automotive crash survival

MASS PROPERTIES & AUTOMOTIVE

CRASH SURVIVAL Brian Paul Wiegand, PE

74TH SAWE International Conference on Mass Properties EngineeringAlexandria, VA, 18-22 May 2015

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HUMAN CRASH SURVIVAL……WAS INITIALLY CONSIDERED SOMETHING

ABOUT WHICH LITTLE COULD BE DONE. A DECELERATION LEVEL GREATER THAN 18 G’s WAS THOUGHT TO BE UNAVOIDABLY FATAL. SAFETY EFFORT WAS FOCUSSED ON AVOIDING THE CRASH THROUGH BETTER BRAKES, HANDLING, LIGHTING, SPEED LIMITS, TRAFFIC LIGHTS, ROADWAY CONSTRUCTION, DRIVER EDUCATION, ETC. THE PASSIVE ASPECT OF AUTOMOTIVE CRASH SAFETY WAS IGNORED…

74th SAWE International Conference

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HUMAN CRASH SURVIVAL……ATTITUDES BEGAN TO CHANGE IN THE

1930’s. DR. CLAIR L. STRAITH (1891-1958), JOESEPH CHAMBERLAIN FURNAS (1906-2001), HUGH DeHAVEN (1895-1980), COL. JOHN PAUL STAPP (1910-1999), & RALPH NADER (1934-????) INVESTIGATED AND/OR AGITATED FOR GREATER AUTOMOTIVE PASSIVE CRASH SAFETY.


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HUMAN CRASH SURVIVAL……DEPENDS ON A NUMBER OF FACTORS:1. MAGNITUDE OF DECELERATION.2. RATE OF ONSET OF DECELERATION.3. DURATION OF DECELERATION.4. POSITION W.R.T. THE DECELERATION

VECTOR.5. OSCILLATION OF THE DECELERATION.6. ANGULAR COMPONENT PRESENCE.7. PHYSICAL CRUSH &/OR PENETRATION.


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HUMAN CRASH SURVIVAL……IS POSSIBLE FOR VERY HIGH LEVELS OF

DECELERATION IF:1. THE DURATION IS SHORT. 2. THE RATE OF ONSET LOW.3. THE POSITION W.R.T. DECELERATION

VECTOR FAVORABLE, WITH PROPER RESTRAINT AND SUPPORT.

4. THE DECELERATION PULSE IS SMOOTH.5. ANGULAR COMPONENT LACKING.6. NO BODILY CRUSH AND/OR

PENETRATION.74th SAWE International

Conference

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HIGH LEVELS OF DECELERATION


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HIGH LEVELS OF DECELERATION


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RATE OF ONSET


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POSITION W.R.T. DECELERATION VECTOR


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RESTRAINT AND SUPPORT


THE CONVENTIONAL >>>

<<<< THE ULTIMATE

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NO BODILY CRUSH AND/OR PENETRATION


PACKAGING CONCEPT: PROPER RESTRAINT AND SUPPORT WITHIN AN INVIOLATE PASSENGER COMPARTMENT SURROUNDED BY SACRIFICIAL CRUSHABLE STRUCTURE.

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WHEN A VEHICLE CRASHES…


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THE FORCE “F” IS NOT CONSTANT BUT FLUXES AS THE VEHICLE STRUCTURE

CRUSHES IN SPURTS:

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THE KINETIC ENERGY AT IMPACT WILL BE DISSIPATED MAINLY AS THE WORK DONE

CRUSHING THE VEHICLE STRUCTURE:

EXPRESSED IN RAMP MODEL TERMS:

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HIGH DEGREE OF UNCERTAINTY REGARDING “me” VALUE…


Wt = Weight of the vehicle (lb).g = Gravitational constant, “g” = 32.174 ft/s2.I1 = Rotational inertia about front axle line (lb-ft2).I2 = Rotational inertia about the crankshaft axis (lb-ft2).I3 = Rotational inertia about transmission 3rd motion axis (lb-ft2).

I4 = Rotational inertia about rear axle line (lb-ft2). TR = Transmission gear ratio (dimensionless). AR = Axle gear ratio (dimensionless). RD = Dynamic rolling radius at drive wheels (ft).

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NHTSA CRASH TESTING


TWO TYPES: 1- FMVSS or COMPLIANCE TESTING 2- NCAP or 5-STAR RATING TESTING

NCAP TESTING IS THE MORE “RIGOROUS” (35 MPH vs. 30 MPH FIXED

BARRIER CRASH, ETC.) AND MANUFACTURERS TEND TO DESIGN SO

AS TO GET A HIGH NCAP 5-STAR RATING.

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NHTSA NCAP CRASH TESTING


CONSISTS OF A NUMBER OF TESTS:

1) 35 MPH FRONT FIXED BARRIER CRASH

2) 38.5 MPH SIDE MOVING DEFORMABLE BARRIER CRASH 3) 20 MPH SIDE POLE CRASH

4) ROLLOVER RESISTANCE (SSF CALC + “FISHHOOK” TEST) THE 35 MPH FRONT FIXED BARRIER CRASH IS THE MOST SIGNIFICANT TEST, AND DRIVES THE DESIGN OF VEHICLE

FRONT STRUCTURES

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NCAP 35 MPH FRONT FIXED BARRIER CRASH TEST CRITERIA


HEAD INJURY CRITERION (HIC): FOR FMVSS THE HIC VALUE MERELY HAS TO BE LESS THAN 1000 FOR THE 95th PERCENTILE DUMMY AND LESS THAN 700 FOR THE 5th PERCENTILE DUMMY. FOR NCAP RATING IS BASED ON BEST SCORE IN CLASS.

NECK INJURY CRITERION: FOR FMVSS THIS CRITERION MERELY HAS TO BE LESS THAN 937 lb TENSION/899 lb COMPRESSION FOR THE 95th PERCENTILE DUMMY AND LESS THAN 589 lb TENSION/566 lb COMPRESSION FOR THE 5th PERCENTILE DUMMY. FOR NCAP RATING IS BASED ON BEST SCORE IN CLASS.

CHEST ACCELERATION/COMPRESSION CRITERION: FOR FMVSS HAS TO BE LESS THAN 60 g’s DECELERATION OR LESS THAN 2.5 in COMPRESSION. FOR NCAP RATING IS BASED ON BEST SCORE IN CLASS.

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NCAP VEHICLE CLASSES


PC/Mi (Passenger Car/Mini): 1,500-1,999 lb (680-906 kg).

PC/L (Passenger Car/Light): 2,000-2,499 lb (907-1133 kg).

PC/C (Passenger Car/Compact): 2,500-2,999 lb (1134-1360 kg).

PC/Me (Passenger Car/Medium): 3,000-3,499 lb (1361-1587 kg).

PC/H (Passenger Car/Heavy): 3,500 lb and up (1588 kg and up).

LTV (Light Trucks, Vans): includes SUV’s.

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HEAD INJURY CRITEREON


Where:HIC = Head Injury Criterion (dimensionless).t1 = Time at start of interval of interest (seconds).t2 = Time at end of interval of interest (seconds).a = Resultant (total) deceleration (g’s) as per:

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LARGE HEAVY vs. SMALL LIGHT VEHICLES IN NCAP CRASH TEST


1996 Dodge Neon

2006 Honda Ridgeline

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LARGE HEAVY vs. SMALL LIGHT VEHICLES IN NCAP CRASH TEST


24.34 g’s 21.61 g’s

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LARGE HEAVY vs. SMALL LIGHT VEHICLES IN HEAD-ON CRASH


24.34 g’s

14.31 g’s

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EFFECT OF NCAP 35 MPH FIXED BARRIER CRASH TEST


LIGHTER VEHICLES ARE NOW AT AN EVEN GREATER DISADVANTAGE TO HEAVIER VEHICLES IN A CRASH; THE LIGHTER VEHICLE OCCUPANTS ARE MORE LIKELY TO BE INJURED OR KILLED.

THE OCCUPANTS OF ALL VEHICLES ARE MORE LIKELY TO BE INJURED OR KILLED WHEN THE CRASH IS NOT ORTHOGONAL TO A FIXED FLAT BARRIER, OR WHEN THE BARRIER IS NOT SMOOTH AND FLAT, OR WHEN THE IMPACT VELOCITY IS GREATER THAN 35 MPH.

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EFFECT OF NCAP 35 MPH FIXED BARRIER CRASH TEST


MANUFACTURER’S DESIGN VEHICLES TO HAVE THE LOWEST DECELERATION POSSIBLE WITHIN THE AVAILABLE CRUSH DISTANCE (I.E., WITHOUT ENGAGING THE PASSENGER SPACE STRUCTURE). THIS MEANS THAT HEAVIER VEHICLES WILL ALWAYS HAVE SIGNIFICANTLY STIFFER FRONT STRUCTURE THAN LIGHTER VEHICLES, AND THAT ALL VEHICLES ARE NOW ONLY FIT FOR FRONT END CRASHES THAT EXACTLY DUPLICATE CRASH TEST CONDITIONS.

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CONCLUSION


THE NCAP 5-STAR RATING SYSTEM AS IT IS NOW CONSTITUTED INSTUTIONALIZES A MINIMUM LEVEL OF SAFETY AND PENALIZES MANUFACTURES WHO WOULD AIM HIGHER. HUMAN BEINGS CAN SURVIVE FAR HIGHER “G” LOADINGS THAN THOSE RESULTING FROM PRESENT NCAP SYSTEM, AND SMALL LIGHT VEHICLES SHOULD BE ALLOWED HIGHER “G” LOADINGS WITH ATTENDENT BETTER PACKAGING SO AS TO “EVEN THE PLAYING FIELD” W.R.T. LARGER HEAVIER VEHICLES.

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Q&A

FIVE MINUTES ARE ALLOCATED FOR ASKING QUESTIONS OF THE

AUTHOR


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Q&A


WHEN CRUSH DISTANCE IS EXCEEDED: g’s

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Q&A


SHEDDING KINETIC ENERGY (PARTS): g’s

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Q&A


CRASH MODELING SUMMARY: g’s

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Q&A


WHEN CRASHES DO NOT FOLLOW NCAP SCENARIO: g’s

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Q&A


RACE CAR DRIVERS ROUTINELY SURVIVE WHAT NHTSA CALLS FATAL g’s

“…(Purley) survived an estimated 179.8 g’s when he decelerated from 173 km/h (108 mph) to 0 in a distance of 66 cm (26 inches)… This was the highest measured (sic) g-force ever survived by a human being…(until in 2003, Kenny Bräck's crash violence recording system measured 214 g).

“David Charles Purley…(26 January 1945 – 2 July 1985) was a British racing driver… best known for his actions at the 1973 Dutch Grand Prix, where he abandoned…(his race car)…and attempted to save…fellow driver Roger Williamson, whose car was…on fire...Purley was awarded the George Medal for his courage in trying to save Williamson, who suffocated...During pre-qualifying for the 1977 British Grand Prix Purley sustained multiple bone fractures (when)…he crashed into a wall. His deceleration from 173 kph (108 mph) to 0 in a distance of 66 cm (26 in) is thought to be one of the highest G-loads in human history…He died in a plane crash in…1985.”

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Q&A


1948 TUCKER “TORPEDO” AFTER 100 MPH ROLLOVER INDY DEMONSTRATION

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