Using Inventor Analysis and Simulation to Enhance Students Comprehension of Stress Analysis Theories in a Design of Machine Elements Course.

Transcription

1 Using Inventor Analysis and Simulation to Enhance Students Comprehension of Stress Analysis Theories in a Design of Machine Elements Course. Julie Moustafa, Center for Learning Technologies Moustafa R. Moustafa, Department of Mechanical Engineering Technology Amy Adcock, Department of Educational Curriculum and Instruction Old Dominion University

2 Abstract This article presents an overview of the use of AutoDesk Inventor software s analysis and simulation feature and its effects on student comprehension. The feature was employed in an undergraduate Engineering course to create worked examples of stress analysis theories. A solid understanding of the principles of stress analysis is crucial to student success in a machine element design course but many students are failing to make the transfer of problem solving skills from a lower level strength of materials course to the subsequent higher-level design of machine elements course. The design principles applied to the developed Inventor animations are intended to reduce cognitive load, and increase transfer of problem solving skills to maximize learning outcomes. Narrated, annotated animations were created using cognitive load principles and then employed in an undergraduate engineering course. This study did not show a significant increase in student learning outcomes after presenting students with animations in classroom instruction but future research will investigate whether viewing narrated, annotated animations asynchronously in a course management system will increase significantly in transfer to isomorphic problems.

3 Introduction Student problem solving abilities in stress analysis theory are crucial to success in an Engineering Machine Elements design course but many students report difficulty in comprehension of these theories after receiving traditional instruction in a lower level Strength of Materials course. Professors and students in mechanical engineering courses reported serious issues with student comprehension of the complex interrelated concepts of stress analysis in both the lower level strength of material courses and the upper level design courses (Hall, Hubing, Philpot, T, Flori &Yellamraju, 2004). A new tool, Autodesk Inventor allows the creation of 3D animations to show the concepts of stress analysis in color animation recently. This software is being employed to develop materials that will enhance student comprehension of this critical engineering concept. It is hoped the use of this tool will have a positive effect on students ability to understand stress analysis theory and positively impact their understanding of higher-level engineering concepts. The Autodesk Inventor tool has been employed in the Engineering department previously but for a different purpose. Mechanical engineering technology students were already learning to use the new feature of the software in a solid modeling course to show stress analysis in 3D animation and the mechanical engineering technology with a measure of success. From this, the instructor of the Design of Machine Elements course recognized the value in using 3D simulations as a teaching tool. Both the civil and mechanical engineering departments were eager to use this new tool to solve their common problem of student comprehension. After consultation with instructional design staff at the university, a collection of learning objects were created using principles of multimedia design rooted in Cognitive Load Theory (CLT) (Sweller, 1999). Learning objects were developed to include narration and animation to assist students visualization of stress analysis theories. The research presented in this paper describes the implementation of AutoDesk Inventor to create animations that demonstrate the principles of stress analysis theories in a way that facilitates student learning. Instructional design principles based in CLT were applied to these animations to create the most effective and efficient means of presenting complex concepts using animation. Data were

4 collected to examine the efficacy of this approach. Future efforts of this study will include development of learning objects to strengthen metacognitive skills in multifaceted problems and to improve student epistemology by demonstrating the connection of stress analysis principles from lower level courses through upper-level courses and into the workplace (Ogilvie, 2007). The use of AutoDesk Inventor to create animations of stress analysis theories to be delivered in synchronous traditional classroom instruction is examined in detail in this paper. Possibilities for asynchronous use are also considered. The examples in this paper were selected based on the principles detailed in Tennyson & Cocchiarella (1986). The concepts in stress analysis theories contain variable dimensions and coordinate relationships so an expository example treatment of animation with narration was chosen as the treatment for this instruction according to the recommendations of Tennyson &Cocchiarella, (1986). This preliminary study addressed the following question: Does the application of CLT principles to the design of animations increase student understanding of stress analysis theory? Key Research Complex Problems in Engineering The goal of mechanical engineering coursework is to move the student from a solid understanding of how well structured problems and principles can be applied to the ill structured problems represented in a senior design capstone project. According to Jonassen s (2000) typology of problems the lower-level courses (including strength of materials and design of machine elements) use an algorithmic type of problem where the student applies procedural knowledge to create a correct answer. Once the concept knowledge is strengthened, procedural knowledge and the links between the concept and structured knowledge are strengthened to allow the student a robust set of skills to solve algorithmic type of problems instead of students searching for an algorithm to apply without understanding the concepts and procedure behind the algorithm (Ogilvie, 2007). Cognitive Load Theory Cognitive Load Theory (CLT) is defined as interactions between information structures and knowledge of human cognition to determine instructional design (vanmerrienboer & Sweller, 2005).

5 CLT is based on the contention that human memory capacity is limited and while some of the resources are used processing and assimilating information, instructional materials should be deliberately designed to reduce the load on working memory (Sweller, 1999). For this research, both extraneous (determined by design) and intrinsic (determined by content complexity) are important. Along with the complexity of the material, which provides a high degree of intrinsic cognitive load due to its complexity, the traditional instructional materials have a high degree of extraneous cognitive load. In attempting to present a concept better visualized in three dimensions, designers traditionally present the instructional material in a visual manner and splitting the attention of the learner between images and textual information (Sweller & Chandler, 1994). The instruction designed and evaluated here sought to address issues with both the complexity of the information by reducing the extraneous load of the presentation material by reducing split attention when presenting worked examples. Worked Examples Incorporating worked examples in instruction is a way for the learner to examine the expert problem solving model for that particular problem (vanmerrienboer & Sweller, 2005). Worked examples in may take many forms including diagrams, text, audio or animations. Narrated animations were chosen as the delivery medium for demonstrating worked examples of these ill structured problems. It was important to design these animations in a way that reduces extraneous cognitive load as much as possible by addressing split attention. Split Attention Effect Initially, one would assume that the learner could benefit from as much information about a complex concept as possible but the way in which the information is presented could interfere with the learner s ability to process the information. Split attention effect (CITE) occurs when information is presented in different modalities but is presented is separate places (i.e., illustration and annotation on different pages of a textbook). Presenting instruction in this way requires learners to move back and forth between the two pieces of information causing extraneous cognitive load. Meaningful learning can occur when the working memory resources are streamlined by presenting all related information in a format that

6 reduces this extraneous load (Baddely, 1986, 1992; Mayer and Moreno, 1998). Presenting complex diagrams with detailed textual information outside of the diagram, requires the learner to split their attention between the text and the diagram thus increasing cognitive load and actually interfere with learning. To design the instructional materials described in this paper, aural and visual information were integrated into animations in dual presentation mode to avoid the split attention effect. (Mousavi, Low, & Sweller, 1995; Mayer & Moreno, 2003). Transfer of Learning The purpose of creating these worked examples for instruction is to facilitate the transfer of learning from simple to complex concepts and increase student performance in both the strength of materials course and the design of machine elements course. Paas (1992) found that practice with partially worked-out or completely worked out problems is superior for problem transfer than conventional problems. An example of worked examples that were designed to facilitate transfer of learning follows in the engineering graphics section. The first example is a simple rectangular beam and the second example is a t-section that requires transfer of knowledge from the simple rectangular beam. Applied Cognitive Task Analysis to Identify Need Methodology Applied cognitive task analysis was used to develop solutions to the instructional problem of stress analysis theory. The part of applied cognitive task analysis (ACTA) most used in this project is the simulation interview shown in Table 1. Table 1. Applied Cognitive Task Analysis Events Actions Assessment Critical Cues Potential Errors Identify external loading Find the reactions Look at given Is given in problem magnitude of forces and location of action Use the equilibrium equations Verify the value of the reactions against the solution Look at the arrow and number on diagram Measurement of Some novices skip this step Mistakes in finding distance from force tothe moment may use point of moment the wrong distances.

7 Calculate normal stresses due to bending 1. Cut the beam2. Take moments about that location3. From only one side of the beam verify value of C = distance from neutral axis to most outer surface Do not use the right forces or distances perhaps discard reactions from previous step Wrong bending moment Calculate Transverse shear stress Plot the distribution of normal stresses due to bending and transverse shear stress on the cross section Use the simplified formula for maximum transverse shear stress. Show the complete diagram with distribution of stresses due to bending and transverse shear Verify the shear force Draw diagram diagram is drawn correctly Shear force must be determined by drawing the shear force diagram. Students may guess at this number. Verify the diagram Draw diagram May skip this step because they got the numbers right The potential errors and assessment items provided a clear cue where to use worked examples to help the student identify critical cues like where the neutral axis is located and what the distribution of stresses looks like on each type of shape (Militello & Hutton, 1998). Instructional Design of Materials The two principles addressed in this paper were cantilever beam and T-cross section of cantilever beam. Several animations were created to compile a collection of reusable learning objects to serve both the civil and mechanical engineering technology departments in their courses. The objects will be developed in AutoDesk Inventor and rendered as an animation. The avi file was brought into Camtasia narrated and then annotated using the features of the software.. The finished product will be produced as Flash for future research and use in the course management system for the student to view on their computer, and m4v for itunesu (video podcasting) for the student to view on an ipod. Most instructors know that multiple examples will increase student learning on complex concepts. Research from Reed & Bolstad (1991) confirmed that a simple example and a complex example presented together are better than a simple example accompanied with general procedural information alone or a complex example with procedural information alone. Students used information in

8 a flexible manner to transfer information from the simple and complex examples. For each concept of stress analysis, a simple and a complex example was created and used. The following section discusses the instructional design of the animations by describing the structure of each animation and its purpose. Stress Analysis of the Cantilever Beam Figure 1 shows the stress analysis of the cantilever beam. The distribution of stresses on this cross section will be varying linearly from max tension at the top surface to max compression at the bottom surface. Stress will be zero at the neutral axis. The animation will show both of these results using color graded chart for different stresses. If the learner observes the distribution of stresses over the length of the beam, they notice that it varies from zero at the point of load application to max stress at the support location. At the same time, by looking at the distribution of stresses on the cross-section, the learner can see that it agrees with the calculation results, and shows it in different colors according to the stress value. Figure 1. Stress Analysis of the Cantilever Beam

9 Using the animation and the color spectrum in a dynamic way will show the learner a visual of what the abstract formulas mean. Visualizing in the abstract for this complex concept is difficult for the learner due to the cognitive load demands of the task. For example, it is not easy to relate tension and compression in the horizontal fibers or layers as a result of a vertical force at the end of the cantilever beam. Learners were missing calculating stresses and deformations for some loads because they did not have a good understanding of what the end results in terms of stresses and deformations are. By better understanding of these end results the learner can plan their problem solving strategies more effectively. In Figure 2, the cross section is changed from a rectangular shape (which is symmetric about the neutral axis) to a t-section (which is not symmetric in the y direction about the x-axis). That will place the neutral axis at a location with two different distances to the outer surfaces. Figure 2. T Shaped Cross Section As the animation progresses, the learner can observe the distribution of stresses and can clearly identify the location of the neutral axis which is represented by the color of zero stress. The top surface will adopt the stress color higher than the stress color on the bottom surface which validates the theory.

10 Data Collection Students in a junior/senior level undergraduate mechanical engineering design of machine elements course (n=15), were given traditional instruction using hand drawings, text book diagrams, and verbal explanations. At the end of instruction for the first principle of cantilever beam, an exam was given to measure student performance. The first exam measured students abilities to calculate distribution of stress on a cantilever beam (Principle 1). The students were given traditional instruction plus the use of animation to explain the distribution of stresses. The second exam measured students abilities to calculate distribution of stress on a T-cross sectional beam (Principle 2). The second principle is isomorphic and builds on the first principle. The same steps to solve the first exam problem are present in the second exam problem. The second exam problem contains the same steps from problem one and these steps can be graded separately and compared to the first exam problem. The grades of problems from exam 1 were compared to grades of problems from exam 2 to determine if there was a significant difference between exam 1 problems and exam 2 problems after viewing the animation in regular classroom instruction. Exams are shown in Figures 3 and 4.

11 Figure 3 First Exam Figure 4 Second Exam

12 Findings Data were collected to examine the differences in pre and posttest scores after students viewed the redesigned instructional materials (NOTE: It would be good to include an example of test questions in the appendix-this might be a question that comes up in the presentation so be ready for it). A Paired Samples t-test was used to determine compare pre and posttest scores. Findings indicated there was no significant difference in pre and posttest performance (t =.390, p =.703). An examination of pre and posttest means indicates a slight positive trend in posttest scores indicating a small positive effect from the redesigned materials. Table 2 shows the means and standard deviations of pre and posttest scores. Table 2. Pre and Posttest scores and Standard Deviations M (SD) Pretest 5.21(4.45) Posttest 5.93(4.09) Conclusion Student understanding of the basic principles of stress analysis did not improve significantly. Several reasons may account for these results. First, the sample size for this class was very small due to several students dropping the course after the first exam. This is a normal occurrence for this course and part of the impetus for creating instructional materials to aid in student comprehension. The second reason that needs to be carefully examined is the issue of the pre and post test questions were inside a regular exam given by the instructor and were accompanied by three other problems to solve. The other three principles had not been animated and narrated and may have created interference on the test results. The review of the literature revealed that when solving complex, interrelated problems, issues of increasing extrinsic cognitive load such as split attention effect from presenting visual information about a concept in two different places adds to the already intrinsic cognitive load of the complex problem. Creating narrated animations not only eliminated the split attention effect, but capitalized on the dual modality presentation of animation with narration. Findings from this study indicate that the AutoDesk

13 Inventor analysis and simulation feature combined with CLT principles provides the instructor with effective worked examples to present to students for understanding of complex concepts. By providing the student with narrated animations both during instruction and online for later review, the student may benefit from the animation in their understanding of these complex stress analysis theories once all the animations are created and narrated. Implications for Future Research Developing animations as part of a collection of reusable learning objects in both the mechanical and civil engineering departments to enhance novice student understanding is a priority goal for the engineering department and the learning center. It is a step toward contributing to the call for research on student comprehension of concepts, schema development with simple problems, and then on to more complex, multifaceted problems (Olgivie, 2007). The future for this project includes testing each animation individually for mechanical and civil engineering technology courses followed by creation of narrated animations for each of the identified concepts. The animations will be used in face to face classtime and also deployed in the course management system as part of an online learning unit. This learning unit will include information about each concept plus the narrated animation. User statistics will track the number of views per learner for future analysis. This study may extend to the capstone course in Mechanical Engineering Technology Senior Design Project where students are presented with an illstructured modeling problem. The collection of narrated animations described in this paper are designed to be reused for future offerings of online or hybrid engineering courses. Continuing research in the design and affordances of these animations can contribute to the body of empirical evidence supporting the use of narrated animations designed for complex problem solving.

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