Deformable Body Mechanics Engr.Saeed Ahmed Maitlo Lecturer Institute of Biomedical Technology LUMHS Jamshoro

Applied Mechanics Rigid Body Mechanics StaticsDynamicsKinematicsKinetics Deformable Body Mechanics ElasticityPlasticityViscoelasticity Fluid Mechanmics LiquidsGases

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.

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

Elasticity The beam can bend to conform to the constraints of the supports.

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.

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.

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. 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.

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).

BASIC CONCEPTS Engineering mechanics is based on Newtonian mechanics in which the basic concepts are LengthTimeMass These are absolute concepts because they are independent of each other Length: is a concepts for describing size quantitatively

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.

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).

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; 1000*0.5= Answer = 50 newtons

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

Presentation topics laws of triangle. Parallelogram. Parallelogram. Polygon forces.