Experimental study on mechanical properties of single fracture-hole red sandstone

Various fractures and holes in the natural rock mass affected the mechanical properties of the rock mass and the safety construction of engineering. In this study, we investigated the mechanical properties of a single fracture-hole rock specimen using particle flow code 2D (PFC2D) numerical simulation software and through laboratory tests. We analysed the failure behaviours and mechanical properties of the rock specimen with a single fracture-hole specimen under different fracture angles. The failure modes of single fractured rock samples with different fracture angles were revealed. The fracture propagation and stress evolution of the rock specimen with a single fracture-hole under different fracture angles were investigated. The experimental results shown that the peak strength, peak strain, elastic modulus, initial fracture stress, and damage stress of the single fracture-hole rock specimen with different fracture angles were significantly less than those of the intact rock specimen. Moreover, fracture hole defects accelerated the generation of fractures and promote the failure of the rock specimen. The failure modes were divided into Y, inverted Y, and V types. Before the rock specimen fractures, the stress concentration area was mainly distributed at both ends of the fracture. The stress concentration area at both ends of the fracture gradually decreased, and the stress concentration area near the hole gradually increased as the fracture angle increased. By experiments, the acoustic emission of the model had gone through three stages: initial, steady growth, and rapid decline. The size of the inclination angle affected the number of acoustic emission hits and the generation of acoustic emission signals. Failure behaviours of the rock specimen with a single fracture-hole were systematically investigated, which could promoted the development of fracture rock mechanics and improved the understanding of instability failure mechanism in rock engineering, such as nuclear wasted treatment engineering and deep underground engineering

Investigation of microstructure evolution, mechanical and corrosion properties of SAF 2507 super duplex stainless steel joints by keyhole plasma arc welding

Keyhole plasma arc welding (PAW) of the super duplex stainless steel (SDSS) is expected to achieve full-penetration joints of medium-thickness plates in a single pass with higher efficiency. However, the unique key-holing processes due to the special constricted arc behaviors cause much different thermal cycles of the liquid metals as well as changed microstructures. SDSS 2507 with a thickness of 10 mm was joined by PAW to investigate the joints' microstructure and properties. Microstructure characterization reveals substantial differences in the content of austenite, ranging from 68.9% in weld metal (WM) to 32.1% in the heat-affected zone (HAZ). The oxide inclusions in the WM enhance the hardness of the welded joints, but provide the path for crack propagation to decrease its impact toughness. While complicated microstructure is found in HAZ forming ferrite and diverse austenite, such as grain boundary austenite (GBA), intragrain austenite (IGA), and Widmanstätten austenites (WA). A small amount of secondary austenite (γ2) and chromium nitride are also found in HAZ, and they significantly deteriorate its corrosion resistance. The grain boundary misorientation angle distribution of the austenite in WM is found to be dominated by the low angle boundaries (LABs). However, its content decreases from the WM to base metal (BM). Selective corrosion occurs in all samples, where ferrite is preferentially dissolved when the extrinsic voltage is low (0.5 V), indicating the different electrochemical activity of the two phases

Investigation on the Metal Transfer and Cavity Evolution during Submerged Arc Welding with X-ray Imaging Technology

The physical phenomena of submerged arc welding (SAW) conducted with a 1.6 mm flux-cored wire were investigated using X-ray imaging technique. Three kinds of metal transfer modes were confirmed in this paper, namely the front flux wall-guided droplet transfer, back flux wall-guided droplet transfer, and repelled droplet transfer, of which the corresponding percentages were 47.65%, 45.29%, and 7.06%, respectively. Although the average sizes of the droplets for SAW and FCAW (flux-cored wire welding) were 2.0 mm and 1.9 mm with an average droplet transfer time of 90.3 ms, it required 36.4% more time for the droplet of SAW to finish one metal transfer than it did in FCAW. In addition, the volume of the cavity was not constant but repeated a cycle mode of “expansion and contraction” during the whole process. Thus, the dynamics of the cavity and viscous resistance caused by the flux collectively slowed down the velocity of the droplets from the wire to the weld pool in SAW. Compared with FCAW, a smoother weld without pits and pores was manufactured during the SAW process. Due to the compression effect of the flux, the 14.5 mm average weld width of SAW was 2.9 mm shorter than that of the FCAW. Furthermore, the thickness of slag with a porous structure in SAW was 2.7 times of that in FCAW, indicating that it could provide better protection to the weld of SAW

Process Stability, Microstructure and Mechanical Properties of Underwater Submerged-Arc Welded Steel

In underwater wet welding, the unstable welding process caused by the generation and rupture of bubbles and the chilling effect of water on the welding area result in low quality of welded joints, which makes it difficult to meet the practical application of marine engineering. To improve the process stability and joining quality, a mixture of welding flux with a water glass or epoxy resin was placed on the welding zone before underwater welding. In this paper, welds’ appearance, geometry statistics of welds’ formation, welding process stability, slag structure, microstructure, pores and mechanical properties were investigated. It was found that with the addition of water glass in the mixture, the penetration of weld was effectively increased, and the frequency of arc extinction was reduced. Though the porosity rose to a relatively high level, the joints’ comprehensive mechanical properties were not significantly improved. Notably, the applied epoxy resin completely isolated the surrounding water from the welding area, which greatly improved process stability. Furthermore, it benefited from the microstructure filled with massive acicular ferrite, the average elongation and room temperature impact toughness increased by 178.4%, and 69.1% compared with underwater wet welding, respectively, and the bending angle of the joint reaches to 180°

Assembly-promoted photocatalysis: Three-dimensional assembly of CdSxSe1−x (x = 0–1) quantum dots into nanospheres with enhanced photocatalytic performance

In this paper, through an emulsion-based bottom-up self-assembly method, monodisperse CdSxSe1−x (x = 0–1) quantum dots (QDs) with tailoring compositions have been three-dimensionally assembled into spherical architectures in sub-micrometer sizes. UV–Vis absorption measurements revealed the enhanced light harvesting abilities of the assembled CdSxSe1−x spheres relative to their constituting QDs. HRTEM characterizations over the CdSxSe1−x assemblies suggested the existence of localized oriented adjoining of the CdSxSe1−x QDs and the resulting nano-twin structures that are favorable for photogenerated electron-hole separation. The quenching of photoluminescence and the improvement in IPCE after the assembly of CdSxSe1−x QDs provided a clue to the likely suppressed electron-hole recombination brought about by the unique architectures and interfaces derived from self-assembly. The above findings were coincided with the remarkably improved H2 evolution activities observed for the well-assembled CdSxSe1−x nanospheres in photocatalytic water splitting, underpinning the importance of the alternative strategy to design advanced semiconductor photocatalysts based on architectural engineering

Harnessing Ostwald ripening to fabricate hierarchically structured mullite-based cellular architecture via the gelation network-triggered morphology-regulation method

Gas-in-liquid foam templating is considered as a promising method for commercial-scale production of porous materials. However, Ostwald ripening occurs frequently during the preparation, which could bring about inhomogeneous bubbles with large sizes and deteriorate the performance of resultant products. To tackle this challenging task, we report a gelation network-triggered morphology-regulation strategy during the foaming process. As an exemplar, boehmite sol was incorporated into the andalusite suspension to stabilize the foam framework. After casting, the wet foam was able to maintain its overall shape, since andalusite particles were anchored onto the gas-liquid interface by the gelation network during mechanical frothing. The samples calcined at 1400 degrees C feature homogeneous bubble with hierarchical porous architecture, smaller pore size with a mean value of 5.32 mu m and robust compressive strength of 11.97MPa at a porosity level of 84 %. Our approach substantially broadens the design philosophy of high performance porous ceramics

Enhanced IL-10 inhibits proliferation and promotes apoptosis of HUVECs through STAT3 signaling pathway in sepsis

Aims. The present study aims to determine the expression of interleukin (IL)-10 in peripheral blood of patients with sepsis, and investigate its effects on the biological function of vascular endothelial cells. Methods. Thirty-six sepsis patients and 20 healthy subjects were included. Peripheral blood was collected from all subjects. ELISA was used to determine IL-10 content in serum. A ratio of IL-10+ T cells was determined by flow cytometry. CCK-8 assay was used to investigate proliferation. Cell cycle and apoptosis were analyzed by flow cytometry. Western blotting was used to examine the expression of phosphorylated STAT3 protein. Results. The content of IL-10 and the ratio of IL-10+ T cells were enhanced in pa-tients with sepsis. Serum from patients with sepsis inhibited the proliferation of HU-VECs, and addition of IL-10 antibody reversed this effect. IL-10 in the serum from patients with sepsis promoted the apoptosis of HUVECs. IL-10 inhibited the proliferation and promoted the apoptosis of HUVECs by enhancing the phosphorylation of STAT3. Conclusions. The present study demonstrates that the content of IL-10 and the ratio of IL-10+ T cells in peripheral blood of patients with sepsis are up-regulated, and this inhibits HUVEC proliferation and promotes HUVEC apoptosis through STAT3 sig-naling pathway. The results in this study provide a new experimental basis for further understanding the molecular mechanism of sepsis-induced vascular injury

Identification of PIEZO1 as a potential prognostic marker in gliomas

In multiple solid tumours, including gliomas, the mechanical properties change as the disease progresses. If and how mechanical cues regulate tumour cell proliferation is currently not fully studied. PIEZO1 has recently been identified as a crucial mechanosensitive cation channel in multiple solid tumours. However, we didn't find any clinical data describing the association between PIEZO1 expression and glioma. To investigate the role of PIEZO1 in gliomas, we analysed PIEZO1 gene expression at the transcriptome level, genomic profiles and the association of PIEZO1 with clinical practice. In total, 1633 glioma samples with transcriptome data, including data from the Chinese Glioma Genome Atlas RNAseq, the Cancer Genome Atlas RNAseq and GSE16011 databases, were included in this study. Clinical information and genomic profiles including somatic mutations were also obtained. We found that PIEZO1 expression was highly correlated with malignant clinical and molecular subtypes of glioma. Gene ontology analysis showed that expression of PIEZO1 was correlated with tumour microenvironment-related genes that encode proteins involved in extracellular matrix (ECM) organization, angiogenesis and cell migration. Additionally, PIEZO1 was shown to be involved in tumour progression by serving as the central checkpoint of multiple ECM remodelling-related signalling pathways to modulate tumour cell proliferation and the tumour microenvironment in turn. Finally, high PIEZO1 expression was correlated with reduced survival time and acted as a robust biomarker for poor prognosis in gliomas. Taken together, the results indicated that high PIEZO1 expression is closely associated with highly malignant gliomas. Importantly, PIEZO1 serves as a key factor involved in sensing mechanical properties in the tumour and can regulate both tumour cells and their microenvironment to promote glioma progression, and it is also a potential therapeutic target for the treatment of gliomas