Strain Behavior Research Articles

Impact of attapulgite and basalt fiber additions on the performance of pumice-based foam concrete: mechanical, thermal, and durability properties

This study explored the combined effects of using attapulgite (ATP) as a partial cement replacement and basalt fibers (BF) as reinforcement in the development of high-performance foam concrete (FC) with 100% pumice aggregate. The experimental program included preparing FC mixtures with ATP replacements at 10%, 20%, and 30% by cement weight, and adding BF at volume fractions of 0.5%, 1.0%, and 2.0%. Key properties assessed were fresh flowability, compressive and flexural strengths, stress–strain behavior, thermal conductivity, and durability under sulfate exposure and high temperatures. Findings revealed a synergistic effect between ATP and BF, leading to significant performance enhancements across various parameters. The mixture with 30% ATP and 0.5% BF exhibited the highest compressive strength, reaching 19.45 MPa at 28 days and 22.11 MPa at 90 days, indicating improvements of 129.3% and 85.3% over the reference mix, respectively. This combination also achieved the lowest sorptivity, improved thermal stability, and better sulfate resistance, making it highly suitable for structural applications in harsh environments. In addition, the mixture with 10% ATP and 0.5% BF demonstrated the lowest thermal conductivity, reducing heat transfer by 4.2% compared to the control, which is beneficial for thermal insulation in building materials. Microstructural analysis using Scanning Electron Microscopy (SEM) showed that ATP’s pozzolanic reactivity led to a denser microstructure with stronger bonding, while BF effectively bridged micro-cracks, enhancing the FC matrix's durability. Overall, these results highlighted the potential of ATP and BF to significantly enhance FC’s mechanical, thermal, and durability properties, providing an eco-friendly solution with lower cement use and greater resilience to environmental stressors. This study contributes to sustainable construction technology by showcasing how ATP and BF can optimize FC performance, supporting its wider use in the construction industry.

Strain Analysis of Membrane Structures for Photovoltaic Integration in Built Environment

The integration of photovoltaic (PV) systems into tensioned membrane structures presents a significant advancement for sustainable applications in the built environment. However, a critical technical challenge remains in the substantial strains induced by external loads, which can compromise both PV efficiency and the structural integrity of the membrane. Current design methodologies prioritize stress, deflection, and ponding analysis of tensioned membranes. Strain behavior of whole structures, a key factor for ensuring long-term performance and compatibility of PV-integrated membranes, has been largely overlooked. This study addresses this gap by examining the whole membrane structure designed for PV integration, with the aim of optimizing the membrane to provide suitable conditions for efficient energy transfer while minimizing membrane strains. For this purpose, it provides a comprehensive strain analysis for full-scale hyperbolic paraboloid (hypar) membrane structures under various design parameters and external loads. Employing the Finite Element Method (FEM) via Sofistik software, the research examines the relationship between load type, geometry, material properties, and patterning direction of membranes to understand their performance under operational conditions. The findings reveal that strain behavior in tensioned membrane structures is strictly influenced by these parameters. Wind loads generate significantly higher strain values compared to snow loads, with positive strains nearly doubling and negative strains tripling in some configurations. Larger structure sizes and increased curvature amplify strain magnitudes, particularly in parallel patterning, whereas diagonal patterning consistently reduces strain levels. High tensile-strength materials and optimized prestress further reduce strains, although edge type has minimal influence. By systematically analyzing these aspects, this study provides practical design guidelines for enhancing the structural and operational efficiency of PV-integrated tensioned membrane structures in the built environment.

Structural design optimization and vibration assessment of a base frame for a 3 MW turbo compressor

This study focuses on the design and analysis of a base frame for a 3 MW turbo compressor, aiming to develop a robust and reliable structural framework. The design process included comprehensive simulations, incorporating static stress-strain and dynamic vibration analyses to assess the base frame’ performance under operational conditions. The static analysis evaluated the total deformation and strain behavior of the base frame, ensuring it can withstand the maximum load without yielding or excessive deformation. Dynamic vibration analysis was performed to identify the natural frequencies and potential resonance issues, minimizing the risk of vibrations that could compromise operational stability. Results from the static analysis revealed that the initial design exhibited a maximum total deformation of 0.24 mm, which was reduced to 0.09 mm in the final design—a 62.5% improvement. Elastic strain values were within safe operational limits for both designs. The effective mass ratio analysis showed significant results at frequencies close to 0 Hz, with negligible impact across the operating frequency range. Based on these analyses, an optimized base frame model was developed, meeting the design criteria for mechanical strength and vibrational stability. The results highlight the importance of integrating deformation, strain, and vibration assessments in the structural design of heavy-duty turbo compressor base frame, contributing to enhanced durability and performance.

Transition Behavior of Cellulose Nanocrystal Networks Induced by Nanoconfined Water

Hydrogen bonding (HB) is essential for the mechanical properties of cellulose‐based materials. However, the plastification of cellulose nanocrystals (CNC) caused by the transition of HB in the presence of water is still insufficiently understood. In this work, the rigid–soft transition of nanoconfined chains in non‐ordered regions of CNC surfaces is quantitively described by comparing their strain behaviors with amorphous cellulose. Moreover, this softening (referred to as the “hydro‐glass transition”) with increasing relative humidity (RH) is explored, and a threshold RH value (RHt) is identified to characterize the transition. The phenomenon is attributed to the monolayer to multilayer adsorption and eventually capillary condensation of water molecules in wedged mesopores of the CNC films. This triggers a rapid transition of HB from cellulose–cellulose to cellulose–water type in the vicinity of RHt. The hydro‐glass transition is promoted by higher temperatures, for example, RHt at 65 °C decreases to 50%. In addition, the presence of surface groups with lower acid dissociation constant (comparing SO3− and OH/COO− moieties) also accelerates this hydro‐glass transition process. Thus, a detailed understanding of the thermodynamic changes in hydrogen‐bonded nanoconfined polymer chains in the presence of humidity, with implications for developing nanomaterials with RH‐controlled properties, is provided.

Computational methodology to study the effect of cable-stabilized knee brace on anterior cruciate ligament strain during single-leg jump landing.

Knee bracing is commonly used for rehabilitation after ligament surgery. However, the effectiveness of knee bracing in preventing ligament injuries is not widely studied. This study aimed to develop a computational methodology to investigate the effectiveness of a novel type of cable-stabilized knee brace on anterior cruciate ligament (ACL) strain during single-leg jump landing. The brace features a compliant design with nonextensible pretensioned cables integrated within a compression tight garment. A combined in vivo/in silico method was developed for this purpose. A computational model of the cable-stabilized knee brace was developed with linked truss elements used to simulate the cable. The cables were integrated into an existing computational model of the knee. Subsequently, single-leg jump landing simulations were conducted on the model, using muscle forces and joint kinematic/kinetic profiles from 10 participants. Anterior cruciate ligament strain behaviors were then compared between the braced and unbraced configurations. The computational methodology was successful in simulating the differences in ACL strain because of the brace. The average peak ACL strain in the braced configuration was 4.99% ± 2.36% and in the unbraced configuration was 3.23% ± 2.31% (p = 0.091). The methodology developed lays the groundwork for future advancements in optimizing the cable-stabilized knee brace design and refining its potential in preventing ligament injuries.

Optimization and Prediction of the Mechanical Properties of Concrete with Crumb Rubber and Stainless-Steel Fibers Under Varying Temperatures

This research develops an equation to describe the relationship between stress (σ) and strain (ε) in concrete under different conditions. It includes important parameters from earlier studies to improve predictions of stress–strain behavior, especially for concrete with crumb rubber and stainless-steel fibers at various temperatures. The initial phase assessed three existing stress–strain formulas as a basis for optimization. Using the Genetic Algorithm (GA) and the Whale Optimization Algorithm (WOA), a new equation was created to simulate the stress–strain relationship while considering temperature changes and material additions. Results showed that Formula (1), optimized with the WOA, performed much better than other polynomial and exponential formulas, proving the WOA’s effectiveness over the traditional GA. A comparison of the mechanical properties from experiments and those predicted by the new formula showed a high level of accuracy. Key properties like the maximum stress, strain at maximum stress, modulus of elasticity, and toughness were well captured. The findings highlight how temperature and material composition significantly affect concrete’s mechanical behavior. Overall, this research offers important insights into the factors influencing concrete performance, providing a solid framework for future studies and practical applications in engineering and construction. The proposed formula is a reliable tool for predicting concrete’s mechanical properties under various conditions, which aids in better modeling and optimization in concrete design.

Tuning Printability and Adhesion of a Silver-Based Ink for High-Performance Strain Gauges Manufactured via Direct Ink Writing.

Structural health monitoring (SHM) systems are critical in ensuring the safety of space exploration, as spacecraft and structures can experience detrimental stresses and strains. By deploying conventional strain gauges, SHM systems can promptly detect and assess localized strain behaviors in structures; however, these strain gauges are limited by low sensitivity (gauge factor, GF ∼ 2). This study introduces an approach to printing strain gauges with high sensitivity, while also considering stretchability and long-term durability. Through direct ink writing (DIW), these devices can be produced by the extrusion of a wide range of viscoelastic inks. The viscoelastic properties of the ink can be tuned with the help of additives to aid in the processing for a desired application. In this work, a series of inks were prepared from commercially available CB028 (silver ink used in screen printing) by adding a combination of ethyl cellulose (EC) and polyolefin (PO) (additives). With the goal of optimizing the long-term sensing response of the printed strain gauges, a systematic study of the rheological properties (frequency sweep analyses, yield stress, viscoelastic recovery, viscosity measurements, and tack tests) was conducted. A viscoelastic window approach was used to predict the optimal properties of the formulated inks. Using this approach, it was determined that 90% CB028, 5% EC, and 5% PO provided enhanced elastic properties, adhesion, and peel strength compared to commercial CB028. The formulated ink has enhanced tack (129 mN/mm2) and peel strength (23.3 kJ/mm2), which led to a viscoelastic window ideal for direct ink writing of the strain gauges. Printed structures were tested in a three-point bending configuration to record the piezoresistive responses that were correlated to the formulated rheological properties and underlying microstructure. The results revealed gauge factors as high as 106 with stable sensing responses for more than 300 cycles of strain. Scanning electron microscopy analysis also revealed minimal crack formation, which resulted in a stable response. The research demonstrated the feasibility of developing high-performance inks for potential printed strain gauge applications.

The phase composition, relaxor behavior and strain performance of the Pb(Mg1/3Nb2/3)O3-Pb(Zn1/3Nb2/3)O3 single crystal

For exploiting relaxor materials with high strain and low hysteresis, Pb(Mg1/3Nb2/3)O3– Pb(Zn1/3Nb2/3)O3 (PMN-PZN) crystal was designed and grown. The grown crystal is light yellow with a maximum size of 13 × 10 × 8 mm3. Rietveld refinement and domain configuration at room temperature confirm the coexistence of cubic and rhombohedral phases, and the cubic phase is dominant. The Curie temperature of the grown crystal is slightly lower than room temperature and shows a strong frequency dependence. Strong dielectric relaxor performance is demonstrated by means of different ways. At a temperature of 26 ℃ and an electric field of 35 kV/cm, the saturation polarization reaches 22.62 μC/cm2, the residual polarization is almost zero, the strain is about 0.1 %, and the hysteresis degree is 4 ∼ 5 %. Moderate strain and low hysteresis make PMN-PZN crystal display potential application in high-precision actuators. Moreover, in-situ domain evolution under an electric field was observed to understand the polarization and strain behaviors.

Enhancing the Performance of Concrete Coupled Shearwall Using Shape Memory Alloys

ABSTRACTUtilizing self‐centering materials, such as shape memory alloys (SMA), as reinforcement in concrete structures can positively influence their performance during and after earthquakes. Despite the high cost of SMAs, their unique flag‐shaped stress–strain behavior and effective energy dissipation make them an attractive material choice in some structures. This study evaluates the application of iron‐based SMAs in enhancing the seismic performance of coupled concrete shear walls. The purpose is to identify optimal SMA placement strategies within the walls' plastic hinges to improve energy dissipation, reduce residual drift, and enhance ductility. This research explores pre‐tensioned and non‐pre‐tensioned SMA configurations through macro‐element modeling and cyclic analysis. Presenting a comparative framework that balances material efficiency and structural performance differentiates this study from prior studies focused predominantly on SMA benefits in isolated structural applications. Two optimization scenarios are proposed: maximizing energy dissipation and minimizing residual drift, and reducing SMA usage while maintaining structural efficiency. The results indicate that pre‐tensioned SMAs in the wall web provide the most significant improvement in seismic behavior, significantly reducing residual drift and increasing ductility. This approach offers a cost‐effective solution for improving earthquake resilience in structures.

Investigation of imbibition and strain behavior of Longmaxi shale using fiber Bragg grating sensing

Investigation of imbibition and strain behavior of Longmaxi shale using fiber Bragg grating sensing

Study on the scale effect and mechanical properties of gravel materials in riverbed cover layers

To address the challenges of performing in-situ tests on riverbed overburden gravel, this study employs three scaling methods—equal mass substitution, similar gradation, and the mixed method—to investigate the original gradation of the gravel. Large-scale triaxial consolidated drained shear tests were conducted to evaluate the effects of the maximum particle size reduction ratio (M) and confining pressure on the stress–strain behavior, fractal dimension, particle breakage, and the parameters of the Duncan-Chang model (an elastic model describing nonlinear stress-strain relationships). The study explores how scaling, based on fractal dimension and particle breakage rate, impacts the strength and deformation characteristics of gravel materials. The results show that increasing confining pressure typically leads to higher material strength. As confining pressure increases, particle breakage becomes more pronounced across the various scaling methods. Gravel processed using the similar gradation method exhibited the highest strength, the smallest change in fractal dimension, and the lowest breakage rate, followed by the mixed method. Furthermore, as the M value increases, peak stress also rises, with the modulus coefficient (k) and bulk modulus coefficient (Kb) in the Duncan-Chang model increasing by 4.5 times and 3.3 times, respectively, for M = 15 compared to M = 0. A clear relationship was observed between the change in fractal dimension before and after testing and the breakage index (Bg). As the M value increases, both the difference in fractal dimension and the breakage rate decrease, suggesting that larger M values lead to reduced particle breakage and improved mechanical stability.

Application of computer models of rock mass quality and stress–strain behavior for stability assessment of mine openings

Application of computer models of rock mass quality and stress–strain behavior for stability assessment of mine openings

Effect of surface condition on fatigue life of 7075 aluminium alloy

ABSTRACT This study investigates the effects of surface treatments on the mechanical properties of 4 mm thick flat test specimens made from annealed AA 7075 alloy in three conditions: as-received, shot-peened, and electropolished. Experimental investigations, including cyclic stress response, fatigue life, microstructural observations, and mechanical properties, are conducted to provide insights into the fatigue behaviour of the alloy. The surface roughness (Ra) values were measured at 546 nm for as-received, 830 nm for shot-peened, and 72 nm for electropolished samples. Push–pull fatigue tests conducted at a stress amplitude of 500 MPa with a load ratio (R) of -1 yielded average fatigue lives of 1200 cycles for as-received, 990 cycles for shot-peened, and 2700 cycles for electropolished samples. These results align with the general observation that smoother surfaces yield better fatigue life, which can be explained by the influence of surface conditions on stress–strain behaviour, microstructure, and fracture mechanisms. The smoother surfaces have lower stress concentration points, so the propensity for crack nucleation and propagation is lower in these samples, leading to improved mechanical properties.

Axial compressive performance of low-carbon high-strength recycled aggregate concrete

AbstractThis paper introduces a novel material, low-carbon high-strength recycled aggregate concrete (LCHRAC), developed by activating ground granulated blast-furnace slag (GGBS) and silica fume (SF) in an alkaline environment and integrating recycled aggregate. To evaluate its mechanical properties, uniaxial compressive tests were performed, systematically analyzing the effects of recycled concrete aggregate (RCA) substitution ratios, as well as the characteristic parameters of steel and polypropylene(PP) fibers, on LCHRAC’s mechanical behavior. The results indicated that compressive strength shows a gradual decline as the RCA substitution ratio increases, with a moderate reduction of 7.1% up to 50% replacement, and a more significant drop, retaining only 68.6% at 100% replacement. In contrast, the peak strain increases linearly, showing a 29% improvement at full replacement, while the toughness index exhibits a consistent upward trend, increasing by approximately 123% at a 100% replacement rate. Based on experimental data, empirical models were developed to predict the influence of key control variables on the compressive strength, peak strain, elastic modulus, and the uniaxial compressive stress–strain behavior of LCHRAC. Additionally, advanced characterization techniques, including X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS), were employed to elucidate the hydration mechanisms of the slag-silica fume composite system. These findings provide a comprehensive understanding of the mechanical performance and microstructural characteristics of LCHRAC, contributing to its potential application in sustainable construction practices.

Mechano-Graded Contact-Electrification Interfaces Based Artificial Mechanoreceptors for Robotic Adaptive Reception.

Triboelectrification-based artificial mechanoreceptors (TBAMs) is able to convert mechanical stimuli directly into electrical signals, realizing self-adaptive protection and human-machine interactions of robots. However, traditional contact-electrification interfaces are prone to reaching their deformation limits under large pressures, resulting in a relatively narrow linear range. In this work, we fabricated mechano-graded microstructures to modulate the strain behavior of contact-electrification interfaces, simultaneously endowing the TBAMs with a high sensitivity and a wide linear detection range. The presence of step regions within the mechanically graded microstructures helps contact-electrification interfaces resist fast compressive deformation and provides a large effective area. The highly sensitive linear region of TBAM with 1.18 V/kPa can be effectively extended to four times of that for the devices with traditional interfaces. In addition, the device is able to maintain a high sensitivity of 0.44 V/kPa even under a large pressure from 40 to 600 kPa. TBAM has been successfully used as an electronic skin to realize self-adaptive protection and grip strength perception for a commercial robot arm. Finally, a high angle resolution of 2° and an excellent linearity of 99.78% for joint bending detection were also achieved. With the aid of a convolutional neural network algorithm, a data glove based on TBAMs realizes a high accuracy rate of 95.5% for gesture recognition in a dark environment.

Mechanism Study on the Intrinsic Damage and Microchemical Interactions of Argillaceous Siltstone Under Different Water Temperatures

Argillaceous siltstone is prone to deformation and softening when exposed to water, which poses a great threat to practical engineering. There are significant differences in the degrees of damage to this type of rock caused by solutions with different water temperatures. This study aimed to better understand the effect of temperature on argillaceous siltstone by designing immersion tests at water temperatures of 5, 15, 25, and 35 °C, analyzing the mechanical properties and cation concentration shifts under each condition. A water temperature–force coupled geometric damage model for argillaceous siltstone was developed, incorporating a Weibull distribution function and composite damage factors to derive a statistical damage constitutive model. The findings reveal that, with increasing water temperature, the peak strength and elastic modulus of argillaceous siltstone display a concave trend, initially decreasing and then increasing, while the cation concentration follows a convex trend, first increasing and then decreasing. Between 15 and 25 °C, the stress–strain behavior transitions from a four-phase to a five-phase pattern, with pronounced plasticity. The model’s theoretical curves align closely with experimental data, with the Weibull parameters m and λ effectively capturing the rock’s strength and plastic characteristics. Changes in water temperature notably influence the damage variable D12 in the context of water temperature–peak stress coupling, with D12 initially increasing and then decreasing with higher temperatures. These research results can provide new methods for exploring the paths of soft rock disasters and provide guidance for designing defenses in geotechnical engineering.

Optimization of carbon nanotubes in carbon black‐filled natural rubber: Constitutive modeling and verification using finite element analysis

AbstractCarbon nanotubes (CNTs) are novel one‐dimensional nanomaterials with a large aspect ratio and specific surface area, exhibiting excellent electrical and thermal properties that have led to their extensive utilization in rubber nanocomposites. In this paper, the effect of CNTs and carbon black juxtaposition on the properties of natural rubber is investigated using two different structures of CNTs, namely GC‐30 and GT‐210. The experimental results show that GT‐210 CNTs exhibit superior performance when incorporated into natural rubber. In addition, finite elements are employed for constitutive modeling to facilitate meaningful explorations in mechanical calculation and characterization of rubber filled with CNTs. Simulating the mechanical behavior of rubber materials under different working conditions (tensile and compressive) offers a cost‐effective and time‐efficient approach to predicting and optimizing material performance.Highlights Characterization of filler dispersion by Mooney–Rivlin curves. Fitting material stress–strain behavior using constitutive models. Offers an approach to predicting and optimizing material performance.

Optical Visualization of Stretchable Serpentine Interconnects using Chiral Liquid Crystal Elastomers.

The shapes and structures of stretchable interconnects are pivotal in determining their functionality, allowing them to withstand bending, stretching, and twisting while maintaining their operational integrity. However, all stretchable interconnects are subjected to dynamically changing, non-uniform strains during mechanical deformation. Therefore, achieving an accurate understanding of stretchable interconnect properties, including tracking and analyzing these dynamic, non-uniform strains in real-time, remains a challenging endeavor. Herein, a method for analyzing the strain behavior of stretchable interconnects using a chiral liquid crystal elastomer (CLCE), which exhibits immediate structural color changes of nano periodic molecular arrangement in response to dynamic stretching deformations, is presented. Beyond the uniform color change of simple CLCE, by further engineering the modulus and shape geometry of the serpentine CLCE, an intuitive strain capturing visualization of dynamically changing serpentine structures is performed. Moreover, by expanding the serpentine CLCE into a 2×2 array, the real-time strain distribution of the stretchable interconnects under various multi-stretching properties (uniaxial and biaxial) is investigated. This optical visualization provides an accurate and precise understanding of the structure of stretchable interconnects under dynamic stretching conditions and is a promising breakthrough to enable enhanced design and optimization of stretchable serpentine structures for broadband stretchable applications.

Oleaginous Yeast Biology Elucidated With Comparative Transcriptomics.

Extremophilic yeasts have favorable metabolic and tolerance traits for biomanufacturing- like lipid biosynthesis, flavinogenesis, and halotolerance - yet the connection between these favorable phenotypes and strain genotype is not well understood. To this end, this study compares the phenotypes and gene expression patterns of biotechnologically relevant yeasts Yarrowia lipolytica, Debaryomyces hansenii, and Debaryomyces subglobosus grown under nitrogen starvation, iron starvation, and salt stress. To analyze the large data set across species and conditions, two approaches were used: a "network-first" approach where a generalized metabolic network serves as a scaffold for mapping genes and a "cluster-first" approach where unsupervised machine learning co-expression analysis clusters genes. Both approaches provide insight into strain behavior. The network-first approach corroborates that Yarrowia upregulates lipid biosynthesis during nitrogen starvation and provides new evidence that riboflavin overproduction in Debaryomyces yeasts is overflow metabolism that is routed to flavin cofactor production under salt stress. The cluster-first approach does not rely on annotation; therefore, the coexpression analysis can identify known and novel genes involved in stress responses, mainly transcription factors and transporters. Therefore, this work links the genotype to the phenotype of biotechnologically relevant yeasts and demonstrates the utility of complementary computational approaches to gain insight from transcriptomics data across species and conditions.

Computational Study of the Influence of Crack Orientation in SCM440 Cracked Shaft on Strain Alteration under Transverse Excitation

Previous studies have demonstrated that crack geometry influences strain generation in cracked shafts under excitation loading. The behavior of strain generation varies notably under transverse loading suggesting that the crack orientation could have a significant effect on strain behavior under excitation. This computational study aims to investigate the influence of different crack orientations on strain behavior. The analysis examines the strain at crack tips and the effects of loading on crack alignment under transverse excitation. Crack-controlled parameters, such as shape factor, characteristic length, and orientation parameter, are found to be significant factors governing strain behavior. Specifically, cracks with greater circularity and larger characteristic lengths exhibit higher strain levels under excitation. Crack orientation becomes particularly significant in conveying the strain from the affected area of excitation loading through the crack front, especially in the case of a straight crack, resulting in high strain levels at both tips and distinct strain generation behavior. The findings highlight the significant impact of excitation-affected areas near the excitation location on strain generation over crack geometry. This underscores the potential risk of existing cracks in the shaft and the importance of these factors on strain generation behavior. This study enhances understanding of how crack orientation impacts strain behavior, offering valuable insights for structural integrity assessment and design optimization in engineering applications.