Stress concentration

About: Stress concentration is a research topic. Over the lifetime, 23250 publications have been published within this topic receiving 422911 citations.

Quasi-static crack propagation

Abstract: When cracks of any size spread in brittle materials and when large cracks spread in large structures of ductile materials, irreversible deformation is confined to a small volume of material contiguous with the crack surfaces. A general theory of quasi-static crack propagation under such conditions is formulated. The stability of crack propagation is subject to chosen constraints, and general stability criteria under monotonically increasing load and displacement are presented. Experiments in which cracks are spread quasi-statically are described, and by recording both load and corresponding displacement of load, the local specific work of crack spreading, or fracture toughness ( R ) may be deduced without calculation of the elastic stress distribution or even measuring the shape of the test piece. By causing the crack to spread at a range of speeds, variation of R with speed of crack front may be found. When R is independent of scale, it is shown that the stress intensity to propagate geometrically similar cracks in geometrically similar structures varies inversely as the square root of the size. A principle controlling the path of a quasi-static crack is proposed and some experimental confirmation is offered. An interpretation of crack spreading under cyclic loading is given.

Size Effect in Fatigue Fracture of Concrete

Abstract: Crack growth caused by load repetitions in geometrically similar notched concrete specimens of various sizes is measured by means of the compliance method. It is found that the Paris law, which states that the crack length increment per cycle is a power function of the stress intensity factor amplitude, is valid only for one specimen size (the law parameters being adjusted for that size) or asymptotically, for very large specimens. To obtain a general law, the Paris law is combined with size-effect law for fracture under monotonic loading, proposed previously by Bazant. This leads to a size-adjusted Paris law, which gives the crack length increment per cycle as a power function of the amplitude of size-adjusted stress intensity factor. The crack growth is also characterized in terms of the nominal stress amplitude.

Anisotropic mechanical properties of porous copper fabricated by unidirectional solidification

Abstract: Porous copper whose long cylindrical pores are aligned in one direction has been fabricated by unidirectional solidification of the melt in a mixture gas of hydrogen and argon. The porosity depends on the melting temperature of copper melt, while the orientation of the pores is controlled by the freezing direction. The anisotropy in the uniaxial tensile behavior of the porous copper is examined. The ultimate tensile strength and the yield strength of the porous copper with the cylindrical pores orientated parallel to the tensile direction decrease linearly with increasing the porosity. For the porous copper whose pore axes are perpendicular to the tensile direction, the ultimate tensile strength decreases significantly with increasing the porosity at low porosity, while the yield strength reaches a maximum at a low porosity and then decreases with increasing the porosity. These results are explained in terms of the stress concentration induced in the vicinity of the pores during tensile deformation.