Hamburg University of Applied Sciences Computational Mechanics for Car Body Design I

Crash Simulation of Car Bodies with FEM Part 1Fabian Duddeck f.duddeck@qmul.ac.uk

June 2007

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Fabian Duddeck

First Motor Cars, 1886

Carl Benz (1844 1929)

Benz Car (1886)June 2007 Crashworthiness, 2 Fabian Duddeck

First Pedestrian Fatality, 1896

Mrs. Bridgette Driscol of Croyden was the first person killed by a car when she left the Crystal Palace in London. June 2007 Crashworthiness, 3 Fabian Duddeck

First Crash Tests, 1937 The AUTO UNION AG, based in Chemnitz, Germany, was the first car manufacturer to develop an empirical crash program in 1937/38. They performed frontal, side, pole impacts and rollover tests. The rollovers were captured in a test film, the other tests were too fast. The cars were dropped sideways from a ramp. The intention was to test the strength of the bodies as part of the development program for the introduction of plastic or wooden structures. The studies were motivated by the aim to replace metal for car structures by wood or plastics without loosing crashworthiness.June 2007 Crashworthiness, 4

DKW Auto-Union, 1937/38Fabian Duddeck

First Biomechanics, 1944 In 1944, John Stapp started research in aerospace medicine for the U.S. air force. The first rocket-sled deceleration research program at Edwards Air Force Base on the Mojave Desert was Stapp's first project related to passive safety. His assignment was to determine human tolerance to deceleration and protection from crash forces. John Stapp started to be concerned not with the structure but with the human body. Often, he himself was the test object.

John Paul Stapp, 1944June 2007 Crashworthiness, 5 Fabian Duddeck

First Biomechanics, 1944 The rocket-sled accelerated 400 m on tracks to attain aircraft landing speeds, then was subjected to aircraft crash deceleration. Metal scoops beneath the sled plowed into a trough of water for the slow-down. Thirty-two rocket runs were made with a dummy passenger before Stapp took his first ride in Dec. 1947. By May 1948 he had taken 16 rides in the backward-facing position, with stresses up to 35 times the pull of gravity. This was double the stress that had previously been set as the limit of human tolerance. These experiments proved that backward-facing seats would give air transport passengers optimum crash protection.June 2007

John Paul Stapp, 1944Fabian Duddeck

Crashworthiness, 6

First Conferences on Passive Safety, 1955 The first Car Crash Conferences were organized in 1955 by John P. Stapp. He presented at the Holloman Air Base sled tests and auto crash tests; aspects of automotive design and safety features were discussed. Many of the safety features discussed and recommended were passed along to traffic experts and automotive engineers, e.g.: - moving dashboards - energy absorbing padding; - fitting doors with safety locks; - removing rear window shelves; - fastening seats - bumper design;June 2007

John Paul Stapp

50th Stapp Car Crash Conference November 6-8, 2006

http://www.stapp.orgCrashworthiness, 7 Fabian Duddeck

Accident Analysis

Is this a safe vehicle?June 2007 Crashworthiness, 8

Is this a safe vehicle?Fabian Duddeck

First Sled Tests, 1950sInsights: The possibility to survive in a crash with 50 km/h was almost zero; 25% of the fatalities happened because the occupants were thrown out of the vehicles; The design of the interior is not adequate to prevent severe head injuries; The steering wheel and the instrumental board should be adopted to head and chest impacts. Nils Bohlin invented the three-point belt and introduced it into the Volvo cars in 1959. The belting systems are really improving safety;Mercedes Benz June 2007 Crashworthiness, 9 Fabian Duddeck

Crash Crumble Zone, 1951

Bla Barnyi, 1907 1997

Patent for the Crash Crumble Zone, 1951June 2007 Crashworthiness, 10 Fabian Duddeck

Crash-safe Door Lock, 1961

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Safety Steering Wheel, 1963

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Safety Steering Wheel, 1963

Bla Barnyi

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Rocket Wagon for Crash Tests, 1962 For acceleration (14 m/s), a hot water rocket wagon was developed (pressurized container, fast opening valve, ejection nozzle). The container is filled with water and heated up (temperature: 260 C, 50 at). After opening of the valve, the water is vaporizing outside of the container. It was not possible to integrate the rocket into the vehicle itself without modifying the structure remarkably.

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Full Car Crash Tests, 1960s

Barrier tests

Car-to-car and roll-over tests

Mercedes-BenzJune 2007 Crashworthiness, 15 Fabian Duddeck

New Acceleration Method for Crash Tests, 1970s New acceleration method based on an electric linear motor that runs underneath the vehicles along a 100-meter trench. New video and lightning systems have been developed. Deformable and non-deformable barriers were used.

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Current Test Tracks, 2005

UTAC, ParisJune 2007 Crashworthiness, 17 Fabian Duddeck

Current Crash Tests, 2005

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Causes of Fatalities50.0%

40.0%

Total number of fatalities in Germany (1989): 697,730

30.0%

20.0%

10.0%

Respiratory organs

Nervous system

Digestive organs

Other causes

Cancer

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Circulation system

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Accidents and crime

0.0%

Causes of Fatalities (Accident and Crime)40.0%

Total number of fatalities in traffic accidents in Germany (1989): 7,812 (=1,12 %)

30.0%

20.0%

10.0%

Domestic accidents

Traffic accidents

Work accidents

Sport and leisure

Other accidents

0.0%

Suicide

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Violence

Road Fatalities, 2005France (2005) Persons killed Persons seriously injured Child fatalities Motorcyclists fatalities Cyclists fatalities Pedestrians fatalities Registered accidents 5,318 39,811 143 1,237 180 635 Germany (2005) 5,361 76,952 159 982 575 686 2 253 992 UK (2005) 3,201 28,954 141 569 148 671 U.S.A. (2005) 43,443 2,348 4,553 784 4,881 -

http://www.cemt.org/irtad/IRTADPUBLIC/index.htm http://www.securiteroutiere.equipement.gouv.fr http://www.destatis.de/ June 2007 Crashworthiness, 21

http://www.dft.gov.uk/ http://www.nhtsa.dot.gov http://www-fars.nhtsa.dot.gov/ Fabian Duddeck

Traffic deaths per 100,000 population since 1970

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Fatalities and Road Traffic (Germany)Germany 54.1 million Number of vehicles 33.8 million 15,050 Fatalities due to road traffic 5,361 Accidents with injuries

But: NHTSA (USA) 22nd August, 2006: Rise in Motorcycle and Pedestrian Deaths Led to Increase in Overall Highway Fatality Rate in 2005

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Active and Passive Safety

Human being

Vehicle

Environment

Active Safety : Avoid accidentssafety instructions, safety informations, medicine, legal security stable driving conditions, intuitive control, intelligent driving systems, optimal perception traffic steering, road construction, laws, accident recording

Passive Safety : Mitigate the consequences of accidentsmotivation to use safety items, rescue facilities, assurances auto-protection, partner protection low danger roads, securing of the accident places

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Active and Passive SafetyAutomotive Safety Accident Avoidance Human Condition (physical, psych.) Vehicle Environment Mitigation of Injuries During the Accident After the Accident

Vision, Lights

Weather

Self Protection Protection of own Occupants Occupant Protection

Partner Protection

Rescue Capability

Perception

Braking, Acceleration

Traffic, Routing

Protection of the other Occupants

Protection of Two-Wheeler and Pedestrian Prevention of Sharp-edged Body Parts

Handling, (Driver Vehicle Environment)

Comfort, Acoustics, Climate, Spring-Damper

Traffic Density

Handling Characteristics

Traffic Control Signal

Occupant Cell (Steering Wheel, Dashboard, etc.) Deformation Characteristics Restraint Systems Bumper and Hood Design Medical Care

Information System June 2007

Prevention of fire

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Percentiles of Car-to-Car Collisions Frontal impact is the dominating type (ca. 56 %); Second probable type is the lateral impact with ca. 38 %; Rear impact is happening rather seldom (ca. 6 %); Until some years ago, the frontal impact was the most dangerous of all impact types; Due to new restraint systems, frontal crash becomes less severe while the percentage of fatal side impacts is rising. The risk of being severely injured or killed by a side impact is much higher than in the frontal crashes.Side Door Impact Type V / VI: 21.6% Side Impact Type VII/VIII: 16.1% Frontal Offset Type II / IV: 34.1%

Rear Impact Type IX / XI: 4.0% Rear Offset Type X / XII: 2.5%

Frontal Impact Type I / III: 21.7%

1998 June 2007 Crashworthiness, 26 Fabian Duddeck

Passive SafetyRoof Interior Dashboard Pedestrian protection Head restraint

Rear impact Belt system Frontal impact Bumper Steering wheel Lateral impact Seats

http://www.easi.de June 2007 Crashworthiness, 27 Fabian Duddeck

Rising Complexity of Passive SafetyCurrent product line Rollover Side air bags Sensor system Trim parts Euro NCAP US LINCAP Right-hand drive car crash Pole impact Suspension and steering column Head impact

FE dummies

Rear impact US side ECE side impact AMS Offset impact against rigid wall FMVSS-208 US NCAP Old product lineJune 2007

AZT / Danner tests IIHS side impact

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Frontal Impact Case Study

http://www-nrd.nhtsa.dot.gov June 2007 Crashworthiness, 29 Fabian Duddeck

Frontal Impact Case StudyV1 - First vehicle Honda Civic, 1997, m=1064 kg, v1 = 63.4 km/h 53 year old male, weight = 90kg, height = 160 cm, unrestrained, airbag;

V2 - Second vehicle Ford Taurus, 1992, m=1430 kg, v2 = 47.1 km/h

http://www-nrd.nhtsa.dot.gov, John H. Siegel June 2007 Crashworthiness, 30 Fabian Duddeck

Frontal Intrusion Honda Civic

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Frontal Impact Principle TestsType 1: Full width, rigid barrier

FMVSS: ECE-R 12: US-NCAP:

v=48.3 km/h v=48.3 km/h v=56.0 km/h.

Type 2: Offset (40 %), deformable barrier (ODB)

ECE-R 94: AMS, ADAC EuroNCAPJune 2007

v=56.0 km/h v=64.0 km/h v=64.0 km/hCrashworthiness, 32 Fabian Duddeck

Frontal Impact Principle TestsType 3: Frontal pole test (tree)

In-house

v=30.0 km/h

Type 4: Danner test (AZT test) Insurance

AZT:June 2007

v=16.0 km/hCrashworthiness, 33 Fabian Duddeck

Frontal Impact Full Width TestType 1: Full width, rigid barrier

FMVSS: ECE-R 12: NCAP:

v=48.3 km/h v=48.3 km/h v=56.0 km/h.

The integrity of the occupant compartment should be assured (safety cage); The rebound (negative velocity) shows that 10% of the deformation is elastic; the total change in velocity is higher than the original velocity. The deceleration of the occupants is very high (special demand of the restraint systems).June 2007

Deceleration, velocity, and deformation as a function of time. Seiffert and Wech, 2003 Fabian Duddeck

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40 % Offset Test, Deformable Barrier (ODB)Type 2: Offset (40 %), ODB

ECE-R 94: AMS, ADAC EuroNCAP

v=56.0 km/h v=64.0 km/h v=64.0 km/h

Only one side of the front end hits the barrier; a smaller area of the structure must manage the crash energy. The front end on the struck side crushes more than in a full-width test (higher intrusion). Full-width tests are especially Deceleration, velocity, and deformation demanding of restraints but less as a function of time. For different types demanding of structure, of crash. Seiffert and Wech, 2003 while the reverse is true in offsets.June 2007 Crashworthiness, 35 Fabian Duddeck

Consumer Tests NHTSA Star Ratings In 1994, the U.S. National Highway Traffic Safety Administration (NHTSA) changed the way they rated frontal crash test performance. Instead of a numerical scale, they created a 5-star rating system. Probability of life-threatening injury Less than 10 % 10 19 % 20 34 % 35 45 % More than 45 %Driver

5 stars 4 stars 3 stars 2 stars 1 starPassenger

Frontal Crash (NHTSA)

Head injury criterion (HIC) Chest deceleration Femur load

847

670

46

47

538/664

697/699

BMW Z4 tested by the NHTSA, 2004June 2007 Crashworthiness, 36 Fabian Duddeck

Consumer Tests EuroNCAP

maximal 16 points

maximal 16 points + 2 points for the head protection system

Good Adequate Marginal Weak Poor Front Side

+ maximal 6 creditsCrashworthiness, 37 Fabian Duddeck

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Consumer Tests EuroNCAPfrontal impact side impact

good adequate marginal weak poor

Frontal impact (max. 16 points) + side impact (max. 16 points) + pole impact (max. 2 points) + 6 additional credits

33 - 40 25 - 32 17 - 24 9 - 16 1-8 0

points points points points points points

Head and Neck Chest Knee, Femur, Pelvis Leg and Foot -

4 points 4 points 4 points 4 points

The only value taken from the structure (100 200 mm intrusion into the footwell)

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Consumer Tests EuroNCAP

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Consumer Tests EuroNCAP

www.euroncap.com BMW 3-Series 28th June, 2005June 2007

Occupant protection 5 starsCrashworthiness, 40

Child protection 4 stars

Pedestrian protection 1 star

Fabian Duddeck

Deformable Barriers For the Euro-NCAP frontal impact (64 km/h, 40% offset) a deformable barrier was developed. The barrier's deformable face is made of aluminum honeycomb, which makes the forces in the test similar to those involved in a frontal offset crash between two vehicles of the same weight, each going just less than 64 km/h.

Honeycomb structure

Continuum model June 2007 Crashworthiness, 41 Fabian Duddeck

Crash Barrier - Repeatability ?Low strength honeycomb (large cell size) High strength honeycomb (small cell size)

FE-model with solid elements and constitutive model for honeycombJune 2007 Crashworthiness, 42 Fabian Duddeck

Lateral Impact Case StudyIsuzu Hombre: Driver: 56-year-old male 173 cm (5 7.5 ), 111kg ( 245 lb) 3-point belt worn Driver airbag non-deployed MAIS: 4 ISS: 36 Change in velocity: v = 21 mph Head: AIS 2 Loss of consciousness