Search

In the extension project of the China National Academy of Painting, the radial spherical plain bearing (RSPB) is used in a structural joint with an inserted plate. This new structural RSPB joint has complicated mechanical behaviors and universal rotational performance. In this work, the simulation and experiment methods were used to investigate the RSPB joint mechanical properties (uniaxial ultimate bearing capacity, failure mode) and reliability. Furthermore, the out-of-plane rotational performance was studied with eight finite models for the application. According to FEA and test results, this new RSPB joint has functional mechanical properties. It is useful in steel truss structures and provides a possibility for engineers to design hinge joints in building structures.

We design high-sensitive fiber-optic sensor based on modal interference for temperature measurements. The core mismatch-offset sensor is fabricated by splicing a section of multimode fiber (MMF) between two single-mode fiber (SMF) and offset splicing of SMF. We use the finite-difference beam propagation method to numerically analyze the mode and intensity distributions of the light field in the sensor. We optimize the structure parameters such as the length of MMF, the length of sensing SMF, and the offset of sensor; the optimum parameters of proposed sensor are 4.0 mm, 1.73 cm, and 3.5 μm, respectively. Experimental results show that the proposed sensor is successfully used to monitor the variation of ambient temperature, and it possesses a high temperature sensitivity of 167.2 pm/°C with good linearity. The core mismatch-offset sensor with high sensitivity and compact structure provides a new method for designing fiber-optic sensor and temperature sensing.

We propose and demonstrate a low-cost and simple fiber optic cantilever accelerometer with a spherical tip based on Gaussian beam focusing. The accelerometer consists of ceramic ferrule, ceramic sleeve, receiving fiber and emitting fiber, where both fibers are single mode fiber, the ferrule and sleeve have characteristics of high precision, which reduce the difficulty of optical alignment. The end of the emitting fiber is made into a spherical tip for focusing the Gaussian beam to improve sensitivity. When the accelerometer is in operation, the emitting fiber acts as a cantilever beam, the acceleration can be measured by detecting the transmission power. Further, our experimental results show that the spherical fiber tip can improve the acceleration sensitivity by 67% over 10 Hz–1000 Hz without reducing the working bandwidth. In addition, it is found that the fiber accelerometer has a high signal-to-noise ratio (SNR) up to 60 dB, and a low harmonic distortion of better than -30 dB, rendering a quasi-8-shaped directionality at the working frequency ranging from 10 Hz to 1200 Hz. This clever sensor structure may have potentials for developing high-performance and cost-effective accelerometers and hydrophones.

The effluent of pharmaceutical wastewater had the characteristics of high salt and high COD. After discharge, it had a certain impact on the biological treatment of the sewage plant in the industrial park, which makes the effluent difficult to meet the standard. Therefore, it was necessary to screen out microorganisms with salt tolerance and the ability to reduce organic matter to improve the biochemical treatment effect of the sewage treatment plant. Therefore, the purpose of this study was to isolate and screen salt tolerant microorganisms to improve the biochemical treatment efficiency of sewage plant. Two salt tolerant strains T3 and T4 were screened from the sludge of the secondary sedimentation tank of an industry park sewage plant. Through morphological observation and 16S rRNA sequence analysis, it was identified that T3 strain was Mangrovibacter yixingensis and T4 strain was Thauera selenium. The effects of process conditions such as salinity and pH on the degradation of COD in actual high-salt wastewater were investigated by single factor experiment, and the optimum combination of conditions was determined by orthogonal experiment. T3 strain had high COD degradation efficiency at the best condition (salinity 2%, inital pH 6 and inoculation ratio 5%). The best condition on organic matter removal of T4 was salinity 1%, initial pH 6 and inoculation ratio 10%. Therefore, salt-tolerant bacteria had a certain application prospect on degradation of organic matter in high-salt wastewater.

Ceramic micro-shot peening (CMSP) and steel micro-shot peening (SMSP) were utilized to investigate the effect of micro-shot peening (MSP) on the high-cycle fatigue properties of Al-7Si-0.3Mg casting aluminum alloy in a previous study. However, the improvement effects of CMSP and SMSP on the fatigue strength (at 5 × 107 cycles) were only 33% because the depth of harden layers was only 20 and 55 μm while the depth of compressive residual stress affected layers was only 37 and 68 μm. In this study, conventional shot peening (CSP) was utilized, and the results were compared with those of MSP, with the expectation that CSP would provide a greater improvement in the fatigue strength. The affected surface layers of the shot-peened specimens were characterized using surface morphology, microhardness, and residual stress analyses. In addition, the effect of CSP on the fatigue strength at 5 × 107 cycles was investigated using a rotating bending fatigue test (R = − 1). An investigation of the extensive surface compressive residual stress relaxation process for the three different shot-peened specimens during cyclic loading was conducted using x-ray diffraction. In addition, the initiation sites for fatigue cracks on the fracture surface were observed using scanning electron microscopy. Furthermore, the fatigue life of the samples with the internal casting defect failure mode was predicted using linear elastic fracture mechanics, while that for samples with the surface crack initiation failure mode was predicted using the modified Morrow model considering the residual stress.

Peptides with strong antioxidant activity have been increasingly extracted from various edible aquatic animals, as natural substitutes for synthetic antioxidants. In this paper, a systematic review of the research progress on the enzymatic hydrolysis strategy and structure-activity relationship of antioxidant peptides from edible aquatic animals, especially marine animals, over the last decade was presented. The selection of enzymes varied markedly among organs and tissues. Tools and indicators used in the purification and identification process were clarified. The similarity and the difference in structure and antioxidant activity between vertebrate-derived peptides and invertebrate-derived peptides were discussed. The stability of antioxidant peptides was reviewed. Most peptides could maintain activity under mild conditions, but they hardly resisted gastrointestinal digestion. The poor ability of peptides to cross the small intestinal epithelium in prototype form brought a challenge for food and pharmaceutical applications.

When an underwater target moves in viscous fluid, it may cause the periodic movement of the surrounding fluid and generate ultra-low-frequency (ULF) gravity waves. The initial domain of the gravitational surface wave propagating above the moving target is named circular wave. This article studies the ULF circular wave generated by underwater oscillating sphere, which will provide basis for underwater long-range target detection. Firstly, the circular wave caused by the sphere oscillation in a finite deep fluid is studied based on the theory of linear potential flow. Meanwhile, the multipole expansion theory is established to solve the circular wave field. Secondly, the interface wave generated by the target oscillation in a two-layer fluid are numerically analyzed by comparison with the free surface fluctuation of a single-layer fluid. The results show that the amplitude of the internal interface displacement (AIID) is smaller than that of the free surface (AFSD). When the sphere is in the lower layer, the layering effect of the fluid has significant influences on the AFSD. Finally, the results of the pool experiment verified that the wave generated by the oscillating sphere is the surface gravity wave. Furthermore, the change trend of the test result is consistent with the simulation result.

Polyester-coated fabric has been widely used in membrane structures. However, the mechanical properties of polyester-coated fabric at elevated temperatures have not been well studied, limit...

In this study, quare, kagome and triangular grid sandwich structures about carbon fibre reinforced epoxy (CF/EP) composite, were designed and manufactured. Mechanical properties of these designed sandwich structures were performed by three-point bending and finite element analysis (FEA). The bending stiffness and core shear stress were calculated and then compared. Results obtained indicate that stress concentration was found at loading regions that cracks occurred on the interface. The face yielding and core shear failure also play a key role in the sandwich grid structure. The results show that the carbon fibre fabricated triangular grid core has a much stiffer and stronger character than other structures.

In order to analyze the possible impact of the election of different candidates in the U.S. general election on the U.S. economy and the Chinese economy, and put forward economic countermeasures and policy recommendations in related fields in China, this paper applies two models, Time Series Model and BP Neural Network.

Investigation of the mechanical properties of steel rods at elevated temperatures is important for the fire-resistant design and fire simulation analysis of steel rod structures. In China, ...

In this study, the tensile and fatigue tests were conducted on precipitate strengthened Cu-Ni-Si alloy. The fatigue properties of specimens with cold working and without cold working in air, as well as that of the specimen with cold working in salt atmosphere were investigated. The results show that the monotonic tensile strength and the yield strength are improved obviously, while the elongation decreases by cold working. The S-N curves of all the types of specimens show a continuous decrease. The fatigue strength of specimens in air is slightly reduced by cold working, however, that of the specimen with cold working at 107 cycles is largely decreased from 190 MPa to 120 MPa in salt atmosphere. All the fatigue cracks initiate from the specimen surface by slip deformation. In air condition, the specimens with cold working show shear mode fracture with transgranular crack propagation and it is caused by the obvious texture, while that without cold working show normal mode fracture with both transgranular and intergranular crack propagation. However, in salt atmosphere condition, the specimens with cold working show normal mode fracture with totally intergranular crack propagation.

In order to investigate the influence of Mg content on the fatigue properties in Al-Si-Mg alloy, uniaxial tensile tests and rotating bending fatigue tests were conducted on two Al-7Si-Mg casting alloys, with different Mg contents of 0.3 and 0.6 wt.%. The fracture surfaces of the specimens were observed by scanning electron microscopy, and the fatigue crack growth process was obtained by the replica method. The results indicate that the increase in Mg content enhances the yield strength and tensile strength of the alloy, whereas it reduces its elongation. There is an obvious knee point in the S–N curves of Al-7Si-0.6Mg alloy while that of Al-7Si-0.3Mg alloy shows continuous decrease. The fatigue strength at 5 × 105 cycles is 60 MPa for Al-7Si-0.3Mg alloy and 80 MPa for Al-7Si-0.6Mg alloy. For the two types of specimens, the fatigue failure can initiate from crystal slip and casting defects. The replica results suggest that cracks in Al-7Si-0.6Mg alloy grow more slowly than that in Al-7Si-0.3Mg alloy.

For the transportation pipeline with the diameter 1.219 m and the internal pressure 3-12 MPa, the leakage and diffusion of the natural gas of the pipeline in the soil was studied by numerical simulation. First, the finite model containing both pipeline and soil was established, and the porous media was used to simulate the real soil environment. And, the leakage amount of the natural gas was calculated at the cases with different porosities, the pressures inside the pipeline and the diameters of leakage port. Based on the classical theoretical leakage model of small hole in the air and simulation results analysis, the formula of the leakage amount was modified by the soil coefficient α to be suitable for soil environment. Then, the variation trends of the diffusion concentration of methane along different directions in the soil were analyzed by simulation, the influences of internal pressure of pipeline, the diameter of leakage and the porosity of soil were also discussed. Besides, the relationship of the safety distance with time was obtained.

To investigate the fire resistance of stainless steel-concrete composite beams (referred to as stainless steel composite beam), numerical simulations of rectangular section stainless steel composite beams under fire were carried out. The influences of load ratio, thickness of concrete slab, width of concrete slab, reinforcement ratio of concrete slab, height of stainless steel beam, width of stainless steel beam and span of composite beam on the fire resistance of rectangular section stainless steel composite beams were analyzed. Due to the large coefficient of thermal expansion of stainless steel material, the expansion of stainless steel beam will produce an additional bending moment in the stainless steel composite beam under fire, which has a great influence on the fire resistance of stainless steel composite beams. Finally, a simplified calculation method of temperature field distribution of rectangular section stainless steel composite beam was proposed. To adjust and enlarge the maximum bending moment at the mid-span of stainless steel composite beam, the coefficient of temperature additional bending moment was introduced into the calculation formula of critical temperature of stainless steel composite beams, which effectively improves the accuracy of the fire-resistant design method for stainless steel composite beams.

A multi-sideband filtering demodulation scheme with enhanced high sensitivity was proposed to demodulate weak fiber Bragg grating signals, and a novel data processing method was employed to reduce the influence of the background noise. The relationship of the sensing sensitivity, number of sidebands, and their slope coefficients were researched theoretically, numerically, and experimentally. The results showed that the sensing sensitivity was in proportion to the number of the sidebands and their slope coefficients. The power sensitivities for single and double CWDMs demodulating FBG in the experimental system were 6.960 dB/nm and 15.187 dB/nm, respectively, which were in agreement with the theoretical results. In addition, the data processing method we used to obtain the optical power was experimentally proven to be better than the method of directly measuring the optical power because it reduces the background noise.

The cable-supported barrel vault (CSBV) structure system is a new type of hybrid spatial steel structure based on a beam string structure (or truss string structure), suspendomes, and cylindrical lattice shells. Steel cables (e.g., steel wire rope cables, steel strand cables, semiparallel steel tendons, and steel rods) are key components of CSBV structures. However, they have different elastic moduli and thermal expansion coefficients. In this study, the roof of a textile workshop (the first CSBV structure in China) was analyzed with four types of cables under the effect of varying temperature. Under half-span loading and full-span loading, the structural internal force and displacement at varying temperatures were obtained from finite element models employing four different types of steel cables. The internal force, displacement, and horizontal arch thrust changed linearly with increasing temperature. Moreover, the dynamic characteristics of CSBV with varying temperature were analyzed. The frequency of the CSBV changed linearly with increasing temperature. Based on the dynamic characteristics of CSBV with varying temperature, a seismic response time-history analysis was performed. The variation in the maximum responses of the internal force, displacement, and horizontal arch thrust was obtained. In each case, the mechanical behavior of the CSBV with semiparallel steel tendon cables was strongly affected by the temperature. Therefore, semiparallel steel tendons are not recommended as components of CSBV in cases where large temperature changes can be expected. Thereafter, a scale model of a CSBV was designed and used for experiments and corresponding finite element analyses under varying temperature. Experimental results show that the finite element method is effective for analyzing the mechanical behavior of CSBV under varying temperature.

In this work, the mechanical properties and corresponding microstructural evolution of the as-cast Al0.3CoCrFeNiTi0.3 high-entropy alloy (HEA) under quasi-static and dynamic compressive loadings were investigated. The HEA consisted of FCC/L12 + BCC/B2 mixed solutions exhibited a good combination of high strength and large ductility upon quasi-static loading, which is mainly due to the strengthening effect of coherent L12-nanoparticles. The HEA exhibited a significant positive strain rate effect, and its yield strength rised from 810 to 1181 MPa when the strain rate increased from 10−3 to 4700 s−1. Compared with the quasi-static condition, the density of stacking fault (SF) networks and immobile Lomer–Cottrell (L-C) locks were greater under dynamic loading. Furthermore, the deformation mode of the HEA was dominated by planar glide under high strain rate loading, and the dislocation substructure showed Taylor lattice, high-density dislocation walls and intersected microbands with the increase of strain. The dynamic Hall–Petch and microband-induced plasticity effects could be responsible for the excellent dynamic compressive properties. Fractographic observations indicated that the fracture of the HEA is controlled by the mixed ductile-brittle mechanism under dynamic compressive loading. An improved Johnson-Cook (J-C) constitutive model considering adiabatic temperature rise was employed to predict the plastic flow behavior of the HEA under dynamic conditions and the improved J-C model was in good agreement with the experimental results.

A novel as-cast Al0.7CoCrFeNiTi0.3 high entropy alloy was prepared by vacuum arc melting and its microstructure and compression properties were investigated. The alloy has an excellent combination of high strength and large plasticity. The yield strength, fracture strength and compressive plasticity of the alloy at room temperature were as high as 1438 MPa, 2990 MPa, and 37.7%, respectively. The alloy was composed of alternating nano-scale face center cubic (FCC), body center cubic (BCC) and ordered L21 phase. The excellent mechanical properties of the alloy are attributed to the combination of the soft FCC phase and the hard BCC/L21 phase. In addition, the large number of phase interfaces provided by the nano-scale lamellar microstructure and precipitated ordered phase also produce a strengthening effect. The fracture mechanism of the alloy is mainly performed at compound fracture mode.

A current sensing method based on giant magnetostrictive material (GMM) and fiber Bragg grating (FBG) was proposed, which not only combines the advantages of FBG such as wavelength encoding, compatibility with fiber and distributed measurement system realization, but also the advantages of GMM as large flexible coefficient, high electromechanical coupling coefficient and short response time. The minimal residual method was put forward to effectively identify the Jiles-Atherton model parameters of ferro-magnetic material. The parameters of the giant magnetostrictive ( Terfenol-D bar ) and the Jiles-Atherton model was established and optimized by using the Mathematica software. Then the optical fiber current test system with ferromagnetic loop was set up to investigate the current sensing properties of the sensor. The relationship between current excitation and GMM-FBG reflected wavelength was obtained, which provides basic support for further current sensing experiment research.

A high sensitivity micro/nano-fiber sensor with asymmetric double tapered structure based on Mach-Zehnder interferometer (MZI) was designed for refractive index (RI) and humidity measurements. The sensor is composed of two different lengths tapered region fabricated in a single-mode fiber, which demonstrated higher sensitivity and better integration with material compared to conventional double tapered fiber sensor. The results showed that the RI sensitivity of the fabricated sensor was 68.6 nm/RIU with the RI ranged from 1.348 to 1.403. Furthermore, the sensing region was deposited with graphene for humidity detection, and the graphene has exhibited great enhancement in terms of sensing performance. The obtained humidity sensitivity of the fabricated sensor was 68.7 pm/%RH with the environment humidity ranged from 50 to 90 %. This work provides a new strategy for designing optical fiber sensor by double tapered fiber sensor, which exhibited the immense potential of tapered optical fiber sensor for future advancements.

In this study, EA4T axle steel specimens were subjected to three shot peening treatments: conventional shot peening (CSP), micro-shot peening (MSP) and their combination, i.e. dual shot peening (DSP). The residual stress, surface roughness, morphology, microhardness, were used to characterize the affected surface layer. The results indicated that MSP achieved maximum surface compressive residual stress (SCRS), minimum surface roughness, high surface microhardness. Moreover, compared to CSP, DSP improved the SCRS and microhardness while reducing surface roughness. However, scanning electron microscopy (SEM) observations indicated the presence of intensive defects of the DSP-treated specimens, which hindered the fatigue strength of the specimens. Fatigue tests were conducted to evaluate the effect of different treatments on fatigue life, the median S - N curve demonstrated that the fatigue limit at 10 7 cycles was improved by 24, 32, and 27% for the CSP, MSP, and DSP specimens, respectively. Furthermore, SEM observation was conducted to analyze the fracture mechanisms, the results indicated that the failure of all specimens originated at the surface and the fracture mechanisms were not changed by the shot peening treatments. The SCRS during the cyclic loading have also been analyzed. Moreover, the factors influencing fatigue limit improvement were discussed.

A new kind of power frequency current mutual inductance device based on the optical fiber measurement technology was proposed in this paper. The new device was made up of excitation current source, sensing system and magnetic circuit. The bus-bar was selected as excitation current source. The giant magnetostrictive material and fiber Bragg Grating (GMM-FBG) were combined as the sensing system. The magnetic circuit was consisting of the magnetic materials and permanent magnet materials. The numerical analysis of the magnetic field which generated in the sensors was achieved through the finite element analysis. In the simulation, the quiescent operating point of GMM-FBG sensor was confirmed; the size of the material in the magnetic circuit system was optimized to ensure the good output performance of sensing system. Finally, the numerical relationship between excitation current and the internal magnetic field of the Terfenol-D rods was established. Meanwhile, the calibration of sensor was achieved through the experiment system of the GMM-FBG current transformer sensor.