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

local yielding and stress redistribution is seen in Ductile material.

Explanation:

Gold Tensile Testing: Necking Phenomenon

Definition: Tensile testing is a fundamental mechanical test where a sample is subjected to a controlled tension until failure. The objective is to measure the material’s strength, ductility, and other mechanical properties. During tensile testing, a phenomenon known as necking may occur, particularly in ductile materials. Necking is characterized by a localized reduction in cross-sectional area of the material, typically leading up to fracture.

Option 1: A is true but R is false.

• Gold, being a ductile and malleable metal, exhibits necking during tensile testing due to its ability to undergo significant plastic deformation before fracture. Necking is a characteristic behavior of ductile materials, not brittle ones. Brittle materials typically fail without significant plastic deformation, and hence, they do not exhibit necking. The assertion (A) correctly states that necking occurred during the tensile testing of gold, which aligns with gold's known ductility. However, the reason (R) incorrectly classifies gold as a brittle material, which is factually incorrect. Therefore, option 1 is the accurate choice.

Explanation:

Ductility:

• Ductility is the property by which materials can be stretched.
• Large deformations are thus possible in ductile materials before the absolute failure or rupture takes place.
• These materials have post-elastic strain (plastic strain) greater than 5%.
• Example: mild steel, aluminum, copper, etc.

Additional Information

Brittleness:

• Brittleness is the lack of ductility i.e. materials can not be stretched in brittle materials, fracture takes place immediately after elastic limit with relatively smaller plastic deformation.
• For the brittle materials, fracture and ultimate points are the same and after the proportional limit, very small strain is seen.
• Brittle materials have post elastic strain less than 5%.
• Example: cast iron, concrete, and glass.

Explanation:

The relationship between E, C, K is given by

\(E =\frac{9KC}{3K+C}\)

Where, E = Modulus of elasticity, C = Modulus of rigidity, K = Bulk modulus

Derivation:

We Modulus of rigidity is given by 

\(C =\frac{E}{2(1+μ )}\)       ---(1)

And Bulk modulus is given by

\(K =\frac{E}{3(1-2μ )}\)        ---(2)

Taking the value of μ from 1

2C( 1 + μ ) = E

⇒ 2C + 2μC = E

⇒ \(μ =\frac{E-2C}{2C}\)

Now put μ in equation 2

\(K =\frac{E}{3(1-2μ )}\)

⇒ \(K = \frac{E}{3\left ( 1-\left ( \frac{E-2C}{C} \right ) \right )}\)

⇒ \(3K = \frac{EC}{-E+3C}\)

⇒ 9KC = E(C + 3K)

⇒ \(E =\frac{9KC}{3K+C}\)

Explanation:

Poisson's ratio:

The ratio of lateral strain to the longitudinal strain is a constant for a given material. When the material is stressed within the elastic limit this ratio is called Poisson's ratio.

\(μ = \frac{{ - lateral\;strain}}{{longitudinal\;strain}}\)

In general, for engineering purpose value of Poisson's ratio vary from 0 to 0.5.

The value of μ for some important material is listed below;