6. Brittleness.
It is the property of a material opposite to ductility. It is the property of breaking of a material with little permanent distortion. Brittle materials when subjected to tensile loads, snap off without giving any sensible elongation. Cast iron is a brittle material.
7. Malleability.
It is a special case of ductility which permits materials to be rolled or hammered into thin sheets. A malleable material should be plastic but it is not essential to be so strong. The
malleable materials commonly used in engineering practice (in order of diminishing malleability) are lead, soft steel, wrought iron, copper and aluminium.
8. Toughness.
It is the property of a material to resist fracture due to high impact loads like hammer blows. The toughness of the material decreases when it is heated. It is measured by the amount of energy that a unit volume of the
material has absorbed after being stressed upto the point of fracture. This property is desirable in parts subjected to shock and impact loads.
9. Machinability. It is the property of a material which refers to a relative case with which a material can be cut. The machinability of a material can be measured in a number of ways such as comparing the tool life for cutting different materials or thrust required to remove the material at some given rate or the energy required to remove a unit volume of the material. It may be noted that brass can be easily machined than steel.
10. Resilience. It is the property of a material to absorb energy and to resist shock and impact loads. It is measured by the amount of energy absorbed per unit volume within elastic limit. This property is essential for
spring materials.
FIRST MULTICOLOUR EDITION
A TEXTBOOK OF
Machine
Design
(S.I. UNITS)
[A Textbook for the Students of B.E. / B.Tech.,
U.P.S.C. (Engg. Services); Section ‘B’ of A.M.I.E. (I)]
R.S. KHURMI
J.K. GUPTA
EURASIA PUBLISHING HOUSE (PVT.) LTD.
RAM NAGAR, NEW DELHI-110 055
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