Torsion and Tension Tests of Metals

Torsion & Tension Tests of Metals CE 307-01

Nathaniel R. Gant

Date Submitted: October 25, 2011

Submitted To: MAJ Moore

Virginia Military Institute Department of Civil and Environmental Engineering

Help Received:

Introduction When using different material in society, especially when construction is involved, it is crucial that the properties of the material are known. Besides the standard measurements of lengths, widths, and height, the mechanical properties that are affected by applied loads should be known too. These types of properties are tested using various machines that analyze the information and regurgitates the information itself. Tension and Torsion are two properties that are often tested. Tension is the pulling force that acts on any material and it causes a material to stretch. Torsion is twisting force that acts on any material; in other words, torque is applied in the opposite direction to each end of an object. The purpose of this lab was to measure the tension and torsion of different type of metals. The metals used for the tension test were aluminum, cast iron, brass, and steel. The metals used for the torsion test were aluminum, cast iron, and steel. For each experiment, each type of metal had the same length and diameter. Using the analysis from the machines, a plot of the stress-strain relationship was determined and used to find the yield stress, maximum stress, and rupture stress along with other various properties to compare each metal.

Results Torsion Test Table 1: Dimension of each metal used for torsion test.

Dimensions of Each Metal Gage Length

11.3125

in

Diameter

0.785

in

Table 2: Torsion test raw data and calculated stress and strain for each metal.

Aluminum

Cast Iron

Steel

Angle 째

Torque in-lbs

stress psi

strain -

Torque in-lbs

stress psi

strain -

Torque in-lbs

stress psi

strain -

0 5 10 15 20 25 30 35 40

0 578 1015 1500 2120 2560 2825 2980 3145

0 6085398 10686296 15792555 22320144 26952627 29742645 31374543 33111724

0 0.017348 0.034696 0.052044 0.069392 0.08674 0.104088 0.121436 0.138785

0 N/A N/A N/A N/A N/A N/A N/A N/A

0 N/A N/A N/A N/A N/A N/A N/A N/A

0 N/A N/A N/A N/A N/A N/A N/A N/A

0 600 1230 2300 3200 4300 5100 5900 6059

0 6317022 12949895 24215251 33690784 45271991 53694687 62117383 63791394

0 0.017348 0.034696 0.052044 0.069392 0.08674 0.104088 0.121436 0.138785

45 50 55 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 700 720 740 760

3228 3310 3456 3538 3645 3775 3896 4020 4192 4222 4282 4350 4425 4498 4562 4625 4675 4730 4769 4826 4852 4902 4929 4975 4993 5049 5066 5081 5100 5132 5143 5192 5203 5229 5242 5255 5268 -

33985578 34848905 36386047 37249373 38375909 39744597 41018530 42324047 44134927 44450778 45082480 45798410 46588037 47356608 48030424 48693711 49220130 49799190 50209797 50809914 51083651 51610070 51894336 52378641 52568151 53157740 53336723 53494648 53694687 54031595 54147407 54663297 54779109 55052847 55189716 55326584 55463453 -

0.156133 0.173481 0.190829 0.208177 0.277569 0.346961 0.416354 0.485746 0.555138 0.62453 0.693923 0.763315 0.832707 0.902099 0.971492 1.040884 1.110276 1.179669 1.249061 1.318453 1.387845 1.457238 1.52663 1.596022 1.665414 1.734807 1.804199 1.873591 1.942983 2.012376 2.081768 2.15116 2.220552 2.289945 2.359337 2.428729 2.498122 -

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A

6198 6264 6299 6430 6580 6709 6780 6889 6970 7023 7071 7126 7158 7199 7231 7266 7285 7311 7338 7356 7378 7387 7415 7432 7446 7465 7479 7496 7508 7526 7536 7549 7566 7573 7585 7590 7610 7619 7628

65254837 65949710 66318203 67697419 69276675 70634834 71382349 72529941 73382739 73940743 74446104 75025165 75362073 75793736 76130644 76499137 76699176 76972913 77257179 77446690 77678314 77773069 78067864 78246846 78394243 78594282 78741679 78920662 79047002 79236513 79341796 79478665 79657648 79731346 79857687 79910328 80120896 80215651 80310406

0.156133 0.173481 0.190829 0.208177 0.277569 0.346961 0.416354 0.485746 0.555138 0.62453 0.693923 0.763315 0.832707 0.902099 0.971492 1.040884 1.110276 1.179669 1.249061 1.318453 1.387845 1.457238 1.52663 1.596022 1.665414 1.734807 1.804199 1.873591 1.942983 2.012376 2.081768 2.15116 2.220552 2.289945 2.359337 2.428729 2.498122 2.567514 2.636906

Table 3: Additional steel torsion properties calculated using excel.

Steel Data Yield Stress (psi) 65254837.37

Max Shear Stress (psi) 80310406

Shear Stress vs Shear Strain Aluminum

Steel

Steel Peak Shear Stress

Steel Yield Stress

Aluminum Shear Modulus

Steel Shear Modulus

90,000,000 80,000,000

Shear Stress (psi)

70,000,000 60,000,000 50,000,000 40,000,000 30,000,000 20,000,000 10,000,000 0 0

0.5

1

1.5

2

Shear Strain

Figure 1: Shear stress versus shear strain plot of metals.

2.5

3

Tension Test Table 4: Dimension of each metal used for tension test.

Dimensions of Each Metal Gage Length

3.5

in

Diameter

0.25

in

Table 5: Rupture strength of each metal determined by machine.

Rupture Strength psi Aluminum

47088.59

Brass

43367.23

Cast Iron

28592.89

Steel

109617.25

Table 6: Additional steel tension properties determined by machine.

Steel Data Yield Stress (ksi)

Rupture Stress (ksi)

Peak Max Stress (ksi)

97.516

124.510

109.617

Tensile Stress vs Tensile Strain Steel

Aluminum

Cast Iron

Brass

Steel Yield Stress

Steel Rupture Stress

Steel Peak Max Stress

Steel Shear Modulus

140

Tensile Stress (ksi)

120 100 80 60 40 20 0 -20 -0.02

0

0.02

0.04

0.06

0.08

Tensile Strain

Figure 2: Tensile stress versus Tensile strain plot of metals.

0.1

0.12

*Used the Trapezoid Rule to find the Area under the curves in excel.

Discussion Torsion and tension affects every material in a different way. The group’s initial hypothesis about the metals turned out to be correct. One thought was that steel would be the strongest, and the other was that cast iron would be the weakest. In this lab, the metal that had the highest tension also had the highest torsion, which was steel. Steel had a maximum tensile strength of about 110 ksi and a max shear stress of about 803 ksi. On the other hand, cast iron had a maximum tensile stress of about 29 ksi and the

max shear stress could not be determined. It took nearly 10 seconds for the cast iron to split once it was tested for torsion each time. Though the rate at which the machine increased the angle was around 20 degrees per minute the first go round, the cast iron still split rapidly at a rate of about 3 degrees per minute. In other words, it was impossible for the group to record the torques at each angle. However, the fact the cast iron split so quickly revealed that it had a very low rupture stress compared to the metals. For the tensile tress, aluminum and brass showed similar strengths; but out of the two, brass showed to be more ductile. If the metals were rated by toughness from greatest to least the order would be steel, brass, aluminum, and cast iron. A few observations that were noticed in the tension and torsion test were the way that certain metals split when ruptured. For the tension test, steel split at a cup cone configuration; but for the torsion test, steel split in a clean 90-degree angle. For aluminum, it split at a 45-degree angle for tension and a 90-degree split for torsion. Cast iron, split at a 90degree angle for tension but a 45-degree angle for torsion. The differences kinds of split under different type of forces is crucial to known because depending on what type of load a member of a structure will encounter, a engineering must be able to choose the right material to make the structure as structurally sound as possible. Also, the group noticed that during the torsion test the aluminum and steel were hot after that ruptured, but cast iron was not hot. This observation reveals that those metals gained additional energy when the loads were applied on them. This is vital to know as well because it prevents someone from being burned by a beam or metal support under too much stress. Steel is a perfect material to use for cables because they have a high max tensile stress. Aluminum would be a good material to use for a screwdriver because it is cheaper than steel and it can take in a lot of torsion. Cast iron could be used to make cheap screws because they can withstand a good amount of tension and torsion. Cast iron will make heat up when under intense stress.