Expert report AM vs KIA CASE No. GT03014900-00 SPORTS ... · In this report a rear-end impact accident that occurred on Eastbound Route 5 at the intersection with Brickbat Road also

CLIVE CHIRWA-AM-TT-00/SUV ROOF CRUSH UNCLASSIFIED 2007

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Expert report – AM vs KIA

CASE No. GT03014900-00

SPORTS UTILITY VEHICLE (SUV) REAR END CRASH

WHIPLASH QUADRIPLEGIC INJURY

The Hermitage, Coed Pella Road, Colwyn Bay, LL29 7BA, United Kingdom

“The Centre of Excellence That Offers Future Safe Mobility”

Prepared for: TA, PA, Arkansas, USA

Prepared by: E. Clive Chirwa, BEng (1st Hon.), MSc(Auto. Trans.), MSc (Auto. Struct),

PhD (Struct. Dyn.), FZIE, MSAE


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Table of Contents

Executive summary ............................................................................................. 4

CHAPTER I: INTRODUCTION .......................................................................... 5

Preamble....................................................................................................... 5

Characteristics of the rear impact collision ................................................. 6

Characteristics of the rear impact crash on 28 November 2003 .............. 7

CHAPTER II: DOCUMENTATION AND VEHICLE EXAMINATION .............. 9

Documentation ............................................................................................. 9

Measurements and Inspection .................................................................10

The Measurements ...........................................................................10

CHAPTER III: ANALYSIS OF THE REAR STRUCTURAL COMPONENTS14

Rear Structural Collapse Mechanism .......................................................14

The right side panel and structure .....................................................14

The tail gate ........................................................................................15

The bumper and its energy absorbing system .................................16

The rear side members ......................................................................18

Reaer seat collapse mechanism ...............................................................20

The seat design configuration ...........................................................20

The rear shoulder seatbelts ...............................................................20

CHAPTER IV: EXPERIMENTAL TESTING AND RAMPING ANALYSIS....22

Experimental testing of a car seat .............................................................22

The selection of seat back or backrest angles..................................22

The methodology employed ..............................................................23

The set-up ...........................................................................................24

The run ................................................................................................26

The results ..........................................................................................27

Kinematics responses .............................................................27


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Torso ramping phenomenon ..................................................28

CHAPTER V: DISCUSSION AND ALTERNATIVE DESIGNS .....................32

CHAPTER VI: CONCLUSIONS .......................................................................33

CHAPTER VII: REFERENCES .......................................................................35


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Executive summary

In this report a rear-end impact accident that occurred on Eastbound Route 5 at the intersection with Brickbat Road also known as Route 613, on 28 November 2003 at approximately 1:15 pm, is being analysed in order to offer an expert opinion on how the KIA rear-end structure collapsed in the resulting failure mechanism. In addition, it assesses the likelihood of AM’s roof contact and other loading conditions that precipitated the serious C5-C6 vertebral body & spinous process fractures, resulting in AM’s quadriplegic state. The KIA Sedona VIN No. KNDUP131826299373 in which AM was travelling in at the time of the accident is not compatible with other vehicles that have high centres of gravity, especially not with the Jeep Cherokee. Therefore, in such cases a stronger upper structure will be required and can be achieved by eliminating the large cut-outs that are on each side. The screw jack can be accommodated in the floor. The side members in KIA are not designed to absorb kinetic energy progressively either at the front or at the rear. The design fault is in the side member being curved rather than to be straight at the front and at the rear for maximum energy absorption through pure concertina collapse mode. The rear row of seats is located inside the collapsible zone. This means that the rear structure cannot collapse enough to maximise its energy absorption. Instead the rear row of seats absorbs the chunk of that load. Since these seats are not design to absorb energy, the entire load goes into the seat and the occupant who is ramped at high velocity. This is a design fault and the rear row seat should be moved outside the collapsible zone. The seatbelt top anchorage point in the pillar allowed Amanda to freely move upwards without her body being retained while ramping process is going on. This must be rectified so that in future occupants in those rear seats within the collapsible zone should have seatbelts fitted to the top of the seats. Otherwise, normal seatbelts should have pre-tensioner mechanism fitted as a recommendation. The headroom begins with 36.75 inches at the front, 39.25 inches in the middle and a mere 34.25 inches at the rear. This is a difference of 5 inches in the headroom and not suitable for anybody over 5 foot 10 inches.

It will be advisable to remove the third row from the vehicle. Otherwise the KIA Sedona rear passengers are not only susceptible to severe or fatal injuries in rear impact, but are also not safe in rollover.


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CHAPTER I: INTRODUCTION

Preamble

Rear impact type of accident is categorised as the fourth most dangerous collision type after frontal, side and rollover. Rear impacts are usually associated with low velocity of between 5 mph and 15 mph, and frequently occur at junctions, roundabouts, and in slow moving traffic. In addition, there are rear impacts that occur at very high velocities especially on interstate roads and in fast moving traffic. In such cases, rear collisions occur at locations were the lead vehicle has suddenly either applied brakes, or changed lanes without indicating, or is legally stationary in the fast moving lane ready to turn and move out of the flowing traffic into a feeder road. This is a common rear-end crash as we can see from the AM’s KIA Sedona people’s carrier that was struck while legally stationary on Route 5 at the junction with Route 613. These types of crashes form a significant proportion of all accidents. Statistically, there are approximately 1.5 million passenger vehicle rear-end crashes per year. This accounts for about 23% of all accident types. Thereby, resulting in about 2000 deaths and 950,000 injuries per year according to the General Estimates System (GES) of the National Automotive Sampling System (NASS) and the Fatality Analysis Reporting System (FARS). Economically, this constitutes a societal cost of around $18.3 Billion per year per passenger [1]. These figures have long suggested the necessity for developing crash countermeasures that could prevent serious injuries in rear-end collisions. Solutions have and are being incorporated into vehicle rear-ends, but it is becoming increasingly apparent as in the KIA Sedona’s case that these are not sufficient to cushion the high impact loadings. Therefore, new developments of any rear-end crash countermeasure will require a better rear-end structural design that absorbs kinetic energy in any rear-end collision eventuality and a better understanding of the driver behaviour including associated performance [1]. Much of the $18 Billion societal cost is attributed from the fact that rear-end collision is not death threatening in many cases, but is a source of serious neck injury mechanism known as whiplash and spinal injuries in general. In high velocity rear impact cases like the AM’s, where vehicles are incompatible, occupant injuries are sometimes characterised by both head and neck injuries. This multiple injury mechanism is the most severe head-neck system loading as it involves a phenomenon called ramping, which can be eliminated through good energy absorbing rear structural design.


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In this report a rear-end impact accident that occurred on Eastbound Route 5 at the intersection with Brickbat Road also known as Route 613, on 28 November 2003 at approximately 1:15 pm, is being analysed in order to offer an expert opinion on how the KIA rear-end structure collapsed in the resulting failure mechanism. In addition it assesses the likelihood of AM’s roof contact and other loading conditions that precipitated the serious C5-C6 vertebral body & spinous process fractures, resulting in AM’s quadriplegic state.

Characteristics of the rear impact collision

From the NASS data, rear end collisions in the USA point at the following distribution:

50% of rear impact collisions involve a ∆V of < 13 mph

94% of rear impact collisions involve a ∆V of < 25 mph

85% of rear impact collisions involve a ∆V of < 16 - 20mph It is this last range that is used in the test protocol FMVSS 301 that looks at fuel system integrity. While the European standard ECE 32 is more for the assessment of the rear structure and how it performs in protecting occupants. The ECE 34 regulation also states that the rearward displacement of the “R” point of the rear seats shall not exceed 75 mm (2.95 inches). The KIA KNDUP131826299373 has exceeded this norm to beyond a 100 mm (3.93 inches). The “R” point is the seating reference point and is a design point defined by the vehicle manufacturer for each seating position, Figure 1.

Figure 1. Rear structure excessive intrusion beyond the required 2.95 inches


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Characteristics of the rear impact crash on 28 November

2003

From the police report [2], it is evident that the vehicle in which AM was travelling in was legally stationary at the intersection prior to the accident. The pre-accident scenario according to the police report is therefore as follows: The AM family’s KIA vehicle was Eastbound on Route 5, Figure 2. Travelling behind it at a distance of more than 25 ft (11.8 m), also Eastbound was a 4-WD Jeep Cherokee driven by BR [3].

Figure 2. Junction at close range and KIA’s intended route

The position of the KIA prior to the accident showing the intended route

The path the Jeep should have taken if the driver was vigilant and observing the road


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Figure 3. The post impact final position showing a considerable gap As the AMs approached the intersection, RM, the driver, in very good time activated the left turn signal, slowed and stopped behind another vehicle that had also yielded to oncoming traffic before turning into Route 613. Soon after RM’s KIA was stationary with left turning signal on, BR in a Jeep Cherokee had caught up with the KIA and to some unknown reason despite that he had a lot of distance to avoid the accident slummed into the back of the KIA. As a result the KIA Sedona Van/people’s carrier experienced extensive structural deformation in the back, with the highest intrusion distance in the vicinity where AM was occupying the most rear right seat of a three row seating configuration. The Jeep Cherokee on the other hand experienced a collapse mechanism that is seen in off-set impacts with a minor V-shape final deformation. The accident happened at around 1:15 pm on a clear dry day. Figure 3 shows the final position of the two vehicles post impact. This is the result of the bullet vehicle travelling at about 50 mph, according to BR’s own deposition, making contact with the stationary target vehicle at approximately that speed. However, the speed specified by BR and that calculated from the police recorded skid marks of 10 – 15 feet (18 – 19 mph) does not add up. According to simple calculations, we should have had at least good 110 feet of skid marks to meet the 50 mph speed. This shows that BR saw the AM’s car very late, because he was either not looking ahead, distracted, or micro slept.

The post impact final position showing a gap between the two vehicles that indicate a high impact collision


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CHAPTER II: DOCUMENTATION AND VEHICLE EXAMINATION

Documentation

To facilitate the analysis, Turner and Associates, PA provided the following documentation for perusal:

1. The Virginia State Police Accident Report dated 28 November 2003 and filed 30 November 2003;

2. A new case report dated 10 January 2006 (3 pages); 3. Photographs of AM post accident; 4. A photocopy of the post final resting positions of the two vehicles; 5. Photographs showing the scene/main road Route 5; 6. Scene photographs taken by FMG on 01 December 2003; 7. Vehicle photographs taken by FMG on 01 December 2003; 8. Photographs of a high achiever AM prior to the accident; 9. Photographs of AM post accident in hospital, wheelchair, being cared

for and looked after; 10. KIA Vehicle/tyre photographs taken by T A; 11. Photographs of AM depicting cervical spine fractures & spine injury; 12. Articles about AM; 13. Deposition of BR; 14. Complete transcript of the testimony and other incidents in this case,

heard before The Honourable Colleen Killilea, Judge; 15. AM’s Medical records:

- James City County EMS Pre-Hospital patient report - Medical Records Index Volume I - Medical Records Index Volume II - Richmond ambulance report - May physical therapy services, LLC - Shriners hospitals for children letter by RZ - Temple University hospital children’s medical center operative

report - Clay home medical records - Chester paediatrics records - The Virginia urology center records - Bon Secours St Mary’s hospital operative report

16. FMG investigations summary dated 12 December 2003; 17. Images of the deformed KIA Sedona Van or people’s carrier vehicle in

which AM was travelling in at the time of the accident, Vehicle Chassis No. KNDUP131826299373;

In addition to the above provided documentation, Professor Clive Chirwa travelled to North Little Rock, Arkansas, USA to physically inspect and take strategic measurements of the KIA Sedona vehicle with chassis No.


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KNDUP131826299373 that was located at TA, PA warehouse in North Little Rock. The inspection was carried out on 14th February 2007 between 09:15 am and 09:30 pm.

Measurements and Inspection

CASE - AM vs KIA

- Case No. GT03014900-00

INSPECTION DATE - 14th February 2007

TIME OF INSPECTION - 09:15 AM TO 09:30 PM

WEATHER -Clear blue sky – Full sunshine/full lighting

INSPECTION TYPE -Qualitative

INSPECTION APPARATUS -Tape measure, level, angle measure, and still camera

INSPECTED VEHICLE -2002 KIA Sedona Van (Black) -Chassis or VIN No. KNDUP131826299373

VISUAL DOCUMENTATION -Accident Report, medical reports, still images and all that listed on page 7

OCCUPANTS AT THE TIME OF ACCIDENT

-RM (Driver) - MM - ATM - NM - AM (serious injuries)

THE MEASUREMENTS The vehicle general geometry was inspected from outside and inside. The collapsed vehicle itself in which Am was travelling in at the time of the accident is given in Figure 4. Overall the rear final collapse pattern is not similar to what we have observed in many of other rear impact crashes of similar vehicle class that have defined rear structure energy management systems. The collapse of the structure chassis No. KNDUP131826299373 in which Am was travelling in at the time of the accident can be summarised as follows:

(i) Figure 5 shows the rear view of the KIA vehicle depicting the geometrical boundaries that have been distorted due to the rear impact. The collapse mechanism of the rear structure is characterised by irregular plastic hinges that are random and have made the tailgate to twist, while the D-pillars to bend towards the third row of the car seating arrangement, hence protruding into the survival space. Indeed Figure 6 illustrates the residual distance


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from the outermost structure in the rear to the back of the seat in which Am was seating in to be just 100 mm (3.94 inches). Much of this distance was recovered elastically. This exposed the seat as the total permanent deformation of the rear structure was about 340 mm (13.4 inches). This constitutes over 77% intrusion into the occupant cell. For a vehicle of this type the deformation is somehow excessive and we will later in this report see the reasons why this is the case.

Figure 4. The Vehicle inspected and measured on 14 February 2007


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(ii) Due to the nature of the off-set rear impact covering just over 30%, the intrusion begins clearly at about 530 mm from the right hand side and maximises at the right edge. In the process the right hand side experiences plastic hinges or ripples that are random (Figure 6) showing the unpredictability of the side structure. What I would have expected in such an offset impact is to have many plastic hinges that are logically distributed in a concertina form. This signifies good design that has energy absorption mechanism built into the design. Especially in the lightweight structure like the one in KIA with the rear most seat just inches away from the tail gate, extra energy systems should be built-in to offer extra protection to the occupants occupying the third row, which are last seats in the people’s carrier.

Figure 5 Final rear structure deformations into the survival space

(iii) Figure 6 also shows the right hand side structure of the KIA to be deformed so much that the door was jammed. This can be seen by the wheel arch crash distance if you compare the left side with no significant deformation with the right side with extreme collapse that has made the wheel arch to lock into the tyre and render it

Edge Line of the Jeep contact

30% overlap


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non-operational. By assessing the wheel arch area one can see a complex collapse mechanism characterised by horizontal shunting of the right wheel arch and its vertical deformation as the vehicle overall structure was lifted upwards resulting in permanently elevated wheel arch that lifted the vehicle floor. This type of collapse will always induce a vertical force into the seat thereby allowing the seat to move forward on occupants as well as instigate the ramping force on occupants.

Figure 6 Side views of the Final rear structure deformations

Max Deformation On right side

No significant deformation

Front

Left Side

Right Side

KIA right side rear with only 100 mm residual distance to the seat occupied by Amanda. δ = 340 mm

δ


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CHAPTER III: ANALYSIS OF THE REAR STRUCTURAL COMPONENTS

Rear structural collapse mechanism

THE RIGHT SIDE PANEL AND STRUCTURE (Figures 6 & 7) Figure 6 lower image depicts the right hand side structure final collapse mechanism. The failure is characterised by the rear most end that has shifted towards the front of the vehicle and in the process jamming the door. This shows a poor load path and indicates the inadequacy of the side structure ability to absorb kinetic energy, hence transferring high loads into the vehicle body from the point of application at the rear to the front. For the side structure to have efficient energy absorbing capability it should be able to maximise the energy being absorbed in the rear side structure so that the collapse is concentrated in the structure behind the rear seat. The KIA Sodano final collapse mechanism shows the contrary since it does not depict the pre-determined concertina side structure failure that is seen in good designs. Figure 7. The inner panel of right side structure showing the large opening Figure 7 shows one of the reasons why the load path in the side structure is none existent. The inside panel has a large opening that has cut-off the load path and hence created a stress raiser. It is this opening that is contributing to the energy absorption inadequacy and hence rendering the right side structure to behave in the manner shown in Figures 6 and 7.


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The other point that needs discussing is the randomly distributed plastic hinges that do little in absorbing kinetic energy. Through the cut-out, deformations are showing inefficient collapse and a poor way to absorb energy and as well as transfer in load. THE TAIL GATE (Figure 8) Figure 8 depicts rear door or commonly known as tail gate in a five door configuration. In rear impact the tail gate acts as a membrane that slows the target vehicle through its bending deformation. The collapse mechanism in Figure 8 reiterates the inability of the tail gate in the AM’s KIA to have done much in protecting the rear seating occupants who were just inches away from the point of loading, especially in case of Amanda who was loaded the most because of the offset impact scenario. In this collapse mechanism, the tail gate bent in a V-shape with some plastic bending deformations spread over the surface. By bending in this manner the bulk of the energy is absorbed in a major single plastic hinge. This is not good enough and tail gates, therefore are not designed to protect occupants in rear impacts.

Figure 8. The tail gate deformation by a single major plastic hinge The other plastic lines were due to forcing open the tail gate. They were induced later in order to gate access to the injured AM.


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THE BUMPER AND ITS ENERGY ABSORBING SYSTEM (Figure 9) The bumper system on the KIA in which AM was travelling in at the time of the accident is depicted in Figure 9. No tests were carried out on the bumper, therefore it is assumed, based on modern manufacturing techniques, that this bumper is made from either Expanded Polypropylene (EPP), Polypropylene (PP) or Polyurethane Cast Elastomer (EP).

Figure 9. Rear bumper system and associated failure mechanisms These materials are usually tough, of good strength and possess good multiple impact resistance. However, overall performance depends on the geometry of the component and the direction of applied load plus intensity of that load. Figure 9a shows the bumper and the region of deformation where the load was applied or the contact with the front end of the Jeep was made with the KIA. Figure 9c depicts from the top the bending behaviour that

The rear bumper cover moulded out of a thermoplastic

a) b)

d) c)

The failure mechanism of the randomly reinforced glass composite C-section beam underneath the rear bumper cover characterised by tearing, fibre delamination, matrix cracking and showing unpredictable behaviour for an energy absorber

The roll bar located a distance away from the energy absorbing C-channel beam showing none participation in the energy absorbing process as it is intact


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illustrates the maximum plastic bending that has straightened the bumper flanges. Thereby making the bumper absorb energy through local bending plastic deformation, straightening of the flanges and global bending of the bumper. By removing the bumper cover, a C-channel beam made of random glass fibre reinforced composite is exposed, Figures 9b, 9c and 9d. This is designed in this KIA vehicle as the main energy absorber in any rear impact above 5 mph (bumper cover design speed). The failure mechanism of the energy element of the bumper system in Figures 9b and 9d show fibre fracture and matrix crack, delamination and some element of local bending. The random nature of the failures indicates poor design consideration in an area that requires pre-determined energy absorption characteristics using efficient and effective energy absorbers. In this region, it would have been advantageous to have composite tubes and closed box beams that maximises the energy absorption, hence arresting much of the impact energy from the Jeep. The C-channels are the most poor energy absorbers as they quickly bend without reaching their maximum capacity and fracture. The random fibre composite makes it worse, as this type of composite architecture cannot be used in high energy components that are load bearing. This type of construction is only used in functional structures. The reason being that the architecture has no properly defined load path and hence the stresses quickly build up making the component becomes saturated and hence premature failure. From Figures 9c and 9d, it is evident that the failure begins from the energy bumper flanges outer most fibres and propagates quickly to the base. The mechanics is as follows:

(i) As the load increases, the flanges outermost random fibres experience tensile loading. In a well structured architecture with defined load path through proper weaving, the load is transferred from the loading point to the rest of the vehicle structure. In this case, due to the random nature of the fibres load is instead concentrated in one location and saturation follows quickly and hence failure without maximising work done or energy absorbed;

(ii) Once the crack has appeared due to the fact that the random outermost fibres fracture and matrix cracking has occurred, the failure is catastrophic and will follow through the weak regions of the structure without pre-determined pattern. This is seen clearly in Figures 9c and 9d with fracture distributed all over the component.

(iii) The fixing of the energy element part of the bumper shown in Figure 9d is just bolting connections to the vehicle structure. This is not good connection type as we can see some of the bolts have sheared away due to impact.


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Figure 9c clearly depicts the roll bar that is located a distance away from the bumper system. The roll bar is not part of the energy absorption system in the rear end. However, it can be engaged in absorbing kinetic energy. In this case the roll bar is too low for the Jeep and hence no direct contact was made. However, the jeep pushed it downwards as it just went above it, resulting in the roll bar cantilever failure. If the roll bar was located at optimised height, it would have been engaged in the energy absorbing process and by doing that would have absorbed much of the Jeep energy and hence reduce intrusion and the impulse. THE REAR SIDE MEMBERS (FIGURE 10) Side members in the KIA are the chassis elements that run from the front of the vehicle to the rear. Their geometry at the front and especially at the rear does not offer that natural line to concertina when load is applied. Instead they bend at predictable locations due to the nature of their geometry, Figure 10. In the people carrier of this type like the KIA, the side members are usually designed to act as energy absorbers. Their performance is characterised through multiple plastic hinge creation and thereby maximising the energy absorption. These rear side members in the KIA are not designed to do that. Indeed, their collapse mechanism is one of the worse and extremely inefficient as energy absorption is concentrated in limited number of plastic hinges located naturally at regions that experience high stress. That is the point of bend, while the bulk of the material remains unstressed hence does not absorb energy, Figure 10. Figure 10a shows that side member was loaded through its end. The failure of the spot welds and the section eccentric behaviour indicate the loading to have passed through another loading direction. It can be seen in here that the load path from the Jeep passed above the side member, hence loading the rear vehicle structure rather than going through the side members. Figures 10b and 10d illustrate the side member geometry and the regions or locations where plastic hinges are localised. It is natural to have such a deformation pattern due to the side members not being loaded axially. Research has shown that the more the oblique angle of applied load the more pronounced the localised failure. If the angle is not great up to about critical then the side members will promote progressive buckling. In this case where we have low strength bumper system, the load applied does not promote progressive buckling to the structure around systems that are meant to maximise energy absorption. This does not constitute a design fault, but can be improved to increase energy absorption.


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In a well designed rear end the energy dissipation hierarchy is first the bumper cover absorbs the little energy, followed by the load bumper system that is suppose to absorb more than the cover and then the side members that are suppose to absorb the bulk of the load together with the rear end body structure. If the main energy absorbing systems such as the side members are not engaged in the process, then much of that load will be transferred in the upper body structure that dissipate little work and hence the rear seat positioned a few hundred millimetres away will be carrying much of that load. This means if there was a passenger in the rear seat, that passenger will be heavily loaded as in the case of AM.

Figure 10. Side members position in the energy absorption hierarchy

Rear side member showing some distortion and failure of the spot welds.

This natural curvature of the rear side member showing deformations at precisely the location of change in geometry

Steel material floor fracture showing failure with little energy absorption capability

d)

a) b)

c)


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Rear seat collapse mechanism

THE SEAT DESIGN CONFIGURATION (Figure 11) The KIA Sedona in which Amanda was travelling at the time of the accident has three rows of seats. The driver and front passenger seats are good design with seat belt anchorages right in place. The mid row has also two captain arm chair type seats. These can swivel to offer maximum room for entry and exit to the rear row of seats. The rear row seats are both removable and adjustable depending on what you want to do to the space behind the third row. In the case of AM, the rear seats were in the most backward position so that Amanda and her brother could be given more leg room. By bringing the third row seat right back, two problems arose:

One is that the distance between the outside and the “R” point in the seat reduced tremendously and the allowable distance of collapse under ECE 34 rear impact regulations was just an inch away before the regulation was violated. The rear seats are just too close to the outer structure of the rear end;

The second point was that the more the rear seats moved backwards, the less was the headroom. The headroom changed drastically from the front, where we see a good distance of 36.75 inches that comfortably accommodate different physiques of 5%, 50% and 95% occupants; through the middle where there is excellent headroom of 39.25 inches to the rear of the KIA Sedona where the headroom is the smallest measuring at 34.25 inches. Any 5%, 50% and 95% occupants here will feel very uncomfortable. Indeed reviews about the KIA have all highlighted the headroom at the rear seat to be extremely inadequate and dangerous. Amanda was 13 years old at the time of the accident and according to her size she would fit the 5% occupant. If she sustained horrific injuries while such small, I do not see how the 50% and the 95% occupants could survive such head contacts as they will be fatally injured.

The seats in the KIA were covered in leather. According to the work carried by Latchford [4], he found that such seat covers precipitated the ramping phenomenon. This will looked at length later. THE REAR SHOULDER SEATBELTS (Figure 11) The seatbelts for the rear seats do not offer the best protection with the current anchorage locations. Latchford and others have shown that seatbelts fixed at the top of the seat protect occupant better in ramping phenomenon. The shoulder seatbelts in the case of Amanda do not retain the occupant in the seat as they offer excessive vertical excursion due to the fact


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that they do not arrest ramping. In the case of the KIA Sedona lack of headroom at the back makes contact with the roof by any person inevitable.

Figure 11. Rear seat arrangement and seatbelt anchorage points

The undamaged side showing the seat location and the seatbelt anchorage points. The distance from the rear to the seat is too small for occupant safety

a) b)

d) c)

The damaged roof padding showing indentation of approximately 8.2 inches in major diameter and 7 inches in minor diameter. The depth was between 0.3 – 0.4 inches. For the head to create such a crater the vertical force must have been high despite that Amanda a was a small little child of 13 years.

The residual headroom is about 32 inches at the rear seat occupied by Amanda . This was also due to the seat lifted upwards


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CHAPTER IV: EXPERIMENTAL TESTING AND RAMPING ANALYSIS

Experimental testing of a car seat In order for us to clearly understand the behaviour of the KIA Sedona rear structure behaviour and its relation to the car seat with its occupants, we revisited some tests we carried out in 2004 on the Ford car seat. The reasons we had again to use the Ford seat is because we did not have access to the KIA Sedona seat in Europe and the other is to show that ramping mechanics is independent of seat design profile. The work by Latchford [4-6, 8] and Chirwa [7] have shown that ramping is a function of seatback angle and the impact velocity. Nothing so far in science has shown that the design profile of the seat affects ramping phenomenon. However, it has been shown that the cover materials affect ramping. The reason we had to repeat the 2004 tests was to see the difference in values when new sophisticated instrumentation is used. The piezoelectric accelerometers used last time were measuring the load in two directions only, while the new accelerometers allow us to have a thre- dimensional record of the loading history. The results between the 2004 and the ones carried out in May 2007 were not much different. The reason being that the important parameters in the global longitudinal X- and global vertical Z-axes were exactly the same as measured in 2004. This to us meant that we had to stop the new tests and use the results obtained 2004.

THE SELECTION OF SEAT BACK OR BACKREST ANGLES (Figure 12) Real world accident data have shown that the degree of injuries to occupants in rear impact is dependent on the seat back positioning. This is because of different physique in people who adjust their seat back for ultimate comfort. Therefore, the aim of these tests are carried out herein for two reasons, namely to assess the effects of backrest angle changes and the second is to assess ramping phenomenon. The University of Bolton carried out an extensive survey of the seating position of drivers in cars [5]. The results of that study showed that most of the drivers had their seat back at angles between 20 and 30 degrees to the vertical datum line. This has also been shown in the work by IIHS in the USA. According to test protocols by RCA and IIWPG, the evaluation is carried out at fixed backrest angle of 25 degrees. This is the angle that has been adopted by many companies designing seats and studying the loading between the seat back and the BioRID II dummy used in such rear impact evaluations.


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But the work we carried out at Bolton had shown a range of seat back angles used in real world. Therefore, we decided to find out the effect of these other seat back angles on the BioRID II dummy loading and the ramping phenomenon. We chose three angles of 20˚, 25˚ and 30˚ as shown in Figure 12.

Figure 12. Backrest angle settings for The University of Bolton Tests THE METHODOLOGY EMPLOYED The measurements taken from the KIA Sedona of AM, the backrest on the 14th February 2007, that is date of inspection, was approximately 22 degrees. This means it was 3 degrees out of the standard used internationally. Please note that this may or may not be the angle at which the seat back was at the time of the accident. Therefore, taking a range of angles will cover the AM’s backrest angle.

25º

30º

University of Bolton backrest angle test range

Backrest angle setting for international test protocols

25˚ 20˚

30˚


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The mechanics is that following a vehicle rear impact, the sudden displacement of the torso relative to the head has a range of physical effects on the spine shearing, bending, tension and compression, etc. These experiments show that a change in backrest angle will result in a sensible relative change in these physical effects and will show the relationship between backrest angle and potential neck injury. TEST SET-UP All the tests on the Hyper-G accelerator sled rig were carried out by Bolton using test facilities at Thatcham in England. The first thing was to calibrate the seat and adjust the seat back angle in accordance with the Society of Automotive Engineers procedure, SAEJ826 using SAE approved H-point test manikin shown in Figures 13a and 13b. For these tests the manikin is equipped with a Head restraint Measuring Device (HRMD) to enable backrest measurement. This was then followed by positioning the BioRID II dummy, Figures 13c and 13d.

Figure 13. Determining the H-point position of the manikin and BioRID II

on the Hyper-G accelerator sled rig

a) b)

c) d)

HRMD

H-point


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For each impact, the seat was prepared and adjusted to receive the BioRID II as follows:

The seat was covered with a cotton woven sheet of a prescribed weave so as to present a specific interface surface;

The H point test manikin was positioned in the seat and loaded by pressing the pelvis into the backrest with force of 500N;

The backrest was adjusted so that the manikin torso inclination from the vertical, measured at the hip joint, was as close to the required test angle (20, 25 and 30 degrees) as possible;

The H point position was located and recorded using a FARO arm and probe as shown in Figure 13c. The head restraint stem angle and cushion backseat were measured and the manikin removed;

The BioRID II was positioned in the seat in accordance with ECE-R4, the lower torso being pressed into the backrest with the same force, 500 N;

The hip joint was positioned relative to the seat also using the FARO arm;

Finally the baseline of the head was adjusted to the horizontal position so that the axis of the head accelerometer was parallel to the horizontal plane. The head restraint stem angle and the back of the head restraint cushion from the dummy head were then measured, Figure 13d.

Figure 14. Relationships between stem angle with manikin and BioRID II The results of the settings are shown in Figure 14 that depicts a close correlation between manikin torso angle and head restraint stem angle thus confirming consistent positioning and loading of the manikin over the three


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tests at 20, 25 and 30 degrees backrest angle. Also, a reasonably linear relationship between manikin torso angle and the corresponding head restraint is found for the BioRID II, reflecting again a consistent positioning and loading of the crash test dummy. Taken together these results are evidence of a very consistent relationship between the H point test manikin and the BioRID II crash test dummy over the range of appointed test angles. TEST RUN All the three rear impact tests were carried out at 20, 25 and 30 degrees backrest angle as shown in Figure 15. SL5/03 @ 20˚ SL5/01 @ 25˚ SL5/02 @ 30˚ Figure 15. Three test run configurations

Figure 16. Input histogram known as the IIWPG 10kph ∆V with peak a=6.3g


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For each test, a uni-modal crash pulse having a delta V (∆V) of 10 kph and a peak acceleration of 6.3g was applied to the Hyper-G accelerator sled rig, Figure 16. This is in accordance with the International Insurance Whiplash Prevention Group, IIWPG protocol. High speed photography was employed to record the observable dummy and seat responses. These tests are carried out in low energy input because we had only one seat and we did not want to break it, but use for all the three test configurations. TEST RESULTS Kinematics responses The kinematics responses generated by the BioRID II are summarised in Table 1. These results show a correlation rating of each response being expressed as to how close it is to a linear relationship with the change in backrest angle. The correlation value of 1.0 is an indication of an absolutely linear relationship. Table 1 Test No. SL25/03 SL25/01 SL25/02

Backrest Angle 20˚ 25˚ 30˚

Kinematics Response Units Correlation

Lower Neck Load Index, LNL - 0.41 0.54 0.7 0.999

Nkm (rear impact) - 0.16 0.2 0.26 0.998

Neck Injury Criterion, NICmax M2/S2 13.11 12.31 16.47 0.797

Upper neck shear (+Fx) (head rearward) N 26.12 50.9 70.6 0.992

Lower neck shear (+Fx) (head rearward) N 264.99 295.7 347.9 0.996

Upper neck tension (+Fz) N 330.09 401.9 521.0 0.996

Lower neck tension (+Fz) N 60.31 92.9 101.1 0.925

Head, x, acceleration g 16.46 16.90 20.29 0.925

Thorax, T1, acceleration g 8.25 8.26 9.20 0.897

Pelvis acceleration X (horizontal) g 6.11 6.59 6.86 0.976

Pelvis acceleration Z (vertical) g 2.24 0.98 2.13 0.520

Pelvis acceleration (resultant) g 6.37 6.68 7.2 0.996

The test results are consistence as evidenced by the close correlation between nine or ten of the twelve dummy kinematic responses. The tests produced relatively high levels of lower neck shear and upper neck tension. These are plotted in Figure 17 to show the correlation between these kinematics responses with the backrest angle. The characteristic is a linear function showing that they are interrelated. In addition the characteristics in Figure 17 depict that the backrest angle plays a major role in the loading of occupant’s body. The greater the backrest angle the heavily loaded will be the neck in shear and in tension.


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The tension of the neck is especially important to us in the case of AM because this load in the neck once the head is restricted from above, that load will cause injury to the neck. In the case of AM she was restricted by the low roof with little headroom and hence the neck tensile load was to a greater extent absorbed by the very low stiffness neck. Hence, the injuries that were sustained in the neck. Lower Neck Shear Upper Neck Tension Figure 17. Lower neck shear and Upper neck tension Vs backrest angle It has to be understood for AM to sustain those injuries, she had to moving upwards during the rear impact. Therefore it will be appropriate for us to assess the ramping phenomenon. Torso Ramping Phenomenon The results shown in the sequence of still images depict ramping even at low energy input, Figure 18. Acceleration of the seat in the rear-end impact causes the torso to ramp-up the seat backrest, the greater the angle of inclination the larger the degree of ramping. The change in the physical relationship between the seat and its occupant resulting from ramping changes the nature of the protection offered to the neck. The indication that ramping is present can be seen in the torso movement shown by the small but significant changes in the pelvis acceleration in Table 1. The increasing in pelvis acceleration in the vertical, albeit small, with increasing backrest angle is evidence of torso ramping, Figure 19.


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What these results also show is that for a steep backrest angle (small backrest angle) most of the torso is in contact with the backseat. Hence the upper and the lower parts of the body are accelerated together. In the case when the angle of inclination increases or the backrest angle is larger, the occupant tilts the head forward to enable the eyes to comfortably maintain a level ahead. This in turn lowers the upper point of contact and the area of contact between the backrest and the torso. Accordingly, the lower body, including the pelvis is accelerated first and followed by the upper torso as it progressively rolls back into the backrest and immediately ramping begins. At high velocity rear impact the process will be almost simultaneously. Figure 18. Tests at low energy input showing some sign of ramping In addition Figure 19 shows that the backrest angle is directly proportion to the resultant pelvis acceleration. If the pelvis accelerates upwards, the whole torso will be moving in the upward direction imposing the load on the neck and hence the heavy loading of the neck. At high speed rear impact, the

0 ms 50 ms 100 ms

150 ms 200 ms 250 ms

300ms 320 ms 340 ms


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pelvis acceleration is high and hence the speed of ramping is also high according to the linear correlations we have achieved. This will cause the ramping phenomenon to send the body upwards throughout the rear impact process. If there is an upper limit of some sort as in the case of AM, it was the padded roof, the head will make contact with the roof causing the neck system to compress and bend, thereby absorb much of the impact between the body and the roof. The intensity of that load depends on two factors, the backrest angle and impact velocity that is causing high vertical accelerations. AM would have had minor injuries if the padded roof headroom was not so small. KIA knows that in rear impact there is a phenomenon called ramping. In the design of the headroom, this is taken into account so that roof- head contacts are not made in rear and frontal impacts. This is a design fault that needs rectifying in the KIA Sedona.

Figure 19. Pelvis acceleration Vs backrest angle


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CHAPTER V: DISCUSSION AND ALTERNATIVE DESIGNS

In order to offer adequate protection for passengers occupying third row in the KIA Sedona, the following must be considered in future modifications:

The incompatibility the KIA Sedona has with other vehicles must be rectified. You would expect that the KIA Sedona will be compatible with the Jeep Cherokee because of their high centre of gravity. Not so in this case because the energy absorbing elements on the KIA are down in line more to accommodate the compatibility with passenger cars. This is not a criticism, but the upper structure would have been made stronger by eliminating the large cut-outs that are on each side. On the left side there is an enormous cut-out that is accommodating a screw jack. This is a design fault and the screw jack should be moved to a place under the seat and as a result block the cut-out for extra required strength of the side structure. On the right side, there is also an enormous cut-out that is doing nothing. This should be blocked. By redesigning the side structure so that both the outer and inner metal shells offer increased stiffness and strength, the KIA Sedona back closed structure will absorb more energy through progressive collapse mode and reduce or eliminate the load that is induced in the rear seats.

Although the side members exist, they are not doing the dual jobs they are meant to do in modern vehicles. The dual jobs are to support the vehicle weight by providing stiffness in terms of being the chassis and to absorb impact energy through a concertina mode in case of an accident. The former is well catered for, but the latter is not. The side members in KIA are not designed to absorb kinetic energy progressively either at the front or at the rear. The design fault is in the side member being curved rather than to be straight at the front and at the rear for maximum energy absorption through pure concertina collapse mode.

The rear row of seats is located inside the collapsible zone. This means that the rear structure cannot collapse enough to maximise its energy absorption. Instead the rear row of seats absorbs the chunk of that load. Since these seats are not design to absorb energy, the entire load goes into the seat and the occupant who is pushed upwards due to high ramping velocity.


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This is a design fault and the rear row seat should be moved outside the collapsible zone if injuries of this experienced by Amanda that involve ramping do not occur in the future. Unfortunately, the later models of the KIA have not improved but worsen since they have been shortened by four and three quarters of an inch.

The seatbelts anchor points for the occupants in the rear seats are not located in an optimised location. The three-point seatbelt is good for frontal impact and does well for those occupants seating at the front in terms of rear impact. But for those in the rear, especially for those whose seats are located in the collapsible zone, it will be better to design seatbelts that are anchored at the top of the seats rather than on the pillars as in the case of Amanda’s KIA Sedona. The seatbelt top anchorage point in the pillar allowed AM to freely move upwards without her body being retained while ramping process is going on. This must be rectified so that in future occupants in those rear seats within the collapsible zone should have seatbelts fitted to the top of the seats. Otherwise, normal seatbelts should have pre-tensioner mechanism fitted as a recommendation.

The biggest paradox is the enormous differential in headroom from the front to the rear of the 2000 KIA Sedona Amanda was travelling in at the time of the accident. The headroom begins with 36.75 inches at the front, 39.25 inches in the middle and a mere 34.25 inches at the rear. This is a difference of 5 inches in the headroom. What this means in terms of safety is that anybody seating in those seats at the rear will be susceptible to uncomfortable seating if that person is above a certain height. Reviewers who test ran the KIA reckon that if you are above 5 foot 10 inches, then you should not seat at the back. For a thirteen year old, AM was a tall girl although perhaps she was not 5 foot 10 inches. She was seating pretty close to that. It just required a small ramping for her to make contact with the roof padding. Since the rear impact was about 50 mph according to BR himself, the ramping velocity was therefore very high and hence AM experienced high vertical acceleration and hence the induced quadriplegic injuries.

Based on the current KIA Sedona design, It will be advisable for the manufacturer to remove the third row from the vehicle unless they make the necessary changes that have been proposed herein. Otherwise the KIA Sedona rear passengers are not only susceptible to severe or fatal injuries in rear impact, but are also not safe in rollover.


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CHAPTER VI: CONCLUSIONS

1. The KIA Sedona VIN No. KNDUP131826299373 in which AM was travelling in at the time of the accident is not compatible with other vehicles that have high centres of gravity, especially not with the Jeep Cherokee. Therefore, in such cases a stronger upper structure will be required and can be achieved by eliminating the large cut-outs that are on each side. The screw jack can be accommodated in the floor. By redesigning the side structure so that both the outer and inner metal shells offer increased stiffness and strength, the KIA Sedona back closed structure will absorb more energy through progressive collapse mode and reduce or eliminate the load that is induced in the rear seats.

2. The side members in KIA are not designed to absorb kinetic energy progressively either at the front or at the rear. The design fault is in the side member being curved rather than being straight at the front and at the rear for maximum energy absorption through pure concertina collapse mode.

3. The rear row of seats is located inside the collapsible zone. This means that the rear structure cannot collapse enough to maximise its energy absorption. Instead the rear row of seats absorbs the chunk of that load. Since these seats are not design to absorb energy, the entire load goes into the seat and the occupant who is pushed upwards due to high ramping velocity. This is a design fault and the rear row seat should be moved outside the collapsible zone if injuries of this type that involve ramping do not occur in the future.

4. The seatbelt top anchorage point in the pillar allowed AM to freely move upwards without her body being retained while ramping process is going on. This must be rectified so that in future occupants in those rear seats within the collapsible zone should have seatbelts fitted to the top of the seats. Otherwise, normal seatbelts should have pre-tensioner mechanism fitted as a recommendation.

5. The headroom begins with 36.75 inches at the front, 39.25 inches in the middle and a mere 34.25 inches at the rear. This is a difference of 5 inches in the headroom. What this means in terms of safety is that anybody seating in those seats at the rear will be susceptible to uncomfortable seating if that person is above a certain height. Reviewers who test run the KIA reckon that if you are above 5 foot 10 inches, then you should not seat at the back. For a thirteen year old,


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AM was a tall girl although perhaps she was not 5 foot 10 inches. She was seating pretty close to that. It just required a small ramping for her to make contact with the roof padding. Since the rear impact was about 50 mph according to BR himself, the ramping velocity was therefore very high and hence AM experienced high vertical acceleration and hence the induced quadriplegic injuries.

6. The KIA Sedona VIN No. KNDUP131826299373 has a number of design flaws. It is advisable for the manufacturer to remove the third row from the vehicle unless they make the necessary changes of increasing the distance behind the third row rear seat so that these move out of the collapsible zone. Also to maintain the headroom throughout at 39.25 inches or higher. If not then rear passengers will be susceptible to severe or fatal injuries in rear impact, and also in rollover.


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CHAPTER VII: REFERENCES

1. http://www-nrd.nhtsa.dot.gov. 2. Police Report _ James City County, Virginia State Police, 28 November

2003, and filed 30 November 2003. 3. B R, “Deposition, LAW 37571-VC”, 10 May 2004, Newprot News,

Virginia, USA. 4. Latchford J and Chirwa EC, “The relationship of seat backrest angle

and neck injury in low velocity rear impacts”, Proc. IMEchE, Vol. 219 Part D: J . Automobile Engineering, pp. 1293 – 1302, 2005.

5. Latchford J and Chirwa EC, “Development of a third generation mechanically inflated airbag head restraint system and its characterisation under impact loading”, Int. J. of Crashworthiness Vo. 8 No. 2, pp 201 – 209, 2003.

6. Latchford J and Chirwa EC, “Airbag head restraint system”, Proc. IMEchE, Vol. 214 Part D: J . Automobile Engineering, pp. 229 – 241, 2000.

7. Chirwa EC, “Structural crashworthiness simulation of rear end collision of a small European Car”, Int. J. of Crashworthiness Vo. 1 No. 1, pp 21 – 35, 1996.

8. Chirwa EC and Wang W, “Mechanics of mechanically triggered airbag head restraint for occupant protection in rear impact”, Int. J. of Crashworthiness Vo. 2 No.2, pp 165 – 189, 1997.

Documents

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