mechanical elements, with independent viscous (dashpot), elastic (spring), and plastic (slider) responses. Solutions to this equation describe features observed under load-controlled indentation of polymers, including creep, negative unloading tangents, and loading-rate dependence. The model describes a full range of viscous–elastic–
2014-8-1 · As a result, deformation at a strain rate lower than 1 x [10.sup.-4] [s.sup.-1] should be studied using notch-free specimen at an appropriate crosshead speed. In view of the time required in service for the SCG initiation and propagation, strain rate involved must be much lower than 1 x [10.sup.-4] [s.sup.-1]. In an arbitrary coordinate system, the viscous stress ε and the strain rate E at a specific point and time can be represented by 3 × 3 matrices of real numbers. In many situations there is an approximately linear relation between those matrices; that is, a fourth-order viscosity tensor μ such that ε = μE . Where the trace-less viscous strain-rate is defined by: (5) The heat-flux, , is given by Fourier's law: (6) Where the laminar Prandtl number is defined by: (7) Where the trace-less viscous strain-rate is defined by: (5) The heat-flux, , is given by Fourier's law: (6) Where the laminar Prandtl number is defined by: (7)
Poly(γ-glutamic acid) (γ-PGA) is a biopolymer with many useful properties making it applicable for instance in food and skin care industries, in wastewater treatment, in biodegradable plastics or in the pharmaceutical industry. γ-PGA is usually produced microbially by different Bacillus spp. The produced γ-PGA increases the viscosity of the fermentation broth.
2014-9-20 · strain increase along a straight line of the slope of Young’s modulus. Upon unloading, the stress and strain decrease along the same straight line. We next increase the stress again, beyond the initial yield strength, so that the stress-strain curve bends, and the metal deforms plastically. This statement means several important things. An Elastic-Viscoplastic Model for Time-Dependent Behavior To describe the time-dependent behavior of soft clay, this paper extended one-dimensional Nishihara model to three-dimensional stress state based on the framework of Perzyna’s overstress theory and modified cam-clay model. The yield criterion of modified cam-clay model was used to describe the plastic properties of soft clay, and the overstress theory was used to describe the strain rate effect. Frontiers of Structural and Civil Engineering
Full text of "Grain and forage research of the United States Department of Agriculture and cooperative agencies; a summary of current program and preliminary report of progress"
spontaneous heterogeneous flows (strain rate) and/or deformations (strain). We find two modes of instability. The first is a viscous mode, associated with strain rate perturbations. It dominates for relatively small values of τC and is a simple generalisation of the instability known previously without polymer. The fluid static pressure and density are, respectively, p and ρ, μ is the fluid viscosity and τ i j are the Reynolds stresses resulting from the averaging process of the momentum equations, which are treated on the basis of the Boussinesq hypothesis, then proportional to the trace-less mean strain rate tensor times the eddy viscosity μ T Furthermore, we distinguish two contributions to the inelastic strain rate of individual grains, due to crystal plasticity (subscript p) and due to transport of matter (diffusion; subscript d), such that . We assume these straining mechanisms to be volume conserving; i.e., the strain rates are trace‐less (). While the rates can formally be