Manufacturing Processes Multiple Choice Questions 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
c) Weldability
d) Tensile strength
Answer: b
Clarification: 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
Answer: a
Clarification: 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
Answer: a
Clarification: 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
Answer: b
Clarification: 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
Answer: d
Clarification: 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
Answer: c
Clarification: 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 .
7. Laser welding efficiency can be calculated by formula _____
a) Velocity*thickness/power
b) Velocity*power/thickness
c) Power*thickness/velocity
d) Velocity*thickness*power
Answer: a
Clarification: 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 _____
a) 105-107
b) 105-108
c) 1010-1012
d) 1012-1014