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Machine Design Definitions |
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Stress : Stress is a measure of the average amount of force exerted per unit area.
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Bending Stress : It characterizes the behavior of a structural element subjected to an external load applied
perpendicular to the axis of the element.
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Tolerance : It is the maximum permissible variation in size of the part.
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Clearance : The actual difference in the size of the mating parts is called clearance or interference.
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Allowance : The difference between basic dimensions of the mating parts is called allowance.
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Machine Vibrations : When variable forces acts on elastic parts in machinery, vibratory motions arise. Generally
these motions are not desirable but in some cases such as vibratory conveyors concrete vibrators, etc are deliberately
designed into the machine.
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Free Vibrations : The vibrations are free vibrations when no external force is acting.
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Strain Energy : Strain energy is released when the constituent atoms are allowed to rearrange themselves
in a chemical reaction or a change of chemical conformation.
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Endurance Limit or Fatigue Limit : Fatigue limit, endurance limit, and fatigue strength are all expressions
those are used to describe a property of materials.
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Fatigue Strength : Fatigue strength can be increased by selecting suitable material, cold working shot peening, under
stressing and overressing. Also called endurance strength.
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Notch Sensitivity : It is a measure of the reduction in strength of a metal which is caused by the presence of
a notch. It is defined as the degree to which the theoretical effect of stress concentration is actually reached.
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Modes of Failure : There are many different kinds of mechanical failure such as overload, impact, fatigue, creep,
rupture, stress relaxation, stress corrosion cracking, corrosion fatigue and so on.
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Keys : A key is defined as a that is piece inserted between the joints of two parts to prevent their relative
movement or it is defined as the piece of steel which is used to fasten pulleys, levers, crank arms, etc. to a shaft.
It is designed to avoid relative motion of a shaft and the member to which it is connected.
The type of keys : square, flat, kennedy, woodruff, round, spline fitting, etc.
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Riveted Joints : They make a connection which has strength to avoid failure of the joint and tightness to
prevent leakage.
A joint which describes a technique for joining two pieces of material by overlapping them is called Lap Joint.
A joint that is a joinery technique in which two members are joined by simply butting them together is called Butt Joint.
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Chain Riveting : The riveting method which consists of rivets one behind the other in rows along the seam is
called chain riveting.
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Zig-Zag Riveting : The riveting method in which the rivets in adjacent rows are not opposite to each other but
these are staggered.
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Diamond Riveting : The riveting method in which the rivets in adjacent rows may not be opposite to each other,
but outermost row contains only one rivet.
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