Abstract
The article presents a comprehensive study on the tooth bending strength of spur gears with a progressive curved path of contact, or so-called S-gears. Systematic gear meshing simulations ...were conducted to study the effects of S-gear geometry parameters on tooth bending strength. Different S-gear geometries were analysed in a systematically organized manner, and a comparison was made against a standard 20° pressure angle involute shape. Furthermore, different material combinations, e.g. polymer/polymer, steel/polymer, and steel/steel, of both drive and driven gear were analysed within a meaningful range of loads. The gear profile shape, material combination of the drive and the driven gear, and the transmitted load were found as the main parameters affecting gear tooth bending stress. Complex, non-linear relations between the recognized effects and the corresponding root stress were observed. Based on the numerical results, a shape factor, which considers the above-mentioned effects, was introduced, and a model for root strength control of S-gears was proposed and verified employing the finite element method (FEM).
Graphical Abstract
Graphical Abstract
•S-gears could be a possible solution for polymer gear drives in many applications.•S-gears demonstrate less sliding and lower operating temperature than E-gears.•Tooth melting was observed as the ...most frequent failure of S-gears made of POM.•Tooth root fracture was observed as the most frequent failure of S-gears made of PA66.•S-gears demonstrate higher load capacity than E-gears in the area of high loading.
A comprehensive experimental failure analysis of S-polymer gears is presented in this study. The analysed gears, made of two often used polymers (POM and PA66) in gear manufacturing, were machined using the standardised cutting tool, and then tested on a custom made gear testing device which allows a continuous torque setting by using a drive and braking asynchronous electric motors. The experimental testing has been done under different external loading of the gear pair (torque) until the occurrence of final failure, which has appeared in three different types: tooth root fracture, tooth deformation, or tooth melting. The obtained experimental results for S-gears are also compared to the results of standardised involute E-gears. This comparison has shown that S-gears demonstrate better load capacity than E-gears in the case of high loading and softer gear material (POM), where the increased temperature may involve the melting of gear teeth.
Noise Evaluation of S-Polymer Gears Trobentar, Boštjan; Hriberšek, Matija; Kulovec, Simon ...
Polymers,
01/2022, Letnik:
14, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In this study, an acoustic behaviour of S-polymer gears made of the material combination POM/PA66 was investigated and compared to the standardised involute gears (E-gears). Basic evaluating ...characteristics included noise during operation, which is of particular significance when noise reduction is expected. The measured signals were analysed in time and frequency domains and the levels of acoustic activity were compared. The experimental results have shown that the sound pressure level of both E- and S-polymer gears are proportional to the torque. However, the comprehensive noise evaluation has shown some advantages of S-polymer gears if compared to the E-polymer gears. In that respect, S-polymer gears were found more appropriate for noise reduction of gear drive systems in the case of normal loading and typical drive speed. Future studies in the operating behaviour of S-polymer gears could also cover noise evaluation using new methods of sound signal analysis at different temperatures of gears.
In practical use, most gears have an involute shape of tooth flanks. However, external involute gears have some drawbacks, such as unfavourable kinematic conditions at the beginning and end of ...meshing, a limited minimum number of teeth, and the highly loaded convex-convex (i.e., non-conformal) contact. Researchers have developed and analysed various non-involute forms of tooth flanks, but they have not been widely accepted. The main reasons are higher manufacturing costs and sensitivity to manufacturing and assembly errors. Analyses of non-involute forms of teeth are mostly theoretical (analytical and numerical), while there is a lack of experimental confirmations of theoretical assumptions. This paper reviews external non-involute shapes, their operating characteristics and possibilities of use compared to involute gears. Established criteria, such as Hertzian pressure, oil film thickness, bending stress at the root of the tooth, contact temperature, and gear noise, were used for assessment. The results of analytical studies and experimental research on S-gears are presented in more detail. S-gears have a higher surface durability and a lower heat load when compared to involute gears. The usability of non-involute gears is increasing with the development of new technologies and materials. However, the advantages of non-involute shapes are not so significant that they could easily displace involute gears, which are cheaper to manufacture.
This article presents a lifespan testing analysis of polymer gears manufactured by cutting. Compared to injection molding, machine cutting provides higher accuracy of gear geometry. Two different ...tooth flank geometries were tested; i.e. involute and S-gears. In theory, S-gears have several advantages over involute gears due to the convex/concave contact between the matching flanks. The theoretical tooth flank geometry of S-gears provides more rolling and less sliding between the matching flanks, compared to involute gears. The convex/concave contact leads to lower contact stress, which in combination with less sliding means lower losses due to sliding friction and consequently less heat generated. The goal of our research was to prove that tooth flank geometry affects the lifetime of polymer gears, and to find the mechanisms and quantitative differences in the performance of both analyzed geometries. The gears were tested on specially designed testing equipment, which allows exact adjustment of the central axis distance. Two different material pairs (POM/POM and POM/PA66) of the drive and driven gears were tested. Each test was done at a constant moment load and a constant rotational speed. Several tests were conducted using the same conditions due to repeatability analysis. All the tests were performed till the failure of the gear pair and without lubrication. In lifespan testing, the polymer S-gears showed better performance and longer lifespan than involute polymer gears.
U radu se predstavlja opsežno istraživanje dviju različitih geometrija boka zuba t.j. evolventnih i S-zupčanika. Zapažena je značajna razlika između te dvije analizirane geometrije tijekom ...ispitivanja njihovog vijeka trajanja. Ispitivanja su provedena na posebnoj opremi za ispitivanje s udaljenošću vratila od 20 mm. Materijal ispitivanih zupčanika bio je POM za pogonski zupčanik i PA6 za pogonjeni zupčanik. Rabljene su iste veličine pogonskog i pogonjenog zupčanika (m = 1 mm, z = 20). Zupčanici te veličine su naročito pogodni za mikro zupčanični prijenos. Ispitivanja su provedena uz različite brzine vrtnje i okretne momente, između 0,8 N·m i 1,5 N·m. Tijekom ispitivanja toplinskom se kamerom mjerilo toplinsko stanje zupčanika. Analize naprezanja i deformacije ispitivanih zupčanika provedene su numeričkom simulacijom primjenom metode konačnih elemenata.
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