Knock out the wrong constant counts

Exercise and reference answers

Questions

1. Question

   Three of these counts of independent elastic constants sit with the wrong material class.

   Choices

   1. Item

      Isotropic materials need two

      Correct

      Yes

   2. Explanation

      Five is the transversely isotropic count.

      Item

      Orthotropic materials need five

   3. Explanation

      Nine is the orthotropic count, not the general one.

      Item

      Anisotropic materials need nine

   4. Explanation

      Twenty one belongs to the fully anisotropic case.

      Item

      Transverse isotropy needs twenty one

2. Question

   Three of these claims about stress at a point are false.

   Choices

   1. Explanation

      Symmetry removes three of the nine.

      Item

      Nine stress components are independent

   2. Item

      Six stress components are independent

      Correct

      Yes

   3. Explanation

      Traction is bound to its point and its surface.

      Item

      Traction is a free vector that can slide

   4. Explanation

      Engineering shear is twice the tensorial value.

      Item

      Engineering shear equals tensorial shear

Instructions

Tap the three false lines in each set about elastic constants and stress, leaving the true one.

Explanation