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Nanoparticles (NP) embedded into a matrix material have been shown to improve mechanical properties such as strength, hardness, and wear-resistance. However, the tendency of NPs to agglomerate in the powder mixing process is a major concern. This study investigates five different mechanochemical processing (MCP) routes to mitigate agglomeration to achieve a uniform dispersion of ZrC NPs in an Fe-based metal matrix composite. Our results suggest that MCP with only process controlling agents is ineffective in avoiding aggregation of these NPs. Instead, the uniformity of the carbide NP dispersion is achieved by pre-dispersing the NPs under ultrasonication using suitable surfactants followed by mechanically mixing of the NPs with iron powders in an alcohol solvent which is then dried. High-energy MCP is then used to embed the NPs within the powders. These collective steps resulted in a uniform dispersion of ZrC in the sintered (consolidated) Fe sample.

A closed-form extension to the Dugdale strip yield model allowing the consideration of strain hardening effects under small-scale yielding conditions has been developed. This model incorporates a nonuniform singular plastic zone cohesive stress which is a function of the material strain hardening exponent n and is an extension of a numerical model developed by M. Hoffmann and T. Seeger [The Crack Tip Opening Displacement in Elastic-Plastic Fracture Mechanics, pp. 57–77. Workshop on the CTOD Methodology, Geesthacht, Germany (1985)]. The model presented employs an empirical modification of the Hoffmann and Seeger cohesive stress distribution. This modification results in improved crack surface displacement predictions. In addition, the degree of material hardening which may be considered has been extended. Attention is confined to the center cracked panel; however, the model employs weight function techniques and is applicable to arbitrary two-dimensional cracked geometries under plane stress for which a weight function is available. Closed-form analytical expressions for the plastic zone size and crack surface displacement are presented for a center cracked panel, and comparisons are made with displacements from the more rigorous HRR solution and finite element predictions.

Weight functions have been widely used to compute stress intensity factors and crack surface displacements in cracked bodies under arbitrary applied stress fields. For many geometries and applied stress fields of interest, these computations require the application of numerical integration or quadrature. Weight functions exhibit a crack tip singularity. This singularity, if ignored, can lead to inaccurate or inefficient stress intensity factor and crack surface displacement computations. The numerical integration of weight functions using Qauss-Chebyshev quadrature is demonstrated. This type of quadrature is ideally suited for weight function integration as it allows removal of the integrable crack tip singularity, enabling accurate and efficient computation of stress intensity factors and crack surface displacements. Stress intensity factors and crack surface displacements for the edge cracked half-plane under uniform tension have been computed applying both Gauss-Chebyshev and Gauss-Legendre quadrature. Gauss-Chebyshev quadrature is shown to be superior in terms of both accuracy and computational efficiency.

In the present paper, generalized Paris and Wohler equations are derived according to dimensional analysis and incomplete similarity concepts. They provide a rational interpretation to a majority of empirical power-law criteria used in fatigue. In particular, they are able to model the effects of the grain size, of the initial crack length, as well as of the size-scale of the tested specimen on the crack growth rate and on the fatigue life. Regarding the important issue of crack-size dependencies of the Paris’ coefficient C and of the fatigue threshold, an independent approach, based on the application of fractal geometry concepts, is proposed to model such an anomalous behavior. As a straightforward consequence of the fractality of the crack surfaces, the fractal approach provides scaling laws fully consistent with those determined from dimensional analysis arguments. The proposed scaling laws are applied to relevant experimental data related to the crack-size and to the structural-size dependencies of the fatigue parameters in metals and in quasi-brittle materials. Finally, paying attention to the limit points defining the range of validity of the classical Wohler and Paris power-law relationships, correlations between the so-called cyclic or fatigue properties are proposed, giving a rational explanation to the experimental trends observed in the material property charts.

This paper shows the evolution of the surface crack front in round bars constituted of different materials (determined by the exponent m of the Paris law), subjected to fatigue tension loading (with free ends) or fatigue bending loading. To this end, a numerical modeling was developed on the basis of a discretization of the crack front (characterized with elliptical shape) and the crack advance at each point perpendicular to such a front, according to a Paris-Erdogan law, using a three-parameter stress intensity factor (SIF). Each analyzed case was characterized by the evolution of the semielliptical crack front, studying the progress with the relative crack depth a/D of the following three key variables: (i) crack aspect ratio a/b (relation between the semiaxes of the ellipse which defines the crack front); (ii) maximum dimensionless SIF; and (iii) minimum dimensionless SIF.

Our research aims to determine the optimal screw configuration of a dynamic compressive plate (DCP) implant on a human femoral bone. The number of screws and the positioning are sensitive parameters of DCP implant stress repartition. Several previous studies have assessed the influence of thescrew configuration of a DCP implant. Using a realistic geometry of a human left femur and the finite element method (FEM), the calculations in those papers were based on a safe femoral bone. This study evaluates the influence of the application of a simulated fracture gap in the diaphyseal part on the stress repartition of the bone, plate, and screws. The main purpose is to complete the existing studies in order to provide surgeons with information on an optimal prosthesis screw configuration. The plate and screws were modeled and assembled on a cracked femoral bone. The hip region of the femur was loaded with vertical and horizontal forces. The femoral bone was cut into two parts because of the gap: the top part, close to thehip, and the bottom part, close to the knee. The FEM analysis shows that the stresses in screws located in the top part of the femoral bone had significantly increased, whereas the stresses on the plate and the bone had been reduced.