This study was carried out on the background of Sutong Bridge project based on fracture mechanics, aiming at analyzing the growth mechanism of fatigue cracks of a bridge under the load of vehicles. Stress intensity factor (SIF) can be calculated by various methods. Three steel plates with different kinds of cracks were taken as the samples in this study. With the combination of finite element analysis software ABAQUS and the J integral method, SIF values of the samples were calculated. After that, the extended finite element method in the simulation of fatigue crack growth was introduced, and the simulation of crack growth paths under different external loads was analyzed. At last, we took a partial model from the Sutong Bridge and supposed its two dangerous parts already had fine cracks; then simulative vehicle load was added onto the U-rib to predict crack growth paths using the extended finite element method.

The usefulness of elastic compliance measurements to estimate crack closure in structural steel and the validity of the assumption of a constant compliance value for the fully open crack is examined. Based on considering different issues related to the experimental technique and compliance data processing, local compliance measurements and the compliance offset method recommended by the ASTM standard are selected to be most suitable for structural steel. The compliance data generated in fatigue tests on I 8G2A steel conducted under a variety of loading conditions enabled to choose an optimal strain gauge positioning and appropriate offset criterion values for the original compliance offset method and its modified (normalized) version. The adequacy of the closure measurements is assessed through checking the ability of the resulting effective stress intensity factors to account for the observed effects of the loading conditions on fatigue crack growth rates.

The strip yield model from the NASGRO computer software has been applied to predict fatigue crack growth in two different aircraft aluminium alloys under constant amplitude loading and programmed and random variable amplitude load histories. The computation options realized included either of the two different strip yield model implementations available in NASGRO and two types of the input material data description. The model performance has been evaluated based on comparisons between the predicted and observed results. It is concluded that altogether unsatisfactory prediction quality stems from an inadequate constraint factor conception incorporated in the NASGRO models.

Effects of specimen thickness and stress ratio on fatigue crack growth and crack closure levels under constant amplitude loading and after a single overload have been studied experimentally for a structural steel ( I 8G2A). The corresponding crack growth data from the fatigue tests have been presented and evaluated. The experimental trends have been compared to those reported in the literature for various steels. The ability of the effective stress intensity factor range based on crack closure measurements to correlate the observed crack growth response has been investigated.

The present paper investigates the effects of variable-amplitude loads on fatigue crack growth rates for the 2024-T3 aluminium alloy on the basis of microfractographic analyses and its capacity to reconstruct load-time histories of failed components. For this purpose, there were applied three different variable-amplitude load sequences with single and multiple overloads and underloads. Subsequently, images of fatigue striations on components’ fracture surfaces were examined. The aforementioned loads were employed when simulating fatigue crack behaviour in aeronautical alloys.

A strip yield model implementation by the present authors is applied to predict fatigue crack growth observed in structural steel specimens under various constant and variable amplitude loading conditions. Attention is paid to the model calibration using the constraint factors in view of the dependence of both the crack closure mechanism and the material stress-strain response on the load history. Prediction capabilities of the model are considered in the context of the incompatibility between the crack growth resistance for constant and variable amplitude loading.

The paper presents kinetic fatigue crack growth curve for IOHNAP steel, which is verified experimentally. An energy approach based on the M-integral range is shown. The tests have been carried out on plane specimens With notches under tension-compression for three values of stress ratio R. The J-integral is calculated analytically and by the finite element method. A relationship for the description of the whole kinetic crack growth curve including J-integral is presented. It is shown that at the constant loading and the change of stress ratio R from - 1 to O the fatigue crack growth rate increases. A relationship is proposed in the paper for description of the kinetic crack growth curve. It gives results that are consistent with experimental ones and those obtained with the use of the finite element method (FEM).

The paper presents the results of tests on fatigue crack growth under bending in an elastic-plastic material. Specimens with rectangular sections and stress concentrator in the form of external one-sided sharp notch were used. The tests were performed under the stress ratios R = - I, - 0.5, O. The test results were described by the /'i ]-integral range and compared with the /'i K stress intensity factor range. It has been found that there is a good agreement between the test results and the empirical formula of fatigue crack growth rate, which includes the /'i ]-integral range.

Fatigue crack growth for 2024-T3 Alclad aluminium alloy sheet being subjected to two load programs: a constant stress amplitude cyclic tension (R=O. l) (CA) and a variable amplitude tension with either a single or multiple overloads (OVL) periodically repeated is analysed in the paper. The latter load program corresponds to a simple flight simulation spectrum of wing structure of civil aircraft. The investigation was developed in order to learn about interaction between the applied load and formation of fatigue striations. Experimental results of surface crack growth rate provided by optical observations were compared with the rate determined on the basis of microfracture analysis. Good correspondence found under CA loading between the surface growth rate and the growth rate in the sheet depth means that the direction of specimen's cutting does not change essentially the crack growth behaviour. In the case of second loading (OVL) this factor influences the crack growth behaviour. Microfracture analysis revealed either retardation and acceleration of crack growth rate under OL V loading. This behaviour of growth rate results from a plastic zone formed in the front of crack tip and a crack closure effect.