The statistical-thermodynamic dislocation theory developed in previous papers is used here in an analysis of yielding transitions and grain-size effects in polycrystalline solids. Calculations are based on the 1995 experimental results of Meyers, Andrade, and Chokshi [Metall. Mater. Trans. A 26, 2881 (1995)MMTAEB1073-562310.1007/BF02669646] for polycrystalline copper under strain-hardening cond...

The industrially-important WC-Co composite materials provide a useful, albeit complicated materials system for understanding the combined influences on hardness and strength properties of the constituent WC particle strengths, the particle sizes, their contiguities, and of Co binder hardness and mean free paths, and in total, the volume fraction of constituents. A connection is made here betwee...

A theoretical model is suggested which describes the yield stress dependence on grain size in fine-grained materials, based upon competition between conventional dislocation slip, grain boundary diffusional creep (Coble creep) and triple junction diffusional creep. In the framework of the model, the contribution of diffusional creep mechanisms to plastic deformation increases with reduction of ...

Fusarium head blight (FHB) is an important disease of wheat and causes significant economic and yield losses. The principal pathogen associated with FHB in Manitoba is Gibberella zeae (Schwein.) Petch (anamorph = Fusarium graminearum Schwabe). Trichoderma harzianum Rifai is a well-known biocontrol agent of many plant pathogens. The extracts from 11 T. harzianum isolates and cellfree filtrates w...

The susceptibility of preimaginal and adult olive fruit fly, Bactrocera oleae (Gmelin) (Diptera: Tephritidae), to a strain of the mitosporic ascomycete Metarhizium brunneum (Petch) (Hypocreales: Clavicipitaceae) and the insecticidal activity of its crude extract to olive fruit fly adults were investigated. Strain EAMb 09/01-Su caused 60% mortality to B. oleae adults, with average survival time ...

INTRODUCTION Several arthropod pests infest strawberry crop in California and cause a significant yield loss according to Zalom, Bolda, Dara, and Joseph [1]. Strawberry is an important commercial crop and the annual report from California Department of Pesticide Regulations [2] indicates that large quantities of acaricides, fungicides, herbicides, and insecticides are applied to manage a variet...

High-pressure torsion (HPT) is applied to a face-centered cubic CoCrFeMnNi high-entropy alloy at 293 and 77 K. Processing by HPT at 293 K produced a nanostructure consisted of (sub)grains of ~50 nm after a rotation for 180◦. The microstructure evolution is associated with intensive deformation-induced twinning, and substructure development resulted in a gradual microstructure refinement. Deform...

We examine the role of atomistic simulations in multiscale modeling of mechanical behavior of stressed solids. Theoretical strength is defined through modes of structural instability which, in the long wavelength limit, are specified by criteria involving elastic stiffness coefficients and the applied stress; more generally, strength can be characterized by the onset of soft vibrational modes i...

Molybdenum alloys are excellent candidates for extremely high temperature environments, such as in nuclear thermal propulsion spaceflight systems. Spark plasma sintering is a useful manufacturing technique that allows rapid fabrication of refractory materials difficult to sinter using more traditional methods. Pre-alloyed molybdenum with 30 wt% tungsten powder was consolidated spark under varie...

Yield phenomena during the tensile testing of pure titanium sheets 0.2 mm and 0.4 in thickness were investigated detail focusing on effects grain size (d), (t), t/d ratio direction. With decreasing size, yielding behavior changed from continuous to one accompanied with yield point drop. Upper lower stresses 0.2%-proof stress followed Hall–Petch relationship; however, coarse-grained specimens (d...