Ultimate Degradation Research Articles

Impact of Cu content on the activity of TiO2-based catalysts for toluene oxidation

Toluene is one of the most toxic contaminants in industrial waste gases, it can enter the body through the respiratory system and skin. Long-term exposure to it can lead to skin inflammation and neurasthenia, and even cause lesions in organs. Over the years, catalytic oxidation technology has been extensively employed to the remove of toluene, and oxides, especially copper oxide, is considered to be an effective catalyst technology and has been extensively studied. In this work, we introduced CuO as an active species to investigate the impact of Cu content in TiO2@CuO (TC-x, x=1, 2, 3, and 5) catalyst on the activity, reusability, and stability of toluene oxidation. The result demonstrated that the addition of Cu species, facilitating the generation of active oxygen obviously reduced the complete oxidation temperature of toluene. Among them, TC-3 catalyst exhibited the highest activity (T50 = 234 ℃, T90 = 289 ℃, and T100 = 310 ℃, with Ctoluene=1000 ppm, WHSV=20,000 mL/ (g h)), great reusability, and stability for toluene degradation. According to the in-situ DRIFTS, the ultimate degradation products of toluene were CO2 and H2O, which were clean and free of secondary pollution.

Compression behavior of CFST columns under combined influence of gap and freeze-thaw

Owing to factors related to construction quality and environment, concrete-filled steel tube (CFST) structures that have been in use for many years in regions experiencing seasonal freeze–thaw cycles are susceptible to the combined effects of a spherical-cap gap and freeze–thaw cycling. Therefore, in this study, a combination of experiments and the finite element method is used to investigate the effects of these two factors on the axial compression behavior of CFST stub columns. The experimental results show that the main failure mode of the specimen is local buckling at the end or the middle and inward depression of the steel tube on the existing gap side. The degradation of mechanical parameters, such as the ultimate bearing capacity and ductility of the specimens, gradually increased with increasing gap ratio and number of freeze–thaw cycles. In the numerical simulation section, the change in the stress response to freeze–thaw cycling on the gap side is analysed. The impact of the constraint effect coefficient on the ultimate bearing capacity degradation of the specimens is also investigated. Finally, a formula for calculating the ultimate capacity of CFST stub columns affected by the two factors is proposed, and the formula for calculating the ultimate bearing capacity in the code is improved. The results of this study can provide a reference for durability prediction and structural safety evaluation of CFST structures with a spherical-cap gap in cold regions.

Corrosion evolution and axial mechanical performance degradation of corroded M24 high-strength bolts

To investigate the axial static performance degradation of high-strength bolts subjected to long-term atmospheric corrosion in coastal environments, a neutral salt spray accelerated corrosion test was performed on M24 high-strength bolts over a period ranging from 0 to 330 days. Microscopic morphology observations and axial tensile tests were conducted after corrosion. A linear relationship between mass loss rate and corrosion period was established, and the evolution of pit depth and aspect ratio was proposed. Based on the tensile test, the failure modes of corroded high-strength bolts were categorized as bolt breakage and thread shear-out. The critical mass loss rate for the transition between these two modes was found to be 7.05% (corrosion period of 180 days). Equations characterizing the degradation of residual ultimate strength and relative stiffness as a function of mass loss rate were derived. Furthermore, based on average thickness loss and pit loss, a theoretical analysis on ultimate strength degradation was conducted, and its results were compared to the refined numerical simulations. Both methods were found to provide acceptable outcomes, and numerical results demonstrated more precise and conservative. With numerical method, parametric analysis was conducted, involving 5 groups and 222 models, leading to the formulation of a general ultimate bearing capacity assessment equation concerning bolt diameter and thread pitch.

Aquaporin splice variation differentially modulates channel function during marine teleost egg hydration.

Aquaporin-mediated oocyte hydration is a developmentally regulated adaptive mechanism that co-occurs with meiosis resumption in marine teleosts. It provides the early embryos with vital water until osmoregulatory systems develop, and in the majority of marine teleosts causes their eggs to float. Recent studies have shown that the subdomains of two water channels (Aqp1ab1 and Aqp1ab2) encoded in a teleost-specific aquaporin-1 cluster (TSA1C) co-evolved with duplicated Ywhaz-like (14-3-3ζ-like) binding proteins to differentially control their membrane trafficking for maximal egg hydration. Here, we report that in species that encode the full TSA1C, in-frame intronic splice variants of Aqp1ab1 result in truncated proteins that cause dominant-negative inhibition of the canonical channel trafficking to the plasma membrane. The inhibition likely occurs through hetero-oligomerization and retention in the endoplasmic reticulum (ER) and ultimate degradation. Conversely, in species that only encode the Aqp1ab2 channel we found an in-frame intronic splice variant that results in an intact protein with an extended extracellular loop E, and an out-of frame intronic splice variant with exon readthrough that results in a truncated protein. Both isoforms cause dominant-negative enhancement of the degradation pathway. However, the extended and truncated Aqp1ab2-type variants can also partially escape from the ER to reach the oocyte plasma membrane, where they dominantly-negatively inhibit water flux. The ovarian follicular expression ratios of the Aqp1ab2 isoforms in relation to the canonical channel are lowest during oocyte hydration, but subsequently highest when the canonical channel is recycled, thus leaving the eggs endowed with >90% water. These findings suggest that the expression of inhibitory isoforms of Aqp1ab1 and Aqp1ab2 may represent a new regulatory mechanism through which the cell-surface expression and the activity of the canonical channels can be physiologically modulated during oocyte hydration in marine teleosts.

In vitro digestion under simulated saliva, gastric and small intestinal conditions and fermentation of nicotinamide mononucleotide, and its effects on the gut microbiota

Nicotinamide Mononucleotide (NMN) is a derivative of vitamin B3, which plays a significant role in a plethora of metabolic reactions in the human body and is intricately associated with both immunity and metabolism. Nonetheless, in the intestine metabolic pathway of NMN and the relationship between NMN, gut microbiota, and SCFAs remain hitherto obscure. This study examined the digestion of NMN in simulated saliva, gastric, and small intestine environments, as well as exploring the interaction between NMN and human gut microbiota utilizing an in vitro fermentation model. NMN was progressively degraded into nicotinamide ribose (NR), nicotinamide (NAM), and ribose, with niacinate (NA) constituting the ultimate degradation product due to hydrolysis and metabolism by microbiota. NMN was ingested by human intestinal microbiota with a slower fermentation rate. As a result of NMN ingestion by human gut bacteria，the concentrations of propionate and butyrate increased by 88% and 23%, respectively, compared to the blank control group, the proliferation of beneficial gut bacteria (Bifidobacterium, Phascolarctobacterium, Faecalibacteriun, and Alistipes) significantly increased, while the proliferation of some harmful bacteria (Sutterella, Desulfovibrio and Pseudomonas) drastically declined. These findings illustrated the metabolic processes of NMN in the intestine, elaborating the relationship between NMN, SCFAs and gut microbiota. NMN might be a potential prebiotic to improve intestinal health.

Degradation of trichloroethylene by biochar supported nano zero-valent iron (BC-nZVI): The role of specific surface area and electrochemical properties

Direct electron transfer and the involvement of atomic hydrogen (H⁎) are considered the main mechanisms for reductive dechlorination promoted by nano zero-valent iron (nZVI) supported on highly conductive carbon. It is still unclear how precisely H⁎, the specific surface area, and the electrochemical characteristics contribute to biochar supported nano zero-valent iron (BC-nZVI) activity in chlorinated hydrocarbon contaminant removal. In this study, a range of BC-nZVIs were prepared by a liquid-phase reduction process, and the contributions of specific surface area and electrochemical performance to H⁎ generation and electron transfer have been assessed. The mechanism of trichloroethylene (TCE) dechlorination by BC-nZVIs has been evaluated in terms of removal efficiency and the ultimate degradation products. The results have demonstrated that BC-nZVIs exhibit a higher specific surface area and TCE degradation efficiency compared with the bare nZVI. Ethane, ethylene, and acetylene were the principal TCE degradation products. The elimination of TCE was not significantly affected by differences in BC-nZVI specific surface area, but electron transfer and sustained generation of H⁎ were dependent on the catalyst electrochemical characteristics. The electrochemical properties of biochar serve to lower the corrosion potential of nZVI, improving electronic transfer capability and reactivity and promoting direct electron transfer for the degradation of TCE. In addition, the enhanced electrochemical properties also facilitate the reaction of nZVI with water and can promote the sustained generation of H⁎. Generation of H⁎ played a key role in reductive dechlorination over BC-nZVIs, which was related to the properties of the biochar support. This study focuses on the role of H⁎ and electrochemical performance in TCE reductive dechlorination, and provides a theoretical foundation and experimental support for the practical application of BC-nZVIs.

Pesticide transport through the vadose zone under sugarcane in the Wet Tropics, Australia

Abstract. Photosystem II (PS II) pesticides, recognized as a threat to ecological health, were targeted for reduction in sugarcane farming in Great Barrier Reef (GBR) catchments. Alternative herbicides, the non-PS II herbicides (including glyphosate, paraquat, 2,4-D, imazapic, isoxaflutole, metolachlor, and S-metolachlor), continue to be used in these catchments. However, the potential ecological fate, transport, and off-site environmental effects of non-PS II herbicides, with respect to their usage scheme, local rainfall patterns, and infiltration dynamics, have not been investigated previously. A vadose zone monitoring system, instrumented beneath sugarcane land in a GBR catchment, was applied for real-time tracing of pesticide migration across the unsaturated zone, past the root zone during 2017–2019. The regularly applied pesticides (fluroxypyr and isoxaflutole) exhibited substantial migration through the unsaturated zone. Within 1 month of application of fluroxypyr, it leached to 2.87 m depth in the vadose zone, with declining concentrations with depth. Isoxaflutole, which was applied yearly, was found only once, in November 2018, at 3.28 m depth in the soil profile. Other pesticides (imazapic, metolachlor, glyphosate, and haloxyfop) applied during the same period were not detected in the vadose zone. However, imidacloprid, which was not applied at the site during the monitored period, was detected across the entire vadose zone, revealing substantial resistance to degradation. The results show no evidence of any regularly applied pesticides in the site bores at the end of the study, indicating their ultimate degradation within the vadose zone before reaching the groundwater.

Degradation of water soluble poly(vinyl alcohol) with acoustic and hydrodynamic cavitation: laying foundations for microplastics

Water-soluble poly(vinyl alcohol) (PVOH) is widely used in the textile and paper industries and in households as detergent pods. In addition to conventional microplastics, water-soluble PVOH poses an environmental threat because it is usually washed down the drain unnoticed and unobstructed. If not treated during wastewater treatment, it enters the aquatic ecosystem in estimated quantities of several thousand tons annually. The present study aims to address the degradation of PVOH on a laboratory scale by acoustic and hydrodynamic cavitation, assisted or not with an oxidative agent. A hydrodynamic cavitation generator, designed with consideration for real-life application, presents an innovative technology adapted for wastewater treatment. The effects of temperature, addition of external oxidant, and methanol as a hydroxyl radical (•OH) scavenger to PVOH solutions were systematically studied. At optimal operating conditions, PVOH molar mass averages significantly decreased (from weight average molar mass of 124 to 1.6 kg mol−1 in case of 60 min treatment with hydrodynamic cavitation and addition of external oxidant) with concomitant narrowing of molar mass distribution. The SEC/MALS, FTIR, and 1H NMR results show that mechanical degradation of PVOH chains predominates in acoustic cavitation, while chemical effects also play an important role in hydrodynamic cavitation. Findings from this study could serve as model research for the degradation of other carbon-backbone polymers and provide a route to improved ultimate (bio)degradation of functionalized polymers in the environment.

Primary and ultimate degradation of benzophenone-type UV filters under different environmental conditions and the underlying structure-biodegradability relationships

Ten common benzophenone-based UV filters (BPs), sharing the same basic structure and differing only in their substituents, were investigated with respect to their primary and ultimate biodegradability. This study was carried out in order to gain deeper insights into the relationship between structure and biodegradability. The primary biodegradation of the selected BPs was studied in river water at environmentally relevant concentrations (1 µg/L) while varying specific, crucial environmental conditions (aerobic, suboxic, supplementation of nutrients). For this purpose, both batch and column degradation tests were performed, which allowed a systematic study of the effects. Subsequently, the ultimate biodegradation, i.e. the potential to achieve full mineralization of BPs, was examined according to OECD guideline 301 F. The results indicate that mineralization is limited to derivatives in which both aromatic rings contain substituents. This hypothesis was supported by docking simulations showing systematic differences in the orientation of BPs within the active site of the cytochrome P450 enzyme. These differences in orientation correspond to the substitution pattern of the BPs. This study provides valuable insights for assessing the environmental hazards of this class of trace organic compounds.

Investigation into shale softening induced by water/CO2-rock interaction

To investigate the shale softening behavior induced by water/Carbon dioxide (CO2)-rock interaction, a series of scanning electron microscope (SEM) observation and nanoindentation tests were performed on carbonate-rich shale specimens after high-temperature and high-pressure static soaking treatments. The characteristics of shale surface softening and the evolution of micromechanical properties were analyzed. It was indicated that water/CO2-rock interaction resulted in different extents of micromechanical degradation, which was closely related to both the type of soaking fluid and the soaking time. According to the shale surface observation by SEM images, the aperture of hydration-induced fractures after soaking with water was larger than that of adsorption-induced fractures after soaking with CO2. The statistical results of nanoindentation tests show that when soaking with water, the Young's modulus and the hardness ultimately decreased by 34.6% and 57.6% with the soaking time increased from 2 to 6 d, respectively. When soaking with CO2, the extent of shale softening was alleviated. After soaking for 6 d, the ultimate degradation extents were 14.8% and 30.0% for the Young's modulus and the hardness, respectively. Furthermore, due to the higher penetrability of CO2, the micromechanical degradation of the shale surface mainly occurred in the first 2 d. Indents located in the vicinity of shale laminas or induced fractures tended to possess the lower Young's modulus and the hardness than those located in shale matrix, meanwhile resulting in crushed zones or fracture compaction.

Laminar membranes assembled by ultrathin cobalt-copper oxide nanosheets for nanoconfined catalytic degradation of contaminants

• Nanoconfinement catalysis is implemented within Co-Cu ONS membrane nanochannels. • Co-Cu ONS membrane achieves ∼ 100% removal of organic pollutants within 86 ms. • The degradation rate is 10 3−5 times faster compared with the best state-of-the-art. • Oxygen vacancies facilitate electron transfer between metal cations and PMS. • DFT calculations illustrate the mechanism of nanoconfinement catalysis. Practical applications for the degradation of organic contaminants by conventional batch-mode heterogeneous advanced oxidation processes remain elusive due to mass-transfer limitations of short-lived reactive oxygen species (ROS). Nanoconfinement catalysis has received increasing attention because of enhanced reaction efficiency and mass and electron transfer. Here, we implemented the concept of nanoconfinement catalysis using a two-dimensional membrane. Ultrathin cobalt-copper oxide nanosheets (Co-Cu ONS) rich in active sites and oxygen vacancies were prepared through a facile solution reduction method. The assembled Co-Cu ONS membrane with active sites confined within membrane nanochannels spontaneously activates peroxymonosulfate and facilitates the generation of ROS and the redox cycles of metal cations. Therefore, an ultimate degradation efficiency (∼100%), ultrafast (∼86 ms) decomposition of organic pollutants, and excellent catalytic stability (greater than120 h) were achieved. The degradation rate is 10 3−5 times faster than the best state-of-the-art. This approach offers an attractive alternative for water purification with membrane-based nanoconfinement catalysts.

Making Industrial Pittsburgh Modern: Environment, Landscape, Transportation, Energy, and Planning

Making Industrial Pittsburgh Modern: Environment, Landscape, Transportation, Energy, and Planning

Mixtures of CO2 and poly(fluoroacrylate) based on monomers containing only six or four fluorinated carbons: Phase behavior and solution viscosity

Homopolymerization of fluoroacrylate monomers containing a segment with eight fluorinated carbons, (CH2CHCOO(CH2)2(CF2)7CF3), yield poly(fluoroacrylate) (PFA) with remarkably high solubility in CO2, but the corresponding ultimate PFA degradation product perfluorooctanoic acid (PFOA) is bio-accumulative. Based on cloud point loci in the 1–4 wt% PFA in CO2 concentration range at temperatures of 25, 50, 75, 100 and 125 oC, it is shown that C6F13-based and C4F9-based PFA, with relatively benign degradation products perfluorohexanoic acid (PFHxA) and perfluorobutanoic acid (PFBA), respectively, retain the same level of CO2-solubility as that of C8F17-based PFA. Further, both C6F13-based and C4F9-based PFA can increase the viscosity of single-phase CO2-PFA solutions (i.e. thicken CO2) as much as C8F17-based PFA in the 25–125 oC range. Therefore, the design of CO2-soluble PFA need not be constrained to monomers containing the C8F17 moiety; fluoroacrylate monomers containing shorter fluoroalkyl segments with only four or six fluorocarbons can be utilized.

Towards closed-loop material flow in additive manufacturing: Recyclability analysis of thermoplastic waste

Thermoplastic is one of the most popular materials used in additive manufacturing (AM). As the adoption of AM technologies has been rapidly increasing, the feasibility of recycling AM waste and the quality of recycled materials need to be investigated to facilitate closed-loop material flow and cleaner production. In current literature, studies have been performed to compare material property changes before and after recycling, and a certain level of mechanical degradation has been observed. Some material properties such as molecular weight distribution have not yet been investigated in AM recycling. In addition, the recyclability of waste materials under multiple rounds of recycling has not yet been well studied. These knowledge gaps indicate a research need for AM material recyclability evaluation and improvement. In this research, an assessment framework is proposed and implemented to evaluate the recyclability of acrylonitrile butadiene styrene in extrusion-based AM, providing guidelines for quantifying variations of molecular weight distribution, material density, fabrication quality, and mechanical properties under multiple rounds of recycling. Different process parameters and their impact on material recyclability in each round are also studied. Experimental results indicate that the ultimate tensile strength degradation after each recycling round varies from 27% to over 50%; surface roughness increases 29.54% after three rounds of recycling; molecular weight distribution of recycled materials demonstrates obvious shifts, and the polydispersity is decreased by 13.16% after three rounds of recycling. The results of this research will help AM users better understand and implement waste recycling, which will positively impact the AM community by contributing towards achieving cleaner production and enhancing the material efficiency and environmental sustainability of AM.

Lysosomal protein transmembrane 5 promotes lung-specific metastasis by regulating BMPR1A lysosomal degradation

Organotropism during cancer metastasis occurs frequently but the underlying mechanism remains poorly understood. Here, we show that lysosomal protein transmembrane 5 (LAPTM5) promotes lung-specific metastasis in renal cancer. LAPTM5 sustains self-renewal and cancer stem cell-like traits of renal cancer cells by blocking the function of lung-derived bone morphogenetic proteins (BMPs). Mechanistic investigations showed that LAPTM5 recruits WWP2, which binds to the BMP receptor BMPR1A and mediates its lysosomal sorting, ubiquitination and ultimate degradation. BMPR1A expression was restored by the lysosomal inhibitor chloroquine. LAPTM5 expression could also serve as an independent predictor of lung metastasis in renal cancer. Lastly, elevation of LAPTM5 expression in lung metastases is a common phenomenon in multiple cancer types. Our results reveal a molecular mechanism underlying lung-specific metastasis and identify LAPTM5 as a potential therapeutic target for cancers with lung metastasis.

Influence of Heat Treatment on Microstructure and Performance of Degradable Mg Matrix Composites Reinforced with Hollow Glass Microsphere

Recently degradable Mg matrix composites as a promising candidate for degradable downhole tools application have aroused extensive interest. In the present work, the effects of heat treatment (solution treatment and artificial aging) on the microstructure, mechanical properties and degradation behaviors of the newly developed hollow glass microsphere reinforced Mg-Al15-Zn6-Cu1.5 composites were investigated. The results show that the solution treatment causes the β-Mg17Al12 phase and Mg32(Al,Zn)49 phase to dissolve into the α-Mg matrix and the coarse eutectic τ-Al2CuMg phase to translate into blocky morphology. Aging treatment causes the β phase to precipitate at the grain boundaries or the edge of the residual second phases in lamellar and blocky morphology. After solution treatment, the ductility of the composites was significantly increased, while the following aging treatment could significantly increase the ultimate compressive strength (UCS), hardness and degradation rate. The composites solution treated at 420 °C for 20 h and aged at 200 °C for 24 h shows the higher degradation rate of 6.5 mg·cm-2·h-1 in 3 wt.% KCl at ambient temperature, with UCS of 471 MPa, Brinell hardness of 115 HB and fracture strain of 8.7 %, this outstanding comprehensive performance is more suitable for degradable downhole tools application.

Mechanical properties of HRB400E/316L stainless steel clad rebar under low-cycle fatigue

Under severe disasters, the longitudinal rebars in the plastic hinge areas of concrete structures are prone to sustain significant buckling and then suffer low-cycle fatigue, due to the cracking and detachment of covering concrete. Based on a novel type of stainless steel clad rebar with HRB400E hot rolled ribbed carbon steel core covered by 316L stainless steel clad (HRBSC), this paper conducted experimental studies to investigate the mechanical properties of HRBSC under low-cycle fatigue with buckling, considering strain amplitude, strain rate and nominal diameter. Based on the test results, the ultimate strength, strength degradation and fatigue life evaluation methods of HRBSC are discussed and proposed. It is validated that HRBSC possesses desirable material properties and can be used as longitudinal load carrying rebar in seismic designed structures. The elastic modulus of HRBSC is proved to be affected by the clad ratio. It is found that the strain rate and nominal diameter have limited effects on the ultimate strength and strength degradation of HRBSC during low-cycle fatigue, while the key factor is strain amplitude. Test results show that the increase of strain rate influences the low-cycle fatigue mechanism and reduces the fatigue life of HRBSC under small strain amplitude, while the growth of nominal diameter brings positive effects on the fatigue life.

New 19F NMR methodology reveals structures of molecules in complex mixtures of fluorinated compounds.

Although the number of natural fluorinated compounds is very small, fluorinated pharmaceuticals and agrochemicals are numerous. 19F NMR spectroscopy has a great potential for the structure elucidation of fluorinated organic molecules, starting with their production by chemical or chemoenzymatic reactions, through monitoring their structural integrity, to their biotic and abiotic transformation and ultimate degradation in the environment. Additionally, choosing to incorporate 19F into any organic molecule opens a convenient route to study reaction mechanisms and kinetics. Addressing limitations of the existing 19F NMR techniques, we have developed methodology that uses 19F as a powerful spectroscopic spy to study mixtures of fluorinated molecules. The proposed 19F-centred NMR analysis utilises the substantial resolution and sensitivity of 19F to obtain a large number of NMR parameters, which enable structure determination of fluorinated compounds without the need for their separation or the use of standards. Here we illustrate the 19F-centred structure determination process and demonstrate its power by successfully elucidating the structures of chloramination disinfectant by-products of a single mono-fluorinated phenolic compound, which would have been impossible otherwise. This novel NMR approach for the structure elucidation of molecules in complex mixtures represents a major contribution towards the analysis of chemical and biological processes involving fluorinated compounds.

Development and characterization of a hydrogel-based adhesive patch for sealing open-globe injuries

Full-thickness wounds to the eye can lead to serious vision impairment. Current standards of care (from suturing to tissue transplantation) usually require highly skilled surgeons and use of an operating theater. In this study, we report the synthesis, optimization, and in vitro and ex vivo testing of photocrosslinkable hydrogel-based adhesive patches that can easily be applied to globe injuries or corneal incisions. According to the type and concentration of polymers used in the adhesive formulations, we were able to finely tune the physical properties of the bioadhesive including viscosity, elastic modulus, extensibility, ultimate tensile strength, adhesion, transparency, water content, degradation time, and swellability. Our in vitro studies showed no sign of cytotoxicity of the hydrogels. Moreover, the hydrogel patches showed higher adhesion on freshly explanted pig eyeballs compared to a marketed ocular sealant. Finally, ex vivo feasibility studies showed that the hydrogel patches could seal complex open-globe injuries such as large incision, cruciform injury, and injury associated with tissue loss. These results suggest that our photocrosslinkable hydrogel patch could represent a promising solution for the sealing of open-globe injuries or surgical incisions. Statement of significanceCurrent management of severe ocular injuries require advanced surgical skills and access to an operating theater. To address the need for emergent management of wounds that cannot be handled in the operating room, surgical adhesives have gained popularity, but none of the currently available adhesives have optimal bioavailability, adhesive or mechanical properties. This study describes the development, optimization and testing of a light-sensitive adhesive patch that can easily be applied to the eye. After solidification using visible light, the patch shows no toxicity and is more adherent to the tissue than a marketed sealant. Thus this technology could represent a promising solution to stabilize ocular injuries in emergency settings before definitive surgical repair.

Surface topography and stress concentration analysis for corroded high strength steel plate

In this paper, salt spray tests were firstly conducted for Q690 high strength steel plates. After the corrosion tests, the corrosion products were removed and the weight loss ratio was obtained. Then the topographies of the rough surfaces were scanned by a 3D surface profiler, and the 3D coordinates of the corroded surfaces were exported. Based on the data, the topographic feature parameters were determined, the uniform corrosion depth was calculated, and the extreme value analysis was conducted for the pitting corrosion depth to investigate its stochastic features. Finally, the corroded surfaces were restored and the finite element models of the scanned segments were established, which were validated by the experimental results and used to conduct the stress concentration analysis. The experimental results showed that the topographic feature parameters were linearly related to the weight loss ratio, and the maximum pitting depth conformed to the Frechat distribution. By conducting finite element analysis, it was concluded that under the uniaxial tensile load, the corroded steel plate showed an obvious stress concentration effect and most nodes were in a multiaxial stress state. In terms of the characteristic loads, both uniform and pitting corrosion induced the yield load and the ultimate load degradation. Regarding the uniform corrosion component, the loss percentage of the characteristic load was equal to the corresponding weight loss ratio. However, the loss percentages of the characteristic loads caused by pitting corrosion were smaller than the pitting weight loss ratio due to the stress concentration.