فهرست مطالب سعید فطورچی

The proportional hazards model (PHM) that is a regression model was used to analyze the reliability of Komatsu 988 wheel loader system at Azerbaijan Molybdenum-Copper mine (Sungun Copper mine). Hazard rate in a system in PHM is the product of an arbitrary and unspecified baseline hazard rate, depending on time only, and a positive functional term, basically independent of time, incorporating the effects risk factors (covariates). The required data for PHM analysis were extracted from a database of 15 months, which collecting from different sources, such as daily reports, workshop reports, weather reports, meetings, and direct observations in format of time between failures and risk factors. At the first step, trend and serial correlation tests were used for evaluation of assumptions of independent and uniform distribution of data for determining base function of risk rate. The evaluation failed to show independency and uniform distribution. Therefore, power law process was used. In the next step, the regression coefficient of covariates were estimated. According to the results, shift, working place, proportionality of truck, weather conditions, temperature and road conditions have had a significant effect. Finally, the reliability of loaders based on the time and six risk factors was calculated, and analysis showed about three times alteration in productivity of analysis with the ignoring of risk factors compared with inserting them. The formal definition of reliability performance is ‘‘the ability of an item to perform a required function under given conditions for a given time interval’’. The ‘‘given conditions’’ are important keywords in the definition of the reliability performance concept and its related concepts. Given conditions can be such as the surrounding environment, conditions indicating parameters, the operating history of a machine, the skill of the operator or maintenance crew, etc. Thus, it is important that the statistical approach, which is used for reliability analysis, should be able to model the operational environment effect as the way it influences the failure process. There is a need for a careful and well-structured approach, access to all data and information, design and analysis tools, as well as effective design routines and procedures. The aim of this paper is to assess the different operating environment conditions and their effect on the reliability as the two main goals. PHM was proposed in order to predict hazard rate and reliability considering the operating environment condition. The stated points in this section can be classified as follows:
The common parametric methods were reviewed
PHM for analyzing covariates is discussed
The application of this method is demonstrated using a real case study
The reliability analysis showed about three times alteration in productivity of analysis with the ignoring of risk factors compared with inserting them.

Availability, due to the complexity of modern systems, operation costs, and guaranteed functioning of the product, is considered as a challenge; it is also regardeded as one of the most characteristic aspects of quality in the 21st century. While availability in the past was a concern in sensitive and complex industries such as military, nuclear, and aerospace industries, today this issue has become a universal concern in most industries, especially the mining industry with gigantic equipment. In mathematical terms, availability includes up time and down time. These two parameters are presented in the form of two indicators of reliability and maintainability. In this study, after introducing the concept of availability, its variants, its constituent parts and the importance of availability are discussed. Finally, a mining system constituting of a WA470-3 loader, D155A bulldozer, and HD785-5 dump truck is considered from Sungun copper mine () in Iran, and analyzed for a period of 15 months. The failure data (time between failures) and repairs data (time to repair) were analysed, and the fitted best function or model as well as subsystems and subsystem availability were calculated using statistical analysis. In last step, availability importance measure concept for subsystem prioritizing in mining system configuration was used. Availability importance measure indicated that the performance of loader must be immediately improved. In addition, results showed that improving maintainability has priority over reliability.