Tensile and shear capacity of metals

In summary, when discussing the properties of metals, tensile strength is commonly quoted, while shear strength is less common but typically taken as half the allowable tensile stress. However, when actual data is available, the difference between the two is often closer to 70%. The practical reason for this discrepancy could be due to the reduced energy or work required for the type of deformation that occurs in the cubic crystal structure of metals under shear load.
  • #1
LT Judd
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TL;DR Summary
What is the underlying reason for the difference in tensile stress capacity and shear stress capacity in metals?
Steel and other metals data sheets and mill specs most commonly quote some tensile strength metric, like Proof, Yield or Ultimate Tensile Stress. Less common is the value for shear strength. Often as rule of thumb the allowable shear stress is taken as half the allowable tensile stress but, when you do find actual data, its often more like 70%. Example Source: https://www.engineersedge.com/materials/material_tensile_shear_and_yield_strength_15798.htm.
My question is what the underlying theoretical reason is why metals are weaker in shear than in tension, and what is the practical reason why the actual difference is less than the theoretical.
 
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  • #2
The reason could be the reduced energy or work that is required for the type of deformation that the metal cubic crystal structure suffers under shear load.

Copied from:
https://engineeringlibrary.org/reference/properties-of-metals-doe-handbook

"When metal experiences strain, its volume remains constant. Therefore, if volume remains constant as the dimension changes on one axis, then the dimensions of at least one other axis must change also. If one dimension increases, another must decrease."
 
  • #3
LT Judd said:
Summary: What is the underlying reason for the difference in tensile stress capacity and shear stress capacity in metals?

and what is the practical reason why the actual difference is less than the theoretical.
I don't see in your post anything that backs up that statement.
 

1. What is the difference between tensile and shear capacity of metals?

Tensile capacity refers to the maximum amount of tensile stress that a metal can withstand before it breaks. Shear capacity, on the other hand, refers to the maximum amount of shear stress that a metal can withstand before it fails. Tensile stress is a pulling force, while shear stress is a sliding force.

2. How is the tensile and shear capacity of a metal determined?

The tensile and shear capacity of a metal is determined through testing and analysis. Tensile tests involve pulling a metal sample until it breaks, while shear tests involve applying a sliding force to a metal sample until it fails. The results of these tests are then used to calculate the tensile and shear capacities of the metal.

3. What factors can affect the tensile and shear capacity of metals?

The tensile and shear capacity of metals can be affected by various factors, such as the type of metal, its composition, and its processing method. Other factors that can influence these capacities include temperature, loading rate, and the presence of defects or imperfections in the metal.

4. How can the tensile and shear capacity of metals be improved?

The tensile and shear capacity of metals can be improved through various methods, such as alloying, heat treatment, and cold working. Alloying involves adding other elements to the metal to improve its strength and toughness. Heat treatment involves heating and cooling the metal in a controlled manner to alter its properties. Cold working, also known as strain hardening, involves deforming the metal at room temperature to increase its strength and hardness.

5. Why is it important to know the tensile and shear capacity of metals?

Knowing the tensile and shear capacity of metals is crucial in engineering and construction, as it helps ensure the safety and reliability of structures and products. It also allows for the proper selection of materials for specific applications, as different metals have different capacities and may be more suitable for certain purposes than others. Understanding these capacities can also aid in predicting and preventing potential failures or accidents.

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