Measuring Tensile Strength in an alternative way

In summary, the conversation discusses an alternative method for measuring the tensile strength of a material by creating a cylinder and applying pressure to it until it ruptures. The yield strength of the material can then be determined by multiplying the maximum fluid pressure by a factor of 3 or 5. The second question revolves around linking Young's Modulus to the tensile strength of the material, but the validity of this method is questioned. The conversation also highlights the importance of considering boundary conditions and different types of stress when conducting material tests.
  • #1
weezy
92
5
So I've been looking at a few material tests and they all start with a rectangular sample of the material, loaded into a machine which extends them by increasing load at a constant rate and measures the strain/stress till the point of material fracture. The yield stress is measured in usually MPa which has the same units of pressure.

So I was wondering if I could measure the tensile strength of a material in an alternative way. Say I have made a cylinder out of the material whose tensile strength is to be measured. I then fill up the cylinder with some fluid and apply pressure to it and measure the YIELD STRENGTH at the point when my disc ruptures. Now I'm aware that compared to the previous uniaxial loading, now I'm loading it in possibly two or three directions. The material at any point is being pushed in negative and positive x directions and also in a positive z direction, maybe even in positive and negative y directions. This means that I might have to include a multiplication factor of 3 or 5 to the fluid pressure in order to obtain the total stress on the material.

This comes purely from my speculation that since dimensions of tensile strength and pressure are the same, they can in principle be thought of as the same, just like work and energy. My second question is how can we link Young's Modulus to tensile strength of a material?

SUMMARY: I make a cylindrical disc out of material X. Fill it with fluid and apply pressure on top of the disc which pushes the curved part of the cylinder outwards till fluid pressure breaks it. The tensile strength can then be determined by doing 5 X Maximum Fluid pressure. This should give the same answer as uniaxial loading. If I'm wrong please correct me. Thank you!
 
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  • #2
Question 1:
Search engine is your friend, start with search terms: stress in thin cylinder. That will lead to stress in thick cylinders. Note carefully the references to hoop stress, radial stress, and axial stress. Also note the assumptions applicable to each of those three stresses. Note that yield point (search that also) is not the point where it ruptures.

Question 2:
Hint: Look up the Young's Modulus and tensile strength for various steels, ranging from hot rolled low carbon, to heat treated alloy steels.

Question 3:
I do not understand your question, but it sounds completely wrong.

Suggestion: Always consider posting a diagram to clarify your text. It never hurts, and frequently helps.

General observation: Just because units match does not mean that they are measuring the same thing. As an example, Newton-meters can be torque or work (AKA joules).
 
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  • #3
When you roll the material into a cylinder, you prestress the wall, so that is one place this test differs from the conventional tensile test.

Secondly, there is the matter of sealing the ends of your cylinder. Any feasible sealing technique is going to change the boundary conditions, again modifying the nature of the test.

In short, it will not be an equivalent test.
 
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Related to Measuring Tensile Strength in an alternative way

1. What is tensile strength?

Tensile strength is the maximum amount of stress that a material can withstand before breaking or fracturing.

2. How is tensile strength typically measured?

Tensile strength is typically measured by applying a force to a material until it breaks, and then calculating the stress at the point of fracture.

3. Why would someone want to measure tensile strength in an alternative way?

There are a few reasons why someone might want to measure tensile strength in an alternative way. One reason could be to test the strength of a material that is difficult to break, such as a very strong metal. Another reason could be to avoid damaging the material during testing, as traditional methods involve breaking the material.

4. What are some alternative methods for measuring tensile strength?

Some alternative methods for measuring tensile strength include using ultrasonic waves to measure the material's response to stress, using lasers to measure the material's deformation, and using computer simulations to predict the material's strength based on its molecular structure.

5. Are alternative methods for measuring tensile strength as accurate as traditional methods?

Alternative methods for measuring tensile strength can be just as accurate as traditional methods, but it depends on the specific method being used and the material being tested. It's important to validate the accuracy of any alternative method before relying on it for important measurements.

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