This set of Design of Steel Structures Multiple Choice Questions & Answers (MCQs) focuses on “Weld Defects & Types of Joints”.
1. The production of sound welds is not governed by ______
a) type of joint
b) choice of electrode
c) type of metal plate
d) arc length
View Answer
Explanation: The production of sound welds is governed by type of joint, its preparation, root opening, etc. The choice of electrode, welding position, welding current and voltage, arc length, rate of travel also affect the quality of weld.
2. Which of the following is not a reason for incomplete fusion?
a) surfaces to be jointed are coated with oxides
b) insufficient current supplied by welding equipment
c) high rate of welding
d) use of large electrode
View Answer
Explanation: Incomplete fusion may result if surfaces to be jointed have not been cleaned properly and are coated with oxides and other foreign materials. Insufficient current supplied by welding equipment and high rate of welding will result in incomplete fusion.
3. Which of the following is true?
a) incomplete penetration is found in fillet welds
b) it is due to use of large size of electrodes
c) it is due to excessive welding current
d) it is due to insufficient welding rates
View Answer
Explanation: Incomplete penetration is due to failure of weld metal to penetrate the complete depth of joint where full penetration has been specified. This defect is found in groove welds sue to unsuitable groove design for selected welding process, use of large size of electrodes, insufficient welding current, excessive welding rates.
4. Which of the following is not true?
a) Porosity is caused due to insufficient current
b) It is caused due to longer arc length
c) It may be due to poor welding procedure
d) It results in stress concentration
View Answer
Explanation: Porosity is formed when gas pockets or voids are draped during cooling process. It may be due to excessively high current or longer arc length or due to poor welding procedure. Porosity results in stress concentration and reduced ductility of metal.
5. Which of the following is true regarding undercutting defect?
a) Undercutting is due to local increase of thickness of parent metal at weld toe
b) It is due to insufficient current
c) It can be corrected by depositing additional weld material
d) It is not easy to detect
View Answer
Explanation: Undercutting is due to local decrease of thickness of parent metal at weld toe. This results in groove in base metal adjacent to toe of weld and left unfilled by weld metal during welding process. Undercutting may result in loss of gross section and will act as stress riser. This defect may be due to excessive current or longer arc length. It can be easily detected visually and can be corrected by depositing additional weld material.
6. Hot cracks can be prevented by __________
a) faster cooling
b) non uniform heating
c) pre-heating
d) slower cooling
View Answer
Explanation: Hot cracks form as weld begin to solidify and are caused by brittle constituents (presence of sulphur, carbon, silicon and hydrogen). They can be prevented by more uniform heating and slower cooling.
7. Cold cracks can be prevented by __________
a) uniform heating
b) by use of low hydrogen electrode
c) faster cooling
d) slower cooling
View Answer
Explanation: Cold cracks occur under room temperature run parallel to but under the weld in base metal. Use of low hydrogen electrodes along with proper pre-heating and post-heating may reduce possibility of cold cracks.
8. The types of welded joints does not depend on _________
a) size of members connected at joint
b) type of loading
c) area available for welding
d) size of weld
View Answer
Explanation: The types of welded joints depends on (i) size and shape of members connected at joint, (ii) type of loading, (iii) area available for welding at the joint, (iv) relative cost of various types of weld.
9. Which of the following are correct regarding butt joints over lap joints?
a) Lap joints eliminates eccentricity whereas butt joints develops eccentricity
b) Butt joints minimizes the size of connection
c) Lap joints are aesthetically pleasing over butt joints
d) Butt joint obtained from full penetration groove weld has 50% efficiency
View Answer
Explanation: Butt joints eliminates eccentricity developed using lap joints. Butt joints minimizes the size of connection and are aesthetically pleasing over lap joints. Butt joint obtained from full penetration groove weld has 100% efficiency.
10. What is face reinforcement used in butt joint?
a) It is extra weld metal that makes throat dimensions greater than the thickness of the welded material
b) It is extra weld metal that makes the throat dimensions smaller than the thickness of the welded material
c) It is extra weld metal that makes the throat dimensions equal to the thickness of the welded material
d) It is parent metal makes that the throat dimensions smaller than the thickness of the welded material
View Answer
Explanation: Face reinforcement is extra weld metal that makes the throat dimensions greater than the thickness of the welded material. The provision of reinforcement increases the efficiency of joint and ensures that depth of weld is at least equal to thickness of the plate.
11. When plates of two different thicknesses and/or widths are joined, the wider or thicker part should be reduced at the butt joint to make __________
a) thickness less than smaller part, the slope being steeper than one in five
b) thickness greater than smaller part, the slope being steeper than one in five
c) thickness equal to smaller part, the slope not being steeper than one in five
d) thickness equal to smaller part, the slope being steeper than one in five
View Answer
Explanation: When plates of two different thicknesses and/or widths are joined, the wider or thicker part should be reduced at the butt joint to make thickness equal to smaller part, the slope not being steeper than one in five. When reduction is not possible, the weld metal shall be built up at the junction with thicker part to dimensions at least 25% greater than those of thinner part, or alternatively to the dimensions of thicker member.
12. Which of the following is not true regarding lap joint?
a) Connection using lap joint requires large number of erection bolts
b) It can accommodate minor errors in fabrication
c) Lap joints are well suited for shop as well as field welding
d) It introduces some eccentricity of loads
View Answer
Explanation: Lap joints offer ease of fitting and ease of jointing. It can accommodate minor errors in fabrication or minor adjustment in length. They are well suited for shop as well as field welding. Connection using lap joint requires a small number of erection bolts. The main drawback of lap joint is that it introduces some eccentricity of loads, unless a double lap joint is used.
13. T-joints are not used to fabricate _________
a) I-shapes
b) T-shapes
c) Brackets
d) Plates joined at straight angles
View Answer
Explanation: T-joints are used to fabricate built up sections such as T-shapes, I-shapes, plate girders, brackets and stiffeners where two plates are joined at right angles.
14. Match the pair
Types of joints Use / Application A) Butt joint i) used to keep two or more plats in given plane B) Lap joint ii) used to join ends of flat plates of nearly equal thickness C) Tee joint iii) used to form built-up rectangular box sections D) Corner joint iv) used to fabricate built-up sections E) Edge joint v) plates with different thickness can be joined without any difficulty
a) A-i, B-ii, C-iii, D-iv, E-v
b) A-ii, B-v, C-iv, D-iii, E-i
c) A-ii, B-iii, C-iv, D-v, E-i
d) A-v, B-iv, C-iii, D-ii, E-i
View Answer
Explanation: Butt joint is used to join of flat plates of nearly equal thickness. Plates with different thickness can be joined without any difficulty using lap joints. Tee joint is used to fabricate built-up sections, where two plates are joined at right angles. Corner joint is used to form built-up rectangular box sections, which may be used as columns or beams to resist high torsional forces. Edge joints are not used in structural engineering applications, they are used to keep two or more plats in given plane.
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