Piezoelectric Force Transducer Research Articles

Centrifugal balance for the detection of mass fluctuations in advanced propulsion concepts

Propellantless propulsion with a greater thrust-to-power ratio than photon rockets and functioning independently from the Sun or Earth-based lasers promise to revolutionize interstellar space travel. Claims of micronewtons in force for a Mach-Effect-Thruster on a torsion balance in vacuum, along with theories predicting mass fluctuations in a device with large fluctuations in internal energy, have paved the way for experimental investigations. In this experiment originally conceived by Woodward, devices are subjected to high centrifugal acceleration for direct measurement of mass fluctuations using an embedded force transducer. The test devices included a capacitor stack, a toroid and a pre-stressed, multi-layer piezoelectric stack in which electromechanical energy was varied. This paper first describes the design of a centrifugal balance: a rotating apparatus with low eccentricity and maximal angular frequency of 3600 rpm, capable of applying an acceleration above 1000 g's to the test device. The piezoelectric force transducer was characterized and calibrated under quasi-static conditions using an electrodynamic test instrument. The second harmonic response of the force transducer was then examined at different rotational rates to identify the presence of mass fluctuations. The experiment revealed a maximal resolution of 40 μg over a 100 kHz measurement bandwidth. Results with the electrostatic and inductive devices did not show mass fluctuations, orders of magnitude below the prediction. Even if the measurement resolution with the piezoelectric stack was more strongly affected by the centrifugal force, electromagnetic interaction, and nonlinear behavior, the measured noise reached one order of magnitude below the mass fluctuation prediction as well. Despite some limitations with the calibration and with the piezoelectric test device, the experiments have successfully demonstrated the feasibility of the centrifugal balance for high-frequency and high-precision mass variation measurements and have ruled out the postulated Mach-Effect mass fluctuations.

An objective bone conduction verification tool using a piezoelectric thin-film force transducer.

All hearing aid fittings should be validated with appropriate outcome measurements, whereas there is a lack of well-designed objective verification methods for bone conduction (BC) hearing aids, compared to the real-ear measurement for air conduction hearing aids. This study aims to develop a new objective verification method for BC hearing aids by placing a piezoelectric thin-film force transducer between the BC transducer and the stimulation position. The newly proposed method was compared with the ear canal method and the artificial mastoid method through audibility estimation. The audibility estimation adopted the responses from the transducers that correspond to the individual BC hearing thresholds and three different input levels of pink noise. Twenty hearing-impaired (HI) subjects without prior experience with hearing aids were recruited for this study. The measurement and analysis results showed that the force transducer and ear canal methods almost yielded consistent results, while the artificial mastoid method exhibited significant differences from these two methods. The proposed force transducer method showed a lower noise level and was less affected by the sound field signal when compared with other methods. This indicates that it is promising to utilize a piezoelectric thin-film force transducer as an in-situ objective measurement method of BC stimulation.

Experiments on the localized interaction at the interface fuel rod/spacer grid in pressurized water reactors

The release of fissile material into the coolant caused by fretting of the fuel rods at the interface with spacer grids is a significant safety issue and cause of financial losses in the operation of Pressurized Water Reactors (PWRs). Each fuel rod is kept in position inside spacer grids through friction from the preload exerted by retaining elements (springs and dimples). Fretting of the fuel rods occurs at the contact with the springs and dimples. In severe fretting cases the integrity of the fuel rod cladding is compromised and fission byproducts enter the primary coolant circuit. The reciprocating motion at the contact interface of the fuel rods and spacer grids resulting in material fretting is due to the Flow-Induced Vibrations (FIV) of fuel rods, caused by the unstable surrounding coolant flow, which in PWRs is predominantly parallel to the length of fuel rods (axial flow). Under specific flow conditions, fretting develops rapidly. The vibrations of fuel rods, as well as the relationship of fretting wear mechanisms with several factors associated with the fission process and coolant flow dynamics and stability (vibration amplitude, preload, oscillating loads, irradiation, axial slip, spring relaxation, temperature, oxidation, material of spacer grids and fuel rods), have been considered in the literature. However, direct experimental measurements of the contact force and axial slip during FIV have not been treated in the literature, likely because of the absence of suitable measurement methods. This gap in experimental measurement techniques is addressed in this work, specifically for the analysis of PWR fuel assemblies, by installing a piezoelectric stack and aiming laser Doppler vibrometers on a one-meter-long fuel rod, supported by two full-scale spacer grids, in-air or immersed in quiescent water. In the presence of small- and large- amplitude forced vibrations, the signal of the piezoelectric force transducer increases with the amplitude of vibration, but it is also affected by vibrations perpendicular to the excitation, which appear for large-amplitude excitations. The axial motion of the fuel rod at the spacer grid has a complex evolution and is significant for large-amplitude vibrations only. At any rate, the time histories of contact force and axial motion display the effects of impacts and slips, particularly during the tests in water. The measurement system shows that the severity of the interaction at the spacer grid interfaces is influenced strongly by the amplitude of the forced fuel rod vibrations. Since fuel rods and fuel assemblies are prone to several nonlinear phenomena, as demonstrated by recent studies, it follows that the usage of nonlinear models will be essential to numerically estimating the severity of fretting.

Investigation of the effect of load rate on creep and hysteresis errors in strain gauge and piezoelectric force transducer

This study includes measurements carried out according to ISO 376 international standard and DKD-R 3-9 guideline by using different low pass filters and continuous data acquisition, with the purpose of comprehensively investigate creep, influence of load rate and influence of load rate on hysteresis in force sensors that have two different measuring principles. It has been revealed and evaluated the contribution of these parameters to the measurement uncertainty.

Effect of peri-implant bone resorption on mechanical stress in the implant body: In vivo measured load-based finite element analysis.

Research on resolving implant fracture is still gaining attention as it can be a serious treatment failure outcome. The implant fracture is likely to occur due to increased stress in implant body associated with peri-implant bone resorption. This study aimed to investigate the relationship between degree of peri-implant bone resorption and stress distribution in implant body by using finite element analysis (FEA). The magnitude and direction of loads on implants at the mandibular molar region were measured with 3D piezoelectric force transducers in a patient during maximal voluntary clenching, grinding and tapping to obtain input for the FEA as the loading condition. Simplified finite element bone models were generated to simulate the six patterns of peri-implant bone resorption progression which the bone levels from implant platform were set at 0, 1, 2, 3, 4 and 5mm. Three types of implants with different diameters (3.5, 4.0 and 5.0mm), corresponding abutments and screws were created. FEA using the in vivo measured load was conducted to investigate how peri-implant bone loss affects stress distribution in the implant body. Loading condition affected stress distribution in the implant body. As bone resorption increased, von Mises stress in the implant body became larger, which was marked in smaller diameter implants, and this change was amply demonstrated when the bone resorption increased from 0 to 2mm. The FEA demonstrated that as peri-implant bone loss increased, the magnitude of stress in the implant increased, especially in small diameter implants.

DIRECT MEASUREMENT OF REACTION FORCES DURING FAST DYNAMIC LOADING

The presented paper is focused on embedding of the serially manufactured piezo-electric impact loadcell into Open Hopkinson Pressure Bar (OHPB) and it’s modifications for a direct force measurement during dynamic loading. Conventionally, during the SHPB test dynamic force equilibrium is investigated by a comparison of the transmitted signal wave and the difference between the incident, reflected and transmitted signals measured by strain gauges [1]. However, in the experiments with specimens with low mechanical impedance, a major portion of the incident wave is reflected back on the interface between the bar and the specimen. Comparison between two-large amplitude incident and reflected pulse and a small-amplitude transmitted pulse can be influenced by large error and resulting force equilibrium can be inaccurate. Therefore, a piezo-electric quartz impact force transducer was used to directly measure the axial forces in the vicinity of the specimen end surfaces.

Transient dynamic analysis of laminated shallow spherical shell under low-velocity impact

The impact of transient response laminated shallow shells due to transverse foreign object was investigated analytically and experimentally. The analytical analysis is presented by using the new higher order shear deformation shell theory. The contact force ishassumedhtohbe a known inputhtohthehanalysis. Contact force and transverse deflection of laminated shell have been measured with a piezoelectric force transducer (load cell) and a piezoelectric bending transducer respectively. Laminates made from E-glass polyester and E-glass/carbon/polyester having different thickness and stacking sequences have been used. The analysis can be used to calculate the difference between the transient stresses, displacements, velocities, accelerations and energy observation at the center of laminated shell are plotted as function of time during impact between E-glass/polyester and E-glass/carbon/polyester by MATLAB code at different impact heights to determine whether they have a good resistant ability to impact. Finally, it was compared with the results of an experimental test to verify the accuracy and reliability of the theoretical analysis.

Correction: Sex reversal induces size and performance differences among females of the African pygmy mouse, Mus minutoides (doi: 10.1242/jeb.157552).

There was an error published in J. Exp. Biol. (2017) 220 , [1947-1951][1] ([doi: 10.1242/jeb.157552][2]). The in vivo bite force values were overestimated as a result of incorrect settings of the piezoelectric force transducer used to measure bite forces; all bite force values are 2.4 times higher

Experimental studies on the effect of Reynolds and Weber numbers on the impact forces of low-speed droplets colliding with a solid surface

The impact force of low-speed droplets colliding with a solid surface was recorded with an experimental setup involving a highly sensitive piezoelectric force transducer and a high-speed camera recording the droplet shape. Water, ethanol, pure glycerin and aqueous glycerin solutions were used. Experimental results showed that dimensionless force is independent of the Weber number in the experimental range of 68–858 but varies with the Reynolds number. The impact is categorized into three types of processes according to the data on dimensionless peak force against the Reynolds number. The first type is a viscosity-dominated one, in which the Reynolds number ranges between 2.9 and 20. In the second type, transition process, the Reynolds number is in the range of 20–230. In the inertia-dominated type, the Reynolds number is larger than 230. In the viscosity-dominated impact, dimensionless peak force decreases rapidly with increasing Reynolds number, and the effect of viscosity could not be ignored. In the inertia-dominated impact, dimensionless peak force remains constant with varying the Reynolds number, that is, impact force is directly proportional to the product of liquid density, velocity squared and diameter squared but is unaffected by the changes in viscosity and surface tension. Furthermore, the deformation of droplet shape due to oscillation affects the impact force; a small horizontal-to-vertical ratio results in small impact force and vice versa.

Strength and Power Acute Responses to Suspension Training

Suspension Training (ST) is a form of resistance training aiming at improving strength, endurance, coordination, flexibility, power, and core stability. Although ST is thought to elicit higher muscle activations than traditional exercises, only limited information is available on its acute effects on strength and power performances. PURPOSE: To evaluate strength and power acute responses after group ST in relation to gender. METHODS: 32 college students (16 M, 16 F; Age: 25.8±3.9years; Body Mass: 65.8±11.2Kg; Height: 166.9±8.9cm; BMI: 23.5±2.4kg/m2) volunteered to participate in the study. Before (PRE) and after (POST) a 45-min ST group session, Squat (SJ) and Countermovement (CMJ) Jumps were performed on a portable force plate, while lower limb Maximum Voluntary Contraction (MVC) at 90° angle isometric knee extension and grip strength (HG) were measured in preferred and non-preferred limbs through a piezoelectric force transducer and a hydraulic hand dynamometer, respectively. ANOVA for repeated measures was use to evaluate differences (p<0.05) in relation to gender and experimental session. RESULTS: As expected, M always showed highest strength and power values (p<0.02). In the POST condition, no significant improvements were found for HG, with best performances (p<0.02) emerging for the preferred limb (M-PRE: 429.3±31.2N; M-POST: 445.7±30.2N; F- PRE: 254.1±12.6N; F- POST: 256.4±13.5N) with respect to the non-preferred one (M-PRE: 399.4±16.2N; M-POST: 407.6±28.6N; F-PRE: 231.7±15.9N; F-POST: 236.1±18.1N). For MVC, only F showed differences between limbs (p<0.02), with highest values in the preferred leg (PRE: 238.8±15.1N; POST: 246.9±20.1N) and lowest in the non-preferred one (PRE: 222.4±19.9N; POST=230.9±14.5 N). After the session, M only showed improvements (p<0.02) in CMJ (PRE: 32.3±1.8cm; POST: 33.7±1.7cm) and MVC for the non-preferred leg (PRE: 276.1±16.6N; POST: 292.4±24.1N), while no differences emerged for SJ. CONCLUSIONS: Results shown that ST is a form of exercise useful to maintain and improve acute strength and power performances, in particular in male subjects. ST could be added in warm-up programs for sports where strength and power are key components.

The incremental Virtual Fields Method and prestretching method applied to rubbers under uniaxial medium‐strain‐rate loading

AbstractConventional dynamic experiments on rubbers have several limitations including low signal‐to‐noise ratio and a long time period during which the specimen is not in static equilibrium, which causes difficulties separating constitutive material behaviour from specimen response. In order to overcome these limitations, we build on previous research in which the Virtual Fields Method (VFM) is applied to dynamic tensile experiments. A previous study has demonstrated that the VFM can be used to identify the material parameters of a hyperelastic model for a given rubber based on optical measurements of wave propagation in the rubber, eliminating the need for force measurements by instead using acceleration fields as a “virtual load cell.” In order for us to successfully characterise the strain hardening in the material, large deformations are required, and these were achieved by applying static preloads to the specimen before the dynamic loading. In order for us to then apply the VFM, measurements of the static force, or strain, or both, are required. This paper explores different methods for applying the VFM, in particular, comparing the use of a static force measurement, as in the previous research, to methods that only require strain fields in order to apply the incremental equation of motion. Finite element method simulations were conducted to compare the identification sensitivity to experimental error sources between the 2 VFM implementations; the experimental data used in the previous studies were then applied to the incremental VFM. A further experimental comparison is provided between constitutive parameters obtained in tensile experiments using the VFM and compressive measurements from a modified split Hopkinson bar technique equipped with a piezoelectric force transducer. Finally, there is a discussion of the effects of preloading and relaxation in the material.

Effect of Configurations of Implants Supporting a Four-Unit Fixed Partial Denture on Loading Distribution.

This study aimed to evaluate the effect of the configuration of implants supporting a four-unit fixed partial denture on load distribution. An epoxy resin model missing teeth from the first premolar to the second molar was used. Three-dimensional piezoelectric force transducers were set on implants placed in the missing teeth area with a four-unit experimental superstructure. Three-dimensional loads on the implants were measured with four different implant configurations when a static load of 100 N was applied. The loads on the implants changed significantly depending on the implant number and position and the applied loading points.

Simulation of multi-stage nonlinear bone remodeling induced by fixed partial dentures of different configurations: a comparative clinical and numerical study.

This paper aimed to develop a clinically validated bone remodeling algorithm by integrating bone's dynamic properties in a multi-stage fashion based on a four-year clinical follow-up of implant treatment. The configurational effects of fixed partial dentures (FPDs) were explored using a multi-stage remodeling rule. Three-dimensional real-time occlusal loads during maximum voluntary clenching were measured with a piezoelectric force transducer and were incorporated into a computerized tomography-based finite element mandibular model. Virtual X-ray images were generated based on simulation and statistically correlated with clinical data using linear regressions. The strain energy density-driven remodeling parameters were regulated over the time frame considered. A linear single-stage bone remodeling algorithm, with a single set of constant remodeling parameters, was found to poorly fit with clinical data through linear regression (low [Formula: see text] and R), whereas a time-dependent multi-stage algorithm better simulated the remodeling process (high [Formula: see text] and R) against the clinical results. The three-implant-supported and distally cantilevered FPDs presented noticeable and continuous bone apposition, mainly adjacent to the cervical and apical regions. The bridged and mesially cantilevered FPDs showed bone resorption or no visible bone formation in some areas. Time-dependent variation of bone remodeling parameters is recommended to better correlate remodeling simulation with clinical follow-up. The position of FPD pontics plays a critical role in mechanobiological functionality and bone remodeling. Caution should be exercised when selecting the cantilever FPD due to the risk of overloading bone resorption.

A generalised multiple-mass based method for the determination of the live mass of a force transducer

Many applications in Experimental Modal Analysis (EMA) require that the sensors’ masses are known. This is because the added mass from sensors will affect the structural mode shapes, and in particular its natural frequencies. EMA requires the measurement of the exciting forces at given coordinates, which is often made using piezoelectric force transducers. In such a case, the live mass of the force transducer, i.e. the mass as ‘seen’ by the structure in perpendicular directions must be measured somehow, so that compensation methods like mass cancelation can be performed. This however presents a problem on how to obtain an accurate measurement for the live mass. If the system is perfectly calibrated, then a reasonably accurate estimate can be made using a straightforward method available in most classical textbooks based on Newton’s second law. However, this is often not the case (for example when the transducer’s sensitivity changed over time, when it is unknown or when the connection influences the transmission of the force). In a self-calibrating iterative method, both the live mass and calibration factor are determined, but this paper shows that the problem may be ill-conditioned, producing misleading results if certain conditions are not met. Therefore, a more robust method is presented and discussed in this paper, reducing the ill-conditioning problems and the need to know the calibration factors beforehand. The three methods will be compared and discussed through numerical and experimental examples, showing that classical EMA still is a field of research that deserves the attention from scientists and engineers.

The Biomechanical Responses of Mandibular Bone Installed with Fixed Partial Denture

This study aimed to evaluate the biomechanical responses in the peri-implant bony structure installed with the fixed partial dentures (FPDs). Unlike traditional configuration, the FPD considered here comprises a superstructure and is supported by three implants. The computational model of mandibular bone and the implant prosthesis were constructed based on patient-specific computerized tomography (CT) images and Computer Aided Design (CAD) tools. To better reflect the real clinical situation, the 3D real-time loading data of maximum voluntary clenching measured using piezo-electric force transducers in patient were adopted in the 3D finite element (FE) analyses (FEA). The von Mises equivalent stress, maximum shear stress, equivalent strain and strain energy density in the peri-implant bone regions are quantified. The peak stresses and strains in the peri-implant bone were observed around the neck of the implant, indicating risk of micro-motion and bone resorption. In this study, we successfully conducted a computational simulation in silico based on in vivo 3D force measurement of a specific patient. The results provided important biomechanical data for clinical treatment, potentially helping enhancing the longevity and reliability of the implant-supported FPD restoration.

Load distribution on abutment tooth, implant and residual ridge with distal-extension implant-supported removable partial denture

PurposeThe aim of this study was to evaluate the effect of implant location on load distribution in the abutment tooth, implant and residual ridge with a distal-extension implant-supported removable partial denture (ISRPD). MethodsA mandibular unilateral distal-extension edentulous simulation model was used. Implants were inserted at the second premolar (mesial implant) and second molar (distal implant) positions in the edentulous area. An experimental ISRPD was fabricated of acrylic resin with a cobalt-chromium alloy framework. Loads on the implants and abutment tooth were measured with piezoelectric force transducers. The load on the residual ridge was measured with pressure-sensitive film. A vertical load of 100N was applied at the first molar region. Measurements were made under the following three conditions: with conventional removable partial denture (CRPD), with mesial-implant-supported removable partial denture (MISRPD), and with distal-implant-supported removable partial denture (DISRPD). In each condition, the unused implants were made inactive by eliminating contact with the inner surface of the denture. ResultsThe load on the abutment tooth was greatest with DISRPD, followed by CRPD and MISRPD (P<0.01). The load on the implant was greater with DISRPD than with MISRPD (P<0.01). The load on the residual ridge was lowest with DISRPD, followed by MISRPD and CRPD (P<0.01). ConclusionsThis experimental study provided quantitative data regarding the effect of implant location on load distribution with ISRPDs. Further investigation regarding the effect of denture design on the load distribution is needed for determining the proper implant location of ISRPD.

Influence of Process Parameters on Spinning Force Using Finite Element Analysis and the Taguchi Method

Metal spinning process is widely used for producing complex symmetry components. Main advantage of spinning process is a lower power requirement for large deformation with good surface finish. The aim of this paper is to investigate the influences of spinning process parameters, on spinning force. A three dimensional finite element model of the spinning process of SPCC sheet was successfully developed using elastic-plastic material property. The spinning experiments were carried out on a turning lathe and spinning forces were measure forces using a piezoelectric force transducer. The finite element prediction was compared with the experimental measurements and the results agreed well. Applying the Taguchi method, the effect of four process parameters, i.e. roller diameter, spindle speed, feed rate and feed depth, on spinning force were studied. The Taguchi main effect analysis and ANOVA results show that roller diameter and feed depth are the most important factor influencing the spinning force.

The Tensile Properties of PVB at Intermediate Strain Rate Using the &lt;i&gt;In Situ&lt;/i&gt; Hopkinson Bar

Polyvinyl butyral (or PVB) is commonly used as interlayer in architectural laminated glass and windshield in automobiles for its strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. A modified in-situ Hopkinson bar system is used to measure the tensile properties of the PVB with the strain rates of 30~100 s-1. In this system, a high impedance striker tube with the rubber pulse shaper is use to generate a long loading pulse of 50ms. Two X-cut quartz piezoelectric force transducers are sandwiched between the specimen and two bars respectively to directly measure the dynamic loading forces, and the strain field of the specimen is calculated by the Digital Image Correlation (DIC) method via photos obtained by the high speed camera. The local deformation of the full-field specimen was clearly displayed and the fracture strain of the specimen was evaluated. The results show that the tensile strengths of the PVB increase with increasing loading strain rates.

Effect of attachment type on load distribution to implant abutments and the residual ridge in mandibular implant-supported overdentures.

This study aimed to investigate the effect of attachment type on the load transmitted to implants and the residual ridge in a mandibular two-implant-supported overdenture in a model study. Ball attachments, locator attachments, and round-bar attachments were selected and examined. Static and dynamic vertical loads of 100 N were applied in the right first molar region. The load on the implants was measured by piezoelectric three-dimensional force transducers, and the load on the residual ridge beneath the denture base was measured using a tactile sheet sensor. The load on the implants with ball attachments was significantly higher than that with the other two attachments. The load on the residual ridge with round-bar attachments was significantly higher than that with the other two attachments. Our findings indicate that the three-dimensional load on implants and the residual ridge beneath the denture base is significantly associated with the type of attachment used in implant-supported overdentures.

Investigating the use of contact electrical conductance for the measurement of particle impact force

The measurement of impact force by use of a piezoelectric force transducer or similar device is complicated by: (i) the transducer is mechanically resonant, and the output signal is therefore not necessarily a direct measure of the input force, particularly if the contact time is near to the period of resonance; and (ii) the transducer’s mechanical characteristics, such as mass and stiffness, mean that the transducer itself affects the impact characteristics and force profile.This paper describes an attempt to measure impact force profiles without the use of a separate force transducer. However it has been found that the technique is not suitable due to poor repeatability.