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Descriptive Statistics
Published in Seong-woo Woo, Design of Mechanical Systems Based on Statistics, 2021
MTBF is the forecasted elapsed time between the failures of a mechanical system during normal system operation. MTBF can be calculated as the average time between failures of a system. MTBF is a reliability standard utilized to report the average lifetime of repairable components such as airplanes, automobiles, construction machines, and refrigerators. A repairable system is the one that can be replaced to adequate operation by any action, including component replacements or changes to adaptable settings.
Reliability Requirements, Modeling, and Allocation
Published in Ali J Jamnia, Khaled Atua, Executing Design for Reliability within the Product Life Cycle, 2019
MTBF is defined and calculated as the total time of operation of the entire population of a product in the field divided by all failures of the entire population in that period of time. Realistically, both the population and the failure data are noisy. For this reason, to remove the noise, manufacturers adopt an averaging period of 3, 6, or even 12 months to track and monitor MTBF.
Modeling and Calculating Resilience
Published in Ron Burch, Resilient Space Systems Design: An Introduction, 2019
where MTBF is the Mean Time Between Failures, and MTTR is the Mean Time to Repair. This form of the equation is directly derived from system reliability through Equations (5.13) and (5.14): MTBF=1λRel=e−λ
Buffer allocation design for unreliable production lines using genetic algorithm and finite perturbation analysis
Published in International Journal of Production Research, 2022
Khelil Kassoul, Naoufel Cheikhrouhou, Nicolas Zufferey
This example was initially proposed by Ho, Eyler, and Chien (1979) and used in different papers as a benchmarking case (Gershwin and Schor 2000; Massim et al. 2012; Demir, Tunali, and Eliiyi 2011; Kose and Kilincci 2015). The total buffer size is 31, and the parameters of the five machines are presented in Table 4. For this example, the average production rate is estimated by simulating 100,000 parts with 50 replications. MTTR and MTBF denote the mean time to repair and the mean time between failures, respectively. Table 4 presents the buffer sizes configuration and the corresponding average production rates obtained by the different approaches. GA-FPA obtains a slightly better production rate with the buffer size configuration (7, 11, 9, 4), which has the same allocation at the extremities of the line as Kose and Kilincci (2015), Demir, Tunali, and Eliiyi (2011), Massim et al. (2012) and Gershwin and Schor (2000). The allocation of small capacities at the beginning and at the end of the line, and important sizes in the middle, is likely to be efficient for facilitating the passage of the parts and thus bypassing a possible congestion of the line. Again, we can see that GA-FPA obtains the best results.
Performance-based contract design under cost uncertainty: A scenario-based bilevel programming approach
Published in The Engineering Economist, 2018
Mohammadreza Sharifi, Roy H. Kwon
The performance measure in a PBC is usually the average availability of the asset. Availability is characterized by mean time between failures (MTBF) and mean time to repair (MTTR). MTBF is the average time between two consecutive failures of an asset that make the system inoperable. In this article, we consider failures in a fleet of assets and instead use the term mean time between fleet failures (MTBFF). The inspection and maintenance policy and product reliability have an impact on the value of MTBFF. Mean time to repair is the average time from the moment the asset is not in an operable state to the moment it is up and running. MTTR is the downtime due to shortage of spare parts in stock, repair time of the failed asset, logistics time, and installation time. The level of support in maintenance depends on the contract between the supplier and the customer, and the level of each supporting service can vary. For instance, the supplier can be responsible for the whole process of repairing and making the asset operable and the customer merely measures and controls the downtime as one single value.
Performance evaluation of the remanufacturing system prone to random failure and repair
Published in International Journal of Sustainable Engineering, 2020
Ronak Savaliya, Walid Abdul-Kader
Another reason for work interruption is a sudden failure of the machinery. Any failure needs to be fixed by means of corrective maintenance. Corrective maintenance is a time-consuming and costly activity because the maintenance crew needs time to diagnose and repair the failed machine. In fact, increments in buffer capacity beyond the optimal level sometimes decreases the production output more than other factors. In addition, machine availability depends on its MTBF. The MTBF for any machine can be improved by introducing preventive maintenance, (PM). This policy helps to restore the reliability of a machine that has deteriorated over time. Hence, preventive maintenance is necessary to improve the availability and increase the remanufacturing rate.