INCORPORATING COMPLETE COMPUTER-AIDED ENGINEERING (CAE) TOOLS IN A TYPICAL UNDERGRADUATE DESIGN COURSE

Transcription

1 INCORPORATING COMPLETE COMPUTER-AIDED ENGINEERING (CAE) TOOLS IN A TYPICAL UNDERGRADUATE DESIGN COURSE Amir Salehpour 1 Abstract The use of computer simulation is limited in the undergraduate engineering curriculum that teaches basic engineering concepts in conjunction with those covered in the lecture. This paper will introduce and incorporate the use of computer-aided engineering (CAE) in an undergraduate course. The software used was SolidWorks. A crank-slider and a Slider-Crank used to teach the motion analysis. The results of the motion analysis were then compared to the published results for the accuracy of the 3D mode. Likewise, for the simulation analysis the students were asked to compare the results for a curved beam under load and a plate with notches in the middle. The maximum stress in the curved beam and the stress concentration factors for the plates were then compared to the published results to determine the accuracy. The accuracy of the results for both the motion and simulation analysis gave the students a better understanding of the CAE process. INTRODUCTION The motivation for this paper was to incorporate and adopt Computer-Aided Engineering tools which include creating 3D models, perform motion analysis, and be able to predict failure in an upper-level undergraduate course in the Mechanical and Materials Engineering (MME) department at the University of Cincinnati. The usefulness and effectiveness of computer simulation in teaching fundamentals of engineering concepts has been reported throughout the engineering literature. Waldorf et al. [1] reported on their work titled Computer-Aided Engineering for Tool Design in manufacturing Engineering Curriculum at Cal-Ploy University-San Luis Obispo. They incorporated Finite Element Method (FEM) for analysis of tool design into the Tool Engineering course. Stern at al. [2] reported on their work titled Integration of Simulation technology into undergraduate engineering courses and laboratories that using Computational Fluid Dynamics (CFD) computer software interface is an effective educational tool helping students both in learning the concepts and the implementation of CFD in their work and for their future careers. Also, they reported that their outcome of two years formative and summative student evaluation data, identified successful learning outcomes, as well as areas of improvements. They concluded that there is a need for an efficient, hands-on, computational fluid dynamics educational interface which can better simulate engineering practices. Baidurja et al. [3] also developed strategies for teaching CFD using commercial software ANSYS-FLUENT into the upper-level undergraduate and graduate course. They concluded that carefully designed out-of-class learning modules are very crucial to student s learning CFD concepts. On the other hand, Mazzei et al. [4] presented their work related to Integration of simulation software into an undergraduate Dynamic course. They have used MSC- ADAMS as the computer interface for teaching Kinematics and Kinetics concepts in their undergraduate level Dynamic course at Kettering University ME department. Recently Watson et al. [5] implemented FEA using SolidWorks Simulation commercial software package into an undergraduate Heat Transfer course at the University of the Pacific. They performed an extensive study of the use of FEA and its impact on student learning. The outcome of their assessment showed that through the use of pre- and post-learning quizzes and student surveys there is an increase in student performance. This is due to the fact that use of FEA reinforces the basic heat transfer concepts at the same time they are experiencing the use of simulation in solving basic engineering problems. Also Moazed et al. [6] used FEA to teach undergraduate design courses by introducing it in the Strength of Materials course and later in the Machine Design course. In the review of the research done in this area, it is clearly evident the need and the importance of computeraided engineering into undergraduate engineering courses and laboratories. Much of the work done in the literature to introduce computer simulation in engineering curriculum used a single computer interface such as FEA or CFD in teaching undergraduate courses and laboratories. More uncommon is the use of a series of computer engineering software to teach many phases of engineering discipline such as 3D modeling all the way to predicting a failure analysis in a single design course. This paper will present in detail the process of achieving this goal. To accomplish this task, we implemented the CAE software in the laboratory portion of a junior-senior level design course. A brief description and overview of each of the phases of the CAE software were given to the students in the beginning of the lab and they performed exercises related to the topic. The results of the exercises obtained by the software were then verified with the theory that was stated in the workbooks to emphasize and understand the underlying use of computer simulation. This paper presents the discussion and conclusion of the use of CAE and provides future work that may be needed in this area. 1 Amir Salehpour, Associate Professor, University of Cincinnati College of Engineering and Applied Science (CEAS), Mechanical and Materials Engineering (MME), Cincinnati, Ohio, USA, Amir.Salehpour@uc.edu DOI /INTERTECH Formatted: English (United States) Formatted Formatted: English (United States) Formatted: Centered

2 METHODOLOGY The process of teaching design concepts and design procedures in a typical engineering curriculum has been traditionally the same for many years. The teaching process usually involves lectures where the concepts are defined and taught. Homework usually is given to practice and understand the topics covered in the lectures. In many cases, the lectures are complimented by laboratory work where the students will get the opportunity to apply and emphasize their understanding and knowledge gained in the classroom to either perform a hands-on experiment or use computer engineering software. There have been many studies showing that the use of computer engineering software such as commercial software packages [7]-[10] reinforces and strengthen students knowledge of the topics covered in engineering courses. The notion of using computer-aided engineering has been growing in recent years and companies are searching for graduates with the knowledge and training in the use of computers to solve engineering problems. In addition, ABET s criteria for accrediting engineering programs criterion 3: Student Outcomes states that the programs must have documented student outcomes (a) through (k). Specifically, the student outcome (k) states: an ability to use the techniques, skills, and modern engineering tools necessary for engineering practice. The concepts of modern engineering tools such as CAE are rather involved in mathematical derivation and could not be easily taught in an undergraduate engineering curriculum. However, the purpose of this paper is to introduce a CAE commercial software package in a way that the upper-level undergraduate students can utilize them to perform and solve some basic engineering problems. The intent here is to provide the students with the necessary knowledge to set-up, analyze, and obtain results. The students gain confidence by verifying the results obtained from the simulation and those that they performed by hand calculations or obtained from the examples given in the workbooks. MME department we have a premium educational software license which includes all of the modules such as CAD, Load Simulation, Motion, Flow Simulation, and other addins. The intent for the lab portion of the course is to introduce the use of CAE which includes most phases of the design related to topics covered in the lecture. The CAE tools that were covered in the lab started with being able to create a 3D part model, create functional assemblies with the appropriate degrees of freedom (DOF), create 2D mechanisms using Blocks in SolidWorks, Perform Motion Analysis, and be able to apply FEA to determine stress and deformation simulations. Most of the students that started in the program are familiar with the CAD portion of SolidWorks. Freshman start to use SolidWorks when they take the Engineering Design Graphics and they should have a good knowledge of how to create a 3D part already. With students already knowing how to use the software, it was easier to cover the other CAE tools. The labs were designed so that the first portion of each lab was devoted to the introduction and overview of the topics that we needed to cover for that specific lab. An in-class tutorial was immediately performed so that the students were able to perform the exercises on their own. The exercises were closely related to the materials covered in the lab. Most of the exercises for the labs were obtained from the workbooks related to the use of SolidWorks simulation software [11]- [13]. Students were given the opportunity to complete the exercises on the same day of the lab or by the next lab session. The following sections describe the flow in which the CAE tools were utilized in the lab: Lab (1): 3D Part Modeling and Assembly [11] The purpose of this lab was to get familiar with the SW assembly environment and how to apply the mates in order to create a mechanism. The first part of the lab is to create bottom up assembly (Bench Vice) by uploading each individual part and then inserting them into the assembly. Then apply the mates (Standard, Advance, and Mechanical) IMPLEMENTATION OF CAE IN A MECHANICAL DESIGN COURSE (MET4077) This Mechanical Design course is upper-level and is geared towards the kinematics and dynamics of machinery. The textbook used is by Robert Norton: Design of Machinery. The first part of the course is concentrated more towards the kinematics, analytical linkage synthesis, and CAM design. The second part of the course is more involved with the Dynamics of machinery and more specifically dynamic force analysis of the mechanisms and linkages. The course is complimented by laboratory instruction in which the students meet for 3 hours per week. The labs are basically designed to cover the topics discussed in class lectures. All labs are tailored to use commercial engineering software SolidWorks. In the to create the mechanisms with the appropriate DOF. FIGURE. 1 A COMPLETE BENCH VICE ASSEMBLY WITH ALL MATES APPLIED Lab (2): 2D Mechanism Using Blocks in SW [11] 13

3 First the topic of Blocks and how to use them in SW was covered and then a tutorial was given in the lab to show the students how to use Blocks to create a working 2D mechanism to predict the intended motion. Then the students were given an exercise to practice creating the mechanism and show the intended motion. This is the statement of the lab (2): In this lab we are going to model the Reciprocating Mechanism using Blocks option within Solidworks. We need to first sketch the entities in the sketch environment then convert them into Blocks individually, adding the required relations and making sure that the motion is what you need. Then, we need to create a new assembly and invoke the Layout within the assembly. Insert the Blocks onto the Layout and then mate them to create the required motion. When the motion you need is achieved then we need to convert the Blocks into 4) And the angular velocity of the revolute joint between the driver and the rod (link 3) 5) Check the Interference between parts. FIGURE. 3 3D ASSEMBLY OF THE CRANK-SLIDER ASSEMBLY READY FOR MOTION ANALYSIS USED FOR LAB 3 AND 4 82 Acceleration2 (inch/sec**2) D objects. This will complete the requirement for this lab 2. FIGURE. 2 RECIPROCATING MECHANISM IS CREATED WITH THE USE OF BLOCKS IN SW Lab (3): Crank-Slider Kinematics Analysis [12] In this lab, students are introduced to the Motion Analysis program within the SW. This lab uses the kinematics analysis in SW to determine the motion of the piston and angular velocity of the connecting rod (coupler). The statement of the exercise in this lab is: In this lab you are to analyze kinematics of a Crank-Slider mechanism and detect the interferences. The part drawings are given to your team in BB, and each team is to create a working assembly of the Crank-Slider. After the assembly is completed, each team member needs to analyze the kinematics of the components of the slider for crank input which provides a constant angular velocity of 60rpm. Specifically, you need to find the following: 1) Position of the pistons mass center in the x- direction 2) Linear velocity of the piston in the x-direction 3) Linear acceleration of the piston in the x- direction Time (sec) The following are the results of the Kinematics study of the Crank-Slider mechanism. We have shown here only the linear acceleration of the connecting rod. FIGURE. 4 LINEAR ACCELERATION OF THE PISTON Lab (4): Slider-Crank Mechanism Dynamic Force Analysis In this lab, the kinetics of SW Motion Analysis was covered to determine the dynamic forces between the piston and the coupler or connecting rod as shown in Figure 3. There are three motion studies within the SW motion. They are Animation, Basic Motion, and Motion Analysis. Animation is for animating assemblies with the proper DOF. It is limited to just showing the motions between components in an assembly. You can add motors to create the motion as well. Basic Motion is for approximating the effects of motors, springs, contacts, and gravity on assemblies. However, it does not provide the effects of mass and inertia for calculating the dynamic forces. Motion Analysis is a comprehensive tool for simulating and analyzing the effects of forces, dampers, springs on an assembly. It also takes into account the mass, material properties, and inertia in computations. The first part of this lab, SW Motion Analysis was covered describing the steps needed to set-up the assembly and how to obtain the results and be able to plot them. An exercise covering the SW motion analysis was then given to 14

4 the students to determine the dynamic forces. The statement of the lab exercise is: Apply a force of 3lb onto the piston for a 0.1 second. Then determine, the reaction force at the pin where the piston is attached to the coupler rod. Also, verify the results with those that were calculated by the analytical analysis of the linkage. Excel was used to formulate and plot the equations for the X-displacement and X-velocity of the piston and then compared the results with those obtained from SW Motion analysis. Figure 6 shows the reaction force generated as the piston fires for one cycle. Reaction Force3 (pound_force) Time (sec) As the figure shows, the highest reaction force occurs when the piston is at the top dead center and it is 11lb. 3D MODEL OF THE CURVE BEAM WITH LOAD APPLIED AT THE HOLE Once the model was prepared, meshed, and applied the appropriate boundary conditions, it was ready to be solved. SW Linear Static analysis was perform to obtain the results. Figure 8 shows the stress contours indicating the highest stress in red. The highest stresses are on the concave side of the beam where both the bending and compressive stresses add. The models and the results that were generated by the students where closely compared with the results obtained from the theory as it was shown in the workbook. All of the FIGURE. 6 REACTION FORCE AT THE PIN CONNECTION BETWEEN PISTON AND CONNECTING ROD Lab (5): Curved Beam under Load (FEA Study) [13] The intention for this lab was to introduce FEA to solve a typical engineering problem and be able to compare the results with the theory so that the students get the confidence in using FEA for their future work. As part of the lab, the basic mathematical derivation of FEA based on stiffness method was presented to the students. It was shown that the formulation is rather intensive when we are dealing with large number of elements. Next, element types (solid, shell, and beam elements) were introduced and the usage of them in problems explained. Then, students were introduced to the SW simulation by giving step-by-step instructions on how to prepare the problem, solve, and obtain the results. A curved beam exercise was chosen to be solved in SW which was the example in the workbook [12]. The Figure 7 shows the model of the beam created in SW. A force of 3800lb was applied in the hole near its upper end. The materials is 2014 Aluminum Alloy and the bottom of the beam is fixed. FIGURE. 7 students were able to complete the analysis and their FEA results were closely matched to the theoretical values. FIGURE. 8 STRESS CONTOURS SHOWING THE HIGHEST STRESSES IN RED Lab (6): Determining Stress Concentration Factor (FEA Study) In this lab, we study the effects of geometric discontinuity in members and components that are under loads. Depending on the shape and the size of these discontinuities there are variations in the stress concentration. Stress concentration can be determined from the charts for a variety of loading conditions and shapes. In general the effects of higher stresses due to stress concentration is obtained by a multiplier factor K. The maximum stress in a member can then be determined by: Maximum Stress = (K) X (Nominal Stress).Students are now familiar with the use of linear static FEA. In this lab, we required the students to determine the stress concentration factor from the SW simulation results and compared them to the K factor obtained from the chart for the specific problem. The problem statement given in the lab is: Determine the stress concentration factor for the beam shown. The material is Alloy Steel and left end of the beam is fixed while the other end receives a 6000lb load. The notch radius is 0.25 inches and the thickness of the plate is 0.5 inches. The plate is a 6 x1.5. Compare the results you obtain from FEA with those from the chart. In addition, the students were introduced to Mesh Control with-in SW simulation. Mesh Control gives the ability to use finer mesh only in the 15

5 areas where experiences higher stresses. In this exercise, there are two studies, one with the default mesh and one with using a mesh control to determine the K factor. The Figures 9 and 10 show the difference in the stresses. It is determined that the K factor using mesh control is much closer to the actual K factor. As you can see in the Figure 10 assemble them to get it ready for Motion Analysis and finally be able to use FEA to conduct stress analysis all within SolidWorks software. It is our belief that we can broaden the scope of the work to include the use of SW in graphical linkage synthesis and be able to include Impact analysis and thin- and thick-wall pressure vessel designs. that there are finer elements created near the notch as compared to Figure 9. FIGURE. 9 STRESS CONTOUR SHOWING THE HIGHEST STRESSES AROUND THE NOTCH: DFAULT MESH FIGURE. 10 STRESS CONTOUR SHOWING THE HIGHEST STRESSES AROUND THE NOTCH: CONTROL MESH CONCLUSION The intent of this paper was to show how we can utilize a set of CAE tools in an undergraduate design course. Knowing and experiencing of using computer engineering software, may provide the necessary experiences and background that can both be used in the future work and also companies that are looking for graduates with these kinds of knowledge. The students that are taking this upper level design course will need to have covered some of the applications of CAE tools before they start their senior design courses. We covered here in this paper the methods and the processes in which we incorporated and adopted the use of CAE tools. The exercises and examples in the labs were those that are typically found in basic mechanics textbooks and workbooks related to the use of SolidWorks simulation software. One of the important factors is to be able to integrate a single computer engineering software within the engineering curriculum. This way students will get familiar and again confident in using the software to perform their engineering related work. What we have accomplished here was to give the students the ability to start with creating part models, ACKNOLEDGMENT The author would like to appreciate the editing and review of this paper by Kathy Haas and Muthar Al-Ubaidi. REFERENCES [1] Waldorf, D, J, Computer-Aided Engineering for Tool Design in Manufacturing Engineering Curriculum, ASEE Annual Conference, 6.283, 2001, 1-9. [2] Stern, F. et al, Integration of Simulation Technology into Undergraduate Engineering Courses and Laboratories, Int. J. of Learning Technology, 2(1), 2006, [3] Baiduja R, Bhaskaran, R, Integrating Simulation into the Engineering Curriculum: A Case Study, International Journal of Mechanical Engineering Education, 41.3, 2013, [4] Mazzie, A, Integrating Simulation Software into an Undergraduate Dynamics Course: A Web Based Approached, ASEE Annual Conference and Exposition, 8.742, 2003, [5] Watson, K, A, et al, Finite Element Analysis Learning Modules for an Undergraduate Heat Transfer Course: Implementation and Assessment, ASEE, , 2012, [6] Moazed, A, R, et al, Teaching Finite Element Analysis in Undergraduate Technology Curriculum, Web Document: rofessional/teaching-finite-element-analysis-in- Undergraduate-Technology-Curriculum.pdf. [7] Stern, F. et al, Hands-on CFD Educational Interface for Engineering Courses and Laboratories, J. Engineering Education, 95 (1), 2006, [8] Diefes-Dux, H, A, et al, Kirkpatrick s Level 1 Evaluation of the Implementation of a Computer- Aided Process Design Tool in a Senior-Level Engineering Course, J. of Engineering Education, 93,4, 2004, [9] Kurowaski, P, M, Teaching Finite Element Analysis for Design Engineers, Proceedings of CDEN2006, 2005, [10] Avouris, N, M, e al, Development and Evaluation of a Computer-Based Laboratory Teaching Tool, John Wiley and Sons Inc., Computer Application Engineering Education, 9, 2001,

6 [11] Tickoo, S, SolidWorks for Designers, CADCIM Technologies, [12] Chang, k-h, Motion Simulation and Mechanism Design with SolidWorks Motion, SDC Publications, [13] Steffen, J, R, Analysis of Machine Elements Using SolidWorks Simulation, SDC Publications,