Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/appro...Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/approach-Finite element method was employed to analyze the stress and strain distribution on the track wheel web surface under varying wheel-rail forces.Locations with minimal coupling interference between vertical and lateral forces were identified as suitable for strain gauge installation.Findings-The results show that due to the track wheel web’s unique curved shape and wheel-rail force loading mechanism,both tensile and compressive states exit on the surface of the web.When vertical force is applied,Mises stress and strain are relatively high near the inner radius of 710 mm and the outer radius of 1110mmof the web.Under lateral force,high Mises stress and strain are observed near the radius of 670mmon the inner and outer sides of the web.As the wheel-rail force application point shifts laterally toward the outer side,the Mises stress and strain near the inner radius of 710 mm of the web gradually decrease under vertical force while gradually increasing near the outer radius of 1110 mm of the web.Under lateral force,the Mises stress and strain on the surface of the web remain relatively unchanged regardless of the wheel-rail force application point.Based on the analysis of stress and strain on the surface of the web under different wheel-rail forces,the inner radius of 870 mm is recommended as the optimal mounting location of strain gauges for measuring vertical force,while the inner radius of 1143 mm is suitable for measuring lateral force.Originality/value-The research findings provide valuable insights for determining optimal strain gauge locations and designing an effective track wheel force measurement system.展开更多
The measurement accuracy of a wind tunnel balance is the key factor to improve the measurement accuracy for a test model in the wind tunnel. In order to improve the measurement accuracy of the wind tunnel balance, a g...The measurement accuracy of a wind tunnel balance is the key factor to improve the measurement accuracy for a test model in the wind tunnel. In order to improve the measurement accuracy of the wind tunnel balance, a great deal of investigation is carried out in China. This paper summarizes a program to improve the measurement accuracy of wind tunnel balances. In the program, the investigation is carried out in three aspects (1) designing a drag component of the balance in low interactions (2) choosing high quality foil strain gauges with temperature self-compensation (3) choosing the excellent gauges and mounting them meticulously. As an example, these research achievements are applied in a φ18 six component balance. The measurement accuracy of a GB-04 standard model in a transonic wind tunnel with the φ18 six component balance comes up to the advanced world standard.展开更多
A cable net structure is selected to support its reflecting triangular aluminum panels of FAST(five-hundred-meter aperture spherical radio telescope).To ensure the security and stability of the supporting structure,ca...A cable net structure is selected to support its reflecting triangular aluminum panels of FAST(five-hundred-meter aperture spherical radio telescope).To ensure the security and stability of the supporting structure,cable force of typical cables must be monitored on line.Considering the stringent requirements in installation,accuracy,long-term stability and EMI(Electromagnetic interference),most of the commonly used cable force measurement methods or sensors are not suitable for the cable force monitoring of the supporting cable-net of FAST.A method is presents to accomplish the cable force monitoring,which uses a vibrating wire strain gauge to monitor the strain of linear strain area at the anchor head.Experiments have been carried out to verify the feasibility.The method has a series of advantages,such as high reliability,high accuracy,good dynamic performance and durability,easiness of maintenance,technical maturity in industry and EMI shielding.Theoretical analysis shows that there is a linear relationship between the cable body force and anchor head surface strain,and experimental results proves a good linear relationship with excellent repeatability between the cable body force and anchor head surface strain measured by the vibrating wire strain gauge,with a linear fit better than 0.98.Mean square error in practical measuring is 2.5t.The relative error is better than 4%within the scope of the cable force in FAST operation which meets practical demand in FAST engineering.展开更多
Metal foil strain gauges remain the state-of-the-art transducers for wind tunnel balances.While strain gauge technology is very mature,piezoresistive semiconductor sensors offer alternatives that are worth exploring t...Metal foil strain gauges remain the state-of-the-art transducers for wind tunnel balances.While strain gauge technology is very mature,piezoresistive semiconductor sensors offer alternatives that are worth exploring to assess their unique benefits,such as better strain resolution and accuracy,which would enable balances to be designed with higher factors to safety and hence longer fatigue lifetimes.A new three-component balance,based on temperature compensated semiconductor strain gauges,is designed,calibrated and tested in a hypersonic low density wind tunnel.The static accuracy of the semiconductor balance is calibrated better than 0.3%FS,and the dynamic accuracy of the balance is established using a HB-2 standard model in a Mach 12 hypersonic flow.Good experimental repeatability is confirmed to be better than 2.5%FS,and the effectiveness of the balance is demonstrated by comparing the forces and moments of measured data with computational fluid dynamics simulations,as well as reference wind tunnel results under similar conditions.展开更多
Electrical resistance strain gauges(SGs) are useful tools for experimental stress analysis and the strain sensing elements in many electromechanical transducers including load cells,pressure transducers,torque meters,...Electrical resistance strain gauges(SGs) are useful tools for experimental stress analysis and the strain sensing elements in many electromechanical transducers including load cells,pressure transducers,torque meters,accelerometers,force cells,displacement transducers and so forth.The commonly used commercial crystalline strain sensing materials of SGs are in the form of wire or foil of which performance and reliability is not good enough due to their low electrical resistivity and incapacity to get thin thickness.Smaller SGs with single straight strand strain sensing materials,which are called ideal SG,are highly desirable for more than seven decades since the first SG was invented.Here,we show the development of a type of minuscule length scale strain gauge by using a bare and single straight strand metallic glassy fiber(MGF) with high resistivity,much smaller lengthscale,high elastic limits(2.16%) and especially the super piezoresistance effect.We anticipate that our metallic glassy fiber strain gauge(MGFSG),which moves toward the ideal SGs,would have wide applications for electromechanical transducers and stress analysis and catalyze development of more micro-and nanoscale metallic glass applications.展开更多
The reliability and sensitivity of a strain gauge made from a nanoparticle monolayer intrinsically depend on electron tunneling between the adjacent nanoparticles, so that creating nanoscale interstitials with uniform...The reliability and sensitivity of a strain gauge made from a nanoparticle monolayer intrinsically depend on electron tunneling between the adjacent nanoparticles, so that creating nanoscale interstitials with uniform distribution and tuning the interparticle separation reversibly during cyclic mechanical stress are two vital issues for performance enhancement. In this work, one assembly technique is initialized to fabricate parallel nanoparticle strips by precisely tailoring the contact angle of a gold colloid on a substrate. The assembly of a nanoparticle monolayer with a close-packed pattern can be simultaneously switched on and off by independently varying the contact angle across a threshold value of 4.2~. This nanoparticle strip shows a reversible and reliable electrical response even if a mechanical strain as small as 0.027% is periodically supplied, implying well-controlled electron tunneling between the adjacent nanoparticles.展开更多
We demonstrate an ultrasensitive strain gauge based on a discontinuous metal film with a record detection limit as low as 8.3 × 10^-6. Constructed by well-tunable crevices on the nanometer scale within the film, ...We demonstrate an ultrasensitive strain gauge based on a discontinuous metal film with a record detection limit as low as 8.3 × 10^-6. Constructed by well-tunable crevices on the nanometer scale within the film, this gauge exhibits an ultrafast dynamic response to vibrations with a frequency range of 1 Hz to 10 kHz. More importantly, the temperature coefficient of resistivity （TCR） of the metal film is tunable owing to the cancellation effect caused by the possibility of tunneling across the nanoscale crevices （showing a negative temperature dependence） and the electron conduction within the metal islands （showing a positive temperature dependence）. Consequently, a nullified TCR is achievable when the crevice size can be precisely controlled. Thus, a fabrication strategy to precisely control the nanoscale crevices was developed in this study through the real-time tracking of the electrical conductivity during thermal evaporation. The ultrasensitive strain gauge with a tunable thermal drift introduces numerous opportunities for precision devices and wearable electronics with superior reliability.展开更多
Karma alloy thin film strain gauges were fabricated on alumina substrates by magnetron sputtering. The electrical properties of strain gauges annealed at different temperatures were then tested. The surface morphology...Karma alloy thin film strain gauges were fabricated on alumina substrates by magnetron sputtering. The electrical properties of strain gauges annealed at different temperatures were then tested. The surface morphology and phase structure of the Karma alloy thin films were analyzed using X-ray diffraction and scanning electron microscopy. The effect of the annealing temperature on the performance of the Karma alloy thin film strain gauge was also investigated. As the annealing temperature increased, it was found that the resistivity of the thin films decreased, whereas the temperature coefficient of resistance (TCR) of the thin films increased. A Karma alloy thin film strain gauge was annealed at 200 °C, thereby obtaining a gauge factor of 1.7 and a corresponding TCR of 64.8 × 10−6 K−1. The prepared Karma alloy thin film strain gauge had a lower TCR than other strain gauges at room temperature. This result can provide a reference for the preparation and application of Karma alloy thin film strain gauges in specific scenarios.展开更多
The technology of continuously welded rails （CWRs） is important in modern railway track structures. To measure rail stress, resistance strain gauges are preferred due to their good stability, sensitivity, and esist...The technology of continuously welded rails （CWRs） is important in modern railway track structures. To measure rail stress, resistance strain gauges are preferred due to their good stability, sensitivity, and esistance to external interference. Based on the bi-directional strain method, we present a new method for measuring longitudinal rail stress using resistance strain gauges and develop a monitoring device for rail stress to realize long-term and multi-point measurement. Also relevant experimental verification and analysis are conducted. Results indicate that under various constraints the rail stress–strain values can be calculated just with the measured total longitudinal strain and total vertical strain. Considering the measurement error caused by sectional feature of sensors, we put forward a correction equation applicable to different stress conditions. Although the temperature values of the four full-bridge stress gauges can offset each other, the measurement error caused by rail flexural strain can also be eliminated to a certain extent at the same time, the nonuniform distribution of rail cross section temperature and unbalanced flexural strain still affect the measurement error. The experimental results also show that the developed rail-stress-monitoring sensor is suitable for measuring rail stress with reliable working performance.展开更多
We studied the variability in longitudinal growth strains and wood basic density in five-year old trees from five clones （one tree per clone） of Eucalyptus tereticornis. Mean longitudinal growth strain in clones ran...We studied the variability in longitudinal growth strains and wood basic density in five-year old trees from five clones （one tree per clone） of Eucalyptus tereticornis. Mean longitudinal growth strain in clones ranged from 466 to 876 μm. There was a significant difference between clones in growth strains and wood basic density. Clone 10 exhibited maximum growth strains and basic density, whereas clone 3 and clone 7 exhibited minimum growth strains and basic density, respectively. Within a tree, the growth strain variation with tree height was high but statistically insignificant while within tree variation in basic density was very small. There was no specific trend in variation in either strain or density within a tree. There was 5% 200% difference in growth strain on opposite sides of the logs. However two strains showed a strong positive correlation. There was a moderate positive association of wood basic density and mean growth strains in logs. The variation around the periphery emphasize the need to measure strain more than one, preferably on opposite sides at the same height, on a tree to know the mean strain level for the purpose of selection of clones.展开更多
Environmental contamination has been caused by petroleum-based polymeric materials in the melt deposition process.Nowadays biodegradable materials have been widely used in the fused deposition modeling(FDM)industry,su...Environmental contamination has been caused by petroleum-based polymeric materials in the melt deposition process.Nowadays biodegradable materials have been widely used in the fused deposition modeling(FDM)industry,such as polylactic acid(PLA).However,internal complex thermal stress and deformations in part caused by an uneven distribution of PLA filament deposition temperatures during FDM,which will seriously affect the geometric accuracy of the printed part.In order to reduce material waste and environmental pollution during the printing process,the accuracy of PLA part can be improved.Herein,numerical simulation was carried out to investigate the temperature field and stress field during the building and cooling process of cuboid specimens.The effects of printing path on the thermal stress and temperature field during the building process were mainly studied.The results show that the printing path has a significant effect on the stress distribution.The most uni-form stress distribution and the smallest deformation were obtained using the Zig Zag printing path.Finally,the residual stress during the cooling process was collected using strain gauges embedded at the mid-plane of the FDM built cuboid specimens.The simulation results are consistent with the experimental results.展开更多
Railway switches and crossings constitute a small fraction of linear track length but consume a large proportion of the railway track system maintenance budget.While switch and crossing(S&C)faults rarely prevent t...Railway switches and crossings constitute a small fraction of linear track length but consume a large proportion of the railway track system maintenance budget.While switch and crossing(S&C)faults rarely prevent trains from running,switches and crossings are the source of many faults and need continual attention.On the rare occasions when trains are prevented from running the cost of the disruption is very high.Condition monitoring of the point operating equipment that moves the switchblades has been in use for many years but condition monitoring of the state of the switch in terms of the support and mechanical damage as trains pass over has only recently started to become possible.To this end,it is important to understand the correlation between S&C faults and sensor data that can detect those faults.This paper assesses some of the data collected from multiple sensors variously positioned on and around a switch and crossing on the UK mainline for a few days of normal train operation.Accelerometers,geophones,and strain gauges were installed at the locations where they were anticipated to be most useful.Forces at the load transfer point on the crossing nose were estimated from two separate strain gauge bridges and possible use of acceleration on the crossing is discussed.Correlations between different data are analysed and assessed and correlation between peak estimated load transfer forces and accelerations is presented.Based on the analysis,conclusions are drawn about the different types of dynamic information around S&Cs that can be obtained from a variety of sensor types.展开更多
Current research focussed on the assessment of metal machining process parameters and on the development of adaptive control, shows that machine performance, work-piece and tool material selections, tool life, quality...Current research focussed on the assessment of metal machining process parameters and on the development of adaptive control, shows that machine performance, work-piece and tool material selections, tool life, quality of machined surfaces, the geometry of cutting tool edges, and cutting conditions are closely related to the cutting forces. This information is of great interest to cutting tool manufactures and users alike. Over the years there have been significant developments and improvements in the equipment used to monitor such forces. In 1930 mechanical gauges were replaced by resistance strain gauges, and some 30 years later compact air gauge dynamometers were invented. Since this time intensive research has continued being directed to- wards developing new approaches to cutting force measurement. The Kistler Company, well-known manufacturer of acceleration and piezoelectrical dynamometers, has worked in this field for more than three decades, and developed very sensitive devices. While leading manufacturing research laboratories are often equipped with this technology, classical electrical strain gauges and other dynamometers of individual designs are still commonly used in industry. The present paper presents data obtained using different techniques of force measurement in metal machining processes. In particular, areas of uncertainties, illustrated through results concerning the turning process, are analysed, leading to an appraisal of the current status of these measurements and their significance.展开更多
A new measurement and analysis method was proposed to investigate the changes in elbow joint moments that occur with the use of a front-wheeled walker. A strain gauge-based walker instrumentation system was developed ...A new measurement and analysis method was proposed to investigate the changes in elbow joint moments that occur with the use of a front-wheeled walker. A strain gauge-based walker instrumentation system was developed to monitor the hand loads during walker-assisted walking and integrated with an upper extremity biomechanical model, Preliminary system data were collected for 12 subjects following informed consent. Bilateral upper extremity kinematic data were acquired with a six-camera motion analysis system. Internal joint moments at the elbow were determined in the three clinical planes using the inverse dynamics method. Results showed that during a walker-assisted gait elbow joint moments mainly distributed in the walker stance period. There was a noted demand on the elbow extensor in the sagittal plane with the greatest record as 0.381 N.m/（kg.m）, An interesting “bare phase” of mean elbow joint moments was also found in phase angle-240°-340° of gait cycle. Complete description of elbow joint moments of walkerassisted gait may provide insight into walker use parameters and rehabilitative strategies.展开更多
The method to detect the crack initiation point of Charpy pre-cracked specimen under dy- namie loading was studied using strain gauge.The load-time curve and nominal strain-time curve at the crack tip for impact testi...The method to detect the crack initiation point of Charpy pre-cracked specimen under dy- namie loading was studied using strain gauge.The load-time curve and nominal strain-time curve at the crack tip for impact testing specinens may be shnultaneously measured by twin-channel oscilloscope with high speed sampling and diskette storing.Based on the dynam- ic finite element simulation of impact response of Charpy specimen,the measuring method of dynamic fracture toughness was analysed and some problems in previous dynamic fracture toughness measurement were discussed.展开更多
In order to overcome stress concentration and increase fatigue life of ellipsoidal shells with inner guide structure,the stress analysis for strength check is very important. Owing to the main sectional profile with e...In order to overcome stress concentration and increase fatigue life of ellipsoidal shells with inner guide structure,the stress analysis for strength check is very important. Owing to the main sectional profile with ellipsoidal shape,the stress distribution for perfect ellipsoidal shell is firstly conducted based on the theoretical calculation and strain gauges measurement. The experiment results show that the stresses increase gradually from pole region to equatorial plane,but still within elastic range. Secondly,strain gauge measurement for ellipsoidal shells with inner guide structure is conducted. The results show that stresses are concentrated at the vicinity of bottom plate and beyond elastic range,so the structural redesign is needed. Finally based on the analysis mentioned above,a redesigned structure with local thickening is proposed. Experimental research shows that the stress varies more even after structural redesign and within allowable range. Numerical simulation shows that both the deformation and fatigue life after redesign are acceptable.展开更多
This paper aims at monitoring the autogenous shrinkage （AS） of a high-performance concrete （HPC） column specimen using an embedded strain gauge just after concrete pouring. A real size specimen （40 cm×40 cm&...This paper aims at monitoring the autogenous shrinkage （AS） of a high-performance concrete （HPC） column specimen using an embedded strain gauge just after concrete pouring. A real size specimen （40 cm×40 cm×100cm） was made to simulate the structural members in construction site. The results show that the amount of HPC AS is comparable to that of drying shrinkage and even larger than it, so AS can not be omitted for HPC. By comparing the plain HPC and reinforced HPC specimens, the influences of reinforced bars on autogenous shrinkage and temperature distribution were obtained.展开更多
The torsional vibration of power transmission shaft is a phenomenon whose analytical modeling can be represented by a differential equation of motion proposed by technical literature. The solutions of these equations ...The torsional vibration of power transmission shaft is a phenomenon whose analytical modeling can be represented by a differential equation of motion proposed by technical literature. The solutions of these equations need coefficients and parameters that, usually, must be experimentally estimated. This work uses a resistive electric SG （strain gage） to dynamically determine strains produced in the shaft due to harmonic oscillatory motion under multiaxial loading. This movement is simulated on a prototype specially developed for this purpose. It comprises a pulley attached to the end of a stepped cantilevered shaft, which is clamped at the opposite end. In this configuration, a cam generates a torque to the system, springs regulate the stiffness and the damping coefficient of the assembly, as well as they can be suitably adjusted to produce an underdamped condition. The main advantage, highlighted in this study, refers to a major simplification. Although the system under study shows multiple degrees of freedom （torsion and bending）, the shape and the positioning of linking SGs with the resistor bridge （Wheatstone Bridge）, allow ＂to evaluate the loading effects independently, as if only one degree of freedom of the system exists at a time domain. Strains graphs for two forms of cyclic torsional oscillation, analytical and experimental, were successfully generated.展开更多
Inside the second experimental wave energy converter (WEC) launched at the Lysekil research site on the Swedish west coast in March 2009 a number of sensor systems were installed for measuring the mechanical performan...Inside the second experimental wave energy converter (WEC) launched at the Lysekil research site on the Swedish west coast in March 2009 a number of sensor systems were installed for measuring the mechanical performance of the WEC and its mechanical subsystems. One of the measurement systems was a set-up of 7 laser triangulation sensors for measuring relative displacement of the piston rod mechanical lead-through transmission in the direct drive. Two measurement periods, separated by 2.5 month, are presented in this paper. One measurement is made two weeks after launch and another 3 months after launch. Comparisons and correlations are made between different sensors measuring simultaneously. Noise levels are investigated. Filtering is discussed for further refinement of the laser triangulation sensor signals in order to separate noise from actual physical displacement and vibration. Measurements are presented from the relative displacement of the piston rod mechanical lead-through, from magnetic flux in the air gap, mechanical strain in the WEC structure, translator position and piston rod axial displacement and active AC power. Investigation into the measurements in the time domain with close-ups, in the frequency domain with Fast Fourier transform (FFT) and with time-frequency analysis with short time Fourier transform (STFT) is carried out to map the spectral content in the measurements. End stop impact is clearly visible in the time-frequency analysis. The FFT magnitude spectra are investigated for identifying the cogging bandwidth among other vibrations. Generator cogging, fluctuations in the damping force and in the Lorenz forces in the stator are distinguished and varies depending on translator speed. Vibrations from cogging seem to be present in the early measurement period while not so prominent in the late measurement period. Vibration frequencies due to wear are recognized by comparing with the noise at generator standstill and the vibration sources in the generator. It is concluded that a moving average is a sufficient filter in the time domain for further analysis of the relative displacement of the piston rod mechanical lead-through transmission.展开更多
Blade strain distribution and its change with time are crucial for reliability analysis and residual life evaluation in blade vibration tests.Traditional strain measurements are achieved by strain gauges(SGs)in a cont...Blade strain distribution and its change with time are crucial for reliability analysis and residual life evaluation in blade vibration tests.Traditional strain measurements are achieved by strain gauges(SGs)in a contact manner at discrete positions on the blades.This study proposes a method of full-field and real-time strain reconstruction of an aero-engine blade based on limited displacement responses.Limited optical measured displacement responses are utilized to reconstruct the full-field strain.The full-field strain distribution is in-time visualized.A displacement-to-strain transformation matrix is derived on the basis of the blade mode shapes in the modal coordinate.The proposed method is validated on an aero-engine blade in numerical and experimental cases.Three discrete vibrational displacement responses measured by laser triangulation sensors are used to reconstruct the full-field strain over the whole operating time.The reconstructed strain responses are compared with the results measured by SGs and numerical simulation.The high consistency between the reconstructed and measured results demonstrates the accurate strain reconstructed by the method.This paper provides a low-cost,real-time,and visualized measurement of blade full-field dynamic strain using displacement response,where the traditional SGs would fail.展开更多
基金funded by the Fund Project of China Academy of Railway Sciences Corporation Limited[Grant No.2022YJ194,2023YJ254].
文摘Purpose-This paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/approach-Finite element method was employed to analyze the stress and strain distribution on the track wheel web surface under varying wheel-rail forces.Locations with minimal coupling interference between vertical and lateral forces were identified as suitable for strain gauge installation.Findings-The results show that due to the track wheel web’s unique curved shape and wheel-rail force loading mechanism,both tensile and compressive states exit on the surface of the web.When vertical force is applied,Mises stress and strain are relatively high near the inner radius of 710 mm and the outer radius of 1110mmof the web.Under lateral force,high Mises stress and strain are observed near the radius of 670mmon the inner and outer sides of the web.As the wheel-rail force application point shifts laterally toward the outer side,the Mises stress and strain near the inner radius of 710 mm of the web gradually decrease under vertical force while gradually increasing near the outer radius of 1110 mm of the web.Under lateral force,the Mises stress and strain on the surface of the web remain relatively unchanged regardless of the wheel-rail force application point.Based on the analysis of stress and strain on the surface of the web under different wheel-rail forces,the inner radius of 870 mm is recommended as the optimal mounting location of strain gauges for measuring vertical force,while the inner radius of 1143 mm is suitable for measuring lateral force.Originality/value-The research findings provide valuable insights for determining optimal strain gauge locations and designing an effective track wheel force measurement system.
文摘The measurement accuracy of a wind tunnel balance is the key factor to improve the measurement accuracy for a test model in the wind tunnel. In order to improve the measurement accuracy of the wind tunnel balance, a great deal of investigation is carried out in China. This paper summarizes a program to improve the measurement accuracy of wind tunnel balances. In the program, the investigation is carried out in three aspects (1) designing a drag component of the balance in low interactions (2) choosing high quality foil strain gauges with temperature self-compensation (3) choosing the excellent gauges and mounting them meticulously. As an example, these research achievements are applied in a φ18 six component balance. The measurement accuracy of a GB-04 standard model in a transonic wind tunnel with the φ18 six component balance comes up to the advanced world standard.
基金Supported by the National Natural Science Foundation of China(No.11173035,11273036)
文摘A cable net structure is selected to support its reflecting triangular aluminum panels of FAST(five-hundred-meter aperture spherical radio telescope).To ensure the security and stability of the supporting structure,cable force of typical cables must be monitored on line.Considering the stringent requirements in installation,accuracy,long-term stability and EMI(Electromagnetic interference),most of the commonly used cable force measurement methods or sensors are not suitable for the cable force monitoring of the supporting cable-net of FAST.A method is presents to accomplish the cable force monitoring,which uses a vibrating wire strain gauge to monitor the strain of linear strain area at the anchor head.Experiments have been carried out to verify the feasibility.The method has a series of advantages,such as high reliability,high accuracy,good dynamic performance and durability,easiness of maintenance,technical maturity in industry and EMI shielding.Theoretical analysis shows that there is a linear relationship between the cable body force and anchor head surface strain,and experimental results proves a good linear relationship with excellent repeatability between the cable body force and anchor head surface strain measured by the vibrating wire strain gauge,with a linear fit better than 0.98.Mean square error in practical measuring is 2.5t.The relative error is better than 4%within the scope of the cable force in FAST operation which meets practical demand in FAST engineering.
文摘Metal foil strain gauges remain the state-of-the-art transducers for wind tunnel balances.While strain gauge technology is very mature,piezoresistive semiconductor sensors offer alternatives that are worth exploring to assess their unique benefits,such as better strain resolution and accuracy,which would enable balances to be designed with higher factors to safety and hence longer fatigue lifetimes.A new three-component balance,based on temperature compensated semiconductor strain gauges,is designed,calibrated and tested in a hypersonic low density wind tunnel.The static accuracy of the semiconductor balance is calibrated better than 0.3%FS,and the dynamic accuracy of the balance is established using a HB-2 standard model in a Mach 12 hypersonic flow.Good experimental repeatability is confirmed to be better than 2.5%FS,and the effectiveness of the balance is demonstrated by comparing the forces and moments of measured data with computational fluid dynamics simulations,as well as reference wind tunnel results under similar conditions.
基金support from the National Natural Science Foundation of China (Grant Nos. 50921091 and 50731008)the National Basic Research Program of China (973) (Grant Nos. 2007CB613904 and2010CB731603)
文摘Electrical resistance strain gauges(SGs) are useful tools for experimental stress analysis and the strain sensing elements in many electromechanical transducers including load cells,pressure transducers,torque meters,accelerometers,force cells,displacement transducers and so forth.The commonly used commercial crystalline strain sensing materials of SGs are in the form of wire or foil of which performance and reliability is not good enough due to their low electrical resistivity and incapacity to get thin thickness.Smaller SGs with single straight strand strain sensing materials,which are called ideal SG,are highly desirable for more than seven decades since the first SG was invented.Here,we show the development of a type of minuscule length scale strain gauge by using a bare and single straight strand metallic glassy fiber(MGF) with high resistivity,much smaller lengthscale,high elastic limits(2.16%) and especially the super piezoresistance effect.We anticipate that our metallic glassy fiber strain gauge(MGFSG),which moves toward the ideal SGs,would have wide applications for electromechanical transducers and stress analysis and catalyze development of more micro-and nanoscale metallic glass applications.
基金Acknowledgements This work was partially supported by the National Science Foundation of Hubei Province （Grant No.2011CDB295）, Innovation Funding of HUST （No. 2012TS031）, Spedalized Research Fund for the Doctoral Program of Higher Education （No. 20130142120089）, and the National Science Foundation of China （No. 51371084）. We acknowledge the assistance from the staff in the Analytic and Testing Center of HUST.
文摘The reliability and sensitivity of a strain gauge made from a nanoparticle monolayer intrinsically depend on electron tunneling between the adjacent nanoparticles, so that creating nanoscale interstitials with uniform distribution and tuning the interparticle separation reversibly during cyclic mechanical stress are two vital issues for performance enhancement. In this work, one assembly technique is initialized to fabricate parallel nanoparticle strips by precisely tailoring the contact angle of a gold colloid on a substrate. The assembly of a nanoparticle monolayer with a close-packed pattern can be simultaneously switched on and off by independently varying the contact angle across a threshold value of 4.2~. This nanoparticle strip shows a reversible and reliable electrical response even if a mechanical strain as small as 0.027% is periodically supplied, implying well-controlled electron tunneling between the adjacent nanoparticles.
基金Acknowledgements This work was partially supported by Innovation Funding of HUST for International Collaborations （No. 2014ZZGH018）, Specialized Research Fund for the Doctoral Program of Higher Education （No. 20130142120089）, and National Natural Science Foundation of China （Nos. 51371084 and 91545131）.
文摘We demonstrate an ultrasensitive strain gauge based on a discontinuous metal film with a record detection limit as low as 8.3 × 10^-6. Constructed by well-tunable crevices on the nanometer scale within the film, this gauge exhibits an ultrafast dynamic response to vibrations with a frequency range of 1 Hz to 10 kHz. More importantly, the temperature coefficient of resistivity （TCR） of the metal film is tunable owing to the cancellation effect caused by the possibility of tunneling across the nanoscale crevices （showing a negative temperature dependence） and the electron conduction within the metal islands （showing a positive temperature dependence）. Consequently, a nullified TCR is achievable when the crevice size can be precisely controlled. Thus, a fabrication strategy to precisely control the nanoscale crevices was developed in this study through the real-time tracking of the electrical conductivity during thermal evaporation. The ultrasensitive strain gauge with a tunable thermal drift introduces numerous opportunities for precision devices and wearable electronics with superior reliability.
文摘Karma alloy thin film strain gauges were fabricated on alumina substrates by magnetron sputtering. The electrical properties of strain gauges annealed at different temperatures were then tested. The surface morphology and phase structure of the Karma alloy thin films were analyzed using X-ray diffraction and scanning electron microscopy. The effect of the annealing temperature on the performance of the Karma alloy thin film strain gauge was also investigated. As the annealing temperature increased, it was found that the resistivity of the thin films decreased, whereas the temperature coefficient of resistance (TCR) of the thin films increased. A Karma alloy thin film strain gauge was annealed at 200 °C, thereby obtaining a gauge factor of 1.7 and a corresponding TCR of 64.8 × 10−6 K−1. The prepared Karma alloy thin film strain gauge had a lower TCR than other strain gauges at room temperature. This result can provide a reference for the preparation and application of Karma alloy thin film strain gauges in specific scenarios.
基金the fund support by the National Natural Science Foundation of China (No. 51425804, No. U1234201 and No. U1334203)
文摘The technology of continuously welded rails （CWRs） is important in modern railway track structures. To measure rail stress, resistance strain gauges are preferred due to their good stability, sensitivity, and esistance to external interference. Based on the bi-directional strain method, we present a new method for measuring longitudinal rail stress using resistance strain gauges and develop a monitoring device for rail stress to realize long-term and multi-point measurement. Also relevant experimental verification and analysis are conducted. Results indicate that under various constraints the rail stress–strain values can be calculated just with the measured total longitudinal strain and total vertical strain. Considering the measurement error caused by sectional feature of sensors, we put forward a correction equation applicable to different stress conditions. Although the temperature values of the four full-bridge stress gauges can offset each other, the measurement error caused by rail flexural strain can also be eliminated to a certain extent at the same time, the nonuniform distribution of rail cross section temperature and unbalanced flexural strain still affect the measurement error. The experimental results also show that the developed rail-stress-monitoring sensor is suitable for measuring rail stress with reliable working performance.
文摘We studied the variability in longitudinal growth strains and wood basic density in five-year old trees from five clones （one tree per clone） of Eucalyptus tereticornis. Mean longitudinal growth strain in clones ranged from 466 to 876 μm. There was a significant difference between clones in growth strains and wood basic density. Clone 10 exhibited maximum growth strains and basic density, whereas clone 3 and clone 7 exhibited minimum growth strains and basic density, respectively. Within a tree, the growth strain variation with tree height was high but statistically insignificant while within tree variation in basic density was very small. There was no specific trend in variation in either strain or density within a tree. There was 5% 200% difference in growth strain on opposite sides of the logs. However two strains showed a strong positive correlation. There was a moderate positive association of wood basic density and mean growth strains in logs. The variation around the periphery emphasize the need to measure strain more than one, preferably on opposite sides at the same height, on a tree to know the mean strain level for the purpose of selection of clones.
基金funded by Shanxi Province Technology Innovation Guidance Special Project(2020QFY03-05)Shanxi Province Printing and Packaging Key Laboratory Project(16JS081).
文摘Environmental contamination has been caused by petroleum-based polymeric materials in the melt deposition process.Nowadays biodegradable materials have been widely used in the fused deposition modeling(FDM)industry,such as polylactic acid(PLA).However,internal complex thermal stress and deformations in part caused by an uneven distribution of PLA filament deposition temperatures during FDM,which will seriously affect the geometric accuracy of the printed part.In order to reduce material waste and environmental pollution during the printing process,the accuracy of PLA part can be improved.Herein,numerical simulation was carried out to investigate the temperature field and stress field during the building and cooling process of cuboid specimens.The effects of printing path on the thermal stress and temperature field during the building process were mainly studied.The results show that the printing path has a significant effect on the stress distribution.The most uni-form stress distribution and the smallest deformation were obtained using the Zig Zag printing path.Finally,the residual stress during the cooling process was collected using strain gauges embedded at the mid-plane of the FDM built cuboid specimens.The simulation results are consistent with the experimental results.
基金Financial support has come from the Smart S&C project,Innovate UK Grant Agreement 104427 AIR5the Track2Future project,EPRSC Grant Agreement No.EP/M025276/1.
文摘Railway switches and crossings constitute a small fraction of linear track length but consume a large proportion of the railway track system maintenance budget.While switch and crossing(S&C)faults rarely prevent trains from running,switches and crossings are the source of many faults and need continual attention.On the rare occasions when trains are prevented from running the cost of the disruption is very high.Condition monitoring of the point operating equipment that moves the switchblades has been in use for many years but condition monitoring of the state of the switch in terms of the support and mechanical damage as trains pass over has only recently started to become possible.To this end,it is important to understand the correlation between S&C faults and sensor data that can detect those faults.This paper assesses some of the data collected from multiple sensors variously positioned on and around a switch and crossing on the UK mainline for a few days of normal train operation.Accelerometers,geophones,and strain gauges were installed at the locations where they were anticipated to be most useful.Forces at the load transfer point on the crossing nose were estimated from two separate strain gauge bridges and possible use of acceleration on the crossing is discussed.Correlations between different data are analysed and assessed and correlation between peak estimated load transfer forces and accelerations is presented.Based on the analysis,conclusions are drawn about the different types of dynamic information around S&Cs that can be obtained from a variety of sensor types.
基金Project supported by the Postgraduate Award of University of SouthAustralia, Australia
文摘Current research focussed on the assessment of metal machining process parameters and on the development of adaptive control, shows that machine performance, work-piece and tool material selections, tool life, quality of machined surfaces, the geometry of cutting tool edges, and cutting conditions are closely related to the cutting forces. This information is of great interest to cutting tool manufactures and users alike. Over the years there have been significant developments and improvements in the equipment used to monitor such forces. In 1930 mechanical gauges were replaced by resistance strain gauges, and some 30 years later compact air gauge dynamometers were invented. Since this time intensive research has continued being directed to- wards developing new approaches to cutting force measurement. The Kistler Company, well-known manufacturer of acceleration and piezoelectrical dynamometers, has worked in this field for more than three decades, and developed very sensitive devices. While leading manufacturing research laboratories are often equipped with this technology, classical electrical strain gauges and other dynamometers of individual designs are still commonly used in industry. The present paper presents data obtained using different techniques of force measurement in metal machining processes. In particular, areas of uncertainties, illustrated through results concerning the turning process, are analysed, leading to an appraisal of the current status of these measurements and their significance.
基金National Natural Science Foundation of China (No. 60501005)National High Technology Research and Development Program of China(No. 2007AA04Z236)Key Program of Tianjin Science and Technology Support Plan (No. 07ZCKFSF01300)
文摘A new measurement and analysis method was proposed to investigate the changes in elbow joint moments that occur with the use of a front-wheeled walker. A strain gauge-based walker instrumentation system was developed to monitor the hand loads during walker-assisted walking and integrated with an upper extremity biomechanical model, Preliminary system data were collected for 12 subjects following informed consent. Bilateral upper extremity kinematic data were acquired with a six-camera motion analysis system. Internal joint moments at the elbow were determined in the three clinical planes using the inverse dynamics method. Results showed that during a walker-assisted gait elbow joint moments mainly distributed in the walker stance period. There was a noted demand on the elbow extensor in the sagittal plane with the greatest record as 0.381 N.m/（kg.m）, An interesting “bare phase” of mean elbow joint moments was also found in phase angle-240°-340° of gait cycle. Complete description of elbow joint moments of walkerassisted gait may provide insight into walker use parameters and rehabilitative strategies.
文摘The method to detect the crack initiation point of Charpy pre-cracked specimen under dy- namie loading was studied using strain gauge.The load-time curve and nominal strain-time curve at the crack tip for impact testing specinens may be shnultaneously measured by twin-channel oscilloscope with high speed sampling and diskette storing.Based on the dynam- ic finite element simulation of impact response of Charpy specimen,the measuring method of dynamic fracture toughness was analysed and some problems in previous dynamic fracture toughness measurement were discussed.
基金Spondored by the High-End CNC Machine Tools and Basic Manufacturing Equipment Technology Major Project(Grant No.2011ZX04001-011)
文摘In order to overcome stress concentration and increase fatigue life of ellipsoidal shells with inner guide structure,the stress analysis for strength check is very important. Owing to the main sectional profile with ellipsoidal shape,the stress distribution for perfect ellipsoidal shell is firstly conducted based on the theoretical calculation and strain gauges measurement. The experiment results show that the stresses increase gradually from pole region to equatorial plane,but still within elastic range. Secondly,strain gauge measurement for ellipsoidal shells with inner guide structure is conducted. The results show that stresses are concentrated at the vicinity of bottom plate and beyond elastic range,so the structural redesign is needed. Finally based on the analysis mentioned above,a redesigned structure with local thickening is proposed. Experimental research shows that the stress varies more even after structural redesign and within allowable range. Numerical simulation shows that both the deformation and fatigue life after redesign are acceptable.
文摘This paper aims at monitoring the autogenous shrinkage （AS） of a high-performance concrete （HPC） column specimen using an embedded strain gauge just after concrete pouring. A real size specimen （40 cm×40 cm×100cm） was made to simulate the structural members in construction site. The results show that the amount of HPC AS is comparable to that of drying shrinkage and even larger than it, so AS can not be omitted for HPC. By comparing the plain HPC and reinforced HPC specimens, the influences of reinforced bars on autogenous shrinkage and temperature distribution were obtained.
文摘The torsional vibration of power transmission shaft is a phenomenon whose analytical modeling can be represented by a differential equation of motion proposed by technical literature. The solutions of these equations need coefficients and parameters that, usually, must be experimentally estimated. This work uses a resistive electric SG （strain gage） to dynamically determine strains produced in the shaft due to harmonic oscillatory motion under multiaxial loading. This movement is simulated on a prototype specially developed for this purpose. It comprises a pulley attached to the end of a stepped cantilevered shaft, which is clamped at the opposite end. In this configuration, a cam generates a torque to the system, springs regulate the stiffness and the damping coefficient of the assembly, as well as they can be suitably adjusted to produce an underdamped condition. The main advantage, highlighted in this study, refers to a major simplification. Although the system under study shows multiple degrees of freedom （torsion and bending）, the shape and the positioning of linking SGs with the resistor bridge （Wheatstone Bridge）, allow ＂to evaluate the loading effects independently, as if only one degree of freedom of the system exists at a time domain. Strains graphs for two forms of cyclic torsional oscillation, analytical and experimental, were successfully generated.
基金supported by The Swedish Energy AgencyThe Gothenburg Energy Research Foundation,The Goran Gustavsson Research Foundation,Angpanneforeningen’s Foundation for Research and Development,The Olle Engkvist Foundation,The J.Gust.Richert Foundation,CF Environmental Fund,Vargons Research Foundation,The Swedish Research Council grant No.621-2009-3417 and the Wallenius Foundation.
文摘Inside the second experimental wave energy converter (WEC) launched at the Lysekil research site on the Swedish west coast in March 2009 a number of sensor systems were installed for measuring the mechanical performance of the WEC and its mechanical subsystems. One of the measurement systems was a set-up of 7 laser triangulation sensors for measuring relative displacement of the piston rod mechanical lead-through transmission in the direct drive. Two measurement periods, separated by 2.5 month, are presented in this paper. One measurement is made two weeks after launch and another 3 months after launch. Comparisons and correlations are made between different sensors measuring simultaneously. Noise levels are investigated. Filtering is discussed for further refinement of the laser triangulation sensor signals in order to separate noise from actual physical displacement and vibration. Measurements are presented from the relative displacement of the piston rod mechanical lead-through, from magnetic flux in the air gap, mechanical strain in the WEC structure, translator position and piston rod axial displacement and active AC power. Investigation into the measurements in the time domain with close-ups, in the frequency domain with Fast Fourier transform (FFT) and with time-frequency analysis with short time Fourier transform (STFT) is carried out to map the spectral content in the measurements. End stop impact is clearly visible in the time-frequency analysis. The FFT magnitude spectra are investigated for identifying the cogging bandwidth among other vibrations. Generator cogging, fluctuations in the damping force and in the Lorenz forces in the stator are distinguished and varies depending on translator speed. Vibrations from cogging seem to be present in the early measurement period while not so prominent in the late measurement period. Vibration frequencies due to wear are recognized by comparing with the noise at generator standstill and the vibration sources in the generator. It is concluded that a moving average is a sufficient filter in the time domain for further analysis of the relative displacement of the piston rod mechanical lead-through transmission.
基金supported by the National Natural Science Foundation of China (Grant No.52075414)the National Science and Technology Major Project,China (Grant No.2017-V-0009).
文摘Blade strain distribution and its change with time are crucial for reliability analysis and residual life evaluation in blade vibration tests.Traditional strain measurements are achieved by strain gauges(SGs)in a contact manner at discrete positions on the blades.This study proposes a method of full-field and real-time strain reconstruction of an aero-engine blade based on limited displacement responses.Limited optical measured displacement responses are utilized to reconstruct the full-field strain.The full-field strain distribution is in-time visualized.A displacement-to-strain transformation matrix is derived on the basis of the blade mode shapes in the modal coordinate.The proposed method is validated on an aero-engine blade in numerical and experimental cases.Three discrete vibrational displacement responses measured by laser triangulation sensors are used to reconstruct the full-field strain over the whole operating time.The reconstructed strain responses are compared with the results measured by SGs and numerical simulation.The high consistency between the reconstructed and measured results demonstrates the accurate strain reconstructed by the method.This paper provides a low-cost,real-time,and visualized measurement of blade full-field dynamic strain using displacement response,where the traditional SGs would fail.
