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mh1985
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Why can there sometimes be a difference observed between them?
The yield stress from tensile test is a measure of the stress at which a material begins to deform plastically. It is determined by applying a gradually increasing tensile force to a material until it reaches its yield point. On the other hand, yield stress from hardness tests is determined by measuring the indentation hardness of a material using a standardized test method, such as the Rockwell or Brinell hardness tests. This value is then correlated to the material's yield stress using empirical relationships.
Both methods have their own advantages and disadvantages. Tensile tests provide a direct measurement of yield stress, but they can be time-consuming and require specialized equipment. Hardness tests, on the other hand, are quicker and easier to perform, but they rely on empirical correlations and may not be as accurate for all types of materials.
In some cases, yes. Yield stress from hardness tests can be a good estimate of the yield stress from tensile test for certain materials, such as metals. However, it may not be accurate for other materials, such as polymers, where the relationship between hardness and yield stress may not be well-defined.
Yield stress values are important parameters in designing and selecting materials for various engineering applications. They can help determine the maximum load a material can withstand before it begins to deform plastically, and can also provide information about the material's ductility and strength. Yield stress values from both tensile and hardness tests can be used in conjunction with other mechanical properties to make informed decisions about material selection and design.
The accuracy of yield stress measurements can be affected by several factors, such as the type and condition of the material being tested, the test method used, and the expertise of the person performing the test. It is important to follow standardized testing procedures and ensure proper calibration of equipment to obtain more accurate results.