50N.

      Here below are the main properties of the two POM materials.

      POM A

      POM B

      Tensile Modulus [MPa]

      2850

      1950

      Yield Stress [MPa]

      64

      44

      Yield strain [%]

      9

      9

      Nominal strain at break [%]

      30

      40

      At DAES, we use our material modelling skills to choose the adequate non-linear model that will fit to experimental material tests data.

      Thanks to simulation, we can evaluate the push-in reaction forces, which are 70.6N for POM A and 47.6 for POM B, so we can recommend the designer to choose POM B for this product.

      Moreover, the analysis of the Von Mises stress at this peak force shows that the material is below the yield stress for POM B (44MPa).

       

       

       

      Virginie Pouzols – Engineer at DAES

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