Alternatives for Finite Element Analysis of Blade Forging
Doctoral thesis, 1997
This thesis is a theoretical and numerical study of the weaknesses and capabilities of alternative finite element procedures for simulation of the blade forging problem and also an analysis of the practical aspects of that process.
An overview is presented of the finite element method for non-linear problems with elastoplastic constitutive relations, focusing on quasistatic implicit and dynamic explicit approaches. It is shown that in bulk metal forming problems the application of the dynamic explicit method using increased velocity or mass scaling, can compete well with the quasistatic implicit method. Numerical comparisons show that the dynamic explicit method is more stable, has enough accuracy, consumes less CPU- time, and is more simple to use than the implicit one.
In a second part of the study, the efficiency of the solid and flow approaches is investigated and a new approach is proposed. Deformations, strains, stresses and load curves are compared for both loading and unloading simulations. It is demonstrated that the flow approach shows a good convergence but that it can not predict the volume change which is very important in closed die forging. On the other hand, the solid approach shows convergence problems. A new approach, a combined flow-solid approach, is proposed. It is explained how the solution can automatically switch from the flow to the solid approach and how both can work in the same solution environment. The flow-solid approach is examined numerically and compared with the two previous approaches in the loading and unloading simulations. In comparison with the solid approach, most of the convergence difficulties are removed in the new approach while the same accurate results are obtained with less computational time. In comparison with the flow approach, the new approach is was much more accurate for a little more computational time.
Comparing all tested methods, it is concluded that the dynamic explicit procedure and the flow-solid approach are the two best ones when accuracy, efficiency and simplicity are considered.
From strains and stresses internal and surface properties can be obtained. The press load and the optimal initial location of the billet are among the results which have practical importance for the process. Forming of the blade without any defects and the possibility to include the process in one stage from a circular stock are also very important aspects of the process. By means of the numerical simulations these aspects could be realized.
finite element method
closed die forging