Vibration Cycle Research Articles

Heat effect on the material removal in the machining of fibre-reinforced polymer composites

Abstract This paper aims to investigate the heat effect on the material removal mechanisms in the machining of fibre-reinforced polymer (FRP) composites. A coupled thermal-mechanical microstructured-model was established to investigate the cutting processes both with and without ultrasonic tool vibration. A systematic cutting experiment was also conducted to assess the reliability of the theoretical predictions. It was found that the cutting temperature influences significantly the material removal process, but has a little effect on the cutting forces. The fibres and matrix deform and fracture in brittle modes when the temperature is below the glass transition point of the matrix material, Tg. The matrix material becomes softer and its deformation turns to be ductile when the temperature exceeds the glass transition point. This consequently brings about significant deformation and fracture of fibres in the subsurface. During cutting, with increasing the cutting time, the cutting-induced heating zone spreads quite ahead of the cutting edge. However, with the assist of ultrasonic vibration, the high-frequency motion of the cutting tip dramatically reduces the tool-work interaction time at each vibration cycle; thereby slows down the heat generation and temperature rise. The high-frequency motion also leads to rapid chip removal and reduces temperature rising rate and heat accumulation. As a result, both the tool and workpiece temperature can be maintained to be below the Tg of the matrix material. Nevertheless, the advantage of the vibration-assisted process becomes trivial once the feed rate is larger than its maximum vibration speed.

A Friction Control Strategy for Shock Isolation

A control strategy is presented incorporating friction which can be adapted within a cycle of vibration. During base shock input, the friction is switched on and off based on specified response parameters. The predicted response of a semi active system is compared with that of a passive isolation system. The strategy is shown to produce an improved displacement reduction and a smaller maximum displacement compared to the base input; a result which cannot be obtained with a typical passive system. The models are then validated using an experimental rig, representing a two degree of freedom system, having an electromagnet to switch on and off friction via the control logic. Good agreement is obtained in addition to identifying optimum parameter choices.

Large angle flexure pivot development for future science payloads for space applications

An innovative design of a Large Angle Flexure Pivot (LAFP) is described. It combines the advantages of flexure mechanisms while surpassing one of their few flaws, small displacement strokes. The LAFP design exceeds these angular limitations to reach a deflection of 180° (±90°). The centre shifts laterally by less than ±35 μm throughout the full rotation range. The LAFP is meant to be mounted in pairs, coaxially and with the payload between them. The intended application of the LAFP is to angularly guide an optical component in a space environment for future science missions operating in a cryogenic environment. A dedicated performance test bench was developed and manufactured to test the pivot characteristics notably the lateral shift using Eddy current sensors. The test bench incorporates a representative dummy payload for mass and inertia. Extensive FEM analysis has been performed to validate the design at component level and further analysis with the pivots mounted with a representative payload on a test bench for random vibration, shock and thermal cycling environment. The second test bench for the vibration and shock tests has been manufactured incorporating a simplified launch locking device. The performance tests have confirmed a lateral shift of less than ±35 μm over an angular range of ±90°. The pivots have been successfully tested and survived vibration loads for high level sine at 24 g and random vibration at 12 grms in all three directions.

Two Approaches to the Problem of High-cycle Fatigue of Materials and Structures

Creation of new types of materials and development of new methods aimed at extending the lifetime of structures are two interconnected approaches to solve the problem of metallic structures fatigue. The paper considers a method for estimating the efficiency of damping implemented in metallic structures by means of energy-intensive materials. The results of comparative calculation are given on the ultimate number of transverse vibration cycles in bridge girders. The calculation uses a linear hypothesis of fatigue-caused damage summation and a model of cyclic material degradation. Notable increase of the vibration decrement for foam-filled metallic structures is predicted, with the lifetime of products lengthening as a result.

Mechanical-activated digital microfluidics with gradient surface wettability.

This paper reports a simple yet effective droplet manipulation approach that can displace aqueous droplets over a long distance within the working plane. Repeated patterns with surface gradient wettability were created on a super-hydrophobic surface by laser irradiation. Aqueous droplets as small as 2 μL are moved on the patterns over a long distance under in-plane symmetric cyclic vibration. Typical droplet manipulation actions including droplet movement along a pre-determined trajectory, droplet mixing, and selective movement of multiple droplets were successfully demonstrated. Biochemical detection using this approach was demonstrated via a bicinchoninic acid (BCA) assay. This approach allows for long-distance droplet movement and simultaneous manipulation of multiple droplets without sacrificing the manipulation efficiency or increasing the cross-contamination risk. The device can be fabricated outside cleanrooms and operated without special equipment. It provides a solid technical basis for developing the next generation of affordable open channel microfluidic devices for various applications.

Kinematic model for simulating mucosal wave phenomena on vocal folds

Mucosal waves have been found to be important for evaluating vocal fold vibrations in laryngological practice. While they are routinely evaluated visually, the knowledge on the physical phenomena related to mucosal wave propagation is limited. Kymographic imaging, in particular, reveals various mucosal wave features that deserve more understanding in order to advance functional diagnostics of voice disorders. Here, a kinematic model is presented which simulates mucosal waves on human vocal folds. The vocal fold geometry is based on a parametrically adjustable M5 model. A kinematic rule is used for simulating the propagation of the mucosal wave from the bottom of the vocal folds upwards and laterally over the upper vocal fold surface. The model maps the changes of the coronal shape of the vocal folds through vibration cycles. The vibration characteristics including the mucosal wave movements are then visualized using a synthetic kymogram graphically obtained through a local illumination method. The model can serve as an educational and research tool for studying the mucosal wave features and their appearance in laryngeal kymographic images.

Intermittent failure in electrical interconnection of avionics system

The intermittent failure is one of the causes of No-Fault-Found (NFF). Intermittent failure in electrical interconnections of avionics is intensively investigated. An avionics system vulnerable to the intermittent failure is identified and its mockup is constructed. Vibration and thermal cycling tests are conducted to generate intermittent failures in the interconnections of the mockup. Intermittent failures occur after the accelerated thermal cycling test in vibration environment. Failure analysis reveals a line of crack at the interconnection. The mechanism for the crack generation is explained by a numerical simulation. A hypothesis is suggested for the explanation of the occurrence of intermittent failure from the crack. A combined vibration and temperature test is conducted to verify the hypothesis. The test results follow the expectation of the hypothesis.

Vibration Tribology Research of Fish Head and Fishtail Directional Equipment for Larimichthys Crocea

The fish head and fishtail directional sorting of larimichthys crocea is a very important pretreatment auxiliary processes in automated fish processing, The theory of fish head and fish tail directional equipment for larimichthys crocea is studied in this research. Analysed the two transient conditions in a vibration cycle, they were intermittent relative sliding condition and scceleration along the plane. Through the analysis of the movement of larimichthys crocea, effective dynamic friction coefficient is calculated. Finally, according to the principle, the fish head and fishtail directional equipment for larimichthys crocea was developed.

Improved Methods Aid Understanding and Mitigation of Stick/Slip Torsional Vibrations

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 189673, “Improved Methods To Understand and Mitigate Stick/Slip Torsional Vibrations,” by J.R. Bailey, SPE, G.S. Payette, SPE, and L. Wang, SPE, ExxonMobil, prepared for the 2018 IADC/SPE Drilling Technology Conference and Exhibition, Fort Worth, Texas, USA, 6–8 March. The paper has not been peer reviewed. Historically, prediction of stick/slip vibrations in advance of drilling has been fraught with challenges. Although the factors influencing stick/slip, and the directional changes required to mitigate it, are known, a need exists for a simple method to determine quantitatively the degree of dysfunction and the effects of redesign parameters. This paper will show how stick/slip vibration distributions can be used to guide drillstring and parameter redesign to mitigate stick/slip in the next well. Background Torsional vibrations, also known as stick/slip, occur as the rotational speed of the bit and drillstring vary because of stiffness, inertia, and torsional friction interactions. In some wells, these torsional/rotational fluctuations are not severe and may not reach full stick/slip, which occurs when the bit comes to a full stop in the torsional vibration cycle. The drilling data obtained in the drilling of a well are displayed typically as time or depth tracks, with different parameters shown on the same or adjacent tracks over the corresponding time or depth interval. Although of interest, this display of data is limited. It does not provide a direct indication of the amount of dysfunction present over the duration of the interval. A histogram is a particularly useful display of the distribution of data values. In the case of stick/slip vibrations, the torsional-severity estimate (TSE) is a measure of proximity to full stick/slip. A TSE value of 0.0 represents no torsional vibrations, where the entire drillstring is turning at a constant angular velocity. A TSE of 1.0 represents full stick/slip, in which the rotary speed at the surface is constant but the bit speed varies sinusoidally between zero and twice the surface rotary speed. Values of TSE greater than 1.0 indicate time intervals in which the bit comes to a complete stop and then accelerates to more than twice the surface rotational speed. The most severe cases may even involve negative rotation of the bit. Analytical tools that help assess the degree of torsional vibrations can be useful, especially in those instances where known remediation techniques are not available or may be costly. A variety of methods exists to address torsional vibration problems, and the most-cost-effective method may be the method of choice. The authors are not aware of simple analytical methods that can provide quantitative evaluation to address the following: How will the stick/slip problem change if the drillstring design is modified? How will stick/slip change if the operating parameters are modified? The bit-design parameters may be varied to increase or decrease bit torque. How will changes to the bit friction factor affect stick/slip vibrations in a certain application?

Sealing pipe top enhancing transportation of particulate solids inside a vertically vibrating pipe

Particles can move against gravity inside a vibrating tube inserted in a static granular bed. This offers a new approach for transporting bulk material. In this work, we demonstrate a method to enhance the conveying of powder by sealing the tube top. With the same vibration conditions, a comparison of particle motion in an opened tube and closed top (sealed) pipe is made. Compared to an un-sealed pipe, particle upward motion within a sealed pipe is improved. With low vibration strength, only particles in the sealed tube can ascend. With increasing vibration strength, particles can climb in both tubes while particles in sealed pipe move faster and higher. The enhancement effect works well for particles of smaller size (d < 1 mm), and the positive effect becomes weaker with an increase in particle diameter. In a sealed tube, the final height of the granular column increases as the tube length increases while the growth velocity is reduced. Particle conveying in sealed tube shows less dependence on tube diameter compared to an un-sealed tube. Sealing the tube top introduces air pressure difference during each vibration cycle, which induces an additional upward drag force on the particles in the tube. The drag force becomes significant compared to other relevant forces for small diameter particles at high levels of vibration.

Theoretical 3D Model of Thermoelastic Damping in Laminated Rectangular Plate Resonators

Thermoelastic damping (TED) can lead to energy loss in microscale resonators, which is an intrinsic mechanism. To minimize the energy loss, it is required to determine the TED of resonators. Laminated plate resonators are commonly used in practice. However, existing researches on TED of the laminated resonators use mainly the one-dimensional (1D) heat conduction model, as the 3D governing equation is complicated, which cannot show the influences of boundary conditions along the supporting edges. In this paper, the governing equation of thermoelastic problems with 3D heat conduction was established for the out-of-plane vibration of the laminated rectangular plate. The analytical expression of the TED was derived using its physical meaning, namely, the ratio of the energy dissipated to the total elastic strain energy stored per cycle of vibration. It was found that the size and shape of the plate affect crucially the TED. The values of TED for higher-order vibration modes were also evaluated. Most importantly, the influences of supporting conditions and heat conduction conditions along the four edges were studied, which is the first report for laminated plates. The present approach can provide guidance for the design of high-quality bilayered resonators.

Failure study of Sn37Pb PBGA solder joints using temperature cycling, random vibration and combined temperature cycling and random vibration tests

In this paper, the tin-lead (Sn-37wt%Pb) eutectic solder joints of plastic ball grid array (PBGA) assemblies are tested using temperature cycling, random vibrations, and combined temperature cycling and vibration loading conditions. The fatigue lives, failure modes for the solder joints and the typical locations of the failed solder joints for single-variable loading and combined loading conditions are compared and analyzed. The results show much earlier solder joint failure for combined loading than that for either temperature cycling or pure vibration loading at room temperature. The primary failure mode is cracking within the bulk solder under temperature cycling, whereas the crack propagation path is along the intermetallic compound (IMC) layer for vibration loading. The solder joints subjected to combined loading exhibit both types of failure modes observed for temperature cycling and vibration loading; in addition, cracking through the IMC and the bulk solder is observed in the combined test. For temperature cycling and vibration loading, the components in the central region of the printed circuit board (PCB) have more failed solder joints than other components, whereas for combined loading, the number of failed solder joints in the components in different locations of the PCB is approximately the same.

Survey for Transition of Normal Reaction

Transition of reaction is a short-lived unstable molecule in a reaction which is formed in between the reaction when reactants change into products. Whereas, transition state is just the state before formation of new molecule (involves breaking of bonds of reactants and formation of new ones) Transition of reaction differs from a transition state in that the intermediate has a discrete lifetime (be it a few nanoseconds or many days), whereas a transition state lasts for just one bond vibration cycle. Intermediates may be unstable molecules (in which case they are called reactive intermediates) or highly stable molecules. The difference between them can be better described through the energy profile diagram.

Does vibration superimposed on low-level isometric contraction alter motor unit recruitment strategy?

Objective. Beneficial effects, including improved muscle strength and power performance, have been observed during vibration exercise (VE) and partially ascribed to a specific reflex mechanism referred to as Tonic vibration reflex (TVR). TVR involves motor unit (MU) activation synchronized and un-synchronized with the vibration cycle; this suggests VE to alter the temporal MU recruitment strategy. However, the effects of VE on MU recruitment remain poorly understood. This study aims to elucidate the influence of VE on MU recruitment indirectly, by investigating the effects of low-intensity VE on muscle activation. Approach. Twenty volunteers performed isometric contractions on the biceps brachii of the right arm at a baseline (low) force equal to 30% of the maximum voluntary contraction without vibration (control) and with vibration at 20, 30, 40, and 55 Hz. Three vibration amplitudes were employed at 12.5%, 25%, and 50% of the baseline. Mean muscle-fiber conduction velocity (mCV), mean frequency (MF), and root mean square (RMS) value were estimated from surface electromyography as indicators of the alteration in MU recruitment strategies. Main results. The mCV estimates during VE were significantly (p < 0.05) higher compared to the control condition. Furthermore, six VE conditions produced significantly larger RMS values compared to control condition. The estimated MF did not show any consistent trend. Significance. These results suggest that vibration superimposed on low-level isometric contraction alters the MU recruitment strategy, activating larger and faster MUs.

Historical development of damping models in structural acoustics and vibrations

This presentation discusses historical developments of damping models most commonly used in the analysis of structural acoustics and vibrations today. This presentation represents all damping models as frequency-dependent complex-valued matrices that appear in the equations of motion. The historical development of damping models has benefited from research on two fronts. The first is satisfaction of passivity and causality conditions by the damping model. The passivity condition requires no net power flow from the material over a cycle of vibration, while the causality condition requires that the material cannot respond before the excitation begins. The passivity condition is clearly stated in the frequency domain but is less obvious in the time domain. Conversely, the causality condition is clearly stated in the time domain but less obvious in the frequency domain. The second front is the affect of each damping model on computational methods used to evaluate the equations of motion. Discussion will include the use of undamped eigenvectors and Krylov spaces to create reduced-order models. Examples involving a rectangular plate will be presented to illustrate the features of commonly used damping model.

Significantly Enhanced Energy-Harvesting Performance and Superior Fatigue-Resistant Behavior in [001]c-Textured BaTiO3-Based Lead-Free Piezoceramics

Energy-harvesting utilizing piezoelectric materials has recently attracted extensive attention due to the strong demand of self-powered electronics. Unfortunately, low power density and poor long-term stability seriously hinder the implementation of lead-free piezoelectrics as high-efficiency energy harvesters. For the first time, we demonstrate that tailoring grain orientations of lead-free ceramics via templated grain growth can effectively produce ultrahigh power generation performance and excellent endurance against electrical/mechanical fatigues. Significantly improved fatigue resistance was observed in (Ba0.94Ca0.06)(Ti0.95Zr0.05)O3 grain-oriented piezoceramics (with ∼99% [001]c texture) up to 106 bipolar cycles, attributed to the enhanced domain mobility, less defect accumulation, and thus suppressed crack generation/propagation. Interestingly, the novel energy harvesters, which were developed based on the textured ceramics with high electromechanical properties, possessed ∼9.8 times enhancement in output power density compared to the nontextured counterpart while maintaining stable output features up to 106 vibration cycles. The power densities, which increased from 6.4 to 93.6 μW/mm3 with increasing acceleration excitation from 10 to 50 m/s2, are much higher than those reported previously on lead-free energy harvesters. This work represents a significant advancement in piezoelectric energy-harvesting field and can provide guidelines for future efforts in this direction.

Influence of process parameters on average particle speeds in a vibratory finisher

Vibratory finishing (VF) employs vibrationally-fluidized granular media to finish the surfaces of workpieces that are entrained in the flowing media. Its application has been based mostly on experience and trial-and-error due to the complexity of the granular material behavior. The present study used discrete element modeling (DEM) to investigate how the movement of a commercial two-dimensional tub finisher influenced the average particle speed of the media in a bed of smooth, steel, spherical particles, and thus the work that would be done on an entrained workpiece. The parameters governing the tub wall motion (frequency, in-plane amplitudes, and phases of vibration) and the coefficient of friction between the media and the wall were systematically varied in 71 three-dimensional DEM simulations. The average particle speed was affected mostly by the vertical amplitude of tub motion rather than by the frequency, and was mostly independent of other parameters of motion and of the wall friction. A strong relationship was found between the average particle speed and the work done by the wall per cycle of vibration. The normal force on the wall was also found to correlate strongly with the normal component of the wall velocity. Together, these relationships offer the potential to enable the analytical prediction of the average particle speed based on the motion parameters of the tub alone. The paper provides a set of practical guidelines for the control of the average particle speed in VF that are explained by the forces between the media and walls of the tub finisher.

Highly durable piezoelectric energy harvester based on a PVDF flexible nanocomposite filled with oriented BaTi2O5 nanorods with high power density

Rapid developments in personal electronics and sensor networks have raised urgent and challenging requirements for portable and sustainable power sources. As a result, fabrication of highly durable piezoelectric energy harvesters with high power density has become a priority. In this work, a sensitive flexible piezoelectric energy harvester (FPEH) was constructed by filling a poly(vinylidene fluoride) (PVDF) polymer matrix with oriented BaTi2O5 nanorods (BT2). Synthesizing the BT2 nanorods by the molten salt method gave them a strong polarity along the b-axis, and they were then further aligned in the horizontal direction in the PVDF matrix by hot pressing, which helped to give them a textured structure that would ensure a significant increase in power generation in the cantilever beam mode. Out of all the compositions, 5 vol% BT2/PVDF FPEH exhibited the optimal energy harvesting performance with a high power density of 27.4 μW/cm3 together with excellent mechanical properties under a large acceleration of 10 g. More importantly, the FPEH retained its performance even after an extended period of cantilever vibration cycles (~ 330,000). Because of their excellent performance, FPEHs show great potential for harvesting mechanical energy for self-powered systems and can be used to harvest energy from rotating wheels to charge a capacitor and instantly power up various sensors.

Measurement of ultrasonic-frequency repetitive impulse cutting force signal

An innovative system for measuring ultrasonic-frequency repetitive impulse cutting force signals is proposed in this paper. Compared with the traditional cutting force measurement methods, it can realize the measurement of the transient cutting force signal of around 20 KHz rather than the average cutting force. A piezoelectric force sensor of a resonant frequency around 180 KHz is used instead of the traditional dynamometers that only can measure the cutting force signal of no more than 500 Hz. Besides, a clamp circuit is used to stabilize the decayed repetitive impulse signal due to the characteristic of piezoelectric sensors. After building the measurement system, experiments and finite element simulations are carried out based on an orthogonal one-directional ultrasonic vibration cutting model, respectively. The results have validated this proposed measurement system through force signal shapes, values of duty cycle and average cutting forces. In this regard, the separation effect of ultrasonic vibration cutting is firstly detected and the cutting process during one vibration cycle can be monitored through the measured transient cutting force signal, both of which will be great significant to the further researches for the deeper understanding of the machining mechanism influenced by the ultrasonic vibration.

Investigation of Intermittent Failure in Electrical Interconnections of Avionics System

If a failure of a function is reported for a limited period of time and subsequent recovery of the function in a product, it’s called intermittent failure. The intermittent failure is one of the causes of no-fault-found (NFF). It was reported that electrical interconnections are one of the most detrimental sources for the intermittent failure of electronic devices in vibration environment. In this study, intermittent failure in electrical interconnections is investigated. Printed circuit board (PCB) and flexible PCB (FPCB) are designed with several types of electrical interconnections. Electronic devices are also developed to measure the intermittent failure of the interconnections. Vibration and thermal cycling tests are conducted for the interconnections and intermittent failures are monitored in real-time. The failure analysis for the site of intermittent failure occurrences reveals the cause of the failure