Procedure to analyze fracture:

In any failure analysis it is important to get as much

information as possible from failed part itself along with an

investigation of the condition at the time of failure.

Some of question to be asked are

Q1: How long the part was in service?

Q2: What was the nature of stress at the time of Failure?

Q3: Was the part subjected to overload?

Q4: Was the part properly installed?

Q5: Was it subject to service abuse?

Q6: Was there any change in the environment?

Q7: Was the part properly maintained?

A study of the fractures surface should answer the following

question

Q1: Type of fracture either Ductile or Brittle or the combination of

both?

Q2: Did failure start at or below the surface?

Q3: Did failure start at one point or start at several point?

Q4: Did the crack started recently or had it been growing for a long

time?

Steps or Procedure for investigating a failure: 1. Initial Observation

2. Background Data

3. Laboratory Studies

4. Synthesis of Failure

1. Initial Observation:

A detailed visual study of the actual component that failed should

be made as soon after the failure as possible.

Record all details by many photographs for later review.

2. Background Data:

Collect all available data concerned with specification and

drawing, component design, fabrication, repairs, maintenance

and services use.

3. Laboratory Studies:

Verify that chemical composition of the material is within the

specified limit, check dimension and properties of the component.

Supplementary test may be made as needed-for example

Hardness, check microstructure to check heat treatment, NDT to

check for processing defects, study fracture surface by Stereo

SEM and TEM.

4. Synthesis of Failure

Study all the facts and evidence, both positive and negative, and

answer to the typical question given earlier.

This combined with theoretical analysis, should indicate a

solution to the problem of failure.

The usual sequence for the examination of fractured components is as follows.

1. Chemical Analysis.

2. Visually survey the entire component to obtain an overall

understanding of the component and the significance of the

fractured area.

3. Classify the fracture from a macroscopic view point as ductile,

brittle, fatigue, torsion, and so forth.

4. Determine the origin of failure by tracing the fracture back to its

starting point or points.

5. Based on the observed fracture features, estimate the manner

of loading (tension, compression, shear, bending, and so on),

the relative stress level (high, medium, or low), and the stress

orientation.

6. Examine area selected by macroscopic examination at higher

magnifications by light microscopy, SEM,or replica

transmission electron microscopy (TEM) to determine the

fracture mode, to confirm the fracture mechanism (observation

of cleavage facets, ductile dimples, fatigue striations, and so

on), and to detectfeatures at the fracture origin.

7. Examine metallographic cross sections containing the origin to

detect any microstructural features that promoted or caused

fracture initiation, and determine if crack propagation favors

any microstructural constituent.