Detailed Solution

Theory | Suitable Material |
---|---|

Maximum Normal Stress Theory Or Maximum Principal Stress Theory Or Rankine’s Theory | Brittle material |

Maximum Normal Strain Theory Or Maximum Principal Strain Theory Or St.Venant’s Theory |
Ductile and brittle material but results are not accurate in both |

## Which theory is best for brittle material?

For Brittle material:- **Maximum Principal Stress Theory** (Rankine criteria) is used.

## What theories are followed by brittle materials?

15.6 **Mohr’s modified shear stress theory** for brittle materials (sometimes referred to as the internal friction theory) Brittle materials in general show little ability to deform plastically and hence will usually fracture at, or very near to, the elastic limit.

## Which theory of failure is used for brittle material?

The Mohr Theory of Failure, also known as the Coulomb-Mohr criterion or internal-friction theory, is based on the famous Mohr’s Circle. Mohr’s theory is often used in predicting the failure of brittle materials, and is applied to cases of 2D stress.

## Which theory is best suitable for ductile and brittle materials?

For Brittle material:- Maximum Principal Stress Theory (Rankine criteria) is used. Maximum Shear Stress Theory (Tresca theory), Total strain energy theory, Maximum Distortion Energy Theory (von Mises) useful for a ductile material. Tresca’s theory fails in the hydrostatic state of stresses.

## Which failure theories are best for ductile and brittle materials?

For example, the **maximum principal stress/strain theory** would be appropriate for brittle materials like cast iron or glass. On the other hand, the failure of ductile materials such as steel is best represented by the Tresca or Von-Mises criteria.

## Why there is a Griffith theory for brittle materials?

The Griffith theory states that **a crack will propagate when the reduction in potential energy that occurs due to crack growth is greater than or equal to the increase in surface energy due to the creation of new free surfaces**. This theory is applicable to elastic materials that fracture in a brittle fashion.

## Which theory explains brittle fracture?

**Orowan and Irwin theory** is given for cracking in brittle materials.

## Why normal stress theory is not suitable for ductile materials?

This theory is not suitable for the safe design of machine components made of ductile materials because **ductile materials are weak in shear**.

## What is Rankine theory of failure?

Rankine’s Theory **assumes that failure will occur when the maximum principal stress at any point reaches a value equal to the tensile stress in a simple tension specimen at failure**. This theory does not take into account the effect of the other two principal stresses.

## Which theories of failure are used for ductile material?

Assertion (A): For a ductile material the **maximum shear distortion theory** is most suitable. Reason (R): The maximum shear distortion theory of failure assumes that yielding can occur in a general three-dimensional state of stress.

## What is modified Mohr theory?

The modified Coulomb-Mohr theory is **a three-parameter theory**, but all three parameters in principle can be obtained from only two simple tests. It is shown that in the case of cast iron there is an extremely close relationship between cohesive resistance in shear and nominal ultimate strength in single or double shear.

## Why fatigue failure is brittle?

Fatigue failure is brittle-like (**relatively little plastic deformation**) – even in normally ductile materials. Thus sudden and catastrophic! Applied stresses causing fatigue may be axial (tension or compression), flextural (bending) or torsional (twisting).

## Can von Mises be used for brittle materials?

The Von Mises criterion is a good option for ductile materials with equal tensile and compressive strength, but **it fails with brittle materials**.

## Which theory explains brittle fracture?

**Orowan and Irwin theory** is given for cracking in brittle materials.

## Which of the theory is related to brittle fracture?

The **Griffith theory** states that a crack will propagate when the reduction in potential energy that occurs due to crack growth is greater than or equal to the increase in surface energy due to the creation of new free surfaces. This theory is applicable to elastic materials that fracture in a brittle fashion.

## What causes a brittle fracture Mcq?

Explanation: **When stress exceeds the cohesion**, brittle fracture occurs. It occurs below yield stress. It occurs at a lower level of stress. 10.

## What is the breaking stress of brittle materials Mcq?

What is the breaking stress of brittle materials? Explanation: It was found that the tensile strength of two adjacent atomic planes was Y/6. However, brittle materials may break at a stress of the order of **Y/1000**.