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ME310 Mechanical Design: Introduction to Machine Elements
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ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University ME310 MECHANICAL DESIGN Module 1 Introduction ME310 MECHANICAL DESIGN Dulyachot Cholaseuk Mechanical Engineering Department Thammasat University Contents 1. 2. 3. 4. 5. 6. 7. ME310 Module 1: Introduction Overview Design Process Design Consideration Units Critical Point Safety Factor Review of Engineering Materials 2 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University 1 Overview Course description Design of machine elements for power transmission: clutches, brakes, bearings, belts, chains, gears, and cams. Design exercises of mechanical parts and mechanical systems. Design for manufacturing and assembly. Reverse engineering case study. Computer aided design. ME310 Module 1: Introduction 3 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Tentative Schedule # Topics 1 Machines and machine components. Power, power sources and power transmission. Basic design principles. Design procedures. Critical points. Safety factors and service factors. 2 Engineering Materials. Material selection. Minimum weight index. 3 Review of Solid Mechanics. Theory of failure. 4 Design of simple machine elements. Beams. Shafts. 5 Principle of power transmission. Reverse engineering case study. 6 Welding joints. 7 Threaded fasteners. Bolted joints. 8 Power screws. 9 Springs. Project 1 presentation 10 Couplings and keys. Clutches 11 Brakes. 12 Belts and Chains. 13 Gears. 14 Bearings. Flywheels. 15 Course summary. Project 2 presentation. Final ExaminationModule 1: Introduction ME310 4 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University References Shigley, J. E., Mechanical Engineering Design, 6th Metric Edition, McGrawHill, 2003 Hamrock, B. J., et. al., Fundamentals of Machine Elements. McGraw Hill, 1999. วริทธ์ ิ อึ๊งภากรณ์ และ ชาญ ถนัดงาน, การออกแบบ เครื่องจักรกล เล่ม 1 และ เล่ม 2, ซีเอ็ด Manufacturer’s catalogs ME310 Module 1: Introduction 5 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University http://www.dulyachot.me.engr.tu.ac.th/me310/me310.htm Class web page MS TEAMS Code ME310 Module 1: Introduction 6 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Grading Assignments – 20% Project 1 – 20% Project 2 – 20% Midterm Exam – 20% Final Exam. – 25% • 80%+ for A. ME310 Module 1: Introduction 7 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Machine A combination of mechanism and other components that transforms, transmits or uses energy, load or motion for specific purposes. Lets look at an engine ME310 Module 1: Introduction 8 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University More Definition of a Machine A machine is a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motions (Franz Reuleaux ) ME310 Module 1: Introduction 9 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Primitive Machines ME310 Module 1: Introduction 10 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Davinci’s Machines and Machine Elements ME310 Module 1: Introduction 11 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Modern Day Machines ME310 Module 1: Introduction 12 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Modern Day Machines ME310 Module 1: Introduction 13 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Our Recently Built Machines ME310 Module 1: Introduction 14 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Our Recently Built Machines ME310 Module 1: Introduction 15 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Typical Machine Elements ME310 Module 1: Introduction 16 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Design Design (in engineering context) = The management of constraints Manipulate design variables to satisfy non-negotiable constraints and optimize the negotiable constraints Usually, no unique solution. Do not copy. Decision Making ME310 Module 1: Introduction 17 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Machine Design Not this ME310 Module 1: Introduction 18 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Machine Design This is more like it. ME310 Module 1: Introduction 19 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Components of design problem Design variables Constraints Design objectives ME310 Module 1: Introduction 20 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Skill and Knowledge Required Solid mechanics Statics/Dynamics Mathematics Engineering Graphics Computer – CAD/CAE, Excel • Heat Transfer • Fluid Mechanics • Thermodynamics • Manufacturing Processes • Ergonomics • etc. ME310 Module 1: Introduction 21 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University 2 Design Process Coconut meat is quite hard to remove from the shell. Even with help from the rabbit. ME310 Module 1: Introduction 22 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University System design example ME310 Module 1: Introduction 25 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Sub-system design example ME310 Module 1: Introduction 26 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Component design example ME310 Module 1: Introduction 27 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Design optimization example X Y ME310 Module 1: Introduction Z 28 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University 3 Design Consideration Stress vs strength Deformation Uncertainty Availability Ergonomics Manufacturing and assembly Standards ME310 Module 1: Introduction 29 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Stress vs Strength Stress > Strength Failure ME310 Module 1: Introduction 30 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Deformation Excessive deformation Failure ME310 Module 1: Introduction 31 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Uncertainty There are external and internal noise ME310 Module 1: Introduction 32 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Availability ME310 Module 1: Introduction 33 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Ergonomics ME310 Module 1: Introduction 34 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Ergonomics ME310 Module 1: Introduction 35 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Manufacturing and assembly ME310 Module 1: Introduction 36 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Manufacturing and assembly ME310 Module 1: Introduction 37 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Standards มาตรฐานอุตสาหกรรมไทย (ม.อ.ก.) ME310 Module 1: Introduction 38 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University 4 A Note on units Follow SI unit: kg m s Be prepare for unit conversion Stress/pressure/elastic modulus N/m2 ME310 Module 1: Introduction 39 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Basic Quantities ME310 Module 1: Introduction 40 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Prefix ME310 Module 1: Introduction 41 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Greek symbols ME310 Module 1: Introduction 42 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Length ME310 Module 1: Introduction 43 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Force ME310 Module 1: Introduction 44 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Energy ME310 Module 1: Introduction 45 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Power ME310 Module 1: Introduction 46 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University 5 Critical Point Critical point Critical component Critical point defines strength of a component. The weakest component define capacity of a machine ME310 Module 1: Introduction 47 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Critical Point in a Component ME310 Module 1: Introduction 48 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Critical Point in a Component ME310 Module 1: Introduction 49 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Critical Point and Shape Design [will be discussed in Module 3] ME310 Module 1: Introduction 50 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Reshape to eliminating the critical point [will be discussed in Module 3] ME310 Module 1: Introduction 51 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Safety Factor 6 There are many uncertainties in the real world. Some margin is needed to account for the uncertainties. Design the part such that stress < material strength Ns = Strength Stress How much Ns should we use? ME310 Module 1: Introduction 52 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Safety Factor from Hamrock ME310 Module 1: Introduction 53 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Safety Factor from Hamrock ME310 Module 1: Introduction 54 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Safety Factor from วริทธิ ์ ME310 Module 1: Introduction 55 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University HW – Safety Factor in Trees Nature is the greatest engineer in the universe. How much safety factor does she put in her design? Reading assignment: Safety factor in trees Questions How did the researcher perform the experiment? How much is the safety factor in trees? How can we find our own safety factor? ME310 Module 1: Introduction 56 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Safety Factor in Trees ME310 Module 1: Introduction 57 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Safety Factor in Trees Isotropic model 1/3 ME310 Module 1: Introduction 58 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University ! Check Point: Safety Factor of a System Name 3. Pulley set Capacity 500T = 30 degrees Ns I Safety Factor 1. Hook 2. Ropes 30/IOT 50/20 S00/20 4. Boon 350/80 T 200/POT 2. Hoisting rope Capacity 80T 20Tons steel ball ME310 Module 1: Introduction 4.Boom Sy = 350 MPa Actual stress at critical member 80 MPa 2. S ⑧ 3. Pulley 5. Pope 1.Hook Capacity 50T T 2 What's the N, of 4.37 Syste & 2.5, we select the smallest member 5.Gantry rope Capacity 200T Tension = 48T 45 degrees 59 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University 7 Review of Engineering Materials & Material shape Metals - Ferrous metals - Cast iron - Steel (<2.11% Carbon) - Non-ferrous Polymers and Plastics -Thermo Plastic - PE, PVC, ABS, etc. -Thermosetting - Epoxy, Melamine Ceramics Composite Materials This course only covers isotropic material under elastic range ME310 Module 1: Introduction 60 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Important Properties Main Focus Density Strength [yield and ultimate strengths] Stiffness [Young's modulus and shear modulus] Poisson ratio Hardness Coefficient of thermal expansion Thermal conductivity Specific heat ME310 Module 1: Introduction 61 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Ductile vs. Brittle Materials Young's Models = = = = ใ GEN - Elastic ME310 Module 1: Introduction 62 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Yield strength By : yeild strengt Ne = Num of Safety Factor 6 = A: # By Ne = = MR By = 300 A: = x 1000 3 08 =23 nn => d = & ME310 Module 1: Introduction 63 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Brittle Materials Higher compressive strength than tensile strength Stress Sut Strain Suc ME310 Module 1: Introduction 64 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Ferrous Metal 1-5 USD/kg 4-50 USD/kg ME310 Module 1: Introduction 65 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Non-ferrous Metal 2-3 USD/kg 7-10 USD/kg 24-100 USD/kg 730 USD/kg 10-35 USD/kg ME310 Module 1: Introduction 66 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Strength vs density First carbon nanotube #o ·minieice mass = Weight /AL - m & M - Ns Fl => Y /1) ( For tension) ley ↑ instan e & = =( 1 NET ( PALIPHOTO M= ME310 ↳ Module 1: Introduction 67 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Minimum Weight Indices – Strength/stiffness vs density Minimum weight indices Loads Stress constraint Deflection constraint Axial load Bending and/or torsion Transverse load on a plate high index light weight ME310 Module 1: Introduction 68 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Other Indices for Material Selection ME310 Module 1: Introduction 69 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Minimum Weight Indices – Ferrous Materials Materials Iron Grey cast iron Nodular cast iron Malleable cast iron Steel 1 – 5 USD/kg (kg/m^3) (Mpa) (Gpa) Ro Sy E 7870 130 207 7150 220 7120 275 165 7200 220 172 Low carbon steel AISI1020 Med. carbon steel AISI1040 High carbon steel AISI1080 Alloy steel Cr-Mo AISI4130 Alloy steel AISI 4335V Stainless steel Ferric SS 446 Austenitic SS 304 SS 316 Martensitic SS 410 SS 410S 4 – 20 USD/kg (Prices based on random sellers in Aliexpress 2023) Axial Sy/Ro x1000 16.5 30.8 38.6 30.6 Minimum Weight Indices Stress constraint Deflection constraint Bending/Torsion Plate Bending/Torsion Plate Axial E^(1/2)/Ro E^(1/3)/Ro Sy^(2/3)/Ro Sy^(1/2)/Ro E/Ro x1000 x1000 x1000 x1000 x1000 3.26 1.45 26.30 1.83 0.75 5.10 2.07 5.94 2.33 23.17 1.80 0.77 5.06 2.06 23.89 1.82 0.77 7860 7850 7840 7850 7840 295 350 380 435 1448 207 207 207 205 200 37.5 44.6 48.5 55.4 184.7 5.64 6.33 6.69 7.31 16.33 2.19 2.38 2.49 2.66 4.85 26.34 26.37 26.40 26.11 25.51 1.83 1.83 1.84 1.82 1.80 0.75 0.75 0.75 0.75 0.75 7500 8000 8000 7800 7800 345 215 207 275 896 200 200 193 200 200 46.0 26.9 25.9 35.3 114.9 6.56 4.49 4.37 5.42 11.92 2.48 1.83 1.80 2.13 3.84 26.67 25.00 24.13 25.64 25.64 1.89 1.77 1.74 1.81 1.81 0.78 0.73 0.72 0.75 0.75 All indices may be useless if there are geometric constraints ME310 Module 1: Introduction 70 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Minimum Weight Indices – Non-Ferrous Materials Stress constraint Materials Titanium(>99%) Titanium TI6AL4V AL6061-O AL6061-T6 AL7075-O AL7075-T6 Magnesium Magnesium AZ91D Copper Brass Bronze Molybdinum Nikel(>99%) Silver(>99%) (kg/m^3) (Mpa) (Gpa) Ro Sy E 4510 240 107 4430 880 113.8 12 – 32 USD/kg 2700 55 68.9 2 – 4 USD/kg 2700 276 68.9 2810 103 71.7 2810 503 71.7 1740 41 45 25 – 30 USD/kg 1810 160 45 8 -10USD/kg 8940 69 69 8530 75 75 8500 152 152 10230 565 324 8900 138 207 10490 55 76 Axial Sy/Ro x1000 53.2 198.6 20.4 102.2 36.7 179.0 23.6 88.4 7.7 8.8 17.9 55.2 15.5 5.2 Bending/Torsion Sy^(2/3)/Ro x1000 8.56 20.73 5.36 15.70 7.82 22.51 6.83 16.28 1.88 2.08 3.35 6.68 3.00 1.38 Minimum Weight Indices Deflection constraint Bending/Torsion Plate Plate Axial E^(1/2)/Ro E^(1/3)/Ro Sy^(1/2)/Ro E/Ro x1000 x1000 x1000 x1000 3.44 23.73 2.29 1.05 6.70 25.69 2.41 1.09 2.75 25.52 3.07 1.52 6.15 25.52 3.07 1.52 3.61 25.52 3.01 1.48 7.98 25.52 3.01 1.48 3.68 25.86 3.86 2.04 6.99 24.86 3.71 1.97 0.93 7.72 0.93 0.46 1.02 8.79 1.02 0.49 1.45 17.88 1.45 0.63 2.32 31.67 1.76 0.67 1.32 23.26 1.62 0.66 0.71 7.24 0.83 0.40 (Prices based on random sellers in Aliexpress 2023) All indices may be useless if there are geometric constraints ME310 Module 1: Introduction 71 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Minimum Weight Indices – Other Materials Stress constraint Materials (kg/m^3) (Mpa) (Gpa) Ro Sy E Axial Sy/Ro x1000 Bending/Torsion Sy^(2/3)/Ro x1000 Minimum Weight Indices Deflection constraint Plate Axial Bending/Torsion Plate 3 Sy^(1/2)/Ro E/Ro E^(1/2)/Ro E^(1/3)/Ro 2 x10 x10 x1000 x1000 x1000 x1000 Metals Med. carbon steel AISI1040 Alloy steel AISI 4335V SS 410S Titanium TI6AL4V AL6061-T6 AL7075-T6 Magnesium AZ91D 7850 7840 7800 4430 2700 2810 1810 350 207 1448 200 896 200 880 113.8 276 68.9 503 71.7 160 45 44.6 184.7 114.9 198.6 102.2 179.0 88.4 6.33 16.33 11.92 20.73 15.70 22.51 16.28 2.38 4.85 3.84 6.70 6.15 7.98 6.99 26.37 25.51 25.64 25.69 25.52 25.52 24.86 1.83 1.80 1.81 2.41 3.07 3.01 3.71 0.75 0.75 0.75 1.09 1.52 1.48 1.97 Carbon Fibre Composites Std CF (UD 0deg)* Std CF (Fabric 0deg)* Std CF (Fabric 45Deg)* 1600 1600 1600 1000 600 120 175 70 19.1 625.0 375.0 75.0 62.50 44.46 15.21 19.76 15.31 6.85 109.38 43.75 11.94 8.27 5.23 2.73 3.50 2.58 1.67 Ceramic Composites** Alumina(tensile load) Sut=69 - 665 Mpa Alumina(compressive load) Suc=690 - 5500 Zirconia (tensile load) Zirconia (compressive load) SiliconNitride (tensile load) SiliconNitride (compressive load) Concrete (tensile load) Concrete (compressive load) 3000 3000 6010 6010 3310 3310 2300 2300 220 2000 248 2500 360 689 3.5 30 215 215 207 207 317 317 30 30 73.3 666.7 41.3 416.0 108.8 208.2 1.5 13.0 12.15 52.91 6.57 30.65 15.29 23.57 1.00 4.20 4.94 14.91 2.62 8.32 5.73 7.93 0.81 2.38 71.67 71.67 34.44 34.44 95.77 95.77 13.04 13.04 4.89 4.89 2.39 2.39 5.38 5.38 2.38 2.38 2.00 2.00 0.98 0.98 2.06 2.06 1.35 1.35 Bio materials*** Human cortical bone (axial dir. tensile) Human cortical bone (transv dir. tensile) 1850 1850 133 51 17 11.5 71.9 27.6 14.08 7.43 6.23 3.86 9.19 6.22 2.23 1.83 1.39 1.22 * 1.CF has no shear strength, 2. Based on standard grade (there are lower&higher grades) 3.Vf=60% ** 1. Ceramic composites are mostly brittle. 2.Properties varie. Example values presented. *** 1. Properties varie with test subjects 2. Compressive strength higher than tensile strength ME310 Module 1: Introduction 72 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Commercial Steel Shafts in Thailand Strength (approx.) Materials Sy* Su* Applications 235 385 General Black เพลาดํา SR24/JIS G112 245 400-510 General White เพลาขาว SS400, S20C/JIS G3101 450 585 Mech. parts Red เพลาแดง SC45/AISI1045 SC50/AISI1050 580 690 Mech. parts Blue เพลาฟ้ า SCM440/AISI4140/SCM4 850 1000 Tools * Mpa. Depend on shape, size and manufacturing processes ME310 Module 1: Introduction 73 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Material Selection ME310 Module 1: Introduction 74 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Elastic Modulus vs density ME310 Module 1: Introduction 75 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Elastic Modulus vs density ME310 Module 1: Introduction 76 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Elastic Modulus vs Strength ME310 Module 1: Introduction 77 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Elastic Modulus vs Cost x Density ME310 Module 1: Introduction 78 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Material Technologies ME310 Module 1: Introduction 79 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Hardness vs Strength of Ferrous Metal ME310 Module 1: Introduction 80 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University HW – Minimum Weight Index T 1. ,35baht/kg ,150baht/kg ,600baht/kg 2. 3. Reselect the material for minimum cost Make a comparison table, if L=0.8m, T=100N-m, Ns=3 Note: ME310 Module 1: Introduction 81 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Design Exercise ? Determine diameter of the bar. ME310 Module 1: Introduction 82 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Concluding Remarks Component design (most of the course) System/ sub system design (late in the course) ME310 Module 1: Introduction 83 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Component Design Stress vs. Strength Operate under elastic range Focus on Critical Point Optimize the design ME310 Module 1: Introduction 84 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University System and Sub-system Design Function vs. component Input – machine – output relationship Power = Force x Speed ME310 Module 1: Introduction 85 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University Next Module Review of Solid Mechanics ME310 Module 1: Introduction 86 ME TU Mechanical Engineering Department Faculty of Engineering, Thammasat University
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