finite element modelling for numerical simulation of ... charpy test remains associated ... charpy...
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International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 32
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-03-1 | © 2012 Bonfring
Abstract--- The Charpy test remains associated with impact testing on notched specimens. At a time when many
steam engines explored, engineers were preoccupied with studying the resistance of steels to impact loading. The
Charpy test has provided invaluable indications on the impact properties of materials. The Charpy test is of great
importance to evaluate the Embrittlement of steels. Dynamic fracture properties of most engineering materials are
generally assessed using the Charpy test. The first objective of this paper is to present the force time history
obtained using an Instrumented impact test on steel at various impact velocities in the range 3.0 to 4.2m/sec .The
Second objective is to predict the stress concentration factor at the root of the V-notch in the test specimen using
Finite Element Analysis. Finite Element Modelling is defined here as the analyst’s choice of material
models(constitutive laws), finite elements(of different types/shape/orders),meshes, constraints equations, analysis
procedures, governing matrix equations and their solution methods, specific pre-processing and post processing
options available in a chosen comment Finite Element Analysis software for the numerical simulation of the Charpy
impact test. The focus here is to use ANSYS software and perform Transient Response Analysis with measured
impact force-time history as the input. Significant results from the simulation are graphically presented and
discussed.
Keywords--- Charpy Impact Test, Finite Element Analysis, Transient Response, Stress Concentration Factor.
I. INTRODUCTION
MPACT tests are designed to measure the resistance to failure of a material to a suddenly applied force or load.
The test measures the impact energy or the energy absorbed prior to fracture. The most common methods of
measuring impact energy are: Charpy Test and Izod Test.Charpy impact test is a low-cost and reliable test method,
which is commonly required by the construction codes for fracture critical structures such as bridges and pressure
vessels. Charpy impact test was developed in the 1960's as a method of determining the relative impact strength of
metals. It is a standardised high strain-rate test that can measure the amount of energy absorbed in a material. The
absorbed energy is considered as a measurement of the toughness of a given material and also acts as a tool to study
the ductile-brittle transition of the material independent on the temperature during the testing procedure. With this
impact test, one can evaluate the reliability of the structure based on the measured energy absorption of the material
(specimen) and understanding the deformation and failure process during the test, Dynamic fracture properties of
most engineering materials are generally assessed using the Charpy test. The dynamic responses of the standard
Charpy impact machine are studied by running experiments using strain gauges and a specific data acquisition
system in order to obtain the impact response and for this reason the numerical analysis by means of the finite
element method has been used [1].
II. PENDULUM IMPACT TESTER (TINIUS-OLSEN MODEL T 84)
The Tinius Olsen Model 84 Pendulum Impact Tester is a versatile and reliable machine. Complies with latest
requirements of ASTM Method E 23 and ISO 442.Interchangeable tooling lets you do Charpy, lzod or Tension
Impact tests. Single piece pendulum plus integral base and anvil eliminate errors induced by loose parts.
Specifications of this Impact Tester: Velocity: 0.1 to 5.1m/sec,Energy:0.2 to 359Joules, Data Acquisition: Instron
930-I.However, a data acquisition/machine control software package is available as an option, Exceptionally high
K. Mohan Kumar, Department of Mechanical Engineering, S.J.C.Institute of Technology, Chickballapur.
M.R. Devaraj, Department of Mechanical Engineering, S.J.C.Institute of Technology, Chickballapur.
H.V. LakshmiNarayana, Dayananda Sagar College of Engineering, Bangalore.
PAPER ID: MED06
Finite Element Modelling for Numerical
Simulation of Charpy Impact Test on Materials
K. Mohan Kumar, M.R. Devaraj and H.V. LakshmiNarayana
I
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 33
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-03-1 | © 2012 Bonfring
accuracy with minimal energy losses due to windage and friction as shown in Fig.1.
Figure 1: Tinius-Olsen Model T 84 Pendulum
Impact Tester
Figure 2: Charpy Test specimen
Fig.2 shows the Charpy Test Specimen Diagrammatically with the dimensions and Fig.3 shows the Charpy
impact Test specimen after Impact test at different velocity ranges from 3.0 m/sec to 4.2m/sec on Tinius-Olsen
Model T84 Pendulum Impact Tester and its Force-Time History are captured using the data acquisition system
attached to the tester [2] and is as shown in Fig.4.
Figure 3: Specimen after Impact Test Figure 4: Force-Time History
III. FE MODELLING
Commercial ANSYS finite element analysis software was utilized in order to carry out the dynamic transient
analysis of the Charpy impact test. The standard Charpy impact specimen with dimensions of 10 mm in depth, 10
mm in width and 55 mm in length and a V-shaped notch, 2mm deep, with 45° angle and 0.25mm radius along the
base and specimen is fabricated (as required in the ISO 179/ASTM E23) is used for the finite element analysis. In
the finite element simulation, the mesh of the Charpy impact specimen is mainly constructed by using the Quad
plane 42 element with plane stress condition, this type of mesh was chosen due to the irregular geometry of the
Charpy impact specimen[3]. Quad 4-noded PLANE42 is used for 2-D modeling of solid structures as shown in
Fig.5. The element can be used either as a plane element (plane stress or plane strain) or as an axisymmetric
element. The element is defined by four nodes having two degrees of freedom at each node: translations in the nodal
x and y directions. The element has plasticity, creep, swelling, stress stiffening, large deflection, and large strain
capabilities. The material used for the analysis model is assumed to be isotropic, homogeneous, and temperature
independent. The material of the impact specimen is Mild Steel and the properties for these materials are as
tabulated in Table.1 [4].
Time Vs Load
0
2
4
6
8
10
-2 0 2 4 6 8 10 12
Time(msec)
Lo
ad
(kN
)
At Velocity 3.0 m/sec At Velocity 3.4 m/sec
At Velocity 3.8 m/sec At Velocity 4.2 m/sec
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 34
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-03-1 | © 2012 Bonfring
Table 1: Properties for Mild Steel Materials in FEM Model
Component Material Young‟s
Modulus
GPa
Density
kg/m3
Poisson‟s
ratio
Charpy
specimen
Mild
steel
200 7840 0.3
Figure 5: Quad 4-noded Plane 42 Geometry
The finite element meshed model for the impact tests are shown in Fig.6 and the mesh model data for is as
shown in Table.2.
Table 2: Mesh Model Data
Component Element Total
Element
Total
Nodes
Charpy
specimen
Quad
plane 42
with
plane
stress
980 1050
Figure 6: Model Meshed
IV. TRANSIENT DYNAMIC ANALYSIS
Transient dynamics analysis, sometimes called „Time-History Analysis‟, is a technique used to determine the
dynamic response of a structure under the action of any general time dependant loads. This type of analysis is used
to determine the time-varying displacements, stresses, strains, stresses and forces. In ANSYS, Transient dynamic
analysis can be carried out using 3 methods: Full Method, Reduced Method, and Mode Superposition Method [5]. In
this case we will be using Full Method of Transient Dynamic Analysis by inputting the obtained Force-Time History
by Tinius-Olsen Model T 84 Pendulum Impact Tester and the obtained results are shown in Fig.7.
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 35
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-03-1 | © 2012 Bonfring
Figure 7: Dynamic Transient Response
From the Dynamic Transient response results eat force are tabulated in Table.3.
Table 3: Dynamic Transient Response Result
Velocity(m/sec) Maximum 1st principal
stress(N/m2)
Maximum Force(N)
3.0 1340 4375.4
3.4 1360 4431.95
3.8 1350 4407.55
4.2 1420 4616.15
Applying the Dynamic Transient Response Force to the Static analysis to get the Static response as shown in
Fig.8.
Figure 8: Static Response
From the Static response results are tabulated in Table .4.
Table 4: Static Response Result
Force(N) Maximum 1st
principal stress(N/m2)
4375.4 1340
4431.95 1350
4407.55 1360
4616.15 1410
International Conference on Challenges and Opportunities in Mechanical Engineering, Industrial Engineering and Management Studies 36
(ICCOMIM - 2012), 11-13 July, 2012
ISBN 978-93-82338-03-1 | © 2012 Bonfring
Now Stress Concentration Factor (SCF) for Different velocities at different force time history is tabulated in
Table.5.
Table 5: Stress Concentration factor
Velocity(m/sec) Dynamic Stress
Concentration Factor
3.0 1.0
3.4 1.0
3.8 1.0
4.2 1.0071
V. CLOSURE
This paper presents the results of Charpy impact test on Mild steel as measured impact force time history. A
detailed Finite Element model of the Charpy impact test specimen is developed using Ansys software Numerical
simulation of impact test is performed as transient dynamic analysis. The effect of impact velocity on the maximum
force on the maximum stress at the root of the notch is predicted. However the velocity range does not induce any
dynamic effect over the static analysis results. Obviously at very high velocities the difference between the static
and dynamic analysis and test result will be significant.
ACKNOWLEDGEMENTS
The authors would like to express their gratitude to for B G S R & D Centre, Department of Mechanical
Engineering, S J C Institute of Technology, Chickballapur and Material Engineering Department IISC, Bangalore
for supporting the research.
REFERENCES
[1] Ali.M.B, Abdullah.S, Nuawi.M.Z, Ariffin.A.K, Mohammad.M: Evaluating Charpy impact signals using power
spectrum densities: A finite element method approach. International Journal of Mechanical and Materials
Engineering (IJMME), 2011, Vol.6, No.1, 92-101.
[2] Anton Shterenlikht, Sayyed H. Hashemi, John R. Yates, Ian C. Howard and Robert M. Andrews: Assessment of
an instrumented Charpy impact machine. International Journal of Fracture 2005, 132:81–97.
[3] Rossoll, Berdin.C and Prioul.C: Determination of the fracture toughness of a low alloy steel by the instrumented
Charpy impact test. International Journal of Fracture 2002, 115: 205–226.
[4] Hisashi Serizawa, Zhengqi WU, Hidekazu Murakawa: Computational analysis of Charpy impact test using
interface elements. Trans. JWRI, 2001, Vol.30, 97-102.
[5] ANSYS 12.1 Software Tutorials.