Tooth Root Bending Strength Research Articles

Investigations on the tooth root bending strength and the fatigue fracture characteristics of case-carburized and shot-peened gears of different sizes

This paper contains data of the research project FVA 293 III by Schurer et al. and investigates the tooth root bending strength and the fatigue fracture characteristics of case-carburized and shot-peened gears of different sizes. The investigated carburized and shot-peened gears are made out of high-purity steel batches of the materials 20MnCr5 and 18CrNiMo7-6. Three different gear sizes with the normal modules mn = 1.5, 5, and 10 mm are examined in pulsator test rigs. Additionally, gear running tests in the FZG back-to-back gear test rigs for the gear size mn = 1.5 are performed.

Alternative microstructures and their influence on mechanical properties of case-hardened gears

Case hardening is one of the most common heat treatment processes for highly loaded shafts and gears. Due to numerous investigations, a microstructure consisting of martensite with retained austenite (less than 30%) represents a high sustainable microstructure. Besides this, there are some alternative microstructures compared to the commonly specified martensitic layer. The central question is how they influence the load carrying capacity of gears. A former research project was focused on the mechanical properties of carbonitrided parts by varying the amount of retained austenite. The investigations revealed that a microstructure containing a significantly increased amount of retained austenite can increase the flank load carrying capacity in comparison to standard case carburized gears. The tooth root bending strength was not influenced in a negative way. A microstructure containing an increased amount of retained austenite can also be reached by gas carburizing. Furthermore, a variant containing bainite in the case hardened layer was adjusted. In an actual research project, the influence on the load carrying capacity of gears made out of the material 20MnCr5 was investigated in experimental test-runs, using spur gears. The results of the variants with alternative microstructure show some differences, e. g. in the hardness profiles, compared to results of standard case hardened gears. In comparison to the case hardened reference, the flank load capacity of the gears with the alternative microstructures showed increased flank load capacity numbers, whereas the tooth root bending fatigue was not influenced in a negative way.

Influence of surface layer properties on tooth root bending strength of cylindrical gears

The trend of resource-efficient machine elements confronts design engineers with new challenges. Reduced component weight and ever increasing power densities require a gear design that enters the border area of material capacity. To embrace the potential offered by modern construction materials, calculation methods for component strength must rely on a deeper understanding of fracture and material mechanics in contrast to empirical-analytical approaches. The aim of lightweight designs in drive technology – particularly in relation to E‑mobility – can lead conventional design methods towards larger dimensioned and therefore heavier gears. Calculation methods that empower an accurate depiction of local load and material properties are able to safely push the boundary of gear design into areas that are closer to the ultimate fatigue limit of the material and help to conserve resources that way. For this reason, the aim of the report is to prove a general applicability of the higher-order calculation approach developed by Henser for all gear geometries and material properties. This method will make for more cost- and weight-effective gear design in the future. A two step approach shows the accuracy of the Inclusion-Based Weakest Link Model by validation on a small module helical gear and a parameter study proves the effectiveness of the Inclusion-Based Weakest Link Model by showing the influences of different sized gear geometries and material properties on calculated bending strength. In addition, the main influence parameters on the model and material properties that have different effects depending on gear size are identified.

Influence of profile shift on the spur gear pair optimization

Due to the established load capacity calculations and extensive literature, gearbox design process is rather simple. In order to gain a competitive edge, transmission designers and manufacturers are forced to constantly improve the design process and the product quality. The gearbox design process can be improved by using genetic algorithm to determine the optimal values of gear pair parameters. In this paper, besides the frequently used gear optimization variables, i.e. the module, the face width, and the number of teeth, profile shift coefficients of both gears are included to create a five-variable process. Since the profile shift influences the form, zone and stress factors, as well as the transversal and face load factors, it affects the optimization results significantly. The gear pair volume served as a fitness function, while the tooth root bending strength and the contact pressure calculations were used as constraints. Optimization results of the pair without profile shift and the arbitrary profile shifted pair were compared. The genetic algorithm solution is found for three data sets; the solution is verified using commercial gear optimization software.

歯車用高強度鋼材の接触・曲げ複合疲労試験

Many high strength steels for gear materials have been launched in these days. Conventional material tests; e.g., pulsator test for tooth root bending strength and twin-disc tests for rolling-sliding contact strength, might not accurately evaluate their strength in gear teeth. It is because a failure mode which frequently appears on gear teeth made of a high strength steel is not so simple as a breakage and pitting, but is a combination of these two modes. This failure mode could be simulated with contact-bending-fatigue (CBF) tests in which a test piece is subject to a bending stress similarly in the rotary-bending-fatigue tests and a contact pressure similarly in twin-disc tests. The present paper describes the concept of the CBF test and its possibilities for evaluating high strength gear materials.

Research on Meshing Theory of Involute Helical Gear with Asymmetric

This paper analyzes the relationship between cutter parameters and gear profile parameters on the basis of rack cutter with asymmetric, and proves the new type gear can be manufactured by traditional methods. The meshing theory of involute helical gear with asymmetric is researched. Equation about involute profile helicoids is derived. The 3D model of involute helical gear with asymmetric is built, and the model establishes the basis of FEA of tooth root bending strength and tooth surface contact strength.

Optimization Design of the Composite Hub Connection Structure Based on ANSYS Software Technology

This article through analysing coupler's structure, involute spline's stress situation, the tooth face contact intensity, the tooth root bending strength, the tooth root shearing strength, tooth face wear ability and the external spline reverse and curving bearing capacity carry on the precise computation and the examination, simultaneously a multianalysis bulge tight joint set of structure and the correlation computation examination, has established the shaft bossing compound coupler main spare part structure type. In this article based on the shaft bossing composite construction optimization design is targeted mainly flexibility swelling ring shape to optimize the design, change that flexibility swelling ring cone-cone angle, which makes flexible swelling ring Auxiliary T-twisting greater. In the analysis, it is necessary to use the software ANSYS, through the creation of the shaft bossing composite construction of the parametrization model, a flexible swelling ring cone-cone angle of the design variables and flexibility swelling ring allowable material stress as binding conditions, bulging with flexible support ring-twisting as the objective function of T,right propeller shaft coupler hub composite structure axisymmetric analysis, contact analysis and design optimization, inflation reached a flexible support ring largest T-twisting, work stress does not exceed the allowable material stress, elastic swelling ring-cone angle of the optimal solution.

916 浸炭焼入れ平歯車の歯元曲げ強度に及ぼすボス幅の影響(機素潤滑設計III)

916 浸炭焼入れ平歯車の歯元曲げ強度に及ぼすボス幅の影響(機素潤滑設計III)

Effects of machining errors, assembly errors and tooth modifications on loading capacity, load-sharing ratio and transmission error of a pair of spur gears

Abstract This paper quantitatively investigates effects of machining errors (ME), assembly errors (AE) and tooth modifications (TM) on loading capacity, load-sharing ratio (LSR) and transmission error (TE) of a pair of spur gears by using special-developed finite element method (FEM) software in a personal computer. Tooth surface contact stress (TSCS) and tooth root bending stress (TRBS) of a pair of spur gears with ME, AE and TM are analyzed by the FEM software. Effects of ME, AE and TM on TSCS and TRBS are also defined as “Influence factors” and the influence factors of ME, AE and TM on TSCS and TRBS are calculated quantitatively. It is found that misalignment error of gear shafts on the plane of action of the spur gears exerts great effects on TSCS and TRBS while misalignment error of gear shafts on the vertical plane of the plane of action almost exerts no effects on TSCS and TRBS. It is also found that ME and lead crowning have greater effects on TSCS and TRBS. When the maximum tooth surface machining error is 40 μm, influence factor of ME on TSCS and TRBS are about 2.2 and 1.5. When quantity of lead crowning is 40 μm, influence factor of lead crowning on TSCS and TRBS are about 2.0 and 1.4. These influence factors can be used as references when ISO standards are used for tooth surface contact strength and root bending strength calculations of a pair of spur gears with ME, AE and TM. Methods for LSR calculation of a pair of spur gears with ME, AE and TM are also presented in this paper. Effects of ME, AE and TM on LSR are analyzed quantitatively. It is found that ME has greater effect on LSR. When the maximum tooth surface machining error is greater than 10 μm, double pair tooth-contact shall become single pair tooth-contact for sake of the effect of ME. This means that when ME on tooth surface is large, outer limit of the single pair tooth-contact area can not be used as the so-called “worst load position”. It is safe and reasonable to use tooth tip as the “worst load position” when to perform tooth bending strength calculation. Methods for TE calculation of a pair of spur gears with ME, AE and TM are also presented in this paper. Effects of ME, AE and TM on TE of the gears are analyzed quantitatively. It is found that ME not only changes waveform of TE easily, but also makes TE greater and greater when ME is increased. AE and TM also make TE greater and greater when they are increased, but do not change waveform of TE.