Forging MCQ Quiz in తెలుగు - Objective Question with Answer for Forging - ముఫ్త్ [PDF] డౌన్‌లోడ్ కరెన్

Explanation:

Cold forging is a metal shaping & manufacturing process in which bar stock is inserted into a die and squeezed into a second closed die.

• The process, completed, is at room temperature or below the metal’s recrystallization temperature to form a metal into a desired shape or configuration.
• Cold forging is an efficient and economical metal deforming process for the production of high volumes of parts at low cost.
• There are three methods of cold forging that differ according to temperature, which can be cold, warm, or hot and involve the use of hammers, dies, or presses to shape, squeeze, deform, and roll metals.
• Cold forging should not be confused with machining or casting since the end result is a stronger and higher quality product.
• Unlike warm or hot forging, cold forging shapes and deforms bar stock at room temperature using localized, compressive force.
• Depending on the requirements of the parts design, the workpiece may pass through multiple dies or be struck several times in succession to achieve the proper shape.

Thus, option (4) is the correct answer.

Concept:

True strain:

If no friction happens between work and die surface, then homogenous deformation occurs so that radial flow is uniform throughout work part height.

The true strain, in this case, is given by:

\(\epsilon_t=\ln\left(\frac{h_{initial}}{h_{final}}\right)=2\ln\left(\frac{d_{final}}{d_{initial}}\right)\)

Calculation:

Given:

d_i = 200 mm, d_f = 400 mm, h_i = 60 mm.

\(\epsilon_t=\ln\left(\frac{h_{initial}}{h_{final}}\right)=2\ln\left(\frac{d_{final}}{d_{initial}}\right)\)

\({\rm{\epsilon_t}} = 2\ln \left( {\frac{{{d_{final}}}}{{{d_{initial}}}}} \right) =2\ln \left( {\frac{{{400}}}{{{200}}}} \right)\Rightarrow2\ln2= 1.386\)

Explanation:

Upsetting

• Upsetting is a forging operation whereby the length of a piece of metal is reduced and its cross-sectional area is increased.

Additional Information

Drawing down

• Drawing down or “Cogging” is an operation similar to fullering with the difference that the stock is reduced at only one end (and its length increased) instead of at a central place as in fullering.

Spinning

• It sometimes called spin forming, which is a metal forming process used to form cylindrical parts by rotating a piece of sheet metal while forces are applied to one side.
• A sheet metal disc is rotated at high speeds while rollers press the sheet against a tool, called a mandrel, to form the shape of the desired part.
• Spun metal parts have a rotationally symmetric, hollow shapes, such as a cylinder, cone, or hemisphere.
• A spinning operation is carried out on Lathe.
• Examples include cookware, hubcaps, satellite dishes, rocket nose cones, and musical instruments.

Concept:

The power-law behaviour shows the material is a strain-hardening material.

For a strain-hardening material, with ideal work and efficiency, the maximum strain per pass is given by 

ϵ = n + 1;

Calculation:

Given \(\overline \sigma = 50{\overline \varepsilon ^{0.3}}\)

⇒ n = 0.3;

Now the maximum strain per pass in annealing with ideal work and efficiency η = 1 will be 

ϵ = n + 1 = 0.3 + 1

⇒ ϵ = 1.3

Concept:

In a forging process

Volume before forging = Volume after forging

In the case of cylinder 

πd12h1 = πd22h2

where d1 = initial diameter, d2 = final diameter, h1 = initial height, h2 = final height

Calculation:

Given:

d1 = 50 mm, h1 = 22.5 mm, h2 = 10 mm, d₂ = ?

The volume before forging = Volume after forging

\(π d_1^2\;{h_1} = π d_2^2\;{h_2}\)

\({d_2} = {d_1} \times \sqrt {\frac{{{h_1}}}{{{h_2}}}}\)

\({d_2} = 50 \times \sqrt {\frac{{22.5}}{{10}}} = 75~mm\)

Forging is a process in which material is shaped by the application of localized compressive forces exerted manually or with power hammers, presses or special forging machines. The process may be carried out on materials in either hot or cold state.

Forging is an effective method for producing many useful shapes. The process is generally used to produce discrete parts. Typical forged parts include rivets, bolts, crane hooks, connecting rods, gears, turbine shafts, hand tools, railroads, and a variety of structural components used to manufacture machinery. The forged parts have good strength and toughness; they can be used reliably for highly stressed and critical applications.

Upset forging involves increasing the cross-section of material at the expense of its corresponding length. Examples of upset forged parts are fasteners, valves, nails, and couplings.

An upset forging operation is used to form a head on a bolt.

Concept:

Drop forging is a metal forming process that a billet is inserted into a die and then hammered until it has assumed the shape of the die.

The lower die is a stationary part, while the upper part is a moving hammer dropped onto the workpiece in order to deform it.

Concept:

\(Engineering\;strain = \frac{{{\rm{\Delta }}L}}{L} \)

\(True~strain= ln(1 + \varepsilon _E)\)

Concept:

\(Engineering\;strain = \frac{{{\rm{\Delta }}L}}{L} = \frac{{40 - 20}}{{20}} = 1\)

True strain = ln(1 + 1) = ln2

\(Engineering\;stain = - \left( {\frac{{40 - 10}}{{40}}} \right) = \frac{{ - 3}}{4}\)

\(True\;strain = \ln \left( {1 - \frac{3}{4}} \right) = \ln \left( {0.25} \right)\)

Total true strain = ln 2 + ln 0.25 = -0.693

Concept:

Forging is a basic process in which the workpiece is shaped by compressive forces applied through various dies and tooling.

Forged parts now include large rotors for turbines; gears; bolts and rivets; cutlery hand tools; numerous structural components for machinery, aircraft, and railroads; and a variety of other transportation equipment. 

• Forging is the plastic deformation of metals, typically at elevated temperatures, using compressive forces exerted through a die to conform the metal to the desired shape.
• It is carried out either hot or cold. Hot forging is done at temperatures above recrystallization temperatures, typically 0.6 T_m, or above, where T_m is melting temperature. Warm forging is done in the temperature range: 0.3 T_m to 0.5 T_m.
• Cold forging has advantages such as a good surface finish, high strength, and greater accuracy. 

Forging has several advantages.

• Closer dimensional accuracies achieved require very little machining after forging.
• Material saving is the result.
• Higher-strength, greater productivity, favorable grain orientation, high degree of surface finish are other merits.
• Closing of voids in the metal 
• Reduced machining time

Because the metal flow in a die and the material's grain structure can be controlled, forged parts have good strength and toughness, and are very reliable for highly stressed and critical applications.

The formation of a grain structure in forged parts is elongated in the direction of the deformation. The workpiece undergoes recrystallization, therefore, provide finer grains compared to the cast dendritic structure resulting in improved mechanical properties

Explanation:

Coining:  It is a cold press working operation in which the starting material is in the form of a blank of sheet metal. Coining is a pressing operation, it does not base on metal deformation.

• It is essentially a cold forging operation expects for the fact that the flow of metal occurs only at the top layers and not the entire volume.
• Coining is a simple application of closed die forging in which fine details in the die impression are impressed into the top or/and bottom surfaces of the workpiece.
• Coining is the operation of the production of coins, medals, or other ornamental parts by squeezing operation.