Gauge Position Research Articles

Experimental study on bond performance of recycled coarse aggregates concrete with circular steel tubes after freeze–thaw cycling

AbstractExtrusion tests were conducted on recycled coarse aggregate concrete with circular steel tubes (RCCST, 100% replacement of recycled coarse aggregate) to investigate the impact of freeze–thaw cycles on bond properties. RCCST samples were subjected to 0, 25, 50, 75, 100, 125 and 150 freeze–thaw cycles and their bond properties were then compared with those of natural coarse aggregate concrete with circular steel tubes (NCCST) after 0, 100 and 150 freeze–thaw cycles. The experimental results indicate that freeze–thaw cycling damages the internal structure of RCCST, causing a significant decrease in interfacial bond strength with an increase in the number of freeze–thaw cycles. Freeze–thaw RCCST exhibits lower peak load and higher peak slip compared to NCCST, with increases of 25.2%, 73.2%, and 70.3% after 0, 100, and 150 freeze–thaw cycles, respectively. Regression analysis was used to derive an exponential equation that describes the relationship between longitudinal strain and strain gauge position. Additionally, a segmented fitting method was employed to obtain an expression for the bond slip of the freeze–thaw RCCST with a circular steel pipe.

Evaluation of Microstrain in the Regions Surrounding Morse Taper and External Hexagon Implants.

The aim of this study was to compare the Morse taper (MT) + titanium base (Ti-Base) abutment with the external hexagon (EH) + Ti-Base abutment by using the strain gauge method in the mesial, distal, and apical-buccal areas around these types of implants. This study investigated two groups, MT and EH, each comprising five polyurethane samples with a dental implant in the area of artificial tooth 15 (3.75 × 11.5 mm) of a dental manikin. The strain gauges were glued to the mesial, distal, and apical-buccal polyurethane areas of all samples in relation to the implant. Ti-Base nonangled abutments measuring 5.0 × 4.7 × 1.0 mm (DSP, Brazil) were installed on the implants in each group. Ten identical zirconia crowns were constructed by scanning and milling and were subsequently cemented onto the Ti-base abutments with calcium hydroxide cement. Then, an axial load of 100 N was applied to the occlusal region of the zirconia crowns, and strain gauge measurements were taken. Strain gauge data were assessed by a two-way analysis of variance (ANOVA) with "implant connection" and "strain gauge position" factors, followed by the Bonferroni test (p < 0.05). The MT group exhibited a statistically significant reduction in microstrain in the mesial and apical strain gauge measurements compared to the EH group. The MT group exhibited less microstrain in the mesial and apical areas of the polyurethane samples near the implant. Consequently, the MT connection was considered more biomechanically advantageous.

Neutron radiography with simultaneous deformation measurements demand rethinking the modelling of imbibition in cement paste

During capillary imbibition, there are changes in the pore structure that reduce the water ingress rate, leading to anomalous behaviour. However, the relation of those deformations with the C-S-H content is still unclear. We performed simultaneous measurements of external deformations and water ingress through neutron radiography. Cement pastes of water/cement of 0.4 and 0.6, using both Portland and white cement were tested after 1 year curing. Porosity and calcium silicate hydrate (C-S-H) content of the pastes were determined. Strain gauges were attached perpendicular and parallel to the water flow. Results indicate that the degree of internal restriction of the mix influences the shape of the water profile and that C-S-H deformations affect internal changes more than external. Water ingress visualisation indicated the lack of a sharp front during imbibition and the saturation degree variation at the position of the strain gauges. We propose a model to address the dynamic porosity.

Determination of Ductile Tearing Resistance parameter of Interstitial-Free Steel Sheet

The present work deals with the characterization of ductile tearing resistance of 1 mm thick interstitial free steel sheet using crack tip opening angle (φ), and δ5 concepts with some experimental modification. CTOA (φ) measurements on the specimen surface at the growing crack tip have been performed using light microscope on both pre-cracked DENT and SENT specimens at three ramp rates following the essence of ASTM E 2472. In order to determine the effect of pre-cracking, CTOA of the notched (ρ:0.1 mm) SENT specimen has also been measured at 10-4 s-1. The transferability of φ−Δα and δ5−Δα between two geometries has been verified. It is concluded that for a specified thickness both φ−Δα and δ5−Δα plots can be used for crack growth characterisation of sheet metals even without using pre-cracked specimens. However, the angle φ(δ5) determined from δ5−Δα curve is not the true measure of optical CTOA,φ as the δ5 gauge position does not follow the tip position of the growing crack.

Stress Simulation on Four-Bar Link-Type Transplanting Device of Semiautomatic Vegetable Transplanter

The aim of this study is to analyze the stress exerted on a four-bar link-type transplanting device using two distinct methods: stress measurement performed during a field test and stress simulation. A field test is conducted to measure stress using a strain gauge positioned at 15 specific points on the transplanting device. Subsequently, the measured strain data are converted into calculated stress data. In another method, stress is simulated using specialized multibody dynamic simulation software. The simulation results are compared with the stress measured during field tests to verify the simulation model. Based on the results, the maximum stress derived from the simulation correlates with the measured results, although notable discrepancies are shown, particularly at strain gauge positions 11 and 13. The maximum stress derived from the simulation is used to calculate the static safety factor of the transplanting device. The peak stress derived from the simulation aligns with the measured results, although significant discrepancies are observed at positions corresponding to strain gauges 4 and 10. The maximum stress (150.82 MPa) is observed on the link of the transplanting device, and the static safety factor determined via the simulation is 1.39.

Stress Simulation on Cam-Type Transplanting Device of Semiautomatic Vegetable Transplanter

Stress measurements play a crucial role in safety analyses of transplanting devices. Strain gauges for stress measurements during field tests can be expensive and time-consuming. The aim of this study was to investigate the stress on the transplanting device of a cam-type semiautomatic vegetable transplanter using a simulation method. A three-dimensional simulation model was established, considering the dimensions and material properties of the transplanting device. The stress distribution and maximum stress values were obtained through simulations. The maximum stress values at 15 points within the transplanting device determined via the simulation were compared with the experimental stress data to verify the stress simulation model. The results show that the maximum stress obtained from the simulation correlated with that of the measured results, although differences were observed at different locations, particularly at strain gauge positions 11 and 13. Based on the simulation results, the maximum stress occurs at the upper link of the cam-type transplanting device, reaching a magnitude of 201.21 MPa, and the static safety factor is 1.04.

Fatigue Strength Analysis of a Prototype Francis Turbine in a Multilevel Lifetime Assessment Procedure Part III: Instrumentation and Prototype Site Measurement

Part I of this series of publications addressed the background and fundamentals of the lifetime assessment of prototype Francis turbines. Part II concentrated on the developed methods of numerical calculation and assessment procedures. The present contribution (Part III) deals with the instrumentation and the metrological range of the assessment procedure. The most important sensors, measurement tools, and data acquisition units are presented (background). The instrumentation of the prototype Francis turbine is used, on the one hand, for machine unit monitoring and plant operating and, on the other hand, for generating measurement data to validate and adjust/correct the numerical simulations. Measurement data form the basis for further evaluations at various levels. A wide variety of measured variables are required to carry out the remaining lifetime of a component using fatigue analysis. Those variables include pressure and acceleration signals, vibration monitoring, and strain gauge applications for mechanical stress analysis. The available measurement signals are divided into groups based on the developed method. Thus, already-available data from the control room are compared with machine monitoring and temporarily measured data. The correlation of all available data is essential today to determine an exact idea of the occurring flow phenomena and their effects on the mechanical stresses on the component. This interaction of the different data sources and, subsequently, the use of selected quantities for the numerical calculation are part of the newly developed concept for fatigue strength analysis of mechanical components of a turbine unit (methods). The results of this journal article are divided into the discussion of the necessary instrumentation and mounting of the sensors and into the evaluation, presentation, and interpretation of the measurement data. In addition, a fatigue strength assessment is made at the position of the strain gauges. These results serve as a basis for validating the numerical stress calculation. It is worth mentioning that the validation of the numerical results and the discussion of the deviations and error consideration is carried out in Part IV of this publication series (results). This journal article of the series on condition assessment of prototype Francis turbines ends with a discussion of the results and conclusions for further data processing (conclusion).

Research on identification of multiple target signals based on φ-OTDR

Phase sensitive optical time domain reflectometer (φ-OTDR) is widely employed in pipeline safety early warning, perimeter security, Pipeline inspection gauge (PIG) positioning and tracking, etc. Generally, equipment is applied in outdoor environments. There is a high probability that multiple intrusion signals exist simultaneously at a common position. Therefore, it is significant to unmix and identify each signal. In this paper, a multi-target signal recognition method based on φ-OTDR is proposed. The basic principles of φ-OTDR system and fixed point algorithm based on negative entropy maximization (FASTICA) are briefly introduced. The blind source separation and recognition of the mixed signals of hammer and motor are carried out, which proves the effectiveness of the method. In order to further quantitatively evaluate the effect of separation, the feature extraction of hammer signal and motor signal is carried out from two aspects respectively from time and frequency domain. The feature vector describing signal characteristics in terms of both time and frequency domain is proposed and used as the evaluation criterion of the separation performance. The experimental results show that the separated signal basically conforms to the feature vector, and the time domain feature is the most stable, with a maximum error of only 3.08%.

Parametric Study of Drilling Method Performed on One-Way Post-Tensioned Slabs

Abstract Determination of the stress state in concrete structures is a very important, but difficult task. In the case of new structures, it is possible to easily instal measurement instruments which can provide important data as a part of real-time monitoring. However, the evaluation of stresses in existing structures is much more challenging. Currently, stress relief methods are a well-established approach for the evaluation of the actual state of existing structures. The so-called Drilling method (also known as Stress-relief coring technique) is one of the possible techniques for such analysis. For practical use of this method, knowledge of pivotal factors which influence stress relief is crucial. Therefore, this paper presents a parametric study performed on a one-way post-tensioned slab which can help to understand the effect of the depth of the core and the distance from the edge of the hole (position of strain gauges) on the change in stress in the vicinity of the drilled core. Finally, based on the obtained data, the recommendations for the subsequent experimental program will be summarized. According to the study, it seems that the depth of drilled core does not significantly influence the stress relief and the main impact can be attributed to distance from the edge of the hole.

Experimental Investigation of the Forklift Truck Impact on CFS Pallet Racks

Background: Storage pallet racks are commonly formed by Cold-Formed-Steel (CFS) members and are used worldwide to store goods on pallets. The main racking system is denoted as “selective pallet racking”. This racking system is one pallet deep and is separated by aisles, allowing for each pallet, stored on horizontal beams, to be always accessible. Steel racking systems are frequently subjected to accidental impact forces from operating forklift trucks. If international racking design codes provide an arbitrary value of impact force to design members, several impacts can produce damages, which can lead to system failure, highlighting the fundamental role played by monitoring. Methods: Results of an experimental campaign on a full-size selective rack are presented. The investigated rack is subjected to the impact of a forklift truck and hammer test at different points. The propagation of the acceleration among adjacent bracing frames is investigated with the magnitude of the recorded strains in structural members. Results: Results highlight that an accelerometer every two spans can establish whether the monitored racking system is accidentally hit. Compressed diagonal and tensile diagonal work in parallel. Only one diagonal brace, every two spans, can be monitored through a strain gauge to establish the forklift truck impact point and estimate the stress distribution on adjacent members. Conclusion: The study suggests an optimization in the number, type and position of accelerometers and strain gauges in monitoring racking systems to identify forklift truck impact and its effects.

Data processing of wave propagation in viscoelastic split Hopkinson pressure bar

In this study, the polymethyl methacrylate (PMMA) bar was taken as an example to study the data processing of the viscoelastic Split Hopkinson pressure bar (SHPB) during shock wave propagation. First, SHPB tests of the PMMA bar were conducted, and the strain data measured at the position of the strain gauges on the viscoelastic PMMA bar were processed by using the improved Lagrange analysis method (LAM) to obtain the full-field strain, particle velocity, and stress data. Then, the Zhu–Wang–Tang dynamic viscoelastic constitutive model was adopted, and the parameters were calibrated to determine the dynamic constitutive equation of the PMMA bar. By combining the characteristics method and the dynamic constitutive equation, numerical simulation was conducted to obtain the physical quantity data at each point on the PMMA bar, so as to realize the closed-loop test. By comparing the data obtained by the improved LAM with the data obtained by the characteristics method, it was found that the improved LAM can improve the calculation accuracy at the later loading stage and was more consistent with the actual situation, and the validity of data processing and the applicability of the dynamic constitutive equation at the early loading stage were verified as well. The improved LAM can be extended to the propagation calculation of the attenuation wave in SHPB tests of soft materials or low density materials.

Research on Dynamic and Static Test Methods for Evaluating the Poisson’s Ratio of Oriented Strand Board

In this article, dynamic method and static method of testing Poisson’s ratio of OSB (Oriented Strand Board) were proposed. Through modal and static numerical analyses, the position where the transverse stress is equal to zero was determined. The binary linear regression method was applied to express the gluing position of the strain gauge as a relational expression that depended on the length-width ratio and width-thickness ratio of the cantilever plate. Then the longitudinal and transverse Poisson’s ratios of OSB were measured by the given dynamic and static methods. In addition, the test results of OSB Poisson’s ratio were analyzed with the probability distribution of random variables. The results showed that using the proposed dynamic method and static method, the test results for longitudinal and transverse Poisson’s ratios of OSB were quite consistent, despite the gluing position of the strain gauges being different. And these OSB Poisson’s ratios were accorded with that obtained by the axial tensile method and the four-point bending method. OSB longitudinal and transverse Poisson’s ratios followed Weibull distribution.

Digital Twin for Fatigue Analysis

As part of fatigue from finite elements (FE) analysis inputs (geometry, material, and loading), the stress level in a component is a key input for representativity of simulation. To illustrate, assuming a simplified power law between stress and life in excluding all plasticity, sequence effect and any other non-linearities, a small variation in the stress input value may propagate into a large variation in the output simulated life.To reduce these epistemic uncertainties, correlation with strain gages is a fundamental added value to any FE model, as it permits to validate mesh convergence, model, stiffness, and boundary conditions. The construction of a robust digital twin heavily benefits from this important tool for further usage and to improve predictability.The current work shows how to extract insights from strain gages measurements. First of all, improving FE/test correlation may be helped by virtual strain gage analysis. However, strain gage measurement accuracy highly relies on strain gage position and orientation. Consequently, the optimization of sensors positions and orientations, regarding representativity of each independent load case, will reinforce Test Engineer expertise in his test plan specification. Then, the core subject of this paper depicts the load reconstruction process, which means how to get load histories from both strain gage measurements and independent unitary FE load cases, in quasi-static and dynamic framework. As a result, obtaining input loads is a way to extrapolate stress level and life results from discrete points (strain gages) to full component, accessing life results in hot spots with large stress concentration.The theorical background will be described and the methodology on an application case illustrated.

Gearbox Mechanical Efficiency Determination by Strain Gauges Direct Application

This article describes a unique method of measuring the efficiency of gearboxes using foil strain gauges, which allows maintaining the current configuration of the gearbox within the overall assembly of the machine and its functional condition. The presented method is applicable to gearboxes located in the original equipment assembly without the need to use a test rig. Using foil strain gauges, the torque at the input and output of the gearbox is detected. Therefore, the accuracy of torque measurement is key. The crucial step is the calibration of the instrumentation to the given application conditions, which, in this case, is ensured by a virtual calibration using a very accurate FEM analysis. The accuracy of the position of strain gauges and virtual calibration of measurements generate inaccuracies affecting the resulting uncertainty of the determined efficiency. The present article shows, on the example of several measurements, that when using 24-bit converters, after processing the obtained data, mechanical stress with a sensitivity better than hundredths of an MPa can be reliably detected even without signal amplification from strain gauges. It follows that the efficiency is determined with an accuracy of better than low units of tenths.

Pipeline Inspection Gauge Positioning System Based on Optical Fiber Distributed Acoustic Sensing

To maintain pipeline transportation’s optimal efficiency and safety, pipelines must be regularly inspected and cleaned by the pipeline inspection gauge (PIG). Since the PIG passes through the whole pipeline, which is generally tens of kilometers, observing where the PIG is working in real-time is necessary. When the PIG passes through the pipe joint, the vibration signal will generate by the collision between the PIG and the girth weld, which can transmit along the fiber cable besides the pipeline. In this paper, we demonstrate that the optical fiber distributed acoustic sensing (DAS) can acquire the collision vibration in terms of the V pattern in the waterfall diagram, whose vertex is the collision position of PIG. The vertex will not exist when the cable positions are far away from the pipeline, which is relatively common in practice. We proposed an algorithm based on the clustering algorithm and the Hough transform to detect the position of the PIG even when the vertex of the V pattern does not exist. A field experiment shows that the proposed positioning algorithms applied to the DAS can effectively track the PIG online.

Rates of Natural Subsidence along the Texas Coast Derived from GPS and Tide Gauge Measurements (1904–2020)

AbstractThis study investigated the rate of natural subsidence along the Texas coast using multidecadal to century tide gauge (TG) and global positioning system (GPS) data sets. The rates of land s...

An inverse approach for load identification of cracked wind turbine components

ABSTRACT To assess the integrity of a structure, it is necessary to be familiar with the applied loads on its components. In this paper, an inverse modeling procedure was developed to identify the unknown static loads of a cracked component made from a brittle material, using a recently developed phase-field fracture modeling approach. The main goal was to define the optimal number, position, and orientation of the strain gauges on the structural component needed to accurately determine the imposed loads leading to different crack sizes and crack orientations. This enables an accurate assessment of the structural integrity of the components throughout their entire service life, including the process of crack initiation and its stable growth to a critical length. To verify the inverse approach, several numerical benchmark examples as well as the vital components of the wind turbine, such as the axle pin were analyzed. It is shown that the proposed approach with optimally placed strain gauges enables the accurate estimation of complex loads in a fractured component.

Effect of type of reinforcement on clinical denture base deformation with telescopic attachments of implant retained overdentures. A within-subject clinical study.

Abstract Aim: The aim of this within-subject study was to evaluate and compare clinical denture base deformation with two types of denture base reinforcement for telescopic implant retained overdentures. Materials and methods: Six completely edentulous participants received two implants in the canine region of the mandible and the implants were connected to the overdentures with resilient telescopic attachments. Each patient received 2 types of denture reinforcement for the mandibular overdentures; 1) metal reinforced overdentures, 2) PEEK reinforced overdentures. Four strain-gauges were adhered to the lingual polished surface of each denture abutment top (C1 and C3), and 5 mm below abutment top (C2 and C4). Strain registrations were performed during maximum voluntary clenching. Results: The measured strains and implant positions C1 and C3 were tensile in nature and the measured strains at implant positions C2 and C4 were compressive in nature. The highest microstrain was noted at C3, followed by C1, then C2, and the lowest strain was noted was with C4 for both groups. There was no significant difference in recorded microstrains between C1 and C3 or between C2 and C4. For all strain gauge positions, PEEK reinforced overdentures recorded significantly higher microstrains than metal-reinforced overdentures. Conclusion: Within the limitation of this short term cross over trial, cobalt-chromium metal reinforcement for mandibular implant assisted overdentures is recommended than PEEK reinforcement as it reduced denture base strains and deformation during maximum voluntary clenching.

A novel approach for characterising the cause of disc formation by the shear cutting process in a punching machine

The objective of this paper is to validate a method for identifying the cause of disc formation by numerical and experimental investigations for a single-stage shear cutting process in a tool-bound punching machine. To this end, first a 2D simulation model for the deep-drawing steel DC01 is developed, which enables the sophisticated requirement of tracking the material flow behaviour in the cutting process to be met by using the FEM Software DEFORM. Furthermore, the plastic flow behaviour is measured in an equivalent experiment with strain gauges near the cutting process. Then, the measurement results from the experimental investigation are contrasted with those from the simulation and compared for reliability at the measuring position of the strain gauges. The main contribution of this paper is a numerically and experimentally performed comparative study, in which the verified results of the first investigation near the shearing process are transferred into the cutting area and are validated subsequently.

A Laboratory Forced-Oscillation Apparatus for Measurements of Elastic and Anelastic Properties of Rocks at Seismic Frequencies

In presented paper, we describe the technical and physical aspects of the application of a low-frequency (LF) apparatus based on a longitudinal type of forced oscillations. In particular, we investigate the influence of the strain gauge position on a tested sample on measurement results, we also examine the creep effect associated with the mineralogy of rocks, as well as the dispersion and attenuation in a liquid-saturated rock sample caused by the presence of the volume of pore fluid exterior to the sample (dead volume). The effect of the position of the strain gauges is investigated using a cylindrical acrylic sample and two pairs of strain gauges fixed in the middle and at one of the sample ends under a uniaxial pressure of 15 MPa. The obtained results demonstrate that elastic and anelastic parameters of the tested sample are independent from the location of the strain gauges. The impact of the creep phenomenon on elastic moduli was studied using three room-dry samples of Savonnieres limestone, Berea sandstone and Eagle Ford shale. The measurements were conducted for 120 h at a frequency of 2 Hz under a uniaxial pressure of 10 MPa and demonstrated that the LF moduli of all rocks were noticeably reduced with time. The effect of dead volume was investigated at seismic frequencies using limestone saturated with n-decane. It was found that the Young’s and bulk moduli exhibit strong dispersion at frequencies above 10 Hz if the dead volume is close to or greater than the pore volume of the sample. We also found that the characteristic frequency of dispersion corresponding to the attenuation peak is independent of the size of the dead volume and determined only by the physical parameters of the sample and pore fluid. We present also the results of the Young’s modulus and attenuation measurements conducted at seismic frequencies on vertical and horizontal shale samples saturated with water. It was shown that the relationship between the extensional attenuation and the Young’s modulus dispersion observed in the samples saturated at a relative humidity of 97.5% is consistent with the Kramers–Kronig relation.