Material Selection, Study Guides, Projects, Research of Design

Download Material Selection and more Study Guides, Projects, Research Design in PDF only on Docsity! B. Konh, T. Sorensen, A Trimble 1 of XXME 481 – Fall 2017 Material Selection Senior Design ME481 Fall 2017 Dr. Bardia Konh B. Konh, T. Sorensen, A Trimble 2 of XXME 481 – Fall 2017 Materials Selection in Design This Lecture: - Importance of material selection in design - Exploring materials using materials property charts - Materials selection process - Selecting materials: materials indices - Case studies Material selection is critical part of almost all engineering designs So many factors to consider: strength, stiffness, durability, corrosion, cost, formability, etc. Design is… “…the process of translating a new idea or a market need into detailed information from which a product can be manufactured.” M. F. Ashby, “Materials Selection in Mechanical Design”, B. Konh, T. Sorensen, A Trimble 5 of XXME 481 – Fall 2017 Need for a new product and new materials Development of a new materials http://hleelabhome.wixsite.com/mysite/research2 http://hleelabhome.wixsite.com/mysite • Soft active materials • Biologically inspired design principles Soft robotics Dr. Howon Lee Rutgers University Soft multi-material actuators Dr. Conor Walsh Harvard University https://biodesign.seas.harvard.edu/soft-robotics • Large bending motions B. Konh, T. Sorensen, A Trimble 6 of XXME 481 – Fall 2017 Evolution of materials [ASHBY99] - Materials Selection In Mechanical Design http://www.utc.fr/~hagegebe/UV/MQ12/CORRECTIONS_TD/%5BASHBY99%5D%20- %20Materials%20Selection%20In%20Mechanical%20Design%202Ed.pdf B. Konh, T. Sorensen, A Trimble 7 of XXME 481 – Fall 2017 Material Properties Physical – Density – Melting point – Vapor pressure – Viscosity – Porosity – Permeability – Reflectivity – Transparency – Optical properties – Dimensional stability Chemical – Corrosion – Oxidation – Thermal stability – Biological stability – Stress Corrosion – …. Electrical – Conductivity – Dielectric constant – Coersive force – Hysteresis Thermal – Conductivity – Specific Heat – Thermal expansion – Emissivity Mechanical – Hardness – Elastic constants – Yield strength – Ultimate strength – Fatigue – Fracture Toughness – Creep – Damping – Wear resistance – Spalling – Ballistic performance – ……. B. Konh, T. Sorensen, A Trimble 10 of XXME 481 – Fall 2017 Material stiffness B. Konh, T. Sorensen, A Trimble 11 of XXME 481 – Fall 2017 Metals Metal Examples of application Ferrous Metals Carbon Steels Utensils, construction, automotive, transmission towers … Stainless Steels Off shore drilling rigs, naval construction, chemical transport, food preparation, medical instruments Cast Irons Cylinders, pistons, motor blocks, construction, wear resistant materials Light Alloys Aluminum Alloys Aerospace, construction, transport, packaging, electrical conductors Magnesium Alloys Aerospace, automotive, sporting equipment Titanium Alloys Aerospace, chemical industry Copper Alloys Copper Electrical conductors Bronze Heat exchangers, chemical industry, maritime industry Brass Pressure vessels, fittings Nickel Alloys Aerospace, currency B. Konh, T. Sorensen, A Trimble 12 of XXME 481 – Fall 2017 Interactions Material Process Shape Functionality Materials Selection Methodology Ashby Methodology 1. Translation: express design requirements as constraints & objectives 2. Screening: eliminate materials that cannot do the job 3. Ranking: find the materials that do the job best 4. Supporting information: explore pedigrees of top-ranked candidates B. Konh, T. Sorensen, A Trimble 15 of XXME 481 – Fall 2017 Example: Materials for a Light, Strong Tie Function: Support a tension load Objective: Minimize mass Constraints: Length specified Carry load F, w/o failure Free variables: Cross-section area Material B. Konh, T. Sorensen, A Trimble 16 of XXME 481 – Fall 2017 Example: Materials for a Light, Strong Tie Objective: Constraints: Rearrange to eliminate free variable: Minimizing weight by minimizing B. Konh, T. Sorensen, A Trimble 17 of XXME 481 – Fall 2017 Second Step: Screening Eliminate materials that cannot do the job Need effective way of evaluating large range of material classes and properties Metals Steels Cast irons Al-alloys Cu- alloys Ti-alloys Ceramics Alumina Si-carbide Si-nitride Ziconia Hybrids Composites Sandwiches Lattices Segmented Polymers PE, PP, PC, PS, PET, PVC, PA (Nylon) Polyester Epoxy Glasses Soda glass Borosilicate Silica glass Glass ceramic Elastomers Isoprene Butyl rubber Natural rubber Silicones EVA B. Konh, T. Sorensen, A Trimble 20 of XXME 481 – Fall 2017 Heat Sink Screening: Bar Chart 200 ºC λ > 100 W/mK R > 1020 µ ohm cm temp > 200 C B. Konh, T. Sorensen, A Trimble 21 of XXME 481 – Fall 2017 Third Step: Ranking “Find the materials that do the job best” - What if multiple materials are selected after screening? - Which one is best? - What if there are multiple material parameters for evaluation? B. Konh, T. Sorensen, A Trimble 22 of XXME 481 – Fall 2017 Single Property Ranking Example Function: Transmit electricity Objective: Minimize electrical Resistance Constraints: Length L and section A are specified Must not fail under wind or ice-load Required tensile strength > 80 MPa Free variables: Material choice >> Screen on strength, rank on resistivity Electrical resistivity Overhead Transmission Cable B. Konh, T. Sorensen, A Trimble 25 of XXME 481 – Fall 2017 Optimized Selection Example: Tension Load, strength limited - Maximize: M = σ/ρ - In log space: log σ = log ρ + log M - This is a set of lines with slope=1 - Materials above line are candidates Using Material Indices & Property Charts: Strength B. Konh, T. Sorensen, A Trimble 26 of XXME 481 – Fall 2017 Material Indices & Property Charts Example: Stiff beam - Maximize: M = Ε1/2/ρ - In log space: log E = 2 (log ρ + log M) - This is a set of lines with slope=2 - Candidates change with objective Stiffness B. Konh, T. Sorensen, A Trimble 27 of XXME 481 – Fall 2017 Considering Multiple Objectives/Constraints With multiple constraints: Solve each individually Select candidates based on each Evaluate performance of each Select performance based on most limiting May be different for each candidate With multiple objectives: Requires utility function to map multiple metrics to common performance measures Design performance is determined by the combination of: Shape / Materials / Process Underlying principles of selection are unchanged: - BUT, do not underestimate impact of shape or the limitation of process Method for Early Technology Screening B. Konh, T. Sorensen, A Trimble 30 of XXME 481 – Fall 2017 Summary • Material affects design based on - Geometric specifics - Loading requirements - Design constraints - Performance objective • Effects can be assessed analytically • Keep candidate set large as long as is feasible • Materials charts give quick overview; software can be used to more accurately find options • Remember, strategic considerations can alter best choice B. Konh, T. Sorensen, A Trimble 31 of XXME 481 – Fall 2017 Function Objective Constraint "What does component do?" "What is to be maximized or minimized?" "What specific requirements must be met?" Any engineering component has one or more functions (to support a load, to contain a pressure, to transmit heat, etc.). The designer has an objective (to make it as cheap as possible, or as light as possible, or as safe as possible or some combination of these). The objective must be achieved subject to constraints (e.g. the dimensions are fixed; the component must carry the given load without failure, it should function in a certain temperature range, etc. Free variables: What is the designer free to change? Defining the Design requirements B. Konh, T. Sorensen, A Trimble 32 of XXME 481 – Fall 2017 1. List the constraints (e.g. no buckling, high stiffness) of the problem and develop an equation for them, if possible. 2. Develop an equation of the design objective in terms of functional requirements, geometry and materials properties (objective function). 3. Define the unconstrained (free) variables. 4. Substitute the free variable from the constraint equation into the objective function. 5. Group the variables into three groups, functional requirements (F), geometry (G) and materials functions (M), to develop the performance metric (P): 6. Read off the materials index, M, in order to maximize the performance metric (P).