Influence of hardening pattern, base material and residual stress condition on the tooth root bending strength of induction hardened gears

2016 ◽  
pp. 287-294 ◽  
Author(s):  
F. Dobler ◽  
T. Tobie ◽  
K. Stahl ◽  
D. Nadolski ◽  
M. Steinbacher ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Condition ◽  
Bending Strength ◽  
Base Material ◽  
Tooth Root

Effects of low-temperature treatments on surface hardness, retained austenite content, residual stress condition and the resulting tooth root bending strength of case-hardened 18CrNiMo7-6 gears

2019 ◽  
Vol 233 (21-22) ◽  
pp. 7350-7357
Author(s):  
D Kratzer ◽  
F Dobler ◽  
T Tobie ◽  
T Hoja ◽  
M Steinbacher ◽  
...  
Keyword(s):  
Residual Stress ◽  
Low Temperature ◽  
Retained Austenite ◽  
Stress Condition ◽  
Bending Strength ◽  
Surface Hardness ◽  
Tooth Root ◽  
Austenite Content ◽  
Temperature Levels ◽  
Low Temperature Treatments

This paper contains parts of the research project FVA 612 and investigates the correlation between low-temperature treatments of case-hardened gears made from the material 18CrNiMo7-6 and the resulting surface hardness, retained austenite content, and residual stress condition. These parameters were further investigated with regard to the tooth root bending strength obtained with pulsating test rigs. The tested gears were subjected to various low-temperature treatments including different temperature levels before or after tempering. Other investigated parameters were the application of a shot blasting treatment and the effect of low-temperature treatments on gears with increased retained austenite content after the carburizing process.

scholarly journals Influence of grinding zones on the tooth root bending strength of case carburized gears

2021 ◽  
Author(s):  
Karl Jakob Winkler ◽  
Thomas Tobie ◽  
Karsten Stahl
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Bending Strength ◽  
Decisive Role ◽  
Experimental Investigations ◽  
Tooth Root ◽  
Industrial Practice ◽  
Application Range ◽  
Residual Stress State ◽  
Root Area

AbstractKnowledge of the expected tooth root bending strength plays a decisive role in the design of gear sets. Due to dimensional and shape changes resulting from distortion due to the heat treatment, unintentional, partial grinding in the tooth root area may occur, particularly in the application range of large gears. The influences of an unintentional grinding zone on the tooth root bending strength have not yet been clarified with sufficient accuracy. As a result, grinding zones lead to uncertainties when evaluating the tooth root bending strength and thus to a loss of time and cost in the field of industrial practice.This paper presents experimental investigations on the influence of grinding zones on the tooth root bending strength of case carburized gears. For the experimental investigations, there are three unground reference variants with different blasting treatments: non-blasted, mechanical cleaned by shot blasting and shot peened. The unground reference variants are examined regarding their tooth root bending strength. For the other test gear variants, different grindings zones are applied resulting in light and strong material removal by grinding. The variants with the different grinding zones are examined analogously regarding their tooth root bending strength and are subsequently compared to the reference variants.The results of the experimental investigations show that grinding zones can have diverse influences on the tooth root bending strength of case carburized gears– Non-blasted gears do not show changes regarding the tooth root bending strength with regard to light or strong grinding zones applied within this investigation.– Shot blasted (mechanical cleaned) gears show no change in the tooth root bending strength for light grinding zones (grinding application does not significantly alter the original residual stress state in the tooth root area).– Shot blasted (mechanical cleaned) gears show a reduction of the tooth bending strength of up to 20 % with regard to strong grinding zones (grinding application does significantly alter the original residual stress state in the tooth root area).– Shot peened gears show a behavior similar to that of shot blasted gears with reductions of the tooth root bending strength of up to 30 %.– Shot peening the strong grinding zones as a repair measure can increase the reduced tooth root bending strength again. However, for the investigated test gears, the resulting tooth root bending strength was below the shot blasted reference variant.The results of this paper help to evaluate the influence of grinding zones on the tooth root bending strength of case carburized gears more precisely compared to the generalized reductions of current standards and classifications. The results can be incorporated in standards such as DIN 3390 as well as ISO 6336 and can be applied in the field of industrial practice. Eventually, the findings help to reduce the current loss of time and cost caused by uncertainties regarding grinding zones.

In-depth analysis of crack area characteristics of fisheye failures influenced by the multiaxial stress condition in the tooth root fillet of high-strength gears

2021 ◽  
pp. 095440622110616
Author(s):  
Daniel Fuchs ◽  
Sascha Rommel ◽  
Thomas Tobie ◽  
Karsten Stahl
Keyword(s):  
Residual Stresses ◽  
Stress Condition ◽  
Bending Strength ◽  
High Strength ◽  
Tooth Root ◽  
Multiaxial Stress ◽  
Depth Analysis ◽  
Standard Specimens ◽  
Compressive Residual Stresses ◽  
Model Approach

Modern high-strength gears have to satisfy many requirements, such as improved tooth root bending strength. The process of shot-peening is correlated to the introduction of compressive residual stresses in the surface layer of a gear to achieve a higher tooth root bending strength. However, due to the compressive residual stresses fisheye failures can occur and can have a determining effect on the endurance of high-strength gears. By preventing such failures, it should be possible to increase further the tooth root bending strength of high-strength gears. However, this requires a deeper understanding of the crack initiation and propagation processes. Especially the unique multiaxial stress condition in the tooth root fillet of a gear could influence the crack area characteristics significantly. Though, in the literature there is no proper characterization of crack area characteristics in the tooth root fillet of gears in detail, so far. Furthermore, in previous work a model approach for the evaluation of the tooth root bending strength of gears was presented, which is based on the results of Murakami. A first comparison with experimental data showed a basic applicability of the model approach on gears. However, the derived model approach showed some room for improvement. Questions arose as to whether the approach is really fully applicable to gears, whether further modifications are needed, or whether further extension is even practical, since the fisheye fracture characteristics of gears might differ significantly from those of standard specimens. The aim of this paper is therefore to present an extensive in-depth analysis of the crack area characteristics in the event of tooth root fracture damages caused by a fisheye failure in high-strength gears. Furthermore, a case study is used to verify whether a detailed evaluation of the characteristics of non-metallic inclusions leads to more accurate results of the model approach.

scholarly journals Shear cutting induced residual stresses in involute gears and resulting tooth root bending strength of a fineblanked gear

2021 ◽  
Author(s):  
Daniel Müller ◽  
Jens Stahl ◽  
Anian Nürnberger ◽  
Roland Golle ◽  
Thomas Tobie ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Residual Stresses ◽  
Carrying Capacity ◽  
Bending Strength ◽  
Tooth Root ◽  
Load Carrying Capacity ◽  
Near Surface ◽  
Load Carrying ◽  
Involute Gears ◽  
Cut Surface

AbstractThe manufacturing of case-hardened gears usually consists of several complex and expensive steps to ensure high load carrying capacity. The load carrying capacity for the main fatigue failure modes pitting and tooth root breakage can be increased significantly by increasing the near surface compressive residual stresses. In earlier publications, different shear cutting techniques, the near-net-shape-blanking processes (NNSBP’s), were investigated regarding a favorable residual stress state. The influence of the process parameters on the amount of clean cut, surface roughness, hardness and residual stresses was investigated. Furthermore, fatigue bending tests were carried out using C-shaped specimens. This paper reports about involute gears that are manufactured by fineblanking. This NNSBP was identified as suitable based on the previous research, because it led to a high amount of clean cut and favorable residual stresses. For the fineblanked gears of S355MC (1.0976), the die edge radii were varied and the effects on the cut surface geometry, hardness distribution, surface roughness and residual stresses are investigated. The accuracy of blanking the gear geometry is measured, and the tooth root bending strength is determined in a pulsating test rig according to standardized testing methods. It is shown that it is possible to manufacture gears by fineblanking with a high precision comparable to gear hobbing. Additionally, the cut surface properties lead to an increased tooth root bending strength.

Measurement of Residual Stresses in Linear Friction Welded In-Service Inconel 718 Superalloy

2016 ◽  
Vol 879 ◽  
pp. 1800-1806 ◽  
Author(s):  
M. Smith ◽  
L. Bichler ◽  
D. Sediako
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Base Material ◽  
Peak Stress ◽  
Weld Interface ◽  
Aerospace Alloys ◽  
Aero Engine ◽  
Linear Friction ◽  
Inconel 718 Superalloy ◽  
Residual Strains

Measurement of residual strains by neutron diffraction of linear friction welded Inconel® 718 (IN 718) superalloy acquired from a mid-service aero-engine disk was undertaken in this study. Residual strain and stress throughout the various weld regions including the heat affected zone (HAZ), thermomechanical affected zone (TMAZ) and dynamically recrystallized zone (DRX) were characterized. The residual stresses were observed to increase from the base material to the weld interface, with a peak stress at the weld interface in all orthogonal directions. The trends for residual stress across the weld are in agreement with other work published in literature for solid state welding of aerospace alloys, where high residual stresses were commonly reported at the weld interface.

Modelling of Dilution Effects on Microstructure and Residual Stress in a Multi-Pass Weldment

2018 ◽  
Author(s):  
Yongle Sun ◽  
C. J. Hamelin ◽  
M. C. Smith ◽  
A. N. Vasileiou ◽  
T. F. Flint ◽  
...  
Keyword(s):  
Residual Stress ◽  
Weld Metal ◽  
Phase Distribution ◽  
Measurement Data ◽  
Base Material ◽  
Cross Sectional ◽  
Gas Tungsten Arc ◽  
Compressive Stresses ◽  
Thermal Solution ◽  
Dilution Effects

Three-pass gas tungsten arc welding in a 20-mm thick SA508 steel plate is modelled using a sequentially coupled thermal-metallurgical-mechanical model. The dilution for each pass is estimated as the proportion of base material in the weld metal, based on an analysis of the cross-sectional area of each fusion zone. The thermal solution of the weld model is validated using thermocouple measurement data and cross-weld macrographs. The predicted microstructure is qualitatively compared with that observed in cross-weld optical micrographs. The measured hardness distribution is used to quantitatively validate the post-weld ferritic phase distribution (e.g. the ferrite, bainite and martensite fractions), based on a hardness-microstructure correlation. The predicted residual stresses are compared with those measured by neutron diffraction. The results show that dilution significantly influences the metallurgical and mechanical properties of weld metal (either as-deposited or reheated), and its consideration notably improves microstructure and residual stress predictions for a multi-pass steel weldment. For the weldment considered, an increase in dilution promotes the formation of martensite, enhances the hardness and leads to lower tensile stresses (or higher compressive stresses) in the weld metal. Such behaviour arises due to the higher hardenability of the base material, coupled with delayed austenite decomposition on cooling.

Residual-Stress, Material Characterization in P22 HRSG-Pipeline Butt Joint

2020 ◽  
Author(s):  
Ottaviano Grisolia ◽  
Lorenzo Scano ◽  
Francesco Piccini ◽  
Antonietta Lo Conte ◽  
Massimiliano De Agostinis ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Level ◽  
Outer Surface ◽  
High Stress ◽  
Base Material ◽  
Longitudinal Direction ◽  
Tangential Direction ◽  
Butt Joint ◽  
Hole Drilling ◽  
Plane State

Abstract Previous study evaluated residual stress in a circumferential “V”-groove butt joint of a heat-recovery steam generator (HRSG) pipeline; the material was ASTM A-335-Grade P22. Aim had been to check on the influence over creep-relaxation previously found out for a tee made of the same material. The butt joint had been operating for the same period of 200,000 hours, same temperature of 528°C at almost a half pressure (0.46 Kg/mm2 vs. 1.06 Kg/mm2). X-ray diffraction (XRD) technique applied close to the weld highlighted anomalously high stress-level on the outer surface for all four butt-joint samples tested. Residual-stress over 400 MPa observed along the cylinder’s tangential direction was statically not acceptable. On the inner surface where deposited beads may have tempered adjacent base material, measurement via blind hole-drilling (BHD) technique showed a symmetrical plane-state residual-stress of 199 MPa. It was consistent with that observed via XRD on the outer surface in the cylinder’s longitudinal direction. Supposing a case of incomplete post heating planned for the weld may have explained the occurrence of being much higher than 40 MPa, value predicted after 200,000 hours. Similar influence over creep results found out for the tee and the butt joint had validated modeling welding simulation considered for both joints. A comprehensive new series of XRD tests aims now at measuring residual stress across the cylinder’s wall, both inner and outer sides. The shallow layer considered has thickness sufficient for building a map of measurements covering different depths and locations on the surface. The experimental plan includes also BHD tests supporting the XRD ones. Comparison with previous measurements roughly shows stress level increasing similarly across the cylinder’s wall from the inner side on: Average stress values, however, appear lower than previous measurements, showing better compatibility to the analysis results.

scholarly journals Effect of grinding residual stress on bending strength of ceramics.

1989 ◽  
Vol 38 (429) ◽  
pp. 582-588 ◽  
Author(s):  
Kenji SUZUKI ◽  
Keisuke TANAKA ◽  
Yuji YAMAMOTO ◽  
Heizaburo NAKAGAWA
Keyword(s):  
Residual Stress ◽  
Bending Strength

Bending Fatigue Strength of Innovative Gear Materials for Wind Turbines Gearboxes: Effect of Surface Coatings

2012 ◽  
Author(s):  
Carlo Gorla ◽  
Francesco Rosa ◽  
Franco Concli ◽  
Horacio Albertini
Keyword(s):  
Bending Strength ◽  
Test Procedure ◽  
Base Material ◽  
Fatigue Tests ◽  
Research Project ◽  
Bending Fatigue ◽  
Gear Manufacturing ◽  
Tungsten Carbide Coating ◽  
Traditional Manufacturing ◽  
Set Up

In order to better exploit the available resources, wind turbine size is constantly increasing: the need of bigger gearboxes is an obvious and immediate consequence of this evolution tendency. The traditional manufacturing methods exhibit some difficulties for a mass-production of such large and high quality gears. The aim of the XL-Gear research project is to identify an alternative gear manufacturing procedure. This procedure mainly relies on the selection of innovative and adequate materials to manufacture the gears. Two innovative materials (Jomasco and Metasco) have been identified. A common gear material has been selected to define a baseline from which variations can be evaluated. In addition, the effects of a thermal spray tungsten carbide coating on the base material will be also investigated. In the first part of this research project, the bending resistance is evaluated, while, in the second part, the pitting resistance will be evaluated. In order to assess to bending strength, adequate gear geometry has been designed and some parts manufactured with the above mentioned materials. These gears have then been used to perform STF (Single Tooth Fatigue) bending fatigue tests. In the paper, the STF test procedure design and set-up will be described and the STF tests results on the baseline and coated gear will be presented and discussed.

High Dynamic Mechanical Strength of Zirconium-Based Bulk Amorphous Alloys

1998 ◽  
Vol 554 ◽  
Author(s):  
Tao Zhang ◽  
Akihisa Inoue
Keyword(s):  
Residual Stress ◽  
Mechanical Strength ◽  
Amorphous Alloys ◽  
Compressive Residual Stress ◽  
Bending Strength ◽  
Tensile Fracture ◽  
Uniaxial Tensile ◽  
Cast Sample ◽  
Bulk Amorphous Alloys ◽  
Squeeze Cast

AbstractA bulk amorphous Zr55Al10Ni5Cu30 alloy prepared by squeeze casting was found to exhibit high mechanical strength values, i.e., uniaxial tensile fracture strength (σt) of 1850 MPa, three-point bending strength (σb) of 3200 MPa, bending fatigue strength (σf) of 1100 MPa, Charpy impact fracture energy (Ef) of 135 kJ/m2 and fracture toughness of 68 MPa√m. The σb, σf and Ef are about two times higher than those for the corresponding bulk amorphous alloys prepared by unidirectional solidification and powder consolidation techniques, though the σt of the squeeze cast sample is higher by about 15 % than those for the other samples. The remarkable increases in the σb, σf and EF are presumably due to the introduction of high compressive residual stress of about 1240 MPa in the outer surface region only for the squeeze cast sample. The finding of the effectiveness of the compressive residual stress on the increase in the mechanical strength under the bending stress mode is important and expected to be widely used as a new strengthening mechanism for bulk amorphous alloys, as is the case for reinforced oxide glasses subjected to strengthening treatment.

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