Unformatted text preview: ES140 Day 3 ES140 Day 3 Problem Solving
August 28, 2006 Homework: Engineering Homework: Engineering Failures Responsibility of engineer Analysis, analysis, analysis Analysis: Why did this fail? Analysis: Original Design As Constructed Top design: >Each nut is supporting ½ the weight of one box beam. >Rod would need to be threaded along much of its length—threads would get damaged during construction >Rod is too long to be practical for construction Bottom design: >Nuts on upper rods are supporting the weight of both box beams—twice as much load as first design In the beam design homework problem, In the beam design homework problem, what factor had the biggest impact on the deflection of the beam? 1. The width of the beam 2. The height of the beam 3. The modulus of elasticity of the beam 1. A decrease in E 2. An increase in the length of the beam 3. An increase in the width of the beam (b) 4. A decrease in the height of the beam (h) 5. Answers 1, 2 and 4 Which of the following causes an Which of the following causes an increase in ymax? Did you need a systematic way to Did you need a systematic way to solve the problem? Challenge: What tools and approaches might engineers use in the process of solving problems? What are their strengths and weaknesses? To answer these questions, what do you already know? What do you need to know? Goal of this module Goal of this module Apply engineering problem solving process Learn to use a variety of problem solving tools Determine which types of problems each is best suited for Engineering Process Engineering Process Define the problem and make a problem statement Diagram and describe Assumptions: simplify Apply theory and equations Solve the necessary problems Verify solution Requires careful use of UNITS Dimension and Units Dimension and Units A physical quantity is a dimension Length Measurable value in units Mass SI system – MKS & CGS 7 Base Units Time American system (foot, Electric current poundforce, second) Thermodynamic temp. Amount of substance Luminous intensity Dimension Unit Name Meter Kilogram Second Ampere Kelvin Mole Candela Symbol m kg s A K mol cd Units Units Helpful tables in Chapter 3: p.48,49,63 Always include units in calculations Make sure units agree Be careful to use correct abbreviation of units Convert units in organized manner Caution: mass and weight are different Practice with Practice with weight, mass and units A 90kg astronaut biologist searches for microbial life on Mars where the gravitational acceleration is g=3.71 m/s2. What is the weight of the astronaut in units of N and lbf? Use: N=kg*m/s2 1N = 0.22481 lbf Astonaut’s Weight Astonaut’s Weight 1. 334 N and 20.23 lbf 2. 90 N and 75 lbf 3. 90 N and 1485 lbf 4. 334 N and 75 lbf Engineering problem solving requires… good understanding of units organized way to present information Common Practices Common Practices
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Course Number Problem Number Pg # Name # of pgs DO Note Use DO Note Use Example Example Example Engineering problem solving requires… good understanding of units organized way to present information Methods of diagramming, sketching problem Diagramming: Choose Diagramming: Choose representation to fit problem Simplified model of inputs and outputs, forces, flows relevant to problem Block diagram Freebody diagram Electrical circuit sketch Flow schematic Functional Block Diagram of Functional Block Diagram of Metal Detector Diagrams Diagrams Engineering Process Engineering Process Define the problem and make a problem statement Diagram and describe Assumptions: simplify Apply theory and equations Solve the necessary problems Verify solution Now try it… Homework Homework Buy engineering paper at the bookstore Skim Chapter 3: Units Chapter 3 Problems 13, 22, 37 and 42 due on engineering paper at the beginning of class Wed. – be neat and show all steps Skim Chapter 4: Analysis Methodology Chapter 4 problems 16 and 19 due *using engineering approach* on engineering paper at the beginning of class Wednesday. Don’t forget Excel and Matlab tutorials! ...
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 Spring '07
 Wittig
 SI base unit, International System of Units, Kilogram, beam design homework, design homework problem, Engineering Process Engineering

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