RESHAPING THE APPROACH TO THE MECHANICAL ENGINEERING LABORATORY

ABSTRACT

Changes in the undergraduate curriculum were made to meet several goals for our students: improving abilities to utilize fundamental concepts to solve multidisciplinary engineering problems, improving skills in solving open-ended design problems, focusing on proficiency in using fundamental engineering concepts, and improving teamwork and communication skills. An aspect of this revision was our common belief that the laboratory curriculum should help to achieve those goals, including making engineering education more interesting. A revised laboratory curriculum was developed and implemented that includes four lab courses. We have moved towards multifocus lab exercises that encourage discovery and open-ended exercises. The paper examines each of the four laboratory courses, the rationale, the objectives and the expected outcomes. Highlights include a sophomore 'discovery' lab, a two-semester junior measurements lecture/lab sequence, and a senior design-oriented lab. Our intent is to develop a student engineer who can plan, build, execute and report to meet an engineering test objective.

INTRODUCTION

The undergraduate mechanical engineering laboratories serve several purposes within a curriculum. These include (in no order of emphasis): reinforcement and exercise of engineering principles and measurement principles, exposure to instrumentation and systems and engineering practice, training in test techniques, development of creative thinking and diagnostic skills, developing proficiency in data analysis and presentation, and a platform for practice in technical communication. With such a broad set of intentions, the laboratory syllabus can become cluttered leading to unrealistic expectations. This is complicated by the technical level of the student. In an effort to focus, the subject specific laboratory course has become a common format. However, the thrill of discovery and the multidisciplinary nature of engineering can be lost with such formats, just as the time commitment required by the student can not be easily balanced against the rewards gained.

The faculty of the Department of Mechanical Engineering at Clemson University have been implementing changes in the undergraduate curriculum based on several goals for our students: improving abilities to utilize fundamental concepts to solve multidisciplinary engineering problems, improving skills in solving open-ended design problems, focusing on proficiency in using fundamental engineering concepts, and improving teamwork and communication skills ¹. An aspect of this revision was the common belief that the laboratory curriculum should help to achieve those goals, including making engineering education more interesting.

The mechanical engineering lab curriculum has been revised. The previous subject specific lab sequence has been replaced with labs having a much broader, but pedagogically sound, focus. We attempt to incorporate a nurturing to build technical maturity, discovery to add breadth, and a vertically integrated lab structure to introduce teamwork. Both our expectations and our approach to lab conduct change with the student's technical age and subject exposure. Recognizing that engineering involves multidisciplinary decisions, we have revised our labs eliminating subject specific lab courses. We now attempt to integrate traditional subject topics, often within the same lab exercise objective. We continue to expose the student to the concepts of test design to meet an objective.

In effect, we have disassembled our narrow focus laboratories, such as those dedicated solely to heat transfer or vibrations, and have put broader engineering lab courses in their place. We believe that we have done this without losing focus of the importance of fundamental concepts, including those dealing with measurements themselves. In fact, we are finding that the fundamental concepts can be more effectively reinforced in this new format which more closely reflects engineering practice.

Our former lab sequence consisted of two junior year labs: a 1 semester credit hour strengths of materials lab and a 3-credit measurements lab, and three 1-credit senior year labs: a thermal systems lab, a mechanical systems lab, and a materials processing lab. The new lab sequence contains a 1-credit sophomore lab, two 2-credit junior labs, and a 1-credit senior lab. We use a common text ² for the labs and lectures and supplement each course with a Laboratory Manual of exercises, policies, and specific equipment information. In this paper the labs will be discussed along with supporting requirements to meet the needs of our students.

SOPHOMORE 'DISCOVERY' LABORATORY

The typical engineering student today has excellent visual and computer skills but tends to lack previous hands-on exposure to mechanical devices. Brought up on television and video games, we find many juniors unable to conceptualize the interaction of mechanical devices (piston/cylinders, motors, linkages, etc.) common to engineering science texts mostly because they have not been exposed to or handled such devices in their developing years. They have difficulty with freebody diagrams and line drawings mostly because they have little appreciation for basic elements. Manufacturing and assembly methods are new to them. They can not appreciate the simple beauty of a well-made, simple to operate part, preferring something that is animated or interactive. In most ways this is just social evolution so our teaching methods must evolve to take advantage of their strengths in visualized learning.

Accordingly, we have introduced a sophomore lab devoted to the discovery of how things operate and how they are put together. The main principle that each lab assignment must adhere to is discovery learning. Pre-prepared data sheets are not used. Prescribed instructions are limited and replaced mostly by prompting questions. We wanted to create hands-on, inquiring exercises with substantial communication and group learning. Communication skills are exercised both in the interaction and the formal reporting stage.

A typical exercise has each student within a small group examining a mechanical device or system. The group provides written and oral feedback on issues such as: How does it work, what are the critical parts and why, why is it made as it is, how could it be done differently, and/or how would you access (measure or document) its function(s). To prepare students for the lab experience, we allow two one-week lab exercises devoted to safety and communication formats, proper use of hand tools, and basic calibration techniques.

The format of this lab has students working in small groups of three or less. The physical laboratory space uses partial space reserved for the upper division labs bringing the sophomores in contact with junior and senior level students. A typical 14-week semester schedule includes up to eight specific assignments. This allows weeks for discussion and exploratory learning. A selection of example topics are given in Table 1. The assignments can be staggered to allow best scheduling of equipment. Each lab section of 12 students is manned by two teaching assistants under the direction of a faculty coordinator and a technician. We have been careful to assign some of our most experienced, articulate, and energetic graduate teaching assistants to this lab. From a faculty teaching load management perspective, lab coordination has counted the same as a three-credit course.

Consider the lab exercise on IC Engines. In this lab, students operate and then tear down a five horsepower, 2-stroke engine. They are instructed to identify each working part in terms of the engine operation and its relation to generating and regulating power and motion. They deduce, measure and compute values, such as the displaced volume. They reassemble the engine and comment on possible ease of maintenance with suggestions. Graduate assistants interact by asking questions of each group as they progress through the exercise. Students see, touch and measure the hardware, relate it to physical operations, and observe packaging methods.

Lectures (Table 2) are oriented towards instruction in measurement science concepts, including uncertainty analysis and test design. Typical lab exercises (Table 3) allow students to understand basic measurement methods with reinforcement of engineering science concepts common to the junior year. Also stressed is the cause and effect related to uncertainty in testing and methods to minimize uncertainty by proper test design. Students in this lab interact with Senior Lab students in one exercise, by assisting in evaluating or calibrating devices planned for use in senior lab experiments.

Most lab exercises are planned to run for two weeks to allow time for test planning and conduct, test preparation, and discussion. Students are provided an objective and a specific procedure to perform but must decide for themselves the test range, number of data points, and analysis methods to be used to meet the objective. Again here, prompting questions tend to replace prescribed steps. Still in Junior Lab I, experiments tend to be more prescribed than in Junior Lab II, reflecting the maturity level achieved by the student in each course. For example, rather than ask students in Junior Lab II simply to calibrate a flowmeter at prescribed flowrates, students are asked to plan and execute a test to answer the question: What is the operating range for which the flowmeter meets a 5% uncertainty? Published Codes are provided from which the students themselves extract the only "prescribed" feature of this experiment.

Students are required to bring a prelaboratory test plan at the beginning of each new experiment. Here the student anticipates the approach that he/she will take, the range and number of data required, how the data will be analyzed into a result that answers the basic question or meets the objective. Groups critique each others plan, discuss and assess a logical approach and coordinate a group plan. We find that this forces students to plan ahead and think about the upcoming experiment. The method is neither perfect nor popular but it has been effective.

The expected outcome of these courses is for students to become proficient in measurement methodology, test conduct, reporting, and test planning. Students should become comfortable in developing a plan to meet specified objectives. Students should understand that the manner and tools used in a test can affect the resulting conclusions drawn from the test.

A broad scale lab, which focuses on systems, processing and manufacturing, is taken in the senior year. These lab exercises tend to have well-defined goals but are open-ended in terms of meeting those goals. Ideally, the lab exercises involve some combination of concepts from the thermal, mechanical, manufacturing, and/or materials behavior stems. By this level, we expect that students provided an objective can: Plan, build, execute and report. Students specify major elements of the test and are responsible for instrumentation and data acquisition selections. Accordingly, students take up to several weeks to plan, prepare and calibrate, execute, and report their test results. A critical feature of these labs is that each exercise involves the process of design.

The one-semester course consists of three to four lab exercises and meets one afternoon per week. Students work in groups of three. Lab exercises (Table 4) are staggered to permit best use of equipment. Two teaching assistants are assigned per lab section of twelve to ensure for safety and work under a faculty coordinator. The lab exercises change with each semester but tend to make use of the large equipment and facilities assigned to this lab, including: furnace, rolling mill, controlled lathe with instrumented cutting tools, MTS testing machine, subsonic wind tunnel, engine dynamometer, ASME/ANSI fan test facility, small-scale cooling tower, 100-kg shaker, packed/fluidized bed, and HVAC loops.

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