March 21 2018 Quiz 4 Note Select the most suitable options o

March 21, 2018 Quiz 4 Note: Select the most suitable options of the statements given below, no overwriti 1. The ultimate tensile strength of a material is obtained by dividing then a. Area at the time of fracture b. Original cross section area c. Minimum area after the fracture d. None of above The most suitable definition for a ductile material is: a. A highly elastic material b. A highly plastic material c. High strains under low stress d. None of above 2. 3. Which one of the following is effectively tested by tension test: a. b. c. d. A clay brick A brass bar A concrete block All of above Strain is defined as the ratio of: a. b. 4. Change in volume to original volume Change in length to original length Change in cross-sectional area to original cross-sectional area Any of above d. 5. When force is applied to an elastic member, it will: a. Not deform b. Stretch c. Not stretch d. None of above 6. Hooke\'s law hold its validity up to: a. Yield point b. Maximum stress c. Plastic limit d. Breaking point 7. In 0.2% offset method for measuring yield strength, the line is dr a. Parallel to yielding region b. Parallel to promotional limit c. Perpendicular to the maximum stress d. None of above

Solution

1) (b) Original cross section.

Practically, the area at the time of failure should be used, but it will be more safe if we use original area as ultimate strength gets reduce.If area at failure is used, you will get higher value of ultimate strength.

Ultimate strength = Ultimate load / original area.

2) (B) A highly plastic material

A ductile material is a material which can sustain loads even after yield stress and deform plastically and then reaches to ultimate strength and fails. Whereas brittle material will reach its ultimate strength even before yield point (i.e. they don\'t yield).

3) b) A brass bar

Because it is an isotropic and homogenous material. Whereas concrete and bricks are hetrogeneous material and have different properties in different direction. But still tensile test is used to concrete and brick.

4) d) Any of the above

Strain is defined as change in dimension / original dimension. If length is changed it is called linear strain. If there is a change in volume it is volumetric strain. So, strain is a general term which can be used in length, area or volume.

5) (B) Stretch

Elastic materials are the materials which deforms upon application of force & then regain there shape after force is removed. Whereas plastic material dont regain their original shape.

6) A) Yield point

Hookes\' law is valid upto yield point only because stress is directly proportional to strain upto yield stress only. After that, the show non-linear behaviour.

7) B) Parallel to proportionality limit.

0.2% offset method is used for materials whih don\'t have definite yield point. For that purspose a line is drawn at 0.2% strain offset parallel to proporstionality limit and the point at which it intersects curve, that is called 0.2% yield strength.