Review on Vibration Analysis of Cracked Cantilever Beam

A unique feature of fiber-reinforced composite materials is that it allows structural tailoring for favorable dynamic performance, due to the directional nature of composite materials. Because of the directed character, material coupling occurs, resulting in coupled vibration modes and complicating dynamic analysis. A transverse triangular force impulse modulated by a harmonic motion excites the beam. For the substance of the beam, the Kelvin–Voigt model is employed. The fractured beam is represented by two sub-beams linked by a massless elastic rotating spring. The beams are designed to function in wet environments, which cause rusting. Corrosion causes cracks to form in beams, altering their inherent frequency and mode shape. The present paper examines the different investigations that have been done to investigate the impact of fracture on the dynamic properties of beams. The researchers provided a comprehensive evaluation of the impact of crack design factors (crack depth, crack location) on cantilever beam transverse and torsional frequencies. It is also given the analytical approach, numerical method, and experimental methods for studying the impact of fracture on vibration characteristics. Keywords: Cantilever Beam, Crack dimensions, Damage, Kelvin–Voigt model.

On the Lightweight Truss Structure for the Trash Can-Handling Robot

With the rapid development of cities, the automated and intelligent garbage transportation has become an important direction for technological innovation of sanitation vehicles. In this paper, a vehicle-mounted trash can-handling robot is proposed. In order to reduce the cost of the robot and increase the loading capacity of the intelligent sanitation vehicles, a lightweight design method is proposed for the truss structure of the robot. Firstly, the parameters of the robot that are related to the load are optimized by multi-objective parameter optimization based on particle swarm optimization. Then, the material distribution of the truss structure is optimized by topology optimization under multiple load cases. Finally, the thickness of the truss structure parts is optimized by discrete optimization under multiple load cases. The optimization results show that the mass of the truss structure is reduced by 8.72%, the inherent frequency is increased by 61.08%, and the maximum stress is reduced by 10.98%. The optimization results achieve the goal of performance optimization of the intelligent sanitation vehicle, and prove the feasibility of the proposed lightweight design method.

Cost-Effective and Ultraportable Smartphone-Based Vision System for Structural Deflection Monitoring

This work demonstrates the viability of using a smartphone-based vision system to monitor the deflection of engineering structures subjected to external loadings. The video images of a test structure recorded by a smartphone camera are processed using the state-of-the-art subset-based digital image correlation (DIC) algorithm to extract the vertical image displacement of discrete calculation points defined on the test object. The measured vertical image displacement can be converted to deflection (vertical displacement) by easy-to-implement scaling factor determination approaches. For accuracy validation, laboratory experiments using a cantilever beam subjected to external loadings were performed. The deflection and inherent frequency of the test cantilever beam measured by the proposed smartphone-based vision system were compared with those measured by conventional dial gauges and a dynamic strain gauge. The relative errors were estimated as 1% and 0.15% for deflection and inherent frequency, respectively. Outdoor real bridge deflection monitoring tests were also carried out on an overpass with subway passing by, and the measured deflection-time curves agree well with actual situations. The cost-effective, ultraportable, and easy-to-use smartphone-based vision system not only greatly decreases the hardware investment and complexity in deflection measurement system construction, but also increases the convenience and efficiency of deflection monitoring of engineering structures.

Experimental investigation on nozzle diameter of vortex gripper

Purpose Vortex grippers use tangential nozzles to form vortex flow and are able to grip a workpiece without any physical contact, thus avoiding any unintentional workpiece damage. This study aims to use experimental and theoretical methods to investigate the effects of nozzle diameter on the performance. Design/methodology/approach First, various suction force-distance curves were developed to analyze the effects of nozzle diameter on the maximum suction force. This study determines the tangential velocity distribution on the workpiece surface by substituting the experimental pressure distribution data into simplified Navier-Stokes equations and then used these equations to analyze the effects on the flow field. Subsequent theoretical analysis of the distribution of pressure and circumferential velocity further validated the experimental results. Next, by rearranging these relationships, the study considered the effects of nozzle diameter on the inherent vortex gripper characteristics. In addition, this study developed various suction force-energy consumption curves to analyze the effects of nozzle diameter. Findings The results of this study indicated that the vortex gripper’s circumferential velocity and maximum suction force decrease with increasing nozzle diameter. Nozzle diameter did not significantly affect the inherent frequency of the vortex gripper-workpiece inertial system or the corresponding suspension stability of the workpiece. However, an increase in nozzle diameter did effectively increase the vortex gripper’s suspension region. Finally, as the nozzle diameter increased, the energy required to achieve the same maximum suction force decreased. Originality/value This study’s findings can enable optimization of nozzle design in emerging vortex gripper designs and facilitate informed selection among existing vortex grippers.

Effect of Adhesive Debonding on the Performance of Piezoelectric Sensors in Structural Health Monitoring Systems

Piezoelectric (PZT) ceramic elements are often subjected to complex loads during in- service lifetime in structural health monitoring (SHM) systems, and debonding of both excitation actuators and receiving sensors have a negative effect on the monitoring signals. A first systematic investigation of debonding behaviors by considering actuators and sensors simultaneously was performed in this paper. The debonding areas of actuators were set in different percentage range from 0% to 70%, and sensors in 0%, 20%, 40% and 60%. The signal-based monitoring method was used to extract the characteristic parameters of both the amplitudes and phases of received signals. Experimental results revealed that as the debonding areas of the actuators increase, the normalized amplitude appears a quick decrease before 35% debonding area of actuators and then a slow rise until 60% of debonding reached. This may be explained that the 35% debonding turning point correspond to the coincidence of the excitation frequencies of peripheral actuators with the inherent frequency of the central piezoelectric sensor, and the 60% be the result of the maximum ability of piezoelectric sensor. The degrees of debonding of actuators and sensors also have significant influence on the phase angle offset, with large debonding of actuators increases the phase offset sharply. The research work may provide useful information for practical monitoring of SHM systems.

Numerical Investigation on Unsteady Separation Flow Control in an Axial Compressor Using Detached-Eddy Simulation

Unsteady excitation has proved its effectiveness in separation flow control and has been extensively studied. It is observed that disordered shedding vortices in compressors can be controlled by unsteady excitation, especially when the excitation frequency coincides with the frequency of the shedding vortex. Furthermore, former experimental results indicated that unsteady excitation at other frequencies also had an impact on the structure of shedding vortices. To investigate the impact of excitation frequency on vortex shedding structure, the Detached-Eddy Simulation (DES) method was applied in the simulation of shedding vortex structure under unsteady excitations at different frequencies in an axial compressor. Effectiveness of the DES method was proved by comparison with URANS results. The simulation results showed a good agreement with the former experiment. The numerical results indicated that the separation flow can be partly controlled when the excitation frequency coincided with the unsteady flow inherent frequency. It showed an increase in stage performance under the less-studied separation flow control by excitation at a certain frequency of pressure side shedding vortex. Compared with other frequencies of shedding vortices, the frequency of pressure side shedding vortex was less sensitive to mass-flow variation. Therefore, it has potential for easier application on flow control in industrial compressors.

Modeling and Studying Acceleration-Induced Effects of Piezoelectric Pressure Sensors Using System Identification Theory

Transient pressure testing is often accompanied by shock acceleration. Aiming at the acceleration-induced effects of pressure sensors, a dynamic compensation method combining empirical mode decomposition (EMD) with system identification theory (SIT) is proposed in this paper. This method is more effective at reducing the error of the acceleration-induced effects without affecting the sensor’s sensitivity and inherent frequency. The principle and theoretical basis of acceleration-induced effects is analyzed, and the static and dynamic acceleration-induced effects on the quartz crystal of a piezoelectric pressure sensor are performed. An acceleration-induced effects dynamic calibration system is built using a Machete hammer, which generates acceleration signals with larger amplitude and narrower pulse width, and an autoregressive exogenous (ARX)mathematical model of acceleration-induced effects is obtained using empirical mode decomposition-system identification theory (EMD-SIT). A digital compensation filter for acceleration-induced effects is designed on the basis of this model. Experimental results explain that the acceleration-induced effects of the pressure sensor were less than 11% after using the digital compensation filter. A series of test data verify the accuracy, reliability, and generality of the model.

Dynamic Reliability Analysis of Rotary Steering Drilling System

Vibration and high shock are major factors in the failure of downhole tools. It is important to study the causes of vibration and shock formation to prevent failure of the drillstring and bottom hole assembly (BHA). At present, it is generally recognized that the vibration of drillstring is the main reason for the failure, especially the lateral vibration. In this paper, the bottom tool of Rotary Steering Drilling System (RSS) calculation model was established based on the secondary development of ABAQUS software. Starting from the initial configuration of drilling tool, considering the contact impact of drilling tool and borehole wall, the dynamic excitation of guide mechanism and the drilling pressure, torque, rotational speed, gravity, buoyancy, drilling fluid damping. The dynamic characteristics of the inherent frequency and dynamic stress of the bottom hole assembly (BHA) were calculated and analyzed, and risk assessment method based on the quantitative vibration intensity was established. The reliability of typical drilling tool is evaluated, which provides a reference for the optimization design of BHA of Rotary Steering Drilling System.

Research on measurement of film thickness of lithium battery by laser in unknown noise environment

Factors affecting the on-line detecting thickness of lithium battery pole by laser sensor are mainly the accuracy of the sensor, the inherent frequency and dynamic error of the C scanning mechanism. Improved highly redundant optimal atomic parameters for the thickness of lithium battery pole piece under different circumstances are obtained. The best atomic parameters are extracted in the training phase to construct the sub-optimal atomic function. The results show that, compared with wavelet algorithm and conventional sparse decomposition algorithm, the improved sparse decomposition algorithm has better denoising performance under the condition of lacking prior knowledge.