LDRD research activities have focused on increasing the robustness and efficiency of optimization studies for computationally complex engineering problems. Engineering applications can be characterized by extreme computational expense, lack of gradient information, discrete parameters, non-converging simulations, and nonsmooth, multimodal, and discontinuous response variations. Guided by these challenges, the LDRD research activities have developed application-specific techniques, fundamental optimization algorithms, multilevel hybrid and sequential approximate optimization strategies, parallel processing approaches, and automatic differentiation and adjoint augmentation methods. This report surveys these activities and summarizes the key findings and recommendations.
During the 1980s Sandia designed, developed, fabricated, tested, and delivered hundreds of thousands of radiation hardened Integrated Circuits (IC) for use in weapons and satellites. Initially, Sandia carried out all phases, design through delivery, so that development of next generation ICs and production of current generation circuits were carried out simultaneously. All this changed in the mid-eighties when an outside contractor was brought in to produce ICs that Sandia developed, in effect creating a crisp separation between development and production. This partnership had a severe impact on operations, but its more damaging effect was the degradation of Sandia`s microelectronics capabilities. This report outlines microelectronics development and production in the early eighties and summarizes the impact of changing to a separate contractor for production. This record suggests that low volume production be best accomplished within the development organization.
This report describes the results of composites fabrication research sponsored by the Laboratory Directed Research and Development (LDRD) program at Sandia National Laboratories. They have developed, prototyped, and demonstrated the feasibility of a novel robotic technique for rapid fabrication of composite structures. Its chief innovation is that, unlike all other available fabrication methods, it does not require a mold. Instead, the structure is built patch by patch, using a rapidly reconfigurable forming surface, and a robot to position the evolving part. Both of these components are programmable, so only the control software needs to be changed to produce a new shape. Hence it should be possible to automatically program the system to produce a shape directly from an electronic model of it. It is therefore likely that the method will enable faster and less expensive fabrication of composites.
In the assessment of a system, understanding the system is central. Even so, most of the current literature takes a narrow view of understanding, making only the catalog of system ``assets`` explicit, while maintaining the balance of the analyst`s understanding inside the analyst`s head. This can lead to problems with non-repeatability and incompleteness of assessment results. This paper introduces the notion of using explicit system models to document the analyst`s understanding of the system and shows that, from these models, standard assessment products, such as fault trees and event trees, can be automatically derived. This paper also presents five ``views`` of a system that can be used to document the analyst`s understanding of the system. These views go well beyond the standard instruction to identify the system`s assets to show that a much richer understanding of the system can be required for effective assessment.
In parameter estimation considerable insight is provided by examining sensitivity coefficients. This paper focuses on the use of sensitivity coefficients in connection with estimating thermal properties in the heat conduction equation. A general methodology for computing sensitivity coefficients can be an important design tool. The use of such a tool is demonstrated in this paper. A control volume, finite element program is used, and briefly described, to implement numerical sensitivity coefficient calculations. In this approach general problems can be studied. Several example problems are presented to demonstrate the insight gained from sensitivity coefficients. The problems are selected from experimental studies to characterize the thermal properties of carbon-carbon composite. Sensitivity coefficients show that in an experiment that is not well designed, additional materials in the experimental configuration can have a larger impact on the temperature than the material of interest. Two-dimensional configurations demonstrate that there can be isolated areas of insensitivity and the difficulty of estimating multiple parameters.
Effective use of resources that are shared among multiple products or processes is critical for agile manufacturing. This paper describes the development and implementation of a computerized model to support production planning in a complex manufacturing system at the Pantex Plant, a US Department of Energy facility. The model integrates two different production processes (nuclear weapon disposal and stockpile evaluation) that use common facilities and personnel at the plant. The two production processes are characteristic of flow-shop and job shop operations. The model reflects the interactions of scheduling constraints, material flow constraints, and the availability of required technicians and facilities. Operational results show significant productivity increases from use of the model.
Capacitance-voltage and thermally-stimulated-current techniques are used to estimate trapped hole and electron densities in MOS oxides as functions of irradiation and isochronal anneal temperature. Trapped-charge annealing and compensation effects are discussed.
Highly porous sol-gel films have potential applications as electrical and thermal insulators, catalyst supports, sensors, and membranes for gas separations. Pore dimensions in these sol-gel films are usually small e.g., on the order of tens of nanometers or less. Their successful fabrications, however, greatly depend on the fundamental understanding of mechanisms that underlie the phenomena of pore evolution, network shrinkage, and stress development since the final microstructure of a solid gel film is strongly affected by composition of its starting sol and its processing conditions. This report documents a simplified one-dimensional analysis of drying a solidifying sol-gel thin film coating supported by an impermeable solid substrate. Portions of this work were presented at the 1994 Annual Joint Meeting of the New Mexico Section of the American Ceramic Society and Materials Research Society in Albuquerque. The authors considered the solid/liquid two phase coexistent regime during the drying solidifying process in which solvent is removed continuously via evaporation, the solid phase grows significantly in mechanical strength, and pore space shrinks appreciably. From overall and differential mass balances and a force balance at equilibrium, coupled with empirical correlations of solid phase modulus and permeability to strain or deformation, the authors followed the evolution of pore space, solid phase elastic stress, and liquid phase hydrodynamic pressure; they also determined their respective values at equilibrium. By assuming microscopic pore shape models, they estimated and compared the predicted mean pore radii. Their simplified one-dimensional analysis shows that the final mean pore radius is controlled by four parameters: pore-liquid surface tension, solid phase modulus, mean pore radius, and porosity at the initial stress-free state. The one-dimensional model can be employed to guide process design and optimization in sol-gel film fabrications.
Practical work of adhesion measurements are being studied for several types of polymer/metal combinations in order to obtain a better understanding of the adhesive failure mechanisms for systems containing encapsulated and bonded components. The primary question is whether studies of model systems can be extended to systems of technological interest. The authors report on their first attempts to obtain the work of adhesion between a PDMS polymer and stainless steel. The work of adhesion measurements were made using three techniques -- contact angle, adhesive fracture energy at low deformation rates and JKR. Previous work by Whitesides` group show a good correlation between JKR and contact angle measurements for PDMS. Their initial work focused on duplicating the PDMS measurements of Chaudury. In addition, in this paper the authors extend the work of adhesion measurement to third technique -- interfacial failure energy. The ability to determine the reversible work of adhesion for practical adhesive joints allows understanding of several issues that control adhesion: surface preparation, nature of the interphase region, and bond durability.
Gate oxide electric fields are expected to increase to greater than 5 MV/cm as feature size approaches 0.1 micrometers in advanced integrated circuit (IC) technologies. Work by Johnston, et al. raised the concern that single event gate rupture (SEGR) may limit the scaling of advanced ICs for space applications. SEGR has also been observed in field programmable gate arrays, which rely on thin dielectrics for electrical programming at very high electric fields. The focus of this effort is to further explore the mechanisms for SEGR in thin gate oxides. The authors examine the characteristics of heavy ion induced breakdown and compare them to ion induced damage in thin gate oxides. Further, the authors study the impact of precursor damage in oxides on SEGR threshold. Finally, they compare thermal and nitrided oxides to see if SEGR is improved by incorporating nitrogen in the oxide.
Sandia National Laboratories has initiated many joint research and development projects with the two premier Russian nuclear laboratories, VNIIEF and VNIITF, (historically known as Arzamas-16 and Chelyabinsk-70) in a wide spectrum of areas. One of the areas in which critical dialogue and technical exchange is continuing to take place is in the realm of system surety. Activities primarily include either safety or security methodology development, processes, accident environment analyses and testing, accident data-bases, assessments, and product design. Furthermore, a continuing dialog has been established between the organizations with regard to developing a better understanding of how risk is perceived and analyzed in Russia versus that in the US. The result of such efforts could reduce the risk of systems to incur accidents or incidents resulting in high consequences to the public. The purpose of this paper is to provide a current overview of the Sandia surety program and its various initiatives with the Russian institutes, with an emphasis on the program scope and rationale. The historical scope of projects will be indicated. A few specific projects will be discussed, along with results to date. The extension of the joint surety initiatives to other government and industry organizations will be described. This will include the current status of a joint Sandia/VNIIEF initiative to establish an International Surety Center for Energy Intensive and High Consequence Systems and Infrastructures.
Preliminary work is presented on an effort to generate synthetic constitutive data for random composite materials. The long-ranged goal is to use the overall response determined from finite element simulations of representative volumes (RV) of the heterogeneous material to construct a homogenized constitutive model. A simple composite of a matrix containing polydispersed spheres was chosen as the first configuration to simulate. Here the accuracy of the numerical simulation tools is tested by determining effective elastic constants of the ordered elastic composite in which equal-sized spheres are arranged in each of three cubic lattice configurations. The resulting anisotropic effective elastic constant values agree with theoretical results to better than 10%, with typical agreement being better than 4%.
The thermal conduction of a portion of an enhanced surface heat exchanger for a gas fired heat pipe solar receiver was modeled using the boundary element and finite element methods (BEM and FEM) to determine the effect of weld fillet size on performance of a stud welded pin fin. A process that could be utilized by others for designing the surface mesh on an object of interest, performing a conversion from the mesh into the input format utilized by the BEM code, obtaining output on the surface of the object, and displaying visual results was developed. It was determined that the weld fillet on the pin fin significantly enhanced the heat performance, improving the operating margin of the heat exchanger. The performance of the BEM program on the pin fin was measured (as computational time) and used as a performance comparison with the FEM model. Given similar surface element densities, the BEM method took longer to get a solution than the FEM method. The FEM method creates a sparse matrix that scales in storage and computation as the number of nodes (N), whereas the BEM method scales as N{sup 2} in storage and N{sup 3} in computation.
This paper explores one woman`s journey through her recent promotion into management, and will identify key factors that helped prepare and position her to be ready to exercise leadership through a formal management role. It discusses assessment of qualifications and skills, acquisition of needed skills, the influence of luck and timing, and the use of mentors and delegation as survival skills to get through the transition period and become fully functional as a manager. It also includes insights into sensitive issues such as how to relate to former peers, how to gain credibility as the junior member of the management team, and how to juggle family responsibilities with increased time commitments at work. It emphasizes the importance of acknowledging the help the authors receive in reaching their own career goals and offering the same kind of help and support to those in the early stages of their careers.
The traditional method for determination of alpha-emitting isotopes on air filters has been to process the samples by radiochemical methods. However, this method is too slow for incidents involving radioactive materials where the determination of personnel dose is urgent. A method is developed to directly analyze the air filters taken from personal and area air monitors. The site knowledge is used in combination with alpha-spectral information to identify isotopes. A mathematical function is developed to estimate the activity for each isotope. The strengths and weaknesses of the method are discussed.
The reliability of microengines is a function of the design of the mechanical linkage used to connect the electrostatic actuator to the drive. We have completed a series of reliability stress tests on surface micromachined microengines driving an inertial load. In these experiments, we used microengines that had pin mechanisms with guides connecting the drive arms to the electrostatic actuators. Comparing this data to previous results using flexure linkages revealed that the pin linkage design was less reliable. The devices were stressed to failure at eight frequencies, both above and below the measured resonance frequency of the microengine. Significant amounts of wear debris were observed both around the hub and pin joint of the drive gear. Additionally, wear tracks were observed in the area where the moving shuttle rubbed against the guides of the pin linkage. At each frequency, we analyzed the statistical data yielding a lifetime (t50) for median cycles to failure and σ, the shape parameter of the distribution. A model was developed to describe the failure data based on fundamental wear mechanisms and forces exhibited in mechanical resonant systems. The comparison to the model will be discussed.
The monolithic integration of MicroElectroMechanical Systems (MEMS) with the driving, controlling, and signal processing electronics promises to improve the performance of micromechanical devices as well as lower their manufacturing, packaging, and instrumentation costs. Key to this integration is the proper interleaving, combining, and customizing of the manufacturing processes to produce functional integrated micromechanical devices with electronics. We have developed a MEMS-first monolothic integrated process that first seals the micromechanical devices in a planarized trench and then builds the electronics in a conventional CMOS process. To date, most of the research published on this technology has focused on the performance characteristics of the mechanical portion of the devices, with little information on the attributes of the accompanying electronics. This work attempts to reduce this information void by presenting the results of SPICE Level 3 and BSIM3v3.1 model parameters extracted for the CMOS portion of the MEMS-first process. Transistor-level simulations of MOSFET current, capacitance, output resistance, and transconductance versus voltage using the extracted model parameters closely match the measured data. Moreover, in model validation efforts, circuit-level simulation values for the average gate propagation delay in a 101-stage ring oscillator are within 13-18% of the measured data. These results establish the following: (1) the MEMS-first approach produces functional CMOS devices integrated on a single chip with MEMS devices and (2) the devices manufactured in the approach have excellent transistor characteristics. Thus, the MEMS-first approach renders a solid technology foundation for customers designing in the technology.
Proceedings - International Carnahan Conference on Security Technology
Garcia, M.L.
The Southwest Surety Institute was formed in June, 1996 by Arizona State University (ASU), New Mexico Institute of Mining and Technology (NM Tech), New Mexico State University (NMSU), and Sandia National Laboratories (SNL) to provide new educational programs in Security Engineering. This is the first science-based program of its kind in the United States, directed at educating Security Engineers to help government and industry address their security needs. Current courses include security system design, evaluation, principles, and technology, the criminal justice system, and each member brings a unique educational capability to the institute. NMSU provides a security technology minor, merging programs in Criminal Justice and Electronics Technology. NM Tech has a formidable explosives testing and evaluation facility. ASU is developing a masters program in Security Engineering at their School of Technology located on a new campus in Mesa, Arizona. The Sandia National Laboratories security system design and evaluation process forms the basis for the security engineering curricula. In an effort to leverage the special capabilities of each university, distance education will be used to share courses among institute members and eventually with other sites across the country. The Institute will also pursue research and development funding in the areas of physical security information security, computer modeling and analysis, and counter-terrorist technology. Individual Institute members are currently working with sponsors from government and industry in areas such as counter-terrorism, microelectronics, banking, aviation, and sensor development.
Design and analysis of physical protection systems requires (1) identification of mission critical assets, (2) identification of potential threats that might undermine mission capability; (3) identification of the consequences of loss of mission-critical assets (e.g., time and cost to recover required capability and impact on operational readiness), and (4) analysis of the effectiveness of physical protection elements. CPA (cost and performance analysis) addresses the fourth of these four issues. CPA is a methodology that joins activity based cost estimation with performance-based analysis of physical protection systems. CPA offers system managers an approach that supports both tactical decision making and strategic planning. Current exploratory applications of the CPA methodology address analysis of alternative conceptual designs. Hypothetical data is used to illustrate this process.
We discuss the development, design and operation of a walk-through trace detection portal designed to screen personnel for explosives. Developed at Sandia National Laboratories (SNL) with primary funding from the Federal Aviation Administration (FAA) and additional support from the Department of Energy Office of Safeguards and Security, this portal is intended primarily for use in airport terminals and in other localities where a very high throughput of pedestrian traffic is combined with stringent security requirements. The portal is capable of detecting both vapor and particulate contamination, with the collection of explosive material being based upon the entrainment of that material in air flows over the body of the person being screened. This portal is capable of detecting high explosives of interest to the FAA. We discuss the results of field testing of the portal in the Albuquerque International Airport in September, 1997 and more recent steps towards commercialization of the portal.
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Wong, C.C.; Hudson, M.L.; Potter, D.L.; Bartel, T.J.
A reliable micro gas pump is an essential element to the development of many micro-systems for chemical gas analyses. At Sandia, we are exploring a different pumping mechanism, gas transport by thermal transpiration. Thermal transpiration refers to the rarefied gas dynamics developed in a micro-channel with a longitudinal temperature gradient. To investigate the potential of thermal transpiration for gas pumping in micro-systems, we have performed simulations and model analysis to design micro-devices and to assess their design performance before the fabrication process. Our effort is to apply ICARUS (a Direct Simulation Monte Carlo code developed at Sandia) to characterize the fluid transport and evaluate the design performance. The design being considered has two plenums at different temperatures (hot and cold) separated by a micro-channel of 0.1 micron wide and 1 micron long. The temperature difference between the two plenums is 30 Kelvin. ICARUS results, a quasi-steady analysis, predicts a net flow through the micro-channel with a velocity magnitude of about 0.4 m/s due to temperature gradient at the wall (thermal creep flow) at the early time. Later as the pressure builds up in the hot plenum, flow is reversed. Eventually when the system reaches steady state equilibrium, the net flow becomes zero. The thermal creep effect is compensated by the thermo-molecular pressure effect. This result demonstrates that it is important to include the thermo-molecular pressure effect when designing a pumping mechanism based on thermal transpiration. The DSMC technique can model this complex thermal transpiration problem.
This paper summarizes results of metal cutting tests using an actively damped boring bar to suppress regenerative chatter. PZT stack actuators were integrated into a commercially available two-inch diameter boring bar to suppress bending vibrations. Since the modified tool requires no specialized mounting hardware, it can be readily mounted on a variety of machines. A cutting test using the prototype bar to remove metal from a hardened steel workpiece verifies that the actively damped tool yields significant vibration reduction and improved surface finish as compared to the open-loop case. In addition, the overall performance of the prototype bar is compared to that of an unmodified bar of pristine geometry, revealing that a significant enlargement of the stable machining envelope is obtained through application of feedback control.
