دانلود رایگان مقاله لاتین شکاف در فیبر کربن از سایت الزویر
عنوان فارسی مقاله:
ترک بازدید ازدحام برای برآورد محل شکاف در فیبر کربن، پلاستیک، شیشه: مطالعه عددی
عنوان انگلیسی مقاله:
Crack swarm inspection for estimation of crack location in carbon fiber reinforced plastics: A numerical study
سال انتشار : 2016
مقدمه انگلیسی مقاله:
The applications of carbon fiber reinforced plastics (CFRPs) have expanded, particularly in the field of aeronautics, because of its outstanding specific strength and stiffness as compared with metals [1,2]. However, when CFRP laminated plates are used as a structural component, even small impacts can easily lead to delamination, considerably reducing strength . To ensure the structural integrity (and to reduce the high costs incurred by periodic inspections), there is an urgent need for a health monitoring system for CFRP laminated plates. Previously, the following nondestructive inspection techniques have been used: ultrasonic inspection [4–6], X-ray inspection [7,8], acoustic emission (AE) [9,10], optical fiber inspection [11–13], and visual inspection. However, these methods are costly and time-consuming, or may decrease the structural strength by requiring an embedded sensor. Against this backdrop, there is a demand for a simple, non-destructive health monitoring process that detects delamination during periodic inspections or during operation. The monitoring method must be suitable for existing structures, and must not cause a reduction in strength by requiring sensors to be embedded. As a useful health monitoring technique that can be applied during operation, the electrical resistance change method [14,15] has been proposed for monitoring fiber fractures [16,17], strain , and fatigue . In this technique, the electrical resistances that arise because of delamination are measured using electrodes attached to the structural surface, so as not to cause a reduction in strength. The suggested technique was applied to monitoring the occurrence of delamination in CFRP laminated plates based on changes in the electrical resistance between a number of electrodes on the CFRP surface [20–23]. However, this method does present complex challenges for measurement systems because it is necessary to measure the electrical resistance of every current in all of the spaces between adjacent electrodes to measure the delamination-dependent changes in electrical resistance between electrodes. To address this problem, the electric potential difference technique is used; it involves installing a pair of electric current electrodes and a large number of voltage electrodes, making it possible to identify cracks using a single electric current [24–27]. However, these techniques require multiple tests and expensive numerical analyses; thus, there is a need to develop a technique that is simpler to implement. A simple technique has been proposed for analyzing electric current density in CFRP, in which changes in voltage due to delamination are analyzed by installing a string of anisotropic doublets at separation points [28,29]. This technique makes it possible toanalyze the electric current density of a CFRP laminated plate using a mirror image relationship. However, even though it is possible to calculate voltage changes with this technique in situations where delamination is known to have occurred, it is difficult to estimate the location and size of delamination from the voltage change. Therefore, in this research, crack swarm inspection (CSI) is proposed, which estimates crack size and location based on a large number of virtual microscopic cracks in the inner layers of the CFRP using anisotropic electric potential functions and doublet strings. A genetic algorithm (GA) is used to minimize the difference with the voltage true value distribution and voltage distribution with virtual microscopic cracks in CFRP by changing the virtual crack position; thereby, the virtual cracks form a swarm, and the crack location and size are estimated from the crack swarm. CSI is applied to crack detection in unidirectional laminated plates, and its validity is investigated.
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