Durability of an Elastic Bar Under Tension With Linear or Nonlinear Relationship Between Corrosion Rate and Stress

2012 ◽  
Vol 79 (2) ◽  
Author(s):  
Isaac Elishakoff ◽  
Guillaume Ghyselinck ◽  
Yohann Miglis
Keyword(s):  
Corrosion Rate ◽  
Closed Form ◽  
Average Diameter ◽  
Large Error ◽  
Nonlinear Relationship ◽  
Time To Failure ◽  
Linear Quadratic ◽  
Yield Level ◽  
Elastic Bar

In this study we investigate the durability of a bar subjected to tension in the presence of corrosion. Various possible relationships are considered between the corrosion velocity and stress. We concentrate on linear, quadratic, purely cubic, and general cubic relationships. Closed-form expressions are obtained for the structure’s durability, which is identified with time to failure, with failure defined as the stress reaching the yield level. Among other things, we evaluate the validity of the assumption that the average diameter of the bar remains constant, as suggested by Dolinskii (1967, “Analysis of Loaded Tubes Subjected to Corrosion,” Khimicheskoe I Neftianoe Mashinostroenie (Chemical and Oil Machinery), 2, pp. 9–10, (in Russian)). We show that in certain circumstances this assumption may lead to an unacceptably large error.

Reliability optimization for non-repairable series-parallel systems with a choice of redundancy strategies and heterogeneous components: Erlang time-to-failure distribution

2020 ◽  
pp. 1748006X2095257
Author(s):  
Meisam Sadeghi ◽  
Emad Roghanian ◽  
Hamid Shahriari ◽  
Hassan Sadeghi
Keyword(s):  
Lower Bound ◽  
Closed Form ◽  
System Reliability ◽  
Parallel Systems ◽  
Closed Form Expression ◽  
Erlang Distribution ◽  
Time To Failure ◽  
Form Expression ◽  
Integrodifference Equation ◽  
Cold Standby

The redundancy allocation problem (RAP) of non-repairable series-parallel systems considering cold standby components and imperfect switching mechanism has been traditionally formulated with the objective of maximizing a lower bound on system reliability instead of exact system reliability. This objective function has been considered due to the difficulty of determining a closed-form expression for the system reliability equation. But, the solution that maximizes the lower bound for system reliability does not necessarily maximize exact system reliability and thus, the obtained system reliability may be far from the optimal reliability. This article attempts to overcome the mentioned drawback. Under the assumption that component time-to-failure is distributed according to an Erlang distribution and switch time-to-failure is exponentially distributed, a closed-form expression for the subsystem cold standby reliability equation is derived by solving an integrodifference equation. A semi-analytical expression is also derived for the reliability equation of a subsystem with mixed redundancy strategy. The accuracy and the correctness of the derived equations are validated analytically. Using these equations, the RAP of non-repairable series-parallel systems with a choice of redundancy strategies is formulated. The proposed mathematical model maximizes exact system reliability at mission time given system design constraints. Unlike most of the previous formulations, the possibility of using heterogeneous components in each subsystem is provided so that the active components can be of one type and the standby ones of the other. The results of an illustrative example demonstrate the high performance of the proposed model in determining optimal design configuration and increasing system reliability.

Prediction of the Average Diameter of Laser Ablated Silver Nanoparticles Colloid Based on Artificial Neural Networks

2011 ◽  
Vol 391-392 ◽  
pp. 488-492
Author(s):  
Bing Xu ◽  
Ren Guo Song
Keyword(s):  
Neural Network ◽  
Silver Nanoparticles ◽  
Network Model ◽  
Neural Network Model ◽  
Average Diameter ◽  
Nonlinear Relationship ◽  
Colloidal Solutions ◽  
The Neural Network ◽  
Experimental Process ◽  
Relative Errors

In order to shorten the fussy experimental process in preparing colloidal solutions of silver nanoparticles by pulsed laser ablation in distilled water, a LmNet PF neural network model is developed to approach the complex nonlinear relationship between technology parameters and the average diameter for preparing colloidal solutions of silver nanoparticles. By using the constructed neural network model, the relationship between the technology parameters ( laser fluence, laser repetition, ablation time) and the average diameter is discussed, and the weakness that the nonlinear relationship could not be approached more accurately, effectively by using single-factor-experiment method is overcome. Predicted and test results showed that all the relative errors between the desired values and predicted outputs of the network are less than 10 %, but the predicted data of the neural network model are well acceptable when comparing them to the real test values, hence providing an effective, economical way for preparing colloidal solutions of silver nanopartilces.

scholarly journals A Note on the Time to Failure of a Two-Unit Parallel Redundant System with Deterioration on a Lattice

2020 ◽  
Vol 6 (1) ◽  
pp. 3-14
Author(s):  
Tadashi Dohi ◽  
Junjun Zheng ◽  
Hiroyuki Okamura
Keyword(s):  
Laplace Transform ◽  
Closed Form ◽  
Exponential Distribution ◽  
System Failure ◽  
Time To Failure ◽  
Redundant System ◽  
Bivariate Exponential Distribution ◽  
Multi Stage ◽  
Bivariate Exponential ◽  
The Laplace Transform

In this paper, we consider a two-unit parallel redundant system with deterioration on a lattice, where each unit has multi-stage deterioration levels, say, n levels. The transition from one deterioration level to the subsequent level occurs following the well-known Marshall-Olkin bivariate exponential distribution. We derive the closed form of the Laplace transform of the time to system failure in the two-unit parallel redundant system with deterioration on n×n lattice without repair and simultaneous failure, as well as the simple system on 3×3 lattice.

Reliability optimization for non-repairable series-parallel systems with a choice of redundancy strategies: Erlang time-to-failure distribution

2017 ◽  
Vol 231 (5) ◽  
pp. 587-604
Author(s):  
Meisam Sadeghi ◽  
Emad Roghanian
Keyword(s):  
Closed Form ◽  
System Reliability ◽  
High Performance ◽  
Parallel Systems ◽  
Erlang Distribution ◽  
Time To Failure ◽  
Allocation Model ◽  
Design Problems ◽  
Proposed Model ◽  
Engineering Design Problems

This article deals with a new redundancy allocation model for non-repairable series-parallel systems with multiple strategy choices. The proposed model simultaneously determines the type of components, number of active and standby components to maximize system reliability subject to design constraints. Traditionally, due to complexity and difficulty in obtaining the closed form version of system reliability, a convenient lower-bound on system reliability has been widely applied to approximate it. Assuming that switching mechanism time-to-failure is exponentially distributed, the closed form version of the reliability of subsystems with cold standby redundancy is derived analytically for the first time. This is successfully performed using Markov process and solving the relevant set of differential-difference equations. With respect to the obtained formulation, a semi-analytical expression for the reliability of subsystems with mixed redundancy strategy is also extracted. Component time-to-failure is assumed to follow an Erlang distribution which is suitable for most engineering design problems. The presented model is linear and in the form of standard zero-one integer programs and thus using integer programming algorithms guarantees optimal solutions. The computational results of solving a well-known example indicate the high performance of the proposed model in improving system reliability.

Consecutive k-out-of-n lines with a change point

2016 ◽  
Vol 230 (6) ◽  
pp. 545-550 ◽  
Author(s):  
Serkan Eryilmaz
Keyword(s):  
Closed Form ◽  
Reliability Analysis ◽  
Change Point ◽  
Reliability Evaluation ◽  
Telecommunication Networks ◽  
Pipeline System ◽  
Time To Failure ◽  
Oil Pipeline ◽  
Vacuum Systems ◽  
Mean Time

Reliability analysis of consecutive k-out-of- n systems and their generalizations has attracted a great deal of attention in the literature. Such systems have been used to model telecommunication networks, oil pipeline systems, vacuum systems in accelerators, spacecraft relay stations, etc. In this paper, nonrecursive closed form equations are presented for the reliability functions and mean time to failure values of consecutive k-out-of- n systems consisting of two types of nonidentical components. The results are illustrated for reliability evaluation of oil pipeline system.

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