Properties Materials Tensile Strength

While studying physics you meet with different types of strength, and tensile is just one of them. The concept of tensile strength is not that hard to grasp, as it’s the measurement of the force needed for something (e.g. a rope) to break.

While this is a rare element of discussion in daily life, it’s a big concept in engineering, probably the main one. Without this concept, it would be impossible to talk about civil engineering and architecture.

When someone mentions that the tensile strength of a specific object equals something, it means that particular object can take just that amount of pressure, tensile stress before it breaks, deforms or fails in some way. That being said, if the tensile strength of human skin is 20 MPa, it can’t take more than that.

There are some common strengths for materials, that way brass is 500 MPa and diamond is 2800 MPa. However, with the majority of materials, measuring tensile strength with tensometer (the procedure also known as tensile testing) is crucial. You have to do it with different types of materials as there is no single measurement that could fit all.

Types of Tensile Strength

There are also the types of tensile strengths you have to know before measuring anything.

  1. Ultimate strength.
    This is the maximum for any given material. The measurements for the ultimate strength have to be really precise.
  2. Yield strength.
    This type of strength, commonly marked as the yield point on different diagrams, is the one that shows how much stress that material can cope with not breaking. If the load is removed, there won’t be any deformations on that object. This way, returning to that human skin’, the yield point is 15 MPa, but the ultimate strength is 20 MPa.
  3. Breaking strength.
    This is the point of rupture. To understand how this works, you have to check different diagrams. The breaking point is always shown clearly there.

Types of Tensile Failures

  • Ductile.
    It could technically be divided into different stages, which shows that ductile failures occur slowly and steadily. In the scientific community, a ductile failure is more tolerated, though it’s still a failure. The first stage is when there is yielding, then some hardening usually happens, and then there is a snap.
  • Brittle.
    This is when the breaking occurs suddenly (sometimes even when it technically shouldn’t be there). It can occur at any stress levels, but typically brittle failures are associated with low stress. They are normally really fast.

If you’re working with metals, you should know that even with ductile metals, brittle failures are still possible. Those happen if the conditions for metals are altered quickly. Different types of steel, for example, are ductile with elevated temperatures, but they turn brittle if the temperature is lowered quickly.

If you’re planning to run tensile measurements, you have to know that the data you’re getting could vary each time. Some materials are just plain hard to measure, such as spider silk. There are too many factors to consider, so there is no “ultimate” number of MPa’s. The same applies to human skin or hair. The numbers will vary from a person to a person (so the data is always somewhere in between), also depending on ethnicity, sometimes gender and different treatments. It is really important to know the exact tensile strength of materials in building, engineering and other projects.

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