Training Booklet on Drive Shafts and Cosmetic Fittings

This training booklet provides comprehensive information on drive shafts and cosmetic fittings. It covers the materials used in drive shafts, principles and features applied in material selection, non-destructive methods for checking materials, mechanical tests conducted on different materials, and the failure of cosmetic fittings in the automotive sector. The booklet is a valuable resource for understanding the design and manufacturing of drive shafts and cosmetic fittings.

TRAINING BOOKLET ON DRIVE SHAFTS AND COSMETIC FITTINGS
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Materials used in the manufacture of drive shafts
Abstract
A drive shaft is a mechanical structure that is applied for the purposes of transmitting rotation
and torque. Drive shafts are torque carriers hence are subjected to shear and torsion stresses.
These stresses should match the differences that exist between the load and the input torque. This
means that the strength of the shafts should match the strength of the stress that is applied to
them.
Introduction
In selecting materials used in making drive shafts some factors come into play. In most cases,
aluminium, stainless steel and carbon steel are the most common materials that are used in
making drive shafts due to their good mechanical properties.
The principles, mechanical tests, as well as non-destructive methods applied in assessing the
materials selected in making drive shafts are discussed in detail in this report.
Background
Principles and features applied in material selection
These principles and features that are applied when selecting the materials used in making drive
shafts are discussed are as follows;

Tensile strength
This is the ability of materials to bear the load that is applied to them before breaking or
deforming. It is measured using tensile testing (Davis, 2011). Tensile testing is a basic type of
mechanical testing that is widely applied in choosing the material used in making of drive shafts
more so based on the quality and how the material reacts when subjected to the different kinds of
force. To test for tensile strength, a drive shaft is placed in a square area depending on the
standard machine gauge length (Aldous, 2015). Then, the shaft is held using the crossheads and
subjected to force up to a point where it fractures. The measurement of the elongated section is
taken to determine the tensile strength.
Impact strength
This is the ability of materials to absorb energy before they fracture as a result of deformation.
Impact testing is applied in determining how tough the material used in making drive shafts is.
This test outlines the quantity of energy that is taken in by a material as it fractures.
Hardness
This is the ability of materials to bear mechanical abrasion and indentation before they reach the
point of deformation (Royster, 2011). In measuring for this feature, a hardness testing machine is
applied. A disc cutter is used to cut the drive shaft into a number of pieces and then placed on the
hardness testing machine. The results obtained will form a U-shaped curve when the data is put
in the graph as the hardness levels decline when close to the middle section of the shaft. The
hardness number can range between 79- 100.2.

Fatigue resistance
This is the ability of materials to maintain their structure regardless of the cyclic loading that is
applied to them. The fatigue resistance test examines how the materials react in cases where
there is fluctuation of loads. A standard mean load as well as a constantly changing load is
placed on the drive shaft and checked for premature failure or conflicting results (Moore, 2010).
The results should be based on how the material can be able to endure as many stress cycles as
possible without fracturing whereby there is a standard limit failure value and beyond it cracks
will develop hence causing fractures.
Creep strength
This is the stress that tends to produce raptures due to alterations in environmental conditions.
Creep failure manifests as a result of the accumulation of the creep strain causing deformation of
the drive shafts (Keyes, 2012).
Torsion strength
This gauges how the materials used in making drive shafts are able to tolerate a load that is
twisting. Here the ultimate material strength is tested by placing a torsion load and checking the
amount of torsion strength material can withstand before rupturing (T. Kevin O'Brien, 2011).
Methods applied
Non-destructive methods applied in checking materials
These methods are discussed one after another below;

Dye penetrant method
This technique is vital in pinpointing surface breaking weaknesses like seams, cracks, laps and
porosity. It can be used for checking non-ferrous and ferrous substances as well as materials that
are non-porous (Knight, 2018). The drive shaft is first cleaned and then sprayed, brushed or
dipped into the penetrant. Next, the excess penetrant is dried off using an instrument called a
developer thereby creating a visible indication of any flaw available on the surface of the drive
shaft. The shaft is visually inspected using ultraviolet light to show any flaws in the materials
used.
The dry penetrant technique is the best when applied in detecting flaws in weldments, forgings,
and castings especially for the shafts used in aerospace, oil, gas, and power generation industries.
Magnetic particle
This is a non-destructive method used in detecting any flaws like material cracks in precision
parts. This technique uses magnetic fields and magnetic particle components in pinpointing
cracks and defects of materials used in making a drive shaft. In most cases, these methods work
on steel, iron and also other magnetic alloys because the various materials must be magnetized
before conducting this test (Christoph, 2014). When applied in inspecting a drive shaft, this
method shows how maximum operational torque affects the shaft surface indicating it is the
weakest point of the shaft.
Magnetic particle inspection is best applied in cases where actual imperfection as it defines the
lines that show the whole crack in materials which is an added advantage when compared to the
other methods.

Ultrasonic
The ultrasonic method produces a 3D cross-section of the shaft thereby visually showing if there
is a crack on the surface of the drive shaft. The data obtained from the different measurements
taken is useful more so when such data is compared to get the progress of the cracks.
Ultrasonic can be applied in the end to end in situ examination of the nature of a drive shaft
thereby determining its structural integrity (Graff, 2018).
Radiography
Radiography involves the use of radiation, gamma and x- rays in creating an internal image of a
drive shaft. Computed tomography (CT), as well as digital X-ray, provide dimensional data on
the inward and outward features of the materials used in making drive shafts.
Apart from drive shafts, radiography is applied in process development, screening of products,
analysis of the porosity, and quality control of items like brake components, castings, fuel
injectors, airbags and even tires.
Data and Results
Formulas applied in calculating mechanical test values
Shear strength can be calculated as,
τ = Tr / J, where
τ = shear stress (Pa, psi)
T = twisting moment (Nm, in lb)
r= distance from centre to the stressed area
in the stated position (m, in)
j = Polar moment of Inertia of area (m4, in4)
Maximum torque in a circular shaft is
calculated in the following way;

Tmax = τmaxJ/R where,
Tmax = maximum twisting moment (Nm, in
lb)
τmax = maximum shear stress (Pa, psi)
R = radius of the shaft (m, in)
The calculation for a solid shaft is;
Tmax = (π / 16) τmax D3
The calculation for a hollow shaft is done
by;
Tmax= (π / 16) τmax (D4 – d4) / D
The polar moment of inertia of a solid shaft
is calculated as follows;
J = π R4 /2
= π (D / 2)4 /2
= π D4 / 32, where, D = shaft outside
diameter (m, in)
The polar moment of inertia of a hollow
shaft is calculated as follows;
J = π (D4 – d4) / 32, where d = shaft inside
diameter (m, in)
Diameter of a solid shaft is obtained by;
D = 1.72 (Tmax / τmax) 1/3
The angular deflection of a torsion shaft is
calculated by;
a= L T / (J G), where,
a= angular shat deflection (radians)
L= length of shaft (m, in)
G= shear modulus of rigidity (Pa, psi)
The angular deflection of a solid torsion
shaft is calculated by;
a= 32 L T / (G π D4)
The angular deflection of a hollow torsion
shaft is calculated by;
a= 32 L T / [G π (D4 – d4)]
The angle (a degrees) is arrived at by;
a degrees = θ (in radians) X 180/ π

The angle of a solid shaft (π is changed) is;
a degrees = 584 L T / G D4
The angle of a hollow shaft (π is changed)
is;
a degrees = 584 L T / [G (D4 – d4)]
Torsion resisting moments of solid shaft is
given by;
(π/ 16) τmax (2 r)3 = (π/ 16) τmax D3
Torsion resisting moments of hollow shaft is
given by;
(π/ 16) τmax [(2 R)4 – (2 r)4 ]/ 2 R = (π/ 16)
τmax (D4 – d4)
Mechanical tests and results
Mechanical tests conducted on materials gave the following results;
Material
used
Mechanical
test type
Test results Conclusion Where material
can be used in
the drive shaft

Composites Tensile
Torsion
Drive shaft
geometry
Shaft length- 500mm
Shaft diameter-
51mm
Shaft thickness- 1.75
mm
Mechanical results
Tensile strength –
734 MPa,
Stress proof – 496
MPa,
% elongation – 10 %
Hardness – 219-229
BHN
Data obtained from
tensile testing of
composites are used
in a making diagram
that shows stress-
strain levels thereby
allowing the design
and manufacture of
parts that can endure
the application force.
Data obtained from
torsion testing is vital
in determining the
load transfer of
materials used in
making shafts.
The composite
material is best
applied in making
the shaft tube.
Polymer Tensile Mechanical results
Tensile strength – 50
MPa
% elongation to
Tensile testing of
polymers often
provide data that is
used in measuring
Polymers can be
used to make
different
components of

Torsion
break – 150 %
Young’s modulus – 2
GPa
tensile strain,
strength, modulus,
and the elongation
levels at material
yield and break.
Torsion testing
provides data on the
response features of
the plastic in terms of
its viscous and
elasticity nature.
the drive shaft
because of its
weight.
Ceramic Tensile
Torsion
Mechanical results
Flexural strength-
466 – 1200 MPa
Hardness - 1840
BHN
Grain size - < 2 μm
Fracture toughness –
2.78 – 4.1 MPa4 in4
Tensile testing of
ceramic materials is
important in the
detection of surface
and internal
imperfections of the
material.
Torsional testing of
ceramics pinpoints
subcritical length
Ceramics can be
useful in making
the coatings on
the drive shaft’s
seal section

parameters as well as
fracture of the
material.
Metal Tensile
Torsion
Drive shaft geometry
Plate thickness – 9.5
mm
Mechanical results
Tensile strength –
1000 MPa
Elongation length –
over 50 mm
Hardness – 353- 553
BHN
Yield strength – 0.2
%
Data obtained from
tensile testing of steel
alloy drive shafts is
vital in determining
the forces that are
acting on the shaft
more so bending
stresses.
Torsional testing
provides data on the
shear stresses on how
the torque is
transmitted as a result
of torsional load.
Metal is
commonly
applied in making
the end joints of
shafts.
Table 1.1 showing test values obtained from mechanical tests conducted on specific materials
Discussion
Based on the data provided by this report, it is possible to use materials like composites, ceramic,
polymers and metals in making drive shafts.

The metal alloys are the best to use when making drive shafts as they possess better mechanical
properties than the other materials.
Conclusion
The testing of materials used in making drive shaft is important in knowing the best material to
use in production. Currently, the world has opened the window for new possibilities allowing
new production methods using better materials. It is important that the material used in making
drive shafts prove its worthiness bypassing all the relevant tests.
Failure in Cosmetic fittings
Abstract
Cosmetic fittings are automotive parts that enhance the customization, comfort, safety,
convenience and performance of the automobiles and they tend to be added on to add the visual
beauty of the motor vehicle. The rate of growth of the automotive sector is high due to the new
innovations that meet the demands of the customers. Cosmetic fittings appear on this list of
innovations as they not only add beauty features but also vehicle performance.
Introduction
The automotive sector is currently experiencing new constant challenges caused by the ever-
rising need for super quality and cheap automotive components and fittings. The engineers
should be very keen when designing and manufacturing these fittings so that they are capable of
withstanding the selected environments in which they are to be put. It is vital to use systematic
analysis in determining the occurrence of any failures and suggest the best ways of producing

and maintaining these automotive cosmetic fittings. This article will analyze the different failure
mechanisms of these cosmetic fittings and the production and maintenance recommendations in
preventing such failures from occurring in future.
Background
Types of cosmetic fitting failures
These fittings undergo the following types of failures;
Ductile failure
This occurs when materials tend to be overloaded thus surpassing the standard tensile strength.
Ductile failures tend to occur due to design errors or even excessive loading than what is
anticipated (Omar, 2013). Also, this type of failure tends to occur when the yield strength of the
material is low more so in cases where materials are subjected to in excess fire or heat. The
appearances of ductile fracture tend to be torn and rough due to the plastic deformation and
yielding state of the material used in making cosmetic fittings.
Trans-granular failure
This type of failure happens when a crack ceases to follow the available grain boundaries thereby
jumping from material grain to grain. A good example is a fatigue crack.
Intergranular failure
When a crack occurs in materials and furthermore follows only one kind of grain along with the
available grain boundaries just like in stress cracking, then this type of failure is known as an
intergranular failure.

Creep failure
In engineering, creep failure is described as a process in which materials deform completely due
to the various effects of constant mechanical stress. Automotive components also tend to be
affected by creep failure due to the constant exposure to maximum stress levels regardless of
whether the yield strength of the material is reached or not. Cosmetic fittings deform due to the
characteristics of its materials, amount of time exposed to stress, level of temperature and also
the applied structural load (Palazzolo, 2013).
Fatigue failure
This type of failure is as a result of the applied stresses that tend to fluctuate and in most cases
lower amounts of stress cause this failure even if it is just applied only once.
Degradation
In assessing degradation, the feature that should be put to the test should include the reliability of
the fittings putting full consideration on the peak frequency and degradation features that rely on
temperature. Degradation failures mean that these cosmetic fittings fail the robustness and
reliability tests thus cannot be used in automobiles.
Data and results
The following data were obtained on how the cosmetics artefacts fail as described in the table
below;
Artefa
ct
Ductile
failure
Trans-
granular
failure
Intergranul
ar failure
Creep failure Fatigue
failure
Degradatio
n

Dyed
fibred-
glass
aerofoil
They will
fracture over
time
depending
on the
amount of
time,
humidity
and
temperature
they are
exposed to.
They will
crack
depending
on the
magnitude
of the stress
like water
that is
applied.
The trans-
granular
concept
applies here
too.
They will
undergo
deformation due
to
environmental
factors that they
are exposed to.
They form a
fatigue
fracture due
to the
external
environment
al factors as
well as the
time of
exposure.
They tend
to degrade
faster when
exposed to
humid
environmen
ts like snow
and rainfall
hence fade
over time.
Cerami
c brake
discs
The brake
disc will
fracture over
time due to
the build-up
of residual
stress that
affects the
tensile
strength.
The
distribution
of stress and
extreme
temperature
s in the act
of braking
forms a
thermal
stress cycle
that leads to
The trans-
granular
concept
applies here
too.
They undergo
deformation and
deflection due
to the
thermomechani
cal loads that is
applied as a
result of the
friction caused
by braking.
Ceramic
brake discs
tend to get
damaged as
a result of
thermal
fatigue due
to long term
usage.
The
ceramic
brake disc
tends to
have a
brake
which
decreases
the rate at
which the
wheel is

cracking of
the discs.
rotating by
the use of
friction.
The more
the brake is
applied the
more
friction is
applied to
the discs
causing
brake
fading.
Split-
rim
alloy
wheels
The wheels
crack as a
result of the
poor quality
as well as
the potholes
that are
found on the
roads.
There is a
hairline
fracture that
forms due to
constant
exposure to
the road and
it will widen
as a result of
weather
The trans-
granular
concept
applies here
too.
When one
doesn’t notice
the cracked
formed in split
rim alloy
wheels then the
crack will get
bigger and un-
repairable.
The wheels
and rims
form fatigue
cracking due
to
continuous
exposure to
harsh
conditions
like bad
The wheels
will
become
road
unworthy
after
constant
exposure to
the bad
road

corrosion
and
pressure.
roads. surfaces.
Dyed
polyme
r
bumper
s
They will
crack due to
continuous
exposure to
harsh
environment
al
conditions.
They will
fracture due
to
continuous
exposure to
harsh
environment
al conditions
The trans-
granular
concept
applies here
too
Environmental
conditions
ultimately lead
to deformation
of these
bumpers.
Long term
exposure to
the harsh
environment
causes
fatigue
failure.
They
undergo
photo-
induced,
thermal,
chemical
and
biological
degradation
due to
exposure to
the
environmen
t.
Table 2.1 showing how the artefacts fail
Discussion
The cosmetic artefacts and best production and maintenance methods are as described in the
table below;
Artefact Suggested production methods Suggested maintenance methods

Dyed fibred-
glass aerofoil
Pultrusion Ultrasonic condition monitoring.
Repairing of broken fibreglass
aerofoil.
Reinforcing of repaired aerofoil
Ceramic
brake disc
Metal casting process
Mould casting process
Ensure that you drive light not
overloading the vehicle.
Be responsible for driving by avoiding
sudden braking as a result of rapid
acceleration.
Be keen on the traffic that is ahead by
being ready for any potential braking
events.
Split rim alloy
wheel
Forging process
High pressure die casting
Low pressure die casting
Gravity casting
Maintenance personnel should always
adhere to the stipulated control
measures of safety when replacing or
repairing split rims.
Also, the automobile owner should
know the type of wheel that is fitted in
their own cars in order to get the right
personnel to repair or replace the split
rim wheels.
Dyed polymer Reaction injection moulding Clean the bumper always.

bumper Repairing the bumper using plastic
welding if it is broken.
Reinforce the bumper if it was
repaired.
Table 2.2 showing best production and maintenance methods
Further discussion
Magnesium alloy wheels are made using forging and casting methods. Cast and forged wheels
tend to fracture and bend respectively when loaded beyond their yield strengths. This is due to
the porosity nature the wheels have. Continuous overloading of magnesium wheels will cause
deformation and fatigue failure.
Conclusion
The cosmetic fitting can also undergo different types of failures as described in the report. In
most cases, these failures occur naturally due to external stresses that are applied to these fittings
from the environment. The design engineers and manufacturers should, therefore, be well
informed on these failures and make quality products.

Bibliography
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