Search Results for gear failures

Gears can fail in many different ways, and except for an increase in noise level and vibration, there is often no indication of difficulty until total failure occurs. This article reviews the major types of gears and the basic principles of gear-tooth contact. It discusses the loading conditions and stresses that effect gear strength and durability. The article provides information on different gear materials, the common types and causes of gear failures, and the procedures employed to analyze them. Finally, it presents a chosen few examples to illustrate a systematic approach to the failure examination.

This article first reviews variations within the most common types of gears, namely spur, helical, worm, and straight and spiral bevel. It then provides information on gear tooth contact and gear metallurgy. This is followed by sections describing the important points of gear lubrication, the measurement of the backlash, and the necessary factors for starting the failure analysis. Next, the article explains various gear failure causes, including wear, scuffing, Hertzian fatigue, cracking, fracture, and bending fatigue, and finally presents examples of gear and reducer failure analysis.

Mechanical tests are performed to evaluate the durability of gears under load. Gear tooth failures occur in two distinct regions, namely, the tooth flank and the root fillet. This article describes the common failure modes such as scoring, wear, and pitting, on tooth flanks. Failures in root fillets are primarily due to bending fatigue but can be precipitated by sudden overloading (impact). The article presents contact stress computations for gear tooth flank and bending stress computations for root fillets. Specimen characterization is a critical part of any fatigue test program because it enables meaningful interpretation of the results. The article describes four areas of the characterizations: dimensional, surface finish/texture, metallurgical, and residual stress. The rolling contact fatigue test, single-tooth fatigue test, single-tooth single-overload test, and single-tooth impact test are some of the gear action simulating tests discussed in the article.

This article summarizes the various kinds of gear wear, including fatigue, impact fracture, wear, and stress rupture, describes how gear life in service is estimated. It presents the rules concerning lubricants in designing gearing and analyzing failures of gears. The article presents the equations for determining surface durability and life of gears. It tabulates the situations and concepts of pitting failures in gears. The article analyzes some of the more common flaws that affect the life of gear teeth. It reviews the components in the design and structure of each gear and/or gear train that must be considered in conjunction with the teeth.

Induction hardening is a prominent method in the gear manufacturing industry due to its ability of selectively hardening portions of a gear such as the flanks, roots, and/or tips of teeth with desired hardness, wearing resistance, and contact fatigue strength without affecting the metallurgy of the core. This article provides an overview of gear technology and materials selection. It describes different gear-hardening patterns, namely, tooth-by-tooth hardening, tip-by-tip hardening, gap-by-gap hardening, spin hardening, single-frequency gear hardening, dual-frequency gear hardening, simultaneous dual-frequency gear hardening, and through heating for surface hardening. It provides information on the different inspection methods based on the American Gear Manufacturers Association, revealing metallurgical data, hardness, and dimensions of gears. In addition, the article presents a comparative study on the mechanical properties of contour-hardened and carburized gears. It concludes by describing typical failures of induction-hardened steels and the corresponding prevention methods.

This article is concerned with gear tooth failures influenced by friction, lubrication, and wear, and especially those failure modes that occur in wind-turbine components. It provides a detailed discussion on wear (including adhesion, abrasion, polishing, fretting, and electrical discharge), scuffing, and Hertzian fatigue (including macropitting and micropitting). Details for obtaining high lubricant specific film thickness are presented. The article describes the selection criteria for lubricants, such as oil, grease, adhesive open gear lubricant, and solid lubricants. It discusses the applications of oil and gear lubricants and the types of standardized gear tests. The article presents some recommendations for selecting lubricants and lubricant viscosity for enclosed gear. It provides some examples of failure modes that commonly occur on gears and bearings in wind turbine gearboxes.

This article provides a discussion on the design, in-process, storage, and in-field problems and their considerations associated with armament corrosion with examples. Design considerations include geometry, material selection, assembly, pretreatment, coatings, and working and storage environments. In-process corrosion concerns include processing locations, in-process storage of parts, time between processing steps, and quality control of each processing step. The article also discusses the analysis of the in-field corrosion of the finished product, including physical environments, repair of corrosion-protective coatings, general corrosion-protection maintenance, and appropriate fixes and procedures that can be implemented by soldiers in-field to stop continued corrosion of armament equipment.