Mechanical Engineering Department of Cal Poly Incorporates ADAMS into Graduate-level Coursework: Machinery Vibration and Rotor Dynamics
During the MSC VPD conference of 2009 in Phoenix, Arizona, I gave a presentation entitled "Integrating MSC-ADAMS Software into an Upper Division Mechanical Design and Analysis Course," which was awarded the best paper. In this presentation, I systematically explained how to use ADAMS and CAD software to teach students the mechanical design and analysis skills necessary for entry level engineers. "Machinery Vibration and Rotor Dynamics" (ME518) for graduate students, is a unique industrial-oriented course supported by the Donald E. Bently Center for Engineering Innovation of California Polytechnic State University (Cal Poly). Since 1999 when Dr. Jim Meagher, professor and co-author of Cal Poly, first created this class for graduate students, it integrated challenging hands-on laboratories and prepared the students for their future engineering career. As ME518 becomes more and more popular, more students who have industrial experiences take the class. They are not satisfied with only understanding the theories of machinery vibrations and multi-body dynamics. They are more interested in solving practical problems by CAD and ADAMS.
This year, we have Dr. Dewen Kong, a visiting scholar of Cal Poly and a professor from College of Mechanical Science and Engineering of Jilin University, China. The mechanical engineering department of Jilin University has applied ADAMS in their teaching, senior design projects and research for many years. Professor Kong's expertise is in designing and analyzing all kinds of crawler-driving gearboxes of large mining excavators. Based on his rich industrial experience, he designed five types of practical gear boxes, among which three are planetary gear trains, for use in the ME518 class. During the winter quarter of 2009, I successfully introduced the excellent software ADAMS to our students at Cal Poly. The planetary gearbox is widely used in transmission design of automobiles and helicopters due to the numerous advantages over traditional fixed-axis gearboxes. One notable advantage is its distinctive combination of both compactness and wonderful power transmission efficiencies.
To realize the design of complex mechanisms, the students have to employ skills ranging from concept development of planetary gears to vibration and failure analysis. After preliminary kinematic design of a practical gearbox using CAD software, students were asked to analyze expected vibration signals of both an ideal and defective gear transmission in order to quantify machinery health monitoring metrics. The students verified their models by comparing the simulation results with the outputs from simplified theoretical parametric mathematical models of the system. The signals of dynamic forces in both time domain and frequency domain under different loading conditions were analyzed for gear fault detection. With the visualization capabilities of Adams, I find that the students' performance is significantly better in terms of understanding the concepts associated with abstract design, the dynamics of mechanical systems, and vibration analysis of rotating machinery which is essentially time-varying. Through the intuitive animations and post-processing plots in ADAMS, the students are able to understand the comprehensive picture of a dynamic gearing system. As a result of incorporating this software, students were able to analyze the steady state and transient loading of a complex mechanism as part of a design, build, and analysis scenario using practical components.
In conclusion: 1. ADAMS software can be used effectively to facilitate mechanical design with a short learning curve. 2. The introduction of ADAMS into the course allowed students to experience a culminating design experience that combined previous coursework. 3. ADAMS can predict the fault patterns of a gear train and may obviate some costs of field testing. 4. The authors have found the ADAMS software to be a useful teaching and research tool.
The following are some of the sample projects the students worked on:
Project 1. Crank Slider Mechanism with Gear Driving Train Design and Analysis. The students are required to design and analyze a crank-slider mechanism using ADAMS software. The mechanism must satisfy the following design conditions: input power P1 = 22kW, input angular velocity n1 = 1500 rpm, total gear ratio of a fixed-axis gearbox i = 13.375, the radius of the crank r = 150mm, and the linkage length L = 520mm.
Figure 1. Crank Slider Mechanism with Gear Driving Train: Number of teeth: N1=17, N2=60, N3=19, N4=72, Gear Modules: m1=4, m2=5
Figure 2. Time base and FFT plots of the contact forces in gear pair 1-2 for a healthy crank-slider mechanism.
Figure 3. Time base and FFT plots of the contact forces in gear pair 1-2 for a crank-slider mechanism with a damaged pinion tooth.
Project 2. Planetary Gear Transmission 3Z(I) Design and Analysis: The students are required to design and analyze a practical planetary gear 3Z(I) using ADAMS software. The design conditions are the following: input power P1 = 22kW, input angular velocity n1=1500 rpm, total gear ratio ip=99 and its relative error tolerance Δip=0.04.
Figure 4. Planetary Gear Transmission 3Z(I).
Project 3. Planetary Differential Drive: The students are required to design and analyze a planetary differential drive that is commonly used in automobiles. The differential drive combines two inputs and results in an output that is the difference of these inputs. The design conditions are the following: P1 = 7.5kW; n1 = 980 rpm for motor 1; P2 = 5.5kW; n2 = 750 rpm for motor 2; z1 = 28, z2 = 98, za = 20, zc = 37, zb = 94.
Figure 5. Planetary Differential Drive
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Finally, I gratefully acknowledge the contributions from the ME518 students. Should you need more information about our projects, please do not hesitate to contact me at xwu@calpoly.edu.
By Dr. Xi Wu
28-Aug-2009