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Stress Analysis - The engineers at PNNL have performed a variety of stress analysis investigations. These range from design code analyses such as those performed in accordance with ASME PVP, ACI, AISC to others of a less structured nature. TN members are well represented with these organizations and have several individuals who are currently active committee members.

In addition to design code analyses, members of this TN routinely perform stress analyses requiring special techniques and often software development. Some projects of this nature include:

• Geomechanics and soil mechanics simulations
• Glass solidification and cracking simulation
• Creep and relaxation of concrete structures
• Fatigue investigations of numerous applications

Stress analysts in the TN are well supported with state of the art computer capabilities and training so that a wide variety of stress analysis tasks can be performed rapidly and efficiency. The group communicates routinely with structure software vendors regarding potential enhancements of their products and occasionally supports these vendors to expand their products with new features.

Thermal Analysis - Engineers and computer specialists with expert knowledge of heat transfer and other engineering properties of materials are proficient at using their expertise to solve a wide range of thermally induced problems in complex mechanical and structural systems. The results of a typical analysis determines the steady state or transient temperature profiles at a specific location in the system at a specific instant in time. Specific capabilities include:

Closed Form Solutions: The experience of the staff allows them to simplify problem such that quick answers can be approximated by the application of appropriate analytical tools.

Finite Element Modeling: Application of the ANSYS finite element computer code is a cost-effective method of solving complex problems. Steady state and transient solutions are readily obtained. Temperature distributions or thermal flux due to conduction, convection, or radiation are all routinely modeled.

Coupled Structural Analysis: Finite element results are commonly followed by structural analyses to determine displacements or stresses due to thermal effects.

Experimental: Experienced teams of engineers and technicians instrument and test full-scale mockups to provide realistic data to compliment thermal analyses.

Seismic Engineering - Staff have developed extensive capabilities seismic engineering. Specific capabilities include:

Evaluation of Existing Facilities: Seismic evaluations of existing facilities at the Hanford site are of the SAR process and must address unique concerns. The existing facilities are usually on the order of thirty to forty years old and have been modified many times over their lives. The impact of successive modifications and the effects of degradation due to age must be accounted for in the analyses. Typical seismic evaluations for DOE are based upon the response spectrum method. This method includes the use of response spectra and nonlinear time history analyses. Standard response spectra curves are based upon acceptable probabilities of occurrence probabilities of occurrence of the seismic event. To perform the analyses, building geometry and other physical properties are modeled using commercial structural mechanics codes. The appropriate response spectrum is applied and the resulting stresses and displacements are checked against the allowable values from the seismic code.

Seismic Hazard Assessment: PNNL geo-sciences staff are involved with several projects related to probabilistic seismic hazard assessment and analysis of regional seismic network data for test ban treaty verification applications. In the area of seismic hazard, PNNL staff have been the developers of the earthquake recurrence relationship and tectonic models used for the Hanford site design criteria. Studies performed by PNNL include site-specific probabilistic seismic hazard assessments, development of design response spectra, and the formulation of strong ground motion simulations.

Impact Analysis -The researchers at the Pacific Northwest National Laboratory has the experience and computational tools to perform penetration mechanics analyses in support of a wide variety of program applications.

Our engineers have used these skills to support the following research tasks:

• Development of advanced shielding concepts for micro-meteorite impact of space structures
• Validation of hypervelocity (5- to 20-km/sec) impact models with impact experiments performed in a light-gas gun
• Evaluation of reactive (explosive) armor concepts to deflect kinetic energy projectiles upon impact and reduce damage to military vehicles
• Simulation of internal ballistics phenomena and the effectiveness of attached charges in accelerating kinetic energy penetrators
• Evaluation of the effectiveness of a liquid jet to break up and mix gelled sludge in a process waste tank.

PNNL has the latest high-speed workstation computers, super-computers and an extensive library of computational codes for performing highly dynamic continuum mechanics and impact mechanics analyses.

Computational Fluid Dynamics - PNNL staff have extensive experience in the computational simulation of fluid systems. Areas of application include computational fluid dynamics computer programs for thermal-hydraulic analysis of engineering systems. PNNL staff developed the COBRA-SFS and RADGEN computer programs which have been approved by the Nuclear Regulatory Commission for the thermal-hydraulic analysis of spent fuel storage systems.

Probabilistic Finite Element Analysis - Engineers always face uncertainties in design, whether it be in the prediction of future loads, variability of material properties, or uncertainties in predicting system response under load. For aging structures, stochastic mechanics provides the means to quantify the safety of the structure. For new design, stochastic mechanics provides the means to explicitly treat uncertainties to achieve truly optimal design. Stochastic methods provide the engineer with a way to quantify uncertainties and treat all problem uncertainties consistently. The traditional approach of using arbitrary design safety factors does not provide a means to quantify the design reliability and can sometimes lead to unbalanced designs wherein some components are overdesigned and some may be actually be underdesigned.

PNNL's in-house software uses state-of-the-art techniques in stochastic mechanics including FORM/SORM, Monte-Carlo simulation, and adaptive importance sampling. We are at the forefront in stochastic analysis of nonlinear systems, but our experience does not stop with these numerical methods.

Advanced Computing - The corner stone machine for the advanced manufacturing computing facility is a 128 node massively parallel IBM SP machine. This machine consists of 128 fat nodes with an aggregate memory of 12.3 Gigabytes. Each node is accompanied with 4.5GB of disk for a total storage of 576 GB. For more information, contact Tony Hess.

Impact Mechanics Computer Codes - PNNL has the latest high-speed workstation computers, super-computers and an extensive library of computational codes for performing highly dynamic continuum mechanics and impact mechanics analyses. These codes include:

HULL - is a system of codes for the solution of highly dynamic continuum mechanics problems where the propagation of shock waves and material failure are the dominant behaviors of interest. Hull includes hydrodynamic material models for many common materials and it has been used successfully to simulate the penetration and breakup of projectiles through a target.

HULL Penetration Analysis

EPIC - is a system of 2-D and 3-D finite element codes that was specifically developed for solving ballistic impact and penetration

mechanics problems. The material models can treat isotropic or anisotropic behavior, and strain-rate, work-hardening, and temperature effects are included.

The failure criteria in EPIC are based on the maximum volumetric strain, equivalent plastic strain, or a combination of both. The code includes extensive slideline capabilities that permit sliding with or without friction, void formation and collapse, tunneling, and erosion of material.

Present and Past Engineering Analysis Activities

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