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What is design? 이대길 KAIST 기계공학과 교수 한국과학기술한림원 정회원 한국복합재료학회 부회장

What is design? 이대길 KAIST 기계공학과 교수 한국과학기술한림원 정회원 한국복합재료학회 부회장. Contents:. Normal design processes Motorola’s 6 s Program 3. Axiomatic design process. Normal design processes. Ref. J. E. Shigley, C. R. Mischke and R. G. Budynas, Mechanical Engineering Design , 7th Edition,

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What is design? 이대길 KAIST 기계공학과 교수 한국과학기술한림원 정회원 한국복합재료학회 부회장

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  1. What is design? 이대길 KAIST 기계공학과 교수 한국과학기술한림원 정회원 한국복합재료학회 부회장

  2. Contents: • Normal design processes • Motorola’s 6s Program • 3. Axiomaticdesign process

  3. Normal design processes Ref. J. E. Shigley, C. R. Mischke and R. G. Budynas, Mechanical Engineering Design, 7th Edition, McGraw Hill, 2003

  4. What is engineering? Engineering= Design + Manufacturing

  5. What is design? Design is an interplay between what we want to achieve and how we want to achieve it.

  6. What is design? The designers (mechanical engineer, electrical engineer, mayor, CEO, etc) must do the following. 1. Know or understand their customers’ needs. 2. Define the problem they must solve to satisfy the needs. 3. Conceptualize the solution through synthesis. 4. Perform analysis to optimize the proposed solution (Adequacy assessment). 5. Check the resulting design solution to see if it meets the original customer needs.

  7. What is design?

  8. Adequacy of Design • Design product should be • Functional: satisfy the intended need and customer expectation. 2. Safe: not hazardous to the user, bystanders, or surrounding property with appropriate directions or warnings provided. 3. Reliable: perform its intended function satisfactorily or without failure at a given age. 4. Competitive: product survival.

  9. Adequacy of Design-continued Design product should be 5. Usable: user friendly product. 6. Manufacturable: suited to mass production with a minimum number of parts (or information). 7. Marketable: purchasable with repair available.

  10. Interaction between Design Process Elements 1. Functionality 2. Strength/stress 3. Distortion/deflection/stiffness. 4. Wear 5. Corrosion 6. Safety 7. Reliability 8. Manufacturability 9. Utility (electricity, gas. etc) 10. Cost 11. Friction 12. Weight 13. Life 14. Noise 15. Styling 16. Shape 17. Size 18. Control 19. Thermal Properties 20. Surface 21. Lubrication 22. Marketability 23. Maintenance 24. Volume 25. Liability 26. Remanufacturing/resource recovery

  11. Design Tools and Resources • Computational Tools • CAD (Computer-aided design) software: Aries, AutoCAD, CadKey, I-deas/Unigraphics, ProEngineer, etc. • CAE (Computer-aided engineering): Finite element analysis/method (FEA or FEM): Algor, ANSYS, MSC/NASTRAN, ABAQUS, etc. Computational fluid dynamics: CFD++, FIDAP, Fluent, etc. Dynamic force and motion in mechanics: ADAMS, DADS, Working Model, etc. • Acquiring Technical Information Libraries, Government sources, Professional societies, commercial vendors, internet and TRIZ.

  12. Satisfy the needs of customers (management, clients, consumers, etc.). Communicate your ideas clearly and concisely, or your technical proficiency may be compromised. The design engineer’s professional obligations include conducting activities in an ethical manner. (There’s no engineers in the hell). Engineer’s Creed from the National Society of Professional Engineers (NSPE). Design Engineer’s Professional Responsibilities

  13. Standard: a set of specifications for parts, materials, or processes intended to achieve uniformity, efficiency, and a specified quality. • Code: a set of specifications for the analysis, design, manufacture, and construction of something. All of the organizations and societies have established specifications for standards and safety or design codes. AA, AGMA, AISC, AISI, ANSI, ASM, ASME, ASTM, AWS, ABMA, BSI, IFI, I. Mech. E., BIPM, ISO , NIST, SAE, JIS, DIN Codes andStandards

  14. Standard sizes Large tolerances Breakeven points Cost estimates (cost per weight, number of parts, area, volume, horsepower, torque, capacity, speed and various performance ratios). Economics

  15. The strict liability concept of product liability generally prevails in the United States. The manufacturer of an article is liable for any damage or harm that results because of a defect. It does not matter whether the manufacturer knew about the defect, or even could have known about it. Safety and Product Liability

  16. Reliability The reliability method of design is one in which we obtain the distributions of stresses and the distribution of strengths and then relate these two in order to achieve an acceptable success rate.

  17. Reliability Should an automotive engineer increase the cost per car by 10,000 Won in order to avoid 100 failures in a production run of a million cars, where the failure would not involve safety, but would entail a 100,000 Won repair?

  18. Reliability Should 10 billion Won be spent to save 10 million Won plus some customer inconvenience? 6s=1/109

  19. 2. Motorola’s 6s Program

  20. 2. Motorola’s 6 s Program • The 6s quality is a phrase made famous by Motorola once it decided to refocus on quality in the late 1970s and early 1980s. • It is a quality assurance program that has the goal of reducing the defective parts in a bath to as low as 3.4 parts per million (106). • A rigorous interpretation of 6 s is really 2 defects per billion parts (109) made. • If we consider each side of center, then 6.8 components per million will lie in the tails with 3.4 on each side.

  21. Motorola’s 6 s Program

  22. Motorola’s 6 s Program • When the center of the normal distribution curve drifts by 1.5 s to the right, and is viewed still window, there will be virtually no defects in the left-side tail but a rather large number in the right-side tail (1350 parts per million). • If we view with the window of , the right tail contains 3.4 parts per million, with negligible number of parts in the left signal. • There is an infinite combination of “ms offset plus ns viewing window” for quality performance of 3.4 parts per million. • The number of 3.4 parts per million is used as the bench mark rather than the rigorous definition of 6s.

  23. Calculations and Significant Figures • Usually three or four significant figures are necessary for engineering accuracy. • Make all calculations to the greatest accuracy possible and reports the results within the accuracy of the given input.

  24. Calculations and Significant Figures • To display 706 to four significant figures: 706.0, 7.060ⅹ102, 0.7060ⅹ103 • To display 91600 to four significant figures: 91.60ⅹ103 • When d=0.40 in pd=3.1(0.40)=1.24in=1.2 in pd=3.141592(0.40)=1.256in=1.3 in

  25. 3. Axiomaticdesign process

  26. Introduction to Axiomatic Design • References: • Dai Gil Lee and Nam P. Suh, Axiomatic Design and Fabrication of Composite Structures, Oxford University Press, August, 2005. • 2. Nam P. Suh, Axiomatic Design, Oxford University Press, 2000. • 3. Nam P. Suh, The Principles of Design, Oxford University Press, 1990.

  27. Introduction to Axiomatic Design • ▪ There are several key concepts that are fundamental to axiomatic design. • ▪ They are the existence of domains, mapping, axioms, and decomposition by zigzagging between the domains, theorems, and corollaries.

  28. Introduction to Axiomatic Design

  29. Key Concepts of Axiomatic Design Theory • ▪ The customer domain is characterized by the needs (or • attributes) that the customer is looking for in a product • or process or system or material. • ▪ In the functional domain, the customer needs are • specified in terms of functional requirements (FRs) and • constraints (Cs). • ▪ In order to satisfy the specified FRs, we conceive design • parameters (DPs) in the physical domain. • ▪ Finally, to produce the product specified in terms of DPs, • we develop a process that is characterized by process • variables(PVs) in the process domain.

  30. Key Concepts of Axiomatic Design Theory • Once we identify and define the perceived customer needs, these needs must be translated to FRs. • This must be done within a "solution-neutral environment." without ever thinking about existing products or what has been already designed or what the design solution should be (Japanese method). • Often designers and engineers identify solutions first by looking at existing materials or products before they define FRs, which leads to a description of what exists rather what is needed.

  31. TWO AXIOMS Axiom 1: The Independence Axiom Maintain the independence of the functional requirements (FRs). Axiom 2: The Information Axiom Minimize the information content of the design.

  32. 1.3Key Concepts of Axiomatic Design Theory • Independence Axiom: • FRs are defined asthe minimum set of independent requirements that characterize the design goals. • ▪ Information Axiom: • The design that has the smallest information content is the best design.

  33. Knob Design for a Shaft FR1=Grasp the end of the shaft tightly with axial force of 30 N FR2=Turn the shaft by applying 15 N-m of torque DP1=Interference fit between the shaft and the inside diameter of the knob DP2=The flat surface

  34. Knob Design for a Shaft FR1=Grasp the end of the shaft tightly with axial force of 30 N FR2=Turn the shaft by applying 15 N-m of torque DP1=Interference fit between the shaft and the inside diameter of the knob DP2=The flat surface

  35. Probability density Target Bias System pdf Design range Area within common range (Acr) Variation from the peak value

  36. 1.3Key Concepts of Axiomatic Design Theory • Information content Ii for a given FRi is defined • in terms of the probability Pi of satisfying FRi. (1.6) • The probability is determined by the overlap between the design range and the system range.

  37. Key Concepts of Axiomatic Design Theory • ▪ The design that has the highest probability of • success is the best design. • ▪ In an ideal design, the information content should • be zero to satisfy the FR every time and all the • time. • ▪ The design goals are often subject to constraints • (Cs). Constraints provide bounds on the • acceptable design solutions and differ from the • FRs in that they do not have to be independent.

  38. Key Concepts of Axiomatic Design Theory • FRs and DPs (as well as PVs) must be decomposed to the leaf-level until we create a hierarchy. • From an FR in the functional domain, we go to the physical domain to conceptualize a design and determine its corresponding DP. • Then, we come back to the functional domain to create FR1 and FR2 at the next level that collectively satisfies the highest-level FR.

  39. 1.3Key Concepts of Axiomatic Design Theory DP FR DP1 DP2 FR1 FR2 DP11 DP12 FR11 FR12 DP123 FR123 DP122 FR122 DP121 FR121 DP1231 FR1231 DP1232 FR1232 Physical domain Functional domain • FR1 and FR2 are the FRs for the highest level DP. • Then we go to the physical domain to find DP1 and DP2 by conceptualizing a design at this level, which satisfies FR1 and FR2, respectively.

  40. DP FR DP1 DP2 FR1 FR2 DP11 DP12 FR11 FR12 DP123 FR123 DP122 FR122 DP121 FR121 DP1231 FR1231 DP1232 FR1232 Physical domain Functional domain 1.3Key Concepts of Axiomatic Design Theory • This process of decomposition is continued until the FR can be satisfied without further decomposition when all of the branches reach the final state. • The final state is indicated by thick boxes, which is called a “leaf” or “leaves”.

  41. 1.3Key Concepts of Axiomatic Design Theory FRs: FR1= provide access to the food in the refrigerator . FR2= minimize energy consumption DPs: DP1 = Vertically hung door DP2 = Thermal insulation material

  42. Design Example • Bend a titanium tube to prescribed curvatures maintaining the circular cross section of the bent tube. • Titanium has a hexagonal close packed (hcp) structure so that its mechanical properties anisotropic, and it cannot be bent repeatedly because it will fracture. FR1 = Bend a titanium tube to prescribed curvatures. FR2 = Maintain the circular cross section of the bent tube.

  43. Fixed set of counter-rotating grooved feed rollers 1 1 = 2 2 Pivot axis Tube between the two bending rollers 1 Flexible set ofcounter-rotatinggrooved rollers for bending 1 > 2 2 DP1 = Differential rotation of the bending rollers to bend the tube DP2 = The profile of the grooves on the periphery of the bending rollers

  44. Cutting a Rod Target pdf Design range System pdf 90 100 c m 110 FR (Length, cm) To cut Rod A to 1  10-6 m and Rod B to 1  0.1m. Which has a higher probability of success?

  45. Buying a house FR1 = Commuting time must be in the range of 15 to 30 minutes. FR2 = The quality of the high school must be good, i.e., more than 65 % of the high school graduates must go to reputable colleges. FR3 = The quality of air must be good over 340 days a year. FR4 = The price of the house must be reasonable, i.e., a four bedroom house with 3000 square feet of heated space must be less than $ 650,000.

  46. Buying a house FR1 = Commuting time must be in the range of 15 to 30 minutes. FR2 = The quality of the high school must be good, i.e., more than 65 % of the high school graduates must go to reputable colleges. FR3 = The quality of air must be good over 340 days a year. FR4 = The price of the house must be reasonable, i.e., a four bedroom house with 3000 square feet of heated space must be less than $ 650,000.

  47. Estimating the height of Washington Monument K=stiffness FR 1 FR DP DP DP Students were asked to estimate the height of the George Washington Monument. They were given tape measures that can measure the length of the shadow of the monument accurately. Then they were asked to eyeball the angle from the end of the shadow to the top of the monument. Which will give the closer height when it was measured at 1 P.M. and 5 P.M.?

  48. Hot and Cold Water Faucet

  49. Hot and Cold Water Faucet

  50. Van Seat Assembly

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