Estimation and ModelingUNIVERSITY OF MINNESOTAME 4054WSpring 2010Prof. Bohlmann4ThUNIVERSITY OF MINNESOTAEstimationCombining your judgment with the formulasand relationships you’ve learned in yourengineering education are the keys to estimationes⋅ti⋅mate (v. es-tuh-meyt)to form an approximate judgment or opinion regarding the worth, amount, size, weight, etc., of; calculate approximatelywww.dictionary.comUNIVERSITY OF MINNESOTAEstimation ProcessQuick Calculations+Quick Measurements+Quick ModelsLearn when to say:"THAT DOESN'T SOUND RIGHT"UNIVERSITY OF MINNESOTARounding is OK when EstimatingRound off 8 10 23 20 32 ft/sec230 Pi 3 Conversions (know them, use them)1 atm = 14.7 (15) psi = 760 (750) mmHg 1 g = 32.2 (30) ft/sec2= 9.81 (10) m/s21 hp = 550 ft-lb/s = 746 (750) W 1 psi = 6894 (7000) Pa etc... 1 N 0.22 lbUNIVERSITY OF MINNESOTAdeltamax= FL3/3EIdeltamax= wL4/8EI Bounding is often more usefulthan "exact" answers!UNIVERSITY OF MINNESOTAMotivation to Estimate• As a Design Engineer • Builds intuitive knowledge • Sanity check on data• Allows you to quickly bound the problem and focus your efforts• As a Manager • Ask correct questions • Determine if answers make sense • As an ME 4054W Team Member • Facilitate concept generation & selection • Focus calculations • Enable project completion by design showUNIVERSITY OF MINNESOTADevelop competence in all four! Components of the Estimation Process1. Observe 2. Model 3. Measure or recall 4. CalculateUNIVERSITY OF MINNESOTAObservation• Good estimation starts with good observationNotice what is around you. Calibrate what is around you. • How much does steel cost? • How heavy is polystyrene? • Will epoxy bond steel to polystyrene? • What font size is readable at the back of the room? • How did they make that?UNIVERSITY OF MINNESOTARoadside data collection unit Estimation Keep it simple. Very simple.Examples • Uniform acceleration (from rest): x = 0.5 a t2• Natural frequency: omega2= K / M • Axial tension / compression of a rod: delta = PL/AE • Deflection of cantilever beam: delta = PL3/3EI • 1-D heat transfer • etc. ...UNIVERSITY OF MINNESOTAQuick Models: Engineering Formulas• Rourke’s Formulas for Stress and Strain• Intro to Mechanical Engineering by WickertUNIVERSITY OF MINNESOTAQuick Measurements Density/ ViscosityKnow the density and viscosity of typical fluids (order of magnitude will suffice) Size: hair diameter 100 microns (0.004 in)floor tile 1 ftcity block 300 feetUNIVERSITY OF MINNESOTAQuick Measurements• Elastic Modulii:UNIVERSITY OF MINNESOTAQuick Measurements StrengthMaterial Yield Stress Ultimate Stress(MPa) (MPa)Aluminum [Al] 20 70 Aluminum Alloy 35 - 500 100 - 550Brass 70 - 550 200 - 620 Copper [Cu] 55 - 330 230 - 380 Iron (Cast) 120 - 290 69 - 480 Iron (Wrought) 210 340 Steel 280 - 1600 340 – 1900Titanium [Ti] - 500UNIVERSITY OF MINNESOTATypical Quantities Engineers should know: Efficiency• Solar Cell 5-15%• IC engine 15-40%• Wind Turbine 30-50%• Hot Water Heater 60-65%• Electric Motor 80-90%• Furnace 80-95%UNIVERSITY OF MINNESOTADrag• Economy sedan at 60 mph• Sports Car at 60 mph• SUV at 60 mph• Racing bike rider• PersonRange from 0.3 to 1.20.340.290.450.91.2Quick Calculations• Example Reynolds number:vlRe Round off, check unitsWater through a 1 cm pipe, 0.5 m/sRe = 50000.3 in diameter bullet at 2400 ft/sRe = 3.7 E5Submarine with hull of 33ft, 15 knotsRe = 6.7 E7Other Examples of Quick CalculationsFluids Engineering Thermal and Energy SystemsUNIVERSITY OF MINNESOTABuilding your personal estimation toolbox• Course web page • Your textbooks• Handbooks• www• etc...UNIVERSITY OF MINNESOTAEstimation Insights• Practice! Measurements & conversions: engineer :: anatomy: doctor• Build your personal library!• Your career direction will determine the most valuable tools for your toolbox. Learn them and use them.• The ability to use estimation is one mark of a seasoned professional • Estimate throughout your project! How little work can you do to get a useful answer?• Estimation will save you or help to advance your career at least once in the next 5 years!UNIVERSITY OF MINNESOTAModelingmod⋅el⋅ing (v. mod-l-ing)the representation, often mathematical, of a process, concept, or operation of a system, often implemented by a computer program.www.dictionary.comUNIVERSITY OF MINNESOTAProduct: Front LoaderModelModeling• Abstracting a Real-World Object or System to a Mathematical ModelUNIVERSITY OF MINNESOTAWhy Model?• Confirm basic feasibility • Far faster & cheaper than constructing hardware • Enables sizing prior to construction • Great opportunity for optimization • First order: Vary parameters • Second order: Mathematical optimization tools Engineer a Solution vs. "Build & Break"UNIVERSITY OF MINNESOTAModeling Tools• Abstraction: Approximate a complex thing as a simpler thing • Assumptions: Document them!UNIVERSITY OF MINNESOTAModeling Example• Analytical modeling of a thermal sealing headUNIVERSITY OF MINNESOTAHardware Model Modeling Example• Motor / generatorUNIVERSITY OF MINNESOTAGear Reducer ProductIdler Shaft ModelModeling Example• Gear reducer shaftUNIVERSITY OF MINNESOTAProduct: Truck Exhaust Filter 1-Dimensional Heat Flow ModelModeling Example• Exhaust Filter SystemUNIVERSITY OF MINNESOTAFinal Thoughts onEstimation and Modeling• Estimation and modeling are closely related. • The required accuracy and fidelity of the answer determines which approach is appropriate.• However, your skills at estimation (“does that answer make sense?”) should always be