The Use of Standards in an Introductory Design Course at Penn State University
Although engineering education has always blended science with its application, it was the Accreditation Board for Engineering and Technology ABET 2000 accreditation criteria that placed both on an equal par and, further, emphasized a rounded skill set to ready students for professional practice. One outcome is an international understanding that learning to engineer involves synthesis, creativity and management as well as analysis, rote memorization and following directions. Another is that graduate engineers must be aware of the world in terms of business, cultures, ethics, the environment, etc.
To this end, universities have modified the teaching of all engineering courses to reflect this more general outlook. A prime example of this is the teaching of design and, of course, that brings in technical standards.
At Penn State University, several faculty in the hallowed analytical discipline of mechanics adopted this more general outlookand the vehicle to introduce this balanced approach is design. It was quickly recognized that learning design is best done progressively over time in order to develop an appropriate mindset for doing it rather than focusing design only in first- and last-year project courses, a typical approach. But under the constraints of a busy curriculum, this had to be done without adding credits. Hence, time for design was created by eliminating some analytical topics and focusing on fundamental theory.
The result is the series of courses shown in the “Design in Mechanics Course Series” sidebar (below) that optionally can substitute for traditional courses. (It should be noted that this series follows a first year “Design as a Process” course that all engineering students take.)
|Design in Mechanics Course Series
|Second Year: Mechanics of Materials with Design
|Third Year: Computer Methods in Design: numerical methods; interpolation, splines and drawing curves; computer graphics; solid modeling; and simulation
|Fourth Year: Advanced Mechanics of Materials with Design
|Importantly, we include design without adding credits
Is there a gain? If so, what is it? While the world’s engineering infrastructure engineering societies, technical standards and databases, among many others is deemed “soft” information, we view it as critical to the practice of engineering in the world-wide economy, and just as critical for students to learn about. Although finding and applying standards is just one of many topics covered in teaching design, it is an important one.
The focus of this article is the use of standards in the second-year course “Mechanics (or Strength) of Materials.” The theories covered in the course are fundamentals of stress and deformation in axial, bending and rotational loading of elastic structural elements. Learning design as a process is integrated into the course; students working in teams of three to four apply this process in a ten-week design project.
We accomplish this by (1) teaching six hours of design and scheduling theory just in time to support learning design and doing the project and (2) providing a design Web site (see Figure 1) to supplement the textbook and guide students in the management of their projects.
Use of Standards
Our use of standards mainly covers four concerns of engineering design: materials, manufacturing, human factors and standards/codes (Figure 2). However for second-year students, the topic is new, so the picture is broad yet the coverage in class is shallow; it is an introduction. We introduce standards from the very beginning: we cover standards umbrella organizations like the International Organization for Standardization (ISO) and the American National Standards Institute and explain communications between them and their affiliates; we explain the concept of consensus, legal issues and standards vs. codes; and we discuss the influence of government standards such as U.S. military specifications. And in some detail we cover resources for standards searches, e.g., Penn State’s libraries, ANSI’s NSSN and U.S. military specifications. Indeed, when it comes to Web searching, students are experts, but not so for library searching the problem here is that the Web is more convenient and easier to use, though in general its sources lack authority. Our design Web site plays an important role by directing students to both library and Web sources.
While the coverage of standards in class is shallow, the Web site provides entry to information as deep as any student may wish to plunge. Consider, referring to Figure 2:
• “Materials” include metals, plastics, concrete, ropes, fabrics, fasteners and chains;
• “Manufacturing,” a field unto itself, is introduced and processes listed, but our goal at this level is to point out its importance in modern concurrent methods of design;
• “Human factors” focuses upon anthropometric data that arise in most projects because of our focus upon product design; and
• “Standards and codes” comprises a very deep subject.
Standards in the Design of a Hand Truck
As an example of how students learn from standards, we can draw from student reports and piece together some of what they did, in this case, in designing a hand truck (variously named handcart and dolly). The project is initiated by issuing client (instructor) specifications that include a concept sketch, which for a combination hand truck/handcart, is shown in Figure 3. The students then brainstorm and draw up specific specifications to guide their particular design. One place to start is a search for pertinent standards. Another is to do a market search for competing products. (It was rumored that one student team, designing an automobile trailer hitch, purchased a hitch to reverse engineer the design and returned it after the project was over! Although contrary to expectations, this is akin to common practice in the auto industry, and others, who tear each other’s automobiles apart to gather information.)
In a search of STINET, go to STINET, click “Find a Document,” check “DoD Index of Specs & Standards” and search for “dolly.” This turns up:
MIL-T-19147D: Trucks, Dolly, Rectangular, with Four Swivel Casters
As shown in Figure 4, the result leaves one less than excited. Nevertheless, students can learn a lot from reading this specification:
• A search of STINET can be a rather arcane experience, hence one must think and proceed carefully (e.g., success required search on “dolly,” not “hand truck,”);
• The document contains so much detail there is little wiggle-room for creative design (such detailed specification would not be recommended practice in the business world);
• The specification provides ideas of what to consider, e.g., choice of material (in the military specification, ASTM A36 steel was specified, again constraining creativity), level of design/test load above rated capacity, choice of wheels and/or casters and consideration of packaging; and
• Pertinent and new terminology.
To sum up, even standards that only approximate the design object can provide valuable information and insight into doing the design at hand.
In design of the handgrips, some students chose aluminum tubing for the material. In the Penn State Engineering Library they found Carla Hook’s 1996 Index and Directory of Industry Standards, which cites ASTM B 483, Specification for Aluminum and Aluminum Alloy Drawn Tubes for General Purpose Applications. After some analysis and decision-making, it was found that alloy 6061, with an allowable stress of 42 ksi, is available in tubing that ranges in wall thickness from 0.025 to 0.5 inches. With further analysis, a wall thickness to three-digit accuracy is calculated. But what should be specified? A search of vendors’ stock reveals that the three-digit theoretical answer is not stocked. So now what?
Students learn that nominal size tubing that meets or exceeds specifications is available off the shelf. In selecting standard-size tubing, one only uses the three-digit theoretical answer as a minimum wall thickness and seeks to find a nominal size greater than or equal to this that satisfies both safety and economical constraints. In a way, this works to teach students that, although there is no one right answer, there is an optimal one. This exercise demonstrates the value of using standards and vendor data to optimally and economically solve the design problem.
In design for assembly, many students chose threaded fasteners and in doing so discovered the difficulty of doing a search for seemingly “standard standards.” For example, consider the following scenario.
1. Go to NSSN and click “Search for Standards.” Enter “hex nut,” click “All Words,” click “All Developers,” and start search. This yields 37 documents, but not one from the American Society of Mechanical Engineers. Clearly the search is incomplete, so repeat search. (But recall, most second-year students have not yet heard of ASME, so they may have no idea that this search is flawed; the instructor must through experience foresee this or otherwise become aware of it and apprise the students accordingly. Then students learn of ASME and one of its roles in the profession.)
2. Enter American National Standard for Square and Hex Bolts and Screw Inch Series and click “All Words,” click “All Developers,” and start search. We get “The query is too complex or invalid syntax has been used.” The system simply cannot handle this long sequence of keywords. So, repeat the search again.
3. Enter “hex bolts and screw inch series.” Click “All Words,” “All Developers,” and start search. The system says: “No documents were found.”
4. All right, search again. Click “hex bolts inch series,” click “All Words,” “All Developers,” and start search. Voila! The system now displays: “ANSI/ASME B18.2.1-1996: Square and Hex Bolts and Screws (Inch Series).” (Note that students will only recognize the value of this if they have some knowledge of ASME. This too is educational.)
So after all this frustration, even for a professional, what do students get out of it? A student designer remarked, “It contains a table which gives dimensions and nominal sizes of hex bolts where we find that 0.35 inches is not a nominal size for bolts. Hence we choose to use bolts that are 3/8 of an inch in size because this is the closest nominal size that is larger than the minimum diameter we calculated.” Now that is one small, but important step in learning how to do engineering design.
Learning the physics of material mechanics as well as learning to apply it is an arduous task for students and instructors. Therefore, to learn theory and design, students must be taught progressively, just as theory has always been taught, through a sequence of courses that take them through knowledge levels on to graduation. This is the philosophy we follow in integrating design with theory. In so doing, we lay open the profession of engineering to students and provide them with a vision of their future so they can better plan for it.
As for instructors, it is very helpful to come into the classroom with some engineering experience because design is more than theory and methods; it requires creativity, insight and awareness of professional tools. Design conjoins all of this learning gathering information, understanding theory, developing skills, and so forth. Standards comprise a small, yet very important part of it.
At Penn State, the introductory mechanics of materials course with design is the first exposure most students have to technical standards, so learning that they exist and how to find them is a learning outcome in itself. Of course we go further. Learning to do design (see our Web site) is enhanced by learning about standards.
The concept of consensus between concerned parties who must agree upon a standard crosses over into concepts of concurrent engineering wherein all aspects of marketing a product are important from conception through its production to its disposal by the customer. When students read a standard, they gain information whether or not it is directly applicable to their design.
For an example not mentioned above, there are no American standards for the design of a sailboat mast, but if one reads the American Bureau of Shipping’s standard (Guide for Building and Classing Offshore Racing Yachts), one discovers key information, particularly on the selection of materials. Yet many standards are found that pertain directly to student projects: for one, Building Officials and Code Administrators standards on snow loads; for another, ASTM and other standards dealing with play and playground equipment and, as cited above, ASTM standards on materials.
In order to use standards, one must first find them. In this regard the NSSN plays a major role. Once standards are found, they must be made accessible for reading. This is a major problem because of cost. In an academic course setting, only single, specific standards are usually needed and these, if affordable, are often not available in a timely manner. Some standards collections, ASTM International, BOCA, and the Society of Automotive Engineers, to name three, are available to us, but others are not. ANSI’s educational committee continues to work on this problem.
With pertinent, specific standards in hand, students learn to set specifications, find guidance in doing their design and discover some support for design decisions they must learn to make (a difficult task for learners because they still seek “correct” answers to verify their understanding). To this end, performance standards are preferred over strict detailed standards (like the military specification for a truck dolly) because these do not constrain creativity. Indeed they aid in learning by thwarting the one-answer-fits-all mindset and encouraging students to seek unique solutions. This leads us to the bottom line: standards expose students to the world of engineering and technology, ratchet them up to state-of-the-art thinking about their design object and underpin decision-making in doing design iterations. //