Modal Model Correlation of Commercial Vehicle Frame

Design decisions based on the virtual simulations leads to reduced number of prototype testing. Demonstrated correlation between the computer simulations and experimental test results is vital for designers to confidently take simulation driven design decisions. For the virtual design evaluation of durability, ride, handling and NVH performance, demonstration of correlation of structural dynamic characteristics is critical. Modal correlation between CAE and physical testing validates the stiffness and mass distribution used in the FE model by correlating mode shape and mode frequency in the desired frequency range. The objective of this study is to arrive at a method for establishing modal correlation between CAE and experimental test for a bare frame and thereby enabling evaluation of design iterations in virtual environment to achieve modal targets. In modal model correlation of frame, virtual simulation of the finite element (FE) model is carried out in free-free condition to extract the modal frequencies up to 100 Hz. Based on the mode shape information of modes in this range, the optimum number of response and excitation locations for experimental test setup is arrived, using the analysis tool LMS pre-Test. Experimental testing is carried out by keeping the frame on an inflated rubber tube. The experimental modal frequencies and shapes are derived from the measured frequency response functions (FRFs). Correlation of modal characteristics is evaluated based on absolute percentage difference in frequency values and correspondence in mode shapes.