Mechanics & Materials
The Mechanics and Materials Section has extensive experience in the development and application of advanced methods for component life prediction and probabilistic structural analysis. Many of these advanced methods are now available as licensable software tools with user-friendly graphical user interfaces. Major companies around the world are using these software tools to analyze material and structural integrity and reliability. Brief descriptions of these tools are provided below, along with links to more detailed web sites for each software product.
NESSUS® is a modular computer software system for performing probabilistic analysis of structural/mechanical components and systems. NESSUS combines state-of-the-art probabilistic algorithms with general-purpose numerical analysis methods to compute the probabilistic response and reliability of engineered systems. Uncertainty in loading, material properties, geometry, boundary conditions, and initial conditions can be simulated. Many deterministic modeling tools can be used such as finite element, boundary element, hydrocodes, and user-defined subroutines. NESSUS offers a wide range of capabilities, a graphical user interface, and is verified using hundreds of test problems.
NASGRO® is a suite of fracture mechanics and fatigue crack growth analysis computer programs that performs assessments of structural life, computes stress intensity factors, and processes and stores fatigue crack growth properties. The previous version NASGRO 3.0 has more than 2,000 users in the space, aircraft, rotorcraft, turbine engine, petrochemical, nuclear, and ground vehicle industries in more than 40 countries. NASGRO 4.0 has been jointly developed by SwRI and NASA Johnson Space Center under the terms of the Space Act Agreement.
DARWIN® integrates finite element stress analysis results, fracture-mechanics-based life assessment for low-cycle fatigue, material anomaly data, probability of anomaly detection, and inspection schedules to determine the probability of fracture of a rotor disk as a function of applied operating cycles. The program also indicates the regions of the disk most likely to fail and the risk reduction associated with single and multiple inspections. This software will be enhanced to handle anomalies in cast/wrought and powder nickel disks and manufacturing and maintenance-induced surface defects in all disk materials in the near future.
COATLIFE is a life-prediction software developed at SwRI under DOE and EPRI sponsorship, for predicting the remaining life of combustion turbine coatings in land-based gas turbine machines. The primary failure modes of combustion turbine (CT) coatings are coating degradation caused by oxidation and thermomechanical fatigue (TMF) cracking. The coating failure caused by degradation is commonly observed in blades that operated in a base-loaded machine, while coating cracking caused by TMF is widely seen in blades that operated in peak loaded machines. The blades are normally refurbished when the TMF cracks are limited to the coating thickness. Both coating failure modes are separately treated in COATLIFE-4.0, which now includes a user-friendly Excel-based spreadsheet program for ranking, selecting, and estimating remaining service life of a variety of metallic coatings, including overlay, diffusion, and duplex coatings, as well as air-plasma-sprayed (APS) thermal barrier coatings (TBC). COATLIFE-4.0, has been extensively validated for both oxidation and thermomechanical fatigue failure mechanisms for both metallic and APS-TBC coatings.
NESSUS • mechanics and materials • structural integrity • reliability assessment • mechanical behavior • mechanical characterization, fatigue life characterization • crack growth • corrosion fatigue • probabilistic mechanics • uncertainty modeling • NASGRO • DARWIN • software development