GATE Questions & Answers of Casting, Forming and Joining Processes Mechanical Engineering

The type of weld represented by the shaded region in the figure is

 

The maximum reduction in cross-sectional area per pass ( $R$ ) of a cold wire drawing process is

                                                   $ R=1\;-e^{-\left(n+1\right)} $,

where $n$ represents the strain hardening coefficient. For the case of a perfectly plastic material, $R$ is

The percentage scrap in a sheet metal blanking operation of a continuous strip of sheet metal as shown in the figure is _______ (correct to two decimal places).

 

Match the following products with the suitable manufacturing process

 Product  Manufacturing Process
P Toothpaste tube 1 Centrifugal casting
Q Metallic pipes 2 Blow moulding
R Plastic bottles 3 Rolling
S Threaded bolts 4 Impact extrusion

 

A steel wire is drawn from an initial diameter $ \left(d_i\right) $ of 10 mm to a final diameter $ \left(d_f\right) $ of 7.5 mm. The half cone angle $ (\alpha) $ of the die is $ 5^\circ $ and the coefficient of friction $ \left(\mu\right) $ between the die and the wire is 0.1. The average of the initial and final yield stress $ \left[{\left(\sigma_Y\right)}_{avg}\right] $ is 350 MPa. The equation for drawing stress $ \sigma_f $ , (in MPa) is given as:

                              $ \sigma_f={\left(\sigma_Y\right)}_{avg}\left\{1+\frac1{\mu\;cot\alpha}\right\}\left[1-\left(\frac{d_f}{d_i}\right)^{2\mu\;cot\alpha}\right] $

The drawing stress (in MPa) required to carry out this operation is _________ (correct to two decimal places).

For sand-casting a steel rectangular plate with dimensions 80 mm × 120 mm × 20 mm, a cylindrical riser has to be designed. The height of the riser is equal to its diameter. The total solidification time for the casting is 2 minutes. In Chvorinov’s law for the estimation of the total solidification time, exponent is to be taken as 2. For a solidification time of 3 minutes in the riser, the diameter (in mm) of the riser is __________ (correct to two decimal places).

A welding operation is being performed with voltage = 30 V and current = 100 A. The cross-sectional area of the weld bead is 20 mm2 . The work-piece and filler are of titanium for which the specific energy of melting is 14 J/mm3 . Assuming a thermal efficiency of the welding process 70%, the welding speed (in mm/s) is __________ (correct to two decimal places).

In a metal forming operation when the material has just started yielding, the principal stresses are $\style{font-family:'Times New Roman'}{\sigma_1=+180\;\mathrm{MPa},\;\sigma_2=-100\;\mathrm{MPa},\;\sigma_3=0.}$ Following von Mises' criterion, the yield stress is ____________ MPa.

In an arc welding process, welding speed is doubled. Assuming all other process parameters to be constant, the cross sectional area of the weld bead will

A 10 mm deep cylindrical cup with diameter of 15 mm is drawn from a circular blank. Neglecting the variation in the sheet thickness, the diameter (upto 2 decimal points accuracy) of the blank is _________ mm.

A sprue in a sand mould has top diameter of 20 mm and height of 200 mm. The velocity of the molten metal at the entry of the sprue is 0.5 m/s. Assume acceleration due to gravity as 9.8 m/s2 and neglect all losses. If the mould is well ventilated, the velocity (upto 3 decimal points accuracy) of the molten metal at the bottom of the sprue is  ________________m/s

It is desired to make a product having T-shaped cross-section from a rectangular aluminium block. Which one of the following process is expected to provide the highest strength of the product?

A rod of length 20 mm is stretched to make a rod of length 40 mm. Subsequently, it is compressed to make a rod of final length 10 mm. Consider the longitudinal tensile strain as positive and compressive strain as negative. The total true longitudinal strain in the rod is

A strip of 120 mm width and 8 mm thickness is rolled between two 300 mm-diameter rolls to get a strip of 120 mm width and 7.2 mm thickness. The speed of the strip at the exit is 30 m/min. There is no front or back tension. Assuming uniform roll pressure of 200 MPa in the roll bite and 100% mechanical efficiency, the minimum total power (in kW) required to drive the two rolls is____________

Under optimal conditions of the process the temperatures experienced by a copper work piece in fusion welding, brazing and soldering are such that

The part of a gating system which regulates the rate of pouring of molten metal is

A cylindrical job with diameter of 200 mm and height of 100 mm is to be cast using modulus method of riser design. Assume that the bottom surface of cylindrical riser does not contribute as cooling surface. If the diameter of the riser is equal to its height, then the height of the riser (in mm) is

A 300 mm thick slab is being cold rolled using roll of 600 mm diameter. If the coefficient of friction is 0.08, the maximum possible reduction (in mm) is __________

The welding process which uses a blanket of fusible granular flux is

Gray cast iron blocks of size 100 mm × 50 mm × 10 mm with a central spherical cavity of diameter 4 mm are sand cast. The shrinkage allowance for the pattern is 3%. The ratio of volume of the pattern to volume of the casting is ________ 

The voltage-length characteristic of a direct current arc in an arc welding process is $ V= $ ( 100 + 40 ), where $ l $ is the length of the arc in mm and $ V $ is arc voltage in volts. During a welding operation, the arc length varies between 1 and 2 mm the welding current is in the range 200-250 A. Assuming a linear power source, the short circuit current is _________ A.

Equal amounts of a liquid metal at the same temperature are poured into three moulds made of steel, copper and aluminum. The shape of the cavity is a cylinder with 15 mm diameter. The size of the moulds are such that the outside temperature of the moulds do not increase appreciably beyond the atmospheric temperature during solidification. The sequence of solidification in the mould from the fastest to slowest is
 
(Thermal conductivities of steel, copper and aluminum are 60.5, 401 and 237 W/m-K, respectively. Specific heats of steel, copper and aluminum are 434, 385 and 903 J/kg-K, respectively. Densities of steel, copper and aluminum are 7854, 8933 and 2700 kg/m3, respectively.)

Spot welding of two steel sheets each 2 mm thick is carried out successfully by passing 4 kA of current for 0.2 seconds through the electrodes. The resulting weld nugget formed between the sheets is 5 mm in diameter. Assuming cylindrical shape for the nugget, the thickness of the nugget is________mm.
 
  Latent heat of fusion for steel   1400 kJ/kg
  Effective resistance of the weld joint   200 μΩ
  Density of steel   8000 kg/m3

 

In a sheet metal of 2 mm thickness a hole of 10 mm diameter needs to be punched. The yield strength in tension of the sheet material is 100 MPa and its ultimate shear strength is 80 MPa. The force required to punch the hole (in kN) is __________

Match the following products with preferred manufacturing process:

Product Process
P Rails 1 Blow molding
Q Engine crankshaft 2 Extrusion
R Aluminium channels 3 Forging
S PET water bottles 4 Rolling

In a linear arc welding process, the heat input per unit length is inversely proportional to

A DC welding power source has a linear voltage-current (V-I) characteristic with open circuit voltage of 80 V and a short circuit current of 300 A. For maximum arc power , the current (in Amperes) should be set as_______.

The solidification time of a casting is proportional to VA2 ,Where V is the volume of the casting and A is the total casting surface area losing heat. Two cubes of same material and size are cast using sand casting process. The top face of one of the cubes is completely insulated. The ratio of the solidification time for the cube with top face insulated to that of the other cube is

In a slab rolling operation, the maximum thickness reduction $\left(\triangle h_{max}\right)$ is given by $\triangle h_{max}=\mu^2R$, where R is the radius of the roll and μ is the coefficient of friction between the roll and the sheet. If μ = 0.1 , the maximum angle subtended by the deformation zone at the centre of the roll (bit angle in degrees) is________.

A cube and a sphere made of cast iron (each volume 1000 cm3) were cast under identical conditions. The time taken for solidifying the cube was 4 s. The solidification time ( in s) for the sphere is ________.

In a two stage wire drawing operation, the fractional reduction (ratio of change in cross sectional area to initial cross sectional area) in the first stage is 0.4. The fractional reduction in the second stage is 0.3. The overall fractional reduction is

The flow stress (in MPa) of a material is given by

σ=500ε0.1,

Where ε is true strain. The Young’s modulus of elasticity of the material is 200 GPa. A block of thickness 100 mm made of this material is compressed to 95 mm thickness and then the load is removed. The final dimension of the block (in mm) is ____

During a TIG welding process, the arc current and arc voltage were 50 A and 60 V, respectively, when the welding speed was 150 mm/min. In another process, the TIG welding is carried out at a welding speed of 120 mm/min at the same arc welding voltage and heat input to the material so that weld quality remains the same. The welding current (in A) for this process is

In full mould (cavity-less) casting process, the pattern is made of

Which two of the following joining processes are autogeneous?

(i) Diffusion welding
(ii) Electroslag welding
(iii) Tungsten inert gas welding
(iv) Friction weding

In a rolling operation using rolls of diameter 500 mm, if a 25 mm thick plate cannot be reduced to less than 20 mm in one pass, the coefficient of friction between the roll and the plate is__________

Ratio of solidification time of a cylindrical casting (height=radius) to that of a cubic casting of side two times the height of cylindrical casting is________

The dimensions of a cylindrical side riser (height = diameter) for a 25 cm × 15 cm × 5 cm steel casting are to be determined. For the tabulated shape factor values given below, diameter of the riser (in cm) is ______.

Shape factor 2 4 6 8 10 12
Raiser volume/ Casting volume 1.0 0.70 0.55 0.50 0.40 0.35

The major difficulty during welding of aluminium is due to its

In solid-state welding, the contamination layers between the surfaces to be welded are removed by

An aluminium alloy (density 2600 kg/m3) casting is to be produced. A cylindrical hole of 100 mm diameter and 100 mm length is made in the casting using sand core (density 1600 kg/m3). The net buoyancy force (in newton) acting on the core is _______

With respect to metal working, match Group A with Group B:

Group A Group B
P: Defect in extrusion I: alligatoring
Q: Defect in rolling II: scab
R: Product of skew rolling III: fish tail
S: Product of rolling through cluster mill IV: seamless tube
  V: thin sheet with tight tolerance
  VI: semi-finished balls of ball bearing

A mild steel plate has to be rolled in one pass such that the final plate thickness is 2/3rd of the initial thickness, with the entrance speed of 10 m/min and roll diameter of 500 mm. If the plate widens by 2% during rolling, the exit velocity (in m/min) is _______

A rectangular hole of size 100 mm × 50 mm is to be made on a 5 mm thick sheet of steel having ultimate tensile strength and shear strength of 500 MPa and 300 MPa, respectively. The hole is made by punching process. Neglecting the effect of clearance, the punching force (in kN) is

Match the casting defects (Group A) with the probable causes (Group B):

Group A Group B
P: Hot tears 1: Improper fusion of two streams of liquid metal
Q: Shrinkage 2: Low permeability of the sand mould
R: Blow holes 3: Volumetric contraction both in liquid and solid stage
S: Cold Shut 4: Differential cooling rate

The hot tearing in a metal casting is due to

A  cylindrical blind  riser with diameter d and  height h, is placed on the top of the mold cavity of a closed type sand mold son as shown in the figure. If the riser is of a constant Volume  then the rate of solidification in the riser is the least when the ratio h:d is

For spot welding of two steel sheets (base metal) each of 3 mm thickness, welding current of 10000 A is applied for 0.2 s. The heat dissipated to the base metal is 1000 J. Assuming that the heat required for melting 1 mm3 volume of steel is 20 J and interfacial contact resistance between sheets is 0.0002 Ω, the volume (in mm3) of weld nugget is __

Within the Heat Affected Zone (HAZ) in a fusion welding process, the work material undergoes

A cylindrical riser of 6 cm diameter and 6 cm height has to be designed for a sand casting mould for producing a steel rectangular plate casting of 7 cm × 10 cm × 2 cm dimensions having the total solidification time of 1.36 minute. The total solidification time (in minute) of the riser is _______

A butt weld joint is developed on steel plates having yield and ultimate tensile strength of 500 MPa and 700 MPa, respectively. The thickness of the plates is 8 mm and width is 20 mm. Improper selection of welding parameters caused an undercut of 3 mm depth along the weld. The maximum transverse tensile load (in kN) carrying capacity of the developed weld joint is _______

Match the CORRECT pairs.

Processes Characteristics / Applications
P. Friction Welding 1. Non-consumable electrode
Q. Gas Metal Arc Welding 2. Joining of thick plates
R. Tungsten Inert Gas Welding 3. Consumable electrode wire
S. Electroslag Welding 4. Joining of cylindrical dissimilar materials

A cube shaped casting solidifies in 5 min. The solidification time in min for a cube of the same material, which is 8 times heavier than the original casting, will be

Calculate the punch size in mm, for a circular blanking operation for which details are given below.

Size of the blank 25 mm
Thickness of the sheet 2 mm
Radial clearance between punch and die 0.06 mm
Die allowance 0.05 mm

In a DC arc welding operation, the voltage-arc length characteristic was obtained as Varc = 20 + 5l where the arc length l was varied between 5 mm and 7 mm. Here Varc denotes the arc voltage in Volts. The arc current was varied from 400 A to 500 A. Assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation are

The operation in which oil is permeated into the pores of a powder metallurgy product is known as

Green sand mould indicates that

Which one among the following welding processes uses non-consumable electrode?

The shear strength of a sheet metal is 300 MPa. The blanking force required to produce a blank of 100 mm diameter from a 1.5 mm thick sheet is close to

A cubic casting of 50 mm side undergoes volumetric solidification shrinkage and volumetric solid contraction of 4% and 6% respectively. No riser is used. Assume uniform cooling in all directions. The side of the cube after solidification and contraction is

In a gating system, the ratio 1:2:4 represents

Two pipes of inner diameter 100mm and outer diameter 110mm each joined by flash butt welding using 30V power supply. At the interface, 1mm of material melts from each pipe which has a resistance of 42.4Ω. If the unit melt energy is 64.4MJm-3, then time required for welding in seconds is

In a shear cutting operation, a sheet of 5mm thickness is cut along a length of 200mm. The cutting blade is 400mm long and zero-shear (S=0) is provided on the edge. The ultimate shear strength of the sheet is 100MPa and penetration to thickness ratio is 0.2. Neglect friction.

Assuming force vs displacement curve to be rectangular, the work done (in J) is

In a shear cutting operation, a sheet of 5mm thickness is cut along a length of 200mm. The cutting blade is 400mm long and zero-shear (S=0) is provided on the edge. The ultimate shear strength of the sheet is 100MPa and penetration to thickness ratio is 0.2. Neglect friction.

A shear of 20mm (S=20mm) is now provided on the blade. Assuming force vs displacement curve to be trapezoidal, the maximum force (in kN) exerted is

Two streams of liquid metal which are not hot enough to fuse properly result into a casting defect known as

Match the items in Column I and Column II.

Column I Column II
P.  Metallic Chills 1.  Support for the core
Q. Metallic Chaplets 2.  Reservoir of the molten metal
R. Riser 3.  Control cooling of critical sections
S. Exothermic Padding 4.  Progressive solidification

While cooling, a cubical casting of side 40 mm undergoes 3%, 4% and 5% volume shrinkage during the liquid state, phase transition and solid state, respectively. The volume of metal compensated from the riser is

In arc welding of a butt joint, the welding speed is to be selected such that highest cooling rate is achieved. Melting efficiency and heat transfer efficiency are 0.5 and 0.7, respectively. The area of the weld cross section is 5mm2 and the unit energy required to melt the metal is 10 J/mm3. If the welding power is 2 kW, the welding speed in mm/s is closest to

In the deep drawing of cups, blanks show a tendency to wrinkle up around the periphery (flange). The most likely cause and remedy of the phenomenon are, respectively,

Which one of the following is a solid state joining process?

Volume of a cube of side ‘l’ and volume of a sphere of radius ‘r’ are equal. Both the cube and the sphere are solid and of same material. They are being cast. The ratio of the solidification time of the cube to the same of the sphere is

A direct current welding machine with a linear power source characteristic provides open circuit voltage of 80 V and short circuit current of 800 A. During welding with the machine, the measured arc current is 500 A corresponding to an arc length of 5.0 mm and the measured arc current is 460 A corresponding to an arc length of 7.0 mm. The linear voltage (E) – arc length (L) characteristic of the welding arc can be given as (where E is in Volt and L is in mm)

Two metallic sheets, each of 2.0 mm thickness, are welded in a lap joint configuration by resistance spot welding at a welding current of 10 kA and welding time of 10 millisecond. A spherical fusion zone extending up to the full thickness of each sheet is formed. The properties of the metallic sheets are given as:

ambient temperature = 293 K  
melting temperature = 1793 K density = 7000 kg/m3
latent heat of fusion = 300 kJ/kg specific heat = 800 J/kg K

Assume : (i) contact resistance along sheet – sheet interface is 500 micro-ohm and along electrode – sheet interface is zero; (ii) no conductive heat loss through the bulk sheet materials; and (iii) the complete weld fusion zone is at the melting temperature.

The melting efficiency (in %) of the process is

The thickness of a metallic sheet is reduced from an initial value of 16 mm to a final value of 10 mm in one single pass rolling with a pair of cylindrical rollers each of diameter of 400 mm. The bite angle in degree will be

Match the correct combination for following metal working processes.

  Processes Associated state of stress
P. Blanking 1. Tension
Q. Stretch Forming 2. Compression
R. Coining 3. Shear
S. Deep Drawing 4. Tension and Compression
    5. Tension and Shear

A 200 mm long down sprue has an area of cross – section of 650 mm2 where the pouring basin meets the down sprue (i.e. at the beginning of the down sprue). A constant head of molten metal is maintained by the pouring basin. The molten metal flow rate is 6.5 × 105 mm3/s. Considering the end of down sprue to be open to atmosphere and an acceleration due to gravity of 104 mm/s2, the area of the down sprue in mm2 at its end (avoiding aspiration effect) should be

The force requirement in a blanking operation of low carbon steel sheet is 5.0 kN. The thickness of the sheet is ‘t’ and diameter of the blanked part is ‘d’. For the same work material, if the diameter of the blanked part is increased to 1.5 d and thickness is reduced to 0.4 t, the new blanking force in kN is