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MODELLING AND SIMULATION


”You might not ever have to have a CAD file for a part that needs to be replaced from 1960, you’d just need to know its position, its volume, its load cases, and you could quickly generate the ideal shape, have it printed and you’ll have a replacement overnight”


calliper, rotor and knuckle. Additionally, the component models are created to incorporate manufacturing variability. After the initial import, the software automatically detects and performs the setup for the contacts or joints between parts of an assembly. Ansys meshing software then provides multiple methods to generate a hex-dominant mesh or a tet mesh, depending on analysts’ requirements. Successfully simulating brake squeal


An example of this can be found in a


recent project completed by Ansys and TRW Automotive, which looked to reduce friction-induced brake squeal in disk brakes. This is an issue that has become particularly important today as other sources of noise have been reduced or eliminated making the issue more acute. TRW Automotive and other brake


producers previously relied on a brake- squeal simulation method. This uses interfaces between brake pads, rotors and other components that were manually modelled prior to performing structural analysis. The weakness of this approach is that it requires assumptions of how the components contact each other that they must be validated by physical testing. This takes considerable time and money and delays the product development process. However, TRW and Ansys validated a


new method that uses Ansys Mechanical to establish the initial contact and compute the sliding contact between the


www.scientific-computing.com | @scwmagazine


pads and the disc. Simulation studies have determined that this approach accounts for system contact conditions, enabling brake noise to be simulated and reducing the need for physical testing to tune the models. ‘The entire simulation process is


contained within a single environment, which saves time by automating many aspects of the process and setting up batch runs for design optimisation or manufacturing variation analysis. This method has made it possible to design and build quieter brakes in less time than is possible with traditional methods,’ said Ansys area director Mike Hebbes in a case study published on the Ansys website. The new simulation process – jointly


developed by TRW and ANSYS – begins with importing the CAD model into Workbench. The production-intent parametric CAD model of the brake assembly incorporates component- level models such as the pad assembly,


then requires capturing the linear behaviour of the structure based on its prior linear or nonlinear pre-loaded status. The TRW team uses linear perturbation analysis to solve a linear problem from this pre-loaded stage – a process that is essentially automated in Ansys Mechanical. Next, engineers employ a nonlinear


static solution to establish the initial contact and compute the sliding contact between pads and disc. The applied stresses and rotation of the disc create the pre-loaded effect, and friction contact generates an asymmetric stiffness matrix during static structural analysis. In the second phase of the linear perturbation analysis, TRW engineers perform a QR- damped or unsymmetric modal analysis. ‘The new simulation approach proved


its capability in a series of simulations that the TRW team validated with physical testing. These confirmation studies demonstrated that it is possible to simulate brake noise and other output parameters, such as mode shapes and frequencies, without using physical testing to calibrate the results,’ commented Hebbes. ‘This new approach can more accurately model the physics behind brake noise


February/March 2020 Scientific Computing World 21


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Alexander Tolstykh/Shutterstock.com


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