Meccanica最新文献

Surface integrity has a significant influence on the tooth contact fatigue performance of carburized gears. This paper proposed a total contact fatigue life prediction model considering the hardness gradients, residual stress, and surface roughness. The contact pressure distributions are determined using the elastohydrodynamic lubrication numerical model. The crack initiation life and location are forecasted by the modified Brown-Miller fatigue criterion, considering the surface integrity, loading conditions, and lubrication state. The tooth surface of the spur gear is divided into layers through the thin slicing technique, and the fatigue performance parameters for each layer are determined using the multilayer approach. The crack propagation path and lifespan are predicted by the extended finite element method based on linear elastic fracture mechanics. Contact fatigue life testing is employed to verify the effectiveness of the proposed method for predicting total fatigue life. The damaged areas measured by image analysis are used to monitor crack initiation and determine fatigue failure. Fracture surface analysis conducted with SEM identifies the path of crack propagation. The predicted total contact fatigue life, crack initiation location, and crack extension path agree well with the experimental findings.

Here, novel geometric conservation law representations are established in two-dimensional magnetohydrodynamics whereby a triad of admitted conducting motions is derived. Application is then made of a magnetohydrodynamic superposition principle to generate extended multi-parameter classes of associated conducting motions. In addition, under a correspondence between the magnetogasdynamic system and nonlinear elastostatics an associated invariance is established for a linked canonical neo-Hookean plane strain system.

The energy harvesting potential of flapping airfoils has garnered significant research interest, inspired by the natural movements of birds and marine creatures. In this study, a semi-passive flapping airfoil device with a prescribed pitching motion was examined using a transient numerical simulation method that employed an overlapping grid technique. The influence of pitching amplitude (({theta }_{m})) on the energy harvesting characteristics of the flapping airfoil device was analyzed using the momentum theorem and dynamic mode decomposition. The results suggested that the energy harvesting efficiency of the semi-passive flapping device varied with ({theta }_{m}), increasing gradually from ({theta }_{m}) = 10° until reaching a peak at ({theta }_{m}) = 80°, after which it started to decline. Lift-induced work was identified as the dominant factor contributing to the flapping energy harvesting. The wake structures of the flapping device with different ({theta }_{m}) values could be categorized into three types: the BVK (({theta }_{m}) < 30°), mS (({theta }_{m}) = 30°–50°), and 2S + mS (({theta }_{m}) > 50°) types. As ({theta }_{m}) increased, large-scale vortices merged with adjacent small-scale vortices of the same rotation direction while suppressing small-scale vortices with the opposite rotation direction, leading to a reduction in the number of small vortices and rapid dissipation along the flow direction. The momentum theorem was utilized to identify that the vortical force term C_y^(V) and the local fluid acceleration term C_y^(A) predominantly contribute to the energy harvesting efficiency. Under small pitching amplitudes, the dynamic mode decomposition revealed a stripe-like pattern in all the modes. As the wake transitioned to the mS type, Mode1 exhibited three rows of shedding vortices. When the wake transformed to the 2S + mS type, the vortex structures within Mode1 reorganized into two orderly rows of vortices, while higher order modes dissipated rapidly along the flow direction.

The impact of the axial length of the flexspline on the overall structural reliability of harmonic drives is commonly underestimated in research. To address this issue, this study introduces an improved equation for accurately calculating flexspline stress. In assessing the reliability of harmonic drives, the study takes into account the interplay of flexspline strength failure, flexspline contact failure, and flexspline tooth wear failure, using the Copula function and the Monte Carlo method. Through numerical simulations, the study investigates the influence of flexspline length, revealing a growing impact as the length decreases. Furthermore, considering both flexspline length and multiple failure modes leads to an increased likelihood of failure as calculated. The proposed model significantly enhances the precision of reliability assessments for harmonic drives, thereby allowing for more accurate predictions regarding their operational lifespan.

Multi-point loading is the main approach for the deviation control of large panel structures. Panel deformation subjected to multi-point loads is significantly affected by the interactive effects between the loads due to the nonlinear mechanical behavior, which is difficult to be computed by conventional theoretical methods. The solutions of locations and magnitudes of multi-point loads are thus obtained with massive simulations for deviation compensation. In this paper, the interactive effect between the loads is modeled by a semi-analytic method to provide a rapid deformation prediction. Deformation of the multi-point loaded panels is decomposed into basic deformation solutions of individually loaded panels. Numerical correlation between these individual loads and the panel deformation is firstly constructed by simulations. Then, the interaction effects between the individual loads are equivalent as additional interactive forces and expressed as variables in the basic solutions according to the numerical correlations. Consequently, the deformation of multi-point loaded panel is rapidly predicted by the superposition of basic solutions with the interactive forces which are solved by the Betti reciprocity theorem and the principle of minimum potential energy. The results of the proposed method show satisfactory agreement with the experiment and a high computational efficiency. The capability of the proposed method in predicting the large deformation of multi-point loaded panels is thus demonstrated.

An accurate mathematical model for the tooth surface of spiral bevel gears incorporating manufacturing errors has been developed. A gear pair meshing model with consideration of assembly error has been derived. The impact of comprehensive errors of manufacturing and assembling on the tooth surface contact patterns has been investigated. A low sensitivity design method for tooth surfaces considering comprehensive errors of manufacture and assemble has been proposed. The results show that with the error changing from negative to positive, the tooth surface contact pattern of the cutter mean radius, ratio of roll, and the pinion axial displacement error move from toe-top to heel-root sides. The tooth surface contact pattern of the radial distance, horizontal, work offset error move from heel-root to the toe-top sides. For the comprehensive errors, the five parameters of the cutter mean radius, radial distance, horizontal, ratio of roll, and pinion axial displacement error have the most significant impact on the tooth surface contact pattern, directly leading to severe edge contact. With surface modification, the movement of parameters under error conditions decreases substantially, and except for a little edge contact in the ratio of rolling error, no edge contact occurs in other parameter errors.

The magnetic track brake is a mechanical contact (with friction) based braking system that is typically actuated electromagnetically and used as an emergency brake in railway transport. Within this paper, the practically relevant task of predicting the effective local and global forces of the contacting bodies and the respective deformations during the quasi-static braking process is addressed. Therefore, a simplified, yet efficient and accurate numerical contact model is developed to treat the frictional sliding contact problem. In order to verify and validate the model a couple of numerical experiments are carried out. The proposed model and algorithm are first tested against an analytic benchmark problem of a parabolic indenter indenting an elastic half-space. The developed model is then compared against a reference Abaqus finite element simulation in application-oriented braking simulations that treat the contact problem between a single braking element (pole shoe) and the rail. The results demonstrate and highlight the applicability and efficiency of the proposed model but also show the current limitations and shortcomings that hint at possible future augmentations.

This paper introduces an engineering algorithm that utilizes PYTHON as an interface and integrates MATLAB and ABAQUS software. The algorithm enhances the Bi-directional Evolutionary Structure Optimization soft killing method, enabling it to perform topology optimization for multiple materials. Additionally, we incorporate adaptive dynamic evolution rates(ER) to accelerate the acquisition of stable topology optimization results. This method consists of a main function and four dependency functions. The main function includes element sensitivity calculation, sensitivity filtering, updating design variables, and optimization loop function. The other functions are responsible for creating new inp files for optimization calculation, extracting node information, and obtaining finite element analysis results. The algorithm’s effectiveness and efficiency were verified through numerical examples. Researchers can directly create models in ABAQUS, apply loads, and perform analysis without the effort to write custom code.

The inverse finite element method (iFEM) plays an important role in deformation monitoring of the laminated plate structure by using surface strain measurements, which is also called “shape sensing”. The standard iFEM needs to divide the plate structure into several inverse elements and deformation field of each inverse element is reconstructed based on the measured strain information of each inverse element. Further, the full-field displacements can be obtained by assembling the displacement matrix of the each inverse element. However, in practical engineering, due to the installation of electronic equipment, the surface strains of some inverse elements cannot be measured, which makes it impossible to establish the shape sensing model. To this problem, this paper proposes a novel shape sensing algorithm for laminated plate structure, where the strain sensors are not required to be installed in each inverse element. In this approach, the non-uniform rational B-spline basis functions are adopted for interpolating the kinematic variables, and the scaled boundary finite element method can transform the local into global displacement fields, where the laminated plate structure is discrete into the 2D in-plane dimension. A cantilever laminated plate is used as study cases. The numerical results demonstrate that the proposed method can accurately reconstruct the displacement field and the accuracy is with in 6%. Therefore, the established shape sensing model can be used as an efficient tool for deformation monitoring of the laminated plate structure in practical engineering.

This article introduces a round-wheel compound dynamic model to simulate the force process after the release of the compound bow. This model is developed in the static model established by M.Tiermas, a more refined model was obtained through the kinetic energy theorem, which considers the influence of the mass distribution of bow limb and bowstring on the dynamic process, rather than simplifying the parameters of bow limb and bowstring to concentrated mass. This article analyzes the changes in force and energy of each component of the compound bow over time and drawing distance after the release of the bowstring. The analysis reveals that the string is the primary factor affecting the efficiency of the compound bow and is also the most vulnerable component, as the peak force it experiences during rebound is much greater than the force when in a static state. This model provides a theoretical basis for the design of the round-wheel compound bow structure.