Project-based course of Applied Dynamics with computer simulation Tools Working Model 2D

Transcription

1 Project-based course of Applied Dynamics with computer simulation Tools Working Model 2D Prof. Ti Lin, Liu Department of Manufacturing & Mechanical Engineering Technology/Packaging Science Rochester Institute of Technology, Rochester, NY Abstract: The project-based course of applied dynamics is developed in RIT mechanical and manufacturing engineering technology department for the mechanical engineering technology students to design and analyze dynamic system. The easy-to-learn Working Model 2D allows students simulate and explore dynamic behavior of their mechanical and manufacturing systems, which provides an effective and attractive learning environment and a visualization learning procedure to our students. In weekly project, it is required the comparison of simulation results with the analytical results. Some case studies will be illustrated in this paper, which includes particle, rigid body motion analysis. Key Words: Project-Based Course, Computer simulation, Working Model 2D, Learningby-doing, problem-based-learning. Introduction: Working Model 2D simulation is used to build the virtual prototypes of dynamic system, which helps student to understand the nature of dynamic process of systems. Learningby-doing is the major approach in this course which transition from the traditional classroom approach towards a free independent learning environment, which add student responsibility for their learning. Learning-by-doing promotes understanding and retention. Weekly project is a problem-based-learning mechanism to get students to think and challenges students learn to learn. The weekly project reports must be done in a professional format. This includes objective, summary, sketch, major input and output, free body diagram, calculation, tabular results, chart results, discussion, and conclusion. 1. Package System Dynamic Analysis Kinetics of Particle A 0.5x0.7m, 25kg package is moving down the 22deg chute (slope) and collides with an 18kg vessel which is at rest on the ground (Fig.1). The ground is 2.2m below the end of the chute. The friction coefficient between the package and the chute is 0.3 and the friction coefficient between the vessel and the ground is 0.1. The velocity, acceleration, and force analysis are required. The motion of the package can be illustrated and analyzed in four major stages based on its dynamic behaviors. 1. Package is running down the slope. 2. Projectile motion of package. 3. Impact between the package and

2 the vessel. 4. Package and the vessel moving on the ground. The simulation model is created in Working Model 2D. The force acceleration, work energy and impulse momentum methods are used in the analytical calculations for comparison. Fig.1. Computer simulation model and velocity results of package in Working Model 2D The tabular results of Computer simulation with analytical solutions Fig.2. Tabular results of velocity, acceleration, dynamic force of package Computer simulation versus analytical solutions

3 2. Crate-Pulley-Slope System Dynamic Analysis (Fig.3) Objective: The motion of Crate-Pulley-Slope System is investigated. Both Analytical and computer simulation approaches are used for comparison. In analytical solution both force-acceleration and work-energy methods are used. Computer Simulation Results: Fig.3. Computer Model of Crate-Pulley-Slope System 3. Four Bar Linkage (Printer Head) velocity analysis (Fig.4) The velocity and acceleration polygons of relative motion analysis are drawing inside of working model 2D which provides high accuracy of graphical results comparing with regular hand-drawing of polygons. Fig.4. Four Bar Linkage (Printer Head mechanism) velocity analysis at theta2=30, 45, and 60-deg. The velocity polygon of Four Bar Linkage at 45-deg is illustrated.

4 4. Rock-Crusher mechanism dynamic analysis (Fig.5, 6) R2=2-in, R3=3-in, R5=4-in, Omega2=-2-rad/sec, AD=3-in The coordinates of three corners of Link 3 are (0, 0), (3, 0), and (1.5, 3) respectively. The velocity, acceleration, and force polygons provide the analytical results with graphical approach inside of working model 2D, which gives very high accuracy of the results comparing with the regular solution which is drawn by hand. (Fig.5, 6) This is the middle project of this course and it takes two weeks. Fig.5. Computer model, analytical solution with graphical approach of velocity and acceleration polygons with relative motion method inside of working model 2D at theta2=75-deg

5 Fig.6. Computer model, analytical solution with graphical approach of force triangles, Torque and Power Requirement at theta2=80-deg and resistant force F=10,000-lb 5. Rigid Body Kinetics Project Fork-Lift Truck (Fig.7) Analytical Solution with D Alembert s Principle is used for comparison with computer simulation results. The reaction forces at the wheels of the fork-lift truck and tipping condition is also considered in this project. Fig. 7 Modeling of Fork-Lift Truck in Working Model 2D 6. Final Project of Dynamics: Paper Roll Delivery. The original problem is introduced in Machine Design Textbook Robert L Norton 2 nd Ed. (P.247 Prob to 4.47, P. 439 Prob to 6-47), and has be modified by author using for dynamics. In this project, the dynamic analysis of six-bar linkage, the motion of paper roll, and the dynamic analysis of fork-lift truck are included.

6 Fig. 8. Paper Roll Project description and modeling in Working Model 2D Fig. 9 Velocity and acceleration polygons at theta2=200-deg of Six-Bar Linkage in Working Model 2D:

7 Force analysis of Six-Bar Linkage Fig. 10. Force analysis of Six-Bar Linkage at theta2=200-deg Fig.11. Velocity, acceleration, and force analysis of Paper Roll in Working Model 2D

8 Fig.12. Computer Simulation Tracking of the System Fig. 13. Dynamic Force analysis of Folk-Lift Wheels

9 Fig.14. Computer Simulation Measurement of Impact Results between Paper Roll and Forklift in Working Model 2D 7. Introduction of First Degree of Freedom Vibration One degree-of-freedom free vibration, under-damping vibration, and force vibration of mass-spring system are introduced at the end of this course with Working Model 2D tool.

10 Fig. 15. One degree-of-freedom free vibration, under-damping vibration, and force vibration of mass-spring system Conclusion: The project-based study of applied dynamics with Model 2D simulation provides an effective and an attractive learning environment for engineering technology student. Learning-by-doing is the major approach in this course which transition from the traditional classroom approach towards a free independent learning environment, which add student responsibility for their learning. Learning-by-doing promotes understanding and retention. Most of students work in teams where they are working cooperatively in groups to seek solutions to real world problems. These problems are used to engage student curiosity and initiate learning the subject matter, help students to think critically and analytically, and to find and use appropriate learning resources.