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Fundamental Concepts Related to Risk and Uncertainty Reduction by Using Algebraic Inequalities
Published in Michael T. Todinov, Risk and Uncertainty Reduction by Using Algebraic Inequalities, 2020
The physics-of-failure approach was very successful in addressing the underlying causes of failure and eliminating failure modes, and contributed to the widespread view among reliability practitioners that only physics-of-failure models can deliver a real reliability improvement. However, it is necessary to point out that building accurate physics-of-failure models of the time to failure is not always possible because of the complexity of the physical mechanisms underlying the failure modes, the complex nature of the environment and the operational stresses. Physics-of-failure modelling certainly helps, for example, to increase the strength of a component by conducting research on the link between microstructure and mechanical properties of the material. However, this approach requires arduous and time consuming research, special equipment and human resources. Furthermore, despite their success and popularity, physics-of-failure models cannot transcend the narrow domain they serve and cannot normally be used to improve reliability and reduce risk in unrelated domains.
Humidity-Sensor Testing and Calibration
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2020
Those tests use accelerated life and mechanical-integrity testing to determine the lifetime reliability statistics for sensors. Potential failure mechanisms are determined by the materials, processes, and process variability that can occur in the manufacturing of a particular sensor. Identifying minimum expectations and critical application factors that limit the life of a device is part of a methodology known as a physical failure approach for reliability testing. The physics of failure approach involves analyzing the potential failure mechanisms and modes. For example, Figure 26.1 shows 10 product-related and 8 process-related areas with 73 different items that can affect reliability (Maudie and Tucker 1991; Maudie and Wertz 1997; Frank 2013).
Thermal Management and Reliability
Published in Dorin O. Neacsu, Switching Power Converters, 2017
As an alternative, the physics of failure represents a design technique that relies on understanding the physical processes of stress, strength, and failure at a very detailed component level. This helps the redesign of each component to reduce the probability of failure. Most typically such evaluation of the physics of failure comes down to the test and introduction of new materials. The issues related to the reliability of the highly-integrated power modules as well as of various passive components represent a very active and promising field of research, requiring a multiphysics approach to thermal-mechanical strain control for controlled reliability and full capacity utilization.
A review of electro-hydraulic servovalve research and development
Published in International Journal of Fluid Power, 2018
Paolo Tamburrano, Andrew R. Plummer, Elia Distaso, Riccardo Amirante
A servovalve is usually composed of a main stage (also called second stage) housing the main spool used for metering flow (four-way spool valves are extensively used) and a pilot stage (also called first stage) serving as a hydraulic amplification system, thus forming a two-stage configuration. Three- and four-stage servovalves also exist for controlling larger flows, incorporating one or two larger spools, respectively. Although servovalves are usually provided with filters, erosion of the metering edges may occur over long periods of operation because of particle contamination (Hunt and Vaughan 1996). The effects of degradation and life prediction under erosive wear were thoroughly described in Zhang et al. (2014). A series of physics of failure models for particle erosion wear of electro-hydraulic servovalves were established in Fang et al. (2013).
Effectively communicating developmental system reliability growth plans and risk
Published in Australian Journal of Multi-Disciplinary Engineering, 2022
Paul Nation, Martin Wayne, Mohammad Modarres
Reliability engineering is often seen as a complex endeavour that emphasises statistics, complex mathematical models, and a deep understanding of the physics of failure aspects across mechanical, electrical, chemical and structural spectrums. Based on the author’s professional experiences, other engineering specialisations beyond the reliability domain often find reliability efforts complex and challenging to comprehend. Targeting a specific communication technique to a particular audience can be challenging. Understanding the myths and fundamentals associated with general engineering and technical communication can significantly assist the reliability engineering practitioner in tailoring a message for a specific audience.
Mandibular reconstruction system reliability analysis using probabilistic finite element method
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
S. Kargarnejad, F. Ghalichi, M. Pourgol-Mohammad, A. Garajei
Probabilistic physics of failure (PPoF) is an extremely useful approach in which uncertainty sources are incorporated in the physics-of-failure method (Modarres et al. 2017). The probabilistic response of the reconstruction system is modeled as: where is the applied stress at a single point (node or element) and symbolizes the random variables (describing input of the model). In this case, the random variables consist of bite force and the elasticity modulus of the cortical and cancellous bones and the titanium.