المؤلفون: Huang, Jin¹ (AUTHOR), Zhang, Jian¹ (AUTHOR) zhangjian178@whut.edu.cn, Zhu, Ke¹ (AUTHOR), Zhang, Ruizhi^1,2 (AUTHOR), Luo, Guoqiang¹ (AUTHOR), Shen, Qiang¹ (AUTHOR)

المصدر: Journal of Applied Physics. 2/28/2024, Vol. 135 Issue 8, p1-12. 12p.

مصطلحات موضوعية: *STRAINS & stresses (Mechanics), *CASCADE impactors (Meteorological instruments), *INTERMETALLIC compounds, *DENSITY

مستخلص: In gas gun experiments, a graded density impactor (GDI) is used to achieve quasi-isentropic loading. However, inconsistency between the designed and experimental loading profiles, mainly caused by by-products during preparation, limits the application of GDI for a long time. In this work, a kind of W/Ti GDI with advantages of a wide density range of 4.5–19.3 g/cm3 and high structural designability was designed and synthesized. Each of mid-layers of the W/Ti GDI was composed of W and Ti without the formation of an intermetallic compound, and had good parallelism and flatness. This provides a prerequisite for good agreement between the designed and experimental loading profiles. Due to the high designability of the GDI, quasi-isentropic loading with different stress-paths was achieved by controlling the structure of the GDI. Then, independently controlling peak stress and strain rates of loading was successfully achieved by changing the flyer velocity and the type of the W/Ti GDI. The W/Ti GDI has enormous application potential in studying the dynamic response of materials under quasi-isentropic loading with stress and strain rate controlled. [ABSTRACT FROM AUTHOR]

المؤلفون: Wang, Kaiduo^1,2 (AUTHOR), Zhou, Qi¹ (AUTHOR), Liu, Yandong^1,2 (AUTHOR), Li, Mingtao^1,2 (AUTHOR) limingtao@nssc.ac.cn, Wang, Yirui^1,2 (AUTHOR)

المصدر: Acta Astronautica. Jun2024, Vol. 219, p291-299. 9p.

مصطلحات موضوعية: *ASTEROIDS, *CASCADE impactors (Meteorological instruments), *LAGRANGIAN points, *WARNINGS

مستخلص: Near Earth asteroids with diameters less than 50 m possess distinct characteristics including a large population, a high likelihood of Earth impact, and limited warning time. While small asteroid impacts may not induce global disasters, they can still result in localized hazard. This study focuses on investigating the feasibility and strategies for disrupting small-sized asteroid structures through kinetic impact under short-term warning scenarios. Initially, a dataset comprising ten asteroids ranging from 20 m to 50 m in diameter is compiled by correcting their orbital parameters to simulate potential impacts on Earth. Subsequently, a space-based interception constellation is designed and deployed at the L3, L4, and L5 points of the Cislunar space. The study further examines the trajectory design methodology for achieving rapid interception of asteroids, enabling timely response within a warning period of 7 to 14 days. Additionally, the paper discusses the feasibility of impactors in disrupting asteroids through analytical models and Adaptive Smoothed Particle Hydrodynamics (ASPH) numerical simulation method. Lastly, the defense capability of the space-based interception constellation against Earth-impacting asteroids approaching from various directions is assessed. The simulations show that C and S-type asteroids below 40 m can be effectively fragmented using an impactor with an initial mass of 2 tons within the specified 7 to 14-day warning time. Furthermore, the deployment of impactors at L3, L4, and L5 allows for comprehensive coverage of asteroids approaching from diverse directions. • Design of interception constellation for small-size asteroid defense under short warning time. • Fragmentation efficiency analysis of small size asteroids via multiple criterions. • Defense capability of the interception constellation against asteroids approaching from various directions. [ABSTRACT FROM AUTHOR]

المؤلفون: Kakati, Sasanka¹ (AUTHOR), Chakraborty, D.¹ (AUTHOR) chakra@iit.ac.in

المصدر: Mechanics of Advanced Materials & Structures. 2024, Vol. 31 Issue 6, p1199-1213. 15p.

مصطلحات موضوعية: *IMPACT response, *CASCADE impactors (Meteorological instruments), *HERTZIAN contacts, *FINITE element method, *IMPACT (Mechanics), *LAMINATED materials

مستخلص: Even though the influence of impact energy on the low velocity impact of laminated plate is well reported, the influence of relative mass of the impactor has not been addressed extensively. This work investigates the effect of impactor mass relative to that of target and other associated factors like impactor velocity and the target plate size on the impact response of a GLARE plate. A 3 D finite element analysis incorporating Newmark-β method and Hertzian contact is used considering appropriate contact stiffness to evaluate the contact force. Results show that the impactor mass significantly influences the contact force and interfacial delamination. [ABSTRACT FROM AUTHOR]

المؤلفون: Leliwa-Kopystynski, J¹ (AUTHOR), Wlodarczyk, I² (AUTHOR) astrobit@ka.onet.pl

المصدر: Monthly Notices of the Royal Astronomical Society. 3/15/2024, Vol. 528 Issue 4, p6312-6318. 7p.

مصطلحات موضوعية: *CASCADE impactors (Meteorological instruments), *FAMILIES, *ASTEROIDS, *BODY size, *SMALL solar system bodies

الشركة/الكيان: UNITED States. National Aeronautics & Space Administration

مستخلص: The minimal sizes of impactors that produced asteroid families were calculated, and their maximal sizes, i.e. the size that corresponds to head-on collisions, were estimated. We used data for 16 large families and the physical parameters of some members of these families available in NASA's JPL updated in 2022. We found that the typical minimal sizes of family-forming impactors were of the order of one-tenth the size of the parent bodies (PBs). The Themis family, for which the ratio of the radii r imp/ R PB = 0.08 and the mass loss is as large as 0.55, presents an example. The families of Juno and Euphrosyne, with the impactor to PB size ratio of an order of 0.01, are rather exceptional. The PBs of Juno and Euphrosyne families lost only 0.0014 and 0.0061 of their mass, respectively. It was found that the double structure of the Vesta family could have originated from two impacts by the bodies with radii as small as about 4 km, at least. [ABSTRACT FROM AUTHOR]

المؤلفون: Zhou, Yiheng, Tan, Ye, Zhang, Ruizhi, Li, Zhiguo, Chen, Han, Bai, Jingsong, Li, Lei, Shen, Qiang, Luo, Guoqiang

المصدر: Journal of Applied Physics; 12/14/2023, Vol. 134 Issue 22, p1-15, 15p

مصطلحات موضوعية: STRESS waves, ELASTIC wave propagation, THEORY of wave motion, CASCADE impactors (Meteorological instruments), EQUATIONS of state, LOADING & unloading

مستخلص: Quasi-isentropic loading and unloading, employing graded density impactors (GDIs) as flyers in gas gun-driven plate impact experiments, can provide novel and valuable insights into the equation of state and strength properties of the loaded material. However, the internal ballistic process may lead to spalling or debonding of the GDI due to the intricate interactions between stress waves and interfaces. In this study, the wave propagation in the GDI was analyzed using the multimaterial Lagrangian elastic-plastic model and elastic wave propagation theory. The impact of gradient direction, power-law constant p, and thickness of the first and last layers on the tensile stress was investigated. The outcomes reveal that the mechanism of generating tensile stress varies for two gradient directions. Moreover, adjusting the constant p and the layer thickness may decrease the maximum tensile stress by 74.1% (forward graded) and 95.8% (reverse graded), respectively. The outcomes of this research provide a theoretical and simulation basis for designing and fabricating GDIs to be utilized in quasi-isentropic experiments. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Applied Physics is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Aslam, Tariq D.¹ (AUTHOR) aslam@lanl.gov, McBride, Michael A.² (AUTHOR), Rai, Nirmal¹ (AUTHOR), Hooks, Daniel E.³ (AUTHOR), Stull, Jamie A.² (AUTHOR), Jensen, Brian J.⁴ (AUTHOR)

المصدر: Journal of Applied Physics. 6/14/2022, Vol. 131 Issue 22, p1-9. 9p.

مصطلحات موضوعية: *CASCADE impactors (Meteorological instruments), *MULTIPHASE flow, *TRAFFIC safety, *DENSITY, *TIME pressure, *FUNCTIONALLY gradient materials

مستخلص: Graded density impactors (GDIs) are multi-material composite impactors used in gas gun experiments to tailor the drive conditions imparted to a sample test material. Previous graded density impactors generally rely on thin, but discrete, layers of different materials. The thinner and the greater number of layers will result in smoother compression. Taken to the limit of very thin layers would be pure material 1 at one surface, such as the front surface of an impactor, smoothly transitioning at the atomic scale to pure material 2 on the back surface. Such an impactor can initially shock, then smoothly compresses a material during a dynamic experiment. This type of experiment can serve to explore a larger region of thermodynamic space than a single or even multi-shock experiments. An overview of how graded density impactors are made is reviewed and sample results are given. A strategy for modeling these kinds of impactors is presented. The length scales of constituent mixing are given from the experimental build through electrochemical-deposition. Equation of state models for pure constituents and their subsequent mixtures are presented. It is demonstrated that the time scales for pressure and temperature equilibration, for atomically mixed GDIs, are short enough to be a justifiable closure for the resulting multiphase flow. Furthermore, we present simulation results of dynamic shock followed by a ramp compression, utilizing a silver/gold graded density impactor, onto a tantalum sample. [ABSTRACT FROM AUTHOR]

المؤلفون: Fedyai, V. V.¹ (AUTHOR) shakirzyanova@bmstu.ru, Selivanov, V. V.¹ (AUTHOR), Petyukov, A. V.¹ (AUTHOR)

المصدر: Journal of Applied Mechanics & Technical Physics. Dec2023, Vol. 64 Issue 6, p1108-1118. 11p.

مصطلحات موضوعية: *CASCADE impactors (Meteorological instruments), *COMPUTER simulation, *BULLETS

مستخلص: An experimental method is developed that makes it possible to visualize the onset and spreading of damage in each layer of transparent armor. The damage development dynamics in multilayer packages consisting of four -mm layers and eight -mm layers is analyzed. The evolution of damage is obtained under the influence of a 12.7-mm bullet with a two-component core with a total mass of 59.2 g and a 7.62-mm bullet with a two-component core with a total mass of 10.9 g along the normal and at an acute angle in a range of impact velocities of 777–797 m/s. The experimental data are compared with the numerical simulation of interaction between an impactor and a multilayer transparent target. [ABSTRACT FROM AUTHOR]

المؤلفون: Specht, Paul E.¹ (AUTHOR) pespech@sandia.gov, Alexander, C. Scott¹ (AUTHOR), Reinhart, William¹ (AUTHOR)

المصدر: AIP Conference Proceedings. 2023, Vol. 2844 Issue 1, p1-5. 5p.

مصطلحات موضوعية: *CASCADE impactors (Meteorological instruments), *METALS, *MEASUREMENT

مستخلص: Two experimental platforms were developed to obtain measurements of the tensile strain-rate dependence of the spallation strength in metals. The first experimental platform utilizes a target containing five samples of varying thicknesses impacted by five unique impactors. This configuration keeps the peak compressive stress constant, while using the spreading of the rarefaction waves to varying the tensile strain-rate. The second experimental platform employs a wedge-shaped impactor to continuously vary the tensile strain-rate along a line on the sample. Hydrocode simulations are used to illustrate the change in tensile strain-rate, tensile pulse duration, and tensile pulse rise time as the configuration of each experimental platform changes. [ABSTRACT FROM AUTHOR]

المؤلفون: Schweitzer, Y.¹ (AUTHOR) yonatansc@soreq.gov.il, Gudinetsky, E.² (AUTHOR), Glam, B.¹ (AUTHOR), Sudai, M.¹ (AUTHOR), Yosef-Hai, A.² (AUTHOR), Eliezer, S.¹ (AUTHOR)

المصدر: AIP Conference Proceedings. 2023, Vol. 2844 Issue 1, p1-5. 5p.

مصطلحات موضوعية: *PHASE transitions, *CASCADE impactors (Meteorological instruments)

مستخلص: Overtake method is commonly used in impact experiments to determine and calibrate the equation of state outside the principle Hugoniot. The method is based on measuring the time of arrival of either consecutive shock waves or rarefaction waves from an impactor at targets of different thickness. In some cases, the leading shock wave that was created at the impact splits into two waves (e.g., elastic precursor or due to phase transition), so the speed of the second wave cannot be determined by the overtake method. In this work we investigate the difficulties that arise from such wave splitting, and specifically show that additional target widths do not add any new information that can be used when calculating wave velocities. We look at special cases where the speed of the second wave may nevertheless be approximated, albeit with lesser precision, and identify the main error sources. 1-dimensional simulations were carried out to support our calculations in good agreement. The present work may act as a basis for additional calculations that will expand our knowledge of equations of state in uncharted areas. [ABSTRACT FROM AUTHOR]

المؤلفون: Singh, Satyendra Pratap, Singh, Harpreet, Mahajan, Puneet

المصدر: Defence Science Journal; May2024, Vol. 74 Issue 3, p345-353, 9p

مصطلحات موضوعية: IMPACT response, TRAVEL time (Traffic engineering), ELASTICITY, CASCADE impactors (Meteorological instruments), ANALYTICAL solutions

مستخلص: When an impactor strikes a layered target, both the impactor and the target experience waves. The waves produced travel and engage in interactions with other waves as well as the interfaces in the impactor-target system. For the impact problems on a layered mediumwith periodic properties and layered elastic media of Goupillaud-type (each layer has the same wave travel time), researchers have presented an analytical solution for stress variation with position and time within the target. However, the solution for an elastic media not satisfying the above conditions is not available in the literature. The present study fills this gap and finds the behaviour of a generalized layered medium to an impact problem. The response of the material at any position inside the layered medium is found by solving the interaction between waves, interfaces, and boundaries. The mass, momentum balance and constitutive relationship are solved to get the exact analytical expressions for particle velocity and stress for each possible wave interaction happening in the impactor and the layered medium. The expressions are utilized in a computer program to study the impact behaviour of a layered media. The code tracks each wave as it travels through the system and identifies those interactions that occur in the shortest time, uses the stress and velocity expression for that interaction, and updates the state of the material. When stress produced at the impact surface is tensile in nature, the impactor and target can be separated. The work can be applied to both finite and semi-infinite impactors and targets, and the layered medium does not necessarily have to be a periodic layered media or a Goupillaud-type medium. [ABSTRACT FROM AUTHOR]

: Copyright of Defence Science Journal is the property of Director, DESIDOC, DRDO, Publisher of DESIDOC Bulletin of Information Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)