Proceedings - Electronic Components and Technology Conference
Frear, D.R.
Thermomechanical fatigue tests were performed on two near-eutectic Sn-Pb solder alloys, 60Sn-40Pb and 62Sn-36Pb-2Ag, to examine the effect silver additions have on solder joints. The cyclic load was found to have consistent trends between the two silver alloys (for given amounts of total strain and strain rates). It was found that a decreasing strain rate increased the life of both alloys equally in thermomechanical fatigue. At slower strain rates, the dislocation substructure recovers faster than it work-hardens, which tends to minimize subsequent recrystallization and heterogeneous coarsening of the solder joint. The microstructure of 62Sn-36Pb-2Ag contained large whisker-like Ag3Sn precipitates that nucleate and grow out from the Cu6Sn5 interfacial intermetallics. At this size, the Ag3Sn precipitates have little effect on the deformation behavior of the solder. The intermetallics are not detrimental in that they do not prematurely crack, nor are they beneficial because they are too large to stabilize the microstructure. It does not appear, from a microstructural viewpoint, that adding silver to near-eutectic Sn-Pb has any significant effect on improving the thermomechanical fatigue behavior.
Shock and unloading experiments on quartz and silicate rocks indicate that the release adiabats lie below the Hugoniot. The hysteresis and energy dissipation inherent in this situation have important wave propagation implications. On loading, there is a pressure-induced transition to the stishovite phase which does not occur under conditions of thermodynamic equilibrium, in that the Hugoniot passes through a metastable mixed-phase region for several tens of GPa. One interpretation of the unloading data is that the transition is not reversible, and the phase mixture remains frozen on unloading. However, material strength may also play a role. A complete thermodynamically consistent equation of state which includes phase transitions and strength effects has been developed and used to examine shock and release data on quartz and silicate rocks in order to quantify the kinetics of the reverse transition and to separate the hysteretic effects due to reverse phase transition kinetics from those due to material strength. The model allows quantitative determination of the effect of reverse transition kinetics on ground shock propagation in silicate materials.
Severe nuclear reactor accidents - accidents involving the melting of the reactor core - dominate the residual risk associated with the use of nuclear power. The uninterrupted progression of a severe reactor accident is expected to lead to the expulsion of core debris into the reactor containment. Many safety-significant phenomena may be hypothesized to occur when core debris is expelled from the reactor coolant system. The exact nature of these events depends on whether or not the coolant system is pressurized at the time of melt expulsion and whether or not expulsion is into water. Regardless of what transient events are associated with the initial expulsion of core debris from the reactor coolant system, a protracted period of core debris interactions with the structural concrete of the reactor is expected in most analyses of severe reactor accidents.
Results for Cr/Fe/Ni films are reported, showing that the simulation of electron scattering in solids by Monte Carlo techniques is well suited to parallel computation. Significant gains in computation time are realized and make explicit calculation of convoluted composition profiles possible. Computation time is sufficiently shortened to enable such simulations to be used in a real-time experimental environment. Because such simulations break naturally into independent computational pieces that require little intercommunication, they are ideal candidates for fast parallel implementation on a MIMD machine such as the NCUBE 2. Similar performance gains should be possible for other kinds of Monte Carlo transport simulations.
The history and current status of dish-Stirling receiver development are presented and discussed. The technical challenges to be addressed by the dish-Stirling community and the future plans at Sandia National Laboratories are outlined. Stirling tube and reflux solar receiver technologies are discussed. Pool-boiler receiver technology has been successfully tested and a number of promising heat-pipe receiver designs are very close to hardware demonstrations. The high-efficiency potential of reflux receivers has been demonstrated. However, many of the technical challenges that led to the change from tube to reflux receivers-especially life and reliability, systems integration, and hybridization-are just beginning to be addressed by the dish-Stirling community.
Superconducting crystals of La2CuO4+x prepared by high-pressure oxygenation have been analyzed by Raman spectroscopy. A direct comparison of the role of excess oxygen was made by examining the same crystals with and without excess oxygen. La2CuO4+x, like non-superconducting La2CuO4.0, is found to have a soft phonon that derives an orthorhombic to tetragonal phase transition. In both its tetragonal and orthorhombic forms, La2CuO4+x has a phonon peak at 630 cm-1 that is absent in La2CuO4.0. The frequency of this peak is suggestive of a peroxide-like species in La2CuO4+x. Surprisingly, the Ag phonons of La2CuO4.0 and La2CuO4+x occur at essentially the same frequency. While La2CuO4.0 has a well-defined peak from double-magnon scattering, no well-defined double-magnon scattering is observed in La2CuO4+x, even in its phase-separated form.
A procedure for updating estimates of an object's pose using information from one or more monocular images is presented. Features in monocular images are assigned correspondence with modeled three-dimensional (3-D) features based on estimated object position. An improved position estimate is computed based on the feature correspondence. The method accommodates partial occlusion or contact among objects. Features need not appear in multiple views to be used for estimation. Results from this system are presented which demonstrate the location of multiple objects within approximately 0.1 in. in translation and 2° in rotation.
A general-purpose robotic grasping system for use in unstructured environments is described. Using computer vision and a compact set of heuristics, the system automatically generates the robot arm and hand motions required for grasping an unmodeled object. The utility of such a system is most evident in environments where the robot will have to grasp and manipulate a variety of unknown objects, but where many of the manipulation tasks may be relatively simple. Examples of such domains are planetary exploration and astronaut assistance, undersea salvage and rescue, and nuclear waste site clean-up. A two-stage model of grasping is described. Stage one is an orientation of the hand and wrist and a ballistic reach toward the object; stage two is hand preshaping and adjustment. Visual features are first extracted from the unmodeled object. These features and their relations are used by an expert system to generate a set of valid reaches/grasps for the object. These grasps are then used in driving the robot hand and arm to bring the fingers into contact with the object in the desired configuration.
A method is described for obtaining the boundary equations of configuration obstacles for stick-figure manipulators in three-dimensional environments. Polyhedral obstacles are represented as a collection of planar triangular patches, and the intersection conditions between a line segment and a triangular patch are used to derive boundary equations. It is shown that the boundary equation for the nth joint variable can be solved explicitly in terms of the 0th, 1st, ..., (n-1)th joint variables. The expressions can be used to compute configuration obstacles or to analyze the geometry of contacts between manipulators and obstacles.
The experimental results of model-based and sensor-based control strategies for a two-link, flexible, planar robot arm are analyzed. Off-line optimization determines a minimum-time, straight-line tip trajectory which stays within the torque constraints of the motors and ends in a quiescent state, i.e., no vibrational transients. An efficient finite-element model is used in the optimization to approximate the flexible arm dynamics. Control schemes tested include an open-loop torque profile, a closed-loop proportional-derivative (PD) joint controller, and a feedforward controller. This last scheme uses the torque profile created from the optimization, along with PD feedback of the joint angles and proportional feedback of the strain gages, to correct for errors in the model. The results show that the best performance is achieved with this feedforward approach.
The use of one or more monocular images to estimate the three-dimensional position of objects is investigated. The identities of the objects are known, and geometric models are assumed to be available. Linear features extracted from sensor data are interpreted as corresponding with model features by search of an interpretation tree built using prior position estimates. Object positions are updated by maximum-likelihood estimation. Position estimation results from an implemented system are presented, demonstrating the location of partially occluded objects in a cluttered scene.
On-line chemical monitoring systems can help ensure safe, environmentally sound operation of industrial processes using hazardous chemicals. Using polymer-coated surface acoustic wave (SAW) sensors, we have demonstrated monitors that are capable of detecting dilute concentrations of volatile organic species. Using changes in both wave velocity and wave attenuation, the identity and concentration of an isolated chemical species can be determined. A polysiloxane coating has been found to provide unique properties for monitoring chlorinated hydrocarbons (CHCs) such as trichloroethylene: good discrimination of CHCs from most other organic species, rapid and reversible sensor response, and low detection limits. Using this technology, a portable acoustic wave sensor (PAWS) system has been constructed.
Quantitative analysis routines based on the Bence-Albee, the ZAF, and the {Phi}({rho}Z) techniques are available for the TASK8 microprobe operating system. All of the routines are able to be run from within TASK8 or as stand alone programs. For quick analyses, energy dispersive x-ray data can be collected and processed by running the Tracor standardless quantitative (SQ) routine from within TASK8. For normal analyses, data are collected via the wavelength spectrometers. The procedures and routines described in this document permit the interactive collection and processing of data via joystick control or the automatic collection and processing of data from up to seven line traces or an essentially unlimited number of preselected points. 7 refs., 5 figs., 1 tab.
Sandia National Laboratories operates the Primary Standards Laboratory (PSL) for the Department of Energy, Albuquerque Operations Office (DOE/AL). This report summarizes metrology activities that received emphasis in the first half of 1990 and provides information pertinent to the operation of the DOE/AL system-wide Standards and Calibration Program.
Sandia National Laboratories, Albuquerque, has been designated as Lead Center for the Exploratory Battery Technology Development and Testing Project, which is sponsored by the US Department of Energy's Office of Energy Storage and Distribution. In this capacity, Sandia is responsible for the engineering development of advanced rechargeable batteries for both mobile and stationary energy storage applications. This report details the technical achievements realized in pursuit of the Lead Center's goals during calendar year 1989. 4 refs., 84 figs., 18 tabs.
This report describes some field tests of the CUBIC CR-100 distance measuring equipment. The distance measurements depend on the refractivity of the atmospheric. The CR-100 uses 320 for the refractivity. For the Albuquerque area on a clear spring day, 220 is a more realistic value for refractivity. This difference of 100 between the actual and assumed refractivities causes the range error to accumulate at the rate of 1 meter per 10,000 meters of range. For example, a difference of 100 in refractivity forces the measured range to contain an error of 5 meters for a 50,000 meter baseline. 12 figs.
The Explosive Components Facility (ECF) is to be a new major facility in the Sandia National Laboratories (SNL) Weapons Program. The ECF is a self-contained, secure site on SNL property and is surrounded by Kirtland Air Force Base which is located 6-1/2 miles east of downtown Albuquerque, New Mexico. The ECF will be dedicated to research, development, and testing of detonators, neutron generators, batteries, explosives, and other weapon components. It will have capabilities for conducting explosive test fires, gas gun testing, physical analyses, chemical analyses, electrical testing and ancillary explosive storage in magazines. The ECF complex is composed of a building covering an area of approximately 91,000 square feet, six exterior explosive service magazines and a remote test cell. Approximately 50% of the building space will be devoted to highly specialized laboratory and test areas, the other 50% of the building is considered nonhazardous. Critical to the laboratory and test areas are the blast-structural design consideration and operational considerations, particularly those concerning personnel access control, safety and environmental protection. This area will be decoupled from the rest of the building to the extent that routine tests will not be heard or felt in the administrative area of the building. While the ECF is designed in accordance with the DOE Explosives Safety Manual to mitigate any off-site blast effects, potential injuries or death to the ECF staff may result from an accidental detonation of explosive material within the facility. Therefore, reducing the risk of exposing operation personnel to hazardous and energetic material is paramount in the design of the ECF.
This report describes the Phase 1 drilling operations for the Magma Energy Exploratory Well near Mammoth Lakes, California. An important part of the Department of Energy's Magma Energy Program, this well is designed to reach an ultimate depth of 20,000 feet or a bottomhole temperature of 500{degree}C, whichever comes first. There will be four drilling phases, at least a year apart, with scientific investigations in the borehole between the drilling intervals. Phase 1 of this project resulted in a 20 inch cased hole to 2558 feet, with 185 feet of coring beyond that. This document comprises a narrative of the daily activities, copies of the daily mud and lithologic reports, time breakdowns of rig activities, inventories of lost circulation materials, temperature logs of the cored hole, and a strip chart mud log. 2 figs.
The validity of scale model impact evaluation of the SST Transportation System is acceptable based on Dimensional Analysis (Buckingham Pi Theorem) and the work of numerous programs that have evaluated the agreement among dimensional analysis, several different reduced-size models and full-scale impact test data. Excellent accuracy has been demonstrated between scale models and full-scale impact data when collected in conformance with the Buckingham Pi Theorem. 20 refs., 4 figs.
A five-step procedure was used in the 1990 performance simulations to construct probability distributions of the uncertain variables appearing in the mathematical models used to simulate the Waste Isolation Pilot Plant's (WIPP's) performance. This procedure provides a consistent approach to the construction of probability distributions in cases where empirical data concerning a variable are sparse or absent and minimizes the amount of spurious information that is often introduced into a distribution by assumptions of nonspecialist. The procedure gives first priority to the professional judgment of subject-matter experts and emphasizes the use of site-specific empirical data for the construction of the probability distributions when such data are available. In the absence of sufficient empirical data, the procedure employs the Maximum Entropy Formalism and the subject-matter experts' subjective estimates of the parameters of the distribution to construct a distribution that can be used in a performance simulation. 23 refs., 4 figs., 1 tab.
This report documents the data available as of August 1990 and used by the Performance Assessment Division of Sandia National Laboratories in its December 1990 preliminary performance assessment of the Waste Isolation Pilot Plant (WIPP). Parameter values are presented in table form for the geologic subsystem, engineered barriers, borehole flow properties, climate variability, and intrusion characteristics. Sources for the data and a brief discussion of each parameter are provided. 101 refs., 72 figs., 21 tabs.
A theoretical model was developed for the minimum charge to trigger a gaseous detonation in spherical geometry as a generalization of the Zeldovich model. Careful comparisons were made between the theoretical predictions and experimental data on the minimum charge to trigger detonations in propane-air mixtures. The predictions are an order of magnitude too high, and there is no apparent resolution to the discrepancy. A dynamic model, which takes into account the experimentally observed oscillations in the detonation zone, may be necessary for reliable predictions. 27 refs., 9 figs.
The Salado Formation is a thick evaporite sequence located in the Permian Delaware Basin of southeastern New Mexico. This study focuses on the intense diagenetic alteration that has affected the small amounts of clay, feldspar, and quartz washed into the basin during salt deposition. These changes are of more than academic interest since this formation also houses the WIPP (Waste Isolation Pilot Plant). Site characterization concerns warrant compiling a detailed data base describing the clays in and around the facility horizon. An extensive sampling effort was undertaken to address these programmatic issues as well as to provide additional insight regarding diagenetic mechanisms in the Salado. Seventy-five samples were collected from argillaceous partings in halite at the stratigraphic level of the Waste Isolation Pilot Plant (WIPP). These were compared with twenty-eight samples from cores of the Vaca Triste member of the Salado, a thin clastic unit at the top of the McNutt potash zone, and with a clay-rich sample from the lower contact of the Culebra Dolomite (in the overlying Rustler Formation). These settings were compared to assess the influence of differences in brine chemistry (i.e., halite and potash facies, normal to hypersaline marine conditions) and sediment composition (clays, sandy silt, dolomitized limestone) on diagenetic processes. 44 refs., 11 figs., 5 tabs.
The Waste Isolation Pilot Plant (WIPP) is planned as the first mined geologic repository for transuranic (TRU) wastes generated by defense programs of the United States Department of Energy (DOE). Before disposing of waste at the WIPP, the DOE must evaluate compliance with the United states Environmental Protection Agency's (EPA) Standard, Environmental Radiation Protection Standards for Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes (40 CFR Part 191, US EPA, 1985). Sandia National Laboratories (SNL) is evaluating long-term performance against criteria in Subpart B of the Standard. Performance assessment'' as used in this report includes analyses for the Containment Requirements ({section} 191.13(a)) and the Individual Protection Requirements ({section} 191.15). Because proving predictions about future human actions or natural events is not possible, the EPA expects compliance to be determined on the basis of specified quantitative analyses and informed, qualitative judgment. The goal of the WIPP performance-assessment team at SNL is to provide as detailed and thorough a basis as practical for the quantitative aspects of that decision. This report summarizes SNL's late-1990 understanding of the WIPP Project's ability to evaluate compliance with Subpart B. 245 refs., 88 figs., 23 tabs.
