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Electromagnetic induction quenching is one of the common surface strengthening approaches conducted engineering application, especially for the steel parts. In this paper, first a 3D finite element model was built and the electromagnetic thermal coupling simulation was used to determine the temperature field after quenching and coolant cooling process. Then the mechanical-thermal coupling simulation was used to obtain the residual stress field remaining in the crankshaft after air cooling. Finally the fatigue property of the treated crankshaft was predicted based on the residual stress and the different mean stress models. Validations between the predictions and the experimental results showed that the combination of the simulation and Goodman model can obtain the fatigue property of this type of crankshaft accurately, thus was suitable for actual engineering applications.

For critical engine parts, such as crankshafts, fatigue strength is one of the most important parameters in the design and manufacturing stage. In previous work, fatigue limit loads of the crankshafts with different structural features were predicted based on different theories of critical distance (TCDs). The results showed that the definition of the TCD had an obvious impact on the accuracy of such predictions. This paper, first the critical distance was determined based on the limit stress distribution of a given crankshaft and the definition of the approach. Then, the fatigue limit load of another crankshaft was predicted based on the parameters obtained in the previous step. Finally, corresponding experimental verification and model parameter error influence analysis were conducted to evaluate the accuracies of the predictions. The results showed that for the modified indirect-defined TCD (ITCD), the predictions based on the line and point methods were approximately equal, and the parameter errors had an obvious impact on the predictions. However, for the direct-defined TCD (DTCD), the critical line approach had much better accuracy than the critical point approach, and the DTCD was much less sensitive to the model parameter errors than the ITCD approach, therefore, the DTCD approach is much more suitable for actual engineering applications.

Prussian blue (PB) and its analogues (PBAs) have been considered as promising cathodes for room temperature sodium-ion batteries (SIBs) because of their rigid open framework and low-cost synthesis. Herein, we have synthesized slight-etching PB cubes with low amounts of coordinated water and [Fe(CN)6] vacancies using an optimized hydrothermal method with the aid of acid. Interestingly, synchronous crystal growth and etching processes are observed, accompanied by recrystallization behaviors during the etching process. With the increasing acid amount, yield of the as-prepared PB improves greatly. The acid etching mechanism is further clarified. Notably, such one-step acid-etching hydrothermal approach can realize the rational composition and architecture design of PB. The correlation between physical properties and cell performance of PB is systematically investigated. The optimized PB cubes with slight surface etching deliver a high reversible specific capacity of 99 mA h g−1, a capacity retention of 79% for 500 cycles and 74 mA h g−1 at a high current density of 1500 mA g−1. Such superior rate capability and long cycle life are ascribed to the synergistic effects of the structure and morphology of PB, which possesses low amounts of coordinated water and [Fe(CN)6] vacancies, large unit cell volume, and slight-etching surface in the cubic structure, good crystallinity and uniform particle size distribution.