Elasticity (Physics)
Monday, November 26, 2012 | Unknown
Elasticity is a branch of physics which
studies the properties of elastic materials. A material is said to be elastic
if it deforms under stress (e.g., external forces). Thus, elasticity is a physical property of materials which return to their original shape and size after the stress that caused their deformation is no longer applied.
Each object having character to be elastic and
inelastic which divided into:
- Perfectly Elastic Body:
- Perfectly Inelastic / Plastic Body:
When experience force,
there some condition happen. Changes in the shape and size of the
object depends the direction and the
location of external forces is given. There are several type of deformation
depend on the characteristic of object’s elasticity , such as stress (stress)
and strain (strain).
Basically there are two types:
- Tensile stress:
If there is an increase in the length or extension of the body in the
direction of the body in the direction of force applied.
- Compression stress: If there is decrease in length of the wire or compression of the body due to force applied
Strain
Strain is a measure of how far The
object changes its shape. Stress is
applied to the object from the outside, while the strain is the response of
object against stress. In the elastic region, the magnitude stress proportional
to the strain.
Elasticity
Modulus
The coefficient that relates a particular type of
stress to the strain that results is called a modulus(plural, moduli).
Elastic
Modulus=Stress/Strain
In a very
real sense it is a comparison of what is done to a solid object (a force is
applied) and how that object responds (it deforms to some extent)
Elastic modulus are properties of materials, not
objects. There are three basic types of stress and three associated modulus
A.
Young
Modulus
Young’s
Modulus measures the resistance of a solid to a change in its length. The
description of the elastic properties of linear objects like wires, rods,
columns which are either stretched or compressed, a convenient parameter is the
ratio of the stress to the strain, a parameter called the Young's modulus of
the material. Young's modulus can be used to predict the elongation or
compression of an object as long as the stress is less than the yield strength
of the material.
B. Shear
Modulus
Shear
Modulus measures the resistance to
motion of the planes of a solid sliding past each other. The shear modulus describes
the material's response to shearing strains (like cutting it with dull
scissors).The shear modulus is concerned with the deformation of a solid when
it experiences a force parallel to one of its surfaces while its opposite face
experiences an opposing force (such as friction).
C. Bulk
Modulus
Bulk
Modulus which measures the resistance of solids or liquids to changes in their
volume
The bulk elastic
properties of a material determine how much it will compress under a given
amount of external pressure. The ratio of the change in pressure to the
fractional volume compression is called the bulk modulus of the material.
Hooke’s
Law
Hooke's law of elasticity is an approximation that states that the
extension of a spring is in direct proportion with the load applied to it. Many materials obey this law
as long as the load does not exceed the material's elastic limit. Materials for which Hooke's law is a useful approximation are known as linear-elastic or "Hookean" materials. Hookean
materials is a necessarily broad term that may include the work of muscular
layers of the heart. Hooke’s law does have its
limits though. If a force is too great, the elastic limit will be exceeded.
After the elastic limit is an area called the plastic region. The object may be
stretched further in this area, however it will not returned to its original
shape and will be permanently distorted. Eventually, the object will reach its
breaking point. If the force applied is within the elastic limit, the object
will return to its original shape.
Hooke's law in simple terms says that stress is directly
proportional to strain. Mathematically, Hooke's law states that
F= -kx
where
x = the displacement of the spring's end from its equilibrium position (a distance in SI units:
metres);
F = the restoring force exerted by the spring
on that end (in SI units: N or kg·m/s2)
k = a constant called the rate or spring
constant (in SI units: N/m or
kg/s2).
When this
holds, the behavior is said to be linear.
If shown on a graph, the line should show a direct
variation.
There is a negative sign on the right hand side of the equation because the
restoring force always acts in the opposite direction of the displacement (for
example, when a spring is stretched to the left, it pulls back to the right)
The elastic limit
The elastic limit of a substance is
defined as the maximum stress that can be applied to the substance before it
becomes permanently deformed. It is possible to exceed the elastic limit of a
substance by applying sufficiently large stress, as seen in in the figure
Initially a stress strain curve is a
straight line. As the stress increases, however the curve is no longer a
straight line.When the stress exceeds the elastic limit the object is
permanently distorted and it does not return to its original shape after the
stress is removed.
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3 comments:
materi elastisitas disampaikan secara jelas dan lengkap. Hal-hal yang dibahas seperti modulus elastisitas, tegangan, regangan dan beberapa yang lain. Ada beberapa bagian yang ditandai dengan garis bawah, apakah itu bertujuan untuk menandai hal-hal yang penting atau tidak sengaja dibuat.
Terima Kasih, garis bawah itu dikarenakan ada beberapa materi yang saya ambil dari Wikipedia, tetapi selebihnya saya kombinasikan dengan pemahaman saya :)
thank you for those reference about elasticity
you wrote it thickly and completely
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