Mechanics of Time-Dependent Materials最新文献

The thermal performance of the solar collectors is enhanced by the addition of nanomaterial to the radiative surface, which increase its stability and lifetime. Due to its numerous applications, this study utilizes machine learning framework to simulate the energy and hydrodynamic behavior of a time-dependent Prandtl tri-hybrid nanofluid (HNF) over a radiated Riga surface. The Cattaneo–Christov heat flux model, mixed convection, radiant heat, dissipating, and magnetic effects are considered. A Crank-Nicolson computational method (CNM) is used to solve the controlling pressure-driven, unsteady flow equations, and the generated dataset is used to assess and train the artificial neural network (ANN) model. he generated solution data are used to train a feed-forward artificial neural network (ANN) with tan-sigmoid hidden activation, and Levenberg–Marquardt training, using a dataset of 320 samples. The results show that increasing the thermal relaxation parameter reduces the peak temperature by up to about 14%, mitigating thermal stress, whereas stronger thermal radiation and higher nanoparticle concentration raise the temperature by up to about 26%. A higher modified Hartmann number lowers the velocity by roughly 10–17% while slightly increasing the temperature, and a larger Grashof number enhances the velocity by nearly 22%. The ANN attains minimum validation mean-squared-error values of (1.35times 10^{-9}) for velocity and (1.25times 10^{-9}) for temperature, overall prediction errors within ±3.8%, and regression coefficients exceeding 0.9996.

Decarbonizing road infrastructure has intensified interest in renewable substitutes for petroleum-derived diluents in asphalt binders. This study presents a full-chain evaluation of a bio-based binder (SDR-VO) in which a vegetable-oil derivative replaces the aromatic extract as diluent of a pre-salt deasphalting residue, benchmarked against the conventional counterpart (SDR-AE) sharing the same base and 50/70 penetration grade. Both binders were characterized through Multiple Stress Creep Recovery (MSCR), Linear Amplitude Sweep (LAS), and aging-resistance testing. The bio-based formulation reproduced the high-temperature response of SDR-AE (true Performance Grade, PG ≈ 64 ^∘C) and delivered a modest improvement in rutting-relevant rheology, a lower MSCR J_nr3.2 that brings SDR-VO into the Standard traffic class (PG 64S-22), unlike SDR-AE, while matching its fatigue, aging, and low-temperature indicators, including an equivalent continuous low-temperature PG (({approx }{-}23) ^∘C). A three-point Balanced Mix Design supported by FlexPAVE BR simulations identified the optimal volumetric envelope. Two experimental sections (400 and 340 m) were built in Rio de Janeiro under identical conditions; as-built mixtures showed equivalent fatigue and marginally better rutting for SDR-VO (Flow Number 428 vs. 319 cycles), and FlexPAVE BR projected a marked fatigue advantage of SDR-VO (2.3% vs. 15.6% cracked area at (10^{7}) equivalent single axle loads, ESALs) with equivalent rutting. Field surveys yielded maximum Falling Weight Deflectometer (FWD) deflection reductions of 35% (SDR-AE) and 38% (SDR-VO), rut depth below 1 mm, International Roughness Index (IRI) of 3.9 and 2.6 m/km, and equivalent macrotexture. The results substantiate the viability of vegetable-oil derivatives as renewable diluents in pre-salt-based binders.

The shear failure characteristics of bolted persistent joints are crucial for the stability control of rock mass engineering. Direct shear tests on bolted and unbolted rock-like joints under five normal stress levels were conducted, combined with acoustic emission (AE) monitoring and joint surface scanning, to investigate the influence of normal stress on the mechanical properties, AE characteristics, and morphological evolution of the two types of joints. The results show that the shear stress–displacement curves of unbolted joints consist of four stages—compaction, elastic, yield, and residual—whereas those of bolted joints exhibit an additional plastic hardening stage due to the bolt action. The peak strength and pre-peak shear stiffness of both joint types increase linearly with normal stress. Under the same normal stress, bolted joints exhibit a higher peak ring-down count, and a higher normal stress delays the occurrence of the peak ring-down count in unbolted joints. Damage in unbolted joints intensifies with increasing normal stress, whereas damage in bolted joints is concentrated around the bolt. Among the three-dimensional morphological parameters, the maximum peak height decreases linearly with normal stress, while the other parameters decrease nonlinearly. The bolt undergoes tensile–shear failure under the combined action of axial and shear forces, generating an additional normal pressure upon fracture, which increases the effective normal stress on the shear plane and enhances the shear strength of the joint. This study can provide a theoretical reference for the prevention and control of instability and the support design of anchored jointed rock masses.

The linear viscoelastic behaviour of highly modified bitumen such as crumb rubber modified bitumen (CRMB) is commonly characterised using time-temperature superposition (TTSP), although its validity depends on the assumption of thermorheological simplicity. This assumption is often violated in highly modified bitumen, reducing the reliability of conventional master curve construction and increasing experimental effort. This study evaluates a three-parameter Fractional Maxwell Model for characterising five CRMBs containing 5%, 10%, 15%, 22%, and 30% CR by weight of base bitumen. Frequency sweep tests were conducted using a dynamic shear rheometer at 10, 30, 50, and 70 °C, and model parameters were determined through nonlinear optimisation. The fractional Maxwell model accurately reproduced the measured storage and loss moduli, with (mathrm{R}^{2}) values above 0.96 and normalised root mean square errors (NRMSE) below 5% in 50 of the 53 fitted datasets. Model-reconstructed master curves closely matched experimentally shifted TTSP master curves for unaged and short-term aged conditions, with (mathrm{R}^{2}) values above 0.989 in log space and NRMSE below 3.1%. After long-term ageing, the model retained high accuracy for CRMB-22 ((mathrm{R}^{2} = 0.998)), but deviations increased for the other bitumen, with NRMSE reaching 10.3% for CRMB-30. The fractional order parameter ((alpha )) increased approximately linearly with temperature, while its temperature sensitivity decreased with increasing CR content. Interpolated (alpha ) values at 30 and 50 °C differed from fitted values by less than 0.06, indicating that fractional modelling may reduce the number of test temperatures required, particularly for low-CR bitumen.

The review focuses on the utilization of bio materials for the modification of bitumen, with the aim of achieving enhanced performance, sustainability, environmental and economic benefits as well as utilization of renewable resources, mostly discarded as waste earlier. Amongst various bitumen modifiers which are derived from biological sources, extensive research was observed in the use of four specific bio materials. It includes waste cooking oil, waste wood-based oil, swine manure, and natural rubber. Disposal of these materials is an issue and use of these as bio-modifier for bitumen can be an important sink. Literature suggests that optimized bio-oil addition on bitumen is preferred at 1-20% of bitumen, 200-4000 rpm, mixing time and temperature being 10-40 min and 135 - 150 °C respectively, and also indicate the possibility of using these oils as rejuvenators. Moreover, incorporating these bio materials into bitumen, notable improvements have been observed in terms of decrease in viscosity and softening point of the modified bitumen, while penetration and ductility are observed to increase. The rheological studies of the bio-modified bitumen exhibited significant improvements, especially in terms of fatigue performance. These changes contribute to enhanced pavement performance, durability, and flexibility, which are crucial for the durability of road infrastructure. To corroborate laboratory findings, it is important to assess the usage of bio-modified binders with carbon footprint analyses, and techno-economic evaluations and cradle-to-grave life cycle assessment (LCA). It is envisioned that such wastes to rejuvenate aged binders will promote environmental sustainability by easing use of already depleting natural resource. Various stretches are being developed Worldwide to check the long-term viability.

This study develops a unified fractional nonlinear creep constitutive theory for bedded rocks under the coupled influence of bedding orientation and transverse anchorage. A full-stage one-dimensional framework is constructed by connecting an elastic spring, a fractional viscoelastic element, and a damage-coupled fractional viscoplastic element. A acceleration switch is introduced and generalized through an effective-stress measure based on the deviatoric stress invariant, enabling the onset of accelerated creep to be driven by the time-varying confinement provided by the anchorage system. To account for bedding-induced anisotropy, the model is extended to three dimensions using a compliance-substitution strategy and an explicit transversely isotropic compliance transformation, yielding a closed-form orientation–parameter mapping through the dimensionless matrix (U(theta )). The anchorage effect is homogenized as an equivalent unidirectional lateral constraint stiffness (K_{b}(t)) that decays exponentially, leading to explicit expressions for axial strain, lateral confinement stress, and bolt force under constant axial stress. The accelerated creep initiation time shows an orientation-dependent decreasing trend from 0° to 90°. The fitting results show that the proposed model reproduces the instantaneous jump, steady-state creep and third-order acceleration across the stress level, and is superior to Burgers and Nishihara models in capturing non-stationary post-response.

Surgical mesh used in hernia repair is subjected to repetitive cyclic loading during daily activities. Changes in mechanical properties induced by cyclic loading may reduce mesh performance and contribute to patient discomfort or hernia recurrence. Therefore, these meshes require robust mechanical performance under physiological loading conditions, yet the influence of mesh structural architecture on cyclic tensile behavior and anisotropy remains insufficiently understood. This study investigated the influence of loading direction (course, 45° diagonal, and wale, where the course and wale directions correspond to the principal horizontal and vertical directions of the knitted structure) on the static and cyclic tensile behavior of polypropylene surgical meshes with five different structures (Tricot, pin-hole-net, Sandfly, quasi-Sandfly, and quasi-Marqussite). Static testing revealed pronounced anisotropy in all meshes, with elastic modulus values strongly dependent on the orientation of underlaps, chain loops, and inlay yarns. Under cyclic loading, stretching work, energy dissipation, and elastic strain decreased with increasing cycle number, with the most substantial reduction occurring between the first and second cycles. A strong inverse correlation was observed between elastic modulus and both energy dissipation and minimum-load strain. The degree of anisotropy ranged from 0.15–0.50 before cycling and narrowed to 0.07–0.27 after ten cycles, indicating that cyclic loading promotes convergence of mechanical properties between the course and wale directions. The Tricot mesh exhibited the lowest anisotropy both before and after cyclic loading, while Sandfly was the most anisotropic. These findings demonstrate that mesh structural architecture and loading direction critically govern mechanical performance and that cyclic loading reduces anisotropy across all designs, with the Tricot configuration offering the most balanced, isotropic-like properties for hernia repair applications.

This study presents a novel numerical and artificial neural network (ANN) investigation of three-dimensional magnetohydrodynamic (MHD) bioconvective flow of a Carreau ternary hybrid nanofluid (THNF) over a bidirectional-stretching Riga plate embedded in a porous medium. The mathematical model adopted is derived from the Buongiorno model and includes the effects of thermal radiation, Joule heating, Brownian motion, thermophoresis, heat generation/absorption, activation energy, and binary chemical reaction. Similarity variables are introduced into the governing partial differential equations to convert them into ordinary differential equations, which are then solved numerically using the MATLAB solver bvp4c. A Levenberg-Marquardt-based backpropagation neural network (LMS-BPNN) is trained to predict the key transport properties, using 70% of the data for 15% of training to validate and test the network. The results show that the velocity profiles decrease with the increase of the Weissenberg number because of the dominant elastic forces, and the temperature profile increases with the increase of the Brownian motion and thermophoresis parameters. The Nusselt number increases with the increase of Brownian motion and thermophoresis, while the skin friction coefficient increases with the increase of the magnetic and chemical reaction parameters. The results obtained from ANN agree fairly well with the numerical results, and the mean square error value is in the range of (1 0^{-9}) to (1 0^{-8}). The high agreement between the numerical and ANN predictions with previous studies demonstrates the accuracy and robustness of the proposed computational framework, which has the potential to predict complex transport phenomena in advanced thermal systems.

The steady Casson nanofluid flow over a curved stretched sheet is numerically analyzed in this work while taking viscous dissipation and mixed convection into account. Nanoparticles improve heat transport, the non-Newtonian behavior is described by the Casson model. To represent boundary-layer flow over a curved surface, a local non-similarity transformation converts the nonlinear PDEs into linked ODEs with variable coefficients. MATLAB bvp4c is used to numerically solve the resulting equations. Analysis is done on the effects of the Eckert number, mixed convection, curvature, Casson parameter, and nanoparticle volume percent. The findings indicate that while viscous dissipation and mixed convection have opposing thermal effects, curvature greatly modifies the flow. In addition to improving thermal performance, the introduction of nanoparticles increases the system’s sensitivity to buoyancy and viscosity effects. The results directly affect high-precision heat systems in polymer extrusion, microfluidics, and bioengineering applications and advance our knowledge of intricate transport processes in curved geometries.

Reinforced concrete structures exposed to aggressive environments often deteriorate due to carbonation and the penetration of harmful agents through the pore network. Cementitious protective mortars are an effective solution to improve surface durability. This study investigates the mechanical and durability behavior of cementitious mortars incorporating binary sand mixtures of limestone sand and dune sand, two abundant local materials in arid regions of Algeria. Twelve mortar mixtures were prepared with different proportions of limestone and dune sands while maintaining a constant water-cement ratio of 0.55. Mechanical strength, immersion water absorption, capillary water absorption, and accelerated carbonation resistance were evaluated. The results indicate that binary sand significantly improves mortar performance. The highest compressive strength, averaging 46 MPa at 28 days, was obtained for mixtures containing 60–70% limestone sand and 30–40% dune sand. Immersion water absorption ranged from 6.85% to 7.46%, with most binary mixtures showing slightly lower values than the reference mortar. Capillary absorption was also reduced, with cumulative water uptake decreasing from approximately 15 kg/m² for the control mixture to 8.5–10 kg/m² for the optimized mixtures, indicating improved pore structure and reduced permeability. Accelerated carbonation tests revealed a significant improvement in carbonation resistance. After 56 days, carbonation depth decreased from 10.2 mm for the reference mortar to 5.13–5.97 mm for the optimized mixtures, corresponding to a reduction of about 40–50%. These results demonstrate that binary limestone-dune sand mortars provide improved durability and represent a sustainable solution for protective cementitious coatings.