Probabilistic Mechanics and Reliability Engineering

In today's market-driven environment, industry must develop high-performance, low-cost products that meet increasing reliability requirements and safety standards, under stringent time and resource constraints. For the past decade, Southwest Research Institute (SwRI) has pioneered the integration of state-of-the-art reliability methods and failure models to develop faster, better, and cheaper ways to design, manufacture, and maintain engineering systems. The Institute develops reliability technology to:

  • Quantify reliability and safety
  • Identify key variables
  • Integrate cost and risk assessments into engineering decisions

Coupling an explicit dynamic finite element program with SwRI probabilistic analysis software, engineers determine the probability that an underground tunnel or its contents would survive above-ground blasts. The Institute specializes in interfacing probabilistic methods with a variety of finite element programs, such as NASTRAN, ABAQUS, ANSYS, PRONTO, and DYNA.


As a leader in developing and applying probabilistic methods, SwRI uses this technology to resolve complicated engineering reliability problems. Teams integrate engineering mechanics and reliability expertise to solve problems using:

  • Mechanistic and empirical performance/failure models
  • Reliability models
  • Statistical data analysis
  • Computer-based probabilistic risk assessment and design optimization
  • Risk-based decision analysis
  • Probabilistic analysis software
  • Application-oriented, tailored probabilistic analysis codes
  • Methodology review and development

SwRI has applied reliability analysis and risk assessment in a number of technology areas. Applications include:

  • Aerospace propulsion systems
  • Aircraft
  • Automotive structures
  • Biomechanics
  • Gas turbines
  • Geomechanics
  • Nuclear waste packaging
  • Offshore structures
  • Pipelines
  • Rotordynamics

Institute engineers develop and use PC- and workstation-based probabilistic analysis tools to solve structural reliability problems. Shown here is the user-friendly WINFPI Windows-based program, which provides a graphical interface to define probabilistic data and visualize results.



Structural system failures involve multiple failure modes, locations, and components that are statistically dependent due to common loads, temperatures, and manufacturing processes. To compute efficiently and accurately the reliability of structural systems, SwRI developed a probabilistic fault tree analysis method that takes into account the correlations and dependencies.


The SwRI-developed risk assessment computer code NESSUS integrates highly efficient reliability methodology with finite element analysis using minimal computational time. Through tailored interfaces, NESSUS has been integrated with client in-house programs and several commercial finite element codes. The Institute licenses probabilistic analysis software and offers education in the use and application of probabilistic methods and software through short courses and computer workshops.

This brochure was published in March 1998. For more information about probabilistic mechanics and reliability engineering, contact Ben H. Thacker, Reliability and Engineering Mechanics, Mechanical Engineering Division, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Phone (210) 522-3896, Fax (210) 522-6965. structural reliability, mechanical reliability, probabilistic mechanics, probabilistic mechanics and reliability, stochastic mechanics, probabilistic engineering analysis, probabilistic engineering design, uncertainty analysis,

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