Failure Analysis

This blog page can be used for a last minute revision on the topic of ' Failure Analysis' from the material science course.

Failure Analysis

What is failure ?

- It is a machine or a component that is unable to function as intended. Types of failures are distortion , fracture and wear.

What is failure analysis ?

- It is an examination of the failed component and of the failed situation which will help us to determine the causes of the failure.

Types of failure and it's description

Fracture - It is the separation of  an object or material into two or more pieces under the action of stress .

Wear - Wear is a failure where the fracture toughness causes the material to degrade . Undesirable removal of the materials from the contacting surfaces .

Fatigue - Material fatigue is the weakening of the materials due to repeatedly applied loads . The progressive and the localised strutural damage happens when a material undergoes cyclic loading . The maximum stress values are less than the ultimate tensile stress limit .

Corrosion -  It is the gradual destruction of materials due to the chemical reaction with it's environment.

Distortion - Undesirable alteration in shape of the material

Creep - It is the tendency of a material to move slowly or to be deformed permanently due to mechanical stresses. 

Failure Analysis process

Step 1 : Background review

Step 2 : Catalogue Evidence

Step 3 : Examine and Test Evidence

Step 4 : Analyse all Data

Step 5 : Conclusions and Recommendation

Macroscopic Examination

- The macroscopic examination are being conducted with an  unaided eye , magnifying glass or microscope at lower magnification . The magnification ranges from 1 to 50 times .

Microscopic Examination

- The microscopic examination are conducted at higher magnifications . The magnification ranges up to 200000 times . This examination is essential for providing micro structure feature of failed surface and also to provide the evidences of the failed mechanism,

Non- Destructive Testing

- It is a test method that allows physical properties of the failue mechanism to be examined without taking the samples out of service. The test must not destroy the material taht is being examined or damage it's future serviceability .

- Examples are radiographic and ultrasonic .

Destructive Testing

- This test involves removing a metal component form service and sectioning the component for analysis. The purpose for this test is to find out whether the design met the required standards with the process or not and also find out the process defect .

- Examples are tensile testing , impact testing