Jinfeng Sun

Calibration of Measured FRFs Based on Mass Identification Method

It is necessary to calibrate the equipment during each test in modal testing. This paper presented a practical method for the calibration of the measured FRFs based on mass identification method. One advantage of this proposed method is that the calibration is performed directly on the test structure. Thus, it is more reliable and convenient. It is shown that if the mass identification method is applied to the uncalibrated system, a different level between the identified mass and the given exact mass reveals that the set up is not calibrated. And the measured FRFs can be calibrated using the ratio factor of the identified mass and exact mass. The simulation testing demonstrates good performance. In practical testing, however, the accuracy of mass identification results may be vulnerable to the noise and further work is necessary in order to solve this difficulty.Copyright

Tooth Number Matching and Its Software Development for 2KH Planetary Gear Mechanism

2K-H planetary gear is a commonly seen gear structure, but it has proven troublesome to match its tooth numbers through hand computation. This paper introduces a calculation method for the 2K-H planetary gear and develops a software written with the use of computer software technology for matching gear units, thus greatly reducing the workload in matching tooth numbers. In addition, they can be applied to tooth number matching for all kinds of 2K-H planetary gears. Introduction In calculating the tooth numbers for the 2K-H planetary gear, due to its many limitations, we often need to resort to hand computation, thus making the tooth number matching extremely complex. Moreover, hand computation is time-consuming, because the 2K-H planetary gear involves four different kinds of gear mechanisms. At present, a growing number of designing personnel have begun to complete this task through computers since they came out. This paper introduces the experience of realizing the tooth number matching for 2K-H planetary gear through computer programs. 2K-H Planetary Gear Mechanism 2K-H planetary gear mechanism is featured by small size, high self-weight transmission efficiency, light weight, large transmission ratio, low noise and high reliability, etc. With the development of science and technology, planetary gearing has been widely applied into the machinery of such fields as metallurgy, mining, lifting, chemical engineering, electrics, textile and oil production. However, planetary gearing is a highly advanced system, especially all kinds of large-scale reducers. To satisfy the work needs and ensure relatively high operating reliability and longer service life of the mechanical system, we can not willfully choose the tooth number for each gear in designing the planetary gear mechanism; but instead, we have to work out the correct tooth number for the planetary gears according to the schematic diagrams and satisfy certain conditions according to the characteristics of planetary transmission, with a view to guaranteeing normal operation. By virtue of our needs, we divide the planetary gear into four kinds as evidenced by the following figures, namely 2KH-NGW, 2KH-WW, 2KH-NW and 2KH-NN, among which N stands for internal gear, W for external gear and G for composite gear. Fig1. 2KH-NGW planetary gear mechanism Fig 2. 2KH-WW planetary gear mechanism 446 Advances in Engineering Research (AER), volume 105 3rd Annual International Conference on Mechanics and Mechanical Engineering (MME 2016) Copyright

Topology Optimal Design of Wind Turbine Blades Considering Aerodynamic Load

For the conceptual design problem of the complex blade aerodynamic structure, the parametric finite element model of the wind turbine blade was established using 3D blade integrated expressed functions. The blade section topology structure technology which can solve the whole hexahedral grid problem for the solid blade was presented. Based on the modified blade element momentum theory, the aerodynamics were loaded to the blade surface. A procedure combining MATLAB and APDL to put the pressure distribution on the blade finite element model is developed. The solid blade model which the objective function was the minimum weight was optimized. Compared with the traditional blade structure, the location of main beams with no web for the optimized blade which exhibit asymmetric property were near to blade leading edge. Moreover, the trailing edge of the newly blade had reinforced structure. The newly topology structure of the blades had important guiding significance for the sizing optimization of wind turbine blades. Introduction With the wind power more and more large, the blade size is also longer and longer. How to improve the effectiveness of the structure of the blade is particularly important. An effective method is to ensure the quality of the blade structure under the premise of how to reduce the quality of the blade. Researchers at home and abroad have done a lot of research work on how to improve the performance of wind turbine blades and reduce their quality. X. D. Wang [1] et al. proposed a multidisciplinary optimization design model of the blade of the wind turbine. The optimal output of a 5MW wind turbine blade was designed with the energy cost of the wind turbine as the objective function, which reduced the energy cost per unit output of the wind turbine by 2.6%. The effectiveness of the method has been verified by comparing the load distribution as well as the power characteristics of the optimized blade and the original blade. Q. Wang [2] et al. proposed a new one-way blade fluid-solid coupling method, and applied the method to the parametric composite finite element model of wind turbine blade. The thickness of the blade and the position of the main beam were designed and optimized. The optimization results show that the blade quality is reduced by 7.14% under the condition of failure criterion and displacement. In recent years, the application of topology to the design and optimization of blade structure of wind turbine has gradually become a hot research field. Some scholars abroad have also carried out relevant research. In 2010, E. Lindgaard and E. Lund [3] of the University of Elborg in Denmark proposed a topological optimization method that takes into account the structural stability of the composites. The laying angle can be used as a design variable and applied to the wind turbine blade main girder optimization of Linear and Nonlinear Buckling Stability. The above results are used to evaluate the merits of the optimization results by eigenvalues and sensitivity analysis. In 2012, J. P. Blasques [4] combined the structural topology with beam section mechanical properties and regarded the minimum compliance as the objective function, the material volume ratio for the design variable, the blade section weight and the center of gravity as the constraint function to design the composite beam cross section Material topology optimization. Then he verified the effectiveness of the method by taking the blade cross section of the composite wind turbine as an example. In 2013, N. Buckney [5] et al. analyzed the blade structure effectiveness of a 3MW wind 211 This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Copyright

Full Rotatability of Watt Six-Bar Linkages

The full rotatability of a linkage refers to a linkage in which the input may complete a continuous and smooth rotation without the possibility of encountering a dead center position. Full rotatability identification is a problem generally encountered among the mobility problems that may include branch (assembly mode or circuit), sub-branch (singularity-free) identification, range of motion, and order of motion in linkage analysis and synthesis. In a complex linkage, the input rotatability of each branch may be different while the Watt six-bar linkages may be special. This paper presents a unified and analytical method for the full rotatability identification of Watt six-bar linkages regardless of the choice of input joints or reference link or joint type. The branch of a Watt without dead center positions has full rotatability. Using discriminant method and the concept of joint rotation space (JRS), the full rotatability of a Watt linkage can be easily identified. The proposed method is general and conceptually straightforward. It can be applied for all linkage inversions. Examples of Watt linkage and a six-bar linkage with prismatic joints are employed to illustrate the proposed method.Copyright

Singularity Analysis of Planar Multiple-DOF Linkages

Singularity analysis of multi-DOF (multiple-degree-of-freedom) multiloop planar linkages is much more complicated than the single-DOF planar linkages. This paper offers a degeneration method to analyze the singularity (dead center position) of multi-DOF multiloop planar linkages. The proposed method is based on the singularity analysis results of single-DOF planar linkages and the less-DOF linkages. For an N-DOF (N>1) planar linkage, it generally requires N inputs for a constrained motion. By fixing M (M<N) input joints or links, the N-DOF planar linkage degenerates an (N-M)-DOF linkage. If any one of the degenerated linkages is at the dead center position, the whole N-DOF linkage must be also at the position of singularity. With the proposed method, one may find out that it is easy to obtain the singular configurations of a multiple-DOF multiloop linkage. The proposed method is a general concept in sense that it can be systematically applied to analyze the singularity for any multiple-DOF planar linkage regardless of the number of kinematic loop or the types of joints. The velocity method for singularity analysis is also used to verify the results. The proposed method offers simple explanation and straightforward geometric insights for the singularity identification of multiple-DOF multiloop planar linkages. Examples are also employed to demonstrate the proposed method.Copyright