research

In this paper that was published a few months ago, we reported the size effects on the elastic modulus and fracture strength of silicon nanowires. In addition, we observed that the silicon nanowires are linear elastic until fracture with a very large fracture strain up to 12%.



Y. Zhu, F. Xu, Q. Qin, W. Y. Fung, and W. Lu, Nano Letters 9, 3934-3939, 2009



Abstract:

Hi everybody,

I have done some experiments on the fracture toughness in mode II of wood specimens using attached geometry;so using

formula KIIc= 5.11P(3.1415*a)^0.5 /(2BW) I was able to calculate the frcature toughness of wood, but I am quite suprised

why this equation does not iclude depth of the specimens and moreover, I think that I have obtained higher values for the

fracture toughnes values. Is there any other formulation for obtaining the fracture toughness in mode II for this specimen?

P.s. dimension of my specimens is 100*100*63mm

In this paper we first obtain the order of stress singularity for a dynamically propagating self-affine fractal crack. We then show that there is always an upper bound to roughness, i.e. a propagating fractal crack reaches a terminal roughness. We then study the phenomenon of reaching a terminal velocity. Assuming that propagation of a fractal crack is discrete, we predict its terminal velocity using an asymptotic energy balance argument. In particular, we show that the limiting crack speed is a material-dependent fraction of the corresponding Rayleigh wave speed.

When an indenter is pressed into a gel to a fixed depth, the solvent in the gel migrates, and the force on the indenter relaxes. Within the theory of poroelasticity, the force relaxation curves for indenters of several types are obtained in a simple form, enabling indentation to be used with ease as a method for determining the elastic constants and permeability of the gel. The method is demonstrated with a conical indenter on an alginate hydrogel.