Experimental study on the influences of cutter geometry and material on scraper wear during shield TBM tunnelling in abrasive sandy ground

When shield TBM tunnelling in abrasive sandy ground,the rational design of cutter parameters is critical to reduce tool wear and improve tunnelling efficiency.However,the influence mechanism of cutter parameters on scraper wear remains unclear due to the lack of a reliable test method.Geometry and material optimisation are often based on subjective experience,which is unfavourable for improving scraper geological adaptability.In the present study,the newly developed WHU-SAT soil abrasion test was used to evaluate the variation in scraper wear with cutter geometry,material and hardness.The influence mechanism of cutter parameters on scraper wear has been revealed according to the scratch characteristics of the scraper surface.Cutter geometry and material parameters have been optimised to reduce scraper wear.The results indicate that the variation in scraper wear with cutter geometry is related to the cutting resistance,frictional resistance and stress distribution.An appropriate increase in the front angle(or back angle)reduces the cutting resistance(or frictional resistance),while an excessive increase in the front angle(or back angle)reduces the edge angle and causes stress concentration.The optimal front angle,back angle and edge angle for quartz sand samples areα=25°,β=10°andγ=55°,respectively.The wear resistance of the modelled scrapers made of different metal materials is related to the chemical elements and microstructure.The wear resistances of the modelled scrapers made of 45#,06Cr19Ni10,42CrMo4 and 40CrNiMoA are 0.569,0.661,0.691 and 0.728 times those made of WC-Co,respectively.When the alloy hardness is less than 47 HRC(or greater than 58 HRC),scraper wear decreases slowly with increasing alloy hardness as the scratch depth of the particle asperity on the metal surface stabilizes at a high(or low)level.However,when the alloy hardness is between 47 HRC and 58 HRC,scraper wear decreases rapidly with increasing alloy hardness as the scratch depth transitions from high to low levels.The sensitive hardness interval and recommended hardness interval for quartz sand are[47,58]and[58,62],respectively.The present study provides a reference for optimising scraper parameters and improving cutterhead adaptability in abrasive sandy ground tunnelling.

Theoretical analysis of ultra-short pulsed laser ablation of SiO_2 material based on a Coulomb explosion model

Based on the kinetic theoretical Vlasov-Poisson equation, a surface Coulomb explosion model of SiO2 material induced by ultra-short pulsed laser radiation is established. The non-equilibrium free electron distribution resulting from the two mechanisms of multi-photon ionization and avalanche ionization is computed. A quantitative analysis is given to describe the Coulomb explosion induced by the self-consistent electric field, and the impact of the parameters of laser pulses on the surface ablation is also discussed. The results show that the electron relaxation time is not constant, but it is related to the microscopic state of the electrons, so the relaxation time approximation is not available on the femtosecond time scale. The ablation depths computed by the theoretical model are in good agreement with the experimental results in the range of pulse durations from 0 to 1 ps.

Ultra-Short Pulsed Laser Manufacturing and Surface Processing of Microdevices

Ultra-short laser pulses possess many advantages for materials processing.Ultrafast laser has a significantly low thermal effect on the areas surrounding the focal point;therefore,it is a promising tool for micro-and submicro-sized precision processing.In addition,the nonlinear multiphoton absorption phenomenon of focused ultra-short pulses provides a promising method for the fabrication of various structures on transparent material,such as glass and transparent polymers.A laser direct writing process was applied in the fabrication of high-performance three-dimensional(3D)structured multilayer microsupercapacitors(MSCs)on polymer substrates exhibiting a peak specific capacitance of 42.6 mF·cm^-2 at a current density of 0.1 mA·cm^-12.Furthermore,a flexible smart sensor array on a polymer substrate was fabricated for multi-flavor detection.Different surface treatments such as gold plating,reducedgraphene oxide(rGO)coating,and polyaniline(PANI)coating were accomplished for different measurement units.By applying principal component analysis(PCA),this sensing system showed a promising result for flavor detection.In addition,two-dimensional(2D)periodic metal nanostructures inside 3D glass microfluidic channels were developed by all-femtosecond-laser processing for real-time surfaceenhanced Raman spectroscopy(SERS).The processing mechanisms included laser ablation,laser reduction,and laser-induced surface nano-engineering.These works demonstrate the attractive potential of ultra-short pulsed laser for surface precision manufacturing.

Virtual straightening of scraper conveyor based on the position and attitude solution of industrial robot model

The movement of the floating connecting mechanism between a hydraulic support and scraper conveyor is space movement;thus,when the hydraulic support pushes the scraper conveyor,there is an error between the actual distance of the scraper conveyor and the theoretical moving distance.As a result,the scraper conveyor cannot obtain the straightness requirement.Therefore,the movement law of the floating connecting mechanism between the hydraulic support and scraper conveyor is analyzed and programmed into the Unity3D to realize accurate pushing of the scraper conveyor via hydraulic support.The Coal Seam?Equipment Joint Virtual Straightening System is established,and a straightening method based on the motion law of a floating connection is proposed as the default method of the system.In addition,a straightening simulation of the scraper conveyor was performed on a complex coal seam floor,the results demonstrate that the average straightening error of the scraper conveyor is within 2-8 mm,and is in direct proportion to the fluctuation of the coal seam floor in the strike of the seam with high accuracy,the straightness of scraper conveyor is more affected by the subsidence terrain during straightening than by the bulge terrain.And some conclusions are verified by experiment.Based on the verification of the relevant conclusions,a comparison and analysis of Longwall Automation Steering Committee(LASC)straightening technology and default straightening method in the simulation system shows that the straightness accuracy of LASC straightening technology under complex floor conditions is slightly less than that of the default straightening method in the proposed system.

CFD studies of scraper built in SPA clarifying tank based on mixture solid-liquid two-phase flow model

In the industrial process of producing the strong phosphoric acid(SPA),clarification of the solution is essential to the ultimate product.However,the large viscosity of sediment and the induced interface interaction result in difficulties when the SPA is clarified.CFD numerical methodology was applied to simulate internal flow field and performance of the low speed scraper based on Mixture solidliquid two-phase flow model.Sediment deposition was generated by loading solid particles at the bottom of clarifying vessel.The moving mesh and RNG k-εmodel were used to simulate the rotational turbulent flow in clarifying tank.Variables studied,amongst others,were the scraper rotation speed and the mounting height,which could affect the solid suspension height.Features of flow field and solid volume fraction distribution in computational domain were presented and analyzed.The numerical reports of the scraper torque and velocities of inlet and outlet filed were obtained.It seems the torque value of rotatio-nal axis and particle suspending height augment with an increasing rotating speed.Meanwhile,a high revolving speed is good for the deposition discharge.The particle fraction distribution in meridional surface and horizontal surface at fixed rotation speed were analyzed to determine the corresponding optimal installation height.The simulating results reflect the flow field is marginally stirred by the scraper and proper working parameters are obtained,in which case the comprehensive properties of the scraper and the clarifying tank are superior.

Theoretical and Experimental Studies of the Effect of Inclined Scraper on Removal of Raw Cotton from Mesh Surface

The present manuscript deals with theoretical and experimental studies of the effect of inclined scraper on removal raw cotton from mesh surface. The mathematical model of the problem and theoretical studies of the motion of cotton mass on plane of scraper is derived taking into account material point by accomplishing plane motion in the mesh surface. Graphs of the experiment shows that performance of scraper inclined to the radius of the disk by the value α=30° to the surface mesh β=110°, optimally allows to reduce the formation of technological defects of raw cotton. The presence of zero-pressure portion on the mesh surface of separator may provide complete removal of cotton from its surface and to eliminate grid clogging.

Wavelength tunable ultra-short pulses based on a flat broadband spectrum generated in a nonlinear ytterbium-doped fiber amplifier

We present a nonlinear ytterbium-doped fiber amplifier based on enhanced nonlinear effects that can produce a flat broadband spectrum ranging from 1050–1225 nm with a maximum average output power of 7.8 W at 14 W pump power.Its repetition rate is 89 MHz. Using a pair of gratings and two knife edges as a filter, wavelength tunable picosecond pulses of tens to hundreds of milliwatts can be obtained in the broadband spectrum range. The output power, pulse width, and spectrum（center wavelength and linewidth） are adjusted by tuning the distance of the grating pair and/or the knife edges.Fixing the distance between the two gratings at 15 mm and keeping the output spectrum linewidth at approximately 20 nm,the shortest pulse width obtained is less than 1 ps centered at 1080 nm. The longest wavelength of the short pulses is around1200 nm, and its output power and pulse width are 40 m W and 5.79 ps, respectively. The generation of a flat broadband spectrum is also discussed in this paper.

A review on glass welding by ultra-short laser pulses

Glass welding by ultra-short pulsed(USP)lasers is a piece of technology that offers high strength joints with hermetic sealing.The joints are typically formed in glass that is transparent to the laser by exploiting nonlinear absorption effects that occur under extreme conditions.Though the temperature reached during the process is on the order of a few 1000°C,the heat affected zone(HAZ)is confined to only tens of micrometers.It is this controlled confinement of the HAZ during the joining process that makes this technology so appealing to a multitude of applications because it allows the foregoing of a subsequent tempering step that is typically essential in other glass joining techniques,thus making it possible to effectively join highly heat sensitive components.In this work,we give an overview on the process,development and applications of glass welding by USP lasers.

Taper Angle Correction in Cutting of Complex Micro-mechanical Contours with Ultra-Short Pulse Laser

The objective of this work was to investigate the possibility of taper angle correction in cutting of complex micro-mechanical contours using a TruMicro ultra-short pulse laser in combination with the SCANLAB precSYS micro machining sub system. In a first step, the influence of the process parameters on the kerftaper angle of metallic alloys was systematically investigated without beam inclination. A set of base parameters was derived for the subsequent investigations. In a second step, the kerftaper angle was controlled by static beam inclination. In a third step, the same optics was used in its dynamic precession mode to fabricate micro-mechanical components of complex contours with perpendicular 0~ taper angles. It was found that taper angle adjustments of up to 7.5~ are possible with the used setup for cutting applications. Taper angle control is possible both in the static beam inclination mode and in the dynamic precession mode. The static mode could be interesting for contours with sharp inner radii and for achieving faster cutting times similar to results with fixed optics, but would require excellent synchronization of beam inclination and axis motion. The dynamic precession mode would allow an easier integration of the optics into a laser machine but will result in longer cutting times and limitations with respect to achievable inner radii.

Generation of time-dependent ultra-short optical pulse trains in the presence of self-steepening effect

Starting from the extended nonlinear Schrodinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step Fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as time goes on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intensity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider.

Decommissioning analysis of the scrapers in the NSRL Linac using depth profiling

For a high-energy electron facility, estimates of induced radioactivity in materials are of considerable importance to ensure that the exposure of personnel and the environment remains as low as reasonably achievable. In addition, accurate predictions of induced radioactivity are essential to the design, operation, and decommissioning of a high-energy electron linear accelerator. In the case of the 200-MeV electron linac of the National Synchrotron Radiation Laboratory(NSRL), the electrons are accelerated by five acceleration tubes and collimated by copper scrapers. The scrapers, which play a vital role in protecting the acceleration cavity, are bombarded by many electrons over a long-term operation, which causes a significant amount of induced radioactivity. Recently, the NSRL Linac is the first high-energy electron linear accelerator in China to be out of commission.Its decommissioning is highly significant for obtaining decommissioning experience. This paper focuses on the measurement of induced radioactivity on the fourth scraper, where the electron energy was 158 MeV. The radionuclides were classified according to their half-lives. Such a classification provides a reliable basis for the formulation of radiation protection and facility decommissioning. To determine the high-radioactivity area and to facilitate the decommissioning process, the slicing method was applied in this study. The specific activity of60 Co in each slice was measured at a cooling time of ten months, and the results were compared with the predictions generated by Monte Carlo program FLUKA. The trend of the measured results is in good agreement with the normalized simulation results. The slicing simulation using Monte Carlo method is useful for the determination of high-radiation areas and proper material handling protocols and, therefore, lays a foundation for the accumulation of decommissioning experience.

Thermal analysis and tests of W/Cu brazing for primary collimator scraper in CSNS/RCS

To the transverse beam collimation system in a rapid cycling synchrotron,an important component is the primary collimator,which improves emittance of the beam halo particles such that the particles outside the predefined trajectory can be absorbed by the secondary collimators.Given the material properties and power deposition distribution,the beam scraper of the primary collimator is a0.17 mm tungsten foil on a double face-wedged copper block of 121.5 mm x 20 mm.The heat is transferred to the outside by a φ34 mm copper rod.In this paper,for minimizing brazing thermal stress,we report our theoretical analysis and tests on brazing the tungsten and copper materials which differ greatly in size.We show that the thermal stress effect can be controlled effectively by creating stress relief grooves on the copper block and inserting a tungsten transition layer into the copper block.This innovation contributes to the successful R&D of the primary collimator.And this study may be of help for working out a brazing plan of similar structures.

Differential protein expression during colonic adaptation in ultra-short bowel rats

AIM： To investigate the proteins involved in colonic adaptation and molecular mechanisms of colonic adapration in rats with ultra-short bowel syndrome （USBS）. METHODS： Sprague Dawley rats were randomly as- signed to three groups： USBS group （10 rats） undergoing an approximately 90%-95% small bowel resection; sham-operation group （10 rats） undergoing small bowel transaction and anastomosis; and control group （ten normal rats）. Colon morphology and differential protein expression was analyzed after rats were given postsurgical enteral nutrition for 21 d. Protein expression in the colonic mucosa was analyzed by two-dimensional electrophoresis （2-DE） in all groups. Differential protein spots were detected by ImageMaster 2D Platinum soft-ware and were further analyzed with matrix-assisted laser desorption/ionization-time-of-flight/time-of-flightmass spectrometric （MALDI-TOF/TOF-MS） analysis. RESULTS： The colonic mucosal thickness significantly increased in the USBS group compared with the control group （302.1 ± 16.9 um vs 273.7 ± 16.0 um, P 〈 0.05）. There was no statistically significant difference between the sham-operation group and control group （P 〉 0.05）. The height of colon plica markedly improved in USBS group compared with the control group （998.4 ± 81.2 um vs 883.4 ± 39.0 um, P 〈 0.05）. There was no statistically significant difference between the shamoperation and control groups （P 〉 0.05）. A total of 141 differential protein spots were found in the USBS group. Forty-nine of these spots were down-regulated while 92 protein spots were up-regulated by over 2-folds. There were 133 differential protein spots in USBS group. Thirty of these spots were down-regulated and 103 were upregulated. There were 47 common differential protein spots among the three groups, including 17 down- regulated protein spots and 30 up-regulated spots. Among 47 differential spots, eight up-regulated proteins were identified by MALDI-TOF/TOF-MS. These proteins were previously reported to be involved in sugar and fat metabolism, protein synthesis and oxidation reduction, which are associated with colonic adaption. CONCLUSION： Eight proteins found in this study play important roles in colonic compensation and are associated with sugar and fat metabolism, protein synthesis, and molecular chaperoning

Case of pancreatic metastasis from colon cancer in which cell block using the Trefle^■ endoscopic scraper enables differential diagnosis from pancreatic cancer

Endoscopic transpapillary brush cytology and forceps biopsy during endoscopic retrograde cholangiopancreatology are generally used to obtain pathological evidence of biliary strictures. Recently, the new endoscopic scraper Trefle~? has been reported and demonstrated high cancer detectability in malignant biliary strictures. This device is used to scrape the stricture over the guidewire, and, in the original method, the tissue and/or cell samples obtained are subjected to histological and/or cytological analysis separately. However, discrimination of chunks of tissue is hampered by the opacity of the surrounding fluid. We have developed a cell block technique for the Trefle~? device without dividing obtained specimens into tissue and cellular components, which is the simplest method and enables immunohistochemical analysis. We present a case of obstructive jaundice diagnosed immunohistochemically as pancreatic metastasis from colon cancer using cell block sections obtained with the Trefle~? device, which procedure is as easy as conventional brush cytology.

Effect of Foil Target Thickness in Proton Acceleration Driven by an Ultra-Short Laser

Proton acceleration experiments were carried out by a 1.2× 1018 W/cm2 ultra-short laser interaction with solid foil targets. The peak proton energy observed from an optimum target thickness of 7 μm in our experiments was 2.1 MeV. Peak proton energy and proton yield were investigated for different foil target thicknesses. It was shown that proton energy and conversion efficiency increased as the target became thinner, on one condition that the preplasma generated by the laser prepulse did not have enough shock energy and time to influence or destroy the target rear-surface. The existence of optimum foil thickness is due to the effect of the prepulse and hot electron transportation behavior on the foil target.

Study on Ultra-Short Laser Pulse Ablation of Metals by Molecular Dynamics Simulation

The dynamical progresses involved in ultra-short laser pulse ablation of face-centered cubic metals under stress confinement condition are described completely using molecular dynamics method. The laser beam absorption and thermal energy turning into kinetics energy of. atoms are taken into account to give a detailed picture of laser metal interaction. Superheating phenomenon is observed, and the phase change from solid to liquid is characterized by a destroyed atom configuration and a decreased number density. The steep velocity gradients are found in the systems of Cu and Ni after pulse in consequence of located heating and exponential decrease of fluences following the Lambert-Beer expression. The shock wave velocities are predicted to be about 5 000 m/s in Cu and 7 200 m/s in Ni. The higher ablation rates are obtained from simulations compared with experimental data as a result of a well-defined crystalline surface irradiated by a single pulse. Simulation results show that the main mechanisms of ablation are evaporation and thermoelastic stress due to located heating.

The extending length calculation of hydraulic drive non-metallic completion screen pipe running into ultra-short radius horizontal well

Focusing on the extending length restriction of the completion screen pipe resistance running into ultra-short radius horizontal well,this paper proposed technology of hydraulic drive completion tubular string running into ultra-short radius horizontal well.Innovative hydraulic drive tools and string structure are designed,which are composed of guide tubing,hydraulic drive tubing and non-metallic completion screen pipe from inside to outside.A novel mechanical-hydraulic coupling model is established.Based on the wellbore structure of an ultra-short radius horizontal well for deep coalbed methane,the numerical calculations of force and hydraulic load on tubular strings were accomplished by the mechanical-hydraulic coupling model.The results show that the extending length of completion tubular string with the hydraulic drive is 17 times that of conventional completion technology under the same conditions.The multi-factor orthogonal design is adopted to analyze the numerical calculations,and the results show that the extending length of the completion tubular string is mainly affected by the completion tubular string structure and the friction coefficient between the non-metallic composite continuous screen pipe and the wellbore.Two series of hydraulic drive completion tubular string structures suitable for ultra-short radius horizontal wells under different conditions are optimized,with the extending limits of 381 m and 655 m,respectively.These researches will provide theoretical guidance for design and control of hydraulic drive non-metallic composite continuous completion screen pipe running into ultra-short radius horizontal wells.

Modelling and Simulation of Scraper Reliability for Maintenance

A scraper conveyor is a kind of heavy machinery which can continuously transport goods and widely used in mines, ports and store enterprises. Since scraper failure rate directly affects production costs and production capacity, the evaluation and the prediction of scraper conveyor reliability are important for these enterprises. In this paper, the reliabilities of different parts are classified and discussed according to their structural characteristics and different failure factors. Based on the component＇s time-to-failure density function, the reliability model of scraper chain is constructed to track the age distribution of part population and the reliability change of the scraper chain. Based on the stress-strength interference model, considering the decrease of strength due to fatigue failure, the dynamic reliability model of such component as gear, axis is developed to observe the change of the part reliability with the service time of scraper. Finally, system reliability model of the scraper is established for the maintenance to simulate and calculate the scraper reliability.

Cooling rate calibration and mapping of ultra-short pulsed laser modifications in fused silica by Raman and Brillouin spectroscopy

This paper focuses on the preparation of a new extended set of calibrations of cooling rate(fictive temperature)in fused silica determined by inelastic light scattering and its subsequent use to characterize the local cooling rate distribution in ultra-short pulsed(USP)laser modification.In order to determine the thermal history(e.g.cooling rate and fictive temperature)of fused silica,high-resolution inelastic light-scattering experiments(Raman and Brillouin spectroscopy)were investigated.Calibrations were performed and compared to the existing literature to quantify structural changes due to a change of fictive temperature.Compared to existing calibrations,this paper provides an extension to lower and higher cooling rates.Using this new set of calibrations,we characterized a USP laser modification in fused silica and calculated the local fictive temperature distribution.An equation relating the fictive temperature(Tf)to cooling rates is given.A maximum cooling rate of 3000 K min-1 in the glass transition region around 1200℃ was deduced from the Raman analysis.The Brillouin observations are sensitive to both the thermal history and the residual stress.By comparing the Raman and Brillouin observations,we extracted the local residual stress distribution with high spatial resolution.For the first time,combined Raman and Brillouin inelastic light scattering experiments show the local distribution of cooling rates and residual stresses(detailed behavior of the glass structure)in the interior and the surrounding of an USP laser modified zone.

超长柔性悬挂固体充填刮板输送机异常工况表征及自主调控方法

固体充填刮板输送机是固体充填开采技术的关键装备,其高效智能化的程度制约着固体智能充填开采技术的进步,暂难突破超大采长、大功率、高可靠性的瓶颈,运行状态受地质条件、充填工艺等主控因素影响显著,异常工况自主调控问题亟待解决。总结了固体充填刮板输送机特征;构建了固体充填刮板输送机位姿形态与运输状态表征方法;通过分析异常工况的形成机理,选取异常工况判别指标,结合位姿与运输状态表征方法,给出了其空间位姿、牵引状态等异常工况判别准则与典型异常工况的调控路径,揭示了多工况状态下固体充填刮板输送机运载调控机制,提出了实时调控充填材料运输量、直线及水平程度组合的异常工况自主调控方法。全国首个260 m工作面长固体充填工程案例表明:通过异常工况自主调控,平均最大水平偏移距每减少100 mm,刮板链牵引力可减少85 kN,输送功率损耗可减少55 kW;平均最大垂直偏移距每减小100 mm时,输送功率损耗可减少7.2 kW;单位长度货载运量每减少100 kN/m,刮板链牵引力可减少31.9 kN,输送功率损耗可减少38.2 kW。所提出的异常工况自主调控方法可显著提升固体充填刮板输送机的输送效能,可助力实现固体智能充填开采。