دراسة عملية ونظرية لاهتزاز أنابيب الراتنج المدعمة بألياف الكاربون الناقلة للموائع

Experimental and Theoretical Investigation on the Vibration of Epoxy – Carbon Tubes Conveying Fluid

Abstract

Composite tubes are usually made of two or more laminated composite materials. These tubes can be used for fuel lines, hydraulic tubes, house and industrial uses.
In the current study, the most common types of composite materials will be used to manufacture the tube which is carbon fiber – epoxy. It is widely used due to its significant properties, including high strength to weight, good toughness and suitable prices.
Because of the tendency to use successful tubes with less vibration and low corrosion rate, this study is directed to the dynamical behavior of tube made of the composite material conveying fluid.
The effect of flow velocity and internal damping on free vibration of tube made of the composite material , which represents the main parameter in this work, is investigated using different types of boundary conditions.
A systematic evaluation of the fundamental aspects of the dynamic behavior of tube made of the composite material with the effect of flow velocity and internal damping on free vibration of tube made of the composite material , which represents the main parameter in this work, is investigated using different types of boundary conditions.
The mathematical model of tube made of the composite material is solved analytically to calculate the effect of the related parameters and variables. The theoretical results are presented in a dimensionless form for with the mechanical properties.
The natural frequency was determined in the theoretical part by deriving the governing equation using the Euler-Bernoulli theorem and substituting the boundary conditions into the equation to extract the roots of the polynomial equation and writing it in the form of a matrix consisting of four terms to be substituted in the (Q-basic) program to determine the value of the natural frequency.
It was found that increasing flow velocity causes the natural frequency to decrease gradually. The rate of decrease increased until the natural frequency value was nearly zero at point called “critical flow velocity” which is the flow velocity at which the natural frequency decreases. The simply supported composite tube has a dimensionless critical flow velocity of 3.12. In contrast, the clamped support tube has a dimensionless critical flow velocity of 6.23, and the dimensionless critical flow velocity for clamped-pinned is 4.42. These results were without the effect of internal damping.
According to the theoretical results , the critical flow velocity increased when the mode of vibration was increased. Furthermore, the critical flow velocity of a clamped composite tube is 50% higher than that critical flow velocity of simply supported composite tubes. The internal damping affects the natural frequency by up to 4.79 % when the internal damping increases by 0.01%.
In the experimental part, a device was manufactured to confirm the theoretical results of calculating the natural frequency by using the tachometer to determine the rotational speed of the crankshaft, where the number of revolutions displayed on the digital screen of the device represents the value of the experimental natural frequency of the tube made of composite materials and compare the experimental results with the theoretical results.