Impact Force Signal Research Articles

Characterization of the concentration of agar-based soft tissue mimicking phantoms by impact analysis

In various medical fields, a change of soft tissue stiffness is associated with its physio-pathological evolution. While elastography is extensively employed to assess soft tissue stiffness in vivo, its application requires a complex and expensive technology. The aim of this study is to determine whether an easy-to-use method based on impact analysis can be employed to determine the concentration of agar-based soft tissue mimicking phantoms. Impact analysis was performed on soft tissue mimicking phantoms made of agar gel with a mass concentration ranging from 1% to 5%. An indicator Δt is derived from the temporal variation of the impact force signal between the hammer and a small beam in contact with the sample. The results show a non-linear decrease of Δt as a function of the agar concentration (and thus of the sample stiffness). The value of Δt provides an estimation of the agar concentration with an error of 0.11%. This sensitivity of the impact analysis based method to the agar concentration is of the same order of magnitude than results obtained with elastography techniques. This study opens new paths towards the development of impact analysis for a fast, easy and relatively inexpensive clinical evaluation of soft tissue elastic properties.

Estimation of Nondestructive Compressive Strength of Concrete Using Impact Force Response Signal

Abstract This study examined the potential of the impact force response signal induced by impacting an object to estimate the compressive strength of concrete nondestructively. For this study, an automatic impacting device was devised, a system was set up to measure impact force signal, and a program was developed to analyze the obtained signal and estimate the compressive strength. Concrete test specimens were manufactured and tested. Impacts were carried out on the specimens, and the impact force signals were obtained. The signals were analyzed to obtain the total impact force signal energy, and a uniaxial compressive strength test was carried out on each specimen to measure the compressive strength directly. A good relationship was formed between the total impact force signal energy and the uniaxial compressive strength. The strength was estimated from the obtained relationship for new test specimens and compared with the directly measured strength. The comparison indicated that the estimated strength and the measured strength had a close relationship. In addition, a Schmidt hammer test was carried out on the new specimens before the uniaxial compressive test, and the test results were compared with those from the impact force signal energy. The strength estimation using the impact force signal energy had a better result. The study results show that the compressive strength of concrete materials could be estimated nondestructively using the proposed method.

Characteristics and fabrication of piezoelectric GFRP using smart resin prepreg for detecting impact signals

To develop a composite that also functions as an impact sensor, a piezoelectric glass fiber-reinforced polymer (GFRP) was fabricated using a mixture of Pb(Ni1/3Nb2/3)O3-Pb(Zr, Ti)O3 (PNN-PZT) piezoelectric powder and epoxy as a smart resin. Prepreg sheets were prepared by impregnating glass fiber with the smart resin and the specimen was fabricated by autoclave molding. To utilize the composite as a sensor for detecting impacts, electrodes were added to the two sides of the composite, and the specimen was poled briefly at room temperature to activate its piezoelectric properties. A calibrated and instrumented impact test was conducted to demonstrate impact response and measure the sensitivity; a signal processing device was developed that matched the high impedance of the piezoelectric GFRP. The sensitivity of the piezoelectric GFRP sensor was measured by comparing the impact force signals from an impact hammer with the corresponding output voltage from the sensor. The threshold for detection of impacts was below 15 N. The tests confirmed that the piezoelectric GFRP itself could be utilized as an impact sensor.

The Study of Polymer Material Characterisation Using M-Z-N Statistical Analysis Method

This paper proposes an implementation of alternative statistical signal analysis method in characterising material properties of polymer using impulse excitation technique (IET) in accordance with ASTM E1876 standard. Five types of cylindrical shape polymer specimens are used, namely acrylics (AC), poly vinyl chloride (PVC), polyethylene (PE), cast nylon (MC), and polyoxymethylene (POM). Experimental procedure is done based on non-destructive testing (NDT) concept by tapping the specimens using an impact hammer within a specific range of impact force, while accelerometer sensor Endevco 751-100 is used to detect the vibration produced. The detected vibration and the impact force signal which is triggered by impact hammer are captured using NI 9234 data acquisition device and computer. The signal is interpreted and statistically analysed using Mesokurtosis Zonal Non-parametric (M-Z-N) analysis method. As a result, mathematical model equations for determining two material properties which are tensile strength and thermal conductivity have been successfully developed. They are derived through correlation between the signal data and M-Z-N coefficient. Verification of the equation is done and the calculated errors to be in the range of 5.55% to 9.74%. Hence, this proves that the correlation can be used as a standard for determining these material properties through M-Z-N method, which is efficient and low cost.

Estimation of the acetabular cup implant stability using impact analysis

Event Abstract Back to Event Estimation of the acetabular cup implant stability using impact analysis Adrien Michel1, Romain Bosc1 and Guillaume Haiat1 1 CNRS, Laboratoire MSME UMR 8208, France Introduction: Press-fit procedures for the insertion of cementless hip prostheses aim at obtaining an optimal implant stability. Primary stability of the acetabular cup (AC) implant is an important factor for long term surgical success. The aim of this study is to determine the feasibility of the application of an acoustical method to retrieve the AC implant stability based on the analysis of the signal corresponding to the time variation of the force applied between the hammer and the ancillary. Materials and Methods: 1) In vitro Study: The first objective of this work was to investigate whether the AC implant primary stability can be evaluated using the signals obtained with an impact hammer in vitro. The experimental configuration is shown in Fig. 1. A hammer equipped with a force sensor was used to impact the AC implant in 20 bovine bone samples. For each sample, different stability conditions were obtained by changing the cavity diameter. For each configuration, the inserted AC implant was impacted four times with a maximum force comprised between 2500 and 4500 N. An indicator I was determined based on the partial impulse estimation and the pull-out force F was measured. 2) In silico study: The second aim of this study was to investigate the dynamic interaction occurring between the hammer, the ancillary and bone tissue during the impact and to assess the potential of impact analysis to retrieve AC implant insertion conditions. A dynamic two-dimensionnal axisymmetric finite element model was developed to simulate the impaction of the AC implant into bone tissue assuming friction at the bone-implant interface and large deformations. Different values of interference fit (from 0.5 to 2 mm) and impact velocities (from 1 to 2 m.s-1) were considered. For each configuration, the variation of the force applied between the hammer and the ancillary was analyzed and an indicator I was determined based on the impact momentum of the signal. 3) Cadaveric study: The third objective was to assess the potential of the method to retrieve the primary stability of acetabular cup (AC) implants inserted in cadaveric specimens. AC implants were implanted in 12 cadaveric hips. A hammer instrumented with a piezoelectric force sensor was used to measure the impacts signals between the hammer and the ancillary. The tangential pull-out force F was measured. Results: The implant stability and the value of the indicator I reached a maximum value for an interference fit equal to 1 mm for 18 out of 20 samples. When pooling all samples and all configurations, the implant stability and I were significantly correlated (R2=0.83, see Fig. 2)[1]-[4]. The value of the polar gap decreases as a function of the impact velocity and increases as a function of the interference fit. The bone implant contact area was significantly correlated with the resonance frequency (R²=0.94) and the indicator (R²=0.95). Concerning the cadaveric experiments, a significant correlation (R2 = 0.69) was found between the indicator I and the pull-out force F. Discussion and Conclusion: The AC implant primary stability can be assessed through the analysis of the impact force signals obtained using an impact hammer. This study opens new paths for the development of a medical device which could be used as a decision support system to assist the surgeon during the insertion of the AC implant.

Ex vivo estimation of cementless acetabular cup stability using an impact hammer

Obtaining primary stability of acetabular cup (AC) implants is one of the main objectives of press-fit procedures used for cementless hip arthroplasty. The aim of this study is to investigate whether the AC implant primary stability can be evaluated using the signals obtained with an impact hammer.A hammer equipped with a force sensor was used to impact the AC implant in 20 bovine bone samples. For each sample, different stability conditions were obtained by changing the cavity diameter. For each configuration, the inserted AC implant was impacted four times with a maximum force comprised between 2500 and 4500 N. An indicator I was determined based on the partial impulse estimation and the pull-out force was measured.The implant stability and the value of the indicator I reached a maximum value for an interference fit equal to 1 mm for 18 out of 20 samples. When pooling all samples and all configurations, the implant stability and I were significantly correlated (R2 = 0.83).The AC implant primary stability can be assessed through the analysis of the impact force signals obtained using an impact hammer. Based on these ex vivo results, a medical device could be developed to provide a decision support system to the orthopedic surgeons.

Experimental rig to estimate the coefficient of friction between tire and surface in airplane touchdown simulations.

To estimate the coefficient of friction between tire and runway surface during airplane touchdowns, we designed an experimental rig to simulate such events and to record the impact and friction forces being executed. Because of noise in the measured signals, we developed a filtering method that is based on the ensemble empirical mode decomposition and the bandwidth of probability density function of each intrinsic mode function to extract friction and impact force signals. We can quantify the coefficient of friction by calculating the maximum values of the filtered force signals. Signal measurements are recorded for different drop heights and tire rotational speeds, and the corresponding coefficient of friction is calculated. The result shows that the values of the coefficient of friction change only slightly. The random noise and experimental artifact are the major reason of the change.

In vitro evaluation of the acetabular cup primary stability by impact analysis.

The implant primary stability of the acetabular cup (AC) is an important parameter for the surgical success of press-fit procedures used for the insertion of cementless hip prostheses. In previous studies by our group (Mathieu, V., Michel, A., Lachaniette, C. H. F., Poignard, A., Hernigou, P., Allain, J., and Haiat, G., 2013, "Variation of the Impact Duration During the in vitro Insertion of Acetabular Cup Implants," Med. Eng. Phys., 35(11), pp. 1558-1563) and (Michel, A., Bosc, R., Mathieu, V., Hernigou, P., and Haiat, G., 2014, "Monitoring the Press-Fit Insertion of an Acetabular Cup by Impact Measurements: Influence of Bone Abrasion," Proc. Inst. Mech. Eng., Part H, 228(10), pp. 1027-1034), the impact momentum and duration were shown to carry information on the press-fit insertion of the AC within bone tissue. The aim of the present study is to relate the impact momentum recorded during the AC insertion to the AC biomechanical primary stability. The experimental protocol consisted in testing 13 bovine bone samples that underwent successively series of 15 reproducible mass falls impacts (5 kg, 5 cm) followed by tangential stability testing. Each bone sample was tested with different hole sizes in order to obtain different stability configurations. The impact momentum and the tangential primary stability reach a maximum value for an interference fit equal to around 1 mm. Moreover, a correlation between the impact momentum and the stability was obtained with all samples and all configuration (R2 = 0.65). The implant primary stability can be assessed through the measurement of the impact force signal analysis. This study opens new paths for the development of a medical device which could be used as a decision support system to assist the surgeon during the insertion of the AC implant.

Detection of internal cracks in rubber composite structures using an impact acoustic modality

The objective of this study is to investigate the use of impact acoustic signals to non-intrusively inspect rubber composite structures for the presence of internal cracks, such as those found in an automobile tyre. Theoretical contact dynamic models for both integral and defective rubber structures are developed based on Hertz's impact model, further modified for rubber composite materials. The model generates the prediction of major impact dynamic quantities, namely the maximum impact force, impact duration and contact deformation; such parameters are also theoretically proven to be correlated with the presence of internal cracks. The tyre structures are simplified into cubic rubber blocks, to mitigate complexity for analytical modelling. Both impact force and impact sound signals are measured experimentally, and extraction of useful features from both signals for defect identification is achieved. The impact force produces two direct measurements of theoretical impact dynamic quantities. A good correlation between these experimental discriminators and the theoretical dynamic quantities provide validation for the contact dynamics models. Defect discriminators extracted from the impact sound are dependent on both time- and frequency-domain analyses. All the discriminators are closely connected with the theoretical dynamic quantities and experimentally verified as good indicators of internal cracks in rubber composite structures.

Frequency Content of Cartilage Impact Force Signal Reflects Acute Histologic Structural Damage

Objective:The objective of this study was to determine if acute cartilage impact damage could be predicted by a quantification of the frequency content of the impact force signal.Design:Osteochondral specimens excised from bovine lateral tibial plateaus were impacted with one of six impact energies. Each impact force signal underwent frequency analysis, with the amount of higher-frequency content (percentage of frequency spectrum above 1 kHz) being registered. Specimens were histologically evaluated to assess acute structural damage (articular surface cracking and cartilage crushing) resulting from the impact.Results:Acute histologic structural damage to the cartilage had higher concordance with the high-frequency content measure than with other mechanical impact measures (delivered impact energy, impact maximum stress, and impact maximum stress rate of change).Conclusions:This result suggests that the frequency content of an impact force signal, specifically the proportion of higher-frequency components, can be used as a quick surrogate measure for acute structural cartilage injury. Taking advantage of this relationship could reduce the time and expense of histologic processing needed to morphologically assess cartilage damage, especially for purposes of initial screening when evaluating new impaction protocols.

Numerical Simulation and Experimental Investigation of the Gas-Liquid-Solid Three-Phase Flow Outside of the Abrasive Water Jet Nozzle

Simulation of the gas-liquid-solid three-phase flow field of outside the abrasive water jet(AWJ) nozzle is studied by the computed fluid dynamic software- FLUENT, and the velocity field of the three-phase flow is obtained, the velocity value of the flow between the nozzle and work-pieces is also obtained. Serial experiments have been done to verify the simulation method. In the experiments, the impact force signal of the AWJ outside the nozzle is collected by the piezoelectricity ergometer, then it is filtered by the vibration signal and dynamic signal software. The testing values are transformed to the velocity values, which will be compared with the simulation values. The comparison result indicates that the value of the simulation is changing similarly with the experiment value, and both value is almost the same, which proves that the simulation method is successful, the simulation model and the boundary conditions are right.

Suppression of time aliasing in the solution of the equations of motion of an impacted beam with partial constrained layer damping

Signal processing issues encountered when an analytical spectrum is converted in the time domain with an inverse discrete Fourier transform are investigated. In the analytical model of the transient time response of an impacted beam with partial constrained layer damping (PCLD) developed in Ref. [D. Granger, A. Ross, Effects of partial constrained viscoelastic layer damping parameters on the initial transient response of impacted cantilever beams: experimental and numerical results, Journal of Sound and Vibration 321 (1–2) (2009) 45–64, doi:10.1016/j.jsv.2008.09.039], noncausal effects were observed for lightly damped structures. As discussed in the present paper, the noncausal effects were due to time aliasing occurring when continuous frequency spectra were discretized. To suppress such errors, the numerical Laplace transform is introduced and applied to the previous model, which was based on Fourier transforms. The equations of motion of the system and the viscoelastic properties of the core are formulated in the Laplace domain. A window is used in the Laplace domain to avoid amplification of the Gibbs oscillations that are caused by the truncation of the spectrum. The new solution technique is compared to the previous method. It is shown that noncausal effects appearing in the first milliseconds of time signals with the use of discrete Fourier transforms are avoided with the Laplace transform solution method. Numerical results are validated for transient responses using experimental impact force signals. The results are in good agreement with experimental data.

Effects of partial constrained viscoelastic layer damping parameters on the initial transient response of impacted cantilever beams: Experimental and numerical results

The effects of partial constrained viscoelastic layer damping on the first milliseconds of the transient vibration of an impacted beam is studied using an analytical model. The viscoelastic properties of the core are frequency dependent and the shear modulus is modelled using a Prony Series. The equations of motion of the system are obtained using Lagrange's equations. The equations of motion are converted in the frequency domain using a Fourier Transform and they are solved for frequency displacements using the assumed modes method. They are then converted back in the time domain using an inverse Fourier Transform. The technique is validated for transient responses using experimental impact force signals. The numerical results are in good agreement with experimental data. Four partial constrained viscoelastic layer damping parameters are studied: the length, the placement, the viscoelastic layer thickness and the constraining layer thickness. It turns out that the length of the partial constrained viscoelastic layer damping has the most important effect on the initial transient displacement while the viscoelastic layer thickness has little effect. Noncausal effects in the model are discussed and are mainly induced when the partial constrained viscoelastic layer damping treatment is poorly effective.

Characterisation of a Potato-shaped Instrumented Device

Instrumented spheres are used worldwide in food processing chains to locate bruising risk zones and to prevent quality loss of commodity. Risk zone location and optimisation of machine settings can be executed with a satisfying accuracy by comparing test results mutually, but measurement data are often hard to interpret, especially if predictions are desired on real damage. An extensive knowledge of the instrumented device and indications on the bruise susceptibility of a product are two indispensable conditions for successful damage prevention and reduction. As data acquisition techniques become more sophisticated and the autonomy of the measurement equipment tends to be better, the new generation of electronic potatoes, such as the Danish made PTR 200, seems promising for bruise prevention purposes. This is mainly due to improved memory capacity and more accurate data acquisition techniques. The main topic of this research was to determine the properties of the recently developed tool PTR 200 and to expand the knowledge of the device for a good use in practice. The research work was focussed on four important device characteristics: (1) the sensitivity of sensor zones; (2) the impact force—signal output relationship; (3) the consistency and reproducibility of measuring results; and (4) the signal transmission range. Under laboratory conditions, the sensitivity of sensor zones, the relationship between impact force and signal output, and the consistency and the reproducibility of measuring results were examined. One on-field procedure was executed to determine the signal transmission range. Laboratory characterisations were conducted with a pendulum impactor and revealed a varying impact force on 22 impact zones in case of application of an equal energy amount of 0·3525 J. A distinct relationship was found between impact force and signal response. Measurement results were consistent and reproducible; high standard deviations emphasise the importance of repetitive measurements to obtain relevant mean values. The maximum signal transmission range was identified as between 10 and 15 m. However, if there was an obstacle between the receiver and the transmitter the signal was immediately lost.

Evaluation of methods to remove inertial force from measured model wave impact force signals

The subject of wave impact on offshore structures and their components is important to vessel designers and operators for many reasons. They are often required to quantify these impact loads. Standard methods for wave load prediction will underestimate the forces on these structures due to intermittent loading. This necessitates the use of physical model tests to establish wave impact loads. The model measurement systems are designed to have high stiffness. This ensures that the natural frequency of the structure is above the wave frequency. However, it is widely believed that impacting waves contain high-frequency energy components that cause the structure to vibrate at its modal frequencies. This impact-induced vibration is recorded by the measuring system as a force (inertial force), and corrupts the actual applied force measurement. Before scaling can occur, the inertial force must be removed from the measured signal. A number of techniques for removing inertial force from measured signals are described in the published literature. Three methods are discussed, implemented and compared in this paper. The algorithms and procedures are presented. Each technique contains inherent and unique problems, while some are common to all methods. Neither of the techniques produced results that are fully satisfactory. The main problem is unwanted high-frequency content after the application of the methods. While neither method offers the perfect solution, the use of digital filtering techniques is recommended based on their relative performance and ease of implementation.

APPLICATION AND CORRECTION OF THE EXPONENTIAL WINDOW FOR FREQUENCY RESPONSE FUNCTIONS

Applying windows to experimental data is a common practice in modal testing to minimise the effects of leakage, and the exponential window is used for the transient signals measured with impact testing and burst random excitation. Used properly, the exponential can minimise leakage errors on lightly damped signals and can also improve the signal-to-noise of heavily damped signals. The time constant of the exponential window is specified typically by the user, and this paper discusses guidelines for specifying the window for both types of response signal. The effect of the exponential window is to increase the apparent damping of the measured system, and the correction for this effect on the estimated modal parameters is developed by utilising the shift property of the Laplace transform. In addition, the transfer function of a half-period sine pulse, which is a representative model of an impact force signal, is studied to show the need for, and consequences of, applying the exponential window to both the force signal and response signals. Finally, several numerical simulation test cases of sdof system as presented to demonstrate the issues discussed in preceding sections.

Biomechanical Variables and the Perception of Cushioning for Running in Various Types of Footwear

Using a 15-point rating scale, subjects rated perception of cushioning during running on a treadmill with three different footwear constructions of varying midsole hardness. During overground running, various biomechanical ground reaction force and pressure variables were collected and compared to the perception of cushioning scores. The perception scores identified the three shoes as very hard, medium soft, and soft. Peak pressures in the heel, the force rate, and the median power frequency of the impact force signal demonstrated increases in values with the perception of less cushioning. In the harder shoes, the subjects altered the loading patterns under their feet, resulting in lower impact forces and increased weight bearing of the forefoot structures.

Determination of Peach Firmness by Analysis of Impact Forces

ABSTRACT IMPACT forces of peaches striking a rigid surface were analyzed as a means for prediction of firmness and, hence, maturity. The impact force characteristics C2 (peak force/(time to peak force)^) and F295 (295 Hz spectrum magnitude) were highly correlated with fruit elastic modulus and penetrometer measurements of flesh firmness, and poorly correlated with mass and radius. These characteristics could be used to distinguish immature and mature peaches from threshold mature fruit, but the firmness sorting resolution was affected by variations in impact location. A band-pass filter circuit was constructed and tested to automatically sense the desired frequency components of the impact force signal.

The measurement of water-drop impact forces with a piezo-electric transducer

The development of a device for measuring raindrop impact force is described. The apparatus records the amplitude of voltage outputs produced by water-drops striking the surface of a piezo-electric transducer. Voltage output can be calibrated in terms of kinetic energy or impact force. The apparatus can record either the force of individual water-drop impacts or the integrated impact force exceeding a particular threshold value. Impact force and transducer output signal are linearly related to each other. The effect of the height of fall on impact force is discussed. Transducer measurements are compared with amounts of sand splashed by faling water-drops. The similarity of the results suggests that the apparatus is recording an important erosive property of the water-drops used in the experiments.