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 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

How is the polar moment of inertia calculated?

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