We present a nanoindentation study to detect time-dependent deformations in non-polymeric hydrogenated amorphous carbon films. When the bonded hydrogen content increases from 18 to 36 at.%, as measured by Fourier transform infrared spectroscopy, we find that the film becomes less graphitic and softer. Moreover, its hardness shows a larger sensitivity to strain rate and the film with the higher ...

A constitutive model is developed within the framework of Perzyna’s viscoplasticity for predicting the stress-strain-time behaviour of soft porous rocks. The model is based on the hyperelasticity and multisurface viscoplasticity with hardening. A time-stepping algorithm is presented for integrating the creep sensitive law. An example of application to one-dimensional consolidation is presented....

Objectives: Nanocrystalline (nc) metals present excellent mechanical properties such as strength and fatigue resistance but often show low ductility. Furthermore, nc systems show moderate to high rate sensitivity at room temperature which might help restoring the ductility but can have disadvantage of creep/relaxation effects in applications. Thin metallic films constitute ideal candidates for ...

Creep response in a rotating disc made of anisotropic Al-SiC(particle) composite having linearly varying thickness has been carried out using anisotropic Hoffman yield criterion in present study. The steady state creep behavior is described by Sherby’s constitutive model. The material parameters characterizing difference in yield stresses have been used from the available experimental results i...

In this article, the problem of time-dependent stress redistribution of a piezomagnetic rotating thick-walled cylinder under an axisymmetric hygro-thermo-magneto-electro-mechanical loading is analyzed analytically for the condition of plane strain. Using the constitutive equations, a differential equation is found in which there are creep strains. Primarily, eliminating creep strains, an analyt...

We present experimental evidence that pressure solution creep does not establish a steady-state interface microstructure as previously thought. Conversely, pressure solution controlled strain and the characteristic length scale of interface microstructures grow as the cubic root of time. Transient creep with the same scaling is known in metallurgy (Andrade creep). The apparent universal scaling...

Original scientific paper The nonlinear creep characteristics of typical clays in the coastal area of Tianjin were studied by consolidated-undrained triaxial creep tests. The tests were performed via the stepwise loading method, and the creep curves of the soft clays under different stress states were obtained from the raw data processed by Chen and Kang’s method. The experiments showed that th...

One of the yet unresolved engineering problems is forecasting the creep lives of weldment in a pragmatic way with sufficient accuracy. There are number of obstacles to circumvent including: complex material behavior, lack of accurate knowledge about the creep material behavior specially about the heat affected zones (HAZ),accurate and multi-axial creep damage models, etc. In general, creep life...

When sufficient force is applied to a glassy polymer, it begins to deform through movement of the polymer chains. We used an optical photobleaching technique to quantitatively measure changes in molecular mobility during the active deformation of a polymer glass [poly(methyl methacrylate)]. Segmental mobility increases by up to a factor of 1000 during uniaxial tensile creep. Although the Eyring...