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In this study, it is aimed to convert the radiator bracket of a heavy commercial vehicle to a load cell using the optimum design method. Knowing the forces to which the parts are exposed is one of the most important needs of the product development process. Although commercially available load cells are available on the market for such tasks, it is not always possible to take measurements in the working conditions by replacing the part with a load cell. Also, since the part is removed from the system and replaced with such load cell, the calculated forces vary somewhat from the actual forces because the system changes the stiffness matrix and the load path.
Increasing competition in the automotive sector, legally mandated carbon emissions and weight constraints, customers' low cost and high performance expectations, and perhaps even the highest levels of electric vehicle trends of recent years, are increasingly pushing on the engineers for working on vehicle projects to produce parts that are durable enough as well as lightweight as little as possible. In such a situation, companies that can accurately calculate the forces that their parts are exposed have a very important advantage over their competitors.
In the section of force identification methods, the studies done in the literature about calculation of the forces over part's itself have been referred. Based on the optimum design technique in these studies, a parametric code is written in Matlab program to calculate the optimal strain-gage positions on the model from the results obtained by the finite element analysis. After validation of the algorithm and code is done through simple specimens, the method is applied on the radiator bracket.
The bracket was instrumented with strain-gages from the positions determined by the analysis, and then strain measurements were taken by assembling the bracket to the fixture and applying known forces with hydraulic pistons. After the recorded data are processed and ready for use, the force data is calculated from the strain measurements using the sensitivity matrix determined by the analysis.
When the measured forces and the calculated forces are compared, X and Z axis errors were found to be below 1% and Y axis error was found to be below 5%.
As a result, optimum strain-gage positions on the radiator bracket were determined with the optimum design method and it was successfully demonstrated how precisely the forces can be calculated with the tests made. The method developed in this work and the validity of the Matlab code will not be confined to this part alone and can be used in all structurally enforced parts where the superposition principle is inherent and the loadings are in the elastic region. |
