Structural dynamics of electric machine stators: Modelling guidelines and identification of three-dimensional equivalent material properties for multi-layered orthotropic laminates

Abstract

International audienceSimulating the dynamic behaviour of heterogeneous finite-element structures such as electric motors often requires to homogenise the models in the first place. Current homogenisation methods do not always imply computing an equivalent homogeneous material's elasticity matrix and are often restrained to specific uses. In this document, a novel approach of equivalent material identification is developed for multi-layered orthotropic structures. A finite-element model of a 3D stratified structure is created, as well as its equivalent homogeneous medium. The dynamic behaviour of the homogeneous structure with the equivalent material identified by the new method is compared at low frequencies to the reference stack and to equivalent materials created using other existing homogenisation techniques. It is shown that this approach is more accurate than existing reference homogenisation methods. Applied to the magnetic core's finite-element model of a real laminated electric machine stator, the method enables simulating the experimental behaviour with good accuracy, without need of time-consuming model updating procedures

Review of multidisciplinary homogenization techniques applied to electric machines

“…The basic idea is to take the volume ratio cPn of each of the component into account to calculate the weighted averages of each constitutive parameters. Details about this method and equations to retrieve the unknown parameters are avail able in the work of M. van der Griet [38] and Millithaler [40] [41].…”

“…The latest referenced approach belongs to Millithaler .. Base unit cell used for coefficient identification -Picture from [40] et al [41][40] [46]. His work introduces a novel approach in which transverse anisotropic and orthotropic [40] or anisotropic [41][46] equivalent material properties are identified for laminated steel stacks.…”

Introduction of Welds into the Dynamic Model of Laminated Structures

“…An efficient contact model in the field of multibody dynamics was presented in [9], which separates between the normal and tangential influences of contact parameters on a highly flexible body. Laminated structures are also commonly modelled using orthotropic material properties [10], [11] and [12] that are obtained experimentally, by measuring a real structure and consequently updating the numerical model. Simplified models are used in order to reduce the complexity, number of components in the analysis, number of details and number of degrees of freedom.…”

“…Many of these models were developed for the modelling of composite structures. These methods are commonly referred to as homogenisation methods [12].…”

“…Many of these models were developed for the modelling of composite structures. These methods are commonly referred to as homogenisation methods [12].Some of the methods employ "template" -2018/2/19 -9:53 -page 2 -#2 Modelling of the structure using the orthotropic material properties is performed by modifying the shear and elastic moduli of the equivalent homogeneous structure.The obtained material parameters are applicable to the specific laminated structure and assume a uniform pressure distribution and friction forces between the lamina.Thus, each modification regarding the geometry, number of laminae, number and position of welds, etc. has to be evaluated experimentally and then the valid numerical model can be created.…”