Effects of ultrasonic vibration on microstructure and mechanical properties of 1Cr12Ni3MoVN alloy fabricated by directed energy deposition.

Due to the rapid melting and solidification during directed energy deposition (DED) process, the defects and columnar crystals are likely to generate in the deposition layers, which reduce the quality and performance of the whole parts. Therefore, in order to improve the microstructure and mechanical properties of 1Cr12Ni3MoVN alloy manufactured by DED method, ultrasonic vibration (UV) has been employed to assist directed energy deposition process in this work. The results indicate that the high-intensity ultrasonic vibration can weaken the epitaxy growth tendency of crystal grains, and significantly improve plasticity while keeping an approximate strength. In addition, a two-dimensional numerical model is established to simulate the effect of ultrasonic vibration in the molten pool. The simulation results show that ultrasonic vibration remarkably improves the flow velocity and pressure in the molten pool, inducing the cavitation effect that breaks dendritic crystal and affects crystal characteristics. Meanwhile, the acoustic streaming effect changes the thermodynamic conditions and promotes high-temperature diffusion, which uniforms temperature distribution and reduces the temperature gradient in the molten pool. Thus the reduced temperature gradient G and raised solidification growth rate R promote the formation of fine equiaxed crystal characteristics after UV treatment. The product G × R increases and the ratio G/R decreases after UV treatment, resulting in the formation of fine equiaxed crystals.

Exploring the Effect and Mechanism of Si-Miao-Yong-An Decoction on Abdominal Aortic Aneurysm Based on Mice Experiment and Bioinformatics Analysis.

Background: Abdominal aortic aneurysm (AAA) is a fatal disease characterized by high morbidity and mortality in old population. Globally, effective drugs for AAA are still limited. Si-Miao-Yong-An decoction (SMYAD), a traditional Chinese medicine (TCM) formula with a high medical value, was reported to be successfully used in an old AAA patient. Thus, we reason that SMYAD may serve as a potential anti-AAA regime. Objective: The exact effects and detailed mechanisms of SMYAD on AAA were explored by using the experimental study and bioinformatics analysis. Methods: Firstly, C57BL/6N mice induced by Bap and Ang II were utilized to reproduce the AAA model, and the effects of SMYAD were systematically assessed according to histology, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA). Then, network pharmacology was applied to identify the biological processes, pathways, and hub targets of SMYAD against AAA; moreover, molecular docking was utilized to identify the binding ability and action targets. Results: In an animal experiment, SMYAD was found to effectively alleviate the degree of pathological expansion of abdominal aorta and reduce the incidence of Bap/Ang II-induced AAA, along with reducing the damage to elastic lamella, attenuating infiltration of macrophage, and lowering the circulating IL-6 level corresponding to the animal study, and network pharmacology revealed the detailed mechanisms of SMYAD on AAA that were related to pathways of inflammatory response, defense response, apoptotic, cell migration and adhesion, and reactive oxygen species metabolic process. Then, seven targets, IL-6, TNF, HSP90AA1, RELA, PTGS2, ESR1, and MMP9, were identified as hub targets of SMYAD against AAA. Furthermore, molecular docking verification revealed that the active compounds of SMYAD had good binding ability and clear binding site with core targets related to AAA formation. Conclusion: SMYAD can suppress AAA development through multicompound, multitarget, and multipathway, which provides a research direction for further study.

Grain refining of Ti-6Al-4V alloy fabricated by laser and wire additive manufacturing assisted with ultrasonic vibration.

The formation of the coarse columnar crystal structure of Ti-6Al-4V alloy in the process of additive manufacturing greatly reduces the mechanical performance of the additive manufactured parts, which hinders the applications of additive manufacturing techniques in the engineering fields. In order to refine the microstructure of the materials using the high intensity ultrasonic via the acoustic cavitation and acoustic flow effect in the process of metal solidification, an ultrasonic vibration technique was developed to a synchronous couple in the process of Laser and Wire Additive Manufacturing (LWAM) in this work. It is found that the introduction of high-intensity ultrasound effectively interrupts the epitaxial growth tendency of prior-ß crystal and weakens the texture strength of prior-ß crystal. The microstructure of Ti-6Al-4V alloy converts to fine columnar crystals from typical coarse columnar crystals. The simulation results confirm that the acoustic cavitation effect applied to the molten pool created by the high-intensity ultrasound is the key factor that affects the crystal characteristics.

Metallic structure functional sensor based on embedded PANDA fiber by ultrasonic additive manufacturing.

The aim of this study is to embed PANDA fiber into metal aluminum by using the ultrasonic additive manufacturing (UAM) technique. The functional sensing characteristics of the metallic structure were realized by structure design, precise positioning, and laying of the optical fiber and a tip coating (gold film) technique. The sensing characteristics of the metallic structure sensor including temperature, bending, tensile straining, and twist responses have been systematically investigated. Experimental results show that moderate sensitivity, good repeatability, and exactly linear spectral responses are obtained with -476.2pm/∘C for temperature, 1304pm/m-1 for bending, 0.6314pm/µÎµ for tensile straining, and -332.3pm/(rad/m) for twisting. Based on its simple fabrication process and multifunctional measurement, it is clearly demonstrated that the metallic matrix structure with embedded PANDA fiber produced by the UAM technique is a functional structure with capabilities to monitor the structure health conditions and mechanical operation changes in applications.

Investigations on Mechanical Properties of Lattice Structures with Different Values of Relative Density Made from 316L by Selective Laser Melting (SLM).

Nine variants of regular lattice structures with different relative densities have been designed and successfully manufactured. The produced structures have been subjected to geometrical quality control, and the manufacturability of the implemented selective laser melting (SLM) technique has been assessed. It was found that the dimensions of the produced lattice struts differ from those of the designed struts. These deviations depend on the strut orientation in relation to the specimen-building direction. Additionally, the microstructures and phase compositions of the obtained structures were characterized and compared with those of conventionally produced 316L stainless steel. The microstructure analysis and X-ray diffraction (XRD) patterns revealed a single austenite phase in the SLM samples. Both a certain broadening and a displacement of the austenite peaks were observed due to residual stresses and a crystallographic texture induced by the SLM process. Furthermore, the mechanical behavior of the lattice structure material has been defined. It was demonstrated that under both quasi-static and dynamic testing, lattice structures with high relative densities are stretch-dominated, whereas those with low relative densities are bending-dominated. Moreover, the linear dependency between the value of energy absorption and relative density under dynamic loading conditions has been established.

Linc-ROR targets FGF2 to regulate HASMC proliferation and migration via sponging miR-195-5p.

Atherosclerosis is a common cardiovascular disorder and is characterized by damage of endothelial cells, cell inflammation, hyper-proliferation of vascular smooth muscle cells and the accumulation of extracellular lipids and fibrous tissues. In this study, we firstly examined the expression level of long intergenic non-protein coding RNA, regulator of reprogramming (linc-ROR) in homocysteine (Hcy)-stimulated human aortic smooth muscle cells (HASMCs), and then looked into the potential molecular signaling axis of linc-ROR in regulating the proliferation and migration of HASMCs. Hcy promoted HASMC proliferation and up-regulated linc-ROR expression. Functional studies showed that linc-ROR exerted enhanced actions on the proliferation and migration of HASMCs. In addition, linc-ROR acted as a competing endogenous RNA for miR-195-5p and repressed the miR-195-5p expression in HASMCs. Linc-ROR was up-regulated the miR-195-3p was down-regulated in the plasma from CAD patients when compared to normal controls. Furthermore, fibroblast growth factor 2 (FGF2) was identified as a target of miR-195-5p and was negatively regulated by miR-195-5p in HASMCs. The rescue experiments revealed that linc-ROR-mediated HASMC proliferation and migration may be via regulating miR-195-5p/FGF2 axis. Linc-ROR inhibition blocked the miR-195-5p/FGF2 signaling in Hcy-treated HASMCs, and this effect may also involve in the miR-195-5p/FGF2 axis. To summarize, the data of the present study identified the up-regulation of linc-ROR in Hcy-stimulated HASMCs, and further mechanistic functional studies revealed that linc-ROR promoted HASMC proliferation and migration via regulating miR-195-5p/FGF2 axis. The present study provided the novel actions of linc-ROR in regulating HASMC proliferation and migration, which may be related to the pathophysiology of atherosclerosis.

Modification of Residual Stresses in Laser Additive Manufactured AlSi10Mg Specimens Using an Ultrasonic Peening Technique.

Ultrasonic peening treatment (UPT) has been proved to be an effective way of improving residual stresses distribution in weld structures. Thus, it shows a great potential in stress modification for metal parts fabricated by additive manufacturing technology. In this paper, an investigation into the ultrasonic treatment process of AlSi10Mg specimens fabricated by selective laser melting (SLM) process was conducted by means of experimental and numerical simulation. The specimens were prepared using a SLM machine, and UPT on their top surface was carried out. The residual stresses were measured with an X-ray stress diffraction device before and after UPT. Meanwhile, a finite element simulation method for analyzing the influence of UPT on the residual stress field of specimens was proposed and validated by experiments. Firstly, the thermal mechanical coupling numerical simulation of the SLM process of the specimen was carried out in order to obtain the residual stress distribution in the as-fabricated specimen. Then, the transient dynamic finite element simulation model of the UPT process of the specimen was established, and the UPT effect analysis was implemented. In the UPT simulation, the residual stress was applied as a pre-stress on the specimen, and the specimen's material mechanical property was described by the Johnson⁻Cook model, whose parameters were determined by Split Hopkinson Pressure Bar (SHPB) experiment. The residual stress distribution before and after UPT predicted by the finite element model agree well with the measurement results. This paper concludes with a discussion of the effects of ultrasonic peening time, as well as the frequency and amplitude of the peening needle on residual stress.

Elasto-Plastic Mechanical Properties and Failure Mechanism of Innovative Ti-(SiCf/Al3Ti) Laminated Composites for Sphere-Plane Contact at the Early Stage of Penetration Process.

A novel silicon carbide (SiC) continuous ceramic fiber-reinforced (CCFR) Ti/Al3Ti Metal-Intermetallic-Laminate (MIL) composite was fabricated. A high-efficiency semi-analytical model was proposed based on the numerical equivalent inclusion method (NEIM) for analyzing the small-strain elasto-plastic contact in the early stage of the penetration process. The microstructure and interface features were characterized by the scanning electron microscopy (SEM). Quasi-static compression tests were performed to determine the contact response and validate the proposed model. A group of in-depth parametric studies were carried out to quantify the influence of the microstructure. The comparison between results under the sphere-plane and plane-plane contact load indicates that, under the first sphere-plane, the compressive strength and failure strain are both lower and the SiC reinforcement effect on strength is very clear while the effect on ductility is not clear. The maximum plastic strain concentration (MPSC) in the Al3Ti layer is closest to the upper boundary of the central SiC fiber and then extends along the depth direction as the load increases, which are also the locations where cracks may initiate and extend. Moreover, the CCFR-MIL composite shows better mechanical properties when the center distance between adjacent SiC fibers is four times the fiber diameter and the volume fraction of Ti is 40%.

Exploration of the mechanisms by which 3,4-benzopyrene promotes angiotensin II-induced abdominal aortic aneurysm formation in mice.

OBJECTIVE: This study examined the influence of 3,4-benzopyrene (BaP), a compound found in cigarette smoke, on the formation of angiotensin II (Ang II)-induced abdominal aortic aneurysm (AAA) formation in mice and the underlying mechanisms. METHODS: C57/B6n mice were divided into four groups. The control group received a weekly intraperitoneal injection of medium-chain triglycerides. The Ang II group received a daily Ang II infusion (0.72 mg/kg) and a weekly intraperitoneal injection of medium-chain triglycerides. The Ang II/BaP group received a daily Ang II infusion (0.72 mg/kg) and a weekly intraperitoneal BaP injection (10 mg/kg, dissolved in medium-chain triglycerides). The BaP group received a weekly intraperitoneal BaP injection (10 mg/kg). After 5 weeks, abdominal aortic diameter was determined. Aortic tissues underwent hematoxylin and eosin, Masson, and immunochemistry staining for evaluation of vascular wall structure, collagen, macrophage infiltration, matrix metalloproteinases (MMPs), and apoptosis. RESULTS: The Ang II infusion and BaP injection induced AAAs in 41.67% of mice vs 25% in the Ang II group (P < .05). The average aortic diameter increased in the Ang II/BaP group compared with the Ang II group (1.40 ± 0.25 vs 1.2 ± 0.23 mm; P < .05). Average aortic muscular cell apoptosis was higher in the Ang II/BaP group (31% ± 12%) than in the Ang II (19% ± 5%; P < .05) or BaP groups (23% ± 4%; P < .05). Aortic macrophage infiltration and expression of MMP-2, MMP-9, MMP-12, and nuclear factor-κB increased (0.56 ± 0.12, 0.47 ± 0.13, 0.49 ± 0.14, 0.49 ± 0.11, and 0.42 ± 0.12, respectively) in the Ang II/BaP group compared with the Ang II group (0.27 ± 0.08, 0.25 ± 0.06, 0.24 ± 0.09, 0.24 ± 0.09, and 0.23 ± 0.06, respectively; P < .05 for all). CONCLUSIONS: BaP promotes Ang II-induced AAA formation in mice via elevating infiltration of macrophages, activating nuclear factor-κB, upregulating the expression of MMP-2, MMP-9, and MMP-12, and increasing the apoptosis of vascular muscle cells in its synergistic effect with Ang II in aortic wall.

Screening for glycosylphosphatidylinositol-modified cell wall proteins in Pichia pastoris and their recombinant expression on the cell surface.

Glycosylphosphatidylinositol (GPI)-anchored glycoproteins have various intrinsic functions in yeasts and different uses in vitro. In the present study, the genome of Pichia pastoris GS115 was screened for potential GPI-modified cell wall proteins. Fifty putative GPI-anchored proteins were selected on the basis of (i) the presence of a C-terminal GPI attachment signal sequence, (ii) the presence of an N-terminal signal sequence for secretion, and (iii) the absence of transmembrane domains in mature protein. The predicted GPI-anchored proteins were fused to an alpha-factor secretion signal as a substitute for their own N-terminal signal peptides and tagged with the chimeric reporters FLAG tag and mature Candida antarctica lipase B (CALB). The expression of fusion proteins on the cell surface of P. pastoris GS115 was determined by whole-cell flow cytometry and immunoblotting analysis of the cell wall extracts obtained by ß-1,3-glucanase digestion. CALB displayed on the cell surface of P. pastoris GS115 with the predicted GPI-anchored proteins was examined on the basis of potential hydrolysis of p-nitrophenyl butyrate. Finally, 13 proteins were confirmed to be GPI-modified cell wall proteins in P. pastoris GS115, which can be used to display heterologous proteins on the yeast cell surface.

Benzo[a]pyrene induces oxidative stress and endothelial progenitor cell dysfunction via the activation of the NF-κB pathway.

Smoking is a major risk factor for atherosclerosis. In this study, we evaluated the effects of benzo[a]pyrene (BaP, a prominent component of tobacco smoke) on the function and pro-inflammatory response of human endothelial progenitor cells (EPCs). EPCs were isolated from umbilical cord blood and treated with different concentrations (10, 20 and 50 µmol/l) of BaP. The proliferation, migration, adhesion and angiogenesis of BaP-treated EPCs were evaluated using the cell counting kit-8 (CCK-8), Transwell assay, adhesion assay and in vitro tube formation assay, respectively. The activation of nuclear factor-κB (NF-κB) was evaluated by measuring the mRNA expression of NF-κB p65 and p50 by real-time RT-PCR and NF-κB translocation assay. Reactive oxygen species (ROS) production was determined by the reduction of fluorescent 2',7'-dichlorofluorescein diacetate (DCFH-DA). The results demonstrated that BaP treatment significantly inhibited the proliferation, migration, adhesion and angiogenesis of EPCs in vitro. In addition, BaP induced the release of interleukin (IL)-1ß and tumor necrosis factor-α from these cells. Moreover, the exposure of EPCs to BaP induced ROS generation and the activation of NF-κB. Experiments with EPCs pre-treated with pyrrolidine dithiocarbamate, an inhibitor of NF-κB, revealed that the BaP-mediated inhibition of proliferation, migration, adhesion and angiogenesis of EPCs is mainly regulated by NF-κB. Thus, tobacco smoke may induce oxidant-mediated stress responses in EPCs and impair their function via the activation of the NF-κB pathway.

Computer vision based method and system for online measurement of geometric parameters of train wheel sets.

Train wheel sets must be periodically inspected for possible or actual premature failures and it is very significant to record the wear history for the full life of utilization of wheel sets. This means that an online measuring system could be of great benefit to overall process control. An online non-contact method for measuring a wheel set's geometric parameters based on the opto-electronic measuring technique is presented in this paper. A charge coupled device (CCD) camera with a selected optical lens and a frame grabber was used to capture the image of the light profile of the wheel set illuminated by a linear laser. The analogue signals of the image were transformed into corresponding digital grey level values. The 'mapping function method' is used to transform an image pixel coordinate to a space coordinate. The images of wheel sets were captured when the train passed through the measuring system. The rim inside thickness and flange thickness were measured and analyzed. The spatial resolution of the whole image capturing system is about 0.33 mm. Theoretic and experimental results show that the online measurement system based on computer vision can meet wheel set measurement requirements.

Loading rate effects on the R-curve behavior of cortical bone.

Rising resistance curve (R-curve) behavior in bone during quasi-static experiments has demonstrated the importance of microstructural toughening mechanisms in resisting fracture. However, despite clinical bone fracture primarily occurring under dynamic loading and the significant changes in material behavior observed with increasing strain rates, there have been no previous investigations into whether crack growth resistance is maintained during dynamic fracture. Using a novel modified split-Hopkinson pressure bar coupled with a high-speed camera to measure crack propagation, we present the first evidence of rising R-curve behavior in bone under dynamic loading (∼2 × 10(5)MPam(1/2)s(-1)). Results indicate that rising R-curve behavior is maintained, although with lower crack initiation toughness and propagation resistance than observed in quasi-static experiments. Observations of crack initiation and propagation in double-notched specimens using confocal fluorescence microscopy and electron microscopy suggest that this is due to subtle differences in toughening mechanisms between quasi-static and dynamic fracture.

Effects of age and loading rate on equine cortical bone failure.

Although clinical bone fractures occur predominantly under impact loading (as occurs during sporting accidents, falls, high-speed impacts or other catastrophic events), experimentally validated studies on the dynamic fracture behavior of bone, at the loading rates associated with such events, remain limited. In this study, a series of tests were performed on femoral specimens obtained post-mortem from equine donors ranging in age from 6 months to 28 years. Fracture toughness and compressive tests were performed under both quasi-static and dynamic loading conditions in order to determine the effects of loading rate and age on the mechanical behavior of the cortical bone. Fracture toughness experiments were performed using a four-point bending geometry on single and double-notch specimens in order to measure fracture toughness, as well as observe differences in crack initiation between dynamic and quasi-static experiments. Compressive properties were measured on bone loaded parallel and transverse to the osteonal growth direction. Fracture propagation was then analyzed using scanning electron and scanning confocal microscopy to observe the effects of microstructural toughening mechanisms at different strain rates. Specimens from each horse were also analyzed for dry, wet and mineral densities, as well as weight percent mineral, in order to investigate possible influences of composition on mechanical behavior. Results indicate that bone has a higher compressive strength, but lower fracture toughness when tested dynamically as compared to quasi-static experiments. Fracture toughness also tends to decrease with age when measured quasi-statically, but shows little change with age under dynamic loading conditions, where brittle "cleavage-like" fracture behavior dominates.

Preparation, characterization and mechanical performance of dense beta-TCP ceramics with/without magnesium substitution.

Beta-tricalcium phosphate (beta-TCP) powder was prepared by a two-step process: wet precipitation of apatitic tricalcium phosphate [Ca(9)(HPO(4))(PO(4))(5)(OH)] (beta-TCP 'precursor') and calcination of the precursor at 800 degrees C for 3 h to produce beta-TCP. Magnesium-substituted tricalcium phosphate (beta-TCMP) was produced by adding Mg(NO(3))(2) . 6H(2)O into Ca(NO(3))(2) solution as Mg(2+) source before the precipitation step. The transition temperature from beta-TCP to alpha-TCP increases with the increase of Mg(2+) content in beta-TCMP. beta-TCMP with 3 mol.% Mg(2+) has beta-TCP to alpha-TCP transition temperature above 1,300 degrees C. Dense beta-TCMP (3 mol.% Mg(2+)) ceramics ( approximately 99.4% relative density) were produced by pressing the green bodies at 100 MPa and further sintering at 1,250 degrees C for 2 h. The average compressive strength of dense beta-TCP ceramics sintered at 1,100 degrees C is approximately 540 MPa, while that of beta-TCMP (3 mol.% Mg(2+)) ceramics is approximately 430 MPa.

Experimental investigation of dynamic effects in a two-bar/three-point bend fracture test.

A Hopkinson pressure bar has been modified to measure the dynamic fracture properties of materials at loading rates greater than approximately 10(6) MPa ms. Some fundamental dynamic effects associated with the incident stress pulse, such as stress wave propagation characteristics along the Hopkinson bar and within the cracked specimen, the specimen's dynamic response excited by the stress pulse, and the specimen contact situations with the impactor and supports, need to be understood. To better comprehend these fundamental issues, an experimental investigation of these dynamic effects with the emphasis on "loss of contact" was first performed on a two-bar/three-point dynamic bend fracture test setup using a voltage measurement circuit across the specimen/loading-pin interfaces and high-speed photographs. It was demonstrated here that the three-point bend specimen employed with the current two-bar/three-point bend test setup remains in contact with the impactor and supports throughout the first loading duration and that "loss of contact" does not occur. A further improvement using a pulse-shaping technique was employed for achieving a tailored incident pulse. The effect of pulse shaper on the rise time and duration of the incident pulse as well as the dynamic stress equilibrium in the cracked three-point bend has been investigated, for the first time here, with profound implications for significantly improved dynamic three-point bend fracture testing.