FZG gear testing is widely used to evaluate the performance of lubricants, gear materials, and gear-tooth geometries under different loads. During these tests, gear tooth wear results in the loss of ...gear profile in the form of micro-pitting, pitting and scuffing, can be observed. However, gear wear is usually measured by weighting. This method cannot be used to study the wear depth on a specific point on the gear-tooth surface. In this study, tooth profiles were measured via a profilometer during the FZG gear-pitting test. Moreover, an algorithm was developed to quantitatively evaluate the distributed cumulative wear and wear progress at a certain test stage. Simultaneously, the real tooth profile was obtained. Experiments were performed to validate the proposed method, and the results showed that gear-tooth-surface wear can be quantitatively determined. Thus, the proposed method can be used for further gear-failure-prediction experiments.
•Gear tooth profiles are measured via a profilometer during FZG gear-pitting tests.•No wear region on the profiles are used in orthogonal-distance regression.•Distributed cumulative wear and wear at various test stages are quantitatively evaluated.•The method is experimentally validated and agrees with the previous simulation.
In this paper, an experimental investigation on a FZG test rig is presented. The proposed approach aims to at highlight the influence of micropitting on power losses and temperatures in this geared ...system. Micropitting has been gradually developed on the gear pair by applying increasing load levels. The influence of this defect on power losses and temperatures has been evaluated with specific characterization tests performed alongside micropitting growth. The modification of the gear surface roughness was monitored during these tests. This study shows power loss and oil temperature increase due to micropitting development. Furthermore, it is possible to correlate power loss and temperature variations to surface feature measurements.
•The impact of micropitting on gear power losses and temperatures has been investigated using a FZG test rig.•Tests showed that micropitting has a significant impact on power losses and temperatures.•Surface analysis permitted to correlate power loss and temperature variations to surface roughness feature evolutions.
This paper investigates the resistance of micropitting on two materials, using an FZG back-to-back test rig with C-PT gears. The materials are wrought steel (16MnCr5) and a commercial powder ...metallurgical material (Astaloy™ Mo). Two finishing methods were studied: grinding and superfinishing. Experimental results show that the superfinishing prevented micropitting, but led to premature failure due to cracks in the root caused by tip-to-root interference. Micropitting was initiated at a higher load stage for the powder metallurgical steel compared to the ground wrought steel. The failure mechanisms were similar between materials with the same surface finish. The powder metallurgical steel showed subsurface initiated fatigue compared to the wrought ground steel having surface-initiated fatigue. Testing new finishing methods and materials, one has to be aware of the influence of the gear micro geometry.
•The use of in-situ surface profile measurements can be used for evaluating the progress of micropitting damage.•Quantitative profile measurements were used to track damage initiation on the tooth flank during a pitting test.•The lack of tip relief in FZG pitting tests can lead to failure of the surface if the surface has low surface roughness.•The damage on ground wrought and powder metal gears are similar, but the powder metal gears also show subsurface damage.
Modern gearing applications, in particular electrification, impose new challenges in many different fields of engineering and research. In specific, new demands are imposed on gears, including higher ...rotational speed, lower noise acceptance, and increased efficiency, as well as increased resistance against pitting and scuffing. To meet these demands, a better understanding of gear contacts is needed. The Eurostars project Effigears proposes a novel multi-perspective methodology for assessment of gear efficiency and contact analysis. The methodology consists of using a novel surface treatment method, Triboconditioning (R), implemented in a streamfinishing process, surface measurements using a scattered light method, experimental testing using the standardized FZG test rig, and contact simulations using a novel thermal elasto-hydrodynamic lubrication tool. It is found, in preliminary tests, that enhanced gear performance may be enhanced due to Triboconditioning (R) surface treat-ment. Findings also include better understanding of how surface characteristics and lubricants affect scuffing and pitting, and the effect of load distribution on gearset behavior.
During their lifetime, gears may undergo starved lubrication operating conditions. Starvation has an impact on friction between gears and leads to modified gearbox efficiency. In this article, ...lubricant starvation tests on an FZG test rig adapted to this condition are presented. Gears were equipped with an embedded thermocouple sensor to measure their operating bulk temperature. An experimental method to isolate the test box power loss of the FZG machine is proposed. A thermal model of this test rig draws up the power loss distribution into the test box for a nominal condition of lubrication. A numerical method based on experimental results is proposed to estimate gear power loss variation during lubricant starvation.
•The influence of mounting error on tooth profile measurement using a profilometer is confirmed.•A fish-shaped tooth profile form measurement error caused by mounting error has been identified.•A ...mounting error compensation method based on projection is proposed.•The fish-shaped measurement error can be effectively compensated by the projection method.
A profilometer can be used to monitor the tooth surface topography evolution during gear pitting tests. Due to the mounting relationship variation between the instrument and the gear, the tooth profile’s measurement position deviation from its theoretical location will introduce a measurement error. In this study, the tooth profile measurement error introduced by mounting using a tactile profilometer was theoretically analysed and experimentally confirmed as a fish shape. A mounting error compensation method based on projection onto the perpendicular plane to the gear’s datum axis was proposed. The results show that the fish-shaped tooth profile measurement error can be effectively compensated, benefitting the evaluation of the gear tooth surface wear during gear pitting tests.
A thermomechanical model of the FZG test rig is presented. The numerical model is based on the thermal network method and takes into account power losses due to tooth friction, rolling element ...bearings (REBs), oil churning, and shaft seals. Some measurements underline that REB rings run at different temperatures. To investigate this difference, several REB models are proposed and compared to measurements. Their influence on the global thermal behavior of the gear unit is discussed and analyzed.
Plastic gears are mostly used in the textile, food, and automotive industries due to their silent operation, corrosion resistance, and light and cheap advantages. Plastic gears are generally ...manufactured by injection molding or hobbing methods. The excess costs of the molds used to produce parts in injection molding and the problems of wastes that occur during production in hobbing lead companies to additive manufacturing, which is an alternative application. In the additive manufacturing method, the desired amount of product is produced without the problem of waste. In this study, the wear resistance of plastic spur gears produced by the Fused Deposition Modeling (FDM) method was determined theoretically. In order to determine the service life of gears, wear tests were carried out in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) type test device at the same load and rotational speeds. polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyethylene terephthalate (PETG) thermoplastic polymer materials were used in the production of gears. When the gears rotate at the same load and rotational speeds, the most wear was observed in ABS, PLA, and PETG at the theoretically calculated wear depths. PETG is the most resistant material in terms of wear.
To increase the efficiency of a gearbox, research on gear mesh loss is of importance. Britton et al. concluded that the surface finishing method affects the gear mesh efficiency. The efficiency ...benefits of superfinishing a surface and reducing the surface roughness have been reported by Kahraman. A novel method for calculating the bearing loss torque was proposed by Tu et al. Andersson et al. found that the efficiency can vary between 2 and 5% during repeated efficiency tests due to variations in the assembly process. This work investigates how the honing surface finishing process and DIN 3962 quality class affect the gear mesh efficiency by performing tests in an FZG back-to-back test rig. Two materials, a powder metal and a wrought steel, were tested. All gears were finished using a honing process and sorted according the measured quality class. Powder metal gears of class 6, 7, 8, and ≥9 and wrought steel gears of class 6, 7, and ≥9 were tested. The efficiency were calculated from measuring the torque required to maintain a constant velocity of the FZG test rig. The results from the efficiency tests showed no significant difference in efficiency between the wrought steel and powder metal steel gears. In addition, no obvious correlation between the DIN 3962 quality class and the gear mesh efficiency could be found. When examining the wrought steel material it was found that the reproducibility of the efficiency was comparable to the assembly error of the test rig, despite the variation in quality class.
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