As a green and efficient processing method, minimum quantity lubrication(MQL) has the advantages of small amount of cutting fluid using, low cutting force, preventing adhesion, prolonging tool life and improving the surface quality of workpiece.However, there are some problems such as inadequate lubrication and low cooling performance under the specific conditions.Therefore, experts have proposed several kinds of minimum quantity lubrication synergistic technology. The latest research progress in the principle is summarized, implementation scheme and process application of minimum quantity lubrication synergistic technology. The purpose is to extend the application scope of minimum quantity lubrication technology and provide theoretical support and scientific guidance for further research on minimum quantity lubrication synergistic technology.
Lightweight high-strength carbon fiber reinforced resin matrix composite (CFRP) is the preferred material for weight reduction and efficiency improvement of transportation equipment, which can significantly improve equipment performance. The assembly connection of such material members requires a large number of connection holes to be processed, and the hole damage tolerance is demanding. However, CFRP is a typical difficult-to-machine material. When drilling holes, compared with homogeneous materials such as metal, the material failure behavior and removal mechanism are very different, which is easy to cause serious damage in the exit area, which poses severe challenges to existing processing technologies. The application of CFRP limits the performance of equipment. In this paper, the cutting mechanism and temperature influence law of CFRP are studied. The method of controlling cutting force and reducing the influence of cutting temperature is proposed. The key technologies of drilling tools and process are
The heat transfer coefficient and thickness of the atomized liquid film are important factors in determining the spray cooling effect.The numerical simulation method is used to analyze the effect of spray pressure, height and tilt angle on the heat transfer characteristics of spray cooling based on three angles of liquid film thickness, heat transfer coefficient and temperature distribution on the heating wall. The results show that the spray pressure is an important factor affecting the heat transfer effect. Compared with the low pressure working condition, the liquid film formed on the wall surface is small in the high pressure working condition, the average wall temperature is low, and the heat exchange capacity is strong. The greater the pressure condition, the higher the wall temperature drop. Mainly because the injection pressure is increased, the movement speed of the liquid film is increased, resulting in a strong disturbance between the air and the air, which promotes liquid film breakage and droplet
Hydraulic system widely used in various electrical and mechanical equipment, and the hydraulic pressure in the hydraulic system is a valve for controlling liquid flow rate and direction of the core member, the hydraulic system performance, reliability and economic Sex has an important influence. The flow valve is one of the three types of hydraulic valves by changing the opening of the throttle port to regulate the flow rate and thus the speed of the load equipment. The multi-stage flow valve realizes the displacement control of the pilot spool to the main spool by various stages of feedback, and then completes the flow adjustment through the main spool.
To improve the signal to noise ratio(SNR) and lateral resolution, phase coherence imaging(PCI) post-processing algorithm is presented and applied in ultrasonic time-of-flight diffraction(TOFD) inspection for heavy-walled welds. Firstly, delay and sum operation for the aperture data of TOFD-B image is implemented by synthetic aperture focusing technique(SAFT). Secondly, phases of aperture data were used to establish phase coherence factor which represented the phase dispersion for each pixel in the B-SAFT image. Finally, the B-SAFT image is dynamically weighted by phase coherence factor. The results show the PCI is capable of suppressing structure noise and enhancing SNR by amplifying the contribution of phase information. For austenitic weld with 78 mm thickness, the average SNR of three ?3 side drilled hole were more than 30 dB, higher 20 dB than TOFD-B image. Furthermore, the PCI could improve the lateral resolution by enhancing aperture beam directivity. Compared to TOFD-B image, the half lateral width of
Machining allowance for a blisk is mainly removed in the rough milling, so selecting the appropriate machining method toremove the allowance of blisk tunnel in the rough milling is key to reducing the tunnel cutting costs and making the blisk machiningeconomically. As the wire cut electrical discharge machining machine processing unit cost is low, wire cutting is used to remove theallowance of tunnel. The processing boundary of tunnel is determined by the offset surface of blade and hub of blisk.The optimalvector is determined by comparing the size of the projected area after the projection of the boundary of the tunnel. Then, the cuttingarea and the angle between the line cutting wire and the end face of the blisk are determined according to the optimal vector, and thecutting area is maximized. This method can effectively solve the economic problems of blisk in the rough milling. The demonstrationshows that the wire cutting can be applied to remove the allowance of blisk, and compared with the traditional CN
HEC solutions of varying concentration are used as water-based lubricant. FT-IR Spectrum and Molecular Dynamics were used to study the interaction between HEC and water. 3D optical surface profiler is used to measure the surface of friction pairs. The friction tests for effect of speed, load and concentration on lubricating behavior of HEC in surface contact are carried out on a modified friction tribometer (UMT-2). The results indicate that strong hydrogen bond occurs between HEC and water;the lubrication action isn’t enhanced by changing the rotation speed;the lubricant spread evenly under heavier load, which made the coefficient of friction (COF) decrease with the increasing load;the COF of the 1. 00 wt. %solution was the lowest under different loads, while the COF increased in other solutions. The water-based lubricating film contains water layer and hydration layer of hydroxyethyl cellulose, in which the latter is dominant.
The rapid development of wearable and portable electronic devices towards "lightweight" and "miniaturization" has greatly stimulated the strong demand for high energy/power density, lightweight and portable and flexible energy storage devices in modern society. As a new type of micro-power storage device, in-plane micro-supercapacitors(IPMSCs) are considered as an important energy storage device for integrated electronic devices due to their ultra-thin thickness, high power density and long cycle life.However, with the development of IPMSC processing technology towards high efficiency, high precision, and low cost, the commonly used processing technologies cannot meet its requirements. A laser processing technology with easier operation, more scalable, higher precision and lower cost has been proposed and has become the research focus of IPMSC processing technology.The working principle and electrochemical performance of different types of IPMSCs are summarized, as well as the types and processing techniques
In order to study the combined effect of tension and bending moments conditions on the acid pickling process of hot rolledstrips, an elastic-plastic mechanics analysis method is conducted to analyze the influence of tension and bending moment on thecurvature and elongation. Taking hot-rolled electrical steel sheet as an example, a mathematical model is established on theconsideration of the relationship between curvature/elongation and tension/bending moment. Regarding the target values of curvaturesand elongations, the relationship between tension and bending moment is established through the static equilibrium equations undervarious plastic bending stages. Electrochemical pickling experiments is also applied to investigate the effects of different curvaturesand elongations on the acid pickling time, and to build a prediction model about the pickling time shortening rate withcurvature/elongation. On the basis of pickling time shortening rate, the pickling efficiency is assessed with different curvatures ande
In order to overcome the problem that the traction of wheeled rover on loose terrain is limited by the wheel-soil mechanism. A four wheeled Mars rover with wheel-legged mobility is proposed. The adhesion of the brake wheel and the traction of the driving wheel is compared based on terramechanics, the sole mechanism of wheel-legged is clarified. A double pendulum walking mechanism is presented. Two rotate joints of double pendulum walking mechanism are associated with a belt drive. The driving motor takes less load and costs less energy than that the joints are drove independently. One planetary gear train and two brakes are utilized to control the four operating states of mobile system:wheel, step, wheel-legged and brake. The calculation methods of transmission ratio of wheel motion and step motion are given according to the load analysis of slope wheeled climbing and slope wheel-legged walking. The design and manufactured of the prototype is completed after the set of reducers is clarified. The typical gaits
Approximate optimization strategies using design of computer experiments(DoCE) and metamodels have been widely applied in design of modern complex engineering systems. Mode pursuing sampling method(MPS) is a representative of such optimization algorithms. A rapid mode pursuing sampling method using significant design space concept(notated as RMPS-SDS) is proposed in this work to alleviate the low efficiency problem of MPS in solving high dimensional optimization problems. The idea of significant design space is incorporated into the MPS framework, and a sample point allocation strategy is designed to enhance the local search capability and convergence speed of MPS. RMPS-SDS is tested on a number of standard numerical benchmark problems and two engineering design problems and compared with MPS and GA. The comparison results indicate that with the same computational budget(i.e., the same number of function evaluations), results of RMPS-SDS are much closer to the theoretical global optima with lower standard dev
A parallel manipulator(PM) with three-translation and one-rotation(3T1R) output, possessing zero coupling degree and partial input-output motion decoupling(I-O decoupling), can not only make the analyses of kinematics and dynamics simple, but also simplify the motion control and path planning. These PMs have potential applications in the manufacturing. A new 3T1R PM with zero coupling degree and partial motion-decoupling is designed, i.e., 2-(RPa3R)3R, according to the design theory for parallel mechanism topology based on position and orientation characteristics(POC) equation. The key topological properties such as POC,degrees of freedom DOF, coupling degree κ are analyzed. The closed-form direct position algebraic equations of the PM are derived by using the modeling principle based on the ordered single-open-chain(SOC) proposed in an earlier work, and the solutions for direct position of this PM are solved. In addition, the geometrical conditions of three types of singularity are analyzed based on the inve
An auto-collimation measurement method for space vectors is proposed to precisely calibrate coordinate systems of satellite on-board sensors. With this method, high-precision automatic measurement of the angle between normal vectors of cube faces is achieved by employing the photoelectric auto-collimation theodolite, satellite turntable, reference mirror array, and coordinate translation system. The measurement model is provided and the error model is constructed based on the principle of error propagation.Then the upper limit of the uncertainty is derived. The sensitivity of the sensors' accuracy on the measurement error is analysed via simulation, based on which error is distributed. An auto-collimation measurement system for space vectors of satellite on-board sensors is designed and developed. Calibration experiments show that the angle accuracy of the theodolite is up to 0.6″, the verticality error between two axes is less than 0.2″, and the systemic measurement accuracy of the space angle is up to 3″. T
Train-like vehicle, with advantages of large capacity and high one-way traffic flow conveying rate etc., can effectively solve the problem of traffic jam in cities, and meet the travel requirements of urban resident on working and living trips. However,due to the increase of the length of the train-like vehicle, the flexibility of movement decreases, which increases the difficulty of the maneuverability of the train-like vehicle. Therefore, the steering control method of the train-like vehicle is studied in this paper. Based on the principle of the virtual displacement and the virtual work, this paper establishes a general dynamic equation of the train-like vehicle, then proposes a multi-axis coordinated steering control law for the car model, and constructs a Lyapunov function. The Lyapunov direct method is used to prove that the train-like vehicle can travel along the target route. Finally, a simulation model of train-like vehicle with 3-body and 4-axle is established to track the step route and the sinusoi
Gear shifting process in electrical mechanical transmission(EMT) is a complicated nonlinear multi-body dynamic process.Because of the difficulty in system modeling and huge uncertainty of this process, it is difficult to obtain favorable control performance by using traditional control methods. Hence, these problems largely hinder the development of corresponding control methods for this process. In face of these problems, the paper analyzes the characteristics of the entire process and consider that the process is a repetitive execution, then presents an approach of adopting iterative learning control(ILC) method to optimize gear shifting process. To realize this purpose, unknown input observer is used to estimate the gear shifting load force, then design a linear state feedback controller to generate initial control inputs. After that, ILC is adopted to compensate the control error and considering the construction of the desired trajectory. Finally, experimental results have shown that the proposed scheme i
According to the characteristics that the driving torque of each wheel of a four-wheel hub motor drive electric vehicle can beindependently controlled, the stability control of the electric vehicle could be realized by controlling the output torque of wheel hub motor(i.e., adjusting the wheel driving force or brake force) to generate additional yaw moment. The hierarchical control strategy is applied forthe vehicle stability control. The upper layer is a yaw moment controller, which includes two fuzzy controllers based on yaw rate andsideslip angle, respectively, and an extension combination controller. The lower layer is a driving force distribution controller, whichutilizes the pseudo inverse algorithm to optimize the driving torque allocation of each wheel. Its control modes are divided into stabilitycontrol, minimum energy consumption control and combination control. The gray control model is used to preprocess the actual yaw rateand sideslip angle. According to the electric vehicle driving state, the con
In order to reduce the twist springback appearing after the stamping of high-strength steel, a compensation method withgradient die radius is proposed. The double C rail of TRIP780 high-strength steel is taken as the research object. The sheet metalstamping simulation software DYNAFORM is used to numerically simulate the stamping and twist springback processes of thedouble C rail. An index to evaluate the twist springback of the double C rail is proposed. The experiment of twist springback for thedouble C rail is carried out. The twist springback angle is measured by means of a three-coordinate measuring instrument, and thefinite element model is validated. The twist springback appearing after stamping is taken as the optimization target, and the relatedprocess parameters are taken into account. BP neural network is used to establish the network model between the gradient variation ofdie radius, process parameters and the twist springback angle based on orthogonal test. Finally, the model is iteratively optim
Under the new decoupling development pattern of economic development and environmental pollution, combined cooling,heating and power system(CCHP) using renewable energy sources such as solar energy has become a hot spot. Integrated with solar energy, a CCHP system which can meet cooling load in summer, provide heat in winter and supply electricity throughout the year is investigated. The system contains a parabolic trough collector(PTC) circuit, a heat storage tank, an auxiliary boiler, an organic Rankine cycle(ORC) and an absorption cooling system. A design method to determine the PTC area of the system, the capacity of the storage tank and the backup boiler is proposed, which can choose system energy efficiency, annual total cost or the coupling between efficiency and cost as evaluation criteria. Based on this method combined with a building simulation load, the capacity of the key components is determined using the evaluation criteria of coupling between efficiency and cost as an example. The sensitivity o
Grinding plays the critical role in manufacturing the aero-engine components composed of nickel-based superalloys. Inorder to further improve the material removal rate and workpiece quality, a large number of researches on grinding technology ofnickel-based superalloys are conducted in terms of the fundamental theory and process expending. In this review article, the basicprinciple and development process of grinding are firstly introduced briefly. Then, the technologies are reviewed detailed concerningthe material removal mechanism, the grinding characteristics, and the novel application type of grinding for nickel-based superalloys. Finally, the development trends during grinding of nickel-based superalloys are proposed as well as the difficulties in grinding of suchmaterials.
Based on the movement model and the structural characteristics of worms, a bionic wheel-walking squirming soft robot with a double-cavity structure is proposed. The main body of the soft robot is made of hyperelastic silicon rubber, and its multi-air-bag structures would expand and extrude each other to bend the robot body when air at a certain pressure is pumped into the air bags. The inchworm-like peristaltic movement of the soft robot is realized by periodically charging and releasing air. In addition,the peristaltic motion of the soft robot is changed into rotational motion of the wheels to accelerate its moving speed because of the ingenious wheel-walking device. And a large angle turn can be achieved by fill the two chambers with air of different pressure. The periodic motion and steering movement of the squirming robot are analyzed. the nonlinear mechanical properties of the robot are studied. The relationship between the deformation and the pressure is tested when the two cavities are filled with air