A Novel 3D Laser System that Can Emit and Measure Guided Wave for Monitoring Rail Track Structural Integrity

Abstract

Laser-generated guided wave (GW) is an emerging NDT technology in recent year. This paper reports the use of laser to emit GW and measure its reflected signal for monitoring the integrity of train rails. The inspection system is a completely non-contact type of laser system. A Nd: YAG laser acted as an emitter to emit a broadband guided wave onto the inspected rail. The propagation of GW along the rails was then measured by a 3D Laser scanner. Experiments were conducted on a healthy rail and a defective rail. The GW’s interactions with rail structure were recorded. Two interesting observations have been found. First, the defective area will be excited by the continuous emission of laser pulses. This area will generate higher displacement and vibration than that of the other healthy areas of the rail. Second, when the incident wave hit the defective area, the incident wave becomes much wider suddenly. These two phenomena can be used to distinguish defective and healthy areas of the rail during inspection. The above results are the first time reported here and demonstrated the effectiveness of this 3D laser system in the capability of rail structural health monitoring.