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.

Gear root bending strength: a comparison between Single Tooth Bending Fatigue Tests and meshing gears

2021 ◽  
pp. 1-17
Author(s):  
Luca Bonaiti ◽  
Ahmed Bayoumi Mahmoud Bayoumi ◽  
Franco Concli ◽  
Francesco Rosa ◽  
Carlo Gorla
Keyword(s):  
Failure Modes ◽  
Bending Strength ◽  
Gear Tooth ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Gear Design ◽  
Single Tooth ◽  
Actual Strength ◽  
Meshing Gears ◽  
Definition Of

Abstract Gear tooth breakage due to bending fatigue is one of the most dangerous failure modes of gears. Therefore, the precise definition of tooth bending strength is of utmost importance in gear design. Single Tooth Bending Fatigue (STBF) tests are usually used to study this failure mode, since they allow to test gears, realized and finished with the actual industrial processes. Nevertheless, STBF tests do not reproduce exactly the loading conditions of meshing gears. The load is applied in a pre-determined position, while in meshing gears it moves along the active flank; all the teeth can be tested and have the same importance, while the actual strength of a meshing gear, practically, is strongly influenced by the strength of the weakest tooth of the gear. These differences have to be (and obviously are) taken into account when using the results of STBF tests to design gear sets. The aim of this paper is to investigate in detail the first aspect, i.e. the role of the differences between two tooth root stress histories. In particular, this paper presents a methodology based on high-cycle multi-axial fatigue criteria in order to translate STBF test data to the real working condition; residual stresses are also taken into account

Mechanical Characterizations of Saxidomus purpuratus Shells

2010 ◽  
Vol 434-435 ◽  
pp. 601-604 ◽  
Author(s):  
W. Yang ◽  
Y. Jiang ◽  
G.P. Zhang ◽  
Y.S. Chao ◽  
Xiao Wu Li
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Bending Strength ◽  
Target Material ◽  
Organic Matrix ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Three Point Bending ◽  
Saxidomus Purpuratus ◽  
Scanning Electron

A sort of biological shells (Saxidomus purpuratus), which belongs to Bivalve, was selected as the target material, and hardness and dynamic three point bending fatigue tests were conducted to examine its mechanical properties. Microhardness measurements showed that the inner layer is the hardest. The indentation on the specimen with a lower bending strength was damaged more seriously by the same load. Three point bending fatigue tests demonstrated that this kind of the shells with a special structure comprising mineral and organic matrix can experience the repeated loads instead of immediate breaking. The fatigue results on a single shell investigated here indicated that the fatigue strength is usually less than the static bending strength. Most of the fatigue lives of the specimens are less than 2105 cycles. In addition, fatigue fracture surfaces are observed by scanning electron microscopy.

CHARACTERISTICS OF A NEW TEST RIG AND METHODOLOGY FOR CYCLIC TESTING OF GEAR TOOTH BENDING FATIGUE STRENGTH

Tribologia ◽  
2019 ◽  
Vol 283 (1) ◽  
pp. 57-65
Author(s):  
Waldemar TUSZYŃSKI ◽  
Michał GIBAŁA ◽  
Marek KALBARCZYK ◽  
Eugeniusz MATRAS ◽  
Remigiusz MICHALCZEWSKI ◽  
...  
Keyword(s):  
Research Methodology ◽  
Bending Strength ◽  
Gear Tooth ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Strength Parameter ◽  
Bending Fatigue ◽  
New Device ◽  
Engineering Materials ◽  
Materials Used

Tooth fracture is the most dangerous form of gear wear that excludes the gear from further use. In order to counteract the occurrence of this type of damage, it is very important to properly design the toothed gear. To calculate the gear tooth bending strength, a strength parameter called the nominal stress number σFlim is necessary. ISO 6336-5:2003(E) and available material databases provide σFlim values for the most popular engineering materials used for gears, including those for case-hardened steels. There is, however, no data for a new generation of nanostructured engineering materials, which are the subject of research conducted at the Tribology Department of ITeE – PIB. The σFlim parameter is most often determined in cyclic fatigue tests on toothed gears with specially selected tooth geometry. In order to determine the above strength parameter, a pulsator (symbol T-32) was developed and manufactured at ITeE-PIB in Radom. The article presents a new device, research methodology, and the results of verification tests for case-hardened steel 18CrNiMo7-6, confirming the correctness of the adopted design assumptions and the developed research methodology. The results of tooth bending fatigue tests are the basis for the selection of a new engineering material dedicated to gears, which later undergoes tribological testing.

scholarly journals Gear Root Bending Strength: A New Multiaxial Approach to Translate the Results of Single Tooth Bending Fatigue Tests to Meshing Gears

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 863
Author(s):  
Franco Concli ◽  
Lorenzo Fraccaroli ◽  
Lorenzo Maccioni
Keyword(s):  
Material Properties ◽  
Bending Strength ◽  
Load Ratio ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Design Data ◽  
Bending Fatigue ◽  
Relevant Effect ◽  
Accurate Design ◽  
Single Tooth

Developing accurate design data to enable the effective use of new materials is undoubtedly an essential goal in the gear industry. To speed up this process, Single Tooth Bending Fatigue (STBF) tests can be conducted. However, STBF tests tend to overestimate the material properties with respect to tests conducted on Running Gears (RG). Therefore, it is common practice to use a constant correction factor fkorr, of value 0.9 to exploit STBF results to design actual gears, e.g., through ISO 6336. In this paper, the assumption that this coefficient can be considered independent from the gear material, geometry, and loading condition was questioned, and through the combination of numerical simulations with a multiaxial fatigue criterion, a method for the calculation of fkorr was proposed. The implementation of this method using different gear geometries and material properties shows that fkorr varies with the gears geometrical characteristics, the material fatigue strength, and the load ratio (R) set in STBF tests. In particular, by applying the Findley criterion, it was found that, for the same gear geometry, fkorr depends on the material as well. Specifically, fkorr increases with the ratio between the bending and torsional fatigue limits. Moreover, through this method it was shown that the characteristics related to the material and the geometry have a relevant effect in determining the critical point (at the tooth root) where the fracture nucleates.

Effect of Moisture Absorption on the Residual Strength after Bending Fatigue of CFRP

2011 ◽  
Vol 415-417 ◽  
pp. 2142-2145
Author(s):  
A Ying Zhang ◽  
Di Hong Li ◽  
Cheng Li Liang ◽  
Jiu Si Jia ◽  
Dong Xing Zhang
Keyword(s):  
Moisture Content ◽  
Composite Laminates ◽  
Immersion Time ◽  
Moisture Absorption ◽  
Bending Strength ◽  
Fatigue Tests ◽  
Material Strength ◽  
Bending Fatigue ◽  
Residual Properties ◽  
Effect Of Moisture

This study investigates the effect of moisture content on the residual bending strength after bending fatigue of T300/914 composite laminates immersed in water for 7 days and 14 days. Displacement-controlled three-point bending fatigue tests were conducted on specimens. After 40,000 cycles the fatigue test was stopped and the residual properties were measured on the tested specimens. Reduction in material strength was found to depend on the level of moisture content. Experimental results reveal that the moisture content in the laminates increased with immersion time. Compared to the unaged specimens, the residual bending strength after bending fatigue decreased by 6.67% and 37.04%, respectively. The residual bending strength and strength retention decreased with increased immersion time.

Gear root bending strength: statistical treatment of Single Tooth Bending Fatigue tests results

2021 ◽  
Author(s):  
Luca Bonaiti ◽  
Francesco Rosa ◽  
Prasad Mahendra Rao ◽  
Franco Concli ◽  
Carlo Gorla
Keyword(s):  
Bending Strength ◽  
Statistical Treatment ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Single Tooth

Fatigue Life Characterisation of Interference Fitted Joints

2013 ◽  
Author(s):  
D. Croccolo ◽  
M. De Agostinis ◽  
G. Olmi
Keyword(s):  
Fatigue Life ◽  
Stress State ◽  
Numerical Model ◽  
Local Stress ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Notched Specimen ◽  
Bending Fatigue ◽  
Local Stress State ◽  
Set Up

Reversed bending fatigue tests to be performed on full scale assemblies, joined by interference fitting, are very complicated to set up, as well as very expensive to carry out, due to material costs and to low achievable testing frequencies. Moreover, along with the interference level and the shape of the hub edge, the method by which interference is created is deemed to influence the fatigue behaviour of the assembly. A quicker and cheaper way to obtain information about the fatigue behaviour of such assemblies could be performing fatigue tests on down scaled specimens, similar to those suggested by standard ISO 1143. Since no standardized specimen exists for characterising the fatigue behaviour of interference fitted shaft hub joints, the authors designed an ad-hoc specimen (“notched” specimen) and set up a convenient assembly procedure for performing rotating bending fatigue tests. The present investigation focuses on an interference fitted joint, made of EN 10083-2 C40 low carbon steel, whose hub bore edge is rounded. The rationale of the experimentation is retrieving the fatigue stress concentration factor by comparing the endurance limit results of the “notched” specimen to those of a plain specimen manufactured according to ISO 1143. Results were analysed according to standard ISO 12107. Furthermore, a three dimensional numerical model was developed, suitable for evaluating the local stress state of an axisymmetric interference fitted joint. The numerical model accounts for the effect of an external bending moment applied to the shaft. Experimental results are then compared to those given by finite elements analyses, in order to find out the relationship between the fatigue life and the local stress state of interference fitted components.

Four Point Bending Fatigue Tests of Forged Ti 6Al 4V

2009 ◽  
Vol 51 (9) ◽  
pp. 580-586 ◽  
Author(s):  
Bernd Oberwinkler ◽  
Martin Riedler ◽  
Heinz Leitner ◽  
Ataollah Javidi
Keyword(s):  
Fatigue Tests ◽  
Bending Fatigue ◽  
Four Point Bending

Bending fatigue of single-wall and double-wall corrugated paperboards under sinusoidal and random loads

2021 ◽  
pp. 109963622110204
Author(s):  
Zhi-Wei Wang ◽  
Yang-Zhou Lai ◽  
Li-Jun Wang
Keyword(s):  
Energy Dissipation ◽  
Fatigue Failure ◽  
Fatigue Tests ◽  
Stiffness Degradation ◽  
Random Load ◽  
Bending Fatigue ◽  
Random Loads ◽  
Vibration Fatigue ◽  
Sinusoidal Load ◽  
Double Wall

The bending fatigue tests of single-wall and double-wall corrugated paperboards were conducted to obtain the εrms– N curves under sinusoidal and random loads in this paper. The εrms– N equation of corrugated paperboard can be described by modified Coffin–Manson model considering the effect of mean stress. Four independent fatigue parameters are obtained for single-wall and double-wall corrugated paperboards. The εrms– N curve under random load moves left and rotates clockwise compared with that under sinusoidal load. The fatigue life under random load is much less than that under sinusoidal load, and the fatigue design of corrugated box should be based on the fatigue result under random load. The stiffness degradation and energy dissipation of double-wall corrugated paperboard before approaching fatigue failure are very different from that of single-wall one. For double-wall corrugated paperboard, two turning points occur in the stiffness degradation, and fluctuation occurs in the energy dissipation. Different from metal materials, the bending fatigue failure of corrugated paperboard is a process of wrinkle forming, spreading, and folding. The results obtained have practical values for the design of vibration fatigue of corrugated box.

Fatigue Behaviour of Friction Stir Welded Steel Joints

2014 ◽  
Vol 891-892 ◽  
pp. 1488-1493 ◽  
Author(s):  
José Azevedo ◽  
Virgínia Infante ◽  
Luisa Quintino ◽  
Jorge dos Santos
Keyword(s):  
Base Material ◽  
Welding Process ◽  
Steel Structures ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Welded Steel ◽  
Shipbuilding Industry ◽  
Friction Stir ◽  
Steel Joints

The development and application of friction stir welding (FSW) technology in steel structures in the shipbuilding industry provide an effective tool of achieving superior joint integrity especially where reliability and damage tolerance are of major concerns. Since the shipbuilding components are inevitably subjected to dynamic or cyclic stresses in services, the fatigue properties of the friction stir welded joints must be properly evaluated to ensure the safety and longevity. This research intends to fulfill a clear knowledge gap that exists nowadays and, as such, it is dedicated to the study of welded steel shipbuilding joints in GL-A36 steel, with 4 mm thick. The fatigue resistance of base material and four plates in as-welded condition (using several different parameters, tools and pre-welding conditions) were investigated. The joints culminate globally with defect-free welds, from which tensile, microhardness, and fatigue analyses were performed. The fatigue tests were carried out with a constant amplitude loading, a stress ratio of R=0.1 and frequency between 100 and 120 Hz. The experimental results show the quality of the welding process applied to steel GL-A36 which is reflected in the mechanical properties of joints tested.

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