Volume 20 - Materials Selection and Design Part 2 ppsx

The most important element in the successful practice of robust design is the characterization of the performance. As an example, consider an electrical resistor. Its performance is usually characterized by the resistance, R. However, the value of R is not important to quality and reliability. Any nominal value of R that is desired is easily achieved. The characterization R already assumes a linear relationship between voltage and current, with R being the slope of the assumed straight-line relationship between voltage and current. The specific value of R is not of primary interest in optimizing the robustness of the resistor. Rather the quality of the straight-line relationship between voltage and current is important. Therefore, voltage is plotted versus current with two noise conditions: noise values that cause small current and noise values that cause large current. The most robust resistor is the one that has the least deviation from a straight line, which is the ideal performance of the resistor. The smallest value of the ratio of the deviation from the straight line divided by the slope of the straight line is needed. After further analysis, the square of the ratio is taken. Therefore, the ratio of the average of the square of the deviations (averaged over all data points) is divided by the square of the slope of the best-fit straight line through the data. This is the measure of robustness. Taguchi developed a set of such metrics to which he gave the name signal-to-noise (SN) ratios. Larger values of any SN ratio represent more robustness. The most important steps in robust design are: 1. Define the ideal performance - often not simple to do 2. Select the best SN definition to characterize the deviations from ideal performance 3. Develop the sets of noises that will cause the performance to deviate from the ideal After some experience, the use of the design of experiments to rapidly increase the SN value is relatively straightforward. As an example, a subsystem is considered for which the PDT has identified the 13 most critical control parameters. Initial judgments are made of the best nominal values for each of the 13 control factors. Seeking improvement, a larger value and a smaller value are selected as representing feasible but significant changes to the initial design. This gives three candidate values for each of the 13 critical control factors. The total number of candidate sets of values is 3 13 , which is 1,594,323. Even a relatively simple subsystem gives a large number of candidates from which the PDT must select the best one, or better yet, quickly pick one of the best candidates. This requires systematic trials, that is, designed experiments. A standard orthogonal array is found that has 13 columns and 27 rows. The 13 critical control factors are assigned to the 13 columns. Each row defines one candidate for the critical values of the 13 parameters. The 27 rows define a balanced set of 27 candidates from the total of 1,594,323 candidates. For each of the selected 27 candidates, the appropriate sets of noises are applied and the performance is determined, either analytically or experimentally. The SN ratio (robustness) of each of the 27 candidates is calculated. A simple interpolation among the 27 values of the SN ratio predicts the candidate from the total of 1,594,323 that is probably the best. Typically the PDT iterates two or three times. The control factors that had little effect are dropped, and some others are introduced. The ranges of the values for the control factors are reduced to fine tune the optimization. Then a confirmation trial is conducted to verify the magnitude of the improvement. It is very important to do this parameter design early and quickly. The results of the parameter design are best captured in a critical parameter drawing. This drawing shows the system (usually a subsystem) with only as much detail as is needed to make the critical parameters clear, and it shows the values of the critical functional parameters that have been optimized. These then become specifications for the detailed design. By constraining the detailed design to the optimized values of the critical functional parameters, the robust performance is ensured. Tolerance Design. The optimization of robustness (SN value) often brings very large improvements. After the nominal values of the critical control factors are optimized, tolerance design is done. Of course, most of tolerance design is guided by standards and knowledge-based engineering. However, some decisions require more in-depth analysis. The primary step in tolerance design is to select the production process (or the precision of a purchased component) that provides the best tradeoff between initial manufacturing cost and quality loss in the field. Taguchi developed methods for this analysis. After the production process is selected, tolerances are calculated to be put on the drawings and other specifications. However, selecting the production process is the most important step in tolerance design, as it controls the inherent precision. The timing of robust design is critical for success. The optimization of robustness must be done early to achieve the benefits of problem prevention. As shown in Fig. 10, most of the optimization of robustness (parameter design) should be done to new technologies before they are pulled out of the stream of new technologies and integrated into any specific product. Any remaining product parameter design (SPD) is done early in the product program, before detailed design has progressed very far. The final verification of the robustness is done in the system verification test (SVT). The SVT is usually performed on the first total-system prototypes, which are made after the detailed design has been completed. (In the concept phase, the decisions of the first row of Fig. 9(c), total system decisions, are made. In the design phase, the decisions of the second row of Fig. 9(c), subsystem decisions, and the decisions at the other more detailed levels are made. In the readiness phase, the decisions are deployed to the factory floor, as indicated at the right of Fig. 9(b). Also in the readiness phase, mistakes are eliminated.) Fig. 10 Timing of Taguchi robust design steps. PD, parameter design (new product and process technologies); SPD, system (product) parameter design; TD, tolerance design; SVT, system verification test; PPD, process parameter design; QC, on line quality control (factory floor) Robust design is very important. Robust systems provide customer satisfaction, because they work well in the hands of the customer. They have lower costs because they are less sensitive to variations. Robust subsystems and components can be readily integrated into new systems because they are robust against the noises that are introduced by new interfaces. Most important of all, the early optimization of robustness reduces time to market by eliminating much of the rework that has traditionally plagued the latter stages of product development. This section is a brief introduction to the subject that has emphasized the primary features. Additional information is provided in the article "Robust Design" in this Volume. Mistake minimization is completely different from the optimization of robustness. Robustness optimization is done for concepts that are new, for which the best values of the critical functional parameters are unknown. Mistake minimization applies to system elements for which there is experience and a satisfactory design approach is known, but was not applied. Examples range from a simple dimensional error to a gear that is mounted on a cantilever shaft that is too long. The excessive deflection of the shaft causes too much gear noise and wear. The design of gears and shafts is well understood, so one that has a problem is a mistake. The mistake could be a simple numerical error. It could be that the person (or computer program) with the necessary knowledge was not readily available. The first approach is to avoid making mistakes by using a combination of: • Knowledge-based engineering (and standards) • Concurrent engineering (multifunctional teams) • Reusability Knowledge-based engineering helps to design standard elements, such as gears and shafts, using design rules and computers to implement proven approaches. Multifunctional teams help to avoid mistakes by having the needed expertise available. (A common source of mistakes is that the knowledgeable person was not involved in the design.) Reuse of proven subsystems, which have demonstrated that they are not plagued with mistakes, will also reduce mistakes. Despite all of the best efforts to avoid the occurrence of mistakes, some mistakes will still occur. Then they must be rooted out of prototypes of the system by the problem solving process. This process is basically: • Identify problems. • Determine the root causes of the problems. • Eliminate the root causes while ensuring that no new problems are being introduced. Failure-modes-and-effects analysis (FMEA) is very useful in doing this (see the article "Risk and Hazard Analysis in Design" in this Volume). The combination of robust design and mistake minimization will achieve excellent system quality and reliability. It is important to recognize that reliability is not a separate subject above and beyond robust design and mistake minimization. The traditional field that is called reliability is primarily devoted to keeping score of reliability and projecting it into the future based on certain assumptions. Robust design and mistake minimization achieve early and rapid improvement of reliability. This will rapidly develop new concepts to capture their full potential. Concurrent Engineering Don Clausing, Massachusetts Institute of Technology Conclusions The fundamental core of concurrent engineering is the multifunctional team that carries out the concurrent process to make holistic decisions. These decisions integrate the many diverse specialties to develop a product that provides customer satisfaction. Simply having a multifunctional team improves the decision making by bringing all of the relevant information to bear on each decision. The concurrent process also gains the commitment of all of the participants to the decisions, which leads to effective implementation. However, multifunctional teams can improve their decision making relative to the ad hoc approach into which it is all too natural to fall. The judicious application of structured methods described in this article and elsewhere in this Volume enables sound decisions and makes it possible to reduce complexity to workable tasks. A multifunctional team that makes holistic decisions by using the best structured decision-making processes while concentrating on both customer satisfaction and business goals provides the greatest leverage for the abilities of the product development people. The products that they develop will: • Be quick to market • Satisfy customers • Have constrained costs • Be flexible in responding to changes in the marketplace The ultimate purpose of concurrent engineering is to provide products that customers want and will purchase. Concurrent Engineering Don Clausing, Massachusetts Institute of Technology Selected References • K. Clark and T. Fujimoto, Product Development Performance, Harvard Business School Press, 1991 • D. Clausing, Total Quality Development, ASME Press, 1994 • D. Clausing, EQFD and Taguchi, Effective Systems Engineering, First Pacific Rim Symposium on Quality Deployment, Macquarie University Graduate School of Management (Sydney, Australia) 15-17 Feb 1995 • L. Cohen, Quality Function Deployment, Addison Wesley, 1995 • M. Phadke, Quality Engineering Using Robust Design, Prentice Hall, 1989 • S. Pugh, Total Design, Addison Wesley, 1990 • S. Pugh, Creating Innovative Products Using Total Design, Addison Wesley, 1996 Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. Introduction REGARDLESS OF THE MATERIAL to be used, most design projects are exercises in creative problem solving. If the project is a very advanced one, pushing the boundaries of available technical knowledge, there are few guidelines available for the designer. In such instances, basic science, intuition, and discussions with peers are common approaches that combine to produce an approach to solving the problem. With the application of skill, daring, a little bit of luck, money, and patience, a workable solution usually emerges. However, most design projects just are not that challenging or different from what has been done in the past. In mechanical and structural design, for example, a tremendous amount of solid experience has been accumulated into what has been called good practices. Historically, such information was carefully guarded and was often kept secret. With the passage of time, however, these privately developed methods of solving design problems became common knowledge, ever more firmly established. Eventually they evolved into published standards of practice. Some government entities, acting under their general duty to preserve general welfare and to protect life and property from harm, added the standards to their legal bases. This gave the added weight of authority to the standards development movement. In some cases, use of a standard may be optional to the designer. In others, adherence to standard requirements may be mandatory, with the full backing of the legal system to enforce it. In any case, as soon as the problem has been defined, a competent designer should make a survey of any existing standards that may apply to the given problem. There are two obvious advantages to this effort. First, the standards may give valuable guidance to the problem solution. Second, conformance to standards can avoid later legal complications with product liability lawyers. Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. Historical Background Anyone who has taken a course in elementary physics has been taught about the "fundamental" quantities of mass, length, and time. When the metric system of measurements was established in 1790, a standard was set for the unit of length: one ten-millionth of the distance from one of the earth's poles to the equator. It was, by definition, the meter. However, there were a couple of problems with it. Because there was no way to make such an actual measurement at that time, there was a certain degree of error, and the standard suffered from a lack of portability. Some improvement was made in 1889, when an international convention on weights and measures agreed that the standard meter would be defined by the distance between two marks on a metal bar. This improved both accuracy and portability, and this standard was used until 1960. Then the standard changed to the wavelength of an orange-red line in the spectrum of Krypton 86. In 1983 the standard of length changed again, this time to a measurement based on the speed of light in a vacuum. The point here is that even the most basic standard units are subject to change as methods of measurement become more and more refined. While basic standards change only infrequently, technical standards and codes are all subject to more frequent modification. The thousands of published standards and codes are reviewed and updated periodically, many of them on an annual basis. Therefore, when making the recommended survey of applicable standards, the designer should check to make certain they are the most current ones. In addition, because of the periodic review process, it is advisable to query the publisher of the standard to find out if a revised version is being worked on, and if it may be released before the design is scheduled for completion. Obviously, to avoid instant obsolescence, any oncoming changes should be factored into the decisions made by the designer. Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. The Need for Codes and Standards The information contained in codes and standards is of major importance to designers in all disciplines. As soon as a design problem has been defined, a key component in the formulation of a solution to the problem should be the collection of available reference materials; codes and standards are an indispensable part of that effort. Use of codes and standards can provide guidance to the designer as to what constitutes good practice in that field and ensure that the product conforms to applicable legal requirements. The fundamental need for codes and standards in design is based on two concepts, interchangeability and compatibility. When manufactured articles were made by artisans working individually, each item was unique and the craftsman made the parts to fit each other. When a replacement part was required, it had to be made specially to fit. However, as the economy grew and large numbers of an item were required, the handcrafted method was grossly inefficient. Economies of scale dictated that parts should be as nearly identical as possible, and that a usable replacement part would be available in case it was needed. The key consideration was that the replacement part had to be interchangeable with the original one. Large-scale production was not possible until Eli Whitney invented the jig. Although he is best remembered for his invention in 1793 of a machine for combing the seeds out of cotton, the gin (which any good mechanic could copy it and many did), Whitney made his most valuable contribution with the jig. Its use enabled workers to replicate parts to the same dimensions over and over, thus ensuring that the parts produced were interchangeable. Before the Civil War, the Union Army issued a purchase order for 100 rifles, but included a unique requirement that all the rifles had to be assembled, fired, taken apart, the parts commingled, and then reassembled into 100 working rifles. Interchangeability was the key problem. Whitney saw that the jig was the solution. By using jigs, Whitney was the only bidder able to meet the requirement. With that, the industrial age of large-scale production was on its way. Standardization of parts within a particular manufacturing company to ensure interchangeability is only one part of the industrial production problem. The other part is compatibility. What happens when parts from one company, working to their standards, have to be combined with parts from another company, working to their standards? Will parts from company A fit with parts from company B? Yes, but only if the parts are compatible. In other words, the standards of the two companies must be the same. Examples of problems resulting from lack of compatibility are common. For years, railroads each had their own way of determining local times. A particular method may have been useful for the one railroad that used it, but wrecks and confusion demanded that standard times be developed. There used to be several different threads used on fire hose couplings and hydrants. All of them worked, but emergency equipment from one town could not be used to assist an adjoining town in case of need. So a national standard was agreed upon. Any international traveler knows that the frequency and voltage of electric power supplies vary from one country to another. Some are 110 V, others 220. Some are 50 Hz, others 60. In addition, all the connecting plugs are different. Even the side of a road on which one drives presents compatibility problems. Approximately 50 countries, notably the United Kingdom and Japan, use the left side; other countries use the right lane. With the global market for automobiles, manufacturers must produce two different versions to meet the incompatible local market requirements. Perhaps someday there will be a global standard, but the costs of any changeover will be enormous. This situation points out the near- irreversibility of somewhat arbitrary standardization decisions. Because of the relative permanence of their decisions, standards writers bear a Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. Purposes and Objectives of Codes and Standards The protection of general welfare is one of the common reasons for the establishment of a government agency. The purpose of codes is to assist that government agency in meeting its obligation to protect the general welfare of the population it serves. The objectives of codes are to prevent damage to property and injury to or loss of life by persons. These objectives are accomplished by applying accumulated knowledge to the avoidance, reduction, or elimination of definable hazards. Before going any further, the reader needs to understand the differences between "codes" and "standards." Which items are codes and which are standards? One of the several dictionary definitions for "code" is "any set of standards set forth and enforced by a local government for the protection of public safety, health, etc., as in the structural safety of buildings (building code), health requirements for plumbing, ventilation, etc. (sanitary or health code), and the specifications for fire escapes or exits (fire code)." "Standard" is defined as "something considered by an authority or by general consent as a basis of comparison; an approved model." As a practical matter, codes tell the user what to do and when and under what circumstances to do it. Codes are often legal requirements that are adopted by local jurisdictions that then enforce their provisions. Standards tell the user how to do it and are usually regarded only as recommendations that do not have the force of law. As noted in the definition for code, standards are frequently collected as reference information when codes are being prepared. It is common for sections of a local code to refer to nationally recognized standards. In many instances, entire sections of the standards are adopted into the code by reference, and then become legally enforceable. A list of such standards is usually given in an appendix to the code. Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. How Standards Develop Whenever a new field of economic activity emerges, inventors and entrepreneurs scramble to get into the market, using a wide variety of approaches. After a while the chaos decreases, and a consensus begins to form as to what constitutes "good practice" for that economic activity. By that time, the various companies in the field have worked out their own methods of design and production and have prepared "in-house" standards that are used by engineering, purchasing, and manufacturing to ensure uniformity and quality of their product. In time, members of the industry may form an association to work together to expand the scope of their proprietary standards to cover the entire industry. A "trade" or "industry" standard may be prepared, one of its purposes being to promote compatibility among various components. This is usually done on a consensus basis. However, this must be done very carefully because compatibility within an industry may be regarded as collusion by the justice department, resulting in an antitrust action being filed. A major example of this entire process is the recent growth of the Internet, where compatibility plays a primary function in the formulation of networks, but so far regulators have used a light hand. As an industry matures, more and more companies get involved as suppliers, subcontractors, assemblers, and so forth. Establishing national trade practices is the next step in the standards development process. This is usually done through the American National Standards Institute (ANSI), which provides the necessary forum. A sponsoring trade association will request that ANSI review its standard. A review group is then formed that includes members of many groups other than the industry, itself. This expands the area of consensus and is an essential feature of the ANSI process. ANSI circulates copies of the proposed standard to all interested parties, seeking comments. A time frame is set up for receipt of comments, after which a Board of Standards Review considers the comments and makes what it considers necessary changes. After more reviews, the standard is finally issued and published by ANSI, listed in their catalog, and available to anyone who wishes to purchase a copy. A similar process is used by the International Standards Organization (ISO), which began to prepare an extensive set of worldwide standards in 1996. One of the key features of the ANSI system is the unrestricted availability of its standards. Company, trade, or other proprietary standards may not be available to anyone outside that company or trade, but ANSI standards are available to everyone. With the wide consensus format and easy accessibility, there is no reason for designers to avoid the step of searching for and collecting any and all standards applicable to their particular projects. Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. Types of Codes There are two broad types of codes: performance codes and specification or prescriptive codes. Performance codes state their regulations in the form of what the specific requirement is supposed to achieve, not what method is to be used to achieve it. The emphasis is on the result, not on how the result is obtained. Specification or prescriptive codes state their requirements in terms of specific details and leave no discretion to the designer. There are many of each type in use. Trade codes relate to several public welfare concerns. For example, the plumbing, ventilation, and sanitation codes relate to health. The electrical codes relate to property damage and personal injury. Building codes treat structural requirements that ensure adequate resistance to applied loads. Mechanical codes are involved with both proper component strength and avoidance of personal injury hazards. All of these codes, and several others, provide detailed guidance to designers of buildings and equipment that will be constructed, installed, operated, or maintained by persons skilled in those particular trades. Safety codes, on the other hand, treat only the safety aspects of a particular entity. The Life Safety Code, published by the National Fire Protection Association (NFPA) as their Standard No. 101, sets forth detailed requirements for safety as it relates to buildings. Architects and anyone else concerned with the design of buildings and structures must be familiar with the many No. 101 requirements. In addition to the Life Safety Code, NFPA publishes hundreds of other standards, which are collected in a 12-volume set of paperbound volumes known as the National Fire Codes. These are revised annually, and a set of loose-leaf binders are available under a subscription service that provides replacement pages for obsolete material. Three additional loose-leaf binders are available for recommended practices, manuals, and guides to good engineering practice. The National Safety Council publishes many codes that contain recommended practices for reducing the frequency and severity of industrial accidents. Underwriters' Laboratories (UL) prepares hundreds of detailed product safety standards and testing procedures that are used to certify that the product meets their requirements. In contrast to the ANSI standards, UL standards are written in-house and are not based on consensus. However, UL standards are available to anyone who orders them, but some are very expensive. Professional society codes have been developed, and several have wide acceptance. The American Society of Mechanical Engineers (ASME) publishes the Boiler and Pressure Vessel Code, which has been used as a design standard for many decades. The Institute of Electrical and Electronic Engineers (IEEE) publishes a series of books that codify recommended good practices in various areas of their discipline. The Society of Automotive Engineers (SAE) publishes hundreds of standards relating to the design and safety requirements for vehicles and their appurtenances. The American Society for Testing and Materials (ASTM) publishes thousands of standards relating to materials and the methods of testing to ensure compliance with the requirements of the standards. Statutory codes are those prepared and adopted by some governmental agency, either local, state, or federal. They have the force of law and contain enforcement provisions, complete with license requirements and penalties for violations. There are literally thousands of these, each applicable within its geographical area of jurisdiction. Fortunately for designers, most of the statutory codes are very similar in their requirements, but there can be substantial local or state variations. For example, California has far more severe restrictions on automotive engine emissions than other states. Local building codes often have detailed requirements for wind or snow loads. Awareness of these local peculiarities by designers is mandatory. Regulations. Laws passed by legislatures are written in general and often vague language. To implement the collective wisdom of the lawmakers, the agency staff then comes in to write the regulations that spell out the details. A prime example of this process is the Occupational Safety and Health Act (OSHA), which was passed by the U.S. Congress, then sent to the Department of Labor for administration. The regulations were prepared under title 29 of the U.S. Code, published for review and comment in the Federal Register, and issued as legal minimum requirements for design of any products intended for use in any U.S. workplace. Several states have their own departments of labor and issue supplements or amendments to the federal regulations that augment and sometimes exceed the minimums set by OSHA. Again, recognition of the local regulatory design requirements is a must for all design professionals in that field. Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. Types of Standards Proprietary (in-house) standards are prepared by individual companies for their own use. They usually establish tolerances for various physical factors such as dimensions, fits, forms, and finishes for in-house production. When out- sourcing is used, the purchasing department will usually use the in-house standards in the terms and conditions of the order. Quality assurance provisions are often in-house standards, but currently many are being based on the requirements of ISO 9000. Operating procedures for material review boards are commonly based on in-house standards. It is assumed that designers, as a function of their jobs, are intimately familiar with their own employer's standards. Industry consensus standards, such as those prepared by ANSI and the many organizations that work with ANSI, have already been discussed. A slightly abridged list of ANSI-sponsoring industry groups and their areas of concern will be given under the following section on Codes and Standards Preparation Organizations. Government specification standards for federal, state, and local entities involve literally thousands of documents. Because government purchases involve such a huge portion of the national economy, it is important that designers become familiar with standards applicable to this enormous market segment. To make certain that the purchasing agency gets precisely the product it wants, the specifications are drawn up in elaborate detail. Failure to comply with the specifications is cause for rejection of the seller's offer, and there are often stringent inspection, certification, and documentation requirements included. It is important for designers to note that government specifications, particularly Federal specifications, contain a section that sets forth other documents that are incorporated by reference into the body of the primary document. These other documents are usually federal specifications, federal and military standards (which are different from specifications), and applicable industrial or commercial standards. They are all part of the package, and a competent designer must be familiar with all branches of what is called the specification tree. The MIL standards and Handbooks for a particular product line should be a basic part of the library of any designers working in the government supply area. General Services Administration (GSA) procurement specifications have a format similar to the military specifications and cover all nonmilitary items. Product definition standards are published by the National Institute of Standards and Technology under procedures of the Department of Commerce. An example of a widely used Product Standard (PS) is the American Softwood Lumber Standard, PS 20. It establishes the grading rules, names of specific varieties of soft wood, and sets the uniform lumber sizes for this very commonly used material. The Voluntary Standards Program uses a consensus format similar to that used by ANSI. The resulting standard is a public document. Because it is a voluntary standard, compliance with its provisions is optional unless the Product Standard document is made a part of some legal agreement. Commercial standards (denoted by the letters CS) are published by the Commerce Department for articles considered to be commodities. Commingling of such items is commonplace, and products of several suppliers may be mixed together by vendors. The result can be substantial variations in quality. To provide a uniform basis for fair competition, the Commercial Standards set forth test methods, ratings, certifications, and labeling requirements. When the designer intends to use commodity items as raw materials in the proposed product, a familiarity with the CS documents is mandatory. Testing and certification standards are developed for use by designers, quality assurance agencies, industries, and testing laboratories. The leading domestic publisher of such standards is the American Society for Testing and Materials (ASTM). Its standards number several thousand and are published in a set of 70 volumes divided into 15 separate sections. The standards are developed on a consensus basis with several steps in the review process. Initial publication of a standard is on a tentative basis; such standards are marked with a T until finally accepted. Periodic reviews keep the requirements and methods current. Because designers frequently call out ASTM testing requirements in their materials specifications, the designer should routinely check ASTM listings to make certain the applicable version is being called for. International standards have been proliferating rapidly for the past decade. This has been in response to the demands of an increasingly global economy for uniformity, compatibility, and interchangeability demands for which standards are ideally suited. Beginning in 1987, the International Standards Organization (ISO) attacked one of the most serious international standardization problems, that of quality assurance and control. These efforts resulted in the publication of the ISO 9000 Standard for Quality Management. This has been followed by ISO 14000 for Environmental Management Standards, which is directed at international environmental problems. The ISO has several Technical Committees (TC) that publish handbooks and standards in their particular fields. Examples are the ISO Standards Handbooks on Mechanical Vibration and Shock, Statistical Methods for Quality Control, and Acoustics. All of these provide valuable information for designers of products intended for the international market. Design standards are available for many fields of activity, some esoteric, many broad based. Take marinas for example. Because it has so many recreational boaters, the state of California has prepared comprehensive and detailed design standards for marinas. These standards have been widely adopted by other states. Playgrounds and their equipment have several design standards that relate to the safety of their users. Of course one of the biggest applications of design standards is to the layout, marking, and signage of public highways. Any serious design practitioner in those and many other fields must be cognizant of the prevailing design standards. Physical reference standards, such as those for mass, length, time, temperature, and so forth, are of importance to designers of instruments and precision equipment of all sorts. Testing, calibration, and certification of such products often call for reference to national standards that are maintained by the National Institute for Standards and Technology (NIST) in Gaithersburg, MD, or to local standards that have had their accuracy certified by NIST. Designers of high precision products should be aware of the procedures to be followed to ensure traceability of local physical standards back to the NIST. Designing to Codes and Standards Thomas A. Hunter, Forensic Engineering Consultants Inc. Codes and Standards Preparation Organizations U.S. Government Documents. For Federal government procurement items, other than for the Department of Defense, the Office of Federal Supply Services of the General Services Administration issues the Index of Federal Specifications, Standards and Commercial Item Descriptions every April. It is available from the Superintendent of Documents, U.S. Government Printing Office. Washington, D.C. 20402. General Services Administration item specifications are available from GSA Specifications Unit (WFSIS), 7th and D Streets SW, Washington, D.C. 20407. Specifications and standards of the Department of Defense are obtainable from the Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, PA 19120. To order documents issued by the National Institute of Standards and Technology it is first necessary to obtain the ordering number of the desired document. You get this from NIST Publication and Program Inquiries, E128 Administration Bldg., NIST, Gaithersburg, MD 20899. With the ordering number, the documents are available from the Government Printing Office, Washington, D.C. 20402, or the National Technical Information Service, Springfield, VA 22161. Underwriters' Laboratories documents can be obtained from Underwriters' Laboratories, Inc., Publications Stock, 333 Pfingsten Road, Northbrook, IL 60062. ASTM Standards. Publications of the American Society for Testing and Materials can be ordered from ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428. National Fire Codes and other NFPA publications can be ordered from the National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02269-9101. Building codes are issued by three organizations. The southern states use the Standard Building Code published by the Southern Building Code Congress International, Inc. (SBCCI), 900 Montclair Road, Birmingham, AL 35213-1206. The western states use the Uniform Building Code published by the International Conference of Building Officials (ICBO), 5360 Workman Mill Road, Whittier CA 90601-2298. The central and eastern states use the BOCA National Building Code obtainable from Building Officials and Code Administrators International, Inc. (BOCA), 4051 West Flossmoor Road, Country Club Hills, IL 60478-5795. A separate building code, applicable only to one and two family dwellings, is published by the Council of American Building Officials (CABO), 5203 Leesburg Pike, Falls Church, VA 22041, as a joint effort of SBCCI, BOCA, and ICBO and is obtainable from any of them. The International Mechanical Code is published by the International Code Council, Inc., as a joint effort of the BOCA membership. It is intended to be compatible with the requirements of the Standard, Uniform, and National Building Codes and can be obtained from any CABO organization. The International Plumbing Code is also published by the International Code Council as a CABO joint effort and is obtainable from any member organization. The Model Energy Code is published under the auspices of CABO as a joint effort of BOCA, SBCCI, and ICBO with heavy input from the American Society of Heating, Refrigerating, and Air Conditioning Engineers, Inc. (ASHRAE) and the Illuminating Engineering Society of North America (IESNA). Copies are obtainable from any CABO member. ANSI Documents. The American National Standards Institute (ANSI), 11 West 42nd Street, New York, NY 10036, publishes and supplies all American National Standards. The American National Standards Institute also publishes a catalog of all their publications and distributes catalogs of standards published by 38 other ISO member organizations. They also distribute ASTM and ISO standards and English language editions of Japanese Standards, Handbooks, and Materials Data Books. ANSI does not handle publications of the British Standards Institute or the standards organizations in Germany and France. As mentioned previously, there are many organizations that act as sponsors for the standards that ANSI prepares under their consensus format. The sponsors are good sources for information on forthcoming changes in standards and should be consulted by designers wishing to avoid last-minute surprises. Listings in the ANSI catalog will have the acronym for the sponsor given after the ANSI/ symbol. For example, the standard for Letter Designations for Radar Frequency Bands, sponsored by the IEEE as their standard 521, issued in 1984, and revised in 1990, is listed as ANSI/IEEE 521- 1984(R1990). All of one sponsor's listings are grouped under one heading in alphabetical order by organization. The field of interest of each sponsor is usually obvious from the name of the organization. Table 1 is slightly abridged from the full acronym tabulation in the ANSI catalog. Addresses and phone numbers have been obtained from listings in association directories. ANSI does not give that data. [...]... 4.89 0.31 -2 .17 18 98.76 100 .22 4.77 0 .22 -4 .66 19 109.37 100.70 5.07 0.70 1.40 20 94.80 100.41 5.11 0.41 2. 13 21 106.41 100.69 5.15 0.69 2. 90 22 103.53 100. 82 5.06 0. 82 1 .22 23 96 .28 100. 62 5.04 0. 62 0. 72 24 103.70 100.75 4.97 0.75 -0 .64 25 101.99 100.80 4.87 0.80 -2 . 52 26 103.34 100.90 4.80 0.90 -3 . 92 27 1 02. 49 100.96 4. 72 0.96 -5 . 52 28 96.60 100.80 4.71 0.80 -5 .83 29 105.19 100.95 4.70 0.95 -6 .09 30... 101.34 2. 95 1.34 -4 1.05 5 111 .21 103.31 4.75 3.31 -5 .05 6 98.10 1 02. 44 4.75 2. 44 -5 .03 7 100.84 1 02. 21 4.43 2. 21 -1 1.37 8 106.16 1 02. 71 4.35 2. 71 -1 3.08 9 96.33 1 02. 00 4.56 2. 00 -8 .77 10 105.94 1 02. 39 4.49 2. 39 -1 0 .28 11 97.91 101.98 4.47 1.98 -1 0.65 12 98.41 101.69 4.39 1.69 -1 2 .20 13 92. 55 100.98 4.87 0.98 -2 .59 14 1 02. 00 101.06 4.70 1.06 -5 .99 15 100.95 101.05 4.54 1.05 -9 .17 16 91.06 100. 42 5. 02 0. 42. .. Spring, MD 20 9 10 (301) 58 7- 820 2 AISC American Institute of Steel Construction, Inc 1 E Wacker Dr., Chicago, IL 60601 -2 00 1 (3 12) 67 0 -2 400 ANS American Nuclear Society 555 N Kensington Ave., La Grange Park, IL 60 525 (708) 35 2- 6 611 API American Petroleum Institute 1 22 0 L St., N.W., Washington, D.C 20 0 05 (20 2 ) 68 2- 8 000 ARI Air-Conditioning and Refrigeration Institute 4301 N Fairfax Dr., Arlington, VA 2 22 03 (703)... 10017 (21 2) 66 1-4 26 1 CEMA Conveyor Equipment Manufacturers Association 9384-D Forestwood Ln., Manassas, VA 22 110 (703) 33 0-7 079 CGA Compressed Gas Association 1 725 Jefferson Davis Highway, Arlington, VA 2 22 02 -4 100 (703) 41 2- 0 900 CRSI Concrete Reinforcing Steel Institute 933 Plum Grove Rd., Schaumburg, IL 60173 (708) 51 7- 120 0 DHI Door and Hardware Institute 14170 Newbrook Dr., Chantilly, VA 22 02 1 -2 22 3 (703)... Dr., Chantilly, VA 22 02 1 -2 22 3 (703) 22 2 -2 01 0 EIA Electronic Industries Association 25 00 Wilson Blvd., Arlington, VA 2 22 01 (703) 90 7-7 550 FCI Fluid Controls Institute P.O Box 9036, Morristown, NJ 07960 (20 1 ) 82 9-0 990 HI Hydraulic Institute 9 Sylvan Way, Parsippany, NJ 0705 4-3 8 02 (20 1 ) 26 7-9 700 HTI Hand Tools Institute 25 North Broadway, Tarrytown, NY 10591 (914) 33 2- 0 040 ICEA Insulated Cable Engineers... Table 1 Cycle interval × 106 0. 0-0 .5 0. 5-1 .0 1. 0-1 .5 1. 5 -2 .0 2. 0 -2 .5 2. 5-3 .0 3. 0-3 .5 3. 5-4 .0 4. 0-4 .5 4. 5-5 .0 No of failures 1 5 7 4 2 2 1 0 0 1 Cumulative failures 1 6 13 17 19 21 22 22 22 23 Fig 5 Cumulative distribution function for fatigue data from Table 1 based on assumed normal distribution For example, the first rank value in this case can be approximated as (1 - 0.3)/ (23 + 0.4) = 0.030 Each of the... 100.58 100.94 4. 62 0.94 -7 .66 31 100.95 100.94 4.54 0.94 -9 .16 32 99.06 100.88 4.48 0.88 -1 0.35 33 97.86 100.79 4.44 0.79 -1 1.11 34 97. 42 100.69 4. 42 0.69 -1 1.69 35 94.88 100.53 4.46 0.53 -1 0.84 36 103 .26 100.60 4. 42 0.60 -1 1. 62 37 100.51 100.60 4.36 0.60 -1 2. 83 38 110. 72 100.87 4.60 0.87 -8 .08 39 100.18 100.85 4.54 0.85 -9 .24 40 91.76 100. 62 4.70 0. 62 -6 .00 41 110.71 100.87 4.90 0.87 -2 .07 42 95.90 100.75... 0.8599 0.8 621 1.1 0.8643 0.8665 0.8686 0.8708 0.8 729 0.8749 0.8770 0.8790 0.8810 0.8 820 1 .2 0.8849 0.8869 0.8888 0.8907 0.8 925 0.8944 0.89 62 0.8980 0.8997 0.9015 1.3 0.90 32 0.9049 0.9066 0.90 82 0.9099 0.9115 0.9131 0.9147 0.91 62 0.9177 1.4 0.91 92 0. 920 7 0. 922 2 0. 923 6 0. 925 1 0. 926 5 0. 927 9 0. 929 2 0.9306 0.9319 1.5 0.93 32 0.9345 0.9357 0.9370 0.93 82 0.9394 0.9406 0.9418 0.9 429 0.9441 1.6 0.94 52 0.6463 0.9474... Life interval, 106 cycles Number of failures Cycles to failure, 106 cycles 0. 0-0 .5 1 0. 425 0. 5-1 .0 5 0.583, 0.645, 0.77, 0.815, 0.94 1. 0-1 .5 7 1.01, 1.09, 1.11, 1 .21 , 1.30, 1.41, 1.49 1. 5 -2 .0 4 1.61, 1.70, 1.85, 1.97 2. 0 -2 .5 2 2.19, 2. 32 2. 5-3 .0 2 2.65, 2. 99 3. 0-3 .5 1 3. 42 3. 5-4 .0 0 4. 0-4 .5 0 4. 5-5 .0 1 4.66 Total observations 23 The resulting approximate density function for these data is shown in Fig... Washington, D.C 20 0 36 (20 2 ) 46 3 -2 700 NFiPA National Fire Protection Association 1 Batterymarch Park, P.O Box 9101, Quincy, MA 022 6 9-9 101 (617) 77 0-3 000 NFlPA National Fluid Power Association 3333 N Mayfair Rd., Milwaukee, WI 5 322 2- 3 21 9 (414) 77 8-3 344 NISO National Information Standards Organization 4733 Bethesda Ave., Bethesda, MD 20 8 14 (301) 65 4 -2 5 12 NSF National Sanitation Foundation, International 420 1 Wilson . (708) 51 7- 120 0 DHI Door and Hardware Institute. 14170 Newbrook Dr., Chantilly, VA 22 02 1 -2 223 (703) 22 2 -2 01 0 EIA Electronic Industries Association. 25 00 Wilson Blvd., Arlington, VA 2 220 1 (703). Inc. 127 5 K St., N.W., Washington, D.C. 20 0 05 (20 2 ) 37 1- 520 0 TIA Telecommunications Industries Association. 20 0 1 Pennsylvania Ave., N.W., Washington, D.C. 20 0 0 6-4 9 12 (20 2 ) 45 7-4 9 12 Standards. N.W., Washington, D.C. 20 0 01 (20 2 ) 62 4-5 800 AATCC American Association of Textile Chemists and Colorists. P.O. Box 122 15, Research Triangle Park, NC 22 70 9 -2 215 (919) 54 9-8 141 ABMA American