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17Force identification using inverse technique is important especially when direct measurement 18 through force transducer is not possible. Considering the effects of impact excitation force on the 19 integrity of a lightweight structure, impact force identification has become the subject of several 20 studies. A methodology utilising Operating Deflection Shape (ODS) analysis, Frequency Response 21 Function (FRF) measurement and pseudo-inverse method to evaluate the dynamic force is 22 presented. A rectangular plate with four ground supports was used as a test rig to simulate the 23 motions of a simple vehicle body. By using the measured responses at remote points that are away 24 from impact locations and measured FRFs of the test rig, unknown force locations and their time 25 histories can be recovered by the proposed method. The performance of this approach in various 26 2 cases such as under-determined, even-determined and over-determined cases was experimentally 27 demonstrated. Good and bad combinations of response locations were selected based on the 28 condition number of FRF matrix. This force identification method was examined under different 29 response combinations and various numbers of response locations. It shows that in the over-30 determined case, good combination of response locations (i.e. low average of condition number of 31 FRF matrix) and high number of response locations give the best accuracy of force identification 32 result compared to under-determined and even-determined cases. 33 34 Keywords: condition number; frequency response function; impact force identification; pseudo-35 inverse method; response combination 36 INTRODUCTION 37Identification of dynamic force excitation on a system is important for performance evaluation, 38 design optimisation, noise suppression, vibration control as well as condition monitoring. However, 39 there are many situations where the direct measurement of the excitation forces is not possible or 40 feasible. For example, engine torque pulses and shaking forces are difficult to measure since these 41 forces are distributed throughout the engine [1]. In such a case, direct measurement by using force 42 transducer is not possible due to the difficulty of installation and dynamic characteristic altering 43 problem [2]. Therefore, force identification using the inverse method has been developed widely to 44 solve the problem. Much research has been carried out to find the unknown dynamic forces by 45 using the inverse method [3 -6]. 46 Impact force is the main cause for material fatigue of many structures especially in 47 lightweight structures, so it is useful to understand the characteristics of loading profile, such as 48 impact location and its time history [7]. At the development and modification stage of a lightweight 49 structure design, better information about the loads experienced by the structure through the 50 iteration process will assist the development resulting in a better design. Identification of the input 51 3 forces and their...

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Featured Application: This investigation is to improve the Vortex Induced Vibration effect in Piezoelectric Vibration Energy Harvester System through structural design and vibrational resonance. The outcome could be featured in a small-scale energy harvesting application that is installed at any location with forced flow.Abstract: Inspired by vortex induced vibration energy harvesting development as a new source of renewable energy, a T-shaped design vibration energy harvester is introduced with the aim of enhancing its performance through vortex induced vibration at near resonance conditions. The T-shaped structural model designed consists of a fixed boundary aluminum bluff splitter body coupled with a cantilever piezoelectric vibration energy harvesters (PVEH) plate model which is a piezoelectric bimorph plate made of a brass plate sandwiched between 2 lead zirconate titanate (PZT) plates. A 3-dimensional Fluid-Structure Interaction simulation analysis is carried out with Reynolds Stress Turbulence Model under wind speed of 7, 10, 12, 14, 16, 18, 19, 20, 22.5, and 25 m/s. The results showed that with 19 m/s wind speed, the model generates 75.758 Hz of vortex frequency near to the structural model's natural frequency of 76.9 Hz. Resonance lock-in therefore occurred, generating a maximum displacement amplitude of 2.09 mm or a 49.76% increment relatively in vibrational amplitude. Under the effect of resonance at the PVEH plate's fundamental natural frequency, it is able to generate the largest normalized power of 13.44 mW/cm 3 g 2 .

Identification of material properties is one of the key issues in composite materials research. This information is the most important database for an accurate Computer-Aided Engineering (CAE) simulation and various design enhancement purposes. For example, it can be used to estimate deflections and stress state of composite structure under static or dynamic load. The mechanical properties of composite materials depend on diverse factors such as configuration of the laminates, constituent materials used, production method adopted, etc. Hence, it is generally impossible to find these properties in standard tables. Conventional testing approach tends to be time-consuming, expensive and destructive. Moreover for properties such as shear modulus, these tests often yield poor results. As an alternative, a hybrid approach which utilises experimental and numerical techniques is proposed. This approach is a rapid, inexpensive and non-destructive evaluation of the mechanical properties of composite materials which involves both Experimental Modal Analysis (EMA) IntroductionComposite materials are composed of two or more different materials at macro-scale with each of the materials will contribute to the final properties. When the materials are combined, composites are generally more superior as compared to the individual components. Composite structures are usually constructed in multiple laminates where each layer is oriented specifically to achieve optimal strength and stiffness performance. Composites are preferred in applications due to their high strength-to-weight ratio, high-stiffness-to-weight ratio, high wear resistance, high corrosion resistance.The determination of mechanical properties is one of the important parts in composite materials research. Production method, materials used, and laminates configuration of the composites are among the contributing factors in changing the mechanical properties of composite materials. These properties are could not be found in any standard databases and tables. Conventional test procedures based on static loading are destructive, time and cost consuming. In addition, these tests often produce poor results especially in determining properties such as shear modulus. This has encouraged the development of specific methods to improve the accuracy in the identification method. Modal parameter such as mode shape or the combination of both natural frequencies and mode shapes are rarely used in elastic constants determination.In this paper, a non-destructive evaluation of the mechanical properties of composite materials which involves EMA and Finite Element (FE) model updating method is proposed. This approach utilises Background theories