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Engineering is concerned with the creation of systems, devices, and processes useful to, and sought by, society. The process by which these goals are achieved is engineering design.
The process can be characterized as a sequence of events as suggested in Fig. 1. The process may be said to commence upon the recognition of, or the expression of, the need to satisfy some human want or desire, the “goal,” which might range from the detection and destruction of incoming ballistic missiles to a minor kitchen appliance or fastener.
The first obligation of the engineer is to develop more detailed quantitative information which defines the task to be accomplished in order to satisfy the goal, labeled on Fig. 1 as task specification. At this juncture the scope of the problem is defined, and the need for pertinent information is established. Generation of ideas for possible solutions to the problem is the creative stage, called the concept formulation. When great strides in engineering are made, this represents ingenious, innovative, inventive activity; but even in more pedestrian situations where rational and orderly approaches are possible, the conceptual stage is always present. The concept does not represent a solution, but only an idea for a solution. It can only be described in broad, qualitative, frequently graphical terms. Concepts for possible solutions to engineering challenges arise initially as mental images which are recorded first as sketches or notes and then successively tested, refined, organized, and ultimately documented by using standardized formats.
Concepts are accompanied and followed by, sometimes preceded by, acts of evaluation, judgment, and decision. It is in fact this testing of ideas against physical, economic, and functional reality that epitomizes engineering's bridge between the art of innovation and science. The process of analysis is sometimes intuitive and qualitative, but it is often mathematical, quantitative, careful, and precise.
Production considerations can have a profound influence on the design process, especially when high-volume manufacture is anticipated. Evolutionary products manufactured in large numbers, such as the automobile, are tailored to conform with existing production equipment and techniques such as assembly procedures, interchangeability, scheduling, and quality control. New techniques such as those associated with space exploration, where volume production is not a central concern, factor into the engineering design process in a very different fashion.
Similarly, the design process must anticipate and integrate provisions for distribution, maintenance, and ultimate replacement of products. Well-conceived and executed engineering design will encompass the entire product cycle from definition and conception through realization and demise and will give due consideration to all aspects.
Hierarchy of design
An adequate description of the engineering design process must have both general validity and applicability to a wide variety of engineering situations: tasks simple or complex, small- or large-scale, short-range or far-reaching. That is to say, there is a hierarchy of engineering design situations.
Systems engineering occupies one end of the spectrum. The typical goal is very broad, general, and ambitious, and the concepts are concerned with the interrelationships of a variety of subsystems or components which, taken together, make up the system to accomplish the desired goal. See Systems engineering
Time–worker-power resource dynamics
Another dimension of the dynamics of the engineering design process is the elapse of time and expenditure of worker-hours in the evolution of an engineering design project. Figure 2 plots time as the abscissa and resources (worker-power or dollars) as the ordinate. The various stages of the engineering design process are set out in time sequence from left to right.
Goal refinement, task specification, and first-order concept and analyses iterations are conducted by one to a few engineers in the early stages to establish the feasibility of the idea and to block out possible approaches. This is usually called the advanced design stage.
As the design concept becomes more specific and substantive, more and more engineers, technicians, and draftsmen become involved in the project. In projects of significant size, the problem of coordinating and integrating the efforts of the many participants of different talents and skills becomes itself a major consideration. See PERT
Use of the computer in design
The use of the computer, both analog and digital, in the engineering design process has increased. Where economically justified, the overall engineering design process for a product is mechanized via computer programming. See Computer, Computer-aided design and manufacturing, Computer storage technology, Multiaccess computer
The speed, memory, and accuracy of the computer to iteratively calculate, store, sort, collate, and tabulate have greatly enhanced its use in design and encouraged the study, on their own merits, of the processes and subprocesses exercised in the design process. These include optimization or sensitivity analysis, reliability analysis, and simulation as well as design theory. See Digital computer
Optimization analyses, given a model of the design and using linear and nonlinear programming, determines the best values of the parameters consistent with stated criteria and futher studies the effects of variations in the values of the parameters.
Reliability is a special case of optimization where the emphasis is to choose or evaluate a system so as to maximize its probability of successful operation, for example, the reliability of electronics. See Circuit (electronics)
Simulation, as of dynamic systems, is mathematical modeling to study the response of a design to various inputs and disturbances. The analog computer has been widely used for simulation through its physical modeling of the mathematic analytical relationships of the proposed design. See Analog computer, Simulation
Decision theory deals with the general question of how to choose between a great number of alternatives according to established criteria. It proposes models of the decision process as well as defining techniques, that is, programs or algorithms, of calculation by which to make choices.
In many fields of design—notably architecture; design of airplanes, automobiles, and ships; and almost all mechanical design—the designer works largely in visual terms. A way has been found to set up the computer to interpret drawings. Moreover, the computer has become an active partner in the act of drawing, so that it can provide a certain superskill in preparing the drawing once the human operator has made intentions clear. See Computer graphics
the process of creating a design that is an original representation, that is, a prototype, for a proposed object or system.
Various design phases and stages are distinguished, each with a specific character. The subject area of engineering design is constantly expanding. In addition to traditional areas—architecture, civil engineering, machine building, and production process design—new independent design specializations have appeared. Examples include the designing of systems with a man-machine interface, such as decision-making, recognition, heuristic, forecasting, planning, and control systems; planning in labor processes and organizations; ecological, social, and industrial-psychology planning; and genetic engineering. In addition to this differentiation, there is a tendency toward integration in the design process based on the discovery of general regularities and methods.
I. I. LIAKHOV
Design in construction and technology. Design in construction and technology involves the development of design and other engineering plans for executing capital construction work or for development of new product models and prototypes. The design process includes the preparation of engineering and economic calculations, charts, graphs, explanatory notes, scale models, specifications, estimates, and reports; the detailed project report is a specified set of the said plans and documents. A detailed project report for capital construction of a project (enterprise, building, or structure) may be unique or standardized. Standardized structural and architectural members and assembly parts, as well as standard patterns of their arrangement, are widely incorporated in the development of unique designs.
In all branches of industry, the design of new models and prototypes of machines, equipment, and other devices involves the development of initial data necessary for the production and operation of a product (blue prints, lists of parts, specifications, instructions for assembly and adjustment, operation manuals and other documents). Such design also involves a wide use of standardized parts, modules, and subassemblies.
In the USSR, the procedure of development, examination, and approval of designs and detailed project reports is determined by government decrees, State Standards (GOST), and other norms. Designing is carried out by state design organizations, which may serve particular branches of industry or work in some specialized, narrower field. An industry’s design office, which develops the engineering part of the design, is usually the prime contractor and may delegate part of a job to specialized organizations (subcontractors) when necessary in order to complete individual sections of the design. The client, such as a ministry, department, or enterprise, sets the design assignment, including the design goal, construction site, list of products to be manufactured, output capacity for the completed design, and other construction data and conditions. This is done in collaboration with the design organization concerned. Engineering surveys for construction are made to obtain the needed data for practical engineering and economic solutions of the principal design, construction and operational problems.
A design for the construction or reconstruction of an industrial enterprise, building, or structure may be carried out in two stages (the detailed project report and the working blueprints) or in one stage (contract design). The detailed project report contains solutions to the fundamental problems of organization, technology, and production economics, architectural and structural decisions concerning the buildings and structures, construction cost estimates, and the specifications for cost effectiveness of the project. In developing the working blueprints, the solutions specified by the detailed project report are detailed and refined to the extent required for construction and erection work. Single-stage designing is preferable for projects that are to be constructed according to standardized plans and for technically simple projects; the same problems are resolved as in two-stage designing. The procedure of examination and approval of designs depends on the cost estimates.
The development stages are the design assignment, or a preliminary design, the detailed project report, and, finally, the detail design. The agency responsible for developing new product models and prototypes for industry and the contents of the design documentations. This is done on the basis of the state-of-art in science and technology, product demand on the part of the national economy or the consumer, and export demands. The project specifications are approved by the client—the principal user of the product. As a rule, the blueprints and other designs for industrial products, including structural members, are completed by design project offices of the manufacturers. Research and development work associated with the testing of various engineering solutions is carried out during the development of new production models and prototypes. Extensive use is made to the utmost reasonable degree of office machines and computers, which save time, improve design quality, and increase the labor productivity of planners and designers.
In May 1964, the All-Union Conference of Workers in Design and Engineering-Survey Organizations adopted recommendations for the further improvement of design-estimate work, paying particular attention to the need for development of the technical and economic bases of design and construction. In view of this, a shift to mainly single-stage designing is predicted.
In other socialist countries, engineering design is based on Soviet practice, particularly with regard to the planning and organization of design work, regulation of stages in the development of the design, the procedure of review and approval, and the use of standardized designs. Two-stage and three-stage design methods are used, with particular attention given to pre-characteristics study. In many cases, execution of the working blueprints is begun before completion of the second design stage.
In developed capitalist countries, engineering design is handled mainly by private firms and independent architects and engineers. As a rule, design staging is not fixed, and deadlines for the completion of designs are determined by agreement between the client and the architect or engineer. In the first design stage, the analysis phase, the project’s range and production volume, production technology, and general economic factors are determined, markets are researched for the sale of the finished products, and the designs for the engineering of the buildings and structures are proposed. In the second phase, preliminary design is developed, in which the proposed solutions are sufficiently specified so that estimates of construction costs can be made. Often the designing or parts of it is done on a competitive basis; that is, there is bidding for contracts. The company designated to perform the construction as a result of the bidding signs a contract and completes the design by preparing the working blueprints; it may either use its own resources or retain an engineering design firm for this purpose.
Design is the most important link in the technological progress that connects science with production. The results of research and the achievements of advanced technology are incorporated directly into designs. The rate of technological progress depends to a large extent on the quality of design. In the interest of accelerating such progress, design projects in the USSR are developed in accordance with fundamental engineering design guidelines established by ministries and departments, based on the prospects of future development of science and technology. Advanced production processes, highly productive equipment, the most advanced means of mechanization, automated control systems, new and efficient construction materials, and light-weight structural elements are called for in designs for enterprises and structures.
Special attention should be devoted to the accurate determination of construction cost estimates. New models of industrial products are developed in accordance with scientific forecasts and the necessity of lowering the consumption of labor and materials while providing durability and reliability. New models of machines and equipment must meet the highest quality standards. Further upgrading of the engineering design level and shortening of the design development time will facilitate the rapid introduction of new production facilities, the creation of new instruments of labor and materials, increased labor productivity, and more efficient public production.
REFERENCESMaterialy XXIV s”ezda KPSS. Moscow, 1971.
“Ob uluchshenii proektno-smetnogo dela. Post. TsK KPSS i Soveta Ministrov SSSR.” Pravda, June 22, 1969.
Gosstroi SSSR: Vremennaia instruktsiia po razrabotke proektov i smet dlia promyshlennogo stroitel’stva SN 202-69. Moscow, 1969.
Girovskii, V. F., M. L. Razu, and R. Z. Alaverdov. Ekonomika, organizalsiia i planirovanie proektnykh rabot. Moscow, 1972.
Ekonomika stroitel’stva. Edited by P. D. Podshivalenko. Moscow, 1973.
Razrabotka i postanovka produktsii na proizvodstvo: Osnovnye polozheniia: GOST 15001–73. Moscow, 1974.
Bartashev, L. V. Tekhniko-ekonomicheskie raschety pri proektirovanii i proizvodstve mashin. 2nd ed. Moscow, 1968.
Sergeev, N. D., and A. I. Bogatyrev. Problemy optimal’nogo proektirovaniia konstruktsii. Leningrad, 1971.
Orlov, P. I. Osnovy konstruirovaniia, book 2. Moscow, 1972.
Kogut, A. E., and V. I. Novozhilov. Vybor ekonomichnykh parametrov mashin pri konstruirovanii. Leningrad, 1974.
L. L. KESLER
Design automation. Design automation is the use of computers, general-purpose and specialized software, automatic devices, and office equipment that are organized in an automated design system with a man-machine interface; the system is used for designing machinery, ships, control systems, structures, and industrial and computer systems. Unlike nonautomated design, the results of which are restricted in many respects by the engineering training of the personnel involved and their practical experience and professional intuition, automated design eliminates subjectivity in decision-making and significantly increases the accuracy of calculations. It can select the best design variants for production based on strict mathematical analysis and evaluation of the technological, engineering, and economic factors in the production and operation of the object or project. It substantially raises the quality of the design documentation while reducing the design period and the time needed to deliver the design documentation to the manufacturers. It also utilizes program-controlled equipment more effectively. Design automation allows for greater use of standardized products as a project’s components.
The methods and means of design automation vary, depending on the nature and purpose of the object designed. The most tangible results are obtained in the automated design of intricate engineering systems and structures and in the preparation of design documentation for program-controlled actuators. Thus, for example, in designing a computer, automated design systems are used to determine the computer structure, the technical parameters and structural and functional format of the devices incorporated in the computer, the circuiting and wiring diagrams for subassemblies, and elements to optimize performance and to calculate reliability. Through the use of graph-plotting devices, printers, and other data-output devices, the design results are automatically presented in document form on sheets of drafting paper, punch cards, magnetic tape, microfilms, and microfiches, either in the form of a schematic diagram or a blueprint of the product or structure or a graph or table on the screen of a data display device.
In the automated design of machinery and mechanisms, automated design systems use initial data to determine the best product configuration, rate and calculate the individual components and the assembly as a whole, optimize tolerances and fit, determine shapes for conjugated surfaces and their smoothness, and select the necessary materials. The initial data used include the specifications of the product, the operating conditions for the product’s assemblies and links, the forces acting on the unit, the weight of the workpieces, and the type of material used. The Institute of Cybernetics of the Academy of Sciences of the Byelorussian SSR has developed an “automatic draftsman” that produces extremely precise blueprints of pieces with complex shapes, such as ship propellers, aircraft wings, and hydroturbine runner vanes.
Of particular importance is the automated design of flow sheets, particularly for program-controlled machine tools. In this case, data concerning the machining of the product, usually contained in the blueprints, are coded and translated into a machine language for processing in a computer. Using these data, the computer compiles a program for the machining process according to the design’s algorithm; the program is recorded in the computer’s data carrier for direct input into the machine-tool control unit. Special algorithmic languages, such as Tekhnol, Geometr-66, and SAP-2, have been developed in the USSR for this type of design automation.
Design automation is of prime importance in civil engineering. The automated design system helps project designers to conduct engineering surveys efficiently, evaluate the geologic and climatic features of the construction site more fully, compile the project plans more quickly, and optimize construction scheduling. Use of a computer is often the only way to solve many problems that arise in the designing of high-rise structures, dams for hydroelectric power plants, bridges, and structural elements.
Design automation is one of the trends in the automation of production, which embraces practically all branches of the national economy. All major design organizations have their own computer centers available in their particular industries. By freeing man from complicated and time-consuming calculations and the compilation of numerous charts and tables, automation of design paves the way for the discovery of new design methods.
REFERENCESVychislitel’naia tekhnika v mashinostroenii: Sb. st. Minsk, 1967.
Primenenie vychislitel’nykh mashin dlia proektorovaniia tsifrovykh ustroistv: Sb. st. Moscow, 1968.
Avtomatizatsiia v proektirovannii: Sb. st. Moscow, 1972. (Translated from English.)
“Mashinnoe proektirovanie.” Elektronnaia promyshlennost’, 1972, issue 2(8).
G. I. BELOV and A. N. NAGOLKIN