IRJET- Investigation and Analysis of Multiple Cracks in Cantilever Beam by using FEM

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 11 | Nov 2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 1231
Investigation and Analysis of Multiple Cracks in Cantilever Beam by
Using FEM
Heera Lal Choudhary1, Jayant Koshta2, Anshul Choudhary3
1,2M.tech Student, Department of Mechanical Engineering, SRIT, Jabalpur (M.P) 482004, India
3Assistant Professor, Department of Mechanical Engineering, SRIT Jabalpur (M.P) 482004, India
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Abstract: The present study outlines free vibration analysis of
uniform and stepped beam subjected with single to multiple
cracks victimization Finite part methodology (FEM). The crack
thought-about is transversal crack that open in nature.
Because of the presence of crack, the overall flexibility matrix
is established by adding native extra flexibility matrix to the
flexibleness matrix of the corresponding intact beam part .The
native extra flexibility matrix is obtained from Linear Elastic
Fracture Mechanics theory. An experimental study is
administrated to examine the accuracy of the numerical
results. Soft-cast steel specimens of sq. space of cross section
square measure thought-about for the experiment and also the
experimental results square measure compared with
numerical analysis victimization Finite part methodology
(FEM) in MATLAB atmosphere. The results obtained from
experimental square measure checked for accuracy with the
current analysis by plotting non- dimensional frequencies for
initial 3 modes as perform of crack depth ratios for various
locations of cracks.
Keywords- Vibration based mostly detection, multiple
crack, crack location and crack depth.
I. INTRODUCTION
For several engineering applications, beams square measure
essential models for the structural components and are studied
extensively. Optimization necessities crystal rectifier to
reduction within the weight of structure ensuing to increased
in operation stress levels. A number of the applications of
beam-like components square measure chopper rotor blades,
robot arms, craft wings, artificial satellite antennae, and long
span bridges. Structural components and systems are terribly
of subject to hundreds dynamic with time. Ignoring the
presence of fabric defects whereas planning crystal rectifier to
spectacular failures. Because of this fatigue changes within the
part conceive cracks that hinders the potential of the part to
resist its capability. The sharp failure of structures is results of
the crack injury propagation if it's not detected well before. So,
it becomes essential relating to safety question of the structure
performance to watch such defects. winning style of
engineering structures for future life needs the understanding
of various modes of failures and degradation mechanisms
(crack growth because of service hundreds, corrosion, atomic
number 1 embrittlement etc); in order that sufficient margins
against these mechanisms will be inbuilt throughout the look
part itself.
The natural frequencies suggest the dynamic stiffness of any
structure. The frequency being higher indicates that the
structure is stiffer dynamically. It depends on the
values of mass, stiffness distributions and also the
finish conditions. The vibration response is affected
because of the native flexibility that is initiated
because of presence of crack in support. It results in
decrease in frequencies in comparison to the
frequencies that occurred naturally and changes in
mode patterns of vibrations. Any discover in of those
variations makes doubtless to detect cracks.
II. LITERATURE REVIEW
A. Vibration of Uniform beam with cracks
Vibration of Uniform beam with cracks Kisaetal
(2000) sculptural cracked structures by
desegregation the finite part methodology, the linear
elastic fracture mechanics theory and also the part
mode synthesis methodology. The experimental
investigations of the consequences of cracks on the
primary 3 modes of vibratory beams for each hinged-
hinged and stuck -fixed boundary condition are
elaborate by Owolabi (2003). The Frequency
Response perform (FRF) amplitudes and changes in
natural frequencies obtained from the measurements
of dynamic responses of cracked beams as a perform
of crack depth and site of crack square measure used
for the detection of crack. Zheng et al. (2004)
obtained the natural frequencies and mode shapes of
cracked beam victimization Finite part methodology
(FEM). The overall flexibility matrix is established by
adding overall extra flexibility matrix to the
flexibleness matrix of the corresponding intact beam
element. Patil et.al (2005) verified a way to imagine
the placement and depth of crack by experimentation
for cantilever beams with 2 and 3 edge cracks. The
energy approach methodology is employed for
analysis and also the crack is delineate as a motility
spring. For a specific mode, variable crack location, a
plot of stiffness versus crack location is obtained. The
intersection of those curves subsequent to the 3
modes offers the crack location and also the
associated motility spring stiffness. Yoon et.al (2007)
investigated analytically and by experimentation
have an effect on of presence of 2 open cracks on the
dynamic response of a double cracked hinged-hinged
terminated beam.

III. MATHEMATICAL FORMULATION
Introduction the idea associated with vibration and also the
Linear Elastic Fracture Mechanics (LEFM) square measure
conferred. Then the eye is given to the mathematical
formulation of a cracked uniform cantilever beam. The
presence of crack reduces the native stiffness matrix that alters
the dynamic response of the system. / Figure 3.1 Input-Output
relationship of a moving system.
Figure 3.1 Input-Output relationship of a vibratory system.
IV. METHODOLOGY
A cracked uniform cantilever beam part of rectangular space
of cross section with depth h” and breadth„ b” with crack
depth„ a” is as shown in Figure 1.Theleftsideendwhichis
mounted is denoted with node „I” and right facet node is
denoted with „j‟. The cracked beam part is subjected to
cutting force, 𝑃1′ and bending moment,
𝑃2′. The governing equations of the vibration analysis of the
uniform beam with open transversal crack square measure
patterned on the idea of the FEM model projected by Zheng
(2004).
Figure 3.3 A typical cracked beam element subjected to
shearing force and bending moment
According to Zheng (2004), the additional strain energy due
to the presence of crack is π =
∫
G = the strain energy release rate and
= the effective cracked area
Where, G = strain energy release rate
are stress intensity factors for opening, sliding
and tearing type cracks. According to the principle of Saint-
Venant, the strain field is affected solely within the region
adjacent to the crack.
Figure 1: Convergence of fundamental frequency of
uniform cantilever beam with single crack
The part stiffness matrix, aside from the cracked
part, could also be considered unchanged
underneath an exact limitation of part size.
Considering the result of cutting force and bending
moment the (neglecting action of axial force) higher
than equation becomes,
V. RESULTS AND DISCUSSIONS
A. Convergence study
In this section, the convergence study is done to
verify the accuracy of the present FEM analysis.
B. Uniform Cantilever Beam with crack
The convergence study is done for the cantilever
uniform beam of square cross-section with single
crack with the case considered in Lee et.al (2000). A
300mm cracked cantilever beam of cross section
(20х20) mm with Young's modulus, E=206GPa and
mass density ϱ=7750 kg/𝑚3. It is observed that
convergence starts when the number of elements is
14 and convergence up to 30 numbers of elements, is
shown in Fig. As per the convergence study, 20

elements are considered for the discretization of whole
structure.
C). Two-stepped cantilever beam without crack
The convergence study for the two-stepped cantilever of
rectangular cross-section is done with the case considered in
Zhang et.al (2009). The thickness of beam is 12mm. The
material properties of the beam are modulus of elasticity, E=
210Gpa, length of beam, L =500mm, density, ϱ = 7860 kg/𝑚3,
ℎ1= 20mm, ℎ2= 16mm. It is observed that convergence starts
when the number of mesh divisions is 10 and convergence up
to 30 numbers of elements is shown in Fig. Hence for the
present study for all stepped beams, mesh division of 30
elements is considered.
Figure 2: Convergence of fundamental
VI. COMPARISON WITH PREVIOUS STUDY
A. Free Vibration Analysis of Cracked Uniform Cantilever
Beam
The present FEM formulation is validated with literature. The
variation of natural frequency with respect to the uniform
cantilever beam with single crack is studied and compared
with Shiffrin (1999) as shown in the Table.
The material properties of the beam are, Elastic modulus of the
beam, E = 210MPa, Poisson's Ratio, υ = 0.3, Density, Q = 7800
kg/m3, Beam Width, b = 0.02m, Beam depth, h=0.02 m, Beam
length, L = 0.8m, Position of the crack from clamped end x1=
0.12m, Crack depth a1=0.002 m.
Figure 3: Cracked cantilever beam (mm)
Table 2: Comparison of natural frequency drawn between
Shiffrin (1999) and present FEM analysis
B. Free Vibration Analysis of Cracked Stepped
Beams of Rectangular Cross-Section
The problem contains computation of natural
frequencies for cracked Bernoulli-Euler Cantilever
beam using Finite Element Analysis are validated
with the results obtained by Zhang et.al (2009).The
thickness of beam is 12mm. The material properties
of the beam are modulus of elasticity, E= 210Gpa,
length of beam, L =500mm, density, ϱ = 7860kg/𝑚3,
ℎ1= 20mm, ℎ2= 16mm.
Figure: Cracked cantilever stepped beam (mm)
Free vibration of uniform beam subjected to
single crack
Uniform fixed-free beam
The geometrical properties of the beam shown in Fig
5.5 are administrated for free of charge vibration
analysis.
Figure: Cracked uniform beam
Location of crack (x/L)
Figure: Comparison of FEM and experimental results
for non -dimensional first natural
For all the various locations of crack thought-about,
the elemental frequency is a lot of affected once
crack is found at x=0.0325L , the primary mode of
non-dimensional frequency decreases by 0.15%,
0.92%, 9.70% compared to intact beam for the crack
depth ratios 0.1, 0.2, 0.4 respectively.

Figure: Comparison of FEM and experimental results for non -
dimensional second natural
Figure: single cracked cantilever beam with location of
crack(x/L) for varying crack depth ratios.
From the plot, it will be inferred that for crack locations, x/L=
0.60, a forceful amendment within the third mode of non-
dimensional natural frequency happens. once the crack is
found at x/L = 0.0325, the non-dimensional frequency
decreases by 0.34%, 2.13%, 18.41% compared to intact beam
for the crack depth ratios 0.1,0.2,0.4 respectively. And it's
additionally ascertained that for x/L = 0.375, 0.734 because
of existence of nodal points, the reduction is slightly detected.
The result of crack close to mounted and free ends of the
beam on the third mode non-dimensional natural frequency
has terribly less result.
VII. CONCLUSIONS
Free vibration analysis of uniform and stepped beam
subjected with single to multiple cracks is finished
victimization Finite part methodology (FEM). An
experimental study is administrated to examine the accuracy
of the numerical results. Mathematical formulation for free of
charge vibration of uniform and stepped beam with
transversal open cracks is conferred well. All told the modes
of vibration, because the crack depth magnitude relation will
increase, the frequency reduction will increase no matter
uniform or stepped beam and condition. The natural
frequencies of the beam are a lot of influenced by the
placement of cracks than the depth of crack. Within the case
of uniform cantilever beam, crack positioned close to the
mounted finish affects the natural frequency in initial mode
quite the crack gift within the free finish of the beam. This can
be explained from the explanation that position of crack is
critical within the region of upper bending moment. Due to
the presence of node points, the result of crack close to
mounted and free ends of the beam on the third mode non-
dimensional natural frequency has terribly less result. For
free-free condition, the crack positioned within the
center of beam is a lot of crucial for the primary and
third mode natural frequency. The second mode
natural frequency is barely affected once cracks
square measure placed at free ends and middle span
of beam.
REFERENCES
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Jena, Giridhari lal Agrawal ― CFBP Network A
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Characterization (ICMPC2014).
[2] Labib, D. Kennedy, C. Featherstone Free
vibration analysis of beams and frames with
multiple cracks for damage detection ‖Journal of
Soundand Vibration 333 (2014) 4991-5003.
[3] A. Ghadmi, A. Maghsoodi, H. R. M iradamadi A
new adaptable multiple-crack detection
algorithm Arch. Mech., 65, 6, pp. 469-
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[4] Ameneh M., Amin G. and Hamid R. M., “Multiple-
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[5] Celalettin Karaagac, Hasan Ofztuf rk , Mustafa
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in structures using wavelet finite element
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[11] Khiem N.T., Lien T.V., “Multi-crack detection for beam by
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[12] Kisaet.al, “Free vibration analysis of multiple open- edge
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[13] Yatika Gori*, Pushpendra Kumar1, Pravin P. Patil “FEA
Simulation of Vibrating Cantilever Plate with Transverse
Surface Crack” Materials Today: Proceedings 4 (2017)
9466–9470 ICEMS 2017
AUTHOR
Heera Lal Choudhary
M.Tech (Machine Design)
Srit, Jabalpur, (M.P)

IRJET- Investigation and Analysis of Multiple Cracks in Cantilever Beam by using FEM

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