Finite Element Modelling for Numerical Simulation of ... Charpy test remains associated ... Charpy Test and Izod Test.Charpy impact test is a ... Obviously at very high velocities

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.