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We investigated how twin modes in hexagonal close packed materials can affect large inelastic strain behavior and fracture. We considered the two twin mode systems of ( 11 2 ¯ 1 ) [ 1 ¯ 1 ¯ 26 ] and (0001) [ 1 ¯ 1 ¯ 20 ] in zircaloy-2, with each mode having 24 unique twin systems. We then incorporated these twin and parent slip systems with a dislocation-density crystalline plasticity, a non-linear finite-element, and fracture framework that accounts for crack nucleation and propagation. We investigated how these twin modes affect the interrelated effects of crack nucleation and propagation, dislocation density and inelastic slip evolution, stress accumulation, and lattice rotation. The predictions indicate that twin modes significantly affect local deformation and fracture behavior, and, therefore, are essential for the accurate representation of behavior at different physical scales in heterogeneous crystalline hexagonal close packed systems. [ABSTRACT FROM AUTHOR]

Abstract: Formability of four magnesium AZ31B sheet materials, produced either by direct chill or twin roll continuous casting, was investigated at 400°C and 5×10−3 s−1 using pneumatic stretching. Sheet specimens were deformed through a series of four elliptical die inserts, with aspect ratios ranging between 1.0 and 0.4, producing ellipsoidal domes with different biaxial strain combinations. Testing was carried out in two scenarios, i.e. with the major strains aligned either along or across the rolling direction of the material. Circle grid analysis was then used to map the planar strains of the deformed specimens; the latter were used to generate comprehensive material forming limits curves (FLCs) that bound the safe, marginal and failure deformation zones. Orientation effects were quantified by constructing a “composite FLD” for each of the four sheets; the diagrams collectively showed that greater formability limits are achieved along the material''s rolling direction. Furthermore, detailed comparisons between the four sheets were carried out based on formability limits, deformation uniformity, maximum dome height prior to failure, and fracture surface morphology and chemistry. Disparities in formability were linked to differences in grain structure and material inhomogeneities. [Copyright &y& Elsevier]

Abstract: This paper presents the orientation effects on residual stress release by pulsed magnetic field treatment. Specimens are produced by tungsten inert gas (TIG) welding and the initial residual stresses in them are measured by the hole-drilling method. With different orientations these specimens are treated in the same magnetic field and the residual stresses are measured for the second time. By comparing the stress values before and after treatment it is obvious that magnetic field treatment effects are related to orientations. Based on a referred ferromagnetics formula, a supposition is proposed and a further survey of the magnetostriction constant is carried out. All experimental results support the proposed model and a prescription is given for pulsed magnetic field treatments. [Copyright &y& Elsevier]