Enhanced internal stress aided fatigue resistance in friction stir processed Al/NiTi composites by Nelson GOMES AFFONSECA NETTO


December 13, 2022



Place Sainte Barbe, auditorium BARB93

For the degree of Doctor of Engineering Sciences and Technology

Embedding particulate reinforcements in aluminum matrices to form aluminum matrix composites (AMCs) is an attractive, alternative and innovative process to enhance the mechanical properties of aluminum alloys. Shape memory alloys (SMA), e.g. NiTi (nitinol), are good candidates of reinforcement agents and have the unique property of being able to recover their shape before deformation throughout heating, the so called shape memory effect (SME).

Friction stir processing (FSP) was shown to be an appropriate manufacturing process for particulate AMCs due to mitigation of critical intermetallic formation between particles and matrix. Moreover, multiple FSP passes can homogenize the particles in the aluminum matrix. The present work aims at developing an innovative and functional Al 7075/NiTi composite incorporating internal stresses in the vicinity of reinforcements and understanding their effect on fatigue crack growth (FCG).

The internal stresses are introduced via SME of the embedded NiTi particles in the Al matrix. The patchwork of residual stresses induces dissipation of energy on the crack tip, in combination with crack trapping and deflection mechanism, enhancing fatigue crack growth resistance. The damage mechanism at the crack tip with the presence of internal stresses is investigated on FCG and correlated with the plastic zone size.


Jury members :

  • Prof. Aude Simar (UCLouvain, Belgium), supervisor
  • Prof. Thomas Pardoen (UCLouvain, Belgium)
  • Prof. Renaud Ronsse (UCLouvain, Belgium), chairperson
  • Prof. Lv ZHAO (Huazhong University of Sciences and Technology, China)
  • Prof. Eric Charkaluk (Ecole Polytechnique, France)
  • Prof. Leo Kestens (Ghent University, Belgium)


Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_YzkxOGRkOGUtYWIxMy00NWFlLTlmMTMtNjg5YWQ1ZTY2OTNk%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22ba2d3121-8905-462e-a553-c66f3f5c54ba%22%7d


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