Search Results for hydro power

The use of renewable energy has grown strongly in all end-use sectors such as power, heat, and transport. This article describes thermal spray applications that improve efficiency, lower maintenance costs, and prolong operational life in the renewable energy technologies, including wind power, hydro power, biomass and biofuels, solar energy, and fuel cells.

Mechanical cutting methods are widely used by the metal fabrication industry. This article introduces the welding fabricator to some of the mechanical equipment used to shape or prepare metals for welding. The most prevalent equipment used for mechanical cutting includes shears, iron workers, nibblers, and band saws. The article provides details on each of these.

Induction processes for melting and heating of metals belong to the high-energy-consuming industrial processes, and continuous improvement of energy efficiency of competitive melting and heating technologies is of increasing interest. This article discusses the energy demand of various melting processes and the improvements in the efficiency of melting processes in induction crucible furnaces. It provides energetic and ecological comparisons of different furnaces for melting of cast iron and aluminum. The article also describes the energy and power management of induction melting processes.

Sheet forming comprises deformation processes in which a metal blank is shaped by tools or dies, primarily under the action of tensile stresses. This article discusses the classification of sheet-forming processes for obtaining desired dimensional features. It describes different process-related developments, namely, superplastic forming of aluminum, forming of tailor-welded blanks, rubber-pad forming, and high-velocity metal forming. The article explains cost-effective approaches of evaluating tooling designs prior to the manufacture of expensive steel dies and dieless forming techniques such as thermal forming and peen forming. It provides information on the application of advanced high-strength steels, magnesium alloys, and various ultrafine-grain materials for superplastic sheet forming. The article concludes with information on the development and application of simulation, design, and control of sheet-forming processes.

Thermal spray is a generic term for a group of coating processes used to apply metallic, ceramic, cermet, and some polymeric coatings for a broad range of applications. This article provides a brief description of commercially important thermal spray processes, namely, powder-fed flame spray, wire- or rod-fed flame spray, electric arc spray, plasma arc spray, vacuum plasma spray, high-velocity oxyfuel spray, detonation gun deposition, and cold spray, and their advantages. It provides details on the microstructural characteristics of thermal spray coatings. The article also presents information on a wide variety of materials that can be thermal sprayed, such as metals, ceramics, intermetallics, composites, cermets, polymers, and functionally gradient materials. Tables are included, which list the thermal spray processes and coating properties of importance for various industrial applications.

Stray current can be defined as a current in structures that are underground or immersed in an electrolyte that most often accelerate corrosion on a structure where a positive current leaves the structure to enter the earth or an electrolyte. This article provides a description of the principles of stray current and a discussion on the major types of stray current and their properties and prediction methods. It discusses the consequences of stray current and describes the interference tests used for mapping the path of the stray currents. The article also highlights the methods of mitigating the source of stray current.

For a wide range of new or better products, solidification processing of metallic materials from the melt is a step of uppermost importance in the industrial production chain. This article discusses the casting and solidification of molten metallic alloy along with the application of low-gravity platforms and facilities for solidification processing. It provides a description of dendritic growth studies and electromagnetic levitation. The article concludes with information on the in situ and real-time monitoring of solidification processing.

This article provides a clear but nonexhaustive description of the general principle of atomic emission, with a particular focus on instrumentation, and summarizes the main characteristics of the inductively coupled plasma optical emission spectrometer technique. Basic atomic theory as well as the instrument characteristics and their influence on the instrument performances are presented. The advantages, drawbacks, and developments of this technique are discussed, and, finally, alternative techniques and examples of applications are provided.

This article reviews the classical models for the pseudo-steady-state temperature distribution of the thermal field around moving point and line sources. These include thick- and thin-plate models and the medium-thick-plate model. The analytical solutions to the differential heat flow equation under conditions applicable to fusion welding are provided. The article also provides an overview of the factors affecting heat flow in a real welding situation using the analytical modeling approach because this makes it possible to derive relatively simple equations that provide the required background for an understanding of the temperature-time pattern.

Hardfacing is defined as the application of a wear-resistant material, in depth, to the vulnerable surfaces of a component by a weld overlay or thermal spray process Hardfacing materials include a wide variety of alloys, carbides, and combinations of these materials. Iron-base hardfacing alloys can be divided into pearlitic steels, austenitic (manganese) steels, martensitic steels, high-alloy irons, and austenitic stainless steel. The types of nonferrous hardfacing alloys include cobalt-base/carbide-type alloys, laves phase alloys, nickel-base/boride-type alloys, and bronze type alloys. Hardfacing applications for wear control vary widely, ranging from very severe abrasive wear service, such as rock crushing and pulverizing to applications to minimize metal-to-metal wear. This article discusses the types of hardfacing alloys, namely iron-base alloys, nonferrous alloys, and tungsten carbides, and their applications and advantages.

Life-cycle engineering is a part-, system-, or process-related tool for the investigation of environmental parameters based on technical and economic measures. This article focuses on life-cycle engineering as a method for evaluating impacts. It describes the four steps of life-cycle analysis, namely, goal definition and scoping, inventory analysis, impact assessment and interpretation, and improvement analysis. The article discusses the applications of life-cycle analysis results and presents a case history of life-cycle analysis of an automobile fender.

Erosion of solid surfaces can be brought about solely by liquids in two ways: from damage induced by formation and subsequent collapse of voids or cavities within the liquid, and from high-velocity impacts between a solid surface and liquid droplets. The former process is called cavitation erosion and the latter is liquid-droplet erosion. This article emphasizes on manifestations of damage and ways to minimize or repair these types of liquid impact damage, with illustrations.

Plasma (ion) nitriding is a method of surface hardening using glow-discharge technology to introduce nascent (elemental) nitrogen to the surface of a metal part for subsequent diffusion into the material. This article describes the procedures and applications of plasma nitriding methods of steel. These methods include direct-current plasma nitriding, pulsed-current plasma nitriding, and active-screen plasma nitriding. The article reviews cold-walled and hot-walled furnaces used for plasma nitriding. It provides information on the importance of controlling three process parameters: atmosphere, pressure, and part temperature. The article includes a discussion on the influence of nitrogen concentration on case structure formation on nitrided steel, and explains the significance of microstructure, hardness, and fatigue strength on nitrided case. It also discusses processing, laboratory studies, and applications of nitrocarburizing of steel.

This article discusses the advantages and disadvantages of field metallography and describes the important material characteristics and other aspects to be considered before performing any metallographic procedure. It investigates the various stages of sample preparation in the metallographic laboratory: grinding, polishing, etching, preparing a replica, and obtaining a small sample. The article also illustrates the applications of field metallography with case studies.

Advanced thermoplastic composites possess impact resistance, fracture toughness, and elevated temperature endurance properties due to their melt-fusible nature. This article presents the material options available for thermoplastic composites such as pseudothermoplastics, post-impregnated thermoplastics, and true thermoplastics. It describes the processing methods of thermoplastic composites, including weaving, seaming, autoclaving, preconsolidation, roll consolidation, roll forming/pultruding, thermoforming, press forming, hydroforming, and diaphragm forming. The article provides information on different types of joints, namely, fastened, adhesive bonded, dual polymer bonded, co-consolidated, and welded joints. It explains the joining methods of thermoplastic composites, such as press forming, diaphragm forming, autoclaving, ultrasonic welding, resistance welding, and induction welding.

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 various quenchants, namely, water and inorganic salt solutions, polymers (polyvinyl alcohol, polyalkylene glycol, polyethyl oxazoline, polyvinyl pyrrolidone and sodium polyacrylates), quench oils, and molten salts, which are used for heat treatment of ferrous alloys. It also provides information on the steps for controlling quenching performance for polymer quenchants and oils with an emphasis on measuring quenchant performance, safety measures, and oxidation.

Arc welding methods can be classified into shielded metal arc welding, flux-cored arc welding, submerged arc welding, gas metal arc welding, gas tungsten arc welding, plasma arc welding, plasma-metal inert gas (MIG) welding, and electroslag and electrogas welding. This article provides information on process capabilities, principles of operation, power sources, electrodes, shielding gases, flux, process variables, and advantages and disadvantages of these arc welding methods. It presents information about the arc welding procedures of hardenable carbon and alloy steels, cast irons, stainless steels, heat-resistant alloys, aluminum alloys, copper and copper alloys, magnesium alloys, nickel alloys, and titanium and titanium alloys.

Ultraviolet/visible (UV/VIS) absorption spectroscopy is a powerful yet cost-effective tool that is widely used to identify organic compounds and to measure the concentration of principal and trace constituents in liquid, gas, and solid test samples. This article emphasizes the quantitative analysis of elements in metals and metal-bearing ores. The instrumentation required for such applications consists of a light source, a filter or wavelength selector, and some type of visual or automated sensing mechanism. The article examines common sensing options and provides helpful information on how to set up and run a variety of UV/VIS absorption tests.