An instrument for measuring the creep response of a material maintained under a controlled environment of temperature and vapor pressure is described. The temperature range of the instrument is 20-250 degrees C while the range of vapor pressure is 0-1 atm. Data are presented for tests conducted on this instrument with Nafion, a perfluorinated ionomer developed by DuPont and used as a membrane i...

Determining the dynamic response of frozen soil is important for the study of the deformation, strength and stability of frozen soil under dynamic loading conditions for engineering design in cold regions. This paper discusses the recent progress in research on the dynamic response of frozen soil from the following three aspects: (1) influence of various testing conditions (confining pressure, ...

We present a constitutive model capturing some of the experimentally observed features of soft biological tissues: nonlinear viscoelasticity, nonlinear elastic anisotropy, and nonlinear viscous anisotropy. For this model we derive the equation governing rectilinear shear motion in the plane of the fiber reinforcement; it is a nonlinear partial differential equation for the shear strain. Special...

The elastic properties of dentin, a biological composite consisting of stiff hydroxyapatite (HAP) nano-platelets within a compliant collagen matrix, are determined by the volume fraction of these two phases and the load transfer between them. We have measured the elastic strains in situ within the HAP phase of bovine dentine by high energy X-ray diffraction for a series of static compressive st...

A linear system of differential equations describing a joint motion of thermoelastic porous body and incompressible thermofluid occupying porous space is considered. Although the problem is linear, it is very hard to tackle due to the fact that its main differential equations involve non-smooth oscillatory coefficients, both big and small, under the differentiation operators. The rigorous justi...

Creep aging behavior of a pre-strain and under-age treated 7B04 aluminum alloy (7B04-P for short) was systematically investigated under different temperatures applied stresses. A lot dislocation tangles η’/GPzs were formed in the Al matrix 7B04-P al alloy. With increase temperature stress, total creep strain steady-state rate increased significantly. However, mechanical properties creep-aged ar...

We calculated thermo-elastic properties of pyrope (Mg3Al2Si3O12) at mantle pressures and temperatures using Ab initio molecular dynamic simulation. A third-order Birch-Murnaghan equation at a reference temperature of 2 000 K fits the calculations with bulk modulus, K0=159.5 GPa, K0’=4.3, V0=785.89 Å, Grüneisen parameter, γ0=1.15, q=0.80, Anderson Grüneisen parameter δT=3.76 and thermal expansio...

We consider a thermo-elastic plate system where the elastic equation does not account for rotational forces. We select the case of hinged mechanical B.C. and Neumann thermal B.C., which are coupled on the boundary. We show that the corresponding s.c. contraction semigroup (on a natural energy space) is analytic and, hence, uniformly stable. Because of the boundary (high) coupling, this case of ...

Constitutive Modeling of Creep of Single Crystal Superalloys. (August 2005) Sharat Chand Prasad, B.Tech., Indian Institute of Technology, Kanpur; M.S., Texas A&M University Chair of Advisory Committee: Dr. K. R. Rajagopal In this work, a constitutive theory is developed, within the context of continuum mechanics, to describe the creep deformation of single crystal superalloys. The constitutive ...

This paper develops a theoretical model for wrinkling of an elastic film on an elastic–plastic metal layer caused by cyclic temperatures. The film is compressively strained and bonded to the metal layer, which in turn lies on a thick substrate. The thermal expansion mismatch between the metal and the substrate induces a biaxial stress, which is assumed to be large enough to cause the metal to d...