Mesh Conditions Research Articles

Static Modelling and Analysis of a Novel Movable Tooth Drive with Logarithmic Spiral Tooth Profiles

This paper presents a static model for a novel movable tooth drive with logarithmic spiral tooth profiles, to research contact force and load distribution during the meshing period. According to the geometric properties of the conjugate tooth profiles, their compatibility law considering the multi-tooth elastic meshing effect are investigated to reveal load distribution characteristic of the teeth. The static model of the mechanism is thus developed to systematically analyze variation in contact force during the rise travel. The results indicate that the contact force between the tooth and ring gear is proportional to the curvature radius of the contact point, and it increases exponentially and monotonically corresponding to the curvature radius of logarithmic spiral tooth profile; in the multi-tooth meshing condition, the load distribution of the teeth coincides with the ratio of the curvature radius of each contact point, and periodical pulsations of total contact force occur at the alternation of the teeth. Finally, the proposed model is validated by the FEM simulation of a prototype, and the influence of dimensional parameters is further discussed for the self-locking and force transmission characteristics of the tooth. The outcomes provide critical technical support for the static modelling and design of such transmission mechanism.

Measured load spectra of the bearing in high-speed train gearbox under different gear meshing conditions

The load spectrum is a crucial factor for assessing the fatigue reliability of in-service rolling element bearings in transmission systems. For a bearing in a high-speed train gearbox, a measurement technique based on strain detection of bearing outer ring was used to instrument the bearing and determine the time histories of the distributed load in the bearing under different gear meshing conditions. Accordingly, the load spectrum of the total radial load carried by the bearing was compiled. The mean value and class interval of the obtained load spectrum were found to vary non-monotonously with the speed and torque of gear meshing, which was considered to be caused by the vibration of the shaft and the bearing cage. As the realistic service load input of bearing life assessment, the measured load spectrum under different gear meshing conditions can be used to predict gearbox bearing life realistically based on the damage-equivalent principle and actual operating conditions.

Nutraceutical Quality and Soluble Solids of Cucumis melo Developed in Vermicompost-River Sand Mixtures, Under Shade Mesh Conditions.

<b>Background and Objective:</b> There is ample evidence that the consumption of fruits and vegetables, with a high content of secondary metabolites, favours better human health. In the same sense, the application of organic fertilizers has favoured the content of phenolic compounds and a greater antioxidant capacity in various crops. Factoring that the application of Vermicompost (VC) increases the nutritional quality of plants. This research determined the content of soluble solids, biochemical components and the antioxidant capacity of the melon fruits (<i>Cucumis melo</i> L.) developed under shade net conditions with VC as a source of fertilization. <b>Materials and Methods:</b> During the 2020 spring-summer season, a hybrid melon Honeydew type was grown under five mixtures of VC: River sand (RS), with ratios 0:1, 1:1, 1:2, 1:3 and 1:4. Nutrient Steiner solution was applied only in the first mixture (control) while VC was used as an organic nutrient for all other mixtures. The five formulated mixtures, with five replications, were randomly distributed. The total phenolic content, total flavonoids, antioxidant capacity and the total soluble solids of the melon fruit were determined. Data obtained were statistically analyzed by analysis of variance and means were compared by Tukey 0.05 test. <b>Results:</b> The ANOVA indicates that no statistical differences were registered for any of the variables under study, however, the levels of the parameters were high. <b>Conclusion:</b> VC treatment of melon fruit is proven to be a promising source of nutrients to plants increasing their natural antioxidants and content of soluble solids.

Geometric contact characteristics and sensitivity analysis of variable hyperbolic circular-arc-tooth-trace cylindrical gear with error theory considered

Gear transmission characteristics are the most important research contents in gear transmission, and contact characteristics are important factors that affect gear transmission performance. The establishment of tooth surface contact analysis (TCA) model of a gear pair plays a guiding role in analyzing its contact characteristics. The rotary surface equation of the variable hyperbolic circular-arc-tooth-trace (VH-CATT) cylindrical gear cutter is obtained with the large cutter forming principle, and the mathematical model of the gear tooth surface is established based on the gear meshing conditions. With the influence of installation error on gear contact performance considered, a TCA model with installation error was established. The influence of different installation errors and different design parameters on the geometric contact characteristics and sensitivity of the gear pair is analyzed. The analysis results show that the central distance error may affect the contact ratio of the VH-CATT cylindrical gear pair and that the shaft parallelism error has a great influence on its transmission characteristics, greatly changing the size and position of the gear pair contact area. The design parameters also affect the size and location of the contact area to various degrees.

Research on the meshing characteristics of asymmetric gears considering the tooth profile deviation

This paper establishes a time-varying meshing stiffness (TVMS) analytical model for asymmetric gear pair based on the potential energy principle to analyze the TVMS, transmission error, and load share ratio of asymmetric gears. The model considers the adjacent teeth' influence on the body deformation of the gear teeth and is verified the reasonableness by finite element analysis. The effect of tooth tip relief on the characteristics of asymmetric gear pairs is analyzed in this paper. Considering the tooth profile deviation due to tip relief and tooth profile error of the asymmetric gear can obtain results that are closer to the original meshing condition. The results show that the gear contact ratio decreases with the increase of one side of the gear pressure angle. Conversely, the TVMS of spur gear will increase in a certain extent. During modification section of tooth profile, some significant variations will happen on the behaviors of asymmetric gears such as TVMS, transmission error and load share ratio. Slight tooth profile errors on the surface produce conspicuous fluctuations in gear meshing characteristics.

Modal Analysis, Fatigue Analysis and Optimization of Tractor Drop Arm Using FEM

Abstract: The Drop Arm is part of the steering component in a Tractor. It is connected to the sector shaft and moves in angular motion with the help of the sector shaft. This motion causes the wheels to move left or right, depending on which way the steering wheel is moved. It is important you have your drop arm in good working condition because poor steering can be hazardous to you and those around you. A performance study will be carried to perform Failure, Fatigue & Modal Analysis of pitman arm using Ansys. The structural optimization will be done on the drop arm by changing the structure of pitman arm by modifying the geometry where stress values are critical. The meshing and boundary conditions will be applied and analysis will be carried out using Ansys 16.0. Keywords: Finite element analysis, Fatigue analysis, Modal analysis, Drop arm, FEM.

An explicit weak Galerkin method for solving the first order hyperbolic systems

In this paper, we present and analyze a space–time weak Galerkin finite element (WG) method for solving the time-dependent symmetric hyperbolic systems. By introducing the discrete weakly differential operator, we construct a stable WG scheme which may be in the local or global form. The local scheme can be solved explicitly, element by element, under certain mesh condition. Then, we establish the stability and derive the optimal L2-error estimate of O(hk+12)-order for the WG solution when the k-order polynomials are used for k≥0. Numerical examples are provided to show the effectiveness of the proposed WG method.

Modeling of reverberation chambers for sound absorption measurements using a diffusion equation

The sound field in reverberation chambers used for measuring sound absorption coefficients is usually non-diffuse, leading to inaccuracies and disagreements in the results. In this paper, a diffusion equation model is applied to simulating reverberation chambers in order to obtain reverberant energy distributions and sound energy flows of the chamber under investigation in a more efficient way than wave-based simulation models. The computational efficiency of the diffusion equation lies in the fact that the meshing condition of the simulation domain is dictated by the room's mean-free path length (MFPL). Further investigation shows one-twelfth of MFPL as the meshing condition is considered practically sufficient for obtaining random incidence absorption coefficient of standardized sample sizes. With the computational efficiency given by a meshing of up to twelfth MFPL, an inversion calculation of random incident absorption coefficients of highly absorptive materials is possible with a mixed boundary condition [Jing and Xiang, JASA 123, pp. 145–153 (2008)]. Based on analysis of both chamber-based measurements and simulated data, ways to scrutinize measurement results of absorptive materials are investigated.

Finite element analysis of infra-acetabular screw fixation for the treatment of acetabular posterior column fracture.

Infra-acetabular screws have been described to increase the fixation strength of acetabular fractures with separation of the columns. Previous studies were based on the simulation of the anterior column fractures without modelling the biomechanical effect of the screw in the posterior column fractures. The purpose of this study was to compare the stability of different internal fixation models of posterior column fracture and to provide a theoretical basis for the clinical application of infra-acetabular screws. Five internal fixation models of acetabular posterior column fracture were simulated using five implants, including one reconstruction plate (PCP model), one posterior column screw (PCS model), one infra-acetabular screw (PIS model), one infra-acetabular screw and one reconstruction plate (PIS + PCP model), and one infra-acetabular screw and one posterior column screw (PIS + PCS model). After meshing, material parameter, and boundary condition settings, a vertical downward load of 500N was applied on the surface of the sacrum. To evaluate the biomechanical properties, the stress distribution and von Mises peak stress were recorded and analyzed, and the displacement distributions of the upper and lower fracture surfaces were compared. In model PCP, the maximum stress of the plate is 71.952MPa; in model PCS, the maximum stress of the screw is 52.740MPa; in model PIS, the maximum stress of the screw is 68.985MPa; in model PIS + PCP, the maximum stress of the plate is 64.695MPa and the maximum stress of the screw is 39.679MPa; and in model PIS + PCS, the maximum stress of the posterior column screw is 48.197MPa and the maximum stress of the infra-acetabular screw is 65.201MPa. The maximum stresses of implants are all located on the fracture surfaces. The average displacement differences of the upper and lower fracture surfaces are compared as follows: model PIS + PCS (0.03503mm) < model PIS + PCP (0.08205mm) < model PCP (0.10096mm) < model PCS (0.19007mm) < model PIS (0.23546mm). With sufficient biomechanical stability, infra-acetabular screws can be used as a supplementary fixation for the treatment of acetabular posterior column fractures. It is recommended to fix the fracture by the combined application of the infra-acetabular screw and posterior column screw.

“Fatigue Analysis Of Epoxy Composite Material Reinforcement On Propeller Shaft”

Propeller shaft, also known as propeller shaft is the most important component to any power transmission application; automotive propeller Shaft is one of this. A propeller shaft is a mechanical part that transmits the generated torque by a vehicle's engine into motive force which is usable to propel the vehicle. Substituting composite structures for metallic which is structures has many advantages because of higher specific stiffness and strength of composite materials. This work deals with the conventional replacement of steel propeller shafts with fiberglass epoxy composite propeller shaft for an automotive application. The parameters of design were optimized with the objective of minimizing the weight of a propeller shaft. The design optimization also improves the performance of propeller shaft. Present work deals with FEA analysis of composite shaft with different degree of orientation of glass fibers. It includes the modeling of shaft in CATIA. The meshing and boundary condition application will be carried using Hypermesh, Fatigue analysis of composite shaft will be carried out using ANSYS.

Difference finite element method for the 3D steady Stokes equations

In this paper, a difference finite element (DFE) method is presented for the 3D steady Stokes equations. This new method consists of transmitting the finite element solution (uh,ph) of the 3D steady Stokes equations in the direction of (x,y,z) into a series of the finite element solution (uhk,phk) of the 2D steady Stokes equations. Here the 2D steady Stokes equations are solved by the finite element space pair (P1b,P1b,P1)×P1, where the 2D finite element pair (P1b,P1b)×P1 satisfies the discrete inf-sup condition in a 2D domain ω. Here we design the weak formulation of the DFE method based on the 3D finite element pair ((P1b,P1b,P1)×P1)×(P1×P0) under the quasi-uniform mesh condition, prove that the 3D finite element pair satisfies the discrete inf-sup condition in a 3D domain Ω and provide the existence, uniqueness and stability of the DFE solution (uh,ph)=(∑k=0l3uhkϕk(z),∑k=1l3phkψk(z)) and deduce the first order convergence of the DFE solution (uh,ph) with respect to the exact solution (u,p) of the 3D steady Stokes equations. Finally, some numerical tests are presented to show the accuracy and efficiency for the proposed method.

Computational Techniques and their Usage to Optimize Car Design for Better Performance

This paper describes the use of different computational fluid dynamics (CFD) models and other techniques that can be used to get low coefficient of drag. The upper body of a car is designed using surface modeling in CATIA. It is analyzed using K-epsilon realizable model in ANSYS Fluent. Changes in design are made based on the high coefficient of drag at high speeds. Then, K-epsilon realizable model is used for analysis. To get better accuracy, a refined mesh for the wake region is used. Afterwards, k-omega standard model is used. At the end, the upper body of the passenger car and its tyres are examined to get the final results of the coefficient of drag. The same design with the same meshing conditions is also analyzed in Star CCM+ to verify the results.&#x0D; INDEX TERMS: ANSYS Fluent, computational fluid dynamics (CFD), coefficient of drag, Star CCM+

Weight Optimization of Drive Shaft Using Various Composite Materials in FEA

In sesctor of Automobile Engineering the power transmission through the shaft is very much important and in any power transmission, the drive shaft plays very important role. The torque generated through the engine of vehicle is converted in usable motive force and transmitted a drive shaft, is a mechanical part that transmits the torque generated by a vehicle's engine into usable motive force to propel the vehicle. By replacing the composite structure with conventional metallic structure one can achieve more advantages with respect to the strength and specific stiffness which is very high in composite material. In current study the fiber composite, fiber glass epoxy and hybrid material is used instead of conventional metallic drive shaft. The optimized design parameters is induced with the composite drive shaft which give the objective of reduction in weight of the drive shaft as well as it enhance the overall performance of the drive shaft. Present work deals with FEA analysis of composite shaft with different composite material. It includes the modeling of shaft in CATIA. The meshing and boundary condition application will be carried using Hypermesh; Structural analysis of composite shaft will be carried out using ANSYS. Composite shaft will be fabricated and tested to validate with numerical values.

P137 DEGRADATION RESISTANCE OF PVDF MESH IN VIVO IN COMPARISON TO PP MESH

Abstract Aim To researched the degradation resistance of PVDF mesh by comparing its morphological and chemical condition with PP mesh. Material and Methods PVDF and PP meshes analysed in this study were received from a previous animal experiment. To expose the surface of explanted meshes, a tissue removing method with protease was used and the result of this cleaning process was tested by X-ray Photoelectron Spectroscopy (XPS). The morphological condition of the mesh surface was compared using Scanning Electron Microscopy (SEM) and the chemical condition concerning degradation was analysed through Fourier Transform Infrared Spectroscopy (FTIR). The surface condition of PVDF mesh after 3-, 6-, 12- and 24-month implantation was illustrated and compared with two types of PP meshes. Results XPS revealed an absence of nitrogen, confirming the successful removal of tissue residues using protease. SEM results presented no notable morphological surface change of the PVDF mesh and progressive surface cracking processes over time of both types of PP meshes. FTIR spectra of the implanted PVDF meshes had no considerable difference from the spectrum of the pristine mesh, while FTIR spectra of both types of PP meshes had extra chemical functional groups increasing with implantation time, indicating progressive degradation. Conclusions PVDF mesh does not show signs of degradation up to 24 months after implantation while PP meshes progressively degrade with increasing time under the same conditions, which appears as worsening Environmental Stress Cracks. This study highlights the morphological and chemical stability of the PVDF mesh and demonstrates that the PVDF mesh is more resistant to degradation in comparison to the PP meshes.

An adaptive high-order unfitted finite element method for elliptic interface problems

We design an adaptive unfitted finite element method on the Cartesian mesh with hanging nodes. We derive an hp-reliable and efficient residual type a posteriori error estimate on K-meshes. A key ingredient is a novel hp-domain inverse estimate which allows us to prove the stability of the finite element method under practical interface resolving mesh conditions and also prove the lower bound of the hp a posteriori error estimate. Numerical examples are included.

Finite Element Analysis of Fracture Fixation.

Fracture fixation aims to provide stability and promote healing, but remains challenging in unstable and osteoporotic fractures with increased risk of construct failure and nonunion. The first part of this article reviews the clinical motivation behind finite element analysis of fracture fixation, its strengths and weaknesses, how models are developed and validated, and how outputs are typically interpreted. The second part reviews recent modeling studies of the femur and proximal humerus, areas with particular relevance to fragility fractures. There is some consensus in the literature around how certain modeling aspects are pragmatically formulated, including bone and implant geometries, meshing, material properties, interactions, and loads and boundary conditions. Studies most often focus on predicted implant stress, bone strain surrounding screws, or interfragmentary displacements. However, most models are not rigorously validated. With refined modeling methods, improved validation efforts, and large-scale systematic analyses, finite element analysis is poised to advance the understanding of fracture fixation failure, enable optimization of implant designs, and improve surgical guidance.

Degradation resistance of PVDF mesh in vivo in comparison to PP mesh

Mesh implant has been applied in hernia repair and urogynecological reconstruction. Polypropylene (PP) is now the most widely used material for non-resorbable mesh implants. A degradation phenomenon of PP mesh, which is apparent on the mesh surface as cracking, flaking and peeling, was discovered in the 1990's. This phenomenon of mesh implant has drawn attention because of mesh-related litigations. Polyvinylidene fluoride (PVDF), due to its high biocompatible performance, has been used since 2003 as an alternative material for non-resorbable mesh implants. Till now, no such degradation phenomenon of PVDF mesh has been reported, although limited study on PVDF mesh is available.In this paper, we researched the degradation of PVDF meshes taking the degradation of PP mesh as a reference. The meshes analysed in this study were received from a previous animal experiment. To expose the surface of explanted meshes, a tissue removing method with protease was used and the result of this cleaning process was tested by X-ray Photoelectron Spectroscopy (XPS). The morphological condition of the mesh surface was compared using Scanning Electron Microscopy (SEM) and the chemical condition concerning degradation was analysed through Fourier Transform Infrared Spectroscopy (FTIR). The surface condition of PVDF mesh after 3-, 6-, 12- and 24-month implantation was illustrated and compared with two types of PP meshes.XPS revealed an absence of nitrogen, confirming the successful removal of tissue residues using protease. SEM results presented no notable morphological surface change of the PVDF mesh and progressive surface cracking processes over time of both types of PP meshes. FTIR spectra of the implanted PVDF meshes had no considerable difference from the spectrum of the pristine mesh, while FTIR spectra of both types of PP meshes had extra chemical functional groups (carbonyl (CO) and hydroxyl (-OH) groups) increasing with implantation time, indicating progressive degradation. This study highlights the morphological and chemical stability of the PVDF mesh and demonstrates that the PVDF mesh is more resistant to degradation in comparison to the other two types of PP meshes.

Computational modeling to predict the micromechanical environment in tissue engineering scaffolds

Cell fate in tissue engineering (TE) strategies is paramount to regenerate healthy, functional organs. The mechanical loads experienced by cells play an important role in cell fate. However, in TE scaffolds with a cell-laden hydrogel matrix, it is prohibitively complex to prescribe and measure this cellular micromechanical environment (CME). Accordingly, this study aimed to develop a finite element (FE) model of a TE scaffold unit cell that can be subsequently implemented to predict the CME and cell fates under prescribed loading. The compressible hyperelastic mechanics of a fibrin hydrogel were characterized by fitting unconfined compression and confined compression experimental data. This material model was implemented in a unit cell FE model of a TE scaffold. The FE mesh and boundary conditions were evaluated with respect to the mechanical response of a region of interest (ROI). A compressible second-order reduced polynomial hyperelastic model gave the best fit to the experimental data (C10 = 1.72 × 10−4, C20 = 3.83 × 10−4, D1 = 3.41, D2 = 8.06 × 10−2). A mesh with seed sizes of 40 µm and 60 µm in the ROI and non-ROI regions, respectively, yielded a converged model in 54 min. The in-plane boundary conditions demonstrated minimal influence on ROI mechanics for a 2-by-2 unit cell. However, the out-of-plane boundary conditions did exhibit an appreciable influence on ROI mechanics for a two bilayer unit cell. Overall, the developed unit cell model facilitates the modeling of the mechanical state of a cell-laden hydrogel within a TE scaffold under prescribed loading. This model will be utilized to characterize the CME in future studies, and 3D micromechanical criteria may be applied to predict cell fate in these scaffolds.

Dynamic elastic analysis of flexible pavements under moving vehicles: a semi-analytical finite element treatment

Semi-analytical finite element method has great advantages in computational efficiency compared with three-dimensional, because it only requires a two-dimensional mesh in the cross-section by incorporating the Fourier series along the third dimension. This study utilised the method to analyse pavement responses induced by moving vehicles. Combined with the structural property of pavement, the method is improved in terms of meshing and boundary conditions based on existing research. Using the Fourier series to represent loading functions along the driving direction, the load motion can be expressed as the translation of trigonometric functions. Spring element is applied at bottom to simulate the soil support, and viscous element is applied at vertical boundary to control the interference of reflected wave. The whole algorithm was realised by MATLAB programming. This algorithm was first used to analyse a layered structure under a rectangular load. Its accuracy and efficiency were verified by comparing it with a three-dimensional finite element model in ABAQUS. Then this algorithm was utilised to simulate a test road under a moving truck. The material assembly used the parameters calibrated by several nondestructive tests. Analysis results were compared with the field monitor of sensors for verification. This study also has some reference value about applying semi-analytical finite element method in pavement engineering.

Computerized determination of the qualified region of main design parameters of face-milled hypoid gears with low shaft angle

The influence of main design parameters of hypoid gears with low shaft angle, namely, the offset, shaft angle, cutter radius, gear ratio, and the spiral angle of wheel, on the geometrical morphology the gear tooth surfaces has been investigated. Checks for obtaining appropriate top-land widths and spiral angles at the toe and heel sides have been developed and applied. The limits for the main design parameters that yield non-adequate tooth surfaces because- of top-land pointing, undercutting, or having a negative value of the spiral angle of wheel at the toe side have been investigated based on the results obtained by the simulation of a large number of cases of design. A specific computerized flow chart has been designed to iterate among the main design parameters to obtain a qualified region for them. With those results, a limiting graph has been proposed to get the list of recommended values of main design parameters and provide a reference for their selection. Finally, the results of loaded tooth contact analysis of two cases of design arbitrarily chosen from the proposed limiting graph of recommended values are shown to verify its applicability to yield to successful designs with favorable conditions of meshing and contact.