seven rules for lightweight design · rule # 4: illustration aluminium magnesium gfrp/cfrp...
TRANSCRIPT
(title of presentation – go to ‘slide master’ to put in)
Seven rules for lightweight design
Erik Tempelman, DeFabrique, 20.11.2012 Constructeursdag Out of the Box ontwerpen
Acknowledgements go to…
Richard van der Windt
Olatunji Ladojah
Paul Kengen
Ruben van der Laan
Bastiaan de Jong
Luc van den Heuvel
Fon-Wang Chan
Elena Ferrari
Tijn Huttenhuis
Erik Baas
Jeroen Vlek
Daan Tenwolde
Sander Nieuwveld
Thijs de Vries
Floor Baas
Barend Vermeulen
Bjorn-Evert van Eck
Veronie Croese
Lindy Hensen
Anke Kempen
Tom Schouten
Kim Rutten
Alexander Verhuizen
Sven Herberigs Paul van Adrichem
Ivo Roos
Marijn Hooghoudt
Nienke Veenendaal
Ruud van Gool
Marcel Bolten
Leonie van Andel
Arend-Jan van Lent
Niels van Velzen
Steven Buskermolen
Stephan Maaskant
Michiel Verhaar
Alexander Ettema
Arnold Dijkstra Antonio Recamier Elvira
Sander Homs
Tsu-Han Kuo
Ridzert Ingenegeren Joep Oberendorff Maarten Kamphuis
What it is…
Lightweight design is the science and the art of making things
as light as possible, always within constraints
Why lightweight design matters…
• Motor vehicles: better performance and/or lower fuel consumption
• Portables & wearables, bikes etc.: improved comfort
• Mass-produced products: reduced cost
But also: any product can
have a lower eco-impact
if it requires less material
Apart from all of that,
lightweight design is
challenging and fun
Courtesy NPSP and Maarten van Severen and Fabian Schwärzler for Pastoe
What it is…
Lightweight design is the science and the art of making things
as light as possible, always within constraints
products, structures
numbers, methods, predictions
choice, creativity, style
product constraints
process constraints
knowledge constraints
from pure tension… to pure compression
What it isn’t…
Taking a perfectly normal product and replacing the materials inside with ‘lightweight’ alternatives IS NOT lightweight design
results: - not very much lighter (usually) - not quite as functional (often) - much more expensive (always)
Rule # 1
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Clarence L. ‘Kelly’ Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
Rule # 1: illustration
Rule # 2
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Kelly Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
Rule # 2: illustration
Rule # 3
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Kelly Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
Rule # 3: illustration Same force, different direction! Slender beam, with L/H = L/B = 10 What about stiffness? δtension = FL/(EA) with A = BH
δbending = FL3/(3EI) with I = BH3/12
And what about strength? σtension = F/A σbending = FL/W with W = BH2/6
Then σbending / σtension = 60 NB2: comparison gets even worse for torsion
NB1: for hollow beams (T/H = 10), the two ratios are ‘just’ 244 and 44
Then δbending / δtension = 400
solid square beam LxBxH
δ
δ
F
F
Rule #3: another illustration (1 of 3)
F
Rule #3: another illustration (2 of 3)
F
Rule #3: another illustration (3 of 3)
F
Rule # 4
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Kelly Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
Rule # 4: illustration
aluminium
magnesium
GFRP/CFRP
extrusion (+)
roll-forming blanking, bending deep drawing die pressing
casting forging machining
extrusion (-)
(rare) casting (+)
forging (-) machining
pultrusion
thermoforming filament winding RTM, autoclaving
(rare)
(continuous fibres)
+/- denotes relative suitability
‘Ashby criterion’: 2√E/ρ 3 √E/ρ 1 √E/ρ
Rule # 4: another illustration
Kirk precision: cast magnesium frame Lotus: CFRP monocoque frame ‘standard’ aluminium frame
steel ‘tensegrity frame’ courtesy Frans de la Haye
Rule # 5
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Kelly Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than absolutely necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
Rule #5: illustration
Rule #5: another illustration
load
deflection
Rule # 6
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Kelly Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than absolutely necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
Rule # 6: illustration
Bone Chair (inspired by Klaus Matteck) courtesy Joris Laarman Lab
EADS: 3D printed plastic bike
Rule # 7
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Kelly Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than absolutely necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
Yield Strength, MPa
Stra
in-t
o-f
ailu
re, %
Yield Strength, MPa
interstitial-free
mild
interstitial-free, high strength
bake-hardening
chrome-manganese
high strength, low alloy
dual-phase
transformation-induced plasticity
martensitic
twinning-induced plasticity
Stra
in-t
o-f
ailu
re, %
Rule # 7: illustration
AW-6082 (T4-T6) Source: Praktijkboek Hoge Sterkte Staal, FDP
Summarizing…
• DO NOT over-specify “Let the mission design the plane, not the other way around” (Kelly Johnson)
• DO NOT use factors of ignorance instead, use factors of safety
• DO NOT allow bending and torsion … but if you have to, make optimal use of the available space
• DO NOT choose material, shape and production process independently instead, find the right combination
• DO NOT use more joints than absolutely necessary bonus: cost benefit
• DO NOT stop optimizing until it cannot possibly get any lighter “if the plane doesn’t fall from the sky it’s too heavy” (anonymous Boeing engineer)
• DO NOT rule out steel – not yet instead, discard your prejudice and see what’s really out there
PS: want one more rule?
Rule # 8: be inspired by Nature
Reference: “Lightweight Materials, Lightweight Design?” E. Tempelman, 2012, Delft University of Technology. To appear in: “Materials Experience: Contemporary Issues in Materials and Product Design”, Karana, Pedgley and Rognoli (Eds.), Elsevier, Sept. 2013