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Figure . Peak chest deflection for mechanical THOR dummy and mathematical THOR dummy model. Solid bars are mechanical test results and dotted bars are mathematical model predictions. Error bars correspond to the standard deviation measured in the repeats of mechanical THOR tests.
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Objectives: The objective of this study was to determine the potential chest injury benefits and influence on occupant kinematics of a belt system with independent control of the shoulder and lap portions.
Methods: This article investigates the kinematics and dynamics of human surrogates in 35 km/h impacts with 2 different restraints: a pretensioni...
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As the number of elderly drivers and occupants continues to increase, it is important that vehicle safety equipment and restraint systems are investigated to understand if current systems are protecting these occupants during frontal collisions. The objective of this study is to examine thoracic injury to post mortem human subjects over the age of...
A common understanding is that in a frontal crash an early coupling of the occupant to the vehicle deceleration is required. This is provided by pretensioning of the belt system. The objective of our study was to set up a rating criterion for pretensioner performance, to benchmark current pretensioner systems, to define requirements for an optimal...
Citations
... Nevertheless, performance can be improved. Pretensioned and forcelimiting seatbelts in combination with airbags have been shown to significantly reduce thoracic loading and consequently thorax injuries for a driver [11,14,15]. As an output of the restraint system, the seatbelt behavior can be influenced by different parameters, for example, occupant anthropometries, belt geometry, and crash severities [16]. ...
... A′ A = 0.05 · (ln Q) 2 − 0.57 · (ln Q) + 2.41 (15) where A and A ′ are the real and truncated contact areas. ...
The reconstruction of traffic accidents has grown as an interdisciplinary field, encompassing bodies of research from automotive engineering, traffic and transport engineering, biomechanics, and forensic sciences. In this work, a method is proposed by which the value of the force in the safety belt buckle can be determined provided the belt buckle is equipped with a pretensioning system with a pyrotechnic trigger in the pretensioner tube, PBP—Pyrotechnical Buckle Pretensioner, or PLP—Pyrotechnical Lap Pretensioner type. The anti-return system of the pretensioner mechanism, which prevents the passenger’s body from moving forward, contains a set of balls that block the movement of the piston in the pretensioner tube after its activation. When limiting the movement, the force the human body exerts on the safety belt webbing is transformed into the deformation of the pretensioner tube by the balls of the anti-return system. Depending on the magnitude of the force, the marks left by the balls differ. This is an alternative method for determining the force that occurs in a seatbelt and causes injury to the occupants of a vehicle. The advantage of this method is that the force in the seatbelt buckle cable can be determined relatively quickly and accurately by analyzing the deformations in the pretensioner tube, without a need for expensive laboratory equipment. The limitation of the model resides in the consideration of a static system with rigid bodies. The correlation between the normal force causing the deformation of the tube and the force in the belt buckle cable is obtained by means of a mechanical model that explains the operation of the anti-return system. By comparing the values of the normal force given by the proposed model and the elastoplastic model, a good correlation is found. Finally, a regression curve is determined to help the expert in approximating the force in the buckle cable depending on the deformation size in the pretensioner tube. The value of this force also enables biomechanical or medical specialists to correlate the degree of injury to occupants of a vehicle depending on the force in the seatbelt.
... Nevertheless, performance can be improved. Pretensioned and force-limiting seat belts in combination with airbags were shown to significantly reduce thoracic loading and consequently thorax injuries for a driver [1,4,5]. As an output of the restraint system, the seat belt behavior can be influenced by different parameters; for example, occupant anthropometries, belt geometry, and crash severities [6]. ...
... The reaction forces, N1 and N2, which cause the deformation of both the cylinder and the piston, are determined from relations (4) and (5). The friction coefficient between the ball and the piston, respectively the pretensioner tube, is chosen, in accordance with the data from [30][31][32], at a value of 0.15-0.2. ...
The reconstruction of traffic accidents has grown as an interdisciplinary field since the first accident occurred. Various methods have been developed over time, starting with primary data collected at the scene of the accident. In this work, I proposed a method by which the value of the force in the safety belt buckle can be determined when it is equipped with a pretensioning system with pyrotechnic trigger in the tube, PBP or PLP type. The anti-return system of the pretensioner mechanism, which prevents the passenger's body from moving forward, contains a set of balls that block the movement of the piston in the pretensioner tube after its activation. When limiting the movement, the force the human body exerts on the safety belt webbing is transformed into the deformation of the pretensioner tube by the balls of the anti-return system. Depending on the magnitude of the force, the marks left by the balls differ. I propose a relationship of dependence between the acting force and the deformation of the tube. An experimental test bench was created to perform shock traction tests on the pre-tensioning system, under similar conditions to those of the human body acting on the belt in case of a frontal collision. Following the tests, the force value of the seat belt buckle cable and the diameter of the spherical indentations that the balls left in the pretensioner tube were measured. A mathematical model was proposed to determine the normal force with which a ball from the anti-return system deforms the tube. The normal force was also determined by two other methods specific to contact mechanics and used in the specialized literature. By comparing the normal forces obtained by the three methods, a good correlation between the proposed mathematical model and the Komvopoulos-Ye method resulted, the "Hardness" method not being suitable for this study. The determined polynomial regression curve allows finding out the force in the cable of the closer depending on the size of the deformations produced by the balls in the tube. The forces in the belt webbing can be thus determined and biomechanics specialists can evaluate the injuries to the chest and abdomen of the occupants of a vehicle.
... Despite their unquestionable contribution to reduce the number and severity of injuries, Anthropometric Test Devices (ATD) have shown limited capabilities to predict the spinal kinematics compared with Post Mortem Human Surrogate (PMHS) sled tests even in frontal impacts (Lopez-Valdes et al. 2010;Pipkorn, L opez-Vald es, Juste-Lorente, Insausti, et al. 2016). When lateral bending and axial torsion of the spine are induced by the asymmetric load of the three-point seatbelt, these ATD limitations can lead not only to unrealistic spine and neck loads, but also to errors in the estimation of chest deflections that are evaluated with respect to the spine (Shaw et al. 2013). ...
Objective: The objective of this study is to analyze the 6 degrees of freedom (DOF) motion of the spine using the finite helical axis (FHA) in three postmortem human surrogates (PMHS) sled tests.
Methods: The sled test configurations corresponded to a 30° nearside oblique impact at 35 km/h. Two different restraint system versions (RSv) were used. RSv1 was used for PMHS A and B while RSv2 was used for PMHS C. The 6 DOF motion of the head and three selected vertebrae have been analyzed using the FHA which describes the 3 D motion of a rigid body between two instants of time as a rotation about and a translation along a unit vector. A minimal amount of rotation is necessary to the FHA calculation, thus the FHA components have been calculated based on a pre-defined interval of 8° of rotation.
Results: The analysis of the FHA components demonstrated right lateral bending until around 100 ms, when the rebound phase was reached and the head and the lower spine undergoes left lateral bending. The three PMHS exhibited, in general, flexion movement of the whole body and torsion to the right side of the occupant. This general motion can be associated to the effect of the seatbelt acting as a fulcrum of the rotational movement of the bony landmarks. The interaction of the PMHS with the retention system can be noted by analyzing the time in which the head and the upper spine initiated the rotation and the sudden changes of rotational direction of the three PMHS’s head.
Conclusions: The rotational analyses have shown to be more sensitive to experimental events than the trajectory analyses for the studied physical tests. Additionally, the results presented in the present study contributes to the analysis of the body kinematics during an oblique impact and adds new experimental data for Human Body Models (HBM) and Anthropometric Test Devices (ATD) benchmarking.
... Furthermore, the performance of standard ATD dummies is often supplemented with PMHS (postmortem human surrogates). Research has shown that dummy models and human models give different results [19,20]. The low-speed sled and low acceleration sled test with a volunteer, which focuses on body dynamics and the influence of pre-crash muscle tension, was described in [21] and [22]. ...
Safety tests are generally performed in accordance with strict procedures that involve the use of a carefully positioned dummy. Safety tests are rarely conducted with the occupant being in a non-standard position. In real life driving, occupants, especially passengers, choose a more comfortable reclined position, and in such a case the body dynamics are different from those investigated in the standard safety test. Furthermore, with the rapid development of autonomous vehicles, which provide the possibility of the position of occupants being unrestricted, the investigation of "out of position" body kinetics is becoming more important. The presented study aimed to evaluate body dynamics with various seatback reclinations. Body dynamics were verified by simulating frontal impact on a sled system with the use of a standard 50 percentile Hybrid III dummy. Points of interest located on the dummies head, neck, pelvis, and legs were traced, which allowed its trajectory to be evaluated. Additionally, the maximal extrusion and the time of motion were evaluated. It was found that the maximal extrusion in the longitude direction is the same for semi and fully reclined seats. Furthermore, a reclined seat causes head rotation, which can result in neck injuries.
... Innovations in seat belt design [52,53] and greater penetration of pretensioners and load limiters [44,[54][55][56], may also improve torso and other injury outcomes in older adults. ...
Purpose
Previous studies have shown elderly individuals receive less relatively less protection from seat belts against fatal injuries, however it is less clear how seat belt protection against severe and torso injury changes with age. We estimated age-based variability in seat belt protection against fatal injuries, injuries with maximum abbreviated injury scale greater than 2 (MAIS3+), and torso injuries.
Methods
We leveraged the Crash Outcome Data Evaluation System (CODES) to analyze binary indicators of fatal, MAIS3+, and torso injuries. Using a matched cohort design and conditional Poisson regression, we estimated age-based relative risks (RR) of the outcomes associated with seat belt use.
Results
Seat belts were highly protective against fatal injuries for all ages. For ages 16-30, seat belt use was associated with 66% lower risk of MAIS3+ injury (RR 0.34, 95% CI 0.30, 0.38), whereas for ages 75 and older, seat belt use was associated with 38% lower risk of MAIS3+ injury (RR 0.62; 95% CI 0.45, 0.86). The association between restraint use and torso injury also appeared to attenuate with age.
Conclusions
Seat belt protection against MAIS3+ and torso injury attenuated with age. We encourage that injury prevention continues to be tailored to vulnerable populations like the elderly.
... Occupants were restrained by a nonretractor three-point seat belt. The position of the anchoring points of the seat belt was chosen based on previous studies to allow the comparison of the results (López-Valdés et al., 2016;Pipkorn et al., 2016a). The position of the footrest and of the seat belt D-ring were adjusted depending on each volunteer's anthropometry, but ensuring that the loading scenarios were dynamically similar. ...
Cervical pain and injuries are a major health problem globally. Existing neck injury criteria are based on experimental studies that included sled tests performed with volunteers, post-mortem human surrogates and animals. However, none of these studies have addressed the differences between young adults and elderly volunteers to date. Thus, this work analyzed the estimated axial and shear forces, and the bending moment at the craniocervical junction of nine young volunteers (18–30 years old) and four elderly volunteers (>65 years old) in a low-speed frontal deceleration. Since the calculation of these loads required the use of the mass and moment of inertia of the volunteers' heads, this study proposed new methods to estimate the inertial properties of the head of the volunteers based on external measurements that reduced the error of previously published methods. The estimated mean peak axial force (Fz) was −164.38 ± 35.04 N in the young group and −170.62 ± 49.82 N in the elderly group. The average maximum shear force (Fx) was −224.42 ± 54.39 N and −232.41 ± 19.23 N in the young and elderly group, respectively. Last, the estimated peak bending moment (My) was 13.63 ± 1.09 Nm in the young group and 14.81 ± 1.36 Nm in the elderly group. The neck loads experienced by the elderly group were within the highest values in the present study. Nevertheless, for the group of volunteers included in this study, no substantial differences with age were observed.
... Toyota Central R&D Labs., Inc. and Toyota Motor Corporation jointly developed a whole human body FE model named THUMS (Total HUman Model for Safety) to predict kinematics and injuries of occupants or pedestrians during various crash situations seen in traffic accidents and reported on the applicability of the model [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] . A human body FE model used in this study was developed based on the THUMS Version 3 34 by incorporating 282 individual muscle models of the whole body into the THUMS to investigate effect of muscle activity on kinematics and injuries of the whole body [35][36][37] . ...
Little is known about the effects of posterior tethers on the development of proximal junctional kyphosis (PJK). We evaluated the ability of posterior tethers to the proximal motion segment stiffness in long instrumented spinal instrumentation and fusion using a whole body human FE model. A series of finite element (FE) analysis of long segmental spinal fusion (SF) from the upper thoracic vertebra (T1) or lower thoracic vertebra (T9) to the sacrum with pedicle screws and rods were performed using an entire human body FE model (includes 234,910 elements), and compressive stresses (CS) on the anterior column, and tensile stresses (TS) on the posterior ligamentous complex (PLC) in the upper-instrumented vertebra (UIV) and the vertebra adjacent to the UIV (UIV + 1) were evaluated with posterior tethers or without posterior tethers. The models were tested at three T1 tilts (0, 20, 40 deg.), with 20% muscle contraction. Deformable material models were assigned to all body parts. Muscle-tendon complexes were modeled by truss elements with a Hill-type muscle material model. The CS of anterior column decreased with increasing T1 slope with tethers in both models, while the CS remained relatively large in T9 model compared with T1 model (T1 UIV; 0.96 to 1.56 MPa, T9 UIV; 4.79 to 5.61 MPa). The TS of the supraspinous ligament was markedly reduced in both T1 and T9 models with posterior tethers (11–35%). High vertebral CS on UIV and UIV + 1 were seen in the T9 UIV model, and the TS on the PLC were increased in both UIV models. Posterior tethers may decrease PJK development after SF with a proximal thoracic UIV, while both posterior tethers and vertebral augmentation may be necessary to reduce PJK development with a lower thoracic UIV.
... Modifications included remodelling of the ribcage [11] and recalibration of the lumbar spine properties [12]. To evaluate the kinematic response of this HBM, four PMHS sled tests in frontal and frontal oblique load cases were carried out [13]- [14]. The sled test fixture (Gold Standard) consisted of a rigid metallic frame allowing complete visual access to the occupant while preserving the basic geometry of a standard seat of a passenger car. ...
The goal of this study was to quantify the effect of improving the geometry of a human body model on the accuracy of the predicted kinematics for 4 post-mortem human subject sled tests. Three modifications to the computational human body model THUMS were carried out to evaluate if subject personification can increase the agreement between predicted and measured kinematics of post-mortem human subjects in full frontal and nearside oblique impacts. The modifications consisted of: adjusting the human body model mass to the actual subject mass, morphing it to the actual anthropometry of each subject and finally adjustment of the model initial position to the measured position in selected post-mortem human subject tests. A quantitative assessment of the agreement between predicted and measured response was carried out by means of CORA analysis by comparing the displacement of selected anatomical landmarks (head CoG, T1 and T8 vertebre and H-Point). For all three scenarios, the more similar the human body model was to the anthropometry and posture of the sled tested post-mortem human subject, the more similar the predictions were to the measured responses of the post-mortem human subject, resulting in higher CORA score.
... In this section, the pretension characteristics of the BLP, DP and BP restraint system were studied at two constant pretension forces, i.e. 2000 N [18][19][20][21] and 4000 N, respectively. The initial trigger time was 18 ms. ...
... In Figure 8c, raising the BL, the value of femur force increases, which is caused by the increase of the submarine effect [21]. The other three parameters, i.e. ...
... As shown in Figure 9a, HP is the most significant factor for the head injury, and the mechanism has been described in Section 4.1. The four design variables are ranked as follows according to their effect (from the highest to the lowest) on HIC 36 as follows: HP, IT, BL and ER. Figure 9b shows that BL is the most important variable affecting C comp ; due to its influence on the submarine effect [21] and then the movement of the the thorax. The descending sequence of design variables according to their contribution to chest injury response is as follows: BL, HP, IT and ER. ...
The aim of this study is to design a novel, high-efficiency and low-cost Bilateral Pretensioner (BLP) and evaluate it using a computational approach, i.e. coupling of FEA and multibody dynamics. The BLP system was designed by changing the rotation axle of the conventional retractor. The computational models for BLP, and the other two designs, namely Double Pretension (DP) and Buckle Pretention (BP) were further constructed based on a validated restraint system model to study their pretension characteristics and injury prevention capabilities. Then a range analysis design was conducted on the newly developed BLP system to identify the optimal values of four design parameters and analyze the sensitivity of injury responses to these parameters. The results show that the BLP system would have a higher pretension efficiency and injury prevention capability than the traditional BP system. Although the DP system could retract more webbing, BLP is superior due to its slightly higher injury pretension capability and lower cost of a single pretensioner. The range analysis of BLP system suggests the optimal parametric values and the sensitivity of responses to these parameters.
... Modifications included remodelling of the ribcage [11] and recalibration of the lumbar spine properties [12]. To evaluate the kinematic response of this HBM, four PMHS sled tests in frontal and frontal oblique load cases were carried out [13]- [14]. The sled test fixture (Gold Standard) consisted of a rigid metallic frame allowing complete visual access to the occupant while preserving the basic geometry of a standard seat of a passenger car. ...
