Chapter Three Engineering Design Process

What is Design ?

WHAT IS DESIGN: 'Design is the decision making process by which an idea is transformed into an outcome” ( product or service)

Engineering Design Process

Group Assignment You have been asked to carry 100 student to attend activity in Muscat with maximum cost not more than 350 RO. Now you will contract with travel agent to carry the students. The travel agent offer you tow type of buses. The 1st type is 30 passengers which cost 100 RO/bus, and 2nd type of buses is 10 passengers which cost 40 RO/bus. You have to decide the minimum number of buses you need.

3.3 Engineering Economics Economic factor always play important role in engineering design decision making. If you design a product that is too expensive to manufacture, then it can not be sold at a price that consumers can afford and still be profitable to your company. The fact is that companies design products and provide services not only to make our lives better but also to make money. 13 13

3.4 Material Selection As design engineers, whether you are designing a machine part, a toy, or frame for car or a structure, the selection of materials is an important design decision. There are a number of factors that engineers consider when selecting a material for a specific application. For example, they consider the properties of materials such as density, ultimate strength, flexibility, machinability, durability, thermal expansion, electrical and thermal conductivity, and resistance to corrosion. They also consider the cost of the material and how easily it can be repaired. Engineers are always searching for ways to use advanced materials to make products lighter and stronger for different applications. 14 14

3.5 Teamwork A design team may be defined as a group of individuals with complementary expertise, problem solver skills, and talent who are working together to solve a problem or achieve a common goal. The goal might be providing a service; designing, developing, and manufacturing a product; or improving an existing services or product. A good team is one that gets the best out of each other. Communication is an essential part of successful teamwork.

3.6 Common Traits of Good Teams Successful teams have the following components: The project that is assigned to a team must have clear and realistic goals. These goals must be understood and accepted by all members of the team. The team should be made up of individuals with complementary expertise, problem solving skills, background, and talent. The team must have a good leader. The team leadership and the environment in which discussion take place should promote openness, respect, and honesty. Team needs and goals should come before individual needs and goals.

3.7 Conflict Resolution When group of people work together conflict sometimes arise. Conflicts could be the result of miscommunication, personality differences, or the way events and actions are interpreted by a member of a team. Those in a team who try to avoid conflicts, it demonstrate low assertiveness and a low level of cooperation. Under these conditions, the person who is assertive will dominate, make progress as whole difficult. Accommodating team members are highly cooperative, but their low assertiveness could result in poor team decision. Compromising team members demonstrate a moderate level of assertiveness and cooperation.

3.7 Conflict Resolution A better approach is the collaborative “conflict resolution” approach, which demonstrates a high level of assertiveness and cooperation by the team. With this approach, the conflict is treated as a problem to be solved by the team. Good communication is an integral part of any conflict resolution. Team member must listen to each other. Good listeners do not interrupt; they allow the speaker to feel at ease and do not get angry or criticize.

3.8 Project Scheduling and Task Chart Project scheduling is a process that engineering managers use to ensure that a project is completed on time and within the allocated budget. A good schedule will assign an adequate amount of time for various project activities. It will also make use of personnel and the available resources for planning, organizing, and controlling the completion of the project. A well planned schedule could also improve the efficiency of the operation and eliminate redundancy in task assignments. See Example Next Page

3.8 Project Scheduling and Task Chart

3.9 Evaluating Alternatives Once you have narrowed down your design to a few workable concepts, it is customary to use an evaluation table similar to the one shown in the next page. You start by assigning a level of importance (I) to each design criterion. For example, you may use a scale of 1 to 5., with I=1 indicating little importance, and I=5 extremely important . Next you will rate ® each workable concept in terms of how well it meets each design criterion. You may a scale of R=3 for high, R=2 and R=1 for medium and low, respectively. The design criteria vary depending on a project. (See Table 3.4 page 56)

3.11 Engineering Standards and Codes Standards and codes have been developed over the years by various organizations to ensure: a)product safety and reliability in services, such as: 1-safe food supplies, 2-safe structures, 3-safe water systems, 4-safe and reliable electrical systems, 5-safe and reliable transportation systems, b) uniformity in the size of parts and components that are made by various manufacturers around the world to ensure that parts manufactured in one place can easily be combined with parts made in other places

Examples of Standards and Codes Organizations in the United States 1-The American National Standards Institute (ANSI) The American National Standards Institute (ANSI) was founded in 1918 by five engineering societies and three government agencies to administer and coordinate standards in the United States. The ANSI is supported by various public and private organizations. The institute itself does not develop the standards, but instead it assists qualified groups, such as various engineering organizations, with the development of the standards and sets the procedures to be followed.

2-The American Society for Testing and Materials-ASTM Founded in 1898 The ASTM publishes standards and test procedures that are considered authoritative technical guidelines for product safety, reliability, and uniformity. Testing is performed by its national and international member laboratories. The ASTM collects and publishes the work of over 100 standards-writing committees dealing with material test methods. For example, 1-ASTM sets the standard procedures for tests and practices to determine elastic properties of materials, (Mechanical properties) such as: impact testing, shear and torsion properties, bend and flexure testing, compression, ductility, and thermal expansion. 2-ASTM also sets the standards for medical devices and equipment, including bone cements, screws, bolts, pins, prostheses, and plates, and specifications for alloys used in surgical implants. Electrical insulation etc

3-Additional examples of ASTM work include the following: Test guidelines for evaluating mechanical properties of silicon or other procedures for testing semiconductors, such as germanium dioxide. • Testing methods for trace metallic impurities in electronic-grade aluminum- copper and aluminum-silicon. • Standards related to the chemical analysis of paints along with tests to measure the physical properties of applied paint films, such as film thickness, physical strength, and resistance to environmental • Standard procedures for evaluating properties of motor, diesel, and aviation fuels, crude petroleum, hydraulic fluids, and electric insulating oils. • Test procedures for measurements of insulation properties of materials. • Standard procedures for soil testing, such as density characteristics, soil texture, and moisture content. • Building-construction-related tests and procedures, such as measuring the structural performance of sheet metal roofs. • Tests for evaluating the properties of textile fibers, including cotton & wool • Standards for steel piping, tubing, and fittings.

Examples of International Standards and Codes: 1-The International Organization for Standardization (ISO) Established in 1947, consists of a federation of national standards from various countries. The International Organization for Standardization promotes and develops standards that can be used by all countries in the world, with the objective of facilitating standards that allow for free, safe exchange of goods, products, and services among countries. 2-CЄ Standards All products sold in Europe must now comply with C Є standards. C Є provides a single set of safety and environmental standards that is used throughout Europe. The C Є marking on a product ensures conformity to European standards.

Other Internationally Recognized Standardization Organizations 1-The British Standards Institute (BSI) is another internationally known organization that deals with standardization. In fact, BSI, founded in 1901, is one of the oldest standardization bodies that organizes and distributes British, European, and International standards. 2- the German Deutsches Institut für Normung (DIN), 3-the French Association Française denormalisation (AFNOR), 4-The Swedish Standardiserigen I Sverige (SIS), 5-the China State Bureau of Quality and Technical Supervision (CSBTS). Visit the Web sites of these organizations to obtain more information about them. Searching for information about organizations dealing with engineering standards and codes as example: American Institute of Chemical Engineers (www.aiche.org), The American Society of Agricultural and Biological Engineers (www.asae.org), American Society of Civil Engineers (www.asce.org)