Laser-Speckle-Based Sensor for the Measurement of Mechanical Deformation on Stacked Metal Sheet Structures

Abstract:
Stacks of metal sheets are widely used in electrical motors, transformers and generators to reduce for eddy current loss in their magnetic circuit. During their design process these electrical machines are optimized for their cost-performance ratio and/or their weight with respect to its given application area, and so the mechanical behaviour of the laminated sheet stacks becomes more and more important to be considered during the mechanical and fatigue design of these electromechanical systems. This work describes a contactless measurement system based on the digital speckle photography principle for evaluating mechanical deformation states on stacked laminated metal sheet structures, enabling the measurement of displacements and subsequently strain of individual layers of stacked metal plates. A thorough investigation of the obtained measurement performance for real world experiments demonstrate an achievable measurement resolution in the order of a single µm for estimating the relative displacement between individual metal layers, with measurement rates of 50 Hz and above. Measurement results from real world load experiments on stacked metal sheet structures proof the high potential of the realized sensor system, allowing for valuable experimental verifications in the development and parameterization of simulation models for a proper mathematical description of the non-linear mechanical behaviour of stacked metal structures.