The Reliability Analysis Software (RAS) is a software frame work to carry out probabilistic and reliability analysis for any problem that can be described as a performance function or limit state using a set of random and deterministic variables.

The reliability analysis requires determination of probability of failures of the component or system to meet specific performance criteria or limit states. In mathematical terms, the probability of failure (Pf) of a component or system may be described as given below:

Where X is vector of random variables that are used to define the set of performance functions g(X). When there is only one performance function, it is called component level reliability analysis. The f(X) is joint probability density function (pdf) of X. The g(X) =0 is called limit state� dividing performance of the� component into failure state (i.e. g(X) <0) and safe state (i.e. g(X) > 0). The g(X) ≤0 defines the failure domain over which integration of the probability integral is to be performed to determine probability of failure.

The Reliability Analysis Software provides requisite support to define a design problem for probabilistic analysis. A functional block diagram of the Reliability Analysis Software is given in Figure 1 showing various software components and their interactions. Apart from providing core computational capability for probability integral, the RAS is built on windowing system providing easy to use Graphic User Interfaces and environment for rapid setting of reliability problems and carrying out analysis (Figure 2). The data wizard allows easy setting of project data such as random variables, deterministic variables, random variables correlations, system diagram for system reliability analysis and other related functionalities. The RAS comes with a number of probability distributions to model random design variables.

Figure 1 The functional block diagram of reliability analysis software

Figure 2 The reliability analysis software (RAS)

An important feature of the Reliability Analysis Software (RAS) is the methods for defining of limit states and performance functions. The software provide a comprehensive set of tools for definition of performance function including mathematical expression, data regression (response surface and artificial neural network), the programming codes such as C/C++, FORTRAN and Python. The programming codes base performance function evaluation methods may be used� for developing of specialized performance function along with interfaces to existing software tools such as finite element analysis (FEA) software most commonly used in engineering product design. Interfaces to popular FEA software such as ANSYS and ABAQUS are available in the RAS Professional version.

In conventional design methods, analytical or empirical formula are used for analysis. The RAS provides a very convenient text notepad like interface for entering of mathematical expression for limit state and its derivatives. It is possible in RAS to define multiple limit states for component level as well as system level reliability analysis.

In order to carry out reliability analysis on the basis of experimental data, the RAS allows defining of limit state using response surface method or artificial neural network. Apart from commonly used built-in response models, the software has provisions for users to define their own models suitable to the problem domain in question. These features can also be used for the data generated through Finite Element Methods and other computational tools to carry out reliability analysis. The RAS, however, provide built-in support for interfacing reliability analysis to commonly used finite element analysis software and it is also possible to use other external codes for limit state evaluation.�

Further, specialization in definition of limit state and performance function may be achieved using programming language interfaces. The software provide interface for FORTRAN, C/C++ and python programming languages. These interfaces allow endless possibilities for definition of limit states and existing codes for design analysis.

The RAS have a built-in command shell environment enabling user to write their own scripts for analysis. The software also provide requisite support for project management allowing definition of projects, collection of project files in single directory/folder, project report generation and other common processes.

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