stress analysis Unit 2 Flashcards
isotropic material?
when they are loaded they exhibit uniform mechanical properties in all directions
axial stress arises when a material is subjected to tensile or compressive forces along a geometric axis
axial stress is defined as the force per unit area
equation for maximum shear stress?
tmax = axial stress6/2
the largest shear stress occurs in the planes at 45degrees to the axial loading and is equal to half of the loading stress
y
units of maximum shear stress?
Pa
what distinguishes the neutral axis from any other axis in a bent beam?
the neutral axis maintains the same length when the beam is bent - it is neither elongated or compressed
how to convert degrees to radians?
radians = degrees x Pi/180
equation for MIS….
MISYER bent
how to calculate I for rectangle?
bd3/12
CIRCULAR?
pi d 4/64
hollow circular?
pi ( outer d 4 - inner d 4) / 64
unit of shear strain?
radian
modulus of rigidity?
shear stress/shear strain
to calculate maximum shear stress?
find stress and divide by 2
units for maximum shear stress?
Pa
ski boot fracture - what kind of bending causes this?
3 point
a bar is sad to be in pure torsion wen its cross section is?
retaining its shape
sheer stress in torsional stress?
G theta r AB/L
what is G?
modulus of rigidity
for a solid circular cross section, it can be shown that J=
pi d 4/32
for a hollow circular cross section?
j= pi(d4 outer - d4 inner) / 32
what is J?
polar second moment of area
when are bones strongest?
in compression
what can muscles do to reduce chance of fracture?
contract to produce compressive loading on the bone and because bones are stronger in compression than in tension, this reduces likelihood of a fracture
why is it sometimes desireable for muscles to contact even when its not to produce movement?
muscle contraction can put compressive load on a bone, bones are stronger in compression than tension
what role to microscopic voids play in ductile fracture?
microscopic voids are small holes at the centre of the bar. they are formed when a high stress causes a separation of the metal at grain boundaries. as the local stresses increase, the microscopic voids start to join together and produce larger cavities. eventually the metal contact is reduced and a fracture occurs, at an angle of 45 degrees to the applied tensile load.
what is the difference in the fracture surface in a brittle fracture?
the fracture surface is flat, rather than 45 degrees in a ductile fracture. it has a granular appearance
