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Analysis of Delta Velocity and PDOF by Means of Collision Partner and Structural Involvement in Real-Life Crash Pulses With Modern Passenger Cars
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery. ÅF Industry , Gothenburg.ORCID iD: 0000-0001-9360-0707
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.ORCID iD: 0000-0001-8338-4078
2014 (English)In: Traffic Injury Prevention, ISSN 1538-9588, Vol. 15, no 1, 56-65 p.Article in journal (Refereed) Published
Abstract [en]

Objective: In the widely used National Automotive Sampling System (NASS)-Crashworthiness Data System (CDS) database, summary metrics that describe crashes are available. Crash angle or principal direction of force (PDOF) is estimated by the crash examiner and velocity changes (V) in the x- and y-directions are calculated by the WinSMASH computer program using PDOF and results from rigid barrier crash testing combined with deformations of the crashed car. In recent years, results from event data recorders (EDRs) have been added to the database. The aim of this study is to compare both PDOF and V between EDR measurements and WinSMASH calculations. Methods: NASS-CDS inclusion criteria were model-year 2000 through 2010 automobiles, frontal crashes with V higher than 16km/h, and the pulse entirely recorded in the EDR module. This resulted in 649 cases. The subject vehicles were further examined and characterized with regard to frontal structure engagement (large or small overlap) as well as collision properties of the partner (impact location; front, side, or back) or object. The EDR crash angle was calculated as the angle between the lateral and longitudinal V at the time of peak longitudinal V. This angle was compared to the NASS-CDS investigator's estimated PDOF with regard to structural engagement and the collision partner or object. Multiple linear regression was used to establish adjustment factors on V and crash angle between the results calculated based on EDR recorded data and that estimated in NASS-CDS. Results: According to this study, simulation in the newest WinSMASH version (2008) underestimates EDR V by 11 percent for large overlap crashes and 17 percent for small overlap impacts. The older WinSMASH version, used prior to 2008, underestimated each one of these two groups by an additional 7 percentage points. Another significant variable to enhance the prediction was whether the crash examiner had reported the WinSMASH estimated V as low or high. In this study, none of the collision partner groups was significantly different compared to front-to-front impacts. However, with a larger data set a couple of configurations may very well be significantly different. In this study, the crash angle denoted by PDOF in the NASS database underestimates the crash angle calculated from recent EDR modules by 35 percent. Conclusion: On average the V and crash angle are underestimated in NASS-CDS when analyzing the data based on collision partner/object and structural engagement. The largest difference is found in small overlap crashes and the least difference in collision scenarios similar to barrier tests. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

Place, publisher, year, edition, pages
Taylor & Francis, 2014. Vol. 15, no 1, 56-65 p.
Keyword [en]
EDR, real life, PDOF, delta velocity, small overlap, multiple linear regression
National Category
Public Health, Global Health, Social Medicine and Epidemiology
URN: urn:nbn:se:umu:diva-84503DOI: 10.1080/15389588.2013.793796ISI: 000327421900009OAI: diva2:687801
Available from: 2014-01-15 Created: 2014-01-08 Last updated: 2015-05-12Bibliographically approved
In thesis
1. Stochastic finite element simulations of real life frontal crashes: With emphasis on chest injury mechanisms in near-side oblique loading conditions
Open this publication in new window or tab >>Stochastic finite element simulations of real life frontal crashes: With emphasis on chest injury mechanisms in near-side oblique loading conditions
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Introduction. Road traffic injuries are the eighth leading cause of death globally and the leading cause of death among young people aged 15-29. Of individuals killed or injured in road traffic injuries, a large group comprises occupants sustaining a thorax injury in frontal crashes. The elderly are particularly at risk, as they are more fragile. The evaluation of the frontal crash performance of new vehicles is normally based on barrier crash tests. Such tests are only representative of a small portion of real-life crashes, but it is not feasible to test vehicles in all real-life conditions. However, the rapid development of computers opens up possibilities for simulating whole populations of real-life crashes using so-called stochastic simulations. This opportunity leads to the aim of this thesis, which is to develop and validate a simplified, parameterized, stochastic vehicle simulation model for the evaluation of passive restraint systems in real-life frontal crashes with regard to rib fracture injuries.

Methods. The work was divided into five phases. In phase one, the geometry and properties of a finite element (FE) generic vehicle buck model were developed based on data from 14 vehicles. In the second phase, a human FE model was validated for oblique frontal crashes. This human FE model was then used to represent the vehicle occupant. In the third phase, vehicle buck boundary conditions were derived based on real-life crash data from the National Automotive Sampling System (NASS) and crash test data from the Insurance Institute for Highway Safety. In phase four, a validation reference was developed by creating risk curves for rib fracture in NASS real-life crashes. Next, these risk curves were compared to the risk of rib fractures computed using the generic vehicle buck model. In the final phase, injury mechanisms in nearside oblique frontal crashes were evaluated.

Results. In addition to an averaged geometry, parametric distributions for 27 vehicle and boundary condition parameters were developed as guiding properties for the stochastic model. Particular aspects of the boundary conditions such as pulse shape, pulse angle and pulse severity were analyzed in detail. The human FE model validation showed that the kinematics and rib fracture pattern in frontal oblique crashes were acceptable for this study. The validation of the complete FE generic vehicle buck model showed that the model overestimates the risk of rib fractures. However, if the reported under-prediction of rib fractures (50-70%) in the NASS data is accounted for using statistical simulations, the generic vehicle buck model accurately predicts injury risk for senior (70-year-old) occupants. The chest injury mechanisms in nearside oblique frontal crashes were found to be a combination of (I) belt and airbag loading and (II) the chest impacting the side structure. The debut of the second mechanism was found for pulse angles of about 30 degrees.

Conclusion. A parameterized FE generic passenger vehicle buck model has been created and validated on a population of real life crashes in terms of rib fracture risk. With the current validation status, this model provides the possibility of developing and evaluating new passive safety systems for fragile senior occupants. Further, an injury mechanism responsible for the increased number of outboard rib fractures seen in small overlap and near-side oblique frontal impacts has been proposed and analyzed.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 68 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1731
EDR, Real life crashes, Oblique, Finite element, Simulation, HBM, Injury mechanism, Pulse shape, Stochastic, Rib fracture, THUMS, Generic, Statistics
National Category
Research subject
biomechanics; injury prevention
urn:nbn:se:umu:diva-102927 (URN)978-91-7601-293-2 (ISBN)
Public defence
2015-06-05, Sal D, Tandläkarhögskolan 9 trappor, Norrlands Universitetssjukhus, Umeå, 13:00 (English)
Vinnova Project: Real Life Safety Innovations
VINNOVA, 2009-02780 ; 2011-03679
Available from: 2015-05-13 Created: 2015-05-11 Last updated: 2015-05-13Bibliographically approved

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