Chapter 4 Residual Stress and Distortion

Question 1

1. Elastic deformation is best described as:

a. permanent deformation caused by welding stresses
b. stress that causes contraction or shrinkage
c. deformation that does not exceed the yield point
d. an increase in the dimensions of a body

Answer 1

c. deformation that does not exceed the yield point

Question 2

2. The coefficient of thermal expansion of a material is considered a/an:

a. physical property
b. mechanical property
c. chemical property
d. electrical property

Answer 2

a. physical property

Question 3

3. A piece of material that has restricted expansion and restricted contraction is said to be:

a. unrestrained
b. restrained
c. fractured
d. compressed

Answer 3

b. restrained

Question 4

4. Residual stress is produced by:

a. localized heating that causes an upset
b. an elastic deformation
c. a uniform temperature increase
d. cooling the material below -20°C

Answer 4

a. localized heating that causes an upset

Question 5

5. Residual stresses in the outer portions of hot rolled structural shapes are:

a. compressive because these areas are the first to cool
b. tensile because these areas are the first to cool
c. tensile because these areas are the last to cool
d. compressive because these areas undergo the most deformation

Answer 5

a. compressive because these areas are the first to cool

Question 6

6. A butt weld in long thin material will likely produce which type of distortion?

a. Longitudinal buckling
b. Angular
c. Transverse shrinkage
d. Longitudinal shrinkage

Answer 6

a. Longitudinal buckling

Question 7

7. Which are the major factors that affect transverse shrinkage in butt welds?

a. Plate thickness, root opening, cross-sectional area of weld, groove angle
b. Length of the weld, groove angle, weld cap
c. Melt through, plate thickness, groove angle
d. Cross-sectional area of weld, plate thickness, melt through

Answer 7

a. Plate thickness, root opening, cross-sectional area of weld, groove angle

Question 8

8. Distortion in structural shapes with eccentric weld joints will produce which type of distortion?

a. Twisting
b. Angular
c. Bending
d. Shear

Answer 8

c. Bending

Question 9

9. Which of the following will produce the least angular distortion in a fillet joint?

a. Multi-pass welding
b. Single pass welding
c. Welding with high travel speed
d. Welding with low travel speed

Answer 9

b. Single pass welding

Question 10

10. Which of the following statements is the most correct?

a. Uniform pre-heating will increase distortion
b. Localized pre-heating will reduce distortion
c. Uniform pre-heating will decrease distortion
d. Uniform pre-heating has no effect on distortion

Answer 10

c. Uniform pre-heating will decrease distortion

Question 11

11. To achieve proper dimensions, the general rule for cutting shapes from plate is:

a. the workpiece must be kept with the remaining large plate until the last severance is cut
b. the workpiece should be removed with a clockwise cutting direction
c. the workpiece should be preheated before commencing the cut
d. must compensate for the kerf of the cutting process

Answer 11

a. the workpiece must be kept with the remaining large plate until the last severance is cut

Question 12

12. Back step welding on long seam joints, is a technique used to:

a. reduce the preheating required to limit distortion
b. allow the use of wire feed processes
c. reduce the extent of distortion
d. reduce the restraint on the weld joint

Answer 12

c. reduce the extent of distortion

Question 13

13. For a given plate thickness, the distortion is less for a double V groove compared to a single V groove because:

a. the double V groove is easier to prepare
b. the single V is easier to prepare
c. a single V groove is balanced about the neutral axis of the plate
d. the double V is balanced about the neutral axis

Answer 13

d. the double V is balanced about the neutral axis

Question 14

14. Sub-assemblies are used to:

a. reduce cumulative distortions
b. to allow for corrective actions on smaIIer components
c. to allow for better fit-up
d. all of the above

Answer 14

d. all of the above

Question 15

15. The distortion control method that involves adjusting the alignment prior to welding is called:

a. restraint
b. preheating
c. pre-setting
d. fit-up

Answer 15

c. pre-setting

Question 16

16. The main purpose of strongbacks is to:

a. provide joint alignment and restraint during welding
b. reduce the stresses on the joint
c. allow the joint to move freely
d. allow transverse shrinkage to occur

Answer 16

a. provide joint alignment and restraint during welding

Question 17

17. Flame straightening involves:

a. uniformly heating to produce an expansion
b. locally heating the weldment to produce an expansion
c. locally heating the weldment to produce a contraction
d. uniformly heating to produce a contraction

Answer 17

c. locally heating the weldment to produce a contraction

Question 18

18. The principle of flame straightening can be applied to:

a. relieve stresses
b. improve fatigue life
c. produce curvature in a beam
d. adjust the neutral axis of a section

Answer 18

c. produce curvature in a beam

Question 19

19. The temperature reached during flame straightening must:

a. be equal to the melting point of the metal.
b. be high enough to produce upset
c. low enough that yielding does not occur
d. be white-hot

Answer 19

b. be high enough to produce upset

Question 20

20. In order to square a distorted welded frame, the flame straightening heat should be applied:

a. on the outside of the high angle corner
b. on the inside of the high angle corner
c. on the outside of the lower angle corner and inside of the higher angle corner
d. on the outside of the lower angle

Answer 20

c. on the outside of the lower angle corner and inside of the higher angle corner

Question 21

21. The yield strength of a material represents:

a. the maximum stress for elastic behavior
b. the stress that causes failure
c. the minimum stress for elastic behavior
d. the maximum stress reached during a tensile test of mild steel

Answer 21

a. the maximum stress for elastic behavior

Question 22

22. The longitudinal free shrinkage of a welded butt joint in steel plate produces:

a. a high tensile residual stress longitudinally in the weld
b. a high compressive residual stress longitudinally in the weld
c. a low tensile residual stress longitudinally in the weld
d. a high tensile residual stress transverse across the weld

Answer 22

a. a high tensile residual stress longitudinally in the weld

Question 23

23. Flame straightening is not typically used to straighten an aluminum alloy weldment because:

a. aluminum does not expand when heated
b. aluminum does not possess enough ductility
c. elevated temperatures are detrimental to the strength of aluminum alloys
d. aluminum does not upset during heating

Answer 23

c. elevated temperatures are detrimental to the strength of aluminum alloys

Question 24

24. The neutral axis of a welded fabrication is defined as:

a. the axis through the centre of the shape
b. the axis through the centre of gravity of the shape
c. the axis through the centre o1 the largest part of the shape
d. the axis at one corner of the shape

Answer 24

b. the axis through the centre of gravity of the shape

Question 25

25. Restraint can be defined as:

a. the rigidity of the joint prior to welding
b. stresses caused by external forces
c. internally self-balanced stresses
d. the force produced per unit length of the joint

Answer 25

a. the rigidity of the joint prior to welding

Question 26

26. A plate was heated uniformly throughout and was left on top of a table to cool down. What would happen to the plate?

a. The plate would Shrink longitudinal
b. The plate would shrink transversely
c. The plate would be thicker after cooling
d. The plate would have the same dimension as before it was heated

Answer 26

d. The plate would have the same dimension as before it was heated

Question 27

27. What would be the thermal expansion of a steel bar that is heated at 200 BC?

a. 0.00236m
b. 0.00034m
c. 2 m
d. 1.5m

Answer 27

a. 0.00236m

Question 28

28. It is true that restricted contraction may set up internal tensile stresses enough to cause failure if the metal is not ductile enough to accommodate the deformation.

a. It is true
b. It is not true

Answer 28

a. It is true

Question 29

29. According to B.A. Graville, there are three stages of free contraction curves for submerge arc welding process. According to the diagram which stage is the worse?

a. All the same
b. Stage 1
c. Stage 3
d. Stage 2

Answer 29

b. Stage 1

Question 30

30. There is any correlation between the neutral axis and the center of gravity of the cross-section of the shape

a. Yes
b. No

Answer 30

a. Yes