Kinematic assessment of subject personification of human body models (THUMS)

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

Effects of Including a Penetration Test in Motorcyclist Helmet Standards: Influence on Helmet Stiffness and Impact Performance

Regulation ECE-22.05/06 does not require a helmet penetration test. Penetration testing is controversial since it has been shown that it may cause the helmet to behave in a non-desirable stiff way in real-world crashes. This study aimed to assess the effect of the penetration test in the impact performance of helmets. Twenty full-face motorcycle helmets were penetration tested at multiple locations of the helmet shell. Then, 10 helmets were selected and split into two groups (hard shell and soft shell) depending on the results of the penetration tests. These 10 helmets were then drop tested at front, lateral, and top areas at two different impact speeds (5 m/s and 8.2 m/s) to assess their impact performance against head injuries. The statistical analyses did not show any significant difference between the two groups (hard/soft shell) at 5 m/s. Similar results were observed at 8.2 m/s, except for the top area of the helmet in which the peak linear acceleration was significantly higher for the soft shell group than for the hard shell group (230 ± 12 g vs. 211 ± 11 g; p-value = 0.038). The results of this study suggest that a stiffer shell does not necessarily cause helmets to behave in a stiffer way when striking rigid flat surfaces. These experiments also showed that hard shell helmets can provide better protection at higher impact speeds without damaging helmet performance at lower impact speeds. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

The influence of headform/helmet friction on head impact biomechanics in oblique impacts at different tangential velocities

Oblique impacts of the helmet against the ground are the most frequent scenarios in real-world motorcycle crashes. The combination of two factors that largely affect the results of oblique impact tests are discussed in this work. This study aims to quantify the effect of the friction at the interface between the headform and the interior of a motorcycle helmet at different magnitudes of tangential velocity. The helmeted headform, with low friction and high friction surface of the headform, was dropped against three oblique anvils at different impact velocities resulting in three different magnitudes of the tangential velocity (3.27 m/s, 5.66 m/s, 8.08 m/s) with the same normal component of the impact velocity (5.66 m/s). Three impact directions (front, left-side and right-side) and three repetitions per impact condition were tested resulting in 54 impacts. Tangential velocity variation showed little effect on the linear acceleration results. On the contrary, the rotational results showed that the effect of the headform’s surface depends on the magnitude of the tangential velocity and on the impact direction. These results indicate that a combination of low friction with low tangential velocities may result into underprediction of the rotational headform variables that would not be representative of real-world conditions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Guidelines for improving motorcycle helmet testing standards / Directrices para mejorar las normas de ensayo de los cascos de motocicleta

Investigaciones sobre accidentes reales de motocicletas han demostrado que lesiones graves en la cabeza, como las fracturas en la base del cráneo y las lesiones intracraneales, son todavía comunes entre los motociclistas a pesar de todos los avances en el diseño y fabricación de cascos. Curiosamente, este tipo de lesiones parecen estar correlacionadas con las deficiencias y discrepancias existentes entre las actuales normas de ensayo de cascos de motocicleta. Por lo tanto, el objetivo principal de esta tesis es investigar cómo se pueden mejorar las actuales normas de ensayo de cascos de motocicleta para reducir las fracturas en la base del cráneo y las lesiones intracraneales entre los motociclistas. Aunque es bien conocido que las lesiones intracraneales son causadas principalmente por un movimiento rotacional de la cabeza, las actuales normas de ensayo de cascos se centran más en el movimiento traslacional que en el movimiento rotacional de la cabeza. Las cabezas de ensayo utilizadas actualmente en las normativas de ensayo de cascos no fueron inicialmente diseñadas para la evaluación del movimiento rotacional. Se compararon las propiedades de masa e inercia de las cabezas de ensayo EN960 con una base de datos de propiedades físicas de la cabeza humana creada a partir de una revisión de una selección de estudios realizados con cadáveres humanos. La mayoría de los valores de las cabezas de ensayo estaban dentro del intervalo de predicción del 95% para la mayoría de las propiedades físicas de la cabeza humana, pero se observaron algunas diferencias con respecto a los modelos de regresión calculados. Por lo tanto, un nuevo conjunto de cabezas de ensayo con propiedades de masa e inercia más similares a las calculadas con los modelos de regresión sería beneficioso para mejorar las actuales normas de ensayo de cascos. Todas las normas de ensayo de cascos de motocicleta incluyen pruebas de impacto normal, en las que el vector de velocidad de impacto es normal a la superficie de impacto, para evaluar la protección proporcionada por el casco. Sin embargo, los métodos de impacto normal no miden o no permiten la rotación de la cabeza de ensayo. Se expusieron veinte modelos de cascos integrales y la cabeza de ensayo sin casco a pruebas de impacto normal para estudiar la idoneidad de las pruebas de impacto normal para evaluar el riesgo de lesiones intracraneales. Se demostró que el movimiento angular de la cabeza de ensayo equipada con casco disminuye a medida que la aceleración lineal disminuye durante las pruebas de impacto normal, pero el movimiento angular en este tipo de impactos también depende del diseño geométrico del casco. Este resultado sugiere que el movimiento angular de la cabeza de ensayo debe evaluarse en pruebas de impacto normal en combinación con la evaluación en impactos oblicuos, para evaluar el diseño geométrico del casco en una amplia gama de posibles escenarios de impacto en los que se podrían generar lesiones intracraneales. A pesar de que algunas normas de ensayo de cascos incluyen pruebas de impacto oblicuo para evaluar el movimiento de rotación de la cabeza, requieren diferentes coeficientes de fricción entre el interior del casco y la cabeza de ensayo, lo que se ha demostrado que es un factor crítico para la respuesta angular de la cabeza de ensayo en impactos oblicuos. Dieciocho muestras del mismo modelo de casco fueron probadas con la misma magnitud de la componente normal de la velocidad de impacto, pero con tres magnitudes diferentes de la componente tangencial de la velocidad de impacto y usando dos coeficientes de fricción diferentes entre el interior del casco y la cabeza de ensayo. Se concluyó que el coeficiente de fricción entre la cabeza de ensayo y la superficie interior del casco debe ser lo suficientemente alto como para garantizar el movimiento conjunto de la cabeza de ensayo y el casco, especialmente si la velocidad tangencial incluida en las normas de ensayo de cascos es menor que las encontradas en situaciones reales.La carga axial en la zona superior del cuello fue propuesta como criterio de lesión para las fracturas de la base del cráneo y los accidentes reales de motocicleta han demostrado que las fracturas de la base del cráneo están altamente relacionadas con los impactos en la zona de la mentonera. Sin embargo, los métodos actuales de ensayo de la mentonera incluidos en las normas de prueba de cascos, no incluyen el cuello para medir la fuerza axial del cuello. Se utilizó una metodología combinada que utiliza la cinemática medida con una cabeza de ensayo aislada durante un ensayo físico como entrada para un modelo de elementos finitos de cuerpo completo para estudiar si es posible predecir la carga de tracción del cuello que el modelo del Hibrido III de cuerpo completo experimentaría en un impacto similar al de la prueba de la mentonera de la norma ECE 22.06 utilizando solo métricas basadas en la cinemática del ensayo de la mentonera descrito en la norma. Los resultados mostraron que una simple prueba de impacto en la mentonera utilizando las cabezas de ensayo EN960, como la que se incluye en algunas normas de ensayo de cascos, podría considerar el riesgo de fractura de la base del cráneo mediante una combinación del pico de aceleración lineal en el eje Z y la velocidad lineal resultante al final del impacto.El ensayo de penetración es uno de los ensayos más controvertidos entre las normas de ensayo de cascos y actualmente no es requerido por algunos programas de ensayo, mientras que otros continúan exigiendo esta prueba. Basado en los resultados del ensayo de penetración de veinte modelos de casco, cuatro cascos fueron clasificados como cascos de calota dura, mientras que seis de ellos fueron clasificados como cascos de calota blanda. Solo estos diez modelos de cascos fueron sometidos a pruebas de impacto a dos velocidades diferentes para estudiar el efecto de incluir el ensayo de penetración en el comportamiento global de los cascos frente a impactos. Se concluyó que la prueba de penetración podría influir positivamente en el diseño del casco al proporcionar protección contra lesiones en la cabeza inducidas principalmente por la cinemática lineal, mientras que podría influir negativamente en el diseño del casco al proporcionar protección contra lesiones en la cabeza inducidas principalmente por la cinemática de rotación.<br /

Kinematic assessment of subject personification of human body models (THUMS)

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

Differences in the kinematics of booster-seated pediatric occupants using two different car seats

<p><b>Objective</b>: The objective of this article is to compare the performance of forward-facing child restraint systems (CRS) mounted on 2 different seats.</p> <p><b>Methods</b>: Two different anthropomorphic test device (ATD) sizes (P3 and P6), using the same child restraint system (a non-ISOFIX high-back booster seat), were exposed to the ECE R44 regulatory deceleration pulse in a deceleration sled. Two different seats (seat A, seat B) were used. Three repetitions per ATD and mounting seat were done, resulting in a total of 12 sled crashes. Dummy sensors measured the head tri-axial acceleration and angular rate and the thorax tri-axial acceleration, all acquired at 10,000 Hz. A high-speed video camera recorded the impact at 1,000 frames per second. The 3D kinematics of the head and torso of the ATDs were captured using a high-speed motion capture system (1,000 Hz). A pair-matched statistical analysis compared the outcomes of the tests using the 2 different seats.</p> <p><b>Results</b>: Statistically significant differences in the kinematic response of the ATDs associated with the type of seat were observed. The maximum 3 ms peak of the resultant head acceleration was higher on seat A for the P3 dummy (54.5 ± 1.9 <i>g</i> vs. 44.2 ± 0.5 <i>g</i>; <i>P</i> =.012) and for the P6 dummy (56.0 ± 0.8 <i>g</i> vs. 51.7 ± 1.2 <i>g</i>; <i>P</i> =.015). The peak belt force was higher on seat A than on seat B for the P3 dummy (5,488.0 ± 198.0 N vs. 4,160.6 ± 63.6 N; <i>P</i> =.008) and for the P6 dummy (7,014.0 ± 271.0 N vs. 5,719.3 ± 37.4 N; <i>P</i> =.015). The trajectory of the ATD head was different between the 2 seats in the sagittal, transverse, and frontal planes.</p> <p><b>Conclusion</b>: The results suggest that the overall response of the booster-seated occupant exposed to the same impact conditions was different depending on the seat used regardless of the size of the ATD. The differences observed in the response of the occupants between the 2 seats can be attributed to the differences in cushion stiffness, seat pan geometry, and belt geometry. However, these results were obtained for 2 particular seat models and a specific CRS and therefore cannot be directly extrapolated to the generality of vehicle seats and CRS.</p

Differences in the kinematics of booster-seated pediatric occupants using two different car seats

<p><b>Objective</b>: The objective of this article is to compare the performance of forward-facing child restraint systems (CRS) mounted on 2 different seats.</p> <p><b>Methods</b>: Two different anthropomorphic test device (ATD) sizes (P3 and P6), using the same child restraint system (a non-ISOFIX high-back booster seat), were exposed to the ECE R44 regulatory deceleration pulse in a deceleration sled. Two different seats (seat A, seat B) were used. Three repetitions per ATD and mounting seat were done, resulting in a total of 12 sled crashes. Dummy sensors measured the head tri-axial acceleration and angular rate and the thorax tri-axial acceleration, all acquired at 10,000 Hz. A high-speed video camera recorded the impact at 1,000 frames per second. The 3D kinematics of the head and torso of the ATDs were captured using a high-speed motion capture system (1,000 Hz). A pair-matched statistical analysis compared the outcomes of the tests using the 2 different seats.</p> <p><b>Results</b>: Statistically significant differences in the kinematic response of the ATDs associated with the type of seat were observed. The maximum 3 ms peak of the resultant head acceleration was higher on seat A for the P3 dummy (54.5 ± 1.9 <i>g</i> vs. 44.2 ± 0.5 <i>g</i>; <i>P</i> =.012) and for the P6 dummy (56.0 ± 0.8 <i>g</i> vs. 51.7 ± 1.2 <i>g</i>; <i>P</i> =.015). The peak belt force was higher on seat A than on seat B for the P3 dummy (5,488.0 ± 198.0 N vs. 4,160.6 ± 63.6 N; <i>P</i> =.008) and for the P6 dummy (7,014.0 ± 271.0 N vs. 5,719.3 ± 37.4 N; <i>P</i> =.015). The trajectory of the ATD head was different between the 2 seats in the sagittal, transverse, and frontal planes.</p> <p><b>Conclusion</b>: The results suggest that the overall response of the booster-seated occupant exposed to the same impact conditions was different depending on the seat used regardless of the size of the ATD. The differences observed in the response of the occupants between the 2 seats can be attributed to the differences in cushion stiffness, seat pan geometry, and belt geometry. However, these results were obtained for 2 particular seat models and a specific CRS and therefore cannot be directly extrapolated to the generality of vehicle seats and CRS.</p

Analysis of the spinal 3D motion of postmortem human surrogates in nearside oblique impacts

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\ub0 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\ub0 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

Personificación de Modelos de Elementos Finitos de Cuerpo Humano: Evaluación Cinemática

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.El objetivo de este estudio es cuantificar el efecto introducir modificaciones en la geometría de un modelo de cuerpo humano en la precisión de predicción de la cinemática de cuarto ensayos de impacto con sujetos cadavéricos. Se han realizado tres tipos de modificaciones en el modelo de simulación consistentes en: Ajustar la masa del modelo a la masa de cada uno de los sujetos de ensayo, modificar la geometría del modelo de forma que se ajuste a la antropometría de los sujetos y, finalmente, ajustar alineación de la columna inical del modelo de forma que represente la postura de los ocupantes para cada uno de los ensayos. El análisis cuantitativo de la relación entre la respuesta del modelo y la medida en los ensayos físiscos.se ha realizado mediante un análisis CORA comparando el desplazamiento de puntos anatómicos de referencia (Centro de gravedad de la cabeza, vértebras T1 y T8 y punto H). Para los tres escenarios (dos de impacto oblícuo y uno de impacto frontal) se observa que una mayor similitud entre la antropometría y la postura del sujeto físico y el modelo, resultan en una mejora en la predicción de la cinemática del modelo comparada con&nbsp; la respuesta medida en los ensayos reales, obteniendo una mayor puntuacion CORA

Analysis of occupant kinematics and dynamics in nearside oblique impacts

Objective: The objective of this article is to analyze the kinematics and dynamics of restrained postmortem human surrogates (PMHS) exposed to a nearside oblique impact and the injuries that were found after the tests.Methods: Three male PMHS of similar age (64 4years) and anthropometry (weight: 61 9.6kg; stature: 172 +/- 2.7cm) were exposed to a 30 degrees nearside oblique impact at 34km/h. The test fixture approximated the seating position of a front seat occupant. A rigid seat was designed to match the pelvic displacement in a vehicle seat. Surrogates were restrained by a 3-point seat belt consisting of a 2kN pretensioner (PT), 4.5kN force-limiting shoulder belt, and a 3.5kN PT lap belt. The shoulder belt PT was not fired in one of the tests. Trajectories of the head, shoulder, and hip joint (bilaterally) were recorded at 1,000Hz by a 3D motion capture system. The 3D acceleration and angular rate of the head, T1, and pelvis, and the 3D acceleration of selected spinal locations was measured at 10,000Hz. Seat belt load cells measured the belt tension at 4 locations. PMHS donation and handling were performed with the approval of the relevant regional ethics review board.Results: Activation of the shoulder PT reduced substantially the peak forward excursion of the head but did not influence the lateral displacement of the head center of gravity (CG). In all 3 subjects, the lateral excursion of the head CG (291.1, 290, 292.1mm) was greater than the forward displacement (271.4, 216.7, 171.5mm). The hip joint excursion of the PMHS that was not exposed to the shoulder PT seat belt was twice the magnitude observed for the other 2 subjects. The 3 PMHS sustained clavicle fractures on the shoulder loaded by the seat belt and 2 of them were diagnosed atlantoaxial subluxation in the radiologist examination. Avulsion fractures of the right lamina of T1, T2, T3, and T4 were found when the PT was not used. The 3 PMHS received multiple fractures spread over both aspects of the rib cage and involving the posterior aspect of it.Conclusion: In this study of nearside oblique impact loading, the PMHS exhibited kinematics characterized by reduced torso pitching and increased lateral head excursion as compared to previous frontal impact results. These kinematics resulted in potential cervical and thoracic spinal injuries and in complete, displaced fractures of the lateral and posterior aspects of the rib cage. Though this is a limited number of subjects, it shows the necessity of further understanding of the kinematics of occupants exposed to this loading mode