Modelling and measurement of crack closure and crack growth following overloads and underloads

摘要: Abstract Ignoring crack growth retardation following overloads can result in overly conservative life predictions structures subjected to variable amplitude fatigue loading. Crack closure is believed contribute the retardation, although specific mechanism debatable. The delay period and corresponding rate transients overload overload/underload cycles were systematically measured as a function of load ratio ( R ) magnitude. These responses are correlated terms local “driving force” for growth, i.e. effective stress intensity factor range ΔK eff ). Experimental results compared with Dugdale-type model improvements suggested.