Mechanics of Time-Dependent Materials最新文献

The storage and transportation of green hydrogen (GH₂) pose significant challenges for structural materials, particularly due to hydrogen embrittlement (HE), which can degrade the mechanical properties of steels through hydrogen–metal interactions. Understanding the susceptibility of candidate materials to hydrogen-induced damage is therefore essential for the safe deployment of hydrogen infrastructure. This study investigates the hydrogen embrittlement behavior of three stainless steels: ferritic stainless steel 410D, ferritic–martensitic stainless steel 410T, and duplex stainless steel 2205. Hydrogen was introduced through electrochemical charging via chronoamperometry in a 3.5 wt.% NaCl solution, a widely used laboratory approach to promote controlled hydrogen ingress and simulate hydrogen–material interactions relevant to hydrogen service conditions. The influence of charging temperature and exposure time was also evaluated. A comprehensive characterization methodology was employed, including microstructural analysis, chemical composition, hardness and microhardness measurements, uniaxial tensile tests before and after hydrogen exposure, and hydrogen permeation experiments to evaluate hydrogen absorption, diffusion, and transport behavior. The results indicate that hydrogen diffusivity plays a key role in the embrittlement response of the investigated alloys. The ferritic stainless steel 410D exhibited the highest susceptibility to hydrogen-induced degradation, showing the greatest reduction in mechanical properties and the highest hydrogen diffusion coefficient. In contrast, duplex stainless steel 2205 showed comparatively lower hydrogen diffusivity and reduced mechanical degradation under the tested conditions. Overall, the study highlights the critical influence of alloy microstructure, temperature, and exposure time on hydrogen embrittlement behavior and provides a comparative ranking of steel resistance to hydrogen-induced damage under the conditions analyzed.

A nonlinear constitutive model, based on a parallel rheological framework, is proposed to enhance the characterization of the mechanical properties of composite solid propellants. The mechanical response of HTPB propellant is divided into an equilibrium response and a viscous response through cyclic stretch-relaxation experiments. The equilibrium response incorporates the molecular chain elongation response using the extended eight-chain model, while the cross-linking response in the molecular chain network is described by the tube model. The viscous response is determined by the relaxation rheology of the molecular chains. By comparing with propellant cyclic tensile-relaxation tests, as well as tensile and relaxation test results, it is evident that the developed constitutive model effectively captures the nonlinear mechanical behavior of HTPB propellants. These findings establish a robust basis for accurately characterizing propellant mechanical properties and offer a mechanism for swiftly predicting and analyzing propellant mechanical responses.

Permeable pavements are an essential component of green infrastructure for urban stormwater management, yet their long-term durability in cold climates remains a major challenge. This study evaluates the freeze–thaw durability and service-life prediction of permeable concrete incorporating recycled steel slag aggregate under unclogged and clogged conditions using laboratory testing and two predictive frameworks. The Dynamic Elastic Modulus Decay Model and the Cumulative Damage Model were calibrated using measured relative dynamic elastic modulus data. Experimental results revealed that clogging accelerated deterioration, accelerating deterioration and reducing predicted service life from 7.36–6.78 years (unclogged condition) to 5.44–5.28 years (clogged condition). The cumulative damage model demonstrated superior predictive accuracy ((R^{2}=0.982)) compared to the modulus decay model ((R^{2}=0.956)) By linking laboratory durability data with service life forecasting, this research provides a laboratory-validated framework for the planning, design, and maintenance of resilient sponge city pavements. The findings contribute to climate adaptation strategies for cold-region urban environments and promote the sustainable use of industrial by-products in construction materials.

Mineral fillers (Hydrated lime & Quarry dust) play a major role in improving the performance of the mastic. The interaction with bitumen, the aging kinetics of the mastic, and the resulting rheological behavior are primarily controlled by the filler dosage and its physicochemical interaction. This study investigates the impact of different dosages of hydrated lime (HL) and Quarry dust (QD) on unaged and aged bituminous mastic. FTIR spectroscopy was used to evaluate the functionalities present in mastic and thereby understand the interaction effects and aging kinetics. The frequency sweep test was conducted in the temperature range of 30 to 80 °C to evaluate the viscoelastic properties of the mastic. The findings show that the presence of hydroxyl, aliphatics and carbonyl in hydrated lime mastic (HLM) increased the absolute shear modulus of the mastic up to 30%. For 40% HL, the reduction of the aliphatic index due to the scission of the carbon chain resulted in a reduced modulus. HL also assisted in reduced aging of mastic after 50 hours of aging. For QDM only a small improvement in modulus was observed and the phase angle of QDM is found to be dosage-independent. The aging compounds were also higher for QDM resulting in a corresponding increase in absolute shear modulus. To decide the proportion of the filler in the mix, it is important to consider the filler type and its interaction with the bitumen in addition to the density required from particle packing.

Metal laminated composite panels are, in essence, valued for their superior mechanical performance and thermal stability. For a Cu/AA2030 bimetallic sandwich panel, this paper conducted an investigation into its thermo-mechanical behavior during hot rolling with a fully detailed 3D finite element model in ABAQUS/Explicit. An ALE formulation was utilized to accurately capture the large plastic deformation, interlayer interaction, and temperature-dependent material properties. Key process parameters were varied systematically: initial panel temperature, inlet composite thickness, reduction ratio, and convective heat transfer coefficient to investigate their effects on temperature, strain, lateral spread, and final strip geometry. Simulation results indicated that initial temperature increase reduced thermal gradients, internal stresses, and encouraged more homogeneous deformation. However, larger initial thicknesses and higher reduction ratios increased the plastic work heat, thus leading to a remarkable centerline temperature increase and causing greater inter-layer non-uniformity. A higher value of the convective heat transfer coefficients caused high surface cooling and reduced thermal mismatch considerably. Strong correlations were obtained between reduction ratio and both lateral spread and longitudinal elongation, which highlighted the importance of thickness reduction in geometric evolution. The developed model shows promising capabilities in achieving insights into coupled thermal and deformation mechanisms, thus providing a predictive framework to optimize parameters aimed at improved interlayer bonding and dimensional accuracy for industrial applications.

The use of rejuvenators is essential for restoring the properties of aged asphalt binders in reclaimed asphalt pavement (RAP) mixtures. This study examined the effects of three commercially available rejuvenators (A, B, and C) on the physical, rheological, and performance characteristics of RAP binders and mixtures. The optimum rejuvenator dosage was determined using the high-temperature performance grade (PG) criterion. Further, to compare the effect of rejuvenator type, an average dosage of 10% by weight of RAP binder was considered as a reference for all the rejuvenators. Binder-level tests, including softening point, ductility, PG grading, MSCR, and LAS were complemented with stage extraction tests to evaluate rejuvenator diffusivity. Mixture performance was assessed using wheel tracking and IDEAL-CT tests. Results showed that rejuvenation effectively restored RAP binder properties to levels comparable with the target VG40 binder. Rejuvenator A, with lower viscosity and better diffusion efficiency, enhanced fatigue resistance and cracking tolerance, whereas rejuvenators B and C, with higher aging indices and limited diffusivity, improved rutting resistance. Mixture-level testing confirmed these trends, with recycled mixtures outperforming the control in rutting and cracking resistance. Overall, the study highlights that rejuvenator properties, particularly viscosity, aging index, and diffusivity, govern their effectiveness in restoring binder rheology and ensuring balanced mixture performance. The stage extraction test proved useful for distinguishing rejuvenators based on diffusion efficiency, offering a more realistic assessment than conventional binder tests.

The creep behavior of red-stratum mudstone plays a critical role in the long-term stability and safety of major engineering projects, making a systematic investigation of its consolidation creep characteristics of significant engineering relevance. In this paper, one-dimensional consolidation creep experiments were conducted on red-stratum mudstone using an incremental loading method to determine the effects of initial dry mass density, moisture content, and normal stress on its consolidation creep behavior. Based on the observed characteristics of the consolidation creep curves, a hyperbolic empirical consolidation creep constitutive model incorporating the effects of initial dry density, moisture content, and normal stress was developed. The experimental results indicate that the consolidation creep behavior of red-stratum mudstone can be divided into three stages: instantaneous creep, decelerated creep, and stable creep. Higher moisture content, lower initial dry density, and greater normal stress result in increased total deformation, larger secondary consolidation coefficients, and longer durations to reach creep stability. The proposed constitutive model accurately captures the consolidation creep characteristics of red-stratum mudstone, providing a theoretical basis for assessing and improving geological safety in red-mudstone engineering regions.

To investigate dynamic fatigue behavior of foam in military protective applications, such as helmets, additively manufactured (AM) foams were compressively strained into the plateau region using a reduced design of experiments. A simple power law was found to govern the decline in dynamic stiffness (complex modulus) as the foams underwent the purchase order requirement of 10,000 cycles of small deformation in the plateau region. This rate of decline was newly found to correlate with the degree of nonlinearity in the material’s deformation, quantified using total harmonic distortion. Materials with low nonlinearity exhibited relatively stable stiffness across cycles, while those with high nonlinearity experienced greater losses. The observed nonlinearity depended on both applied stress and strain rate. A strong linear correlation ((mathrm{R}^{2} = 0.78)) was identified between second-order nonlinearity and the time-dependent stiffness response. Two lattice structures were examined: face-centered tetragonal (FCT) and simple cubic (SC). The SC material exhibited higher total harmonic distortion (5%) and lower stiffness retention than the FCT (2%). These results suggest that for cyclic compression applications in a wide variety of industries such as packaging, personal protective equipment, or aerospace, selecting materials with lower stress and greater structural uniformity can enhance the stability of dynamic performance.

Based on the characteristics of microplastic strain and strain hardening during single loading process of rock materials, high-cycle and low-cycle fatigue damage models describing the characteristics of micro-plastic strain and strain hardening of rocks under freeze-thaw cycles were obtained; a fatigue life equation linking microplastic strain and strain hardening is established. According to the high cycle and low cycle fatigue damage models and freeze-thaw cycle experimental data, the fatigue life and other model parameters in the high cycle and low cycle fatigue damage models are determined under double logarithmic coordinate system. In view of the micro pore expansion and the stress increase caused in rocks due to freeze-thaw cycles, the coupled damage variables and its damage range under the combined action of freeze-thaw and stress were derived. The research results indicate that with the increase of freeze-thaw cycles, the coupled damage shows a high cycle fatigue damage followed by low cycle fatigue damage; when determining the damage value of freeze-thaw rock, low cycle fatigue damage can be equivalent to the increase of high cycle fatigue cycle number; the equivalent damage model based on the Lemaitre strain equivalence hypothesis and high-cycle fatigue damage model only describe the damage evolution within the microplastic strain range; whereas the low-cycle fatigue damage model can reveal the damage evolution from microplastic strain to strain hardening range; in the process of microplastic strain to strain hardening development, the damage evolution rate of freeze-thaw rock gradually decreases, showing brittle reduction and plastic increase.

Under prolonged wet–dry cycling, the structural integrity of reef limestone in island and reef coastal zones deteriorates, resulting in significant reductions in rock strength and engineering stability. This study investigates the degradation behavior and mechanisms of reef limestone subjected to repeated wet–dry cycles. Uniaxial compression, splitting tensile, and Split Hopkinson Pressure Bar (SHPB), combined with X-ray Fluorescence Spectrometer (XRF) and Scanning Electron Microscope (SEM) analyses, were conducted to evaluate strength degradation, damage evolution, and microstructural changes under varying cycle numbers ((N)). Fractal analysis of fracture debris established a linear relationship between (N) and the fractal dimension, quantitatively linking macroscopic mechanical degradation with microstructural evolution. Results show that as (N) increases, compressive and tensile strengths decline from 7.45 MPa to 3.13 MPa and 4.20 MPa to 2.08 MPa, respectively, with failure modes shifting from brittle to shear failure. Dynamic compressive strengths decreased to 20.43 MPa, 23.49 MPa, and 25.50 MPa. Increasing fractal dimensions indicate progressive fragmentation, while SEM and XRF reveal mineral dissolution, pore expansion, and microcrack connectivity as key degradation mechanisms. Overall, reef limestone exhibits significant mechanical and structural weakening under wet–dry cycling, highlighting the strong coupling between microstructural evolution and macroscopic damage—of critical importance to island and reef engineering.