"P" is for Properties of People and Materials

Yeah, that's a mouthful, so how about we call this one Engineering for Writers?

How many times have you read a story and seen a character described as strong, or tough, or unstable?  That's a little like asking how many times you've seen conjunctions or the definite article.  These are properties that can describe not only people but inanimate objects and materials, and engineers use those words even more than writers.  I thought it might be of some interest for the writer to see what engineers mean when they use those words and to see how well the materials science definition lines up with their usage.  Who knows, it may even provide some insights into your writing.  Or not.  But it won't do any harm.

(For our first two words, it might be useful to define a couple of terms first.  Think of a hacksaw blade clamped vertically by the bottom end in a bench vise.  If you push on the top end a half inch or so, it will bend, but rebound to its original position like a spring when we let go.  We call that elastic deformation.  Push on it more than a few inches and it will yield and stay in its bent position.  That's plastic deformation.)

Rigidity.  With people and with materials science, rigid means unbending.  In engineering, whether this is desirable depends on the application, but with people it's usually seen as a negative, i.e., "overly rigid."  

Strength.  We usually seem to think of human physical strength as power, or the ability to apply force, in an active sense.  On the other hand, we tend to see mental or emotional strength as resistance to yielding under stress, in a passive sense, and the latter is how engineers define it.  In materials, strength is resistance to yielding plastically, i.e., permanently.

We like people who are strong and unyielding, but not rigid, completely unbending.  We don't want our heroes to compromise on core beliefs under duress, but we value their ability to examine their beliefs and modify them if it proves to be the right thing to do.

Toughness.  Strong and tough are often used interchangeably, but they are different.  Toughness in a person is the ability to absorb punishment without breaking.  Similarly, in materials science, it's how much energy a material will absorb before failure (breakage or yielding).  Remember the fight scene in Cool Hand Luke?  Lucas wasn't as strong as Dragline, but he was tough; no matter how many times he got knocked down, he kept getting back up.  He lost the fight, but won the respect of Dragline and their fellow inmates.  But what really comes to mind when I think of toughness are little green plastic army men.  Those suckers could take any punishment my six-year-old mind could conjure up, short of fire. You could bend them, but you couldn't tear them with your bare hands.  The polyethylene they're made of is tough stuff.

Brittleness.  In engineering terms, brittleness is the tendency of a material to break suddenly rather than gradually.  Think of a glass rod.  Brittleness in a person can be physical, as in an older person's bones, but is usually used as an emotional quality.  An emotionally brittle person is weak and may "lose it" without warning.

Hardness.  Can be conflated with strength and toughness (Those Marines on Guadalcanal were hard bastards!), but is also used to denote a lack of emotion, or an impenetrable shell.  Not exactly the same in engineering terms, where hardness is resistance to abrasion; the hardness of diamonds makes them ideally suited for cutting and grinding.

Ductility and Malleability.  Ductility is the ability to deform without breaking under tensile stress, often expressed as the ability to be drawn into wire.  Malleability refers to deformation under compressive stress and is usually thought of as the ability to be hammered into thin sheets.  (They don't necessarily go together; gold is ductile and malleable, while lead is only malleable).  With people, the words could be used interchangeably, but I don't recall ever seeing an easily-yielding person called ductile.  I have, however, often seen malleable used to describe people who are easily shaped and influenced by others, and I think it's a great, descriptive word.  Ductile?  You might want to run it by a trusted editor.

If you've made it through this long-winded post, dear reader, you can now use these dual-purpose words with precision and confidence.  No need to thank me, it's just one of the many services I offer!