Final Presentation

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Team members

Yicheng Zhu

Lab designer

Felipe Augusto

Schwarzbach Caron

Leader

FEA analysis designer

Andrew Oh

Editor/Communications

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Customer Requirements (contract) 1. Select concept for a locomotive bumper

a. 100kph impact

b. Cannot be longer than 6m

c. Low Cost (price should be a small fraction of the total cost of a train)

1. FEA analysis and experimental data on feasibility of a material in these conditions

a. Impact yields Head Injury Criterion or (HIC) < 700

1. Ethical position on prevented-suicide

2. Qualitative Discussion on overall design

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Proposed Concept

“Catch Design”

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need to design material

Background: Accident Numbers

•In 2015, 1211 total caualties (244 deaths and 967 injuries) in US, and 145 total casualties in California •In EU&US, from 2007~2012,29,800 consider suicide, 18,850 for suicide!

• The deaths per ton mile for rail are 37% higher than for truck transportation•Economic costs associated with pedestrian impacts are measured in billions of dollars.

[1] http://safetydata.fra.dot.gov/OfficeofSafety/default.aspx.

[2] European Railway Agency, “Railway safety in the European Union,” Tech. Rep., 2014. http://business.tenntom.org/

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Ethics of Suicide Prevention

• Where Are They Now? - published study by Dr. Seiden followed up on five hundred and fifteen people who were prevented from attempting suicide at the bridge

• The findings confirm previous observations that suicidal behavior is crisis-oriented and acute in nature,’ Seiden concluded;

• If you can get a suicidal person through his crisis—Seiden put the high-risk period at ninety days—chances are extremely good that he won’t kill himself later

http://www.ncbi.nlm.nih.gov/pubmed/2171316

Design Concept

Catch and decelerate

Carry the load until it stops

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[1] B. E. Paden, P. M. Kelly, J. Hines, D. Bothman and C. Simms, “On the feasibility of life-saving locomotive bumpers,” submitted for publication

Qualitative Design

Qualitative discussion on catch systems

Possible sources of failure

Train rolls the pedestrian under the tracks

Partial catch of pedestrian

Collision with unwanted objects

Material degradation (debris and weather)8

Qualitative Design

Qualitative discussion on catch systems

Possible sources of failure and proposed solutions

Train rolls the pedestrian under the tracks => Integrated Ramp

Partial catch of pedestrian => Motorized Platform

Collision with unwanted objects => Safety Net and Layers of Foams

Material degradation (debris and weather) => Weatherproofing

Government safety regulations for material replacement

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Layered foam design. Low yield: green; medium yield: yellow; viscoelastic:

orange

The Head Injury Criterion (HIC)

High HIC Low HIC, Smooth deceleration

Bumper

Acceleration Vs. Time Acceleration Vs. Time

http://www.intmath.com/applications-integration/hic-part2.php11

HIC constant acceleration analysis for high

level (initial) material selection.

Material Selection

Phenolic Foam

Crushable

Low Density/Strength

Available

Easy to form

Cheap13

Methodology

1. Select the material suitable for a locomotive bumper. [phenolic foam]

a. material data with compression test [MTS Test] = stress vs strain curve

b. material data with ball drop test [ballistics lab] = acceleration vs time of

impact material

c. Simulate ball drop test with MTS data

d. Compare experimental and accuracy [HIC vs Velocity of impact material]

2. Analyze the comparison to confirm the accuracy of simulation

Simulate high velocity impact to obtain material feasibility.

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Quasistatic Compression Tests

Procedure

○ crushes 80% of specimen’s initial length

● Yields

○ the stress-strain curve

○ material strength and other properties

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Quasistatic Compression Tests - Machined Specimens

Solid Foam Foam with Axial

Holes

Foam with

Transversal Holes 16

vs.

Transversal

Loading

Axial

LoadingHoles in

blocks

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Quasistatic Compression Tests

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Desired

Material

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Quasistatic Compression Tests - Different composition

Green

high density

Phenolic foam

Blue

low density

Phenolic foam

Pink

high density

Phenolic foam

Brown

low density

Phenolic foam 21

Data from Compression TestsPhenolic foams can be engineered to obtain different strength characteristics.

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Ballistic Lab - Low Velocity impacts

In the Ballistic Lab an Al alloy with a head-form

was mounted in a tripod drop system (Triax

2010, Alpha Automation Inc, Ewing

Township, NJ)

It was dropped from differents height yielding to

impacts at different low velocities.

The HIC, peak acceleration, impact velocity,

and impact angle were outputs of the

equipment. Triax 2010 HIC test setup

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Ballistic Lab - Low Velocity impacts

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Ballistic Lab Tests

Test

number

height (ft) Acceleration

peak (g's)Velocity

(m/s)

HIC

1 2 26 3.51 28

2 3 34 4.28 61

3 4 38 4.89 82

4 5 40 5.36 98

Ballistic Lab - Low Velocity impactsGreen high density phenolic foam

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Ballistic Lab - Low Velocity impacts

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Ballistic Lab Tests

Test

number

height (ft) Acceleration

peak (g's)Velocity

(m/s)

HIC

1 3 25 4.16 31

2 4 32 4.90 64

3 5 33 5.39 75

Ballistic Lab - Low Velocity impactsPink high density phenolic foam

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FEA simulation: quasistatic compression

Material definition:

Density

Poisson's ratio

Young’s modulus

Compressive stress-strain curve (MTS data) 30

FEA simulation: quasistatic compression

107mm

70 mm

Quasistatic compression model built to

check material definition inside

software

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FEA simulation: quasistatic compression

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FEA simulation: low velocity impacts

To reproduce data from the ballistic laboratory tests.

Material definition from the quasistatic compression model (MTS data).

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An Al alloy missile impacting in

a phenolic foam

Input for simulation: Initial

velocity of the impact

Time step of 15 ms based on

the HIC equation

FEA simulation: low velocity impacts

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Validation for low velocity impacts

Parameters data were taken from the MTS!

FEA simulation: low velocity impacts

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Strain-rate dependence

M. F. Ashby, T. Evans, N. A. Fleck, L. J. Gibson, J. W. Hutchinson, and H. N. G. Wadley, Metal

Foams: A Design Guide. Woburn, MA: Society of Automotive Engineers Inc, 2000.

● No temperature dependence

● Rigid polyurethane data

● Strain-rate of 30/s

Plastic collapse strength of a foam

σ : material yield strength at

: strain-rate

T : operating temperature

A and i : material properties

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The effect of the strain rate

dependence in a foam.

Strain-rate dependence

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Initial velocity of 100kph as input

Material definition from the

simulations previously done

Strain-rate dependency was

implemented

FEA simulation: high velocity impacts

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FEA simulation: high velocity impacts

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● Our FEA model predicts that we

meet the design requirement.

Conclusions

Select a concept for locomotive bumper [catch design]

Impact yields HIC < 700 [confirmed with abacus]

FEA analysis and Experimental data on feasibility of a material

[quasi static compression test, drop test, and FEA analysis]

Low Cost (price should be a small fraction of the total cost of a train)

[cost to build new locomotive = $1.5million, cost of bumper is a simple structure phenolic foam]

Ethical position on suicide [study shows prevented suicide lowers the risk of future suicidal attempts]

Qualitative Discussion on design of the bumper [possible solutions discussed]

Our FEA model is validated with 2 lab tests. (MTS & Drop test)

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Future work for a Locomotive Bumper

High velocity experiments

Analyze material strain-rate dependence

Full body dynamic analysis (FEA simulation)

Real impact experiments

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Thank you...

UCSB Faculty:

Brad Paden

Frank Zok

Kirk Fields

Tyler Susko

UCSB Students:

Wessam Aziz

James

Company:

Oasis® Floral Products

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Questions or Comments?

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HIC tests - Blue Foam

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Bumper length analysis.

[1] B. E. Paden, P. M. Kelly, J. Hines, D. Bothman and C. Simms, “On the feasibility of life-saving locomotive bumpers,” submitted for publication 48

4 Concepts for bumper

• bumper 1 catches the pedestrian and carries him/her with the locomotive until the train can stop.

• bumper 2 impacts the pedestrian and accelerates him/her off the track.

• bumper 3 first accelerates and then decelerates the pedestrian off the track at zero velocity.

• bumper 4 is a mechanism that is disconnected from the locomotive at the time of impact with the pedestrian.

[1] B. E. Paden, P. M. Kelly, J. Hines, D. Bothman and C. Simms, “On the feasibility of life-saving locomotive bumpers,” submitted for publication 49

Project scope: material design

• Material needs

• Low Density (small inertial forces)

• Low Strength (small forces)

• Reasonable Toughness (absorb energy)

Soft impact

In the Qualitative Ashby map

Material field chosen == Foams.

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Abaqus Model – For Head ImpactWhy Abaqus?

• Simulation of nonlinear

materials.

• Material user definition.

• Using the same model

that we have in the lab.

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