13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- CASE I II III IV V VI Figure 8. Change of max min K K along the crack front during crack development CASE I II III IV V DEPTH POINT VI CASE I II III IV V SURFACE POINT VI Figure 9. Stress intensity factor variations along both depth and surface points during crack growth 5. Concluding remarks The effect of different crack face loads on fatigue crack growth of a surface crack in a plate has been investigated by using a multiple degree-of-freedom numerical method, which is based on a series of 3D FE analyses with including contact elements in cracked area and is able to directly obtain the crack shape development in a complex crack face stress field. It has been concluded that complex crack shape evolution in fatigue crack growth can be successfully predicted by the multiple degree-of-freedom numerical method. The crack profiles adopted by cracks are strongly dependent on the applied load. They might significantly deviate from the widely assumed semi-elliptical shape, although in many cases they can be approximated to such a shape. It has been also found that crack surface contact can be simulated by the contact elements introduced in the SIF calculations, so that negative SIF results can be correctly avoided.
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