Gear Stress Research Articles

Characterization of Boeing 777 Nose Landing Gear to Better Withstand Rough Landing

An important role a landing gear plays is that it aids in the landing and takeoff of aircraft. The landing gear must be designed in such a way that it can take these stresses in static and dynamic situations. This is to accommodate both rough and smooth landings that result from various loads acting upon it, such as drag force, vertical load, and side load. In the aviation industry, landing gear stress is a key concern, and different research in this field has previously yielded excellent results. However, the time has come to raise the bar even higher. This report will focus on the optimization of the Boeing 777's nose landing gear to better withstand rough landings. During the timeframe of this research, SOLIDWORKS was utilized to model and analyze various components of the landing gear. The results summarize that a single material should be avoided throughout the components of the landing gear. Components such as pistons with a larger stress allocation should be made of titanium alloy, while components with a lesser stress allocation should be made from aluminum alloy.Abstract. An important role a landing gear plays is that it aids in the landing and takeoff of aircraft. The landing gear must be designed in such a way that it can take these stresses in static and dynamic situations. This is to accommodate both rough and smooth landings that result from various loads acting upon it, such as drag force, vertical load, and side load. In the aviation industry, landing gear stress is a key concern, and different research in this field has previously yielded excellent results. However, the time has come to raise the bar even higher. This article will focus on the improvement of the Boeing 777's nose landing gear to better withstand rough landings. During the timeframe of this research, motion study in SOLIDWORKS 2020 (Stand-alone license) was utilized to model and analyze various components of the landing gear. The results summarize that a single material should be avoided throughout the components of the landing gear. Components such as pistons with a larger stress allocation should be made of titanium alloy, while components with a lesser stress allocation should be made from aluminum alloy.

Tooth root stress reduction of plastic gears with biological inspired shape optimization

The geometry of plastic gears used today is usually based on conventional steel gears, which are bound to the restrictions of the machining production of gears. The injection molding process provides more design freedom. This paper presents an approach to reduce the tooth root stress of plastic gears using a biologically inspired shape optimization method called CAO (Computer-Aided Optimization). CAO imitates the biological growth behavior from nature, such as bones or trees, which adapt to the load. It strengthens more heavily loaded areas of the surface and weakens less heavily loaded areas, resulting in an increase in load-bearing capacity. The simulation method is based on finite element analysis and considers the complex material behavior of short fiber reinforced plastics as well as the inhomogeneous fiber orientation. Object of the study are polymer gears made of polyamide 46 with and without short fiber reinforcement. By using the method presented here, it is possible to reduce the tooth root stress by up to 24% compared to a trochoidal tooth root with maximum rounding.

Investigating teeth root stresses of various spur gears using stress function and FEM

AbstractThe gear is the most efficient and reliable portion of the transmission system. In machine tools, gears are utilized to handle heavy loads. These gears are used indefinitely if the prerequisites are met. Gear tooth bending stress for numerous spur gears has been examined in this research. The influence of changing the pressure angles on the spur gear tooth root stress has been investigated. The purpose of this study is to look for a new way of finding the stresses generated in the roots of the gear teeth as well as the effect of changing pressure angles on these stresses. Solidworks 2021 uses parametric formulation to model gears, analyzed for deformation and maximum bending stress in ANSYS. The airy stress function is used to conduct the nominal root tooth stress. The enhancement percentages of modified cases are 5.92%, 1.70%, 10.70%, 17.22%, 10.86%, 24.32%, 20.91%, and 26.15% for the cases 2, 3, 4, 5, 6, 7, 8, and 9, respectively according to the stress function findings.

Advances in simulations of displacements and stresses in light-weight gears

Advances in simulations of displacements and stresses in light-weight gears

Analytical and Numerical Contact Stress Analysis of Spur Gears

The damage that occurs on the teeth flank of cylindrical gears is a complex phenomenon and depends on many factors. The most common cause for these damages is the high contact stress of the meshing gears. Although this contact pressure, by itself, cannot be a criterion for determining the durability of the gears, a good correlation has been found between the contact or Hertz pressure and the damage that occurs on the tooth flank. This paper analyzes the influence of the pressure angle α on the contact stress. Analytical calculation according to the ISO 6336-2:2006 and finite element method (FEM) was used for the analysis. Four cases were analyzed with a change in the pressure angle, i.e., cylindrical spur gears and pressure angles of 17.5°, 20°, 22.5° and 25°. In the results, it was noted that by increasing the pressure angle, the contact stress decreases. It can also be concluded that by increasing the pressure angle, the difference in the results between the analytical and FEM analysis, also increases.

COMPARISON OF STANDARD AND NONSTANDARD GEAR ROOT FILLET CONSIDERING ROOT STRESS AND MANUFACTURING POSSIBILITIES

In this paper, root stress, manufacturing possibilities and limitations of standard and nonstandard tooth root fillet of spur gears are examined. Nowadays, standard trochoidal root fillet is used the most as an economical trade-off between tooth strength and manufacturing complexity. A disadvantage of the trochoidal root fillet, especially in spur gears with less than 17 teeth, is undercutting which minimises strength of tooth root, introduces stress concentration, and deteriorates meshing conditions. This study focuses on different root designs, namely elliptical and novel cycloidal root fillets. Root stress in gears with different root designs is analysed by FEM and compared with analytical equations according to ISO. The possibility of producing nonstandard root fillet gears by hobbing and limitations of surface finishing are considered as well. Analysis reveals stress differences between each of the root fillet shapes and their relative advantages and disadvantages.

Mechanical property analysis and structure optimisation of worm gear reducer

ABSTRACT In the process of lightweight design, there will be problems such as stress concentration and structural weakening. In order to improve the design defect of serious insufficient life caused by the bending failure of worm gear, the bending stress of worm gear tooth root was analyzed by solution method and finite element simulation method. The main research contents include: firstly, the bending stress of worm gear is calculated by analytical solution method; Secondly, CAD is used to reconstruct the model; Finally, HyperMesh is used for analysis of the structure. The maximum bending stress obtained from theoretical calculation is 34.56Mpa, and the maximum stress from simulation is 39.3Mpa, 29.6Mpa and 26.3Mpa respectively in the three areas of gear root A, B and C (figure 7). Compared with the finite element, the maximum stress difference between them is 4.74Mpa. The stress concentration point is determined, and the structure optimization is carried out; CAE analysis of the optimized model shows that stresses in A, B and C regions of the worm gear root are 33.4 MPa, 22.5 MPa and 5.9 MPa, respectively. After optimization, the maximum stress difference between the two is 1.16Mpa.The above analysis results provide theoretical support for the design of worm gear reducer.

Whole Field Analysis of Asymmetric Helical Gear Using Photo Stress Method and FEA Method

Objectives: To carry out dynamic state analysis of asymmetrical helical gears for contact stresses using photo stress technique and suitable finite element software. Methods: Currently the Hertz contact stress equation is used to calculate the contact stress which is based on certain speculations. The value of load transmitted by a gear may be known but whether it is taken by a single or more pairs of teeth are based on some assumptions and stresses thus calculated may not be true stresses. To get precise evaluation of stress field in gear tooth it is decided to carry out experimental work on asymmetric helical gear in actual working condition. The photo stress method not only provide magnitude of stress but also gives idea about stress distribution in gear. Finite element method is used for asymmetrical helical gear to validate experimental results. Findings: The stress values obtained by photostress method and FEA method has minimum error of 2.17% and maximum of 8.89% respectively. The error values are less than 10% and within the limit. We can observe close agreement between these two methods. Novelty: This study has provided a more accurate result than theoretical method of stress calculation. Photostress analysis method is one of the best test methods for evaluation of contact stress of asymmetric helical gear with different torque condition in actual working that is dynamic condition. Maximum error of 8.89% has been found with photostress method. Keywords: Asymmetric Gears; Contact Stress; Experimental Method; Reflection Polariscope; PhotoStress; Finite Element Analysis

Numerical and experimental research of helical gear contact stress considering the influence of friction

Helical gears are widely used in various mechanical transmissions. Thus, analysing gear contact stresses is crucial to improve the fatigue limit and life of gears. In this paper, the contact stress of helical gear is analyzed by finite element simulation and experimental verification. The effect of coefficient of friction on the contact stress of helical gears is analysed, with given coefficients of friction. The following conclusions can be drawn through simulation and test. 1) The contact stress increases with the coefficient of friction in the early stage of meshing. 2) The contact stress decreases with the increase in the coefficient of friction in the late stage of meshing. 3) The gear contact fatigue test shows that the location of fatigue pitting on the tooth surface is consistent with that of the simulated maximum stress point. The friction-reducing coating on the gear surface can decrease the coefficient of friction between the tooth surfaces and thus effectively improve the gear contact fatigue life.

Optimization Design of Landing Gear Structure based on Fatigue Life Constraint

To decrease the weight of the landing gear and expand the application area of the optimization method with fatigue life constraint in complex mechanisms, the optimization models of the landing gear with fatigue life and stress as constraints are established, respectively. The comparison results show that the optimization results with fatigue life as a constraint are more reasonable, as stress and life requirements of the landing gear can be taken into account simultaneously. Finally, the static test was carried out to verify the accuracy of the optimization results. Test results indicate that the optimization method based on fatigue life constraint has good applicability and application value in practical engineering.

Composite Spur Gear Static Stress Analysis using First Order Shear Deformation

Due to its benefits and superior capabilities, composite laminate is one of the most widely utilized materials today. With the use of this cutting-edge technology, the world will be less dependent on the use of traditional materials, particularly metal. In the current work, the behaviour of laminated composite gear with different fibre reinforcing configurations is covered. For the current FE formulation, first-order shear deformation theory (FSDT) is used. The focus of fibre orientation on gear stress behaviour is highlighted in the current work. In the current FE formulation, which is a new development in the field of composite gears and deflection behaviour of the composite gear, focus is placed on the accurate computation of material properties with respect to fibre orientation in gears.

A Numerical Analysis of Hybrid Spur Gears with Asymmetric Teeth: Stress and Dynamic Behavior

Hybrid gears are composed of high-strength steel, carbon fiber reinforced plastic (CFRP), and adhesive bond to join these materials. In this study, the effect of rack tip radius (TR), drive side pressure angle (DSPA), and rim thickness (RT) on the stress of hybrid gears is investigated numerically. In addition, the stress results of hybrid gears are compared with steel gears that are used for validation of the numerical results. Single tooth stiffness (STS) values are calculated based on tooth deformations obtained from numerical analyses. The 2-DOF model is used to observe the influence of DSPA and RT on the dynamic factor (DF) and static transmission error (STE). According to the results, increasing RT has a positive effect on stress, STS, and STE, while DSPA is effective on the dynamic factor at most.

An investigation into the impact of grinding residual stress on the meshing stress of spiral bevel gear

An investigation into the impact of grinding residual stress on the meshing stress of spiral bevel gear

A Comprehensive Optimization Model of Tooth Surface Parameters for the Minimization of Contact Stress of Helical Face Gears by Considering the Avoidance of Edge Contact

Optimization with edge contact avoidance and contact stress minimization is essential for gear design. Due to the complex geometry of modified helical face gear drives, it is complicated to find the optimal design parameters with the consideration of issues including loading, assembly errors, and edge contact. As the finite element method is tedious and time-consuming, an optimization model with a simplified algorithm of the loaded tooth contact analysis with errors (ELTCA) for modified helical face gears is presented, and it can programmatically optimize the contact stress with edge contact avoidance. Firstly, a simplified ETCA algorithm is introduced, which reduces the five unknowns in the traditional contact equations to three. Secondly, the LTCA is analytically implemented according to the Hertz theory. Subsequently, an optimization model with the objective function of avoiding edge contact and reducing maximum contact stress is proposed. Furthermore, the proposed model is applied to reveal the effects of design parameters and assembly errors on the optimized contact path and stress. The results show that the optimization model is accurate and efficient; the design parameters and assembly errors have great effects on the meshing of modified helical face gears.

Numerical and Theoretical Analysis of a Spur Gear Using Composite and Conventional Materials

A spur gear is one of the most common forms of precision cylindrical gear. In the industry, reducing the weight of gears while keeping their useful properties has become an even more pressing challenge. As a result, the investigators have made many attempts to reduce the weight of the gears. Despite these efforts, the problem still requires more research. This study presented a spur gear's modeling and finite element analysis using different materials. A three-dimensional spur gear was designed, modeled, and simulated using ANSYS software. Five different materials, including two conventional materials (stainless steel and copper alloy) and three different composite materials, including 50% carbon fibers reinforced in epoxy resin, 1.5% filler containing acetal, i.e., Graphene Reinforced Acetal, and glass-filled polyamide. Composites were fabricated by varying the graphene quantity in Acetal nanocomposites. The spur gear stress was calculated theoretically using the Hertzian equation, and FEM was analyzed using ANSYS 14.0 under limited loading conditions and rotational speed. Although the obtained results showed that both methods were comparable, there was a significant difference between the two methods when 50% carbon fibers reinforced in epoxy resin matrix were used, which is Hertzian analysis was 250.13 MPa. In contrast, this result was reduced up to 152.13 MPa in FEM. The study concluded that among the different presented materials, 50% carbon fibers reinforced in epoxy resin matrix were the optimal material for spur gear fabrication due to their high strength and low density. Hence, the spur gear material can be replaced by 50% carbon fibers reinforced in the epoxy resin matrix.

Sensitivity Analysis Contact Reliability of VH-CATT Cylindrical Gear and Its Reliability with Material Strength Degradation

VH-CATT cylindrical gear is a new transmission mechanism. In order to study the influence of design parameters and material strength degradation of the VH-CATT cylindrical gear on its transmission reliability. The Kriging surrogate model based on improved quantum particle swarm optimization (QPSO) algorithm was used to establish the limit state equation of contact stress for the VH-CATT cylindrical gear based on the stress-strength interference theory. The state equation of contact stress of the VH-CATT cylindrical gear was obtained with higher precision. Also, the strength degradation model with gamma distribution was established by using the P-S-N curve to estimate the parameters of the strength degradation model with gamma distribution. The reliability sensitivity of the VH-CATT cylindrical gear was analyzed by improved first order second moment method (AFOSM) based on the limit state equation of contact stress of the VH-CATT cylindrical gear, the reliability of gear considering strength degradation was studied by using the improved first order second moment method (AFOSM). The analysis results show that the failure rate decreases with the increase of pressure Angle, tooth width, modulus and tooth radius. The failure rate increases with increasing torque. Strength degradation has a certain influence on the reliability of gear and opinion. And the reliability of the gear is lower than that of the opinion, Strength degradation has a greater influence on the failure probability of gear, at the same time, the reliability of the gear pair decreases with the strength degradation. After 15000 hours of operation, the reliability of the gear pair is only 0.63155.

Optimal Stress and Strain of Helical Gear and Rack in the Steering System

The steering system in the car assumes the task of navigating when the car is in motion. It not only plays a technical role but also performs a crucial role in vehicle safety. In this study, the model of a steering system with helical gear and incline rack was created by Solidworks. And the maximum principal stress, and maximum principal strain of helical gear and rack were determined by finite element analysis in ANSYS. The data of simulation were used to minimize the stress and the strain by the Taguchi method based on grey relational analysis. The results of finite element analysis indicated that input variables have significantly affected on stress and strain of gear and rack. And then the problems are verified by analysis of the signal to noise, analysis of variance, and regression analysis. All are in good agreement with the error of the predicted value and optimal value of GRG is 0.022%. The optimal results of the stress and strain of gear and rack achieved 0.1638 MPa and 0.0188 MPa, 7.676 x10-7 mm and 3.5687x10-7 mm, respectively.

Computational Analysis of Contact Stresses In Involute Spur Gears

The present paper investigates computational analysis of the contact stresses involved in an involute gear system using ANSYS simulation software. Gearing is one of the most critical components in mechanical power transmission systems. The computational simulation of contact stresses of two cylinders is carried out to validate the methodology with available analytical method, Hertz contact stress equation, which are originally derived for contact between two cylinders. The simulation of contact problems with ANSYS is carried out with the stiffness relationship between the two contact areas is usually established through a contact element, spring type is placed between the two contacting areas. The results of the two dimensional FEM analyses using ANSYS, a FEM solver software are presented. The results simulated are in agree with the theoretical values calculated using Hertz contact stress equation

Static and vibration analysis of functionally graded gears

In this study, static and vibration analyses of functionally graded gears (FGGs) have been performed using the FE-based numerical method. The gear body is divided into uniform thickness homogeneous sub-domains conforming to the gear tooth profile. Material properties vary in the radial direction according to power-law gradation with metal at the innermost and ceramic at the outermost surface. Three FG gear cases are studied, assuming the gradation for the entire body, radially outer half, and the outer quarter of the gear. Parameters like root stress, weight reduction, tooth stiffness, and natural frequencies of FG and bi-material gears are studied and presented with steel gear as a reference. For FGGs, root stress increases and the weight of the gear reduces with an increase in gradient index. It has been observed that the maximum difference in the fundamental frequencies of FGGs and steel gears is 12% compared to 25% for bi-metal gears.

Design and Optimization Analysis of Coreless Stator Axial-Flux Permanent Magnet In-Wheel Motor for Unmanned Ground Vehicle

In this article, a coreless stator axial-flux permanent magnet (CSAFPM) indirect drive (ID) in-wheel motor is proposed and researched taking into consideration the multiphysics constraints, including electromagnetic performance and mechanical strength for unmanned ground vehicles (UGVs). At first, two 12-slot-14-pole CSAFPM motors with different rotor structures are designed to meet the vehicle rim space and driving system demand. In addition, the rotor parameters are optimized to obtain higher torque density based on the response surface method (RSM) and finite element model (FEM). Meanwhile, the electromagnetic performance of optimized motors with different rotors is compared, including back electromotive force (EMF), output torque capability, and efficiency characteristics. The results indicate that the Halbach-array PM rotor has higher torque and efficiency than the spoke-type PM rotor. On that basis, the thermal stress and deformation of the stator support are analyzed and optimized, considering material property and temperature distribution. In addition, the stress of PM rotor, annular gear, and gear reducer are analyzed and optimized to achieve higher torque density. Finally, a 35-kW prototype is manufactured and tested to verify the performance of the design.