lymer is initially exposed to 13.8 MPa of axial tension at room temperature. If the polymer features a relaxation time of 26.2 hr at room temperature, how long will it take for the tensile stress in the polymer to reach 10.3 MPa

Amixture of slurry and mud is to be pumped through a horizontal pipe of diameter 500 mm. the fluid behaves as a bingham plastic with a yield stress of 30 pa and viscosity 0.04 pa.s. describe the effects of the shear stress through a transverse section of the pipe by plotting the variation in shear stress and velocity profile: (i) just before the slurry starts to move (ii) as the slurry flows when the pressure gradient is double that in part (i)