CN112797856B - Method for rapidly evaluating position load of minimum risk bomb of transport aircraft - Google Patents

Method for rapidly evaluating position load of minimum risk bomb of transport aircraft Download PDF

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CN112797856B
CN112797856B CN202110131766.3A CN202110131766A CN112797856B CN 112797856 B CN112797856 B CN 112797856B CN 202110131766 A CN202110131766 A CN 202110131766A CN 112797856 B CN112797856 B CN 112797856B
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mach
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overpressure
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解江
冯振宇
傅博宇
姜超
段竹煊
高斌元
潘汉源
甄婷婷
王立轩
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Civil Aviation University of China
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
    • F42B35/00—Testing or checking of ammunition

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Abstract

The invention discloses a method for quickly evaluating the position load of a minimum risk bomb of a transport plane, which comprises the following steps of firstly, placing a detonation center at a selected position; secondly, calculating pressure pulses acting on the internal points of the fuselage; finally, the dynamic load is converted into an equivalent static load for predicting structural failure caused by explosion. The equivalent static pressure is obtained through calculation, the scale of structural damage caused by explosive explosion can be estimated through the value, and whether the residual structure can continuously bear the flight load or not is evaluated in an auxiliary mode through the estimated value.

Description

Method for rapidly evaluating position load of minimum risk bomb of transport aircraft
Technical Field
The invention relates to the field of rapid evaluation of minimum risk bombs, in particular to a rapid evaluation method for position loads of minimum risk bombs of a transportation type airplane.
Background
The federal aviation administration of the united states issued a FAR 25-127 amendment on 28/10/2008, requiring manufacturers to design a "minimum risk bomb position" on the aircraft for placement of the discovered suspect devices. Through the comprehensive design of the structure and the system, the key structure and the system related to the safety of the airplane can be protected to the maximum extent once the key structure and the system are exploded, so that the safety level of the airplane is effectively improved.
The validity of the aircraft minimum risk bomb position (LRBL) does not need to be verified experimentally, i.e. the validity of the position does not need to be verified by exploding the aircraft with "real bombs". However, depending on the design, other experiments related to LRBL are required, so how to establish a method for quickly evaluating the location load of the minimum risk bomb is an effective means for supporting the LRBL design and compliance verification.
Disclosure of Invention
In order to solve the existing problems, the invention provides a method for quickly evaluating the position load of a minimum risk bomb of a transport aircraft.
The technical solution for realizing the purpose of the invention is as follows:
the method for rapidly evaluating the position load of the minimum risk bomb of the transport plane is characterized by comprising the following steps of:
step 1: placing the detonation center at a selected position, recording coordinates of the position as (a, b, c), defining parameters of the airplane body, and initializing the parameters: radius R, length L, thickness t and explosive equivalent w;
and 2, step: based on the coordinates and initialization parameters of the calculated point in the fuselage, the relevant parameters of the shock wave acting on the point in the fuselage and the load holding time t are calculated 0 And the shock wave related parameters include: mach number M of incident wave x Reflection overpressure p r Mach number M of Mach wave s Mach overpressure p ms And angle of maximum Mach reflection beta max ；
And 3, step 3: by calculating the maximum overpressure p max The dynamic coefficient y is used for converting the dynamic load generated by explosion into the equivalent static load under the equivalent quantity and predicting the structural damage caused by explosion;
and 4, step 4: according to the maximum overpressure p obtained max And the dynamic coefficient y, calculating to obtain the equivalent static pressure based on the detonation distance and the explosive equivalent;
and 5: the stress condition of the aircraft structure after the bomb explosion can be solved according to the obtained equivalent static pressure, and then whether the residual strength of the aircraft structure can continuously bear the flight load or not is evaluated in an auxiliary mode.
Further, the incident wave Mach number M obtained in the step 2 x Reflection overpressure p r Mach number M of Mach wave s Mach overpressure p ms Angle of maximum Mach reflection beta max And time of load t 0 Respectively as follows:
Figure BDA0002925605260000021
wherein, according to the cube root law of proportionality: if two same explosive charges are provided, the geometrical shapes of the charges are similar to each other, the charges have different sizes, and when the charges are exploded in the same atmosphere, the charges are at the same proportional distance
Figure BDA0002925605260000031
Will generate similar shock waves, D is the space distance, and w is the equivalent of the explosive;
Figure BDA0002925605260000032
Figure BDA0002925605260000033
M s ＝M x /sinβ (4)，
wherein beta is the contained angle between the ray that sends out from the initiation point and the intersection point tangent line of fuselage outline, and b is the horizontal radial distance of explosive and equivalent static load point to:
β＝90-arctan(R/b) (5)，
Figure BDA0002925605260000034
Figure BDA0002925605260000035
Figure BDA0002925605260000036
further, the maximum overpressure p of step 3 max Comprises the following steps:
Figure BDA0002925605260000037
further, modeling the aircraft structure as a one-dimensional system with the natural frequency as a characteristic, wherein the static load in step 3 is the static load which generates the same deformation as the dynamic explosion, and estimating the natural frequency T of the structure, wherein the estimation formula is as follows:
Figure BDA0002925605260000038
wherein f is the cycle frequency;
and:
Figure BDA0002925605260000039
wherein t is the skin thickness, C is the frequency constant, k is the material factor, and l is the distance between the reinforcement frames.
Further, step 4 calculates the equivalent static pressure P for each of the firing distances and the explosive equivalent E The formula of (1) is as follows:
P E ＝p max y (12)。
compared with the prior art, the method has the following beneficial effects:
firstly, the damage range of the explosion shock wave obtained by calculation on the aircraft skin can meet the requirement of any precision;
secondly, the invention can quickly provide the equivalent static pressure calculated by each explosion distance and the explosive equivalent, estimate the structural damage scale caused by explosive explosion according to the obtained equivalent static pressure, and assist in evaluating whether the residual structure can continuously bear the flight load by using the estimated value.
Drawings
FIG. 1 is a process flow diagram of an evaluation method of the present invention;
FIG. 2 is a schematic diagram of a Mach number versus proportional distance fit curve in the present invention;
FIG. 3 is t 0 T and p E /p max The graph of (a), namely a curve diagram of the kinetic coefficient y;
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the following further describes the technical solution of the present invention with reference to the drawings and the embodiments.
Referring to fig. 1, the method for rapidly evaluating the minimum risk bomb position load of a transport aircraft provided by the invention comprises the following operation steps:
step 1: placing the detonation centre at a selected location, the location point coordinates being (a, b, c), defining aircraft fuselage parameters, and initializing the parameters: radius R, length L, thickness t and explosive equivalent w;
step 2: based on the coordinate and initialization parameter of the calculated point in the fuselage, calculating the shock wave related parameter acting on the point in the fuselage and the load time t 0 And the shock wave related parameters include: mach number M of incident wave x Reflection overpressure p r Mach number M of Mach wave s Mach overpressure p ms And maximum Mach angle of reflection beta max ；
And 3, step 3: by calculating the maximum overpressure p max The dynamic coefficient y is used for converting the dynamic load generated by explosion into the equivalent static load under the equivalent quantity and predicting the structural damage caused by explosion;
wherein, the dynamic load refers to that the explosive load is in a changing state (dynamic pressure), and the static load refers to the static load (static pressure); the maximum overpressure is the maximum value of dynamic pressure, and the power coefficient y is a parameter for converting the maximum value of dynamic pressure into static pressure;
and 4, step 4: according to the maximum overpressure p obtained max And the dynamic coefficient y, calculating to obtain the equivalent static pressure based on the detonation distance and the explosive equivalent;
and 5: the stress condition of the aircraft structure after the bomb explosion can be solved according to the obtained equivalent static pressure, and then whether the rest structure of the aircraft structure can continuously bear the flight load or not is evaluated in an auxiliary mode.
The equivalent static pressure is acted on the airplane structure, so that the stress of the airplane structure after the bomb explodes can be solved, and the residual strength can be evaluated in an auxiliary manner;
preferably, in step 2, the proportional distance z of any position of the fuselage is solved, an explicit Shocks inner air addendum table is fitted, and the proportional distance z and the mach number M are obtained x The Mach number M of the incident wave is obtained by the piecewise function between x Comprises the following steps:
Figure BDA0002925605260000061
wherein, according to Hopkinson's law of proportionality, also called cube-root's law of proportionality: if two same explosive charges are provided, the geometrical shapes of the charges are similar to each other, the charges have different sizes, and when the charges are exploded in the same atmosphere, the charges are at the same proportional distance
Figure BDA0002925605260000062
Generating similar shock waves, wherein D is the space distance, and w is the equivalent weight of the explosive;
according to the obtained incident wave Mach number M x Obtaining the overpressure at this point, the reflected overpressure p r Mach number M of Mach wave s Mach overpressure p ms Angle of maximum Mach reflection beta max And time of load t 0 Respectively as follows:
Figure BDA0002925605260000063
Figure BDA0002925605260000064
M s ＝M x /sinβ (4)，
wherein β =90-arctan (R/b) which represents the angle of a ray drawn from the initiation point with the tangent to the intersection of the fuselage contours, and b is the horizontal radial distance of the explosive from the point of equivalent static loading;
Figure BDA0002925605260000065
Figure BDA0002925605260000066
Figure BDA0002925605260000067
preferably, in step 3, said maximum overpressure p max Comprises the following steps:
Figure BDA0002925605260000068
Figure BDA0002925605260000071
at this time, a static load which is the same as the static load generated by the dynamic explosion in the process of generating deformation is determined, the natural frequency T of the structure must be estimated, and since the deformation of the structure under the dynamic load is related to the natural frequency of the structure (the ratio of the explosion action time to the natural frequency is linearly related to the ratio of the equivalent static load to the dynamic load), the natural frequency of the structure is considered when the dynamic load is equivalent to the static load, and the calculation formula is as follows:
Figure BDA0002925605260000072
wherein f is the cycle frequency;
and:
Figure BDA0002925605260000073
wherein t is the skin thickness, C is the frequency constant, k is the material factor, and l is the distance between the reinforcement frames.
According to the abscissa as t 0 T, s, ordinate p E /p max I.e. the curve of the kinetic coefficient y, the fitted piecewise function is:
Figure BDA0002925605260000074
in FIG. 3, t is 0 T and p E /p max The abscissa of the graph of (a) is s, the ordinate of the graph of (b) is y, y is linearly related to x, the curve thus obtained is a curve of the kinetic coefficient y, so that the value of s can be determined by a series of equations preceding equation (13), p max It can also be found that P can be obtained according to the formula (13) E 。
Further, an equivalent static pressure P can be calculated for each of the explosive distance and the explosive equivalent E Comprises the following steps:
P E ＝p max y (12)。
examples
Assuming that the explosive equivalent is 80g, the skin thickness is 2mm, the distance l between the reinforcing frames is 300mm, and the explosion distance is the incident wave Mach number M x Reflection overpressure p r Mach number M of Mach wave s Mach overpressure p ms ，
Angle of maximum Mach reflection beta max And time of load t 0 Respectively as follows:
M x ＝20.6266-44.3921z+28.3631z 2 ＝3.4681；
inputting R and b values by a program according to the parameters of the airplane and the coordinate points for calculating the static load,
and calculates: β =90-arctan (R/b) =1.2558;
Figure BDA0002925605260000081
Figure BDA0002925605260000082
M s ＝M x /sinβ＝Inf；
Figure BDA0002925605260000083
Figure BDA0002925605260000084
Figure BDA0002925605260000085
in this case, beta is not more than beta max Maximum overpressure p max Comprises the following steps:
p max ＝p r ＝76.7230Psi；
at this time, the natural frequency T of the structure is:
Figure BDA0002925605260000091
s＝t 0 /T＝0.0641；
the kinetic coefficient y is obtained by equation (13):
y＝0.02+s＝0.0841；
converting the dynamic load into equivalent static load for predicting structural damage caused by explosion and equivalent static pressure P E Comprises the following steps:
P E ＝p max y＝6.4563Psi。
according to the obtained equivalent static pressure P E The size of the structural damage caused by the explosive blast is estimated and this estimate is then used to assist in assessing whether the remaining structure can continue to withstand the flight loads.
Those not described in detail in this specification are within the skill of the art. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and modifications of the invention can be made, and equivalents of some features of the invention can be substituted, and any changes, equivalents, improvements and the like, which fall within the spirit and principle of the invention, are intended to be included within the scope of the invention.

Claims (5)

1. The method for rapidly evaluating the position load of the minimum risk bomb of the transport-type airplane is characterized by comprising the following steps of:
step 1: placing the detonation center at a selected position, recording coordinates of the position as (a, b, c), defining parameters of the airplane body, and initializing the parameters: radius R, length L, thickness t and explosive equivalent w;
and 2, step: based on the coordinates and initialization parameters of the calculated point in the fuselage, the relevant parameters of the shock wave acting on the point in the fuselage and the load holding time t are calculated 0 And the shock wave related parameters include: mach number M of incident wave x Reflected overpressure p r Mach number M of Mach wave s Mach overpressure p ms And maximum Mach angle of reflection beta max ；
And step 3: by calculating the maximum overpressure p max The dynamic coefficient y is used for converting the dynamic load generated by explosion into the equivalent static load under the equivalent quantity and predicting the structural damage caused by explosion;
and 4, step 4: according to the maximum overpressure p obtained max And the dynamic coefficient y, calculating to obtain the equivalent static pressure based on the detonation distance and the explosive equivalent;
and 5: the stress condition of the aircraft structure after the bomb explosion can be solved according to the obtained equivalent static pressure, and then whether the rest structure of the aircraft structure can continuously bear the flight load or not is evaluated in an auxiliary mode.
2. The method for rapidly estimating the location load of the minimum risk bomb of a transport-type aircraft according to claim 1, wherein the incident wave Mach number M obtained in step 2 x Reflection overpressure p r Mach number M of Mach wave s Mach overpressure p ms Angle of maximum Mach reflection beta max And time of load t 0 Respectively as follows:
Figure FDA0003961639280000021
wherein, according to the cube root law of proportionality: if two same explosive charges are provided, the geometrical shapes of the charges are similar to each other, the charges have different sizes, and when the charges are exploded in the same atmosphere, the charges are at the same proportional distance
Figure FDA0003961639280000022
Similar shock waves are generated, D is a space distance, and w is the equivalent weight of the explosive;
Figure FDA0003961639280000023
Figure FDA0003961639280000024
M s ＝M x /sinβ (4)，
wherein beta is the contained angle between the ray that sends out from the initiation point and the intersection point tangent line of fuselage outline, and b is the horizontal radial distance of explosive and equivalent static load point to:
β＝90-arctan(R/b) (5)，
Figure FDA0003961639280000025
Figure FDA0003961639280000026
Figure FDA0003961639280000027
3. the method of claim 1The method for rapidly evaluating the position load of the minimum risk bomb of the transport-type airplane is characterized in that the maximum overpressure p in the step 3 max Comprises the following steps:
Figure FDA0003961639280000031
4. the method for rapidly estimating the location load of the minimum risk bomb of transportation aircraft as claimed in claim 1, wherein the aircraft structure is modeled as a one-dimensional system characterized by natural frequency, the static load in step 3 is the static load which generates the same deformation as the dynamic explosion, the natural frequency T of the structure is estimated, and the estimation formula is as follows:
Figure FDA0003961639280000032
wherein f is the cycle frequency;
and:
Figure FDA0003961639280000033
wherein t is the skin thickness, C is the frequency constant, k is the material factor, and l is the distance between the reinforcement frames.
5. The method for rapidly evaluating the minimum risk bomb position load of a transport-type aircraft as claimed in claim 1, wherein the formula for calculating the equivalent static pressure in step 4 is as follows:
P E ＝p max y (12)。
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB719771A (en) * 1950-01-18 1954-12-08 British Electricity Authority Improvements in or relating to tele-communication equipment
CN101151504A (en) * 2005-04-08 2008-03-26 独立行政法人产业技术综合研究所 Blasting treating method
CN204713434U (en) * 2015-04-02 2015-10-21 中国人民解放军空军勤务学院 Aerial bomb ammunition carrier
CN106197184A (en) * 2016-08-01 2016-12-07 西北工业大学 A kind of civil aircraft main cabin portable directional explosion-proof device
CN109780956A (en) * 2019-03-06 2019-05-21 西安近代化学研究所 A kind of cumulative pressure release civil aircraft main cabin directional explosion-proof device

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