Introduction to Mechanical Engineering Design MTE 427 Machine Design Introduction to Mechanical Engineering Design 1st teaching Pichet PINIT

What will we learn in this course? Introduction to Mechanical Engineering Design Engineering Materials (short version) Load and Stress Analysis Deflection and Stiffness Failure Theories for Static and Dynamic Loading Design of Machine Elements Shafts and Its Components Screws and Fasteners Mechanical Spring Roller Contact Bearing Gears (Spur, Helical, Bevel, and Worm Gears) Flexible Mechanical Elements Clutches, Breaks and Coupling

Introduction to Mechanical Engineering Design What is design? Design is the application of creativity to planning the optimum solution of a given problem and the communication of that plan to others. Given problem Creativity Planning Optimum solution (the best solution for such problem at a time) Communication

Introduction to Mechanical Engineering Design What is design? Design is the application of creativity to planning the optimum solution of a given problem and the communication of that plan to others. Given problem Creativity Planning Optimum solution (the best solution for such problem at a time) Communication Given problem Society’s needs

Introduction to Mechanical Engineering Design What is design? Design is the application of creativity to planning the optimum solution of a given problem and the communication of that plan to others. Given problem Creativity Planning Optimum solution (the best solution for such problem at a time) Communication Creativity Information from society that needs Designer’s knowledge related to such information Coming up with something NEW

Introduction to Mechanical Engineering Design What is design? Design is the application of creativity to planning the optimum solution of a given problem and the communication of that plan to others. Given problem Creativity Planning Optimum solution (the best solution for such problem at a time) Communication Planning Guide map to optimum solution based on such something NEW

Introduction to Mechanical Engineering Design What is design? Design is the application of creativity to planning the optimum solution of a given problem and the communication of that plan to others. Given problem Creativity Planning Optimum solution (the best solution for such problem at a time) Communication Optimum solution Solutions to such something NEW are infinite. Make decision using Engineering Tools such as Mathematics, Statistics, Computers, Graphics coupled with society’s information. Optimum solution should be functional, safe, reliable, competitive, usable, manufacturable, and marketable.

Introduction to Mechanical Engineering Design What is design? Design is the application of creativity to planning the optimum solution of a given problem and the communication of that plan to others. Given problem Creativity Planning Optimum solution (the best solution for such problem at a time) Communication Communication Tell other people (society) what you have done Engineer’s success depends on communication skill (writing, presenting, and speaking)

Introduction to Mechanical Engineering Design Phases in design

Introduction to Mechanical Engineering Design What is engineering design? Design is the application of creativity to planning the optimum solution of a given engineering problem and the communication of that plan to others. Focus on engineering problem. What is mechanical engineering design? Design is the application of creativity to planning the optimum solution of a given mechanical engineering problem and the communication of that plan to others. Focus on mechanical elements.

Introduction to Mechanical Engineering Design Why do we design? To response such need What are to be considered when designing? Functionality, Safety, and Reliability Strength and Stress Deflection, Distortion, and Stiffness Wear, Corrosion, Friction, Thermal, Surface, Noise, and Lubricant Weight, Shape, Size and Life Cost, Competition, and Marketability Much more …

Introduction to Mechanical Engineering Design Designers’ tools and resources Computational Tools CAD/CAM/CAE Acquiring Technical Information Libraries Government sources Professional societies (Standards: ISO, DIN, JIS, TIS, etc.) Commercial vendors Internet (Lots of information )

Introduction to Mechanical Engineering Design Designing action steps Understand the problem clearly Identify what are known Identify what are unknown and formulate solution strategy State all assumptions and decisions Analyze the problem with the solution strategy Evaluate your solution (Is it sound good for real life?) Present your solution As seen in phase design, the design process are interactive and iterative. Therefore, it may be necessary to repeat some or all of the above steps more than once if less than satisfactory results are obtained.

Introduction to Mechanical Engineering Design Economics and environment Use standard sizes as possible (stock sizes). Use large tolerances as possible. Think of mass products (breakeven point). Think hard of environmental effect. Safety and product Liability Manufacturer and designer always take responsibility no matter how long is the life of a product. Be careful of excessive promises Be sure to provide adequate warning and instruction Designer should always review, test, and control the quality of a product.

Introduction to Mechanical Engineering Design Stress and strength Strength is a build-in or inherent property of a material used to manufacture a product. Depending on the choice, the treatment, and the processing of the material Obtaining by testing (tension test, torsion test, etc.) Stress is an induced property of a product under a service. Depending on the external load applied on the product, geometry, temperature, etc. Obtaining by analyzing (Mechanics of Materials, Theory of Elasticity, etc.)

Introduction to Mechanical Engineering Design Uncertainty concerning stress and strength Composition of material and effect of variation on properties (Isotropic, anisotropic, orthotropic materials) Variation on properties for different places or stocks Effect of assemblies Intensity and distribution of loading Validity of mathematical models used to represent reality (do not forget your assumptions when making analysis) Stress concentration Influence of time (time edge effect, creep) Effect of corrosion and wear Much more … Designers themselves

Introduction to Mechanical Engineering Design Design factor and factor of safety How to deal with such uncertainties? Use a design factor. The design factor is defined as (1-1) The parameter can be load, stress, deflection, etc. If the parameter is load, the maximum allowable load is, then, (1-2) Ex 1.1

Introduction to Mechanical Engineering Design Design factor and factor of safety After the design completed, the actual design factor may change as a result of changes such as rounding up to a standard size for cross section or using off-the-shelf components with higher ratings instead of using what is calculated by the design factor. The factor, now, refers to as the factor of safety, . n Factor of safety has the same definition as the design factor, but it generally differs numerically. Generally, . n  1.3

Introduction to Mechanical Engineering Design Design factor and factor of safety Stress may not vary linearly with load, using load as the loss-of-function parameter may not be acceptable. The best way is to use the design factor in terms of a stress and a relevant strength. Then, (1-3) The stress and strength terms must be of the same type and unit. Ex 1.2

Introduction to Mechanical Engineering Design Units Use SI unit system (see more details by yourself). Some useful rules for number: 1924 or 1 924 but not 1,924 0.1924 or 0.192 4 but not 0.192,4 (Decimal point should always be preceded by a zero for number less than unity.) 192 423.618 50 but not 192,423.61850 Use prefixes for large and small numbers of possible. Use the right symbols (k means kilo not K)

Introduction to Mechanical Engineering Design Calculations and significant figures The number of significant figures is usually inferred by the number of figures given (except for leading zeros) showing the accuracy of a measurement of physical parameters. Ex. 706, 3.14, and 0.002 19 have three significant figures. In engineering work, report your results with three or four significant figures. Use scientific notation to clarify the accuracy. 91 600 should be 91.6  103 or 91.60  103. Never report a number of significant figures of a calculation any greater than the smallest number of significant figures used for the calculation. Make all calculations to the greatest accuracy possible and report the results within the accuracy of the given input.

Introduction to Mechanical Engineering Design Be Professional Be ethical people (know what is right and wrong, what should and shouldn't do.)

Introduction to Mechanical Engineering Design Assignment Read the text book on Load and Stress Analysis.

Introduction to Mechanical Engineering Design Phases in design (just a copy slide) Identification of need Definition of problem Synthesis or conceptual design Analysis and optimization Evaluation Presentation Iteration process