Statistical effects in X-ray diffraction lattice strain measurements of ferritic steel using crystal plasticity. (5th September 2018)

• Record Type: Journal Article
• Authors: Erinosho, T.O.; Collins, D.M.; Todd, R.I.; Wilkinson, A.J.; Dunne, F.P.E.
• Is Part Of: Materials & design. Volume 153(2018)
• Page Start: 159
• Page End: 165
• Publication Date: 2018-09-05
• Subjects: Lattice strain -- Statistics -- Crystal plasticity -- X-ray diffraction -- Texture -- Hardening; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2018.04.071
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: The influence of statistics on calculated lattice strains has been studied by comparing crystal plasticity finite element (CPFE) calculations with strains measured experimentally. Experimentally, when Bragg's law is obeyed, a plane normal must lie within a narrow orientation range (∼ 0.02° for synchrotron diffraction), or Bragg tolerance. However, CPFE models consider only a small number of grains compared to experiments, necessitating a justification of the statistically representative volume. It also becomes necessary to assess the threshold of Bragg tolerance allowable for the determined statistically representative volume. In this study, an 8 × 8 × 8 model was deemed as statistically representative such that only small benefits are obtained in terms of lattice strain calculations by adopting larger models such as 10 × 10 × 10. Based on the selected model, an allowable Bragg tolerance of approximately 5° was calculated. Also highlighted was the coupling between lattice strain, texture, hardening and applied boundary condition which are discriminators that will affect the choice of model size and Bragg tolerance threshold. Graphical Abstract: Highlights: A statistical study of virtual diffraction data from a crystal plasticity finite element model of ferritic steel deformation is presented. Lattice strains from in-situ X-ray diffraction analysis of biaxial or uniaxial deformation were used to benchmark modelled results. Simulating 512 grains and a diffraction angle (Bragg) tolerance of 5° demonstrates suitable fidelity to experiments measurements of lattice strain. The choice of hardening rule or texture was not shown to affect the choice of simulation parameters for ferritic steel.