MBD software goes much further than kinematics tool by providing large displacement dynamics modeling capabilities that capture the full gamut of real-world complexity. MBD tools overcome the limitations of FEA by modeling rigid bodies, flexible bodies, springs, damper, joints and other mechanical components while substantially reducing the time required both to create and solve the model. The result is that MBD enables manufacturers of complex products to take full advantage of the benefits of simulation by evaluating the performance of their products, not one part at a time but as an entire system, in the early stages of the design process prior to the availability of prototypes.
A case study of an automobile that experienced brake moan – a single stationary vibration whose fundamental frequency is less than 500 Hz – provides an example of the importance of simulating the entire system. The original equipment manufacturer blamed the brake supplier and asked for cost relief. The supplier performed dozens of bench tests but was unable to replicate the problem. So the supplier used MBD to model the rear disc brake system as well as the vehicle suspension trailing arm on which the brake was mounted. The MBD simulation showed that the brake excited a natural frequency in the trailing arm, resulting in the audible noise. Neither the brake nor the trailing arm had a faulty design – the problem was specific to the entire system. The OEM’s and supplier’s engineers worked together to simulate possible countermeasures on both the brake and suspension. Stamping a stiffening rib into the trailing arm solved the problem. The supplier now uses MBD early in the process of designing new brakes to identify brake moan and other system-level problems when they can be corrected at little or no cost.