Automotive Materials

Andrew SloanAndrew hiking the Overland Track in Tasmania

M.A.Sc. Candidate

Department of Mechanical and Materials Engineering

Nicol Hall Rm. 303
Queen's University
Kingston, ON, Canada K7L 2N8
Tel: (613)-533-3229

Email: sloana@me.queensu.ca

Current Research Keywords

  • Advanced High Strength Steels (AHSS)
  • Dual-phase (DP) Steels
  • Micro-computed X-ray Tomography
  • Digital Image Processing
  • Finite Element Modeling (FEM)

Andrew hiking the Overland Track in Tasmania

Academic Background

B.Sc.Eng. - Mechanical Engineering (Materials Option) - Queen's University

Current Research

A continuing trend in the automotive industry of North America is a shift towards lighter vehicles with greater fuel efficiency. Such a trend has necessitated changes in structural material selection from conventional high strength steels (HSS) towards thinner and higher strength sheet steels such as dual-phase (DP) steels of the advanced high strength steel (AHSS) class. The high strengths of these advanced dual-phase steel grades often come at a price of reduced ductility, which has been known to result in costly premature failure via shear fracture during structural component forming operations. Traditional forming limit criteria are unsuccessful in predicting these shear fractures.

It is well known that the brittle martensite particles within the soft ferrite matrix of DP steels can act as nucleation sites for void damage during deformation. Voids form most commonly at the ferrite-martensite interfaces due to strain incompatibility or via martensite particle cracking. Developing an understanding of the failure/void formation mechanisms prevalent in these new AHSS automotive materials under typical stress states is imperative to the prevention of such premature failures through predictive models. Failure to accomplish this goal will be of severe detriment to the recovery of the Ontario automotive economy, acknowledging the large driving force that the reduction of vehicle weight currently has on the sector.

Recent advancements in the spot size of micro-focus X-ray tubes have produced the opportunity to use lab-scale X-ray microtomography to characterize damage evolution/void development in DP steels. The advantages of such a technique include that is non-destructive, relatively fast, and provides 3-D information on the morphology of voids at high resolution (~ 1µm). X-ray microtomography of in-situ, failed, and partially strained mechanical testing specimens will be used to quantitatively and qualitatively determine how void damage evolves under several typical automotive forming operation loading conditions, and will be coupled with research into the microstructural involvement in the process. Specifically, the effects of martensite volume fraction and martensite morphology are of great interest. This extensive and robust data will provide the means for collaboration within the AUTO21 network to develop microstructurally-sensitive constitutive equations within a finite element method (FEM) model for the damage development of DP steels.

Such a tool will be tremendously useful to steel producers for developing new DP steel microstructures with increased strength/ductility and reduced susceptibility to certain modes of failure. These capabilities will provide an impressive market advantage to Canadian steel producers; remaining on the cusp of the technological advancement of steels for lightweight applications. For part suppliers and automobile manufacturers, this damage model will allow full-scale forming operations and crash scenarios to be accurately studied in a virtual environment, representing a significant cost savings.

Micro-CT

Reconstructed X-ray tomography slices of a failed as-received DP600 in-plane plane strain sample displaying preferential void nucleation at sheet mid-thickness due to heavy banding of martensite at this location. (A) 3D filtered back-projection reconstruction of sample volume. Insertion of a scale bar is inappropriate due to perspective view. (1) Slice at mid-thickness (normal to sheet surface). (2) Slice normal to sheet thickness. (3) Slice normal to failure surface. Pixel size of 1.1 µm in all slices.

Other Interests

Andrew is also actively involved in and/or enjoys:

  • Hockey
  • Queen's University Varsity Development Rowing Crew
  • Innertube waterpolo
  • Yoga
  • Squash
  • Mountain biking
  • Guitar
  • Camping adventures