scholarly journals Calibration of piezoresistive shape-memory alloy strain sensors

2021 ◽  
pp. 1045389X2110572
Author(s):  
Thomas Mäder ◽  
Jonas v Heusinger ◽  
Björn Senf ◽  
Martin Zoch ◽  
Anja Winkler ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Glass Fibre ◽  
Strain Sensors ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Standard Strain ◽  
Four Point Bending ◽  
Glass Fibre Reinforced ◽  
Mechanical Sensors

Continuous strain measurement on fibre-reinforced structures demands mechanical sensors with superior fatigue resistance. Shape-memory alloy wires are predestined for strain sensors utilising their strong piezo-resistance. Calibration of these sensors is necessary in order to extract mechanical data. Therefore, four-point bending of glass-fibre reinforced plastic specimens with applied strain sensors and an optical reference measuring system is used to calibrate and compare shape-memory alloy sensors and standard strain gauges. The gauge factor and its standard deviation is successfully measured by this calibration method. Shape-memory alloy sensors show strain-dependent gauge factor whilst standard strain gauges show a constant strain sensitivity, both with a narrow stochastic distribution. Shape-memory alloy mechanical sensors are reliable to determine strain of fibre-reinforced structures. This offers the possibility to use them in structural health monitoring applications of such structures. Consequently, the four-point bending calibration using glass-fibre reinforced specimens represents a suitable possibility for calibration of strain sensors exposed to higher strain amplitudes.

Highly Elastic Strain Gauges Based on Shape Memory Alloys for Monitoring of Fibre Reinforced Plastics

2017 ◽  
Vol 742 ◽  
pp. 778-785
Author(s):  
Thomas Mäder ◽  
Inaki Navarro y de Sosa ◽  
Björn Senf ◽  
Peter Wolf ◽  
Martin Hamm ◽  
...  
Keyword(s):  
Structural Health Monitoring ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Health Monitoring ◽  
Strain Sensors ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Resistance Change ◽  
Structural Health ◽  
Reinforced Plastics

Conventional strain gauges made of constantan or CuCr for instance have a low value for structural health monitoring issues in plastic composites. These strain sensor materials exhibit small elastic regions and show fatigue when dynamically loaded with strain levels over 0.3 percent. For this reason, these sensors would break or fail before the composite life-time and thus cannot be integrated into this kind of composite materials. Pseudoelastic thermal shape memory alloys are therefore used as strain sensors and integrated into composites in order to allow piezoresistive strain measurement and structural health monitoring in such materials. Thermal treatments are used to create sensor structures out of shape memory alloy wires. Pseudoelastic shape memory wires can be strained up to 8 percent repeatedly. Their gauge factor is higher than 5. Shape memory strain sensors are successfully embedded into glass fibre reinforced plastics and show a significant and reproducible resistance change when the composite is strained. The dynamic strength is magnificently higher compared to conventional strain gauges. Shape memory strain sensors are an efficient alternative to fiber-bragg-grating sensors and can potentially be used for strain measurements in different plastics and textile materials. Shape memory sensor structures can be embedded or applied and are good candidates for structural characterisation and monitoring applications.

scholarly journals Development of Highly Sensitive Strain Sensor Using Area-Arrayed Graphene Nanoribbons

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1701
Author(s):  
Ken Suzuki ◽  
Ryohei Nakagawa ◽  
Qinqiang Zhang ◽  
Hideo Miura
Keyword(s):  
Graphene Nanoribbons ◽  
Strain Sensor ◽  
Strain Sensors ◽  
Sensitive Strain ◽  
Bending Test ◽  
Gauge Factor ◽  
Four Point Bending ◽  
Current Voltage ◽  
Highly Sensitive ◽  
Current Voltage Relationship

In this study, a basic design of area-arrayed graphene nanoribbon (GNR) strain sensors was proposed to realize the next generation of strain sensors. To fabricate the area-arrayed GNRs, a top-down approach was employed, in which GNRs were cut out from a large graphene sheet using an electron beam lithography technique. GNRs with widths of 400 nm, 300 nm, 200 nm, and 50 nm were fabricated, and their current-voltage characteristics were evaluated. The current values of GNRs with widths of 200 nm and above increased linearly with increasing applied voltage, indicating that these GNRs were metallic conductors and a good ohmic junction was formed between graphene and the electrode. There were two types of GNRs with a width of 50 nm, one with a linear current–voltage relationship and the other with a nonlinear one. We evaluated the strain sensitivity of the 50 nm GNR exhibiting metallic conduction by applying a four-point bending test, and found that the gauge factor of this GNR was about 50. Thus, GNRs with a width of about 50 nm can be used to realize a highly sensitive strain sensor.

scholarly journals Giant gauge factor of Van der Waals material based strain sensors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenjie Yan ◽  
Huei-Ru Fuh ◽  
Yanhui Lv ◽  
Ke-Qiu Chen ◽  
Tsung-Yin Tsai ◽  
...  
Keyword(s):  
Carrier Mobility ◽  
Large Range ◽  
Van Der Waals ◽  
High Sensitivity ◽  
Strain Sensors ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Proof Of Concept ◽  
High Flexibility ◽  
Small Deformations

AbstractThere is an emergent demand for high-flexibility, high-sensitivity and low-power strain gauges capable of sensing small deformations and vibrations in extreme conditions. Enhancing the gauge factor remains one of the greatest challenges for strain sensors. This is typically limited to below 300 and set when the sensor is fabricated. We report a strategy to tune and enhance the gauge factor of strain sensors based on Van der Waals materials by tuning the carrier mobility and concentration through an interplay of piezoelectric and photoelectric effects. For a SnS2 sensor we report a gauge factor up to 3933, and the ability to tune it over a large range, from 23 to 3933. Results from SnS2, GaSe, GeSe, monolayer WSe2, and monolayer MoSe2 sensors suggest that this is a universal phenomenon for Van der Waals semiconductors. We also provide proof of concept demonstrations by detecting vibrations caused by sound and capturing body movements.

Monitoring of Internal Damage of Glass Fibre Reinforced Composite Components Using Strain Measurements with Strain Gauges and Fibre Optic Sensors

2013 ◽  
Vol 486 ◽  
pp. 58-61 ◽  
Author(s):  
Ivo Černý
Keyword(s):  
Fatigue Strength ◽  
Glass Fibre ◽  
Shear Failure ◽  
Dynamic Stiffness ◽  
Strain Gauges ◽  
Shear Stresses ◽  
Fibre Optic ◽  
Internal Damage ◽  
Manufacture Process ◽  
Glass Fibre Reinforced

Glass fibre reinforced polymer (GRP) composites are perspective materials for manufacture of components in different machinery applications. Favourable characteristics of these materials include very high specific strength, ratio of static and dynamic stiffness, particularly beneficial in dynamically loaded structures, and potentially excellent fatigue strength provided that there are no latent internal imperfections, occurring usually in the manufacture process. Defects like insufficient wet-out of glass fibres by resin result in significant reduction of static and fatigue strength in shear. If the component thickness is high and it is loaded by bending, considerable shear stresses occur in the neutral plane, which can cause premature shear failure of the component. Results of static and fatigue tests in bending of full-scale models of longitudinal frames of railway freight vehicle bogies, manufactured from GRP polyester composites, are shown and analysed in the paper. Surface strains measured using strain gauges were monitored during the component loading, its continuous damage and were analysed. The results are in a good agreement with the subsurface strains evaluated using fibre optic sensors embedded in the component during the manufacture process. Asymmetry of strains, both internal and surface, was connected with internal defects and consequently reduced strength. On the contrary, very good fatigue resistance was characteristic for components, where strain values were symmetrical.

An experimental approach to the thermomechanical characterization of a NiTiCu shape memory alloy using strain gauges

2016 ◽  
Vol 231 (1-2) ◽  
pp. 113-121
Author(s):  
Albert Fabregat-Sanjuan ◽  
Francesc Ferrando Piera ◽  
Silvia De la Flor López
Keyword(s):  
Shape Memory Alloy ◽  
Shear Modulus ◽  
Shape Memory ◽  
Twist Angle ◽  
Strain Tensor ◽  
Strain Ratio ◽  
Strain Gauges ◽  
Compression Tests ◽  
Thermal Chamber

In this work, a characterization of a NiTiCu (Ti44.6Ni5Cu (at.%)) shape memory alloy (tube specimens) has been done via tension, compression and torsion tests conditions. Torsion tests were done in a special homemade equipment, which is based on an instrumented dividing head with a specifically designed thermal chamber. This configuration is able to measure torque and twist angle with isothermal tests at different temperatures as well as to apply thermal cycles with a fixed twist angle. Moreover, tube specimens were instrumented with stacked strain gauges rosettes in order to obtain the strain tensor. Strain gauges were also used to calibrate the equipment and to identify the real stress state in torsion tests. The results have shown differences between the shear modulus measured on torsion tests and the shear modulus calculated from the measurements at tension and compression tests due to the tension/compression asymmetry and a non-constant strain ratio value. Thermal cycling tests at different values of fixed twist angles not only have led to characterize the evolution of torque as a function of the temperature but also to understand the different interacting mechanisms in torsion tests.

Shape memory composites based on glass-fibre-reinforced poly(ethylene)-like polymers

2012 ◽  
Vol 21 (3) ◽  
pp. 035004 ◽  
Author(s):  
J M Cuevas ◽  
R Rubio ◽  
J M Laza ◽  
J L Vilas ◽  
M Rodriguez ◽  
...  
Keyword(s):  
Shape Memory ◽  
Glass Fibre ◽  
Shape Memory Composites ◽  
Glass Fibre Reinforced ◽  
Poly Ethylene

Recovery of Preload in Bolted Joint Using Shape Memory Alloy Elements

2003 ◽  
Author(s):  
Mehrdaad Ghorashi ◽  
Daniel J. Inman
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Threshold Level ◽  
Design Stage ◽  
Strain Gauges ◽  
Self Healing ◽  
Bolted Joint ◽  
Cross Sectional ◽  
Bolt Preload ◽  
Joint Behavior

One of the main problems with a bolted joint is losing its preload. In this situation, it cannot provide the required clamping force needed to keep the joint members together or prevent fluid leakages. Although every effort is usually made at the design stage to prevent such failure, because of the numerous factors present in the problem, these efforts are not always successful. After loosening occurs, the joint should be retightened to regain its preload. However, there are circumstances where the joint is very important but it is not easily accessible and retightening cannot be done manually. The shape memory effect (SME) property can be used in such circumstances to produce the necessary preload. The shape memory alloy (SMA) element should be activated if monitoring the bolt preload through the application of strain gauges shows that the preload has fallen below a pre-determined threshold level. This paper presents a mathematical model for the SMA element and the whole joint behavior. The relation between SMA activation (corresponding to the amount of phase change in the SMA) and the resulting preload is estimated. To this end, it is assumed that the SMA element behaves in such a way that either its cross-sectional area or its volume remain constant. The analysis of this model shows the feasibility of the application of SMA for producing the required preload. Hence, if used properly, the required preload is achieved and a self-healing joint is obtained.

The experimental static mechanical performance of ironed repaired GFRP–honeycomb sandwich beams

2012 ◽  
Vol 14 (6) ◽  
pp. 694-714 ◽  
Author(s):  
Benjamin William Mounir Kirollos ◽  
Richard Trede ◽  
Peter Lampen
Keyword(s):  
Glass Fibre ◽  
Mechanical Performance ◽  
Repair Process ◽  
Flexural Stiffness ◽  
Sandwich Beams ◽  
Four Point Bending ◽  
Reinforced Plastic ◽  
Glass Fibre Reinforced Plastic ◽  
Static Mechanical ◽  
Glass Fibre Reinforced

Damaged glass fibre reinforced plastic–honeycomb core sandwich beams are repaired using uncured glass fibre reinforced plastic fabrics and a handheld iron. The effect of iron temperature, application time and pressure on the effectiveness of repair is investigated by measuring the failure load and flexural stiffness of the repaired beams using third span four-point bending tests. Repairs are tested in compression and tension. A repair process is suggested which consistently recovers 95% of the compressive strength and 77% of the tensile strength of the damaged beam. The repair is shown to have little effect on beam flexural stiffness.

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