Material Properties in Flexing Beam Stress Calculations using FE Analysis

Objective: The ISO4049 formula for stress does not include values for the material's elastic modulus (E) and Poisson's Ratio (V). The purpose of this study is to determine by FEA analysis if variations in E and V at different applied loads will produce different outcomes for the calculated stress.

Methods: All analyses were performed with Solid Works v.6 ( Dessault Systemes Solid Works Co) (SW), a 3D computer aided mechanical design program. A 2x2x25mm beam model was created using a split line method. The beam was constrained in the x, y and z directions on one end and in the x and y in the other. Varying loads of 10,20, 30, 40, and 50N  were applied to the middle of the beam in the simulation. For each load, different E values ( 5,8,10, and 15 psi)  and V values (0.1, 0.20, 0.25)  were applied. Mesh was generated and max stress was obtained.

Results: Table 1 shows the calculated stress values from FEA compared to the caculated stress values from the ISO formula. Figure 1 shows the results for one applied load (50N)graphed in a 3D plot. The maximum deviation from the ISO formula for all calculations was 2.1%

Conclusion: Under the constraints of this study it appears that for a large range of E and V the possible error in stress calculations is minimal and that the simple ISO formula provides a reliable estimate for the transverse flexural strength.