Anthony Sances

Acceleration Amplification in Safety Belt Buckle Systems

Multi-planar rollover accidents report belt usage rates that are noted to be significantly lower than that of planar crash modes.1 One explanation for this dramatic difference in reported belt usage in rollovers as compared to planar crashes is that highway patrol officers often conclude that an ejection would not have occurred had the occupant been belted. Restrained occupants can be ejected from the vehicle if the seat belts fail to restrain occupants as a result of belt spool out or buckle unlatching.2,3 Previous studies have documented the susceptibility of certain safety belt buckles to inertially unlatch.4,5,6,7 Under sufficient vertical accelerations, top button safety belt buckles have inertially unlatched in testing which would obviously negate the safety belts ability to restrain the occupant. This study expands on the mechanisms that could lead to inertial release under vertical loading in safety belt buckle systems with stiff attachments to the vehicle floor. An audio transducer was attached to a vehicle floorpan to induce accelerations at variable frequency and amplitude. Accelerations were recorded at the floorpan and safety belt buckle body simultaneously. Accelerations measured at the buckle body were up to 13 times greater than the accelerations measured at the floor pan for frequencies up to 8.5 kHz. The present study provides a first step to better understand the injury biomechanics by quantifying the accelerations at the floor pan and safety belt buckle.Copyright

Analysis of Side Release Motor Vehicle Seat Belt Buckles

The purpose of the current study was to evaluate the likelihood of inertial release of various production side release automotive seat belt buckles under acceleration loading conditions that could be expected to occur in real world accident events. Each test sample was secured to a specially designed vertical acceleration test fixture. This produced a rigid mount, which allowed impacts to be transmitted to the test buckle. A commercially available M/RAD 0909 Pneumatic Shock Machine was used to control the magnitude, shape and duration of the pulses transmitted to the fixture and test buckle. To measure and analyze the shock pulse generated by the M/RAD Pneumatic Shock Machine, an M/RAD SRA-1200 Shock Instrumentation System was used with the capacity to capture, display and analyze half-sine, saw tooth and square wave pulses. A display screen and computer printouts record peak accelerations, pulse durations and change in velocity. An ICP 305A04 accelerometer was attached to the base of the test fixture. All information was recorded at a rate of 8 kHz and was filtered using a digital four pole Butterworth zero phase shift filter, and a low pass filtering system set at L-P1 with a cutoff of 1100 Hz. The current test fixture was designed to accommodate various production side release buckles with interchangeable jaw plates, for the different style buckles, to provide a “rigid mount.” A constant load can be placed on the latch plate and can be varied from 4 to 133 N. The forces for a fixed latch side buckle did not open upto accelerations of about 480 G’s. In contrast, unprotected side release buckle released at accelerations of about one fourth that of protected.Copyright

Biomechanical Analysis of Side Release and Top Release Seat Belt Buckles

Various articles suggest that the maximum release force for buckle according to Federal Motor Vehicle Safety Standards (FMVSS) 109 of 133 N is beyond the capability of a large percentage of our population [1, 2]. Inversion studies with a large male in a three-point production belt showed he could not open a side release buckle [3]. Numerous articles and patents reference the potential for entrapment of inverted occupants unable to release the seat belt buckle [4–11]. Various articles and patents discuss the problems associated with entrapment of individuals in fires, water or emergency situations or where the occupant is deprived of oxygen due to positional asphyxia [12]. While the use of seat belts has increased markedly over the years [13], investigations indicate that rollover accidents showed fatally injured occupants in their seats which were entrapped in their vehicle. The forces to release the buckles under full load of the inverted occupants were beyond the physical capacities of the occupants involved. Canadian motor vehicle safety standard 209 (CMVSS 209) requires that a buckle must release with a force of 133 N to the button with a restraining loop force of 666 N. About 80 % of driver’s could not release a buckle that requires 133 N of force on the button [1]. Females could exert about 80 N with their fingers when opening child restraint buckles [14]. Females were generally found to have about half the physical capacity to open buckles compared to males. The maximum buckle release force of 133 N is not found in literature. Dreyfuss in his book indicates various forces for females and males [15]. European standards require that latch plate be ejected, therefore side release buckles are not allowed.Copyright

Design and Evaluation of a System for Testing and Analysis of Rollovers With Narrow Objects

Recent statistics highlight the significant risk of serious and fatal injuries to occupants involved in rollover collisions due to excessive roof crush. The government has reported that in 2002, Sports Utility Vehicle rollover related fatalities increased by 14% to more than 2400 annually. 61% of all SUV fatalities included rollovers. [1] Rollover crashes rely primarily upon the roof structures to maintain occupant survival space. Frequently these crashes occur off the travel lanes of the roadway and, therefore, can include impacts with various types of narrow objects such as light poles, utility poles and/or trees. A test device and methodology is presented which allows for dynamic, repeatable rollover impact evaluation of complete vehicle roof structures with such narrow objects. These tests allow for the incorporation of Anthropomorphic Test Dummies (ATDs) which can be instrumented to measure accelerations, forces and moments to evaluate injury potential. High-speed video allows for detailed analysis of occupant kinematics and evaluation of injury causation. Criteria such as restraint performance, injury potential, survival space and the effect of roof crush associated with various types of design alternatives, countermeasures and impact circumstances can also be evaluated. In addition to presentation of the methodology, two representative vehicle crash tests are also reported. Results indicated that the reinforced roof structure significantly reduced the roof deformation compared to the production roof structure.Copyright

Biomechanical study of traumatic asphyxia due to thoracic load

The purpose of the study was to determine the force-deflection characteristics of the chest of the human surrogate dummy during the loading typical of traumatic asphyxia conditions. The 5th percentile female Hybrid III and 50th percentile male Hybrid III anthropomorphic dummies were used. The vehicle rear bumper impacted the chest of the dummy at idle speed and was allowed to remain in contact with the chest. A total of 14 tests were conducted. The chest force was measured using the load cell and chest deflection was measured using the potentiometer. High-speed photography was used to collect the kinematics data of the dummy. The measured peak deflection was above the proposed injury assessment reference value for chest compression. The peak force was found to be injurious.

Analysis of Structural Deformation in Vehicular Drop Studies

Various tests are used to evaluate the roof strength of production vehicles. Dynamic rollover tests have been conducted as part of FMVSS 208 and static evaluation using FMVSS 216. The National Highway Transportation Safety Administration (NHTSA) is investigating methods to upgrade FMVSS 216 roof crush resistance to reduce injuries and fatalities in passenger cars, pickup trucks, vans, and multipurpose passenger vehicles from roof intrusion in rollover crashes (1). Roof crush intrusion is estimated to occur and potentially contribute to about 26 percent of serious or fatal injuries. Motor vehicle rollovers have been a concern for more that 30 years because they carry a very high risk of occupant death or risk compared to other types of crashes (2).Copyright

Pediatric Airbag Injuries

The advent of airbag technology has helped to reduce the injuries to belted occupants in motor vehicles during moderate to severe frontal and near frontal crashes [1–3]. Airbags have been in use since the early 1970s. As of July 2001, airbags have saved 7224 lives including 6066 drivers and 1158 front right passengers. However, the airbag deployments at low crash severity showed higher injury probability of occupants. The majority of airbag fatalities are associated with low speed impacts with deployments. As of July 2001, the National Highway Traffic Safety Administration (NHTSA) has reported 144 fatalities and serious life threatening injuries to children due to passenger airbags [4]. It is also reported that four children died and one child sustained life-threatening injury due to a driver side airbag. The publication from Transport Canada noted that the airbags increase the overall risk of injury of children under the age of 10 by approximately 21% [5]. Although the airbags have saved many lives, they are also responsible for fatalities and serious injuries during low speed severity collision. The present study reports pediatric airbag injuries sustained during low speed crashes.Copyright

Vertical Impulse Analysis of Seat Belt Buckles

Review of various buckle testing studies is given. More than 100 different standard production end release seat belt buckles have been tested and repeatability and validation studies have been done. The buckle stalks were modified to accommodate the vertical acceleration test fixture. Some buckles opened with vertical accelerations as low as 91 g’s while others did not release at levels as high as 489 g’s.© 2002 ASME

Biomechanical Analysis of Soft Tissue Neck Injury During Pedestrian Fall

Pedestrians sustain serious injuries when impacted by vehicles [1]. Various biomechanical studies have focused on pedestrian injuries due to direct contact with the vehicle and environment [1–5]. Similar studies on the injuries to the pedestrian due to indirect force such as inertial load are limited [6]. One of the most susceptible regions of the human body to inertial loading is the neck component (cervical spine). The cervical spine connects the head and upper torso, and provides mobility to the head. Direct loading to the head and/or upper torso subjects the cervical spine to indirect loading. For example, in a pedestrian lateral fall on the shoulder, the cervical spine flexes laterally due to inertial loading from the head and upper torso, and may injure its soft tissue components. The purpose of this study is to delineate the biomechanics of the soft tissue neck injury during the pedestrian lateral fall due to vehicular impact using the anthropometric test device.Copyright

Head injury reduction with roll bar padding

Potential injury mitigation of padding on vehicular roll bars was evaluated. After market and metal air gap padding markedly reduced the head injury criterion (HIC) angular acceleration and angular velocity compared to the stock foam roll bar padding.