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RISS 인기검색어
- 검색키워드
- 저자 : Amin Imani (검색결과 3 건)
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A Multi-loop Switching Controller for Aircraft Gas Turbine Engine with Stability Proof
Amin Imani,Morteza Montazeri-Gh 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.6
In this paper,a Min-Max switching controller containing multiple state feedback regulators and fuel flow rate saturation is designed for a high bypass two-spool turbofan engine. Due to the switching nature of Min-Max algorithm and the presence of saturation function, stability analysis is an important issue in the process of controller design. Therefore, amethodology is presented to analyze the stability of the closedloop system. For this objective, the Min and Max selectors and the saturation block are replaced by their nonlinear equivalents and the structure of the control system is transformed into the canonical configuration of Lure’s system. Then, the condition for absolute stability is extracted using the Multivariable Circle Criterion. An asymptotic stability proof is achieved for the closed loop system and the performance of the designed multiregulator Min-Max controller in tracking a desired fan speed scenario and limit management is compared with the well-known Min-Max/SMC technique.
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Effect of brittleness on the micromechanical damage and failure pattern of rock specimens
Hamid Reza Nejati,Mehrdad Imani,Kamran Goshtasbi,Amin Nazerigivi 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.4
Failure patterns of rock specimens represent valuable information about the mechanical properties and crack evolution mechanism of rock. Several kinds of research have been conducted regarding the failure mechanism of brittle material, however; the influence of brittleness on the failure mechanism of rock specimens has not been precisely considered. In the present study, experimental and numerical examinations have been made to evaluate the physical and mechanical phenomena associated with rock failure mechanisms through the uniaxial compression test. In the experimental part, Unconfined Compressive Strength (UCS) tests equipped with Acoustic Emission (AE) have been conducted on rock samples with three different brittleness. Then, the numerical models have been calibrated based on experimental test results for further investigation and comparing the micro-cracking process in experimental and numerical models. It can be perceived that the failure mode of specimens with high brittleness is tensile axial splitting, based on the experimental evidence of rock specimens with different brittleness. Also, the crack growth mechanism of the rock specimens with various brittleness using discrete element modeling in the numerical part suggested that the specimens with more brittleness contain more tensile fracture during the loading sequences.
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Monitoring of fracture propagation in brittle materials using acoustic emission techniques-A review
Hamid Reza Nejati,Amin Nazerigivi,Mehrdad Imani,Ali Karrech 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.1
During the past decades, the application of acoustic emission techniques (AET) through the diagnosis and monitoring of the fracture process in materials has been attracting considerable attention. AET proved to be operative among the other non-destructive testing methods for various reasons including their practicality and cost-effectiveness. Concrete and rock structures often demand thorough and real-time assessment to predict and prevent their damage nucleation and evolution. This paper presents an overview of the work carried out on the use of AE as a monitoring technique to form a comprehensive insight into its potential application in brittle materials. Reported properties in this study are crack growth behavior, localization, damage evolution, dynamic character and structures monitoring. This literature review provides practicing engineers and researchers with the main AE procedures to follow when examining the possibility of failure in civil/resource structures that rely on brittle materials.
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