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Mechanical Engineering Questions and Answers December 12, 2019

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In a polymer fractionation experiment the following data was obtained3 of 100 Mol. Wt. 200 500 1000 2000 3000 4000 5000 fraction Number of Chain 5 12 18 22 15 11 9. 3 Calculate the number average and weight average molecular weight of polymer. Also calculate the polydispersity index.

Write down the names of following crystallographic planes. (a) (b). (c)

What do you mean by biaxial strength of orthotropic lamina ? Compare the maximum stress theory with maximum strain theory.

How dynamic loading is different that static loading DMA plot of a polymer is given as under, read the value of Tg and Tm from the plot.s 10 10 1,5 10 10 0,5 102 100 50 50 100 150 200 Temperature (C) G and G (Pa) g uen

Explain the construction and working of Differential Scanning Calorimeter (DSC). Explain how you will relate the DSC curve with glass transition temperature, crystallization, melting and degradation of polymer.

Differentiate the SSC for metals and polymers. Elaborate the various parameters affecting the nature of stress/strain curve for polymeric materials.

Explain the manufacturing process for sheet molding compound (SMC). Write 3 industrial applications for SMC and name the most common molding technique where SMC is used as raw material.

What do you mean by stereo regularity of polymers? How it influences the properties of polymer, discuss it.

Why polymers are visco-elastic in nature? Explain the difference in the stress strain relationship of a visco-elastic material and a perfectly elastic material.

What do you mean by transition temperatures in polymers? Other than glass transition temperature, explain any other transition temperature. Briefly explain the factors affecting glass transition temperature.

Why the estimation of shear modulus in plane 12 (G12) from stress strain curve in non PMC (i.e ox vs. Ex) yields over estimated result Also describe the correct way of estimating G12.

What do you mean by crystallinity of a polymer How can we regulate the crystallinity during processing of polymer with its effect on the mechanical properties of polymer 7.5

A cylindrical storage tank, 1 m diameter by 1.2 m long has an outside surface temperature of 60 0C, and emissivity of 0.9. Calculate the rate of heat loss by radiation when the tank is in a large room, the walls of which are at 15 0C. Calculate also the reduction in the rate of heat loss by radiation if the tank is painted with aluminum paint of