CN104406728A - Manganin pressure sensor and device for measuring underwater explosion near-field impact wave pressure - Google Patents

Abstract

The invention provides a manganin pressure sensor and a device for measuring near-field shock wave pressure of an underwater explosion, belonging to the technical field of underwater explosive shock measurement. The manganese-copper pressure sensor for underwater explosion near-field shock wave pressure measurement of the present invention sandwiches the sensitive element between two copper-clad thin plates, which increases the overall structural strength of the sensor and prolongs the working life of the sensor; The device for measuring the near-field shock wave pressure of the underwater explosion has strong anti-interference ability, and can resist the interference caused by the explosive explosion products, the residual electric field in the water, and the external electromagnetic field. The realization of precise measurement provides the possibility.

Description

Manganin pressure sensor and device for measuring near-field shock wave pressure of underwater explosion

technical field

The invention belongs to the technical field of underwater explosive explosion impact measurement, in particular to a manganin pressure sensor and a device for measuring near-field shock wave pressure of an underwater explosion.

Background technique

The pressure of the shock wave generated by the underwater explosion of explosives in the near field changes very rapidly, and at the same time has the characteristics of high peak pressure, short duration of positive pressure, and large impulse. Compared with the explosion in air of the same mass of TNT underwater, the peak pressure underwater is 227.15-247.86 times that in air, and the impulse is 8.48-11.80 times. Therefore, it is relatively difficult to measure the pressure of the near-field shock wave of an underwater explosion. The product has not been completely separated in the near-field range, which will cause certain interference to the measurement.

Some experimental research work has been carried out in China on the near-field pressure of underwater explosions, among which Chi Jiachun et al. Journal of the Chinese Academy of Sciences, 1999,13(3):199-204.) used manganese copper piezoresistive pressure gauge and PVDF piezoelectric pressure gauge, which can still work effectively in the high pressure range, to carry out the explosion of TNT/RDX explosive ball in water According to the exploratory research, the attenuation law of the peak pressure of the shock wave is obtained in the range of 1≤R/R ₀ ≤10 (R is the distance from the sensor to the explosion center, and R ₀ is the radius of the explosive). And Zhao Jibo, Tan Duowang et al. (Zhao Jibo, Tan Duowang, Zhang Yuanping. Application of PVDF meter in near-field pressure test of water explosion[J]. Journal of Explosives and Explosives. 2009,32(3):1-4. ) mainly used the PVDF meter to measure the near-field pressure of the underwater explosion within 0.7 to 3 times the radius of the cartridge, and obtained the pressure decay history of the shock wave in the range where the peak value of the shock wave is less than 4GPa.

Although PVDF sensors have been widely used in the measurement of underwater explosion shock wave pressure, they still have the problem of being sensitive to temperature changes, especially when measuring the near-field shock wave pressure similar to underwater explosions, the shock wave affects the medium compression and explosives. The temperature rise caused by the explosion and the pyroelectricity of the PVDF material itself will bring certain errors to the measurement. In addition, the manganin pressure gauge used by Chi Jiachun and others uses low-resistance sensitive elements and a high-voltage pulse constant current source for power supply, which is usually only used for the measurement of pressures above 1GPa, and is not suitable for the measurement of pressures of hundreds of MPa. Furthermore, ordinary piezoelectric sensors are not suitable for the measurement of near-field shock wave pressure of underwater explosions. For commonly used piezoelectric sensors, the maximum range is generally around 100 MPa, such as PCB 138A series sensors, the maximum range is only Measure the pressure of 138MPa. In the near-field area of an underwater explosion, the shock wave pressure and particle velocity are high, which will cause damage to the sensor, and the use of a PCB sensor is very expensive.

To sum up, the near-field shock wave pressure of underwater explosion and its measurement have the following requirements: (1) The near-field shock wave has high peak pressure, large impulse, and fast propagation speed, which lead to its strong destructive ability, so the sensor must have Certain structural strength; (2) Explosive explosive products, residual electric field in water, external electromagnetic field, etc. will cause certain interference to near-field measurement, so the sensor and its measurement system must have sufficient anti-interference ability; (3) Shock wave peak value The response time of the sensor must be very short; (4) In the near-field measurement, the time from the detonation of the explosive to the arrival of the shock wave at the sensor is very short, which requires that the detonation power supply of the explosive can be powered on for a short time, and 100% detonation guaranteed. Prior art still fails to meet above-mentioned requirement.

Contents of the invention

In order to solve the above problems, the present invention provides a manganin pressure sensor and device for measuring the near-field shock wave pressure of an underwater explosion. The manganin pressure sensor sandwiches the sensitive element between two copper-clad sheets, which increases the overall structural strength of the sensor. , prolonging the working life of the sensor; the device used for the measurement of near-field shock wave pressure in underwater explosions has strong anti-interference ability, and can resist the interference caused by explosive explosion products, residual electric field in water, external electromagnetic field, etc. , which provides the possibility for the realization of accurate measurement of near-field shock wave pressure of underwater explosion.

The invention provides a manganese-copper pressure sensor for measuring near-field shock wave pressure of an underwater explosion, which comprises: a sensitive element (2) made of manganese-copper alloy wire, two copper-clad sheets, a measuring cable (8) and a grounding cable (9);

Wherein, each copper-clad sheet is composed of a copper-clad layer (10) and a polytetrafluoroethylene layer (11); the sensitive element (2) is sandwiched between the polytetrafluoroethylene layers (11) of two copper-clad sheets, The copper-clad layer (10) of each copper-clad sheet is covered on the outside of its polytetrafluoroethylene layer (11), and a transparent epoxy potting glue ( 12) Filling makes the sensitive element (2) in a sealed environment;

Wherein, the sensitive element (2) includes: a sensitive part (5), two lead wires (4) and a substrate (3); the sensitive part (5) and the two lead wires (4) are all fixed on the substrate (3); each One end of the lead wire (4) is connected to the sensitive part (5), and the other end is provided with a sensitive component signal output solder joint (6); the two sensitive component signal output solder joints (6) are respectively connected to the core wire and the sheath wire of the measurement cable (9);

Let one copper-clad thin plate be the base plate (1) of the sensitive element (2), and another copper-clad thin plate be the cover plate (7) of the sensitive element (2); The core wire and leather wire of the grounding cable (9) are welded.

Further, the total thickness of the sensitive element (2) is 0.04mm, width 9mm, length 60mm, base plate length 80mm, width 20mm, thickness 0.45mm, cover plate length 52mm, width 20mm, thickness 0.45mm.

Further, the sensitive part (5) of the sensitive element (2) is a spiral body with a diameter of 5mm, and the vertical distance between the center of the sensitive part (5) and the outer boundary of the two copper-clad sheets is 10mm.

Further, the length of the two lead wires (4) is 47 mm, the width is 2 mm, and the distance between the two lead wires is 1 mm.

Further, the signal output solder joint (6) of the sensitive element is 2 mm wide and 2 mm long.

Further, the joints between the sensitive component signal output solder joints (6) and the measuring cables (8), as well as the joints between the copper shells of the cover plate (7) and the bottom plate (1) and the grounding cable (9), are all made of copper Wrapped in foil, forming a Faraday cage.

Further, the joints of the sensitive element signal output solder joints (6) and the measuring cables (8), as well as the joints of the copper shells of the cover plate (7) and the bottom plate (1) and the grounding cable (9), are heated with heat. Melt glue seal.

Further, the base (3) is made of insulating material.

Further, the sensitive element (2) is a manganese-copper alloy wire with a resistance value of 50 ohms.

The present invention also provides a kind of device that is used for underwater explosion shock wave pressure measurement, and it comprises: manganin instrument (13), oscilloscope (14), pulse detonator (15) and above-mentioned four manganin pressure sensors;

Connect the measurement cables of the four manganese copper pressure sensors to the manganin meter (13), the output terminal of the manganin meter (13) is connected to the oscilloscope (14), and the ground wires of the manganin meter (13) and the oscilloscope (14) are connected together Grounding; Pulse detonator (15) connects explosive;

Among them, two manganese-copper pressure sensors are placed symmetrically in the circumferential position of the explosive, two manganese-copper pressure sensors are arranged on one side of the explosive, and the thickness directions of the four manganese-copper pressure sensors are all facing the explosion center of the explosive; the four manganese-copper pressure sensors The sensor is fixed by steel wire;

The pulse detonator (15) is used to detonate the explosive, and the four manganin pressure sensors transmit the resistance change under the action of the shock wave pressure of the underwater explosion to the manganese meter (13) through the cable, and then the manganin meter (13) conditioned and amplifies it and sends it to the oscilloscope (14), obtaining the waveform curve of the shock wave on the oscilloscope (14), and using the waveform curve to calculate the shock wave pressure of the underwater explosion by using the prior art.

Beneficial effect:

1. In the manganin pressure sensor of the present invention, the sensitive element is sandwiched between two copper-clad sheets, and the overall structure of the sensor is in the shape of a sheet, which increases the overall structural strength of the sensor and prolongs the working life of the sensor.

2. The manganese-copper pressure sensor of the present invention connects the copper foil on the surface of two copper-clad thin plates with the copper foil wound at the cable joint to form a Faraday cage, and uses an independent shielding grounding line to reduce detonation electrification Products, external electromagnetic signals, electric fields in water and other factors interfere with the measurement, effectively improving the signal-to-noise ratio of the measurement system.

3. The device for measuring the near-field shock wave pressure of an underwater explosion in the present invention points the thickness direction of the manganin pressure sensor to the explosion center of the explosive during measurement, which makes the propagation distance of the shock wave inside the sensor very short, and the internal stress of the sensor can be quickly The balance is reached, the response time of the sensor is shortened, and the measurement accuracy of the sensor is improved.

4. When the device for measuring the near-field shock wave pressure of an underwater explosion of the present invention is measured, the exposed detonator joint after the explosive detonates will form an electric field in the water, so the power supply of the device adopts a pulse detonator, and its voltage pulse time is adjustable. In the actual measurement, the pulse time is adjusted to be shorter than the ignition time of the detonator, which ensures that the measurement of the shock wave signal will not be disturbed by the residual electric field.

5. The manganese-copper pressure sensor of the present invention separates the grounding cable from the measuring cable to ensure that the charge introduced into the grounding wire due to problems such as leakage of the casing will not affect the internal measurement system.

Description of drawings

Fig. 1 is the structural representation after the cover plate is removed from the manganese-copper pressure sensor of the present invention for measuring the near-field shock wave pressure of an underwater explosion;

Fig. 2 is the front view of the manganese-copper pressure sensor measuring the near-field shock wave pressure of the underwater explosion of the present invention;

Fig. 3 is the A-A cross-sectional schematic diagram of the manganin pressure sensor measuring the near-field shock wave pressure of the underwater explosion of the present invention;

Fig. 4 is the three-dimensional view of the manganin pressure sensor of measuring underwater explosion near-field shock wave pressure of the present invention;

Fig. 5 is a layout diagram of the method for measuring the near-field shock wave pressure of an underwater explosion according to the present invention.

The reference signs are:

1- Copper-clad sheet (bottom plate), 2- Sensitive element, 3- Sensitive element base, 4- Sensitive element lead, 5- Sensitive part of sensitive element, 6- Sensitive element signal output solder joint, 7- Copper-clad sheet (cover plate ), 8-measurement cable, 9-grounding cable, 10-copper clad layer, 11-polytetrafluoroethylene layer, 12-transparent epoxy resin bonding layer, 13-manganin instrument, 14-oscilloscope, 15- Pulse detonator.

Detailed ways

The sensitive element of the manganese-copper pressure sensor for measuring the near-field shock wave pressure of an underwater explosion is a manganese-copper alloy wire with a resistance value of 50Ω. Studies have shown that although the piezoresistive coefficient of manganese-copper alloy is not high, it is better than PVDF material due to its small temperature coefficient of resistance, and it also has the characteristics of fast response and good linearity, which is very suitable for making ultra-high pressure sensors.

As shown in Figures 1 to 4, the present invention mainly consists of two copper-clad polytetrafluoroethylene sheets and a manganese-copper sensitive element. The sensitive element (2) is sandwiched between the thin plates (1) and (7), and they are connected and sealed by a transparent epoxy potting glue (12). The transparent epoxy potting model HT 6308 is better used Glue connection seal.

The dimensions of the sensitive element are: the total thickness is 0.04mm, the width is 9mm, and the length is 60mm. The spiral sensitive part (5) of the sensitive element has a diameter of 5mm. The width is 2mm, the length is 2mm, the base (3) of the sensitive element is made of insulating material, and the whole sensitive element is hermetically sealed and insulated.

The copper-clad PTFE sheet is divided into two sizes, the sheet (1) is 80mm long, 20mm wide, and 0.45mm thick, and the sheet (7) is 52mm long, 20mm wide, and 0.45mm thick. ) and polytetrafluoroethylene layer (11) constitute.

Since the shock wave is too destructive in the near-field measurement, in order to increase the overall structural strength of the sensor and prolong the effective working time of the sensor, the manganese-copper sensitive element is sandwiched between two PTFE sheets for insulation and protection. The role of reinforcement. At the same time, because the explosion products in the near field move fast and are not completely separated from the shock wave, it will cause certain interference to the measurement. Therefore, some additional processing to improve the anti-interference ability of the sensor, such as coating the outer surface of the thin plate with copper, soldering The point is wrapped with copper foil, the entire sensor case is grounded, etc.

After the sensor is connected to the cable at the relevant soldering point, it is sealed and waterproof with hot melt adhesive. At the same time, copper foil is wrapped around the joint. The copper foil is connected with the copper shell of the sensor as a whole and grounded at the same time.

The present invention also provides a device for measuring the near-field shock wave pressure of an underwater explosion, which includes: a manganin meter (13), an oscilloscope (14), a pulse detonator (15) and four manganin pressure sensors;

Connect the measurement cables of the four manganese copper pressure sensors to the manganin meter (13), the output terminal of the manganin meter (13) is connected to the oscilloscope (14), and the ground wires of the manganin meter (13) and the oscilloscope (14) are connected together Grounding; Pulse detonator (15) connects explosive;

Among them, two manganese-copper pressure sensors are placed symmetrically in the circumferential position of the explosive, two manganese-copper pressure sensors are arranged on one side of the end face of the explosive axis, and the thickness directions of the four manganese-copper pressure sensors are all facing the explosion center of the explosive; The copper pressure sensor is fixed by steel wire;

The pulse detonator (15) is used to detonate the explosive, and the four manganin pressure sensors transmit the resistance change under the action of the shock wave pressure of the underwater explosion to the manganese meter (13) through the cable, and then the manganin meter (13) conditioned and amplifies it and sends it to the oscilloscope (14), obtaining the waveform curve of the shock wave on the oscilloscope (14), and using the waveform curve to calculate the shock wave pressure of the underwater explosion by using the prior art.

During the measurement, the sensors are distributed symmetrically around the explosive, and are respectively located in the axial and circumferential directions of the columnar charge. The thickness direction of the sensor is directly facing the explosion center of the explosive, and its position is fixed by a thin steel wire. The specific distribution is shown in Figure 5. The explosive is detonated by a pulse constant current source, and the pulse time is adjustable; the two solder joints of the sensor sensitive element are respectively connected to the core wire and the leather wire of the measurement cable (8), and the copper shell of the sensor is connected to the ground wire (9), and is connected to the manganin meter ( 13), the ground wires of the oscilloscope (14) are grounded together; the measuring cable of the sensor is connected to the manganese copper instrument (13), and the manganese copper instrument (13) plays the role of establishing a bridge circuit, measuring signal, amplifying signal, and outputting signal , the output terminal of the rear manganin meter (13) is connected to the oscilloscope (14).

After the detonator is detonated, if the detonator still has voltage output, the detonating wire is equivalent to two electrodes, forming an electromagnetic field in the water and forming an interference signal in the measurement circuit. In order to reduce the interference of the detonator on the measurement, it is necessary to design a detonator with a controllable detonation voltage output time. Cause interference in the measuring circuit. A pulse detonator (15) is used in the present invention.

In Figure 2, the sensor level is divided into: cover plate - manganese copper sensitive element - bottom plate, the vertical distance between the center of the sensitive part of the sensitive element and the boundary of the thin plate is 10mm, as shown in Figure 1. During the assembly process of the sensor, HT6308 transparent epoxy resin is pre-prepared and spread evenly on the contact surface of the two copper-clad sheets and the sensitive element. It took 24 hours.

After the epoxy resin solidifies, take out the sensor and remove excess epoxy resin. Then, weld the core wire and sheath wire of the signal cable to the two welding spots respectively, and weld the ground wire to the sensor shell. Finally, use hot melt adhesive to seal the joint to play the role of waterproofing and fixing the cable. After the hot melt adhesive is cooled, wrap all the joints with copper foil to shield the external electromagnetic interference.

During the measurement process, the thickness direction of the sensor points to the explosion center of the explosive, which reduces the influence of deformation on the measurement signal and reduces the response time of the sensor at the same time. The explosive is detonated by a pulse constant current source, and the pulse time is set to 50us. The measurement cable of the sensor is connected to the manganin-copper strain gauge, which forms a Wheatstone bridge with the internal circuit of the instrument, and is adjusted by a high-sensitivity multi-turn potentiometer to make the initial output signal tend to zero. Then, the initial output signal is amplified by the amplifying circuit, and the signal is output to the oscilloscope, so that the amplified output signal is obtained.

In the experiment, the amount of TNT is 50g, the sensor is about 90mm away from the surface of the explosive, and it takes about 40us for the shock wave to propagate from the surface of the explosive to the measuring point of the sensor. At the same time, it is measured that it takes 500-1000us from the detonator to the measured signal. This time is greatly affected by the detonator and explosives, which means that the pulse time of the detonation power supply should not be higher than 500us or lower. At the same time, in the experiment, it is indeed observed that the electric field in water has great interference on the measurement, which shows that it is necessary to use a pulsed constant current source for sexual detonation.

After the experiment is completed, the amplitude ΔV(t) of the output signal can be obtained by reading the waveform curve on the oscilloscope, and the relative change of the resistance of the sensitive element ΔR ₀ /R ₀ can be obtained through calculation, and then the measured value can be obtained by calculating the sensitivity coefficient of the sensor. The obtained pressure value P. According to the working principle of the manganin meter, the formula for calculating the relative change in resistance of the sensitive element ΔR ₀ /R ₀ under pressure is as follows:

${\mathrm{<span\; class="notranslate">\; \&Delta;R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;V</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula: ΔR ₀ /R ₀ is the relative change in the resistance of the manganese copper pressure sensor after the pressure is applied, ΔV(t) is the change in the output voltage of the manganese copper instrument caused by the change of the sensor resistance, and K is the system sensitivity of the corresponding channel of the manganin copper instrument , is the voltage output value of the manganin meter caused by the relative change of the unit resistance of the measured resistance, and the system sensitivity K is obtained by system calibration before the experiment.

After the relative change value of the resistance value is measured, the shock wave peak pressure can be calculated by the sensitivity coefficient of the sensor (the relative change amount of the sensor resistance caused by the unit pressure).

In addition, the manganese-copper pressure sensor and device of the present invention can also be used for the measurement of far-field shock wave pressure in underwater explosions. Although the middle and far-field shock wave pressure is very small (such as less than 1MPa range), there are difficulties in measurement, but along with the development of technology, Using the manganese-copper pressure sensor and device of the present invention to measure the mid- and far-field shock wave pressure of underwater explosions by means of signal conversion, increasing input values, etc. also belongs to the protection scope of the appended claims of the present invention.

Of course, the present invention can also have other various embodiments, and those skilled in the art can make various corresponding changes and deformations according to the present invention without departing from the spirit and essence of the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (10)

1. measure the manganin transducer of underwater blast near field shock wave pressure for one kind, it is characterized in that, comprising: the sensitive element (2) be made up of manganin silk, two pieces cover copper sheet, measure cable (8) and ground cable (9);

Wherein, every block covers copper sheet by copper clad layers (10) and polytetrafluoroethylene floor (11) formation; Sensitive element (2) is sandwiched between two pieces of polytetrafluoroethylene floors (11) covering copper sheet, it is outside that the copper clad layers (10) that every block covers copper sheet is overlying on its polytetrafluoroethylene floor (11), and be among sealed environment by the filling sensitive element (2) that makes of transparent epoxy casting glue (12) between two pieces of polytetrafluoroethylene floors (11) covering copper sheet;

Wherein, sensitive element (2) comprising: non-sensitive part (5), two lead-in wires (4) and substrate (3); Non-sensitive part (5) and two lead-in wires (4) are all fixed in substrate (3); Every root lead-in wire (4) one end connects non-sensitive part (5), and the other end arranges sensitive element signal and exports solder joint (6); Two sensitive element signals export solder joint (6) and connect the heart yearn and rubber-insulated wire of measuring cable (9) respectively;

Make one piece to cover base plate (1) that copper sheet is sensitive element (2), another block covers the cover plate (7) that copper sheet is sensitive element (2); The copper shell of cover plate (7) and base plate (1) all welds with the heart yearn of ground cable (9) and rubber-insulated wire.

2. the manganin transducer measuring underwater blast near field shock wave pressure as claimed in claim 1, is characterized in that,

The gross thickness of sensitive element (2) is 0.04mm, wide 9mm, long 60mm, the long 80mm of base plate, wide 20mm, thick 0.45mm, the long 52mm of cover plate, wide 20mm, thick 0.45mm.

3. the manganin transducer measuring underwater blast near field shock wave pressure as claimed in claim 2, is characterized in that,

The non-sensitive part (5) of sensitive element (2) is conveyor screw, diameter 5mm, and the outer boundary vertical range that the centre distance two pieces of non-sensitive part (5) covers copper sheet is 10mm.

4. the manganin transducer measuring underwater blast near field shock wave pressure as claimed in claim 2, is characterized in that,

Two long 47mm of lead-in wire (4), wide 2mm, the spacing 1mm between two lead-in wires.

5. the manganin transducer measuring underwater blast near field shock wave pressure as claimed in claim 2, is characterized in that,

Sensitive element signal exports solder joint (6) wide 2mm, long 2mm.

6. the manganin transducer measuring underwater blast near field shock wave pressure as claimed in claim 1, is characterized in that,

Sensitive element signal exports solder joint (6) and the joint measuring cable (8), and the weld of the copper shell of cover plate (7) and base plate (1) and ground cable (9), all with Copper Foil parcel, form faraday cup.

7. the manganin transducer measuring underwater blast near field shock wave pressure as claimed in claim 1, is characterized in that,

Sensitive element signal exports solder joint (6) and the joint measuring cable (8), and the weld of the copper shell of cover plate (7) and base plate (1) and ground cable (9), all seals with hot melt adhesive.

8. the manganin transducer measuring underwater blast near field shock wave pressure as claimed in claim 1, is characterized in that, substrate (3) is insulating material formation.

9. the as claimed in claim 1 manganin transducer measuring underwater blast near field shock wave pressure, is characterized in that, sensitive element (2) for resistance value be the manganin silk in 50 Europe.

10. measure the device of underwater blast near field shock wave pressure for one kind, it is characterized in that, comprising: copper-manganese instrument (13), oscillograph (14), pulse initiator (15) and four manganin transducer as described in claim 1 to 9;

The measurement cable of four manganin transducer is connected to copper-manganese instrument (13), copper-manganese instrument (13) exports termination oscillograph (14), and the ground wire ground connection together of copper-manganese instrument (13), oscillograph (14); Pulse initiator (15) connects explosive;

Wherein, two manganin transducer are placed in explosive circumferential position symmetry, and two manganin transducer are arranged in an end face side of explosive, and the thickness direction of four manganin transducer is all just to the quick-fried heart of explosive; Four manganin transducer utilize fixation with steel wire;

Utilize pulse initiator (15) detonating powder, resistance variations under the effect of underwater blast wave pressure is sent to copper-manganese instrument (13) through measuring cable by four manganin transducer, oscillograph (14) is sent to after copper-manganese instrument (13) conditioning is amplified, at the upper squiggle obtaining shock wave of oscillograph (14), this squiggle is utilized to utilize prior art to calculate underwater blast wave pressure.