Strain Field Research Articles

Mechanical Properties and Martensitic Transformation Behavior of 316LN Stainless Steel Under Cryogenic Deformation

Digital image correlation (DIC) technology can capture strain anomalies and predict crack initiation providing early warning of material failure. Herein, DIC technique is used to calculate the full‐field strain by analyzing the grayscale patterns of speckle images during the tensile process. This allowed for an analysis of the microstructure evolution of the 316LN austenitic stainless steel (SS) at cryogenic temperatures. Deformation behavior of the 316LN SS at cryogenic temperatures is further analyzed using electron backscatter diffraction technology and transmission electron microscopy. Based on the strain field obtained by the DIC technique, a comprehensive analysis of the martensite volume fraction at different strains can be conducted. The results show that the strain localization under cryogenic deformation is related to martensitic transformation, while the random distribution of slip bands aligns with local strain peak values. Notably, fracture under cryogenic deformation occurs in regions where the strain field reaches its peak, rather than at locations with the maximum strain value.

Application of Video Abnormal Behavior Detection Algorithm in Evaluation of Track and Field Teaching and Training Effect

With the development of track and field, people pay more and more attention to the quality of classroom teaching of track and field technology, and the evaluation of teaching quality plays a key role in it. In today's educational reform, teaching evaluation plays an important role as an important method to test teachers' teaching and students' learning. With the rapid development of machine learning, especially deep learning, image-based individual abnormal behavior detection technology is becoming more and more mature, but there are still many difficulties to be solved in video-based group abnormal behavior detection technology. Therefore, it is necessary to study the detection algorithm. Based on machine vision theory, image processing theory and video analysis technology, this paper studies three key technologies involved in human abnormal behavior detection in video: moving target detection, moving target tracking and abnormal behavior detection.

Fatigue and delamination of 6061 aluminum cold spray on a similar wrought substrate

Fatigue crack growth and fracture of a thick 6061 aluminum cold spray coating on 6061-T6 aluminum substrate were studied through in-situ observation of fatigue crack growth through the coating to the interface in notched four-point bend samples. Mode I cracking was observed through the coating before delamination at the substrate. Crack tip strain fields during the delamination event were plotted with DIC. Interfacial steady-state strain energy release rates were measured using the bimaterial four-point bend solutions by Charalambides. The interfacial crack primarily spread cleanly along the coating/substrate interface, with a post-fracture surface morphology containing a wavy structure with an amplitude on the same order of magnitude as the cold spray particle diameters. The in-situ video of crack propagation and coating-substrate delamination provides lessons for improving the coating-substrate interfacial toughness and thus expands use cases for structural cold spray applications

Effects of aggregate's type and orientation on stress concentration and crack propagation of modeled concrete applied a shear force

This study focused on planarizing natural modeled aggregate concrete (NMC), recycled modeled aggregate concrete (RMC), and brick modeled aggregate concrete (BMC) for analyzing the influences of aggregates on shearing failure mechanism. A designed apparatus was used to load a shear force for the specimens and analyzed the global and local strain fields near the interface transition zone (ITZ) using digital image correlation (DIC) analysis. Additionally, we employed COMSOL software simulation to understand the crack initiation process and damage evolution mechanism of related concrete. Our findings revealed that the brick aggregate leaded to the lowest modulus of elasticity and compressive strength, resulting in poor shear resistance. However, the recycled aggregate model exhibited the highest shear resistance, primarily due to the old mortar acting as a buffer layer in the ITZ. During loading, the stress in the NMC model concentrated in the load transfer zone and gradually moved to the left and right sides of the built-in aggregate model until fracture, as observed through DIC analysis. The stress distribution of the RMC was similar with those of the NMC, but the BMC showed a distinct stress distribution pattern. Furthermore, the corner of the built-in modeled aggregate significantly influenced the crack propagating path and stress distribution. Therefore, the modeled aggregate corner plays a crucial role in the shear behavior of concrete, affecting both crack propagation and overall mechanical performance. The practical implications of our study can inform the design and application of recycled concrete.

Fracture behavior and mechanical properties of engineered cementitious composites exposed to long-term sulfate and chloride environments

The fracture properties of engineered cementitious composites (ECC) exposed to dry-wet cycles in sulfate and sulfate-chloride solutions were studied by three-point bending (TPB) beams at the corrosion periods of 0, 30, 90, 130, 180, 270, and 360 days. The digital image correlation (DIC) technique was used to understand the whole fracture process. The fracture toughness and fracture energy were calculated using the proposed method, and the evolution of the horizontal strain field, displacement field, and fracture process zone (FPZ) were investigated. Meanwhile, the compressive and tensile performance of the specimens at the same corrosion periods were analyzed. The results showed that (1) Compared to water immersion, the environments of sulfate and sulfate-chloride were beneficial in improving the compressive and tensile strength, and weakening the tensile ductility. (2) With increasing the corrosion time, the evolution of the unstable fracture toughness can be distinguished into three phases: a stable phase, an increasing phase, and a rapidly decreasing phase, and the initial fracture toughness followed an increasing and then decreasing trend. The fracture energy initially decreased and tended to stabilize after 130 days. (3) By using DIC technology, as the corrosion time increased, the horizontal opening displacement at the notch tip showed a decreasing trend and stabilized after 90 days generally. The fracture path determined through horizontal displacement was well matched with the macrocrack trajectory. (4) The addition of chloride ions helped to improve the mechanical properties of ECC under long-term corrosion, such as compressive strength, unstable fracture toughness, fracture energy, and opening displacement at the notch tip. Compare to concrete, ECC exhibited greater resistance to sulfate corrosion.

Random fields-triggered strain enhancement in BNT-based materials

Bi0.5Na0.5TiO3 is regarded a potential alternative to lead-based piezoelectric materials due to its large electro-strain. Generally, the improved electro-strain is considered to arise from a relaxor-ferroelectric transition, and the random fields play a critical role. In this study, to investigate the effect of random electric field or strain field on the strain value, the dopant Sb5+, Ta5+, Zr4+, and Hf4+ are introduced into the Bi0.5(Na0.8K0.2)0.5Ti1-xBxO3 matrix, respectively. The 1 % Ta5+ doped sample has the largest unipolar electro-strain, up to 0.49 %, followed by the 3 % Zr4+ doped sample (∼0.448 %). The electro-strain of 1 % Sb5+ and 3 % Hf4+ samples are 0.404 % and 0.377 %, respectively. The results show the random electric field or strain field can effectively regulate the relaxor-ferroelectric transition temperature, which enhances strain, but the strain value cannot be determined directly. The strain value is determined by the lattice structure before and after the electric field is applied.

Crack coalescence prediction and load-bearing mechanism of defective specimen based on computer vision recognition model

The coalescence of cracks in rock, triggered by external stress or geological activities, plays a pivotal role in determining the mechanical properties and stability of rock structures. Consequently, the prediction method of crack coalescence become critical tools in ensuring the safety and stability of geotechnical engineering facilities. In this paper, based on the strain field data obtained by digital image correlation (DIC), a set of programs was developed to automatically identify the values and percentage changes of different strain intervals in the strain field of the specimen. Then, a computer vision recognition (CVR) model is established to study the process and prediction of crack coalescence in sandstone specimens with open flaws. This method overcomes the limitations, subjectivity and unpredictability of the traditional method of identifying cracks through artificial vision. The results show that the increase of the flaw width causes the displacement trend to be squeezed and deflected along the width direction, thereby changing the angle of crack initiation and exhibiting different forms of crack coalescence. The increase in the inclination angle of the flaw leads to an increase in the effective compressive area (ECA) of sandstone, and the magnitude of ECA is positively correlated with the uniaxial compressive strength (UCS) of the sandstone. Additionally, the CVR model identifies two types of numerical fluctuation signals before crack coalescence, namely the plastic characteristic signal (PCS) in the early stage of the experiment and the early-warning signal (EWS) near the period of crack coalescence, where EWS can be used as a predictive signal for crack coalescence. The research results provide a new algorithm technical support for the process analysis and prediction of crack coalescence, and provide a basis for early warning of rock mass engineering disasters.

Dynamic impact mechanical properties of red sandstone based on digital image correlation method

ABSTRACT In the process of underground blasting excavation, the safety and stability of rock mass are significantly influenced by dynamic load. To study the full-field strain and displacement behaviour of rock materials subjected to dynamic compressive force, the impact tests were done on red sandstone specimens using an electromagnetically driven Hopkinson pressure bar. At the same time, the data were collected by a high-speed camera, and non-contact measurements of the red sandstone were carried out with the digital image correlation method. The resulting images were screened and analysed, based on which the stress-strain curve, full-field strain cloud diagram and displacement cloud diagram were obtained. Results show that the dynamic peak stress increases with the increase of impact velocity. During the impact process, substantial internal uneven deformation occurs in the red sandstone close to the transmission bar’s end face. Under the impact load, the cracks initiate from the upper and lower sides near the transmission bar’s end face, followed by formation of cracks in the middle part. These cracks expand throughout the rock to form through-cracks, eventually resulting in complete failure. For rock materials, the evolution of their strain field during the failure process can reflect the initiation and propagation of their internal cracks. Therefore, the use of digital image correlation method proves effective for studying the deformation and failure mechanisms of rock. The conclusions obtained in this study provide a valuable reference for the macro-meso deformation and failure mechanisms of geotechnical materials.

A feasibility evaluation of a peer support intervention for social participation in China

PurposeThis study aims to report on the feasibility, acceptability and outcomes of a peer support program designed to promote social participation for adults with serious mental illness (SMI) in China.Design/methodology/approachThe authors used a community-based participatory research approach to adapt and test a six-month, culturally responsive peer program with 68 participants. Peer supporters were trained and supervised in Guangzhou, China. Peer workers were hired via a competitive process and completed both classroom and field training. Study participants were offered individual and group socialization activities. Participants completed measures on recovery, quality of life, functioning and symptoms at three time points (pre-, post- and follow-up).FindingsNearly 90% of participants expressed satisfaction with their peer supporters and the frequency of services. Findings showed a significant increasing trend for the social relationships domain of quality of life from baseline to follow-up. Female participants reported significantly increased recovery from pre to post and increased psychological quality of life pre-follow-up as compared to their male counterparts. Supervision logs documented positive gains from participants such as increased help-seeking, improved social skills, enhanced emotion regulation and self-confidence and established routine, alongside challenges like inconsistent engagement, low service incentives and an overreliance on social workers. Peer supporters also reported concerns about their own lack of skills and in navigating relationships between participants and their family members.Originality/valuePeer interventions have been well studied in Western countries but underexplored in China. This research addresses this gap by presenting a peer program aimed at enhancing the social participation of Chinese with SMI.

Strain Field Development, Fracturing, and Gas Ejection in Decoupled Charge Blasting Using Granite Cylinders

This study explored the fracture process of granite cylinders with a centric charge, varying decoupling ratios by conducting laboratory-scale experiments and numerical simulations. In experiments, the three-dimensional (3D) digital image correlation (DIC) technique was employed, using frames captured by two synchronized high-speed cameras. This instrumentation permitted the observation of full-field strain variation, the development of fractures, and gaseous products escaping from the cylinders’ surfaces. Granite cylinders measuring 240 mm in diameter and 300 mm in length served as specimens in blasting experiments, and each specimen had a charge of approximately 3 g. Specimens had a centric blasthole with a diameter of either 10 mm, 14 mm, or 20 mm. The corresponding decoupling ratio varied from 1.8 to 3.6, and the gap between the charge and the blasthole wall was filled with water or air. The experimental results showed that: (1) specimens with decoupling ratios of 1.9 and 2.6 exhibited initial strains on the cylindrical surface between 20 μs and 40 μs. (2) Specimens with water-filled blastholes developed fractures faster and in a denser manner compared to those with air-filled blastholes. In addition, fractures resulting from air-filled blastholes appeared smoother than those from water-filled blastholes. (3) The gas ejection time for the air-filled blasthole remained basically consistent across decoupling ratios ranging from 1.5 to 3.61, varying between 400 μs and 520 μs. The utilization of water-filled blastholes effectively minimized the escape of gaseous products from the cylindrical surface. Numerical simulation conducted with LS-DYNA exhibited results that aligned well with the observed fracture patterns in the experiments. This study aims to provide a better understanding of the fundamental mechanisms of rock behaviors in decoupled charge blasting.

Tunable Band Alignment and Optoelectronic Structure of Cu2Se/PtX2 (X=Se,Te) Heterostructures: under Strain and Electric Field

Two-dimensional (2D) material-based van der Waals heterostructures (vdWHs) are an emerging strategy for regulating the electronic properties of two-dimensional materials. This study investigated the effects of a vertical electric field and strain on the band alignment transition and optoelectronic properties of Cu2Se/PtSe2 (PtTe2) vdWHs using density functional theory calculations. Cu2Se/PtSe2 vdWHs exhibited type-I to type-II band alignment transformation under an in-plane strain, interlayer distance, and electric field of 2%, 2.40 Å, and -0.40 V/Å, respectively. Moreover, Cu2Se/PtTe2 vdWH demonstrated a rich transition of types I, II, and III band alignments with in-plane strain. The absorption spectra of Cu2Se/PtSe2 (PtTe2) vdWHs show a certain degree of blue and red shift phenomenon upon the application of strain and electric fields. The predicted power conversion efficiencies at 3% in-plane strain with an interlayer distance of 3.40 Å for Cu2Se/PtSe2 (PtTe2) vdWHs were observed to be as high as 22.58% (19.80%). Thus, our work demonstrated that both strain and electric field can effectively and flexibly control the electronic properties of Cu2Se/PtSe2 (PtTe2) vdWHs, making them a promising candidate material for applications in photodetectors and field-effect transistors.

Quantitative method for measuring the proportion of bacterial cells expressing phase 1 or 2 of flagellin of Salmonella enterica serovar Typhimurium

Salmonella enterica subsp. enterica is a major pathogen that causes zoonotic foodborne diseases worldwide. Some Salmonella serovars possess two antigenic phases for flagellin: phase 1 and 2. In Salmonella enterica serovar Typhimurium (S. Typhimurium), the flagellin is antigenically divided into “Hi” as phase 1 and “H1 or H2” as phase 2. Flagellin phase variation is regulated by inversion of hin gene. We focused on the inversion of hin and developed a real-time PCR system to quantitatively measure the proportion of bacterial cells expressing each phase of flagellin. In this study, we demonstrated that our newly developed real-time PCR system shows high quantitative accuracy and aligns with flagellin expression status. Furthermore, the newly developed real-time PCR system was applicable to various S. Typhimurium laboratory and field strains. This newly developed real-time PCR system has the potential to become a powerful tool for analyzing flagellin phase variation.

Ultra-high electron mobility in Sn-doped two-dimensional Ga2O3 modified by biaxial strain and electric field

2D Ga2O3 exhibits overwhelming advantages over its bulk counterpart, whereas manipulating the carriers is rare. We report strain-dependent electronic structures and transport properties of Sn-doped 2D Ga2O3 using first-principles calculations with deformation potential theory. The band gaps are tunable from 2.23 eV to 1.20 eV due to the strain-mediated σ* anti-bonding and π bonding state variations. Specifically, ultra-high electron mobility of 22579.32 cm2V−1s−1 is predicated under 8% tensile. Further electric field modulations suggest the retaining of band gap and effective mass. These results highlight its property manipulations and nanoscale electronic applications.

Survival of Twelve Pathogenic and Generic Escherichia coli Strains in Agricultural Soils as Influenced by Strain, Soil Type, Irrigation Regimen, and Soil Amendment

Biological soil amendments of animal origin (BSAAO) play an important role in agriculture but can introduce pathogens into soils. Pathogen survival in soil is widely studied, but data are needed on the impacts of strain variability and field management practices. This study monitored the population of 12 Escherichia coli strains (generic, O157, and non-O157) in soils while evaluating the interactions of soil type, irrigation regimen, and soil amendment in three independent, greenhouse-based, randomized complete block design trials. Each E. coli strain (4–5 log10 CFU/g) was homogenized in bovine manure amended or nonamended sandy-loam or clay-loam soil. E. coli was enumerated in 25 g samples on 0, 0.167 (4 h), 1, 2, 4, 7, 10, 14, 21, 28, 56, 84, 112, 168, 210, 252, and 336 days postinoculation (dpi). Regression analyses were developed to understand the impact of strain, soil type, irrigation regimen, and soil amendment on inactivation rates. E. coli survived for 112 to 336 dpi depending on the treatment combination. Pathogenic and generic E. coli survived 46 days [95% Confidence interval (CI) = 20.85, 64.72; p = 0.001] longer in soils irrigated weekly compared to daily and 146 days (CI = 114.50, 184.50; p < 0.001) longer in amended soils compared to unamended soils. Pathogenic E. coli strains were nondetectable 69 days (CI = 39.58, 98.66, p = 0.015) earlier than generic E. coli strains. E. coli inactivation rates demonstrated a tri-phasic pattern, with breakpoints at 26 dpi (CI = 22.3, 29.2) and 130 dpi (CI = 121.0, 138.1). The study findings demonstrate that using bovine manure as BSAAO in soil enhances E. coli survival, regardless of strain, and adequate food safety practices are needed to reduce the risk of crop contamination. The findings of this study contribute data on E. coli concentrations in amended soils to assist stakeholders and regulators in making risk-based decisions on time intervals between the application of BSAAO and the production and harvest of fruits and vegetables.

Explicit phase-field material point method for thermally induced fractures

Thermally induced fractures in solids pose significant challenges in various fields, such as aerospace, deep underground, and civil engineering structures. Numerical methods are effective for addressing such problems, with recent advancements in phase-field and material point methods demonstrating notable advantages in crack simulation. This paper presents a computational approach within an explicit material point method framework for coupling the solutions of temperature, displacement, and phase (damage) fields. The displacement and phase fields are intricately linked through a history-dependent strain field and degradation function. The model incorporates temperature-induced strains from temperature gradients for coupling the temperature and displacement fields. In addition, the model accounts for the detrimental effects of cracks on heat conduction, ensuring a comprehensive representation of the coupled system. Two numerical examples involving thermomechanical coupling and dynamic crack branching were used to validate the effectiveness of the proposed method. Finally, the proposed method was applied to simulate the thermal shock and large deformations of thin circular ceramic specimens, successfully replicating the initiation and propagation of cracks observed during the experiment. The simulated thermally induced fractures exhibited periodic and hierarchical characteristics consistent with the experimental findings.

Synergistic improvement of the compression-after-impact performance of composite laminates by multi-scale CNF/Z-pin reinforcement

This paper investigated the effects of carbon nanofibers (CNF), Z-pin, and multi-scale CNF/Z-pin on the compression-after-impact (CAI) properties and damage morphology of laminates after 10 J, 30 J, and 50 J impact. The deformation and strain field variations of the laminate during the CAI process were clearly characterized by 3D-Digital Image Correlation (DIC). The process from local buckling to the global failure of the laminate was clearly revealed. The mechanical response results showed that the CAI strength of unreinforced, CNF, Z-pin and CNF/Z-pin-reinforced laminates increased in order after impact with the same energy. After 50 J impact, the CAI strength of CNF, Z-pin and CNF/Z-pin-reinforced laminates was increased by 18.6 %, 28.7 % and 36.4 %, respectively, compared to unreinforced laminates. By constructing a simulation model to analyze damage and mechanical response, the model's effectiveness was verified. Additionally, the damage morphology, damage mechanism, and synergistic toughening mechanism between CNF and Z-pin in CAI specimens were revealed from optical photographs and scanning electron microscopy (SEM).

A rescued virus from the infectious clone of a PRRSV NADC34-like strain exhibits high pathogenicity for nursery pigs1

NADC34-like porcine reproductive and respiratory syndrome virus (PRRSV) has been circulating in China for several years and became the dominant field strain in some provinces. Current commercial vaccines could not provide complete cross-protection to NADC34-like PRRSV infection, which led to huge economic losses on pig farms. Co-infections of NADC34-like PRRSV with some other PRRSV strains are commonly found in many clinical cases, and successful isolation of NADC34-like PRRSV strain from the clinical samples has been a challenge to study its biological characters and perform animal experiments to evaluate its pathogenicity. In this study, we constructed a NADC34-like PRRSV infectious clone derived from the isolated JS2021NADC34 PRRSV strain using the reverse genetics technique and investigated its virulence and pathogenicity for nursery pigs. The rescued (rNADC34) strain could proliferate well in porcine alveolar macrophages (PAMs), and the viral copy number and titers were comparable to parental strain. For pathogenicity, the rNADC34 strain-infected pigs showed high body temperature and body weight loss. The histopathological results presented interstitial pneumonia and severe hemorrhage, infiltration of neutrophils and lymphocyte in lungs, lymph nodes, and tonsils. The viral proteins were also detectable in rNADC34 strain-infected pigs using immunohistochemistry staining. Moreover, the trends of PRRSV-specific antibody and viremia in PRRSV rNADC34-infected pigs were similar with the parental strain-infected pigs. These data indicated that rNADC34 strain manifested strong virulence and high pathogenicity for nursery pigs.

Applying of Object ID Stander on the Carpets Collection at the Museum of Islamic Art, Cairo

This research is the first archaeological study that applies standard of Object ID as a principle of museum collection management, that will be on Islamic carpets collection at the Museum of Islamic Art in Cairo as a case study. This paper is a practical field study, which includes in its aspects field training, workshops, lectures, and automatic and manual examination of carpets as a case study, according to the organizational work and the principles available and followed by the museum.

Compression–compression fatigue damage of wrinkled carbon/glass hybrid composite laminates

Compression–compression fatigue tests were carried out to study the compressive fatigue damage mechanisms of a carbon/glass hybrid composite laminate with a manufacturing-induced wrinkle defect. As reported in literature, thin wrinkled composite laminates could show sensibly different fatigue behaviours and damage mechanisms in the presence of tension and compression cyclic loadings. The sensitivities of composites to tension and compression cyclic loadings were not the same. In this study, the damage modes and cracking sequence of a thick wrinkled laminate were identified by the strain fields from digital image correlation (DIC). Acoustic emission (AE) and infrared (IR) thermography were used to detect the damages and explore the potential capabilities of non-destructive evaluation methods when applied to detection of fatigue induced damages in composite structures under operational cyclic loadings. Two primary damage modes were identified and detected before the final failure of the laminate i.e. debonding between the resin-rich layer and the laminate and interlaminar cracks. Debonding occurred earlier than interlaminar cracking. Out-of-plane stresses due to fibre waviness drove the initiation of these damages. Under the settings of AE in this work, AE captured early debonding activities but did not detect the micro damage accumulating before the formation of interlaminar crack. Interlaminar crack initiation was tracked by IR thermography at cross-section of the specimen based on the distinct temperature localisations that occur with this micro damage. No distinct temperature localisations occurred during the formation of debonding as it is mode-I driving under compression–compression cyclic loading, so IR thermography did not detect the debonding crack. The results of this study show the potential of using complementary non-destructive damage evaluation methods to inspect early damages in composite structures. The early detection of damages would give early warning signs before the damages become critical. It is found that AE and IR thermography should be used as complementary tools to detect different damage modes.

Application Analysis of Artificial Intelligence Virtual Reality Technology in Fitness Training Teaching

The application of artificial intelligence virtual reality (VR) technology in fitness teaching and training is becoming increasingly widespread, and its significant advantages provide athletes with a more personalized, efficient and safe training experience. By simulating various fitness scenes, virtual reality technology enables athletes to train immersively, not only improving the fun of training, but also enhancing the training effect. At the same time, the introduction of artificial intelligence technology enables real-time monitoring and analysis of athlete performance during the training process, providing accurate data support for coaches and helping them develop more scientific training plans. This paper explores the application of virtual reality technology in physical education teaching and training, introduces the basic principles and characteristics of virtual reality and proposes several typical virtual reality application scenarios for the needs of physical education teaching and training. In football training, through virtual reality technology, athletes can conduct various technical and tactical exercises in simulated stadiums. At the same time, artificial intelligence systems can analyze the actions and decisions of athletes in real time, and provide feedback and suggestions. In track and field training, virtual reality technology can help athletes simulate competition scenes and improve their psychological adaptability during competitions. Through in-depth research, we have found that this technology provides athletes with a more personalized, efficient, and safe training experience. In football training, virtual reality technology can simulate real game scenes, allowing athletes to engage in various technical and tactical exercises in simulated sports stadiums. At the same time, artificial intelligence systems can analyze the actions and decisions of athletes in real time, provide accurate data support for coaches, and help them develop more targeted training plans.