Laboratory for Dynamics of Machines and Structures 
Introduction of Welds into the Dynamic Model of Laminated Structures
 P. Ogrinec, G. Čepon and M. Boltežar
Journal of Mechanical Engineering, Volume 64, February 2018, Pages 73-81

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Abstract
Laminated structures, like an electric stator package, exhibit orthotropic behaviour and high levels of internal damping due to the inter-laminar friction forces. Modelling the complex geometry, number of laminae, spatial pressure distribution, and the effects of welds on the dynamic response of laminated structure remains a challenging issue. The presence of welds, that serve as a physical connection between laminae, results in non-uniform pressure distribution between laminae. Usually orthotropic material properties are proposed to account for lower stiffness in the sheet stacking direction. These models assume uniform distribution of friction forces and may even lead to occurrence of additional, unrealistic mode shapes. In this paper the dynamics model of the electric machine stator is proposed that employs a new contact formulation using beam elements, characterized by stiffness and damping parameters in the tangential direction and nonlinear contact stiffness in the normal contact direction. The welds and the welding process itself are represented using spring-thermo elasto-plastic bar model. As the contact model assumes nonuniform pressure distribution it is possible to include the effect of residual stresses that occur after the welding process. The validity of developed numerical model is demonstrated by comparing numerically and experimentally obtained eigenfrequencies and modes for three different stator packets that differ in geometry, position and the number of welds.
Authors

Researcher

Primož Ogrinec, PhD Student

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  primoz.ogrinec@gmail.com
  +386 1 4771 228

Assistant Professor

Gregor Čepon, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  gregor.cepon@fs.uni-lj.si
  +386 1 4771 229
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Professor

Miha Boltežar, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  miha.boltezar@fs.uni-lj.si
  +386 1 4771 608
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