155 Matching Results

Search Results

Advanced search parameters have been applied.

EFFECTS OF MATERIALS STRENGTH ON STRONGLY-SHOCKED NONENERGETIC MATERIALS

Description: The role of materials strength in changing the shock dynamics in strongly-shocked nonenergetic materials is still a matter of investigation because materials strength properties become convoluted with other materials properties and the shock strength. The regime under consideration here is one in which the material in question is shocked strongly enough to be treated as a fluid, but not strongly enough to be treated as a simple fluid. The present work takes a case-study approach in which two models of the constitutive properties of the complex fluid are applied to shock instability for two different polymeric materials. The intent here is to obtain some measure of the sensitivity of the model predictions to variations in the complex fluid constitutive properties. The linear time-regime in a Richtmyer-Meshkov instability is modeled with the viscosity dependence of Mikaelian and the nonlinear time-regime is modeled with an aerodynamic viscous-drag model. Each combination of materials and models will be examined as a function of shock strength, Atwood number, and variation in materials constitutive properties. Although the these models are NOT the most advanced, they are useful for illustrating orders of magnitude.
Date: January 1, 2001
Creator: Valone, S. M. (Steven M.)
Partner: UNT Libraries Government Documents Department

On the importance of target materials interfaces during low speed impact

Description: We are conducting a Cooperative Research and Development Project under the sponsorship of the U.S. Department of Energy to determine the applicability of aluminum particulate reinforced alloy laminates to aircraft structures and for containment of aircraft engine turbine blades and debris due to catastrophic engine failure. Within this framework, we are studying the terminal interaction of projectiles impacting targets at speeds of 150- to 500 m/s. Our presentation focuses on a special series of experiments and computational physics analyses of 6061-T6 aluminum alloy targets in single plate and laminate form impacted by steel cylindrical projectiles. Four cases are examined, projectile impact into (1) a single plate, (2) three contiguous plates (frictional interfaces), (3) three contiguous plates separated by Teflon layers (frictionless interfaces), and (4) a spaced array of three plates. We found that the ratio of projectile kinetic energies just at target perforation for the highest to lowest critical projectile speeds over the four targets is 1.75. Considering that target areal density is held constant across the four targets, this is a dramatic result. 2 refs., 7 figs.
Date: July 1996
Creator: Gogolewski, R. P.; Cunningham, B. J.; Riddle, R.; Lesuer, D. & Syn, C.
Partner: UNT Libraries Government Documents Department

Design and analysis of a high-performance shipping container for large payloads

Description: The packaging, designated the H1636A is a high-performing packageing for large payloads. The H1636A is 50 in. in diameter and 113 in. in length and weighs approximately 4600 lb when empty. The design objective was to meet 1996 proposed IAEA Type C criteria for air transport of large quantities of radioactive material (RAM). That is, the package should survive the standard Type B tests and more severe tests such as an impact onto an unyielding target at 280 ft/s and a one-hour jet fuel fire. The packaging consists of a large double-walled stainless steel outer drum filled with uniform density polyurethane foam. A stainless steel containment vessel (CV) with an inside diameter of 23 in. and a length of 78 in. carries the RAM. The CV has a nominal thickness of 0.375 in. and seals with two elastomeric 0-rings. The lid of the CV is joined to the body with a unique closure called a tape joint. The tape joint utilizes interlocking features preloaded with wedges and can withstand significant deformation.
Date: May 1, 1995
Creator: York, A.R. II & Slavin, A.M.
Partner: UNT Libraries Government Documents Department

Brittle failure kinetics model for concrete

Description: A new constitutive model is proposed for the modeling of penetration and large stress waves in concrete. Rate effects are incorporated explicitly into the damage evolution law, hence the term brittle failure kinetics. The damage variable parameterizes a family of Mohr-Coulomb strength curves. The model, which has been implemented in the CTH code, has been shown to reproduce some distinctive phenomena that occur in penetration of concrete targets. Among these are the sharp spike in deceleration of a rigid penetrator immediately after impact. Another is the size scale effect, which leads to a nonlinear scaling of penetration depth with penetrator size. This paper discusses the theory of the model and some results of an extensive validation effort.
Date: March 1, 1997
Creator: Silling, S.A.
Partner: UNT Libraries Government Documents Department

Summary and evaluation of steel billet testing

Description: Tests were performed at Sandia National Laboratories (SNL) and Lawrence Livermore National Laboratory (LLNL) to assess loading conditions on a spent fuel storage cask for end drops, side drops and tipover events. The tests were performed with a 1/3-scale model billet and a 1/3-scale model concrete pad, and included a variety of substrate materials. A NUREG/CR report was prepared for the Nuclear Regulatory Commission (NRC) and provides a summary and an evaluation of all the billet testing conducted. This paper provides a description of the testing and analysis method, and a summary of the results. A generic or representative cask was modeled with the benchmarked finite element analysis approach and evaluated for ISFSI end and side drops and tipover events. The analytical method can be applied to similar casks to estimate deceleration loads on storage casks resulting from low-velocity drop or tipover impacts onto concrete storage pads.
Date: May 1, 1998
Creator: Witte, M.C.; Hovingh, J.; Mok, G.C.; Murty, S.S.; Chen, T.F.; Fischer, L.E. et al.
Partner: UNT Libraries Government Documents Department

Effects of interactive particles on steel weldability

Description: The concept of intragranular ferrite nucleation by specific inclusions is well known from steel weld metals. In this paper it is shown that the idea can be transferred to steel metallurgy. Control of the inclusion composition and thus the nucleation potency with respect to ferrite can readily be achieved by the choice of an appropriate deoxidation procedure. Thermodynamic (Thermo-Calc) calculations in addition to X-ray mappings and microprobe analysis are employed to understand and predict the inclusion formation in the steels. Three different steels, two of them Ti-deoxidized, and one Al-Ca-deoxidized, have been subjected to weld thermal simulation at different peak temperatures and cooling programs followed by Charpy-V notch testing at {minus}40 C to reveal differences in the HAZ toughness. The results from these tests show that the titanium deoxidized steels exhibit excellent toughness in the grain coarsened HAZ after high heat input weld simulation because of a refinement of the microstructure. This observation is in contrast to the more traditional behavior of the conventional Al-Ca deoxidized steels, which show no evidence of intragranular ferrite formation.
Date: November 1, 1998
Creator: Eijk, C. van der; Grong, O.; Babu, S.S. & David, S.A.
Partner: UNT Libraries Government Documents Department

Spallation studies on shock loaded uranium

Description: Several spallation experiments have been performed on uranium using gas gun driven normal plate impacts with, VISAR instrumentation and soft recovery. The shock pressures achieved were 81, 53, and 37 kbar. This paper will focus on modeling the free surface particle velocity trace U with of 300 ppm carbon using the 1 d characteristics code CHARADE. The spallation model involves the growth and coalescence of brittle cracks. Metallographical examination of recovered samples and details of the experimental apparatus are discussed in separate papers.
Date: December 1, 1997
Creator: Tonks, D.L.; Hixson, R.; Gustavsen, R.L.; Vorthman, J.E.; Kelly, A.; Zurek, A.K. et al.
Partner: UNT Libraries Government Documents Department

Impact response of preloaded structures with revolute joints

Description: Many structural components designed to support static loads must also demonstrate the ability to withstand low probability events that can produce impact loading. For some constructs the structure is not only subjected to the initial impact, but is also subjected to rebound impacts as well. In some designs, support structures must be moved in and out of position as part of normal operations. These structures often employ revolute joints to allow the motions. In addition, functional requirements may require that a significant preload exist within the structure during normal operating conditions. This paper present the methodology needed for simulating the impact response of preloaded structures with revolute joints. A three-dimensional revolute joint is presented for use in explicit time integration analysis of problems with severe impacts. The computational engine used for the transient solution of preloaded structures is discussed. These developments are used in the analysis of a preloaded platen subjected to drop loads. The resulting transient response of the system is presented.
Date: September 1, 1997
Creator: Kulak, R.F. & Pfeiffer, P.A.
Partner: UNT Libraries Government Documents Department

Spall wave-profile and shock-recovery experiments on depleted uranium

Description: Depleted Uranium of two different purity levels has been studied to determine spall strength under shock wave loading. A high purity material with approximately 30 ppm of carbon impurities was shock compressed to two different stress levels, 37 and 53 kbar. The second material studied was uranium with about 300 ppm of carbon impurities. This material was shock loaded to three different final stress level, 37, 53, and 81 kbar. Two experimental techniques were used in this work. First, time-resolved free surface particle velocity measurements were done using a VISAR velocity interferometer. The second experimental technique used was soft recovery of samples after shock loading. These two experimental techniques will be briefly described here and VISAR results will be shown. Results of the spall recovery experiments and subsequent metallurgical analyses are described in another paper in these proceedings.
Date: November 1, 1997
Creator: Hixson, R.S.; Vorthman, J.E.; Gustavsen, R.L.; Zurek, A.K.; Thissell, W.R. & Tonks, D.L.
Partner: UNT Libraries Government Documents Department

Laminated metals composites fracture and ballistic impact behavior

Description: Recent advances in the fracture and ballistic impact response of laminated metal composites (LMCs) are reviewed. The laminate structure can provide significant improvements to these properties relative to the component materials. Typical fracture and ballistic impact properties in LMCs are illustrated for systems containing Al alloys and Al matrix composites. The unique mechanisms operating in a layered structure that contribute to fracture or ballistic impact resistance are discussed. The influence of laminate architecture, component material properties and interface strength on mechanisms and properties are briefly reviewed for these Al-based LMCs.
Date: January 20, 1998
Creator: Lesuer, D. R.; Syn, C. K.; Sherby, O. D. & Wadsworth, J.
Partner: UNT Libraries Government Documents Department

Use of self-assembled monolayers to control interface bonding in a model study of interfacial fracture

Description: The relationship between the nature and spatial distribution of fundamental interfacial interactions and fracture stress/fracture toughness of a glassy adhesive-inorganic solid joint is not understood. This relationship is important from the standpoint of designing interfacial chemistry sufficient to provide the level of mechanical strength required for a particular application. In addition, it is also important for understanding the effects of surface contamination. Different types of contamination, or different levels of contamination, likely impact joint strength in different ways. Furthermore, the relationship is also important from the standpoint of aging. If interfacial chemical bonds scission over time due to the presence of a contaminant such as water, or exposure to UV, etc, the relationship between joint strength/fracture toughness and interface strength is important for predicting reliability with time. A fundamental understanding of the relationship between joint strength and fundamental interfacial interactions will give insight into these issues.
Date: March 2, 2000
Creator: KENT,MICHAEL S.; YIM,HYUN; MATHESON,AARON J.; COGDILL,C. & REEDY JR.,EARL DAVID
Partner: UNT Libraries Government Documents Department

Rate-dependent spallation properties of tantalum

Description: Spallation experiments are conducted on high-purity tantalum using VISAR instrumentation for impact stresses of 9.5 GPa and 6.0 GPa. The high-amplitude experiment exhibits very rapid initial spall separation, while the low-amplitude shot is only slightly above the threshold for void growth and thus exhibits distinct rate-dependent spallation behavior. These experiments are analyzed in terms of simple tensile fracture criteria, a standard rate-dependent void-growth model, and a rate-dependent void growth model in which the expected plastic volume strain makes no contribution to the relaxation of the mean stress. Recovery tests and VISAR measurements suggest an additional resistance to spallation that follows the rapid coalescence of voids; this effect is termed the secondary spall resistance and is due to the convoluted nature of the spall plane and the resulting interlocking fracture pattern that is developed and for which the stress remains unrelieved until the spall planes have separated several hundred microns.
Date: September 1, 1995
Creator: Johnson, J.N.; Hixson, R.S.; Tonks, D.L. & Zurek, A.K.
Partner: UNT Libraries Government Documents Department

Three-axis particle impact probe

Description: Three-axis particle impact probes detect particle impact vectors along x-, y-, and z-axes by means of a head mounted on the outer end of a shaft that is flexibly mounted in silicone rubber at the top of a housing so as to enable motion imparted to the head upon impact to be transmitted to a grounded electrode secured to the shaft within the housing. Excitable electrodes are mounted in the housing in a fixed position, spaced apart from the ground electrode and forming, with the ground electrode, capacitor pairs. Movement of the ground electrode results in changes in capacitance, and these differences in capacitance are used for measurement or derivation of momentum vectors along each of the three axes. In one embodiment, the ground electrode is mounted at the base of the shaft and is secured to a silicone rubber layer at the top of the housing, providing for cantilevered movement. In another embodiment, the shaft is mounted at its mid point in a flexible bushing so that it undergoes pivotal movement around that point.
Date: April 2, 1991
Creator: Fasching, G. E.; Smith, N. S. Jr. & Utt, C. E.
Partner: UNT Libraries Government Documents Department

Brittle damage models in DYNA2D

Description: DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.
Date: September 1, 1997
Creator: Faux, D.R.
Partner: UNT Libraries Government Documents Department

High strain rate properties and constitutive modeling of glass

Description: This paper presents experimental data and computational modeling for a well-defined glass material. The experimental data cover a wide range of strains, strain rates, and pressures that are obtained from quasi-static compression and tension tests, split Hopkinson pressure bar compression tests, explosively driven flyer plate impact tests, and depth of penetration ballistic tests. The test data are used to obtain constitutive model constants for the improved Johnson-Holmquist (JH-2) brittle material model. The model and constants are then used to perform computations of the various tests.
Date: March 1, 1995
Creator: Holmquist, T.J.; Johnson, G.R.; Lopatin, C.M.; Grady, D.E. & Hertel, E.S. Jr.
Partner: UNT Libraries Government Documents Department

Plane impact response of PBX 9501 below 2 GPA

Description: The plane impact response of PBX 9501 was measured below 2 GPa using a light-gas gun facility. Time-resolved wave profiles were obtained in a state of uniaxial strain for impact stresses between 0.3 to 1.2 GPa. The dynamic strength of PBX 9501 was measured at high strain rates in both compression and tension. The Hugoniot equation of state was measured.
Date: December 31, 1998
Creator: Dick, J.J.; Martinez, A.R. & Hixson, R.S.
Partner: UNT Libraries Government Documents Department

Mass ejected by impacts with materials of various strengths

Description: Similarity solutions are used to discuss impacts on asteroids of various strengths, concentrating on the voids produced, the mass ejected, and its thermodynamic and mechanical state. Numerical calculations have advantages and limitations for the next step in complexity.
Date: February 1, 1997
Creator: Canavan, G. H.
Partner: UNT Libraries Government Documents Department

Impact of AD995 alumina rods

Description: Gas guns and velocity interferometric techniques have been used to determine the loading behavior of an AD995 alumina rod 19 mm in diameter by 75 mm and 150 mm long, respectively. Graded-density materials were used to impact both bare and sleeved alumina rods while the velocity interferometer was used to monitor the axial-velocity of the free end of the rods. Results of these experiments demonstrate that (1) a time-dependent stress pulse generated during impact allows an efficient transition from the initial uniaxial strain loading to a uniaxial stress state as the stress pulse propagates through the rod, and (2) the intermediate loading rates obtained in this configuration lie between split Hopkinson bar and shock-loading techniques.
Date: October 1, 1997
Creator: Chhabildas, L.C.; Furnish, M.D.; Reinhart, W.D. & Grady, D.E.
Partner: UNT Libraries Government Documents Department

Perforation of HY-100 steel plates with 4340 R{sub c} 38 and T-250 maraging steel rod projectiles

Description: The authors conducted perforation experiments with 4340 Rc 38 and T-250 maraging steel, long rod projectiles and HY-100 steel target plates at striking velocities between 80 and 370 m/s. Flat-end rod projectiles with lengths of 89 and 282 mm were machined to nominally 30-mm-diameter so they could be launched from a 30-mm-powder gun without sabots. The target plates were rigidly clamped at a 305-mm-diameter and had nominal thicknesses of 5.3 and 10.5 mm. Four sets of experiments were conducted to show the effects of rod length and plate thickness on the measured ballistic limit and residual velocities. In addition to measuring striking and residual projectile velocities, they obtained framing camera data on the back surfaces of several plates that showed clearly the plate deformation and plug ejection process. They also present a beam model that exhibits qualitatively the experimentally observed mechanisms.
Date: May 25, 1998
Creator: Forrestal, M.J. & Hanchak, S.J.
Partner: UNT Libraries Government Documents Department

Plane impact response of PBX 9501 and its components below 2 GPa

Description: The Hugoniot equation of state was measured for PBX 9501, the binder, and estane below 2 GPa using a light-gas gun facility. Time-resolved wave profiles were also obtained for these materials as well as for HMX single crystals in a state of uniaxial strain. The dynamic strength of PBX 9501 was measured at high strain rates in both compression and tension. In addition, elastic moduli were obtained from measurements of longitudinal and shear sound speeds.
Date: April 1, 1998
Creator: Dick, J.J.; Martinez, A.R. & Hixson, R.S.
Partner: UNT Libraries Government Documents Department