6 - Materials Flashcards
Define elastic deformation (until limit)
Once the force acting on an object is removed, the object will return to its original shape. The object will behave elastically until it reaches its elastic limit where it starts to behave plastically and no longer obeys Hooke’s Law.
Define plastic deformation
Once the force acting on an object is removed, the object will not return to its original shape and is plastically deformed. The plastic material does not obey Hooke’s Law.
Define force in relation to materials
A push or a pull that can change the shape of an object.
Tensile vs compressive force
Tensile forces extend a spring to cause tension. Compressive forces shorten a spring and cause compression
What is Hooke’s Law?
Hooke’s Law states that the extension of a spring is directly proportional to the force applied to it. F ∝ x or F = kx
What is Hooke’s Law equation?
F = kx
force (N) = spring constant (N/m) x extension (m)
Effect of higher stiffness constant
The higher the stiffness constant, the stiffer the spring is and the harder it is to extend or compress the spring.
What is the spring constant represented by on a force-extension graph?
the gradient of the line
What is does the area under a force-extension graph represent?
energy transferred, work done required to stretch spring
Elastic potential energy equation
E = 0.5kx^2
energy = 0.5 x spring constant x extension^2
What is the area in between the loading and unloading curve of a material?
The energy lost to heating the material
Springs in series
As springs in series increase, spring constant decreases. If the number of springs double, the spring constant halves. (assuming all springs have same k)
Springs in parallel
As springs in parallel increase, spring constant increases. If the number of springs double, the spring constant doubles. (assuming all springs have same k)
Calculate total k when in parallel
k1+k2…
Calculate total k in series
1/k = 1/k1 + 1/k2
