Kuanmin Mao

Sensitivity analysis of modal assurance criteria of damped systems

This paper considers the calculation of the sensitivity of modal assurance criteria (MAC) values of viscously damped systems. A direct method is proposed by constructing a Lagrange function whose Lagrange multiplier only needs to be calculated once for different design parameters. It is efficient in computational time and storage capacity. An extensive numerical analysis is used to show the effectiveness of the derived results. Several applications concerning the sensitivity of MAC values are discussed on the basis of the experimental data and the numerical analysis of a long beam structure with bolted joints.

A Novel Vibration Exciting Method for NC Machine Tools

Considering that NC machine tools are difficult to be excited, a novel method of executing the self-exciting of structural vibration by applying a machine tool movement, which is proved to be effective by machine tool testing, is presented in the proposed study. The influence of movement parameters on the vibration response is studied by testing the designed movement under different parameters and comparing the characteristics of vibration response signals in the time and frequency domains. The proposed method is validated by comparison of the testing frequencies and those of experimental modal analysis (EMA). As this method does not need additional vibration-excitation equipment, it is suitable for online testing and analyses of NC machine tools, especially for heavy-duty machine tools. The latter ones are difficult, even impossible, to be excited.

A new dynamic modeling approach to fixed joint interface in machine tools

The concept of virtual material was presented for the first time when the flexible joint interface may be considered as a virtual material with the same cross area. The virtual material is rigidly connected with two components situated in both sides of flexible joint interface. By adding an element, a complicated assembled part including a joint interface could be equaled as a simple component without any joint interface in order to simplify the complicated problem about flexible joint interface. A series of exact analytical solutions of elastic modulus, shear modulus, Poisson ratio and density were deduced from virtual material by introducing Hertz contact theory and fractal theory. The virtual material model vibration shapes are in excellent agreement with the experimental results.

The multimode frequency analysis and its effect on the position accuracy of the sorting arm during operation

Inertial vibrations are one of the crucial problems in the chip sorting process. High acceleration excites the sorting machine structure up to high frequencies so that the multimode vibration appears. The multiple-input nature of operational excitation depends on the varying machine configurations and running accelerations. In this article, the strain gauges are used to study the dynamic behavior of a light-emitting diode chip sorting arm which runs in high speed with varying configurations. This analysis is done in three stages. In the first step, the structure dynamic characteristics are compared between the static and operation states. It points out that some high frequency may display different characteristics in the states. The second step aims to find the effects of different configurations on the sorting arm dynamic vibration during operation. In the last step, the sorting arm is sorted at different levels of running excitation, and the effects of the multimode vibration on chip accurate position are discussed. This study provides an approach to study the dynamic behavior of high-speed running structure within true boundary conditions and actual force and vibration levels.

A new dynamic modeling method to fixed machined joint interface

The concept of virtual material was developed for the first time when the flexible joint interface may be considered as a virtual material with the same cross area. The virtual material is rigidly connected with two components situated in both sides of flexible joint interface. By adding an element, a complex assembled part including a joint interface could be equaled as a simple component without any joint interface in order to simplify the complicated problem about flexible joint interface. The interaction between normal and tangential characteristics of fixed interface taken into account, a series of exact analytical solutions of elastic modulus, shear modulus, Poisson ratio and density were deduced from virtual material through Hertz contact theory and fractal theory. By using experimental results about a series of test specimens, the exact analytic expressions for virtual material’s parameters were verified in terms of qualitative comparison principle of resembling vibration shapes and quantitative comparison principle of the natural frequencies. The virtual material model vibration shapes are in excellent agreement with the experimental results. The relative errors between the virtual material model natural frequencies and the experimental ones are between -3% and 10%.