In support of the development of American National Standards Institute standards for the, transport of radioactive materials, Sandia has a program to characterize the normal transport environment. This program includes both analytical modeling of package and trailer responses, and over-theroad tests to measure those responses. This paper presents the results of a series of over-the-road tests performed using Chem-Nuclear equipment in the Barnwell, SC, area. The test events included a variety of road types such as rough concrete, shock events such as railroad grade crossings, and driver responses such as sharp turns°The response of the package and trailer to these events was measured with accelerometers at various locations to determine the inertial loads. Ei_her load cells or strain gages were used to measure tledown response. These accelerations and loads were measured on systems with flexible and mrlgid" tiedowns. The results indicated that while significant accelerations occur on the trailer bed, these do not translate into equivalent loads in either the package ol the tiedown system. This indicates that trailer-bed response should not be used in determining the load factor for fatigue calculations • of the package components or in determining design loads for tiedowns, f | '
capabilityof the Rampantportionof the analysis sincea solid canopy parachuteand a ribbon parachutewere A novel CFD/structuralanalysis was performed to alreadybeing examined. This type of parachute is used predictfunctionalityof across parachuteunderloadings for a wide range of applications. Canopies fabricated near the structural limits of the parachute. The from 2.25 oz/yd2 nylon cloth and from 3 oz/yd2 Kevlar determinationof parachute functionality was based on the computed structural integrity of the canopy and cloth, with 200 Ibbraided nylon suspensionlines, were suspension lines. In addition to the standard analyzed.The procedurewas to mesh theparachutewith the geometry modeling and meshing code PATRAN, aerodynamic pressure loading on the canopy, the subject it to an approximatepressure loading with the structuralanalysis considew_ the reduction in fabric strengthdue to the computedaerodynamicheating.The structural analysis code ABAQUS/Explicit to generatea intentwas to illustratethefeasibility of such an analysis shape, use the shape in the Computational Fluid with the commercially available software PATRAN, Dynamics (CFD) code Rampant to fred the surface pressureand temperaturedistributions,andfinally, use ABAQUS/Explicit, and Rampant. ABAQUS/Explicit to determine the parachute's This work was sponsored by the U.S. Departmentof computedby ABAQUS/Explicit are shown in Figure4. EnergyundercontractnumberDE-AC04-94AL85000. Of particular interest is the observation of the small This paper is awork of the U. S. Govermnent and is not subject to copyright protectionin the United States.
Research at Sandia National Laboratories has shown a strain rate dependence of many materials used in the production of parachutes. Differences in strength of 30% have been found between strain rates of 12 sec-' and slow rates normally used to define material properties for lightweight nylon cloth. These structures are sometimes deployed in a rapid fashion and the loading is experienced in milliseconds; the production of material data in the same loading regime is required for full understanding of material response. Also, material behavior suitable for structural analysis of these structures is required for successful analysis. This is especially important when different materials are used in the same fabric structure. Determining the distribution of load to various portions of a nylon and Kevlar parachute requires the correct moduli and material behavior in the analytical model.The effect of strain rate on the material properties of nylon and Kevlar components commonly used in parachute construction are reported in this paper. These properties are suitable for use in analytical models of these fabric structures. TntroductioqUsing analysis tools of structural mechanics on high performance fabric structures is a new area of research at Sandia National Laboratories. Several successful examples have included studies of cross parachutes, analyses of the Jet Propulsion Laboratory Mars Pathfinder Airbag System, and, most recently, the design and analysis of a new generation automobile airbag [1,2,3]. Supplying the correct material behavior is of prime importance to the successful analysis and design of *This work was performed at Sandia National Laboratories, Albuquerque, New Mexico, supported by the United States Department of Energy under Contract DE-ACO4-94AL85000. This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States.these structures. The behavior of the materials under representative rates of loadiig must also be provided because many of these structures are used in dynamic environments. The high strain-rate measurement of fabric behavior at cold, ambient, and high temperatures is even more challenging, but necessary, as differences of 30% are found for various environmental combinations.The purpose of this paper is to provide the basis of high strain rate material properties for the engineering of parachute systems and other high performance fabric structures. A description of the test method is given along with results from representative materials. The difficulties of adapting equipment normally used to test metals for the testing of fabrics is also discussed. Additionally, high speed photography was necessary for the measurement of strain and strain rate of the fabric. All of these complicating factors are necessary for the measurement of fabric high strain rate material behavior.
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