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Ship resistance is an important factor in ship design. Technological developments are carried out to reduce the magnitude of the ship's resistance. By reducing the drag of the ship, it can improve the performance of the ship with the same engine power as the previous design. In this study, we will redesign the hull of the Indonesian Navy's unmanned vessel in order to increase the performance of the ship's speed. The process of redesigning the hull of this unmanned ship uses the numerical method using Maxsurf software in analyzing hydrodynamic performance. The results of the drag analysis carried out with a redesign show a decrease in the value of the ship's resistance by 1143 KN and the required power of 9.98 HP. From the results that this study obtained compared to the initial design of 60%.

The Indonesian Navy's current unmanned vessel is the first unmanned ship made by the Indonesian Navy's Research and Development Service. This vessel is not optimal, it is necessary to redesign the hull using the model simulation method with the assistance of Maxsurf software. By using this maxsurf software, it will be easier to analyze hydrodynamic performance, one of which is the vessel's resistance. The redesign shows the results that there is a reduction in ship resistance. By redesigning, the hull of the Indonesian Navy's unmanned vessel by using the model simulation method with the assistance of the Maxsurf software in analyzing hydrodynamic performance, we get the resistance value at maximum speed. Meanwhile, the power required by the ship is at maximum speed so that the speed shows an increase in maximum ship speed, thereby fulfilling the operational requirements and producing good maneuverability. Therefore, it can be concluded that the ship after being redesigned can be better.

This paper explores the influence of linear hysteretic damping on the performance of passive tunedinerter devices. An inerter is a device that produces a force proportional to the relative acceleration across its two terminals; devices incorporating inerters have received widespread attention in the earthquake engineering community, because they offer the ability to improve the seismic response of structures. However, the majority of this research has assumed that the damping components within the tuned-inerter device exhibit viscous, rather than hysteretic, damping. This restriction imposes an essential question on how the hysteretic damping model will change the performance of the device compared to the viscous damping model. It is shown that the response of viscous and hysteretic inerter systems have significant differences in displacement amplitude due to the frequency-dependency of the damping. Therefore, a new formulation for obtaining the optimum loss factor of the hysteretic damping in the inerter system is proposed. Next, the challenges associated with accurately predicting the time-response of a hysteretically damped system are discussed. A numerical time-integration method is extended to address these challenges, using a new formulation that has the benefit of being broadly applicable to multi-degree-of-freedom hysteretic linear systems and nonstationary random signals. The results show that the earthquake responses from the hysteretic damping model can differ significantly from the ones obtained via the viscous model.

In this paper, a novel iterative finite element method (FEM) for energy harvesting purpose is presented. In this iterative FEM, the electromechanical coupling in the governing piezoelectric energy harvesting equation is separated into two parts. One part is an actuator-like problem and can be evaluated with ease via commercial software. The solution of the other part, for voltage generation, is obtained straightforward utilising the structural response of the earlier part. These two parts are solved iteratively until the convergence in voltage and structural responses is reached. The new iterative FEM is implemented to solve the dynamic problems of piezoelectric-based energy harvester in the frequency and time domains. The application of the present iterative FEM to evaluate the piezoelectric energy harvesting of lifting structures under an aeroelastic condition, i.e., gust load , is shown in some details. The validation against other methods from the literature shows the robustness and capabilities of the iterative FEM.

This paper presents an investigation on flutter speed of cracked composite plates. This work is divided into two sections: (a) variation of crack length at a fixed location on the plate, and (b) variation of crack location on the plate with a fixed crack length, modelled as a unidirectional composite for 0 0 , 90 0 and 135 0 orientations. Mori-Tanaka homogenization model is applied to obtain the effective composite constitutive properties as the function of fiber and matrix volume fraction. Doublet Lattice Method (DLM) is used to calculate the unsteady aerodynamic forces, i.e., lift distributions. It is found that the existence of small crack ratio on the composite plate (less than 0.4) has triggered an increment of the flutter speed. To support this statement, flutter response modes for each crack ratio are plotted, where the structure appears to be more stiffened than the undamaged plate. However, the crack results in the reduction of flutter speed when the crack ratio reaches 0.5. For the crack location assessment, the flutter speed increases as the crack location moves from the root to the tip due to the reduction of flutter frequency. The results show a good agreement with the validation using Strip Theory considering unsteady aerodynamics.

In this paper, the energy harvesting potential from an unmanned aerial vehicle (UAV) wing is discussed. A fixed-wing UAV implemented for surveillance and reconnaissance purposes is investigated in the present work. A piezoelectric patch is embedded into the UAV wingbox, serving as the energy harvesting structure. The structural deformation exerted by a discrete gust load during normal flight condition is utilised as the source of electrical energy. An advanced iterative finite element method (FEM) is applied as the computational tool. The result pointed out that the piezoelectric patch could successfully harvest the energy from the structural vibration.

In this paper, a novel hybrid mathematical/isogeometric analysis (IGA) scheme is implemented to evaluate the energy harvesting of the piezoelectric composite plate under dynamic bending. The NURBS-based IGA is applied to obtain the structural response exerted by the mechanical loading. The dynamic responses conveniently coupled with the governing voltage differential equations to estimate the energy harvested. The capabilities of the scheme are shown with the comparison against analytical and full electromechanical finite element results. As there is no need of fully coupled electromechanical element, the scheme provides cheaper computational cost and could be implemented with standard computational software. Thus, it gives great benefit for early design stage. Moreover, the robustness of the scheme is shown by the couple with high order IGA element which has been proven less prone to the shear locking phenomena in the literature. The computational results show greater accuracy on structural responses and energy estimation for a very thin plate compared to the couple with standard finite element method.

In this paper, an investigation on the energy harvesting exerted by the dynamic bending responses of a piezoelectric embedded wingbox is presented. An innovative hybrid mathematical/computational scheme is built to evaluate the energy harvested by a mechanical system. The governing voltage differential equations of the piezoelectric composite beam are coupled with the finite element method output. The scheme is able of evaluating various excitation forms including dynamic force and base excitation. Thus, it provides the capability to analyse a complicated structure with a more realistic loading scenario. Application to the simulation of a notional jet aircraft wingbox with a piezoelectric skin layer is shown in some detail. The results pointed out that the electrical power generated can be as much as 25.24 kW for a 14.5 m wingspan. The capabilities and robustness of the scheme are shown by comparison with results from the literature.

In this paper, a novel approach in assessing the structural integrity of cracked composite plates under the aeroelastic condition by using XFEM is presented. To the authors’ knowledge, this is the first time that aeroelastic condition is coupled in XFEM to model the crack propagations. Previous researches from the literature had only considered a static crack condition. This research focuses on determining the first failure experienced by the cracked composite plate, either the crack will propagate causing a fracture, or the composite plate will fail due to aeroelastic instability imposed at the critical flutter speed. The proposed scheme is used to solve the limitation in XFEM within Abaqus that only general static and implicit dynamic analysis can be performed. The structure is assumed to interact with minimal gust, and the deflections by time are expressed in the equation of periodic motion based on Fourier Series Function (FSF). The results show that at a particular fibre orientation, once the damaged composite plate is deformed due to the dynamics load at dive speed, it fails due to the crack propagation first instead of the flutter. In contrast, another fibre configuration shows good resistance to crack propagation and fails due to flutter instability.

The present paper illustrates a modelling technique of void damage prediction using constitutive Rousselier damage model in wingbox aircraft structure. The high possibility of aluminium wingbox structure to deform during operating become a driving force in this study. The Rousselier model is implemented by the user-defined material subroutine UMAT in the ABAQUS/ Standard. The wingbox is a part of a commercially-made commuter aircraft prototype, in which steady aerodynamic pressure is applied as the quasi-static, ranging from cruise load factor until the ultimate load factor. This analysis is divided into three assessments: load factor assessment, damage detection and implementation of Rousselier-UMAT-XFEM (RuX) model solution. The results indicate the maximum stress concentration occurs at the bottom-root part of the skin. The void volume fraction and the crack grow as the load factor increases to the ultimate load factor. A comparison with the literature is shown in some details.

In this paper, a new investigation of crack propagation on a commuter aircraft wing is discussed. The aircraft is a 19-seater multi-purpose commuter aircraft designed for a mission on the remote area. The dynamic load acting on the wing is assumed as harmonic load considering aerodynamic lift at a particular excitation frequency. A 3D wingbox CAD model is developed for the numerical simulation. Extended finite element (XFEM) is applied to analyse the crack propagation on the aircraft wing. The crack growth simulation is successfully done, and the results are shown in some details. These results provided a novel insight on the computational simulation of cracked wing structure under dynamic flight load.