High-speed metal fragment micro-damage grading recovery speed measuring device

Abstract

The invention relates to a high-speed metal fragment micro-damage grading recovery speed measuring device which comprises a testing frame, a to-be-tested piece is arranged beside the testing frame, at least one testing recovery assembly is installed on the testing frame in a matched mode, and a single testing recovery assembly is electrically connected with a measuring system. Each testing and recycling assembly comprises at least one speed measuring and recycling unit, each speed measuring and recycling unit comprises a first recycling thin film layer, a second recycling thin film layer and a polyurethane recycling layer which are sequentially arranged, the first recycling thin film layers and the second recycling thin film layers are arranged in a spaced mode, and therefore air layers are formed between the first recycling thin film layers and the second recycling thin film layers. And the second recovery film layer is tightly attached to the polyurethane recovery layer. A plurality of speed measuring and recycling units are arranged, so that micro-damage graded recycling of high-speed metal fragments can be realized; and meanwhile, by arranging the measuring system, the fragment speed can be measured in a grading manner.

Description

Technical Field

[0001] The invention relates to the technical field of fragment recovery speed measurement, in particular to a high-speed metal fragment micro-damage graded recovery speed measurement device. Background Art

[0002] High-speed fragments are usually generated by strong impact loads such as explosions acting on thin-walled structures such as shells. The characteristics of fragments are a comprehensive reflection of the shell material and detonation loading, reflecting the relationship between the dynamic fracture performance of the material and the strain rate. They also carry physical information about the initiation and expansion of cracks in the shell, which has obvious scientific value and engineering application value. Metal fragments are the most common. The parameter detection of high-speed fragments is usually based on the in-situ observation technology of transient processes. The size distribution of fragments at the moment of shell rupture is approximately observed by high-speed photography. However, the fragment boundaries are easily obscured by the explosion products and blurred. The thickness information of the fragments can be obtained by X-ray transmission imaging, and the influence of explosion products on the boundary blur can be eliminated to a large extent. However, due to the limitation of imaging principles, it is difficult to decouple the flying fragment information of complex structures from the X-ray film. In view of the characteristics of high speed, small size, random distribution of metal fragments, and the limitations of in-situ observation technology of transient processes, soft recovery of fragments at the moment of shell rupture and characterization and statistical analysis have gradually become an important means to study the expansion fracture behavior of shells.

[0003] In the prior art, high-speed fragment recovery methods include recovery plate recovery, explosion container recovery, and freezing recovery. However, the fragment recovery rate of traditional high-speed fragment recovery methods is low, and characteristic quantity statistics cannot be performed; at the same time, the recovery system exerts a strong impact load on the fragments, causing the fragments to deform, split due to secondary damage, and affect the quality and size statistics of the fragments; in addition, traditional high-speed fragment recovery methods are usually unable to accurately measure the speed of the fragments while recovering the fragments, resulting in the loss of key information of the fragments. Summary of the invention

[0004] Based on this, it is necessary to provide a high-speed metal fragment micro-damage graded recovery speed measuring device to address the problems that traditional high-speed fragment recovery methods have a low fragment recovery rate, cannot perform feature quantity statistics, will cause fragments to deform, secondary damage and split, thereby affecting the quality and size statistics of fragments, and cannot accurately measure the speed of fragments while recovering fragments, resulting in the loss of key information of fragments.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A high-speed metal fragment micro-damage graded recovery speed measuring device, comprising a test frame, a test piece is arranged on one side of the test frame, at least one set of test recovery components is installed on the test frame, and a single set of test recovery components is electrically connected to a measurement system;

[0007] The single-group test recovery component includes two side plates arranged at intervals, and the bottoms of the two side plates are simultaneously installed with a bottom plate, so as to form a test space between the bottom plate and the two side plates, and at least one speed measurement recovery unit is installed in the test space, and a single speed measurement recovery unit includes a first recovery film layer, a second recovery film layer and a polyurethane recovery layer arranged in sequence, and the first recovery film layer and the second recovery film layer are arranged at intervals, so as to form an air layer between the first recovery film layer and the second recovery film layer, and the second recovery film layer is arranged closely to the polyurethane recovery layer;

[0008] The test piece explodes to generate fragments, which fly into the corresponding test recovery component, thereby successively penetrating the corresponding first recovery film layer and the second recovery film layer. The time difference between the penetration of the corresponding first recovery film layer and the second recovery film layer by the fragments is detected and recorded by the measurement system, and then the speed of the corresponding fragment is obtained according to the thickness of the air layer between the corresponding first recovery film layer and the second recovery film layer.

[0009] As a further improvement of the above technical solution:

[0010] In a single speed measuring recovery unit, both the first recovery film layer and the second recovery film layer are made of speed measuring recovery film.

[0011] The structure of a single speed measuring recovery film is as follows: it includes two plastic sealing layers arranged at intervals, metal film layers are respectively adhered to the opposite inner wall surfaces of the two plastic sealing layers, an insulating layer is arranged between the two metal film layers, and the two side walls of the insulating layer are respectively adhered to the two metal film layers.

[0012] In a single speed-measuring recycling film, a single-layer plastic sealing layer is made of PET plastic with a thickness of 0.2 mm.

[0013] In a single speed measuring recovery film, a lead wire is arranged on the single metal film layer.

[0014] In a single speed measuring recovery film, a single metal film layer is made of aluminum foil with a thickness of 0.2 mm.

[0015] In a single speed measuring recycling film, the insulating layer is made of PET plastic with a thickness of 0.4mm.

[0016] The single speed measuring recovery film is sealed by plastic sealing process.

[0017] At least one card slot group is arranged on one side wall of a single side plate, and the single card slot group includes a first card slot, a second card slot and a third card slot arranged in sequence;

[0018] The first card slot is used to install a first recycling film layer, the second card slot is used to install a second recycling film layer, and the third card slot is used to install a polyurethane recycling layer.

[0019] The measurement system includes at least one set of measurement components, a single set of measurement components includes a first measurement module and a second measurement module, a single first measurement module is electrically connected to a single first recycling film layer, a single second measurement module is electrically connected to a single second recycling film layer, and both the single first measurement module and the single second measurement module use a voltage monitoring module;

[0020] When the fragments break through the first recovery film layer, the corresponding first measurement module detects a step voltage signal;

[0021] When the fragments break through the second recovery film layer, the corresponding second measurement module monitors a step voltage signal.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention has a compact and reasonable structure and is easy to operate. By arranging a plurality of speed measurement and recovery units, micro-damage graded recovery of high-speed metal fragments can be achieved. At the same time, by arranging a measurement system, the fragment speed can be graded and measured. In addition, for fragments scattered over a large area, according to the estimated fragment dispersion range, a plurality of groups of test and recovery components are spatially distributed to obtain the dispersion form of the fragments. By collating and analyzing the mass, shape, dispersion and speed information of the recovered fragments, data support can be provided for the fragment generation mechanism and fragment load analysis.

[0024] The present invention utilizes the adjustable density of polyurethane foam material to distribute polyurethane recovery layers with density ranging from low to high on the flight trajectory of fragments, thereby realizing micro-damage graded recovery of high-speed metal fragments with a maximum speed of 2000m / s; at the same time, by setting up multiple independent measurement components, including independent first measurement modules and second measurement modules, the fragment speed can be accurately measured in a graded manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the present invention (the speed measurement and recovery unit is omitted).

[0026] Figure 2 for Figure 1 A partial enlarged view of point A in the middle.

[0027] Figure 3 It is a schematic diagram of the structure of the speed measurement and recovery component in the present invention.

[0028] Figure 4 It is a schematic diagram of the structure of a single speed measuring recovery film in the present invention.

[0029] Figure 5 It is a schematic diagram of a single voltage monitoring module in the present invention.

[0030] Among them: 1. Test stand; 2. Speed ​​measurement and recovery unit; 3. Measurement system; 4. Detonation source; 5. Test piece; 6. Side plate; 7. Bottom plate; 8. First card slot; 9. Second card slot; 10. Third card slot; 11. Grid plate;

[0031] 201, speed measurement recovery film; 202, air layer; 203, polyurethane recovery layer;

[0032] 2011, plastic sealing layer; 2012, metal film layer; 2013, insulation layer; 2014, lead wire;

[0033] 301, constant voltage power supply; 302, resistor; 303, input pin; 304, capacitor; 305, voltage monitoring device. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0035] The structure and function of the present invention are as follows:

[0036] like Figure 1-Figure 5As shown, a high-speed metal fragment micro-damage graded recovery speed measuring device comprises a test frame 1, a test piece 5 is arranged on one side of the test frame 1, at least one set of test recovery components is installed on the test frame 1, and a single set of test recovery components is electrically connected to a measurement system 3; the single set of test recovery components comprises two side plates 6 arranged at intervals, and a bottom plate 7 is installed at the bottom of the two side plates 6 at the same time, so that a test space is formed between the bottom plate 7 and the two side plates 6, and at least one speed measuring recovery unit 2 is installed in the test space, and the single speed measuring recovery unit 2 comprises a first recovery film layer, a second recovery film layer and a polyurethane recovery layer 203 arranged in sequence. The first recycling film layer and the second recycling film layer are arranged at an interval, so that an air layer 202 is formed between the first recycling film layer and the second recycling film layer, and the second recycling film layer is arranged closely to the polyurethane recycling layer 203; the test piece 5 explodes to generate fragments, and the fragments fly into the corresponding test recovery component, thereby successively penetrating the corresponding first recycling film layer and the second recycling film layer, and the time difference between the fragments penetrating the corresponding first recycling film layer and the second recycling film layer is detected and recorded by the measuring system 3, and then the speed of the corresponding fragment is obtained according to the thickness of the air layer 202 between the corresponding first recycling film layer and the second recycling film layer. By setting up multiple speed measuring and recovery units 2, each speed measuring and recovery unit 2 is a layered composite structure composed of a first recovery film layer, an air layer 202, a second recovery film layer and a polyurethane recovery layer 203 in sequence, so that micro-damage graded recovery of high-speed metal fragments can be achieved; at the same time, by setting up a measurement system 3, the fragment speed can be measured in a graded manner; in addition, for fragments scattered over a large area, according to the estimated fragment dispersion range, multiple groups of test recovery components are distributed in space to obtain the dispersion form of the fragments; by sorting and analyzing the mass, shape, dispersion and speed information of the recovered fragments, data support can be provided for the fragment generation mechanism and fragment load analysis.

[0037] The single-group test recovery component is based on a modular design. According to the different fragment speeds, different numbers of speed measurement recovery units 2 can be stacked along the fragment flight direction. In addition, along the attenuation direction of the fragment speed, the density of the polyurethane recovery layer 203 in the corresponding speed measurement recovery unit 2 is gradually increased. Since too fast speed attenuation may cause structural damage to the flying fragments, such as Figure 3 As shown, assuming that the fragments fly from left to right, the density of the four-layer polyurethane recovery layer 203 in the speed measurement recovery unit 2 increases layer by layer from left to right. By gradually increasing the density of the polyurethane recovery layer 203, the fragment speed is slowly reduced, thereby achieving micro-damage graded recovery of the fragments.

[0038] like Figure 3 As shown, a single test recovery assembly includes two side plates 6, a bottom plate 7, and at least one speed recovery unit 2; Figure 1-Figure 2As shown, at least one card slot group is arranged on one side wall of a single side plate 6, and the single card slot group includes a first card slot 8, a second card slot 9 and a third card slot 10 arranged in sequence; the first card slot 8 is used to install the first recycling film layer, the second card slot 9 is used to install the second recycling film layer, and the third card slot 10 is used to install the polyurethane recycling layer 203. By arranging the side plate 6 and the bottom plate 7, the speed measuring recovery unit 2 can be quickly limited and installed, thereby improving the convenience of the test.

[0039] The fragments in the present application are generated by the close-range blasting of the test piece 5 by the detonation source 4. The test piece 5 is made of a metal plate. Since the test fragments have a large dispersion space, by setting up a test frame 1, multiple groups of test recovery components can be stably supported, thereby ensuring that the recovery speed measuring device of the present application can obtain all the fragments; in addition, a plurality of grid plates 11 are installed on the test frame 1, and test recovery component placement positions in the form of nine-grid, sixteen-grid, etc. can be built on the test frame 1, thereby facilitating the deployment of corresponding test recovery components.

[0040] In a single speed measuring recovery unit 2, the first recovery film layer and the second recovery film layer both use a speed measuring recovery film 201, which is a five-layer film stacking structure, each layer thickness is not greater than 0.5 mm, and the total thickness is not greater than 2 mm; Figure 4 As shown, the structure of a single speed measuring recovery film 201 is: it includes two plastic sealing layers 2011 arranged at an interval, and metal film layers 2012 are respectively bonded to the opposite inner wall surfaces of the two plastic sealing layers 2011, and an insulating layer 2013 is arranged between the two metal film layers 2012, and the two side walls of the insulating layer 2013 are respectively bonded to the two metal film layers 2012.

[0041] In a single speed measuring recovery film 201, the single plastic sealing layer 2011 is made of PET plastic with a thickness of 0.2 mm; the two plastic sealing layers 2011 play the role of waterproofing and protecting the inner layer structure to avoid wear of the inner layer structure.

[0042] In a single speed measuring recovery film 201 , a lead wire 2014 is provided on the single metal film layer 2012 , and the lead wire 2014 is used to be electrically connected to the measurement system 3 .

[0043] In a single speed measuring and recovery film 201, the single metal film layer 2012 is made of aluminum foil with a thickness of 0.2 mm. When the two metal film layers 2012 are broken down, the corresponding speed measuring and recovery unit 2 is short-circuited.

[0044] In a single speed measuring recovery film 201 , the insulating layer 2013 is made of PET plastic with a thickness of 0.4 mm, and the insulating layer 2013 is used to insulate the two metal film layers 2012 .

[0045] The single speed measuring and recovery film 201 is sealed by a plastic sealing process to achieve dust and water resistance inside. The length and width of the speed measuring and recovery unit 2 after plastic sealing are both 580 mm.

[0046] like Figure 5 As shown, the measurement system 3 includes at least one group of measurement components, a single group of measurement components includes a first measurement module and a second measurement module, a single first measurement module is electrically connected to a single first recovery film layer, a single second measurement module is electrically connected to a single second recovery film layer, and both the single first measurement module and the single second measurement module use a voltage monitoring module; at the moment when the fragments break through the first recovery film layer, the corresponding first measurement module monitors a step voltage signal; at the moment when the fragments break through the second recovery film layer, the corresponding second measurement module monitors a step voltage signal.

[0047] A single voltage monitoring module includes a switch circuit and a main test circuit, the switch circuit and the main test circuit are connected in parallel, a constant voltage power supply 301 and a resistor 302 are connected to the main test circuit, the positive electrode of the constant voltage power supply 301 is grounded, the negative electrode of the constant voltage power supply 301 is electrically connected to one plate of a capacitor 304 through the resistor 302, and the other plate of the capacitor 304 is electrically connected to the input end of the voltage monitoring device 305;

[0048] One end of the switch circuit is grounded, and the other end is connected to the main test circuit, and the access point is located between the resistor 302 and the capacitor 304; the switch circuit is connected to an input pin 303, and the input pin 303 is used to achieve electrical connection with the two lead wires 2014 in the corresponding speed measuring recovery film 201, thereby connecting the corresponding speed measuring recovery film 201 to the circuit.

[0049] When the corresponding speed measuring and recovery film 201 is not broken down (i.e. the corresponding two metal film layers 2012 are not conductive), the switch circuit is in an open circuit state; when the corresponding speed measuring and recovery film 201 is not broken down (i.e. the corresponding two metal film layers 2012 are conductive), the switch circuit is in a short circuit state.

[0050] The voltage monitoring device 305 is used to detect the voltage value on the plate side corresponding to the capacitor 304 and record the time when the voltage value change is detected;

[0051] The voltage value of the constant voltage power supply 301 is E, and the capacitor 302 plays a role in protecting the main test circuit to prevent the main test circuit from short circuit;

[0052] When the switch circuit is in an open-circuit state, since the positive pole of the constant voltage power supply 301 is grounded, the potential of the plate side of the capacitor 304 that is not electrically connected to the voltage monitoring device 305 is -E, and the voltage value monitored by the voltage monitoring device 305 at this time is 0; when the switch circuit is in a short-circuit state, the potential of the plate side of the capacitor 304 that is not electrically connected to the voltage monitoring device 305 is 0, and the voltage value monitored by the voltage monitoring device 305 at this time is E, thereby monitoring a step voltage signal and recording the time when the step voltage signal is obtained.

[0053] By comparing the moment when the first measuring module electrically connected to the first recovery film layer in a single speed measuring recovery unit 2 obtains the corresponding step voltage signal, and the moment when the second measuring module electrically connected to the second recovery film layer in the corresponding speed measuring recovery unit 2 obtains the corresponding step voltage signal, and then based on the thickness of the air layer 202 in the corresponding speed measuring recovery unit 2, the speed at which the fragments pass through the speed measuring recovery unit 2 is obtained.

[0054] In the present application, the detonation source 4 uses TNT charge, which is close to the metal plate frame model. The TNT charge explodes to produce fragments, and the maximum speed of the fragments is estimated to be 1500m / s. The process of speed testing the fragments is as follows:

[0055] The first step: making a speed measuring recovery film 201;

[0056] In the single-layer speed measurement recovery film 201, the single-layer plastic sealing layer 2011 is made of PET plastic with a thickness of 0.2 mm, the single-layer metal film layer 2012 is made of aluminum foil with a thickness of 0.2 mm, and the single-layer insulation layer 2013 is made of PET plastic with a thickness of 0.4 mm;

[0057] Initially, the two lead wires 2014 in the single-layer speed measuring recovery film 201 should be in a disconnected state. Before the test, the on-off state of the two lead wires 2014 needs to be monitored. After it is correct, the speed measuring recovery film 201 can be used for subsequent tests;

[0058] Step 2: Assemble and test the recycling components;

[0059] Three sequentially arranged speed measuring and recovery units 2 are arranged in a single group of speed measuring and recovery components. The total thickness of a single speed measuring and recovery unit 2 is 300 mm, the thickness of the air layer 202 is 20 mm, and the thickness of the polyurethane recovery layer 203 is 250 mm.

[0060] In a single set of speed measuring and recycling components, the density of the three layers of polyurethane recycling layers 203 in the three speed measuring and recycling units 2 increases layer by layer, and the density of the first layer of polyurethane recycling layer 203 is 500g / cm 3 The density of the second polyurethane recycling layer 203 is 800g / cm 3The density of the third polyurethane recycling layer 203 is 1200g / cm 3 ;

[0061] In addition, the bottom plate 7 and the side plate 6 are connected by welding;

[0062] Step 3: Build a recovery speed measuring device;

[0063] Correspondingly, the test frame 1 adopts a nine-square grid format, with a length of 600 mm, a height of 600 mm, and a thickness of 950 mm, on which nine sets of speed measurement and recovery components are placed;

[0064] Correspondingly, 27 groups of measurement components (i.e., corresponding to 27 first measurement modules and 27 second measurement modules) are arranged in the measurement system 3, and the 27 groups of measurement components are arranged one by one with the 27 speed measurement recovery units 2. In a single measurement module, the voltage value of the constant voltage power supply 301 is 24V, the resistance value of the resistor 302 is 200Ω, and the capacitance value of the capacitor 304 is 10μF;

[0065] Step 4: Calculate fragment velocity;

[0066] The detonation source 4 is detonated, and the test piece 5 explodes to generate fragments, and the dispersion pattern of the fragments is obtained through nine sets of test recovery components on the test stand 1;

[0067] When a single fragment flies into a speed measurement recovery unit 2 in one of the test recovery components, it first breaks through the corresponding first recovery film layer, passes through the corresponding air layer 202, and then breaks through the corresponding second recovery film layer; at the same time, when the corresponding first recovery film layer is broken down, the corresponding first measurement module detects a step voltage signal and records the corresponding time t1; when the corresponding second recovery film layer is broken down, the corresponding second measurement module detects a step voltage signal and records the corresponding time t2;

[0068] Then, fragment velocity v = d / (t1-t2);

[0069] Wherein, d represents the thickness of the corresponding air layer 202, which is 20 mm in this embodiment;

[0070] By setting the thickness of the air layer 202 to 20 mm, it is possible to effectively avoid excessive velocity attenuation of the fragments, so that the average velocity of the fragments passing through the air layer 202 can be regarded as the instantaneous velocity of penetrating the first recovery film layer and the second recovery film layer.

[0071] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A high-speed metal fragment micro-damage graded recovery speed measuring device, characterized by: The invention comprises a test stand (1), a test piece (5) is arranged on one side of the test stand (1), at least one set of test recovery components is mounted on the test stand (1), and a single set of test recovery components is electrically connected to a measurement system (3); The single-group test recovery component comprises two side plates (6) arranged at intervals, and a bottom plate (7) is installed at the bottom of the two side plates (6) at the same time, so that a test space is formed between the bottom plate (7) and the two side plates (6), and at least one speed measurement recovery unit (2) is installed in the test space, and the single speed measurement recovery unit (2) comprises a first recovery film layer, a second recovery film layer and a polyurethane recovery layer (203) arranged in sequence, and the first recovery film layer and the second recovery film layer are arranged at intervals, so that an air layer (202) is formed between the first recovery film layer and the second recovery film layer, and the second recovery film layer and the polyurethane recovery layer (203) are arranged in close contact; The test piece (5) explodes to generate fragments, which fly into the corresponding test recovery component, thereby successively penetrating the corresponding first recovery film layer and the second recovery film layer. The time difference between the penetration of the corresponding first recovery film layer and the second recovery film layer by the fragments is detected and recorded by the measurement system (3), and then the speed of the corresponding fragments is obtained according to the thickness of the air layer (202) between the corresponding first recovery film layer and the second recovery film layer.

2. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 1, characterized in that: In a single speed measuring recovery unit (2), both the first recovery film layer and the second recovery film layer are made of a speed measuring recovery film (201).

3. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 1, characterized in that: The structure of a single speed measuring recovery film (201) is as follows: it comprises two plastic sealing layers (2011) arranged at an interval, metal film layers (2012) are respectively bonded to the opposite inner wall surfaces of the two plastic sealing layers (2011), an insulating layer (2013) is arranged between the two metal film layers (2012), and the two side wall surfaces of the insulating layer (2013) are respectively bonded to the two metal film layers (2012).

4. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 3, characterized in that: In a single speed measuring recycling film (201), a single plastic sealing layer (2011) is made of PET plastic with a thickness of 0.2 mm.

5. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 3, characterized in that: In a single speed measuring recovery film (201), a lead wire (2014) is arranged on the single metal film layer (2012).

6. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 3, characterized in that: In a single speed measuring recovery film (201), the single metal film layer (2012) is made of aluminum foil with a thickness of 0.2 mm.

7. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 3, characterized in that: In a single speed measuring recycling film (201), the insulating layer (2013) is made of PET plastic with a thickness of 0.4 mm.

8. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 1, characterized in that: The single speed measuring recovery film (201) is sealed by a plastic sealing process.

9. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 1, characterized in that: At least one card slot group is arranged on one side wall surface of a single side plate (6), and the single card slot group comprises a first card slot (8), a second card slot (9) and a third card slot (10) which are arranged in sequence; The first card slot (8) is used for installing a first recycling film layer, the second card slot (9) is used for installing a second recycling film layer, and the third card slot (10) is used for installing a polyurethane recycling layer (203).

10. The high-speed metal fragment micro-damage graded recovery speed measuring device according to claim 1, characterized in that: The measurement system (3) comprises at least one set of measurement components, wherein a single set of measurement components comprises a first measurement module and a second measurement module, wherein a single first measurement module is electrically connected to a single first recycling film layer, and a single second measurement module is electrically connected to a single second recycling film layer, and both the single first measurement module and the single second measurement module employ a voltage monitoring module; When the fragments break through the first recovery film layer, the corresponding first measurement module detects a step voltage signal; When the fragments break through the second recovery film layer, the corresponding second measurement module monitors a step voltage signal.

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