This set of Manufacturing Processes Multiple Choice Questions & Answers (MCQs) focuses on “Laser Welding – 4”.
1. Which of the following material properties should match before joining to components by a transmission welding method.
a) Electrical properties
b) Thermal properties
d) Tensile strength
Explanation: In transmission welding process, the energy is absorbed through novel interfacial absorption methods. Composites can be joined by this process provided that the thermal properties of the matrix and reinforcement are similar.
2. Transmission welding mode is used for materials that______
a) transmits near infrared radiation
b) have high heat capacities
c) have lower melting points
d) absorbs infrared radiations
Explanation: The energy transmission mode of conduction welding is used with materials that transmit near infrared radiation, notably polymer. Absorption of infrared radiation has nothing to do with weldability of materials.
3. In transmission welding mode, absorbing ink is placed at the interface of a lap joint for _____
a) absorbing the laser beam energy
b) cooling the work metal
c) protecting the weld puddle
d) reducing the process time
Explanation: An absorbing ink is placed at the interface of a lap joint. The ink absorbs the laser beam energy, which is conducted into a limited thickness of surrounding material to form a molten interfacial film that solidifies as the welded joint.
4. Butt welds can be made using transmission mode of conduction welding by _____
a) melting the outer surfaced of the joint
b) directing the energy towards the joint
c) applying ink to the joining surface before welding
d) using filler material
Explanation: Butt welds can be made by directing the energy towards the joint line at an angle through material at one side of the joint, or from one end if the material is highly transmissive. Also, thick section lap joints can be made without melting the outer surfaces of the joint.
5. In which of the following processes, the laser beam is used to melt a filler addition?
a) Laser drilling
b) Laser cutting
c) Laser welding
d) Laser soldering
Explanation: In the laser soldering and brazing processes, the beam is used to melt a filler addition, which wets the edges of the joint without melting the base material.
6. Penetration welding is characterised by _____
a) tapered trail
b) irregularities in the weld
c) parallel sided fusion zone
d) planner welds
Explanation: At high power densities all materials will evaporate if the energy can be absorbed. Thus, when welding in this way a hole is usually formed by evaporation. This “hole” is then traversed through the material with the molten walls sealing up behind it. The result is what is known as a “keyhole weld. This is characterized by its parallel sided fusion zone and narrow width.
7. Laser welding efficiency can be calculated by formula _____
Explanation: Efficiency = V.t/P, where
V = traverse speed, mm/s;
t = thickness welded, mm;
P = incident power, kW.
8. The heat source intensity for laser beam welding lies in the range _____
Explanation: The heat source intensities for various welding processes is as follows;
• Flux shield arc welding – 5*106-108
• Gas shielded arc welding – 5*106-108
• Plasma welding – 5*106-1010
• Laser beam or electron beam welding – 1010-1012.
9. The joining efficiency and the energy spent during the welding process are directly proportional.
Explanation: The higher the value of the joining efficiency the less energy is spent on unnecessary heating. Therefore-
• Lower heat affected zone (HAZ)
• Lower distortion in the workpieces.
10. Resistance welding has the smallest heat affected zone as compared to all welding processes.
Explanation: Resistance welding is most efficient in this respect because the fusion and heat affected zone energy is only generated at the high resistance interface to be welded. Laser and electron beam welding also have good efficiencies and high power densities.
Sanfoundry Global Education & Learning Series – Manufacturing Processes.
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