definitions

Question 1

Alloy

Answer 1

A metallic substance that is composed of two or more elements

Question 2

Anisotropic

Answer 2

Exhibiting different values of a property in different crystallographic directions

Question 3

Annealling

Answer 3

A generic term used to denote a heat treatment in which the microstructure and, consequently, the properties of a material are altered. Frequently refers to a heat treatment whereby a previously cold-worked metal is softened by allowing it to recrystallize.

Question 4

Charpy Test

Answer 4

A test used to measure the impact energy or notch toughness of a standard notched specimen. An impact blow is imparted to the specimen by means of a weighted pendulum

Question 5

Design Stress

Answer 5

Produce of the calculated stress level (on the basis of estimated load) and a design factor (which has a greater value than unity). Used to protect against unanticipated failure.

Question 6

Drawing

Answer 6

A forming technique used to fabricate metal wire and tubing. Deformation is accomplished by pulling the material through a die by means of a tensile force applied on the exit side

Question 7

Ductility

Answer 7

A measure of a material’s ability to undergo appreciable plastic deformation before fracture; it may be expressed as percentage elongation(%EL) or percentage reduction in area (%RA) from a tensile test.

Question 8

Elastic deformation

Answer 8

Deformation that is non-permanent - that is, totally recovered upon release of a mechanical stress.

Question 9

elastic recovery

Answer 9

Non-permanent deformation recovered or regained upon release of a mechanical stress.

Question 10

Extrusion

Answer 10

A forming technique by which a material is forced, by compression, through a die orifice.

Question 11

Fatigue

Answer 11

Failure, at relatively low stress levels, of structures that are subjected to fluctuating and cyclic stresses.

Question 12

Forging

Answer 12

Mechanical forming of a metal by heating and hammering

Question 13

Fracture toughness

Answer 13

The measure of a material’s resistance to fracture when a crack is present.

Question 14

Hardness

Answer 14

The measure of a material’s resistance to deformation by surface indentation or by abrasion

Question 15

Hot working

Answer 15

Any metal forming operation performed above a metal’s recrystallization temperature.

Question 16

Impact energy

Answer 16

A measure of the energy absorbed during fracture of a specimen of standard dimensions and geometry when subjected to very rapid (impact) loading. Charpy impact testing is one test to measure this parameter. It is important in assessing the ductile-to-brittle transition behaviour of a material.

Question 17

Modulus of elasticity

Answer 17

The ratio of stress to strain when deformation is totally elastic; also a measure of the stiffness of a material.

Question 18

Plastic deformation

Answer 18

Deformation that is permanent or non-recoverable after release of the applied load. It is accompanied by permanent atomic displacements.

Question 19

poissons ratio

Answer 19

For elastic deformation, the negative ratio of lateral and axial strains that result from an applied axial stress

Question 20

Powder Metallurgy

Answer 20

The fabrication of metal pieces having intricate and precise shapes by the compaction of metal powders, followed by a densification heat treatment.

Question 21

residual stress

Answer 21

A stress that persists in a material free of external forces or temperature gradients.

Question 22

Rupture

Answer 22

Failure accompanied by significant plastic deformation; often associated with Creep failure.

Question 23

Engineering strain

Answer 23

The change in gauge length of a specimen (in the direction of an applied stress) divided by its original gauge length.

Question 24

True strain

Answer 24

he natural logarithm of the ratio of instantaneous gauge length to original gauge length of a specimen being deformed by a uniaxial force.

Question 25

Stress concentration

Answer 25

The concentration or amplification of an applied stress at the tip of a notch or small crack

Question 26

Engineering stress

Answer 26

The instantaneous load applied to a specimen divided by its cross-sectional area before any deformation.

Question 27

True stress

Answer 27

The instantaneous applied load divided by the instantaneous cross-sectional area of a specimen.

Question 28

Tensile strength

Answer 28

The maximum engineering stress, in tension, that may be sustained without fracture. Often termed Ultimate Tensile Strength (UTS).

Question 29

Toughness

Answer 29

A mechanical characteristic that may be expressed in three contexts: 1) the measure of a material’s resistance to fracture when a crack (or other stress concentrating defect) is present; 2) the ability of a material to absorb energy and plastically deform before fracturing; and 3) the total area under the material’s tensile engineering stress-strain curve taken to fracture.

Question 30

Wrought alloys

Answer 30

A metal alloy that is relatively ductile and amenable to hot working or cold working during fabrication.

Question 31

Yielding

Answer 31

The onset of plastic deformation.

Question 32

Yield strength

Answer 32

The stress required to produce a very slight yet specified amount of plastic strain; a strain offset of 0.002 is commonly used.