John M. cavanaugh, Timothy Walilko, Jaekoo Chung, and Albert I. KingWayne State Univ.

962410

Abdominal Injury and Response in Side Impact

Copyright 1996 Society of Automotive Engineers. Inc.

ABSTRACT

The purpose of this paper is to address abdominalinjury and response in cadaver whole body side impactsand abdominal injury risk functions in SID and BIOSIDin whole body impacts. Side impact sled tests wereperformed at Wayne State University using cadavers,SID and BIOSID, with response measured at theshoulder, thorax, abdominal and pelvic levels. The dataat the abdominal level are presented here. These dataprovide further understanding of abdominal toleranceand response in lateral impact and the ability of sideimpact dummies to predict abdominal injury. In addition,the padding data provide insight into tolerable armrestloads.

INTRODUCTION

Abdominal organs are a significant source of injuriesin side impact. Bondy (1980) reviewed abdominalinjuries in the 1980 National Crash Severity Study(NCSS) files from 1977-79 accident data. There were1,519 abdominal injuries in the NCSS file for thisperiod. Abdominal organs accounted for 2.6% of allinjuries and 14.6% of all severe injuries (AIS 3,4,5) tooccupants of towaway vehicles. Injuries to kidney, liverand spleen accounted for 32 % of all injuries to theabdomen. Front damaged vehicles produced 739abdominal injuries and side damaged vehicles 419, with226 of these 419 being AIS 3-5. Contact points in liver,kidney and spleen injuries included side interior surfaces(which were second obly to the steering wheel as acontact point) and to a lesser extent, armrests. Fewinjuries occurred to restrained occupants (2.6% of allAIS 3-5 injuries).

Siegel et aI (1993) studied 76 frontal impact and 45lateral impact motor vehicle accident victims admitted toa Level I trauma center. They utilized accident recon-

1

struction and medical data analysis. Contact with theintruded side door caused lung, aorta, liver and pelvicinjuries. Contact with the side door without intrusionwas responsible for lung, liver and spleen injuries.Abdominal organ injuries occurred in 47 patients, 23 infrontal crashes and 24 in lateral crashes. The organinjuries were to the spleen in 22 patients, the liver in 22,the kidney in eight, the bowel in eight and the colon intwo. The authors concluded that belts did not preventthoracic and abdominal solid organ injuries in lateralcollisions in this group of patients but other investigatorshave pointed out the benefits of seat belts to far sideoccupants in side impact (ie. Warner et ai, 1990).

The side impact sled tests run at the WSUBioengineering Center can shed some light on the overallside impact severity necessary to produce theseabdominal injuries and provides data on padding andarmrest stiffness that can reduce these injuries.

Ratwall tests: In the WSU cadaver flatwall tests theshoulder (Irwin et al 1993), thoracic (Cavanaugh et al1990b, Cavanaugh et al 1993) and pelvic (Cavanauglt etal 1990b, Zhu et al 1993) injury and response data havealready been reported. The SID thoracic response datahas also been reported (Cavanaugh et at 1992, 1994).The abdominal injury and response data has never beenreported and is presented here.

Armrest tests: In addition, the data from a series ofhoneycomb armrest tests run with SID and BIOSID arepresented.

METHODS

Two types of tests were run: flatwall tests with SID,BlOSID and cadavers and armrest tests with SID andBIOSID. All the tests utilized the WSU WHAM ill sled,which was accelerated to 6.7 or 8.9 mls (15 or 20 milesper hour) and suddenly decelerated upon impacting ahydraulic snubber. During the deceleration, the subject

slid across a TeflonTM seat into a wall instrumented withload cells. The velocity of the wall was zero at time ofdummy impact. The velocity of the subject just beforeimpact was close to peak sled velocity. All subjects wereinstrumented with accelerometers to measure rib, spine,pelvic and head accelerations. In addition, the BIOSIDwas instrumented with six potentiometers, including twoat the abdominal ribs (ribs 4 and 5). High speed camerasrun at 500-1000 frames per· second were used to monitorthe impact event.

Flatwall tests

Eight types of SID and BIOSID tests were run.They are listed in Table 1 along with the number ofcadaver tests. The subject's left side impacted the wallwith the arm down. The impact wall included two loadcells at the abdominal level (Figure 1).

Armrest tests

SID and BIOSID were instrumented as for theflatwall tests but in the armrest tests BIOSID was runarm up and the subject's right side impacted the wall.The overall dimensions and padding profile of theimpacted wall also differed from the flatwall tests andincluded a projecting piece of padding at the abdominallevel. Two load cells were placed behind the shoulder,thorax, and abdominal load plates and four behind thepelvic load plate (Figure 2). Figure 2 further describespadding types and dummy placement relative to thepadding. Eight dummy tests were run with two armresttypes as described in Table 2.

Crush data on the soft and stiff paper honeycombarmrests is given in Table 3. The crush strengths werederived from quasi-static tests of 15 x 15 x 10 em (6 x6 x 4 inch) thick samples. A sample was taken fromeach four foot by four foot billet for testing. The crushstrengths listed were the average value of compressivestrength from 1.3 to 7.5 cm (0.5 inch to 3 inches) ofcrush. These values are somewhat less than the previouscrush strengths for this type of paper honeycomb used inour laboratory.

Data processing

In the flatwali tests the data were analog filtered atSAE channel class 1000 and digitized at a 10 kHzsampling rate using a DSP Technologies Inc. off-boarddata acquisition system. In the armrest tests the datawere filtered at 3.57 kHz and digitized at a 14.7 kHzsampling rate using an IDDAS on-board data acquisitionsystem. The data were then filtered at SAE channel class1000. The data were further processed after uploading toa SUN workstation. The acceleration data were

2

processed using NHTSA FIRI00 software and asoutlined in Morgan et al (1986). BIOSID deflection datawere processed using the WSU V-STAR-C program. Ribdeflection, velocity and barrier force data were filteredusing a digital 300 Hz Butterworth filter.

RESULTS

Aatwall tests

Cadavers: Flatwall tests with cadavers demonstratethat at sled velocities of 8.9 mls (twenty miles per hour),injury of abdominal organs is a common occurrence asis fracture of the lower ribs overlying these organs. Offive unpadded tests run at 8.9-10.4 mis, three cadaverssustained lacerations of liver or spleen and these samethree cadavers had 6-8 rib fractures at ribs 8-12 (Table4A). Out of three tests run at 6.7 mls one cadaversustained abdominal organ injuries, and had two ribfractures. The other two cadavers at this impact velocityhad no abdominal injury. Soft paper honeycomb of 55­69 kPa (8-10 psi) crush strength substantially reducedabdominal injury in 9 mls impacts. In five cadavers, noabdominal organs were injured and four of five subjectshad no fractures of ribs 8-12. On the other hand, fourtests were run at 9 mls with stiffer padding and twocadavers sustained abdominal injury and two had 6fractures of ribs 8-12.

Figures 3A-G are scatter plots of abdominal injuryversus biomechanical response. The biomechanicalresponses are listed in Table 4B for each test.Abdominal injury in these plots is the sum of the squaresof the AIS of the three fonowing regions: left ribs 8-12,right ribs 8-12 and abdominal organs. The valueobtained is similar to the Injury Severity Score of Bakeret al (1974) which is used for multiple body regions.Biomechanical response includes peak acceleration of thestruck side eighth rib (100 Hz FIR filtered), average ribacceleration (ARA) of the struck side eighth rib,Average Spine Acceleration (ASA) and Thoracic TraumaIndex (TI1) using peak eighth rib acceleration. Lightersubjects tend to have higher accelerations in an identicalimpact to heavier subjects. A 75 kg standard mass wasused to normalize the response data, as is used in TIl.Older subjects tend to have more injury than youngersubjects in identical impacts (although this was notalways the case in this study, Table 4A). Therefore, thesubjects' ages were nonnalized to a value of 45 years.The acceleration responses in the Figure 3 include valuesadjusted as follows: ASA and ARA were multiplied byAGE/45 x MASS/75. The TTl kernel was multiplied byMASS175 and summed with the product 1.4 x AGE(Eppinger et ai, 1984). These data show that abdominalinjury started to occur at nonnalized T12y values of 72g's, ASA of 37 g's, and TTl of 143 g's. It can also be

TABLE 1

No. of tests per subject

Velocity SID BIOSID CADAVERS PADDING(Mileslhour)

15 4 2 3 unpadded

20 2 2 2 unpadded

20 2 1 3 4 inches of soft paper honeycomb

20 2 1 2 34 inches of stiff paper honeycomb

20 2 2 6 inches of ARCEL 310-

20 2 2 12 inches of soft paper honeycomb-

20 2 2 2 6-8 inches of soft paper honeycomb

20 2 2 8 inches of stiff paper honeycomb-The paper honeycomb used in these tests is a product of Hexacomb Corporation (Kalamazoo, MI). Arcelis a product of ARCa Chemical Co. (Newton Square, PA).

TABLE 2

No. of tests per subject

Velocity SID BIOSID CADAVERS Armrest Padding(Mileslhour)

20 2 2 10 inch thick stiff paper honeycomb-armrest

20 2 2 IO inch thick soft paper honeycomb-armrest

TABLE 3

Proposed armrest Tested Paper Armrest Paddingcrush strength armrest honeycomb

(pounds per crush cell sizesquare inch) strength (inches)

10 (soft) 8.4 I IO inch thick stiff paperhoneycomb armrest

20 (stiff) 19.8 3/4 10 inch thick soft paperhoneycomb armrest

3

NOTE: AU. DlMENSIONS IN mil\.

Figure 1. Diagram of the flatwall test fixture showing the load plate and the twoload cells at the abdominal level.

4

6

Black squares represent load cells.

.00

v

~.~[::;~

~.~

~

~~~ 24t:::~:::.~::::::~I--'

l::"......

Armrest FiXtUre

9.50

L L------J '--_-'

l..3.00~ l.4.00...J

10.00

~ 3,00 ; r- 3.00, I 4~OO i I

~DDD~DDD

PHC = PAPER HONEYCOMB

(ALL DIMENSIONS IN INCHES)

Figure 2. Diagram of armrest fixture used in this test series. The padding affixedto the load plates was three and four inch thick paper honeycomb. The load plateheights are as shown and were twenty inches wide. Each piece of paperhoneycomb was precrushed one-half inch. The armrest padding projected threeinches beyond the other pads. The SID was aligned so that the rib cage impactedthe shoulder and thoracic pads. The SID abdominal insert impacted the armrestpad. The BIOSID was aligned such that ribs 1, 2 and 3 impacted the shoulder andthoracic pads and ribs 4 and 5 impacted the armrest padding. Rib 4 was alignedsuch that the top edge of the rib was the same height as the top edge of theabdomen barrier.

1 OR 3/4 INCH CEll-SIZE PHC-'Oil~DD ~.0.75

1 INCH CELl-SIZE PHC ----.~

3/4 INCH CELL-SIZE PHC---.....

5/8 INCH CELL-SIZE PHC---••

TABLE 4A: ABDOMINAL INJURY SUMMARY, WSU-CDC CADAVER SIDE IMPACT FLATWALLTESTS

ABDOMINAL INTERNAL ORGAN INJURY RIB INJURY, RIBS 8-12 SUM OF

LEFT RIGHT SQUARES

RUN NO. AGE MASS SEX LEFT RIGHT TOTAL RIB RIB OF 3 AIS

(KG) AIS DESCRIPTION RIB FX RIB FX RIB FX ArS AIS

UNPADDED, PELVIC OFFSET +

SICOI 60 70.3 M 2 10 MM LIVER LAC. 4 3 7 3 2 17

SIC02 64 49.4 F 2 LAC. OF CAPSULE OF SPLEEN 6 2 8 3 2 17

SIC03 37 69.9 M Q NONE l Q l l Q 1AVG 54 63.2 1.3 4.0 1.7 5.7 2.7 1.3 12.7

UNPADDED, 9 m/ssrC04 69 57.6 M 2 TWO 25 x. 13 MM LAC. OF SPLEEN 5 1 6 3 1 14

SIC06 60 61.2 M Q NONE Q Q Q Q Q QAVO 65 59.4 1.0 2.5 0.5 3.0 1.5 0.5 7.0

UNPADDED, 6.7 mls

SIC05 67 44.0 M o NONE 0 0 0 0 0 0

SIC07 66 74.8 M o NONE 0 0 0 0 0 0

SlC08 64 73.9 F 1 25 MM LAC SPLEEN x. 2, 10 MM LAC LIVER 1 1 £ ! 1 11AVG 66 64.3 1.0 0.3 0.3 0.7 0.3 0.3 3.7

SOFT PAD (8-10 PSI), 9 m/s

SICI0 60 62.1 M o NONE 0 0 0 0 0 0

SICll 54 55.3 F o NONE 0 0 0 0 0 0

SIC13 62 66.7 M o NONE 1 2 3 1 2 5

SIC15 43 68.9 F o NONE 0 0 0 0 0 0

SICI7 65 93.0 M Q NONE Q Q Q Q 0 QAVO 57 69.2 0.0 0.2 0.4 0.6 0.2 0.4 1.0

STIFFER PAD (13·25 PSI), 9 m/ssrC09 61 54.9 F o NONE 5 I 6 3 1 10

SICI2 68 54.4 F o NONE 2 1 3 2 1 5

SIC14 72 55.3 M 2 50 x. 12 MM LAC. SPLEEN NA NA NA NA NA NA

SICI6 58 56.7 F 1 LAC THROUOH SPLEEN ~ 1 .2 ~ I 26

AVO 65 55.3 1.5 4.0 1.0 5.0 2.7 1.0 13.7

0>

• PELVIC OFFSET TESTS WERE RUN AT 8.9 TO 10.5 m/s NA = NOT AVAILABLE

.....

TABLE 4B: ABDOMINAL RESPONSE SUMMARY, WSU-CDC CADAVER SIDE IMPACT FLATWALL TESTS

300 HZ NORM AGE/45 AGE/45 AGE/45 AGE/45ABD ABD FIRIOO It MASS175 FIR 100 It MASSI75 ll. MASS175 ll. MASS/75

RUN NO. AGE MASS SEX FORCE FORCE T12Y TI2Y RIB 8 RIB 8 R8 R8 ll.RIB 8 T12Y T12Y(KO) (kN) (kN) (O'S) (O'S) (O'S) (G'S) Ttl ARA15 ARA15 ASA15 ASA15

UNPADDED, PELVIC OFFSETSICOI 60 70.3 M 3.52 3.68 --- --- 132.1 165.1 --- 50.1 62.7 --- ---SlC02 64 49.4 F 2.44 3.23 116.0 108.7 114.2 107.0 165.5 57.0 53.4 69.5 65.1

SIC03 37 69.9 M 5.36 5.62 127.7 97.8 164.2 125.7 187.7 22.8 17.5 80.8 61.9

AVG 54 63.2 3.77 4.17 121.8 145.6 136.8 132.6 176.6 43.3 44.5 75.1 63.5

UNPADDED, 9 m/a

SIC04 69 57.6 M 3.77 4.49 75.5 88.9 163.3 192.3 188.3 38.0 44.7 53.2 62.6

SIC06 60 61.2 M 4.10 4.69 92.8 10LO 145.4 158.2 181.2 70.4 76.7 47.1 51.3

AVG 65 59.4 3.93 4.59 84.2 95.0 154.3 175.3 184.8 54.2 60.7 50.2 57.0

UNPADDED, 6.7 m/a

SlC05 67 44.0 M 2.63 3.75 92.3 80.6 100.4 87.7 150.3 76.6 66.9 68.7 60.0

S1C07 66 74.8 M 2.82 2.82 42.0 61.5 117.8 172.4 172.2 30.9 45.2 31.6 46.3

SIC08 64 73.9 F 2.80 2.83 51.4 72.0 --- --- --- --- -_. 36.7 51.5- - - - -AVO 66 64.3 2.75 3.13 61.9 71.4 109.1 130.1 161.2 53.8 56.1 45.7 52.6

SOFT PAD (8-10 PSI), 9 m/s

SIC 10 60 62.1 M --- --- 97.3 107.5 95.0 104.9 163.7 20.9 23.1 32.6 36.0

SICII 54 55.3 F 3.15 3.93 54.7 48.4 81.4 72.0 125.8 41.0 36.3 25.4 22.5

SICI3 62 66.7 M 3.30 3.57 -- -- 79.5 97.4 --- 20.2 24.7 --- ---SIC15 43 68.9 F --- --- 53.0 46.6 57.8 50.7 111.1 21.7 19.0 34.4 30.2

SIC17 65 93.0 M 3.20 2.77 67.0 120.1 87.5 156.8 186.8 15.8 28.3 26.4 47.3

AVG 57 69.2 3.22 3.42 68.0 80.6 80.2 96.4 146.8 23.9 26.3 29.7 34.0

STIFFER PAD (13-25 PSI), 9 m/sSIC09 61 54.9 F --- --- 80.8 80.2 77.7 77.1 143.4 63.8 63.3 41.6 41.2

SlC12 68 54.4 F 3.66 4.62 72.3 79.3 104.4 114.5 159.3 30.2 33.1 48.4 53.1

SIC14 72 55.3 M 3.09 3.79 100.8 118.9 148.4 175.0 192.7 71.7 84.6 38.1 44.9

SIC16 58 56.7 F 3.76 4.53 81.8 79.7 227.2 221.3 198.0 46.0 44.8 38.2 37.2

AVG 65 55.3 3.50 4.31 83.9 89.5 139.4 147.0 173.3 52.9 56.5 41.6 44.1

26 2624 A 24 B

Vl 22 Vl 22< 20 < 208 18

F8 18

~ 16 ~ 16014 M 5 14Vl 12

FVl 12

I") I")

..... 10 F ..... 100 8 0 8~ 6 ~ 6~ F ~Vl 4 M Vl 4

2 20 m '11

"'"~_,Yl' 0

a 20 40 60 80 100 120 140 0PEAK T12Y ACCEL (FlR100, G'S)

100 120 140 160 180 200 220 240TTl (RIB 8)

240

F

F M

F F

F

M F M

F

lY lY 'M' nol

20 40 60 80 100 120 140AGE-MASS NORM T12Y (G'S)

Figures 3A-G. Seatter plots of abdominal injuryversus biomechanical response for the cadaverflatwall teSt series. Abdominal injury is the sum ofthe squares of the AIS of the three followingregions: left ribs 8-12, right ribs 8-12 and abdominalorgans. M and F in the plots stand for male andfemale. Acceleration responses in the figure includevalues adjusted as follows: Values noted as age-massnormalized are multiplied by AGE/45 x MASS/75.The TIl acceleration kernel is multiplied byMASS175 and summed with the product 1.4 x AGE.

26.----------------F-...,

24 DVl 22< 208 18

~ 16o 14Vl 12I")

..... 10o 8

~ 6Vl 4

2o -f---r----r-r-r-i"T'ioI-"",rIIit-""-r---r-~.......__..rM-r-----.-..---l

o 40 80 120 160 200AGE-MASS NORM PEAK RIB 8 ACCEL (G'S)

8

2624 F

Vl 22< 208 18

F M~ 165 14 MVl 12I")

..... 10 F0 8~ 6~ M FVl 4- M

20 "" ov_ -...- ~

80 0 20 40 60 80AGE-MASS NORM ARA (G'S)

240

F

200

M

F

F

F

F

F

F M

F

M F

F

26...----------------F--,

24 CVl 22< 208 18~ 16514Vl 12I")

..... 10o 8

~ 6Vl 4

2o-f---r----,----;;;---i'-'M!;l""MVlIllt-fll---.fl.........-..---,---.----l

o 40 80 120 160PEAK RIB 8 ACCEL (G'S)

26.---------F---------,

24 EVl 22< 208 18~ 165 14Vl 12I")

..... 10o 8~ 6Vl 4

2o-f---r--rf=-----lF-""Iaf--,----l""'......'!'tl..---_...-..------l

o 20 40 60AGE-MASS NORM ASA (G'S)

26.--------------F-----,

24 GVl 22< 208 18

. ~ 16

514Vl 12I")

..... 10o 8~ 6Vl 4

2o+--r--r--r--r-F-,-...--tl,,,.........'kH..,',,......~w~-r-..__..---.....--l

80

Figures 4A-D. Force-time histories of the abdominal load plate in four types of flatwall tests: A. 6.7 m/s with no padding. B. 9 mls with no padding.C. 9 mls with soft padding (8-10 psi honeycomb). D. 9 m/s with stiff padding (18-25 psi honeycomb).

A

P ~

[ F ~~

BA

( I~~

d \~~n /'\.V v

120.0

120.0

90.0

90.0

t!J CADAVERo SID.eo BlOSID

t!J CADAVERo SID.eo BIOSID

30,0 60,0

Time (ms)

30.0 60.0

Time (ms)

~0

4~ ~

~~

~W ~~

ooto

9 m/eec (20 mph) unpadded

9 m/eec. 3-4 inchesstiff honeycomb

ooto

......Zo::I. •

o(\J

OJULalL~

o(\J

I120.0 0.0

......Zo::I..

o(\J

QlULaIt..~

o(\JI

120.0 0.090.0

90.0

t!J CADAVERo SID.eo BIOSID

t!J CADAVERo SID.eo BIOSID

30.0 60.0

Time (ms)

30.0 60.0

Time (ms)

c

~~

d(J !! "\v

ooto

.-..Z::i~

a(\J

OJULalL~

o(\JI0.0

aato

6.7 m/aec (15 mph) unpadded

9 m/selc. 4 inchessoft honeycomb

......Z::1. 0'-' .

a(\J

QlULolL a

a(\JI0.0

tD

seen in the figures that above these threshold values.only male cadavers were uninjured.

Force Comparison: SID, BIOSID and cadaver:Figures 4A-D show force-time histories of theabdominal load plate in four types of flatwall tests: 6.7and 9 mls with no padding, 9 mls with soft padding (8­10 psi [55-69 kPaJ paper honeycomb) and 9 mls withstiff padding (18-25 psi paper honeycomb). Theunpadded tests indicate that both SID and BIOSID hadless effective mass than cadavers at the abdominal loadplate level as indicated by the corresponding areas underthe foree-time history curves in Figures 4A and B.Figure 4C indicates that the soft paper honeycomb actedas a force limiter, with forces in the 2-2.5 kN range overmost of the impact. In stiff paper honeycomb tests, peakforce approached 4 kN (Figure 4D).

BIOSID: The BIOSID responses at ribs four andfive predicted which test conditions were injurious in thecadaver tests, and the benefits of the soft padding overthe stiff padding (Table 5). In unpadded tests VCmax ofnos 4-5 averaged 2.03 mls in 9 mls impacts and 0.39mis in 6.7 mls impacts. In the case of stiff padding(ARCEL 310 and 18-25 psi 3/4 inch cell paperhoneycomb) VCmax of ribs 4-5 was 1.05 to 2.12 mls.In the case of soft padding (8-10 psi, one inch cell paperhoneycomb) VCmax was low (0.20-0.57 m/s).

SID: Table S indicates a marked differencebetween SID and BIOSID in lower rib response. In bothsoft and stiff padded tests, BIOSID lower rib response isgreater than SID. The difference is more pronounced inthe stiff padded tests, where BIOSID lower ribaccelerations are three or more times those incorresponding SID tests. The end result is that BIOSIDTTIs are over 85 g's in stiff padded tests and SID TTIsare not. The SID TIIs indicate a safe impact to theabdominal region of the hard thorax in these impactswith stiff padding while BIOSID TTIs indicate the stiffpadding is injurious. Cadaver data in Table 4A indicatethat the use of stiff padding can result in abdominalinjury while the soft padding does not.

Armrest tests

The SID peak response values are listed in Table 6.In these tests the SID abdominal insert impacted theabdominal load plate. The data in this table includespeak rib and spine accelerations, Thoracic Trauma Index(TII), Average Spine Acceleration (ASA), and peakbarrier load behind the annrest.

The BIOSID peak response values are listed inTable 7. The data in this table includes the same typedata as for SID and also rib deflection and the viscousresponse at the ribs. The peak response of ribs 1-2-3(upper ribs) is listed along with the peak response of ribs4-5 (lower ribs). The responses are separated in this way

10

because ribs 1-2-3 made contact with the shoulder andthoracic load plates and ribs 4 and 5 with the armrest atthe abdominal load plate.

Tn hoth the SID and BTOSID test.e; the peakabdominal barrier load was quite sensitive to paddingcrush strength. Using SID the stiffer honeycomb annrestresulted in peak abdominal loads 85.5% greater thanwith the soft honeycomb armrest. Using BIOSID thestiffer honeycomb armrest resulted in peak abdominalloads 71.6% greater than with the soft honeycombarmrest. These differences are illustrated by the force­time history curves of Figures SA and B. Peakaccelerations were less sensitive to annrest strength.Peak values for the stiffer armrest were at most 29.3 %higher than for the soft armrest (Tables 6 and 7).

In the SID, TIl(d) was not sensitive to change inarmrest stiffness (Table 6). This is to be expected,however, since the SID rib cage did not contact thearmrest, but instead impacted the load plates above theannrest. SID ASA was moderately sensitive to armreststiffness, with the value for the stiffer armrest being29.3% higher than for the soft armrest.

In the BIOSID tests TIl, ASA, Cmax and VCmaxwere calculated and are presented in Table 7. Cmax andVCmax were quite sensitive to armrest stiffness, withCmax for the stiffer armrest being 82.8 % higher than forthe soft armrest and VCmax being 100% higher for thestiffer annrest compared to the soft. However, there wasa large difference in peak VCmax in the two stiffannrest tests (tests nos. 94 and 95). BIOSID ASA andTIl were only moderately sensitive to changes inarmrest stiffness, as can be seen in the last portion ofTable 7.

DISCUSSION

FIatwaIl tests

ASA is an overall dummy response and a review ofTable 5 indicates that SID and BIOSID ASA were not assensitive in predicting the harm of stiff padding as wasBIOSID rib 4-5 response. BIOSID rib 4-5 responses thatwere quite sensitive to changes in padding stiffnessincluded rib acceleration, rib deflection and the viscousresponse. On the other hand. ASA performed better thanSID TTl in predicting the harm of stiff padding at theabdominal level.

Armrest Tests

The viscous criterion was validated for the abdomenby Rouhana et aI (1985) and Lau et aI (1987). TIl wasdeveloped for the "hard thorax" which includes theorgans just below the diaphragm but still within thelateral margins of the rib cage (Eppinger et ai, 1984).

......

TABLE 5: SID AND BIOSID FLATWALL TESTS - LOWER SPINE AND ABDOMINAL RESPONSE DATASID BIOSID FIR100 T12Y SID BIOSID BIOSID SID BIOSID BIOSID BIOSlO

THORAX, SHOULD, PAD PAD SLED SLED (G'S) FIRI00 FIR100 SID 4-5 RIB ASA ASA 4-5 RIB 4-5 RIBTEST ABDOMEN PELVIS THICK. PRE- VEL. VEL. LOW RIB 4-5 RIB TTl TTl 15-85% 15-85% Dmux VCm!lx

TYPE RUN PAD PAD (IN) CRUSH (m/s) (m/s) SID BIOSIO (O'S) (O'S) (O'S) (G'S) (O'S) (G'S) (mm) (m/s)

UNPADDED

1 A NONE NONE 0 --- 6.6 6.6 61 39 113 132 90 85 42 33 29.5 0.32

B NONE NONE a --- 6.6 6.9 61 50 ill 271 90 ill 41 39 32.0 0.46

AVO 6.6 6.8 61 44 112 201 90 123 41 36 30.7 0.39

2 A NONE NONE 0 --- 8.6 8.9 101 98 192 230 147 164 71 65 60.6 1.83

B NONE NONE 0 --- 2:l 9.0 ill --- 209 221 164 --- 74 --- 62.7 2.23- - -AVO 8.9 8.9 108 98 201 226 156 164 73 65 61.6 2.03

SOFT PADDINO

3 A 1 IN PHC 1 IN PHC 12 YES 8.9 8.8 22 20 29 85 29 53 16 15 29.3 0.31

B 1 IN PHC 1 IN PHC 12 YES 8.9 8.7 25 19 36 64 30 42 15 16 18.9 0.22

AVO 8.9 8.8 24 19 33 75 30 47 15 15 24.1 0.27

4 A 1 IN PHC 3/4 IN PHC 8 YES 9.0 8.9 35 28 35 90 39 59 27 25 21.2 0.20

B 1 IN PHC 3/4 IN PHC 8 YES 2:l 8.9 ~ 11 33 85 38 58 26 25 22.9 0.27

AVO 9.1 8.9 34 30 34 88 39 59 27 25 22.1 0.23

5 A 1 IN PHC 3/4 IN PHC 4 NO 8.9 9.1 52 51 74 136 69 94 37 37 35.9 0.57

B 1 IN PHC 3/4 IN PHC 4 NO 8.9 --- 50 --- 63 --- 64 --- 37 --- --- ---- - - - - - -AVO 8.9 9.1 51 51 69 136 67 94 37 37 35.86 0.57

STIFF PADDINO

6 A 3/4 IN PHC 5/8 IN PHC 8 YES 9.1 8.9 55 --- 52 147 57 --- 40 --- 71.6 1.40

B 3/4 IN PHC 5/8 IN PHC 8 YES 9.0 2:l ~ 42 50 149 53 95 40 36 59.5 1.20

AVO 9.1 9.0 53 42 51 148 55 95 40 36 65.5 1.30

7 A 3/4 IN PHC 5/8 IN PHC 4 NO 9.1 9.1 54 46 62 222 60 134 36 38 70.8 2.12

B 3/4 IN PHC 5/8 IN PHC 4 NO 8.9 --- 50 --- 58 --- 54 --- il --- --- ---- - - - -AVO 9.0 9.1 52 46 60 222 57 134 38 38 70.8 2.12

8 A ARCEL 310 ARCEL 310 6 NO 9.0 8.9 56 46 48 178 52 112 46 41 63.1 1.05

B ARCEL 310 ARCEL 310 6 NO 9.0 8.9 60 ~ 47 153 55 102 49 45 53.7 1.08

AVO 9.0 8.9 58 49 48 166 54 107 47 43 58.4 1.06

TABLE 6: SID ARMREST DATA

PEAK BARRIER LOADS (kN, 300 HZ BUTTERWORTH FILTERED)TEST SLED VEL ARMREST

NO. (m/s) ARMREST SHOULDER THORAX ABDOMEN PELVIS DEFL (mm)

85 8.75 SOFT 3.77 2.02 2.63 14.96 77.089 8.73 SOFT 4.15 2.30 2.22 12.56 106.4

AVERAGE 3.96 2.16 2.42 13.76 91.7

86 8.86 HARD 4.03 2.02 4.98 13.63 59.088 8.70 HARD 3.46 1.97 4.01 11.78 66.9

AVERAGE 3.74 2.00 4.50 12.71 62.9

% DIFF: HARDISOFT ARMREST: -5.5 -7.5 85.5 -7.6 -31.4

PEAK ACCELERATIONS (G'S, 100 HZ FIR FILTERED)

TEST SLED VEL UPPER LOWER UPPER LOWERNO. (mls) ARMREST SPINE SPINE PELVIS RIB RIB

85 8.75 SOFT 27.3 42.0 72.0 33.0 41.889 8.73 SOFT 24.8 38.2 71.1 28.0 33.5

AVERAGE 26.0 40.1 71.6 30.5 37.7

86 8.86 HARD 31.9 51.5 76.7 31.5 36.988 8.70 HARD 27.6 42.3 78.4 26.7 38.2

AVERAGE 29.7 46.9 77.5 29.1 37.5

% DIFF: HARD/SOFT ARMREST: 14.1 16.9 8.3 -4.6 -0.3

INJURY CRITERIATEST SLED VEL UPPER LOWER

NO. (mls) ARMREST RIB TTl RIB TTl ASA1585 8.75 SOFT 37.5 41.9 29.689 8.73 SOFT 33.1 35.8 27.6

AVERAGE 35.3 38.9 28.6

86 8.86 HARD 41.5 44.2 37.988 8.70 HARD 34.5 40.3 36.0

AVERAGE 38.0 42.2 37.0

% DIFF: HARD/SOFT ARMREST: 7.6 8.6 29.3

12

TABLE 7: BIOSID ARMREST DATA

PEAK BARRIER LOADS (kN, 300 HZ BUTTERWORTH FILTERED)TEST SLED VEL ARMREST

NO. (mls) ARMREST SHOULDER THORAX ABDOMEN PELVIS DEFL (mm)

92 9.19 SOFT 3.54 1.99 2.44 16.26 114.0

93 9.22 SOFT 4.27 2.34 2.71 13.69 112.0AVERAGE 3.90 2.16 2.57 14.97 113.0

94 9.34 HARD 4.27 2.11 4.40 14.33 59.0

95 9.20 HARD 4.05 2.11 4.44 13.91 100.3

AVERAGE 4.16 2.11 4.42 14.12 79.6

% DIFF: HARD/SOFT ARMREST: 6.7 -2.6 71.6 -5.7 -29.5

PEAK ACCELERATIONS (G'S, 100 HZ FIR FILTERED)

TEST SLED VEL UPPER LOWER UPPER LOWERNO. (mls) ARMREST SPINE SPINE PELVIS RIB RIB

92 9.19 SOFT 26.9 30.9 63.1 64.5 71.3

93 9.22 SOFT 28.1 33.5 61.2 62.4 90.3

AVERAGE 27.5 32.2 62.1 63.5 80.8

94 9.34 HARD 36.7 37.9 64.3 64.9 99.1

95 9.20 HARD 34.4 39.3 71.1 49.9 94.5AVERAGE 35.5 38.6 67.7 57.4 96.8

% DIFF: HARD/SOFT ARMREST: 29.3 19.7 9.0 -9.5 19.8

PEAK DEFLECTION AND VISCOUS RESPONSE

TEST SLED VEL UPPER RIB LOWER RIB UPPER RIB LOWER RIBNO. (mls) ARMREST Dmax (mm) Dmax (mm) VCmax (m/s) VCmax (m/s)

92 9.19 SOFT 15.5 22.4 0.14 0.2993 9.22 SOFT 16.3 22.5 0.11 0.30

AVERAGE 15.9 22.4 0.13 0.30

94 9.34 HARD 17.8 40.8 0.11 0.78

95 9.20 HARD 16.6 41.2 0.08 0.40AVERAGE 17.2 41.0 0.10 0.59

% DIFF: HARD/SOFT ARMREST: 8.5 82.8 -24.0 100.0

INJURY CRITERIA

TEST SLED VEL UPPER LOWER Cmax VCmaxNO. (mls) ARMREST RIB TTl RIB TIl ASA15 (DmaxlI75) (mls)

92 9.19 SOFT 47.7 51.1 27.2 0.13 0.2993 9.22 SOFT 48.0 61.9 26.9 0.13 0.30

AVERAGE 47.8 56.5 27.0 0.13 0.30

94 9.34 HARD 51.4 68.5 31.4 0.23 0.7895 9.20 HARD 44.6 66.9 31.6 0.24 0.40

AVERAGE 48.0 67.7 31.5 0.23 0.59

% DIFF: HARD/SOFT ARMREST: 0.3 19.8 16.5 82.8 100.0

13

14

Figures SA and B. Force-time histories of the abdominal load plate in two types of armrest tests:A. 9 mls SID impacts into soft and stiff paper honeycomb armrests.B. 9 mls BIOSID impacts into soft and stiff paper honeycomb armrests.

120.0

B5-SoftB9-SoftS6-StiffBS Stiff

120.0

92-Soft93-Soft94-Stiff95-Stiff

90.0

I!l No.(!) No..:!l. No.+ No.

90.0

I!l No.(!) No..:!l. No.+ No.

30.0 60.0

Time ems)

30.0 60.0

Time (ms)

B/' JA

{-Jf\/~~ 1\

_I~\A.,

I\.~

olD

C\l

9 m/sec (20 mph)SID Armrest Force

Z::i. o~

illULo!.La

(\J-I-----+---~--+_--_I_---I__--_+_--_I_--_lIC.O

alD

C\J

9 m/sec. (20 mph)BIOSID Armrest Force

Z::i. o~

illULo!..La

C\JI0.0

These organs include the liver and the spleen. In somecadaver tests used in the development of TIl edgeloading may have contributed to liver injury. Eleven sledtests had a 90 mm gap between thoracic and pelvic loadplates (Marcus et al, 1983; Eppinger et al, 1984).Rouhana et al (1989) noted that in sixteen swine left­sided side impact tests run at 7.2 to 15 mls a large gap(203 mm) between load plates produced AIS 2-4 liverinjury in six of eight tests and AIS 2-5 spleen injury inseven of eight tests. When there was no gap there wasno liver injury in eight tests and AIS 2 spleen contusionsin five of these eight tests. The injuries in the tests withthe large gap were thought to be due to edge effects andextrusion of part of the body through the gap.

Animal studies have demonstrated that a forcelimiting interface can reduce abdominal injury. In astudy of214 anesthetized New Zealand White rabbits byRouhana et al (1986), the addition of 33-40 psi Hexcellto the impact face significantly reduced renal lacerationsbut not liver injury. Viano et al (1991) compared theresponse of BIOSID to the injury seen in anesthetizedswine in a side impact test series with impact into sheet­metal armrests of three different stiffnesses (soft, stiffand very stiff). In soft armrest tests an averageabdominal AIS of 2.2 in the swine corresponded with 37mm rib deflection and 0.33 mls VCmax in the BIOSID.In stiff armrest tests an average abdominal AIS of 3.6 inthe swine corresponded with 61.6 mm rib deflection and1.16 mls VCmax in the BIOSID. In our tests, rib 4-5Dmax averaged 22.4 mm with the soft armrests and 41mm with the hard armrests. Rib 4-5 VCmax averaged0.30 mls with the soft armrests and 0.59 mls with thehard armrests. Thus, the WSU paper honeycombarmrests produced a less severe response in BIOSID thanthe corresponding GM sheet-metal armrest.

The cadaver and BIOSID flatwall data suggest thatabdominal injury or lower rib cage injury can occur withpadding of about 20 psi (138 kPa) crush strength atimpact velocities of 8.9 mls while a reduction of crushstrength to 10 psi (69 kPa) will result in little or noinjury. The Viscous Response of the BIOSID abdominalribs provide a reliable measure of this outcome. Theinjury data are based on the use of unembalmed cadaverswith an average age in the early sixties. A tolerablearmrest crush strength is likely to be higher than 10 psifor living middle aged subjects.

CONCLUSIONS

Flatwall tests1) Injury to abdominal organs or lower rib cage was a

common occurrence in 20 mile per hour impactsinto an unpadded wall.

2) With the use of soft padding (8-10 psi crushstrength), no abdominal organ injuries occurred.

15

3) BIOSID no 4-5 response (VCmax, Cmax, TIl)predicted the harm of stiff padding and the benefitof soft padding in impacts to the abdominal region.

4) SID and BIOSID appear to have less effective massat the abdominal level than cadavers.

Armrest tests1) The following measures were quite sensitive

to the change from a soft to a stiff armrest: Peakbarrier load behind the armrest (for both SID andBIOSID tests) and rib 4-5 Cmax and VCmax inBIOSID.

2) The following measures showed moderatesensitivity to changes in armrest stiffness: SID andBIOSID peak Tl2y acceleration, SID and BIOSIDASA, and BIOSID TIl utilizing rib 4-5 response.

3) SID TIl was not sensitive to the change inarmrest stiffness, but a valid test for this was notperformed. The SID rib cage was positioned so thatit did not impact the armrest.

ACKNOWLEDGEMENTS

The data analysis in this paper was supported by CDCGrant No. CCR 502347 as were the cadaver impacttests. Most of the dummy impact tests were supported bythe American Automobile Manufacturers Association.However, the analysis and conclusions contained in thispaper are solely those of the authors and have not beenreviewed or approved by other parties.

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16

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