Recent Patents on Mechanical Engineering - Volume 15, Issue 4, 2022

Background: In the industrial manufacturing process, manually labeling enough datasets is time-consuming, which hinders the training and deployment of defect detection models. Therefore, automatic defect detection and its classification is the premise of industrial production quality. Objectives: The study mainly discusses about the detection of the Hemispherical Surface of the valve core by machine vision method. Methods: The paper put forward a novel semi-supervised algorithm to detect the Hemispherical Surface of the Valve Core. Under the condition of the lack of labeled datasets, the paper used labeled and unlabeled samples for model training. This thesis proposed, for the first time, using the Mean Teacher semisupervised learning framework and then making changes to the model; firstly, this paper proposed to use the Stochastic Weight Average (SWA) algorithm to update the weight of the teaching model to enhance this model’s generalization ability. Furthermore, in order to select reliable datasets and calculate the consistency loss, this study also proposed an Uncertainty Filter (UF) method. Thirdly, the selection of hard-ware equipment, since the hemispherical surface is anisotropic, ring light source is used, which can lit the surface from top to bottom. Results: Experimental results show that in two different conditions, the classification accuracy can raise. On one hand, under the condition of training with a small amount of labeled datasets, the proposed semi-supervised learning model can achieve a classification accuracy of 90.51%; whereas, under the condition of the semi-supervised learning mechanism and a large amount of unlabeled datasets, the accuracy increases from 93.7% to 98.1%. Conclusion: This paper uses hemispherical metal surface as the dataset for the first time, and also innovatively optimizes the semi-supervised model. On the other hand, experimental comparative analysis indicates that the model proposed in this paper is significantly better than the comparison model, which lays the basic position for the defect detection of the hemispherical surface’s metal. At the same time, the novel semi-supervised algorithm can also be used to detect other metal part’s hemispherical surfaces.

Background: The essence of the plastic deformation of the material to be processed during the cutting process is the movement of dislocations. By increasing the density of dislocations, the material’s flow stress inevitably increases by raising the strain rate. Objectives: The three regions are divided quantitatively as thermal activation stage (10¹-3×10³), nonthermal stage (10^-3-10¹), and dislocation damping stage (above 3×10³). Analyzing the chip metallographic diagram of the cutting process, it is believed that the strain rate effect is caused by two reasons. Methods: The three areas are based on the speed of growth and the control mechanism, presenting a more detailed and vivid explanation of these three areas. Using Hopkinson pressure bar (SHPB), the strain rate effect of duplex stainless steel S32760 is studied. Results: The greater austenite deformation is caused by the austenite deformation in S32760 compared to the ferrite softening effect and the insufficient softening effect in the plastic deformation of the material. Conclusion: The grain refinement is caused by the adiabatic shear zone from the deformation zone to the transition zone, making it difficult for dislocations to start slipping and increasing the flow stress.

Background: To obtain the load characteristics and fatigue characteristics of the engine bracket during the working process, the automobile engine bracket is taken as the research object, and the force characteristics are analyzed. Objective: This paper provides a theoretical basis for engine bracket design that improves the reliability and durability of the engine bracket. Methods: Under cyclic loading, the fatigue characteristics are analyzed through the bench test. According to the experimental results, the critical points of the engine bracket are examined. Results: According to the S-N curve, the estimated range of fatigue life of the engine bracket is from 34236 times to 127219 times. When the load level is low, the life span changes significantly with the stress. As the load increases, the fatigue life is less affected and shows a slight decrease. When the stress level is lower than the equivalent stress threshold value, the stress will not cause fatigue failure, and the specimen has an infinite life. Conclusion: This paper lays a foundation for the prediction of fatigue life and the bench test of fatigue durability of the engine bracket subjected to complex and variable random loads. The research method can also be used to estimate the fatigue life of other bearing parts.

Background: In order to reduce global carbon emissions, a cross-critical CO2 singlemachine two-stage compression system was proposed. Due to the characteristics of cooling on the high-pressure side of the cross-critical cycle and bipolar compression on the single-stage, the discharge pressure and the high-low pressure volume ratio have a great influence on its heating performance. Objective: The purpose of this paper is to explore the influence of high-low pressure-volume ratio and discharge pressure on the heating performance of the system, so as to obtain the optimal operating conditions of the system. Methods: By constructing theoretical calculation formula of discharge pressure, high-low pressurevolume ratio and intermediate pressure, combined with experiments. Results: Under certain working conditions, with the increase of the volume ratio of high-low pressure, the intermediate pressure increases, the heating capacity of the system increases due to the increase of the discharge temperature and the increase of the heat exchange temperature difference on the hot water side, while the heating performance coefficient decreases slowly because the rate of the increase of the power consumption of the compressor is greater than the rate of the increase of heating capacity. With the increase of discharge pressure, the increasing rate of CO2 discharge temperature will gradually decrease at the high-pressure side, so the heating capacity of the system increases rapidly first and then tends to slow down, and the heating performance coefficient increases first and then decreases. There is an optimal value, that is, when the evaporation temperature is -20 °C, the maximum heating capacity can reach 3 kW. The system heat production performance coefficient has an optimal value of 3.29, and the optimal discharge pressure is 8.5 MPa. The optimal discharge pressure will increase with the increase of evaporation temperature. Conclusion: The selection of reasonable high-low pressure volume ratio and the control of discharge pressure can effectively improve the heating performance of cross-critical CO2 single-machine twostage compression heat pump water heater.

Background: Gearboxes are used in many industrial fields. Due to uncontrollable external factors and inevitable fatigue damage, gearboxes are likely to fail. It has become a major research trend to collect dynamic signals of gearboxes and develop effective fault diagnosis methods for gearboxes. Objective: The purpose of this paper is to study the dynamic characteristics of herringbone gear transmission (HGT) under different friction coefficients and pitting faults. Methods: A virtual prototype model of the system with different friction coefficients and pitting faults was established jointly with KISSsoft, SolidWorks, and ADAMS. The contact stiffness, penetration coefficient, damping, and other factors were considered in the model. The contact force and angular acceleration signals of the Driven gear are collected and analyzed by simulation. Results: The increase of friction coefficient results in the increase of contact force and instantaneous angular acceleration. The modulation side frequency band on both sides of the frequency becomes dense, and the side frequency band in the frequency domain of angular acceleration becomes sparse. When pitting failure exists, all dynamic signals show fault characteristics. Conclusion: This work provided a theoretical basis for fault diagnosis and gear dynamics research, Due to many nonlinear factors, the fault diagnosis of the HGT system is relatively difficult. The research results can quickly diagnose the fault of the HGT system, which makes up for the shortcomings in the study of the fault diagnosis of the HGT system.

Background: Scroll refrigeration compressors are the critical equipment for the refrigeration system in air conditioners and vehicles. The asymmetric suction structure can be applied to reduce the scroll compressors' size. However, the pressure difference between the symmetric working chambers becomes larger and leads to the special force characteristics of the orbiting scroll. Objective: This paper illustrates the force characteristics of the orbiting scroll in an Asymmetric-suction Scroll Compressor (ASC) to improve its stability and reliability Methods: The theoretical model has been established to calculate the force and moment acting on the orbiting scroll of ASC and the Symmetric-suction Scroll Compressor (SSC) based on the transient numerical simulation results. Results: The variations of gas force and moment in ASC and SSC are displayed and compared. Their pulsation intensities are calculated and discussed. Conclusion: The pressure in the outer compression chamber of ASC was always higher than that in the inner compression chamber, which caused significant discharge loss. Affected by the tangential leakage flow, the radial force of the compressor fluctuated sharply. As the tangential force on the orbiting scroll segments of symmetrical working chambers in ASC led to the negative spin moment, the total average spin-torque decreased by 71.3%. Still, the pulsation intensity increased by ten times. Furthermore, the direction of the spin moment reversed at 275°~355°, which indicated that the orbiting scroll impacted the Oldham ring every rotation. The noise and vibration would happen, and the Oldham ring would be damaged easily.

Aims: An inverted XY-3-RPS hybrid mechanism was designed to apply ultraviolet-induced nano-particle colloid jet machining to polish the complex surface. Background: The hybrid mechanism has been widely used in the ultra-precision polishing field for installing different polishing tools on the moving platform to meet different machining requirements because of its wide working space, good dynamic performance and large bearing capacity. Objective: The main objective of this study is to establish an inverted XY-3-RPS hybrid mechanism for UV-induced nanoparticle colloid jet machining, to realize the ultra-precision polishing of complex surfaces by UV-induced nanoparticle colloid jet machining. Methods: The three-dimensional model of the inverted XY-3-RPS hybrid mechanism was established, and the kinematics and dynamics were analyzed. The Jacobian velocity matrix of the inverted XY-3- RPS hybrid mechanism is derived by vector construction and differential methods, and the dexterity index under different proportional parameters is optimized and simulated. The output Jacobian matrix and stiffness matrix are obtained using the virtual work principle, and their static analysis is carried out. Based on Lagrange dynamics theory, the dynamic mathematical model of the inverted XY-3-RPS hybrid mechanism is established, and its kinematics is verified by software joint simulation. Through dynamic simulation, the variation curves of motion, force and kinetic energy of the mechanism are obtained, which provides a theoretical basis for applying the hybrid mechanism in complex curved surface polishing. Results: The analysis shows that it has the best dexterity index when the ratio of moving and the fixed platform is 2:1. The kinematic simulation results show that the hybrid mechanism moves reliably under the given trajectory. The dynamic simulation results show that the force analysis of each kinematic pair and the kinetic energy change curve of each part changes smoothly, and the dynamic performance is stable under different trajectories. Conclusion: The parameter design and structural design of the inverted XY-3-RPS hybrid mechanism meet the requirements of ultra-precision polishing of complex surfaces.

Background: With the continuous exploitation of shallow mineral resources, the shallow resources are increasingly exhausted. Therefore, the application of multi-rope friction machine in ultradeep, high speed, heavy load mine will be more widely used. The diameter and dead weight of the hoisting-rope in this heavy-duty deep well are larger, and the internal torsion and bending load are more complex, which makes the replacement of the hoisting rope more difficult. According to the "coal mine safety regulations", the working life of the hoisting-rope is not more than two years, and the hoistingrope of friction hoist is not more than eight months in a harsh environment. Although the existing hoisting- rope replacing methods are mature, there are some problems, such as high labor intensity, long replacement time and low safety, which affect the mine production and are not suitable for deep mine hoisting-rope replacement operation. Objective: The purpose of this patent is to provide a new mechanism for safely and efficiently replacing the hoisting-ropes of multi-rope friction hoists. In addition, the dynamic simulation analysis of the key parameters of the mechanism is carried out, and reasonable design suggestions are given. Methods: A new device is designed to achieve continuous retracting and releasing ropes with constant locking force and small impact, which is mainly composed of sprocket, chain, friction block, mechanism of clamping hoisting-rope and so on. Results: The designed new mechanism can efficiently and safely replace the hoisting-rope of various hoisting equipment and realize the continuous hoisting-rope replacement, limiting the load impact to a great extent. The mechanism is responsible for clamping and releasing the new hoisting-rope and retracting the old hoisting-rope during the whole hoisting-rope replacement process. In the condition of some hoisting-rope with large dead weight, it can also provide enough clamping force, and there will be no phenomenon of hoisting-rope sliding. Conclusion: The device not only realizes the synchronous replacement of the old and new hoistingrope, but also greatly improves the replacement efficiency and safety of the hoisting-rope. The patent effectively solves the existing problems in the process of hoisting-rope replacement and greatly improves work efficiency.

Objective: To efficiently exploit the hydrate reservoir, based on the problem of a large amount of sand production in the current hydrate reservoir exploration process, combined with the solid fluidization well testing and production method. Methods: A gas-liquid-solid three-phase flow model is established and hydrate decomposition is taken into consideration. The changes in parameters of wellbore pressure, gas volume fraction, liquid volume fraction, temperature and the decomposition rates of wellbore hydrate under the conditions of different rates of sand production are analyzed. Results: The results show that with the increasing rate of sand production during the solid fluidization well testing and production, the pressure of the wellbore is lifted, gas volume fraction declines, liquid volume fraction declines, and the temperature of the wellbore does not change. Moreover, increasing the rate of sand production also leads to the delay of the position where hydrate begins to decompose. Conclusion: With the decrease in hydrate saturation, the pressure of the wellbore goes up, gas volume fraction is lifted, solid volume fraction rises, and decomposition rate of hydrate declines.