mekanika teknik
DESCRIPTION
Mekanika TeknikTRANSCRIPT
Engineering Mechanics Statics
EEPIS
2012
Objectives
• To understand how to analyze the strength of the structures and materials in order to make good design in engineering
Missions
• To understand the resultant of force system
• To understand the free body diagram and equilibrium eq.
• To understand the types of structure
• To determine the center of mass, inertial moment, and center of force
• To determine internal load
• To understand the mechanical properties of material
• To determine axial load, torque, bending moment, & deformation
Logistics
• Hibbeler, R C., 2004. Statics and Mechanics of Materials, Prentice Hall, Inc
• Merriam, J L, Kraige L G., 2002. Engineering Mechanics Statics, John Wiley and Sons, Inc.
• Hibbeler, R C., 2007. Engineering Mechanics Statics, Prentice Hall, Inc
• Hibbeler, R C, 2011, Mechanics of Materials, Prentice Hall, Inc
Parameters
• Teamwork is recommended
• Mark:– Mid Exam : 25%– Final Exam : 40%– Assignment : 35%
• Cheating is intolerable
1.1 WHAT IS MECHANICS OF MATERIALS ?
1.2 THE FUNDAMENTALS CONCEPTS OF DEFORMABLE-BODY MECHANICS
1.3 PROBLEM - SOLVING PROCEDURES
1.4 REVIEW OF STATIC EQUILIBRIUM ; EQUILIBRIUM OF DEFORMABLE BODIES
1.5 PROBLEMS
1.1 WHAT IS MECHANICS OF MATERIALS
• Mechanics : branch of physical science concerned with the
condition of rest or motion of bodies due to forces
• Statics : mechanics of bodies at rest
• Dynamics : mechanics of bodies in motion
• Statics and dynamics applied for particles and rigid bodies
• Static and dynamics are also fundamental to mechanics of
materials
• Mechanics of materials = strength of materials = mechanics of
solids = mechanics of deformable bodies
1.1 WHAT IS MECHANICS OF MATERIALS (Cont’)
• Deformable bodies is a solid that changes size and/or shape
due to loads or temperature applied
• An example of a deformable body is the diving board
• Diving board change size and/or shape due to the weight of the
diver
• Deformation can be small, invisible to naked eyes
1.1 WHAT IS MECHANICS OF MATERIALS (Cont’)
• Statics can provide the reaction at A and B, if W, L1 , L2 are given
• Mechanics of materials can answer to the following questions :
- W which would cause the diving board to break, and
where it would occur
- the relation of C and W
- would a taper board be ‘better’ than constant thickness
- would fiber glass be preferable than aluminum
1.2 THE FUNDAMENTAL CONCEPTS OF DEFORMABLE-BODY MECHANICS
• Three fundamental concepts :
1. The equilibrium conditions must be satisfied
2. The geometry of deformation must be described
3. The material behavior (i.e. force-temperature-deformation relationship) must be characterized
Equilibrium :
• Principles of statics equations of equilibrium are fundamental
to the study of deformable body mechanics
Geometry of Deformation, including
• Definition of extensional strain and shear strain
• Simplification and idealization (e.g. rigid member, fixed support,
displacements are small)
• Connectivity of members, or geometric compability
• Boundary condition and other constraint
1.3 PROBLEM- SOLVING PROCEDURE
1. Select the system of interest
2. Reduce the real system to an idealized model
3. Convert the idealized model to a mathematical model
4. Perform a test to compare predicted responses to the behavior of
actual system
5. If prediction does not agree with prediction, make changes,
repeat step 1 - 4
• Diving board deformable
• Support rigid
• Diving board BD rigid
• Support deformable
FREE-BODY DIAGRAM (FBD)
• Isolate body of interest (including from it supports)
• Indicate all applied loads
• Show unknown forces and couples at support or connection to
other bodies
• Label significant points and include significant dimensions
SUPPORT REACTION AND MEMBER CONNECTIONS
A support gives reaction and also enforces constraint
1.4 REVIEW OF STATIC EQUILIBRIUM
Equation of equilibrium
• F = 0
(M)o = 0
• For a set of rectangular Cartesian axes, x, y, z
Fx = 0 ( Mx)o = 0
Fy = 0 ( My)o = 0
Fz = 0 ( Mz)o = 0
• Statically determinate : number of unknown = number of
independent equilibrium equation
• Statically indeterminate : number of unknown > number of
independent equilibrium equation
• Redundant : can be removed without destroying the equilibrium
MATERIAL BEHAVIOR
• Also termed constitutive behavior of materials: described the
material behavior (force-temperature-deformation relationships)
• obtained by conducting experiments
EXTERNAL LOADS
• Concentrated loads, including point forces (F) and couples (F.L)
• Line loads (F/L)
• Surface loads (F/L2)
• Body forces (F/L3)
INTERNAL RESULTANTS
• Internal resultants : forces couples that are internal to the original body
• Internal resultants can be obtained by virtually cutting the structure at the interested location
• Six internal resultants resulting from general loading
S-3A Full Scale Static Test. (http://www.voughtaircraft.com/ProdProg/qtls/testOps/StructuresTestLab/testHist.htm#fullScaleAir
S-3A Full Scale Static Test. (http://www.voughtaircraft.com/ProdProg/qtls/testOps/StructuresTestLab/testHist.htm#fullScaleAir