Program studi teknik mesin fakultas teknik universitas udayana
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- PROGRAM STUDI TEKNIK MESIN FAKULTAS TEKNIK UNIVERSITAS UDAYANA THE NATURE OF ENGINEERING DESIGN
- Forced Relationship Technique
- Other Evaluation Techniques
I Ketut Gede Arya Pratama
The problems have grown exceedingly in complexity and diversity. At the same time, advancements in technology have greatly expanded the ability of engineers to improve the comfort and well-being of the people they serve. With advancements in technological knowledge have come more formal institutions and procedures for the transfer of knowledge. Modern engineers must gain experience.
Engineering teams may be used as simply a means of dividing up the workload. Similarly-trained engineers may be assigned specific design tasks by an engineering manager. When complex problems are faced, it may be desirable to establish a nontraditional organizational structure in which team members have a dual reporting relationship to a functional manager or administrative supervisor as well as to a team leader. The design of an industrial plant, for example, may require the knowledge and skills of several types of engineers: industrial, chemical, civil, mechanical, and electrical. Members from each of the specialties could be assigned to a task force.
THE ENGINEERING METHOD
The nature of problems that must be solved by engineers varies both between and among the various branches of engineering. Indeed, an individual engineer may face a variety of problems during the course of his or her daily work activities.
A number of engineering writers have set forth a list of steps or phases that comprise the “engineering design method.” Typically, the list includes:
Identification of the problem.
There is a tendency to think that this phase of the solution process is trivial and unimportant. Such is not the case. An incorrect or improper definition of the problem will cause the engineer to waste time and may lead to a solution that is inappropriate or incorrect.
Gathering needed information.
Once the problem is identified and the needs properly defined, the engineer then begins to gather information and data needed to solve it. The type of information needed will, of course, depend on the nature of the problem to besolved. It could be physical measurements, maps, results of laboratory experiments, patents, results of opinion surveys, or any of a number of other types of information.
Searching for creative solutions.
After completing the preparatory steps in the design process, the engineer is ready to begin identifying creative solutions. Actually, the development of new ideas, products, or devices may result from creativity, a subconscious effort, or from innovation, a conscious effort.
Typically, a brainstorming session consists of 6 to 12 people who spontaneously introduce ideas designed to solve a specific problem. In these sessions, all ideas are encouraged, including those that appear to be completely impractical. Efforts are made to generate as many ideas as possible.
The checklist encourages the user to examine various points, areas, and design possibilities.For example, suppose that you were attempting to improve a certain device. You might make a checklist that includes:
Ways the device could be put to other uses.
Ways the device could be modified.
Ways the device could be rearranged.
Ways the device could be magnified.
Ways the device could be lessened, and so on.
Another technique that can be used by individuals to produce original problemsolving ideas is attribute listing. With this technique, all of the major characteristics or attributes of a product, object, or idea are isolated and listed. Then, for each attribute, ideas are listed as to how each of the attributes could be changed. Every idea is listed.
Forced Relationship Technique
Another group of operational techniques that individuals may use to generate ideas is known as forced relationship techniques. That is, such techniques force a relationship between two or more normally unrelated ideas or products to begin the idea-generating process
An operational technique for idea generation attributed to Fritz Zwicky involves listing every conceivable theoretical solution. This technique consists of first defining the problem in terms of its dimensions or parameters and devising a model that enables one to visualize every possible solution.
Stepping from ideation to preliminary designs (including modeling).
The engineer is now ready to move from ideation to preliminary designs. This is the heart of the design process, and it is the phase that relies most on experience and engineering judgment. Here, unworkable ideas are discarded, and promising ideas are molded and modified to form workable plans and designs. This step may require many decisions to be made about alternative layouts, configurations, materials, dimensions, and other specifications. Conceptual sketches may need to be drawn; preliminary plans may need to be prepared and thought may need to be given to material specifications.
In addition, three types of model are commonly used to facilitate the solution of engineering problems:
Analytical or mathematical models.
A mathematical model consists of one equation or a group of equations that represents a physical system.
where p=wind pressure expressed in pounds per square foot
K=a factor that depends principally on the shape of the structure
V= the wind velocity expressed in miles per hour
When studying complex systems, engineers often employ computer simulation
models. Such a model may incorporate empirically based mathematical models
as components of the total model.
Physical models have long been used by engineers to gain a better understanding of complex phenomena. Such models probably constitute the oldest method of structural design. Physical models have also been used for many years in the fields of hydraulics, hydrodynamics, and aerodynamics. Examples of studies made with physical models include:
Dispersion of pollutants throughout a lake.
Behavior of waves within a harbor.
The underwater performance of submarines of different shapes.
Evaluation and selection of preferred solution.
As the engineering design process evolves, the engineer may evaluate again and again alternate ways of solving the problem at hand. Typically, the engineer winnows the unpromising design choices, yielding a progressively smaller set of options. Feedback, modification, and evaluation may occur repetitively as the device or system evolves from concept to final design. There are many indirect methods for evaluating a proposed design. Such evaluations have traditionally relied on economic analysis, but recent concerns with social and environmental impacts of public projects have produced much broader evaluation techniques. Let us now examine some of these formal evaluation techniques.
For at least 50 years, economic analyses have been used by engineers as a decision-making tool for the building of dams, bridges, highways, and other public works.
Economic studies may be used:
To determine the feasibility of a project.
To compare alternate designs.
To determine the priority of construction of a group of projects.
To evaluate specific features of design.
where I = the interest rate or discount rate per period
n = the number of interest periods, usually years
Other Evaluation Techniques
Over the past several years, there has been increasing awareness of the impact that engineering works may have on people and the environment. Such projects may cause families and businesses to be relocated and subject citizens to noise and water and air pollution.
Suppose that a city considering a new mass transit system has established the following objectives for the system:
The system should provide economy.
There should be minimum disruption of individuals by relocation.
The system should provide a high level of comfort and convenience.
The central area should be highly accessible.
The system should be accessible to low-income areas.
The following criteria were selected to provide a measure of each objective:
Number of persons relocated.
Load factor on transit vehicles in peak hour.
Accessibility index of core areas.
Transit accessibility index to low-income traffic zones.
Preparation of reports, plans, and specifications.
After the preferred design has been selected, it must be communicated to those who must approve it, support it, and translate it into reality. This communication may take the form of an engineering report or a set of plans and specifications. Engineering reports are usually directed to a client or to a supervisor (e.g., if the engineer is employed by a large corporation).
Implementation of the design.
It could be argued that once the plans, specifications, and engineering reports have been completed, the design process is finished. Actually, however, the final phase of the design process is implementation, the process of producing or constructing a physical device, product, or system. Engineers must plan and oversee the production of the devices or products and supervise the construction of the engineered projects. This is the culmination of the design process; to the design engineer, it is the most satisfying phase of all.
It is not uncommon for the work of an engineer to be of such value that it should be protected from exploitation by others. This may be accomplished by patenting.
In order for an invention to be patentable it must be new as defined in the patent law. The law states that an invention cannot be patented if:
The invention was known or used by others in this country, or patented or described in a printed publication of this or a foreign country, before the invention thereof by the applicant for patent, or
The invention was patented or described in a printed publication in this or a foreign country or in public use or on sale in this country more than one year prior to the application for patent in the United States
To apply for a patent, the inventor must submit an application which includes:
A specification, a clear, concise, and exact description of the invention presented in such manner as to distinguish it from other older inventions.
An oath or declaration made by the inventor asserting the belief that he or she is the original and first inventor of the subject matter of the application.
A filing fee. Reference 10 gives a schedule of fees, beginning with a basic fee of $630.
A drawing prepared to Patent Office specifications whenever the nature of the case requires such to understand the invention.
In this relatively brief span of time, the use of computer-based tools for engineering problem solving has become commonplace. These tools are variously referred to as computer-aided engineering (CAE), computer-aided design (CAD), or computeraided design and manufacturing (CAD/CAM). With CAD systems, interactive graphics allow the user to communicate easily with the computer in display-screen pictures. With the speed of modern computers, this communication is carried out in real time; that is, the computer’s response is practically instantaneous. Furthermore, little knowledge of computers is required to operate these user-friendly systems.
Learning from Failures
Despite the best efforts of engineering designers, their designs occasionally fail. Bridges collapse, roofs of buildings cave in, and earthen dams fail, threatening human lives and causing millions of dollars of damage to property.
Engineering failures may be attributed to a wide variety of causes, including:
Mistakes made by inept or careless designers.
Imperfections in building or manufacturing materials and uncertainties as to their variability.
Careless workmanship by technicians or craftsmen who implement the design.
Poor communications between the managers, engineers, technicians, and craftsmen who produce or construct the engineered design.
When an engineering failure occurs, it is usually important that an investigation be conducted to determine the cause of the failure and to identify remedial actions that can be taken to prevent or lessen the likelihood of a reoccurrence. Such investigations may be carried out by:
Government agencies or boards.
Private or professional associations.
Ad hoc committees or commissions.
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