ductiility

8/11/2019 DuctiIlity

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Ductility-the ability of a material to undergo large plasticdeformation after yielding.

Tensile Strength

- the maximum force a member can carry beforeit fails.

Carbon Steel- a common material used in structures (99%iron, 1% carbon)

Deformation- the increase in the length of a bar (strain) as itstretches.

Elastic Behavior-if the load is removed the material'sdeformation will return to zero.

Ultimate Strength-the maximum load a material can withstand.

Brittle-when a material does not undergo plasticdeformation (ruptures without warning).

Compressive Strength-the maximum compressive force a member cancarry before it buckles.

Buckling-a failure that occurs when compression causes amember to bend sideways.

Rupture-failure that occurs when tension causes amember to tear into two pieces.

Yielding-when material undergoes large deformation

with little change in load.



Plastic Deformation-if the load is removed the deformation ispermanent.

Load

-the force (stress) put on a member to test itsstrength.

Load-Deformation Curve-shows how a member deforms and fails as theload is increased.

cross-sectional area-the surface area of the material exposed in across-section.

Modulus of ElasticityThe slope of the line in the linear elastic regioncreated by the stress on the object divided by thestrain.

Yield Point-the point on the load-deformation curve where

yielding begins.

Strength : It is the resistance by which materials oppose the deformation.

Stress : A measure of the average amount of force exerted per unit area.

where is the average stress. It is also known as engineering stress or nominal

stress. Fis the force acting on the area A.

Strain : The deformation of materials caused by the action of stress.

where is strain in measured direction, o is the original length of the material and is

the current length of the material

Hooke's Law: It states that for the materials loaded within elastic limits the stress isproportional to strain.

Total Stress : The resultant internal force which changes the size or shape of a body



which acted on by external forces.

Unit Stress : It is the stress per unit area.

Normal Stress : It is on a section. It is the stress which acts in a direction

perpendicular to section considered.

Ultimate Stress : The ratio of the maximum load which a specimen sustains to its

original area of the cross-section.

Elastic Limit : The maximum unit stress to which a material can be subjected and still

is able to return to its original form after removal of stress.

Yield Point : The unit stress at which the deformation first increases noticeably without

any increase in the applied load. It is always above the proportional limit.

Ultimate Strength : The highest unit stress it can sustain before rupturing.

Breaking Strength : The stress at which the material tested ruptures.

Modulus of Elasticity (E) : The constant that expresses the ratio of unit stress to unitdeformation for all values unit stress not exceeding the proportional limit of material. It

is also called as Modulus of Rigidity.

Factor of Safety : The ratio of ultimate strength of the material to the allowablestress.

Elasticity : The ability of a material to deform and return to its original shape afterremoval of the load. The amount of deformation is called Strain.

Ductility : The ability of a material to undergo large permanent deformations intension i.e., property which enables a material to be beaten or rolled into thin sheets.

Malleability : The ability of a material to undergo large permanent deformation incompression or property which enables a material to be beaten or rolled into thin

sheets. This property is important in metalworking. Gold is the most malleable metalfollowed by aluminium.

Toughness : The ability of a material to withstand high unit stress along with great

unit deformation without fracture.

Stiffness : The ability of a material to resist deformation or deflection under stress.

Hardness : The ability of a material to resist very small indentation abrasion and

plastic deformation. In other words, high resistance of a material to various kinds ofshape change when force is applied.

Creep (Flow of Metals) : The tendency of a solid material to slowly move or deformpermanently under the influence of stresses. It always increases with temperature.



Creep deformation does not occur suddenly upon the application of stress. It is time-dependent deformation.

STRENGTH OF MATERIALS – deals with the relation between externally applied force and their

internal effects on the bodies. The bodies are not rigid since it mostly concerned in

deformation.

AXIAL FORCE – this component measures the pulling(or pushing) action perpendicular to the

section. A pull represent a tensile force that tends to elongate the member, whereas a push is a

compressive force that tends to shorten it. It is often denoted by P.

SHEAR FORCES – these are components of the total resistance to sliding the portion to one side

of the exploratory section past the other. The resultant shear force is usually designated by V,

and its components by Vy and Vx to identify their directions.

TORQUE – This component measure the resistance to twisting the member and is commonly

given the symbol T.

BENDING MOMENT – This component measure the resistance to bending the member about

the y or z axes and are often denoted merely by My or Mz.

SIMPLE STRESS – the condition under which the stress is constant or uniform.

STRESS – Define as the division of differential load dP by the differential area over which it acts

NORMAL STRESS – classified as tensile and compressive stress

TANGENTIAL STRESS – classified as shearing stress

SINGLE SHEAR – one cross-sectional area

DOUBLE SHEAR – two cross-sectional area

DIRECT SHEAR – shear occurs over an area parallel to the applied load

INDUCED SHEAR – shear occurs over sections inclined with the resultant load

Bearing stress - is the contact pressure between the separate bodies. It differs from

compressive stress, as it is an internal stress caused by compressive forces.

Tangential stress – it acts tangent to the surface of the cylinder

Longitudinal stress –

it acts parallel to the longitudinal axis of the cylinder

Gage length – values of the load and the elongation in a specified length

Elongation – longness

Strain (deformation) – it is the elongation over the length in which it was measured

Proportional limit – shows the stress-strain diagram to be a straight line.



Elastic limit – is the stress beyond which the material will not return to its original shape when

unloaded but will retain a permanent deformation called permanent set.

Yield point – is the point at which there is an appreciable elongation or yielding of the material

without any corresponding increase of load; indeed, the load may actually decrease while the

yielding occurs.

Yielding strength – is closely associated with the yield point

Rupture strength – is the stress at failure

Necking – a phenomenon that caused an error

Allowable stress or working stress – is the maximum safe stress a material may carry.

Poisson’s ratio – denoted by v and defined by:

V=-ey/ex =-ez/ex

Where ex, is the strain due only to stress in the x direction, and ey and ez are the strains

induced in the perpendicular directions

Thermal stress – internal stress created cause by internal force or temperature change

Flanged bolt coupling – connection between two shafts, consists of flanges rigidly attached to

the ends of the shafts and bolted together. The torque is transmitted by the shearing force P

created in the bolts.

ductiility

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