BTEC Assignment Brief
Pearson BTEC Level 3 National Extended Diploma in
Qualification Engineering
Unit number and title Unit 25: Mechanical Behaviour of Metallic Materials
Learning aim(s) (For NQF C: Explore the in-service failure of metallic components and
only) consider improvements to their design
Investigating in-service failure of components and proposing
Assignment title design changes to improve their performance.
Assessor Oga I.O
12/01/2023
Issue date
26/01/2023 {23:59pm}
Hand in deadline
You are working as an apprentice technician for a large
company that manufactures hydraulic systems and airframe
components for the aerospace industry. The quality manager
is impressed with your excellent knowledge about the
mechanical properties of metals and your ability to carry out
practical investigations.
Vocational Scenario or
Context
They now move you into the life cycle testing team so you
can work with colleagues who have responsibility for carrying
out endurance tests on components. The data collected is
used to influence improvements in service critical
components working in stress environments that could lead
to fatigue or creep failure and corrosion unless monitored.
You will also be involved in the component redesign process.
You are going to inspect engineered components that have
failed in service, to establish the causes of failure and
propose design modifications to prevent the problems from
reoccurring. You will be investigating mechanical failure, for
example fatigue, and failure due to corrosion. Mechanical
failure is when a component breaks or becomes
unserviceable (fatigue cracks or creep). Corrosive failure is
when a component suffers from surface degradation (e.g.
rusting). Use a log book to record all data, information and
images.
Task 1
To do this:
You will be provided with a small selection of components
and information about the loading conditions under which
they operated for a significant period of time.
You need to:
• Visually inspect at least two components which have suffered
mechanical failure (creep and fatigue) and identify the causes of
the failure modes/problems, for example looking for the classic
, signs of fatigue (crack propagation, growth, crystalline tear) by
comparing with reference sources. Support your investigations
with mechanical testing, for example, by safely carrying out a
hardness check.
• Visually inspect a component which has corroded to the point of
making it unserviceable.
• Investigate design changes that will prevent or mitigate the
problems that you have identified. Design changes could be
modifications to the physical shape of a component (e.g.
reducing the impact of stress raisers by smoothing out abrupt
changes of cross section), changing the material from which the
component is made (e.g. improved performance properties at
high temperature) or a higher grade of surface protection (e.g.
hard anodising).
You then need to:
Present your findings in an organised technical report which
should include:
• Annotated images of the examined components.
• Detailed annotated images of failed surfaces/components and
information about why the failure occurred, with reference to
mechanical design principles.
• A range of design improvements for the failed components, with
reference to mechanical design principles to justify the suggested
modifications.
Checklist of evidence A portfolio containing a log book and report including
required annotated images and commentary, test results, sketching,
learner observation record etc.
Criteria covered by this task:
Unit/Criteria
To achieve the criteria you must show that you are able to:
reference
Evaluate, using language that is technically correct and of a high
standard, the results from safely conducted and accurate checks and tests
25/C.D3
to establish how components failed in service, recommending a design
solution from a range of alternatives
Analyse, using the results, how each component failed and justify how
25/C.M5
each component’s design could be improved.
Conduct a visual inspection check and at least one test safely and
25/C.M4
accurately on components that have failed in service
Explain, using the results, how each component failed and how each
25/C.P7
component’s design could be improved.
Conduct a visual inspection check and at least one test safely on
25/C.P6
components that have failed in service.
Sources of information Books
to support you with this Materials for Engineers and Technicians 6th Edition; Bolton
Assignment W, Higgins R A; Routledge, 2014; ISBN 978-1138778757
Websites
2
BTEC Assignment Brief v1.0
BTEC Internal Assessment QDAM January 2015
, www.doitpoms.ac.uk - includes micrographs of a large range
of materials
http://www.matweb.com/
http://www.makeitfrom.com/
Other assessment Case study + Prepared test specimens
materials attached to
this Assignment Brief
3
BTEC Assignment Brief v1.0
BTEC Internal Assessment QDAM January 2015
, Assignment 3 – In service failure of metallic components
I have been requested to inspect two different engineered components that have failed during
service. I have been requested to identify the mode of failure of these two parts and I must identify
the reason that caused the initial failure of the parts. Both parts were gathered from a Peugeot 206.
There are multiple types of failures however the three main ones that we will discuss in this
assignment is Brittle fracture/failure and Ductile fracture/failure and Chemical corrosion in the form
of water.
Part 1
On page 5 I have discussed about the effect fatigue has on the Hub. The HUB is labelled as material
A. I have talked about how does fatigue and load affect the material and how different loads affect
them.
Hub for break disk for Peugeot 206
In the image we can see the part has failed. The method of failure is
Fatigue Brittle failure and Corrosion. Due to the fact when the part
failed and where it cracked the metal did not deform at all and it
has straight sharp edges which suggest it was a brittle failure.
As we can notice it there is a lot of rust present more notably in the
area where the part has cracked, we can see a very dark orange
spot of rust that is where the crack initiated and then the water got
into the crack and slowly crack propagation started occurring and
then the part ultimately failed.
There are many causes to a brittle fracture however the main one is Trans granular cleaving which is
the process when brittle fracture initiates at a microfracture, These are more commonly known as
voids impurities or in material stress that was accumulated over time. These are all weak points in a
material due to this fact when huge loads are applied onto the part the forces will break the weakest
crystalline, Rather than following the grain boundary it will directly break through the grains of
crystalline due to this reason we can see with the naked eye that when a brittle fracture occurs it has
clear sharp corners and at the point of failure there in a straight line.
Another reason to the failure of the part can be load rate during its operation. Which means that
there was too much load put on the part in a very short time which has caused the grains to split,
First grain dislocation occurred at the weakest bond however due to the fact that the load was
applied all at once the grains did not have time to deform and they rather split in the direction the
forces have acted upon the part.
Another possible reason why the part might have failed is due to
chemical corrosion, it is more commonly known as electrochemical
corrosion and its primary cause is when metal atoms lose their
electrons and become ions which then are carried away or eroded
