Failure Analysis and Prevention

SUPRIYA B
Department of Mechanical Engineering
 Failure Analysis and Prevention

To avoid the failures it is important that the way by which any component can fail is
understood and precautionary measures are taken to avoid such kind of the failures. But
whenever there is a failure it is important to understand the way by which it has failed what
were the causes for the failure. So, in order to understand the root causes of the failure, we
need to see that the any failure which is occurring is analyzed properly and for that purpose are
the failure analysis is carried out. In failure analysis basically we follow a systematic approach; a
systematic approach of investigation to identify the potential causes of the failure most
important causes of the failure to determine the most probable causes of failure. So, this kind
of the step is also called the root cause analysis(RCA)

Identify the causes or potential causes or the most possible causes for the failure so that the
corrective action can be taken to avoid the reoccurrence of the failure. This analysis basically
involves the number of things like observations, inspection and extensive as per the case
extensive laboratory testing of the field component from the location where from failure has
taken place or the location which is away from the fractured zone.
 Failure Analysis and Prevention

So, basically the failure analysis is a multi disciplinary multi discipline approach which involves
the expertise which for which we need the expertise of the people of the different areas and the
different disciplines in order to conclude something effectively regarding the root causes for the
given failure. Failure analysis not only helps to avoid the reoccurrence of the failure, but it also
helps in improving the quality of the product increasing the reliability, improving the performance
and improving the customer satisfaction.
whenever any the failure analysis is carried out on the failed component, it helps to
avoid the recurrence of the such kind of the failures and that basically helps in improving
the quality of the product, it improves the reliability also; and if the
component is more reliable it will be performing well for the long so, performance of the
product is improved and which in turn improves the customer satisfaction
 Failure Analysis and Prevention

Whenever failure occurs what we do? Failure how do we identify?

whenever failure of any component occurs, we will be getting some indicators which you can say as a
symptoms. And then these indicators will be coming up due to certain causes. In presence of only those
causes it the component which is being failed which is failing will be giving certain kind of the
indications and. So, in presence of those causes the certain indications will be coming in, and these
causes will be leading to the existence of the certain mechanisms which will be leading to the failure.

if we take the example of the machine tool. So, during the machining, if the cutting tool fails, in that case
it will start giving lot of chattering lot of noise and vibrations.
noise and vibrations are the indicators and this will be will be occurring due to the like say excessive
the flank wear or the cutter or cutting edge failure under the certain unfavorable conditions like too high
cutting speed feed and depth of cut or the tool geometry is improper or unfavorable for a given set of
the cutting parameters and the work piece which is to be machined.

basically these are the causes which will be leading to the like the failures in form of the flank
wear crater wear or the cutting edge fracture, and this can occur through the number of ways. Like here
cutting edge a failure will involve fracture while the flank and crater wear will involve the wear by
abrasion, adhesion, diffusion. So, all these are the mechanisms
 Failure Analysis and Prevention

Now, we have to choose in light of the work-piece material, we have to choose proper tool
geometry and the cutting parameters like cutting a speed, feed and depth of cut need to be
selected properly. So, that the tool performs the intended function in order to avoid such kind of
failures. So, these are the kind of indications that we get and we need to see what are the
causes, what is the mechanism, to establish the complete understanding about the failure so that
the corrective action can be taken in order to avoid the failure.
Failure Analysis and Prevention

Problem-solving model
 Failure Analysis and Prevention

Consider the example of a butterfly valve that fails in service in a cooling water
system at a manufacturing facility
1). Recognizing the indicators, causes, mechanisms, and consequences helps to
focus investigative actions:

· Indicators: Monitor these as precursors and symptoms of failures.

· Cause: Focus mitigating actions on these.
· Failure mechanism: These describe how the material failed according to the
engineering textbook definitions.

If the analysis is correct, the mechanism will be consistent with the cause. If the
mechanism is not properly understood, then all true cause will not be identified
and corrective action will not be fully effective.
· Consequence: This is what we are trying to avoid.
Failure Analysis and Prevention
Failure Analysis and Prevention

Over many years, and across a wide variety of

mechanical and electronic components and
systems, people have calculated empirical
population failure rates as units age over time
and repeatedly obtained a graph such as
shown below. Because of the shape of this
failure rate curve, it has become widely known
as the "Bathtub" curve or life curve of the
product
 Failure Analysis and Prevention

the first part is a decreasing failure rate, known as early failures.

The second part is a constant failure rate, known as random failures.
The third part is an increasing failure rate, known as wear-out failures.

The initial region that begins at time zero when a customer first begins to use the product is
characterized by a high but rapidly decreasing failure rate. This region is known as the Early Failure
Period (also referred to as Infant Mortality Period, from the actuarial origins of the first bathtub curve
plots). This decreasing failure rate typically lasts several weeks to a few months.

Next, the failure rate levels off and remains roughly constant for (hopefully) the majority of the useful life
of the product. This long period of a level failure rate is known as the Intrinsic Failure Period (also
called the Stable Failure Period) and the constant failure rate level is called the Intrinsic Failure Rate.
Note that most systems spend most of their lifetimes operating in this flat portion of the bathtub curve

Finally, if units from the population remain in use long enough, the failure rate begins to increase as
materials wear out and degradation failures occur at an ever increasing rate. This is the Wearout
Failure Period.
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention

Fundamental sources of failure of the mechanical

component

improper design of the component

improper selection of the material;
improper manufacturing being applied or improper
manufacturing procedures.
improper assembly
improper service conditions
improper maintenance
Failure Analysis and Prevention
Failure Analysis and Prevention

The design of the component, involves the sizing and shaping identification of the
size and shape of the component which needs to be manufactured considering the
given service conditions like the load temperature the environment the type of load
velocities etc
failure comes up due to the various factors with regard to the design of the
mechanical component the first one like, the presence of the stress raisers. This is
one of the most common cause of the failure due to the deficient design presence of
the stress raisers and these stress raisers of course, will be causing the a stress
concentration and increasing the localization of the stresses and so, localized failure
will be triggered.
 Failure Analysis and Prevention

Stress concentration is the accumulation of stress in a body due to sudden change in its
geometry. When there is a sudden change in the geometry of the body due to cracks,
sharp corners, holes and decrease in the cross section area, then there is an increase in
the localised stress near these cracks, sharp corners, holes, and decreased cross section
area. The body tends to fail from these places where the stress concentration is more. So
to prevent a body from getting failed, the concentration of stress should be avoided or
reduced. It is also called as stress raisers

What is Stress concentration factor

It is defined as the ratio of highest stress in the body to the reference stress. It is
denoted by Kt = σmax / σref
Where
σmax = Highest stress or maximum stress
σref = Reference stress

The value of stress concentration factor for

A body free from irregularities is 1.
A body that has maximum irregularities or discontinuity is greater than 1.
 Failure Analysis and Prevention

Methods to Reduce Stress Concentration

1.Avoiding sharp corners by providing a fillet radius at the sharp corners.
By providing the fillet radius at sharp corners, the cross section area decreases
gradually instead of suddenly. And this distributes the stress in the body more
uniformly.
2. By providing small holes near a big hole.
If we have an object, that has an internal hole within it. Then the intensity of stress near
that hole is more. To avoid this, some smaller holes are created near that hole. This
distributes the stress more uniformly than it was before.
3. By decreasing the nominal diameter of a threaded object and make it equal to the core
diameter.
Suppose we have a threaded object. And the intensity of stress at threaded part is more.
The chances of object may fail is more at the threaded part. This can be avoided by
decreasing the nominal diameter of the shank and make it equal to the core diameter.
This will distribute the stress more uniformly in the object with threads.
4.By providing notches or undercut at the sharp corners.
Failure Analysis and Prevention
Failure Analysis and Prevention
Failure Analysis and Prevention

Factors influencing stress concentration

Size and shape of notches
Type of loading (axial ,bending , tortional ,fatigue)
Shape of notch- fillets ,grooves,keyways,dimensions
Metal behavior –linear elastic or isotropic
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
 Failure Analysis and Prevention

To avoid the failures it is important that the way by which any component can fail is
understood and precautionary measures are taken to avoid such kind of the failures. But
whenever there is a failure it is important to understand the way by which it has failed what
were the causes for the failure. So, in order to understand the root causes of the failure, we
need to see that the any failure which is occurring is analyzed properly and for that purpose are
the failure analysis is carried out. In failure analysis basically we follow a systematic approach; a
systematic approach of investigation to identify the potential causes of the failure most
important causes of the failure to determine the most probable causes of failure. So, this kind
of the step is also called the root cause analysis(RCA)

Identify the causes or potential causes or the most possible causes for the failure so that the
corrective action can be taken to avoid the reoccurrence of the failure. This analysis basically
involves the number of things like observations, inspection and extensive as per the case
extensive laboratory testing of the field component from the location where from failure has
taken place or the location which is away from the fractured zone.
 Failure Analysis and Prevention

So, basically the failure analysis is a multi disciplinary multi discipline approach which involves
the expertise which for which we need the expertise of the people of the different areas and the
different disciplines in order to conclude something effectively regarding the root causes for the
given failure. Failure analysis not only helps to avoid the reoccurrence of the failure, but it also
helps in improving the quality of the product increasing the reliability, improving the performance
and improving the customer satisfaction.
whenever any the failure analysis is carried out on the failed component, it helps to
avoid the recurrence of the such kind of the failures and that basically helps in improving
the quality of the product, it improves the reliability also; and if the
component is more reliable it will be performing well for the long so, performance of the
product is improved and which in turn improves the customer satisfaction
 Failure Analysis and Prevention

Whenever failure occurs what we do? Failure how do we identify?

whenever failure of any component occurs, we will be getting some indicators which you can say as a
symptoms. And then these indicators will be coming up due to certain causes. In presence of only those
causes it the component which is being failed which is failing will be giving certain kind of the
indications and. So, in presence of those causes the certain indications will be coming in, and these
causes will be leading to the existence of the certain mechanisms which will be leading to the failure.

if we take the example of the machine tool. So, during the machining, if the cutting tool fails, in that case
it will start giving lot of chattering lot of noise and vibrations.
noise and vibrations are the indicators and this will be will be occurring due to the like say excessive
the flank wear or the cutter or cutting edge failure under the certain unfavorable conditions like too high
cutting speed feed and depth of cut or the tool geometry is improper or unfavorable for a given set of
the cutting parameters and the work piece which is to be machined.

basically these are the causes which will be leading to the like the failures in form of the flank
wear crater wear or the cutting edge fracture, and this can occur through the number of ways. Like here
cutting edge a failure will involve fracture while the flank and crater wear will involve the wear by
abrasion, adhesion, diffusion. So, all these are the mechanisms
 Failure Analysis and Prevention

Now, we have to choose in light of the work-piece material, we have to choose proper tool
geometry and the cutting parameters like cutting a speed, feed and depth of cut need to be
selected properly. So, that the tool performs the intended function in order to avoid such kind of
failures. So, these are the kind of indications that we get and we need to see what are the
causes, what is the mechanism, to establish the complete understanding about the failure so that
the corrective action can be taken in order to avoid the failure.
Failure Analysis and Prevention

Problem-solving model
 Failure Analysis and Prevention

Consider the example of a butterfly valve that fails in service in a cooling water
system at a manufacturing facility
1). Recognizing the indicators, causes, mechanisms, and consequences helps to
focus investigative actions:

· Indicators: Monitor these as precursors and symptoms of failures.

· Cause: Focus mitigating actions on these.
· Failure mechanism: These describe how the material failed according to the
engineering textbook definitions.

If the analysis is correct, the mechanism will be consistent with the cause. If the
mechanism is not properly understood, then all true cause will not be identified
and corrective action will not be fully effective.
· Consequence: This is what we are trying to avoid.
Failure Analysis and Prevention
Failure Analysis and Prevention

Over many years, and across a wide variety of

mechanical and electronic components and
systems, people have calculated empirical
population failure rates as units age over time
and repeatedly obtained a graph such as
shown below. Because of the shape of this
failure rate curve, it has become widely known
as the "Bathtub" curve or life curve of the
product
 Failure Analysis and Prevention

the first part is a decreasing failure rate, known as early failures.

The second part is a constant failure rate, known as random failures.
The third part is an increasing failure rate, known as wear-out failures.

The initial region that begins at time zero when a customer first begins to use the product is
characterized by a high but rapidly decreasing failure rate. This region is known as the Early Failure
Period (also referred to as Infant Mortality Period, from the actuarial origins of the first bathtub curve
plots). This decreasing failure rate typically lasts several weeks to a few months.

Next, the failure rate levels off and remains roughly constant for (hopefully) the majority of the useful life
of the product. This long period of a level failure rate is known as the Intrinsic Failure Period (also
called the Stable Failure Period) and the constant failure rate level is called the Intrinsic Failure Rate.
Note that most systems spend most of their lifetimes operating in this flat portion of the bathtub curve

Finally, if units from the population remain in use long enough, the failure rate begins to increase as
materials wear out and degradation failures occur at an ever increasing rate. This is the Wearout
Failure Period.
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention

Causes of stress concentration The various causes of stress concentration are as follows: (i)
Abrupt change of cross section (ii) Poor surface finish (iii) Localized loading (iv) Variation in
the material properties Methods of reducing stress concentration The presence of stresses
concentration cannot be totally eliminated but it can be reduced, so following are the remedial
measures to control the effects of stress concentration. 1. Provide additional notches and
holes in tension members. a) Use of multiple notches. b) Drilling additional holes. 2. Fillet
radius, undercutting and notch for member in bending. 3. Reduction of stress concentration in
threaded member. 4. Provide taper cross-section to the sharp corner of member
 Failure Analysis and Prevention

Charting Methods for RCA

Many tools exist to assist in performing RCA. The most important element, however, is the
preservation of an open mind by the investigator or investigating team. Preconceived ideas or
the existence of an investigative bias often obstructs effective root-cause investigations.
A visual representation of an RCA is more easily understood than a long narrative description.
Many charting methods have been developed that facilitate the logical organization of
information as an aid in performing an RCA. Although such techniques can be invaluable for
completeness and logistical analysis, one must not inhibit creativity and an open mind.
The following paragraphs outline a brief and somewhat simplified description of several
common charting methods that may be useful in performing an RCA. A fault-tree analysis is a
deductive analysis that identifies a top event, in this case a failure, and then evaluates all
credible
ways in which this event could have occurred by identifying the interrelationships of basic
events or conditions that lead to the failure. The tree is organized by identifying all event strings
that lead to the top event and connecting them with a “gate” that depicts the logical
relationship.
Figure depicts a simplified fault tree.
Failure Analysis and Prevention
Simplified fault tree diagram
Failure Analysis and Prevention

Simplified event and causal factor chart

 Failure Analysis and Prevention

Event and causal factor analysis charting is a very flexible tool that is very useful for performing a
logical analysis of the chronological sequence of events and causal factors. The construction starts
with a basic timeline with the addition of related conditions, secondary events, and presumptions.
To construct the chart, enclose events in rectangles and connect them in sequence from left to
right using solid arrows. The terminal event should be listed at the right-hand end within a circle.
In ovals, list conditions, causal factors, and contributing factors and show the relationship between
events with dashed arrows. Barriers may also be added to the chart to identify barriers that failed,
allowing events to occur. A barrier can take many forms including a physical barrier such as a
locker door or a procedural barrier that was not properly implemented.
The basic elements of the event and causal factor chart are primary events, secondary events,
and conditions. Events make up the backbone of the chart, while conditions are circumstances
pertinent to the situation. The goal of the analysis is to identify the key equipment failures,
process failures, or human errors that allowed the loss event to occur. Once the chart is laid out,
the causal factors are identified. These are identified as the factors that if eliminated would have
prevented the occurrence or lessened the severity of the loss event
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
 Failure Analysis and Prevention

The major steps in the model define the problem-solving process:

1. Identify: Describe the current situation. Define the deficiency in terms of the
symptoms (or indicators). Determine the impact of the deficiency on the
component, product, system, and customer. Set a goal. Collect data to provide a
measurement of the deficiency.
2. Determine root cause: Analyze the problem to identify the cause(s).
3. Develop corrective actions: List possible solutions to mitigate and prevent
recurrence of the problem. Generate alternatives. Develop implementation plan.
4. Validate and verify corrective actions: Test corrective actions in pilot study.
Measure effectiveness of change. Validate improvements. Verify that problem is
corrected and improves customer satisfaction.
5. Standardize: Incorporate the corrective action into the standards documentation
system of the company, organization, or industry to prevent recurrence in similar
products or systems. Monitor changes to ensure effectiveness.
Failure Analysis and Prevention

Root Cause Analysis Process

Failure Analysis and Prevention

Root Cause Analysis Process

And hidden causes may be in the different forms like improper training, improper motivation,
carelessness on the part of the worker, improper calibration improper
installation of the things.
the second one is the human related causes, and third is latent causes So, physical causes is
about like the design is not perfect or material selection is improper or the service conditions
which has been improper. So, these are the things will be leading to the say the fracture due to
the design deficiency, manufacturing or the material related issues.

There is another category may be procedures and everything is fine, but here what will happen
that the training to the human being involved in use of the product or in manufacturing that the
people who are involved in the manufacturing of the product are not properly trained or their,
carelessness is involved. So, these are the human related factors and there are many latent
factors like improper installation; everything is fine the component has not been installed
properly or improper the training to the workers.
Failure Analysis and Prevention

Root Cause Analysis Process

There is another category may be procedures and everything is fine, but here what will
happen that the training to the human being involved in use of the product or in
manufacturing that the people who are involved in the manufacturing of the product are
not properly trained or their, carelessness is involved. So, these are the human related
factors and there are many latent factors like improper installation; everything is fine the
component has not been installed properly or improper the training to the workers.
 Failure Analysis and Prevention

What Is Root Cause Analysis?

RCA (Root Cause Analysis) is a mechanism of analyzing the Defects, to identify its cause. We
brainstorm, read and dig the defect to identify whether the defect was due to “testing miss”,
“development miss” or was a “requirement or designs miss”.

When RCA is done accurately, it helps to prevent defects in the later releases or phases. If we find,
that a defect was due to design miss, we can review the design documents and can take
appropriate measures. Similarly, if we find that a defect was due to testing miss, we can review our
test cases or metrics, and update it accordingly.

RCA is not only used for defects reported from a customer site, but also for UAT defects, Unit
Testing defects, Business, and Operational process-level problems, day-to-day life problems, etc.
Hence it is used in multiple industries like Software Sector, Manufacturing, Health, Banking Sector,
etc.
Failure Analysis and Prevention

Illustration
Conducting Root Cause Analysis is similar to the work of the
doctor who treats a patient. The doctor will first understand the
symptoms. Then he will refer to laboratory tests to analyze the
root cause of the disease.
If the root cause of the disease is still unknown, the doctor will
refer for scan tests to understand further. He will continue the
diagnosis and study until he narrows down to the root cause of
the patient’s sickness. The same logic applies to Root Cause
Analysis performed in any industry.
So, RCA is aimed at finding the root cause and not treating the
symptom, by following a specific set of steps and associated
tools. It is different from defect analysis, troubleshooting, and
other problem-solving methods as these methods try to find
the solution for the specific issue, but RCA tries to find the
underlying cause.
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention

Cause-and-Effect Analysis. Failures are always caused to happen. A cause-and-

effect analysis is a way to relate causes to
a failure in an attempt to find the root cause. Causes can be design problems,
human performance, poor fabrication, and
so forth. A simple cause-and-effect analysis can take the form of a fishbone diagram
(Fig. 36) that can be constructed as
follows:
1. Clearly describe the failure at the right side of the diagram.
2. Identify the main cause categories as branches converging on the failure.
3. Brainstorm and list all causes on each branch.
4. Analyze the data until the root cause(s) are identified (Ref 11).
Failure Analysis and Prevention
 Failure Analysis and Prevention

Five Whys is a simple technique that is intended to lead the user into
deeper levels of cause identification, thus leading
one further into root cause. The overall objective is to ask “why” after
each cause has been identified until true root
causes are identified. There actually may be more or less than five “whys”
to reach the root-cause level desired (Ref 11).
The following example demonstrates this simple concept:
· Event—Highway bridge failure
· Why?—Corrosion damage on structural steel
· Why?—Water collection
· Why?—Debris clogging drainage pipes
· Why?—No maintenance performed to clean pipes
· Why?—Maintenance funding reductions (root cause)
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention

Advantages Of Root Cause Analysis

Enlisted below are some of the benefits, you will get:
•Prevent the reoccurrence of the same problem in the future.
•Eventually, reduce the number of defects reported over time.
•Reduces developmental costs and saves time.
•Improve the software development process and hence aiding quick
delivery to market.
•Improves customer satisfaction.
•Boost productivity.
•Find hidden problems in the system.
•Aids in continuous improvement.
Failure Analysis and Prevention

Types Of Root Causes

#1) Human Cause: Human-made error.
Examples:
Under skilled.
Instructions not duly followed.
Performed an unnecessary operation.
#2) Organizational Cause: A process that people use to make decisions that were
not proper.
Examples:
Vague instructions were given from Team Lead to team members.
Picking the wrong person for a task.
Monitoring tools not in place to assess the quality.
#3) Physical Cause: Any physical item failed in some way.
Examples:
The computer keeps restarting.
The server is not booting up.
Strange or loud noises in the system.
Failure Analysis and Prevention

Steps To Do Root Cause Analysis

A structured and logical approach is required for an effective root cause analysis.
Hence, it’s necessary to follow a series of steps.
Failure Analysis and Prevention

#1) Form RCA Team

Every team should have a dedicated Root Cause Analysis Manager [RCA Manager] who will
collect the details from the Support team and initiate the kick-off process for RCA. He will
coordinate and allocate resources who need to attend RCA meetings depending on the stated
problem.
Teams, who attend the meeting, should have personnel from each team [Requirement, Design,
Testing, Documentation, Quality, Support & Maintenance] who are most familiar with the problem.
The team should have people who are directly linked to the defect as well.
For example, the Support engineer who gave an immediate fix to the customer.
Share the problem details with the team before attending the meeting so that they can do some
initial analysis and come prepared. Team members also gather information related to the defect.
Depending on the incident report, each team will trace what went wrong w.r.t to this scenario in
their respective phases. Being prepared will increase the efficiency of the upcoming discussion.
 Failure Analysis and Prevention

#2) Define The Problem

Collect the details of the problem like, incident reports, problem evidence (screenshot, logs,
reports, etc.), then study/analyze the problem by asking the below questions:
•What is the problem?
•What is the sequence of events that led to the problem?
•What systems were involved?
•How long the problem existed?
•What is the impact of the problem?
•Who was involved and determine who should be interviewed?
Use ‘SMART’ rules to define your problem:
•SPECIFIC
•MEASURABLE
•ACTION-ORIENTED
•RELEVANT
•TIME-BOUND
 Failure Analysis and Prevention

#3) Identify Root Cause

Conduct the BRAINSTORMING session within the RCA team formed to identify the
causes. Use the Fishbone diagram or 5 Why Analysis method or both to arrive at
the root cause/s.
RCA manager should moderate the meeting and set the rules for the Brainstorming
session. For example, the rules can be:
Criticizing/blaming others should not be allowed.
Don’t judge other’s ideas. No ideas are bad they encourage wild ideas.
Build on the ideas on others. Think about how you can build on other’s ideas and
make it better.
Give each participant due time to share their views.
Encourage out of box thinking.
Stay focused.
All ideas should be recorded. RCA manager should assign a member to record the
minutes of the meeting and update of RCA templates.
Failure Analysis and Prevention

#4) Implement Root Cause Corrective Action (RCCA)

Correction action involves giving fix to the solution by identifying the real root cause.
To facilitate this, a delivery manager has to be present who can decide in which all
versions the fix has to be implemented and what should be the delivery date.
RCCA should be implemented in such a way that this root cause will not occur again
in the future. Fix given by the support team will be temporary for the customer site
where the issue is reported. When this fix is merged into an ongoing version, do
proper impact analysis to ensure no existing feature is broken.
Give the steps to validate the fix and monitor the implemented solution to check if
the solution is effective.
Failure Analysis and Prevention

#5) Implement Root Cause Preventive Action (RCPA)

The team needs to come up with a plan for how such a similar issue can be prevented in
the future. For example, Update Instruction Manual, improve skillset, update the team
assessment checklist, etc. Follow proper documents of preventive actions and monitor
whether the team is adhering to the preventive actions taken.
Please refer to this research paper on “Defect Analysis and Prevention for Software
Process Quality Improvement” published in the International Journal of Software
Engineering & Applications to get an idea of the types of defects reported in each
software phase and suggested preventive actions for them.
The information gained from RCA can go as input into Failure Mode and Effect Analysis
(FMEA) to identify points where the solution can fail.
Implement Pareto Analysis with the causes identified during RCA over a period, say half-
yearly or quarterly which will help to identify the top causes which are contributing to the
defects and focus on preventive action for them.
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention

Other Failure Analysis Tools

There are many other “tools” that must be considered in performing

a failure analysis. In addition to root-cause
techniques, tools available to the analyst include:
· Review of all sources of input and information
· People interviews
· Laboratory investigations
· Stress analysis
· Fracture mechanics analysis
 Failure Analysis and Prevention

Sources of Input
Physical data such as failed parts, samples of environmental influences, photographs, data collection
records (pressure, temperature, speed, etc.), and background data are an important part of the
investigative process. Forensic analysis of such parts and data is the backbone of any failure
investigation. Some of the key elements
to an investigation include:
· Physical evidence: Broken parts, samples, malfunctioned components, positions, configurations, and so
forth. The timely preservation, collection, and recording of physical evidence are essential to any
effective failure investigation. The preservation of evidence is done by restricting access to a failure site,
preserving of configurations and positions, taking a photographic record of the as-found situation,
making sketches, recording of process variables (pressure, temperature, position, etc.), marking and
tagging pieces and positions.
Background data: Design data, specifications, technical data, analysis or simulation results, and so
forth
· People: Witnesses, operators, designers, maintenance personnel, participants, experts
Failure Analysis and Prevention

People Interviews
Interviews can provide an essential source of information in any failure investigation.
This information, if
solicited and documented properly, augments that collected by physical data or
research. A very effective way
to collect information from people is through the interview process. There are three
reasons one would collect
data through interviews:
· Firsthand data (witnesses, participants, etc.)
· Background and circumstantial data (historical experiences, related events,
situational insights, etc.)
· Expert information (to elicit technical knowledge)
 Failure Analysis and Prevention

Some important points to consider when performing interviews include:

· Explain why the interviews are being performed and maintain confidentiality when
possible.
· Interview individually or small groups when possible. Never interview somebody with
one's supervisor
or manager present or in any other influencing or restricting environment.
· Make the interview environment as comfortable and unintimidating as possible.
· Ask open-ended questions and do not guide the responses.
· Distinguish between firsthand and secondhand knowledge.
· Solicit specific quantitative data, qualitative data, and opinions.
· Get referrals to others who may have pertinent information and other sources of
data.
· Recognize biases and paradigms when interpreting answers.
Failure Analysis and Prevention

Laboratory Investigations
After pertinent data and samples have been collected, a laboratory investigation is often needed to
fully analyze the physical evidence and to identify the failure mechanism. Good procedures in a
laboratory begin with good sample collections and handling.
In-Situ Sample Collection and Laboratory Receipt. When collecting samples for laboratory
examination, it is a good rule of thumb to collect failed parts, nearby fragments, and lubricant and
fluid samples. Collect evidence beyond what is apparent at the time of the initial assessment.
Collect undamaged samples of similar components for comparison to the damaged one. Draw
diagrams to indicate the position of parts and sample collection locations. Do not be afraid to take
many photographs while photo documenting the scene. Take shots from every angle and always
have a scalable object in the photo, preferably a ruled scale. Make in situ markings of fluid levels
or other positions that should be recorded prior to disturbing. Having the appropriate
documentation and collection tools at a failure site is important to be prepared for activities that
may not be anticipated prior to arrival.
Failure Analysis and Prevention

Laboratory Analysis. Steps taken in a laboratory after proper receipt may include:
· Initial examination
· Photo documentation
· Nondestructive examination
· Material verification
· Fracto-graphic examination
· Metallurgical analysis
· Mechanical properties determination
· Analysis of evidence
· Writing of a report
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention

Root Cause Analysis Techniques

#1) Fishbone Analysis

Fishbone diagram is a visual root cause analysis tool to identify the possible causes
of the identified problems and hence it’s also called Cause and Effect diagram. It
allows you to get down to the real root cause of the issue rather than solving its
symptom.
It’s also called the Ishikawa Diagram as it was created by Dr.Kaoru Ishikawa [a
Japanese quality control statistician

Fishbone analysis is used in analyze phase of six sigma’s DMAIC approach for
problem-solving. It’s one of the 7 basic tools of quality control.
Failure Analysis and Prevention

Steps to create a Fishbone Diagram:

Fishbone diagram resembles the skeleton of a fish with the problem forming the head of fish
and causes forming the spine and bones of the fish.

Follow the below steps to create a fishbone diagram:

Write the problem at the head of the fish.

Identify the category of causes and write at end of each bone [cause category 1, cause
category 2 …… cause category N]
Identify the primary causes under each category and mark it as primary cause 1, primary
cause 2, primary cause N.
Extend the causes to secondary, tertiary, and more levels as applicable.
Failure Analysis and Prevention
Failure Analysis and Prevention

#2) The 5 Whys Technique

5 Why Technique was developed by Sakichi Toyoda and was used at Toyota in their
manufacturing industry. This technique refers to a series of questions where each
answer is responded with a Why question. It can be related to how a child will ask
questions to grown-ups. Based on the answer grown-up gives, they will ask “Why”
questions again and again till they are satisfied.
5 Why technique is used standalone or as part of fishbone analysis to drill down to the
root cause of the problem. The number of steps is not limited to 5. It can be less or more
than 5 until the diagnosis of the problem has arrived. 5 Whys are relatively a simpler
technique and faster way to arrive at the root causes. It facilitates quick diagnosis to rule
out the symptoms and arrive at the root cause.
The success of the technique depends on the knowledge of the person. There can be
different answers to the same Why question. So, selecting the right direction and focus
in the meeting is important.
 Failure Analysis and Prevention

Steps to create 5 Whys diagram

Start the brainstorming discussion by defining the problem. Then follow with subsequent Why and
their answers.
Thank you
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention
SUPRIYA B
Department of Mechanical Engineering
Failure Analysis and Prevention

Fracture Mechanics and Failure Analysis

Historically, the discipline of fracture mechanics was developed to understand the relationships
among cracklike imperfections, stresses, and crack tolerance for the purpose of fabricating
durable structures.
As development of this body of knowledge continues, the usefulness of fracture mechanics in
failure analysis has been recognized and is appropriately applied as one of the tools for failure
analysis
It is instructive to note that the technique is useful in some failure analyses. By performing
careful measurements of relevant fracture features, incorporating known material properties
(such as tensile strength and fracture toughness), and analyzing the loads and mechanics of the
application, relationships can be developed to obtain an estimate of the loads and/or stresses
that were operating at the time of fracture or to determine that the material in fact did not have
the assumed properties.
Failure Analysis and Prevention

Fracture Mechanics and Failure Analysis

These can be compared with the loads or stresses either measured or calculated .
Note that this is only avery brief summary and an oversimplification of the process.
Extreme care must be exercised in performingsuch a fracture mechanics analysis,
since there are uncertainties in failure analysis and in the stress-intensityfactor
solutions of the failed component. The results of the stress analysis and fracture
mechanics analysis must be consistent with the macroscale and microscale
fractographic information and the microstructural
information.
Thank you
SUPRIYA B
Department of Mechanical Engineering