Module 1: Overview of Structural Health Monitoring (SHM) Lecture 3: Structural Health Monitoring versus Non Destructive Evaluation

Transcription

1 The Lecture Contains: Limitations of present day NDE technologies Benefits of Implementation of SHM Envisaged benefits of SHM system Advantages of Structural Health Monitoring file:///d /neha%20backup%20courses% /structural_health/lecture3/3_1.html [4/4/2013 3:31:52 PM]

2 The Lecture Contains: Due to greater complexity of design, high operational loads and longer designed life time, composite structures are prone to unpredicted failures. Present day non-destructive evaluation (NDE) technologies such as ultrasonic testing, acoustic emission, eddy current method, radiography and thermography etc; primarily developed for metallic materials are not always very effective for composites due to their micro-mechanical complexities such as: Anisotropy of composites Conducting properties of the fibers isolative nature of the matrices impact damages beneath the surface, BVID Limitations of present day NDE techniques Require specialized equipment and skilled man power In-situ evaluation and evaluation on real time basis is not always possible Longer downtime Bigger structures may not be kept out of are for longer period. file:///d /neha%20backup%20courses% /structural_health/lecture3/3_1a.html [4/4/2013 3:31:53 PM]

3 Structural Health Monitoring versus Non Destructive Evaluation Many of the existing NDE techniques have been customized for specific SHM uses by integrating sensors and actuators inside the structure to be monitored. Following are the perceptible advantages of SHM over NDE: Reduced inspection down time. Elimination of component tear down and human involvement. Potential prevention of failure during operation. Enabling new possibilities for maintenance concepts influencing design and assembly technologies leading to both maintenance and weight saving benefits. file:///d /neha%20backup%20courses% /structural_health/lecture3/3_2.html [4/4/2013 3:31:53 PM]

4 Benefits of Implementation of SHM Traditional systems are designed for a set of service parameters such as load, speed or life span and are unable to modify its response mechanism in changed circumstances leading to loss of reliability, utility and increase in cost of maintenance. The structures with SHM are capable of accommodating to unpredictable environments and accrue a stable level of reliability over its service life at a constant maintenance cost [Figure 3.1]. Figure 3.1: Advantages of implementation of SHM [Chang, 2002] file:///d /neha%20backup%20courses% /structural_health/lecture3/3_3.html [4/4/2013 3:31:53 PM]

5 Following are the envisaged benefits of SHM system" Replacing schedule based inspection / maintenance of the structure to condition based maintenance brings great cost reduction. Extends the life of over aging structures. Attempts to identify damage in structures on a more global basis. Opens avenues for possible integration of the design of the structure with its full management as a part of still bigger system. file:///d /neha%20backup%20courses% /structural_health/lecture3/3_4.html [4/4/2013 3:31:53 PM]