This is the third issue of the International Journal of Performability Engineering of the year 2016. We are in the process of implementing an on-line paper management system for the journal. Once this is fully operational, it will be informed through the journal and also on the website of the journal. Till that time, authors are encouraged to submit their full research papers, case studies, review papers, short communications, book reviews, and other information such as details on conferences within the scope of the journal to any one of the Co-Editors-in-Chief by e-mail: (ijpe.xu@gmail.com or naikanijpe@gmail.com). The authors are also encouraged to submit the list of four referees with their current affiliation and contact details to accelerate the process of blind review of their paper.

This issue of the journal consists of seven technical papers and a short communication.

In the first paper, damping ratio in layered & bolted sandwich structure is determined by conducting sweep sine test and half power bandwidth method to Frequency Response Function (FRF). The effect of three major parameters on structural damping is investigated by using Design of Experiment analysis. The authors have shown that the number of layers in sandwich construction significantly affects the damping ratio and validated using regression equations. The design concept evolved from this paper using layered structures with bolted joints can be efficiently employed in applications where higher damping is required.

The second paper has proposed a fatigue failure model of an aircraft to assess the economical effectiveness of an airline under a limitation of the fatigue failure rate (FFR) and the limitation of any fatigue failure probability of (FFP) in a fleet of aircraft. The solution of the problem using theory of semi-Markov process is proposed.

The third paper has carried out investigation on hybridization to describe the tribological properties of fibre based hybrid composite achieved by the combination of natural jute and glass fibres reinforced composite for application in underground pipelines and marine applications based on the mechanical properties required. The properties of the prepared hybrid composite are experimentally calculated by various testing like tensile, impact, flexural and hardness according to ASTM standards. The effects of the varying slurry concentration and surface impact velocity at different exposure times on the erosion behavior of the composites have been carried out. The microstructures of the tested specimens have been performed through scanning electron microscope for fracture mode analysis.

The forth paper has formulated an optimum Accelerated life test (ALT) plan for a parallel system with two dependent components under ramp-stress loading scheme and Type-I censoring. The dependency between the two components is modelled by Gumbel-Hougaard copula evaluated at two Weibull survival (reliability) marginals. The stress-life relationship is modelled using inverse power law, and cumulative exposure model is assumed to model the effect of changing stress. The optimal plan consists in finding out the optimum stress rate using D-optimality criterion. The method developed has been explained using a numerical example.

The fifth paper has conducted a holistic examination of railway infrastructure robustness. The paper has presented an overview of robustness and has developed a new road map for railway infrastructure robustness, including a novel definition and a new framework of its management, based on continuous improvement. The paper has explored the opportunities of applying the road map to the infrastructure of railway systems and outlines some practical concerns and remaining challenges for future research. The results provide guidelines for other research into robust infrastructure in railway maintenance.

The sixth paper has shown that the wireless channel can be modelled in a more realistic manner by considering the randomness caused due to shadowing effects. The authors have characterized the connectivity of the MANET in a log–normal shadow fading environment. The simulated results are of practical significance for the design of MANET and offers insights into how the channel randomness has been considered for the MANET reliability evaluation through Monte Carlo Simulation approach to depict the impact of shadowing deviation.

The seventh paper has proposed a vibration based experimental method to relate rotor imbalance and reliability of rotating systems. A stress-strength interference approach together with a simulation-based methodology is used for modeling and analysis of this complex relationship. The paper also has proposed a method for establishing the safe and critical limits of imbalance and rotational speed for achieving the specified reliability targets.

This issue of the journal has one short communication as well.

The short paper has studied lifetime of automatic control systems to make the system tolerant to faults based on importance measures. The paper has proposed to divide the system lifetime into different phases, where the key components that can cause the system to fail can be different. Such key components can be identified by importance measures, which can guide the reliability design of control systems. The reliabilities and importance degrees of system components and sub-systems are first computed. Based on importance analysis results, different automatic control schemes are then developed and integrated. At last, the optimization design of automatic control systems is investigated to improve the system performance in term of system reliability or lifetime.

This issue also consists of three book reviews. The books (Publisher: Elsevier, 2016) reviewed are (1) Design for the Unexpected: From Holonic Manufacturing Systems towards a Humane Mechatronics Society, (2) Inherent Safety at Chemical Sites: Reducing Vulnerability to Accidents and Terrorism through Green Chemistry, and (3) Multiscale Modeling for Process Safety Applications.

I thank all the authors for their contributions and timely submission of revised versions of their papers. A also thank all the reviewers for their timely completion of review of the papers and also for critical comments and suggestions which have helped to improve the quality of papers. I hope the readers will enjoy this issue and get insight into the latest developments.

The damping is an important design consideration for vibrating structures. In this paper, damping ratio in layered & bolted sandwich structure is determined by conducting sweep sine test and half power bandwidth method to Frequency Response Function (FRF). Simple beam [1] is taken as reference point and the methodology is extended for determining the damping ratio in layered and bolted sandwich structure. These structures are excited using an Electro-Dynamic Shaker excitation technique for their fundamental mode. The effect of three major parameters on structural damping is investigated by using Design of Experiment analysis. Analysis of Variance and Signal to Noise ratios analysis is also performed. The results have shown that the number of layers in sandwich construction significantly affects the damping ratio and validated using regression equations. The design concept evolved from this paper using layered structures with bolted joints can be efficiently employed in applications where higher damping is required.

Definitions of binary p-set and binary λ-set functions are given. The use of these definitions allows for any unknown parameter of the model of fatigue failure of aircraft to provide the economical effectiveness of an airline under a limitation of the fatigue failure rate (FFR) and the limitation of any fatigue failure probability of (FFP) in a fleet of aircraft . The solution of the problem using theory of semi-Markov process with rewords is based on a result of an acceptance full-scale fatigue test of an aircraft structure. For this case the maximum of FFP and the maximum of FFR can be limited for any unknown parameter

By nature, Hybridization of inorganic and organic materials leads to the physical and chemical state of new compound or composite. Based on this concept, this article has structured two different hybrid composites prepared experimentally. The investigation taken up on hybridization describes the tribological properties of fiber based hybrid composite achieved by the combination of natural jute and glass fibers reinforced composite for application in underground pipelines and marine applications based on the mechanical properties required. The aim of this investigation is to evaluate the properties of these hybrids and compare their properties through different experimental techniques. The properties of the prepared hybrid composite are experimentally calculated by various testing like tensile, impact, flexural and hardness according to ASTM standards. The effects of the varying slurry concentration and surface impact velocity at different exposure times on the erosion behavior of the composites have been carried out. The microstructures of the tested specimens have been performed through scanning electron microscope for fracture mode analysis. The experimental results were obtained from the basis of their potential structural applications and the tribological tests help in finding their different applications. The results clearly indicates that the hybrid to has more value in all the properties than hybrid 1.

In this paper, we have formulated optimum Accelerated life test(ALT) plan for a parallel system with two dependent components under ramp-stress loading scheme and Type-I censoring. The dependency between the two components is modeled by Gumbel-Hougaard copula evaluated at two Weibull survival (reliability) marginals. The stress-life relationship is modeled using inverse power law, and cumulative exposure model is assumed to model the effect of changing stress. The optimal plan consists in finding out the optimum stress rate using D-optimality criterion. The method developed has been explained using a numerical example.

In the railway industry, most maintenance approaches are based on certain “specified conditions”, e.g., RAMS (Reliability, Availability, Maintainability and Safety) and Risk. But the reality is more complex. Instead of the assumed conditions, “unfavorable conditions” may occur from either natural or operational causes, where robustness can be an effective approach. To adequately consider “unfavorable conditions” and to reduce “uncertainties” in railway maintenance, this study conducts a holistic examination of railway infrastructure robustness. It gives an overview of robustness and discusses some relevant studies. It then develops a new road map for railway infrastructure robustness, including a novel definition and a new framework of robustness management, based on continuous improvement. It explores the opportunities of applying the road map to the infrastructure of railway systems and outlines some practical concerns and remaining challenges for future research. The results provide guidelines for other research into robust infrastructure in railway maintenance.

Several researches on reliability studies of ad hoc network, assumed that the communication links between any two mobile nodes exist if the Euclidean distance between them is not greater than the transmission range of the nodes. These methods are purely distance-dependent models and the randomness in the signal strength in radio communication is not taken care-off. This way of modeling the channel for reliability studies may be intuitively a valid theoretical study. However, the wireless channel can be modeled in a more realistic manner by considering the randomness caused due to shadowing effects. In this paper, we characterize the connectivity of the MANET in a log–normal shadow fading environment. The simulated results are of practical significance for the design of MANET and offers insights into how the channel randomness has been considered for the MANET reliability evaluation through Monte Carlo Simulation approach to depict the impact of shadowing deviation.

Imbalance in rotor systems generates dynamic forces, especially at high rotational speeds. This hypothesis is known to engineers, but how it actually affects the reliability is not established. In this research work a vibration based experimental method is proposed to relate imbalance in terms of vibration amplitude and reliability. A stress-strength interference approach together with a simulation-based methodology is used for modeling and analysis of this complex relationship. The paper also proposes a method for establishing the safe and critical limits of imbalance and rotational speed for achieving the specified reliability targets. Thus the concepts can be effectively used in industrial machinery for controlling the level of imbalance of a rotor designed to operate at a specified rotational speed.

This paper studies lifetime of automatic control systems to make the system tolerant to faults based on importance measures. The system lifetime can be divided into different phases, where the key components that can cause the system to fail can be different. Such key components can be identified by importance measures, which can guide the reliability design of control systems. In this work, through importance analysis, reliabilities and importance degrees of system components (e.g., sensors, actuators, process components) and sub-systems are first computed. Based on importance analysis results, different automatic control schemes are then developed and integrated. At last, the optimization design of automatic control systems is investigated to improve the system performance in term of system reliability or lifetime.

Importance measures are being widely used in risk-informed applications to characterize the importance of component failures, human errors, common cause failures, etc. In order to decrease the impact of external factors and increase the system survivability, a multilevel protection is applied to its components or subsystems. Each level of protection can have multiple states from perfect protection to complete destruction. When the protection of components or subsystems is completely destroyed, the protected components or subsystems can be destroyed. In such protection, different protection states play different roles in providing the system survivability and the sojourn time at different states of one protection has an effect on the system survivability. In this paper, based on the transitions of protection states, the multi-state protection survivability importance is introduced in order to determine which level of protection has the greatest influence on the entire system survivability.