Analysis of Tensile Testing Results for Steel and Aluminum Materials

This report details an experimental investigation into the tensile properties of steel and aluminum. The study involved tensile testing four material specimens, including two steel and two aluminum samples. The methodology section outlines the specimen preparation, machine setup, loading procedures, and the actual testing process, which involved applying a controlled force to elongate the specimens until failure. The results section presents force-displacement graphs for each specimen, illustrating their respective behaviors under tensile stress. The discussion section analyzes the observed data, comparing the tensile strength and ductility of steel and aluminum, with calculations of ultimate tensile strength and Young's modulus. The report concludes with a summary of findings, emphasizing the importance of accurate measurement systems for reliable results and providing a foundation for further analysis. The report also includes references to relevant literature on tensile testing techniques and material properties.

An Experimental Report on tensile testing of materials
Prepared by:
Date:
1. Abstract
This report provides a comprehensive discussion on the experimental results obtained from the
tensile testing done on four material specimens, that is, steel 1 and 2 and Aluminum 1 and 2.
2. Introduction
Normally materials are tested for strength and other desirable properties like ductility. Therefore
materials testing are very critical especially in ascertaining the structural integrity of the material in
question. Now, the common testing technique that is often employed to ascertain the strength limit
is the tensile testing technique. In this case, material specimen is placed on a specially designed
equipment called the tensile testing machine and allowed to be stretched on both ends such that it
extends for sometime if it is a ductile material and fails immediately if it is a brittle material.
Notably, most ductile material includes Aluminum and Steel with the latter often exhibiting greater
strength characteristics. In this report, a tensile analysis of the two materials, that is steel and
aluminum are presented. The aim is to investigate the comparative nature of material combination
as a function of performance of the same. Four sets of data were obtained from the experimental
tensile testing performed on the said materials. This was done by varying the time allotted for
performing the experiment. The materials are governed by the extended Hooke’s Law where force
is translated to stress and displacement translated to strain.
3. Method
There are standard procedures that have been developed for tensile testing such that anyone who
follows them afterwards should be able to reproduce the experiment conducted. The following
provides the major steps to be followed in this case:
(i) Specimen Preparation
In this case, at least 5 specimens were prepared by machining on a lathe machine to size.
The length of Aluminum specimen was 180mm and its initial diameter being:
do= (4x20.32/3.142)0.5= 5.086mm
While the size of Steel specimen was: do= ((4x17.342/3.142)0.5= 4.70mm and its initial
length being Lo= 80mm
The standard shape of specimen was obtained as illustrated in the figure (dog borne
shape):

Figure 1: Tensile test specimen shape (Image courtesy of Any Bramer, Plastics
Technologist)
(ii) Machine set up and configuration
Then next, the machine was configured to be in tandem with the specimen test
requirements. The software being used was aligned to specifically facilitate the test of
these four specimens set. The machine main components were the universal tensile
testing machine, computer system and the extensiometer. The latter measured the
extension of the specimen after elongation just before it breaks and the system
automatically calculated the percent elongation [4]. The computer system performed
computation and display of these results graphically. Transmission of force was done
hydraulically by configuring the machine system with a hydraulic power pack [1]. Trial
test runs were performed beforehand to ascertain the range of accuracy of the system.
(iii) Loading of specimen
Once set up was completed, the specimens were loaded one after another by controlling
the jaws using power buttons. Now, there are buttons to control the grip of the lower jaw
and upper one. Firstly, the upper jaw was signaled to open and specimen placed between
the jaws; after which it was closed [2]. The lower jaw was then powered to open up and
then allowed to grip the specimen with just enough gripping pressure. It should be noted
that too much pressure can destroy the jaw grips in the long run while at the same time
could destroy the specimen material integrity.

(iv) Actual test
Actual test involved allowing specimen rods to be stretched through the application of
vertical extension force on the upper deck of the tensile testing machine [3]. As pointed
out earlier, this is powered via a hydraulic power pack. The force was slowly but steadily
increased. Meanwhile, the computer system sensed the loading activity and kept track of
the tensioning via a real-time graphical display screen. The specimen would undergo
‘necking’ where the cross section area between the gauge marks would drastically
decrease while it was being elongated. At the point of failure, the specimen breaks into
two and this sudden impact is registered on the screen and the output is a graph as shown
in the results section.
(v) Post test analysis
Once the tests were completed, the obtained graphical results were retrieved from the
system and used for the purpose of analysis. Notably, it was critical to retrieve the
ultimate tensile strength of each material specimen, as registered in the test so that
comparison was done with the theoretical and manufacturer’s values. Besides, the
percent elongation was important as it showed how brittle or ductile the material is.
(vi) Report generation
Afterwards, a report detailing the test output parameters was generated and this report, a
brief discussion on the tensile behavior of the material specimen as exhibited graphically
was included [7]. Hence the next section focuses on the discussion of the obtained
experimental results.
4. Results
Steel 1-
-2
0
2
4
6
8
10
12
Force (kN)
Force (kN)
Figure 1: Force-Displacement graph of steel specimen 1

Steel 2
-2
0
2
4
6
8
10
12
Force (kN)
Force (kN)
Figure 2: Force-Displacement graph of steel specimen 2
Aluminum 1
Displacement
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
Force (kN)
Force (kN)
Figure 3: Force-Displacement graph of Aluminum specimen 1

Aluminum 2
Displacement
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
Force (kN)
Force (kN)
Figure 4: Force-Displacement graph of Aluminum specimen 2
5. Discussion
From the graphs above, it can clearly be seen that steel specimen exhibited greater tensile strength
[5] while Aluminum specimen exhibited higher ductility [8] behavior with a UTS of about:
UTSal=F/A= (3/20.32x10-6) = 0.147MPA
It is noted that this value could be higher than the theoretical one which is about 0.12MPA. This was
mainly because of the systematic errors that were accumulated during testing especially in doing
measurements which were done using a ruler.
Similarly the UTS for Steel was: 11.5/17.342x10-6= 0.663MPa
Table 1: Summary Calculation of Tensile properties
Aluminiu
m1
Aluminiu
m2 Steel1 Steel2
Stress 0.1261 0.1291 0.525 0.5093
Strain 0.5038 0.04801 0.285 0.2953
Young
modulus
0.2502977
4
2.6890231
2
1.8421
05
1.7246
87
Force 2.5606 2.625 9.116 8.832
Displaceme
nt 9.067 8.642 22.92 23.629

6. Conclusion
In conclusion, it can clearly be said that although tensile experiments provide the picture of
performance on the said material, there are a number of issues that must be aligned in order to
obtain a more accurate value. Notably, the system of measurements must be reviewed in order to
improve on its accuracy and repeatability [6]. Otherwise, the experimental results obtained provided
a basis onto which further interrogation can be undertaken.
7. References
[1]E. Selig and G. Raumann, "A Hydraulic Tensile Test with Zero Transverse Strain for
Geotechnical Fabrics", Geotechnical Testing Journal, vol. 2, no. 2, p. 69, 1979.
[2]"Correlation of small punch tests with tensile tests on iron-aluminium-silicon", Metal Powder
Report, vol. 52, no. 3, p. 41, 1997.
[3]"High impact and tensile strength PM B-steel by Cu infiltration", Metal Powder Report, vol. 45,
no. 11, p. 787, 1990.
[4]G. Lomaev, "Analytical method for evaluating quality of tensile testing machines", Measurement
Techniques, vol. 12, no. 5, pp. 644-647, 1969.
[5]R. Strimel, "Automated Horizontal Tensile Testing Machines For Rapid Quality Control
Testing", JOM, vol. 32, no. 7, pp. 30-33, 1980.
[6]G. Stepanov and V. Stanotina, "Properties of Steel 12Kh18N10T Tested for Tensile Strength in
Liquid Helium Cooled to 2.4 K", Metal Science and Heat Treatment, vol. 45, no. 910, pp. 373-375,
2003.
[7]Y. Chao, "Ultimate Strength and Failure Mechanism of Resistance Spot Weld Subjected to
Tensile, Shear, or Combined Tensile/Shear Loads", Journal of Engineering Materials and
Technology, vol. 125, no. 2, p. 125, 2003.
[8]P. Gope, H. Kumar and H. Purohit, "Effect of Tensile or Compressive Overload on the Fatigue
Crack Growth of Friction Stir Welded 19501 Aluminum Alloy", Journal of Testing and Evaluation,
vol. 46, no. 1, p. 20170018, 2017.