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Dighe et al, International Journal of Advanced Engineering Research and Studies
E-ISSN2249–8974
Review Article
ASSESSING THE DESIGN OF CRANKSHAFT WHILE
PREDICTING FATIGUE LIFE USING FINITE ELEMENT
MODELLING FOR A POPULAR TWO WHEELER
1
Vaibhav V. Dighe, 2Prof. S.R.Nimbalkar, 3Prof.S.B.Belkar,
4
Swapnil Kulkarni
1
Address for Correspondence
ME, Mechanical Engineering , 2Associate Professor, 3H.O.D & Associate Professor, Mechanical Department,
Pravara College of Engineering, Loni
4
Director-Ethika Engineering Solutions (I) Pvt.Ltd.,Pune India
LITERATURE REVIEW
INTRODUCTION:
1. F.S. Silva et. al., Paper reports an investigation that
The crankshaft is part of an engine that converts
was carried out on two damaged crankshafts. They
reciprocating linear piston motion into rotation. The
were diesel van crankshafts that were sent to be
crankshaft is often connected to the flywheel thus
ground, after a life of about 300,000 km each. After
reducing the pulsation of the four-stroke cycle. In
grinding, and assembling on the diesel van, the
some recent models, the crankshaft is attached to the
crankshafts lasted about 1000 km each, and the
crankshaft sensor. In a reciprocating engine it can
journals were damaged again. The crankshafts were
translates reciprocating linear piston motion into
then sent to be investigated. Different typical
rotational motion, whereas in a reciprocating
crankshaft failures were assessed, and will be
compressor, it converts the rotational motion into
discussed in this paper. The cause of the damaged
reciprocating motion. In order to do the conversion
journals was found to be a wrong grinding process
between two motions, the crankshaft has "crank
that originated small thermal fatigue cracks at the
throws" or "crankpins", additional bearing surfaces
center of the journals, on both crankshafts. These
whose axis is offset from that of the crank, to which
almost invisible cracks, with sharp edges, acted as
the "big ends" of the connecting rods from each
knives originating a very quick damaging of the
cylinder are attached. It is typically connected to
journal bearings, and as consequence damaged the
a flywheel to reduce the pulsation characteristic and
journals themselves.
sometimes a torsional or vibrational damper at the
2. Yuan Kang et. al., Due to measurement errors, the
opposite end, to reduce the torsional vibrations often
caused along the length of the crankshaft by the
final accuracy of rotor balancing may not be satisfied.
cylinders farthest from the output end acting on the
This study is based on a modified influence
torsional elasticity of the metal.
coefficient method associated with multi-plane
technique for the improvement of accuracy in
balancing crankshafts. The feasibility of this
modified approach is carried out by the verification
of accuracy improvement in experiments, balancing
two crankshafts.
3. Zhiwei Yu et. al., A failure investigation has been
conducted on a diesel-engine crankshaft used in a
truck, which is made from 42CrMo forging steel. The
crankshaft was nitrided. The fracture occurred in the
Fig-Typical crankshaft used in the Automotive industry
web between the 2nd journalsan 2nd crankpin. The
FAILURE OF A CRANKSHAFT:
depth of the nitride layer in various regions of the
The failure of a crankshaft can damage other engine
crankshaft particularly in the fillet region close to the
components including the connecting rods or even
fracture was determined by SEM observation and
the engine block itself. Therefore, when the failure of
micro-hardness (HV0.1) measurement, combined
a crankshaft does occur it often results in replacing
with nitrogen content analysis by EDAX. The
the engine or even scrapping the equipment the
mechanical properties of the crankshaft including
engine was used in. Considering the ramifications of
tensile properties, macrohardnes (HB) and surface
a crankshaft failure a crankshaft must be designed to
hardness (HV1) were evaluated. Fractographic
last the lifetime of an engine. The engine of a typical
studies indicate that fatigue is the dominant
gasoline powered automobile has an engine speed
mechanism of failure of the crankshaft. The partial
that varies from 500 to 6,500 rpm and while traveling
absence of the nitrided layer may result from overat highway speeds may be 2,500 rpm. It can easily be
grinding after nitriding. In order to prevent fatigue
shown that a crankshaft has a desired life of many
initiation in the fillet the final grinding has to be done
millions or even billions of cycles. For example if the
carefully and the grinding amount controlled to avoid
life of an automobile is 120,000 miles and has an
grinding down the nitride layer.
average speed of 50 mph and engine speed of 2,500
5. Osman Asi et. al., This paper describes the failure
rpm, the engine, and crankshaft would need to have a
analysis of a diesel engine crankshaft used in a truck,
life of at 360 million cycles.
which is made from ductile cast iron. The crankshaft
was found to break into two pieces at the crankpin
portion before completion of warranty period the
crankshaft was induction hardened. An evaluation of
the failed crankshaft was undertaken to assess its
integrity that included a visual examination, photo
documentation, chemical analysis, micro-hardness
Int. J. Adv. Engg. Res. Studies/IV/I/Oct.-Dec,2014/ 57-59
Dighe et al, International Journal of Advanced Engineering Research and Studies
measurement, tensile testing, and metallographic
examination. The failure zones were examined with
the help of a scanning electron microscope equipped
with EDX facility. Results indicate
ndicate that fatigue is the
dominant mechanism of failure of the crankshaft. It
was observe that the fatigue cracks initiated from the
fillet region of the crankpin-web.
PROBLEM DEFINITION:
Ascertaining the life of the crankshaft in terms
t
of
number of cycles before failure has been a
challenging task. Without
ithout this predictable
information for a new design variant,
variant the design
phase may not be concluded with any reasonable
credibility. The estimate for fatigue life can be based
on a mathematical approach or still over an analytical
solution in the form of Finite Element Modelling of
the given problem. Testing of a numerous prototypes
may seem to be an inefficient alternative
native for deriving
inference. Timeline as is pertinent
tinent to any new
development, needs to be addressed too. Feasible
solution to the problem is being sought
ought by the
Sponsoring Company for ensuring reliability.
r
Number of failures or the warranty claims received in
the previous years
ars needs to be brought down.
OBJECTIVE:
Typically, this study might focus on the static
analysis conducted on a 2W/ 4W crankshaft, with
single crankpin of crankshaft. Finite element analysis
is performed to obtain the variation of stress
magnitude at critical
al locations. For the FEA analysis
of crankshaft, meshing is done using the
HYPERMESH software. This load is applied to the
FE model in ANSYS/ NASTRAN/ RADIOSS and
boundary conditions are applied according to the
engine mounting conditions. The analysis is done for
maximum loading condition.
EXPERIMENTAL SETUP:
controlled monotonic
For specimen testing, strain-controlled
and fatigue tests of specimens made of the forged
steel and cast iron crankshafts were conducted. From
these experiments, both static as well as baseline
cyclic deformation and fatigue properties of both
materials are obtained. Such data provide a direct
comparison
between
deformation,
fatigue
performance, and failure mechanisms of the base
materials, without introducing the effects and
interaction of complex design parameters such as
surface finish, component size, residual stress, stress
concentration, etc.
E ISSN2249–8974
E-ISSN
Expedite Finite Element
lement Modeling using
preprocess or like HyperMesh and assigning
Material properties, loads and boundary
conditions.
• Solve the F.E. Model using a suitable solver
like ANSYS/ RADIOSS/ NASTRAN/
ABAQUS
• View results using post
post-processor like
Hyper View
• Determine Test Plan
lan for experimentation.
• Conduct the tests for validation
MATHEMATICAL/ ANALYTICAL METHOD:
A suitable basic empirical formulation could be
referred for study for understanding the problem and
offering basic mathematical orientation for further
study using FEA. In a reciprocating engine, the
crankpins, also known as crank journals are the
journals of the big end bearings, at the ends of the
connecting rods, opposite to the pistons. If the engine
has a crankshaft, then the crank pins are the journals
of the off-centre
centre bearings of the crankshaft. In a beam
engine the single crank pin is mounted on the
flywheel. In a steam locomotive
otive the crank pins are
often mounted directly on the driving wheels.
Rationalization of the problem with ssuitable
assumptions would help to investigate the problem
using this methodology.
•
Fig-Forces
Forces applied in various directions in crankshaft
Fig-Graphical
Graphical analysis of contact forces & different
crank angles
Fig- Typical Experimental setup
(The actual setup for the Test could vary depending on
scope and feasibility)
STEPS FOR WORK:
• Identify a benchmark for the problem case
under study.
• Conduct research over existing cases
through journal papers.
• Procure 3D design data from the design
Department for the problem case.
Int. J. Adv. Engg. Res. Studies/IV/I/Oct.-Dec,2014/
Dec,2014/ 57-59
Fig- Discretization/ Meshing for the crankshaft
Dighe et al, International Journal of Advanced Engineering Research and Studies
REFERENCES:
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D. Taylor, A.J. Ciepalowicz, P.l. Rogers, et al.,
Prediction of fatigue failure in a crankshaft using the
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Engineering Materials & Structures 20 (1) (1997)
13–21.
Vogwell J. Analysis of a vehicle wheel shaft failure.
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D. Taylor, A.J. Ciepalowicz, P.I. Rogers, et al.,
Prediction of fatigue failure in a crankshaft using the
technique of crack modeling, Fatigue and Fracture of
Engineering Materials & Structures 20 (1) (1997)
13–21.
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Int. J. Adv. Engg. Res. Studies/IV/I/Oct.-Dec,2014/ 57-59
E-ISSN2249–8974