make a paraphrase for this report

make a paraphrase for this report

Abstract:

This experiment puts emphasis on the tensile properties of various materials 

including two polymeric samples and two metals. Results based on this 

test help show how each is distinguished among the others and how they 

complement the basis for a safe design project. The tensile properties are 

gathered by exerting a tensional force that pulls a specimen by each end 

at a fixed rate until failure. Data for the test is obtained by measuring key 

factors such as amount of load, cross-sectional area and elongation.

Description of Work:

The four samples tested were steel, aluminum, low density polyethylene 

(LDPE), and high density polyethylene (HDPE). Each were measured 

for thickness and width, then placed into the United machine for testing 

of tensile properties. It had two grips, each one holding one end of the 

sample part. The machine, running in DOS, was then calibrated to ensure 

appropriate results for the respective sample material. At a set rate, the 

equipment piece would simultaneously pull each end and gather data to 

show elongation and load. A standard 2MB floppy disk was then used to 

record the data and transfer it into a digital spreadsheet to determine stress 

and strain. 

Results and Discussion:

After obtaining the initial dimensional measurements for each sample, they 

were put through the tensile test. The machine gave two sets of values 

being, %strain and Load. With these values the engineering stress and 

strain were then calculated and graphed for all materials. The results were 

surprisingly off. For example the elastic modulus of steel is approximately 

referenced as 30Mpsi, while my experimental value came out to be 

21.487Ksi. The elastic modulus of aluminum is referenced as 10.6Mpsi while 

my experimental value yielded 3.826Ksi. That for Low Density polyethylene 

was 30Ksi while experimentally 0.265Ksi, and for high density polyethylene 

200Ksi was referenced while 0.601 Ksi was obtained experimentally. Being 

that these values were so off it would not be surprising to find the other 

values not to match with the referenced values. This could have to largely 

do with a human error factor in the experiment process. It could range form 

the initial dimensional measurements to the data input in the computer to 

the data manipulation and graphing process. There were many possibilities 

to make a mistake in this experiment unfortunately they seem to have been 

made in a large scale in this experiment. 

The graphs on the other hand seem to have the correct forms. The true 

engineering stress and strain graphs showed much higher values for stress 

than did the engineering stress and strain graphs. this is due to the true 

engineering stress depending on instantaneous cross sectional area and 

not the the initial area. The reason for the decrease in instantaneous cross 

sectional area is due to the necking of the material that happens when the 

material transitions from the elastics region of the stress strain curve into 

the plastic region where it becomes permanently deformed. The values 

for the ultimate tensile strength are as expected with aluminum and high 

density polyethylene. They are high values as one would expect from such 

materials. The problem arises when looking at the ultimate tensile strength 

for steel, the value is lower than that of aluminum, which is incorrect. This 

mistake must be a byproduct of the human error factor that was mentioned 

earlier.

This lab’s purpose was to show and compare the various properties of a 

material at a specific temperature under tensile forces. Although human 

error played a large part in this experiment, the graphs still display the 

majority of the properties the materials exhibit under a tensile test.