Blocksim Reliability Software
Time Dependent System Reliability Analytical Relia. Wiki. From Relia. Wiki Chapter 4 Time Dependent System Reliability Analytical In the RBDs and Analytical System Reliability chapter, different system configuration types were examined, as well as different methods for obtaining the systems reliability function analytically. Because the reliabilities in the problems presented were treated as probabilities e. Blocksim Reliability Software' title='Blocksim Reliability Software' />Thus, in the prior chapter, the life distributions of the components were not incorporated in the process of calculating the system reliability. In this chapter, time dependency in the reliability function will be introduced. We will develop the models necessary to observe the reliability over the life of the system, instead of at just one point in time. In addition, performance measures such as failure rate, MTTF and warranty time will be estimated for the entire system. The methods of obtaining the reliability function analytically remain identical to the ones presented in the previous chapter, with the exception that the reliabilities will be functions of time. In other words, instead of dealing with, we will use. All examples in this chapter assume that no repairs are performed on the components. Repairable systems analysis will be introduced in a subsequent chapter. Analytical Life Predictions. The analytical approach presented in the prior chapter involved the determination of a mathematical expression that describes the reliability of the system, expressed in terms of the reliabilities of its components. So far we have estimated only static system reliability at a fixed time. For example, in the case of a system with three components in series, the systems reliability equation was given by. The values of, and were given for a common time and the reliability of the system was estimated for that time. However, since the component failure characteristics can be described by distributions, the system reliability is actually time dependent. In this case, the equation above can be rewritten as. The reliability of the system for any mission time can now be estimated. Assuming a Weibull life distribution for each component, the first equation above can now be expressed in terms of each components reliability function, or. In the same manner, any life distribution can be substituted into the system reliability equation. Suppose that the times to failure of the first component are described with a Weibull distribution, the times to failure of the second component with an exponential distribution and the times to failure of the third component with a normal distribution. Then the first equation above can be written as. It can be seen that the biggest challenge is in obtaining the systems reliability function in terms of component reliabilities, which has already been discussed in depth. Once this has been achieved, calculating the reliability of the system for any mission duration is just a matter of substituting the corresponding component reliability functions into the system reliability equation. Advantages and Disadvantages. The primary advantage of the analytical solution is that it produces a mathematical expression that describes the reliability of the system. Once the systems reliability function has been determined, other calculations can then be performed to obtain metrics of interest for the system. Such calculations include. Determination of the systems pdf. Determination of warranty periods. Determination of the systems failure rate. Determination of the systems MTTF. In addition, optimization and reliability allocation techniques can be used to aid engineers in their design improvement efforts. Blocksim Reliability Software' title='Blocksim Reliability Software' />System Reliability Analysis An Overview of Basic Concepts. In life data analysis and accelerated life testing data analysis, the objective is to obtain a life. Availability is an important metric used to assess the performance of repairable systems, accounting for both the reliability and maintainability properties of a. RBDs are constructed out of blocks. The blocks are connected with direction lines that represent the reliability relationship between the blocks. Reliability software tools for life data analysis Weibull analysis, accelerated life testing data analysis, system reliability, maintainability and availability. Acca Approved Employer List Malaysia 2011 Pdf. Another advantage in using analytical techniques is the ability to perform static calculations and analyze systems with a mixture of static and time dependent components. Finally, the reliability importance of components over time can be calculated with this methodology. The biggest disadvantage of the analytical method is that formulations can become very complicated. The more complicated a system is, the larger and more difficult it will be to analytically formulate an expression for the systems reliability. For particularly detailed systems this process can be quite time consuming, even with the use of computers. Furthermore, when the maintainability of the system or some of its components must be taken into consideration, analytical solutions become intractable. In these situations, the use of simulation methods may be more advantageous than attempting to develop a solution analytically. The system reliability for this system computed using BlockSim is shown next. The first solution is provided using BlockSims symbolic solution. Fig_4.12.PNG/600px-Fig_4.12.PNG' alt='Blocksim Reliability Software' title='Blocksim Reliability Software' />Simulation methods are presented in later chapters. Looking at a Simple Complex System Analytically. The complexity involved in an analytical solution can be best illustrated by looking at the simple complex system with 1. The system reliability for this system computed using Block. Ntlite Keygen. Sim is shown next. The first solution is provided using Block. Sims symbolic solution. Blocksim Reliability Software' title='Blocksim Reliability Software' />
In symbolic mode, Block. Sim breaks the equation into segments, identified by tokens, that need to be substituted into the final system equation for a complete solution. This creates algebraic solutions that are more compact than if the substitutions were made. Substituting the terms yields. Block. Sims automatic algebraic simplification would yield the following format for the above solution. In this equation, each represents the reliability function of a block. For example, if has a Weibull distribution, then each and so forth. Substitution of each components reliability function in the last equation above will result in an analytical expression for the system reliability as a function of time, or, which is the same as Obtaining Other Functions of Interest. Once the system reliability equation or the cumulative density function, cdf has been determined, other functions and metrics of interest can be derived. Consider the following simple system. Furthermore, assume that component 1 follows an exponential distribution with a mean of 1. Weibull distribution with and. The reliability equation of this system is. The system cdf is. System pdf. Once the equation for the reliability of the system has been obtained, the systems pdf can be determined. The pdf is the derivative of the reliability function with respect to time or. For the system shown above, this is. The next figure shows a plot of the pdf equation. Conditional Reliability. Conditional reliability is the probability of a system successfully completing another mission following the successful completion of a previous mission. The time of the previous mission and the time for the mission to be undertaken must be taken into account for conditional reliability calculations. The systems conditional reliability function is given by. Equation above gives the reliability for a new mission of duration having already accumulated hours of operation up to the start of this new mission. The system is evaluated to assure that it will start the next mission successfully. For the simple two component system, the reliability for mission of 1. Conditional Reliability for Components. Now in this formulation, it was assumed that the accumulated age was equivalent for both units. That is, both started life at zero and aged to 5. It is possible to consider an individual component that has already accumulated some age used component in the same formulation. To illustrate this, assume that component 2 started life with an age of T 1.