ISO 15850:2014 pdf free
ISO 15850:2014 pdf free.Plastics一Determination of tension-tension fatigue crack propagation一Linear elastic fracture mechanics (LEFM) approach
Fatigue crack propagation, particularly when expressed as the fatigue crack growth rate da/dN as a function of crack-tip stress intensity factor range OK or energy release rate range OG, characterizes a material’s resistance to stable crack extension under cyclic loading. Background information on the fatigue behaviour of plastics and on the fracture mechanics approach to fatigue for these materials is given in References [1] and [2].
Expressing da/dN as a function of OK or OG provides results that are independent of specimen geometry,thus enabling exchange and comparison of data obtained with a variety of specimen configurations and loading conditions. Moreover, this feature enables da/dN versus OK or OG data to be utilized in the design and evaluation of engineering structures. The concept of similitude is assumed, which implies that cracks of differing lengths subjected to the same nominal OK or OG will advance by equal increments of crack extension per cycle.
Fatigue crack propagation data are not geometry independent in the strict sense since thickness effects generally occur. The potential effects of specimen thickness have to be considered when generating data for research or design.
Anisotropy in the molecular orientation or in the structure of the material, and the presence of residual stresses, can have an influence on fatigue crack propagation behaviour. The effect can be significant when test specimens are removed from semi-finished products (e.g. extruded sheets) or finished products. Irregular crack propagation, namely excessive crack front curvature or out-of-plane crack growth, generally indicates that anisotropy or residual stresses are affecting the test results.
This test method can serve the following purposes:
a) to establish the influence of fatigue crack propagation on the lifetime of components subjected to cyclic loading, provided data are generated under representative conditions and combined with appropriate fracture toughness data (see ISO 13586) and stress analysis information;
b) to establish material-selection criteria and inspection requirements for damage-tolerant applications;
c) to establish, in quantitative terms, the individual and combined effects of the material’s structure,the processing conditions, and the loading variables on fatigue crack propagation;
d) used as an accelerated test for the evaluation of service life performance of components subjected to static fatigue loading conditions (this would also include ranking between materials一see Annex A).ISO 15850 pdf free download.
