In Belt drives when the belt passes from the slack side to the tight side a certain portion of the belt extends. Similarly when the belt passes from the tight side to slack side it contracts. Hence creep in belt drive is due to uneven extensions and contractions of the belt when it passes from tight side to slack side.
This phenomenon of alternative stretching and contraction of the belt results in relative motion between the belt and the pulley surface. This relative motion is called creep.

Connecting rod is, usually, made from Medium carbon steel

Elasticity: 
Whenever an external force is applied on a metal, it deforms. Elasticity is the property by virtue of which a metal regains its original shape when the external force applied on it is removed. 
es: forming, forging, hammering 

Plasticity: Plasticity is the property by which a metal retains its deformation permanently, when the external force applied on it is removed. 
Examples: forming, forging, hammering 

Ductility: Ductility is the property by which a metal can be drawn into thin wires. It is determined by percentage elongation and percentage reduction in area of a metal. 

Malleability: Malleability is the property by which a metal can be rolled into thin sheets. Highly malleable metals (like Mild Steel) are extensively used in making sheet metals.