Theoretical Analyses Of Magnetic Levitation Detecting Technique And Its Applications

Magneto-Archimedes levitation is a new technique in recent years.This technique is the combination of diamagnetic levitation and principle of buoyancy that can levitate diamagnetic or weak paramagnetic materials with permanent magnets.This paper came up with a model of magnetic levitation detecting method based on magneto-Archimedes levitation.The method can levitate objects at stable positions.And based on the levitation height of the sample,the density of the sample can be easily and accurately calculated out.This paper obtained the following achievements:(1)The relationship between the levitation height and the density can be determined by a curve fitting method.The relationship were fitted by experiment results from levitating a series of standard density glass beads.Then the results can be used to calculate the density of samples whose densities are unknown.A series of experiments were also performed to verify the accuracy of the result.(2)The distribution of the magnetic flux density of the magnetic levitation device was calculated based on the Ampere molecular circulation hypothesis and the Biot-Savart Law.Then,the relationship between the density and the levitation height can be deduced.The verification of the results were a series of measurements for standard density beads.The densities of some common polymer materials were also measured by the magnetic levitation device,and these results were compared with the results of common methods.The experiments indicates that the magnetic levitation method has very high accuracy.Besides,the magnetic levitation device successfully separated two materials with the difference of 0.03g/cm~3 in density.(3)According to the calculation results of the magnetic flux density of the magnetic levitation device and the force acting on the object at any position in the space,this paper analyzed the influence on the measurement character caused by the characters of the magnets and the size of the device.The results testified the phenomenon that the sample can be levitated at a stable position spontaneously.The results also determined the appropriate range for the characters of the magnets and the size of the device.(4)This paper explored the application of the magnetic levitation device for defect detecting.An experiment for detecting the defects of plastic lens were designed.By observing the height,the center's position and the deflection of the lens in the device,this method can detect and locate the appearance detection and interior homogeneity like shrinkage and internal porosity.As theoretical analysis and experiment results showed in this paper,the magnetic levitation method has very high accuracy in measuring density,and is very sensitive to the distribution of the density.The method also showed its high adaptation in measuring densities of small samples.These advantages solved the disadvantages,like low accuracy or the complexity in calculating and manipulating the device,of common density measurements.Besides,this method also has advantages of:(?)the structure of the device is simple;(?)the materials are easy to obtain;(?)strong economy.Based on the advantages above,it can be foreseen that the magnetic levitation method will have great potential in the field based on density measurement,such as defect detecting and characterization of microstructure.