Question

Creep occurs by:- a. constant stress at room temperature, b. high temperatures over 1000C. c. constant stress at temperatures over 0.5 TM in K, d. none of these. Creep rates for polymers at 23C are:- a. high, b. low, c. same as metals. In a low carbon steel the upper yield point depends upon:- a. screw dislocations at grain boundaries, b. carbon atoms at dislocations, c. intersecting slip planes, d. second phases. Compressive surface stresses:- a decrease fatigue life, b, increase fatigue life, c. have no influence. Which of these is surface dominated:- a. creep, b. brittle failure, c. fatigue, d. all of these. Functionality is:- a. unsaturated bonds, b. saturated bonds, c. the bond angle between carbon atoms On thermoset polymers heat has:- a. no effect, b. hardens them, c. softens them, d. destroys them
can you help me with these practice problems

Answer 1

(6) caeep occus by :- [ Constant stress at temp, over 0.5tm ink creep is dependend on temperature and stress. Increase in temp. for a constant stress can crceloorite. Sailure. generally it is o.s to 0.7 Tm ink (melting point of temperature) (4) Creep dates for polymez at 23°C are:- [b ] low - Accoading to stacin vs time plot creep actes are lover at 23°c up to ceotain time. (8) In a low cabbon steel upper yield point depends upon: - [6] carbon atoms at dislocations - This wield point Phenomenan occurs due to the segregation of impurity solute atomes CC, Ninfe) around dislocation as so to reduce the stacin eneogy (9) Compressive surface stresses: [6] Increase fatigue life. Surface compressive stresses are geneally helpful because they seduce the effect of applied tensile stresses, so it contribute to improve of fatigue strength [90] Which of this is surface dominated :- [d] all of these. These property dominates the surface of materiah Creep, boittle sallyoe, satigue. [11] Sunctionality is . [6] saturated bonds [12] on the omaret polymers heat hews : [] soften them - The heat first softens the maledial but as additional heat and pressure heroden the matealul