Mechanical Behavior Research Articles

Fracture toughness evolution and failure mechanisms of two-dimensional SiCf/SiC composites at temperatures up to 1500 °C in air

Silicon carbide fiber reinforced silicon carbide composites (SiCf/SiC) are of the few most promising materials for high-temperature structural applications. In this study, two-dimensional (2D) plain-woven SiCf/SiC composites were prepared by chemical vapor infiltration process and subjected to single-sided notched beam three-point bending tests from room temperature (RT) to 1500 °C in air. The temperature-dependent bending load–deflection curves and fracture toughness were obtained. The results show that the SiCf/SiC composites exhibit linear deformation characteristics initially, followed by nonlinear deformation behavior which become more pronounced with increasing temperature. The fracture toughness decreases in the range of RT to 1000 °C due to the evolution of components properties, and increases at 1200 °C due to the interface property degradation and fiber pull-out. Above 1200 °C, it decreases with increasing temperature owing to the serious high-temperature oxidation. Further, the failure mechanisms of the 2D plain-woven SiCf/SiC composites at different temperatures was analyzed through macro and micro analysis. The evolution of components properties affected by high temperature and oxidation as well as fiber pull-out play a leading role in fracture toughness of composites. The findings of this study provide important support for the mechanical behavior and failure mechanisms of SiCf/SiC composites at ultra-high temperatures in air.

Thermal-Mechanical Coupling Analysis of Permeable Asphalt Pavements

In order to clarify the mechanical response of permeable asphalt pavements under a temperature effect, the mechanical responses of different types of permeable asphalt pavements, which were based on a self-developed drainage SBS-modified asphalt mixture with fiber, were simulated using ANSYS finite element software (APDL 19.2). The influence of temperature and temperature change on the mechanical behavior of the permeable asphalt pavements was studied, and the mechanical responses of the pavements at different driving speeds was analyzed. The results show that the extreme values of surface deflection, compressive strain of the soil foundation top surface, and the shear stress and tensile stress of the upper-layer bottom of the three kinds of pavements under dynamic load were about 10% smaller than those under static loads, and the extreme values under different temperature conditions were 28%~50% larger than the values obtained without different temperature conditions. During the 12 h heating process, the mechanical indexes of the three types of pavements with axle loads were consistent with the change law of temperature, and the peak values of the mechanical indexes under dynamic loads were smaller than those under static loads. In addition, the mechanical indexes of the three types of pavements under dynamic loads had the same law of change with speed under the same conditions, and the values were less than the extreme values under static loads, but the degree of influence was different.

Model prediction of unidirectional fiber-reinforced composites under finite deformation

The intuitive knowledge is that the mechanical modulus of unidirectional fiber-reinforced composites (UD-FRPs) decreases with higher fiber orientation angles. However, numerical results in this work and experimental results in previous literature indicate that the mechanical response of UD-FRPs has a U-shaped dependence on fiber orientation angle. To explain this phenomenon, we develop an anisotropic model to capture the mechanical behavior of UD-FRPs. The strain energy is decomposed into four components: matrix, fiber, fiber-matrix normal, and shear interactions. Each component can be determined by matching the mechanical responses of unit cells with 0°, 45°, and 90° off-axis. The results obtained from the presented model match well with the numerical response of unit cells with 15°, 30°, 60°, and 75° off-axis. With an increasing fiber orientation angle, the matrix part remains unchanged, the fiber component decreases, but the fiber-matrix normal component increases, and the fiber-matrix shear component increases and then decreases. The change in strain energy contributions explains the mechanism of the U-shaped dependence of the mechanical response on fiber orientation angle.

Mechanical Behavior of Synthetic Zeolite-Warm Mix Asphalt Containing Sulfur Waste as a Sustainable Filler

Mechanical Behavior of Synthetic Zeolite-Warm Mix Asphalt Containing Sulfur Waste as a Sustainable Filler

Acoustic emission signatures for quantifying damage patterns in half grouted sleeve connection under tensile load

The half-grouted sleeve connection (HGSC) have been widely used as connection tools for prefabricated concrete (PC) buildings. It is crucial to maintain the safety and stability of the nodes and detecting internal defects in the grouting sleeve for the safety of the entire structure. Therefore, understanding the mechanical behavior and damage mechanism of HGSC is essential for the design and construction of PC. Currently, there are few on-site techniques applicable for monitoring the damage progress. The acoustic emission (AE) as a passive method shows great potential to characterize the damage in the HGSC. Therefore, in this paper, we propose to use AE to quantify the damage of the HGSC with defects under the tensile load. The artificial defects were introduced into HGSC with different defective rates. The monotonic tensile load was applied to each HGSC sample with a loading rate of 0.33 mm/s and tested to the failure. In this process, the AE signals were collected by AE transducers. For the classification and prediction of damage signals, we utilized a machine learning framework tailored for HGSC. This framework integrates unsupervised k-means++ cluster analysis and supervised K-Nearest Neighbors (K-NN) for damage classification and prediction. The experimental results showed that four AE signal clusters can be defined during the progress of tensile failure:(i) microcrack expansion;(ii) the friction signals of rebar and high-strength grouts; (iii)the generation of microcracks; (iv) plastic deformation of rebar. The corresponding AE signatures were identified. The K-NN model trained on the training data provides a high accuracy in predicting different class of defects. It was concluded that the proposed machine learning framework is a promising and powerful tool for realizing the on-site damage detection and prediction for HGSC.

Experimental and numerical mechanical characterisation of additively manufactured polymeric lattice structures under uniaxial tensile load

AbstractAdditive manufacturing enables the production of lighter, more robust components with intricate features like lattice structures. However, since the mechanical behaviour of lattice structures is not fully characterized, the application of such potential is limited today. The challenge with lattice structures tensile tests is defining a suitable design that fits the standard requirements and process characteristics. In the polymeric powder bed fusion process, the problem is to produce powder-free geometries and to avoid stress concentrations zones, adapting the specimen accordingly. In this regard, numerical simulation may provide insightful information and support the analysis of the deformation mechanisms. This paper analyses a new tensile sample for lattice structures using finite element analysis. The sample is designed following the EN ISO 527 standard prescriptions. An area with a controlled gradation of the lattice relative density is designed to ensure both powder-free voids and fracture localization within the lattice specimen gauge length. Experimental tests are performed to validate the numerical results using a modified body cubic centred topology with two different strut diameters. The specimens are produced in polyamide by powder bed AM process. Due to the complexity of the lattice design, a digital image correlation is used to compute the full range of strains at the macroscopic level. Experimental and numerical strain maps results showed a good agreement. The recorded deviation was attributed to the process-induced defect, such as the geometrical accuracy that, if compensated, boosted the capability of the numerical model to predict the mechanical behaviour of the lattice structure.

Rate-dependent damage and failure behavior of lithium-ion battery electrodes

The mechanical properties and failure behavior of composite electrodes are critical to understanding the internal short circuits and ensuring the crush safety of lithium-ion batteries used in electric transportation. This study provides a comprehensive experimental investigation into the strain rate–dependent tensile/compressive behavior and failure mechanism of both anode and cathode, covering a range from quasi-static to dynamic conditions. A universal testing machine equipped with an industrial camera was used to assess the mechanical properties and observe the deformation process of the electrodes under quasi-static conditions. Additionally, a split Hopkinson bar system, coupled with a high-speed camera, was utilized to evaluate the mechanical properties and capture the deformation process of the electrodes under dynamic loading. The detailed deformation and failure modes of the electrodes were revealed by a combination of post-mortem characterization and images from high-speed cameras. The experimental results demonstrate a significant strain rate effect on the tensile and compressive mechanical behavior and failure mechanism of both anode and cathode. The rate dependence of tensile/compressive strength and failure strain were discussed, and the underlying mechanism for strain rate sensitivity was analyzed. The results and conclusions from this study provide an important foundation for the detailed modeling and failure prediction of lithium-ion batteries under impact loading. Further, these findings facilitate the safety design of electric vehicles by informing to enhance crash safety.

Mechanical, wear, fatigue, and water absorption behavior of proso millet husk derived biosilica reinforced nylon 6–6 composite thick plates for friction stir welding process

Mechanical, wear, fatigue, and water absorption behavior of proso millet husk derived biosilica reinforced nylon 6–6 composite thick plates for friction stir welding process

Efficacy of Ni2+ on modification the structure, ultrasonic, optical, and radiation shielding behaviors of potassium lead borate glasses

This paper presents the method of preparing (60 − x) B2O3–20 K2O–20 PbO–x NiO, coded as (NiO x), and x = (0–10 mol%) glass systems fabricated through the melt-quench technique. The prepared glass was characterized through X-ray diffraction spectra (XRD); the mechanical behavior of the glass samples was investigated using the ultrasonic technique, Fourier transform infrared (FTIR) spectra, the optical reflectance R(λ), refractive index (n), optical conductivity (σopt), the dispersion parameters of the studied samples were deduced using Wemple and Di-Domenico models. The results obtained were reported in detail. One of the fundamental parameters used to evaluate the interaction of radiation with shielding material was the mass attenuation coefficient (μm), which was obtained using Phy/X software and PHITS code program. It was used to calculate radiation interaction parameters, e.g., linear (μL) attenuation coefficient, effective atomic number (Zeff), half value layer HVL, mean free path (MFP) and the average atomic cross section, σt. Comparing the shielding behavior of the glass samples revealed that (NiO 10) glass demonstrated the highest μm and μL compared to the other samples. The maximum μm values equal 48.13, 48.73, 49.42, 50.59, and 51.08 cm2/g for (NiO 0) to (NiO 10), recorded at 0.015 MeV, respectively. This study shows that increasing the amount of NiO in the preferred glass samples leads to achieving high-performance radiation shielding materials.Graphical abstract

On the Dynamic Mechanical Behavior of Wrought and AM 17-4 Precipitation-Hardenable Stainless Steels Under Rapid Heating

AbstractDynamic large-strain plasticity problems in metals can produce temperatures high enough to alter the microstructure, but the limited time-at-temperature prevents complete transformation, thereby making the material strength time-dependent. Precipitation reactions (age-hardening) are an important class of transformations that can create time-dependent dynamic plasticity under rapid heating and loading. This work explores the dynamic behavior of a precipitation-hardenable stainless steel (17-4) produced by wrought and Additive Manufacturing (AM) methods with a rapidly-heated Kolsky bar technique. Wrought 17-4, a martensitic stainless steel, is examined in three common heat treatments (solution-treated, peak-aged and over-aged) at temperatures up to 1000 °C and heating times limited to about three seconds. Solution-treated wrought 17-4 is observed to thermally-harden at aging temperatures (> 400 °C) due to rapid precipitate growth. Peak-aged precipitation strengthening becomes ineffective above 550 °C, as peak-aged material becomes indistinguishable from the solution treated-condition. Over-aged wrought 17-4 does not behave like either of the other conditions, owing to the effect of the extended heat treatment on the precipitates and on the martensite matrix. Stress-relieved AM 17-4 exhibits high dynamic strength and strain hardening at room-temperature due to its meta-stable austenite content and partial age-hardening during the build or stress-relief treatment. A plasticity model is developed for solution-treated wrought 17-4 that captures time-dependent aging effects that are derived from separate aging kinetics experiments. A separate model is developed for over-aged wrought 17-4 that contains no time-dependence as the precipitate population in this material appears to be more stable under rapid heating.

Multi-scale-space Grillage Mixed Method of Mechanical Behavior of Composite Box Beams with Finite Element Method (FEM)

Multi-scale-space Grillage Mixed Method of Mechanical Behavior of Composite Box Beams with Finite Element Method (FEM)

Introducing the area under stress–velocity curve: Theory, measurement and association with rock properties

AbstractSince many years ago, ultrasonic velocity has been used to investigate the physical and mechanical behaviour of rocks, thereby playing an important role in reservoir characterization and seismic interpretation. In order to develop the knowledge of ultrasonic tools, we performed a noble analysis on the ultrasonic behaviour of rocks under confining stress and evaluated a distinctive property of porous media that is measured as the area under the stress–velocity curve (here defined as S*). We further investigated its relationship with elastic and mechanical behaviours of rock. To validate the theoretical framework developed in this work, 20 core plugs from various rock units with complex microstructures were subjected to triaxial compressional tests to calculate their area under the curve. Calculations were made for crack‐closing, elastic and post‐elastic stages (e.g. pore collapse) along the ultrasonic velocity–stress curve. Moreover, the selected samples had their microstructure investigated by thin‐section studies to quantify their porosity and pore type. The results were analysed to check for the effect of pore type on S* in different stages of the stress–velocity curve. Based on the outputs of the analysis of variance and Pearson's correlation coefficient analysis, the curve had its shape and underlying area closely related to the porosity and pore geometry. Indeed, the results showed that the shale and sandstone with micro cracks and carbonate with stiff pores correspond to smaller and larger areas under the curve in crack‐closing and inelastic stages, respectively. Cross‐correlating the results to compressibility (inverse of bulk modulus), it was figured out that the calculated area under curve was well consistent with the compressibility. In addition, S* represents both static and dynamic behaviours of the rock, and the results revealed that the shape and curvature of the stress–velocity curve give valuable information about the rock microstructure. Another finding was the fact that the type of fluid and wave velocity seemingly affect the S*. Our findings can help interpret wave velocity behaviour in reservoir rocks and other stressful porous media.

A comprehensive review of experimental studies on shear behavior of bolted rock joints with varying rock joint and bolt parameters and normal stress

AbstractThe shear characteristics of bolted rock joints are crucial for the stability of tunneling and mining, particularly in deep underground engineering, where rock bolt materials are exposed to high stress, water pressure, and engineering disturbance. However, due to the complex interaction between bolted rock joints and various geological contexts, many challenges and unsolved problems arise. Therefore, more investigation is needed to understand the shear performance of bolted joints in the field of deep underground engineering. This study presents a comprehensive review of research findings on the responses of bolted joints subjected to shearing under different conditions. As is revealed, the average shear strength of bolted rock joints increases linearly with the normal stress and increases with the compressive strength of rock until it reaches a stable value. The joint roughness coefficient (JRC) affects the contact area, friction force, shear strength, bending angle, and axial force of bolted rock joints. A mathematical function is proposed to model the relationship between JRC, normal load, and shear strength. The normal stress level also influences the deformation model, load‐carrying capacity, and energy absorption ratio of bolts within bolted rock joints, and can be effectively characterized by a two‐phase exponential equation. Additionally, the angle of the bolts affects the ratio of tensile and shear strength of the bolts, as well as the mechanical behavior of both bolted rock joints and surrounding rock, which favors smaller angles. This comprehensive review of experimental data on the shear behavior of bolted rock joints offers valuable theoretical insights for the development of advanced shear devices and further pertinent investigations.

Theoretical analysis for the mechanical properties of the knitted structures

Abstract Knitting is a technology that has a thousand-year-old history, and can be normally seen in our daily lives. The knitted structure is constructed by the interwoven yarns that constrained by themselves, exhibiting extreme stretchability. The mechanical properties of the knit fabric also enable their integration with the flexible electronic devices. Nonetheless, it is yet problematic to expose the mechanical behaviors of knitting intrinsically. This paper investigates the mechanical characteristics of knitted structures subjected to uniaxial stretching. The analysis includes a structural assessment of the unit cell, with a focus on half of the cell accounting for symmetry. Mechanical analysis for three distinct scenarios (without elongation and friction, with elongation and no friction, with elongation and friction) is also presented. The stress-strain curve of the knitted structure and the correlation between stiffness and geometric parameters are illustrated. Additionally, simulations are carried out based on finite element analysis, yielding consistent results with the theoretical calculations. Subsequently, a uniaxial stretching experiment is conducted, and the experimental outcomes also verifies the theoretical analysis. Our analysis successfully explains the mechanical behavior of knitted structures, and also provides a reference for studying knitted fabrics with other topologies.

High fidelity FEM based on deep learning for arbitrary composite material structure

Due to the outstanding performance, composite materials are widely used and analyzing their properties and designing them based on performance has become a crucial task in the field of many manufacturing industries. Composite materials possess complex multiscale structures, and traditional fine-scale finite element modeling and analysis may lead to severe computational resource challenges. To overcome this difficulty, breakthroughs in key technologies of multiscale accelerated analysis algorithms are required. In this study, an innovative approach based on artificial intelligence and multiscale finite element method is presented. This approach involves partitioning the entire composite material structure into coarse grids that resemble homogenous structures of similar size, providing results consistent to fine-grid finite element analysis. By utilizing CNN for image feature recognition and employing the CGAN adversarial method, coarse-grid equivalent stiffness matrices and multiscale shape functions from completely random microstructures of composite materials can be obtained. Consequently, this enables a rapid response process from microstructure to low-resolution grid to high-resolution physical field, with remarkably accurate physical field results. Moreover, compared to traditional fine-grid finite element methods, this approach significantly reduces memory usage and computation time. This method is applicable to composite materials with varying shaped inclusions, different component properties, and diverse geometric distributions, allowing these materials to perform high-fidelity finite element calculations on coarse grids and predict their mechanical behavior. Furthermore, this breakthrough opens avenues for accelerating the optimization design of composite materials with diverse mechanical functionalities, by employing a bottom-up approach.

Mechanical and tribological behaviour of Al2TiO5 particle-reinforced AA5052 composite

Mechanical and tribological behaviour of Al2TiO5 particle-reinforced AA5052 composite

Study on Cyclic Mechanical Behavior and Damage Constitutive of PVA Fiber Recycled Aggregate Concrete

Study on Cyclic Mechanical Behavior and Damage Constitutive of PVA Fiber Recycled Aggregate Concrete

Permeability: The Driving Force That Influences the Mechanical Behavior of Polymers Used for Hydrogen Storage and Delivery

This article explores the main mechanisms that can generate damage in polymers and polymer-based materials used for hydrogen storage and distribution infrastructures. All of these mechanisms are driven by the permeability process that is enhanced by the operating temperature and pressure conditions. Hydrogen storage and delivery systems typically work under high pressure and a relatively wide range of temperatures, especially during the filling and emptying processes. Therefore, it is of great interest to better understand how this phenomenon can influence the integrity of polymer-based hydrogen infrastructures in order to avoid catastrophic events and to better design/investigate new optimized solutions. The first part of this paper discusses the main storage and delivery solutions for gas and liquid hydrogen. Then, the physics of the permeability is investigated with a focus on the effect of pressure and temperature on the integrity of polymers working in a hydrogen environment. Finally, the main mechanisms that mostly induce damage in polymers operating in a hydrogen environment and that influence their mechanical properties are explored and discussed. Particular focus was placed on the rapid gas decompression and aging phenomena. In addition, some of the limits that still exist for a reliable design of polymer-based storage and delivery systems for hydrogen are pointed out.

Effect of cell diameter variations on the mechanical behavior of aluminum foams: Experiments and modeling

Aluminum foams can be manufactured in a variety of cell sizes; however, existing models focus primarily on density and neglect the effect of cell size. Furthermore, aluminum foams with different cell diameters exhibit diverse mechanical properties. In this study, a quasi-static/dynamic compression test was performed to investigate the mechanical behavior, damage patterns, and damage mechanisms of aluminum foams with different cell diameters. The results demonstrate that the compressive properties of aluminum foams undergo significant changes. As the cell diameter increases, normalized initial damage stress and Young's modulus also increase, leading to enhanced energy absorption. However, this increase in cell diameter negatively affects the energy absorption efficiency, resulting in increased instabilities. A finite element analysis was conducted using the LS-DYNA finite element software to investigate the behavior of aluminum foils under all the experimentally tested loading regimes. The simulation results reveal that the deformation zone formed due to collapse diminishes with increasing cell diameter. More importantly, a new damage mechanism named central cell cleavage was reported, which increased the energy absorption capacity and amplified the instability during deformation. This study offers novel insights into the mechanical behaviors exhibited by aluminum foams, thereby facilitating their application in structural engineering.

Interclonal variability in sensitivity to wind breakage: Comparative analysis of the mechanical behaviour of stems of two Hevea clones

The rubber tree (Hevea brasiliensis) is the main source of natural rubber production, with more than 14 million tonnes produced each year. Unfortunately, throughout their economic lifespan on the plantation (between 35 and 40 years), heveas trees are sensitive to wind damage, especially trunk breakage. Over a 30-year period, it is estimated that losses due to the wind breakage of tree stems reach nearly 40%. Industrial hevea plantations are organized in monoclonal plots. Clones are selected based on their productivity, disease resistance, etc., but not for their mechanical behaviour or sensitivity to wind-induced breakage, as breeders lack the appropriate tools to assess these criteria. Field observations highlight variations among clones in their susceptibility to wind breakage, underscoring the increased importance of evaluating mechanical criteria. Among the known causes of these differences in Hevea trees are competition between latex production and growth, crown shape and the presence of tension wood. In this article, we investigated the mechanical behaviour of the stems of two Hevea clones. One, IRCA825, is recognized as very sensitive, while the other, IRCA41, is known for its resistance to wind breakage. We measured biomechanical parameters such as trunk bending stiffness (EI), green wood stiffness (E) and modulus of rupture (MOR). To assess these parameters, we performed bending tests until breakage on standing trees of clonal fields in Ivory Coast, followed by wood characterisation tests in laboratory. A comparative analysis of the bending tests revealed that clones IRC825 and IRCA41 exhibit equivalent trunk bending stiffness. Nevertheless, IRCA41 differs from IRCA825 by having higher green wood stiffness and breaking strength, attributes that mainly explains its higher wind resistance. Comparative analysis of the wood structure indicated that the differences in wood stiffness and breaking strength are mainly attributed to the higher wood density in IRCA41 compared to IRCA825, with no discernible differences in microfibril angle and specific modulus.