Particle reinforced metal matrix composites are now being produced commerically, and in this paper the current status of these materials is reviewed. The different types of reinforcement being used, together with the alternative processing methods, are discussed. Depending on the initial processing method, different factors have to be taken into consideration to produce a high quality billet. With powder metallurgy processing, the composition of the matrix and the type of reinforcement are independent of one another. However, in molten metal processing they are intimately linked in terms of the different reactivities which occur between reinforcement and matrix in the molten state. The factors controlling the distribution of reinforcement are also dependent on the initial processing method. Secondary fabrication methods, such as extrusion and rolling, are essential in processing composites produced by powder metallurgy, since they are required to consolidate the composite fully. Other methods, suc...

Particle reinforced aluminium and magnesium matrix composites

(2007) A mathematical representation of the multiaxial Bauschinger effect Materials at High Temperatures: Vol 24, No 1, pp 1-26

/pdf/a-mathematical-representation-of-the-multiaxial-bauschinger-1jxyrlbe5g.pdf

A mathematical representation of the multiaxial Bauschinger effect

Constitutive equations for cyclic plasticity and cyclic viscoplasticity

A review of some plasticity and viscoplasticity constitutive theories

https://www.tf.uni-kiel.de/matwis/amat/iss/kap_9/articles/twip_raabe.pdf

Dislocation and twin substructure evolution during strain hardening of an Fe-22 wt.% Mn-0.6 wt.% C TWIP steel observed by electron channeling contrast imaging

"Die-less forming" is a new concept, intended to manufacture long compo nents of continuous-fiber thermoplastic-matrix composites. The concepts behind die-less forming have been tested in experiments on a two-roller demonstration machine. The experiments focused on finding the effects of important forming parameters on the shape. Laminates with special lay-up were also made and formed to study the effect of lay-up on shape.Quasi-isotropic laminates showed an unexpected "excess bending." An elastic/visco- plastic model has been developed to explain and predict this excess bending during die- less forming. The model is rate dependent and captures the shape dependency on strain rate, transverse feed magnitude and the lay-up. The model is based on the application of the principle of virtual displacements. The model predicts the net bend angle well for quasi-isotropic laminates.

A New Approach to the Forming of Thermoplastic-Matrix Continuous-Fiber Composites — Part 2: Experiments and Model

The NONSS method for numerically integrating time-dependent constitutive equations requires evaluation of the partial derivatives of the constitutive equations. A numerical method for evaluating these partial derivatives has been developed, thus avoiding the cumbersome task of analytically re-deriving the partial derivatives when improvements to the constitutive model are evaluated. This method is based upon the adaptive finite-difference algorithm published by Stepleman and Winarsky. Modifications of their algorithm are described that allow its efficient use within an extended version of NONSS, called NONSS-ND.



Using the MATMOD constitutive equations, the capabilities of NONSS-ND are demonstrated by comparing the results of a wide variety of deformation simulations with those of NONSS, for which the derivatives are computed from analytical solutions. The numerical differentiation within NONSS-ND is shown to be sufficiently accurate for use in integrating time-dependent constitutive equations, but results in a 30–100 per cent increase in computation time. Multi-element structural calculations are therefore found to be uneconomical, but NONSS-ND is well suited for testing alternative constitutive models owing to its accuracy and its general applicability to highly non-linear systems of differential equations.

Numerical differentiation for use in integrating unified constitutive equations

An advanced model of nonelastic deformation is proposed which is capable of predicting strain softening in metals during complex non-proportional loading histories. The model, an extension of the MATMOD constitutive equations, now includes representations of the effects of microstructural heterogeneity, strain-activated recovery, and colinearity of internal stress and strain rate; these additions underly the model's ability to predict strain softening in aluminum. This ability is utilized by coupling the new model, MATM0D-4V, with a model of strain localization. Model predictions of strain softening and strain localization caused by strain softening demonstrate some of the capabilities of MATMOD-4V.

A. K. Miller

Papers

A New Approach to the Forming of Thermoplastic-Matrix Continuous-Fiber Composites — Part 2: Experiments and Model

Numerical differentiation for use in integrating unified constitutive equations

A materials model for strain softening with applications in modeling strain localization