Accuracy Of Finite Element Predictions Research Articles

Practical quantification of the effects of flow stress, friction, microstructural properties, and the tribological environment on macro- and micro-structure formation during hot forging

We present a practical approach that improves the accuracy of finite element predictions of hot forging; we emphasize the importance of tribological characterization. We analyze three-stage hot forging of high-strength S45C bearing steel in terms of metal flow lines sensitive to friction. An optimized friction condition is determined by comparing the predicted and experimental flow lines under various conditions. We use a phenomenological approach to predict grain size after dynamic recrystallization when investigating the effects of friction. We explored the relationship between macroscopic and microscopic phenomena with an emphasis on the tribological effect. Friction coefficient optimization improved the predicted metal flow lines and also reduced the error between predicted and measured grain sizes after dynamic recrystallization at all sample points.

Numerical simulation for creep age forming of aluminium alloy 7050 saddle-shaped part

Abstract Unified creep-ageing constitutive equations for aluminium alloy 7050 (AA7050) determined from experimental data were implemented into the finite element (FE) code, ABAQUS, through the user-defined subroutine, CREEP, for creep age forming (CAF) process modelling. The outer contour and yield strength of a saddle-shaped component were predicted, and the accuracy of FE prediction was analysed with experimental results. The research results show that, stress relaxation and creep deformation occur mainly in the early stage of the CAF process. A close agreement has been achieved between the simulation results and measurement data for the formed shape. More than 90% of the area has a surface gap less than 0.5 mm, and the relative error of the yield strength is between -1.18% and +7.22%, which prove the validity of the numerical computation.

Accuracy of finite element predictions in sideways load configurations for the proximal human femur

Subject-specific finite element models have been used to predict stress-state and fracture risk in individual patients. While many studies analysed quasi-axial loading configurations, only few works simulated sideways load configurations, such as those arising in a fall. The majority among these latter directly predicted bone strength, without assessing elastic strain prediction accuracy. The aim of the present work was to evaluate if a subject-specific finite element modelling technique from CT data that accurately predicted strains in quasi-axial loading configurations is suitable to accurately predict strains also when applying low magnitude loads in sideways configurations. To this aim, a combined numerical–experimental study was performed to compare finite element predicted strains with strain-gauge measurements from three cadaver proximal femurs instrumented with sixteen strain rosettes and tested non-destructively under twelve loading configurations, spanning a wide cone (0–30° for both adduction and internal rotation angles) of sideways fall scenarios. The results of the present study evidenced a satisfactory agreement between experimentally measured and predicted strains (R2 greater than 0.9, RMSE% lower than 10%) and displacements. The achieved strain prediction accuracy is comparable to those obtained in state of the art studies in quasi-axial loading configurations. Still, the presence of the highest strain prediction errors (around 30%) in the lateral neck aspect would deserve attention in future studies targeting bone failure.