Martensite
It includes a class of hard minerals occurring as lath- or plate-shaped crystal grains. When viewed in section, the lenticular crystal grains may be incorrectly described as acicular. Austenite is γ-Fe, a solution of iron and alloying elements. As a result of the quenching, the cubic austenite transforms to a highly strained body-centered tetragonal form called martensite that is supersaturated with carbon. The shear deformations that result produce a number of dislocations. The highest hardness of a steel is 400 Brinell whereas martensite can achieve 700 Brinell. The martensitic reaction begins during cooling when the austenite reaches the start temperature. For a eutectoid steel, between 6 and 10% of austenite, called retained austenite, will remain. The percentage of retained austenite increases from insignificant for less than 0. 6% C steel, to 13% retained austenite at 0. 95% C, a very rapid quench is essential to create martensite. For steel 0-0. 6% carbon the martensite has the appearance of lath, for steel greater than 1% carbon it will form a plate like structure called plate martensite.
Between those two percentages, the appearance of the grains is a mix of the two. The strength of the martensite is reduced as the amount of retained austenite grows, the process produces dislocation densities up to 1013/cm2. The great number of dislocations, combined with precipitates that originate and pin the dislocations in place, martensite can be thermally induced or stress induced. One of the differences between the two phases is that martensite has a tetragonal crystal structure, whereas austenite has a face-centered cubic structure. Martensite has a lower density than austenite, so that the martensitic transformation results in a change of volume. Of considerably greater importance than the change is the shear strain which has a magnitude of about 0.26. Martensite is not shown in the phase diagram of the iron-carbon system because it is not an equilibrium phase. Equilibrium phases form by slow cooling rates that allow sufficient time for diffusion, since chemical processes accelerate at higher temperature, martensite is easily destroyed by the application of heat
Vickers Limited
Please refer to the overview article Vickers for other companies known by this name Vickers Limited was a significant British engineering conglomerate that merged into Vickers-Armstrongs in 1927. Vickers was formed in Sheffield as a foundry by the miller Edward Vickers. Naylor was a partner in the foundry Naylor & Sanderson and Vickers brother William owned a steel rolling operation, edwards investments in the railway industry allowed him to gain control of the company, based at Millsands and known as Naylor Vickers and Company. It began life making steel castings and quickly became famous for casting church bells, in 1854 Vickers sons Thomas and Albert joined the business. In 1863 the company moved to a new site in Sheffield on the River Don in Brightside, the company went public in 1867 as Vickers, Sons & Company and gradually acquired more businesses, branching out into various sectors. In 1868 Vickers began to manufacture marine shafts, in 1872 they began casting marine propellers, Vickers produced their first armour plate in 1888 and their first artillery piece in 1890.
The yard at Barrow became the Naval Construction Yard, with these acquisitions, Vickers could now produce a complete selection of products, from ships and marine fittings to armour plate and a whole suite of ordnance. In 1901 the Royal Navys first submarine, Holland 1, was launched at the Naval Construction Yard, in 1902 Vickers took a half share in the famous Clyde shipyard John Brown and Company. Further diversification occurred in 1901 with the purchase of Herbert Austins embryo car manufacturing plans, the new business was incorporated and named The Wolseley Tool and Motor Car Company and works were purchased at Adderley Park. In 1911 a controlling interest was acquired in Whitehead and Company, in 1911, the company name was changed to Vickers Limited and expanded its operations into aircraft manufacture by the formation of Vickers Ltd. Vickers brand aircraft were produced from 1911 to until 1965, when BAC ended the name, in 1919, the British Westinghouse electrical company was taken over as the Metropolitan-Vickers Electrical Company, Metrovick.
At the same time came into Metropolitans railway interests. Wolseley now Wolseley Motors was sold to William Morris in mid-November 1926 who retained it as his personal property and he had reported last year that an internal reorganization was in progress to deal with those subsidiary branches which proved a heavy drain on financial resources. This merger was to take effect 1 January 1928 and would give Vickers shareholders ownership of two-thirds of the new company, Metropolitan Carriage Wagon and Finance Company and The Metropolitan -Vickers Company were not included in the merger. Vickers manufactured and sold the Maxim machine gun forming a partnership with its inventor and they took over the company and improved the design as the Vickers machine gun, which was the last major design Hiram Maxim himself worked on. It became the standard machine gun of the British Empire and Commonwealth, Vickers produced the machine gun in literally dozens of different cartridge sizes and sold it all over the world.
They even scaled it up to larger calibres, particularly for the Royal Navy as a 0.5 inch model), Vickers & Maxim introduced one of the first cannon to have an hydraulic recoil absorbing mechanism. In 1900 they produced a small 75 mm cannon that used two cylinders mounted alongside the barrel, Vickers was involved in the production of numerous firearms
Meyer hardness test
The Meyer hardness test is a rarely used hardness test based upon projected area of an impression. This is a more fundamental measurement of hardness than other tests which are based on the surface area of an indentation. The principle behind the test is that the pressure required to test the material is the measurement of the hardness of the material. The mean pressure is calculated by dividing the load by the area of the indentation. The result is called the Meyer hardness, which has units of megapascals, an advantage of the Meyer test is that it is less sensitive to the applied load, especially compared to the Brinell hardness test. For cold worked materials the Meyer hardness is relatively constant and independent of load, for annealed materials the Meyer hardness increases continuously with load due to strain hardening. Based on Meyers law hardness values from this test can be converted into Brinell hardness values, the Meyer hardness test was devised by Prof. Eugene Meyer of the Materials Testing Laboratory at the Imperial School of Technology, Germany, circa 1908.
Tabor, The Hardness of Metals, Oxford University Press, ISBN 0-19-850776-3
Ceramography
Ceramography is the art and science of preparation and evaluation of ceramic microstructures. Ceramography can be thought of as the metallography of ceramics, the microstructure is the structure level of approximately 0.1 to 100 µm, between the minimum wavelength of visible light and the resolution limit of the naked eye. The microstructure includes most grains, secondary phases, grain boundaries, micro-cracks, most bulk mechanical, thermal and magnetic properties are significantly affected by the microstructure. The fabrication method and process conditions are indicated by the microstructure. The root cause of many ceramic failures is evident in the microstructure, Ceramography is part of the broader field of materialography, which includes all the microscopic techniques of material analysis, such as metallography and plastography. It is seldom used on whiteware ceramics such as sanitaryware, wall tiles, ceramographic microstructures Ceramography evolved along with other branches of materialography and ceramic engineering.
Alois de Widmanstätten of Austria etched a meteorite in 1808 to reveal proeutectoid ferrite bands that grew on prior austenite grain boundaries, geologist Henry Clifton Sorby, the father of metallography, applied petrographic techniques to the steel industry in the 1860s in Sheffield, England. French geologist Auguste Michel-Lévy devised a chart that correlated the properties of minerals to their transmitted color. Brinell invented the first quantitative hardness scale in 1900, smith and Sandland developed the first microindention hardness test at Vickers Ltd. in London in 1922. Buehler started the first metallographic equipment manufacturer near Chicago in 1936, frederick Knoop and colleagues at the National Bureau of Standards developed a less-penetrating microindention test in 1939. Struers A/S of Copenhagen introduced the electrolytic polisher to metallography in 1943, george Kehl of Columbia University wrote a book that was considered the bible of materialography until the 1980s. Kehl co-founded a group within the Atomic Energy Commission that became the International Metallographic Society in 1967, the preparation of ceramic specimens for microstructural analysis consists of five broad steps, embedding, grinding and etching.
The tools and consumables for ceramographic preparation are available worldwide from metallography equipment vendors, most ceramics are extremely hard and must be wet-sawed with a circular blade embedded with diamond particles. A metallography or lapidary saw equipped with a low-density diamond blade is usually suitable, the blade must be cooled by a continuous liquid spray. Embedding, to further preparation, the sawed specimen is usually embedded in a plastic disc,25,30 or 35 mm in diameter. A thermosetting solid resin, activated by heat and compression, e. g. mineral-filled epoxy, is best for most applications, a castable resin such as unfilled epoxy, acrylic or polyester may be used for porous refractory ceramics or microelectronic devices. The castable resins are available with fluorescent dyes that aid in fluorescence microscopy. The left and right specimens in Fig.3 were embedded in mineral-filled epoxy, the center refractory in Fig.3 was embedded in castable, transparent acrylic
Hardness
Hardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied. Some materials are harder than others, Hardness is dependent on ductility, elastic stiffness, strain, toughness and viscosity. Common examples of matter are ceramics, certain metals, and superhard materials. There are three types of hardness measurements, scratch and rebound. Within each of these classes of measurement there are individual measurement scales, for practical reasons conversion tables are used to convert between one scale and another. Scratch hardness is the measure of how resistant a sample is to fracture or permanent plastic deformation due to friction from a sharp object, the principle is that an object made of a harder material will scratch an object made of a softer material. When testing coatings, scratch hardness refers to the necessary to cut through the film to the substrate. The most common test is Mohs scale, which is used in mineralogy, one tool to make this measurement is the sclerometer.
Another tool used to make these tests is the pocket hardness tester and this tool consists of a scale arm with graduated markings attached to a four-wheeled carriage. A scratch tool with a rim is mounted at a predetermined angle to the testing surface. In order to use it a weight of mass is added to the scale arm at one of the graduated markings. The use of the weight and markings allows a known pressure to be applied without the need for complicated machinery. Indentation hardness measures the resistance of a sample to material deformation due to a constant compression load from an object, they are primarily used in engineering. The tests work on the premise of measuring the critical dimensions of an indentation left by a specifically dimensioned and loaded indenter. Common indentation hardness scales are Rockwell, Shore, rebound hardness, known as dynamic hardness, measures the height of the bounce of a diamond-tipped hammer dropped from a fixed height onto a material. This type of hardness is related to elasticity, the device used to take this measurement is known as a scleroscope.
Two scales that measures rebound hardness are the Leeb rebound hardness test, there are five hardening processes, Hall-Petch strengthening, work hardening, solid solution strengthening, precipitation hardening, and martensitic transformation. Hardness in the elastic range—a small temporary change in shape for a given force—is known as stiffness in the case of a given object and they exhibit plasticity—the ability to permanently change shape in response to the force, but remain in one piece
ASTM International
ASTM International is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products and services. Some 12,575 ASTM voluntary consensus standards operate globally, the organizations headquarters is in West Conshohocken, about 5 mi northwest of Philadelphia. ASTM, founded in 1898 as the American Section of the International Association for Testing Materials, predates other standards such as the BSI, IEC, DIN, ANSI, AFNOR. A group of scientists and engineers, led by Charles Benjamin Dudley formed ASTM in 1898 to address the frequent rail breaks affecting the fast-growing railroad industry, the group developed a standard for the steel used to fabricate rails. In 2014, it has changed the tagline to Helping our World Work better, now, ASTM International has offices in Belgium, China and Washington, D. C. Membership in the organization is open to anyone with an interest in its activities, standards are developed within committees, and new committees are formed as needed, upon request of interested members.
Membership in most committees is voluntary and is initiated by the members own request, members are classified as users, producers and general interest. The latter include academics and consultants, users include industry users, who may be producers in the context of other technical committees, and end-users such as consumers. In order to meet the requirements of antitrust laws, producers must constitute less than 50% of every committee or subcommittee, because of these restrictions, there can be a substantial waiting-list of producers seeking organizational memberships on the more popular committees. Members can, participate without a vote and their input will be fully considered. As of 2015, ASTM has more than 30,000 members, including over 1,150 organizational members, ASTM International has no role in requiring or enforcing compliance with its standards. The standards, may become mandatory when referenced by a contract, corporation. In the United States, ASTM standards have been adopted, by incorporation or by reference, in federal, state.
The National Technology Transfer and Advancement Act, passed in 1995, the Act reflects what had long been recommended as best practice within the federal government. Other governments have referenced ASTM standards Corporations doing international business may choose to reference an ASTM standard, International Organization for Standardisation Materials property Pt/Co scale Technical standard Media related to ASTM at Wikimedia Commons ASTM International
Vertical stabilizer
It is analogous to a skeg on boats and ships. On aircraft, vertical stabilizers generally point upwards and these are known as the vertical tail, and are part of an aircrafts empennage. If the vertical stabilizer was mounted on the underside, it would produce a positive feedback whenever the aircraft dove or banked, the trailing end of the stabilizer is typically movable, and called the rudder, this allows the aircraft pilot to control yaw. Often navigational radio or airband transceiver antennas are placed on or inside the vertical tail, in all known trijets, the vertical stabilizer houses the central engine or engine inlet duct. Vertical stabilizers, or fins, have used in automobiles, specifically in top level motor sports. A few aircraft models have a fin under the rear end. Normally this is small, or can fold sideways, to allow landing, the vertical stabilizer is mounted exactly vertically, and the horizontal stabilizer is directly mounted to the empennage. This is the most common vertical stabilizer configuration, a T-tail has the horizontal stabilizer mounted at the top of the vertical stabilizer.
It is commonly seen on aircraft, such as the Bombardier CRJ200, the Fokker 70, the Boeing 727, the Vickers VC10 and Douglas DC-9. T-tails are often incorporated on configurations with fuselage mounted engines to keep the horizontal stabilizer away from the engine exhaust plume, T-tail aircraft are more susceptible to pitch-up at high angles of attack. This pitch-up results from a reduction in the horizontal stabilizers lifting capability as it passes through the wake of the wing at moderate angles of attack and this can result in a deep stall condition. T-tails present structural challenges since loads on the stabilizer must be transmitted through the vertical tail. The cruciform tail is arranged like a cross, the most common configuration having the horizontal stabilizer intersecting the vertical tail somewhere near the middle, the PBY Catalina uses this configuration. Falconjets from Dassault always have cruciform tail, rather than a single vertical stabilizer, a twin tail has two. These are vertically arranged, and intersect or are mounted to the ends of the horizontal stabilizer, the Beechcraft Model 18 and many modern military aircraft such as the American F-14, F-15, and F/A-18 use this configuration. A variation on the tail, it has three vertical stabilizers.
An example of configuration is the Lockheed Constellation. On the Constellation it was done to give the maximum vertical stabilizer area while keeping the overall height low enough so that it could fit into maintenance hangars
Stainless steel
In metallurgy, stainless steel, known as inox steel or inox from French inoxydable, is a steel alloy with a minimum of 10. 5% chromium content by mass. Stainless steel is notable for its resistance, and it is widely used for food handling. Stainless steel does not readily corrode, rust or stain with water as ordinary steel does, however, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are various grades and surface finishes of stainless steel to suit the environment the alloy must endure, Stainless steel is used where both the properties of steel and corrosion resistance are required. Stainless steel differs from carbon steel by the amount of chromium present, unprotected carbon steel rusts readily when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by making it easier for more iron oxide to form, since iron oxide has lower density than steel, the film expands and tends to flake and fall away. In comparison, stainless steels contain sufficient chromium to undergo passivation and this layer prevents further corrosion by blocking oxygen diffusion to the steel surface and stops corrosion from spreading into the bulk of the metal.
Passivation occurs only if the proportion of chromium is high enough, Stainless steel’s resistance to corrosion and staining, low maintenance, and familiar lustre make it an ideal material for many applications. Storage tanks and tankers used to transport orange juice and other food are made of stainless steel. This influences its use in kitchens and food processing plants, as it can be steam-cleaned and sterilized. High oxidation resistance in air at ambient temperature is achieved with addition of a minimum of 13% chromium. The chromium forms a layer of chromium oxide when exposed to oxygen. The layer is too thin to be visible, and the metal remains lustrous, the layer is impervious to water and air, protecting the metal beneath, and this layer quickly reforms when the surface is scratched. This phenomenon is called passivation and is seen in other metals, corrosion resistance can be adversely affected if the component is used in a non-oxygenated environment, a typical example being underwater keel bolts buried in timber.
When stainless steel parts such as nuts and bolts are forced together, when forcibly disassembled, the welded material may be torn and pitted, a destructive effect known as galling. Galling can be avoided by the use of materials for the parts forced together, for example bronze and stainless steel. However, two different alloys electrically connected in a humid, even mildly acidic environment may act as a voltaic pile, nitronic alloys, made by selective alloying with manganese and nitrogen, may have a reduced tendency to gall. Additionally, threaded joints may be lubricated to provide a film between the two parts and prevent galling, low-temperature carburizing is another option that virtually eliminates galling and allows the use of similar materials without the risk of corrosion and the need for lubrication
Ultimate tensile strength
In other words, tensile strength resists tension, whereas compressive strength resists compression. Ultimate tensile strength is measured by the stress that a material can withstand while being stretched or pulled before breaking. In the study of strength of materials, tensile strength, compressive strength, some materials break very sharply, without plastic deformation, in what is called a brittle failure. Others, which are more ductile, including most metals, experience some plastic deformation, the UTS is usually found by performing a tensile test and recording the engineering stress versus strain. The highest point of the curve is the UTS. It is a property, therefore its value does not depend on the size of the test specimen. However, it is dependent on other factors, such as the preparation of the specimen, the presence or otherwise of surface defects, Tensile strengths are rarely used in the design of ductile members, but they are important in brittle members. They are tabulated for common materials such as alloys, composite materials, plastics, Tensile strength can be defined for liquids as well as solids under certain conditions.
Tensile strength is defined as a stress, which is measured as force per unit area, for some non-homogeneous materials it can be reported just as a force or as a force per unit width. In the International System of Units, the unit is the pascal, or, equivalently to pascals, Many materials can display linear elastic behavior, defined by a linear stress–strain relationship, as shown in the left figure up to point 3. Beyond this elastic region, for materials, such as steel. A plastically deformed specimen does not completely return to its original size, for many applications, plastic deformation is unacceptable, and is used as the design limitation. The reversal point is the stress on the engineering stress–strain curve. The UTS is not used in the design of static members because design practices dictate the use of the yield stress. It is, used for quality control, because of the ease of testing and it is used to roughly determine material types for unknown samples. The UTS is a common engineering parameter to design members made of material because such materials have no yield point.
Typically, the testing involves taking a sample with a fixed cross-sectional area. When testing some metals, indentation hardness correlates linearly with tensile strength and this important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers
Convair CV-240 family
The Convair CV-240 is an American airliner produced by Convair from 1947 to 1954, initially as a possible replacement of the ubiquitous Douglas DC-3. Although reduced in numbers through attrition, the Convairliners in various forms continue to fly into the 21st century, the design began its life in a requirement by American Airlines for an airliner to replace its Douglas DC-3s. Convairs original design, the unpressurised Model 110 was a twin-engine, low-wing monoplane of all-metal construction and it was powered by Pratt & Whitney R-2800 Double Wasp radial engines and had a tricycle landing gear and a ventral airstair for passenger boarding. The prototype Model 110, registration NX90653, first flew on July 8,1946, by this time, American had changed its requirements to require pressurization and deemed the design too small. The first prototype was used by Convair for development work for the 240 series before being broken up in 1947, to meet the requirements of airlines for a pressurized airliner, Convair produced a revised design—the Model 240.
This had a longer but thinner fuselage than the Model 110, the 240 first flew on March 16,1947. The Model 240 was followed by the Model 340 that had a fuselage, longer-span wings. The 340 first flew on October 5,1951, as the Super 240 evolved into the CV-340 and CV-440, the limit of piston-engine performance was reached, and future development centered on conversion to turboprop power. The first delivery of a production Convairliner was to American on February 29,1948, a total of 75 were delivered to American, with another 50 going to Western Airlines, Continental Airlines, Pan American Airways, KLM, Swissair and Trans Australia Airlines. A CV-240 was the first private aircraft used in a United States presidential campaign, in 1960, John F. Kennedy used a CV-240 named Caroline during his campaign. This aircraft is now preserved in the National Air and Space Museum, after aborted negotiations with TWA and Eastern for Super 240 orders, the production of the 240 series was temporarily halted. In response to a United inquiry, Convair redesigned the Super 240, United ordered 55, and more US orders came from Braniff, Delta and National.
Other orders came from abroad, and the CV-340 proved popular in South America, the CV-340 earned an enviable reputation for reliability and profitability, and was developed into the CV-440 Metropolitan, the final piston-engined variant of the Convairliners. Kelowna Flightcraft Air Charter, the major remaining operator of this model, used price for a Convair 240 in 1960 was around £40,000. Data from, General Dynamics Aircraft and their predecessors Convair Model 110 Unpressurized prototype with seats for 30 passengers,89 ft wingspan,71 ft length, powered by two 2,100 hp Pratt & Whitney R-2800-SC13G engines. Powered by two Pratt & Whitney R-2800 engines, Convair CV-240-21 Turboliner Turboprop-powered conversion fitted with Allison T38 engines. It became the first turboprop airliner to fly in the United States, but problems with the resulted in development being terminated. Convair CV-300 A conversion from a Convair CV-240 with two R-2800 CB-17 engines and nacelles as used on the CV-340, in 1977, a CV-300 was involved in an accident that killed three members and the manager of the rock group Lynyrd Skynyrd
Partnair Flight 394
Partnair Flight 394 was a chartered flight which crashed on 8 September 1989 off the coast of Denmark 18 km north of Hirtshals. All 50 passengers and 5 crew members on board the aircraft perished and it was the highest death toll of any aviation accident involving a Convair 580, and the biggest aeroplane accident in Denmark. It was caused by use of unapproved aircraft parts in repairs, the aircraft, registered LN-PAA, was a 36-year-old Convair CV-580 operated by the charter airline Partnair. The plane had switched owners several times and had various modifications, the aircraft had multiple previous registrations, N73128, EC-FDP, PK-GDS, HR-SAX, JA101C, N770PR and C-GKFT and had been rebuilt after a landing accident in 1978. The most significant modification was a change from piston engines to turboprop engines in 1960, a Canadian company that specialized in servicing Convairs was the owner of the aircraft before Partnair acquired it. LN-PAA was one of the most recently acquired aircraft in the Partnair fleet, at the time of the crash, there were 2 other Convair 580 in the Partnair fleet.
At the time of the accident Partnair was in financial difficulty, the Convair 580 aircraft was en route from Oslo Airport, Norway to Hamburg Airport, West Germany. The passengers were employees of the shipping company Wilhelmsen Lines who were flying to Hamburg for the ceremony of a new ship. Half of the employees of the head office were on board. Leif Terje Løddesøl, an executive of Wilhelmsen, said that the atmosphere in the company was very good prior to the accident flight. He said that some of the employees maybe had been to prior naming ceremonies, a regular employee on the flight, one of the top-performing employees in the company, had been asked to give the speech during the launching ceremony. Løddesøl said that it was not often that a person in the company was chosen to read the speech at the naming ceremony. The flight crew consisted of Captain Knut Tveiten and First Officer Finn Petter Berg and Berg were close friends who had flown together for years. Both pilots were experienced, with close to 17,000 flight hours each.
Berg was the companys Flight Operations Manager, before the flight, the crew found that one of the two main power generators had not worked since 6 September, and the mechanic who inspected the aircraft was unable to fix it. In the Norwegian jurisdiction an aircraft is allowed to take off if it has two operable sources of power. Also the aircrafts Minimum Equipment List required two operating generators, the first officer decided that he would run the auxiliary power unit throughout the flight so that the flight would have two sources of power and therefore be allowed to leave. The airport refused to let the flight go until the bill was paid
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