Microstructural Damage Research Articles

The effect of secondary phases on microstructure and irradiation damage in an as-built additively manufactured 316 L stainless steel with a hafnium compositional gradient

Additive manufacturing (AM) or rapid prototyping has become a crucial tool for reducing both cost and time while increasing efficiency in qualifying structural materials for reactor use. In this study, directed energy deposition (DED) was used to develop an as-built 316 L stainless steel sample with three regions of increasing Hf-dopant to study the effects of Hf on the irradiation response of the material. Morphological and microstructural changes were analyzed before and after 2 MeV proton irradiation at 360 °C to a damage of 2.5 dpa at ∼ 10 µm below the surface. The addition of Hf effectively suppressed radiation-induced damage (dislocation loops, radiation-induced segregation) due to enhanced point defect recombination. The radiation damage seen in the as-built sample was further compared to a thermo-mechanically treated counterpart of the same fabrication and irradiation parameters which was found to behave superiorly. The increased radiation resistance of this material may be attributed to the as-built microstructure, which includes undissolved Hf particles, delta ferrite grains and cellular sub-grain boundaries that can hinder defect motion.

Exploring the Mechanisms of Modified Bu-Shen-Yi-Qi Decoction for COPD-Related Osteoporosis Therapy via Transcriptomics and Network Pharmacology Approach.

To investigate the effectiveness of modified Bu-Shen-Yi-Qi decoction (MBSYQ) in the treatment of osteoporosis associated with chronic obstructive pulmonary disease (COPD) and its underlying mechanisms of action. Disease targets, active ingredients and targets were predicted by TTD, CTD, DisGeNET, HERB (BenCaoZuJian as its Chinese name), and multiple-TCM databases; In addition, the screened targets were performed via the online platforms DAVID 6.8 and Metascape for GO and KEGG pathway enrichment analysis; The relationship between the MBSYQ and core targets were verified by molecular docking technique. Then we established a COPD-associated osteoporosis rat model by passive 24-week cigarette exposure. We assessed the efficacy of MBSYQ by lung histopathology assessment and distal femur/the first lumbar vertebra (L1) microstructural assay. In addition, we performed tibial RNA sequencing, which was validated by RT-PCR and Western blot. Screening revealed that the 350 active compounds of MBSYQ anchored 228 therapeutic targets for COPD-related osteoporosis; KEGG pathway enrichment analysis showed that the key targets mainly regulated MAPK and PI3K/AKT signaling pathways. In vivo studies showed that MBSYQ treatment alleviated pathological alterations in lung tissue, and reversed the bone loss and microstructure damage in the femur/L1 of model rats. The RNA seq indicated that MBSYQ could upregulate genes associated with anti-oxidative stress and aerobic respiration. The GSEA analysis displayed that MAPK and PI3K/AKT pathways were inhibited by CS exposure and activated by MBSYQ. MBSYQ is effective in the prevention and treatment of COPD-related osteoporosis, partially achieved by improving oxygen metabolism and activating MAPK and PI3K/AKT pathways.

Effects of different drying methods on the physicochemical and functional properties of Pyracantha fortuneana (Maxim.) Li fruit

Pyracantha fortuneana (Maxim.) Li fruits (PFFs) are a traditional food with multiple health benefits. Considering the limited information about how drying methods affect chemical and functional properties, this study aimed to determine the effects of hot-air drying (HAD), far-infrared drying (FIRD), vacuum drying (VD), freeze drying (FD), and sun drying (SD) on the appearance, microstructure, and chemical and functional properties of PFFs. Results showed that the qualities changed considerably with different methods. FD fruits had comparable chemicals (phenolics and flavonoids) and bioactivities (antioxidant activities and digestive enzyme-inhibitory effects) to fresh samples. SD and HAD at 40 °C did not trigger serious degradation of bioactivities. Conversely, higher temperatures (60 °C and 80 °C) resulted in remarkable shrinkage and microstructure damage. HAD60, FIRD60, VD60, and HAD80 decreased the contents of free phenolics (by 59.6%, 58.4%, 56.0%, and 61.0%, respectively, P < 0.05) and flavonoids (by 41.8%, 39.8%, 34.7%, and 48.5%, respectively, P < 0.05) compared with the contents in fresh samples. Heat treatment also reduced bioactivities. Principal component and clustering analyses revealed the relationship between samples and properties, indicating that FD, HAD40, and SD preserved chemicals and bioactivities. Generally, the results suggested that the suitable drying technique for PFFs was low-temperature drying.

NfL and GFAP in serum are associated with microstructural brain damage in progressive multiple sclerosis.

The potential of neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) as biomarkers of disease activity and severity in progressive forms of multiple sclerosis (MS) is unclear. To investigate the relationship between serum concentrations of NfL, GFAP, and magnetic resonance imaging (MRI) in progressive MS. Serum concentrations of NfL and GFAP were measured in 32 healthy controls and 32 patients with progressive MS from whom clinical and MRI data including diffusion tensor imaging (DTI) were obtained during three years of follow-up. Serum concentrations of NfL and GFAP at follow-up were higher in progressive MS patients than in healthy controls and serum NfL correlated with the EDSS score. Decreasing fractional anisotropy (FA) in normal-appearing white matter (NAWM) correlated with worsening EDSS scores and higher serum NfL. Higher serum NfL and increasing T2 lesion volume correlated with worsening paced autitory serial addition test scores. In multivariable regression analyses with serum GFAP and NfL as independent factors and DTI measures of NAWM as dependent factors, we showed that high serum NfL at follow-up was independently associated with decreasing FA and increasing MD in NAWM. Moreover, we found that high serum GFAP was independently associated with decreasing MD in NAWM and with decreasing MD and increasing FA in cortical gray matter. Serum concentrations of NfL and GFAP are increased in progressive MS and are associated with distinct microstructural changes in NAWM and CGM.

Investigation of the damage of L-HPC under stress corrosion

This paper presents a study on the performance damage of lightweight aggregate high performance concrete (L-HPC) under stress corrosion. While L-HPC was undergoing accelerated corrosion in 15% NaCl solution, it was continuously loaded for 90 d, 180 d and 270 d at stress levels with initial L-HPC peak loads of 0%, 50%, 70%. The chloride ion content change, mechanical property deterioration and microstructural damage of L-HPC were studied in detail. The results show that: The dense structure of L-HPC makes it free from obvious cracks at high stress levels (70% peak load), and the quality does not change significantly. The internal curing effect of the lightweight aggregates makes the interfacial transition zone more dense, which hinders the intrusion of chloride ions. The deterioration of L-HPC was slowed down at the initial stage of stress corrosion, but aggravated at the later stage of stress corrosion due to the corrosion of steel fibers.

Experimental Detection of Lubrication Characteristics in a Solid–Liquid Two-Phase Flow Supported Bearing-Rotor System Using Vibration Monitoring Techniques

This work aims to investigate the friction and vibration behaviors of a liquid–solid two-phase flow supported bearing-rotor system for the early monitoring and assessing of oil contamination resulting from externally ingested particles. Based on a Jeffcott rotor test rig, the lubricating oil in journal bearing was mixed with micron-scale silica particles of different sizes and concentrations. The vibration monitoring techniques utilizing eddy current, photoelectric, and piezoelectric sensors were conducted to detect the rotor displacement amplitude and bearing acceleration online. According to the quantitative evaluation, the vibration frequency spectrum, shaft trajectory, and the bearing surface characteristics were analyzed and classified at different conditions of particle parameters. Furthermore, the lubricating mechanism at bearing interface which possesses a strong interactive coupling effect with rotor vibration was deduced and illustrated. The results showed that although the sizes of ingested micron particles were less than the minimum oil-film thickness, they usually exhibited detrimental effects on the flow stability and fluid support. As the particle size or concentration increased, the interaction between particles and bearing surfaces led to the burrs in time-domain waveform, reverse displacements in rotor orbit, higher frequency harmonics in vibration spectrum, and the scratches on the bearing surface. The occurrence of continuous three-body friction could induce misalignment, blockage, oil starvation, and rub-impact fault. Furthermore, the detectability of particle contamination and damage microstructure of bearing surface was described for reference.

Polystyrene microplastics disrupted physical barriers, microbiota composition and immune responses in the cecum of developmental Japanese quails

Microplastics, a new type of emerging pollutant, is ubiquitous in terrestrial and water environments. Microplastics have become a growing concern due to their impacts on the environment, animal, and human health. Birds also suffer from microplastics contamination. In this study, we examined the toxic effects of polystyrene microplastics (PS-MPs) exposure on physical barrier, microbial community, and immune function in the cecum of a model bird species—Japanese quail (Coturnix japonica). The one-week-old birds were fed on environmentally relevant concentrations of 20 µg/kg, 400 µg/kg, and 8 mg/kg PS-MPs in the diet for 5 weeks. The results showed that microplastics could cause microstructural damages characterized by lamina propria damage and epithelial cell vacuolation and ultrastructural injuries including microvilli breakage and disarrangement as well as mitochondrial vacuolation in the cecum of quails. In particular, blurry tight junctions, wider desmosomes spacing, and gene expression alteration indicated cecal tight junction malfunction. Moreover, mucous layer breakdown and mucin decrease indicated that chemical barrier was disturbed by PS-MPs. PS-MPs also changed cecal microbial diversity. In addition, structural deformation of cecal tonsils and increasing proinflammatory cytokines suggested cecal immune disorder and inflammation responses by PS-MPs exposure. Our results suggested that microplastics negatively affected digestive system and might pose great health risks to terrestrial birds.

A mean-field micromechanical incremental approach for brittle damage in particulate microstructures under monotonic loading, using a piecewise uniform damage field

In this work, a mean-field micromechanical approach is proposed to determine the effective behaviour of a microstructure where damage occurs in one phase. Our approach fits into the framework of generalised standard materials proposed by Germain et al. (1983) by defining an incremental potential in the spirit of Lahellec and Suquet (2007), made up of two potentials: the free energy and the dissipation, given in this work by Lorentz and Andrieux (2003). It results in the definition of an elastic nonlinear problem at each time increment but, due to the damage evolution, this incremental potential is non convex. The proposed incremental approach also deviates from Lahellec and Suquet (2007) by considering in the damaged phase two sub-phases characterised by two damage states at the beginning of each time step. Next, this elastic nonlinear problem is regularised by introducing a linear comparison composite whose features are optimised by taking inspiration from the Full Optimised Second Order approach of Ponte-Castañeda (2016). However, the reduction of the number of degrees of freedom of the problem is realised by considering an isotropic linear comparison medium.The abilities of the proposed approach are assessed through a particular case. The composite is made up of two elastic phases : the matrix and the inclusions. The inclusions are subjected to a monotonous increasing swelling while the boundary of the RVE is stress free. For this problem, the resulting solution is given by closed-form expressions. These analytical developments are then used to obtain the effective response of the composite whose dependency on physical parameters (volume fraction of inclusions, toughness of the matrix, elastic contrast ...) is then analysed. The analysis is essentially based on an energy balance between the relaxed stored elastic energy and the dissipated energy. Explicit expressions of the critical values of the unique loading parameter (swelling of the inclusions) related to the onset of damage and the failure of the matrix phase are also given. The theoretical effective response compares well with the results of full fields calculations.

The Influences of Cryopreservation Methods on RNA, Protein, Microstructure and Cell Viability of Skeletal Muscle Tissue.

Background: Different experiments require different sample storage methods. The commonly used preservation methods in biobank practice cannot fully meet the multifarious requirements of experimental techniques. Programmable controlled slow freezing (PCSF) can maintain the viability of tissue. In this study, we hypothesized that PCSF-preserved samples have potential advantages in matching subsequent experiments compared with existing methods. Methods: We compared the differences on skeletal muscle tissue RNA integrity, protein integrity, microstructure integrity, and cell viability between four existing cryopreservation methods: liquid nitrogen (LN2) snap-freezing, LN2-cooled isopentane snap-freezing, RNAlater®-based freezing, and PCSF. RNA integrity was evaluated using agarose gel electrophoresis and RNA integrity number. Freezing-related microstructural damage in the muscle tissue was evaluated using ice crystal diameter and muscle fiber cross-sectional area. Protein integrity was evaluated using immunofluorescence staining. Cell viability was evaluated using trypan blue staining after primary muscle cell isolation. Results: PCSF preserved RNA integrity better than LN2 and isopentane, with a statistically significant difference. RNAlater preserved RNA integrity best. PCSF best controlled ice crystal size in myofibers, with a significant difference compared with LN2. The PCSF method best preserved the integrity of protein epitopes according to the mean fluorescence intensity results, with a significant difference. Cell viability was best preserved in the PCSF method compared with the other three methods, with a significant difference. Conclusion: PCSF protected the RNA integrity, microstructural integrity, protein integrity, and cell viability of skeletal muscle tissue. The application of PCSF in biobank practice is recommended as a multi-experiment-compatible cryopreservation method.

Microwave Treatments and Their Effects on Selected Properties of Portuguese Pinus pinaster Aiton. and Eucalyptus globulus Labill. Wood

The most widespread wood species in the Portuguese forest and the most widely utilized are maritime pine (Pinus pinaster) and eucalyptus (Eucalyptus globulus Labill). In the case of eucalyptus, except for the pulping sector, it might have limited usage due to drying issues and low permeability. Microwave (MW) treatment is a technology that has been used to improve wood species’ permeability. Therefore, the present paper aimed to evaluate the MW treatment of both Portuguese wood species and to investigate the effects of different MW treatments on wood’s density, water uptake capability, modulus of rupture (MOR), and modulus of elasticity (MOE). Using small clear wood specimens, two MW powers were used, 700 and 1200 W, and the samples were submitted to successive MW cycles of 2 min till they reached the required dryness. The results showed that each wood species had a different behavior during the MW drying in terms of drying rate, supply, and consumption of energy. In general, with the increase in MW power, the densities of both species decreased and the water uptake increased, as a possible indicator that a certain level of microstructural damage might have occurred. Regarding the mechanical properties of MW-treated maritime pine and eucalyptus wood specimens, under the harshest conditions (MW power of 1200 W), MOR and MOE were reduced compared with the wood sample without MW treatment.

Spinal cord perfusion is associated with microstructural damage in cervical spondylotic myelopathy patients who underwent cervical laminoplasty.

To investigate the association between spinal cord perfusion and microstructural damage in CSM patients who underwent cervical laminoplasty using MR dynamic susceptibility contrast (DSC), diffusion tensor imaging (DTI), and neurite orientation dispersion and density imaging (NODDI) techniques. A follow-up cohort study was conducted with 53 consecutively recruited CSM patients who had undergone cervical laminoplasty 12-14months after the surgery from April 2016 to December 2016. Twenty-one aged-matched healthy volunteers were recruited as controls. For each patient, decompressed spinal cord levels were imaged on a 3.0-T MRI scanner by diffusion and DSC sequences to quantify the degrees of microstructural damage and perfusion conditions, respectively. The diffusion data were analyzed by DTI and NODDI models to produce diffusion metrics. Classic indicator dilution model was used to quantify the DSC metrics. Mann-Whitney U test was performed for comparison of diffusion metrics between patients and healthy controls. Pearson correlation was used to explore the associations between the metrics of spinal cord perfusion and microstructural damage. DTI metrics, neurite density, and isotropic volume fraction had significant differences between postoperative patients and healthy controls. Pearson correlation test showed that SCBV was significantly positively correlated with RD, MD, and ODI, and negatively correlated with FA and NDI. SCBF was found to be significantly positively correlated with RD and MD, and negatively correlated with FA. Increased spinal cord perfusion quantified by DSC is associated with microstructural damage assessed by diffusion MRI in CSM patients who underwent cervical laminoplasty. This study found that the spinal cord perfusion is associated with microstructural damage in postoperative cervical spondylotic myelopathy patients, indicating that high perfusion may play a role in the pathophysiological process of cervical spondylotic myelopathy and deserves more attention. • Spinal cord microstructural damage can be persistent despite the compression had been relieved 12-14 months after the cervical laminoplasty in cervical spondylotic myelopathy (CSM) patients. • Spinal cord perfusion is associated with microstructural damage in CSM patients after the cervical laminoplasty. • Inflammation in the decompressed spinal cord may be a cause of increased perfusion and is associated with microstructural damage during the recovery period of CSM.

MCC950 ameliorates cognitive function by reducing white matter microstructure damage in rats after SAH

Neuroinflammation and white matter microstructure damage are important causes of cognitive impairment after subarachnoid hemorrhage (SAH). Nod-like receptor protein 3 (NLRP3) plays an important role in neuroinflammation after SAH and may be a potential therapeutic target for treatment of white matter microstructure injury. In this study, we observed whether MCC950, a specific inhibitor of the NLRP3 inflammasome, exerted a therapeutic effect after SAH. The SAH model was induced by endovascular perforation in SpragueDawley rats. MCC950 was injected intraperitoneally 1 h after SAH at a dose of 10 mg/kg. The results showed that MCC950 significantly attenuated white matter microstructure damage in some brain regions, and behavioral experiments confirmed that MCC950 ameliorated cognitive function in rats after SAH, which may provide a new method for the treatment of cognitive dysfunction in SAH patients.

Progress in Experimental Research on Mechanical Behavior of Composite Solid Propellants

Composite solid propellant is a particle reinforced composite material, and its microstructure strongly affects its macroscopic mechanical properties. This article reviews the current research status of macroscopic mechanical experiments and microscopic experiments. In terms of macroscopic mechanical performance testing, based on the description of the number of loading axes used to load the specimen, the development of related experimental research on uniaxial loading is relatively mature, while research on multi-axial loading is still lacking, and a unified standard has not yet been formed. In terms of microscopic experiments, although there are currently many observation methods, each has its own advantages and disadvantages; In experimental studies on the microstructure observation of solid propellants under loading conditions, most of them are based on uniaxial loading devices combined with optical microscopes, scanning electron microscopes, or micro CT devices to conduct research on the microstructure damage process of solid propellants under uniaxial loading. However, the research on the microstructure damage evolution process of solid propellants under multi-axial loading is currently in a research gap at home and abroad. Finally, this article summarizes and comments on the current research status, Proposed the shortcomings of current research and the key areas that need to be studied.

Fatigue damage assessment using nonlinear critically refracted longitudinal (LCR) wave in pure iron: Experiments and FEM

To achieve early-stage microstructure evolution assessment and damage monitoring of fatigue, a new thickness-independent and nondestructive method based on nonlinear critically refracted longitudinal (LCR) wave is proposed. The nonlinear ultrasonic (NLU) parameter is sensitive to the accumulated fatigue damage, showing two peaks around the 5th and 1000th cycles (0.03% and 6% of fatigue life), respectively. This phenomenon is comprehensively discussed in terms of dislocation structure evolution based on the dislocation string model. A correction considering the weakening of nonlinearity induced by the rough surface is applied to the experiment measurements. The corresponding results are closer to the finite element modeling (FEM) quantitation based on the dislocation-dependent nonlinear constitutive relation. Compared to linear LCR wave, nonlinear LCR wave has weaker sensitivity to roughness effect and higher sensitivity to damage such as dislocation, which offers a new method for monitoring fatigue in engineering components.

Fatigue life and failure mechanism of nylon 66 cord/rubber composites under wide temperature range

This work simulates the real harsh service conditions of Fiber-reinforced polymer composites (FRPC), and the dynamic adhesion and failure mechanism of nylon 66 (PA66)-reinforced natural rubber (NR) composites under large deformation and wide temperature range are deeply studied by comprehensive analysis of the interfacial adhesion evolution, microstructure and failure damage location of the composites, interfacial heating rate, and modulus ratio of PA66/NR. The failure mechanism of PA66/NR composites is interfacial debonding at −20 °C, 25 °C and 80 °C, whereas that at 120 °C is matrix cracks. Interestingly, at −20 °C, the crack expansion at the interface is slow, and the samples show two-stage damage during fatigue, resulting in the highest fatigue life. At 80 °C, the interface heating rate and modulus ratio of the PA66/NR composites is the lowest, and thus the fatigue life is higher than that at 25 °C and 120 °C. Keywords: fiber reinforced polymer composites, fatigue life, failure mechanism.

Microstructural damage during electrical discharge machining of a high silicon aluminum alloy for space applications

Microstructural damage during electrical discharge machining of a high silicon aluminum alloy for space applications

Investigation on mechanical and thermal properties of MgAl2O4-Mg2TiO4 solid solutions with spinel-type structure

Magnesium aluminate (MA) spinel has shown potential as a refractory material under harsh environments, such as high temperatures and frequent temperature variations. However, understanding the mechanical and thermal properties of MA spinel is a key step towards further improvement of MA spinel refractory materials in high-temperature fields. The formation of solid solution represents a prominent strategy to improve mechanical and thermal properties. The present study develops novel (1-x)MgAl2O4-xMg2TiO4 (0≤ x ≤ 0.1) solid solutions by single-step reaction sintering method using light-burned magnesia, reactive alumina, and as-prepared Mg2TiO4 (M2T) powders. The effects of M2T content on the crystal structure, mechanical properties, and thermal properties of the MgAl2O4-Mg2TiO4 solid solutions (MATss) were studied. Based on XRD, TEM, and HRTEM results, MATss were highly crystallized with a cubic spinel structure. Besides, the M2T addition facilitated the flexural strength, hardness, and elastic modulus in the MA spinel. Among these solid solutions, the x = 0.08 sample exhibited the highest flexural strength, hardness, and elastic modulus of 219.47 MPa, 19.99 GPa, and 270.2 GPa, respectively. M2T additive played a solid-solution strengthening role, which enhanced the inherent resistance to microstructural damage. Additionally, the x = 0.08 sample had the highest thermal conductivity and thermal diffusivity of 12.45 W/(m·K) and 7.98 mm2/s, respectively. In comparison with pure MA spinel, the x = 0.08 sample showed a lower thermal expansion coefficient (8.63 × 10-6 K-1 at 1550 °C). These excellent mechanical properties and exceptional thermal behavior enabled its widespread application in refractory materials.

Trabecular Bone Score as a More Sensitive Tool to Evaluate Bone Involvement in MEN1-related Primary Hyperparathyroidism.

The skeletal involvement of multiple endocrine neoplasia type 1-related primary hyperparathyroidism (MHPT) is not exactly the same as that of sporadic primary hyperparathyroidism (SHPT). Trabecular bone score (TBS) as a texture parameter has been reported to reflect trabecular bone damage. This study aimed to compare the clinical characteristics, especially the skeletal involvement, between patients with MHPT and SHPT. The clinical characteristics were retrospectively collected in 120 patients with MHPT and compared with 360 patients with SHPT in the same period. Dual-energy X-ray absorptiometry were conducted in some patients with MHPT, in whom bone mineral density (BMD) and calculated TBS derived from lumbar spine dual-energy X-ray absorptiometry images were compared with those of patients with SHPT. Although the duration of disease in the MHPT group was longer, the age at hospital visit was significantly lower than that in the SHPT group (43.5 [interquartile range, 31.5-52.0] vs 52.0 [interquartile range, 40.5-61.0], P < .001). The proportion of skeletal involvement in the MHPT group was significantly lower. However, in the subgroup of MHPT cases (n = 86) with data of BMD, there was no significant difference in skeletal involvement from SHPT cases matched for gender and age. Although the BMD and TBS in the lumbar spines of patients with MHPT were lower than those of patients with SHPT (BMD: 0.91 ± 0.18 g/cm2 vs 1.01 ± 0.17 g/cm2; TBS: 1.22 ± 0.14 vs 1.29 ± 0.11, P < .001). According to TBS, among 34 patients with MHPT with normal BMD, 15 patients had bone microstructure damage. The cancellous bone microarchitecture was more severely damaged in patients with MHPT according to TBS, which suggested that TBS could be a sensitive supplemental index in addition to BMD to identify bone-involvement risk in patients with MHPT.

Mesoscale modelling of dislocation evolution: Physically based requirements on stochastic differential equations

The complexity of collective dislocation behaviour has motivated the use of mesoscopic models, which describe the average behaviour of dislocations. Due to the statistical nature of such models, it has been argued that a stochastic theory provides a more complete physical description. A number of stochastic differential equation (SDE)-based dislocation models have been proposed over the past three decades; however, there is no generally accepted method for transforming a deterministic model into a stochastic model. A range of approaches exist in the literature, but the choice of method is ad hoc and their physical consequences are not considered. Such transformations therefore may not preserve certain properties of the corresponding deterministic theory, namely that of non-negativity of the dislocation density. In the present work, we show that the drift and diffusion coefficients must extend to zero on the semi-closed interval [0,∞) to guarantee non-negativity of the dislocation density. We also demonstrate the breakdown of non-negativity in SDE-based dislocation models through analytical treatment of a class of mesoscale models, and propose a possible modification. We bring to attention a physically motivated method for deriving stochastic models which preserves non-negativity, and in general ensures that trajectories exist almost surely in some given set, so that it obeys the desired physical bounds on the state variables — called the stochastic invariance principle. These results can provide a better understanding of dislocation models used to describe microstructural damage accumulation in metallic structures, which can be incorporated into fatigue lifing models.

Physicochemical effect on soil in sliding zone of reservoir landslides

The fate of reservoir landslides is mainly dictated by the mechanical behavior of soil in the sliding zone. This soil may be altered under changing environmental conditions of both physical and chemical nature. In this paper, we present a laboratory study on the changing soil properties under complex physicochemical interactions. The soil specimens are subjected to 1, 2, 3, 5, 7, and 10 wetting-drying cycles. The soil strength is determined by triaxial tests. These tests are performed with three types of pore water, namely, acidic groundwater (AGW), normal groundwater (NGW), and distilled water (DW). The deterioration of soil strength, the change in soil microstructure and mineral composition are observed and correlated. Interesting findings for reservoir landslides are drawn: acidic underground water considerably damages the soil microstructure and deteriorates the shear strength compared to normal underground water, while distilled water causes minimal disaggregation. A three-stage micromechanism associated with four physicochemical interactions is revealed, providing insights into microstructure damage and mineral transformation.