INTRODUCTION:
Mechanics – is a physical science that deals with the
behavior of bodies under the influence of forces
Categories:
* Mechanics of Rigid Bodies
* Mechanics of Deformable Bodies
* Mechanics of Fluids
Mechanics of Deformable
- deals with how forces
with the deformations
distributions
- these internal forces
which could result in
Bodies
are distributed inside bodies and
caused by these internal forces
produces “stresses” in the body,
the failure of the material itself
Simple Stresses:
- is an expression as the ratio of the applied force
divided by the resisting area; or the expression, force
per unit area
Categories:
* Normal Stresses
* Shear Stresses
* Bearing Stresses
NORMAL STRESSES:
- is developed when a force is applied perpendicular to
cross-sectional area of the material
- it is the strength of material per unit area or unit
strength
Two Types of Normal Stresses
* Tensile Stress – tends to pull the material
* Compressive Stress – tends to compress the material
Illustrative Problem:
For the truss as shown in the figure, determine the
stresses in members DE and DF. The cross-sectional
area of each member is 1.8 sq.inches. Indicate whether
tension (T) or compression (C).
Illustrative Problem:
Determine the largest weight W that can be supported
safely by the structure as shown in the figure. The
working
stresses are 16000 𝑝𝑠𝑖 for the steel cable AB and
720 𝑝𝑠𝑖 for the wood strut BC. Neglect the weight of the
structure. The area of steel cable AB is 0.5 𝑖𝑛2 and the area
of the strut BC is 16 𝑖𝑛2
Illustrative Problem:
A two-member truss supports a block of weight W as shown
in the figure. The cross-sectional areas for the members
are 800 𝑚𝑚2 for AB and 400 𝑚𝑚2 for AC. Determine the safe
value of W if the working stress are 110 𝑀𝑃𝑎 for AB and
120 𝑀𝑃𝑎 for AC.
Illustrative Problem:
A composite bar consists of aluminum section rigidly
fastened between a bronze section and a steel section as
shown in the figure. Axial loads are applied at the
positions indicated. Determine the stresses in each
section and indicate whether tension (T) or compression
(C).