Impact Stress Research Articles

MetaCompare 2.0: Differential ranking of ecological and human health resistome risks

Abstract While numerous environmental factors contribute to the spread of antibiotic resistance genes (ARGs), quantifying their relative contributions remains a fundamental challenge. Similarly, it is important to differentiate acute human health risks from environmental exposure, versus broader ecological risk of ARG evolution and spread across microbial taxa. Recent studies have proposed various methods for achieving such aims. Here, we introduce MetaCompare 2.0, which improves upon original MetaCompare pipeline by differentiating indicators of human health resistome risk (HHRR, potential for human pathogens of acute resistance concern to acquire ARGs) from ecological resistome risk (ERR, overall mobility of ARGs and potential for pathogen acquisition). The updated pipeline's sensitivity was demonstrated by analyzing diverse publicly-available metagenomes from wastewater, surface water, soil, sediment, human gut, and synthetic microbial communities. MetaCompare 2.0 provided distinct rankings of the metagenomes according to both HHRR and ERR, with both scores trending higher when influenced by anthropogenic impact or other stress. We evaluated the robustness of the pipeline to sequence assembly methods, sequencing depth, contig count, and metagenomic library coverage bias. The risk scores were remarkably consistent despite variations in these technological aspects. We packaged the improved pipeline into a publicly-available web service (http://metacompare.cs.vt.edu/) that provides an easy-to-use interface for computing resistome risk scores and visualizing results.

Transverse impact performance and finite element analysis of three‐dimensional woven tubular composite with different structures

AbstractIn this study, experiments combined with finite element analysis (FEA) were used to investigate the damage mechanism of transverse low‐velocity impacts on three‐dimensional woven tubular composites (3DWTC) with different structures. The damage morphology after impact was observed using three‐dimensional microscopy and scanning electron microscopy (SEM). Three mesoscale models were constructed based on the authentic structure of the 3DWTC. Additionally, the effects of the structure type on the impact resistance, stress distribution, and damage morphology of 3DWTC were studied. The impact resistance of the shallow cross‐linked (SCL) structure is the strongest, according to the data. The structure that resists impacts the least is the through orthogonal (TO) structure. The greater the straightness of the warps in the structure, the density of the weft, the volume fraction, the greater the cooperative load‐bearing capacity of the warps and wefts, and the greater the speed of stress propagation. The wefts and inner warps are subjected to tensile forces at the point of impact. The outer warps are subjected to compression. The stresses are distributed in a cross‐shaped pattern. The straightened warp and weft parts of the TO serve a key structural role in load‐bearing. The warps of the SCL and the shallow‐crossed curved joint (SCCJ) structure serve a key structural role in the load‐bearing capacity.Highlights The impact resistance of 3DWTCs was investigated. The tensile state, stress propagation rate of 3DWTC were analyzed using the mesoscale model. The main load‐bearing components are revealed. The differences in damage morphology of 3DWTCs are analyzed.

Fracture and fractal characteristics of high-temperature granite under confined space water jet impact

In the application of jet assisted deep drilling technology, the fracture mode and rock fragment characteristics of high-temperature rock in the confined space of jet drilling are not yet clear. We analyzed the fragmentation and debris distribution of high-temperature granite under confined space jet action using 3D reconstruction technology and statistical fractal theory to examine their fragmentation patterns and fractal characteristics. The results show that high-temperature rocks exhibit obvious thermal fracturing characteristics under the impact of confined water jet, and as the rock temperature increases, vertical compression shear cracks connect with radial tensile cracks. The maximum damage area is located near the bottom of the confined hole, and the distribution of cracks is more complex. As the degree of jet confinement decreases, the rock cracking form changes from radial tensile cracking to vertical compression shear cracking. As the rock temperature increases and the confined space size decreases, the total mass and large debris mass percentages of rock debris increase. The particle size distribution of rock debris follows an Rosin-Rammler (R-R) distribution and has obvious fractal characteristics. The fracture and fragmentation of high-temperature rocks under confined water jet impact are mainly caused by the combination of jet impact stress waves and thermal stress. The temperature difference of rocks affects the heat transfer between jet and rock, and the confined space size directly affects the heat transfer efficiency between jet and rock, which is manifested in different numbers of fracture cracks, internal damage area, and rock debris size distribution. These findings can provide a theoretical and parameter optimization basis for jet-assisted deep reservoir drilling applications.

Decoding Pandemic Stress: Analysing Mental Health of Tea Workers in India

This research article aims to investigate the factors that affected the mental health of tea workers during the COVID-19 pandemic. The study provides essential insights into the psychological factors affecting tea workers during this critical time. Data were collected through semi-structured questionnaires from 532 tea workers in the north-eastern region of India. The collected data were analysed using confirmatory factor analysis and structural equation modelling approaches. The study found that all the factors investigated significantly impacted employee stress during the COVID-19 pandemic. However, safety perception and contagion risk were found to have the strongest influence on stress, followed by unknown and information overload, social exclusion and humiliation, monetary loss and job uncertainty, and quarantine and restraint. Additionally, the study confirms that stress at the onset of the COVID-19 pandemic can lead to depression among tea workers, which is also related to insomnia and relationship troubles. Investigating the various dimensions of COVID-19 stressors among tea workers is crucial for the government and management to understand the root causes of the problem. By understanding the contributing factors to mental health issues, we can develop appropriate interventions to support the well-being of tea workers, providing a blueprint for mitigating the potential adverse effects of future pandemics.

Nourishing the mind: how the EAT-Lancet reference diet (ELD) and MIND diet impact stress, anxiety, and depression

BackgroundPrevious studies have suggested a link between diet and mental health. However, there is a lack of evidence regarding the association between emerging diets such as the EAT-Lancet reference diet (ELD) and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, and mental health in different societies. This study aimed to determine the association between adherence to ELD and MIND diets and the risk of depression, anxiety, and stress.MethodsThis research involved 4579 participants from the PERSIAN Organizational Cohort Study in Mashhad (POCM). To assess dietary intake, a comprehensive 118-item semi-quantitative food frequency questionnaire (FFQ) was employed. The Planetary Health Diet Index (PHDI) was used to assess adherence to the ELD. Mental health status was evaluated using the Depression, Anxiety, and Stress Scale-21 items (DASS-21) questionnaire. Binary logistic regression was utilized to examine the relationship between these scores and mental health indicators.ResultsIn the adjusted model, the highest quartile of PHDI showed a 35% reduced risk of depression compared to those in the lowest quartile (OR: 0.653, 95% CI: 0.483–0.883; P = 0.008). However, compared to the reference quartile, participants in the highest quartile of MIND diet exhibited significantly lower risks of depression (OR: 0.611, 95% CI: 0.447–0.836; P = 0.005), anxiety (OR: 0.559, 95% CI: 0.418–0.746; P < 0.001), and stress (OR: 0.629, 95% CI: 0.419–0.944; P = 0.008).ConclusionsThe ELD and MIND diet were both associated with reduced odds of depression. Additionally, MIND diet was associated with decreased likelihood of anxiety and stress. However, no connection was observed between ELD and anxiety or stress. Further large-scale interventions are required to confirm these findings.Graphical Association between EAT-Lancet reference diet (ELD) and MIND Diet with Stress, Anxiety, and Depression. PHDI: planetary health diet index, MIND diet: Mediterranean-DASH Intervention for Neurodegenerative Delay diet

Investigating the Role of Exercise Pattern in Acute Cardiovagal Recovery.

Research on intermittent training has mainly focused on the effects of exercise intensity while overlooking the specific impact of the modulations associated with alternating exercise and recovery. This study investigated how the frequency of modulations during moderate-intensity exercise affects post-exercise vagal reactivation. Healthy, active females and males aged 18-39 years were recruited for the study. Participants completed three treadmill running sessions on separate days. Each moderate-intensity session accumulated 30 min at 90% of the intensity associated with the second ventilatory threshold and were performed as either high-frequency intermittent (HiFi; 15 x [2 min + 2 min recovery]), low-frequency intermittent (LoFi; 5 x [6 min + 2 min recovery]), or continuous training (MICT; 1 x 30 min). Heart rate recovery (HRrec) at 1 min and heart rate variability recovery (HRVrec; lnRMSSD) were assessed in response to submaximal constant-speed tests performed prior to (CST1) and following (CST2) each of the exercise sessions. HRrec, HRVrec, blood lactate (BLa), and blood pressure were also collected during the exercise sessions. Twenty-one individuals (8 females, 13 males) participated in the study. HRrec from CST2 was faster in HiFi vs. MICT (p < 0.001), while HRVrec post-CST2 was higher following HiFi vs. both LoFi (p = 0.024) and MICT (p < 0.001). BLa increased in all conditions (p = 0.007) but remained lower during HiFi compared to LoFi and MICT (both p < 0.001). Diastolic blood pressure did not change during exercise with HiFi (p = 0.939) but decreased during LoFi (p = 0.006) and MICT (p = 0.008). Exercise pattern influences the physiologic response to exercise. Higher frequencies of modulations can preserve vagal activity and expedite post-exercise recovery, suggesting moderate-intensity intermittent exercise as a potential strategy to mitigate autonomic impact and acute physiological stress while maintaining total work performed.

Navigating the New Normal: Psychological Capital's Mediating Role in the Work-From-Home Paradigm

Working from home (WFH) has become the expected trend as a result of the COVID-19 epidemic. The impact of family conflict, social isolation, distracting environment, job autonomy, and self-leadership on employees' productivity, work engagement, and stress levels have been examined in this study with a mediating role of Psychological capital. There has been little study on the impact of Psychological capital as a mediator and its influence on remote work productivity, work engagement, and stress. The data was collected from employees of IT sector organizations. Through online and print surveys, a sample of 429 respondents was gathered using the convenience sampling method. The dependent variables were workers’ productivity, work engagement, and Stress, the mediating variable was Psychological Capital and the independent variables were family-work conflict, social isolation, distracting environment, job autonomy, and self-leadership under the framework of the Job Demand and Resource model. The PLS-SEM tool was used to investigate the association between research variables. The SPSS tool was used to run the descriptive statistics of respondents. Through this study, it was able to conclude that Job Demand and Job Resources significantly impact productivity, work engagement, and stress through psychological capital. Job Demand negatively impacts productivity, and work engagement and positively impacts stress while Job Resource positively impacts productivity, and work engagement and negatively impact stress.

Experimental study on the buffering mechanism of EPS bead-sand cushions under single and multiple impacts

As a main functional component of rock sheds in rockfall protection projects, traditional sand cushions have shortcomings such as heavy weight and weak buffering capacity. EPS bead-sand cushion can effectively solve these problems, but its buffering mechanism has not been fully revealed. In this study, a series of impact tests were carried out to investigate the performance of EPS bead-sand cushions with different EPS bead contents, and the evolutions of rockfall impact force, penetration depth, earth pressure, and slab vibration under single impact and multiple impacts were comparatively analyzed. The results show that with the addition of EPS beads, the maximum impact force, the peak earth pressure, and the vibration acceleration are significantly reduced. However, the cushion with high EPS bead content is at risk of being penetrated under high energy or multiple impacts, leading to excessive concentration of impact stresses. Furthermore, the EPS beads can alleviate the hardening of the sand cushion under impact through their deformation coordination, but excessive penetration should be prevented in the design of EPS bead-sand cushions. On this basis, combined with traditional sand cushion design theory, an estimation method for the maximum impact force applicable to EPS bead-sand cushion was proposed. The research results can provide a reference for the design and optimization of cushions in actual projects.

Research on the mechanism of electromechanical coupling response of pulse power multilayer ceramic capacitors under high impact and high voltage discharge composite environment

Pulse power multilayer ceramic capacitors (pulse power-MLCC) are commonly used in complex composite environments with high overload and high voltage due to their large size and capacitance. In order to study the electromechanical coupling response characteristics of pulse power-MLCC in high-impact and high-voltage composite environments, a split Hopkinson pressure bar (SHPB) testing system was used to simulate high impact. The mechanical and electrical parameters of pulse power-MLCC were collected under high-impact and voltage environments, and the capacitance changes at different impact velocities were obtained. The stress wave transmission characteristics of pulse power-MLCC were studied by combining numerical simulation and theoretical analysis, and the structural deformation of ceramic dielectric under impact stress was analyzed. The relationship between the capacitance and DC bias of the capacitor was analyzed. A capacitance calculation model for pulse power-MLCC in an electromechanical coupling environment was established, revealing the electromechanical coupling mechanism of pulse power-MLCC.

Study on dynamic mechanical characteristics of specimens with cavity under prestressing conditions

Deep defect-bearing rock bodies are typically subjected to in-situ stresses and dynamic loading. This study investigates the failure characteristics of cavity specimens containing square holes and circular holes by employing different static-dynamic coupled loading experiments using a triaxial SHPB device that can facilitate static-dynamic coupled loading. Based on SHPB experiments, strain field analysis, and 3D laser scanning modelling techniques, this study comparatively analyses the effects of impact velocity and stress environment on the strength, stress–strain curve characteristics, dynamic damage process, and damage characteristics of square and circular hole specimens. The experiment proposes using elevation maps to characterise the damage characteristics of the specimen under impact loading. It ultimately relates the experimental results to field rockbursts and tunnel excavation, which has significant implications for guiding field practice to a certain extent. The experimental results showed that the stress environment under dynamic perturbation has a bidirectional effect (both favourable and unfavourable) on the strength of the specimens containing defects, which manifests as a difference in the characteristics of the stress–strain curves. When damage occurs near the cavity of the specimen, the stress–strain curve exhibits type I characteristics. When the entire specimen destabilises, the stress–strain curve shows type II characteristics. Under the same conditions, the strength of the specimens with square holes is significantly lower than those with circular holes. The 3D laser scanning results indicated that the damage is primarily concentrated near the cavity, and compared to the circular hole specimen, the damage area of the square hole specimen is mainly attributed to shear-tension damage, resulting in the collapse of the slabs on the upper and lower sides of the cavity.

Significance analysis of the attenuation coefficient of vibrations in a boron nitride–carbon nanotube under buckling and fracture: A molecular dynamics study

Boron nitride–carbon nanotubes (BN–CNTs), serving as nanomass sensors, exhibit fatigue characteristics, such as buckling or bond breakage, under impact from measured particles. However, the impact of such damage on the functionality of BN–CNTs remains unclear. Here, we use molecular dynamics simulations to investigate the performance of BN–CNTs mass sensors under impact by C60 particles, focusing on three critical states: buckling, bond breakage, and coexisting buckling and bond breakage. An analysis of the impact stress and mass responsivity shows that damaged beams have a lower mass detection capability than undamaged beams. The results of a paired t-test and an analysis of the decay coefficients and vibration frequencies of damaged nanobeams show that damaged nanobeams have a significantly lower quality factor than undamaged nanobeams. We use an energy equation to analyze the impact process of nanobeams for the first time, revealing that the change in the potential energy of the beam is a crucial influence factor of the beam critical state. This study provides insights into the damage to nanoscale mass sensors caused by impact.

Response of Native and Non-Native Subarctic Plant Species to Continuous Illumination by Natural and Artificial Light.

This study addressed the following questions: How does continuous lighting (CL) impact plant physiology, and photosynthetic and stress responses? Does the impact of CL depend on the source of the light and other environmental factors (natural vs. artificial)? Do responses to CL differ for native and non-native plant species in the subarctic region and, if differences exist, what physiological reasons might they be associated with them? Experiments were conducted with three plants native to the subarctic region (Geranium sylvaticum L., Geum rivale L., Potentilla erecta (L.) Raeusch.) and three non-native plant species (Geranium himalayense Klotzsch, Geum coccineum Sibth. and Sm., Potentilla atrosanguinea Loddiges ex D. Don) introduced in the Polar-Alpine Botanic Garden (KPABG, 67°38' N). The experimental groups included three species pairs exposed to (1) a natural 16 h photoperiod, (2) natural CL, (3) an artificial 16 h photoperiod and (4) artificial CL. In the natural environment, measurements of physiological and biochemical parameters were carried out at the peak of the polar day (at the end of June), when the plants were illuminated continuously, and in the second week of August, when the day length was about 16 h. Th experiments with artificial lighting were conducted in climate chambers where plants were exposed to 16 h or 24 h photoperiods for two weeks. Other parameters (light intensity, spectrum composition, temperature and air humidity) were held constant. The obtained results have shown that plants lack specific mechanisms of tolerance to CL. The protective responses are non-specific and induced by developing photo-oxidative stress. In climate chambers, under constant environmental conditions artificial CL causes leaf injuries due to oxidative stress, the main cause of which is circadian asynchrony. In nature, plants are not photodamaged during the polar day, as endogenous rhythms are maintained due to daily fluctuations of several environmental factors (light intensity, spectral distribution, temperature and air humidity). The obtained data show that among possible non-specific protective mechanisms, plants use flavonoids to neutralize the excess ROS generated under CL. In local subarctic plants, their photoprotective role is significantly higher than in non-native introduced plant species.

Hatha yoga reduces momentary stress but does not impact diurnal profiles of salivary cortisol and alpha-amylase: A randomized controlled trial

Does the practice of yoga impact stress? Various studies have suggested that yoga may reduce both self-reported stress and stress biomarkers, but the evidence for such claims remains inconclusive, especially for yoga styles with a focus on physical postures. In a randomized controlled trial with 98 participants, we therefore examined whether an eight-week Hatha yoga intervention (60 min, 3×/week or more) led to reduced levels of diurnal salivary cortisol (sCort), salivary alpha-amylase (sAA), and subjective momentary stress as compared to a waitlist control group. To ensure the concomitant assessment of self-report and biological measures in an ecologically valid setting, and to capture the diurnal profile of cortisol and alpha-amylase, we employed an ecological momentary assessment approach. Five times per day, participants reported their momentary stress levels on a visual analogue scale and collected saliva samples for the assessment of salivary biomarkers. The intervention led to a significant reduction of subjective momentary stress but there was no change in diurnal sCort or sAA levels. There are several potential explanations for these findings: The intervention may have helped participants to cope better with stress while leaving diurnal levels of stress biomarkers unaffected, or the change may at least not have been reflected in sCort and sAA. Alternatively, there may have been a self-report bias, insofar as a favorable disposition towards yoga may have led participants to report reductions in stress in order to indicate positive effects of the intervention. Our findings contribute to a better understanding of the effects of distinct yoga interventions, demonstrating their potential to serve as low-risk stress relief tools.

Captioning for Clarity: Mastering Stress with Word-Based vs. Phonetic Video Transcriptions

This study explores an understudied aspect of video captioning in language learning: the use of phonetic transcription. While extensive research has examined the effects of traditional word-based captioning, the potential benefits of phonetic transcription captions remain largely unexplored. To address this knowledge gap, a quasi-experimental study was conducted comparing two captioning conditions: traditional word-based captions and phonetic transcription captions. Two groups of English as a Foreign Language (EFL) learners were purposively selected based on their course enrollment, with participants volunteering for the study. The control group viewed videos with standard word captions, while the experimental group watched videos captioned with phonetic transcriptions. Pre- and post-tests were administered to assess improvements in word stress pronunciation. The results revealed no statistically significant difference between the post-test scores of the control and experimental groups. This suggests that both captioning methods - words and phonetic transcription - positively impact stress pronunciation learning. The findings indicate that enhanced stress pronunciation may contribute to overall language intelligibility and fluency, potentially leading to improved language learning outcomes. This study opens avenues for future research on the application of phonetic transcription in other areas of pronunciation, such as intonation and connected speech.

FSI investigation on the discharge valve lift in a R32 rotary compressor and its verification

R32 rotary compressor is commonly applied in the household air conditioner. The valve motion is significant to the performance and reliability of rotary compressor. Valve lift is an important factor which directly affects the valve motion. A suitable valve lift can both reduce power consumption and fracture risk of valve plate. Based on a compressor prototype, this paper developed a FSI model to simulate the working process of discharge valve. The simulation results show that a large valve lift means a large discharge effective flow area and a low indicated power. But both the velocity of valve plate impacting the retainer and the impact stress of valve plate are relatively large, which will lead to the fracture in the valve plate. The simulated initial impact location on the head of valve plate is near the oblique incision due to the uneven pressure distribution in the discharge port and the torsional movement of valve plate. The maximum impact stress distribution areas on the valve plate obtained from simulation results are matched with the fracture areas of two valve plate samples, which proves that the simulation results are accurate enough to guide the optimization design of discharge valve in the rotary compressor.

PROPIEDADES DINÁMICAS DE IMPACTO DE COMPUESTOS DE LODOS DE PAPEL DOPADOS CON OXICLORURO DE MAGNESIO

To address the heavy pollution caused by paper sludge, this study investigates a novel approach by incorporating paper sludge into magnesium oxychloride cement to develop a new type of concrete composite material. To achieve waste utilisation, cost savings and pollution reduction, the impact dynamics properties of the concrete specimens were conducted using an electromagnetically driven Hopkinson pressure bar, while a high-speed camera recorded the specimen destruction process, stress-strain curve, destruction morphology, deformation field, and evolution of energy consumption. Results show that as the paper sludge doping increases, the peak stress of the stress-strain curve and the energy consumption gradually increase. Increasing the voltage leads to a gradual rise in peak stress and energy consumption of the specimen. During the impact test, the transverse fissures gradually are developed in the test block, and as the impact stress increases, the fissures are widened until the specimen eventually being fractured. Moreover, the higher impact voltage and paper sludge content result in the increased specimen displacement and strain. It is expected that nearly 50% of paper sludge will be recycled every year by this method, which will save 10%-20% of raw materials. The conclusions obtained in this study provide a reference for the engineering application of the paper sludge concrete composites. Keywords: Paper sludge, Magnesium oxychloride, Digital image correlation, Energy consumption, Impact dynamic properties.

Response of a Coral Reef Sand Foundation Densified through the Dynamic Compaction Method

Dynamic compaction is a method of ground reinforcement that uses the huge impact energy of a free-falling hammer to compact the soil. This study presents a DC method for strengthening coral reef foundations in the reclamation area of remote sea islands. Pilot tests were performed to obtain the design parameters before official DC operation. The standard penetration test (SPT), shallow plate-load test (PLT), and deformation investigation were conducted in two improvement regions (A1 and A2) with varying tamping energies. During the deformation test, the depth of the tamping crater for the first two points’ tamping and the third full tamping was observed at two distinct sites. The allowable ground bearing capacity at two disparate field sites was at least 360 kPa. The reinforcement depths were 3.5 and 3.2 m in the A1 and A2 zones, respectively. The DC process was numerically analyzed by the two-dimensional particle flow code, PFC2D. It indicated that the reinforcement effect and effective reinforcement depth were consistent with the field data. The coral sand particles at the bottom of the crater were primarily broken down in the initial stage, and the particle-crushing zone gradually developed toward both sides of the crater. The force chain developed similarly at the three tamping energies (800, 1500, and 2000 kJ), and the impact stress wave propagated along the sand particles primarily in the vertical direction.

High-strength, impact-resistant PP/PTFE composite foam with enhanced surface appearance achieved through mold-opening microcellular injection molding

Poor surface appearance and decreased mechanical performance are critical factors limiting the broad application of Microcellular injection molding (MIM) in foamed polymer products. Herein, in-situ polytetrafluoroethylene (PTFE) nanofibrils reinforced polypropylene (PP) foams with high strength, impact resistance, and enhanced surface quality were prepared by mold opening microcellular injection molding (MOMIM). PTFE nanofibers with different diameters were introduced into the PP matrix via twin screw extrusion and significantly enhanced the crystallinity and viscoelasticity of the PP matrix with the enhancement being more pronounced for the finer PTFE fibers. High-density oriented cellular structures were formed in the MOMIM PP/PTFE foams owing to the heterogeneous nucleation of PTFE and the stretching effect of the mold opening process. The optimum MOMIM PP/PTFE foam fabricated possesses a high cell orientation angle close to 90° and a large cell aspect ratio of 5.3, which reached a 34.37 % increase in tensile strength and a 73.08 % increase in impact strength owing to the synergetic effects of the PTFE network and the highly oriented fine cell structure, which effectively dissipated the tensile stress and impact stress by cell wall twisting and folding deformation. Furthermore, the MOMIM PP/PTFE foam showed a significantly enhanced surface quality compared to the MIM foam due to the reduced dragging flow in MOMIM, which greatly hindered cell rupture on the foam surface. Therefore, this work provides insights into the MOMIM of polymer composites containing fibrous fillers and the enhancement of tensile properties, impact resistance, and surface quality of foam products.

Microstructural characteristics with process-microstructure-property relations during high-frequency ultrasonic vibration-assisted cutting of metallic material

Microstructural characteristics of chips and machined surfaces are influenced by the multiphysics fields distribution. This study investigates the multiphysics-induced microstructural deformation behaviors of CuZn37 metallic alloy during high-frequency ultrasonic vibration-assisted cutting (HFUVAC) and conventional cutting (CC). One the one hand, the multiphysics field distribution was established to clarify the chip formation of cutting characteristics and transient deformation process. The multiphysics field distribution of HFUVAC exhibited periodic changes due to tool intermittent movement, resulting in reduced cutting temperature and force. This intermittent movement also enhanced the sharpening shear effect due to instantaneous impact stress, transitioning from fragmented quasi-shear strain to continual multiple-shear strain during chip formation. One the other hand, the microstructural changes were examined to explain material removal mechanisms. The microstructure of CC demonstrated grain refinement and dislocation slip induced by friction and significant shear deformation. The microstructure of HFUVAC revealed the formations of dynamic recrystallization, twinning structures, and stacking faults, which were associated with enhanced plastic activity and limited slipping due to high-frequency impacts. The work reveals the response of the workpiece microstructure under the composite effects of high-frequency impacts and cutting process, which provides theoretical basis for the microstructure modification design through cutting technology.

Impact resistance of polyurethane elastomer enhanced by organic montmorillonite with interlayer anchored polymer chains

AbstractThe development of materials with excellent impact resistance is essential for safety protection. Polyurethane elastomer (PUE) is widely used in impact protection; however, it has low dynamic compressive strength and poor energy absorption efficiency under high‐speed impact, limiting its in‐depth application in the protection field. Herein, an organic montmorillonite (MMT) with interlayer anchored polymer chains, named M@NH3+, was synthesized via the dual modification of MMT involving surface grafting and cation intercalation by macromolecular amino silane, which was used to enhance the impact resistance of PUE. Based on the uniform dispersion of M@NH3+ within the PUE matrix, the strong bonding at the polymer‐filler interface and the synergistic action between M@NH3+ lamellae, PUE‐M@NH3+ composite exhibited excellent mechanical properties and energy absorption capacity. Compared with pure PUE, the elastic modulus (+98.3%), static compressive strength (+37.0%), dynamic compressive strength (+35.4%) and impact energy absorption (+50.8%) of PUE‐2wt%M@NH3+ were significantly improved, which shows that it has potential applications in the field of high‐speed impact protection.Highlights Organic MMT with interlayer anchored polymer chains was prepared. The large interlayer spacing of M@NH3+ facilitates its dispersion within the matrix. The interconnected M@NH3+ lamellae can collaboratively disperse impact stress. The impact energy absorption of PUE composite has been remarkably improved.