Generation and Stress Analysis in New Version of Novikov Helical Gear Combining Double Circular Arc and Crowned Involute Profiles (original) (raw)

New version of Novikov helical gear combining double circular arc profile with crowned involute profile has been proposed in this paper. Generation of this gear is carried out using the required equations for these two profiles which are programmed using SOLIDWORK. To compare the resulting contact and bending stresses, three models of gear pairs are generated and investigated using finite element software package (ANSYS). The profiles of these models are as following: double circular arc for first model, crowned involute for second model, while the third model formed by combining double circular arc with involute crowned profiles. The results of stress analysis show that the generated stresses are lower in the proposed (combined) gear especially when the contact in the circular arc side. Keywords: Generation of gears, versions of Novikov Gears, circular arc gear, crowned involute gear, stress analysis in gears. 1. Introduction: Gears are mostly used to transmit power between shafts in several mechanical applications such that the rotary motion of the driven shaft is perfectly uniform relative to that of driving shaft [1]. In several mechanical applications gearing system is the preferred drive. As we know the toothed gearing has many advantages in compare with other mechanical drives such as its applicability for a wide range of torques and speed ratios, long service life and high reliability, can give constant speed ratio when there is no slipping as well as its small size [2]. These advantages illustrate the importance of developing gear profile. Today, three basic types of teeth profiles are used in gears for power transmission. They are involute, Noviko (or circular arc) and cyc1odial [3, 4]. One of the important causes of gear tooth failure is the presence of large contact and bending stresses in loaded gear tooth. These stresses lead to reduce the overall gear life and can result in tooth failure under loaded conditions [5]. A small reduction in the stresses leads to increase in the fatigue life of the gears considerable. Therefore it is important to find out the method of reducing induced stresses in the gear to increase gears life. Various improvements in gear design have taken place during the last few years such as use of material with improved strength, hardening the surfaces selectively with heat treatment and carburization, and improve the surface finish by shot peening. Many efforts such as using the asymmetric teeth, altering the pressure angle, introducing stress relief feature and using the gear with high contact ratio have been made to improve the strength of the gear [5]. Circular arc gears and crowned profile gears are superior compare with other types of gear profiles and they have higher load carrying capacity. In comparison with involute profile gear, crowned profile gear has a larger contact area, lower noise and vibration, and has a stronger tooth form [6]. Circular arc gears can take three to five times the load on the tooth flanks (in compare with involute gears) without detrimental pitting or wear, They more efficient in power transmission, and They retain lubricants between mating teeth more easily and form a thick oil film. Thus, the wearing of tooth flank is slower [7]. In this paper the asymmetric tooth profiles of two versions of Novikov gears will be used to reduce generated stress and increases gears life. These two profiles are double circular arc and crowned involute profiles. Double circular arc gear has higher bending and contact strength in compare with involute gear for the same parameters. This gear has been widely used in industry machinery [8].