The discussion centers on the relationship between compressive strength and bulk modulus in materials science, particularly concrete. It is established that compressive strength represents the maximum stress a material can withstand before failure, while the bulk modulus measures the material's volume strain under pressure. The conversation clarifies that neither the bulk modulus, shear modulus, nor Young's modulus dictate failure behavior, which is influenced by anisotropic stresses. Participants emphasize the importance of understanding these distinctions for accurate problem-solving in material mechanics.
PREREQUISITESMaterial scientists, civil engineers, and students studying mechanics of materials will benefit from this discussion, particularly those focusing on concrete properties and failure analysis.
The bulk modulus would allow you to calculate the amount volume strain, resulting from a given change in pressure ( ΔP ). The volume strain is dimensionless - think of it like a percentage change. If you draw a stress strain curve, think of the modulus as the slope of the curve in the linear region, and the Compressive strength as the point on the curve where it starts to fail.quicksilver123 said:
Good point. I should have stated that to let the OP know that those are not needed to solve the problem. The Compressive Strength is the maximum pressure that it is designed withstand before you are getting into risk of failure.Chestermiller said:
Actually, it is not the pressure (which is the isotropic part of the stress tensor) that causes failure. It is the anisotropic part (i.e., unequal principal stresses) that causes failure (along shear planes at an angle to the principal stresses). When we talk about compressive strength, we are talking about unixial loading of a bar or column, with zero principle stresses in the transverse directions. If we somehow placed the bar or column under isotropic pressure loading (like lowering it to the bottom of the ocean or placing it in a liquid high compressive chamber), it would not fail until a much higher compressive stress than the uniaxial compressive strength.scottdave said:
Once I learned dyadic notation, all my problems with tensors vanished.scottdave said:Thanks @Chestermiller . Yes it is starting to come back to me. It has been around 20 years, since I took that materials course. But I do remember when I first was introduced to tensors. I had a similar feeling to the first time that I was introduced to imaginary numbers.