Experimental Identification of the Nonlinear Parameters of
an Industrial Translational Guide
Paper no. IMECE2006-14450 pp. 1089-1097 (9 pages)
DOI:10.1115/IMECE2006-14450
ASME 2006 International Mechanical Engineering Congress and Exposition (IMECE2006)
November 5 – 10, 2006 , Chicago, Illinois, USA
Sponsor: Dynamic Systems and Control Division
Author(s):
Jaspreet Dhupia
University of Michigan Bartosz Powalka
Technical University of Szczecin A. Galip Ulsoy
University of Michigan Reuven Katz
University of Michigan Prediction of machine dynamics at the design stage is a challenge due to lack of adequate methods for identifying and handling the nonlinearities in the machine joints, which appear as the nonlinear restoring force function of relative displacement and relative velocity across the joint. This paper discusses identification of such a nonlinear restoring force function for an industrial translational guide for use with the Nonlinear Receptance Coupling Approach (NLRCA) for evaluating machine dynamic characteristics. Translational guides are among the most commonly used joints in machine tools. Both a parametric and nonparametric technique has been employed to identify the nonlinearities. A novel parametric model based on Hertzian contact mechanics has been derived for the translational guide. This model includes the effect of joint geometry, material properties and preload. A nonparametric method based on two-dimensional Chebyshev polynomials is also used. The models derived from the two techniques, i.e., parametric and nonparametric, are fitted to the experimental data derived from static and dynamic tests to get the restoring force as a function of relative displacement and relative velocity across the joint. The resulting joint model exhibits a weakly nonlinear stiffness term and a viscous damping term. The results from both techniques are compared in the frequency domain. The advantages and disadvantages of parametric and nonparametric techniques are also discussed. The
design of experiments for evaluating the nonlinearities in such industrial machine tool joints is a challenge, requiring careful alignment and calibration, because they are typically very stiff. This constrains the dynamic experiments to be carried out at high frequencies (e.g. 2000-7000Hz) where the experimental readings are very sensitive to errors in geometry and calibration.
Journal of Manufacturing Science and Engineering
J. Manuf. Sci. Eng. / Volume 129 / Issue 5 / RESEARCH PAPERS
Effect of a Nonlinear Joint on the Dynamic Performance of a Machine Tool
J. Manuf. Sci. Eng. -- October 2007 -- Volume 129, Issue 5, 943 (8 pages)
DOI:10.1115/1.2752830
Author(s):
Jaspreet S. Dhupia
NSF Engineering Research Center for Reconfigurable Manufacturing Systems, University of Michigan, Ann Arbor, 2250 GGBL, 2350 Hayward Street, Ann Arbor, MI 48109-2125
Bartosz Powalka
Technical University of Szczecin, Piastow 19, 70-310 Szczecin, Poland
A. Galip Ulsoy and Reuven Katz
Research Center for Reconfigurable Manufacturing Systems, University of Michigan, Ann Arbor, 2250 GGBL, 2350 Hayward Street, Ann Arbor, MI 48109-2125
This paper presents the effect of experimentally evaluated nonlinearities in a machine joint on the overall machine tool dynamic performance using frequency response functions and stability lobe diagrams. Typical machine joints are very stiff and have weak nonlinearities. The experimental evaluation of the nonlinear joint parameters of a commercial translational guide has been discussed in Dhupia et al., 2007, J. Vibr. Control, accepted. Those results are used in the current paper to represent the connection between the column and the spindle of an idealized column-spindle machine structure. The goal is to isolate and understand the effects of such joints on the machine tool dynamic performance. The nonlinear receptance coupling approach is used to evaluate the frequency response function, which is then used to evaluate the stability lobe diagrams for an idealized machine structure. Despite the weak nonlinearities in the joint, significant shifts in the natural frequency and amplitudes at resonance can be observed at different forcing amplitudes. These changes in the structural dynamics, in turn, can lead to significant changes in the location of chatter stability lobes with respect to spindle speed. These variations in frequency response function and stability lobe diagram of machine tools due to nonlinearities in the structure are qualitatively verified by conducting impact hammer tests at different force amplitudes on a machine tool.
Journal of Mechanical Design
J. Mech. Des. / Volume 127 / Issue 3 / TECHNICAL PAPERS
Dynamics of a Multibody Mechanical System With Lubricated Long Journal Bearings
J. Mech. Des. -- May 2005 -- Volume 127, Issue 3, 493 (6 pages)
DOI:10.1115/1.1864112
ABSTRACT
REFERENCES (7)
Author(s):
B. J. Alshaer, H. Nagarajan, H. K. Beheshti, and H. M. Lankarani
Department of Mechanical Engineering, Wichita State University, Wichita, KS 67260-0133
S. Shivaswamy
Loads and Dynamics, Cessna Aircraft Company, Wichita, KS 67277
Clearances exist in different kinds of joints in multibody mechanical systems, which could drastically affect the dynamic behavior of the system. If the joint is dry with no lubricant, impact occurs, resulting in wear and tear of the joint. In practical engineering design of machines, joints are usually designed to operate with some lubricant. Lubricated journal bearings are designed so that even when the maximum load is applied, the joint surfaces do not come into contact with each other. In this paper, a general methodology for modeling lubricated long journal bearings in multibody mechanical systems is presented. This modeling utilizes a method of solving for the forces produced by the lubricant in a dynamically loaded long journal bearing. A perfect revolute joint in a multibody mechanical system imposes kinematic constraints, while a lubricated journal bearing joint imposes force constraints. As an application, the dynamic response of a slider-crank mechanism including a lubricated journal bearing joint between the connecting rod and the slider is considered and analyzed. The dynamic response is obtained by numerically solving the constraint equations and the forces produced by the lubricant simultaneously with the differential equations of motion and a set of initial conditions numerically. The results are compared with the previous studies performed on the same mechanism as well a dry clearance joint. It is shown that in a multibody mechanical system, the journal bearing lubricant introduces damping and stiffness to the system. The earlier studies predict that the order of magnitude of the reaction moment is twice that of a perfect revolute joint. The proposed model predicts that the reaction moment is within the same order of magnitude of the perfect joint simulation case.
因篇幅问题不能全部显示，请点此查看更多更全内容