A perusal of the broken parts in almost any scrap yard will reveal that the majority of failures occur at stresses below the yield strength. This is a result of the phenomenon called fatigue which has been estimated to be responsible for up to 90% of the in-service part failures which occur in industry. If a bar of steel is repeatedly loaded and unloaded at say 85% of its’ yield strength, it will ultimately fail in fatigue if it is loaded through enough cycles.
Quiz: Heat Treatment - Quenching & Tempering
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Conventional heat treatment procedures for producing martensitic steels generally involve continuous and rapid cooling of an austenitized specimen in some type of quenching medium, such as water, oil, or air. The properties of a steel that has been quenched and then tempered depends largely on the rate of cooling and tempering times and temperatures. During the quenching heat treatment, the specimen can be converted to a variety of microstructures including soft and ductile spheroidite to hard and brittle martensite. The production of pearlitic and bainitic steels is lower in cost and suffices for most applications. Martensitic steels must be tempered prior to use due to their extreme brittleness. A range of heat treatments producing a variety of microstructures and mechanical properties will be investigated in this experiment beginning with a set of initially equivalent samples of SAE 1040 steel. Pearlite, Bainite and Martensite will all be produced through variations in the cooling rates of initially austenized samples.
Quiz: Precipitation Hardening of Aluminum Alloys
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The strength and hardness of some metal alloys may be enhanced by the formation of extremely small
uniformly dispersed particles of a second phase within the original phase matrix; this must be accomplished
by appropriate heat treatment.
Quiz: Mechanical Testing- Tensile Testing
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The mechanical properties of a material are directly related to the response of the material when it's subjected to mechanical stresses. Since characteristic phenomena or behavior occur at discrete engineering stress and strain levels, the basic mechanical properties of a material are found by determining the stresses and corresponding strains for various critical occurrences.
Quiz: Mechanical Testing- Impact & Hardness Testing
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The mechanical properties of materials are ascertained by performing carefully designed laboratory experiments that replicate, as nearly as practical, the service conditions.
The X-Ray diffraction technique is used to determine the crystal structure and interatomic spacing of crystallinesamples through constructive interference of reflected x-ray beams.
Bragg's Law and X-Ray diffraction data, in combination with the expressions for interatomic spacing in terms of the lattice parameter and Miller indices for acrystal, can be utilized to identify crystal structures, determine lattice constants, and locate defects within astructure.
