No abstract

Fatigue life assessment for two‐phase steel SAE 1045 has been carried out by experimental and simulation techniques. Analytical approach, termed as fatigue lifetime calculation, was employed making use of a load increase testing procedure and constant amplitude tests equipped with measurement techniques – plastic strain amplitude, change in temperature and change in electrical potential difference. The predicted fatigue life has been validated by constant amplitude tests and compared with fatigue life estimation by microstructure‐based simulation. Simulation has been carried out over the complete cross section of the specimen. The simulation uses damage accumulation in the gage section of the specimen culminating in the macro‐crack propagation, taking into account the inhomogeneous fatigue resistance of the material element. The results show that at the initial intervals of high cycle fatigue range at relatively higher stress amplitudes, the experimental and simulation results are in agreement; whereas in the (high cycle fatigue) region at relatively low stress amplitudes, the simulation results were found more optimistic and the corresponding fatigue scatter is also increased. Each scatter is attributed to the relatively small number of analysed models of the material structure. Scanning electron microscope was used to determine volume fraction of the microstructure for simulation. Fatigue fracture surface analysis shows that crack initiated from internal defect of material and crack propagation is driven by silicon oxide inclusion.

No abstract

Fatigue damage of structural details in essence may be attributed to the consequences of the traditional approach of securing the reliability of structures when the design and maintenance are provided by different groups of experts with different principles and different professional training. Progress may be achieved when the whole life-cycle reliability of a structure is provided uniformly in the design and service cycles. A series of actions and appropriate fatigue models composing an automated system to aid in the design and maintenance of ship structures is proposed. Considering the existing and feasible actions, attention is focused on the fatigue design and post-fabrication assessment of fatigue properties at critical locations.