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Background: Clinical evidence has suggested that minimal fixation can reduce complications of mandibular angle fractures, though no detailed biomechanical model has yet explored this unique and somewhat unexpected finding. Methods: The current study uses finite element analysis to biomechanically evaluate different fixation schemes used to fixate mandibular angle fractures. Three fixation scenarios were considered: a single tension band at the superior mandibular border, a single bicortical angle compression plate at the inferior border and the tension band and bicortical plate used together. Results: The dual plate model incurred the lowest von Mises stresses in the plates and the lowest principal strain in the callus. The tension band model observed the highest plate and screw von Mises stresses, but had fracture-site callus strain near to that of the dual plate model. The bicortical angle compression plate model observed the highest fracture-site callus strain. Conclusion: The results from this study support the use of the single tension band configuration as a less invasive fixation approach to fractures of the mandibular angle. This is the first known study to explore and confirm clinical observations of angle fracture fixation outcomes with a detailed biomechanical modeling methodology. [ABSTRACT FROM AUTHOR]

Abstract: In micromechanics, accurate quantification of the elastic field (stress, strain, and displacement) caused by the presence of an inclusion in an infinite body is desired for both the particle and matrix materials. Ideally, the solution should be applicable to any particle geometry or shape and for any distribution of misfit along the interface (i.e. misfit profile). This work presents a dislocation-based numerical method, that is an extension to earlier work in this journal [Lerma, J.D., Khraishi, T., Shen, Y.L., Wirth, B.D., 2003. The elastic fields of misfit cylindrical particles: a dislocation-based numerical approach. Mech. Res. Commun. 30, 325–334], for determining the elastic fields of volume misfit particles with arbitrary misfit distribution or particle shape. [Copyright &y& Elsevier]

Abstract: In this work, a set of parametric experiments was conducted on a superplastic material (eutectic tin–lead alloy) with one or more pre-drilled holes in each specimen. The small-sized holes were for simulating microvoids that occur and grow during superplastic forming. All holes were axially aligned with the tensile axis. The results revealed an increase in ductility with the number of holes up to 10 holes and a decrease thereafter. The ductility enhancement was explained based on the m-curve as due to a rise in the strain rate sensitivity locally around the holes. The decrease was explained due to strong void interaction that resulted in shear failure. This was further verified by a separate set of experiments of only two interacting voids with various interspacing. Finally, the void size versus applied strain was fully characterized and the results supported the ductility observations. [Copyright &y& Elsevier]

3D Dislocation Dynamics (DD) simulations are presented which capture the interaction between gliding dislocations in a ductile metallic matrix and nearby dispersed spherical particles. Here the strengthening effect arises from the stress field caused by the particle-matrix mismatch, and no image stress caused by the particles is considered. A radial misfit strain of 1%, simulating thermal processing induced elastic field in aluminum matrix-silicon carbide particulate composite system, is used. Attention is limited to composites with reinforcement concentrations smaller than about 3.5% and with particle sizes smaller than about 0.8 μm. The simulations show dislocation storage in the matrix, in the form a pileup of glide loops near the particle and as part of stress relief, which in turn exerts a back stress on upcoming gliding dislocations. This manifests itself in the simulations in increased flow stress as demonstrated by the stress–strain curve. The results show increased flow stress with increased particle volume fraction as would be expected. However, flow stress is also sensitive to other microstructural features such as particle radius and the distance between the dislocations and particles, and to a lesser extent to the spatial arrangement between dislocations and particles. Overall, the calculated strengthening effect is comparable with that found in experiments. [Copyright &y& Elsevier]

Analytical solutions for the displacement and stress fields due to a misfit particle in a host matrix can be difficult to obtain, especially for complex particle geometries. In this work, we present a numerical method for finding such fields in the case of infinitely-long particles. The method is based on discretizing the continuous misfit region between the particle and matrix into local misfit regions consisting of interstitial dislocation loops. The results presented here indicate very good agreement with analytical solutions and better convergence with increasing loop density. [Copyright &y& Elsevier]

This paper presents dislocation dynamics simulations of the interaction of a circular dislocation pileup with a short rigid fiber as occurs, for example, in metal–matrix composites. The pile-up is composed of glide dislocation loops surrounding the fiber. Here, this problem is treated as a boundary value problem within the context of dislocation dynamics. The proper boundary condition to be enforced is that of zero displacements at the fiber–matrix interface. Such a condition is satisfied by a distribution of image rectangular dislocation loops meshing the fiber''s surface. This treatment is similar to crack modeling using distributed dislocations and falls under the category of “generalized image stress analysis”. The unknown in this problem is the Burgers vectors of the surface loops. Once those are found, the Peach–Koehler (PK) force acting on the circular dislocation loops, and emulating the fiber–dislocation interaction, can be determined and the dynamical arrangement of the circular pile-up evolves naturally from conventional dislocation dynamics analysis. [Copyright &y& Elsevier]