Specifications of Tensile Test Specimen?

Question

I am Currently Working on Measuring Various Mechanical Properties of Metalic Materials using Universal Testing Machine (UTM) at Various Temperatures. I know that for Testing at Ambient Conditions, ASTM E8/E8M is followed.

By Literature Review, I have Identified the Specimen Dimensions for My Experiments.

Due to Lack of Adequate Experimental Data, I am Unable to Identify the Specimen Dimensions with respect to ASTM E21 and ISO 15579 for Testing at Elevated and Low Temperatures respectively.

Since, These Standards are Quite Costly to be Purchased Individually, Should I take the Specimen Dimensions at Room Temperature for Experiments at Low and High Temperatures ?

Is there a Major Difference in the Dimensions presented by these Standards or Can I Complete the Analysis using My Assumptions ?

Answer 1

This is a general comment/observation regarding standards.

Testing Standards tend to follow a clear line of logic. Usually,they aim to provide the most widely usable and useful test results with the least amount of wasted effort.

Another observation is that, although test standards provide explicit instructions, the user is sometimes given some leeway. Additionally, especially in research/education, it is possible to depart from the instructions, and state in a research article that "the standard XXX was used, with the following changes". Of course, that does not apply to the industry, when a testing standard should be followed as closely as possible.

Now regarding to your specific question, regarding whether on not dimensional measurements should take place at elevated temperatures. If you want to test for a mechanical property such as strength or modulus of elasticity, then it makes sense that you use the same material to make a fair comparison. Therefore, IMHO there is no point in checking the dimensions at elevated temperatures where the specimen will be slightly larger but the mass remains the same. Additionally, it is very impractical to test at 500C for example.

So what I would do is, if I were in your position (and if you are doing this for some research paper): I would measure the specimens at room temperature, and I would make sure to explicitly state on the paper that the specimens were all tested at room temperature.