Atomic force microscopy (AFM) is widely used in many fields, because of its outstanding force measurement ability in nano scale. Some coating layers are used to enhance the signal intensity, but these coating layers affect the spring constant of AFM cantilever and the accuracy of force measurement. In this paper, the spring constants of rectangular cantilever with different coating thickness were quantitatively measured and discussed. The finite element method was used to analyze the nonlinear force-displacement behavior from which the cantilever’s normal and torsional spring constants could be determined. The experimental data and the numerical results were also compared with the results from other methods. By considering the influence of coating layers and real cantilever geometries, the more accurate force measurements by AFM cantilever can be obtained.

The synchrotron radiation is an important light source used to improve the measurement resolution and efficiency of scientific equipments. The electrons in radio frequency system are accelerated by the synchrotron radiation superconducting cavity. Tensile or compressive loads along the axial direction may be applied on this thin-walled shell cavity for compensating the frequency shift due to the variations of surrounding condition. In order to avoid the failure of the thin-walled shell cavity before the frequency tuning process, the finite element method and experiment were used to predict the deformation behavior and limit load of thin-walled shell cavity. The parameters such as thickness, material properties and radius of round beam tube were discussed. The finite element results show that the limit loads were overestimated when the material properties were assumed to be linear elastic. When the cavity becomes thicker, the limit loads and the maximum compressive displacements of thin-walled shell cavity increase. The analysis method used in this paper can help us find the tunable ranges of synchrotron radiation superconducting cavities with different thicknesses, material properties and geometries.