Thermal buckling resistance of a lightweight lead-free piezoelectric nanocomposite sandwich plate

Behdinan, Kamran,Moradi-Dastjerdi, Rasool Techno-Press 2022 Advances in nano research Vol.12 No.6

The critical buckling temperature rise of a newly proposed piezoelectrically active sandwich plate (ASP) has been investigated in this work. This structure includes a porous polymeric layer integrated between two piezoelectric nanocomposite layers. The piezoelectric material is made of a passive polymeric material that is activated by lead-free nanowires (NWs) of zinc oxide (ZnO) embedded inside the matrix. In both nanocomposite layers and porous core, functional graded (FG) patterns have been considered for the distributions of ZnO NWs and voids, respectively. By adopting a higher-order theory of plates, the governing equations of thermal buckling are obtained. This set of equations is then treated using an extended mesh-free solution. The effects of plate dimensions, porosity states, and the nanowire parameters have been investigated on the critical buckling temperature rises of the proposed lightweight ASPs with different boundary conditions. The results disclose that the use of porosities in the core and/or mixing ZnO NWs in the face sheets substantially arise the critical buckling temperatures of the newly proposed active sandwich plates.

Multidisciplinary wing design optimization considering global sensitivity and uncertainty of approximation models

박형욱,정준,Kamran Behdinan,이재우 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6

In recent years, high-fidelity analysis tools, such as computational fluid dynamics and finite element method, have been widely used inmultidisciplinary design optimization (MDO) to enhance the accuracy of design results. However, complex MDO problems have manydesign variables and require long computation times. Global sensitivity analysis (GSA) is proposed to assuage the complexity of designproblems by reducing dimensionality where variables that have low impact on the objective function are neglected. This avoids wastingcomputational effort and time on low-priority variables. Additionally, uncertainty introduced by the fidelity of the analysis tools is consideredin design optimization to increase the reliability of design results. Reliability-based design optimization (RBDO) and possibilitybaseddesign optimization (PBDO) methods are proposed to handle uncertainty in design optimization. In this paper, the extended Fourieramplitude sensitivity test was used for GSA, whereas a collaborative optimization-based framework with RBDO and PBDO wasused to consider uncertainty introduced by approximation models. The proposed method was applied to an aero-structural design optimizationof an aircraft wing to demonstrate the feasibility and efficiency of the developed method. The objective function was to maximizethe lift-to-drag ratio. The proposed process reduced calculation efforts by reducing the number of design variables and achieved the targetprobability of failure when it considered uncertainty. Moreover, this work evaluated previous research in RBDO with MDO for the wingdesign by comparing it with the PBDO result.

Investigation into the effect of piston ring seals on an integrated squeeze film damper model

Tieshu Fan,Kamran Behdinan 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2

This research presents an advanced squeeze film damper model that integrates piston ring seal geometry, fluid inertia, and film cavitation to study their combined features. The configuration of the piston ring seal is inspected, and different sealing scenarios are discussed. The flow rate in the seal arrangement is determined on the basis of the pressure gradient according to thin film theory. Moreover, the governing equation for the flow in the film land that considers fluid inertia is solved using the linear complementarity problem method to address the cavitation phenomenon. Validation is performed by comparing the model prediction with long bearing and short bearing models under different seal dimensions. Results show that an oversized gap in the seal grooves and a large frictional coefficient may lock the piston ring seal in the seal groove and thus reduce seal efficiency.

Thermoelastic static and vibrational behaviors of nanocomposite thick cylinders reinforced with graphene

Rasool Moradi-Dastjerdi,Kamran Behdinan 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.5

Current paper deals with thermoelastic static and free vibrational behaviors of axisymmetric thick cylinders reinforced with functionally graded (FG) randomly oriented graphene subjected to internal pressure and thermal gradient loads. The heat transfer and mechanical analyses of randomly oriented graphene-reinforced nanocomposite (GRNC) cylinders are facilitated by developing a weak form mesh-free method based on moving least squares (MLS) shape functions. Furthermore, in order to estimate the material properties of GRNC with temperature dependent components, a modified Halpin-Tsai model incorporated with two efficiency parameters is utilized. It is assumed that the distributions of graphene nano-sheets are uniform and FG along the radial direction of nanocomposite cylinders. By comparing with the exact result, the accuracy of the developed method is verified. Also, the convergence of the method is successfully confirmed. Then we investigated the effects of graphene distribution and volume fraction as well as thermo-mechanical boundary conditions on the temperature distribution, static response and natural frequency of the considered FG-GRNC thick cylinders. The results disclosed that graphene distribution has significant effects on the temperature and hoop stress distributions of FG-GRNC cylinders. However, the volume fraction of graphene has stronger effect on the natural frequencies of the considered thick cylinders than its distribution.

Uncertainty-based MDO for aircraft conceptual design

Park, Hyeong-Uk,Lee, Jae-Woo,Chung, Joon,Behdinan, Kamran Emerald Group Publishing Limited 2015 Aircraft engineering and aerospace technology Vol.87 No.4

<P><B>Purpose</B></P> <P> – The purpose of this paper is to study the consideration of uncertainty from analysis modules for aircraft conceptual design by implementing uncertainty-based design optimization methods. Reliability-Based Design Optimization (RBDO), Possibility-Based Design Optimization (PBDO) and Robust Design Optimization (RDO) methods were developed to handle uncertainties of design optimization. The RBDO method is found suitable for uncertain parameters when sufficient information is available. On the other hand, the PBDO method is proposed when uncertain parameters have insufficient information. The RDO method can apply to both cases. The RBDO, PBDO and RDO methods were considered with the Multidisciplinary Design Optimization (MDO) method to generate conservative design results when low fidelity analysis tools are used. </P> <P><B>Design/methodology/approach</B></P> <P> – Methods combining MDO with RBDO, PBDO and RDO were developed and have been applied to a numerical analysis and an aircraft conceptual design. This research evaluates and compares the characteristics of each method in both cases. </P> <P><B>Findings</B></P> <P> – The RBDO result can be improved when the amount of data concerning uncertain parameters is increased. Conversely, increasing information regarding uncertain parameters does not improve the PBDO result. The PBDO provides a conservative result when less information about uncertain parameters is available. </P> <P><B>Research limitations/implications</B></P> <P> – The formulation of RDO is more complex than other methods. If the uncertainty information is increased in aircraft conceptual design case, the accuracy of RBDO will be enhanced. </P> <P><B>Practical implications</B></P> <P> – This research increases the probability of a feasible design when it considers the uncertainty. This result gives more practical optimization results on a conceptual design level for fabrication. </P> <P><B>Originality/value</B></P> <P> – It is RBDO, PBDO and RDO methods combined with MDO that satisfy the target probability when the uncertainties of low fidelity analysis models are considered.</P>