Structural sections: shape in action Mike Ashby Department of Engineering, University of Cambridge 2 Learning objectives for this lecture unit Resources Text: Materials Selection in Mechanical Design, 5th edition by M.F. Ashby,
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Presentation Transcript
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Structural sections: shape in action Mike Ashby
Department of Engineering,
University of Cambridge<br>
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2 Learning objectives for this lecture unit Resources
Text: “Materials Selection in Mechanical Design”, 5th edition by M.F. Ashby, Butterworth Heinemann, Oxford, 2016, Chapters 10-11.
Software: The Ansys Granta EduPack Structural sections data-table and the Built Environment Level 2 database<br>
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3 Outline of the lecture unit Content and use of the database Structural sections and their attributes The Granta EduPack data-table for Structural sections<br>
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4 Structural sections All increase
Second moment of area I
Section modulus Z
Bending stiffness E I
Failure moment σy Z (called YZ in the database) When materials are loaded in bending, in torsion, or are used as slender columns, section shape becomes important Ansys Discovery<br>
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5 Data organization: structural sections Standard
prismatic sections<br>
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6 Granta EduPack database for the Built Environment<br>
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7 Part of a record for a structural section *A selection of attributes are shown<br>
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8 Example: selection of a beam Beam Dimension
Width B < 150 mm
Depth D < 200 mm Function Specification Required strength:
y Z > 103 N.m Custom Subset
Structural SubSections<br>
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9 Applying constraints with a Limit stage 5 15 Dimensions Minimum Maximum
Max depth, D m
Max width, B m
Structural Attributes
Bending stiffness E.Imax N.m2
Failure moment Y. Zmax N.m Custom subset of Structural Section
Result : 294 sections out of 1881 meet these constraints<br>
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10 Minimizing mass for given EImax Results
Extruded Aluminum Channel (140x40x1.74)
Extruded Aluminum Channel (152.4x28.6x1.75)
Extruded Aluminum Channel (130x50x1.82) Bending Stiffness EI vs.
mass per unit length<br>
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11 Minimizing cost for given EImax Results
Sawn Softwood section-(175x25x2.41)
Sawn Softwood section-(200x22x2.42)
Sawn Softwood section-(200x25x2.75) Bending Stiffness EI vs.
price per unit length<br>
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12 Minimizing embodied energy for given EImax Results
Sawn Softwood section-(175x25x2.41)
Sawn Softwood section-(200x22x2.42)
Sawn Softwood section-(200x25x2.75) Bending Stiffness EI vs.
Embodied energy per unit length<br>
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13 Minimizing embodied energy for given EImax Results
Sawn Softwood section-(175x25x2.41)
Sawn Softwood section-(200x22x2.42)
Sawn Softwood section-(200x25x2.75)
Sawn Softwood section-(150x36x2.97)<br>
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14 Summary It introduces the idea of choice to optimize weight, price or environmental impact The Granta EduPack Structural sections data-table and the Built Environment database allows standard sections to be explored and selected to meet multiple constraints<br>
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15 Lecture unit series PowerPoint lecture units, as well as many other types of resources, can be found in the Ansys Education Resources webpage. www.ansys.com/education-resources<br>
