Recoil Force Research Articles

Numerical investigations of pedestrian overboard on a compound slope dike due to excessive overtopping waves

Wave overtopping under extreme weather conditions can pose a notable threat to the safety of pedestrians on coastal structures. In this paper, physical experiments and numerical simulations based on scale-down models were conducted in accordance with an actual person overboard accident, highlighting the flow characteristics and the fluid force exerted on the pedestrian by the overtopping and reflecting flow on the berm. The determinations of pedestrian instability under various conditions in the Qingdao incident are presented. The accuracy of the numerical wave flume was validated through a comparison with the experimental results. The findings disclose that under various wave height circumstances, the characteristics of overtopping flow are highly in line with the existing conclusions, yet the prediction for reflecting flows is not satisfactory due to the compound structures. The maximum reverse recoil force acting upon the pedestrian is far more prominent when compared to the impact effect of the head-on overtopping flow, which consequently leads to the pedestrians being washed away into the water. The safety of the pedestrian on the viewing berm under various incident wave conditions is analyzed and predicted by comparing with two approaches for the determination of the pedestrian instability, namely, water flow factors and mechanical analysis.

Interception force assisted optical pulling of a dipole nanoparticle in a single plane wave

The optical pulling force is generally believed to originate from the recoil force due to the simultaneous excitation of multipoles in the particle, which overcomes the interception force contributing to the optical pushing force. However, we show that the interception force can induce optical pulling force on a small isotropic spherical particle with gain in a uniform electromagnetic plane wave, in which multipole excitation is negligible within the dipole regime. Based on the multipole expansion theory, a rigorous analytical expression is derived for optical force acting on a spherical particle of arbitrary size and composition illuminated by a single plane wave, regardless of its polarization. The analytical results show that the interception force, which is typically positive in a conventional dielectric particle under illumination of a single plane wave, undergoes a crossover from positive to negative by introducing appropriate gain into the dipolar dielectric nanoparticle, thereby giving rise to the optical pulling. It’s deserved to be noted that the optical pulling force assisted by the interception force does not weaken in magnitude, in fact, it exhibits a stronger magnitude compared to the optical pushing force experienced by a corresponding conventional dielectric particle.

Morphology-independent general-purpose optical surface tractor beam

Optical tractor beams capable of pulling particles backward have garnered significant and increasing interest. Traditional optical tractor beams are limited to free space beams with small forward wavevectors, enabling them to pull selected particles. Here, we present a comprehensive theory for the optical force exerted by a surface wave using analytical and numerical calculations, revealing the relationship between the canonical momentum and optical forces. Based on this theory, we demonstrate a general purpose optical surface tractor beam that can pull any passive particle, regardless of size, composition, or geometry. The tractor beam utilizes a surface wave with negative canonical momentum characterized by a single well-defined negative Bloch k vector. The tractor beam relies on a mechanism where the negative incident force always surpasses the recoil force. As such, the tractor beam, when excited on the surface of a double-negative index metamaterial, can pull particles with different morphologies.

Blue Laser Conduction Spot Welding of Pure Copper Hairpins

Joining rectangular copper hairpins significantly improves the performance of hairpin motors. Copper welding poses a significant challenge due to its low laser absorptivity when using conventional infrared lasers. Although employing keyhole welding with a high-power and small-spot infrared laser can increase the absorption rate through multireflections, it introduces instabilities caused by the multi-recoil forces within the keyhole and the absorptivity differences among solid, liquid, and keyhole states of copper. The proposed solution adopts a 450 nm blue laser, which exhibits a superior laser absorptivity toward copper and facilitates stable conduction mode spot welding with an enlarged laser spot. This research achieved successful blue laser conduction spot welding of copper hairpins with a gap and, for the first time, systematically analyzed the force and instability factors of a molten pool. The results demonstrated that with a laser power of 1950 W, laser spot diameter of 0.6 mm, and defocusing amount of –3 mm, only 0.7 s of welding time was required to join copper hairpins with a 0.6 mm gap. Notably, there were no noticeable defects in weld beads during blue laser welding. Meanwhile, the study identified recoil force as a significant uncertain factor inducing defects, particularly in the keyhole mode. Compared to infrared technology, the blue laser, characterized by a higher absorption rate and a larger spot diameter, effectively reduced uncertainty through conduction welding. This research showcased the significant potential for blue lasers in manufacturing copper hairpin motors.

Heat treatment effects and variant selection in multi-material laser powder bed fusion of FeNi- and CoCr-based alloys

ABSTRACT This study demonstrates the successful fabrication of a multi-material 18Ni(300) maraging steel – CoCrMo alloy using laser powder bed fusion (L-PBF), which in its as-built state, displays suboptimal mechanical performance. Addressing this, we propose different heat treatments that mutually enhance the properties of both alloys. Comparative analysis of texture development, precipitation sequence and mechanical properties of the dual structures at different scales has been conducted. The results indicate the cooperative strengthening of intragranular γ–ϵ transformation in CoCrMo, and Ni3Ti precipitation in maraging steel. Adding the solution treatment also balanced the formation of acicular Ni3Ti clusters with (Fe, Ni, Co)2(Ti, Mo) precipitates, and revealed that chemical segregation influences austenite reversion. Initial evidence of local grain variant selection has been revealed in as-built samples due to thermal cycling and austenite reversion, which generates residual stresses, recoil forces and convective flow. Surprisingly, the missing variants can also be inherited after heat treatment with insufficient solution temperatures.

Mechanical Measurement Approach to Characterize Venting Behavior during Thermal Runaway of 18650 Format Lithium-Ion Batteries

The propagation of thermal runaway in a battery system is safety-critical in almost every application, such as electric vehicles or home storage. Abuse models can help to undestand propagation mechanisms and assist in designing safe battery systems, but need to be well-parametrized. Most of the heat during thermal runaway is released by venting that is why the characteristic of the vent flow plays an important part in the safety assessment. During venting, the cell generates a recoil force like a rocket, which depends on the flow speed and flow rate of the gas. This principle is used in this work to measure the velocity and mass flow rate of the vent gas. High-power and high-energy 18650 format lithium-ion batteries were overheated and the recoil and weight forces were measured to determine the venting parameter during thermal runaway. Our results show, that the linearized gas flow rate for the high-power and high-energy cell is 22.15gs−1 and 27.92gs−1, respectively. The progress of the gas velocity differs between the two cell types and in case of the high-energy cell, it follows a single peak asymmetrical pattern with a peak of 398.5ms−1, while the high-power cell shows a bumpy pattern with a maximum gas velocity of 260.9ms−1. The developed test bench and gained results can contribute insights in the venting behavior, characterize venting, support safety assessments, simulations and pack design studies.

Generation and Suppression of Pendant Droplet Oscillation in Electron Beam Directed Energy Deposition

Electron beam–directed energy deposition (EB–DED) has emerged as a promising wire-based metal additive manufacturing technique. However, the effects of EBs on pendant droplets at wire tips have not yet been determined. The aim of this study is to enhance the understanding of this action by analyzing the mechanism of droplet oscillation. The pendant droplet oscillation phenomenon hinders the stable transfer of droplets to the molten pool and limits the feasibility of manufacturing complex lattice structures by EB–DED. Hence, another aim of this study is to create an oscillation suppression method. An escalating asymmetric amplitude is the main characteristic of droplet oscillation. The primary oscillation-inducing force is the recoil force generated from the EB-acted local surface of the droplet. The physical mechanism of this force is the rapid increase and uneven distribution of the local surface temperature caused by the partial action of the EB. The prerequisites for droplet oscillation include vacuum conditions, high power densities, and bypass wire feeding processes. The proposed EB–dynamic surrounding melting (DSM) method can be applied to conveniently and effectively suppress oscillations, enable the accurate transfer of droplets to the molten pool, and achieve stable processes for preparing the strut elements of lattice structures. Lowering the temperature and improving the uniformity of its distribution are the mechanisms of oscillation suppression in EB–DSM. In this study, the physical basis for interpreting the mechanism by which EBs act on droplets and the technical basis for using EB–DED to prepare complex lattice structure parts are provided.

Surface recoil force on dielectric nanoparticle enhancement via graphene acoustic surface plasmon excitation: non-local effect consideration.

Controlling optomechanical interactions at sub-wavelength levels is of great importance in academic science and nanoparticle manipulation technologies. This Letter focuses on the improvement of the recoil force on nanoparticles placed close to a graphene-dielectric-metal structure. The momentum conservation involving the non-symmetric excitation of acoustic surface plasmons (ASPs), via near-field circularly polarized dipolar scattering, implies the occurrence of a huge momentum kick on the nanoparticle. Owing to the high wave vector values entailed in the near-field scattering process, it has been necessary to consider the non-locality of the graphene electrical conductivity to explore the influence of the scattering loss on this large wave vector region, which is neglected by the semiclassical model. Surprisingly, the contribution of ASPs to the recoil force is negligibly modified when the non-local effects are incorporated through the graphene conductivity. On the contrary, our results show that the contribution of the non-local scattering loss to this force becomes dominant when the particle is placed very close to the graphene sheet and that it is mostly independent of the dielectric thickness layer. Our work can be helpful for designing new and better performing large plasmon momentum optomechanical structures using scattering highly dependent on the polarization for moving dielectric nanoparticles.

Gyroscopic precession control for maneuvering two‐wheeled robot recoil stabilization

AbstractA two‐wheeled robot has high maneuverability and can spin around with a high velocity but is prone to roll over under a recoil force. Because the wheels are only used to control the maneuver speed of the robot. However, a two‐wheeled robot using a gyroscope does not need the control of the wheels and can maintain the stability of the robot under a recoil force during maneuvers even if the gimbal of the gyroscope is not controlled by a torque. In this study, the equations of motion of the gyroscopic robot are derived via Lagrangian equations, and the balancing performance of the uncontrolled gyroscope is simulated via Matlab to determine a desired configuration for mechatronics system design. Then, a linear‐quadratic regulator (LQR) is implemented to the chosen control moment gyroscope (CMG) configuration and compared in simulations of RecurDyn. LQR controller was used to prevent oscillating motions of double CMGs under the recoil force of a weapon. The simulation results showed that the gyroscopic two‐wheeled robot is improved using an LQR controller and powerfully balanced in static with excellent performance.

Firing Process Modeling of a Soft Recoil Gun Based on Interval Uncertainty Parameter Identification

PurposeThe soft recoil firing technology is an important way to reduce the recoil force of a gun. To further improve the effect of the recoil mechanism and provide a test prediction method for soft recoil firing, a new multi-port structure of the recoil mechanism with a central port and variable depth wall grooves is proposed to research the working characteristics of a soft recoil gun. MethodsTo describe the firing law of a soft recoil gun, this paper establishes its differential equations of firing motion, constructs the analytical model of each subsystem in the system, and acquires a relatively comprehensive way to describe the firing motion process for this soft recoil system. The flow distribution Bernoulli equation is established with CFD fluid simulation to improve the model accuracy. On this basis, the interval uncertainty theory and genetic algorithm are applied to establish the parameter identification model of the firing process. The typical parameters of the soft recoil gun are identified and obtained with the test data of the first round. ResultsThe similarity rate between the simulation and test data can reach up to 92.78%. Moreover, the corresponding simulation results match the test data under the second and third rounds. It is proved that the correct modeling and effective identification results provide theoretical guidance for the design of a soft recoil gun.

Моделирование процесса селективного лазерного плавления в аддитивном производстве

The possibilities of theoretical analysis based on numerical modeling of complex processes of additive manufacturing by selective laser melting method are viewed. Methods of high-precision modeling of the formation of a single melt bath are discussed, taking into account the geometry of the formed powder layer, the energy distribution in the spot, the effects of ray re-reflection, the vapor recoil force, the Marangoni effect and denudation mechanisms. Experimental studies on the cultivation of samples from BrX copper powder with particles of 20...50 microns in size by selective laser melting using continuous fiber laser radiation with a wavelength of 1.064 microns were carried out. In particular, all the experiments were carried out under conditions when growing conditions and modes are completely coincident with the calculated model. To assess the accuracy of the modeling system, the dimensions of the melting region and the morphology of the surface of the melt were compared. The presented computational model was used in the development of technology for growing products from copper alloy powders using selective laser melting method. Research in the field of modeling the stress-strain state in a composite material formed in the SLP process, consisting of an Ak9ch alloy matrix reinforced with titanium carbide particles, is also presented. Calculations were performed to identify the influence of shape (sphere, icosahedron, prism), size (1,0 microns; 5,0 microns; 10 microns) and mass concentration 
 (1,0 %; 3,0 %; 5,0 %; 7,0 %; 10 %; 15 %), taking into account the presence of pores of various shapes. The results of calculations are compared with the results of experiments. Numerical models with subsequent experimental approbation of the optimal variant make it possible to significantly reduce the time spent for the development of new complex and promising additive technologies.

Multi-physical field simulation to yield defect-free IN718 alloy fabricated by laser powder bed fusion

In this study, we used a model that combines thermal, mechanical, and fluid dynamics principles to analyze the melting and solidification process in laser powder bed fusion (LPBF). To ensure accurate simulation results, our computational fluid dynamics model takes into account various factors, such as heat transfer, radiation, molten metal flow, phase change, and the interaction between the laser and the material. We found that the combined effects of recoil pressure, Marangoni convection, and surface tension play a crucial role in the evolution of the melted IN 718 alloy. Excessive recoil force can cause powder spatters and keyholes, while inefficient Marangoni effect leads to non-uniform melting. Through our simulation-experimental investigation, we were able to achieve a high-density (99.96 %) IN 718 alloy at a scanning speed of 700 mm/s. This research demonstrates the ability of a multi-physical model to accurately predict the quality of melted materials and contribute to the development of new materials, not limited to nickel-based alloys in LPBF.

Research on Vibration Control of Paired Inclined Nozzles Dynamic Coupled Tubes

The barrel vibrates violently, which will lead to a serious drop in shooting accuracy. To solve this issue, a barrel vibration control method of the paired oblique nozzle dynamic couple is proposed. A pair of inclined nozzle devices are designed on the barrel to fully use the gunpowder gas energy in the chamber during the shooting process. A dynamic couple is generated to balance the turning moment of the barrel weapon. Simultaneously, the recoil force is reduced by exporting the gunpowder gas in the chamber. Therefore, the vibration of the barrel is reduced. Firstly, the internal ballistic two-phase flow model including the gas transient flow model in the vibration control device is modelled based on the internal ballistic theory of two-phase flow. Secondly, the numerical simulation of the weapon launching process is carried out. Thirdly, the rigid-flexible coupling firing dynamics modelling and simulation research is conducted on a 30mm chain gun equipped with a paired oblique nozzle dynamic couple vibration control device. At last, the effects of the device on the continuous firing vibration control of barrel weapons are analyzed. The results show that the vibration reduction efficiency of the inclined nozzle is better than that of the vertical nozzle and the horizontal nozzle. When the angle of the inclined nozzle is 30°, the barrel shows the highest vibration reduction efficiency. The vibration reduction efficiency of each vibration characteristic is 39.2%, 17.1%, 44.8%, and 48.9%, respectively.

ANALYSIS OF MODELS OF THE DYNAMICS AND STRESS-DEFORMED STATE OF THE ELEMENTS OF THE TRANSITIONAL SUPPORTING STRUCTURE OF THE TURRET SHEET OF LIGHT ARMORED VEHICLES

The work describes a parametric model of the dynamics and stress-strain state of the elements of the transitional supporting structure of the sub-turret sheet of light armored vehicles. The mass-inertial characteristics of the combat module, the thickness and overall dimensions of the underturret transition sheet, as well as the rate of fire and the caliber of the combat module’s weapons are used as varied parameters. The effect of the thickness of the transition unertower sheet on the natural frequencies and forms of vibrations was studied. The response of the structure to the action of impulse reactive recoil forces when firing from a combat module is also determined. Based on the calculations made for the test design, the regularities of the influence of varied parameters on the dynamics and stress-strain state of the elements of the transitional power structure of the underturret sheet of light armored vehicles were established. The developed model makes it possible to form a specialized database. This database accumulates information about the dynamic, stiffness and strength properties of the system «combat module - transitional structure of the underturret sheet of the armored hull of a lightly armored vehicle». This makes it possible to proceed to the analysis of the properties of real structures, as well as to the formation of recommendations regarding the substantiation of the rational parameters of the elements of lightly armored vehicles that are being designed or modernized. Keywords: lightly armored vehicle; combat module; undertower sheet; dynamics; stress-strain state; varied parameters

Timing control of impulse self balancing latch opening of expansion wave gun

Aiming at the problem of accurate latch opening control of expansion wave gun automatic gun, the mathematical model of accurate latch opening time is established, the travel curve of projectile and expansion wave, the velocity curve of projectile and expansion wave are studied, and the occurrence time of expansion wave and the time close to projectile are simulated and analyzed; The time-space evolution relationship between expansion wave velocity and local sound velocity, projectile velocity and gas velocity is simulated; The average pressure time curve and chamber resultant force curve of the two launch modes are compared and analyzed. After the projectile moves for 2.7ms, the chamber pressure and chamber resultant force of expansion wave launch are significantly reduced; The dynamic model of inertial latch opening is established; The changes of projectile initial velocity and recoil force under different latch opening times are studied. The test shows that the recoil force and recoil distance are greatly reduced when the projectile initial velocity decreases very weakly, which shows that the simulation calculation of latch opening time is accurate.

Launching Process Analysis of Aircraft Gun with Closed Type Gas Reflection Device

Recoil reduction is one of the most important issues for the design of aircraft gun. Traditional approaches for this purpose will produce back-blast, which constitutes a hazard to fighter planes or attack helicopters. This paper presents a closed type gas reflection device for the aircraft gun aiming to reduce the recoil force without ejecting the propellant gas rearward. The launching process is modeled by coupling the classical interior ballistic model and the flow equations for the closed type gas reflection device. The fourth order Runge-Kutta method is adopted to solve the modified interior ballistic model to obtain the recoil efficiency of the closed type gas reflection device. On this basis, effects of various parameters on the recoil efficiency and muzzle velocity are studied systematically. Finally, shooting experiments are carried out upon a 30mm caliber aircraft gun. The simulated results agree well with the experiment ones. The results show that, by using the closed type gas reflection device, the recoil efficiency of 26.01% is attained without ejecting the propellant gas rearward, nor decreasing the muzzle velocity dramatically.

Measurement and mitigation of recoil forces of rifles on an unmanned aerial vehicle

Measurement and mitigation of recoil forces of rifles on an unmanned aerial vehicle

Research on the Dynamic Characteristics of a Low Recoil Swing Chamber Gun Based on the Cased Telescoped Ammunition and Rarefaction Wave Gun Technology

Based on the theory of a low-recoil rarefaction wave(RAVEN)gun firing cased telescoped ammunition(CTA), the equation system of interior ballistics and kinematics also dynamics were established. The dynamic characteristic curves were obtained by numerical simulation analysis, and the results were verified by firing tests. Compared with traditional closed-breech guns, the low recoil force swing chamber gun keeps the projectile’s muzzle velocity basically unchanged, while the maximum recoil is reduced by up to 74%. Based on these results, the parameters of the inertial breech buffer spring were optimized by numerical simulation optimization algorithms which efficiency is faster than using virtual prototyping technology, while the maximum recoil force of the breech reduced by 14.2% without affecting system performance and structural installation size, which effectively improved the overall performance of the weapon system.

Research on Recoil Resistance Control Technology of Amphibious Vehicle Weapon

In order to improve the water shooting stability of amphibious vehicle weapon, the recoil motion differential equation of vehicle weapon is established by analyzing the force motion of amphibious vehicle during water shooting. the structure of valve-controlled recoil device and the optimal strategy of grey predictive fuzzy control are determined, and the recoil resistance characteristic curves with or without servo valve and different control voltages are analyzed numerically. And the water motion attitude of the amphibious vehicle under different recoil force. The simulation results show that the valve-controlled recoil device has a good recoil damping platform effect. By adjusting the liquid flow channel of the traditional anti-recoil device by using the servo valve, the recoil resistance of the vehicle weapon can be effectively controlled and the water firing stability of the amphibious vehicle weapon can be improved.

Simulation Research of rigid chain failure in a modular gunpowder delivery machine

Based on the theory of a low-recoil rarefaction wave (RAVEN) gun firing cased telescoped ammunition (CTA), the models of interior ballistics and dynamics were established. The dynamic characteristic curves were obtained by numerical simulation analysis, and the results were verified by firing tests. Compared with traditional closed-breech guns, the low recoil force swing chamber gun keeps the projectile’s muzzle velocity basically unchanged, while the maximum recoil is reduced by up to 74%. Based on these results, the parameters of the inertial breech buffer spring were optimized while the maximum recoil force of the breech reduced by 14.2% without affecting system performance and structural installation size, which effectively improved the overall performance of the weapon system.