Conclusion
In conclusion the polymer that can with stand the most load is the nylon 66 glass which took a load of 5.27kN whilst the LD Polyethythene took the smallest load with a result of 0.43kN. The nylon 66 glass had a high load but gave a brittle failure where as the LD Polyethythene was very ductile which gave a result of the polymer stretching. The effect that the rate of extension has on the polymer depends on the rate, if the rate is of a large rate such as 200mm per minute then the amount that the polymers amount of stretch will decrease. The lower the rate the more the stretch will be, for example in the Lloyds machine test the machine reached its maximum and the polymer had still not broke it just stretched to the full length of the machine.
Tensile testing of metals
Objective
The aim of this is to show the relationship between the load and extension of metals. We are going to test two samples of reinforcement. One shall be the plain R-bar and the other shall be a high strength T-bar. The samples must be in accordance with BS EN 10002-1:1990 using the Denison Tensile Test Machine.
We shall also test eight different metal bars of the same size using the Hounsfield Machine
Method
First we tested the reinforcement bars. The measurements of the diameter and the length of the bars are taken and recorded. The bar is loaded onto the Denison Test Machine and loaded until the bar fails. The maximum load is recorded and the bar removed. You have to measure the diameter and length so the Elongation and Reduction can be calculated. Then the other reinforcement bar is tested in exactly the same way.
Secondly we tested the Hounsfield tests using 8 different types of metal of the same size bars. The metals are carbon steels, Alloy steel, Aluminium alloy, copper, 70/30 Brass and 60/40 brass. They all have the same area of 20mm² apart from the Alloy steel which has an area of 10mm². The metal is loaded on to the Hounsfield and load till failure and the maximum load is recorded, then pieces are used to find the Elongation and Reduction of the metals. All data is added to the table and used to work out the maximum strength of the metal bars.
Reinforcement Bar Results
Hounsfield Test Results
Conclusions
The Elongation of the R-bar was of 50% of the original bar and the reduction was of 45% of the bar stretched which caused a cup and cone failure which is common in mild steel. In the T-bar the Elongation was of 30% and the Reduction of the bar was of 7% which caused the bar to snap instead of stretch. The difference between the yield and the maximum load is that the yield is what the bar can safely take without failing; the maximum loading is the point when then bar fails.
The diameter of the R is 15.96 and has two marked lines; the initial length is 50mm. This is very ductile, it’s not strong therefore is not used as much.
The T-bar s ribbed and has two marks on it which means the test should be quicker, and the failure was angled and there was a reduction in area. This is used as a main reinforcement and has more steel/carbon.
In the Hounsfield tests show the Elongation of the different metals show that the Alloy steel didn’t stretch as much as the 0.1% carbon and the 60/40 brass whilst the Reduction in area is greater in both the brass the less is in the alloy steel. The hardness of metals can be tested using Rockwell hardness test.
Brass is good in terms of corrosion and hardness. You would have to perform these tests in a wide range to be accurate. Brass has a composition of more than one material it is built up of 70copper x 30 brass. That’s why copper pipes are used for electrical / plumbing needs. They don’t use polymers as they are heavy. Copper is not very strong or expensive.
