Mechanical Engineering - Strength of Materials - Discussion

Discussion Forum : Strength of Materials - Section 7 (Q.No. 39)
39.
If the modulus of elasticity for a given material is twice its modulus of rigidity, then bulk modulus is equal to
2C
3C
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
10 comments Page 1 of 1.

Roja rani said:   5 years ago
Thank you @Jyothis.

Jyothis P M said:   6 years ago
Known relations are:

1. E= 2C(1+1/m).
2. E= 3K(1-2/m).
Given, E=2C Therefore by equation (1), Poisson\'s ratio 1/m = 0.
with equation (1) &(2), E = 2C & E = 3K.
Therefore 2C = 3 K, and K = (2/3)C.
(2)

Parmar chirag m said:   6 years ago
If for a given material E = 2G, then the bulk modulus K will be? Please, anyone, tell me.

Rupesh said:   6 years ago
Thank you @Amit.

AQIB said:   7 years ago
Yes, you are right @Amit.

Amit said:   7 years ago
As, E=9KG/(3K+G) by putting E=2G.
2G=9KG/(3K+G).
2G (3K+G)=9KG.
6KG+2G^2=9KG.
2G^2=3KG.
2G=3K. This implies K=2G/3.
Hence, option C is right.

Amrit negi said:   8 years ago
E= 9KG/(3K+G) ... put E= 2G,
2G= 9KG/(3K+G),
2G=K(9G)/K(3+GK),
2G=9G/(3+GK),
3+GK=9G/2G,
GK=(9G/2G)-3,
GK=(9G-6K)/2G,
GK=3G/2G,
K=3/2G ---> answer.

Ankit kumar said:   8 years ago
Ans is c when we put E= 2C in equ E=2C(I + μ) We got μ =0 now again Put value of μ and E=2C in eqn E=3K(1-2μ) then we got the answer as C.

Rishabh Sirvaiya said:   9 years ago
I am getting 2G/9 by using the formula E = 2G (1 + v) ; E = 3K (1-2v).

Am I right?

SRIRAM said:   1 decade ago
E = 9KC/(3K+C), put E = 2C.

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