A real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire

Abstract

The present invention discloses a real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires, which belongs to the technical field of monitoring the stress conditions of engineering tensile components. The real-time tensile stress monitoring method is to attach the ferromagnetic shape memory alloy microwires to the surface of the component or embed them into the component, and subject them to the same tensile stress as the component. Under the action of an external magnetic field, by reading the slope signal of the magnetoresistance curve of the ferromagnetic shape memory alloy microwires, combined with the use of ambient temperature and the volume fraction of the reaction martensite phase, the stress conditions of the component are quantitatively calibrated to achieve real-time monitoring of the stress value. The overall real-time tensile stress monitoring method of the present invention is simple, has high production efficiency, high product quality, can be miniaturized and used, can be recycled and reused, has a short process and low cost, can work within a wide temperature window, and is conducive to large-scale industrial promotion and use.

Description

Technical Field

[0001] The invention belongs to the technical field of monitoring the stress conditions of engineering tensile components and relates to a real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires. Background Art

[0002] In recent years, the sudden destruction and collapse of engineering structures such as bridges at home and abroad have sounded the alarm for people. Structural safety has become a key issue of concern. Real-time monitoring of the stress state and usage of tension components is an extremely important step related to structural safety.

[0003] In existing technologies, the electromagnetic signals of materials can respond to structural changes relatively quickly. However, for non-conductive materials such as concrete, it is necessary to use the characteristics of other materials to output signals without causing damage to the structure.

[0004] Chinese patent CN105818822A discloses a device and method for real-time monitoring of rail temperature stress using laser ultrasonic technology. A pulsed laser emits pulsed laser light onto the rail, generating ultrasonic waves. A laser probe receives the ultrasonic signal and transmits the measured time value to a processor, enabling real-time and accurate monitoring of rail temperature stress. This provides a new approach for nondestructive testing of rails and is of great significance for ensuring safe rail operation. Ultrasonic signal monitoring is suitable for real-time tensile stress monitoring of conductive materials.

[0005] Chinese patent CN114414359A discloses a device for testing the full compressive stress-strain curve of ultra-high-strength concrete under uniaxial compressive conditions at high temperatures. It provides a device for testing the full compressive stress-strain curve of concrete specimens in an electro-hydraulic servo compression-shear testing machine, and is suitable for concrete specimens damaged by high temperatures.

[0006] Chinese patent CN111257113A discloses a concrete uniaxial tensile stress-strain curve testing method and testing device, which is only for concrete test blocks and cannot measure the tensile stress of different tensile components of concrete engineering structures such as domestic and foreign bridges in real time.

[0007] Chinese patent CN110197015A discloses a method for measuring the effective tensile stress of prestressed anchor cables at a dam foundation. The method calculates a monitoring value of the dam foundation horizontal displacement from a statistical model of the dam foundation horizontal displacement by modeling and analyzing observation data that causes deformation. The corresponding simulation value of the dam foundation horizontal displacement is calculated by establishing a three-dimensional finite element model of the dam. The tensile stress value is determined by mutually verifying the monitoring value of the dam foundation horizontal displacement with the simulation value of the dam foundation horizontal displacement. However, the method is not capable of performing real-time tensile stress measurement on different tensile components of concrete engineering structures such as domestic and foreign bridges.

[0008] In summary, based on the technical problems existing in the above-mentioned stress measurement methods, how to provide a tensile stress measurement method for engineering structures such as bridges at home and abroad, especially a real-time measurement method for tensile stress of concrete engineering structures, is a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0009] The technical problem to be solved by the present invention is how to overcome the problem that the stress measurement in the prior art can only measure the tensile stress of concrete blocks, but cannot measure the tensile stress of concrete engineering structures in real time; and the stress measurement device is a fixed structure, and most of the measurements are performed through stress sensors installed in various places. The measurement results are inaccurate and cannot measure the tensile stress of the entire concrete engineering structure; the tensile stress values ​​measured using models and simulation values ​​cannot be measured in real time.

[0010] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0011] A real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires is disclosed. The real-time tensile stress monitoring method comprises attaching the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires to the surface of a component or embedding them in the component, subjecting the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires to the same tensile stress as the component. Under the action of an external magnetic field, the slope signal of the magnetoresistance curve of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires is read, combined with the ambient temperature and the volume fraction of the reactive martensite phase, to quantitatively calibrate the stress condition of the component, thereby achieving real-time monitoring of the stress value.

[0012] Preferably, the Ni—Mn—Ga—Fe—Cu ferromagnetic shape memory alloy microwires are prepared by a glass coating method to obtain glass-coated ferromagnetic shape memory alloy microwires with good surface roundness.

[0013] Preferably, the atomic percentage of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire is Ni 50 Mn 27- x Ga 22 Fe x Cu1(x=0-5).

[0014] Preferably, the Ni—Mn—Ga—Fe—Cu ferromagnetic shape memory alloy microwire has a diameter of 50-400 μm and a length of 100-1000 mm.

[0015] Preferably, the stress condition of the quantitative calibration component is to first obtain the tensile strain-resistance curve of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire, and then perform temperature resistivity test and magnetoresistivity test respectively, and then use the linear slope of the magnetoresistance curve to obtain the volume fraction of the martensite phase, and finally obtain the stress value by corresponding the volume fraction of the martensite phase with the stress-strain curve.

[0016] Preferably, the tensile strain-resistance curve is obtained by first selecting a section of alloy microwire with a length of 3 mm and uniform size for mechanical property characterization, and then using a tensile device to perform axial stress tensile cycle measurement on the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire.

[0017] Preferably, the axial stress stretching cycle: the stretching process is to apply axial tensile stress to the above-mentioned Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire until the martensitic phase transformation is completed, then unload the tensile stress until it reaches 0 MPa, and then apply axial tensile stress again; this cycle is repeated 100 times or 1000 times.

[0018] Preferably, in the tensile strain-resistance curve, the maximum output strain of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire exceeds 13% and is completely recoverable, and can maintain a stable output after 1000 cycles.

[0019] Preferably, the magnetoresistivity test is performed by extending four leads from the alloy wire, connecting current and voltage respectively, and applying an external magnetic field, that is, using a four-terminal method to monitor the magnetoresistivity change of the alloy microwire.

[0020] Preferably, after the mechanical properties test of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire is completed, the alloy microwire is connected to an ammeter and a voltmeter using silver glue wires, and the temperature dependence of the magnetoresistance and the isothermal magnetoresistance of the above alloy microwire are tested under an external magnetic field using a four-terminal method to obtain an isothermal magnetoresistance curve.

[0021] Preferably, according to the isothermal magnetoresistance curve, it can be obtained that within the external magnetic field range of <0.5T, the magnetoresistance change rate of the alloy microwire shows a linear relationship with the external magnetic field, and this linear relationship remains stable with the increase of the number of stretching times.

[0022] Preferably, the martensite volume fraction is not affected by the external magnetic field, and is related to the temperature-induced martensite transformation and the stress-induced martensite transformation. A suitable formula is selected to characterize the quantitative relationship between temperature-martensite volume fraction and stress-martensite volume fraction.

[0023] Preferably, under different ambient operating temperatures, the corresponding linear relationship between the magnetoresistance change rate and the external magnetic field is different. The corresponding formula can be used to establish the relationship between temperature and magnetoresistance change rate, that is, the magnetoresistance change rate corresponding to different martensite phase volume fractions, so as to obtain the stress value corresponding to the magnetoresistance change rate in real time.

[0024] Preferably, the different use environment temperatures are 200-320K and the magnetic field strength is <0.5T.

[0025] Preferably, the above-mentioned ferromagnetic shape memory alloy microwires are applied to structural components such as the tensile parts of concrete bridge decks, inclined cables of bridges, tunnel structures, lower chords of gymnasium roofs, slope protection walls, outer walls of pressure vessels, etc. The magnetic field is applied in the form of an energized coil / permanent magnet, the magnetic field size is 0 to 0.3T, the temperature range is 320 to 200K, the slope of the magnetoresistivity curve is -0.69 to -1.86, the volume fraction of martensite is 0-100%, and the monitored stress is 0 to 173MPa.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] In the above scheme, the present invention uses the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire prepared by the glass coating method, and utilizes the linear response of its magnetoresistance change rate to the magnetic field, and the correspondence between the volume fraction of the martensite phase and stress to monitor the stress state of non-conductive, non-magnetic tensile components such as concrete in real time.

[0028] The present invention solves the problem of low measurement accuracy and great influence of ambient temperature in traditional methods of reflecting stress changes of conductive materials through resistivity, and can be applied to non-conductive and non-magnetic materials such as concrete.

[0029] In the present invention, the linear relationship between the magnetoresistance change rate and the external magnetic field remains stable as the number of stretching times increases.

[0030] The present invention utilizes an energized coil or a magnet to apply an external magnetic field to the alloy microwire.

[0031] The present invention works within a wide temperature window and a stable magnetic field. The wide temperature window is 200-320K, and the stable magnetic field is a magnetic field of <0.5T.

[0032] In the present invention, the resistivity changes significantly before and after the temperature-induced phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0033] The overall real-time tensile stress monitoring method of the present invention is simple, has high production efficiency, high product quality, can be miniaturized and reused, has a short process and low cost, can operate within a wide temperature window, and under certain operating ambient temperature and external magnetic field conditions, the magnetoresistance change rate, martensite phase volume fraction, and stress correspond in sequence through the microwire, which is conducive to large-scale industrial promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 : is a tensile stress-strain curve of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire of the present invention, wherein: Figure 1 (a) is the microfilament cyclic stretching curve. Figure 1 (b) is the SEM image of the microwire surface morphology. Figure 1 (c) is the strain-resistance (voltage signal) curve, Figure 1 (d) Figure 1 (c) Corresponding stretching curve;

[0036] Figure 2 The figure is a graph showing the temperature dependence of the resistance of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire under different magnetic fields after being stretched 1000 times;

[0037] FIG3 is a graph showing the isothermal magnetoresistance curves and magnetoresistance change rate curves of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires of the present invention at different temperatures, wherein: FIG3(a) is at temperature T = 200K, FIG3(b) is at T = 285K, FIG3(c) is at T = 292K; and FIG3(d) is at T = 320K.

[0038] Figure 4 Schematic diagram of the principle of the real-time tensile stress monitoring element of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire of the present invention; wherein: ① is the monitored component, ② is the shape memory alloy microwire; ③ is the external magnetic field; ④ is the voltmeter; ⑤ is the ammeter. DETAILED DESCRIPTION

[0039] The following will describe the technical solutions and technical problems solved in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them.

[0040] Example 1

[0041] The alloy microwires were prepared by glass coating method, and the ferromagnetic shape memory alloy microwires with good surface roundness were obtained. Figure 1 (b) shown.

[0042] Alloy composition is Ni 50 Mn 24 Ga 22 Fe3Cu1, the diameter of the alloy microwire is selected to be 200μm and the length is 3mm.

[0043] The ferromagnetic shape memory alloy microwires were subjected to room temperature axial stress stretching cycles using a dynamic mechanical analyzer (DMA Q800). The stretching process involved applying tensile stress to the ferromagnetic shape memory alloy microwires until the martensitic phase transformation was complete, unloading the stress to 0 MPa, and then reloading and unloading the stress. This cycle was repeated 100 times and 1000 times. The resistance of the first 15 stretching processes was monitored to obtain the strain-resistance curve of the ferromagnetic shape memory alloy microwires. The stress-strain curve is shown in Figure 2. Figure 1 As shown in (a), the recoverable strain is about 13%, and the cycle performance is good. Figure 1 As shown in (c) and (d).

[0044] After the tensile test of the ferromagnetic shape memory alloy microwires was completed, temperature resistivity test and magnetoresistivity test were carried out respectively. Figure 2 and 3. According to Figure 2 The resistivity changes significantly before and after the phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0045] like Figure 4 As shown in FIG, the magnetoresistance test of the ferromagnetic shape memory alloy microfilament requires the use of silver glue wires to connect the ferromagnetic shape memory alloy microfilament and the ammeter and voltmeter. Under an external magnetic field, a four-terminal method is used for testing. According to the curve, it can be obtained that within the external magnetic field range of <0.5T, the magnetoresistance change rate of the ferromagnetic shape memory alloy microfilament presents a linear relationship with the external magnetic field, and this linear relationship remains consistent with the increase in the number of training times.

[0046] Furthermore, Figures 3(a-d) show that the linear relationship described above exists at different temperatures, but with different slopes. Therefore, this parameter can operate within a wide temperature window. The martensite volume fraction can be obtained using the rate of change of the magnetoresistivity, and the corresponding stress value can be obtained from the martensite volume fraction. In other words, the stress value can be indirectly obtained through the rate of change of the magnetoresistivity.

[0047] The ferromagnetic shape memory alloy microwire ② is applied to the tensile portion of the concrete bridge deck (the monitored component ①), wherein the diameter is 200 μm and the length is determined to be 30 mm within 100-1000 mm according to the actual requirements of the bridge's inclined cable. The method is as follows: the two ends of the ferromagnetic shape memory alloy microwire ② are bonded and fixed to the tensile portion of the concrete bridge deck (the monitored component ①) along the tensile direction, an external magnetic field ③ is applied to the alloy microwire using an energized coil, and the ferromagnetic shape memory alloy microwire ② is connected to an ammeter ⑤ and a voltmeter ④ using silver glue wires. Under an external magnetic field of 0.3 T and an ambient temperature of 320 K, a four-terminal test is performed by reading the slope of the magnetoresistance curve of the ferromagnetic shape memory alloy microwire ② as 0.69, obtaining a volume fraction of the martensite phase of 0%. The stress value corresponding to the stress-strain curve is 0 MPa, indicating that the force is 0 at this time. At this temperature, the slope of the magnetoresistance curve is -1.86, corresponding to the volume fraction of the martensite phase being 100% of that at 200K. The stress value corresponding to the stress-strain curve is 173 MPa, which can monitor the stress state of the structural parts in real time.

[0048] Example 2

[0049] The alloy microwires were prepared by glass coating method, and the ferromagnetic shape memory alloy microwires with good surface roundness were obtained. Figure 1 (b) shown.

[0050] Alloy composition is Ni 50 Mn 24 Ga 22 Fe3Cu1, the diameter of the alloy microwire is selected to be 200μm and the length is 3mm.

[0051] The ferromagnetic shape memory alloy microwires were subjected to room temperature axial stress stretching cycles using a dynamic mechanical analyzer (DMA Q800). The stretching process involved applying tensile stress to the ferromagnetic shape memory alloy microwires until the martensitic phase transformation was complete, unloading the stress to 0 MPa, and then reloading and unloading the stress. This cycle was repeated 100 times and 1000 times. The resistance of the first 15 stretching processes was monitored to obtain the strain-resistance curve of the ferromagnetic shape memory alloy microwires. The stress-strain curve is shown in Figure 2. Figure 1 As shown in (a), the recoverable strain is about 13%, and the cycle performance is good. Figure 1 As shown in (c) and (d).

[0052] After the tensile test of the ferromagnetic shape memory alloy microwires was completed, temperature resistivity test and magnetoresistivity test were carried out respectively. Figure 2 and 3. According to Figure 2 The resistivity changes significantly before and after the phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0053] like Figure 4 As shown in FIG, the magnetoresistance test of the ferromagnetic shape memory alloy microfilament requires the use of silver glue wires to connect the ferromagnetic shape memory alloy microfilament and the ammeter and voltmeter. Under an external magnetic field, a four-terminal method is used for testing. According to the curve, it can be obtained that within the external magnetic field range of <0.5T, the magnetoresistance change rate of the ferromagnetic shape memory alloy microfilament presents a linear relationship with the external magnetic field, and this linear relationship remains consistent with the increase in the number of training times.

[0054] Furthermore, Figures 3(a-d) show that the linear relationship described above exists at different temperatures, but with different slopes. Therefore, this parameter can operate within a wide temperature window. The martensite volume fraction can be obtained using the rate of change of the magnetoresistivity, and the corresponding stress value can be obtained from the martensite volume fraction. In other words, the stress value can be indirectly obtained through the rate of change of the magnetoresistivity.

[0055] The ferromagnetic shape memory alloy microfilament ②, having a diameter of 200 μm and a length of 30 mm, was applied to the bridge's inclined cable (monitored component ①). The method involved bonding and affixing the two ends of the ferromagnetic shape memory alloy microfilament ② to the bridge's inclined cable (monitored component ①) along the tensile direction. An external magnetic field ③ was applied to the microfilament using an energized coil. Silver glue wires were used to connect the ferromagnetic shape memory alloy microfilament ② to an ammeter ⑤ and a voltmeter ④. Under an external magnetic field of 0.3 T and an ambient operating temperature of 320 K, a four-terminal test was performed. The slope of the magnetoresistance curve of the ferromagnetic shape memory alloy microfilament ② was -0.69, indicating a volume fraction of the martensite phase of 0%. Corresponding to the stress-strain curve, a stress value of 0 MPa was obtained, indicating zero force. At this temperature, the slope of the magnetoresistance curve is -1.86, corresponding to the volume fraction of the martensite phase being 100% of that at 200K. The stress value corresponding to the stress-strain curve is 173 MPa, which can monitor the stress state of the structural parts in real time.

[0056] Example 3

[0057] The alloy microwires were prepared by glass coating method, and the ferromagnetic shape memory alloy microwires with good surface roundness were obtained. Figure 1 (b) shown.

[0058] Alloy composition is Ni 50 Mn 24 Ga 22 Fe3Cu1, the diameter of the alloy microwire is selected to be 200μm and the length is 3mm.

[0059] The ferromagnetic shape memory alloy microwires were subjected to room temperature axial stress stretching cycles using a dynamic mechanical analyzer (DMA Q800). The stretching process involved applying tensile stress to the ferromagnetic shape memory alloy microwires until the martensitic phase transformation was complete, unloading the stress to 0 MPa, and then reloading and unloading the stress. This cycle was repeated 100 times and 1000 times. The resistance of the first 15 stretching processes was monitored to obtain the strain-resistance curve of the ferromagnetic shape memory alloy microwires. The stress-strain curve is shown in Figure 2. Figure 1 As shown in (a), the recoverable strain is about 13%, and the cycle performance is good. Figure 1 As shown in (c) and (d).

[0060] After the tensile test of the ferromagnetic shape memory alloy microwires was completed, temperature resistivity test and magnetoresistivity test were carried out respectively. Figure 2 and 3. According to Figure 2 The resistivity changes significantly before and after the phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0061] like Figure 4 As shown in FIG, the magnetoresistance test of the ferromagnetic shape memory alloy microfilament requires the use of silver glue wires to connect the ferromagnetic shape memory alloy microfilament and the ammeter and voltmeter. Under an external magnetic field, a four-terminal method is used for testing. According to the curve, it can be obtained that within the external magnetic field range of <0.5T, the magnetoresistance change rate of the ferromagnetic shape memory alloy microfilament presents a linear relationship with the external magnetic field, and this linear relationship remains consistent with the increase in the number of training times.

[0062] Furthermore, Figures 3(a-d) show that the linear relationship described above exists at different temperatures, but with different slopes. Therefore, this parameter can operate within a wide temperature window. The martensite volume fraction can be obtained using the rate of change of the magnetoresistivity, and the corresponding stress value can be obtained from the martensite volume fraction. In other words, the stress value can be indirectly obtained through the rate of change of the magnetoresistivity.

[0063] The ferromagnetic shape memory alloy microwire ②, having a diameter of 200 μm and a length of 30 mm, was applied to a tunnel structure (monitored component ①). The method involved bonding and securing the two ends of the ferromagnetic shape memory alloy microwire ② to the tunnel structure (monitored component ①) along the tensile direction. An external magnetic field ③ was applied to the microwire using an energized coil. Silver adhesive wires were used to connect the ferromagnetic shape memory alloy microwire ② to an ammeter ⑤ and a voltmeter ④. A four-terminal test was performed under an external magnetic field of 0.3 T and an ambient operating temperature of 320 K. The slope of the magnetoresistance curve of the ferromagnetic shape memory alloy microwire ② was -0.69, indicating a volume fraction of the martensite phase of 0%. The corresponding stress value, obtained from the stress-strain curve, was 0 MPa, indicating zero force. At this temperature, the slope of the magnetoresistance curve is -1.86, corresponding to the volume fraction of the martensite phase being 100% of that at 200K. The stress value corresponding to the stress-strain curve is 173 MPa, which can monitor the stress state of the structural parts in real time.

[0064] Example 4

[0065] The alloy microwires were prepared by glass coating method, and the ferromagnetic shape memory alloy microwires with good surface roundness were obtained. Figure 1 (b) shown.

[0066] Alloy composition is Ni 50 Mn 24 Ga 22 Fe3Cu1, the diameter of the alloy microwire is selected to be 200μm and the length is 3mm.

[0067] The ferromagnetic shape memory alloy microwires were subjected to room temperature axial stress stretching cycles using a dynamic mechanical analyzer (DMA Q800). The stretching process involved applying tensile stress to the ferromagnetic shape memory alloy microwires until the martensitic phase transformation was complete, unloading the stress to 0 MPa, and then reloading and unloading the stress. This cycle was repeated 100 times and 1000 times. The resistance of the first 15 stretching processes was monitored to obtain the strain-resistance curve of the ferromagnetic shape memory alloy microwires. The stress-strain curve is shown in Figure 2. Figure 1 As shown in (a), the recoverable strain is about 13%, and the cycle performance is good. Figure 1 As shown in (c) and (d).

[0068] After the tensile test of the ferromagnetic shape memory alloy microwires was completed, temperature resistivity test and magnetoresistivity test were carried out respectively. Figure 2 and 3. According to Figure 2 The resistivity changes significantly before and after the phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0069] like Figure 4As shown in FIG, the magnetoresistance test of the ferromagnetic shape memory alloy microfilament requires the use of silver glue wires to connect the ferromagnetic shape memory alloy microfilament and the ammeter and voltmeter. Under an external magnetic field, a four-terminal method is used for testing. According to the curve, it can be obtained that within the external magnetic field range of <0.5T, the magnetoresistance change rate of the ferromagnetic shape memory alloy microfilament presents a linear relationship with the external magnetic field, and this linear relationship remains consistent with the increase in the number of training times.

[0070] Furthermore, Figures 3(a-d) show that the linear relationship described above exists at different temperatures, but with different slopes. Therefore, this parameter can operate within a wide temperature window. The martensite volume fraction can be obtained using the rate of change of the magnetoresistivity, and the corresponding stress value can be obtained from the martensite volume fraction. In other words, the stress value can be indirectly obtained through the rate of change of the magnetoresistivity.

[0071] The ferromagnetic shape memory alloy microwire ②, having a diameter of 200 μm and a length of 30 mm, was applied to the lower chord of the gymnasium roof (the monitored component ①). The method involved bonding and securing the two ends of the ferromagnetic shape memory alloy microwire ② to the lower chord of the gymnasium roof (the monitored component ①) along the tensile direction. An external magnetic field ③ was applied to the microwire using an energized coil. Silver glue wires were used to connect the ferromagnetic shape memory alloy microwire ② to an ammeter ⑤ and a voltmeter ④. Under an external magnetic field of 0.3 T and an ambient operating temperature of 320 K, a four-terminal test was performed. The slope of the magnetoresistance curve of the ferromagnetic shape memory alloy microwire ② was -0.69, indicating a volume fraction of the martensite phase of 0%. Corresponding to the stress-strain curve, a stress value of 0 MPa was obtained, indicating zero force. At this temperature, the slope of the magnetoresistance curve is -1.86, corresponding to the volume fraction of the martensite phase being 100% of that at 200K. The stress value corresponding to the stress-strain curve is 173 MPa, which can monitor the stress state of the structural parts in real time.

[0072] Example 5

[0073] The alloy microwires were prepared by glass coating method, and the ferromagnetic shape memory alloy microwires with good surface roundness were obtained. Figure 1 (b) shown.

[0074] Alloy composition is Ni 50 Mn 24 Ga 22 Fe3Cu1, the diameter of the alloy microwire is selected to be 200μm and the length is 3mm.

[0075] The ferromagnetic shape memory alloy microwires were subjected to room temperature axial stress stretching cycles using a dynamic mechanical analyzer (DMA Q800). The stretching process involved applying tensile stress to the ferromagnetic shape memory alloy microwires until the martensitic phase transformation was complete, unloading the stress to 0 MPa, and then reloading and unloading the stress. This cycle was repeated 100 times and 1000 times. The resistance of the first 15 stretching processes was monitored to obtain the strain-resistance curve of the ferromagnetic shape memory alloy microwires. The stress-strain curve is shown in Figure 2. Figure 1 As shown in (a), the recoverable strain is about 13%, and the cycle performance is good. Figure 1 As shown in (c) and (d).

[0076] After the tensile test of the ferromagnetic shape memory alloy microwires was completed, temperature resistivity test and magnetoresistivity test were carried out respectively. Figure 2 and 3. According to Figure 2 The resistivity changes significantly before and after the phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0077] like Figure 4 As shown in FIG, the magnetoresistance test of the ferromagnetic shape memory alloy microfilament requires the use of silver glue wires to connect the ferromagnetic shape memory alloy microfilament and the ammeter and voltmeter. Under an external magnetic field, a four-terminal method is used for testing. According to the curve, it can be obtained that within the external magnetic field range of <0.5T, the magnetoresistance change rate of the ferromagnetic shape memory alloy microfilament presents a linear relationship with the external magnetic field, and this linear relationship remains consistent with the increase in the number of training times.

[0078] Furthermore, Figures 3(a-d) show that the linear relationship described above exists at different temperatures, but with different slopes. Therefore, this parameter can operate within a wide temperature window. The martensite volume fraction can be obtained using the rate of change of the magnetoresistivity, and the corresponding stress value can be obtained from the martensite volume fraction. In other words, the stress value can be indirectly obtained through the rate of change of the magnetoresistivity.

[0079] The ferromagnetic shape memory alloy microwire ②, having a diameter of 200 μm and a length of 30 mm, was applied to a slope protection wall (monitored component ①). The method involved bonding and securing the two ends of the ferromagnetic shape memory alloy microwire ② to the slope protection wall (monitored component ①) along the tensile direction. An external magnetic field ③ was applied to the microwire using an energized coil. Silver glue wires were used to connect the ferromagnetic shape memory alloy microwire ② to an ammeter ⑤ and a voltmeter ④. A four-terminal test was performed under an external magnetic field of 0.3 T and an ambient operating temperature of 320 K. The slope of the magnetoresistance curve of the ferromagnetic shape memory alloy microwire ② was -0.69, indicating a volume fraction of the martensite phase of 0%. The corresponding stress value, obtained from the stress-strain curve, was 0 MPa, indicating zero force. At this temperature, the slope of the magnetoresistance curve is -0.72, corresponding to a volume fraction of the martensite phase of 10.9% at 292K. The stress value corresponding to the stress-strain curve is 95MPa, which can monitor the stress state of the structural component in real time.

[0080] Example 6

[0081] The alloy microwires were prepared by glass coating method, and the ferromagnetic shape memory alloy microwires with good surface roundness were obtained. Figure 1 (b) shown.

[0082] Alloy composition is Ni 50 Mn 24 Ga 22 Fe3Cu1, the diameter of the alloy microwire is selected to be 200μm and the length is 3mm.

[0083] The ferromagnetic shape memory alloy microwires were subjected to room temperature axial stress stretching cycles using a dynamic mechanical analyzer (DMA Q800). The stretching process involved applying tensile stress to the ferromagnetic shape memory alloy microwires until the martensitic phase transformation was complete, unloading the stress to 0 MPa, and then reloading and unloading the stress. This cycle was repeated 100 times and 1000 times. The resistance of the first 15 stretching processes was monitored to obtain the strain-resistance curve of the ferromagnetic shape memory alloy microwires. The stress-strain curve is shown in Figure 2. Figure 1 As shown in (a), the recoverable strain is about 13%, and the cycle performance is good. Figure 1 As shown in (c) and (d).

[0084] After the tensile test of the ferromagnetic shape memory alloy microwires was completed, temperature resistivity test and magnetoresistivity test were carried out respectively. Figure 2 and 3. According to Figure 2 The resistivity changes significantly before and after the phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0085] like Figure 4As shown in FIG, the magnetoresistance test of the ferromagnetic shape memory alloy microfilament requires the use of silver glue wires to connect the ferromagnetic shape memory alloy microfilament and the ammeter and voltmeter. Under an external magnetic field, a four-terminal method is used for testing. According to the curve, it can be obtained that within the external magnetic field range of <0.5T, the magnetoresistance change rate of the ferromagnetic shape memory alloy microfilament presents a linear relationship with the external magnetic field, and this linear relationship remains consistent with the increase in the number of training times.

[0086] Furthermore, Figures 3(a-d) show that the linear relationship described above exists at different temperatures, but with different slopes. Therefore, this parameter can operate within a wide temperature window. The martensite volume fraction can be obtained using the rate of change of the magnetoresistivity, and the corresponding stress value can be obtained from the martensite volume fraction. In other words, the stress value can be indirectly obtained through the rate of change of the magnetoresistivity.

[0087] The ferromagnetic shape memory alloy microwire ②, having a diameter of 200 μm and a length of 30 mm, was applied to the outer wall of the pressure vessel (the monitored component ①). The method involved bonding and affixing the two ends of the ferromagnetic shape memory alloy microwire ② to the outer wall of the pressure vessel (the monitored component ①) along the tensile direction, applying an external magnetic field ③ to the microwire using a permanent magnet, and connecting the ferromagnetic shape memory alloy microwire ② to an ammeter ⑤ and a voltmeter ④ using silver glue wires. Under an applied magnetic field of 0.3 T and an ambient operating temperature of 292 K, a four-terminal test was performed. The slope of the magnetoresistance curve of the ferromagnetic shape memory alloy microwire ② was -0.72, indicating a volume fraction of the martensite phase of 10.9%. Corresponding to the stress-strain curve, a stress value of 95 MPa was obtained. When the slope of the magnetoresistance curve is -1.86 at this temperature, the volume fraction of the corresponding martensite phase is 100% of that at 200K, and the stress value corresponding to the stress-strain curve is 173MPa. The stress state of the outer wall of the pressure tank can be monitored in real time, and it can be recycled.

[0088] In the above scheme, the present invention uses the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire prepared by the glass coating method, and utilizes the linear response of its magnetoresistance change rate to the magnetic field, and the correspondence between the volume fraction of the martensite phase and stress to monitor the stress state of non-conductive, non-magnetic tensile components such as concrete in real time.

[0089] The present invention solves the problem of low measurement accuracy and great influence of ambient temperature in traditional methods of reflecting stress changes of conductive materials through resistivity, and can be applied to non-conductive and non-magnetic materials such as concrete.

[0090] In the present invention, the linear relationship between the magnetoresistance change rate and the external magnetic field remains stable as the number of stretching times increases.

[0091] The present invention utilizes an energized coil or a magnet to apply an external magnetic field to the alloy microwire.

[0092] The present invention works within a wide temperature window and a stable magnetic field. The wide temperature window is 200-320K, and the stable magnetic field is a magnetic field of <0.5T.

[0093] In the present invention, the resistivity changes significantly before and after the temperature-induced phase transformation, that is, the volume fraction of the martensite phase at different temperatures can be characterized by the resistivity.

[0094] The overall real-time tensile stress monitoring method of the present invention is simple, has high production efficiency, high product quality, can be miniaturized and reused, has a short process and low cost, can operate within a wide temperature window, and under certain operating ambient temperature and external magnetic field conditions, the magnetoresistance change rate, martensite phase volume fraction, and stress correspond in sequence through the microwire, which is conducive to large-scale industrial promotion and use.

[0095] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire, characterized in that: The real-time tensile stress monitoring method comprises attaching a Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire to the surface of a component or embedding it in the component, subjecting it to the same tensile stress as the component, and reading the slope signal of the magnetoresistance curve of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire under the action of an external magnetic field. The slope signal is combined with the ambient temperature and the volume fraction of the reaction martensite phase to quantitatively calibrate the stress of the component, thereby achieving real-time monitoring of the stress value. The stress condition of the quantitative calibration component is first obtained by obtaining the tensile strain-resistance curve of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire, and then performing temperature resistivity test and magnetoresistivity test respectively, and then using the linear slope of the magnetoresistance curve to obtain the martensite phase volume fraction, and finally obtaining the stress value by corresponding the martensite phase volume fraction with the stress-strain curve.

2. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: The Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwires are prepared by a glass coating method to obtain glass-coated ferromagnetic shape memory alloy microwires with good surface roundness.

3. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: The atomic percentage of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire is Ni 50 Mn 27- x Ga 22 Fe x Cu1, x=0-5.

4. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: The Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire has a diameter of 50-400 μm and a length of 100-1000 mm.

5. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: The tensile strain-resistance curve is obtained by first selecting a section of alloy microwire with a length of 3 mm and uniform size for mechanical property characterization, and then performing axial stress stretching cycle measurement on the alloy microwire using a stretching device.

6. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: According to the tensile strain-resistance curve, the maximum output strain of the Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire exceeds 13% and is completely recoverable, and can maintain a stable output after 1000 cycles.

7. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: The magnetoresistivity test is carried out by drawing four leads from the alloy wire, connecting current and voltage respectively, and applying an external magnetic field, that is, using the four-terminal method to monitor the magnetoresistivity change of the alloy microwire.

8. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: The volume fraction of the martensite phase is not affected by the external magnetic field and is related to the temperature-induced martensite transformation and the stress-induced martensite transformation. An appropriate formula is selected to characterize the quantitative relationship between temperature-martensite volume fraction and stress-martensite volume fraction.

9. The real-time tensile stress monitoring method using Ni-Mn-Ga-Fe-Cu ferromagnetic shape memory alloy microwire according to claim 1, characterized in that: Under different ambient temperatures, the corresponding linear relationship between the magnetoresistance change rate and the external magnetic field is different. The corresponding formula is used to establish the relationship between temperature and magnetoresistance change rate, that is, the magnetoresistance change rate corresponding to different martensite phase volume fractions, so as to obtain the stress value corresponding to the magnetoresistance change rate in real time.

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