Design and analysis of magnetic circuit of permanent magnet eddy current brake

The eddy current brake has the advantages of no frictional contact or hydraulic fluid, high structural reliability, etc. The existing linear eddy current brakes are mostly flat type. A cylindrical permanent magnet eddy current brake is proposed in this paper, whose air gap magnetic field is generated by a series of ring-shaped permanent magnets and guided by iron pole to conductor layers, and can achieve higher air gap magnetic flux density. This paper introduces its basic structure and working principle. In order to obtain the analytical model of magnetic circuit design, the equivalent magnetic circuit method is used to analyze and derive the magnetic circuit, and it is verified by the axisymmetric finite element model. To derive the braking force generated by the eddy current brake, the layer theory approach is applied. The influence of electromagnetic parameters on the force characteristic is obtained by finite element numerical calculation, which provides a theoretical basis for the optimal design of the eddy current brake

Parametric design and analysis of a mortar base plate

In order to improve the efficiency of designing and analyzing a mortar base plate, parametric technology has been applied to the design and analysis of the base plate. By conducting characteristic analysis of the base plate, critical design parameters extracted have been driven as characteristics to perform secondary development on UG, so that the base plate could be automatically modeled in three dimensions. Meanwhile, Python has also been applied in the secondary development of Abaqus, so as to realize the automatic finite element modeling of the base plate. After conducting parametric analysis on the model established, sensitivities of design variables of the base plate have been analyzed using an approximate model in combination with the sample designed by the optimal Latin hypercube approach. Moreover, parametric optimization carrying out on results of sensitivity analysis could give feedback to parametric design for guiding parameter values of design variables to improve the design qualit

Uncertain optimization of in-bore launching performance of artillery based on interval method

In order to study the uncertainty optimization of the in-bore launching performance of larger-caliber artillery, the interior ballistic program was compiled and embedded in ABAQUS finite element software for secondary development, and the dynamic model of in-bore launching was built. The structural parameters of bore, the structural parameters of projectile and parameters of launching propellant were considered, and the uncertainty was described by interval number. BP neural network was used to construct a surrogate model for the dynamic model of in-bore launching. The deterministic transformation of uncertain objective function and uncertain constraints was carried out by using interval order model and interval probability model respectively. The interval uncertainty optimization model of the in-bore launching performance artillery was established by taking the interval radius and midpoint of the projectile muzzle velocity as objective functions and the maximum chamber pressure as constraint. Multi-objective genetic algorithm was used to solve the problem, and the optimal solution and reasonable interval of uncertain parameters were obtained

The application of peridynamics in predicting beam vibration and impact damage

A novel numerical method based on nonlocal peridynamic theory is applied to study the structural vibration and impact damage. Unlike Classical Continuum Mechanics (CCM) where conservation equations are cast into partial differential equations, peridynamics (PD) describes material behavior in terms of integro-differential equations, which may cope with discontinuous displacement fields commonly occurring in fracture mechanics. The main motivation of this paper is to validate the ability of 2D bond-based peridynamics in solving the material deformation in structural mechanics. The numerical results indicate that the peridynamic solutions for beams vibration problems are almost identical to the results based on classical Euler-Bernoulli beam theory. It is also found that the feature of “softer” material near the boundary in peridynamics has a notable effect on the solution of beam vibration. And the problem could be effectively solved by introducing a correction coefficient called “surface correction factor”. For the failure process of three-point bending beam with an offset notch, the simulation naturally captures the crack initiation and growth which is consistent with common failure mode observed in previous experimental investigations

Transverse vibration analysis of an axially moving beam with lumped mass

The transverse vibration and stability of an axially moving simply supported beam with lumped mass is invested. A partial-differential equation governing the transverse vibration of the system is derived from Euler-Bernoulli beam model and Newton’s second law. Based on the Galerkin method, the governing equation is truncated to a set of second order time-varying ordinary differential equations. As the gyroscopic item in the motion equations, the complex mode theory is applied to calculate the natural frequencies of the beam with lumped mass. The effects of axially moving speed, position and weight of the lumped mass on the dynamics and instability of the beam are discussed. The results indicate that the natural frequencies decrease as the axially moving speed and weight of the lumped mass increasing. The first natural frequency decreases first, and then increases with the position of the lumped mass between the two supports while the second natural frequency varies more complicatedly. Therefore, the effect of the lumped mass leads to a lower critical speed of the axially moving system. This implies that the lumped mass tends to make the beam more unstable with reduced natural frequencies

An Analysis of Gear Based on Isogeometric Analysis

Although the CAGD has shown its ability to represent the geometry at a very high precision, the error is inevitable in FEA due to its imprecise mesh. This paper analyzes the stress state of a gear using NURBS-based IGA (Isogeometric Analysis). And the results show great superiority of IGA on efficiency and accuracy compared with traditional FEM (Finite Element Method). The contours of involute gear is non-rational curve and the general way to represent the geometry is the tracing point method. It is almost impossible to accurately descript the involute at the mathematical level either, however, NURBS can supply exact representation of the involute within acceptable error range. As a result, the NURBS-based IGA offers an effective and accurate calculation for gear analysis. Unlike the FEM, the IGA conducts mechanical analysis directly on NURBS geometry and it skips the step of meshing which will reduce a lot of workload

Research on vibration characteristics of a multi-barrel artillery

The vibration of the barrel, induced by the interaction with a high-speed moving projectile, has a considerable influence on the shooting accuracy of a weapon. The finite element model of a multi-barrel was established with the goal to investigate its vibration characteristics in this paper, and the natural frequency and mode shape were analyzed by finite element method. To verify the result of finite element modal analysis (FEMA), a modal testing system basis on SC310W multi-path data-collecting system and hammer hitting method was set up. Results show that the low order vibrations of the multi-barrel artillery were mainly vertical, horizontal and torsional vibration, but the local vibration at high orders. The error of natural frequencies between the results obtained by simulation and test was 8.82 % in the first mode frequency and 1.37 % in the eighth. The FEMA can effectively simulate the actual vibration of the multi-barrel artillery

Simulation of engraving process of large-caliber artillery using coupled Eulerian-Lagrangian method

Based on coupling algorithm of Lagrangian finite element method and Eulerian method (CEL), and rotating band as Eulerian section and other parts as Lagrangian section, the dynamic model of a projectile and rifled barrel coupled system is established. It can remedy the weakness of Lagrangian finite element method (FEM) for applications involving extreme deformation. Then, using CEL method and FEM, the numerical simulations are performed respectively. The curves of projectile motions, the dynamic engraving resistances are obtained, compared and analyzed. The results show that, CEL method can perform well under extreme deformation. What is more, the accuracy and the efficiency are improved remarkably. This provides better method for the future studies of the engraving process of large caliber gun and even for the studies of initial disturbance of projectile with engraving process being considered

Study on dynamic response of moving tank under the action of temperature field

A three-dimensional numerical model of the tank’s barrel was established using the finite element method, and dynamic process of thermal load boundary changing with projectile movement was defined. The evolution of the temperature distribution of the barrel under the firing conditions of the first projectile was obtained through numerical calculations. Furthermore, a multi-body dynamics software was used to build a shooting model for tank with a temperature field, the effects of the temperature field on the vibration of the barrel and the attitude of the projectile were studied and calculated, finally, the regular pattern of the stress of the barrel under the temperature field was analyzed. The simulation results of this model show that temperature field has a negligible effect on the barrel vibration and the projectile attitude

Modeling and dynamic simulation on engraving process of rotating band into rifled barrel using three different numerical methods

The FEM (finite element method), FEM-SPH (smoothed particle hydrodynamics method) adaptive coupling method and the coupled Eulerian-Lagrangian method (CEL) are introduced to simulate the engraving process. Eight-node hexahedral elements were mainly used to build the finite element models of the rotating band engraving into the gun barrel except in CEL simulation. In this case, the rotating band model and mesh are both built in ABAQUS in order to meet the requirements of CEL simulation. The simulation results include the deformation process of the rotating band, the motions of the projectile, the dynamic engraving resistance and the calculating efficiency were obtained, compared and analyzed. The advantages and disadvantages of numerical methods when simulating engraving process are discussed. The results show that the FEM-SPH adaptive coupling method and the CEL method have advantages for applications involving the simulation of the engraving process. The intent is to better understand the numerical methods and eventually broaden the utilizations in analyses of interior ballistics