Assessment of Impact Energy Harvesting in Composite Beams with Piezoelectric Transducers

Piezoelectric energy harvesting (PEH) is studied in the case of a low-velocity impact of a rigid mass on a composite beam. A methodology is outlined, encompassing modelling of the open-circuit impact response in a finite element (FE) package, formulation of a lumped parameter (LP) model for the piezoelectric transducer connected with the harvesting circuit, and experimental verification of the impact using a custom portable configuration with impactor motion control. The subcircuit capacitor charging effect, the impactor mass and velocity on the harvesting subcircuit response, and the obtained output power are quantified. The results indicate that the current methodology can be used as a design tool for the structure and the harvesting circuit to achieve power output from composite beams with piezoelectric patches under impact conditions.

High-Sensitivity Dual Electrochemical QCM for Reliable Three-Electrode Measurements

An electrochemical quartz crystal microbalance (EC-QCM) is a versatile gravimetric technique that allows for parallel characterization of mass deposition and electrochemical properties. Despite its broad applicability, simultaneous characterization of two electrodes remains challenging due to practical difficulties posed by the dampening from fixture parasitics and the dissipative medium. In this study, we present a dual electrochemical QCM (dual EC-QCM) that is employed in a three-electrode configuration to enable consequent monitoring of mass deposition and viscous loading on two crystals, the working electrode (WE) and the counter electrode (CE). A novel correction approach, along with a three standard complex impedance calibration, is employed to overcome the effect of dampening while keeping high spectral sensitivity. Separation of viscous loading and rigid mass deposition is achieved by robust characterization of the complex impedance at the resonance frequency. Validation of the presented system is done by cyclic voltammetry characterization of Ag underpotential deposition on gold. The results indicate mass deposition of 412.2 ng for the WE and 345.6 ng for the CE, reflecting a difference of the initially-present Ag adhered to the surface. We also performed higher harmonic measurements that further corroborate the sensitivity and reproducibility of the dual EC-QCM. The demonstrated approach is especially intriguing for electrochemical energy storage applications where mass detection with multiple electrodes is desired.

Force transmissibility characteristics of a pseudoelastic oscillator

The force transmissibility characteristics of a passive vibration isolator in the form of shape memory alloy bar are investigated. The shape memory alloy bar, together with a rigid mass, constitutes a single-degree-of-freedom system. The force isolation ability of the oscillator is evaluated for both isothermal and convective environmental conditions. The transmissibility curve of an isothermal pseudoelastic oscillator displays single and double jumps depending upon the forcing amplitude. The shape memory alloy oscillator with coupled thermomechanical behaviour depends on the cooling rate near resonant frequencies. Increased cooling rate reduces both peak amplitude and the resonant frequency of the transmissibility curve. The force isolation provided by shape memory alloy oscillator is independent of the operating conditions.

Dynamic modeling of a galloping structure equipped with piezoelectric wafers and energy harvesting

This study presents the analytical solution and experimental investigation of the galloping energy harvesting from oscillating elastic cantilever beam with a rigid mass. A piezoelectric wafer was attached to galloping cantilever beam to harvest vibrational energy in electric charge form. Based on Euler-Bernoulli beam assumption and piezoelectric constitutive equation, kinetic energy and potential energy of system were obtained for the proposed structure. Virtual work by generated charge and galloping force applied onto the rigid mass was obtained based on Kirchhoff's law and quasistatic assumption. Nonlinear governing electro-mechanical equations were then obtained using Hamilton's principle. As the system vibrates by self-exciting force, the fundamental mode is the only one excited by galloping. Hence, multi-degreeof-freedom equation of motion is simplified to one-degree-of-freedom model. In this study, closed-form solutions for electro-mechanical equations were obtained by using multi-scale method. Using these solutions, we can predict galloping amplitude, voltage amplitude and harvested power level. Numerical and experimental results are presented and discrepancies between experimental and numerical results are fully discussed.

Rigid-Mass Vehicle Model for Identification of Bridge Frequencies Concerning Pitching Effect

The concept of vehicle-bridge interaction (VBI) was originally developed to investigate the dynamic behavior of bridges subjected to moving loads such as high-speed trains. In recent years, the VBI system was introduced to further explore the possibility of identifying bridge frequencies in order to monitor the health of bridges via the use of passing vehicles. Among the models of test vehicles, the sprung mass vehicle model with a single-degree-of-freedom vehicle body is the most common adopted one due to its simplicity. Nevertheless, for a test vehicle moving over the uneven pavement, the pitching effect arising from the vertical and rotational movements of the vehicle actually influences the identification of bridge frequencies. As such, a rigid-mass vehicle model is proposed in this work to improve the sprung mass vehicle model by including both vertical and rotational deflections. The analytical solutions to the rigid-mass VBI system are derived to verify the proposed model, and the numerical examples are provided to investigate the dynamic behavior of the VBI system subjected to road irregularity.

PENGARUH PENAMBAHAN LIMBAH B3 PADA KUAT BETON MUTU K-175

Innovations of concrete growing quite rapidly now from reuse and reduce. materials unused or addition of additives in order to increase the quality of concrete include the addition of waste carbide (B3) is an effort to increase the element calcium is required in the reaction pozzolanic when mixed with SiO2 in the fly ash, Pozzolanic reaction is a reaction between calcium, silica or aluminates with water to form a strong and rigid mass similar to the cement hydration process. The mixing process carbide waste as a concrete material is done by laboratory testing in accordance with data from literature Indonesian Standard SK SNI and foreign standards are ASTM with variation of composition dregs carbide 5% as a substitute for cement material with a target quality of concrete K-175. From this result the composition of dregs addition of a mixture of dregs carbide 5% with an average compressive strength of 249,69 kg/cm2. That value greater than 1,77% of the normal concrete 245,36 kg/cm2.

Frequency equation using new set of fundamental solutions with application on the free vibration of Timoshenko beams with intermediate rigid or elastic span

Stepped beams are crucial power transmission components in many mechanical engineering systems. These beams may be dynamically analyzed using the stepped Timoshenko model or the rigid mass model. In this paper, a new set of fundamental solutions is derived in order to normalize the Timoshenko beam equation at the origin of the coordinates. This set of solutions is used to derive the frequency equation of both stepped and rigid mass models. The validity ranges of these models were investigated by comparing the modal frequency results of both models. In addition, selected cases were compared using mode shape analysis. Three different models with classical end conditions are considered through this work. These are free–free, pinned–pinned and clamped–free beam configurations. The numerical results of the current work show that increasing the intermediate diameter ratio and decreasing the length ratio of the rigid mass results in decreasing the percentage deviation between the rigid mass model results and the elastic model results.