Recent Advances in Applied Mechanics and Mechanical Engineering

In this paper, the nonlinear elastic manipulator system is taken as the research object. According to the relevant knowledge of mechanical vibration, the elastic manipulator is simplified to the mode analysis of the robotic arm by the Euler–Bernoulli beam, and the dynamic model of the system is established by using the Lagrange equation, in order to simplify the complexity of the calculation, in order to ignore some tiny amounts of the equation system and some nonlinear terms of high powers, the multi-scale method in the nonlinear vibration approximation analysis method is used to solve the dynamic model of the system. The results show that the approximate solution obtained is perfectly consistent with the analytical solution. And, the amplitude–frequency characteristic curve of the main resonance of the system is obtained, which shows that the peak value of the main resonance of the system is not only related to the amplitude of the excitation force but also related to the damping coefficient of the system.

In this study, the influence of the modulus of elasticity of the jointed material and interlayers in the nodes with an interlayer with a high TCLE was investigated by computer simulation. To establish the general patterns of SSS formation when loading cylindrical nodes with interlayers of soft rigidity and checking the adequacy of the simulation, the average value of the elastic modulus of interlayers with a high TCLE was calculated. The results show that under thermal loading, in all variants, stresses are absent for the greater part of the node, and only in a small zone located near the interlayer near the joint edge (at the outer surface of the cylinder), and in the interlayer, a complex SSS is created. On the outer surface of the node in the greater part of the interlayer, the stiffness coefficient is at the level of 0.76, 0.80, decreasing to 0.64 near the joint in the nodes with a “soft” interlayer, and slightly increasing to 0.81 and 0.91 in the nodes with “neutral” and “hard” interlayers, respectively. The interlayer material is in the volumetric stress state throughout its entire length. This provides reliability guidance for the theory of TLP diffusion welding under large gap.

Aiming at the problem that the conventional missile-borne infrared imaging system is easily affected by aerodynamic thermal effect, the imaging method of the infrared lateral window is studied. A set of imaging system of infrared lateral window is designed, which is suitable for deflecting light path with large incident angle. Theoretical calculation and experimental test results show that the system has fine imaging performance and can obtain good images, which verifies the feasibility of the infrared lateral window imaging method, and can provide a practical reference for similar infrared imaging in the future.

In order to study the injury characteristics of the passenger-side occupant in the process of near-ground side ramp rollover, a finite element model of an off-road vehicle was established, and the acceleration of the center of mass of the vehicle rollover was obtained through simulation, and the accuracy of the model was verified through real vehicle rollover test. Hybrid III 50% male dummy was placed in the three rows of seats on the passenger side, and the restraint system was the same as that of the original vehicle, and the damage to various parts of the dummy was obtained for comparative analysis. The study shows that: the peak injury moments of different positions are similar, only the peak injury moments of the head and chest of the rear dummy appear earlier; the rear occupant's body dives and the neck is compressed, resulting in excessive axial force on the neck, and the subsequent improvement should focus on the restraint system.

To reveal the failure mechanism of Al50Si silicon aluminum alloy under impact loading, MCM modules, and a crystal-integrated receiver/inverter were used as the research object, the pendulum-type shock response spectrum test bench was used to conduct a large number of impact loads test of 1600 g, and the fractured samples were examined by scanning electron microscopy (SEM). The results show that the Al50Si silicon aluminum alloy exhibits direct brittle fracture characteristics under a large impact loads; in order to realize the vibration impact protection of Al50Si silicon aluminum alloy, numerical simulation of the structure with impact loads was carried out using response spectrum analysis and wavelet synthesis time domain method, and the simulation method is highly accurate, with a maximum error of 2.3% compared to the experimental results. The product design has been optimized according to numerical simulation results and verified by 1600 and 2000 g impact tests, which can effectively improve the reliability of the product against large impact levels.

To study the damage to the target plate under the combined action of shock wave and fragment, using the complete restart technique to extract the damage of the target plate after the action of the shock wave, and then a single fragment penetrating target plate is simulated. The Arbitrary Lagrange-Euler (ALE) algorithm and Particle Blast Method (PBM) algorithm are used to analyze the damage to the target plate by prefabricated fragments after the explosion and compare with the test to verify the feasibility of the PBM algorithm. Completely restart the target plate under the action of the shock wave generated by PBM algorithm. The Ls-dyna software is used to simulate the fragment penetration into the target plate, so as to obtain the damage of the target plate under different incidence angles. The simulation results show that the combined action of shock wave and fragment has a strong penetration ability; the end penetration capability of cylindrical fragment is greater than that of lateral penetration; the fragment penetration ability is the strongest at vertical incidence.

Metamaterials or meta-structures are essentially a kind of artificially designed structures with certain specific physical properties or functions, which can often realize some special physical phenomena that natural materials do not possess. Thermal meta-structures can achieve some special thermal properties. Based on the transformation thermal theory and effective medium theory, this work realizes the thermal invisibility and heat flux manipulation through the integrated design of a double-layered thermal cloak meta-structure, with the flexible structural performance. The thermal simulation analysis of the thermal meta-structure was performed. The fabrication feasibility of the double-layered cloak meta-structure was studied by etching copper-clad film. Then, the thermal meta-structural properties were tested and analyzed using a self-built thermal test platform. The flexible thermal meta-structures have value in the field of human wearables and surface adaptation of geometrically complex objects.

Improvements in the topology of continuum structures can effectively enhance structural performance and reduce the weight of the structure itself, resulting in significant economic benefits. This paper takes the above as a background, and addresses the complexity of the current description and algorithms of topology optimization, analyses the shortcomings of its theory, models, and algorithms, summarizes relevant experiences, discusses in depth the current basic theory and algorithms of continuum structure topology optimization, and gives conclusions on the application to bridge modeling, in the hope that it can provide a reasonable reference for workers in the same field.

With the development of automotive lightweight, aluminum alloy and other light alloys have also developed rapidly, high-power ultrasonic welding technology is one of the branches. In this paper, Cu and Al foils with thickness of 0.3 mm are welded by high-power ultrasonic welding method. Using relevant instruments for copper alloy organization characteristics, interface temperature, and interface mechanical properties test, the corresponding results found copper–aluminum current—compound ultrasonic welding, ultrasonic power peak, welding interface temperature and interface the depth, the vertical depth of the plastic flow and increases with increasing the thickness of the IMC as auxiliary current. Too high welding pressure is not conducive to the transmission of ultrasonic energy in the workpiece, reducing the quality of the workpiece connection. During ultrasonic welding, the texture strength of copper and aluminum alloy decreases first and then increases. The texture type of copper does not vary with the welding process.

De Laval nozzles are widely used in industrial areas like aerospace. This study focuses on the two-dimensional nozzle flow with small perturbation on the boundary in the purely subsonic case and the purely supersonic case. The small disturbance equations (SDE) derived from the continuity equation are used in this calculation. To get the numerical solution of velocity potential, the successive over relaxation method (SOR) with different relaxation factors is used in the iterative operation. After hundreds or thousands of iterations, the error is on the order of 10E-13. In the subsonic case, the speed of convergence is really fast with only about 300 times of iteration while the subsonic case needs more than 4500 times. The streamline plot and the velocity contour plot are finally illustrated in the paper. The simulation results reveal that the velocity field is almost triple compared to the initial speed, besides, with a slight adjustment in the shape of the boundary, the velocity field also changes a little bit.

Tooth profile modification (TPM) optimization design has got extensive attention in the design of gear system. To ensure the accuracy of the tooth contact analysis (TCA) and the optimization of the modification parameters, the paper established a 3D finite element model (FEM) of the helical gear with TPM. Loaded TCA and stress calculations of helical gears are carried out precisely. The effects of the modification parameters on transmission error (TE), mesh stiffness, tooth bending, and contact stress of the helical gear are analyzed. The tooth surface modification optimization is conducted. The results indicate that the optimized modification parameters can greatly improve the smoothness of gear transmission, which lays the foundation for the design of low vibration and noise transmission system.

In order to deeply study the specific characteristics of the cross-scale phenomenon of fragmentation and atomization in the process of transverse jet atomization, this paper uses the LES turbulence model and the VTD multiphase flow model to numerically simulate the transverse jet process and analyzes the corresponding results. It can better solve the cross-scale related problems and then obtain a more suitable research method for the phenomenon of transverse jet fragmentation and atomization. The study found that the liquid column gradually narrowed along the jet direction under the action of the lateral airflow, and the liquid column was increased by the force of the lateral airflow, resulting in the expansion form of the liquid column being curved downstream. As soon as the jet enters the flow field, it forms independent droplets under the action of the air flow. With the passage of time, the stripped droplets are further broken up to form droplet particles, which are transformed from liquid phase to Lagrangian particle agglomerates. When the jet is fully developed, the surface of the liquid column is broken near the outlet to form small droplets, and then the jet is broken in a columnar shape to form a large number of ribbon-shaped liquid filaments.

In the non-cooperative space object close-proximity tracking problem, a method of utilizing an impact ball to collide with the object is proposed to change the angular momentum and estimate the inertial parameters of the object. This paper investigates the mechanism of the collision and the adhesion between the impact ball and the spacecraft are studied. Firstly, the structure of the impact ball is analyzed. The impact ball is designed as a rubber ball with a radius of 20 mm. The surface of the ball is a bionic Parthenocissus structure. The sponge-like hole of the structure contains bionic mussel secretion with high adhesion. Secondly, the minimum relative velocity of the impact ball penetrating the spacecraft is calculated. When the relative velocity of the impact ball is less than the minimum relative velocity, the spacecraft will not be penetrated by the ball. Finally, the adhesion performance of the impact ball after the collision is analyzed. Numerical calculation shows that after the collision, the maximum adhesion force is greater than the maximum rebound force. The impact ball can adhere to the surface of the spacecraft after the collision.

The kinematic parameter error of serial robots is the main factor affecting their positioning accuracy, while kinematic parameter calibration is one of the effective methods to improve their positioning accuracy. This paper explores the calibration method for the positioning accuracy of end-effector of serial robots, to provide a calibration method including joint screw and joint variables. First, an actual kinematic model in exponential form is established in comprehensive considerations of kinematic parameter errors. Second, by differentiating the kinematic model, the paper proposes the linearized model between pose error, joint screw error, and joint variable error of end-effector of serial robot. Finally, the calibration simulation test is carried out using an industrial robot. The experimental results show that this method can effectively improve the positioning accuracy of the end effector of the serial robot.

In order to study the rigid-flexible coupling problem of piston-pump tube during the pressurization stage of the secondary light gas gun, based on the Adams rigid-flexible contact theory and considering the elasticity of the pump tube, a piston-pump tube dynamic model and a piston-pump tube are established. contact collision model, and the dynamic simulation of the coupling process between the piston and the pump tube is carried out on the software platform, and the piston velocity curve and the vibration characteristics of the pump tube are obtained. The results show that the speed of the piston is significantly reduced by the contact force during the movement, and the high-speed piston will cause the pump tube to vibrate, and the longitudinal vibration is more obvious. The research results provide a theoretical reference for the research of piston speed and the optimal design of vibration reduction of pump tube.

We perform two-dimensional simulations of unsteady flow separation around a NACA0015 airfoil. The effects of Reynolds number and the angle of attack of the airfoil were studied. With the increase in the angles of attack and the Reynolds number, it reveals a route of the transition in the wake of NACA0015 foil from steady to chaotic flow. We find that the flow transits from steady flow to a chaotic state by a sequence of successive period-doubling bifurcations. Our results provide physical insight into the wake transition of an airfoil from steady to chaotic flow.

To study the kinematic characteristics of revolving chain shell magazine with time-varying inertia parameters, the rigid body dynamics model of the shell magazine system is deduced by considering the change of the equivalent moment of inertia of the shell cartridge at different positions of the chain. Under the changeable condition of the motion law of the driving sprocket, the time-varying characteristics of the equivalent moment of inertia and the output torque that the driving motor needs to satisfy are analysed. Results show that, compared with constant velocity and constant deceleration, the amplitude of change pace of the equivalent moment of inertia of the shell magazine is small under the trapezoidal motion law. The research results can provide theoretical guidance for the structural design and driving control rules of the rotational shell magazine.

As an efficient heat transfer tool, heat pipes have been widely used in many aspects. As a branch of heat pipes, separate heat pipes have also played a good role in many industries. This paper summarizes the application of split heat pipes in passive containment cooling systems at home and abroad and the related research status, and looks forward to the future development prospects and hopes of this direction. At the same time, a new structure of split heat pipes is proposed.

One of the most active areas of research today is 3D printing technology. Since the 1980s, the development of 3D printing technology has aroused interest worldwide and has begun to influence people’s thinking and way of life. Today, 3D printing technology has advanced and is used in many different fields such as aerospace, military and academia. Although the term “3D printing” is widely known, few are familiar with its basic principles. However, numerous studies have shown that mass production 3D printing is not yet feasible. There are not many ways to mass-produce 3D printed products. This article will summarize the current development status of 3D printing technology from the status of 3D printing technology, the classification of 3D printing technology, and the advantages and disadvantages of 3D printing technology, and look forward to its future development prospects. Through the research of this paper, it will provide a certain reference for the future development of 3D printing technology.

With the development of mining in the direction of improving quality, the management of mines has become more and more scientific, and it is particularly important to use high-tech monitoring and monitoring methods to carry out information-based high-quality safety management. The optimization, efficiency and safety of mine management work promote the long-term development of my country’s energy industry. This paper starts with the necessity of the safety monitoring and monitoring system of coal mines and metal and non-metal mines, and systematically analyzes the safety monitoring and monitoring systems of coal mines and metal and non-metal mines. Status, similarity, optimization and development direction.

The vibration of structures is a very common phenomenon, and obtaining vibration information of bridges can effectively analyze their health status. To identify local damage to the structure, using a camera to capture vibrations of the structure, this study uses the optical flow method to calculate the displacement, frequency, and mode shape of the structure from spatiotemporal sequence images. A local weighted modal strain energy change rate index can be calculated, and structural damage can be identified by comparing the energy change rate before and after damage. A cantilever beam was employed to test the way. The results show that the optical flow method correlates well with numerical simulation results, with a maximum error of 5% based on structure frequency. With a weighted modal strain energy change rate index, it is easier to determine the damage location; Comparing different damage degrees of the same unit yields the size of the damage degree.

There are several fresh, promising approaches for solving partial differential equations (PDEs) based on machine learning techniques. In this study, the physics-informed neural network (PINN) is applied to approximate the solution of the full potential equation to simulate airfoil computation. To deal with a PDE system, PINN is capable of working without partial differentiation of the equation and specifically deals with shocks, which mainly uses the physical equations and other constraints like boundary conditions. The PINN method is efficient in solving PDEs, especially in higher dimensions, while it seems impossible to tackle them using traditional numerical methods due to the complex mesh generations and formulations. For the PINN method, the solution of this PDE system is predicted by DNN. The network architecture contains four hidden layers, using the tanh() function as the activation function. It is capable to take a spatial–temporal point as input so that the mean-square error is obtained to calculate loss terms. Then an optimizer is used to specify the mapping between the input and output. To show how well PINN performs in solving the full potential equation for various free-stream Mach number values, three examples are used. The predicted results show that PINN can find solutions successfully. Furthermore, several methods are proposed to optimize our model.

In order to solve the problem of magnetization of bimetallic composite pipe, we establish a non-contact base pipe leakage detection model based on finite element simulation, determine the relationship between the magnetic field in the area where the tri-axis magnetic leakage sensor is located and the parameters of the magnetic excitation structure, quantitatively calculate the law of magnetization of the pipe wall under different excitation parameters, optimize the parameters of magnetic excitation structure, and obtain the range of excitation structure parameters required for the tri-axial magnetic leakage sensor to complete the non-contact base pipe detection. The magnetic excitation structure parameters required by the three-axis leakage sensor for non-contact base pipe detection can provide a basis for the design of the magnetic excitation device for bimetallic composite pipe detection.

According to the characteristics of the influencing factors of the large-scale complex equipment health assessment system, a health state evaluation pattern based on the modified multi-attribute decision ER algorithm is proposed. The model can not only combine the assessment problems of multiple damage factors, but also deal with the uncertainty generated by uncertain information, and give trust in unknown information, which is an effective tool for the health status assessment of large-scale complex equipment. The evaluation results show that the model can comprehensively consider the uncertainty information in the evaluation process, which is of great significance for making scientific and reasonable large-scale complex equipment maintenance decisions.

In this study, the influence of the modulus of elasticity of the jointed material and interlayers in the nodes with an interlayer with a low TCLE was investigated by computer simulation. In order to establish the general mode of SSS formation when loading cylindrical joints with soft stiffness layer and verify the adequacy of the simulation, the average elastic modulus of low TCLE layer was calculated. The results show that under thermal loading, in all variants, stresses are absent for the greater part of the node, a complex SSS is created only in small areas near the middle layer, near the joint edge (the outer surface of the cylinder), and in the middle layer. The stiffness coefficient is 0.8 on the outer surface of the interstory joint, decreasing to 0.62 near the joint in the nodes with a “soft” layer, and slightly increasing (to 0.82 ~ 0.91) in the nodes with “neutral” and “hard” interlayers. The interlayer material is in the volumetric stress state throughout its entire length. This provides reliability guidance for the theory of TLP diffusion welding under large gap.

Airfoils produce lift force for aircrafts, and it is one of the most crucial components of the aircraft. For the purpose of better performance of the aircraft in the sky, it becomes important to design a suitable airfoil for sustaining a stable process of aviation. The overall objective of this very paper is to optimize the design of airfoil, specifically by exploring the effect of changing aspect ratio and angle of attack on aircraft performance, in a simplified case with certain initial conditions and boundary conditions that will be specified later. In order to realize the overall objective of this paper, the feature of flow simulation of Solidworks will be utilized to create a geometrical model and also run various computational fluid dynamics simulations (CFD), in company with python programming for numerical calculations to process various data. The original model of airfoil is the national advisory committee for aeronautics (NACA) 24112. As a consequence of the research and exploration process, it is discovered that under the condition of aspect ratio of 2 and angle of attack of 5°, the performance of airfoil NACA 24112 could be optimized with a lift force to drag force ratio of approximately 5.955.

Through the viscous damping wall test, the displacement time history data of the free vibration test is first obtained by means of the Vic-2D non-contact acquisition equipment. Then, based on the original displacement time history, the damping force time history and velocity time history are calculated by energy method and central difference method respectively. In order to filter the high-frequency noise in the signal, Butterworth low-pass digital filter is used to filter the time history curve, and then a smooth velocity damping force relationship curve is obtained. Select the key control points on the relationship curve to obtain the skeleton curve of velocity damping force. Linear fitting is performed based on the pure damping model to obtain the mechanical model parameters of the damping wall. Finally, Rosenbrock integration method is used for numerical simulation, and the displacement time history curve and displacement damping force relationship curve obtained from the test results and numerical simulation results are compared to verify the reliability of the mechanical model parameter identification method.

In view of the present nursing bed turning over irrationally causes the human body local pressure to be excessively big, is difficult to prevent the bedsore situation, and so on. Based on the principle of ergonomics, establish the model of axial rollover and nursing bed, the complete parameters of the mechanism are determined by numerical simulation. The design has the safe reliable, the function diversification, and the automation degree high nursing bed.

The vehicle landing process is simulated by dropping the air-dropped vehicle, establishing the vehicle finite element model based on the drop test and verifying the accuracy of the model, and deriving the weak components in the vehicle drop process by transient response analysis of LS-DYNA. Based on the complete restart technology, we propose the simulation method of cumulative damage of vehicle fall and realize the simulation analysis of multiple vehicle falls and the cumulative analysis of vehicle stress state and plastic deformation. Finally, the Johnson–Cook failure damage model was combined to calculate the cumulative damage caused by the fall impact; the variation law of the damage was derived, and the structural damage was evaluated according to the failure model, which has certain guiding significance for the study of the cumulative damage of vehicle airdrop.

In order to analyze the detonation wave action process, the variation of detonation pressure and the evolution law of the detonation waveform, of the composite charge structure, established a theoretical analysis model of the composite charge structure with inner and outer layers explosives superimposed. Based on the detonation wave collision theory, the pressure distribution, size, and detonation waveform changes of the detonation wave on the plate under the single-point initiation of the center of the end face of the composite charge structure were carried out; the research obtained the calculation method of the pressure distribution area and the pressure magnitude of the composite charge structure and the waveform difference of the horn-shaped detonation.

Due to the accompanying severe consequences of explosions, the blast puts a great threat to public security. Nonlinear finite element analysis is a possible method for civil engineers to check the integrity of the structures under blast loading without underestimating the limit of the structures. However, different choices of element types would generally put a great influence on the analytical results and the corresponding computational expenses. Therefore, how should civil engineers simplify their physical model into finite element models to gain relatively accurate numerical results with acceptable computational expenses is of great interest. In this article, 6 different types of elements are discussed with different orders and shapes for a certain physical situation, and the corresponding experimental results and the numerical results for a very detailed finite element model are used as the baseline for judgement, which could be helpful for civil engineers to make proper simplifications in the set-up of finite element models.

In this study, the mitigation effects of water mist with different characteristics on quasi-static pressure were studied experimentally in a confined chamber. Experimental results demonstrated that the water mist considerably mitigated the quasi-static pressure and reflected waves when a blast occurred in a confined chamber. The water spray could absorb the energy released by the detonation of charge by means of evaporation and heat absorption. The primary determinants of the mitigation effects were the water's surface area and the diameter of droplets. The mitigation of the quasi-static pressure was made better by increasing the water's surface area and reducing the diameter of the droplets.

Aiming at the fatigue load design technology of motorized transportation, the compiling method of fatigue load spectrum and the present research situation of fatigue load design of motorized transportation were introduced in this article. The deficiencies of the key technology of fatigue load design of motorized transportation were clarified. A method of compiling the normalized fatigue load spectrum of motorized transportation is researched. Based on the normalization process, the equivalent load model, the synthesis method of multi-transportation conditions, and the bench fatigue test spectrum of key structural components are established, which can provide a reference for the structural fatigue design in motorized transportation.

This paper proposes a reliability design method for the typical mechanism of naval gun based on failure form, selects a typical mechanism to analyze its failure mode and failure form, and carries out research using finite element analysis, dynamics simulation, and reliability analysis to provide theoretical support and engineering methods for the development of mechanism reliability design.

A mechanism rapid solving method was proposed based on motion mechanism coding aiming at black-box problems of mechanism design from designers. The mechanism was expressed as directed network models and saved as matrices. A mechanism database was built based on network models. A prototype system that could search mechanism units and combine units to achieve some solutions according to input and output conditions was developed based on CAD software. The system could provide schematic diagrams of mechanism for designers to perform evaluation, selection, and improvement. A typical design task test indicated that this method could search out or combine effective mechanism design cases, reduce requirements of designer mechanical design abilities, and improve design efficiency.

Research on the identification method of mechanical model parameters of damping wall based on free vibration response was carried out. This paper uses a silicone oil silt mixture as the viscous damping material for damping wall free vibration test based on a single degree of freedom system, introduces the basic idea of mechanical model identification method, and derives the calculation formula of damping force based on the energy method in the analysis of test theory method. In order to filter the high-frequency noise in the velocity time history and damping force time history, Butterworth low-pass filter is designed to filter the data. Draw the relationship curve between speed and damping force, and select the key control points on the curve for fitting to obtain the damping parameters and. Numerical simulation analysis is conducted based on Rosenbrock numerical integration method. The final analysis of the theoretical method is consistent with the experimental results, which shows that the application of the model parameter identification method is good.

EDM orbital machining is often used for a large number of precision structure machining due to its good inter-electrode discharge state and high machining accuracy. Aiming at a rough-machined closed impeller blank with inter-blade channels, the electric discharge clean-up machining of the leading edge of the blade was studied. After analysis and univariate comparison experiments to determine the electrode orbiting mode and orbiting axis, the orbiting machining parameters were optimized based on the response surface method, and the orbiting machining parameter combinations with the smallest surface roughness and the smallest profile error were obtained. Finally, the leading edge of the blade was cleaned with comprehensive optimal process parameters, and the machining leading edge met the design requirements, which verified the feasibility of the optimized scheme. The research results of this paper will serve as a reference for the future development and engineering application of EDM orbital machining and have important value.

When measuring the noise level of the aircraft in flight, the vibration generated by the aircraft in flight will be directly transmitted to the noise sensor fixed on the aircraft body. The generated vibration noise results in inaccurate noise measurement. This paper used the control variable method to study the influence of vibration on noise measurement during flight noise measurement. A large number of laboratory measurements and analyses were performed, and it is found that the vibration acceleration of the noise sensor, vibration direction, and noise sensor type are the main factors affecting the magnitude of vibration noise. And the vibration noise correction curve of the common noise sensor is obtained. According to the vibration noise correction curve, the noise flight measurement data of a certain aircraft is corrected. Comparing the sound pressure levels before and after correction, shows that vibration noise has a great impact on the accuracy of aircraft noise measurement. The proposed method can effectively correct the measurement results and provide a reference for the noise measurement test in flight.

Fused Deposition Modeling (FDM) 3D printing is one of the most commonly used additive manufacturing techniques, especially for flexible sensors. At present, there are few researches on flexible sensors that use carbon-based conductive fillers to prepare composite materials and form sensing structures through FDM 3D printing. In this paper, ABS wire drawing extruder is used to mix carbon black to prepare conductive wire. Then, flexible piezoresistive strain sensors with various three-dimensional structures were fabricated by FDM dual-nozzle printing technology. Finally, the sensitivity experiment results are discussed in combination with the sensing principle. The results prove the feasibility of FDM technology to prepare flexible sensors with integrated sensing structure.

To study the influence of the pre-tightening force of the carbon fiber composite barrel of the electromagnetic railgun on the overall performance of the barrel, this paper has built a local finite element model of the fiber composite barrel and analyzed the stress and deformation of the rail after it is prestressed based on the ANSYS element birth and death technology and the multi-step continuous solution method. On this basis, this paper has studied the stress and deformation of each part of the barrel after the electromagnetic expansion force is applied to the barrel, and the relationship between the condition for the stable operation of a form of railgun barrel and the pre-tightening force has been obtained. The results show that the appropriate pre-tightening force of the barrel is necessary for the stable operation of the railgun. The conclusions of this paper can guide railgun design.

The internal debonding occurring in the inlet stealth coating in use will cause the coating to peel off, thereby seriously impacting the overall stealth performance of an aircraft. In order to address this problem, this paper has introduced the nondestructive testing technologies that apply to the detection of the internal debonding defect in stealth coating. Additionally, experiments with infrared thermal imaging and phased array ultrasonic testing technologies and equipment have been carried out in this paper, which will facilitate the real-time testing and maintenance of the stealth coating in service.

Taking a certain type of off-road vehicle as the research object, the corresponding high-fidelity multi-body dynamics whole vehicle model is constructed based on Adams/car, combined with the test approach of U.S. Army TOP01-1-014A, the vertical peak acceleration and vertical vibration dose value (VDV) obtained from simulation are plotted as a function of velocity, and the maneuverability performance limit of a certain type of tactical wheeled vehicle through each size of semi-circular obstacles is obtained through nonlinear interpolation, which provides test, simulation, and analysis experience for China's off-road vehicle maneuverability limit evaluation program.

The resistance characteristics of four positive multi-deformations at microscale were studied numerically with an inlet velocity of 1 m/s. The study involved four sizes of 0.04 mm, 0.06 mm, 0.08 mm, and 0.1 mm pipe inner tangent circle diameters to study the effect of circular pipe expansion boundary in this particular way. The common resistance characteristics among different pipes with the change of pipe diameter and inlet velocity are investigated. For the shape effect of different micro-pipes, the differences in the resistance stability characteristics with diameter and the inlet velocity change are analyzed in a new way, while the resistance distribution at the outlet is also analyzed. The results show the stability of the outlet velocity with pipe diameter changing is related to the shapes of pipes. Besides that, with a unique way to analyze the data, it is found that the positive-even polygon has a special distribution different from that of the integer-odd polygon, and a detailed way to describe the effects of different locations on resistance in pipes.

Airplane wing will experience vibration from various sources due to airflow during flight and mechanical equipment. Vibration is the major consideration to the safety of airplanes since it can lead to resonance, structure failures and system breakdown. Resonance will increase vibration deformation which can cause structure failure. One of the vibration sources is the abnormal vibration resulting from imbalance of fuel weight. Therefore, this project investigates the vibration deformation of a plane wing (Airfoil NACA 2415) under a harmonic load caused by fuel weight. Finite element methods like modal analysis and harmonic response analysis are used. From the results, the first six order natural frequencies of the wing are from 4.5168 Hz to 119.63 Hz, which are much smaller than the harmonic response frequency (around 150 Hz). So resonance will not happen. The maximum deformation of the fourth order of the plane wing is the largest (1.5329 mm) compared to other orders. The fuel weight during a flight is treated as a harmonic load, which is applied to the middle of the wing. The maximum harmonic response is 4.7929e−3 mm. H-convergence study are conducted to verify the numerical results are accurate. Theoretical results from Euler–Bernoulli Beam Theory are in comparison with the numerical results from modal analysis and errors between two results are very small (2.608%), indicating that the results from modal analysis are precise.

The waste water tank is one of the indispensable main equipment in the wet flue gas desulfurization process. Waste water tank is widely used in FGD industry, so the selection of waste water tank agitator is very important. Both companies and research institutes have done a lot of experiments and practices on the mixing of waste water tank, and it is acknowledged that some progress and results have been achieved. In the current FGD industry, the selection of mixers relies heavily on tests and practical engineering experience, which leads to a variety of types of mixers for waste water tanks in the market. Based on many years of engineering experience, this paper selects and optimizes each component and internal component of waste water tank mixer, including stirring blade shape, blade diameter, rotational speed, stirring shaft size, etc. Using the existing performance analysis and comparison, determine the common specifications and models of waste water tank applicable mixer.

Deep groove ball bearings are widely applied and usually work in the Elasto-hydrodynamic lubrication (EHL) state. Grease lubrication is widely used and the analysis of grease lubrication is more complex than oil lubrication. In this paper, the EHL properties of deep groove ball bearings are studied by using an exponential rate rheological model, and a complete numerical solution is obtained. The results show that, for lubrication condition, the roller element and the outer ring are worse than that between the roller element and the inner circle. Regardless of the rheological index value, there is a relatively obvious second pressure peak in the pressure distribution, and the second pressure peak decreases as the rheological index increases.

The principal objective of this research is to analyze the axis trajectory evolution process of sliding bearing under nonlinear shock. Therefore, a transient mathematical model coupled with the average flow equation, G-T contact model, and rotor kinetics equation was established in this paper and was solved by a numerical algorithm. The computations were in comparison with the program results of reference to demonstrate the dependability of the model. This paper analyzed the variation of the mixed lubricated bearing behavior under a pair of shocks in opposite directions. The calculation result shows that when the bearing is subjected to a vertical sinusoidal shock, both the minimum lubricant film gap and the capacity load change sinusoidally. The axis trajectory is a closed curve. And the variation trend of each parameter is opposite and the change range is similar when the shock is in the opposite direction.

In order to accurately obtain the air–water interface characteristics of the high-speed ship, such as the spray height and the wake profile, a model test of the planned hull was carried out. A probe driven by a motor is used to measure the interface, when the probe pins are in contact with water, a short-circuit form is used as a trigger to stop the electric probe, and the coordinates of each point on the wake profile can be directly measured. The test results show that, at the same speed, the wake height increases gradually with the increase of the abscissa; the wake height at the same position increases gradually with the increase of the flow velocity. This method is suitable for the measurement of the water mist generated by the planned hull on the water surface, especially for the direct measurement of the wake of the high-speed ship.

This study compares the fatigue performance of several connections using theoretical and experimental methodologies to forecast the fatigue life of aviation connectors. To determine the matching yield strength and fatigue life of the four specimens, static tensile tests and fatigue tests were performed on four different types of porous single-shear lap joint specimens. Three example S–N models were produced in accordance with the fatigue life determined by the test. The effect that best fits the data is the three-parameter power function S–N model. When the fatigue life of the four different types of specimens is compared, it is clear that each type of specimen has excellent fatigue properties and can fatigue up to 3 × 107 times. In general, the high-lock bolt specimen has a longer fatigue life than the rivet specimen. The fatigue limit is reached by the high-lock bolt specimen, and the associated loading stress is higher than for the rivet specimen.