Study on detonation design of the hottest military

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Research on detonation design of military ships

Abstract: the biggest difference between military ships and general ships is that when military ships perform combat tasks, they are under the detonation environment. The threats faced by ships, including missiles, torpedoes, mines, artillery, etc., lead to fire, flooding, structural damage, shock, explosion and impact; Therefore, detonation design is of great importance to warships. This paper will systematically introduce and study the detonation load borne by military ships, the verification standard, the anti detonation design method of ships, the quoted military regulations and the actual measurement of ship detonation, etc. the compiled warship detonation design program can be used as a reference for warship detonation design

key words: detonation environment, detonation design

I. Introduction

when military ships perform combat missions, they are all in a detonation environment. The so-called shock environment refers to the environment in which the surrounding medium produces rapid displacement, velocity or acceleration due to "non-contact explosion", "contact explosion" or "nuclear explosion", and interacts with the hull structure. The detonation generated in this environment, It is a huge force generated in an instant, and has the characteristics of rapid attenuation and short existence, which will cause deformation, damage, fatigue or loss of function of the hull structure or internal equipment [1]

the threats encountered by the ship, including missiles, torpedoes, mines, artillery, etc. [2] (as shown in Figure 1), the resulting effects are fire, flooding, structural damage, shock, explosion and impact. If a cruiser is hit by a 250 kg missile with a delayed fuse warhead, and the dew point temperature rises, the probability of losing combat power is 75%, and the probability of losing power is 22%, There is a 3% chance that the ship will sink [3]

Figure 1 Schematic diagram of threats encountered by ships [2]

generally speaking, the explosion source encountered by ships is from weapon attack or hull collision caused by improper operation, and the damage caused by it mainly falls into two categories: one is the rupture of the hull itself; First, the internal equipment of the hull is damaged; Because the equipment on the ship is more sensitive to detonation than the ship itself, the damage degree is also higher than the ship itself under the same detonation distance. Therefore, when the ship is built, the specification requirements for the anti detonation ability of the ship generally refer to the anti detonation ability of the important equipment of the ship. Therefore, the ship must have the ability to resist detonation in order to survive on the battlefield; This paper will systematically introduce and study the detonation load borne by the warship, the verification standard, the anti detonation design method of the warship, the quoted military regulations and the actual measurement of the warship detonation. The compiled warship detonation design program can be used as a reference for the warship detonation design

II. Impact of detonation load and verification standards

I. impact of detonation load

detonation load is a huge force. The time of this force is very short, and the instantaneous movement and stress will cause damage to the ship's structure or equipment. As far as ships are concerned, the sources of detonation force can generally be divided into air and water:

water: usually refers to torpedo Water pressure load caused by underwater explosion of mines, etc

in the air: usually refers to missiles, shells or nuclear bombs. The air pressure load generated by the explosion in the air

the sources of the above two types of explosive forces are the same at the same distance from the hull. The main difference is that the load direction caused by the air explosion on the hull is mainly horizontal, and the load direction caused by the underwater explosion on the hull is mainly vertical [4]; When the explosion shock wave reaches the hull, it will be transmitted to the engine base and equipment through the hull plate, frame, deck, bulkhead and other structures. At this time, the hull structure is like a filter. The farther away from the position where the shock wave contacts the hull structure, the smaller the explosion force will be received (as shown in Figure 2 and figure 3). The lighter the equipment weight in the hull, the stronger the instantaneous response will be, and the greater the explosion force will be received. In addition, it will be affected by the water surface boundary layer and ship shape, The vertical blast force is larger than the lateral blast force, and the lateral blast force is larger than the fore and aft direction; Therefore, when a ship is subjected to underwater detonation attack, not all the ship's equipment is subject to the same detonation force. The detonation force of each structure or equipment is affected by the following factors [5]:

Figure 2 U.S. Navy crusier real ship detonation test hull response diagram [5]

Figure 3 U.S. Navy CG II (Chicago) real ship detonation test hull response diagram [5]

1 The weight of the equipment itself and the weight of the machine base carrying the equipment

2. Stiffness of base structure

3. Whether shock absorbers are installed

4. The location where the equipment is installed, such as the outer plate, deck or bulkhead

5. Direction of detonation action, such as horizontal, vertical or fore aft direction

II. Knock verification standard [5]

Figure 4 The design curve of the U.S. Navy's detonation design value [5]

figure f schematic diagram of the definition of various parameters [5]

when the U.S. warship was designed to resist detonation, its detonation requirements used the shock design value (as shown in Figure 4 and figure 5) as the design standard of equipment and frame in the 1950s and 1960s. Under this standard, the detonation capacity of military equipment was about twice that of commercial standards. After the 1970s, the U.S. military's verification standard for detonation value was "keel shock factor (KSF)" as the verification standard. This KSF was defined as:

where (as shown in Figure 5):

W: explosive amount of TNT explosion (kg)

D: distance from the explosion point to the keel (m)

Q: oblique angle between the explosion point and the ship

as for surface ships, the U.S. Navy adopted ksf=0.3 as the ship detonation standard [], This is equivalent to 250 kg TNT explosive. At a distance of 50 meters from the ship, the power generated by the explosion is about 1000 to 10000 times the gravitational acceleration (g), which acts on the keel of the hull

through a series of real ship tests and studies, surface ships can be divided into different levels of seismic resistance according to structure, personnel, equipment, etc. (as shown in Figure 6). Among them, the hull structure is the highest, and its KSF is about 0.8, which is equivalent to the seismic capacity of 250 kg TNT explosive explosion 20 meters away from the hull. Personnel is about 0.6, while non seismic equipment is about 0.1

Figure 6 Schematic diagram of damage caused by underwater detonation at different positions of the ship [5]

III. anti detonation design method of the ship

in order to ensure that the structures and important equipment on the ship can meet the detonation requirements, anti detonation design and analysis should be carried out during the installation of important equipment and systems in the hull structure design stage and construction stage. The anti detonation design and analysis of the ship can be divided into theoretical analysis method and experimental method according to the ship structure Important equipment and systems can be subdivided into four types of research methods (see Figure 7 for details), as described later:

(I) theoretical design and analysis methods

1 Ship structure

(1) finite element method:

such as abaqus-usa, nastran-usa, dyna3d-usa, adina-usa, AUTODYN, DYTRAN, etc.

(2) instantaneous impact response analysis method:

such as plane wave approximation (PWA), virtual mass approximation (VMA) and double asymptotic approximation (DAA)

(3) traditional structural design empirical method

2 Ship's important equipment and systems

(1) dynamic design analysis method (DDAM)

(2) impact dynamic design analysis method (iddam)

(3) revise impact dynamic design analysis method (riddam)

(2) experimental analysis and design method

1 Important equipment and systems of naval ships

(1) fall test method:

use the fall test machine to test, which is generally used in commercial transportation

(2) impact test method:

use light and intermediate impact tests to test light and intermediate weight equipment

(3) underwater detonation platform:

use standard underwater detonation platform and large underwater detonation platform to test heavy weight equipment or overweight weight system

2. Real ship knock test

(1) simple real ship knock test:

test whether the class C equipment (equipment without anti knock ability) of the ship maintains normal function after the real ship knock test

(2) complete real ship knock test:

test whether the ship structure and class a equipment (equipment with anti knock ability) remain normal without damage after the real ship knock test

reference and detonation related military regulations

I. definition and classification of military regulations

in a broad sense, all norms and standards used in military products belong to the scope of military regulations [7]. Because most of China's military equipment in the past relied on the United States, and its standards adopted the U.S. military standards, the military regulations in a narrow sense refers to the "military specification" of the United States Military standard "or" general specification for ships of United States Navy "

in 1907, the U.S. Navy issued the "general specification for U.S. Navy ships" as the blueprint of all ship contract specifications, which has been revised year by year and has been used until now. It has the dual character of "demand" and "standard", as shown in Figure 8; This specification has been used for nearly 90 years, and it is difficult to estimate the number of ships built on it. In this context, as a standardized contract specification template, there is no problem, but the specification system is too large and difficult to quote. In recent years, the U.S. military has also experienced this problem, and is now cooperating with the American Bureau of shipping (ABS), Integrate the general specifications of U.S. naval ships and relevant military regulations with ABS rules and propose a new version of the naval vessel rules [8]

figure 8 Classification diagram of military regulations application in the design and construction stage of military ships

II. The introduction of military regulations in the anti knock design of ship structures

(I) the military regulations quoted

at present, the typical military regulations quoted in the detonation design of ship structures in European and American countries are as follows [2, 5, 9]:

United States: DDS, DDS, mil s901d, mil-std-810e, mil-std-, For example, "1% of the instigation value" is the basic principle of accessory design, which means that the deviation between the measured value and the actual value is within ± 1%, mil-std-, mil-std-1399, NAVSEA 0908 lp-, NAVSEA, NAVSEA, NAVSEA 0900 lp-, NAVSEA 0900 lp-, NAVSEA 0900 lp-, etc.

UK: br3021 (shock manual)

Germany: bv 043 (bauvorschrift)

Netherlands: (Shock Handbook, part)1), (Shock Handbook, Part 2)

nato-stands:4137, 4141, 4142, 4150

see Table 1 for details. Table 1 Statistical table of important military regulations cited in ship detonation design of European and American countries [2, 5, 9]

(II) important military regulations used in U.S. ship detonation design or printing and pasting spoon chopsticks signs (see Appendix A for details) introduction

1 Environmental factors

during World War II, the German army blockaded Britain with mines, causing considerable damage to British ships. As a result, Britain and the United States invested a lot of manpower to review the impact resistance of ship equipment

for products in defense related industries, the product impact environmental test standard mainly refers to mil-std-810e and mil-s-901d specifications

mil-std-810e is the relevant standard of environmental test methods and engineering guidelines of the U.S. military. This military regulation mainly provides the environmental conditions, effects and test methods of military products, and is the guide of environmental test technology when engaged in military product research and development; In terms of impact environment requirements, mil-st

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