Search Results for Rolling contact Mechanical properties

Rolling-contact fatigue (RCF) is a surface damage process due to the repeated application of stresses when the surfaces of two bodies roll on each other. This article briefly describes the various surface cracks caused by manufacturing processing faults or blunt impact loads on ceramic balls surfaces. It discusses the propagation of fatigue cracks involved in rolling contacts. The characteristics of various types of RCF test machines are summarized. The article concludes with a discussion on the various failure modes of silicon nitride in rolling contact. These include the spalling fatigue failure, the delamination failure, and the rolling-contact wear.

A major cause of failure in components subjected to rolling or rolling/sliding contacts is contact fatigue. This article focuses on the rolling contact fatigue (RCF) performance and failure modes of overlay coatings such as those deposited by physical vapor deposition, chemical vapor deposition, and thermal spraying (TS). It provides a background to RCF in bearing steels in order to develop an understanding of failure modes in overlay coatings. The article describes the underpinning failure mechanisms of TiN and diamond-like carbon coatings. It presents an insight into the design considerations of coating-substrate material properties, coating thickness, and coating processes to combat RCF failure in TS coatings.

Tribology is the science and technology of interacting surfaces in relative motion. This article describes in detail the basic structural, operational, and interaction parameters of a tribosystem. The interaction parameters, which characterize the action of the operational parameters on the structural components in the system, consist of three important aspects: contact parameters, friction parameters, and wear parameters. These three aspects embody the complex mechanisms and relationships between the constituents of a tribosystem. The article concludes with information on the selection criteria of a material for wear applications.

This article begins with the basic concept of friction and with the general approaches that can be used to control or minimize it. It focuses on the factors influencing rolling friction: surface topography, composition, subsurface microstructure, and lubrication conditions. The article reviews the microscopic mechanisms generating friction. It concludes by discussing the three components of rolling friction: microslip at the interface, anelastic hyteresis losses, and surface roughness.

The mechanism of contact fatigue can be understood in terms of several sources of stress concentration, or stress raisers, within the macroscopic Hertzian stress field. This article focuses primarily on rolling contact fatigue of hardened bearing steels. It discusses Hertzian shear stresses at and below the contact surfaces and briefly summarizes bearings and gear characteristics. The article provides an overview of the key types of gear and bearing steels. It analyzes two types of macropitting that result from the subsurface growth of fatigue cracks, namely, subsurface-origin macropitting and surface-origin macropitting. The article describes the factors influencing contact fatigue life of hardened steel bearings and gears, including hardness, inclusions, carbides, and residual stresses.

This article examines the deformation processes in metal-forming operations and considers the effects introduced by scale factors when microforming. It discusses the process parameters and variables affecting surface interactions, including temperature, speed, reduction, stiffness, and dynamic response of equipment. The article reviews the determination of friction coefficient using laboratory monitoring methods, indirect measurements, and the inverse method. It considers the determination of the interface heat-transfer coefficient by using the ring test and computer simulations. The article describes the behavior of oxide scale on the surface of hot metal undergoing thermomechanical processing. It concludes with information on the effects of process and material parameters on interfacial phenomena.

This article discusses the composition, properties and applications of bearing steels. It focuses on the typical wear modes that rolling-element bearings experience: contact fatigue wear, abrasive wear, adhesive wear, and corrosive wear. The article provides information on reliability factor and ABMA and ISO environmental factors.

Rolling-contact fatigue (RCF) is a common failure mode in components subjected to rolling or rolling-sliding contact. This article provides a basic understanding of RCF and a broad overview of materials and manufacturing techniques commonly used in industry to improve component life. A brief discussion on coatings to improve surface-initiated fatigue and wear is included, due to the similarity to RCF and the increasing criticality of this failure mode. The article presents a working knowledge of Hertzian contact theory, describes the life prediction of rolling-element bearings, and provides information on physics and testing of rolling-contact fatigue. Processes commonly used to produce bearings for demanding applications are also covered.

This article is dedicated to the fields of mechanical engineering and machine design. It also intends to give a nonexhaustive view of the preventive side of the failure analysis of rolling-element bearings (REBs) and of some of the developments in terms of materials and surface engineering. The article presents the nomenclature, numbering systems, and worldwide market of REBs as well as provides description of REBs as high-tech machine components. It discusses heat treatments, performance, and properties of bearing materials. The processes involved in the examination of failed bearings are also explained. Finally, the article discusses in detail the characteristics and prevention of the various types of failures of REBs: wear, fretting, corrosion, plastic flow, rolling-contact fatigue, and damage. The article includes an Appendix, which lists REB-related abbreviations, association websites, and ISO standards.

This article discusses the physical signs of rolling-contact wear (RCW). It lists the major considerations in gear design and describes the mechanisms of RCW. The article provides a guide to rolling-contact fatigue (RCF) testing methods. It explains the steps involved in the processes of RCF and RCW.

A wide range of flow-formed open- and close-ended shapes are currently available in a variety of difficult-to-form materials, including titanium alloys and nickel-base super alloys. This article describes the two basic methods of flow forming that are characterized by the position of the rolls during the forming process. The flow forming methods include staggered-roll flow forming process and in-line flow-forming process. Typical mechanical properties of flow-formed materials in various conditions are summarized in a table. Proper process controls and subsequent product qualification tests are critical to assure optimal performance of the flow-formed tubular component. The article discusses the most commonly required process control parameters and the effects of forming speed and temperature in the flow forming process.

Rolling is the process of reducing the thickness or changing the cross section of a workpiece by compressive forces applied through a set of rolls. This article emphasizes flat rolling and illustrates basic flat-rolling process used to reduce the thickness of a rectangular cross section. It provides a discussion on hot rolling, cold rolling, and warm rolling, as well as lubrication in rolling. The article reviews the lubrication for iron-base and nickel-base materials, light metals, copper-base alloys, and titanium alloys. It discusses the wear mechanism in rolling: abrasion, adhesion, and fatigue, as well as oxidative and corrosive wear. Surface modification techniques, such as hardening by induction heat treating, weld overlay, thermal spray coating, coating via physical vapor deposition (PVD), and laser surface treatment, are also discussed for improving roll service life.

This article describes the capabilities, limitations, advantages, and disadvantages of the powder metallurgy (PM) gear manufacturing process. It discusses the types of gears that can be produced by PM and presents the design guidelines for PM gears. The article provides information on gear tolerances and performance of PM gears. It also explains various procedures to inspect and test the mechanical properties, dimensional specifications, and surface durability (hardness).

This article reviews the general aspects of product design and provides an overview of the manufacturing processes and their relationship to design, with an emphasis on deformation processes. It discusses the various classes of deformation processes to illustrate their impacts on product design while taking advantage of the benefits of deformation processing.

This article describes the two commonly used standardized tests for determining the mechanical properties of thermal spray coatings: hardness testing and tensile adhesion testing. It discusses the destructive and non-destructive methods of residual-stress measurement. Electrochemical testing methodologies include two distinctly different methods: direct and alternating current impedance techniques for assessing the corrosion resistance of coating attributes. The article also reviews the testing methods for determining thermomechanical and environmental stability of thermal barrier coatings. It discusses the wear testing methodologies that are standardized by ASTM, including the pin-on-disk, block-on-ring, dry sand/rubber wheel, erosion, metallographic apparatus abrasion, fretting wear, cavitation, reciprocating ball-on-flat, impact, and rolling contact fatigue test. The article concludes with a discussion on the methods of testing abradability and erosion resistance in abradable coatings.

This article focuses on environmental and application factors in solid friction. It covers the tribology of contact between a soft and hard material, including mechanisms and testing. The article describes the tribology of contact between a metal and tool during metalworking processes. It also discusses the tribology of metal friction at elevated temperatures.

Transition metal dichalcogenides (TMD) are solid lubricant materials, specifically, intrinsic solid lubricants, whose crystal structure facilitates interfacial sliding/shear to achieve low friction and wear in sliding contacts and low torque in rolling contacts. This article provides information on sliding friction and wear behavior of unbonded, bonded, and vapor-deposited pure and composite MoS 2 and WS 2 coatings. It discusses the rolling-torque behavior and applications of vapor-deposited pure and composite MoS 2 and WS 2 coatings. The article concludes with information on various forms of TMD lubrication, namely, oils, greases, microparticle and nanoparticle additives.

Wear is mechanically-induced surface damage that results in the progressive removal of material. Because different types of wear occur in machinery, many different types of wear tests have been developed to evaluate its effects on materials and surface treatments. This article provides an explanation on mechanisms, forms (sliding, impact, and rolling) and the causes of wear. It describes the wear measuring methods, including the mass loss method, wear width method, and scar depth method. The units used to report wear vary with type of wear and with the purpose for which the data are to be used. Listing the considerations of tribosystem analysis, the article provides information on selection of ASTM wear test methods grouped by wear type. The article concludes by tabulating the testing geometries and parameters that are commonly controlled and reported when conducting wear tests.

This article describes the main advantages of using grease as a lubricant rather than oil. It discusses the formulation, lubricating mechanism, degradation, and characterization of grease. The article describes the parameters that determine lifetime of grease, including low-temperature limit, low-temperature performance limit, high-temperature performance limit, and high-temperature limit. The article concludes with information on the practical use of grease as a lubricant reservoir.