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Vibration Testing of Rearview Mirrors

In everyday life who of us thinks about the fact that even unspectacular parts of the vehicle such as rearview mirrors have to be thoroughly tested? SMR Automotive is one of the world’s largest manufacturers of exterior and interior mirrors and blind spot detection systems for light vehicles. The SMR plant in Portchester/United Kingdom uses m+p international’s SO Analyzer in conjunction with National Instruments’ CompactDAQ hardware to evaluate the performance of its products during prototype development and in production. Testing is performed both in the laboratory and on a driven vehicle.

Modal hammer rearvier mirror hand
Impact hammer test

In the lab, the mirror assembly is mounted on a rigid test rig and subjected to excitation coming from a force hammer. Measurements of the frequency response function (FRF) of the mirror glass are made using m+p SO Analyzer’s FRF Impact Wizard, which provides facilities such as selection of data points/nodes, double impact detection/rejection, and visual measurement feedback to simplify and optimize data acquisition. Measurements are taken using a single three-axis accelerometer mounted at various points on the mirror in turn. The measured FRFs are analyzed by m+p’s Advanced MDOF Wizard to calculate modal parameters: frequency, damping and mode shape. The results are also compared with a finite element analysis (FEA). Based on the results, the design of the mirror’s components can be tuned by small adjustments to the molding process and component shape.

Drive testing is performed on a vehicle driven around a test track at different speeds. Measurements of the frequency spectrum are taken using three-axis accelerometers mounted on each mirror.

Ian Booth, analyst at SMR Automotive, says, “m+p international’s SO Analyzer enables us to perform our measurements accurately and in a repeatable manner with minimum fuss, enabling us to focus on perfecting the design for high-volume manufacturing.”

Download the 1-page “Rearview mirror vibration” article,
Automotive Testing International magazine, September 2015.

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