Dynamic Strain Research Articles

Study on high temperature dynamic characteristics and mesoscopic simulation of HFRC under dynamic and static combined loading

The Φ50mm SHPB system was used to carry out three-dimensional dynamic and static combined loading tests on hybrid fiber reinforced concrete (HFRC) treated at different temperatures (25 °C, 200 °C, 400 °C) under different confining pressure ratios (0, 0.1, 0.2, 0.3). The temperature effect, confining pressure effect and failure characteristics of HFRC under impact load were studied. The effect of fiber was equivalently treated in mortar, and the meso-aggregate model of HFRC considering aggregate, mortar and interfacial transition zone (ITZ) was established. The simulation results were compared with the experimental results. The results showed that the higher the confining pressure ratio, the more significant the temperature effect of peak stress is. The higher the temperature is, the less obvious the enhancement effect of confining pressure on peak stress is. Compared with the influence of confining pressure on dynamic peak strain, the influence of temperature effect on dynamic peak strain is higher. The established three-dimensional meso-aggregate model and calculation method can accurately reflect the dynamic response characteristics of HFRC at different temperatures and confining pressure ratios. Prestress will affect the internal stress distribution of the specimen, thus affecting the compression failure characteristics of the specimen. The confining pressure can constrain the damage course of the specimen and has a good protective effect on the specimen.

High-efficiency CO2 conversion via mechano-driven dynamic strain engineering of ZnO nanostructures

Strain engineering involves intentionally inducing lattice distortion in materials to manipulate their electronic and geometric properties, along with the accompanying bond strength between reactants and catalysts. This approach presents an appealing pathway to optimize catalytic performance. However, it confronts challenges in achieving precise control, scalability and controllable modulation of intermediate species’ adsorption and desorption. Herein, we report a dynamic strain engineering method achieved through ultrasonic cavitation-induced high and low-pressure cycles, enabling periodically adjustable adsorption/desorption properties while bypassing complex synthesis procedures. Illustrated using ZnO and CO2 piezo-reduction reaction as a demonstration, theoretical studies initially predict that adsorption of intermediates *COOH can be regulated within a specific range of strains. Under ultrasonic stimulation, ZnO catalyst with dynamic strain engineering exhibits a CO yield of ∼ 98.8 μmol·g−1·h−1, approximately 16.5 times higher than that achieved under ultraviolet light irradiation without dynamic strain engineering, despite the latter having a considerably stronger input power. Furthermore, we delve into the factors linked to dynamic strain amplitude and frequency. This dynamic strain engineering approach streamlines catalyst preparation and presents innovative possibilities for controlled manipulation of intermediate specie’s adsorption/desorption, with potential applications across a wide range of catalytic systems.

Effect of severe plastic deformation on the structure and properties of the Zn–1%Li– 2%Mg alloy

Through the optimization of processing parameters, including pressure, temperature, and deformation degree, a high pressure torsion (HPT) regime was identified. This regime allows for the creation of a unique microstructure in the biodegradable Zn–1%Li–2%Mg alloy, which exhibits exceptional physical and mechanical properties. Following 10 revolutions of HPT treatment (resulting in an accumulated deformation degree, γ = 571) at the temperature of 150 °C and an applied pressure of 6 GPa, the Zn–1%Li–2%Mg alloy displayed notable mechanical characteristics, including a high yield strength (~385 MPa), ultimate tensile strength (~490 MPa), and ductility (44 %) during tensile tests. To elucidate the underlying reasons for these remarkable mechanical properties, an examination of the alloy’s microstructure was conducted employing electron microscopy and X-ray phase analysis (XPA). The study revealed the formation of a distinct microstructure characterized by alternating bands of the α-phase Zn, a mixture of Zn and ~LiZn3 phases, as well as the α-phase Zn containing Mg2Zn11 particles, as a consequence of HPT treatment. Additionally, it was observed that HPT treatment induced a dynamic strain aging process, leading to the precipitation of Zn particles in the LiZn3 phase and the precipitation of Mg2Zn11 and β-LiZn4 particles in the Zn phase. These precipitated particles exhibited a nearly spherical shape. The application of the XPA method helped to confirm that the Zn phase becomes the predominant phase during HPT treatment, and microscopy data showed the formation of an ultra-fine grained (UFG) structure within this phase. A comprehensive analysis of the hardening mechanisms, based on the newly acquired microstructural insights, revealed that enhanced strength and ductility of the Zn–1%Li–2%Mg UFG alloy can be attributed primarily to the effects of dispersion, grain boundary, and heterodeformation-induced hardening, including dislocation strengthening.

Influence of Prior Fatigue Damage on Tensile Flow Behaviour of Type 316L(N) Austenitic Stainless Steel

The present study aims to understand the influence of prior fatigue loading on the tensile flow behaviour of austenitic 316L(N) stainless steel. The steel specimens were subjected to prior fatigue damage up to various fatigue life fractions. i.e., 5, 10, 30 and 50% of the fatigue life at a strain amplitude of ±0.6% and a nominal strain rate of 3×10-3 s-1 and 300, 823 and 873 K. Subsequently the specimens were subjected to tensile deformation at the above temperature and strain rate and the tensile flow behaviour was evaluated in terms of Hollomon, Swift, Ludwigson and Voce equations. At 300 K, the flow curves of the specimens of as-received, and prior fatigue damaged were well described by the Ludwigson equation, whereas at 823 and 873 K, both Voce and Ludwigson equation could be used to describe the flow behaviour of the specimens. Increase of work hardening with the increase in prior fatigue damage at 823 and 873 K is attributed to the occurrence of dynamic strain ageing (DSA). At 300 K, a three-stage work hardening behaviour with a prominent stage II athermal hardening was observed for all the specimens, whereas at higher temperatures, only the as-received specimen exhibited the three-stage work hardening behaviour. At 823 and 873 K, a two-stage work hardening behaviour, comprising of a transient stage followed by stage III was observed for the specimens subjected to prior fatigue damage up to various fatigue life fractions. The inter relationship between the work hardening parameters of Ludwigson was rationalised in terms of the linearly inverse relationship between the work hardening rate and plastic strain rates.

Planar shock compression of spark plasma sintered B4C and B4C–TiB2 ceramic composites

Blending of ceramic constituent phases enhances sinterability and performance in high strength ceramics. Here, a near fully dense blended boron carbide (B4C)–titanium diboride (TiB2) composite produced through spark plasma sintering (SPS) is probed to understand the mechanical performance under dynamic uniaxial strain, or shock compression. This study on the shock performance of blended B4C–TiB2 measures the effect of initial TiB2 powder size on the dynamic response of the composite and compares results to those of monolithic SPS B4C. These shock experiments reveal a strengthening of the Hugoniot elastic limit (HEL) with an addition of TiB2 and mitigation of the adverse post-HEL response observed in many brittle ceramics, such as monolithic B4C. The TiB2 particle size in the composite does not noticeably influence these results. The tough nature of TiB2 along with compressive residual stresses in the B4C matrix resulting from high temperature processing and a mismatch of the thermal expansion coefficients of the constituent phases are postulated to strengthen the B4C.

High-Frequency Optical Coherence Elastography for Gingival Tissue Characterization: Variability in Stiffness and Response to Physiological Conditions.

Accurate measurement of gingiva's biomechanical properties invivo has been an active field of research but remained an unmet challenge. Currently, there are no noninvasive tools that can accurately quantify tensile and shear moduli, which govern gingival health, with sufficiently high accuracy. This study presents the application of high-frequency optical coherence elastography (OCE) for characterizing gingival tissue in both porcine models and human subjects. Dynamic mechanical analysis, histology studies, and strain analysis are performed to support the OCE result. Our findings demonstrate substantial differences in tissue stiffness between supra-dental and inter-dental gingiva, validated by dynamic mechanical analysis and OCE. We confirmed the viscoelastic, nearly linear, and transverse-isotropic properties of gingiva insitu, establishing the reliability of OCE measurements. Further, we investigated the effects of tissue hydration, collagen degradation, and dehydration on gingival stiffness. These conditions showed a decrease and increase in stiffness, respectively. While preliminary, our study suggests OCE's potential in periodontal diagnosis and oral tissue engineering, offering real-time, millimeter-scale resolution assessments of tissue stiffness, crucial for clinical applications and biomaterial optimization in reconstructive surgeries.

YOLO-v7 Improved with Adan Optimizer: Realizing Orphaned Fiber Bragg Grating to Sense Superimposed Personalized Dynamic Strain

YOLO-v7 Improved with Adan Optimizer: Realizing Orphaned Fiber Bragg Grating to Sense Superimposed Personalized Dynamic Strain

Dynamic strain gradient brittle fracture propagation: comparison with experimental evidence

<p>This paper presented a physico-mathematical model for dynamic fracture propagation in brittle materials with a purely continuum mechanics hemi-variational-based strain gradient theory. As for the quasi-static case, the simulation results, obtained by means of finite elements, revealed that strain gradient effects significantly affected the fracture propagation, leading to finite fracture thickness that was independent of the mesh size. It was also observed that nonsymmetric loading rate lead to a deviation from standard mode-Ⅰ crack propagation that cannot be revealed in the quasi-static case. The model results were compared against experimental data from fracture tests on notched specimens taken from the literature. The comparison showed good agreement between the model predictions and the experimental measurements. The presented model and simulation results can be useful in the design and optimization of structural components subjected to dynamic loading conditions.</p>

Angiography-Based Computational Modeling for In Vivo Assessment of Endothelial Dynamic Strain in Coronary Arteries with De Novo Lesions: Comparison of Treatment Effects of Drug-Coated Balloons Between Small and Large Arteries

Acute morphological changes in de novo coronary lesions after drug-coated balloon (DCB) angioplasty can affect endothelial mechanics and consequently clinical outcomes. Angiography-based computational modeling has been validated to assess endothelial dynamic strain (EDS) in coronary arteries in vivo. The EDS was calculated on the basis of pre- and post-DCB angiography. Parameters of quantitative coronary angiography and EDS were quantified at cross-sections in the treated segments. A total of 336 and 348 lesion cross-sections were included in the small/large vessel groups, respectively. The acute lumen gain after DCB was significantly higher in large than small vessels (relative changes: 21.3% [17.4%, 25.1%] vs. 7.4% [4.8%, 10.1%], P < 0.001). Before treatment, three indices of EDS were significantly higher in small than large vessels (for ED-EDS: 29.2% [19.8%, 44.8%] vs. 20.4% [14.3%, 30.2%]; for ES-EDS: 26.8% [18.9%, 37.7%] vs. 18.3% [13.9%, 25.4%]; for TA-EDS: 19.1% [13.9%, 27.8%] vs. 14.3% [10.5%, 20.1%], P < 0.001). After treatment, the EDS in small vessels significantly decreased (P < 0.001). ED-EDS showed the highest correlation with pre-DCB DSP (r = 0.43, P < 0.001) and post-DCB MLD (r = 0.35, P < 0.001). The levels of EDS parameters for small or large vessel lesions significantly differed. Further study is required to examine the clinical value of EDS in predicting cardiac events after DCB treatment.

The Expanding Role of Drug-Coated Balloons and Endothelial Dynamic Strain Assessment in the Treatment of De Novo Atherosclerotic Coronary Artery Disease

The Expanding Role of Drug-Coated Balloons and Endothelial Dynamic Strain Assessment in the Treatment of De Novo Atherosclerotic Coronary Artery Disease

Enhancement of dynamic strain range based on phase-sensitive OTDR with time-delay double probe pulses

Enhancement of dynamic strain range based on phase-sensitive OTDR with time-delay double probe pulses

Long range static and dynamic strain measurement by using phase-noise-compensated OFDR

Long range static and dynamic strain measurement by using phase-noise-compensated OFDR

TiO2/SiO2 spiral crimped Janus fibers engineered for stretchable ceramic membranes with high-temperature resistance.

The tensile brittleness of ceramic nanofibrous materials makes them unable to withstand the relatively large fracture strain, greatly limiting their applications in extreme environments such as high or ultra-low temperatures. Herein, highly stretchable and elastic ceramic nanofibrous membranes composed of titanium dioxide/silicon dioxide (TiO2/SiO2) bicomponent spiral crimped Janus fibers were designed and synthesized via conjugate electrospinning combined with calcination treatment. Owing to the opposite charges attached, the two fibers assembled side by side to form a Janus structure. Interestingly, radial shrinkage differences existed on the two sides of the TiO2/SiO2 composite nanofibers, constructing a helical crimp structure along the fiber axis. The special configuration effectively improves the stretchability of TiO2/SiO2 ceramic nanofibrous membranes, with up to 70.59% elongation at break, excellent resilience at 20% tensile strain and plastic deformation of only 3.48% after 100 cycles. Additionally, the relatively fluffy ceramic membranes constructed from spiral crimped Janus fibers delivered a lower thermal conductivity of 0.0317 W m-1 K-1, attributed to the increased internal still air content. This work not only reveals the attractive tensile mechanism of ceramic membranes arising from the highly curly nanofibers, but also proposes an effective strategy to make the ceramic materials withstand the complex dynamic strain in extreme temperature environments (from -196 °C to 1300 °C).

Analysis of Fixed and Variable Rigid Pavements in Comparison for Longevity, Durability and Cost-effectiveness

Urbanization has increased significantly during the last century, affecting both rural and urban areas. Due to the growing need for improved connectivity and services, roads and other transportation infrastructure are being built quickly. To meet this need, scientists, designers, and builders have been investigating novel and reasonably priced manufactured goods with the goal of streamlining the building process and improving overall robustness. In recent times, concrete pavements have witnessed a surge in popularity in India, driven by the escalating costs associated with bituminous pavement. The main benefit of using stiff pavement is that it is resilient and can hold its form even under harsh weather and traffic situations. Although concrete pavements may have a higher initial cost, they frequently wind up being more economical in the long run since they require less upkeep and have an excellent design life. This study's primary objective is to present a comparative analysis of pavement appropriateness while accounting for longevity, durability, and cost-effectiveness, among other factors. The simulation can be utilised to gain a quantitative understanding of the dynamic strains and deflections present in a rigid pavement and flexible system. It is discovered that the impact of surface roughness on a slab structure's dynamic response is significant for the pavement structure's useable life span and can be taken into consideration during pavement design. The model can be adjusted to determine the k-value needed to assess a pavement's subgrade support as it ages.

On the Potential Correlation between Dynamic Strain Aging and Liquid Metal Embrittlement in T91/LBE System

In the study of the liquid metal embrittlement (LME) of the T91/lead-bismuth eutectic (LBE) system, it is observed that LME occurs in a temperature interval which is similar to the temperature range where dynamic strain aging (DSA) is observed. However, the potential correlation between DSA and LME has not yet been satisfactorily investigated. This investigation for the T91/LBE system is exactly the topic of this work. For the evaluation of DSA and LME, slow strain rate tensile tests are conducted in the temperature range between 200 °C and 450 °C with strain rates of 5×10−5 s−1 and 5×10−6 s−1 in reference and a molten oxygen-depleted LBE environment. The resulting tensile properties, as well as the fracture surfaces and lateral surfaces of the failed samples, suggest a correlation between DSA and LME in the T91/LBE system. The maximum mechanical degradation of T91 is observed in the case where the effects of both DSA and LME on material properties are found to be at maximum. However, the observation of DSA was not identified as a prerequisite for LME to take place. Therefore, these results may indicate that DSA partly contributes to the ductility minimum observed in the T91/LBE system. In addition, the results of this work show that changes in the fracture surface and lateral surface are more sensitive features to claim for the potential occurrence of LME than the changes in total elongation.

Analysis on the Influencing Factors of Fatigue Damage in Truss Bridge

Truss bridges are susceptible to fatigue damage due to long-term exposure to external factors. This article mainly analyzes the influencing factors of fatigue damage in truss bridges, including load factors and joint factors. The analysis results indicate that load factors have a significant impact on the fatigue damage of truss bridges. Vehicle loads can cause deformation and stress concentration in bridge structures, leading to the generation of shear stress, which in turn triggers the expansion of stress concentration areas and accumulation of fatigue damage in bridge materials. Additionally, improper vehicle operation, such as overloading, can increase the dynamic strain on the bridge deck, causing deformation and fatigue damage to the main girders. As for joint factors, joints are one of the critical areas for fatigue damage in truss bridges. Stress concentration and deformation at joints increase the risk of fatigue crack formation and propagation. In this way, the life and safety of the bridge can be assessed, and appropriate maintenance and repair measures can be taken to improve the fatigue resistance of the bridge and ensure its safe operation.

Experimental Study of the Dynamic Characteristics of PVA-Amended Expansive Soils

Expansive soils are distributed across a wide area in China, and land transport and surface construction will inevitably involve these soils. To mitigate the deficiencies of single-method expansive soil modification, it is highly important to adopt the use of polyvinyl alcohol (PVA) to improve expansive soils and enhance the strength and toughness of modified soils. In addition, solidification technology can be utilized for the resource utilization of expansive soils. In this study, triaxial testing is employed to evaluate the mechanical properties of solidified soil. When the confining pressure is the same and with increasing PVA content, soil particles and PVA combine to form a cemented substance, which fills the internal pores of the soil samples, enhances the cohesion between soil particles, and improves the bearing capacity of the soil. The stress–strain curve for the modified soil first increases and then decreases. The shear strength peaks at a PVA content of 3%. Based on the improved soil with a 3% PVA content, GDS dynamic triaxial tests were carried out to investigate the effects of different confining pressures and frequencies on the dynamic stress–strain curves, dynamic modulus of elasticity, and variation rule for the damping ratio of the improved soil. The results show that the dynamic stress–strain curve for the improved soil increases with increasing confining pressure and frequency and that the dynamic stress–strain backbone curves exhibit significant nonlinearities at different frequencies and circumferential pressures. The dynamic elastic modulus increases with increasing confining pressure and frequency and decreases gradually with increasing dynamic strain. The initial dynamic modulus of elasticity increases with increasing envelope pressure and frequency but is less affected by frequency, and the damping ratio decreases with increasing confining pressure and frequency. Soil treatment can improve the pore distribution, inhibit the extension of soil cracks, and enhance soil compactness.

Stiffness and damping characteristics of jointed rocks under cyclic triaxial loading subjected to prolonged cyclic loading

A modelled rock joint set featuring a rough joint surface inclined at 60° was fabricated, and cyclic triaxial and conventional monotonic triaxial experiment series were carried out at various confining stresses. Cyclic deviatoric loading was applied up to 500,000 cycles at 8 Hz frequency to evaluate the impact of prolonged repeated loading on the stiffness and damping properties of rock joints and their variation with irreversible axial strain. The analysis of the experimental data revealed that, under the tested conditions, the accumulation of irreversible axial strain exhibited a progressive rise as the repeated loading advanced, particularly in the early stage of deformation. Furthermore, the resilient moduli demonstrated a downward trend in relation to cumulative irreversible axial strain, while the damping ratio showed a rapid decrease initially and then increased slowly with cumulative irreversible axial strain. Moreover, with the rise in confining stress, the accumulated irreversible axial strain reduced while resilient moduli and Young’s moduli increased, and the damping ratio decreased. Through nonlinear regression analysis, empirical relationships for the resilient moduli variation with the irreversible axial strain and variation of critical dynamic irreversible axial strain with cyclic stress ratio were developed.

Distributed phase-matching measurement for dynamic strain and temperature sensing based on stimulated Brillouin scattering enhanced four-wave mixing

A Brillouin dynamic grating (BDG) can be used for distributed birefringence measurement in optical fibers, offering high sensitivity and spatial resolution for sensing applications. However, it is quite a challenge to simultaneously achieve dynamic measurements with both high accuracy and high spatial resolution. In this work, we propose a sensing mechanism to achieve distributed phase-matching measurement using a chirped pulse as a probe signal. In BDG reflection, the peak reflection corresponds to the highest four-wave mixing (FWM) conversion efficiency, and it requires the Brillouin frequency in the fast and slow axes to be equal, which is called the phase-matching condition. This condition changes at different fiber positions, which requires a range of frequency injection for the probe wave. The proposed method uses a chirped pulse as a probe wave to cover this frequency range associated with distributed birefringence inhomogeneity. This allows us to detect distributed phase matching for birefringence changes that are introduced by temperature and strain variations. Thanks to the single shot and direct time delay measurement capability, the acquisition rate in our system is only limited by the fiber length. Notably, unlike conventional BDG spectrum recovery-based systems, the spatial resolution here is determined by both the frequency chirping rate of the probe pulse and the birefringence profile of the fiber. In the experiments, an acquisition rate of 1 kHz (up to fiber length limits) and a spatial resolution of 10 cm using a 20 ns probe pulse width are achieved. The minimum detectable temperature and strain variation are 5.6 mK and 0.37 με along a 2 km long polarization-maintaining fiber (PMF).

A dual-mode fiber-shaped flexible capacitive strain sensor fabricated by direct ink writing technology for wearable and implantable health monitoring applications

Flexible fiber-shaped strain sensors show tremendous potential in wearable health monitoring and human‒machine interactions due to their compatibility with everyday clothing. However, the conductive and sensitive materials generated by traditional manufacturing methods to fabricate fiber-shaped strain sensors, including sequential coating and solution extrusion, exhibit limited stretchability, resulting in a limited stretch range and potential interface delamination. To address this issue, we fabricate a fiber-shaped flexible capacitive strain sensor (FSFCSS) by direct ink writing technology. Through this technology, we print parallel helical Ag electrodes on the surface of TPU tube fibers and encapsulate them with a high dielectric material BTO@Ecoflex, endowing FSFCSS with excellent dual-mode sensing performance. The FSFCSS can sense dual-model strain, namely, axial tensile strain and radial expansion strain. For axial tensile strain sensing, FSFCSS exhibits a wide detection range of 178%, a significant sensitivity of 0.924, a low detection limit of 0.6%, a low hysteresis coefficient of 1.44%, and outstanding mechanical stability. For radial expansion strain sensing, FSFCSS demonstrates a sensitivity of 0.00086 mmHg−1 and exhibits excellent responsiveness to static and dynamic expansion strain. Furthermore, FSFCSS was combined with a portable data acquisition circuit board for the acquisition of physiological signals and human‒machine interaction in a wearable wireless sensing system. To measure blood pressure and heart rate, FSFCSS was combined with a printed RF coil in series to fabricate a wireless hemodynamic sensor. This work enables simultaneous application in wearable and implantable health monitoring, thereby advancing the development of smart textiles.