Analysis of Material Behavior Under Tensile Stress: A Report

This report details a laboratory investigation into the tensile strength and mechanical properties of four materials: A-36 steel, polymethylmethacrylate (PMMA), polycarbonate, and 6061-T6 steel alloy. The study employed an Instron load frame and BlueHill data acquisition software to subject the materials to tensile stress, measuring properties such as yield strength, modulus of elasticity, fracture strength, and percentage elongation. The report compares the materials' behaviors, analyzes stress-strain curves, and determines true stress and strain values. The results indicate that A-36 steel exhibited the highest ultimate tensile strength, while 6061-T6 steel showed a higher yield strength. The analysis includes the application of the Ramberg-Osgood model and discusses the significance of these properties in engineering design. The report also addresses the importance of elastic analysis in determining the strength of materials and its role in the design and development of new and improved materials.

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Instructor
Course
07th December 2018
Part 1
Tests on tensile strength are major meant for indulgent properties of diverse materials, besides
their behavior when subjected to loading. This laboratory attempted 4 unmistakable materials,
together with A-36 steel, polymethylmethacrylate, polycarbonate, and6061-T6 steel alloy.
Respective model was attempted on various occasions by means of a BlueHill data getting
programming as well as the Instron stack diagram. The figures obtained from for each test
indicated important properties of material, for illustration, extraordinary unbending nature,
modulus of rigidity, in addition to yield feature. Additional determined properties encompassed
fractural strength, percent stretching or elongation. These measureable properties were applied
for relating the materials with one another, as well as to depict the sample as weak or pliable.
Ideal strain as well as stress were determined for 6061-T6 steel model to determine the
dissimilarity concerning the structure pressure, in addition to the genuine merits. The process of
designing pressure is a suspicion which utilizes the principal zone of the cross area, overlooking
the influences of transverse strain as well as the fluctuating cross segment. This presumption
outcomes in the descent of the designing stress strain curvature subsequent to a conclusive
rigidity, at which necking come about.
Applying the assessments of the true strain, the true plastic strain was set on for a specimen of
steel by deducting value ideal flexible strain. Graphing the logarithm of the certifiable pressure
versus the logarithm of the real plastic strain allowed the plastic piece of the real pressure strain
curve to be exhibited by the Ramberg-Osgood demonstrate as in the later area. Despite the fact
that the model did insufficiently at small plastic strains close by yielding, it attempted to
flawlessness prior to necking and a conclusive malleable strain.
The outcomes of the tractable tests exhibited that the A-36 steel was the strongest model. It
achieved the utmost extreme rigidity that is, imperative extraordinary flexibility, the unsurpassed

modulus of solidness/durability, in addition to the greatest certifiable quality of break. The 6061-
T6 steel achieved a greater yield compared to the A-36 steel, anyway an inferior inflexibility in
addition to veritable crack value as a result of softening besides cementing/setting. Most of the
materials other than the PMMA ended up being malleable, especially the polycarbonate, which
recorded 82.2% elongation. The PMMA examinations landed at the average of a percentage
extending/lengthening of simply 0.7%.
Elastic analysis is a standout concerning the record key assessments for designing, also
contributes important figures relating to a material together with its correlated properties. Such
properties can be applied for plan in addition to an enquiry of designing constructions, in
addition to developing innovative improved materials which would likely suit a predetermined
utilize.
The tensile testing investigation facility was engaged operating an Instron stack outline and the
BlueHill information securing programming. Four distinct materials were tried, including 6061-
T6 steel, A-36 hot moved steel, polymethylmethacrylate (PMMA, cast acrylic), and
polycarbonate. The samples were cask fashioned in cross area, with a lessened gage segment.
The lessened gage segment assured that the most elevated burdens materialized inside the gage,
and not close to the grasps of the Instron stack outline, forestalling strain and break of the
example close or in the holds. The moderated gage area of every example was about 12.7 mm
(0.5 inches). The examples were at that point machined to the correct measurements required for
the test, as per ASTM gauges.
Methodology
Every single specimen was assessed with the calipers to select the distance across of the cross
area. A gage length was determined (normally 50.00 mm) and scribed into the example with the
aim that the separation concerning the two trajectories could be assessed when the elastic test
was done. An average decreased gage segment illustration is indicated in Figure 1, on the
accompanying page. The BlueHill statistics obtaining programming was activated, then the
precise material was chosen. The load cell was fixated to guarantee that the equipment just
assessed the tractable load attached to the model.

The example was stacked into the jaws of the Instron stack framework with the objective that it
was correspondingly divided in the middle of the two clasps. The hub and transverse
extensometers were connected to the shrank gage segment of the specimen, guaranteeing that the
pivotal extensometer was set accurately while joining it to the gage and that the transverse
extensometer was over the entire width of the example. This precautionary measure outcomes in
enhanced figures as well as averts damage to the extensometers.
The figures was collected by making use of the product, and noted. At a fixed valuation of strain
(past the yield strain), the equipment disallowed applying figures from the extensometers, then
began saving the strain data applying the condition of the adjusting crosshead. The testing
technique was reworked for whatnot remains of the models.

Figure 1: An abridged gage fragment model made from 6061-T6 steel.

Figure 2: A distinctive Instron load frame.
Outcomes
Design Stress and design Strain
The figures so obtained were plotted on discrete charts as shown by material. Respective
illustration exhibits the stress versus the strain. Using Equation A.2, the weight was resolved. P
implies the pliable power associated with the model.

Material Properties
A conclusive rigidity meant for each material is logged in Table 1. The valuation of a conclusive
rigidity was determined utilizing equation below separately.
Table 1: a definitive elasticity meant for the each of the materials.
The yield potentials and the modulus of elasticity were determined meant for the materials. The
unfolding standard deviations for the two makings were as well determined.
Table 2: The yield quality, modulus of elasticity, as well as standard deviations for 6061-T6 steel
and A-36 steel.
The modulus of durability and the modulus of flexibility were determined as of the area in the
designing stress as opposed to constructing strain curves. Equations C.1 & C.2 are applied to
compute the modulus of elasticity.

The ideal fracture strength delivers the tangible approximation of the pressure/ stress qualified
based on the model performance when conducting tensile tests when failure is about to occur.
The ideal break feature/ fractural strength is the finest stress that the particular sample can
accommodate at yielding. The percentage lengthening and the percent reduction in area make
available data on the model’s flexibility, and the extent it inclines to be long-drawn-out before
failure.
Equation D.2 is applied to figure the percentage decrease in area.
The averages of each one of the 3 qualities for each one of the 4 materials are indicated in Table
4.
Condition D.3 is applied to establish the ideal length of the model immediately before crack.
Condition D.4 is now applied to ascertain the percentage prolongation for the model/ material.

Ideal/
genuine strain and ideal stress
One example of steel was utilized to locate the genuine stress and the genuine strain experienced
amid a tensile test, and to contrast both with the designing stress and the building strain. The
designing stress and strain does not represent the adjustment in cross sectional region, and
records for the pivotal strain in the example. The ideal strain and stress represent the adjustment
in cross sectional territory, and in this manner the ideal stress is bigger than the designing stress.
The genuine strain is likewise more noteworthy than the designing strain because of strains the
transverse way along the gage of the example. Figure 7 demonstrates the ideal strains against the
genuine/ ideal strain, alongside the building stress in addition to the designing strain for a similar
example.

A-36 steel 6061-T6 Polycarbonate PMMA
0
100
200
300
400
500
600
700
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
percent elongation vs true fracture strength
True fracture strength percent elongation, %EL
Figure showing percent elongation vs fracture strength
The genuine stress and strain at the resolve of most extreme load capacity (the point at which
ultimate elasticity ensues). 6061-T6 steel test achieved an approximation of 404.9 MPa, drawing
a distinction with a greatest rigidity of 376.6 MPa. The ideal strain at similar level achieved an
A-36 steel 6061-T6 Polycarbonate PMMA
0
100
200
300
400
500
600
700
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
percent elongation vs true
fracture strength
True fracture strength percent elongation, %EL

assessment of 0.0723 m/m, paralleled to a strain of 0.0750 m/m. The most extreme genuine
stress at break was 561.5 MPa, with a strain of 0.765 m/m. When cracking occurred, the
designing stress was marked at 261.3 MPa, having a strain of 0.182 m/m.
The Ramberg-Osgood Model
The behavior of the ideal stress for the reason that of the genuine plastic strain can be
specifically validated by making use of the Ramberg-Osgood classical. This provision help to
model the stress strain curvatures as a command setting model, throughout yielding. In figure 8,
this has been plotted against the ideal stress and strain got from the test.
1 2 3
0
50
100
150
200
250
300
350
400
450
0.001 0.01 0.05
true stress vs true plastic strain
True plastic strain(m/m) calculated stress Mpa
Series3
The assessment outcomes were reliable meant for respective materials chosen for testing, as
apparent in Figures 3-6, in which each of the 3 stress strain curvatures were evidently unevenly
casing. A fascinating discernment can be generated by employing the PMMA diagram, in which