Increasing the Overlap Factor in the Elastic Model of a Modified Gear

2019 ◽  
pp. 33-42
Author(s):  
B.P. Timofeev ◽  
N.T. Dang
Keyword(s):  
Mathematical Models ◽  
Load Capacity ◽  
Elastic Model ◽  
Spur Gears ◽  
Cycle Fatigue ◽  
Contact Deformation ◽  
Allowable Stresses ◽  
Hertz Problem ◽  
Overlap Factor ◽  
Overlap Ratio

Coupled and approximate gears are considered in this article. Methods of localization of the contact patch and the elimination of edge impact are analyzed. Based on the solution of the Hertz problem, mathematical models of gearing in the MathCAD program are constructed, with the help of which the overlap ratio of the gearing is calculated taking into account contact deformations. Circular and parabolic modifications for cylindrical spur gears are proposed. The allowed values of the modification parameters are determined. Contact stresses are equal to the allowable stresses when calculating multi-cycle fatigue. The influence of contact deformation on the load capacity of non-conjugate gears is analyzed.

Numerical and experimental studies on the thermal and static characteristics of multi-leaf foil thrust bearing

2021 ◽  
pp. 135065012110110
Author(s):  
Yu Guo ◽  
Yu Hou ◽  
Qi Zhao ◽  
Xionghao Ren ◽  
Shuangtao Chen ◽  
...  
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Failure Process ◽  
Experimental Studies ◽  
Elastic Model ◽  
Static Characteristics ◽  
Bearing Load ◽  
Foil Thrust Bearing ◽  
Cooling Air

Foil bearing is considered to be a promising supporting technology in high-speed centrifugal machinery. Due to the high-speed shearing effect in the viscous lubricant film, heat generation could not be ignored. In this paper, a thermo-elastic model of the multi-leaf foil thrust bearing is proposed to predict its thermal and static characteristics. In the model, modified Reynolds equation, energy equation, and Kirchhoff equation are solved in a coupling way. The contact area between the foil and welding plate is taken into account. Besides, the effect of cooling air on the bearing temperature is investigated. The ultimate load capacity and transient overload failure process of the bearing is analyzed and discussed. The effect of rotation speed on the bearing temperature is more obvious than that of the bearing load. The bearing temperature drops obviously by introducing the cooling air, and the cooling effect is improved with the supply pressure. The transient overload failure of the bearing occurs when the bearing load exceeds the ultimate value.

Safety Factor in Fatigue Under Fluctuating Stresses

1987 ◽  
Vol 109 (4) ◽  
pp. 397-401 ◽  
Author(s):  
V. A. Avakov
Keyword(s):  
Safety Factor ◽  
High Cycle Fatigue ◽  
Stress Amplitude ◽  
Static Strength ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Safety Factors ◽  
Generalize Expression ◽  
Allowable Stresses ◽  
Number Of Cycles

It is common to assume identical allowable safety factors in static strength [m], defined by mean stress (Sm), and in fatigue [a], defined by stress amplitude (Sa), in order to find the full safety factor (F) under asymmetrical cycles, or to plot any type of the Sm–Sa diagram of allowable stresses. Here additional modification is considered to generalize expression of the full factor of safety in fatigue under asymmetrical stresses, utilizing unequal allowable safety factors in static strength (by mean stress) and in fatigue (by stress amplitude): ([a] ≠ [m]). We assume that loading is stationary, and cumulated number of cycles is large enough to consider high cycle fatigue.

scholarly journals Assessment of the load capacity of the anchorage system connecting the textured layer with the structural wall of large slab buildings in the lights of experimental research and FEM analysis

2018 ◽  
Vol 174 ◽  
pp. 03016
Author(s):  
Jerzy K. Szlendak ◽  
Agnieszka Jablonska-Krysiewicz ◽  
Dariusz Tomaszewicz
Keyword(s):  
Load Capacity ◽  
Single Layer ◽  
Fem Analysis ◽  
Experimental Tests ◽  
3D Models ◽  
Elastic Model ◽  
Structural Wall ◽  
Linear Elastic ◽  
Test Elements ◽  
Stainless Steel Screws

The goal of the article is to compare the results obtained from experimental tests of a new type of anchoring, connecting the texture layer with the structural layer in external wall elements, used in large-panel construction with the results from FEM analysis. Two types of samples were subjected to experimental tests: single-layer uniform concrete and three-layer concrete with embedded point anchors and analogous samples with glued anchors. The test elements used C 12/15 and C 30/37 concrete, 12 mm diameter anchors, made of steel corresponding to the grade of stainless steel screws class 5.8, Sika Anchorfix-1 resin and XPS polystyrene. As for the three-layer samples, when testing, two forces were applied: tearing and shearing due to the detachment of the textured layer. The ANSYS program was used for numerical modelling of the analyzed samples. 3D models were built in which solid elements were used. For steel anchors, the material characteristics were taken as a two-line elasticplastic reinforcement. The Drucker-Prager model was used in the concrete elements, the linear-elastic model was adopted for the resin, and the brittle model according to the linear-elastic fracture mechanics for the polystyrene.

Explicit Parametric Method for Optimal Spur Gear Tooth Profile Definition

2013 ◽  
Vol 633 ◽  
pp. 87-102 ◽  
Author(s):  
Ivana Atanasovska ◽  
Radivoje Mitrovic ◽  
Dejan Momcilovic
Keyword(s):  
Gear Tooth ◽  
Load Capacity ◽  
Parametric Method ◽  
Spur Gear ◽  
Tooth Profile ◽  
Spur Gears ◽  
Element Analysis ◽  
Engineering Research ◽  
Profile Optimization ◽  
Current Engineering

The gear tooth profile has an immense effect on the main operating parameters of gear pairs (load capacity, working life, efficiency, vibrations, etc). In current engineering research and practice, there is a strong need to develop methods for tooth profile optimization. In this paper a new method for selecting the optimal tooth profile parameters of spur gears is described. This method has been named the Explicit Parametric Method (EPM). The addendum modification coefficient, radius of root curvature, and pressure angle of the basic rack for cylindrical gears, have been identified as the main tooth profile parameters of spur gears. Therefore, the EPM selects the optimal values for these three tooth profile parameters. Special attention has been paid to develop a method of adjustment for the particular working conditions and explicit optimization requirements. The EPM for optimal tooth profile parameters of gears uses contact nonlinear Finite Element Analysis (FEA) for calculation of deformations and stresses of gear pairs, in addition to explicit comparative diagrams for optimal tooth profile parameter selection.

Bending Fatigue Tests of High Speed Spur Gears

1981 ◽  
Vol 103 (2) ◽  
pp. 466-473 ◽  
Author(s):  
I. Yuruzume ◽  
H. Mizutani
Keyword(s):  
High Speed ◽  
Normal Load ◽  
Load Capacity ◽  
Spur Gear ◽  
Fatigue Tests ◽  
Spur Gears ◽  
Bending Fatigue ◽  
Tooth Width ◽  
Bending Load ◽  
Bending Fatigue Strength

Effects of addendum modification of tooth profiles on the bending fatigue strength of high speed spur gear are discussed in this presentation: A JIS Class O Spur gear of m3, α20 deg, Z1 27, and made of AMS 6260 (AISI 9310) steel precisely ground after carburizing and hardening was meshed with the other gear of Z2 77 and operated at 8550 rpm. In this running test, bending load capacity and running performance comparisons between the gear with standard tooth profile and the two shifted gears of which tooth addendum modification coefficients were 0.35 and 0.8. The maximum normal load of the gear with addendum modification coefficient 0.8 at 107 (10 million) cycles was 1.8 kNsmm per unit tooth width. The maximum Hertz stress of this gear was 2.43 × 109 Nsm2. The allowable normal load of the gear with 0.8 was higher than that of the standard gear by 87 percent and higher than of the 0.35 profile shifted gears by 20 percent.

Twin-rotor hover performance examination using overlap tests

2017 ◽  
Vol 89 (1) ◽  
pp. 155-163
Author(s):  
Farid Shahmiri
Keyword(s):  
Mathematical Models ◽  
Cross Sections ◽  
Test Model ◽  
Test Plan ◽  
Optimal Test ◽  
Content Type ◽  
Hover Performance ◽  
Power Loading ◽  
Overlap Ratio ◽  
Twin Rotor

Purpose The aim of this paper was to experimentally examine twin-rotor hover performance for different rotor overlap ratios at practical rotor loading. Design/methodology/approach The methodology was formed based on data measurements for a designed twin-rotor test model and development of hover performance mathematical models. Thus, measurements were made using a central composite test plan, and then mathematical models for thrust power required power loading (PL) and figure of merit (FM) as functions of collective pitch tip speed; rotor overlap ratio was obtained. In the present paper, the test model consisted of two three-bladed rotors with a diameter of 220 mm and a blade aspect ratio of 16.05. The blades were of a rectangular planform with NACA 0012 cross sections and had no twist or taper. The model was built such that the rear rotor was fixed on the fuselage, and the front rotor could move longitudinally for tests up to about 40 per cent overlap ratio in hover. Findings The best hover aerodynamic efficiency (maximum PL of 14.6 kg/kW) was achieved for non-overlapped rotors at a low value of disc loading (DL) and also at FM of 0.6 at that DL. This result was in agreement with blade element momentum theory predictions. Practical implications Results for the twin-rotor test model can be generalized for actual tandem helicopters through the Reynolds number transformation technique and also some modifications. Originality/value Design and construction of the twin-rotor test model and experimental measurements of hover performance based on an optimal test plan were performed for the first time.

Pitting Load Capacity of Helical Gears

2007 ◽  
Author(s):  
Bernd-Robert Ho¨hn ◽  
Peter Oster ◽  
Gregor Steinberger
Keyword(s):  
Calculation Method ◽  
Load Distribution ◽  
Load Capacity ◽  
Test Results ◽  
Calculation Methods ◽  
Helical Gears ◽  
Capacity Calculation ◽  
Overlap Ratio ◽  
Tooth Flank

In experimental analyzes the pitting load capacity of case carburized spur and helical gears is determined in back-to-back test rigs. The research program with one type of spur and 8 types of helical gears includes tests for the determination of influences of varying load distribution, overlap ratio and transmission ratio. The test results are presented and evaluated on the basis of the pitting load capacity calculation methods of ISO 6336-2/DIN 3990, part 2. A new DIN/ISO compatible calculation method for pitting load capacity is presented. This new calculation method comprehends helical gears more adequate than ISO 6336-2 / DIN 3990, part 2 and has the possibility to consider tooth flank modifications. The new calculation method is applied on test results and gears of a calculation study. It shows better accordance with the experimental test results than the present ISO 6336-2 / DIN 3990, part 2.

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