Evaluation of the Shoulder, Thorax and Abdomen of the WorldSID Pre-production Side Impact Dummy D Hynd and JA Carroll Vehicle Engineering Department, TRL Limited, UK BW Been TNO Automotive Safety, NL AR Payne Impact Analysis, MIRA Ltd., UK ABSTRACT ISO TC22/SC12/WG5 set up a Task Group to develop an advanced, biofidelic, globally acceptable side impact dummy known as WorldSID. The WorldSID TG has developed the dummy to meet the biofidelity requirements in ISO TR 9790. The European Commission (EC) project SID-2000 contributed to the design of the WorldSID head, neck, thorax and pelvis. The follow-on EC project, SIBER, has evaluated the repeatability, reproducibility, sensitivity and biofidelity of the WorldSID prototype and pre-production dummy (PPD). This paper presents the results of the SIBER evaluation of the shoulder, thorax and abdomen of the WorldSID PPD, including temperature sensitivity, biofidelity and impact configuration sensitivity tests. The WorldSID PPD was found to be sensitive to temperature at the thorax and, particularly, the shoulder. It was also found that the dummy generated a noticeable amount of heat internally, from the thorax instrumentation and internal data acquisition system. It is recommended that both the ambient and internal temperature are specified for full-scale testing. The thorax met or was close to meeting the IHRA biofidelity requirements, but exceeded the ISO requirements in the same test condition. The abdomen was found to be too stiff and it is recommended that the stiffness of the WorldSID abdomen ribs is reduced. Earlier test work with the WorldSID prototype had indicated that the rib compression instrumentation was not capable of measuring correctly rib compression in oblique loading conditions. This was confirmed by the results of HyGe sled testing, which examined lateral and oblique impacts in a representative vehicle environment with additional thorax rib instrumentation. Additional tests with an isolated WorldSID rib are also presented. These showed that the measured rib compression markedly underestimates the actual compression in oblique loading conditions. It is recommended that the WorldSID thoracic compression instrumentation is revised to ensure the correct measurement of rib compression in oblique loading conditions up to ±30° from lateral.
Transcript
Evaluation of the Shoulder, Thorax and Abdomen of the WorldSID Pre-production Side Impact Dummy D Hynd and JA Carroll Vehicle Engineering Department, TRL Limited, UK BW Been TNO Automotive Safety, NL AR Payne Impact Analysis, MIRA Ltd., UK
ABSTRACT ISO TC22/SC12/WG5 set up a Task Group to develop an advanced, biofidelic, globally acceptable side impact dummy known as WorldSID. The WorldSID TG has developed the dummy to meet the biofidelity requirements in ISO TR 9790. The European Commission (EC) project SID-2000 contributed to the design of the WorldSID head, neck, thorax and pelvis. The follow-on EC project, SIBER, has evaluated the repeatability, reproducibility, sensitivity and biofidelity of the WorldSID prototype and pre-production dummy (PPD). This paper presents the results of the SIBER evaluation of the shoulder, thorax and abdomen of the WorldSID PPD, including temperature sensitivity, biofidelity and impact configuration sensitivity tests. The WorldSID PPD was found to be sensitive to temperature at the thorax and, particularly, the shoulder. It was also found that the dummy generated a noticeable amount of heat internally, from the thorax instrumentation and internal data acquisition system. It is recommended that both the ambient and internal temperature are specified for full-scale testing. The thorax met or was close to meeting the IHRA biofidelity requirements, but exceeded the ISO requirements in the same test condition. The abdomen was found to be too stiff and it is recommended that the stiffness of the WorldSID abdomen ribs is reduced. Earlier test work with the WorldSID prototype had indicated that the rib compression instrumentation was not capable of measuring correctly rib compression in oblique loading conditions. This was confirmed by the results of HyGe sled testing, which examined lateral and oblique impacts in a representative vehicle environment with additional thorax rib instrumentation. Additional tests with an isolated WorldSID rib are also presented. These showed that the measured rib compression markedly underestimates the actual compression in oblique loading conditions. It is recommended that the WorldSID thoracic compression instrumentation is revised to ensure the correct measurement of rib compression in oblique loading conditions up to ±30° from lateral.
1. INTRODUCTION The predominant cause of fatal and other serious injuries in European road accidents is side impact. This type of impact currently accounts for one third of accidents and for half of the fatalities recorded. Several different dummies are used in side impact vehicle assessment worldwide, for regulations, consumer testing, and research and development testing. The world-wide adoption of a single adult, 50th percentile male side impact dummy would be advantageous for several reasons. It would contribute to the process of global harmonisation of regulatory test procedures, which is the objective of the International Harmonised Research Activities (IHRA) group. The need to develop cars and restraint systems using different dummies for different markets would also be eliminated. This would potentially reduce vehicle and restraint system development costs and allow development efforts to be channelled more effectively towards meeting a single set of objectives. The use of a single dummy by regulatory bodies and by consumer organisations would help to ensure that published results are consistent and unambiguous, resulting in the public being better informed. Furthermore, the availability of an improved dummy with better injury risk assessment capabilities would reduce the severity of injuries sustained in side impacts. A single dummy would drive vehicle design in a single direction, but could lead to increased optimisation of vehicles to the dummy. It is in this context that in November 1997 work began on the development of an entirely new, advanced side impact crash test dummy - the 50th percentile male WorldSID (World-wide Side Impact Dummy). The development of this dummy has been overseen by an international group of experts, the WorldSID Task Group (TG), working under the auspices of the International Organisation for Standardisation (ISO) Working Group on anthropomorphic test devices (ISO/TC22/SC12/WG5). The development of the WorldSID dummy has been supported, either financially or through participation in the activities of the group, by governmental, industrial and research organisations from around the world. Part of the European contribution has been through the participation of the SID-2000 project under the European Commission Framework Programme IV and, subsequently, the SIBER project under Programme V. The WorldSID dummy has been developed with the goal of meeting the dynamic response requirements laid out in the document ISO TR9790 [ISO, 1997], and the general specifications developed by the ISO TG [TG N60r2, 1999]. The ISO biofidelity requirements are not used by the European Enhanced Vehicle-safety Committee (EEVC), but they do constitute a comprehensive set of biofidelity performance requirements for a side impact dummy. The target performance that was specified by ISO was a rating of ‘good’ to ‘excellent’, according to the rating system in the TR9790 report, for all segments of the dummy and for the dummy overall. The dummy was also intended to meet the newer IHRA biofidelity requirements, although these requirements were not published until the pre-production version had already been designed. The International Harmonised Research Activities (IHRA) Working Group on Side Impact is currently developing a new set of harmonised regulatory test procedures for a future potential Global Technical Regulation on Side Impact. It is envisaged that the WorldSID dummy would be used in these procedures, provided that the dummy is recommended for regulatory use by the IHRA Biomechanics Group.
1.1 The WorldSID PPD Shoulder, Thorax and Abdomen Design The WorldSID dummy thorax is a highly innovative design, incorporating new technologies and materials. Six double hoop ribs represent the shoulder (1), thorax (3) and abdomen (2), and are intended to provide human-like compression under impact angles between ± 30º from lateral and ± 10° vertically. The WorldSID specification required the design to allow the evaluation of interaction between driver and passenger in a side impact. With existing dummies like ES-2 and SID2s, this is not possible as the ribs are rigidly attached to the non-struck side of the dummy spine. The dummy is therefore symmetrical with respect to the mid-sagittal plane. The ribs are constructed from a nickel-titanium alloy with super elastic characteristics. The application of this material allows the WorldSID thorax to compress over 75 mm per side, which equates to a quarter of the thorax width of the dummy. The inner bands of the rib hoops are lined with damping material. The response of the individual ribs is tuned by adapting the damping material thickness. The dummy has a centrally located spine box, providing sufficient space to package an in-dummy data acquisition system. The WorldSID dummy is equipped with ‘IR-Tracc’1 rib compression sensors (one per rib), based on infrared light emission and reception (Figure 1), which are designed to measure the compression of each rib.
Figure 1: WorldSID dummy thorax (left), rib hoops and compression sensors (middle) and view inside the spine box showing the in-dummy
data acquisition system - TDAS (right)
1.2 SIBER WorldSID PPD Evaluation. The European SIBER consortium partners ACEA, BASt, MIRA, TRW, TRL and TNO evaluated the WorldSID pre production dummy as part of the European contribution to the WorldSID programme. The test matrix included a full evaluation of the preliminary IHRA side impact dummy response requirements, full-scale car side impact crashes (FMVSS 201 and 214, EC Regulation 95, and EuroNCAP), accident reconstructions and out-of-position dummy arm-airbag interaction testing. As part of this programme TRL, TNO and MIRA evaluated the biofidelity and sensitivity of the WorldSID PPD shoulder, thorax and abdomen, to temperature, loading pulse and impact angle.
1 IR-Tracc: InfraRed Telescoping Rod for Assessing Chest Compression, http://www.ftss.com/
2. BIOFIDELITY The SIBER consortium evaluated the WorldSID PPD against the draft IHRA biofidelity requirements (yet to be published). At the thorax and abdomen, these included requirements specified by European Enhanced Vehicle-safety Committee (EEVC) Working Group 9 (WG9) and requirements based on Post Mortem Human Subject (PMHS) tests undertaken at Wayne State University (WSU). The IHRA requirements are a draft document in terms of the inclusion or otherwise of particular biofidelity requirements, but the definition of any requirement is unlikely to change in the final version of the IHRA document. 2.1 EEVC WG9 Thorax Biofidelity
2.1.1 WG9 biofidelity test procedure In 1991 the European Enhanced Vehicle-safety Committee (EEVC) Working Group 9 (WG9) specified a set of test procedures for defining biofidelity targets for lateral impact test dummies [Roberts et al., 1991b]. The high priority biofidelity design targets included pendulum impactor tests to the thorax based on PMHS tests performed by the Highway Safety Research Institute (HSRI), Robbins et al. [1979]. The dummy was seated on a flat, horizontal, stainless steel surface with a lap belt to restrain the dummy, anchored to the surface on which the dummy was seated. A 23.4 kg, 150 mm diameter eight-wire pendulum impactor was used, with an impact velocity of 4.3 m.s-1, with the centreline of the impactor aligned with the centre of the middle thoracic rib. The lateral T1 (upper thoracic spine) and pendulum accelerations were filtered and normalised according to the WG9 procedures.
2.1.2 WG9 biofidelity test results The pendulum and T1 accelerations are shown in Figure 7 and Figure 8 in Appendix A. The magnitude of the pendulum acceleration slightly exceeded the target corridor, although the pulse duration was correct. The lateral T1 acceleration response had a distinct double-peak shape dissimilar to the single-peak shape of the PMHS responses from which the target corridor was derived. The magnitude of the peak accelerations was within the range of the target corridor limits, but occurred before and after the corridor peak, thereby placing the response outside the target corridor. ISO TR9790 also defines a dummy requirement based on the same PMHS data, but with a different target corridor due to the use of a different normalisation process and corridor generation technique. However, the WorldSID PPD does not meet the ISO TR9790 requirements at this condition as the WorldSID T1 response exceeds the target corridor maximum of 15 g by 4 g (27 %). 2.2 Wayne State University Thorax and Abdomen Biofidelity
2.2.1 WSU biofidelity test procedure Thorax and abdomen biofidelity tests were carried out with a procedure similar to that used at the Wayne State University (WSU), as reported by Viano [1989]. The WorldSID dummy was seated upright on a single sheet of PTFE, with leggings covering the standard dummy suit, and with the arms raised such that they did not interact with the pendulum. The dummy was seated facing perpendicularly to the direction of travel of the pendulum. This was contrary to the WSU test set-up, in which most of the PMHS specimens were rotated by 30°, so that the
point of pendulum contact was forward of lateral and the axis of force was directed through the centre of gravity of the torso. This protocol was used with the PMHS specimens to reduce or eliminate rotation of the PMHS torso about the axis of the spine The WorldSID dummy was impacted laterally, rather than obliquely, because previous testing with the WorldSID alpha prototype dummy had indicated that the rib compression instrumentation could not correctly measure maximum rib compression in oblique loading conditions [Been et al., 2003; Hynd et al., 2004]. In addition, previous dummy biofidelity testing with the EuroSID-1 and BioSID dummies by the same team [Viano et al., 1995] had used lateral impacts as significant differences between oblique and lateral impact results in the original PMHS tests had not been identified. The ISO TR9790 biofidelity requirements, which the WorldSID dummy has been designed to meet, also define lateral thorax and abdomen impact requirements based on the Viano [1989] data. The test specification requires lateral impacts on the basis that the normalised peak force and pulse durations were comparable for lateral and oblique tests and such tests were used in the evaluation of the WorldSID prototype dummy [Cesari et al., 2001]. A 23.4 kg, 150 mm diameter eight-wire pendulum impactor was used, with an impact velocity of 4.3 and 6.7 m.s-1 for the thorax and 4.8 and 6.8 m.s-1 for the abdomen tests. Impacts defined at 9.4 m.s-1 were not undertaken due to the risk of damage to the dummy. The centreline of the impactor was aligned with the centre of the middle thoracic rib for thorax impacts, and the centre of the gap between the top abdominal and bottom thoracic ribs for abdomen impacts. These positions were derived from anthropometric data and the bony landmarks used in the PMHS tests with the CAD model of the WorldSID dummy.
2.2.2 WSU biofidelity results Figure 9 and Figure 10 in Appendix B shows the normalised pendulum force against time for the 4.3 m.s-1 and 6.8 m.s-1 thoracic impacts to the WorldSID PPD. The pendulum force response was a good fit to the target corridor at the 4.3 m.s-1 impact velocity. The pendulum force was also a good fit at the 6.8 m.s-1 test condition (apart from an initial peak at around 3.5 ms) until approximately 14 ms after initial contact with the dummy, when the thorax ribs bottomed-out (probably against the IR-Traccs), causing very high impactor forces. The WorldSID abdomen responses to lateral impacts at 4.8 and 6.8 m.s-1 are shown in Appendix B, Figure 11 and Figure 12, respectively. The pendulum impactor force was up to 1.5 kN (50 %) greater than the target corridor maximum at the 4.8 m.s-1 test condition and 0.5 kN (10 %). greater at the 6.8 m.s-1 test condition. The peak force was earlier than the peak in the target corridor and the duration of the response was shorter, particularly at the low-speed test condition.
3. SENSITIVITY 3.1 Temperature Sensitivity
3.1.1 Temperature sensitivity test procedure The specification for the WorldSID dummy required the dummy to show a uniform response across an ambient temperature range of 16 to 26°C [TG N60r2, 1999], although it was
acknowledged that this was unlikely to be achieved due to the temperature sensitivity of the materials usually used to represent the flesh. To establish the temperature sensitivity of the WorldSID shoulder, thorax and pelvis response, these segments were subjected to tests based on the certification test procedures at a range of ambient temperatures, from 14 to 30°C. Each type of test was conducted at five temperatures and three tests were performed at each temperature. Before a set of tests at a particular temperature, the dummy was soaked at that temperature for a period of at least four hours.
3.1.2 Temperature sensitivity results Figure 13 and Figure 14 show the response of the shoulder load cell and middle thoracic rib to changes in ambient temperature in the range 14 to 30°C. The shoulder showed a clear decrease in shoulder force with an increase in temperature, which was mirrored by an increase in shoulder rib compression with increasing temperature. The middle thoracic rib showed a consistent compression response at 14, 18 and 22°C, with a sharp rise in compression at higher ambient temperatures. This pattern was also noted for the upper and lower thoracic ribs and the T4 spine acceleration. It was also found that the dummy core temperature, measured with the built-in temperature sensor and with a separate thermocouple, rose quickly once the dummy was plugged in. The neoprene suit worn by the dummy means that the heat generated by the in-dummy data acquisition system and the instrumentation cannot easily escape. This also means that it takes a long time for the dummy core temperature to cool once the in-dummy data acquisition system is switched off. 3.2 Sensitivity of the WorldSID PPD Thorax in a Simulated Vehicle Environment
3.2.1 M-SIS test procedure The sled-based MIRA Side Impact System (M-SIS) was used to assess the characteristics and performance of the WorldSID PPD under realistic in-vehicle loading conditions. The M-SIS technique, operating on a HyGe reverse accelerator, accurately reproduces both the vehicle interior using actual vehicle door trims, airbags, seats and side impact dummy location, as well as the velocity profile of the intruding door and vehicle side structure produced in a side impact crash test. Such a technique allows the response of a dummy to be analysed in a more controlled, repeatable and cost effective manner than in full-scale testing. Two test phases were conducted with the WorldSID PPD using the M-SIS technique, both analysing the sensitivity of the dummy to changes in the input velocity profile and dummy location and orientation to the intruding door. Three velocity profiles were used, as shown in Figure 2. In Phase 1, a generic velocity profile from vehicles designed prior to the introduction of the European Side Impact Directive and EuroNCAP was used. With two velocity peaks of 11 m.s-1 and 8 m.s-1, as shown in Figure 2, this velocity profile typically causes large rib compressions in the EuroSID-1 dummy. This should highlight the effect of small changes to the velocity profile and dummy location, which was the objective of this Phase. In Phase 2 a generic velocity profile for a vehicle designed to do well in a EuroNCAP assessment was used, representing current vehicle structural performance. The objective of this Phase was to evaluate the repeatability of the WorldSID PPD and the effect of door impact angle on the thorax response. In order to gain a better understanding of the effect of
door angle on the thorax response, comparative tests were also conducted with the ES-2 and ES-2re (rib extensions) side impact dummies. Pure lateral impacts and impacts with the seat and dummy angled at 20° rear of lateral were undertaken with all three dummies as shown in Figure 3. The angled impacts were representative of the rear-seat occupant in an FMVSS 214 crabbed barrier side impact test, where the rear corner of the deformable barrier face rotates into the rear door before impacting the occupant. One test was performed at each impact condition with the ES-2 and ES-2re. With the WorldSID PPD, two tests were performed at each angle. In the first, the standard dummy instrumentation was used. In the second test, the IR-Tracc in the top thoracic rib was replaced by two string potentiometers mounted on the spine and attached to the upper and lower edges of the rib at a point 15° rearward of the IR-Tracc mounting point.
Figure 2: M-SIS test set-up and velocity profiles used in Phase 1 and Phase 2
ES-2
ES-2re WorldSID PPD
Side impact dummy at t0(start of test)
Side impact dummy at 52 ms (peak rib compression)
Figure 3: ES-2, ES-2re and WorldSID PPD kinematics in oblique impact M-SIS tests
Phase 1 Velocity ProfilePhase 2 Velocity Profile Simulated Pole Test Velocity Profile
3.2.2 M-SIS thorax sensitivity results The rib compressions for the WorldSID PPD, ES-2 and ES-2re in lateral and 20° rearward oblique impacts are shown in Figure 16. In the lateral impacts, the ES-2 and ES-2re showed exactly the same initial thorax response. The peak rib compression at each rib was higher for the ES-2re than for the ES-2. Overall, all three thoracic ribs for each dummy showed similar peak compressions, indicating that the ES-2 and ES-2re remains relatively vertical throughout the impact. Conversely, the peak rib compressions for the WorldSID PPD were highest for the upper rib and reduce for the middle and lower ribs, implying that the thorax leaned into the upper door. Apart from the upper rib, which could be affected by the half arm being initially trapped between the upper rib and the door, the initial rises were lower than for the ES-2 and ES-2re dummies, although the duration of loading remained the same. In the 20° rearward oblique impacts, the ES-2 and ES-2re rotated in to the door, about the dummies’ vertical axis. At initial contact at 30 ms after t0 (start of sled movement) the dummy was angled at 20° to the lateral, and at peak rib compression this had reduced to 5° to the lateral (see Figure 3). By the time the dummy lost contact with the door, at 72 ms after t0, the dummy was at 0° to the lateral. By contrast, however, the WorldSID PPD remained at 20° to the door throughout the impact event. In the oblique impact, the ES-2 and ES-2re rib compressions started 4 ms earlier (see Figure 16) than in the lateral impact, because the thorax was slightly closer to the door. The ES-2 showed a small, but significant, reduction in peak rib compression, while the ES-2re showed consistent peak rib compression in the lateral and oblique impacts. For the WorldSID PPD, the peak upper thoracic rib compression was similar at both impact angles, although the compression dropped off much more quickly in the oblique impact. The measured peak rib compression at the middle and lower thoracic ribs was much lower in the oblique impact than in the lateral impact and the response again dropped off more quickly.
3.2.3 Comparison of different rib compression instrumentation In the tests where the upper rib IR-Tracc was replaced by two string potentiometers, mounted 15° rearward of lateral, the string potentiometers recorded lower rib compressions than did the IR-Tracc in a matching test at the same test conditions (see Figure 15). In the lateral test condition, the initial rise was identical for both measurements until 5 ms after contact with the door, when the string potentiometers showed a lower response than the IR-Tracc. Peak compression measured by the string potentiometers was 4 mm (9 %) less than with the IR-Tracc and 6 ms later in the impact event. In the oblique test condition, the initial and later responses were very similar, but the peak top thoracic rib response measured by the string potentiometers was 12 mm (31 %) less than with the IR-Tracc, but at a similar time.
4. ISOLATED RIB OBLIQUE IMPACT TESTS 4.1 Objective As a result of previous testing with the WorldSID Prototype dummy [Been et al., 2003; Hynd et al., 2004], the single point rib compression measurement system in WorldSID was suspected of not being able to measure the true maximum compression of the rib under oblique loading conditions. This is illustrated in Figure 4 (a) to (c). When the rib is impacted laterally, the IR-Tracc end moves from its initial position (a) towards the spine box (b),
measuring positive compression. When the rib is impacted from the rear, the IR-Tracc end moves inward and forward (c). The forward movement of the IR-Tracc end extends the IR-Tracc resulting in reduced compression measurement. The maximum rib compression occurs at a point rear of the IR-Tracc. To evaluate the rib performance in lateral and oblique loading in a repeatable test condition, a single rib unit was subjected to tests in a drop rig. The objective was to compare the response of the rib in purely lateral impact and under 20º rear oblique loading and to quantify the deficiency of the single point measurement system.
Figure 4: WorldSID rib schematic top view undeformed (a), deformation under lateral impact (b), and deformation under rearward oblique impact (c)
4.2 Method The test set up is shown in Figure 5 and is based on the ES-2 rib unit certification test. The WorldSID single rib unit was attached to the anvil at the base of the drop tower with a simulated spine box. The centreline of the impactor was aligned with the centreline of the compression sensor. For the rear oblique test the rib unit and simulated spine was supported at an angle of 20° by a wooden wedge. The centreline of the impactor was aligned with the centreline of the compression sensor attachement point on the spine box. The IR-Tracc compression sensor was taken out of the rib unit during the tests. The tests were recorded with high speed video at a rate of 1000 frames per second. The video recordings were analysed to find the maximum rib compression as measured by the IR-Tracc and the actual maximum rib compression. The rib unit was impacted with a mass of 3 kg at a velocity of 5 m.s-1 in the lateral and rear oblique tests. 4.3 Results The test results are given in Table 1. The rib initial shape and maximum deformed shape in the two test conditions are shown in Figure 6. The target marker at the top edge of the rib marks the position of fixation of the IR-Tracc to the rib. The figures show the difference in deformation pattern between the lateral and rear-oblique impact. In the lateral impact the target remained at the centreline, resulting in 48 mm of maximum rib compression. In the rear oblique test it is clear that the target moved to the left (forward). The superimposed lines indicate the positions the IR-Tracc would assume before impact and at maximum rib compression. It is also clear that the point of maximum rib compression was close to or on the line of impact. The maximum rib compression derived from the film analyses was 49 mm. The rib compression at the position of the IR-Tracc was 28 mm. In this test condition the IR-Tracc measurement underestimates the maximum rib compression by 21 mm (43 %).
(a) (c) (b)
Figure 5: Test set up drop rig and lateral and oblique rear rib unit mounting (only upper half of rib unit shown)
Figure 6: Test results undeformed shapes (left), deformed shapes (right), lateral tests top and oblique rear bottom (yellow line representing lateral measurement)
Test configuration
Test number Rib compression at IR-Tracc location
(mm)
Rib compression at impact
location (mm) Lateral 20269 48 48
20° rear oblique 20288 28 49
Table 1: Single rib drop rig test results
5. DISCUSSION The general handling and usability of the WorldSID PPD dummy were good and the in-dummy data acquisition system (DAS) was good to use, although the reliability of the system should be improved. 5.1 Biofidelity Although slightly outside the target corridors in the IHRA WG9 thorax biofidelity tests, the WorldSID PPD response compared well with previous results for the EuroSID-1 dummy [Roberts et al., 1991a] in tests at TRL and TNO (with different EuroSID-1 dummies). The repeatability of the dummy in these tests was good (2.9 % for impactor acceleration and 1.3 % for T1 acceleration) and comparable to that of the EuroSID-1. However, the dummy did not meet the ISO TR9790 requirement at this test condition. The WorldSID PPD thorax biofidelity in the IHRA WSU test conditions was good, but the maximum compression of the WorldSID ribs was less than that recorded in biofidelity-level PMHS tests. This is limited by the space available within the dummy and should not be a problem for routine vehicle evaluation. The thorax biofidelity is as good as or better than the biofidelity of the EuroSID-1 or BioSID (Harigae et al. [1991]; Viano et al. [1995]). The abdomen, however, was found to be too stiff in these test conditions, particularly at the lower impact velocity where the pendulum force was up to 50% greater than the target corridor maximum at 4.8 m.s-1 and 10 % greater at 6.8 m.s-1. The response of the WorldSID PPD abdomen, as assessed by impactor force in the WSU test conditions, was between that of the EuroSID-1 and BioSID at the lower impact velocity and better than both dummies at the higher impact velocity (Viano et al. [1995]). 5.2 Temperature Sensitivity The ISO specification for the WorldSID dummy requires it to show a uniform response across a temperature range of 16° to 26°C. The dummy clearly does not meet this specification, but given the materials from which the dummy is constructed this was not unexpected. The shoulder of the WorldSID PPD was found to be sensitive to temperature and the thorax was found to be sensitive to temperatures above 22°C. Across the 14 to 30°C temperature range the shoulder force varied by 10 %, and across the 22 to 30°C temperature range the thorax rib compression varied by up to 10 %. It is recommended that a narrower temperature range than in the ISO specification be defined for the use of the dummy. With the four degree temperature range currently specified within the European side impact regulation [ECE, 1998], 18 to 22°C, the variation of the peak shoulder rib compression and
could be as much as 4.9 mm (12 %). However, given the internal heating of the dummy that was observed in these tests, it may be necessary to specify both the ambient temperature and the internal dummy core temperature ranges that would be acceptable. For instance, the 18° to 22°C ambient temperature range in this test programme corresponded to a 22° to 27°C dummy core temperature range. 5.3 Thorax Sensitivity in M-SIS Tests In simulations of full-scale crash tests it was found that the upper thorax of the WorldSID PPD leaned in to the upper door and did not rotate vertically about the spine. This was in contrast to the ES-2 and ES-2re, which did not rotate much about the pelvis, but which did rotate about the vertical axis when loaded by the door trim. The rotation of the WorldSID PPD in to the door confirms pendulum impactor tests with the WorldSID that have shown a more biofidelic response to pelvis loading for the WorldSID than for the EuroSID-1. The WorldSID PPD rib compression measurements showed much reduced loading at the 20° rearward of lateral impact condition compared with the lateral loading condition for the middle and lower ribs. The upper rib may have been loaded in this condition by the arm, which is set at 40° to the horizontal and which overlaps the upper thoracic rib. In the test in which the IR-Tracc was replaced with two string potentiometers mounted at 15° rearward of lateral, the string potentiometers recorded much lower (12 mm or 31 %) rib compressions than did the IR-Tracc in a repeat test at the same test condition. This shows the sensitivity of the rib compression measurement to the angle of impact, although this was a single test with each instrumentation configuration and the exact nature of the loading to the ribs is difficult to determine due to the interaction with the vehicle trim and door. In contrast, the ES-2 and ES-2re rib compression measurements were relatively insensitive to the impact angle in these test conditions. 5.4 Isolated Rib Lateral and Rear Oblique Impact Tests The isolated rib test results clearly show the inability of the single-point rib compression used in the WorldSID to measure correctly rib compression under oblique loading conditions. It is conceivable that oblique loading could be applied in a car crash test, for instance by the seat frame or through interaction with seat mounted airbags. In addition, side impact test procedures with a clear off-axis component, like the FMVSS 201, FMVSS 208 and proposed IHRA pole side impact procedures, are very likely to apply oblique forces to the dummy. It is hypothesised that WorldSID thorax responds in a more human like way to oblique thorax impacts than any of the other current side impact dummies. However, it has not been possible to test this against the existing oblique biomechanical data due to the deficiency in the rib compression measurement system.
6. CONCLUSIONS General: • The general handling and usability of the WorldSID PPD dummy were good and the in-
dummy data acquisition system (DAS) was good to use, although the reliability of the system needs to be improved.
Biofidelity: • The biofidelity of the WorldSID PPD thorax in the IHRA WG9 test condition was
acceptable and as good as existing side impact dummies. • The biofidelity of the thorax in the IHRA WSU test condition was good. • The biofidelity of the abdomen in the IHRA WSU test conditions was poor and it is
recommended that the stiffness of the abdomen ribs be reduced. It is recommended that the biofidelity of the abdomen be checked in other test conditions to confirm this result. The biofidelity of the WorldSID abdomen was comparable to or better than existing side impact dummies in these test conditions.
Temperature sensitivity: • The shoulder of the WorldSID PPD was found to be sensitive to temperature and the
thorax was very sensitive to temperature above 22°C. • It was also found that the dummy core temperature rose quickly once the data acquisition
system was activated. • It is recommended that the use of the dummy be restricted to an ambient temperature
range of 18° to 22°C and a dummy core temperature range of 22 to 27°C. Kinematic sensitivity: • In simulations of full-scale crash tests using the M-SIS test rig, the interaction of the
WorldSID PPD with an intruding door and door trim was quite different to that of the ES-2 and ES2-re dummies. The change in kinematics was consistent with improvements in the biofidelity of interaction between the pelvis and thorax that have been reported elsewhere.
• The rib compressions measured on the WorldSID PPD were very sensitive to the angle of impact and position of the measurement. By contrast, the ES-2 and ES-2re were relatively insensitive to impact angle in the same test conditions.
Isolated rib sensitivity: • In isolated rib impact tests at an angle of 20° rearward of lateral, the rib compression
measured at the position of the IR-Tracc underestimated the maximum rib compression by 21 mm (43 %). It is recommended that the rib compression instrumentation be improved, possibly by measuring compression at three points on each rib (lateral, 20° forward of lateral and 20° rearward of lateral.
7. ACKNOWLEDGEMENTS The work described in this paper forms part of an EC Research project (SIBER), also supported by the UK Department for Transport (DfT), MIRA Ltd. and TNO Automotive.
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