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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.

This study was designed to determine the appropriate levels of tryptophan (trp) in the diet of Apis mellifera worker bees. Newly emerged worker bees were enclosed in wooden cages in an incubator at 32°C with 55–60% humidity and fed a diet including 9, 10, 11, 12, 13, and 14 mg/g trp for 12 days. When the trp level was 11 mg/g, worker bees demonstrated better performance in terms of food intake, body weight, and total protein accumulation. However, 12 mg/g dietary trp promoted trp deposition in the worker bees, stimulated hypopharyngeal gland development, enhanced the survival rate and expedited the formation of 5-HT (5-hydroxytryptamine). The worker bees fed with 13 and 14 mg/g trp had higher malondialdehyde (MDA) levels, which suggested that a higher level of trp may be disadvantageous in maintaining worker-bee antioxidant ability, because MDA was the end product of lipid peroxidation. We also found that dietary trp regulated the mRNA expression of 5-HTRs and tryptophan hydroxylase (TPH) in a dose-dependent manner, which was related to phototaxis, aggression, and other factors. In conclusion, dietary trp exerts regulatory roles in the growth, development and some physiological and biochemical properties of worker bees. Therefore, 11–12 mg/g tryptophan is optimal for A. mellifera adult worker bees.