In this study, the tapered roller bearing was adopted to explore the effect of the manganese phosphate coating on the friction, wear, and lifespan of bearings. Line friction samples with and without a manganese phosphate coating were prepared. The White Light Interferometry was used to analyze the three-dimensional morphology and roughness, and the Optimal Schwing–Reib–Verschleiss-5 multifunctional friction and wear tester was applied to obtain the tribological parameters before and after the application of the manganese phosphate coating. A scanning electron microscopy and energy dispersive spectrometry were used to characterize the microstructure and element composition of the worn surfaces of the manganese phosphate coating. The influence of the manganese phosphate coating on the contact stress was contrasted and examined by establishing a finite element model of the tapered roller bearing. Finally, a life test of the tapered roller bearings was performed before and after the application of the manganese phosphate coating. The results demonstrate that manganese phosphate coating enhances wear resistance, lowers bearing contact stress, and reduces the coefficient of friction. The fatigue life of the tapered roller bearing can be significantly extended with a manganese phosphate coating. This is a new method that can be used to improve the service life of bearings.

With the increase in engine power density, the temperature and stress carried by the cylinder head during operation also increase. The thermal engine fatigue life prediction of the cylinder head needs to consider accurate and reasonable creep-constitutive models and parameters. In view of the wide range of temperature and stress working conditions of the compacted graphite cast iron (CGI) cylinder head, the creep test of CGI under the conditions of temperature 450~550 °C and stress 100~300 MPa was carried out, and CGI under the conditions of wide temperature and stress was proposed to characterize a creep-constitutive model for minimum creep rate. Research indicated that under wide temperature and stress conditions, CGI was more prone to creep damage than under low load, and creep deformation was dominated by grain boundary sliding (GBS), intragranular dislocation glide (IDG), and dislocation climb (IDC). With the deformation mechanism-based true stress (DMTS) creep model, combined with the multiobjective optimization method, a creep-constitutive model of CGI was constructed, and 73% of the predicted values of the model were within twice the error range. Compared with the linear regression method, the multiobjective optimization method could still fit the accurate model parameters in the case of small samples.

Total protection of fragile goods and equipment during transport has become critically important as fast delivery systems are growing rapidly due to the rise of mass online commerce worldwide. This paper therefore studies the protection of falling eggs —one of the most fragile goods—through packaging. Intensive experiments are first conducted to obtain the critical stress at which the eggshell is damaged by falling impact. Tests are first conducted of unpackaged eggs dropping onto a granite platform from various heights. Finite element method (FEM) models of unpackaged eggs are then built to simulate the behaviour of eggs and compute their stress levels. The experimental data is compared with the results of FEM simulations to determine the critical stress at which the eggshell is damaged. A series of tests and numerical simulations are then carried out for eggs wrapped in expanded polyethylene (EPE) foam. The stress distribution of both a single egg and multiple eggs in packaging are studied. An empirical formula between the drop speed (or height) and the bottom thickness of the EPE foam packaging is obtained, which can be useful in the design of packaging for the total protection of eggs that may fall during usual transport and delivery operations. The experimental and numerical results from this study show that it is viable to protect fragile goods, as long as the EPE form packaging has sufficient thickness. The proposed study and design procedure are helpful for the selection of key parameters of foam packaging to protect fragile industry products from impact.

Metal/composite hybrid thin-walled structure is the most preferential approach to achieve dual contradictive objectives of high crashworthiness and lightweight of auto body. Its collapse with regard to different fiber layup patterns is one of the governing mechanisms of energy dissipation, which is yet to be explored. Especially, the effect of different fiber layup angles and layup sequences on bending collapse, which is one of the most significant performance indicators, has received little attention. To this gap, this study investigates experimentally and numerically the bending characteristics of aluminum/carbon fiber reinforced plastic (Al/CFRP) hybrid structures with different layup angles and layup sequences. To start with, three-point bending tests are carried out on specimens to derive the bending failure behavior and crashworthiness, and the internal section damage is observed by CT scan. Finite element model is then constructed and benchmarked against the test results to be proficient. On this basis, the effects of Al thickness, number of CFRP layers and CFRP wrapping range on the bending performance of hybrid tube are analyzed numerically. The simulation results show that layup angle has greater effect on the bending performance than layup sequence. Increasing Al thickness and the number of CFRP layers can effectively improve the bending resistance of structure, and appropriate partial wrapping of CFRP can increase the specific energy absorption (SEA) by 10.92% compared with that of complete wrapping. The revelation from this study provides sound reference for the crashworthiness design of metal/composite hybrid thin-walled structure.

Rubber mounts are the vital component to reduce the vibration translated from the powertrain to the vehicle body. The dynamic stiffness of the conventional rubber mount increase with the increase of the excitation frequency, and form a peak under high-frequency excitation in the battery electric vehicle (BEV). So the double isolation rubber mount has gradually been used in the BEV powertrain to improve the vibration isolation performance in the high-frequency range. Compared with conventional rubber mounts, the double isolation rubber mount has smaller dynamic stiffness in the high-frequency range. However, the traditional simulation model of the dynamic characteristics cannot consider the influence of the metal bracket of the double isolation rubber mount on the dynamic characteristics. Therefore, it is necessary to carry out the modeling and analysis of the dynamic characteristics simulation model of the double isolation rubber mount. In this paper, a general dynamic model of double isolation rubber mounts is proposed to describe the high-frequency dynamic characteristics. In this general dynamic model, the complex stiffness element representing the viscoelasticity of rubber is expressed using the fractional derivative model and the Maxwell model, respectively, and two high-frequency dynamic models are established. Two model parameter identification methods are proposed for high-frequency dynamic models of double isolation rubber mounts, and the identification results are compared and analyzed. Then, two high-frequency dynamic models are used to simulate the high-frequency dynamic characteristics of double isolation rubber mounts. The simulation results show that both high-frequency dynamic models can calculate the high-frequency dynamic characteristics of double isolation rubber mounts. Among them, the dynamic model based on fractional derivative elements has relatively high accuracy, and the dynamic model based on Maxwell elements has relatively high stability. The high-frequency dynamic characteristic modeling method of double isolation rubber mounts presented in this paper is helpful to the vibration and noise analysis of electric vehicle powertrain systems under high-frequency excitation.