Introduction:
Mechanical properties are essential to engineers as they influence the way products are designed and manufactured. With that said, its paramount to accurately test and record these properties in a standardized fashion. The most common tests used nowadays are tension tests which provide basic design information on the strength of materials by producing parameters such as the yield strength, elastic modulus, toughness, and resilience to name a few. Tension tests are accomplished via a machine called a universal testing machine or UTM for short. The UTM will have 2 cross heads, which grip the material being tested, and then begin to apply an increasing load on the specimen until necking. Throughout the tests, the control system and its software will measure the strain and load at various increments and then tabulate the information. After the test has been completed, the software will accompany the tabulated information with a stress strain diagram along with the various mechanical properties that can be gleaned from the materials behavior under load.
Objective:
The objective of this lab was to run a tensile test on the LDPE bar produced via injection molding in the previous lab. The resulting values will then be compared with the values obtained from the tensile test of the extruded LDPE. This will allow us to analyze and determine the differences between two of the most widely used process in manufacturing plastics.
Procedure:
The LDPE bar was tested using the procedure, which is as follows.
1. The sample is placed between the grips of the cross heads and then secured in place by closing the grips.
2. The sample is then measured for thickness and width in order to determine the cross section area at 3.96 mm in thickness and 11.34 mm in width1
3. Then the load and strain ranges were selected with the strain for both tests selected to start at 0.5 and stop at 0.25.
4. Then after naming each test on the program, the test was executed.
5. After the test was completed, the data obtained was exported to an excel file for further analysis.