Applied Mechanics

1
(No Transcript)
2
Deformable Body Mechanics

• Engr .Saeed Ahmed Maitlo
• Lecturer
• Institute of Biomedical Technology LUMHS Jamshoro

3
Applied Mechanics

• Rigid Body Mechanics
• Statics
• Dynamics
• Kinematics
• Kinetics
• Deformable Body Mechanics
• Elasticity
• Plasticity
• Viscoelasticity
• Fluid Mechanmics
• Liquids
• Gases

4
Deformable Body Mechanics

• The mechanics of deformable bodies is the field
  that is concerned with the deformability of
  objects. An elastic body is defined as one in
  which all deformations are recoverable upon
  removal of external forces. this feature of some
  materials can easily be visualized by observing a
  spring or a rubber band.
• If you stretch (deform) a spring and then release
  it (remove the applied force), it will resume
  its original (unreformed) size and shape.

5

• A plastic body ,on the other hand, undergoes
  permanent (unrecoverable) deformations.
• Again use a spring apply a large force on spring
  so as to stretch the spring extensively, and then
  release it. the spring will bounce back, but
  there may be increase in its length.
• Note that depending on the extent and duration of
  applied forces, a material may exhibit elastic or
  elastoplastic as in the case of spring

6
Elasticity
The beam can bend to conform to the constraints
of the supports.
7
Elasticity vs. Plasticity
Elastic You can bend it, but it will come right
back when you remove the external force (like a
spring). Plastic You can bend it, and it will
stay where it left off (like soldering
wire). Some materials tend to behave elastically,
some plastically, but. Almost all materials will
have both behaviors. Small deflection
elastic. Large deflection plastic.
8
VISCOELASTICITY

• First define what is known as a fluid. in
  general, materials are classified as either solid
  or fluid. When an external force is applied to a
  solid body, the body will deform will certain
  extent. the continuous application of the same
  force will not necessarily deform the solid body
  continuously.

9

• on the other hand , a continuously applied force
  on a fluid body will cause a continuous
  deformation (flow).viscosity is a fluid property
  that is quantitative measure of resistance to
  flow.
• In nature there are some materials that have both
  fluid and solid properties. the term viscoelastic
  is used to refer to the mechanical properties of
  such materials exhibit viscoelastic properties.

10
Elasticity vs. Viscoelasticity
Elastic Force is proportional to deflection
(e.g. a spring). Viscoelastic Force is
proportional deflection AND to rate of deflection
(e.g. silly putty). Viscous Force is
proportional to deflection only (e.g. a shock
absorber or a fluid).
11
BASIC CONCEPTS

• Engineering mechanics is based on Newtonian
  mechanics in which the basic concepts are
• Length
• Time
• Mass
• These are absolute concepts because they are
  independent of each other
• Length is a concepts for describing size
  quantitatively

12

• Time is a concepts for ordering the flow of
  events.
• Mass is the property of all matter and is the
  quantitative measure of inertia. inertia is the
  resistance to the change in motion of matter.

13
Newton's Second Law

• Acceleration is produced when a force acts on a
  mass. The greater the mass (of the object being
  accelerated) the greater the amount of force
  needed (to accelerate the object).

14
Example

• Mike's car, which weighs 1,000 kg, is out of gas.
  Mike is trying to push the car to a gas station,
  and he makes the car go 0.05 m/s/s. Using
  Newton's Second Law, you can compute how much
  force Mike is applying to the car.
• F ma 10000.5
• Answer 50 newtons

15
Newton's Third Law

• Newton's third law states that to every body
  action there is always an equal reaction, and
  that the force of action

16
Presentation topics

• laws of triangle.
• Parallelogram.
• Polygon forces.