In many engineering applications, it is desirable to know the behaviour of structures and
systems under loading conditions. One reason is to help optimize the design and prevent
damage and failure which might occur during in service and operation. Damage represents a
serious problem which can cause catastrophic failure of structures, machines and systems.
Therefore for safe operation, efficient and reliable methods for inspection and monitoring of
damage are required. Different methods for health monitoring of structures such as non
destructive testing (NDT) and strain gauges are widely used. These methods have proven to
be efficient in terms of resolution and response. However, some disadvantages associated
with them include the vicinity of the area under inspection which must be well known,
equipment to acquire the necessary information is expensive and in many cases high skills
are required for operation. On the other hand, advances in materials science and MEMS
systems has promoted the use of new materials with piezoelectric properties. This include
mainly polymeric and ceramic materials which after processed can be used for structural
health monitoring. These materials offer a number of advantages such as lightweight,
sensitivity, toughness, durability, and low cost.
The present research work investigates the feasibility of using a polymeric material,
Polyvinylidene Fluoride (PVDF) as a sensor for deformation and defect detection in
structures. The sensors are embedded in composite cantilevered type beams to detect
defects at distinct locations along the beam’s length. The defect detection method proposed
is based on experimental tests and Finite Element simulations.
Experimental tests on defect free and beams with manufactured internal flaws were
conducted. Numerical (FEM) simulations of defect free and flawed beam models containing
sections of reduced elastic modulus to represent the damage were conducted using ANSYS
software. The experimental tests have been used for the validation of the numerical solution.
Results have shown that the defect location changes the stiffness and indeed the frequency
of vibration. For flaws near the fixed end of the beams, lower frequencies are obtained as
compared to flaws away from the fixed end. PVDF sensors were used to acquire the natural
frequencies of the beams for the first mode of vibration. Good agreement was verified
between experimental and numerical simulation results. The work has demonstrated that
PVDF film sensors can be used as possible candidates for defect detection.
The analysis of the behaviour embedded PVDF sensors near the fixed end of cantilever
beams, represents an initial and important step towards the application of measuring static
and dynamic behaviour of structures as part of a health monitoring process.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/1284 |
| Date | January 2008 |
| Creators | do Nascimento Oliveira, Jose Emidio |
| Publisher | Cape Peninsula University of Technology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
Page generated in 0.0023 seconds