An apparatus for measuring strain on a downhole component includes: at least one strain sensitive device disposed proximate to a surface of a component of a drilling assembly or disposed within a material forming the component; and a processor in operable communication with the at least one strain sensitive device, the processor configured to detect changes in the at least one strain sensitive device and detect at least one of erosion, crack formation and crack propagation in the component surface. An apparatus for measuring strain on a downhole component includes: at least one strain gauge deposited on a surface of a drive shaft or disposed within a material forming the drive shaft; and a processor in operable communication with the at least one strain gauge, the processor configured to detect changes in the at least one strain gauge and detect conditions affecting operation of the drive shaft.