Machine Vibration Research Articles

A Doppler Radar With a Sweeping Lock-in Demodulator for Machine Vibration Sensing

A Doppler Radar With a Sweeping Lock-in Demodulator for Machine Vibration Sensing

Identification of Comparative Collagen Fibril Associated Changes in Normal and Keratoconus Corneas using Vibrational Optical Coherence Tomography and Machine Learning

Vibrational Optical Coherence Tomography (VOCT) is a non-invasive technique that uses infrared light and audible sound to characterize tissues noninvasively.

A JOINT WEARABLE STRUCTURAL REINFORCING DEVICE FOR VIBRATION SUPPRESSION IN ROBOTIC MILLING

The structural vibration caused by poor rigidity is one of the main obstacles limiting the machining efficiency of robot milling. The existing vibration suppression strategies mainly focus on process parameter optimization, passive vibration absorption at the end and feedback control of joint motor. Although these strategies have certain vibration suppression effects, they cannot directly improve the structural rigidity of the robot. In this paper, a joint wearable structural reinforcing device (JWSRD) is proposed, which can achieve vibration suppression effect by improving the rigidity of the robot joints, fundamentally improve the processing ability of the robot, and ensure the processing stability. Firstly, the structure of the device is designed without affecting the processing flexibility. Secondly, the braking torque of the JWSRD is tested. Considering the feedback of joint braking torque, the vibration simulation model under harmonic excitation is derived. Finally, the offset mass experiments are carried out to verify the vibration suppression effect of the JWSRD. The results show that the JWSRD installed on the robot joint has the notable potential to enhance the structural rigidity, reduce the machining vibration and improve the machining efficiency.

Research of energy consumption of the vibration machine for surface restoration of working bodies of tillage units

Research of energy consumption of the vibration machine for surface restoration of working bodies of tillage units

Type series of resonant vibration equipment for concrete mixtures compaction and its main parameters calculation method

Introduction. Increasing the energy efficiency of vibration technology poses a number of challenges for its developers. A promising direction for reducing energy costs for driving vibration machines is the use of the resonance phenomenon. Due to the dynamic properties of the oscillatory system, it is possible to significantly reduce the power consumption of resonant vibration equipment, and in some cases, improve the quality of the products. The purpose of this article is to develop a standard range of resonant vibration equipment for compacting concrete mixtures and a methodology for calculating its main parameters.The object of research is the oscillatory system of a vibrating machine, consisting of two masses connected by the elastic and dissipative elements. In addition, the first mass is connected to a fixed base through elastic and dissipative elements.Materials and methods. The basic principles of theoretical mechanics, mathematical modelling and statistical processing of results were used in the research.Results. According to the research results, it was established that with an increase in the mass ratio of the oscillatory system, the dynamic coefficient decreases, and the width of the resonant zone increases. The regression equations are given. It has been established that with increasing rigidity of the working body, the dynamic coefficient decreases, and the horizontal section on the frequency response, the width of which does not change significantly, shifts to the region of higher frequencies. With an increase in the damping coefficient, the dynamic coefficient decreases, and the width of the resonant zone and the frequency range practically do not change. A wide range of nomenclature and masses of precast reinforced concrete justifies the development of a standard-size range of resonant vibration equipment. A standard range of light (up to 2 tons), medium (2-6 tons) and heavy (6-10 tons) types has been developed. Based on the analysis and generalization of research results, a method for calculating resonant vibration equipment for compacting concrete mixtures has been developed, which makes possible to increase its energy efficiency.

Kinematic Motion Modelling from Differential Inductive Oscillation Sensing for a Servomechanism and Electromechanical Devices and Applications

This paper presents mathematical modeling approach of an inductive sensor producing oscillating output of a given frequency representing displacement of a core moving in and out of a coil of known geometrical dimensions. The technique is hence used in characterizing the speed, acceleration and frequency of the proposed differential inductive transducer. This model uses a double coil arrangement with a freely movable iron core. This is made to oscillate freely thereby producing the proposed output for characterization of oscillating parameters. The application of this work finds utility in generating small amplitude signals from tiny force winds for the purpose of acquiring impulsive electrical signal from sources such as machine vibrations. Using an inductive coil sensing technique in a differential manner, physical parameters of speed, acceleration and displacement are translated into a signal with proportionate output frequency change. The results shown can be used for characterizing the materials and hence sensor with high sensitivity, linearity and responsiveness in harsh environmental condition is obtained.

A Novel Type of Pseudo-Decoupling Method for Two Degree-of-Freedom Piezoelectrically Driven Compliant Mechanisms Based on Elliptical Parameter Compensation.

At present, a large number of two-degree-of-freedom piezoelectrically driven compliant mechanisms (2-DOF PDCMs) have been widely adopted to construct various elliptical vibration machining (EVM) devices employed in precisely fabricating functional micro-structured surfaces on difficult-to-cut materials, which have broad applications in many significant fields like optical engineering and precision manufacturing. For a higher precision of conventional 2-DOF PDCMs on tracking elliptical trajectories, a novel type of pseudo-decoupling method is proposed based on phase difference compensation (PDC). With finite element analysis (FEA), the dependences of elliptical trajectory tracking precision on PDC angles will then be investigated for optimizing PDC angles under different elliptical parameters. As the modification of the PDC-based method, another type of pseudo-decoupling method will be improved based on elliptical parameter compensation (EPC) for much higher tracking precision, an amplification coefficient and a coupling coefficient will be introduced to mathematically construct the EPC-based model. A series of FEA simulations will also be conducted on a conventional 2-DOF PDCM to calculate the amplification and coupling coefficients as well as optimize the EPC parameters under four series of elliptical parameters. The tracking precision and operational feasibility of these two new pseudo-decoupling methods on four series of elliptical trajectories will be further analyzed and discussed in detail. Meanwhile, a conventional 2-DOF PDCM will be practically adopted to build an experimental system for investigating the pseudo-decoupling performances of an EPC-based method, the input and output displacements will be measured and collected to actually calculate the amplification coefficients and coupling coefficients, further inversely solving the actual input elliptical parameters with EPC. The error distances between the expected and experimental elliptical trajectories will also be calculated and discussed. Finally, several critical conclusions on this study will be briefly summarized.

Suppressing Milling Chatter of Thin-Walled Parts by Eddy Current Dampers

Machining vibrations often occur when working with thin-walled workpieces. One effective method to mitigate these vibrations is by using a damper, which can enhance machining accuracy, surface finish, and tool life. However, traditional contact dampers have a drawback in that they require direct contact with the workpiece, leading to friction, wear, increased cutting forces, and reduced machining accuracy. In contrast, electromagnetic eddy current dampers are noncontact dampers that can effectively suppress machining vibrations without the need for physical contact. In this study, a method to suppress machining vibrations in thin-walled workpieces using electromagnetic eddy current dampers is proposed. By establishing a theoretical model for the electromagnetic damper, the damping force and equivalent damping of the damper are determined. Subsequently, the impact of electromagnetic dampers on frequency response functions and machining vibrations are investigated through hammer impact tests. The results indicate that increasing the surface damper voltage and reducing the air gap both enhance the equivalent damping of the electromagnetic eddy current damper. Moreover, cutting experiments are conducted to analyze the surface roughness of thin-walled workpieces with and without dampers. The results demonstrate that the eddy current damper can effectively increase the equivalent damping and provide the necessary damping force to suppress machining chatter. Overall, the proposed method utilizing electromagnetic eddy current dampers presents a promising solution for suppressing machining vibrations in thin-walled workpieces.

Stochastic characterization of the dynamic response of a pile

The design of pile foundations subjected to large harmonic loads produced by machine vibrations is usually controlled by their service limit state. Verification of this condition under current design philosophy requires the estimation of the probability of failure. However, the deterministic nature of current design procedures does not facilitate such calculations. This paper presents a stochastic model for the dynamic pile response under harmonic loading considering the uncertainty in the mechanical parameters of the soil and the pile itself. The purpose of the model is to quantify the uncertainty in the pile response in terms of its impedance. A sensitivity analysis of the design parameters and stochastic variables is performed to quantify their impact on the uncertainty of the pile response. The effect of pile diameter and uncertainty of its properties, mean soil stiffness, and the selection of distribution models for the random variables are evaluated. Useful insights are gained into the stochastic behavior of the model and the characterization of the pile stiffness and damping components of the pile. This approach may provide a valuable first step towards the development of a comprehensive reliability analysis of this foundation type.

Effect of damping and rotor moment of inertia on stability of self-synchronization for two unbalanced rotors

The self-synchronization of rotors in a nonlinear system has both academic and practical importance because of its applicability as a source of excitation for vibratory machines. Although the characteristics of such self-synchronization can be clarified by analyzing the periodic solutions of the equations of motion, only self-synchronization corresponding to the stable periodic solution is realized in actual systems. The stability of the solution is thus one of the most important characteristics of self-synchronization. In this paper, to stabilize periodic solutions suitable for application to vibratory machines, the effects of the damping of the rigid body and the moment of inertia of the rotors on stability are examined using a system that consists of two unbalanced rotors installed in a rigid body. High-precision analysis conducted using the shooting method shows that it is possible to stabilize the instabilities caused by period-doubling and Hopf bifurcations while keeping other characteristics, such as the synchronous frequency and the rigid body amplitude, mostly unchanged. The findings of this study can serve as a guide to extending the range of stable periodic solutions and are thus expected to be useful in the design of systems that utilize the self-synchronization of rotors.

Experimental Investigation on Axial Ultrasonic Vibration Assisted Milling of Cr12MoV

The conventional milling process is difficult due to the high strength and hardness of Cr12MoV, which can cause the rapid tool wear, premature failure,and poor milling quality of work platform. The ultrasonic vibration machining technology has been founded to be effective in the milling process of hard-to-cut materials like die tool steel and nickel alloys. The ultrasonic vibration assisted milling (UVM) technology is carried out the axial milling of Cr12MoV in this paper, and the average impact force Fi is influenced by the vibration amplitude A, the vibration frequency f, and equivalent mass of the vibrating part M. The mean value of cutting force Fx, Fy, and Fz decreases by 25%, 15.04%, and 17.46%, respectively. With the increase of vibration amplitudes, the value of surface roughness firstly decrease and then increase, and it is obviously lower than conventional milling. The experimental results demonstrated that the UVM technology is a feasible method for the low cutting force and high quality process of cutting Cr12MoV.

Development of Deproteinized Natural Rubber Latex Foam for Seat Cushions

In the transportation industry, seat cushions are crucial since they are directly responsible for the comfort and safety of the occupant. In this study, recently developed deproteinized natural rubber (DPNR) latex foam is used to make seat cushions for the first time through the Dunlop batch foaming process. A CONFORMat™ pressure sensor system and a mannequin were used to investigate the pressure-relief performance of seat cushions made from DPNR latex foam. Flexible polyurethane (PU) and memory foam (PM) were used as a comparison. The study found that DPNR latex foam has a lower peak pressure value than PU foam, comparable to PM foam. The vibration transmissibility properties of the foam samples were examined using a UCON VT-9008 vibration machine according to ASTM D3580-95. DPNR latex foam has the lowest attenuation frequency, which could be related to the low stiffness and high resilience properties of the material. Overall, the findings suggest that the novel DPNR latex foam has both excellent pressure-relief and vibration isolation performance, making it an ideal candidate material for seat cushions intended for the transportation industry.

A-BEBLID: A Hybrid Image Registration Method for Lithium-Ion Battery Cover Screen Printing

To address the problem of miss- and false-detection during quality inspection of lithium-ion battery cover screen printing (LBCSP), we propose a hybrid image registration method using a point-based feature extraction algorithm and nonlinear-scale space construction. Our proposed method integrates the AKAZE algorithm with the BEBLID descriptor, and is therefore named A-BEBLID. Facing the challenge of the inevitable offset caused by machine vibration during production, we combine a nonlinear diffusion filter with a local image descriptor to extract features from images, and then use the GMS algorithm to remove the wrong matching pairs. We tested the method on a dataset we created using images taken from actual lithium-ion battery production lines, named LBCSP. We also evaluated the method on the public HPatches dataset. The average precision achieved by A-BEBLID on the LBCSP dataset is 89% (threshold: 2 pixels), with a localization error of 1.11 pixels, while on the HPatches dataset, the average precision is 73% (threshold: 2 pixels), with a localization error of 1.52 pixels. Comprehensive experimental results also showed that the proposed A-BEBLID can outperform other approaches being compared to. The method can be further applied to other industry scenarios with similar image registration requirements.

Zirconia CAD/CAM machining vibrations related to zirconia blank shape and initial digital nesting.

To evaluate CAD/CAM milling vibrations related to zirconia disk design, framework, and location of digital crown nesting during zirconia soft milling. In the present in vitro study, 25 round zirconia disks of 98 mm (R group) and 15 D-shaped zirconia disks of 71 mm (D group) were placed in a 5-axis CAD/CAM milling unit. The R group had 3 crown milling sites (n = 75) and the D group had 2 crown milling sites (n = 30). In the R group, site A was located 57 mm, site B was 92 mm, and site C was 123 mm from the machine holder attachment. In the D group, site A was 57 mm and site C was 123 mm from the machine holder attachment. A vibration meter (VB-8200; Lutron) was connected to the disk holder, and data (mm/second) were collected during the milling process at the different nesting locations. One-way ANOVA with post-hoc tests and Bonferroni correction for multiple tests were used to compare the groups (α = 0.05). In the R group, site C exhibited the highest mean vibration values compared with site A (P = 0.001). The first and second cutting tools (2.5 and 1 mm) exhibited statistically significant differences between the D and R groups at milling sites A and C (P < 0.001 and P = 0.003, respectively). Milling vibration increased as the distance between the machine holder arm and a digitally nested site increased. Round zirconia disks induced higher vibration values compared with D-shaped disks.

A methodological approach for detecting multiple faults in wind turbine blades based on vibration signals and machine learning

Abstract Wind turbines generate clean and renewable energy for the international market. The most ‎‎important aspect of wind turbine maintenance is reducing failures, downtime, and operating and maintenance expenses. ‎This study aims to detect multiple faults exhibited by wind turbine blades; failures such as cracks (tip crack, mid-span crack, and crack ‎near the root) were observed in the blades at different locations. The research suggests a new approach, incorporating vibration signals and machine learning techniques to identify various failures in wind turbine blades. The technology of ranking features such as ReliefF algorithms, chi-squares, and information gains was adopted to discuss a method framework to diagnose several problems in wind turbine blades, such as cracks in different locations. The k-nearest neighbors (KNNs), support vector machines, and random forests are used to classify data based on measured vibration signals. The eight main time-domain features are calculated from the vibration signals. The proposed methodology was validated using four databases. The results showed good classification accuracy in four databases, with at least three non-conventional features in each database’s top nine features of the three classification techniques. The results also showed that when the ReliefF selection algorithm is applied with the KNN classification algorithm, it generates the highest classification accuracy under all failure conditions, and the value is 97%. Finally, the performance of the proposed classification model is compared with other machine learning classification models, and a promising result is obtained. ‎

Development and investigation of the vibration-driven in-pipe robot

Vibratory machines are widely used for monitoring and cleaning various tubes, pipelines, intestines, vessels, etc. The problems of ensuring the prescribed dynamic characteristics of such equipment and simultaneous optimizing the power consumption are currently being solved by numerous researchers. The main purpose of this study is to investigate the locomotion characteristics of the novel vibration-driven design of the pipeline inspecting and cleaning robot actuated by an electromagnetic exciter and equipped with the size-adapting and self-locking mechanisms. The research methodology consists of four main stages: an overview of the enhanced robot design; constructing its dynamic diagram and deriving the differential equations of motion; performing the numerical modeling with the help of the Mathematica software and studying the robot’s kinematic characteristics; conducting virtual experiments by computer simulation of the robot motion in the SolidWorks software. The research results present the time dependencies of the robot’s displacement, speed, and acceleration at different working regimes (excitation forces, disturbing frequencies, etc.). The novelty of the performed investigations consists in substantiating the efficient locomotion conditions of the enhanced vibration-driven in-pipe robot. Further investigations can be focused on developing the full-scale laboratory prototype of the robot and conducting experimental studies. The obtained research results can be interesting for engineers and scientists who deal with similar vibration-driven pipeline robots.

Exposure-response relation for vibration-induced white finger: effect of different methods for predicting prevalence.

A pooled analysis of vibration-induced white finger (VWF) in population groups of workers has been performed using the results of a published meta-analysis as source material (Nilsson T, Wahlström J, Burström L. Hand-arm vibration and the risk of vascular and neurological diseases a systematic review and meta-analysis. PLoS One. 2017:12(7):e0180795. https://doi.org/10.1371/journal.pone.0180795). The methods of data selection follow those described previously by Scholz et al. (in Scholz MF, Brammer AJ, Marburg S. Exposure-response relation for vibration-induced white finger: inferences from a published meta-analysis of population groups. Int Arch Occup Environ Health. 2023a:96(5):757-770. https://doi.org/10.1007/s00420-023-01965-w) to enable comparison with the results of the present work. The analyzed epidemiologic studies contain different prevalences of VWF observed after different durations of employment involving exposure to the vibration of power tools and machines. These prevalences are transformed to 10% prevalence by either linear or polynomial (i.e. "S"-shaped curvilinear) interpolation in order to compare with the exposure-response relation contained in the relevant international standard (ISO 5349-1:2001). An exposure-response relation is constructed using regression analysis for the time (in years) to reach 10% prevalence in a population group, when subjected to a daily vibration exposure calculated according to the procedures specified in the standard, A(8). Good fits to the data are obtained when polynomial and linear prevalence interpolation is used. The 95-percentile confidence intervals (CIs) of the exposure-response relation predicted by polynomial prevalence interpolation lie at somewhat larger lifetime exposures than those obtained by linear prevalence interpolation. Uncertainty in the precision of polynomial prevalence interpolation is mitigated by giving equal weight to linear interpolation when interpreting the results. When the 95-percentile CIs of the exposure-response models obtained by linear and polynomial prevalence interpolation are used to define the most probable exposure-response relation, the resulting common range of values includes the ISO exposure-response relation. It is proposed that an exposure-response relation for the onset of VWF derived from a regression analysis is specified in terms of the lower limit of its CI. Hence, when exposure measures are constructed according to the ISO standard and equal weight is given to the results of the 2 methods for interpolating prevalence described here, the ISO exposure-response relation would be considered to provide a conservative estimate for a 10% prevalence of VWF to develop in a population group, at least for A(8) > 4 m/s2. It thus remains the relation to use for assessing exposure to hand-transmitted vibration in the workplace. Additional research is needed to resolve inconsistencies in the ISO method for calculating daily exposures.

Surface fractures in pre-crystallized and crystallized zirconia-containing lithium silicate glass-ceramics generated in ultrasonic vibration-assisted machining

Machining-induced surface fractures in ceramic restorations is a long-standing problem in dentistry, affecting the restorations’ functionality and reliability. This study approached a novel ultrasonic vibration-assisted machining technique to zirconia-containing lithium silicate glass-ceramics (ZLS) and characterized its induced surface fracture topographies and morphologies to understand the microstructure-property-processing relations. The materials were processed using a digitally controlled ultrasonic milling machine at a harmonic vibration frequency with different amplitudes. Machining-induced surface fracture topographies were measured with a 3D white light optical profilometer using the arithmetic mean, peak and valley, and maximum heights, as well as the kurtosis and skewness height distributions, and the texture aspect ratios. Fracture morphologies were analysed using scanning electron microscopy (SEM). The surface fracture topographies were significantly dependent on the material microstructure, the mechanical properties, and the ultrasonic machining vibration amplitudes. Larger scale fractures with higher arithmetic mean, peak and valley heights, and kurtosis and skewness height distributions were induced in higher brittleness indexed pre-crystallized ZLS than lower indexed crystallized ZLS by conventional machining. Conchoidal fractures occurred in pre-crystallized ZLS while microcracks were found in crystallized state although brittle fractures mixed with localized ductile flow deformations dominated all machined ZLS surfaces. Ultrasonic machining at an ideal vibration amplitude resulted in more ductile removal, reducing fractured-induced peaks and valleys for both materials than conventional processing. This research demonstrates the microstructure-property-processing interdependence for ZLS materials and the novel machining technique to be superior to current processing, reducing fractures in the materials and potentially advancing dental CAD/CAM techniques.

Developing a novel ultrasonic atomization-based cutting fluid spray system and evaluating its performance during milling processes

Cutting fluid has been widespread in the metal cutting industry due to its cooling and lubrication properties. However, the excessive application of cutting fluids can lead to significant environmental issues and raise machining costs. Recently, the ultrasonic atomization-based cutting fluid (UACF) spray using minimum quantity has shown superior cooling and lubrication performance during machining processes, while the precise management of UACF spray and its influence on machining performance requires further comprehension. In this case, this paper developed a novel ultrasonic atomization-based cutting fluid (UACF) spray system, featuring a specialized nozzle unit that included an internal droplet nozzle and an external gas nozzle. Subsequently, the dynamics of droplet impingement on a rotated surface were analyzed, and the spray characteristic parameters were investigated. Then, comparative milling experiments were conducted under different cooling conditions, including dry cutting, flood cooling, high-pressure air cooling, and UACF. The influence of these cooling conditions on machining performance was investigated, in terms of cutting force, temperature, surface roughness, and chip morphology. The results obtained indicate that the critical velocity of droplet spreading was dependent on the cutting fluid properties, ultrasonic frequency, and velocity of the rotated surface. The droplets generated by ultrasonic atomization follow a Gaussian distribution. Flood cooling and UACF exhibit similar effects in reducing cutting force, temperature, and surface roughness due to the efficient penetration of liquid film into tool-workpiece interfaces. Additionally, UACF can significantly reduce the consumption of cutting fluid by up to 98.5 % compared to flood cooling. The effective cooling and lubrication in UACF can improve the surface quality and suppress machining vibration. Moreover, the appropriate droplet velocity can ensure the formation of a thin film on the tool surface, thereby enhancing cooling and lubrication performance in the UACF process.

Detection of hollow heart disorder in watermelons using vibrational test and machine learning

The presence of internal voids in watermelons has an impact on the costs of producers and on consumer confidence. Various studies have shown that the vibrational parameters of the fruit are related to maturity, quality and the existence of internal defects. A method for the detection of internal voids in seedless watermelons based on vibrational parameters obtained in impact hammer tests and machine learning is presented. After a statistical study of the test results, the frequency of the first peak of the vibrational response and the density of the watermelon are selected as predictors to be used in the classification algorithms. The accuracy of detecting hollow watermelons increases if firmness estimator is introduced as a predictor. Probabilities of success above 89% in the detection of internal voids have been achieved using different classification algorithm.