How does the stress and strain tensor look in a monoaxial tension test?
How is the nominal stress and strain defined?
How is the true stress and strain defined?
How is the extension ratio defined for elastomers?
What is the youngs modulus?
The inclination of the linear stress strain curve.
=stress/strain in linear part
With which measurement instruments can a tension test be conducted?
stress measurement:
load cells
strain measurement:
axial extensiometer
transverse extensiometer
Why are ceramic metals not tension tested?
Gripping difficulties due to brittle behaviour
Why do tension test specimens need a sufficient length?
for a uniaxial stress state
How can the general shape of a tension test specimen be described?
dump-bell (Hantel) shaped
How does the stress and strain vector look in a monoaxial compressionß test?
Which length to diameter ratio is required to avoid buckling in a compression test?
L_0/d_0=1.5-2
Why can compression tests on composites not be performed?
the brooming effect
What is the relationship between compressive and tensile modulus for carbon fibre?
What are the effect of temperature and strain rate on the true stress?
How is the moment of area defined?
How is the area moment of inertia defined?
What is the moment of inertia for a rectangle?
What is the moment of inertia for a circle?
What is the moment of inertia for a circular ring?
How can the tension in a three point bending test be determined? Name the components.
y is the distance from the neutral fibre (=the middle of the thickness)
I is the area moment of inertia
E is the youngs modulus
rho is the radious of kurvature(=1/k)
How can the shear stress in a bending test be calculated? Name the components.
V=shear force
Q=first moment of inertia
I=area moment of inertia
b=sample width
How can the shear stress be calculated for a recangular sample?Name the components.
h=height of the sample
y_1=distance to the deformed string
How is the first moment of area defined?
In which 3 variants can a flexural test be conducted?
three point bending test
four point bending test
short beam shear test
How can the normal stress and the maximum normal stress be described in a three point bending test?
P=force acting on the sample
L=distance between supports
y=distance form middle line
B=sample width
h=sample height
(with inserted area moment of inertia and y=h/2)
In which szenario can the shear stress be neglegted for a three point bending test?
If the length of the sample >> the height of the sample
(L/h needs to be at least 16)
How can the shear stress be calculated for a three point bending test?
What is the ration of the maximum normal and shear stress in a three point bending test?
How can the youngs modulus be calculated in the three point bending test?
P=the applied force
v=the displacement
How can the strain be determined from the displacement in a three point bending test?
What are the maximum stresses for a rectangle and circular crossection at the end of the bending test?
rectangle
circle
How is the interlaminar strength between composite laminates determined?
short beam shear tests
What is the importante assumption of a short beam shearing test?
Normal stresses can be neglegted
How is the shear stress in a short beam shear stress calculated?
P=applied force
How is the interlaminar shear strength defined?
P_R=the maximum applied force
What is the main advantage of the four point bending test?
In the central part between the two force contact points, one can assume no shear forces.
How is the maximum normal stress calculated in the 4 point bending test? Give the derivation.
The moment in B is calculated by 2. Insert into the stress equation. Stress is at maximum at outer fibre (=h/2) and insert area inertia moment for rectangle.
What is the condition in a four point bending test, for which shear stresses can be neglegted?
L_1-L_2>>h
What is the quotient of maximum shear stress through maximum normal stress for the 4 point bending test?
What is the maximum shear stress in the 4 point bending test?
Give the formula for shear stress in torsion testing.
How is the torgue calculated in torsion testing? Name the components.
G=shear modulus
I_p=polar moment of inertia
L=length of the sample
phi=stress in degree
How is the torsional shear modulus obtained?
<=> youngs modulus: the inclination between rotation angle and torgue
What is the shape of torsion testing samples?
cylinders
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