High Impact Energy Research Articles

Theoretical Study of Valence Shell Excitation by Electron Impact in CCl4

This paper reports a theoretical study of valence shell excitation in CCl4 by high-energy electron impact. Generalized oscillator strengths are calculated for the molecule at the equation-of-motion coupled-cluster singles and doubles level. To elucidate the influence of nuclear dynamics on electron excitation cross-sections, the effects of molecular vibration are included in the calculation. Based on a comparison with recent experimental data, several reassignments of spectral features are made, and it is found that excitations from the Cl 3p nonbonding orbitals to σ* antibonding orbitals, 7a1 and 8t2, play dominant roles below the excitation energy of ∼9 eV. Furthermore, the calculations reveal that distortion of the molecular structure due to the asymmetric stretching vibration significantly affects the valence excitations at small momentum transfers, where contributions from dipole transitions are dominant. It indicates that vibrational effects have a considerable influence on Cl formation in the photolysis of CCl4.

The effects of filler metal and butter layer on the microstructure and mechanical properties of API 5L X65/AISI 304L joint

The effects of different filler metals on the microstructure and mechanical properties of buttered API X65/AISI 304L stainless steel dissimilar joint have been investigated. The use of a butter layer and a suitable filler metal have major implications for the properties of dissimilar joints. In this study, API X65 high-strength low-alloy (HSLA) steel was first buttered with an austenitic Ni-based ERNiCr3 layer, followed by a post-weld heat treatment (PWHT) at 650 °C. ER308L (W308), ER309L (W309), and ERNiCr3 (WNiCr3) filler metals were then used to join the buttered API X65 side to AISI 304L stainless steel. All joints were first evaluated by radiographic testing to make sure that a flawless weldment has been attained. A scanning electron microscope (SEM), an optical microscope (OM), and energy-dispersive X-ray spectroscopy (EDS) were used to study microstructures of joints. Standard-sized and sub-sized tensile and impact tests were carried out. Microhardness profilometry was also conducted across the joint. Results showed that the finest grain structure was attained in the heat affected zone (HAZ) at the AISI 304L side and the lowest δ ferrite content was achieved in samples with the filler metal ERNiCr3 (WNiCr3). It appears that the heat input, generated by WNiCr3 filler metal, is comparatively lower than those generated in W308 and W309 samples. WNiCr3 weldment showed the highest hardness due to the formation of fine carbide particles such as NbC and TiC. Results of sub-sized impact tests showed that the highest impact energy was attained in the HAZ of the WNiCr3 sample.

Dependence of Charpy Impact Properties of Fe-30Mn-0.05C Steel on Microstructure

Fe-30Mn-0.05C steel specimens with cold-rolled, partially recrystallized, fine-grained, and coarse-grained microstructures were fabricated by means of 80% cold rolling followed by annealing at 550–1000 °C. The initial and deformed microstructures were characterized, and the Charpy impact properties were tested at room temperature (RT) and liquid nitrogen temperature (LNT). It was found that the Charpy absorbed energy increased with the annealing temperature, while the specimens showed different trends: parabolic increase at RT and exponential increase at LNT, respectively. Compared with the fully recrystallized specimens, those with a partially recrystallized microstructure exhibited lower impact energy, especially at LNT. This was because cracks tended to nucleate and propagate along the recovery microstructure where stress concentration existed. The grain size played an important role in the twinning behavior and impact properties. High Charpy impact energy (~320 J) was obtained in the coarse-grained specimen having the grain size of 42.1 μm at both RT and LNT, which was attributed to the activation of high-density deformation twinning. However, deformation twinning was inhibited in the specimen with the average grain size of 3.1 μm, resulting in limited work hardening and lower impact energy.

Metasurface-Enabled Holographic Lithography for Impact-Absorbing Nanoarchitected Sheets.

Nanoarchitected materials represent a class of structural meta-materials that utilze nanoscale features to achieve unconventional material properties such as ultralow density and high energy absorption. A dearth of fabrication methods capable of producing architected materials with sub-micrometer resolution over large areas in a scalable manner exists. A fabrication technique is presented that employs holographic patterns generated by laser exposure of phase metasurface masks in negative-tone photoresists to produce 30-40 µm-thick nanoarchitected sheets with 2.1 × 2.4 cm2 lateral dimensions and ≈500 nm-wide struts organized in layered 3D brick-and-mortar-like patterns to result in ≈50-70% porosity. Nanoindentation arrays over the entire sample area reveal the out-of-plane elastic modulus to vary between 300 MPa and 4 GPa, with irrecoverable post-elastic material deformation commencing via individual nanostrut buckling, densification within layers, shearing along perturbation perimeter, and tensile cracking. Laserinduced particle impact tests (LIPIT) indicate specific inelastic energy dissipation of 0.51-2.61 MJ kg-1 , which is comparable to other high impact energy absorbing composites and nanomaterials, such as Kevlar/poly(vinyl butyral)(PVB) composite, polystyrene, and pyrolized carbon nanolattices with 23% relative density. These results demonstrate that holographic lithography offers a promising platform for scalable manufacturing of nanoarchitected materials with impact resistantcapabilities.

Earth’s volatile depletion trend is consistent with a high-energy Moon-forming impact

The abundance of volatile elements in the silicate Earth relative to primitive chondrites provides an important constraint on the thermochemical evolution of the planet. However, an overabundance of indium relative to elements with similar nebular condensation temperatures is a source of debate. Here we use ab initio molecular dynamics simulations to explore the vaporization behavior of indium from pyrolite melt at conditions of the early magma ocean just after the Moon-forming impact. We then compare this to the vaporization behavior of other minor elements. When considering the volatility of the elements from the magma ocean in the absence of the solar nebula gas, we find that there is no overabundance of indium. On the contrary, there is a slight deficit in the abundance of indium, which is consistent with its moderately siderophile nature. Thus, we propose that a high-energy Moon-forming impact may have had a more significant contribution to volatile depletion than previously believed.

Mechanochemical Synthesis of Shape-Anisotropic Particles through Wet Milling Using High-Energy Mills

A high-energy ball mill, such as a planetary ball mill, is widely used for preparing a homogeneously mixed powder and reducing particle size. Because of the high impact energy generated by the collision of ball media, the planetary ball milling is expected to produce local high-temperature and high-pressure zones. In wet milling, the solubility of the material varies owing to the local and instantaneous changes caused by the collision. Consequently, mechanochemical reactions through a dissolution–precipitation mechanism can be attained without external heating. In this paper, we show the wet mechanochemical process in water to synthesize functional hydrous or hydrate materials with various shapes, including nanosheets, nanotubes, plates, flakes, rods, and nanoparticles. Morphology-controlled particles can be obtained by only adjusting the milling conditions, such as milling time, ball size, and centrifugal acceleration. Further, the products can be converted into electrode materials for Li-ion batteries, retaining the precursor morphologies. This wet mechanochemical synthesis can be also applied in a bead mill, where mass production and continuous processing are possible. The wet mechanochemical process is a new particle synthesis method that can achieve both grinding and crystal growth.

Fractal image analysis and bruise damage evaluation of impact damage in guava

Impact bruise damage and quality of ‘Gim Ju’ guava were investigated for different drop heights and number of drops using fractal image analysis. For the impact test, a stainless-steel metal ball (250 g) was dropped on fruit from three drop heights (0, 0.3, 0.6 m) either once or five times. Fruit quality was evaluated for impact energy, bruise area (BA), bruise volume (BV), bruise susceptibility, bruise score and pulp color (L*, a*, b* and C values). The fractal dimension (FD) value using fractal image analysis was analyzed at the bruise region. Results showed that five drops (0.3 m) with a high impact energy (3 678.75 J) and a single drop (0.6 m) with a low impact energy (1 471.50 J) exhibited no significant in BA, BV, bruise score as well as all color values (L*, a*, b* and C). While the FD value of a single drop from 0.6 m had a higher FD value than that of five drops from 0.3 m. It is indicated that FD exhibited a better performance to classify impact bruising level of guava than BA, BV and color parameters. The FD value gradually decreased with increase of storage time and bruise severity. The correlation coefficient (r) values of FD (r = − 0.794 and − 0.745) between BA and BV were more significant than those L* (r = − 0.660 and − 0.615) and a* (r = 0.579 and 0.473). The coefficient of determination (R2) of the polynomial equation in bruised fruit (R2 = 0.85 to 0.99) was greater than the control (no bruise) (R2 = 0.80). A higher R2val (0.88 and 0.92) was exhibited at five drops. Interestingly, FD analysis showed greater potential than color measurement to assess bruise impact damage in guava.

Fire reaction and post-fire impact properties of flax fibre reinforced composites containing intumescent flame retardants

The current research aims at investigating the fire reaction and post-fire impact characteristics of flax fibre reinforced composites based on different polymer matrices, such as epoxy resin and polypropylene (PP). The effects of stacking sequences of polymer sheets and flax fabrics within the composites are explored by a cone calorimeter. Heat release and smoke production results indicate that a top surface and number of flame-retardant polymer layers played significant roles in determining the fire reaction properties. Furthermore, post-fire impact properties of flax-epoxy and flax-PP composites depending on burning periods are analysed in this study at the first time. A fully instrumented drop-weight impact testing demonstrates that an increase in heat exposure time led a gradual decrease in impact properties of the composites due to fire-induced damages on fibres and polymers. However, pre-melting and re-consolidation of PP are beneficial to have higher impact energy and force of the flax-PP composite over those of the flax-epoxy counterpart. In addition, the char formation of composites due to intumescent flame retardant enhances the fire reaction properties of composites, whereas there is no significant influence on the post-fire impact characteristics due to highly brittle nature of carbonaceous char.

Response of Bilayer and Trilayer Graphene to High-Energy Heavy Ion Irradiation

High-energy heavy ion irradiation is a very useful tool for the nanostructuring of 2D materials because defects can be introduced in a controlled way. This approach is especially attractive for the mass production of graphene nanomembranes when nanopore size and density can easily be tuned by ion irradiation parameters such as ion energy and applied fluence. Therefore, understanding the basic mechanisms in nanopore formation due to high-energy heavy ion impact is of the highest importance. In the present work, we used Raman spectroscopy to investigate the response of bilayer and trilayer graphene to this type of irradiation. Spectra obtained from graphene samples irradiated with 1.8 MeV I, 23 MeV I, 3 MeV Cu, 18 MeV Cu, and 12 MeV Si beams were analysed using the Lucchese model. It was found that the efficiency of damage production scales strongly with nuclear energy loss. Therefore, even for the most energetic 23 MeV I beam, the electronic energy loss does not contribute much to damage formation and ion tracks are unlikely to be formed.

Experimental study on the damage characteristic and assessment of transverse bent frame of high-piled wharf under impact load

Several studies have demonstrated that ship collision is the key reason that leads to the damage of the wharf. In order to examine the damage characteristics and assessment method of the bent frame under the impact load, a model test with four conditions is conducted in this paper. The experimental results highlight that: (1) The damage of the bent frame promotes the characteristics of three stages: micro-damage appearance, crack development, crack penetration; (2) The aggravation of the overall damage of the bent frame results in an increase in the frequency and damping ratio of the structure, but they are not sensitive to low damage; (3) The efficiency of converting kinetic energy into structural deformation energy increases with higher impact energy; (4) Damage degree is a discriminating index of the bent frame performance can represent the current health status of the structure.

Low-velocity impact behavior of interlayer hybrid foldcore sandwich structures with carbon/glass fibers

Interlayer hybrid foldcore sandwich structures have been introduced in this study. Both facesheets and foldcores were hybridized in the same ply sequence with two layers of plain woven carbon (C) and two layers of satin woven glass (G) fiber prepregs (Carbon-to-Glass ratio 1:1). Foldcore sandwich structures with six-ply combinations were designed including two symmetric layups (GCCG and CGGC) and four asymmetric layups (CGCG, GCGC, CCGG, and GGCC). The static compression and low-velocity impact performance of foldcore sandwich structures of different ply sequences were investigated. A user-defined material subroutine (VUMAT) was employed to characterize the damage evolution of composite materials based on selected failure criteria. The findings revealed that hybridization was effective in enhancing its energy absorption value of pure carbon fiber foldcore sandwich structures in terms of static compression performance. The damage degree of the interlayer hybrid foldcore sandwich structures increased gradually with the increasing impact energy. Moreover, the damage of facesheet was mainly caused by fiber tensile, matrix tensile damage and delamination, and damage of foldcore was mainly delamination. GCGC sandwich panel with asymmetrical cross-ply sequence has the optimal load bearing capacity, and CGGC sandwich panel with symmetrical layup has a strong energy absorption capacity under high-energy impact load. The foldcore sandwich structure showed smaller peak load, longer crushing distance, and more energy absorption value under larger oblique impact angle. The simulation and experimental results show good agreement in peak force, maximum energy absorption, and damage mode.

Effects of different intercritical annealing processes on microstructure and cryogenic toughness of newly designed medium-Mn and low-Ni steel

Through the idea of replacing Ni with Mn, a shortened process of ultra-fast cooling and two-step intercritical annealing for medium-Mn and low-Ni steel after rolling was designed. Microstructures were characterized through optical microscopy, electron probe micro analyzer, scanning electron microscopy, electron backscattered diffraction, and X-ray diffractometer. Furthermore, the effects of different intercritical annealing temperatures on austenite including content, stability, and the impact toughness of experimental steel were investigated. The microstructures of the experimental steel comprised retained austenite (RA), fine-grained ferrite, and part of martensite. The results show that fine grain structure and austenite with high stability enriched by Mn and Ni provided excellent mechanical properties for experimental steel with yield strength of 645 MPa, tensile strength of 745 MPa, total elongation of 32%, and high impact energy of 133 J at −150 °C. As the intercritical annealing temperature increased, the microstructures of the matrix coarsened, and the volume fraction and size of RA increased, while the stability decreased significantly. RA with high stability provided long-lasting work hardening ability through continuous deformation-induced transformation (TRIP effect) during the deformation of steel, which played an important role in toughening the multiphase system.

Characteristics of Ground Pressure Disaster and Rockburst Proneness in Deep Gold Mine

Abstract To obtain rockburst characteristics at rock engineering, the rockburst event, in situ stress characteristics, and rockburst proneness are studied in a deep gold mine. The severity of rockburst increases with cover depth at the mine. The main locations of spalling and rockburst events include roof and sidewall. The in situ stress measurement results show this area that is controlled by horizontal constructional pressure, and the self-weight stress also has an important influence. The rockburst mechanism is analyzed from the principal stress and tangential stress. When the maximum tangential stress (MTS) does not exceed 0.4 times UCS of surrounding rock, no obvious disaster in tunnel is found. When the MTS of tunnel is between about 0.4 ~ 0.55 times UCS of rock, the tunnel may suffer spalling. When the MTS of tunnel exceeds 0.55 times UCS of rock, serious failure may occur in tunnel, such as rockburst and large roof collapse. When surrounding rock is relatively hard and complete (high impact energy index, elastic strain energy index, linear elastic energy index, and RQD index), the tangential stress plays a very important role in the rockburst at the mine.

Super-tough, self-sensing and shape-programmable polymers via topological structure crosslinking networks

Shape-memory polymers (SMPs) are smart materials capable of deforming actively under external excitation. Owing to their characteristics, including variable stiffness, programmable deformation, composability, and self-sensing, and its behavior is similar to the intelligent reflection of life, these materials are highly valuable for applications in many fields. We have developed a molecular engineering strategy based on topological cross-linking networks, which form hydrogen bonds, hyperbranching, ring network structure, etc. to obtain shape memory epoxy resin (SMEP) with super toughness, high-temperature resistance and triple shape memory effect (TSME). Additionally, the internal relationship between the molecular network structure and material performance is simulated by molecular dynamics. It has super toughness (1288 %) and high impact energy (216 MJ/m3) above its transition temperature, breaking through the previously reported thermosetting resin. Importantly, the developed SMPs system exhibited outstanding fatigue resistance and was successfully loaded repeatedly for more than 100 cycles. Finally, the intramolecular cyclization effect led to the generation of different linked structures in situ, which endowed SMEP with TSME, thereby rendering such materials potentially applicable in engineering fields, such as aerospace, smart furniture, and soft robotics.

Hinge-lever mechanisms of variable structure and their applications in engineering

The report discusses the transition of hinge-lever mechanisms from one structure to another and the use of these properties to create machines for various purposes. Our research has shown that when some parameters or their ratios change, conditions are created for a possible change in the structure of the mechanism. One of the schemes of hinge-lever mechanisms of variable structure was used in the design of the drilling module as part of the Luna-24 station for drilling a hole on the surface of the Moon, as a generator of power pulses. A major application of lever mechanisms of variable structure was their use as a working body in pressure presses. The report outlines the stages of creating impact machines based on mechanisms of variable structure, from hand-driven perforators to hammers with high impact energy. The design research was accompanied by studies of the kinematics and dynamics of impact machines with mechanisms of variable structure, the identification of new properties, the synthesis of the most optimal design and operating parameters of the power transmission.

STRUCTURE FORMATION IN SURFACE LAYERS OF ALUMINUM AND TITANIUM ALLOYS DURING PLASMA CUTTING

This paper explores the structure and changes in the mechanical properties, chemical composition and surface morphology of aluminum alloys AA5056, AA2024 and Grade2 titanium alloy after high energy impact during plasma cutting. The studies show that plasma cutting causes the formation of a subsurface layer with a dendritic structure typical of cast material and with a partially altered chemical composition. The subsurface layer material is significantly softened when cutting thermally hardened alloy AA2024, but changes slightly when cutting AA5056 alloy. During plasma cutting of Grade2 titanium alloy in protective atmosphere, the presence of even a small amount of atmospheric oxygen leads to the formation of oxides in the layer closest to the surface, which have microhardness values more than 5-7 times higher than the base metal hardness. Below the surface layer with a molten structure, a heat affected zone is formed where the structure of the base metal is changed as a result of thermal influence. Significant changes in this area are characteristic only for thermally hardened alloy AA2024. Metal flow in the cutting zone initiated by the plasma jet and shielding gas flow occurs in both laminar and vortex modes. Inhomogeneous metal flow in the cutting zone and nonoptimal process parameters lead to the formation of structural heterogeneities and defects of different structural and scale levels on the surface of the samples.

Low-velocity impact behavior and mechanical characteristics of basalt/glass hybrid composites with graphene filler for enhancing aircraft nose tip

The growing need for eco-friendly, reliable, lightweight yet rigid materials for aircraft structures served as the inspiration for this work. The intention of this research is to examine the microdamage effects of a hybrid composite made of basalt/glass fiber infused with graphene, on the low energy drop weight impact test. Four main methods are used, which encompass the fabrication of composites, low-velocity impact testing, methods for evaluating impacted composites using ultrasound nondestructive testing, and a study of damage morphology through a scanning electron microscope. An E-glass fiber(400 GSM) combined with natural basalt fiber in an 8:2 ratio and infusing graphene nanoparticles is manufactured, to develop a more appealing hybrid composite for aviation industries. The samples of hybrid composite, each varying with 1 % and 2 % graphene weight ratio of fillers with the fibers are used. Eight outer layers made of glass fiber and two inner layers of basalt fiber composite are prepared using hand layup and compression molding methods. Different impact energy levels ranging from 5 J to 48 J are applied to study the propagation of the damage in the composite at low-impact velocities (1.5–3 m/s). The impact damage for glass/basalt with 2 wt% graphene was comparatively 24 % less than that of glass/basalt without infused graphene nanoparticles at the highest impact energy, thus proving addition of natural basalt and graphene filler improves the strength of the composites.

Fragmentation of tyrosine by high-energy electron impact

Fragmentation of tyrosine by high-energy electron impact

The BCIS-4B method for state-selective and state-summed total cross sections: Proton–helium​ charge exchange at 10–4000 keV

This work is on single electron capture by protons from helium targets at intermediate and high impact energies (10–4000 keV). Assessed is the overall performance of the second-order four-body boundary-corrected continuum intermediate state (BCIS-4B) method by detailed comparisons with all the available measurements. The state-selective Qnl,Qn and state-summed QΣ total cross sections are computed for n≤4, including all the sub-levels. Cross sections Qn are the sum of Qnl for 0≤l≤n−1. The state-summed cross sections QΣ are obtained by using Qn exactly for 1≤n≤3 and approximately for n≥4 through the Oppenheimer n−3 scaling rule. Overall, the measured cross sections are extremely favorably represented by the BCIS-4B method for Qnl,Qn and QΣ, even toward the lowest part of the considered intermediate energy region. Most notably, at all the energies above 10 or 20 keV, e.g. cross sections Q2p,Q3p and Q3d from the BCIS-4B method are in excellent agreement with the corresponding experimental data. This is very important since it is precisely for the non-spherically symmetric states (l≠0) of the captured electron that the existing discrepancies between measurements and other theories are the largest or even enormous.

DETECTION OF STRUCTURAL CHANGES IN A BCC CRYSTAL-LE DYNAMICS UNDER LASER INFLUENCE BY THE METHOD OF MOLECULAR

The presented work presents the results of molecular dynamics modeling of changes in the surface layer of the computational cell under a short-term high-energy impact. Interest in this topic is because the processes occurring in the surface layer, which is in a liquid state, will subsequently have an impact during its crystallization, and, as a result, will affect various physical and geometric characteristics of the surface of the material as a whole. The model constructed and described in the work, in which the temperature of the computational cell is distributed in accordance with the solution of the linear problem of heat conduction, made it possible to reveal the discontinuity of the surface layer, which consists in the localization of excessfree volume in the form of a group of spherical pores. The sizes of these imperfections, as well as the duration of their existence, have differences when modeling different energy densities of laser radiation. Further research made it possible to reveal the conditions under which the pores remain stable throughout the entire simulation time, as well as to reveal the relationship between the crystallographic orientation of the “solid-liquid” interface and the sizes of the formed pores.