Impact Conditions Research Articles

Impact properties of an end of life tires’ rubber. Numerical validation considering large strain and strain rate conditions

The objective of the authors is to demonstrate that the inclusion of renewed rubber from recycled end of life tires (ELT) can improve the performance of any structural system designed to dissipate impact energy. An interesting application would be its use in road safety barriers. This research starts with the rigorous characterization of the recycled material in order to include it in a viable numerical model. The authors presented, in a previous work (*), the experimental viscoelastic properties of recycled rubber, obtained under impact conditions. Bergström–Boyce (BB) nonlinear viscoelastic model was selected as the most suitable to fit the material behavior. This model is defined by nine material constants that are impossible to obtain, uniquely and directly, considering that only compression test results are available as input data. To overcome this challenge, optimization methods were applied resulting in as many sets of parameters as used optimization methods were considered and, moreover, remarkable differences between constants were observed. Solving this problem is the motivation of the present research: the validation of the optimization method by mean of the numerical evaluation of the obtained sets. The software considered for the numerical evaluation of impact tests (LS-DYNA®) had two slightly different implementations for the BB model: the original, based on the work published in 2009 by Dal & Kaliske and a more recent one implemented by Bergström, based on his works published in 1998 and 2000. This leads to a new question: which is the most appropriate implementation-optimization method for calibrating this material? This paper provides the answer to this question carrying out a complete comparative numerical analysis of all sets by means of explicit dynamics simulations. All calibrations, using the original LS-DYNA® implementation, were in perfect agreement with the experimental results. However, only one optimization method produced acceptable results for the most recent approach. A robust method to characterize recycled rubber from recycled tires using the Bergström–Boyce nonlinear viscoelastic model is presented, despite the experimental limitations (González-Vega et al. 2022).

Molten salt biomass torrefaction – A sensitivity analysis of process conditions

Biomass is an abundant renewable resource that can be upgraded via torrefaction. Molten salts catalyze the torrefaction reaction, creating enhanced products for fuel and soil amendment purposes at lower temperatures than inert gas torrefaction. The objective of this study is to elucidate the main effects of molten salt torrefaction process conditions on ponderosa pine (Pinus ponderosa) and cave in rock switchgrass (Panicum virgatum) in a binary salt blend of lithium nitrate and potassium nitrate using a Plackett-Burman screening analysis. The investigated process conditions include sweep gas, temperature, salt to biomass ratio (S-B ratio), residence time, and lithium content. The metrics used to evaluate torrefaction severity include mass yields, chemical composition (lignin, cellulose, hemicellulose, extractives), higher heating value (HHV), carbon and nitrogen content, pH, and water sorption. The results show that switchgrass is more severely torrefied through molten salt torrefaction than pine at the same process conditions. For example, switchgrass mass yields are on average 23.3 % lower than pine mass yields across the test conditions. For both feedstocks, the most impactful process conditions are temperature, time, and lithium content in that order with some exceptions. For instance, the effect of temperature, time and lithium content on HHV are, respectively, 3.4×, 2.3×, and 1.7× larger than the next largest process condition for pine, whereas for switchgrass, these values are 3.6×, 2.7×, and 1×. Particle size, sweep gas, and S-B ratio have minor effects depending on the metric, but are overall not significant compared to temperature. The data suggests that an inert gaseous environment need not be maintained to facilitate molten salt torrefaction. Additionally, molten salt torrefaction can produce torrefied biomass with slightly different characteristics than inert gas torrefaction.

Quantum-inspired modeling of distributed intelligence systems with artificial intelligent agents self-organization

Distributed intelligence systems (DIS) containing natural and artificial intelligence agents (NIA and AIA) for decision making (DM) belong to promising interdisciplinary studies aimed at digitalization of routine processes in industry, economy, management, and everyday life. In this work, we suggest a novel quantum-inspired approach to investigate the crucial features of DIS consisting of NIAs (users) and AIAs (digital assistants, or avatars). We suppose that N users and their avatars are located in N nodes of a complex avatar - avatar network. The avatars can receive information from and transmit it to each other within this network, while the users obtain information from the outside. The users are associated with their digital assistants and cannot communicate with each other directly. Depending on the meaningfulness/uselessness of the information presented by avatars, users show their attitude making emotional binary “like”/“dislike” responses. To characterize NIA cognitive abilities in a simple DM process, we propose a mapping procedure for the Russell’s valence-arousal circumplex model onto an effective quantum-like two-level system. The DIS aims to maximize the average satisfaction of users via AIAs long-term adaptation to their users. In this regard, we examine the opinion formation and social impact as a result of the collective emotional state evolution occurring in the DIS. We show that generalized cooperativity parameters Gi\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$G_i$$\\end{document}, i=1,⋯,N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$i=1,\\dots,N$$\\end{document} introduced in this work play a significant role in DIS features reflecting the users activity in possible cooperation and responses to their avatar suggestions. These parameters reveal how frequently AIAs and NIAs communicate with each other accounting the cognitive abilities of NIAs and information losses within the network. We demonstrate that conditions for opinion formation and social impact in the DIS are relevant to the second-order non-equilibrium phase transition. The transition establishes a non-vanishing average information field inherent to information diffusion and long-term avatar adaptation to their users. It occurs above the phase transition threshold, i.e. at Gi>1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$G_i>1$$\\end{document}, which implies small (residual) social polarization of the NIAs community. Below the threshold, at weak AIA–NIA coupling (Gi≤1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$G_i\\le 1$$\\end{document}), many uncertainties in the DIS inhibit opinion formation and social impact for the DM agents due to the information diffusion suppression; the AIAs self-organization within the avatar–avatar network is elucidated in this limit. To increase the users’ impact, we suggest an adaptive approach by establishing a network-dependent coupling rate with their digital assistants. In this case, the mechanism of AIA control helps resolve the DM process in the presence of some uncertainties resulting from the variety of users’ preferences. Our findings open new perspectives in different areas where AIAs become effective teammates for humans to solve common routine problems in network organizations.

Effect of variable load on centralized dimple in opposite sliding condition

Abstract In ball bearings without a cage, adjacent balls exhibit a zero-entrainment velocity (ZEV) contact condition, which is worse than typical pure rolling or rolling-sliding contact, and the contact between adjacent balls under periodic loading is notably more complicated. In this work, thermal elastohydrodynamic lubrication (EHL) numerical calculation is carried out under the condition of periodic impact and opposite sliding line contact over a wide range of surface speeds. the pressure is solved by multigrid method, the elastic deformation is evaluated using multigrid integration method, the temperature field is calculated by column-by-column scanning technique. The results show that the loading-unloading process exerts significant influence on the variation of the centralized dimple, pressure, and temperature rises as well as the oil characteristics. With the increase of surface speed, the effect of load fluctuations diminishes, and the central dimple exhibits the following evolutionary trend under ZEV conditions: no dimple at very low velocity - small central dimple - large typical dimple - no dimple at high velocity. The result indicates that under the ZEV condition of EHL stage, elevated velocities decrease the coefficient of friction and augment the film thickness.

Stability of granular media impacts morphological characteristics under different impact conditions

Abstract In planetary surfaces, oblique impact events are commonplace, and their study holds significant importance for understanding planetary impact processes and aiding in the design of landers and impactors. Current research predominantly focuses on simplified models to study the force and motion under vertical impact craters in terms of scale and impact loading. For oblique impacts, investigations have primarily concentrated on the final crater shape. However, the specific influence of impact load motion on particle bed movement and the precise impact angle’s effect on the ultimate crater shape during the impact process remain unclear. In this study, we used a custom-built oblique impact experimental setup to analyze changes in the velocity field of the particle bed and the horizontal movement of the impact load. Using quasi-static region to assess ellipticity, we aimed to reveal the state of particle movement during oblique impacts and explore the impact of impact angles and energies on crater formation. The results indicate that under large impact angles, the obliquely acquired kinetic energy is minimal, leading to a predominant static point source movement of the particle bed. At higher energy levels, the impact load primarily excavates downward, resulting in the formation of circular impact craters. These findings underscore the sensitivity of particle bed motion to impact angles, making it a crucial metric for assessing the impact of oblique angles on final crater morphology.

Investigating the Impact of Blunt Force Trauma: A Probabilistic Study of Behind Armor Blunt Trauma Risk.

Evaluating Behind Armor Blunt Trauma (BABT) is a critical step in preventing non-penetrating injuries in military personnel, which can result from the transfer of kinetic energy from projectiles impacting body armor. While the current NIJ Standard-0101.06 standard focuses on preventing excessive armor backface deformation, this standard does not account for the variability in impact location, thorax organ and tissue material properties, and injury thresholds in order to assess potential injury. To address this gap, Finite Element (FE) human body models (HBMs) have been employed to investigate variability in BABT impact conditions by recreating specific cases from survivor databases and generating injury risk curves. However, these deterministic analyses predominantly use models representing the 50th percentile male and do not investigate the uncertainty and variability inherent within the system, thus limiting the generalizability of investigating injury risk over a diverse military population. The DoD-funded I-PREDICT Future Naval Capability (FNC) introduces a probabilistic HBM, which considers uncertainty and variability in tissue material and failure properties, anthropometry, and external loading conditions. This study utilizes the I-PREDICT HBM for BABT simulations for three thoracic impact locations-liver, heart, and lower abdomen. A probabilistic analysis of tissue-level strains resulting from a BABT event is used to determine the probability of achieving a Military Combat Incapacitation Scale (MCIS) for organ-level injuries and the New Injury Severity Score (NISS) is employed for whole-body injury risk evaluations. Organ-level MCIS metrics show that impact at the heart can cause severe injuries to the heart and spleen, whereas impact to the liver can cause rib fractures and major lacerations in the liver. Impact at the lower abdomen can cause lacerations in the spleen. Simulation results indicate that, under current protection standards, the whole-body risk of injury varies between 6 and 98% based on impact location, with the impact at the heart being the most severe, followed by impact at the liver and the lower abdomen. These results suggest that the current body armor protection standards might result in severe injuries in specific locations, but no injuries in others.

Energy absorption and impact response of ballistic resistance laminate

Abstract High-speed impact performance has significantly expanded over the past few decades. The target response based on the impact conditions has been more difficult to visualise and evaluate. In this article, Ansys model analysis has been used to measure, visualise, and predict the projectile and target responses of Kevlar® (K) and Ramie® textile-reinforced unsaturated polyester resin (UP) matrix. The laminate thickness threshold was detected experimentally based on the highest stress intensity factor and energy release rates. Furthermore, tensile strength and bending of the laminate were found. The impact conditions have a significant impact on the target response; thus, an explicit dynamic analysis was used to visualise the impact response based on the number of target fixed supports (FSs). Two FS (2 FS) target absorbs 11% more energy than four FS (4 FS) target. Additionally, the target size has a major effect on the projectile and laminate responses, and a successful arrest of the projectile was detected in both cases. The smallest targets with 2 FS have the highest and wider response, where a successful change in the projectile trajectory was obtained.

Prediction of Residual Compressive Strength after Impact Based on Acoustic Emission Characteristic Parameters.

This study proposes a prediction method for residual compressive strength after impact based on the extreme gradient boosting model, focusing on composite laminates as the studied material system. Acoustic emission tests were conducted under controlled temperature and humidity conditions to collect characteristic parameters, establishing a mapping relationship between these parameters and residual compressive strength under small sample conditions. The model accurately predicted the residual compressive strength of the laminates after impact, with the coefficient of determination and root mean square error for the test set being 0.9910 and 2.9174, respectively. A comparison of the performance of the artificial neural network model and the extreme gradient boosting model shows that, in the case of small data volumes, the extreme gradient boosting model exhibits superior accuracy and robustness compared to the artificial neural network. Furthermore, the sensitivity of acoustic emission characteristic parameters is analyzed using the SHAP method, revealing that indicators such as peak amplitude, ring count, energy, and peak frequency significantly impact the prediction results of residual compressive strength. The machine-learning-based method for assessing the damage tolerance of composite laminates proposed in this paper utilizes the global monitoring advantages of acoustic emission technology to rapidly predict the residual compressive strength after the impact of composite laminates, providing a theoretical approach for online structural health monitoring of composite laminates. This method is applicable to various composite laminate structures under different impact conditions, demonstrating its broad applicability and reliability.

Dynamic damage and non‐shock ignition behavior of polymer bonded explosive under lower velocity impact

AbstractThe accidental ignition of polymer‐bonded explosives (PBXs) caused by hot spots has been the focus of domestic and international research. Micro‐crack friction plays a crucial role in the formation these hot spots. In this study, confined tests were conducted to investigate the ignition response of PBX under impact loading. The experimental results revealed that the PBX underwent ignition under the given conditions of a pressure load with a pulse width of 50 μs and an amplitude of 638 MPa. The viscoelastic statistical cracking model (Visco‐SCRAM) and hot‐spot ignition model were used to describe the damage behaviors and ignition responses of the PBX. The simulation results revealed that more severe damage occurs at the center of the impact face and its vicinity under confined impact conditions, which is consistent with the observed post‐test samples. Additionally, simulation results also predict a trapezoidal shape for the severely damaged region within the PBX. The findings of this study provide insights for understanding the damage behavior and the critical ignition of PBX under impact loading.

On low velocity impact response of Sandwich composite with jute/epoxy facesheet and cenosphere reinforced functionally graded Core: Experimental and finite element approach

AbstractThe assessment of energy absorption behavior has a vital role in determining suitability of lightweight composites for impact protection applications. This study focuses on evaluating the energy absorption characteristics of cenosphere reinforced epoxy syntactic foam core and jute epoxy facesheet sandwich composite subjected to low velocity impact. The syntactic foam is composed of lightweight cenospheres embedded within an epoxy matrix, resulting in a high‐strength and lightweight composite material. Low velocity impact tests were conducted using a drop tower apparatus to simulate realistic impact conditions. The impact force, energy absorption and damage mitigation of the syntactic foam specimens with varied weight percentage of Cenosphere (0%, 10%, 20% and 30%) were measured and analyzed to assess the energy absorption behavior. The gradation revealed that the weight of top layer when compared to bottom layer is 50.49%, 70.23% and 95.74% less in syntactic foam core with 10, 20 and 30 wt% Cenosphere respectively, indicating gradation. The study demonstrates that the addition of Cenosphere up to 20 wt% enhances the energy absorption capacity of the sandwich composites by 59.37%–93.44% compared to sandwich without Cenosphere reinforced core. However, beyond this threshold, a decline in energy absorption is observed when subjected to low‐velocity impact (LVI). Fractography analysis demonstrates that the incorporation of Cenosphere induces a rough fracture surface with deep river‐like topography, indicative of greater energy absorption during impact loading. This substantiates the conclusion that Cenosphere‐reinforced syntactic foams exhibit enhanced impact resistance, making them promising materials for structures subjected to low‐velocity impact events.Highlights Development of functionally graded core sandwich composite for low velocity impact applications. Assessing the performance of developed composites under low velocity impact loading. Determining the optimal weight percentage of cenospshere in functionally graded core. Studying the fractography of developed sandwich composites. Corelation between experimental and finite element studies.

Predicting Erosion Damage in a Centrifugal Fan

Erosion damage can occur in fans and blowers during industrial processes, cooling, and mine ventilation. This study focuses on investigating erosion caused by particulate air flows in a centrifugal fan with forward-inclined blades. This type of fan is particularly vulnerable to erosion due to its radial flow component and flow recirculation. The flow field was solved separately, and the data transferred to the particle trajectory and erosion code. This in-house code implements the Lagrangian approach and the random walk algorithm, including statistical descriptions of particle sizes, release positions, and restitution factors. The study involved two types of dust particles, with a concentration between 100 and 500 μg/m3: The first type is the Saharan (North Africa) dust, which has a finer size between 0.1 and 100 microns. The second type is the Coarse Arizona Road Dust, also known as AC-coarse dust, which has a larger size ranging from 1 to 200 microns. The complex flow conditions within the impeller and scroll, as well as the concentration and size distribution of particles, are shown to affect the paths, impact conditions, and erosion patterns. The outer wall of the scroll is most heavily eroded due to high-impact velocities by particles exiting the impeller. Erosion is more pronounced on the pressure side of the full blades compared to the splitters and casing plate. The large non-uniformities of erosion patterns indicate a strong dependence with the blade position around the scroll. Therefore, the computed eroded mass is cumulated and averaged for all the surfaces of components. These results provide useful insights for monitoring erosion wear in centrifugal fans and selecting appropriate coatings to extend the lifespan.

Aluminum hierarchical tubular structure inspired by skeletal muscle tissues: Quasi-static and low-velocity impact testing

This paper investigates experimentally and numerically the protective capability of skeletal muscle-inspired hierarchical tubular (MHT) structures made of aluminum under both quasi-static and dynamic impact conditions. In the quasi-static compression tests, structures with higher hierarchical order were more deformable and had lower contact force. Dynamic impact tests were conducted for the first time on MHT specimens of three different hierarchical orders using a drop tower facility. The results indicated a significant reduction in both the maximum and mean contact forces on the protected body when shielded by the second- and third-order MHT structures. This suggested that increasing the hierarchical order of the structure effectively enhanced impact protection capability. Numerical models were developed using ABAQUS/Explicit to accurately reproduce the deformation process and force-time functions of the dynamic impact scenarios. A parametric study found that the impact resistance performance of the MHT structures was robust against various impact velocities and masses.

Failure analysis of additively manufactured AuxHex and hierarchical honeycomb-core sandwich panels subjected to projectile impact

Honeycomb sandwich panels (HSPs) are extensively employed across various industries owing to their outstanding strength and capacity for energy absorption. Despite their widespread use, the potential of additively manufactured (AM) honeycombs in ballistic protection remains relatively unexplored. This study aims to comprehensively assess the energy absorption performance of two distinct HSP configurations, namely AuxHex and Hierarchical, through high-velocity impact tests spanning velocities ranging from 220 to 270 m/s. The high-velocity impact experiments are conducted using a single-stage pneumatic gun, complemented by simulations executed via Abaqus/Explicit. Our findings reveal that the hierarchical HSP demonstrated a notable 9.6 % enhancement in energy absorption compared to panels featuring an AuxHex honeycomb. Interestingly, the hierarchical panels also necessitated 4.8 % more energy for perforation. In terms of failure mechanisms, both sheets of the HSPs experienced ductile shearing, with the formation of characteristic petal-like structures. Concurrently, the honeycomb core underwent fragmentation on the side facing the projectile, while plugs were ejected from the back sheet. Moreover, our analysis indicates that the residual deflection of the back sheet surpassed that of the striking sheet by 15–20 %. This disparity can be attributed to prolonged contact duration and variations in interaction forces between the sheets. Overall, this investigation provides valuable insights into the energy absorption capabilities of AM honeycomb-based HSPs under high-velocity impact conditions, shedding light on their potential for enhanced ballistic protection in various applications.

Microstructure and mechanical behavior of rhombic dodecahedron-structured porous β-Ti composites fabricated via laser powder bed fusion

Porous β-Ti composites hold large promise for lightweight components due to their exceptional strength-ductility synergy. However, their microstructural behavior under both impact and compressive conditions have received limited attention. This study investigates the compressive and impact behavior of porous β-type Ti–25Nb (at.%) composites fabricated using laser powder bed fusion (LPBF). The composites feature a rhombic dodecahedron (RD) lattice structure and incorporate a central solid cylinder with varying diameters. Microstructural characterizations and finite element simulations were employed to analyze mechanical properties and stress distribution. Incorporation of 3 mm radius cylinders (TIII ∼45% porosity) significantly enhances compressive yield stress (88 ± 10 MPa), impact yield stress (153 ± 10 MPa), and impact energy absorption (41.2 J/cm³) while maintaining material plasticity. Compressive and impact loading initiate a martensitic transformation from β to α″ phase, strengthening the alloy through refined α″ formation with a finer grain size than β phase. Notably, a β→ α″ transformation and grain refinement occur in the node region that connects the solid cylinder and lattices, which undergoes significant deformation during impact. This observation suggests the impact resistance of porous β-Ti composites can be enhanced through tailored microstructures and strategic structural design.

Experimental study on the damage and fracture mechanism of deep coal beds impacted by water jets at different temperatures

The development of abundant deep coalbed methane (CBM) resources has attracted significant attention due to their commercial development potential. However, developing such resources presents many challenges due to their generation in complex geological environments governed by high temperatures and stresses. Thus, this work investigated coal fragmentation using water jets at different reservoir temperatures. The results show that compared with room temperature conditions, under water jet impact, the threshold fracturing pressure of high-temperature coal is lower, the rock-breaking volume is larger, and thermal stress leads to intensified dynamic damage. Indeed, when the temperature exceeds 75.0 °C, the coal undergoes volume fragmentation, and the depth of water jet-breaking coal increases by 81.0 %, while the specific energy consumption decreases by 52.4 %. The threshold fracturing pressure rapidly decreases as temperature increases and stabilizes, presenting an exponential trend. When the temperature exceeds 75.0 °C, the threshold fracturing pressure is maintained at around 10.0 MPa and no longer decreases with the temperature increase. In addition, three-dimensional (3D) damage field analysis highlights that the coal breaking mode shifts from a “water wedge” dominated mode to a “water wedge-thermal fracture” mode as temperature increases. Finally, the dynamic fracturing mechanism of coal under high-temperature conditions of water jet impact has been revealed. The research results of this paper provide a theoretical basis for the hydraulic permeability enhancement design of deep coal seams.

Stress wave propagation law in CFRP under laser impact conditions

The paper analyzes the propagation law of stress waves in CFRP unidirectional plate specimens and adhesive plate specimens under laser shock conditions using a combination of experimentation and simulation. The finite element model is corrected by using the back particle velocity curve obtained from the experiment. Subsequently, the spatiotemporal stress distribution is extracted from the finite element model. The results indicate an overall attenuation trend of the stress wave propagating in the unidirectional plate. In the adhesive plate, the peak value of the stress wave increases first at the adhesive layer position due to the acoustic impedance mismatch and energy absorption characteristics of the adhesive layer material and CFRP. Then it tends to increase after decay. Moreover, the behavior characteristics of the stress wave differ significantly when it propagates from high-impedance material to low-impedance material compared to when it propagates from low-impedance material to high-impedance material.

Behavior of steel fiber-reinforced coal gangue concrete beams under impact load

In order to promote the use of new sustainable steel fibers (SF) reinforced coal gangue aggregates (CGA) concrete, impact tests were performed in this paper. The impact resistance of steel fiber-reinforced coal gangue concrete was investigated using a self-developed drop-weight facility. The test variables were the CGA replacement rate (0 %, 50 %, and 100 %), the SF volume content (0 %, 0.75 %, and 1.5 %), and the drop height of the drop-weight (0.5 m and 1.0 m). Using 15 kg of hard steel as a drop-weight, the drop-weight impact test was performed on steel fiber-reinforced coal gangue concrete beams with a span of 300 mm; the damage pattern, impact reaction force-time, displacement-time relationships, and energy absorbed by steel fiber-reinforced coal gangue concrete beams were studied. The test shows that, compared with natural aggregate, CGA reduces concrete's static mechanical properties and impact resistance, and adding SF improves the static mechanical properties and impact resistance of coal gangue concrete. As the CGA replacement rate increased from 0 % to 50 % and 100 %, the reaction force of impact of the specimens decreased by 2.54 %− 6.06 % and 3.69 %− 12.33 %. The SF volume content was increased from 0 % to 0.75 % and 1.5 %, and the reaction force of impact of the specimens was increased by 23.05 %− 32.34 % and 72.27 %− 81.84 %, respectively. The impact resistance of steel fiber-reinforced concrete beams under impact loading was investigated numerically using a nonlinear explicit finite element model in LS-DYNA. The Finite Element results were validated with experimental results. Based on the validated finite element model, a parametric study was carried out to investigate the effects of coal gangue replacement rate, steel fiber volume content, and drop height of the drop weight on the behavior of the beams. This study might provide a basis for the future engineering project applications of steel fiber-reinforced coal gangue concrete under impact conditions.

Foreign object damage characteristics of a thin nickel-based superalloy plate at room and high temperatures

Turbine blades with thin-walled structures usually works in harsh environments, and foreign object damage (FOD) is one of the conditions of special concern. In this paper, the FOD characteristics of thin nickel-based superalloy plates are studied by a combination of experimental, numerical and analytical methods, considering room and high temperatures, different impact conditions and plate thicknesses. An easy-to-use test system is developed to realize high speed impact of the thin nickel-based superalloy plate under elevated temperature. Crater morphologies, internal microstructure, and residual stress are analyzed after impact with different conditions. Numerical simulation of the impact process is performed by using Johnson-Cook (J-C) constitutive model. Based on Hertz theory, an analytical method for calculating the crater length and depth is proposed considering the deformation of the impact steel sphere. Results shows that the FOD characteristics at high temperature is significantly different from that at room temperature. The crater has lager dimensions under high speed and elevated temperature. Moreover, significant grain refinement is obvious and the dislocation layer is also thicker at higher speed and higher temperature. Due to the effect of high temperature softening, hardness and residual stress after impact with elevated temperature is lower than that at room temperature. Besides, non-normal impact mainly influences Goss texture and distribution of residual stress after high temperature impact. In addition, it is found that thickness have a significant effect on the FOD characteristics especially when the plate is thinner. The validity of the numerical model and analytical method is proved by comparing with the experimental results. The present study can provide data foundation and numerical analysis support for the damage assessment and maintenance of turbine blades.

Prediction and study of impact performance of mining plastic shell based on PSO-BP neural network

Abstract In order to accurately and quickly predict the anti-impact performance of the plastic shell of a mining sensor, taking the plastic shell of a mine dust concentration sensor as the research object, finite element simulation software is used to simulate and predict its performance in the impact test. Compared with the experimental results, the accuracy of finite element simulation is verified. The batch simulation is carried out by using the finite element method, and the BP neural network and the PSO (particle swarm optimization)-BP neural network are established. The comparison results show that the PSO (particle swarm optimization)-BP neural network has higher accuracy than the BP neural network, and can more accurately predict the mechanical properties of the mine sensor shell under impact conditions. At the same time, compared with the finite element method, it has the advantage of efficiency. The prediction time can be improved to 5-10 milliseconds by using PSO-BP neural network mode, compared to hours of the finite element simulation. This method provides a research method for efficiently and accurately obtaining the impact mechanical performance of mine plastic shells and optimizing structural parameters.

Impact-induced energy release characteristics of Ti-Zr-Hf-Ta high-entropy alloys by using a temperature-pressure synchronous measurement method

Energetic structural materials (ESMs) are a new type of materials with structural strength and reactivity, and their impact-induced energy release characteristics are greatly influenced by the fragmentation behavior. In this study, the dynamic fragmentation behavior and energy release characteristics of Ti-Zr-Hf-Ta high-entropy alloys (HEAs) with different precipitate content were investigated based on split Hopkinson pressure bars (SHPB) tests. To quantitatively evaluate the reactivity of ESMs, a temperature-pressure synchronous measurement method combined with a modified calculation model for quasi-sealed chamber was proposed. The results showed that the precipitates were distributed at the grain boundaries. As the precipitate content increased, the quasi-static yield strengths increased from 1004 to 1132 MPa, the dynamic yield strengths increased from 1672 to 1874 MPa, while the fracture strains decreased from 0.47 to 0.29, and correspondingly, the released energy increased from 14±2–511±154 J/g. The results demonstrated that the impact-induced energy release characteristics of the materials are closely related to the fracture strain. It can be confirmed that the alloys with lower plasticity are more likely to fracture under impact conditions, and the combustion reaction will be more violent, which is well consistent with the measurement of the energy-release amounts. High-speed infrared temperature measurement and microstructural photography also provided the underlying mechanism: the fragment size of low plasticity materials is smaller and the local hot spots are more dispersed, both of which are conducive to the combustion reaction. By using this method, the relationship among mechanical properties, fragmentation behavior, and energy release characteristics can be established, and the results will provide new insights into the development of ESMs with superior energy release under impact loading and applicable mechanical properties for potential applications.