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The residual stresses (RS) generated during the thermal processing processes such as casting and heat treatment is one of the fundamental causes of irreversible deformation of diesel engine bodies (DEBs). However, previous studies only focused on the RS generated from casting or the effect of annealing heat treatment on the RS in castings unilaterally, and the analytical results were far from the actual conditions. Therefore, this paper proposes a comprehensive research method to consider the whole dynamic evolution of the casting from the RS generated by casting to the stress relief by heat treatment. Numerical simulation of DEBs casting process is carried out by PROCAST, and the results of casting RS obtained from the simulation are imported into ABAQUS, and then numerical simulation of annealing heat treatment is carried out for the DEB casting model with casting RS, so as to realize the analysis of dynamic evolution of RS from casting to heat treatment.

Camshaft is a key part of marine diesel engines. However, the large residual stresses resulting from the induction hardening to which the cams are submitted may lead to cracks on their contacting surfaces. These cracks have great influence in the service life of the shaft. In order to find the relationship between the induction hardening process parameters and the residual stress field, the process was simulated by the finite element method, and the SYSWELD and ANSYS software were used. The temperature distribution during hardening process and stress field of the camshaft after the process were obtained and analyzed. The thickness of the hardening layer was calculated. The simulation results were validated by residual stress measurement experiments and showed a good agreement with the practice. The method reported on the present paper provides an efficient way to analyze the camshaft induction hardening process and avoid the surface failure of the cams.

The excessive residual stresses caused by heat treatment and grinding processes is one of the main challenges for Cam manufacturing, because they will lead to delayed cracks and reduce the fatigue life of Cam. Experimental studies are one of the essential ways to keep residual stresses at a reasonable value. Thus, orthogonal and single-factor experiments are carried out to explore the effect of heat treatment and grinding processes on the residual stresses of the Cam. The heat treatment processes include quenching temperature, tempering temperature, and tempering holding time. The grinding process includes grinding speed and feed speed. Besides, the superimposed residual stresses produced by heat treatment and grinding processes are analyzed. The results show that the heat treatment and grinding processes produce compressive residual stresses. The heat treatment process combined with the grinding process increases the superimposed residual stress. In addition, the critical factor for the distribution of the final stresses on the Cam surface is the grinding process, and the grinding speed plays the most important role. Therefore, in order to optimize the Cam machining processes to control the residual stresses, the optimization sequence is grinding speed, quenching power, and tempering temperature. The processes to obtain the least stress are as follows: 128 kW of quenching power, 200 °C of tempering temperature and 8 h of tempering time.

The unequal distribution of residual stress caused by incorrect machining processes will probably distort the machined connecting rods of the diesel engines. Thus, the influence of the machining processes on the residual stress and distortion of the rod need to be studied. Firstly, the finite element model is established based on the geometry of the connecting rod. Based on the life and death unit method, the influence of material removal on the residual stress of the connecting rod is discussed. Secondly, an orthogonal test is designed. The variables of the test include the quenching temperature, tempering temperature, cooling speed and the sequence of the machining processes. The deformation of the connecting rod is analyzed and then predicted based on the generalized regression neural network. The results show that the minimum distortion is achieved when the quenching temperature is 860 °C, the tempering temperature is 620 °C, the cooling speed is 50 °C h−1, and the machining sequence is “drilling the small end hole-milling, the upper planes-sawing, the connecting rod-turning, and the big end hole”. The priority of the influence of the processes on the deformation of the connecting rod is ranked as follows: cooling speed, quenching temperature, tempering temperature, and process sequence. The tensile residual stress is produced inside the connecting rod by machining processes. The generalized regression neural network predicts the connecting rod deformation accurately and the average error is 8.1%.

As an important transmission component of diesel engines, the connecting rod has to meet a very high processing accuracy. However, as an elongated part, the connecting rod has a weak rigidity, and the unevenness of the cutting force and the clamping force during the machining processes will lead to the deformation of the connecting rod. In previous researches, cutting and clamping are always studied separately, and their interactions are neglected. In this paper, the finite element simulation method is used to analyze the deformation of the connecting rod. Based on the Deform-3D software, the article builds a connecting rod milling finite element simulation model and predicts the residual stress of the connecting rod milling simulation and the formation of milling chips. The residual stress of the simulation is compared with the residual stress of the experimental measurement and the simulation chip is compared with the actual chip to verify the accuracy of the simulation model, which provides a theoretical basis for the model construction of the next simulation study. Based on the Deform-3D software, simulation studies the influence of different milling parameters on the deformation of the connecting rods. And optimize the link milling process parameters. Based on ANSYS software, the effect of superposition of cutting force and clamping force on machining deformation of the connecting rod was simulated and analyzed. The resultant milling force should not be greater than 734N. This method makes up for the defects that cutting and clamping are studied separately and their interactions are neglected.

The hard turning process has been widely used in the field of hard material precision machining because of its high efficiency, low processing residual stress, and low environmental pollution. Due to its undesirably processing quality, it is still not a substitute for traditional grinding, so many studies have reported that the process has been optimized. However, there has been little research on the geometry optimization of hard cutting tools, which have a great influence on the traditional machining process. In this paper, two tools with different rake face shapes are designed. The finite element analysis method is used to compare their performance with a conventional plane tool while turning hardened steel. The results show that the cutting performance of the designed tool T1 and T2 (chip morphology, cutting force, and cutting temperature) and the quality of the machined surface are improved compared with the tool. The cutting force decreased by 12.72% and 14.74%, the cutting temperature decreased by 7.56% and 9.01%, respectively, and the surface residual stress decreased by 26.56% and 28.66%.