1. A system for nondestructive evaluation of railroad rails, the system comprising: a carriage including a plurality of wheels movably supporting the carriage on the rails; a source of vibration mounted on the carriage and connected to the carriage to transmit vibrations of a preselected frequency to test regions on the rails through the wheels to cause an increase in temperature of the rails at locations of flaws in the test regions; an infrared detector for recording thermal images of the test regions to detect the increase in temperature at the locations of flaws; and a controller connected to the infrared detector actuate the infrared detector to record the thermal images of the vibrations impacting the test regions, and store the thermal images recorded by the infrared detector.