Properties of materialspe

I would like to first define what some of the properties are to avoid confusion. It may seem pedantic, but proper terminology also makes understanding materials better. Maybe we could compile a glossary.

• Rigid is an absolute. It means a material that would not deflect regardless of the force applied. Therefore there is no property called rigidity. It is used in calculations when the deflection is insignificant to simplify them.
• Stiffness is the property that describes how much a material deflects when a force is applied.
• Toughness is the property of how much energy a material can absorb before breaking.
• Strength is the maaterial's ability to withstand an applied load without failure or plastic deformation. This has subdivisions.
  
• Elasticity is a material that returns to its original shape after being deformed, which is the opposite to plasticity.
• Hardness is the resistance to deformation.
• Specific heat is the amount of energy the material will absorb to change temperature.

 

Apart from expressing my disagreement with some of "your definitions" (I won't get into that discussion with you), what I would be interested in knowing is, in practical terms, how you quantify those properties.

 

https://www.asminternational.org/wp...kfTz6q3LNtDUHjP5brF1QgybhO-MvKedtLfKxzVD45cuT

This is a clearer and more accurate set of definitions for Gonzo's first post.
Tansl wanted quantification for each definition. It is easy to pull this out of the internet though units of measure for toughness Joules per cubic meter (J/m³) in SI units or inch-pounds-force per cubic inch (in·lbf/in³) in US customary units or for hardness the SI unit is N/mm² (or Pascals) without knowing the process/test to which they refer, are probably irrelevant for most people.
Tansl you know where to find this and I suspect the process to obtain them.

 

Indeed, I regularly use several of these properties, which, applied to a certain structure, depend not only on the material but also on the shape and dimensions of the structural element. My only intention was to analyze Gonzo's statements in more depth, trying to clarify the concepts we each use and reveals where the error lies, if there is one.
One question, as an example: how are loads distributed across several beams in a structure, depending on the stiffness of each one? What is meant by stiffness in this context?
Another question: Could we clarify the differences between his definitions of "Elasticity" and "Plasticity," or would those definitions need to be reformulated?
If this topic also interests other forum members, we can, I suppose, clarify many things. From discussion comes clarity (or at least that's what some say)

 

Specific anything is the amount of anything per unit mass.
Something density is the amount of something per unit volume, sorta.


Batteries have energy density and specific energy measures.
They also have power density and specific power measures.

Specific heat (capacity) is a little odd. It is per unit mass and per degree change under specified conditions. This leads to a sizeable set of them for the different unit combinations and constraint conditions. Note that heat of fusion and heat of vaporization are specific heats.

So heat density is the heat per unit volume, right? Well, no (I mean it can be in the context of sauna design and testing, but usually not). As a term, it nearly always refers to heat flux per unit area. So fire codes have heat density requirements to limit the spread of fires in structures. It's usually in BTU per Sqft. Now if we only knew if that was a British Imperial British Thermal Unit, an American Standard British Thermal Unit, or an International British thermal Unit we'd be all set.

So something density can also be something per unit area (per unit time). Or it can be linear - something per unit length (per unit time). Or it can be per area per thickness (per unit time), which looks linear but isn't. And that whole area per length thing shows up a lot. Permeability is measured per area per time and per pressure, all per thickness putting thickness back in the numerator.

The whole "cursed units" meme was invented by Randall Monroe of XKCD fame. It's been expanded by others.
Enjoy this one that includes a particularly obtuse permeability measure.

 

Wow, I'm amazed by all this science. But who's talking about units? Maybe I'm wrong, but I thought we were talking about concepts, not units. ( what is hardness?, not how to mesure it).
Maybe Gonzo vould help uss.

 

Actually, you asked Gonzo (QUOTE in practical terms, how you quantify those properties.[/QUOTE]
You quantify by units.

 

Yes, you're right, I expressed myself very poorly. I meant to clarify the definition of the properties that Gonzo wants to lecture us about, not what units they're measured in.
Please excuse my mistake.
Having said all that, how is the stiffness of a beam quantified?

 

The (internal) stiffness of the beam material is based on the modulus of elasticity, inches per inch or cm per cm. Determining this value is rarely used in design but its value is used in the various beam, column etc calculations. Ie if I am building a boat from steel, the E value is known. If I need less deflection, I would more than likely not be trying to change E. I would increase the I value, thickness, height, etc.
If you are speaking of the deflection of the beam, that deflection is covered by the various beam equations, depending on the end conditions.( and of course loading configurations)
Which as you know includes the E value of the material

 

Thank you very much for your time, @Barry. I don't agree with some of the things you explain, but that's okay, I won't argue further. Do you see how it is possible to define (quantify) stiffness without talking about units?
I think that, for the moment, none of the participants (including myself, of course) have enough knowledge to delve much deeper into all those definitions. Thanks again.

 

As @Barry notes, a few clicks in google will give you what you need.

Stiffness, is another way of saying Young’s Modulus, this being the ratio of stress to strain, in the linear elastic portion of the stress-strain graph.
However, when referring to a structure, it describes the effect of its shape (I), with respect to a material’s properties (E), the EI.

 

Of course, and if you consult Chat GPT (or simmilar), you'll get even better answers. But what people often forget is that it's also necessary to understand what AI is telling us, and for that, we need some basic theoretical knowledge that most people don't have.
It's curious that the OP, the promoter of this friendly (until now) discussion, has disappeared.

 

@Ad Hoc. You bring up a really important point. Stiffness of a structure vs stiffness of a material. They are different but related.

 

Why are they different?.
Not reason at all, imo.

 

For example, an H-beam is stiffer than a rectangular shape beam of the same depth and weight.