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A Better Bike: Eco Material SelectionAdam Kenvarg, Joel Rosenberg, and James Regulinski

Autodesk Sustainability Workshop

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Which of These is Better for the Environment?

http://www.carbonfibergear.com/prototype-carbon-fiber-bicycle-frame-from-independant-fabrication-

looks-pretty/

http://campagnolodelta.blogspot.com/2009/11/bicycle-project-2-day-7_24.html

http://www.renovobikes.com/panda-gallery/pandas-and-panda-bits/2020603

Carbon Fiber Stainless Steel Bamboo

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Or These?Titanium

Stainless Steel

Aluminum

http://www.xacd.com.cn/program/propic/20085121756282.jpg

http://bikerschoice.are-us.com/image/cache/ps/77/77-5268-800x1000.jpg

https://store.velo-orange.com/index.php/grand-cru-rando-handlebar.html

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What are Environmental Properties of Materials?

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What Are Some Important Environmental Considerations for

Bicycle Handlebars?

Toxicity

Recyclable

Sustainably Harvested/Extracted

Carbon Dioxide Impacthttp://www.safetysign.com/images/catlog/product/large/J6574.png

http://media.photobucket.com/image/Toxic%20Waste/Baldur_of_the_Aesir/Sign-toxic_waste.jpg

http://media.photobucket.com/image/Recycle/robynmartin1/recycle.jpg

http://openclipart.org/detail/174965/bamboo-by-artbejo-174965

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What are Physical Properties of Materials?

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What Are Some Important Physical Considerations for Bicycle Handlebars?

Rust-proofStrengthWeight

Manufacturable

$Cost Not Brittle

http://openclipart.org/detail/35719/10-kg-weight-by-klaasvangend-35719 http://openclipart.org/detail/71467/muscle-by-hector-Gomez http://media.photobucket.com/image/rusty%20pipe/mumford_stuff/Abstracts/100_0709.jpg

http://pixabay.com/en/fragile-breakable-glass-breaking-98825/http://kk.org/wp-content/archiveimages/bendable_wood.jpeg

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Embodied Energy and Carbon Footprint:Life cycle analysis

Extraction Refining/Manufacturing

Transportation Packaginghttp://openclipart.org/image/800px/svg_to_png/9580/Anonymous_big_truck.png https://office.microsoft.com/en-us/images/results.aspx?qu=MC900238375&ex=1#ai:MC900238375|

https://office.microsoft.com/en-us/images/results.aspx?qu=MC900318492%7C&ex=1#ai:MC900318492|thttps://office.microsoft.com/en-us/images/results.aspx?qu=MC900318496#ai:MC900318496|

https://office.microsoft.com/en-us/images/results.aspx?qu=MC900297997%7C&ex=1#ai:MC900297997|

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Life cycle analysis includes USE

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More About Embodied Energy and Carbon Footprint

Initial mining and processing If aluminum is recycled

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Eco Material Adviser (EMA)

http://autodeskmfg.typepad.com/.a/6a0148c7f4076d970c0153923fd6d8970b-pi

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Eco Material Adviser Workflow

1. http://sustainabilityworkshop.autodesk.com/sites/default/files/core-page-files/ema_quickguide.pdf

1. Establish design requirements and environmental priorities

2. Set baseline materials and processes

3. Search for alternatives

4. Weigh trade-offs of alternative materials and processes

5. Make and document the material choice

© 2013 Autodesk

1. Establish design requirements and environmental priorities

Requirements (must have):

Optimizations (like to have):

© 2013 Autodesk

1. Establish design requirements and environmental priorities

Requirements (must have):

Non-toxic Ductile fracture Rust-proof Operates from -

30°C to 50°C Will not fail under

expected load Can be

manufactured into required shape

Optimizations (like to have):

High strength Low weight Low cost Low carbon

impact Highly recyclable Ideally

renewable

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2. Set baseline materials and processes Material: Aluminum alloy, wrought Process: Forging/rolling Outer Diameter (O.D.): 23.8 mm Inner Diameter (I.D.): 17.8

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Manufacturing Process: Forging/rolling Energy and water are used in

manufacturing. This is in addition to the energy and water required to mine and extract the metal.

1. http://www.ajax-ceco.com/default.asp?ID=43

From Eco Materials Adviser Forging/Rolling Datasheet

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One thick ropeholds the tire swing

You need many smaller ropes to complete the same task

In lifecycle analysis, the functional unit describes the primary function done by a product. In this example it is to hold up a tire swing that might hang from a tree.

Functional Unit

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A functional unit for a shopping bag might require it to hold 50 pounds of stuff before breaking. A plastic bag will be thinner than a paper bag that meets that requirement.

Functional Unit II

1. http://www.plasticpledge.org/assets/uploads/PaperBag.jpg

1. http://dustyburrito.blogspot.com/2012/09/eco-friendly-trompe-loeil-plastic.html

Plastic thickness

Paper thickness

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There are so many things to think about! How do we find the best material?

Process of elimination is a very useful method!

Consider which factors are most important, and which are least important

For an advanced analysis, one should use engineering principles and tools such as an Ashby diagram

3. Search for alternatives

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Ashby diagram Titanium alloys

SteelsAluminum alloys

http://www.grantadesign.com/download/charts/new_strength_density.pdf

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What Thickness Should Each Material Have?

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Smaller inner diameter,thicker wall, more material used

Bigger inner diameter,thinner wall, less material used

Same outer diameters

Comparing Wall Thickness

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Optional Deep-Dive into Math

(Mechanics of Materials)

Slides 21-31

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How Can We Determine The Thickness Required?

𝑀𝑜𝑚𝑒𝑛𝑡=𝑟 ∗𝐹𝐹

𝑟

Let’s look at a simplified model: a beam fixed at one end and free at the other (known as a cantilevered beam)

A force F at some distance r creates a moment M at the fixed end where M = r * F

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Cantilevered Beam Model

𝑀𝑜𝑚𝑒𝑛𝑡=𝑟 ∗𝐹𝐹

𝑟

Looking at the bike model, the cantilevered beam is a reasonable way of modeling handlebars held by a rider a distance r from where they are fixed to the bike.

© 2013 Autodesk

1. We’ll assume that the reference design (made from aluminum) is able to withstand the expected moments

2. We’ll assume that the outer diameter of the handlebars must stay the same (to fit the mount), along with the shape and length

3. We’ll assume that the other versions of the handlebars must withstand the same expected moments

4. We’ll assume that the yield strength is the most important quantity for resisting bending, so that’s the only one we’ll look at (there are other important quantities, but for this approximation we’ll ignore them)

Assumptions

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Yield Strength, syield: The ability of a material to withstand forces before permanently deforming (“bent out of shape”).

We will use the following yield strengths for the materials we are looking at:

Which is the strongest? Which is the weakest?

Yield strength

Material Yield strength, syield

Aluminum 255 MPaStainless steel (austinitic) 215 MPaTitanium 880 MPa

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Titanium is stronger than…Aluminum, which is stronger than…Stainless Steel

So we need less Titanium than…Aluminum, and less than…Stainless Steel

Let’s Apply This To Our Three MaterialsMaterial Yield strength, syield

Aluminum 255 MPaStainless steel (austinitic) 215 MPaTitanium 880 MPa

http://images-of-elements.com/s/titanium-crystal.jpg

http://images-of-elements.com/aluminium.jpghttp://image.made-in-china.com/3f2j00aZltyPzKbRoF/Stainless-Steel-Round-Bar.jpg

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Section modulus I

We will evaluate the worst case scenario for the aluminum, where the moment, M, is enough to reach the yield strength, syield.

A shape-specific quantity known as the “Section modulus,” S, relates the moment and yield strength:

syield = M / S

Yield strength = Moment / Section modulus

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Section modulus II

The Section modulus, S, for a circular tube with Outer Diameter, O.D., and Inner Diameter, I.D., is:

Scircular tube = π * (O.D.4 – I.D.4)32 * O.D.

For the aluminum tube, the grip is:O.D. = 23.8mm, I.D. = 17.8mm:

SAl = π * (23.8mm4 – 17.8mm4)32 * 23.8mm

SAl = 908mm3

http://www.fishingunited.com/forum/attaches/62_TUBING%20SIZE%20OD

%20ID.gif

© 2013 Autodesk

Moment

We can calculate the yield moment for the original aluminum handlebar design by plugging into the equation:

syieldAl = M / SAl

255 MPa = M / 908 mm3

255,000,000 N/m2 = M / 0.000000908 m3

232 Nm = M

We assume that this will be the same moment for ALL different materials

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Comparing Materials

Since the moment, M, is the same for all materials, we don’t even need it! We can simply equate the yield strength and section modulus for different materials:

syieldAl * SAl = M

syieldSS * SSS = M

syieldSS * SSS = syieldAl * SAl

SSS = syieldAl * Sal = 255MPa * 908mm3

syieldSS 215MPa

= 1.19 * 908mm3

© 2013 Autodesk

Stainless steel I.D.

Since we are keeping the same grip O.D. (23.8mm) for all materials, we are solving for the I.D.:

SSS = π * (23.8mm4 – I.D.4) = syieldAl * SAl

32 * 23.8mm syieldSS

π * (23.8mm4 – I.D.4) = 255MPa * 908mm3

32 * 23.8mm 215MPa

= 1.19 * 908mm3

I.D.SS = 15.6mm

© 2013 Autodesk

Titanium I.D.

Since we are keeping the same grip O.D. (23.8mm) for all materials, we are solving for the I.D.:

STi = π * (23.8mm4 – I.D.4) = syieldAl * SAl

32 * 23.8mm syieldTi

π * (23.8mm4 – I.D.4) = 255MPa * 908mm3

32 * 23.8mm 880MPa

= 0.29 * 908mm3

I.D.Ti = 22.5mm

© 2013 Autodesk

Stronger materials allow for more hollow tubes (i.e. thinner walls, less material used) for equivalent functional units

We can use these numbers to create the correct geometry for our handlebars

This geometry allows for more accurate analysis of material tradeoffs

Math Takeaway

Knowing the dimensions, let’s find out the impacts using Eco-Materials Advisor!

© 2013 Autodesk

Open Handlebars_for_LCA.ipt (your screen should look like above)

Follow the directions and fill out worksheet

4. Weigh trade-offs of alternative materials and processes

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Aluminum

Energy usage: 22 MJ CO2 Footprint: 1.7 kg Water usage: 630 L Material cost: $1.6 USD Recycle: Yes Mass: 0.531 kg

Answers

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Stainless Steel

Energy usage: 44 MJ CO2 Footprint: 3.4 kg Water usage: 290 L Material cost: $10 USD Recycle: Yes Mass: 1.980 kg

Answers

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Titanium

Energy usage: 20 MJ CO2 Footprint: 1.5 kg Water usage: 27 L Material cost: $3.5 USD Recycle: Yes Mass: 0.247 kg

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So What Can We Conclude?

5. Make and document the material choice

© 2013 Autodesk, Inc. All rights reserved.

Autodesk is a registered trademark of Autodesk, Inc., and/or its subsidiaries and/or affiliates in the USA and/or other countries. All other brand names, product names, or trademarks belong to their respective holders. Autodesk reserves the right to alter product and services offerings, and specifications and pricing at any time without notice, and is not responsible for typographical or graphical errors that may appear in this document.