I do not really understand this as you can probably tell, but What is the difference bewteen Linear and Cubic displacement deformation functions in beam bending? For example why would one be used over another to model or calculate beam bending? or how does either type effect what bending behaviour will occur? All my notes just state we will assume linear or cubic for each example, so is it just the intrinsic properties of the material that determine the deformation function. For example is steel more likely to have a cubic relationship and wood a linear one?