Investigation of Mean-Time-to-Failure Measurements from AlGaN/GaN High-Electron-Mobility Transistors Using Eyring Model

We present the mean-time-to-failure (MTTF) calculations for AlGaN/GaN high-electron-mobility transistors (HEMTs) using two independent acceleration factors. MTTF predictions are generally calculated through the Arrhenius relationship, based on channel temperature and acceleration, depend only on one parameter. Although the failure modes of the AlGaN/GaN HEMTs depend largely on the applied electric fields, the Eyring model is introduced to investigate both voltage and temperature dependent degradation of AlGaN/GaN devices. In anticipation of adequate MTTF values, studies were conducted on non-commercial devices. Further, we distinguished the cumulative failure percentages through the Weibull and log-normal distributions. We also explored the increase in gate leakage current at high temperatures for early device deterioration.

On the Generalized Decreasing Mean Time to Failure or Replaced Ordering

In this paper, we establish two new stochastic orders, DMTFR (decreasing mean time to failure or replaced) and GDMTFR (generalized decreasing mean time to failure or replaced), and mainly investigate properties of the GDMTFR order. Some characterizations of the GDMTFR order are given. The implication relationships between the DMTFR and the GDMTFR orders are considered. Also, closure and reversed closure properties of the new order GDMTFR are investigated. Meanwhile, several illustrative examples that meet the GDMTFR order are shown as well.

The Optimal System for Complex Series-Parallel Systems with Cold Standby Units: A Comparative Analysis Approach

The purpose of this research is to propose three reliability models (configurations) with standby units and to study the optimum configuration between configurations analytically and numerically. The chapter considered the need for 60 MW generators in three different configurations. Configuration 1 has four 15 MW primary units, two 15 MW cold standby units and one 30 MW cold standby unit; Configuration 2 has three 20 MW primary units, three 20 cold standby units; Configuration 3 has two 30 MW primary units and three 30 MW cold standby units. Some reliability features of series–parallel systems under minor and complete failure were studied and contrasted by the current. Failure and repair time of all units is assumed to be exponentially distributed. Explanatory expressions for system characteristics such as system availability, mean time to failure (MTTF), profit function and cost benefits for all configurations have been obtained and validated by performing numerical experiments. Analysis of the effect of different system parameters on the function of profit and availability has been carried out. Analytical comparisons presented in terms of availability, mean time to failure, profit function and cost benefits have shown that configuration 3 is the optimal configuration. This is supported by numerical examples in contrast to some studies where the optimal configuration of the system is not uniform as it depends on some system parameters. Graphs and sensitivity analysis presented reveal the analytical results and accomplish that Configuration 3 is the optimal in terms of design, reliability physiognomies such as availability of the system, mean time to failure, profit and cost benefit. The study is beneficial to engineers, system designers, reliability personnel, maintenance managers, etc.

On classes of life distributions based on the mean time to failure function

The performance and effectiveness of an age replacement policy can be assessed by its mean time to failure (MTTF) function. We develop shock model theory in different scenarios for classes of life distributions based on the MTTF function where the probabilities $\bar{P}_k$ of surviving the first k shocks are assumed to have discrete DMTTF, IMTTF and IDMTTF properties. The cumulative damage model of A-Hameed and Proschan [1] is studied in this context and analogous results are established. Weak convergence and moment convergence issues within the IDMTTF class of life distributions are explored. The preservation of the IDMTTF property under some basic reliability operations is also investigated. Finally we show that the intersection of IDMRL and IDMTTF classes contains the BFR family and establish results outlining the positions of various non-monotonic ageing classes in the hierarchy.

Perencanaan Perawatan Mesin Welding Mig Pada Produksi Sub Frame Di PT. XYZ Dengan Metode Reliability Centered Maintenance (RCM)

Pemeliharaan merupakan suatu proses yang dilakukan untuk menjaga keandalan, ketersediaan dan sifat mampu merawat komponen atau mesin. Program pemeliharaan yang efektif dan efisien akan mendukung peningkatan produktifitas sistem produksi. PT. XYZ merupakan perusahaan nasional bergerak dibidang karoseri truck mengalami penurunan produktivitas disebabkan belum adanya strategi perawatan khususnya mesin welding jenis MIG sehingga sering terjadi downtime mesin mengakibatkan proses produksi menjadi terhambat. Berdasarkan alasan tersebut dibutuhkan program pemeliharaan yang efektif dan efisien dengan menerapkan analisis menggunakan metode Reliability Centered Maintenance (RCM) guna menciptakan metode pemeliharaan yang akurat, fokus, dan optimal dengan tujuan mencapai keandalan yang optimal. Penelitian dilakukan dengan mengikuti langkah-langkah perhitungan berdasarkan Failure Mode and Effect Analysis (FMEA) dan penetapan strategi pemeliharaan dengan dibantu menggunakan software minitab 18. Hasil penelitian diperoleh Risk Priority Number (RPN) untuk komponen wire feeder sebesar 611, dengan pola distribusi waktu normal, nilai parameter median 61,9391 dan standar deviasinya 48,6053, nilai Mean Time To Failure (MTTF) sebesar 61,9391 jam dan selang interval waktu penggantian komponen sebesar 10,1349. Berdasarkan hasil perhitungan performance maintenanace diketahui nilai Mean Time Between Failure (MTBF) antara 31,92 ~ 72,09 jam, Mean Time To Repair (MTTR) anatara 1,19 ~ 1,78 jam dan availability antara 94,67% ~ 98,24%, setelah dilakukan tindakan perawatan pencegahan selama periode tersebut dihasilkan nilai availability sebesar 98,01% artinya kerusakan pada komponen wire feeder dapat teratasi.