Rockwell Hardness Test

The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load FO usually I 0 kgf. When equilibrium has been reached, an indicating device, which follows the movements of the indenter and so responds to changes in depth of penetration of the indenter is set to a datum position. While the preliminary minor load is still applied an additional major load is applied with resulting increase in penetration . When equilibrium has again been reach, the additional major load is removed but the preliminary minor load is still maintained. Removal of the additional major load allows a partial recovery, so reducing the depth of penetration. The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

H R = E - e

FO = preliminary minor load in kgf

F1 = additional major load in kgf

F = total load in kgf

e = permanent increase in depth of penetration due to major load Fl measured in units of 0.002 mm

E = a constant depending on form of indenter: I 00 units for diamond indenter, 130 units for steel

ball indenter

HR = Rockwell hardness number

D = diameter of steel ball

FILLET WELD FRACTURE TEST

FILLET WELD FRACTURE TEST Object : To break the joint through the weld to permit examination of the fracture surfaces for flaws and to check root penetration and fusion. Method: The specimen is cut to length and a saw cut, normally 2 mm deep, is made along the center of the weld face. The specimen is fractured by bending or hammer blows. Reporting Results: Thickness of parent material. Throat thickness and leg length. Location of fracture. Appearance of joint after fracture. Depth of penetration / lack of penetration or fusion.

CHARPY V NOTCH IMPACT TEST

CHARPY V NOTCH IMPACT TEST Object : To determine the amount of energy absorbed in fracturing a standardized test piece at a specified temperature. Method : A machined, notched specimen is broken by one blow from a pendulum. Because scatter occurs in the results, at least three specimens are used to assess the joint represented. Testing is carried out at a temperature specified in the appropriate application standard. Reporting Results: Location and orientation of the notch. Testing temperature. Energy absorbed in joules. Description of fracture appearance. Location of any defects. The Charpy impact test, measured in joules, is an assessment of TOUGHNESS. Transition temperature (curve) in steel.

Part - 6 Most commonly asked Mechanical Interview Questions with answer

Most commonly asked Mechanical Interview Questions 1. Why Entropy decreases with increase in temperature? Ans. ds=dQ/T Entropy is inversely proportional to the temperature so, as temp. Increases, entropy decreases. 2. Why different types of sound are produced in different bikes, though they run on SI Engines? Ans. Engine specifications are different in different manufactures like as Bore Diameter (CC), Ignition timing. Also the exhaust passage takes more responsible for sound. 3. How much Watt means 1Hp? Ans. 746.2 Watt 4. Explain Bicycle Rear Wheel Sprocket working? Ans. Rear wheel sprocket works under the principle of ratchet and pawl. 5. Definition of Octane Number and Cetane Number? Ans. Octane No.- Octane number is defined as the percentage, by volume, of iso octane in the mixture of iso octane and h-heptane. It is the measure of rating of SI engine. Cetane No.- Cetane number i

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