Soutenance de Thèse : Shurui ZHANG

" Evaluation of electromagnetic properties affected by mechanical deformation in non-oriented electrical steel using magnetic non-destructive testing "

20/11/2023 - 9h00 -  co-tutelle Tohoku University / INSA Lyon  - VISIOCONFERENCE

Laboratoire INSA : LGEF

Ecole doctorale : ED160 EEA
Résumé  Electrical steel is an iron-silicon alloy with specific magnetic properties such as low power loss  and  high  permeability.  Electrical  steels  are  massively  used  for  the  iron  core  of motors  in  electric  vehicles.  During  manufacturing,  mechanical  stresses  and  strains are inevitably  induced,  leading  to  a  degradation  of  the  magnetic  performance.  Non-destructive  testing  solutions  exist;  they  indirectly  observe  material  states  by  setting conformity thresholds and removing all unsatisfactory specimens. Local properties can be observed with X-rays or advanced imaging techniques (such as EBSD), but their cost and complexity  make  them  questionable  in  the  industrial  context.  Considering  that  the working  principle  of  the  motor  core  is  converting  electrical  energy  to  kinetic  energy through electromagnetic interaction, this work proposes to use magnetic techniques. The IEC  international  standards  describe  classic  experimental  setups  for  magnetic characterization  (Epstein  frame,  single-sheet  tester,  etc.).  These  methods  enable  the evaluation  of  magnetic  behaviors  via  hysteresis  curves,  but  it  is  destructive,  non-local, and  incompatible  with  in-line  production.  Besides,  different  mechanisms  overlap  during the  hysteresis  cycle  characterization,  making  the  influence  of  stress  complex  to  be evaluated.  Current  studies  on  the  electromagnetic  properties  affected  by  mechanical loading  combine  the  hysteresis  curve  and  magnetic  Barkhausen  noise  (MBN) measurements.  However,  a  comprehensive  exploration  of  the  magnetic  behavior influence  caused  by  mechanical  issues  and  the  corresponding  mechanism  still  needs further understanding. In this work, a combination of several techniques was considered.
Integrating  multiple  detection  methods  provided  more  information  and  support  for  the integrated  analysis  of  magnetic  behavior  but  also  introduced  more  parameters accordingly. These parameters, introduced more information into the system, leading to complementary conclusions and a very accurate estimation of the mechanical properties and degradation status.