Development of a Composite Technique for Preconditioning of 41Cr4 Steel Used as Gear Material: Examination of Its Microstructural Characteristics and Properties

Commercial 41Cr4 (ISO standard) steel was treated by a composite technique. An intermediate layer was introduced firstly at the 41Cr4 steel surface by traditional carburizing and nitriding. Then a hard Cr coating was brush-plated on the intermediate layer. Finally, the coating layer was modified by high current pulsed electron beam (HCPEB), followed by quenching and subsequent tempering treatment. The microstructure, mechanical properties, and fracture behavior were characterized. The results show that a nanocrystalline Cr coating is formed at the 41Cr4 steel surface by the treatment of the new composite technique. Such nanocrystalline Cr coating has acceptable hardness and high corrosion resistance performance, which satisfies the demands of the gears working under high speed and corrosive environment. The composite process proposed in this study is considered as a new prospect method due to the multifunction layer design on the gear surface

Identification of crystal orientation for turbine blades with anisotropy materials

A novel approach to identify the crystal orientation of turbine blades with anisotropy materials is proposed. Based on enhanced mode basis, with the main advantages of its efficiency, accuracy and general applicability, the blade vibration mode of each order is linearly constructed by several specified mode shapes, which are obtained from the considered turbine blade with specified crystal orientations correspondingly. Then, a surrogate model based on Kriging method is introduced for constructing the condensed perturbed matrix of stiffness in order to improve the efficiency even further. The constructed surrogate model allows to perform the modal analysis of turbine blades with arbitrary crystal orientations in higher efficiency, due to the fact that the elements of condensed perturbed matrix of stiffness are considered in construction of the surrogate model rather than concerning the perturbation of all the elements of the initial stiffness matrix for the blade. Genetic algorithm is finally employed to optimize the defined fitness functions in order to identify the crystal orientation angles of turbine blades. Several corresponding examples demonstrated the accuracy, efficiency and general applicability of the proposed method

Science and technology innovation and practice of major national science and technology special project of coalbed methane in coal mining area

The scientific and technological innovation system formed by the national major oil and gas projects has the characteristics of “new nationwide innovation system”, and the system of scientific and technological projects has the characteristics of “whole process, multi-stage and full life cycle”. During the 11th Five-Year Plan period and 13rd Five-Year Plan period, major national oil and gas projects have continuously supported scientific and technological breakthroughs and technological innovations in basic theories, key technologies and complete sets of equipment for the development and utilization of coalbed methane. Members of the national major projects of oil and gas projects and project implementation unit, paying great efforts, aim to taking the national major projects of oil and gas as an great opportunity, to enhance the level of coal mine area of coalbed methane of science and technology innovation and form the leading industry of coal mining area of coal bed methane research and development of science and technology innovation system, to fully support the realization of key scientific research goals of major national oil and gas projects. Coal mining area coal bed methane grograms have formed a series of major landmark achievements, built a series of industry innovation platform, comprehensively stired the technological progress and industrial development of coal-bed methane industry in coal mining areas of China, and effectively promoted the construction of the coal-bed methane industry in China. Combined with the organization and implementation of the project (subject)/demonstration project and the characteristics of the coal industry, we have systematically summarize the exploration and practice of CBM technological innovation in national major special coal mine area and formed a national major special project of science and technology, which is “guided by national investment, dominated by enterprise investment, highly integrated with industry, university, research and application, and continuously leading the technological progress of the industry”. In establishing and perfecting the organization and management institutions, continue to strengthen the special management specification, continue to play a role of cohesive ties, coordination to promote the scientific research management innovation, promote the development and use fusion to form coal mining area of coalbed methane from the concrete experience of science and technology innovation practice

The Influence of Interface Roughness on the Vibration Reduction Characteristics of an Under-Platform Damper

Analysis of the vibration reduction characteristics of shock absorbers is crucial for engines. In this study, the fractal theory was applied to the contact surface of an under-platform damper (UPD), and the influence of the excitation force in the same and opposite directions on the roughness of the contact surface was studied. First, based on fractal geometry theory (FGT), the roughness characterization method of a UPD contact surface was proposed. Then, the friction mechanical model of the rough contact surface was established by combining it with a 3D contact mechanical model. Furthermore, a finite element dynamic model of a blade with a UPD structure was set up. Next, the harmonic balance method was used to calculate the nonlinear response characteristics of a blade under different levels of contact surface roughness. Finally, the influence of the contact surface roughness on the vibration reduction ability of a UPD under different excitation modes was analyzed. According to the simulation results, as the contact surface became rougher, the vibration suppression ability of the UPD on the blade became stronger and stronger. With the change in the centrifugal force of the UPD and the amplitude of the same/reverse excitation force, the influencing law of the contact surface roughness on the vibration suppression ability of the UPD remained unchanged, indicating that the rougher the contact surface roughness, the better the vibration suppression effect

The Influence of Interface Roughness on the Vibration Reduction Characteristics of an Under-Platform Damper

Analysis of the vibration reduction characteristics of shock absorbers is crucial for engines. In this study, the fractal theory was applied to the contact surface of an under-platform damper (UPD), and the influence of the excitation force in the same and opposite directions on the roughness of the contact surface was studied. First, based on fractal geometry theory (FGT), the roughness characterization method of a UPD contact surface was proposed. Then, the friction mechanical model of the rough contact surface was established by combining it with a 3D contact mechanical model. Furthermore, a finite element dynamic model of a blade with a UPD structure was set up. Next, the harmonic balance method was used to calculate the nonlinear response characteristics of a blade under different levels of contact surface roughness. Finally, the influence of the contact surface roughness on the vibration reduction ability of a UPD under different excitation modes was analyzed. According to the simulation results, as the contact surface became rougher, the vibration suppression ability of the UPD on the blade became stronger and stronger. With the change in the centrifugal force of the UPD and the amplitude of the same/reverse excitation force, the influencing law of the contact surface roughness on the vibration suppression ability of the UPD remained unchanged, indicating that the rougher the contact surface roughness, the better the vibration suppression effect

Effect of the filling position and filling rate of the insulation material on the insulation performance of the hollow block

Since the self-insulation wall has the same service life as the building, the resources are saved, and the environmental pollution is reduced, so it has been widely used. In order to obtain the optimal filling position and filling rate of the composite self-insulation hollow block, the thermal insulation performance of the composite self-insulation hollow block was optimized. In this experiment, 6 groups of self-insulating block models with different filling positions and filling rates were constructed. A cold and hot test box was used to simulate the working state of 6 groups of composite self-insulation blocks in the continuous operation of air conditioning in cold areas of China in winter. Through comparative analysis: Filling the hollow block with EPS insulation material is conducive to improving the insulation performance of hollow brick, and the higher the EPS filling rate is, the better the insulation performance of the block is. At the same EPS filling rate, the closer EPS is to the inside of the heat box, the better the insulation effect of the wall will be. At the same EPS filling rate, the method of filling EPS on both sides of the cavity has the best insulation effect, which is conducive to saving insulation materials

Effect of Annealing Treatment on Microstructure and Properties of Cr-Coatings Deposited on AISI 5140 Steel by Brush-Plating

Cr-coating was deposited on AISI 5140 steel by electro brush-plating, followed by annealing treatment at different temperatures, from 300 to 1100 °C. The microstructure evolution of the Cr-coating was characterized by backscattered electron imaging (BSEI) and energy dispersive spectrometry (EDS). The results show that the brush-plated sample has a nodular shaped microstructure, which is very stable at 300 °C of annealing. At 500 °C of annealing, the constitution of the microstructure changes from nodules to grains. As the annealing temperature further increases, the grains grow significantly. When the temperature reaches 1100 °C, a Cr-Fe solid-solution layer is formed within the original pure Cr-coatings. With increasing annealing temperature, the number of micro-cracks in the coating increases first and then decreases, reaching a maximum at 500 °C. The hardness and wear-resistance of the coating are improved when the annealing temperature increases to 1100 °C, owing to the decrease of micro-cracks that formed during brush-plating

Supplemental Material - Multi-Objective sliding mode control of proton exchange membrane fuel cell system based on adaptive algebraic observer

Supplemental Material for Multi-Objective sliding mode control of proton exchange membrane fuel cell system based on adaptive algebraic observer by Hao Jing, Tiexiong Huang, Cheng Li, Xiaodong Liu, Guangdi Hu and Chaoping Pang in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy.</p