1. Failure Mode and Effects Analysis (FMEA)
Additional material to execute FMEA exercise

2. Definitions Failure Mode: is the way in which the failure is
manifested.
Failure effect: is the consequence of the failure.
Failure cause: is what induces the failure.
Escalante (2003)

3. Failure Mode and Effects Analysis
Abbreviated Approach O c u r S C D
Actions Results e l
Potential Causes/
Mechanisms(s)
Failure
Current e R
Item
Potential
Potential v a t P
Responsibility s
Controls e N
Failure
Effect(s) of
Recommended
& Target s
Actions S e v O c D e t R P N
Function
Mode
Failure c
Action(s)
Completion Date
Prevention/Detection
Taken
What can be done?
What
How
bad
is it?
- Design changes
are the
Effect(s)?
What did they
do and what
are the
outcomes
- Process changes
How
often
does it
happen?
What are the
functions, features
or requirements?
- Special controls
- Changes to standards,
procedures, or guides
What can go
wrong?
What are
the Cause(s)?
- No Function
How
good is
this
method at
detecting
it?
- Partial/ Over/
Developed by: Edgardo J. Escalante, Auburn University-ITESM
What are the functions? - Land landing of the CEV
What can go wrong? - Airbags partially deploy
What are the effects? - Impact loads significant
How bad is it? - Structural damage to the CEV
Degraded
Function
Who is going
to do it and
when?
- Intermittent
How can this
Function
be prevented
and detected?
- Unintended
Function

4. (9) Name of the item and its intended function (purpose/objective).
FMEA (cont.)
Item/Function Potential Potential S C Potential Cause(s)/
Failure Effect(s) e l Mechanism(s) of
Mode of failure v a failure s
(9)
(10)
(11)
(14)
(12) (13)
(9) Name of the item and its intended function (purpose/objective).
(10) Include specific problems, failures, defects (anti-functions) of
the analyzed system(*) and its functions. Use physical terms.
(11) The effect of failures in the function of the analyzed system,
as they would be perceived by the customer (internal/external).
(12) Evaluation of the severity of the effect of the failure to the
next system or to the internal/external customer. Sometimes large
values of severity can be reduced by means of design reviews that
compensate or mitigate the resulting severity.
(*) subsystem or component

5. FMEA SEVERITY EVALUATION CRITERIA
EFFECT CRITERIA: Severity of Effect RANK
Hazardous-
without
warning
Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with government regulation without warning 10
Hazardous-
with
warning
Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with government regulation with warning 9
Very High
Vehicle/item inoperable (loss of primary function). 8
Vehicle/item operable but at a reduced level of performance. Customer very dissatisfied.
High 7
Vehicle/item operable but Comfort/Convenience item(s) inoperable. Customer dissatisfied.
Moderate 6
Vehicle/item operable but Comfort/Convenience item(s) operable at a reduced level of performance. Customer somewhat dissatisfied.
Low 5
Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by most customers (greater than 75%).
Very Low 4
Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by 50% of customers.
(D,F,GM. FMEA, 2001)
Minor 3
Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by discriminating customers (less than 25%).
Very Minor 2
None
No discernible effect. 1

6. (D,F,GM. FMEA, 2001) Effect PROCESS
Effect
PROCESS
Criteria: SEVERITY of Effect
Ranking
Hazardous-
without
warning
 Very high severity ranking when a potential failure mode affects safe operation and/or involves noncompliance with regulations without warning.
Or may endanger operator without warning. 10
Hazardous-
with warning
 Very high severity ranking when a potential failure mode affects safe operation and/or involves noncompliance with regulations with warning.
Or may endanger operator with warning. 9
In the third edition this table is presented in two columns but the information is the same
(customer effect and manufacturing/assembly effect).
Very high
 Product/item inoperable, with loss of primary function. Or 100% of product may have to be scrapped or repair time >1h. 8
High
 Product/item operable, but at reduced level of performance. Customer dissatisfied. Or product may have to be sorted and less than 100% scrapped. Repair time between 0.5 and 1h. 7
(D,F,GM. FMEA, 2001)
Moderate
Product/item operable, but comfort/convenience inoperable. Customer dissatisfied. Or a portion (less than 100%) of the product may have to be scrapped with no sorting. Repair time less than 0.5h 6

7. Low
Product/item operable, but comfort/convenience operable at a reduced level. Or than 100% of the product may have to be reworked with no sorting. Repairing off-line. 5
Very Low
Fit and finish/squeak and rattle item does not conform. Defect noticed by most customers (greater than 75%). Or product may have to be sorted with no scrap, and a portion (less than 100% reworked. 4
Minor
Fit and finish/squeak and rattle item does not conform. Defect noticed by 50% of the customers. Or a portion (less than 100%) of the product may have to be reworked with no scrap. On-line but out-of-station. 3
Very Minor
Fit and finish/squeak and rattle item does not conform. Defect noticed by discriminating customers (less than 25%). Or a portion (less than 100%) of the product may have to be reworked with no scrap. On-line but in-station. 2
None
No discernible effect. Or slight inconvenience to operation or operator, or no effect. 1
(D,F,GM. FMEA, 2001)

8. (13) Indicates any special characteristic (critical, key, major)
FMEA (cont.)
Item/Function Potential Potential S C Potential Cause(s)/
Failure Effect(s) e l Mechanism(s) of
Mode of failure v a failure s
(9)
(10)
(11)
(14)
(12) (13)
(13) Indicates any special characteristic (critical, key, major)
that will require special controls. Some of the D, F, GM special
symbols can be used.
(An indication of criticality is when severity is 9 or 10, being the
occurrence and detection geater than 3. (Stamatis, 1995)).
(14) Describe what causes the failure modes. Discover the root
causes.

9. Summary of FMEA S C Potential causes/ mechanism of failures Product/
function
Potential
failure mode
Potential
failure effects e l v a s
Name of the item and its
intended function
(purpose/objective).
Include specific
problems, failures,
defects (anti-
functions) of the
analyzed system(*)
and its functions. Use
physical terms
The effect of failures in the
function of the analyzed
system, as they would be
perceived by the customer
(internal/external)
Describe what causes
the failure modes. Find
the root cause.
Typical causes:
Use field data, previous
FMEAs, warranties, etc.
Incorrect material spe-
cified,
Inadequate design
life assumption,
Over-stressing
Insufficient lubrication
capability
Begin with previous
FMEAs, brainstorming.
Use technical terms.
Examples:
Cracked, loosened,
fractured, leaking...
Examples:
Noise, erratic operation,
unstable, inoperative...
Typical mechanisms:
Wear, fatigue, corrosion
Summary of FMEA

10. FMEA (cont)
(15) (16) (17) (18) (19) (20)
(15) Frecuency of the cause from 1 to 10. Statistically assigned if having
information about similar components, systems or sub-systems. Otherwise
use the following table.
(16) List the verification/validation design activities or others related
activities. The prevention controls are preferred. It’s recommended to
use two columns to define the two types of controls: (P) for prevention,
(D) for detection.

11. DESIGN OCCURRENCE EVALUATION
Probability of
Likely Failure Rates Over Design
Ranking
Failure
Life
Very High:
100 per thousand vehicles/items 10
Persistent
failures
50 per thousand vehicles/items 9
High:
20 per thousand vehicles/items 8
Frequent
failures
10 per thousand veh
icles/items 7
DESIGN OCCURRENCE EVALUATION
Moderate:
5 per thousand vehicles/items 6
Occasional
failures
2 per thousand vehicles/items 5
1 per thousand vehicles/items 4
Low: Relatively
0.5 per thousand vehicles/items 3
(D,F,GM. FMEA, 2001)
few failures
0.1 per thousand vehicles/items 2
Remote :
0.01 per thousand vehicles/items 1
Failure is
unlikely

12. FMEA (cont) There are 2 type of controls according to its importance:
(15) (16) (17) (18) (19) (20)
There are 2 type of controls according to its importance:
i) Prevention. To prevent the cause/mechanism or the effect/failure mode,
or reduce its occurrence.
ii) Detection. To detect the cause/mechanism or the effect/failure mode
by either analytic of physical methods.
Preventive controls are related to the reduction of OCCURRENCE and
not to the evaluation of DETECTION

13. DFMEA (cont)
(15) (16) (17) (18) (19) (20)
(17) Is the evaluation associated to the best detection control listed in
the design control (relative evaluation for every individual FMEA).
A scale from 1 to 10 is used. The suggested evaluation criteria is shown
in the following table.
(18) (Risk Priority Number). Evaluation of the design’s risk. Varies
between 1 and 1000: RPN= (S)x(O)x(D)

14. (D,F,GM. FMEA, 2001)

16. FMEA (cont)
(15) (16) (17) (18) (19) (20)
(19) Attention should be focused on high values of severity, and high
RPN, and in general, independently of the RPN when the severity is
9 or 10.
The goal is first to reduce severity, then reduce ocurrence, and last
to reduce detection. It is desirable that the recommended actions reduce
the risk and increase customer satisfaction by means of an improved
design.

17. FMEA (cont) -Only the design reviews can reduce severity.
(15) (16) (17) (18) (19) (20)
-Only the design reviews can reduce severity.
-To reduce occurrence the causes or failure mechanisms must be
eliminated or controlled through design reviews.
-To improve detection, the design verification and validations actions
should be increased. If there are no actions, write “none”.
(20) Define the responsible person and the completion date.

18. (prevention/detection)
Current design
controls
(prevention/detection) R P N
Responsibility
& target completion
date c e
Recommended
actions u t r e r c
List the design verification and
validation activities. Include
current control like field tests,
laboratory studies and prototype
testing applied to this or
to similar designs.
There are 2 type of controls
according to its importance:
i) Prevention. To prevent the
cause/mechanism or the effect/
failure mode, or reduce its
occurrence.
ii) Detection. To detect the
failure mode by either analytic
of physical methods.
Determine and apply improvement
actions. If they are not necessary
write the word “none”
To reduce occurrence the causes or
failure mechanisms must be
eliminated or controlled through
design reviews.
To improve detection, the design
verification and validations actions
should be increased. If there are no
actions, write “none”.
It’s preferable to reduce -in that
order, severity, occurrence and
detection
Define the responsible
person and the completion
date
Summary of FMEA (cont.)

19. FMEA
(21) (22)
(21) Register the implementation date and a brief description of the action
taken.
(22) After the implementation of the corrective actions, re-evaluate the
severity, occurrence and detection. If necessary repeat steps Don´t
forget the follow up actions.

20. Register the implementation date and a
ACTION RESULTS S O D R e c e P
Actions taken v u t N r c
Register the implementation date and a
brief description of the action taken.
Re-evaluate RPN.