阅读说明：本技术 包括冲击接收组件和能量耗散组件的冲击吸收结构 (Impact absorbing structure comprising an impact receiving assembly and an energy dissipating assembly ) 是由 G·蒂尔 于 2019-03-12 设计创作，主要内容包括：提供一种冲击吸收结构(1)。冲击吸收结构(1)包括冲击接收组件(3),其能够在接收初始碰撞冲击波之后,将该冲击波分离成至少第一冲击波(S11)和与第一冲击波(S11)在时间上间隔开的第二冲击波(S122)。冲击吸收结构(1)还包括与冲击接收组件(3)相邻的能量耗散组件(5),使得在时间上间隔开的冲击波(S11、S122)能够穿过从冲击接收组件(3)到能量耗散组件(5)的界面。能量耗散组件(5)包括化学元素或化合物,诸如方解石,其在经历第一冲击波(S11)时表现出从第一相到第二相(52)的第一位移相变,在经历第二、稍后冲击波(S122)时表现出从第二相(52)到第三相(53)的第二位移相变,以及在第二冲击波(S122)之后卸载时表现出从第三或稍后相到第一相(53)的第三位移相变,该化合物因而表现出其中耗散了弹性能量的滞后循环。(An impact absorbing structure (1) is provided. The shock absorbing structure (1) comprises a shock receiving assembly (3) capable of separating an initial impact shock wave into at least a first shock wave (S11) and a second shock wave (S122) spaced in time from the first shock wave (S11) after receiving the shock wave. The impact absorbing structure (1) further comprises an energy dissipating assembly (5) adjacent to the impact receiving assembly (3) such that temporally spaced shock waves (S11, S122) can pass through the interface from the impact receiving assembly (3) to the energy dissipating assembly (5). The energy dissipating assembly (5) comprises a chemical element or compound, such as calcite, which exhibits a first displacement phase transition from the first phase to the second phase (52) when subjected to a first shock wave (S11), a second displacement phase transition from the second phase (52) to the third phase (53) when subjected to a second, later shock wave (S122), and a third displacement phase transition from the third or later phase to the first phase (53) when unloaded after the second shock wave (S122), the compound thus exhibiting a hysteresis cycle in which elastic energy is dissipated.)

1. An impact absorbing structure comprising:

i) a shock receiving assembly capable of separating the shock wave into at least a first shock wave and a second shock wave spaced in time from the first shock wave after receiving an initial impact shock wave;

ii) an energy dissipating assembly adjacent to the shock receiving assembly such that shock waves spaced in time are able to pass through an interface from the shock receiving assembly to the energy dissipating assembly, wherein the energy dissipating assembly comprises a chemical element or compound exhibiting:

a first phase change of displacement from a first phase to a second phase upon experiencing the first shock wave,

-a second phase change of displacement from the second phase to a third phase upon experiencing the second, later shock wave, and

-a third displacement phase transition from the third or later phase to the first phase upon unloading after the second shock wave,

the compound thus exhibits hysteresis cycles in which elastic energy is dissipated.

2. The impact-absorbing structure of claim 1, wherein the chemical element or compound comprises a lattice structure.

3. The impact-absorbing structure of claim 2, wherein the chemical element or compound is calcite, titania, silica, magnesium silicate, sodium, or iron.

4. The impact-absorbing structure of any of the preceding claims, wherein the impact-receiving component is magnesium, periclase, fused silica, polycarbonate, PMMA, aluminum, ethanol, air, or water.

5. The impact-absorbing structure of any of the preceding claims, wherein the impact-receiving component has an impact resistance that is lower than the impact resistance of the energy-dissipating component.

6. The impact-absorbing structure of any of the preceding claims, comprising a laminate formed of one layer of impact-receiving components and one layer of energy-dissipating components.

7. The impact-absorbing structure of any one of claims 1 to 5, comprising a matrix of impact-receiving components containing a distribution of particles of the chemical element or compound.

8. The shock absorbing structure of claim 6 or 7, wherein the shock receiving assembly and the energy dissipating assembly are configured such that after the shock receiving assembly receives an initial impact shock wave, the shock wave separates into the first shock wave and the second shock wave spaced in time from the first shock wave due to reflection of the initial impact shock wave at an interface between the shock receiving assembly and the energy dissipating assembly.

9. The impact-absorbing structure according to any one of claims 5 to 8, wherein the chemical element or compound is calcite and the impact-receiving component is polycarbonate.

10. An armor or armor shell comprising the impact-absorbing structure of any of the preceding claims.

Technical Field

The present invention relates to an impact absorbing structure.

Background

Disclosure of Invention

According to a first aspect, the present invention provides a shock-absorbing structure comprising a shock-receiving component (impact receiving component) capable of separating, after receiving an initial impact shock wave, the shock wave into at least a first shock wave and a second shock wave spaced in time from the first shock wave; an energy dissipation component adjacent the shock receiving component such that shock waves spaced in time are able to traverse the interface from the shock receiving component to the energy dissipation component, wherein the energy dissipation component comprises a chemical element or compound that exhibits a first phase-shifting change from a first phase (phase) to a second phase when subjected to a first shock wave, a second phase-shifting change from the second phase to a third phase when subjected to a second, later shock wave, and a third phase-shifting change from the third or later (e.g. fourth, fifth or sixth, etc.) phase to the first phase when unloaded after the second shock wave, the compound thus exhibiting hysteresis cycles in which elastic energy is dissipated.

In other words, the energy dissipating component comprises a chemical element or compound that exhibits a first displacement phase change from a first phase to a second phase, a second displacement phase change from the second phase to a third phase, any number (including zero) of possible further phase changes from the third phase to a fourth phase, from the fourth phase to a fifth phase, and so on through an nth phase, and then a final displacement phase change from the nth phase to the first phase upon unloading after the second shock wave. The "nth phase" may be the third, fourth, fifth, sixth, etc.

The present invention recognizes that it is possible to design the impact absorbing structure such that, after impact by a projectile, a sequence of impact propagation is generated within the structure which sequentially initiates specific displacement phase transitions within the chemical element or compound. By designing the impact propagation sequence in this way, the hysteresis cycle of the compound or element can be used to dissipate the energy imparted to the impact absorbing structure by the projectile after impact. Thus, such impact absorbing structures are able to dissipate energy and return to their original undeformed, non-impacting shape after a complete hysteresis cycle, thus allowing multiple hysteresis cycles before potential material failure.

The impact absorbing structure is particularly suitable for ballistic impacts. Ballistic impact is defined in this case as impact in which a projectile impacts the impact absorbing structure at a velocity of at least 100 meters per second and at most 300 kilometers per second.

The chemical element or compound may include a lattice structure. The chemical element or compound may be any chemical element or compound that exhibits a displacement phase change and exhibits a hysteresis curve in which energy is dissipated when elastically loaded and unloaded. The chemical element or compound may be calcite, titania, silica, magnesium silicate, sodium or iron. The impact receiving member may be magnesium, periclase, fused silica, polycarbonate, PMMA (poly (methyl methacrylate)), or aluminum. The shock receiving member may be ethanol, air or water.

The shock resistance of the shock receiving assembly may be lower than the shock resistance of the chemical element or compound. The ability of the impact receiving assembly to separate a single incident shock wave generated by the impact of the projectile into two or more shock waves of appropriate velocity and time-distance to induce hysteresis in the energy dissipating assembly depends on the impact resistance of the impact receiving assembly. The impact resistance Z of a material is the material density ρ₀And material sound velocity U_sFunction of (c):

Z＝ρ₀U_s

the term "material" as used herein refers to the impact receiving component and/or the chemical element or compound. The impact resistance of the impact receiving member may be selected to be lower than the impact resistance of a projectile that may impact the impact receiving member. The projectile may comprise or consist of copper, aluminium, steel, lead, tungsten carbide or tantalum.

The impact-absorbing structure may be in the form of a laminate formed of one (or more than one) layer of impact-receiving components and one (or more than one) layer of energy-dissipating components. The impact absorbing structure may comprise a matrix (matrix) of impact receiving members comprising a distribution of particles of chemical elements or compounds. The particles may be randomly shaped and may be randomly distributed/dispersed within the matrix of the impact receiving member. The shock absorbing structure may have a solid architecture in which particles of chemical elements or compounds having a well-defined geometry are distributed/dispersed in a well-defined geometrical order within a matrix of shock receiving elements.

The shock receiving assembly and the energy dissipating assembly may be configured such that after the shock receiving assembly receives the initial impact shock wave, the shock wave is separated into a first shock wave and a second shock wave spaced in time from the first shock wave as the initial impact shock wave is reflected at an interface between the shock receiving assembly and the energy dissipating assembly. The impact absorbing structure may be configured such that the second shock wave is a reflection of the initial impact shock wave, the second shock wave being reflected back into and through the impact receiving assembly to an interface between the impact receiving assembly and a projectile that has impacted the impact receiving assembly. The second shock wave may be reflected at an interface between the shock receiving assembly and a projectile that has struck the shock receiving assembly, after such reflection the second shock wave may travel in the same direction as the first shock wave but after the first shock wave such that the second shock wave enters the energy dissipating assembly at a later time than the first shock wave, thereby temporally spacing the second shock wave from the first shock wave.

Preferably, the chemical element or compound is calcite. By proper design of the shock propagation sequence, calcite can be driven from phase I calcite to phase II calcite by the first shock wave, then from phase II calcite to phase III calcite by the second shock wave, and then allowed to release to ambient pressure. During this process, the amount of calcite dissipated is estimated to be 4 megajoules per cubic meter. In a ratio such as by

The dissipated energy is an order of magnitude lower. However,

the tenacity of the fiber is due to its large plastic strain failure (up to 10%). In contrast, the strain experienced by calcite is less than 2%. Plus the relatively high speed of sound of calcite(7 km per second, compared to 2 km per second for polymer fibers), calcite is able to dissipate energy much faster than existing fiber-based impact absorbing structures in much larger volumes. The energy absorption density and acoustic velocity of calcite mean that calcite can dissipate energy at a rate of 100 kilojoules per square meter per microsecond. Since the hysteresis mechanism is the fundamental thermodynamic process that propagates at impact velocities, it works for projectiles traveling up to 7km/s in speed.

According to a second aspect of the invention there is also provided an armor or armor shell comprising the impact absorbing structure according to the first aspect of the invention.

The armor may be used in a building or vehicle such as a tank, truck, airplane, helicopter, airship, ship, or submarine. Armor may be used to protect windows of buildings or vehicles such that the windows are blast, debris, and/or ballistic resistant. In particular, the building may be part of an airport, a train or bus station, a stadium, an auditorium, a diplomatic and/or government building, an energy generation site or an industrial park. The armor may be personal protection for both military and civilian applications. The armor casing may be a casing for energetic/explosive materials (e.g., explosives or rocket propellants) and sensitive ammunition.

Of course, it should be understood that features described in relation to one aspect of the invention may be incorporated into other aspects of the invention.

Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which:

figure 1 schematically illustrates the hysteresis cycle exhibited during quasi-static hydrostatic loading and unloading of calcite;

figure 2 schematically illustrates a hysteresis cycle during the loading and unloading of calcite under single impact compression; and

figure 3a is a schematic view of a projectile in proximity to an impact absorbing structure according to a first embodiment of the present invention;

FIG. 3b is a schematic view of the impact-absorbing structure of the impact-receiving assembly just after impact with a projectile;

FIG. 3c corresponds to FIG. 3b, but at a later time, where the first shockwave S11 has entered the energy dissipation assembly;

FIG. 3d corresponds to FIG. 3c, but at a later time, where the shock wave S11 has penetrated further into the energy dissipating assembly and is approached by shock wave S12;

FIG. 3e corresponds to FIG. 3d, but at a later time, where the shock wave S122 has penetrated into the energy dissipating assembly and follows the shock wave S11, thus allowing the hysteresis cycle to complete;

Figure 4 shows a schematic position-time diagram of the propagation of a shock wave through a shock absorbing structure after impact with a copper projectile;

figure 5 shows a schematic position-time diagram of a shock wave propagating through a shock-absorbing structure according to the second or third embodiment of the invention after impact with a copper projectile;

figure 6 shows a schematic position-time diagram of a shock wave propagating through a shock-absorbing structure according to a fourth embodiment of the invention after impact with a copper projectile;

FIG. 7 shows an armor according to a fourth embodiment of the invention;

FIG. 8 shows an armor housing according to a fifth embodiment of the invention;

FIG. 9 shows a schematic cross-sectional view of a test piece of the impact absorbing structure; and

figure 10 shows different schematic position-time graphs of the propagation of a shock wave through a shock absorbing structure after impact with a copper projectile.

Detailed Description

In fig. 3a an impact absorbing structure 1 according to a first embodiment of the invention is schematically shown. The impact-absorbing structure 1 is shown in the form of a stack comprising a polycarbonate layer 3 adjacent to a calcite layer 5. Wherein the polycarbonate layer 3 serves as an impact receiving member and the calcite layer 5 serves as an energy dissipating member. As will be discussed in more detail below, the stack is designed such that upon impact of the impact receiving assembly with the copper projectile 7 travelling in the direction of the arrow shown in fig. 3a, an impact propagation sequence is created which ensures that the phase transition from phase I to phase II and from phase II to phase III is initiated sequentially before the calcite is unloaded, thereby ensuring that a hysteresis cycle corresponding to fig. 1 occurs.

An impact propagation sequence occurring upon impact of the impact absorbing structure 1 with the projectile 7 will now be described with reference to fig. 3b to 3 e. Fig. 3b shows the projectile 7 upon impact with the surface of the polycarbonate layer 3, wherein the shock wave S1 propagates into the polycarbonate layer 3 and the shock wave S2 propagates into the projectile 7 in a direction opposite to the direction of travel of the shock wave S1. The shock wave S1 then reaches the interface between the polycarbonate layer 3 and the calcite layer 5 and is divided into shock waves S11 and S12, as shown in fig. 3 c. The shock wave S11 propagates to phase I calcite layer 5 and initiates a phase I to phase II phase transition as it passes through phase I calcite layer 5, leaving phase II calcite 52 behind. Shock wave S12 reflects at the polycarbonate/calcite interface and returns into polycarbonate layer 3 in the opposite direction to shock wave S11.

Fig. 3d shows at a later time in the shock propagation sequence, where the shock wave S12 has been reflected at the interface between the projectile 7 and the polycarbonate and is currently travelling in the same direction as the shock wave S11. Upon reaching the polycarbonate/calcite interface, the shock wave S12 is divided into two components S121 and S122, as shown in fig. 3 e. The shock wave S121 is reflected back into the polycarbonate layer 3. However, shock wave S122 propagates into calcite layer 5, which calcite layer 5 is now phase II calcite 52, and follows shock wave S11. Shock wave S122, spaced from shock wave S11, initiates a phase II to phase III phase transition as it passes through the calcite II layer, leaving phase III calcite 53 behind. Note that the shock wave S122 travels faster than the shock wave S11, so if the calcite layer 5 is thick enough, the shock wave S122 will eventually catch up and intercept the shock wave S11. During the subsequent wave reflection and attenuation, the phase III calcite 53 will unload, thereby initiating the phase III transformation into phase I, and thus the calcite within the shock absorbing structure 1 will undergo a hysteresis cycle corresponding to fig. 1.

In order for this particular type of impact propagation sequence to occur, the impact resistance of the impact receiving component (in this case polycarbonate) must be lower than the impact resistance of the energy dissipating component (in this case calcite) and the projectile 7 (in this case made of copper). To maximize the energy absorbed by the hysteresis cycle, shock wave S11 must convert phase I calcite to phase II calcite, which is at the highest possible pressure in the calcite II stability region.

Furthermore, the thickness of the calcite layer 5 can be optimized. Figure 4 shows a schematic position-time diagram of the propagation of a shock wave through polycarbonate and calcite after impact with the copper projectile 7, the y-axis representing time in milliseconds and the x-axis representing position in millimeters. Along the x-axis, the region labeled "Cu" represents the copper projectile 7, the region labeled "Pc" represents the polycarbonate impact receiving layer 3, the region labeled "I" represents phase I calcite, the region labeled "II" represents phase II calcite, and the region labeled "III" represents phase III calcite. In fig. 4, the copper impactor hits the energy absorbing structure 1, impacting the polycarbonate layer 3 forming a wave S1, which wave S1 propagates as wave S11 into the calcite layer 5 and initiates the transformation of calcite phase I into phase II. The reflected shock wave S12 in the polycarbonate is transferred back into the calcite after approximately 0.4 microseconds, while the shock wave S122 initiates the phase II to III conversion of the calcite. As described above, the wave S122 is faster than the wave S11, and thus catches up with the wave S11 ahead of it at time t of 0.9 microseconds. In this case, the optimal calcite thickness is 550 mm, which is where the S122 wave and the S11 wave of calcite intersect, labeled T in figure 4. Once shock wave S122 exceeds shock wave S11, shock wave S11 will pass through phase I calcite and thus initiate a phase transition from phase I to phase III that exhibits the hysteresis cycle shown in fig. 2 and is undesirable from an energy dissipation standpoint.

In fact, there are other elastic impacts to consider, which means that the optimum thickness must be determined experimentally (for example, the initial wave at the polycarbonate/calcite boundary produces two waves in calcite: the calcite I compressional wave and the phase I to phase II phase transition wave).

The wave positions and time frames given in fig. 4 are for illustration purposes only. In practice, the position and time frame observed for calcite may vary. Figure 10 shows a more recent schematic position-time diagram of the propagation of a shock wave through a shock absorbing structure having a polycarbonate layer with a thickness of 260 microns after impact with a copper projectile. Figure 10 gives a more accurate representation of the wave positions and time frames that would be observed in calcite. The shock wave S12 reflected in the polycarbonate will be transferred back to the calcite after about 0.3 microseconds when the shock wave S122 will initiate a phase change from II to III of the calcite. As already described, the wave S122 is faster than the wave S11, and therefore catches up with the wave S11 ahead of it at time t of 0.98 microseconds. In this case, the optimal calcite thickness is 5 mm, which is the location where the calcite wave S122 intersects the S11 wave, marked T in figure 10.

The invention has been described and illustrated above with reference to embodiments in which the impact receiving assembly has a lower impact resistance than the energy dissipating assembly and the projectile. However, it will be appreciated by persons skilled in the art that the present invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

According to a second embodiment of the invention, the desired hysteresis cycle can be achieved by using an impact receiving component with a fast elastic wave velocity, a slower plastic wave velocity and a yield point that produces an "elastic precursor" (i.e. a purely elastic shock wave traveling in front of the main plastic deformation wave) with appropriate stress to participate in the phase change. Fig. 5 shows a schematic position-time diagram corresponding to this arrangement, wherein the arrow marked "W" indicates the elastic/plastic wave separation.

According to a third embodiment of the invention, an impact receiving assembly that generates a ramp (ramp) is used. Some materials, such as fused silica, or materials with a graded density, may produce a precursor "ramp" (i.e., a steady rise in pressure in about microseconds) rather than a real impact immediately upon impact. Using such an impact receiving assembly would have a similar effect to delivering a single optimized impact as it would allow the energy dissipating assembly to undergo the phase change for the necessary time. A schematic position-time graph corresponding to this arrangement is shown in fig. 6, where the arrow labeled "V" represents a ramp precursor.

Fig. 7 shows an armor 100 according to a fourth embodiment of the present invention. The armor 100 comprises an impact absorbing structure 1 according to a first embodiment of the invention. The armor may be used in a building or vehicle such as a tank, truck, airplane, helicopter, airship, ship, or submarine. Armor may be used to protect windows of buildings or vehicles such that the windows are blast, debris, and/or ballistic resistant. Alternatively, the armor may be used for personal protection in military and/or civilian applications.

Fig. 8 shows an armor shell 200 according to a fifth embodiment of the invention. The armor shell 200 comprises an impact absorbing structure 1 according to a first embodiment of the present invention. The armor casing may be used as a casing for high energy/explosive materials (e.g., explosives or rocket propellants) and/or sensitive ammunition.

In the foregoing description, when integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. The true scope of the invention should be determined with reference to the claims, which should be construed to cover any such equivalents. The reader will also appreciate that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Further, it should be understood that, although there may be benefits in some embodiments of the present invention, such optional integers or features may not be desirable in other embodiments and thus may not be present.

Experimental results

Impact tests were performed on various configurations of impact absorbing structures. A light air gun was used to accelerate the projectile, which was wire cut to ensure flatness and attached to the sabot using a low viscosity epoxy. Fig. 9 shows a schematic cross-sectional view of the impact absorbing structure test piece 10. In this case, the impact absorbing structure tested was in the form of a laminate comprising a layer of impact receiving members 11 and a layer of energy dissipating members 13 bonded to a thicker PMMA backing ring 15. The front surface 17 of the impact receiving member 11 is impacted by the projectile and during the impact the surface velocity of the rear surface 19 of the energy dissipation member 13 is measured using laser interferometry, the position marked L in figure 9, the surface velocity measurement being obtained using a photonic doppler velocimeter. By measuring the impact velocity of the projectile and comparing the impactor yugonot (Hugoniot) (measured by Marsh) with the calcite yugong button (measured by Ahrens and Grady), the pressure exerted within the calcite by the first impact can be determined. In these references, rain tributary buttons were measured by using symmetric impact and pressure density (impact velocity) rankine-rain tributary button jump conditions. (e.g., Grady. Marsh, S.P. (Ed.), (1980), LASL Shock Hugoniot Data (1st Ed.), Los angles: University of California Press. ahrens, T.J. & Gregson, V.G. (1964.) impact compression of crystalline rock Data for quartz, calcite, and plagioclase rocks (Shock compression of crystalline rocks: Data for quartz, calcite, and plagioclase rocks, J.Geophys. Res.,69(22), 4839-4874). The phase transitions within the calcite layer are determined by observing the shock wave instabilities (discontinuities in the velocity of the rear surface particles), where each instability corresponds to one phase transition and the size of the jump corresponds to that phase. The behavior of these discontinuities in velocity caused by phase changes is described in detail in Duvall (Duvall, G., & Graham, R.A. (1977.) phase transitions under shock wave loading, review of modern physics, 49(3), 523-579. http:// doi.org/10.l 103/RevModPhys.49.523).

To ensure that the conditions are as close to one-dimensional as possible, it is crucial to ensure that the projectile does not rotate during flight so that the flat surface of the projectile impacts the flat surface of the impact receiving assembly. To this end, each impact absorbing structural specimen was mounted near the muzzle and aligned with the laser to ensure that it was perpendicular (normal) to the barrel.

Six tests were performed. The test conditions are shown in table 1, which lists the projectile materials used, the impact receiving assembly (i.r.c) and the energy dissipating assembly (e.d.c) of the stack and the impact velocity of the projectile in meters per second (m/s). The test results are shown in table 2, which lists the attributes of the first impact, and, if present, the second impact. Table 2 shows the applied pressure within the calcite (in gigapascals (GPa)) and the calcite phase change caused by the impact for the first and second impacts. For the first impact and the second impact, phase I shows no phase change and phase II shows a phase change from phase I to phase II. For the first impact, phase III indicates a phase change from phase I to phase III, and for the second impact, phase III indicates a phase change from the first impact phase to phase III. Only tests 2 and 6 absorbed energy, with the first impact phase being II and the second impact phase being III.

TABLE 1

TABLE 2