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Cambridge, United Kingdom

Karwaczynski S.K.,U.S. Army | Karwaczynski S.K.,MTU AG | Hoover R.W.,CAPE | Jessup C.P.,IMMI | Paulson K.M.,IMMI
Proceedings of the ASME Design Engineering Technical Conference | Year: 2015

Crash testing and validation of Military vehicles has not to date, accounted for the Soldier gear burden. Actual loads imparted onto the occupant in a representative Military vehicle crash test environment have been limited and do not reflect what an occupant would actually see in this type of an event. The US Army Soldier encumbered with his gear poses a challenge in restraint system design that is not typical in the automotive world. The weight of the gear encumbrance may have a significant effect on how the restraint system performs and protects the occupant during a frontal event. Other system level complications to Military vehicle interiors are secondary impact surfaces, such as instrument panels, ammunition cans and weaponry which provide a path for off-loading the energy generated by the occupant and gear combination. The energy absorption of these surfaces however, is not ideal in current Military vehicle designs and may result in injury or death. The goal of this study was to investigate gear and accelerative pulses as they relate to the restraints and occupant interaction. Data from this study will be used for further restraint development. To limit experimental variation a fixed steel seat structure was utilized throughout the entire testing series. It is hypothesized that determining these effects will lead to a restraint system design that can be optimized to provide restraint for the whole range of occupant sizes and gear variations. Further reductions in occupant injury are achieved by properly tuning the surrounding trim, air bags and cargo contact surfaces. Results of this study indicate the inclusion of the soldier gear may increase the likelihood of occupant excursion and injury. Variation in accelerative pulses resulted in lower injury values and occupant displacements. © Copyright 2015 by ASME.

Van Arsdell W.W.,Engineering Principles LLC | Weber P.,Engineering Principles LLC | Stankewich C.,Engineering Principles LLC | Larson B.,Engineering Principles LLC | And 2 more authors.
SAE Technical Papers | Year: 2016

This paper investigates the role that load-limiters play with respect to the performance of occupant protection systems, with focus on performance in frontal crashes. Modern occupant protection systems consist of not just the seat belt, but also airbags, interior vehicle surfaces and vehicle structure. Modern seat belts very often incorporate load-limiters as well as pretensioners. Published research has established that load-limiters and pretensioners increase the effectiveness of occupant protection systems. Some have argued that load-limiters with higher deployment thresholds are always better than load-limiters with lower deployment thresholds. Through testing, modeling and analysis, we have investigated this hypothesis, and in this paper we present test and modeling data as well as a discussion to this data and engineering mechanics to explain why this hypothesis is incorrect. Research presented in this paper shows that because load-limiters are just one component of a multi-component occupant protection system, the performance of the overall occupant protection system cannot be predicted from the load-limiter performance or specifications alone. The overall occupant protection system is designed such that the load-limiter works in conjunction with the webbing stiffness, airbag, vehicle interior surfaces and vehicle structure to provide effective occupant protection. This paper shows that effective occupant protection has been achieved using different combinations of these parameters. The appropriate method of evaluating the effectiveness of an occupant protection system is to evaluate the overall performance of that occupant protection system in sled and crash tests and/or calibrated modeling. Tests of load-limiters alone or reliance on the load-limiter specification alone is not a good indicator of the overall effectiveness of an occupant protection system. Tests were conducted to establish the level at which certain retractor load-limiters deployed webbing. This data was cross-referenced with publically available test data, and shoulder belt loads, chest deflection and chest compression, among other injury metrics. Computer modeling was conducted to assess the effect of varying initial load-limiter deployment loads. Copyright © 2016 SAE International.

Suderman B.L.,Guidance Engineering and Applied Research | Hoover R.W.,CAPE | Ching R.P.,University of Washington | Scher I.S.,Guidance Engineering and Applied Research | Scher I.S.,University of Washington
Accident Analysis and Prevention | Year: 2014

We evaluated the effectiveness of hardhats in attenuating head acceleration and neck force in vertical impacts from large construction objects. Two weight-matched objects (lead shot bag and concrete block) weighing 9.1 kg were dropped from three heights (0.91 m, 1.83 m and 2.74 m) onto the head of a 50th percentile male Hybrid III anthropomorphic test device (ATD). Two headgear conditions were tested: no head protection and an ANSI Type-I, Class-E hardhat. A third headgear condition (snow sport helmet) was tested at 1.83 m for comparison with the hardhat. Hardhats significantly reduced the resultant linear acceleration for the concrete block impacts by 70-95% when compared to the unprotected head condition. Upper neck compression was also significantly reduced by 26-60% with the use of a hardhat when compared to the unprotected head condition for the 0.91 and 1.83 m drop heights for both lead shot and concrete block drop objects. In this study we found that hardhats can be effective in reducing both head accelerations and compressive neck forces for large construction objects in vertical impacts. © 2014 Elsevier B.V. All rights reserved.

Wang X.,Massachusetts Institute of Technology | Feng Y.,CAPE | Unalan H.E.,Middle East Technical University | Zhong G.,CAPE | And 4 more authors.
Carbon | Year: 2011

The effect of growth conditions and catalyst lifetime on the supergrowth of carbon nanotubes (CNTs) through a water assisted chemical vapor deposition has been investigated. The reasons behind the observed sudden termination of the CNT growth were explored. A proper amount of water was found to improve the activity of the catalyst and enhance the growth rate of CNTs. However, the introduction of water did not extend the catalyst lifetime leading to unavoidable termination of the CNT growth. Further experiments demonstrated that in addition to catalyzing the CNT growth, catalyst particles can also decompose/etch the C sp2/sp3 bonds including those in the CNTs. The existing termination mechanism for the CNT growth fails to explain this. We therefore propose a model based on the catalyst phase transformation using the Johnson-Mehl-Avrami-Kolmogorov theory to predict the growth rate and termination of the CNT growth. © 2010 Elsevier Ltd. All rights reserved.

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