International Journal of Reliability and Safety

Gul, Muhammet

doi: 10.1504/IJRS.2020.113304pmid: N/A

Occupational Risk Assessment (ORA) is so crucial for safety management in the weapons industry since numerous hazards may lead to human casualties. Therefore, occupational health and safety stakeholders suggest proactive approaches in reducing risks to an acceptable level. Therefore, this paper aims to develop a novel hybrid ORA model for the weapons industry. The approach merges TODIM with Fine-Kinney concept. Risk parameters used in traditional Fine-Kinney method are weighted by Fuzzy Analytic Hierarchy Process (FAHP). Then, hazards and associated risks are prioritised using the approach. As an illustration, the gun and rifle assembly line of a weapon factory is handled. The application is carried out to improve operational safety and protect employee health. From both theoretical and practice aspects, it contributes to the literature by handling the problem in an integrated style of Fine-Kinney, FAHP and TODIM and by improving overall safety level of the observed factory and by suggesting potential action plans.

Kadyan, S.; Malik, S.C.; Gitanjali,

doi: 10.1504/IJRS.2020.113317pmid: N/A

Here, stochastic analysis of a three-unit repairable system is carried out with one main unit (class I unit) and two cold standby identical secondary units (class II units). The secondary units are less efficient than the main unit and neither can bear the load of the main unit. However, the secondary units can work simultaneously at the failure of the main unit. The priority is given to the class I unit for operation and repair. Repair activities are handled by a single server and assumed to be perfect. Failures of class I unit and class II units are different but constant. The repair distributions of both types of units are taken as general. The expressions for reliability measures and profit function are derived using Semi-Markov Process (SMP) and regenerative point technique. The application of the proposed model can be visualised in a power supply system.

Wang, Jinhe; Zhang, Xiaohong; Zeng, Jianchao

doi: 10.1504/IJRS.2020.113313pmid: N/A

Imperfect maintenance models, based on general renewal processes, have been extensively researched. However, the virtual age used for measuring the effect of imperfect maintenance is an unintuitive variable in models in the literature, leading to discrepancies between evaluation results and real situations. To solve this problem, a failure rate update model that considers virtual age and failure intensity update factors is proposed. In this model, the virtual age factor is determined by intuitive variables, and the failure intensity update factor is determined on the basis of virtual age, reflected by the virtual age factor. A brief illustration of the validity and feasibility of the proposed model is presented, based on real maintenance data. The results obtained through numerical experiments, sensitivity analysis, and a case study demonstrates that the proposed model can accurately reflect system reliability level in a convenient manner.

Pant, Himani; Singh, S.B.; Pant, Shivani; Chantola, Neelam

doi: 10.1504/IJRS.2020.113315pmid: N/A

The availability and cost rate for a maintained k-out-of-n: G system encountering multiple failure modes undergoing periodic inspection are studied in this paper. Explicitly, a k-out-of-n: G system with a functional state and N failure modes is taken into account. Failure time of each failure mode is random. At each inspection and on failure detection, perfect repairs are carried out. Some theorems on the point availability, limiting availability and long-run average cost rate are obtained in the study. A condition for determining the optimal inspection period for minimum long-run average cost rate is also studied. An illustration is taken to explain the results obtained in the proposed work.

Dai, M.Y.; Tao, Y.R.

doi: 10.1504/IJRS.2020.113287pmid: N/A

Reliable lubrication of a bearing means that the roller and bearing are separated by the oil film, resulting in less wear and longer life. During the bearing lubrication process, some particles are produced due to wear and other reasons. Generally, the particle size in the micropolar fluid gradually increases with time. Moreover, velocity and load of the bearing are uncertain. It is very important to consider the time-varying reliability of bearing lubrication. In this paper, a time-varying reliability analysis method for micropolar fluid elastohydrodynamic lubrication is proposed based on response surface method and first passage method. The response surface method is applied to construct the response function of minimum oil film thickness, and the reliability model of lubrication is developed by the film thickness ratio. Then, the reliability of lubrication is calculated by first passage method. The numerical results show that both the accuracy and efficiency of the proposed method are high.