• ISSN 1001-1455  CN 51-1148/O3
• EI Compendex、CA收录
• 力学类中文核心期刊
• 中国科技核心期刊、CSCD统计源期刊
Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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$v.latestStateEn doi: 10.11883/bzycj-2019-0469 Read OL PDF (0) Abstract: In order to study the impact of the metal jet formed by a shaped charge on a solid-rocket motor, the shaped-charge blasting experiment was carried out, and the jet impingement experiment was deformed for the shaped jet impacting a certain-size engine without protection. A high-speed camera was used to record the response processes of the explosions. Air overpressurees and fragment speeds were measured at different distances and directions. The jet forming process and the jet -impacting-motor process were numerically simulated using the Autodyn. In the process of simulating fluid-structure coupling, the problem of fluid-solid coupling grid leakage was avoided by adjusting the grid thickness. The experimental results show that after the rocket engine was impacted by the jet, a violent explosion occurred, and the propellant completely reacted. The steel rocket engine fixing equipment after the explosion was almost destroyed completely. The speed of fragments could reach above 4700 m/s. The air overpressure at the 1 m away from the engine explosion center could reach 19.78 MPa. Through the pictures collected by the high-speed camera, it could be judged that the explosion center temperature is above 3000 ℃. According to the peak of the air overpressure and the law of air similarity, the energy produced by this type of propellant explosion is judged to be slightly higher than those of explosives such as 8701 and TNT. The simulation results show that when the jet impinges on the engine shell at a head velocity of 7000 m/s, the tip of the jet head is severely ablated, and the speed of the jet head decreases to about 5600 m/s; the propellant reacts violently after being penetrated 1-2 mm by the jet; the shock wave propagates along the propellant in a spherical shape, and the propellant on the other side undergoes shock initiation twice with a retonation; there lie three overpressure peaks at the Gauss point located in the center of the propellant. The first peak is generated by the shock wave from the left side; the second peak is due to the shock wave hitting the solid wall of the propellant and a certain wave surface reflection is generated, causing a pressure rise; the third weak is caused by a new shock wave generated by the retonation. The simulated average air overpressure is 18.75 MPa at the Gauss points set at 1 m from the center of the engine, which is in good agreement with the experimental results.$v.latestStateEn  doi: 10.11883/bzycj-2019-0427
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During blasting in deep rock masses, the rock fragmentation is contributed to the combined effects of blast loading and high in-situ stress. An analysis model based on simplifying assumptions was developed for double-hole blasting in highly-stressed rock masses, and the crack propagation and dynamic stress evolution surrounding the blastholes were studied by using the coupled SPH-FEM method. The results show that the blast-induced rock cracking is mainly caused by the dynamic circumferential tensile stress generated from blast loading. However, in the rock masses subjected to in-situ stress, the dynamic circumferential tensile stress is reduced in magnitude and duration due to the compressive effect of the in-situ stress. Therefore, the in-situ stress plays a role in inhibiting the rock fragmentation caused by blasting. For the case of multi-hole blasting in a hydrostatic in-situ stress field, the crack propagation perpendicular to the connecting line between the adjacent holes is more easily inhibited by the in-situ stress. The length of blast-induced crack growth decreases with an increase in the in-situ stress level. With regard to a non-hydrostatic in-situ stress field, the crack propagation along the direction of the minimum principal in-situ stress is most severely suppressed, and thus the cracks grow preferentially along the maximum principal stress direction. Therefore, arranging the blastholes along the maximum principal stress direction and shortening the spacing between the blastholes will facilitate the crack connections and the formation of excavation surfaces.
$v.latestStateEn doi: 10.11883/bzycj-2019-0423 Read OL PDF (10) Abstract: With the characteristics of light weight and high specific energy absorption, multi-cell thin-wall structures have been widely used in automobile, ship, aerospace and other fields. Previous studies have shown that the crashworthiness of a structure is closely related to its topology and cell number. In order to study the influence of the structural shape and topology optimization on energy absorption, based on regular polygon structures, two kinds of new multi-cell thin-wall structures were designed by embedding polygons in the basic structures given and circumscribing circular tubes to them, respectively. Meanwhile, quasi-static compression and drop-hammer impact tests were carried out on the two kinds of multi-cell thin-wall structures. The deformation modes of the structures were captured by high-speed cameras, and their energy absorption characteristics were studied quantitatively. The experimental results show that local instability occurred in the structures obtained by second-order embedding quadrangles into the basic regular triangle tubes in the later stage of the quasi-static loading test; the other structures were compressed vertically in the quasi-static compression and drop hammer impact tests, and their corresponding deformation modes and energy absorption capacities were excellent. By comparing the experimental results of two kinds of structures, following conclusions are drawn: the energy absorption of the polygon-embedded structures is obviously higher than that of the structures by externally circumscribing a circular tube under quasi-static loading and drop hammer impact tests; the energy absorption performance of the quadrangle-embedded structure is obviously better than that of the triangle-embedded structure with the same mass.$v.latestStateEn  doi: 10.11883/bzycj-2019-0418
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Dynamic response of sandwich tubes subjected to blast loading is investigated numerically. The 3D-Voronoi technology is introduced to establish three-dimensional mesoscopic finite element model of aluminum foam. The influences of the thickness of inner and outer tubes, the relative density of foam core and the core gradient on the blast resistance and energy absorption of the sandwich tubes are analyzed and compared with the double circular tubes with air core. The results show that the relative density of foam materials can be controlled by changing the size and wall thickness of cell, and the calculation results of the sandwich tube constructed by two methods are consistent. The increase of the inner tube thickness can effectively reduce the plastic deformation of outer tube and weaken the energy absorption of foam core. Foam filling is of benefit to reduce the plastic deformation of inner tube and the blast resistance of positive gradient is better than that of negative gradient and uniform core.
$v.latestStateEn doi: 10.11883/bzycj-2019-0414 Read OL PDF (0) Abstract: An arrow-shaped honeycomb pedestal with negative Poisson’s ratio was designed. An analytical formula was derived for the mechanical properties of the cell structures, and the impact resistance of the thickness-graded arrow-shaped honeycomb materials with negative Poisson's ratio was numerically studied by the explicit dynamic finite element method. Based on the concept of functionally-graded materials, honeycomb layers with pathwise thickness gradient, inverse thickness gradient and uniform thickness were designed, by taking the thickness of the cell wall as the independent variable, the relevant model was established. The influence of thickness gradients on the impact resistance of the pedestal was discussed concretely under the premise of constant pedestal mass. The results show that, under the same gradient setting, the change of cell angle will cause the change of equivalent elastic modulus of the honeycomb structure, thus changing the impact resistance of the pedestal. When the honeycomb layer with a thinner cell wall is placed at the impact end, the stress level of the pedestal is significantly reduced. By placing a honeycomb layer with a thicker cell wall on the impact end, the output impact environment of the pedestal panel can be effectively controlled.$v.latestStateEn  doi: 10.11883/bzycj-2019-0401
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To explore the interaction between dynamic and static cracks in brittle materials under impact load, polymethyl methacrylate (PMMA) was chosen as the experiment material, considering that the PMMA has good optical properties and its fracture behavior is similar to rock under dynamic load. The size of the specimens was 220 mm×50 mm×5 mm with a prefabricated crack of 5 mm in length and a static crack of 10 mm in length. The prefabricated crack was located at the center of the bottom edge of the specimen, and the center of the static crack was located at the horizontal axis of the specimen. Three-point bending experiments of different defects in PMMA had been explored by setting the static crack offset distance as the single variable with the digital laser dynamic caustic test system and the fractal law of dynamic crack at different bias distances was studied by combining with the geometric fractal theory. Researches show that when the offset distance is at a critical condition between prefabricated crack and static crack (6 mm in this experiment), the fractal dimension corresponding to the crack track is the largest, the regularity degree of the crack track is the lowest and the failure mode of the crack is the most complicated. When the offset distance is between 0 to 6 mm, crack Ⅰ propagates vertically and intersects with a distant static crack, then produces a secondary crack which penetrates the specimen after a period of stagnation, the linear function relationship between the offset distance and the vertical distance of the intersection point is then obtained. The existence of the offset distance does not affect the crack time and the stress intensity factor of crack Ⅰ, but it can significantly reduce the dynamic stress intensity factor of crack Ⅱ, the length of stagnation decreases with the increase of offset distance. When the offset distance is larger than the critical offset distance, the dynamic crack no longer intersects with the static crack, but extends to the upper edge of the specimen in an arch shape until it penetrates the specimen, and there is also a significant hysteresis in the cracking time and the position of the crack.
$v.latestStateEn doi: 10.11883/bzycj-2019-0377 Read OL PDF (0) Abstract: Zr-based Bulk metallic glass is a type of glass alloy with many excellent properties, such as high strength and high hardness. With the increasing application of Zr-based bulk metallic glasses in military field, it is urgent to construct mechanical model of the material, including equation of state and constitutive relation. Johnson-Holmquist constitutive model (JH-2 model) is the most widely used constitutive model to describe the response of brittle materials with high pressures, large strains, and high strain rates condition. The parameters of JH-2 model for Zr62.5Nb3Cu14.5Ni14Al6 bulk metallic glass were determined by experimental and theoretical methods, as well as “back out” approaches from simulation data. The hydrostatic pressure-volume response was developed by theoretical derivation from plate impact experimental results. Axial compression test results were used to propose the relationship between intact strength and strain, strain rate of the material. The relationship between damage parameters and fracture strength of material was determined by plate impact experiments. The plate impact data were used to “back out” the fracture strength parameters as well. Numerical simulation results including plate impact and fragment penetration were provided to validate the accuracy and applicability of the developed model. The results show that the particle velocity curve of the freedom surface agrees well with the numerical simulation. The penetration depth and cavity radius of the tests are in good agreement with the numerical simulation results, and the developed mode describes the dynamic properties of the material accurately.$v.latestStateEn  doi: 10.11883/bzycj-2019-0355
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By chosing PolyMaxTM PLA as the sample material, thin-walled tube structures with arc-shaped origami patterns were prepared by a 3D printing technology. Based on quasi-static axial compression experiments, their axial quasi-static crushing and impact compression deformation modes and energy absorption were simulated by using the ABAQUS software to investigate the influences of the prefolding angle and the number of in-plane arrays on the crushing mode and energy absorption of the structures. The results by the finite element calculation are in agreement with the experimental ones. The deformation of the tubes can be divided into four stages including initial crushing stage, prefolding-angle plastic rotation stage, web plastic buckling stage, and complete crushing and densification stage. The arc-shaped corrugations demonstrate some obvious advantages at reducing the initial peak force and the fluctuation range of the impact force. The square tube was compared with the arc-shaped origami patterns with the same height and approximately the same mass. For the single-cell models, the specific energy absorption of the model with only 70° crease inclination is higher than that of the square tube under the quasi-static crushing. For the multiple-array tube structures, the specific energy absorption of the single-cell square tube is higher than those of the arc-shaped tubes. When considering the crush force efficiency and specific total efficiency, the arc-shaped tubes have an advantage over the square tubes, the model with a crease inclination of 50° is the best. Under the impact crushing loading condition, the specific energy absorptions of the multiple-array tubes are higher than those of the arc-shaped tubes. The crush force efficiency and specific total efficiency of the arc-shaped tubes are higher than those of the square tubes under the impact velocity of 10 mm/ms, the model with a crease inclination of 50° is the highest. The crush force efficiency and specific total efficiency of the model with only 50° crease inclination are higher than those of the square tube under the impact velocity of 20 mm/ms.
$v.latestStateEn doi: 10.11883/bzycj-2019-0339 Read OL PDF (4) Abstract: In order to improve the anti-explosion ability of steel cylinders subjected to internal blast loading, the effect of aluminum foam lining on the deformation of the steel cylinders was explored. First of all, contrast experiments displayed that under the experimental conditions in this paper, the steel cylinders deformed more greatly due to foam aluminum lining, and were seriously damaged. Then the finite element models were established to study the change mechanism and law of the deformation of the steel cylinders with the equivalent of explosion and the thickness of aluminum foam lining. The results show that the aluminum foam lining with enough thickness will reduce the deformation of the steel cylinders, however, if the thickness of the aluminum foam lining is insufficient, there may be an opposite effect. For the aluminum-foam lined steel cylinder with a fixed size, the effect of aluminum foam lining on the plastic deformation of the steel cylinder mainly includes three modes as the explosive equivalent increases. In mode 1, aluminum foam can absorb explosive loading through plastic deformation, thus reducing the deformation of the steel cylinder. In mode 2, the steel cylinder endures higher load and suffers larger plastic deformation due to adding the foam aluminum lining. For mode 3, the effect of the aluminum foam on the explosive loading can be ignored, and the aluminum foam decreases the plastic deformation of the steel cylinder by increasing the total mass of the structure.$v.latestStateEn  doi: 10.11883/bzycj-2019-0255
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In order to solve the safety problem in the construction of slope and underpass adjacent tunnel by cooperative blasting, based on the expansion project of a domestic petroleum reserve base, the formula of peak vibration velocity considering elevation effect was established, and the vibration energy attenuation mechanism of tunnel blasting along the slope surface was systematically studied by using method combining dimension derivation, field test and signal analysis. The results show that the peak value of particle velocity at the edge of the same step is larger than that at the foot of the inner slope, and there is an elevation amplification effect of vibration velocity on the local slope surface. The blasting vibration formula with relative slope H/D has high accuracy in predicting the particle vibration velocity on the slope, and can reflect the influence of slope angle on the elevation amplification effect of vibration velocity. The vibration velocity and energy decay faster in the near region and slower in the far region with the increase of propagation distance. The energy of tunnel blasting vibration is concentrated in several Sub-vibration frequency bands in the range of 0-300 Hz, and the high frequency energy decays faster along slope surface. The median of dominant frequency band decays exponentially, and the energy concentrates in the low frequency band eventually.
\$v.latestStateEn  doi: 10.11883/bzycj-2019-0254
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In order to accurately and reliably test the dynamic shear characteristics of laser metal deposition GH4169 on a traditional split Hopkinson pressure bar, this study compared the three different dynamic shear sample forms and dimensions to the shear zone stress based on numerical simulation. The influence of the distribution shows that the shear stress of the shear zone of the double shear specimen after optimization is dominant, and the dynamic shear test of approximate pure shear can be realized. Using this specimen form, the shear stress-strain curves of LMD GH4169 specimens with different orientations (scanning direction, deposition direction) at different strain rates were systematically tested, and the specimens were analyzed by SEM. The results show that: (1) The specimen used in this paper has high shear purity and uniform thickness distribution along the shear zone width, which can better obtain the dynamic shear properties of the material; (2) The shear stress-shear strain curves obtained from the experiment were analyzed. It is found that the material shows unobvious anisotropy in the scanning path direction and deposition direction. With the increase of strain rate, it has obvious strain rate strengthening effect. The uniaxial compression and dynamic shear stress-strain curves were simultaneously converted into equivalent stress-strain curves. The comparison confirms that the specimen form in this manuscript can exactly reflect the shear properties of the material; (3) Through the microscopic analysis of the shear deformation of LMD GH4169, the size and depth of the fracture dimple decrease as the strain rate increases, and the toughness decreases. The shear failure is easy under a smaller deformation. Initial microscopic defects are likely to cause dynamic shear failure of the material.
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2020, 40(6).
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2020, 40(6): 1-2.
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2020, 40(6): 061101.   doi: 10.11883/bzycj-2019-0443
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Based on cavity expansion theories, the very essences of static target resistance, i.e. Rt of plastic and brittle materials are discussed by comparing the difference of dynamic behaviors in near region of penetration, and some suggestions about applications of brittle materials for penetration are given. The summary of discussion is shown as follows. Firstly, Rt is the mean and time-averaged stress on the cross section of the projectile, which is the resistance of target materials in solid state against local cavity expanding. The specific value of Rt varies withphysical and mechanical properties of materials, penetration models, impact velocity and other factors, and thus is not an intrinsic property of material. Secondly, for the non-deformable projectile penetrating plastic materials, static cavity expansion theory is proper to predict Rt. For semi-hydrodynamic penetration cases, the results of static cavity expansion theory should be modified. Thirdly, Rt of brittle materials mainly depends on fractured materials, while it is weakly related to intact materials and not completely positively related to uniaxial compressive strength of intact materials. If penetration velocity is relatively low, the strengthening effect of Rt of brittle materials by penetration velocity increasing should be considered in terms of internal-friction. If penetration velocity is high enough, the intrinsic and constant resistance of brittle materials is realized, which is named as dynamic hardness. Fourthly, the key measures to increase Rt of brittle materials are to reduce the amplitude of hoop tensile stress following the peak compressive stress, to lower the crack velocity of materials and to restrain the fragmentation degree of materials. These can be solved by increasing external confining pressure and intensifying the tensile strength and fracture toughness of materials. Furthermore, it is suggested that the dynamic properties of fractured materials should be emphasized to increase the precision of numerical calculations of brittle materials under penetration.
2020, 40(6): 062101.   doi: 10.11883/bzycj-2019-0402
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Ignition delay of ethylene (C2H4) are measured under different temperatures in a rectangle shock tube to recognize the effects from diluent gases (nitrogen or argon) and criteria which is identified by pressure, bulk and radical chemiluminescences of OH and CH at specified wavelengths. Pressures were recorded by piezoelectric sensors (PCBs), and bulk chemiluminescence was detected by a photomultiplier (PMT) and an optical fiber. The chemiluminescences of OH and CH radicals were grated by spectrometer first, and then recorded by the PMT. The ignition delay is determined from the pressure and intensity histories of bulk and radical chemiluminescences at the points which share the same distances from the close end. Ignition delay database was built for mixture of C2H4/O2/N2 and C2H4/O2/Ar. Measurement and methodology are verified by the repeated experimental data under the same conditions. In the case of stoichimetric equivalence and pressure at 0.2 MPa, ignition delays were obtained and fitted with temperature as Arrhenius formula for mixtures of C2H4/O2/N2 and C2H4/O2/Ar at temperature ranging from 905 K to 1 489 K. Results show that the relative error of ignition delays is about 15%. Based on pressure, bulk and radical chemiluminescences, the relationships between the ignition delay and temperature remain the same although the ignition delay from single measurement is a bit different. Basically, the ignition delay of C2H4/O2/N2 is greater than that of C2H4/O2/Ar. The fitting relationship between ignition delay and temperature of C2H4/O2 /Ar in high temperature zone and low temperature zone is different, and the turning temperature is about 1 121 K.
2020, 40(6): 062301.   doi: 10.11883/bzycj-2019-0391
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In order to investigate the shock initiation of missile warhead (cylindrical covered charge) by multiple tungsten spherical fragment impacts under actual combat circumstance, based on the analysis of single fragment impact, the numerical simulations were carried out by using AUTODYN-3D software. The influence on the shock initiation characteristics of different number, distance separation (impact angle θ and axial spherical center distance l), time separation were analyzed, and the critical initiation velocity of covered Comp B was obtained by the up-down method. The obtained simulation results show that, the critical initiation velocity decreases with the tungsten fragments number increase and the distance separation decrease. The critical initiation velocity of cylindrical covered charge impacted by six fragments synchronously is about 50% compare to the single fragment. The cylindrical covered charge is more difficult than plane covered charge to detonate by double fragments when the impact velocity below the critical velocity of a single fragment. The critical initiation velocity decreases initially and then increases with the increase of time separation when fragments impacting asynchronously on the cylindrical covered charge. The minimum critical initiation velocity of cylindrical covered charge impacted by double fragments synchronously is about 95% comparinge with that of impacted by double fragments asynchronously. For |θ2|＜|θ1| (θ1 is the impact angle of the first fragment, θ2 is the impact angle of the second fragment), the cylindrical covered charge is easy to detonate by double fragments asynchronously. The results provide the reference for cumulative damage assessment of cylindrical covered charge by multiple fragment impacts.
2020, 40(6): 063101.   doi: 10.11883/bzycj-2019-0337
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2020, 40(6): 063102.   doi: 10.11883/bzycj-2019-0341
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This paper investigated comparatively the effect of structural parameters (tube direction, tube cross-section shape, tube length ratio) and impact parameters (impact mass, impact energy) on the cushioning energy absorption characteristics (specific energy absorption, stroke efficiency, crush force efficiency, specific total efficiency) of the polyethylene closed-foam single-filling paper corrugation tubes by axial drop impact tests. The results show that the single-filled X-direction tubes hold better dynamic cushioning energy absorption than the single-filled Y-direction tubes, but weaker static cushioning energy absorption than the single-filled Y-direction tubes. The regular quadrilateral single-filled tubes have superior dynamic cushioning energy absorption to the regular pentagonal and hexagonal single-filled tubes, e.g. the regular quadrilateral single-filled X-direction tubes can respectively increase the specific energy absorption by 114.4% and 182.3% for those with tube cross-section shape of regular pentagon and hexagon. During the drop impact process the specific energy absorption, stroke efficiency and specific total efficiency of the single-filled tubes decrease with the increase of tube length ratio, e.g. the single-filled X-direction tube with the tube length ratio of 1.4 can respectively increase the specific energy absorption by 45.8% and 117.9% for those with tube length ratio of 2.2 and 3.0, moreover the crush force efficiency increases as the tube length ratio increases. The characteristics of dynamic cushioning energy absorption increase with the increase of drop impact mass or impact energy, and the single-filled X-direction tube is greatly controlled by the mass of impact block, while the single-filled Y-direction tube is obviously affected by the velocity of drop impact.
2020, 40(6): 063201.   doi: 10.11883/bzycj-2019-0379
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Integrated with the relevant penetrating tests, the ballistic behavior of the tungsten fiber/metallic glass matrix (WF/MG) composite segmented rod is systematically investigated based on the meso-scale finite element method (FEM), and the comparative analysis on the penetrating performance is conducted between the composite segmented rod and the composite long rod. Related analysis shows that the composite long rod has the remarkable “self-sharpening” behavior as well as good penetrating performance, the “self-sharpening” in the composite segmented rod is less significant, and particularly, dispersal of the reinforced fibers is easily to occur in the structure. Correspondingly, the penetrating capability in the composite segmented rod is remarkably weakened compared with that in the long rod. In addition, the segmental number and the segmental interval have considerable effects on the ballistic behavior; however, the penetrating performance of the composite segmented rods with various structures is always lower than that of the composite long rod.
2020, 40(6): 063301.   doi: 10.11883/bzycj-2019-0252
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Based on the research ideas of metamaterials, a novel concrete with wave-absorbing features was designed by introducing local resonant aggregates into plain concrete. First, the effective mass of the designed metaconcrete was calculated by means of structural dynamics. Simplified models for the start and cutoff frequencies of the band gap in the metaconcrete were established, and the theoretical expressions for the band gap start and cutoff frequencies were proposed. The effects of the following parameters on the band gap features of the metaconcrete were analyzed by the proposed theoretical models, including the coating elastic modulus, core density, matrix density, aggregate volume ratio, and ratio of core length to soft thickness. Finally, the numerical simulations were carried out to compare the attenuation effects of shock waves in the metaconcrete to those in the plain concrete. The research results reveal that the flexible coating results in a low-frequency attenuation domain, but the width of the attenuation domain is narrow; while the high elastic modulus coating can form a wider attenuation domain, but the attenuation domain has a higher start frequency. A low frequency and wide band gap can be obtained by selecting large-density core material and small-density matrix material. A wide band gap can be achieved by increasing the proportion of aggregate volume and the ratio of core length to soft thickness. Compared with the plain concrete, the metaconcrete has a better attenuation effect on shock wave.
2020, 40(6): 064201.   doi: 10.11883/bzycj-2019-0340
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The strain growth, caused by vibration superposition, has been anatomized by the membrane strain and the bending strain in existing studies, and the bending wave and deformation spatial periodic distribution of a spherical shell under explosive loading have been found. By referring to the theoretical method for Timoshenko beam bending, based on a plane-section assumption and a small-deformation limit, the relation between the velocity and the wavelength of bending wave was deduced, and the velocities of the shortest bending wave and the bending wave with a frequency similar to that of the membrane vibration were calculated. By combining the relation between the deformation spatial distribution period and the bending wave velocity presented in existing studies, the deformation spatial distribution period was calculated. The main conclusions are as follows: (1) The theoretical results are in good agreement with the numerical results, in which the difference between the numerical and theoretical results of bending wave velocity is within 15%, and the difference between the numerical and theoretical results of the deformation spatial distribution period is within 12%. (2) The shorter the wavelength, the higher the wave velocity, when the wavelength is infinite short, the bending wave velocity tends to the limit value, about 0.574 times the speed of sound. The theoretical method presented in this paper provides a certain theoretical support for anatomizing strain growth.
2020, 40(6): 064202.   doi: 10.11883/bzycj-2019-0408
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In order to study the gasoline/air mixture explosion characteristics in semi-confined spaces with branched structures, a large eddy simulation model based on WALE turbulence model and the Zimont premixed flame model was established. The explosion characteristics of semi-confined space with bilateral branches ware studied through the simulation. The applicability of the established model for the calculation of gasoline/air mixture explosion in semi-confined spaces with bilateral branches is verified by comparing of flame shape, flame propagation velocity and dynamic overpressure. The flow field, flame behavior and overpressure variation during the explosion process were analyzed through the numerical simulation results and the reasons for the formation of “splash-like” flame were pointed out, and the following results were obtained. (1) Before the flame propagates into the branch pipes, two symmetric vortex structure with opposite rotation directions are generated at the junctions of the main pipe and two branch pipes, and develop toward the inside of the branch pipes as the flame propagates continuously. (2) When the flame propagates into branch pipes, the flow field established in the early stage determines the shape of the flame. The flame front forms a “splash-like” flame under the action of the vortex structure. After that, the flame and the flow field interact with each other turning to the turbulent flow and distorted flame front. (3) The growing process of the overpressure can be divided into four stages, which are influenced by the flame front area and the branch pipe pressure unload, indicating that the explosion flow field, flame behavior and dynamic overpressure have significant coupling effects.
2020, 40(6): 065201.   doi: 10.11883/bzycj-2019-0396
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In order to investigate the influence of different explosives type on the blasting effects, three kinds of explosives with the same quality were used to carry out blasting test on iron ore samples. The fractal dimension of surface crack and fragment size distribution of specimens were comparatively studied, and then the damage degree and blasting effects of specimens were quantitatively compared and evaluated. At the same time, the differences of blasting effects are analyzed theoretically from the angle of explosion stress wave superposition, energy release and energy transfer. The results are as follows. (1) Both loose charge and mixed charge will cause the uniformity of the explosion stress field distribution to deteriorate. (2) The greater the explosion heat, the greater the energy released after explosion; the higher the wave impedance matching, the higher the energy transfer efficiency after explosive explosion. (3) In the selection of explosives in blasting engineering, three parameters of explosive including density, explosion heat and detonation velocity should be considered; Explosives with a high degree of wave impedance matching and appropriate explosion heat should be selected so that the bulk and small pieces generated after blasting are less.
2020, 40(6): 065202.   doi: 10.11883/bzycj-2019-0333
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Studies on the attenuating characteristic of blasting seismic waves in propagating process are important in prediction and control of blasting vibration effects by engineering blasting. Field blasting tests of single-hole were conducted to study the quality factor of rock mass. The wave propagation velocities and the pulse rise times can be obtained by using the first arrival of P wave and S wave. Finally, based on the rise time method, the P wave quality factor of rock mass can be calculated. By analyzing the measured blasting vibration signals in Fengning hydropower station and Zhoushan large petrochemical industry, the average P wave quality factors in the above two regions are found to be 19.02 and 14.07, respectively. The experimental results show that the values derived by measuring blasting vibrations are far less than the values predicted by the empirical formulas and measured by the original rock mass. This results indicate that the soft covering layer has great influence on the seismic waves propagation induced by blasting.
2020, 40(6): 065401.   doi: 10.11883/bzycj-2019-0412
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Hydrogen is recognized as one of the most promising energies in the 21st century due to the nature of no pollution and high efficiency, unfortunately, it is likely to suffer from explosion in the process of usage. As one of the important ways of disaster, venting can effectively improve the safety and reliability of the structure under hydrogen explosion. In order to study the dynamical characteristics of the structure under vented hydrogen explosion, experimental and numerical studies were conducted in this paper. On the one hand, a number of scenarios were carried out for vented hydrogen explosion in a large-scale ISO container of 12 m×2.5 m×2.5 m to investigate the effects of hydrogen volume fraction, the position of ignition as well as the arrangement of obstacles on the structural dynamics. The characteristics of internal overpressure load and the evolution mechanism of dynamic response were analyzed. Results indicate that the structural displacements are dominated by the first overpressure peak. The trend of displacement agrees well with that of the overpressure, and there is a linear relationship between their peaks. The acceleration is dominated by high-frequency oscillations of the overpressure caused by unstable combustion. Furthermore, the peak of the displacement is significantly affected by hydrogen volume fraction and increases with the increase of hydrogen volume fraction. The peak acceleration is also affected by the ignition position, and the peak acceleration of central ignition is larger than that of back ignition. Additionally, the effects of the number of obstacles on structural dynamic response are not monotonic. On the other hand, a baseline finite element model of the structure is established based on the ambient vibration testing. The numerical simulation results agree well with those of the experimental results. Therefore, the model can be used to predict structural dynamic responses under vented hydrogen explosion.
2010, 30(1): 1-6.   doi: 10.11883/1001-1455(2010)01-0001-06
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2012, 32(4): 432-438.   doi: 10.11883/1001-1455(2012)04-0432-07
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2011, 31(1): 81-87.   doi: 10.11883/1001-1455(2011)01-0081-07
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2014, 34(6): 641-657.   doi: 10.11883/1001-1455(2014)06-0641-17
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2011, 31(6): 579-584.   doi: 10.11883/1001-1455(2011)06-0579-06
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2010, 30(2): 164-168.   doi: 10.11883/1001-1455(2010)02-0164-05
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2010, 30(5): 456-462.   doi: 10.11883/1001-1455(2010)05-0456-07
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2012, 32(2): 185-189.   doi: 10.11883/1001-1455(2012)02-0185-05
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2012, 32(2): 157-163.   doi: 10.11883/1001-1455(2012)02-0157-07
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2015, 35(1): 116-123.   doi: 10.11883/1001-1455(2015)01-0116-08
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2010, 30(3): 329-332.   doi: 10.11883/1001-1455(2010)03-0329-04
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2010, 30(2): 125-130.   doi: 10.11883/1001-1455(2010)02-0125-06
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2010, 30(2): 131-137.   doi: 10.11883/1001-1455(2010)02-0131-07
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2010, 30(3): 283-287.   doi: 10.11883/1001-1455(2010)03-0283-05
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2010, 30(3): 295-300.   doi: 10.11883/1001-1455(2010)03-0295-06
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2010, 30(3): 276-282.   doi: 10.11883/1001-1455(2010)03-0276-07
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2008, 28(3): 276-282.   doi: 10.11883/1001-1455(2008)03-0276-07
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2010, 30(2): 119-124.   doi: 10.11883/1001-1455(2010)02-0119-06
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2010, 30(3): 308-313.   doi: 10.11883/1001-1455(2010)03-0308-06
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2016, 36(4): 457-464.   doi: 10.11883/1001-1455(2016)04-0457-08
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2010, 30(2): 113-118.   doi: 10.11883/1001-1455(2010)02-0113-06
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2014, 34(6): 641-657.   doi: 10.11883/1001-1455(2014)06-0641-17
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2010, 30(2): 191-196.   doi: 10.11883/1001-1455(2010)02-0191-06
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2017, 37(2): 180-185.   doi: 10.11883/1001-1455(2017)02-0180-06
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2016, 36(2): 170-176.   doi: 10.11883/1001-1455(2016)02-0170-07
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2015, 35(2): 222-228.   doi: 10.11883/1001-1455(2015)02-0222-07
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2015, 35(3): 320-325.   doi: 10.11883/1001-1455-(2015)03-0320-06
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2014, 34(2): 235-240.   doi: 10.11883/1001-1455(2014)02-0235-06
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2015, 35(2): 177-183.   doi: 10.11883/1001-1455(2015)02-0177-07
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2017, 37(2): 169-179.   doi: 10.11883/1001-1455(2017)02-0169-11
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2016, 36(4): 541-547.   doi: 10.11883/1001-1455(2016)04-0541-07
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2016, 36(2): 145-152.   doi: 10.11883/1001-1455(2016)02-0145-08
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2015, 35(4): 603-608.   doi: 10.11883/1001-1455(2015)04-0603-06
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2014, 34(1): 86-92.
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2016, 36(5): 670-679.   doi: 10.11883/1001-1455(2016)05-0670-10
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2015, 35(3): 312-319.   doi: 10.11883/1001-1455-(2015)03-0312-08
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2015, 35(2): 157-163.   doi: 10.11883/1001-1455(2015)02-0157-07
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2016, 36(2): 259-268.   doi: 10.11883/1001-1455(2016)02-0259-10
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2015, 35(4): 449-453.   doi: 10.11883/1001-1455(2015)04-0449-05
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2015, 35(2): 164-170.   doi: 10.11883/1001-1455(2015)02-0164-07
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2014, 34(2): 229-234.   doi: 10.11883/1001-1455(2014)02-0229-06
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2015, 35(6): 807-811.   doi: 10.11883/1001-1455(2015)06-0807-05
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2015, 35(4): 507-512.   doi: 10.11883/1001-1455(2015)04-0507-06
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2014, 34(2): 174-180.   doi: 10.11883/1001-1455(2014)02-0174-07
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2015, 35(1): 51-56.   doi: 10.11883/1001-1455(2015)01-0051-06
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2016, 36(4): 548-556.   doi: 10.11883/1001-1455(2016)04-0548-09
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2015, 35(6): 881-887.   doi: 10.11883/1001-1455(2015)06-0881-07
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2013, 33(5): 456-462.   doi: 10.11883/1001-1455(2013)05-0456-07
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2014, 34(2): 188-195.   doi: 10.11883/1001-1455(2014)02-0188-07
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2016, 36(2): 253-258.   doi: 10.11883/1001-1455(2016)02-0253-06
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2015, 35(3): 380-385.   doi: 10.11883/1001-1455-(2015)03-0380-06
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2014, 34(2): 202-208.   doi: 10.11883/1001-1455(2014)02-0202-07
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2016, 36(3): 326-332.   doi: 10.11883/1001-1455(2016)03-0326-07
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2015, 35(3): 372-379.   doi: 10.11883/1001-1455-(2015)03-0372-08
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2014, 34(1): 80-86.   doi: 10.11883/1001-1455(2014)01-0080-07
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2017, 37(1): 46-52.   doi: 10.11883/1001-1455(2017)01-0046-07
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2015, 35(2): 215-221.   doi: 10.11883/1001-1455(2015)02-0215-07
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2014, 34(4): 385-391.   doi: 10.11883/1001-1455(2014)04-0385-07
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2015, 35(3): 386-392.   doi: 10.11883/1001-1455(2015)03-0386-07
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2013, 33(5): 449-455.   doi: 10.11883/1001-1455(2013)05-0449-07
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2016, 36(2): 269-278.   doi: 10.11883/1001-1455(2016)02-0269-10
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2016, 36(2): 248-252.   doi: 10.11883/1001-1455(2016)02-0248-05
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2015, 35(6): 895-900.   doi: 10.11883/1001-1455(2015)06-0895-06
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2014, 34(3): 307-314.   doi: 10.11883/1001-1455(2014)03-0307-08
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2016, 36(1): 43-49.   doi: 10.11883/1001-1455(2016)01-0043-07
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2010, 30(2): 159-163.   doi: 10.11883/1001-1455(2010)02-0159-05
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2015, 35(6): 769-776.   doi: 10.11883/1001-1455(2015)06-0769-08
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2015, 35(1): 9-15.   doi: 10.11883/1001-1455(2015)01-0009-07
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2015, 35(4): 585-590.   doi: 10.11883/1001-1455(2015)04-0585-06
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2017, 37(1): 10-14.   doi: 10.11883/1001-1455(2017)01-0001-09
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2015, 35(6): 913-918.   doi: 10.11883/1001-1455(2015)06-0913-06
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2015, 35(3): 289-295.   doi: 10.11883/1001-1455-(2015)03-0289-07
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2016, 36(2): 218-223.   doi: 10.11883/1001-1455(2016)02-0218-06
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2017, 37(1): 120-125.   doi: 10.11883/1001-1455(2017)01-0120-06
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2015, 35(6): 907-912.   doi: 10.11883/1001-1455(2015)06-0907-06
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2016, 36(4): 516-524.   doi: 10.11883/1001-1455(2016)04-0516-09
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2015, 35(2): 243-248.   doi: 10.11883/1001-1455(2015)02-0243-06
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2016, 36(5): 596-602.   doi: 10.11883/1001-1455(2016)05-0596-07
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2015, 35(3): 326-334.   doi: 10.11883/1001-1455-(2015)03-0326-09
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2017, 37(3): 396-404.   doi: 10.11883/1001-1455(2017)03-0396-09
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2015, 35(2): 236-242.   doi: 10.11883/1001-1455(2015)02-0236-07
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2015, 35(2): 197-202.   doi: 10.11883/1001-1455(2015)02-0197-06
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2016, 36(1): 135-144.   doi: 10.11883/1001-1455(2016)01-0135-10
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2016, 36(3): 416-421.   doi: 10.11883/1001-1455(2016)03-0416-06
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2015, 35(6): 839-845.   doi: 10.11883/1001-1455(2015)06-0839-07
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2015, 35(3): 343-349.   doi: 10.11883/1001-1455-(2015)03-0343-07
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2016, 36(2): 285-288.   doi: 10.11883/1001-1455(2016)02-0285-04
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2017, 37(1): 21-26.   doi: 10.11883/1001-1455(2017)01-0010-05
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Sponsored byChinese Society of Theoretical and Applied Mechanics
Institude of Fluid Physics, CAEP

Editor-in-ChiefCangli Liu