Fracture Toughness Test Analysis Report

The assignment content presents a fracture toughness test analysis report for NASA's planned use of aluminum alloy in designing a new space station. The report details the experiment's methodology, results, and discussion, concluding that the material is suitable for space applications due to its high plane-strain fracture toughness value (around 2784 MPa) compared to the stress intensity factor (107 MPa).

Fracture toughness test analysis report
Student Name
Roll No:
University
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Table of Contents
Introduction:....................................................................................................................................2
Method:............................................................................................................................................2
Results:............................................................................................................................................4
Discussion:.......................................................................................................................................5
Conclusion:......................................................................................................................................6
References........................................................................................................................................6
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Introduction:
NASA organization planned to use the aluminum alloy for design new space station. In order to
check the feasibility of material, it requires obtaining a plane-strain fracture toughness
experiment of aluminum alloy. As a technical consultant, we are performing a fracture
toughness test to find the behavior of the material. The toughness observe by a variety of fatigue
cracked specimen that has thickness 12 mm
Method:
For this experiment, there is a single edge notched specimen used to obtain material properties.
The ASTM E399 standard machine testing equipment requires performing test. The experiment
uses a single Edge notched specimen (Jandejsek,2017).
Figure: Fracture Test Machine
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There are two methods to perform an experiment, the first is to an applied tensile load in
opposite direction with connected ends of specimen and second is to applied compressive load
over the test specimen at the middle section of the sample. In this case, the compressive load at
the middle section has been applied and keeps applying constant load over the surface of
specimen till fracture (Chorzepa, 2017).
It requires carrying out precut from 12 mm thick plate of the aluminum alloy. The sample was
machined and dimensions are standard as per design consideration. For this experiment, the
sample an instron 4204 Universal Testing machine used and it connects with the programmable
computing device. The specific software (Labview) installed in computer device in order to
obtain material behavior from an experiment.
Figure: Fracture toughness test
As shown in the above figure, the test specimen place horizontally and applying the load at both
ends. The specimen was inserted, attached between crosshead and machine stationary base. The
transverse load applied over the specimen. The applied continuous load was recorded through
the piezo-electric load which mounted between specimen and cross-head (Chorzepa, 2017).
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The load changes and range of the load cell provide through a computer (WANG. 2010). The
load may vary throughout the process.
After arrangement fixed, it is required to running test until a fracture occurs. The approximate
test runs rate of 0.5 to 1 mm per minute and stops the test when the crosshead has obtained 8 to
10 mm of total displacement or around 85% peak load WANG, J. (2010). The fracture surfaces
were obtained by using a stereo microscope. The images of the fracture surface and the range of
scale were taken.
Results:
As performing an experiment, it requires finding a value of plane-strain fracture toughness as
following. For this, use the constraint equation of experiment.
B ≥2.5 ( K IC
σ y )
2
12=2.5 ( KIC
580 )
2
K IC=2784 MPa
Stress intensity factor,
KQ = 4 P
B
❑
√ π
W [ 1.6 ( a
W ) 1
2 −2.6 ( a
W ) 3
2 +12.3 ( a
W ) 5
2 −21.2 ( a
W ) 7
2 +21.8 ( a
W ) 9
2
]
¿ 4 x 5418
12
❑
√ π
24 [1.6 ( 2.4
24 )1
2 −2.6 ( 2.4
24 )3
2 +12.3 ( 2.4
24 )5
2 −21.2 ( 2.4
24 )7
2 +21.8 ( 2.4
24 )9
2
]
¿ 4 x 5418
12
❑
√ π
24 [1.6 x 0.3162−2.6 x 0.0316+12.3 x 0.00316−21.2 x 0.000316+21.8 x 0.0000316]
¿ 236.4048(0.4566)
KQ =107.94 MPa
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Discussion:
From the analytical solution, obtain the stress intensity factor and plain strain fraction
toughness. These both quantities were obtained from given dimensions and a standard equation
of fraction toughness test. From the calculation, it was observed that the value of plain strain
friction toughness higher than the stress intensity factor. The result indicates the given
specimen have sufficient toughness as per given boundary condition (KANBAYASHI, 2011).
This material is suitable for space.
Here, the intensity of factor value was considerable lower compared to plain strain fraction
toughness, so it was qualified under given circumstances. Additionally, during experiment and
research about the fracture mechanism, we observe that material are not broke directly as it
continuously yielding with an applied load over the specimen. That suggests the material have
sufficient ductility which prevents sudden break down before a major accident. The behavior of
material similar to standard stress-strain curve as tensile, yielding and fracture occurs over the
specimen (Chorzepa, 2017).
Conclusion:
The reported article presents a feasibility study of aluminum alloys through the fracture
toughness test and obtains a value of "plane-strain fracture toughness". The aim of this study
was to find aluminum alloy behavior and decide the material is suitable or not. From the result,
the magnitude of plane-strain fracture toughness was obtained around 2784 MPa that
considerable higher than the fracture intensity factor 107 MPa, so that indicates the material
suitable under a given condition. From these results, it concluded that the provided material is
suitable for the design of a new space station code Nautilus-X
The report has obtained only considering "single edge notched specimen test", for more
accuracy there are another methods such as Compact tension test, Disc shape specimen test, and
DCT specimen test.
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References
Jandejsek, I., Gajdoš, L., Šperl, M. and Vavřík, D. (2017). Analysis of standard fracture
toughness test based on digital image correlation data. Engineering Fracture Mechanics,
182, pp.607-620.
Peer review report 1 on “Estimation of fracture toughness KIC from Charpy impact test data in
T-welded connections repaired by grinding and wet welding”. (2016). Engineering Fracture
Mechanics, 151, p.19.
Peer review report 3 on “Fracture toughness measurements using two single-edge notched bend
test methods in a single specimen”. (2015). Engineering Fracture Mechanics, 133, p.123.
QIU, Z. and WANG, J. (2010). Reliability study of fracture mechanics based non-probabilistic
interval analysis model. Fatigue & Fracture of Engineering Materials & Structures, 33(9),
pp.539-548.
TAKAHASHI, M., OKABE, N., ABE, Y., FUJIKI, K. and KANBAYASHI, R. (2011). Fracture
analysis for a ceramic ball in backflow valve. Fatigue & Fracture of Engineering Materials
& Structures, 35(4), pp.291-300.
Yaghoobi, A. and Chorzepa, M. (2017). Fracture analysis of fiber reinforced concrete structures
in the micropolar peridynamic analysis framework. Engineering Fracture Mechanics, 169,
pp.238-250.
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