Search Results for fluid mechanics

This article is a comprehensive collection of fluid dynamic equations for properties of fluids, fluid statics, fluid motion, dimensional analysis, and boundary layer flow. It presents equations for analyzing problems in fluid mechanics, continuity equation, momentum equation, and energy equation for solving various problems related to fluid dynamics.

This article is a comprehensive collection of tables containing formulas for metals processing, namely, casting and solidification, flat (sheet) rolling, conical-die extrusion, wire drawing, bending, and deep drawing. Formulas for compression, tension, and torsion testing of isotropic materials are included. The article also lists the formulas for effective stress, strain, and strain rate (isotropic material) in arbitrary and principal coordinates; dimensionless groups in fluid mechanics; and anisotropic sheet materials at various loading conditions.

This article provides an overview of cavitation erosion with a specific focus on the estimation of mass loss. It describes the mechanisms of cavitation erosion and the types of laboratory devices to evaluate the resistance to cavitation erosion of materials. The laboratory devices include rotating disks, vibratory devices, cavitating liquid jets, and high-speed cavitation tunnels. The article discusses materials selection and surface protection to prevent cavitation erosion. It reviews the fluid-structure interaction that plays a role in cavitation erosion particularly for compliant materials. The article provides information on the numerical prediction of cavitation erosion damage by the finite element method (FEM).

This article provides an overview of the degradation of metals and alloys in aqueous systems. The importance of the hydrogen ion lies in its ability to interact with an alloy surface. The article describes the effects of various conditions of pH on corrosion including strongly acid conditions, near-neutral conditions, and strongly basic conditions as well as the effects of temperature on corrosion. The influence of the fluid flow rate on corrosion depends on the alloy, fluid components, fluid physical properties, geometry in which the fluid is contained, and corrosion mechanism. The article discusses the influence of fluid flow rate through specific examples. It concludes with information on how the concentration of dissolved species works with other variables to influence corrosion behavior.

Metal is removed from the workpiece by the mechanical action of irregularly shaped abrasive grains in all grinding operations. This article discusses three primary components of grinding wheels, namely, abrasive (the cutting tool), bond (the tool holder), and porosity or air for chip clearance and/or the introduction of coolant. It describes the compositions and applications of coated abrasives and types of grinding fluids, such as petroleum-base and mineral-base cutting oils, water-soluble oils, synthetic fluids, semisynthetic fluids, and water plus additives. The article concludes with information on different types of grinding processes, namely, rough grinding, precision grinding, surface grinding, cylindrical grinding, centerless grinding, internal grinding, and tool grinding.

This article provides an overview of different modeling approaches used to capture the phenomena present in the additive manufacturing (AM) process. Inherent to the thermomechanical processing that occurs in AM for metals is the development of residual stresses and distortions. The article then provides an overview of thermal modeling. It presents a discussion on solid mechanics simulation and microstructure simulation.

Erosion is the progressive loss of original material from a solid surface due to mechanical interaction between that surface and a fluid, a multicomponent fluid, an impinging liquid, or impinging solid particles. The detrimental effects of erosion have caused problems in a number of industries. This article describes the processes involved in erosion of ductile materials, brittle materials, and elastomers. Some examples of erosive wear failures are given on abrasive erosion, liquid impingement erosion, cavitation, and erosion-corrosion. In addition, the article provides information on the selection of materials for applications in which erosive wear failures can occur.

This article describes the viscoelastic behavior of plastics in their solid state only, from the standpoint of the material deforming without fracturing. The consequences of viscoelasticity on the mechanical properties of plastics are described, especially in terms of time-dependencies, as well as the dependence of the viscoelastic character of a plastic on chemical, physical, and compositional variables. By examining the viscoelastic behavior of plastics, the information obtained are then applied in situations in which it may be important to anticipate the long-term properties of a material. This includes assessing the extent of stress decay in materials that are pre-stressed, the noise and vibration transmission characteristics of a material, the amount of heat build-up in a material subjected to cyclic deformation, and the extent a material can recover from any prior deformation. Several qualitative graphs are presented, which highlights the possible differences in the viscoelastic behavior that can exist among plastics.

This article illustrates the mechanics of the deep drawing of a cylindrical cup. It discusses the fundamentals of drawing and drawability. Sheet metal is drawn in either hydraulic or mechanical presses. The article summarizes the defects in drawing and factors considered in press selection for drawing. It explains the types of dies used for drawing sheet metal and the effects of process variables and material variables on deep drawing. The process variables that affect the success or failure of a deep-drawing operation include the punch and die radii, punch-to-die clearance, press speed, lubrication, and type of restraint of metal flow used. The article describes the process of redrawing and ironing of metals. Drawing of workpieces with flanges and drawing of hemispheres are also illustrated. The article also provides information on the reducing of drawn shells, methods for expanding portions of drawn workpieces, trimming, and deep drawing using fluid-forming presses.

Mechanical finishes usually can be applied to aluminum using the same equipment used for other metals. This article describes the two types of grinding used in mechanical finishing: abrasive belt grinding and abrasive wheel grinding. It reviews the binders and fluid carriers used in buffing, and discusses satin finishing and barrel finishing. It also describes lapping and honing techniques that are of special interest in treating aluminum parts that have received hard anodic coatings. Honing recommendations for aluminum alloys are presented in a table.

Failures in boilers and other equipment taking place in power plants that use steam as the working fluid are discussed in this article. The discussion is mainly concerned with failures in Rankine cycle systems that use fossil fuels as the primary heat source. The general procedure and techniques followed in failure investigation of boilers and related equipment are discussed. The article is framed with an objective to provide systematic information on various damage mechanisms leading to the failure of boiler tubes, headers, and drums, supplemented by representative case studies for a greater understanding of the respective damage mechanism.

The role of a mixer/agitator in quenching applications is to control the mixing environment in order to meet the process criteria. This article provides the basic fundamentals of the sizing of agitators, tank geometry importance, and other considerations for the application of agitators in quench tanks. It also discusses the differing methods for the sizing and selection of agitators for quench tank applications.

Computational fluid dynamics (CFD) is one of the tools available for understanding and predicting the performance of thermal-fluids systems. This article qualitatively describes the basic principles of CFD. The numerical methods, such as geometry description and discretization, used to solve the CFD equations are discussed. The article also demonstrates the application of CFD to a few casting problems.

The human internal environment plays a vital role in the friction and wear of implants and prosthetic devices. This article describes the tribological/wear behavior of implants. It discusses the classification of active tribological pairs, namely, amphiarthosis joints and diarthosis joints. The article details the classification of total knee replacement, depending on the type of mechanical stability, including nonconstrained knee replacement, semiconstrained knee replacement, and constrained knee replacement. It also discusses the classifications of passive tribological pairs, namely, total disc replacement in the spine, dental implants, and temporomandibular joint. It describes the various testing methods for characterizing the implant materials used in hip, knee, spine, and dental applications. The article also describes the typical standards used for testing wear behavior of tribological pairs, namely, hip-wear simulation standards, knee-wear simulation standards, and spinal disc-wear simulation standards.

Metal-matrix composites (MMCs) are a class of materials with potential for a wide variety of structural and thermal management applications. They are nonflammable, do not outgas in a vacuum, and suffer minimal attack by organic fluids, such as fuels and solvents. This article presents an overview of the status of MMCs, and provides information on physical and mechanical properties, processing methods, distinctive features, and various types of continuously and discontinuously reinforced aluminum, magnesium, titanium, copper, superalloy, and intermetallic-matrix composites. It further discusses the property prediction and processing methods for MMCs.

This article provides a discussion on cutting tools, their materials and design; cutting fluids; and various aspects of machining operations of heat-resistant alloys, with several examples. Operations such as turning, planing and shaping, broaching, drilling, reaming, counterboring and spotfacing, tapping and thread milling, milling, sawing, and grinding are discussed. Nominal compositions of wrought heat-resistant alloys and nickel-base heat-resistant casting alloys, as well as compositions of cobalt-base heat-resistant casting, iron-base heat-resistant casting, and mechanically alloyed (oxide dispersion strengthened) products are also listed.

Designing of induction heating, or, generally electro technological installations, requires mathematical modeling for solving problems related to various physical phenomena, including electromagnetic (EM), thermal, mechanical, fluidic, and metallurgical fields. This article focuses on the solution of Maxwell's equations (MEs) and provides some basic information regarding the heat transfer and fluid equations, because these physical phenomena usually are strongly coupled to magnetic and electric fields. The solutions are usually obtained by using specific numerical methods such as finite-element method, finite difference method, boundary-element method or volume-integral method, and direct-solution method. The article also discusses the typical structure of commercial codes (preprocessor, solver, and postprocessor) to solve field problems mainly in finite-element method.

Seals are mechanical components that prevent the leakage, diffusion, transfer, or mixing of different liquid, gas, solid, and multiphasic substances. This article begins by discussing the classifications of seals: static and dynamic. Static seals involve both self-energizing elastomeric materials such as O-rings, which merely react to a sealed fluid pressure, and passive materials that require clamping forces to achieve sealing, such as gaskets. The types of dynamic seals include rotary seals and reciprocating seals. The article describes the factors affecting seal wear and failure. It provides a list of some common seal wear modes and failures, namely abrasion, cavitation damage, chemical attack, compression set, corrosion, damage during abrupt decompression, dieseling damage, extrusion damage, installation damage, spiral or rolling damage, and vaporization damage. The article concludes with specific recommendations for reducting of seal friction and wear.

Solid particle erosion (SPE) is the loss of material that results from repeated impact of solid particles energized in a carrier fluid. This article reviews important SPE variables, their effects for different classes of materials, composites and coatings, and the mechanisms and theories proposed to explain SPE. It discusses the SPE of metals, steels, and ceramics, as well as erosion of alloys with coarse, nominally two-phase microstructures in which the second-phase particles (SPPs) are typically large compared with the dimensions of the damage zone created by the impact of one particle. The article summarizes the erosion characteristics of polymer matrix composites (PMCs), metal matrix composites (MMCs), ceramic matrix composites (CMCs), and erosion-resistant coatings. The combination of parameters included in most erosion models is also summarized.

The interaction of an implant with the human body environment may result in degradation of the implant, called corrosion. This article discusses the corrosion testing of metallic implants and implant materials. The corrosion environments for medical implants are the extracellular human body fluids, very complex solutions containing electrolytes and nonelectrolytes, inorganic and organic constituents, and gases. The article describes the fundamentals of electrochemical corrosion testing and provides a brief discussion on various types of corrosion tests. It illustrates corrosion current density determination by Tafel extrapolation, potentiodynamic measurement of the polarization resistance, electrochemical impedance measurement, and potentiostatic deaeration. Tests combining corrosion and mechanical forces, such as fretting corrosion tests, environment-assisted cracking tests, and ion-leaching tests are also discussed.