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According to Griffith theory, which of the following are true for the fracture stress in a brittle material?
P. Increases with increasing surface energy
Q. Decreases with increasing elastic modulus
R. Decreases with increasing length of pre-existing crack
S. Decreases with increasing number of pre-existing cracks of same size
Shear stress required to bend a dislocation of radius R and burger vector b is P. What will be shear stress needed to turn a dislocation of radius 2R and burger’s vector 2b to bend the dislocation?
The Burgers vector b is the vector which defines the magnitude and direction of slip. For a pure edge dislocation, the Burgers vector is perpendicular to the dislocation line, while for a pure screw dislocation, the Burgers vector is parallel to the dislocation line.
The interaction of screw dislocation and edge dislocation produces ______ on the edge dislocation and _______ on the screw dislocation.
From an alloy, two specimens are machined and tested separately under tension and compression. The engineering stress-strain curves as well as the true stress-true strain curves for tension and compression are plotted in the same diagram. Identify the correct statements:
P. The engineering stress-strain curves in tension and compression are identical.
Q. The true stress-true strain curve in compression is lower than the true stresstrue strain curve in tension due to Bauschinger effect.
R. The true stress-true strain curve in tension is above the corresponding engineering stress-strain, curve.
S. The true stress-true strain curve in tension and compression are identical.
Presence of tail water in a gravity dam
i) increases the principal stress
ii) decreases the principal stress
iii) increases the shear stress
iv) decreases the shear stress
The correct answer is
The design stress, which is more than the damaging stress, is the least unit stress that will render a member unfit for service before the end of its normal life. The design stress factor or factor of safety indicates the margin between design stress and the __________ stress.
Tresca or maximum-shear stress criteria assumes that yielding occurs when the maximum shear stress reaches a value of the shear stress in the uniaxial tension test. Assume the principal stress being σ1, σ2, σ3 where σ1 is largest, and σ3 is the smallest principal stresses. Find the value of minimum shear stress to cause yielding, given that yield stress in tension is equal to σo?
Which of the following statements regarding stress related factors is/are true and false?
1. Burnout Stress Syndrome (BOSS) is a debilirating psychological condition brought about by unrelieved work stress.
2. 'Good' and 'bad' stresses are also referred to as 'Distress' and 'Eustress' respectively.
3. It is natural and healthy to maintain optimal level of stress.
4. Rustout Stress Syndrome (ROSS) is indicative of stress overload.
5. Anxiety is a state of emotional tension characterised by Apprehension, fearfulness, and psychic pain.
What is the resolved shear stress, when dislocation density in metal is equal to 1012m-2? Given that shear stress needed in the absence of dislocation is 500MPa. Numerical constant is 0.3 and shear modulus is 80GPa, burger vector is 1 nm.