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Showing posts from January, 2021

Heat Treatment of Alloys

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  What is an Alloy? Since metals are insoluble in water, alcohol; they are mixed with other metals in molten state which upon cooling solidifies to a solid mixture called an Alloy. This solid state mixture is also referred as a homogeneous liquid mixture. Alloys are formed by mixing a metal with metal or a metal with a non metal. From the above explanation it is clear that an alloy contains atleast one metal. What are the properties of an alloy? Alloys are harder, less malleable. They possess low melting points, low electrical conductivity. They resist corrosion and actions of acids. What is the purpose of alloying metals? To increase the hardness of the metal To lower the melting points of metals. To resist the corrosion of the metal. To modify the chemical activity of the metal. To modify the colour of the metal. To get good casting of metal. Effects or Functions of Alloying Elements: Addition of small amount of certain metals imparts some special properties like hardness, tensile st

Ultrasonic testing Couplants

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 A study on the couplant effects in contact ultrasonic testing. The primary purpose of a couplant is to provide a suitable sound path between the transducer and the test surface.Ultrasonic Testing couplants usage can be seen here A couplant must effectively wet or totally contact both surfaces of the transducer and the test part. The couplant must exclude all air from between the surfaces as air is a very poor conductor of sound. The couplant fills in and smoots out irregularities on the surface of the part. The couplant aids in the movement of the transducer over the surface in contact testing. The practical couplant must be easy to apply and easy to remove. It must also be harmless to the part surfaces. How to Pick the Right Ultrasonic Couplant for Your Application? Oil or water mixed with Glycerin (2 parts water and 1 Part glycerin) are commonly used couplants. Even wallpaper paste has advantages as couplant. Heavier couplants, such as Grease or heavy Oil can be used

Rebound Hammer Test-Non Destructive testing on Concrete

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  Non destructive testing for concrete Non Destructive Testing is the process of detecting the quality without destructing the material or without changing its actual properties. Rebound Hammer is also called as Schmidt hammer or Swiss Hammer or Concrete hammer test. This NDT method is used to detect the strength of Concrete Slab or rock, by identifying the hardness or elastic property. Principle of Rebound Hammer Test. Schmidt’s hammer test is based on the principle of “rebound of a spring loaded mass depends on the hardness of the concrete mass on which the mass strikes”. This rebound distance of the rebounded Plunger mass is noted down in the graduated scale as Rebound number / rebound  index. The graph in the body of hammer is used to found out the respective compressive strength. The concrete with low energy and low stiffness absorbs more energy from plunger and produces a low rebound value on the scale. Objective of Hammer rebound test : To a