Question

discussion questions: 1. what practical significance does the tensile test have in making material selections for plastic products? give at least one practical example (product plus property use). 2. what do you think happens to most polymers’ tensile strength as the temperature decreases? why? 3. what general property (or properties) of a material are related to tensile strength testing? 4. what would change if you ran the tensile test at a faster speed? 5. does the tensile test performed in this experiment meet astm d638 requirements? if not, what would disqualify this as an astm test? 6. list your materials and corresponding test values for young’s modulus, percent elongation, yield strength and/or ultimate tensile strength, then provide a listing of corresponding published values.

Explanation:

1. A tensile test measures a material's strength under tension. In plastic product - making, it helps select materials that can withstand forces without breaking. For example, in making plastic water bottles, high - tensile strength plastics are chosen to prevent bursting under internal pressure.
2. As temperature decreases, most polymers' tensile strength generally increases. This is because lower temperatures reduce molecular mobility, making the polymer more rigid and less likely to deform under stress.
3. Properties related to tensile strength testing include elasticity (ability to return to original shape after deformation), plasticity (permanent deformation), and toughness (ability to absorb energy before breaking).
4. Running a tensile test at a faster speed can lead to higher measured tensile strength values. This is because the material has less time to deform plastically, and the test may capture a more brittle - like behavior.
5. To determine if a tensile test meets ASTM D638 requirements, factors such as specimen geometry, testing speed, and measurement accuracy are considered. Deviations in these aspects could disqualify it as an ASTM test.
6. Without specific test data, it's not possible to list materials and their test values. Published values can be found in material science handbooks or online databases for different polymers and plastics.

Answer:

1. Tensile tests help select strong plastics. Example: plastic water bottles for pressure resistance.
2. Tensile strength generally increases as temperature decreases due to reduced molecular mobility.
3. Elasticity, plasticity, toughness.
4. Higher measured tensile strength due to less time for plastic deformation.
5. Depends on specimen geometry, testing speed, measurement accuracy. Deviations can disqualify.
6. No specific data provided. Published values in material science resources.