The abrasive waterjet (AWJ) is now widely used in the advanced cutting processes of polymers,metals,glass,ceramics and composite materials like thin multiple-layered material (TMM).Various research and development eff...The abrasive waterjet (AWJ) is now widely used in the advanced cutting processes of polymers,metals,glass,ceramics and composite materials like thin multiple-layered material (TMM).Various research and development efforts have recently been made to understand the science of AWJ.However,the interaction mechanism between a workpiece and high-velocity abrasive particles still remains a complicated problem.In this work,the material removal mechanisms of AWJ such as micro penetration and micro dent were experimentally investigated.In addition,a new computer simulation model considering high strain rate effect was proposed to understand the micro impact behavior of high-velocity micro-sized abrasives in AWJ cutting.展开更多
Silicon carbide (SiC) is highly wear resistant with good mechanical properties, including high temperature strength, excellent chemical resistance, and high thermal conductivity and thermal shock resistance. SiC molds...Silicon carbide (SiC) is highly wear resistant with good mechanical properties, including high temperature strength, excellent chemical resistance, and high thermal conductivity and thermal shock resistance. SiC molds, which can be produced with diverse microstructural features, are now widely used in glass molding owing to their excellent characteristics, and also have potential applicability in IT industries. SiC molds are traditionally fabricated by silicon micromachining or dicing. The fabrication cost of silicon micromachining is very high, however, because several expensive masks are needed. Furthermore, the fabrication time is very long. Meanwhile, it is difficult to make micro-patterned molds with arbitrary shapes using dicing saws. Abrasive water jet (AWJ) is widely applied to cut and drill very brittle, soft and fibrous materials. It offers high energy density, the absence of a heat affected zone(HAZ), high performance, and an environment friendly process. In spite of these advantages, micro-hole drilling via conventional AWJ processing suffers from notable shortcomings. We proposed a new abrasive supplying method of AWJ. The proposed method reduces frosting phenomena, and provides micro-machining of AWJ. The characteristics of a hole machined was investigated by the proposed AWJ process according to the ratio of water and abrasives. With the optimal experimental conditions, 3×3 array SiC molds with the diameter of 700 μm and depth of 900 μm were successfully manufactured.展开更多
An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on t...An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on the formation of perforation by AWJ is unclear yet.In this study,we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope(SEM).The results show that when the grain size is doubled,the perforation depth increases by 16.22%under the same type of structure and properties.In general,fractures are more likely to be created at the position of rough surfaces caused by abrasive impact,and the form of fractures is determined by the mineral type.In addition,microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries.The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet,while the lateral extension is controlled by the backflow.The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.展开更多
The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusio...The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.展开更多
The TZM alloys with different contents of ZrO_(2)were prepared by powder metallurgy and rolling,and the grain size,hardness,and abrasive wear resistance of TZM alloy were studied.The abrasive wear test of TZM alloy wa...The TZM alloys with different contents of ZrO_(2)were prepared by powder metallurgy and rolling,and the grain size,hardness,and abrasive wear resistance of TZM alloy were studied.The abrasive wear test of TZM alloy was conducted under the conditions of 10,15,and 20 N and abrasive particle sizes of 7,11,18,and 38μm.The results show that the added ZrO_(2)particles in TZM alloy are mainly distributed at the grain boundaries.The grains of TZM alloy containing 1.5wt%ZrO_(2)are significantly refined,and the hardness is increased by 16%.The wear test results show that TZM alloy containing 1.5wt%ZrO_(2)has the lowest mass loss rate and excellent wear resistance under all loads and abrasive sizes,and the wear performance is improved by 12%.The ZrO_(2)with high hardness becomes the main bearer of the load,and as the second-phase,it hinders the abrasive particles from entering the matrix and effectively resists the scratch of the abrasive particles,which is the main reason for the excellent wear resistance.展开更多
As a non-contact ultra-precision machining method,abrasive water jet polishing(AWJP)has signi-ficant application in optical elements processing due to its stable tool influence function(TIF),no subsurface damage and s...As a non-contact ultra-precision machining method,abrasive water jet polishing(AWJP)has signi-ficant application in optical elements processing due to its stable tool influence function(TIF),no subsurface damage and strong adaptability to workpiece shapes.In this study,the effects of jet pressure,nozzle diameter and impinging angle on the distribution of pressure,velocity and wall shear stress in the polishing flow field were systematically analyzed by computational fluid dynamics(CFD)simulation.Based on the Box-Behnken experimental design,a response surface regression model was constructed to investigate the influence mech-anism of process parameters on material removal rate(MRR)and surface roughness(Ra)of fused silica.And experimental results showed that increasing jet pressure and nozzle diameter significantly improved MRR,consistent with shear stress distribution revealed by CFD simulations.However,increasing jet pressure and impinging angle caused higher Ra values,which was unfavorable for surface quality improvement.Genetic algorithm(GA)was used for multi-objective optimization to establish Pareto solutions,achieving concurrent optimization of polishing efficiency and surface quality.A parameter combination of 2 MPa jet pressure,0.3 mm nozzle diameter,and 30°impinging angle achieved MRR of 169.05μm^(3)/s and Ra of 0.50 nm.Exper-imental verification showed prediction errors of 4.4%(MRR)and 3.8%(Ra),confirming the model’s reliabil-ity.This parameter optimization system provides theoretical basis and technical support for ultra-precision polishing of complex curved optical components.展开更多
Because the grinding temperature is high when grinding using conventional disordered grinding wheels,the grinding quality improvement is limited when using single abrasive ordered grinding wheels,and the wheel prepara...Because the grinding temperature is high when grinding using conventional disordered grinding wheels,the grinding quality improvement is limited when using single abrasive ordered grinding wheels,and the wheel preparation process is complex and costly when using microstructured grinding wheels,abrasive groups ordered grinding wheels are widely investigated.However,there is a paucity of systematic analyses and comprehensive reviews focused on abrasive groups ordered grinding wheels.Therefore,this paper defines abrasive groups ordered grinding wheels and classifies them,based on their unique characteristics,into groups such as abrasive blocks ordered grinding wheel,fine grain structured grinding wheel,abrasive clusters ordered grinding wheel,and abrasive fibers ordered grinding wheel.We provide an overview of the latest advances in wheel structures,preparation methods,and abrasive selection for various types of abrasive groups ordered grinding wheels.Furthermore,we conduct a comparative analysis of the existing types,significant advantages,and challenges associated with the four types of abrasive groups ordered grinding wheels.Looking ahead,given the potential of abrasive groups ordered grinding wheels in reducing grinding force and temperature,we recommend further exploration of their application in combination with special processing techniques.This could pave the way for the development of machining processes that are more environmentally friendly,energy-efficient,and precise.展开更多
The use of abrasive waterjets(AWJs)for rock drilling offers advantages in urbanized areas,locations that are vulnerable to damage,and piling operations.However,the overall operational cost of AWJ systems remains high ...The use of abrasive waterjets(AWJs)for rock drilling offers advantages in urbanized areas,locations that are vulnerable to damage,and piling operations.However,the overall operational cost of AWJ systems remains high compared to that of conventional drilling methods,which constrains the long-term industrial application of AWJs.For instance,the abrasive costs account for over 60%of the total process cost,but the recycling of abrasives remaining after drilling could significantly reduce machining costs.In this study,the post-impact characteristics of abrasives were explored,aiming to enhance their recyclability.The physical properties and particle distribution of used abrasives vary depending on the jet energy,ultimately affecting their recyclability and recycling rate.The particle properties of used abrasives(particle size distribution,particle shape,and mean particle size)were compared under different waterjet energy variables(standoff distance(SOD)and water pressure)and test conditions(dry and underwater).Furthermore,the collision stages of the abrasive particles within a waterjet system were classified and analyzed.The results revealed that abrasive fragmentation predominantly occurred due to internal collisions within the mixing chamber.In addition,an attempt was made to optimize the waterjet parameters for an economical and efficient operation.The findings of this study could contribute to enhancing the cost-effectiveness of AWJ systems for rock drilling applications.展开更多
Medium-manganese steel exhibits excellent strength and toughness,which are essential features in wear resistance applications.This study examines the impact of annealing temperature on impact abrasive wear.The results...Medium-manganese steel exhibits excellent strength and toughness,which are essential features in wear resistance applications.This study examines the impact of annealing temperature on impact abrasive wear.The results have indicated that samples annealed at different temperatures display plowing and fatigue wear effects.In the initial wear stage,the hightemperature annealed steel outperforms samples annealed at a lower temperature in terms of anti-plowing wear performance.This phenomenon is mainly due to the lower initial hardness of the samples subjected to low-temperature annealing.However,with prolonged wear time,the low-temperature annealed samples exhibit improved plowing wear performance,which is ascribed to a refinement of the lamellar microstructure and an increased residual austenite(RA),which enhances the work hardening effect,improving the hardness of the worn surface.The low-temperature annealed samples consistently delivered superior fatigue wear performance when compared with samples annealed at the higher temperature.The latter effect may be attributed to two factors.Firstly,the finer lamellar microstructure in the low-temperature annealed samples,coupled with greater RA,results in transformation-induced plasticity or twin-induced plasticity effect that hinders crack formation and propagation.Secondly,the low-temperature annealed samples form nanoscale equiaxed grains near the worn surface during the wear process.These grains can withstand crack driving forces in fine-grained regions,suppressing the formation and propagation of cracks.展开更多
During the excavation process of deep hard rock tunnels,precutting rock with an abrasive water jet can weaken their strength and improve the efficiency of mining machinery.However,owing to the complex geological envir...During the excavation process of deep hard rock tunnels,precutting rock with an abrasive water jet can weaken their strength and improve the efficiency of mining machinery.However,owing to the complex geological environment,abrasive jets cannot fully utilize their rock-cutting performance.To fully exploit the advantages of high-pressure abrasive water jets,five orthogonal experiments were designed for rocks with significant differences in strength.Experimental research has been conducted on the performance of rotating abrasive waterjet-cutting rocks.Moreover,a neural network prediction model for predicting rock-cutting characteristics is established by comprehensively considering rock mechanics parameters and abrasive water jet parameters.The results show that the cutting depth of rocks with different strengths increases nonlinearly with increasing work pressure of the abrasive water jet.The cutting depth decreases exponentially with increasing cutting velocity.The cutting depth first increases and then decreases with increasing target distance,and the best target distance is between 4 mm and 6 mm.The effect of the target distance on the cutting width of rock is the most significant,but the cutting width of high-strength rock is not sensitive to changes in the working parameters of the abrasive water jet.The average relative errors of BP(backpropagation)neural networks optimized by global optimization algorithms in predicting rock cutting depth and width are 13.3%and 5.4%,respectively.This research combines the working characteristics of mining machinery to study the performance of abrasive waterjet rotary cutting of rocks and constructs a predictive model for the performance of abrasive waterjet cutting of rocks that includes rock strength factors.This provides a new solution for quickly adjusting the working parameters of abrasive water jets according to mining conditions.展开更多
Manufacturing micro-holes in non-conductive ceramics presents significant challenges in precision machining,particularly due to the absence of central abrasive grains in micro-grinding wheels.This study investigates h...Manufacturing micro-holes in non-conductive ceramics presents significant challenges in precision machining,particularly due to the absence of central abrasive grains in micro-grinding wheels.This study investigates helical grinding under conditions where the central abrasive grain is absent,focusing on the formation of undeformed chips.It was observed that nearly all microgrinding wheels,regardless of their manufacturing process or grain size,exhibit a central grain absence,with larger grain sizes leading to more extensive absence areas.Analysis revealed that residual patterns at the bottom of machined holes depend on the ratio of the absence zone diameter to the wheel's eccentricity.Analytical models were developed to describe the heights of cylindrical and disc-shaped residues,which were subsequently validated through kinematic simulations.The removal mechanisms for these residues differ;cylindrical residues,which cannot be removed by grinding,cause interference and should be avoided,while disc-shaped residues removal depends on the protrusion height of the first grain,influencing contact with the wheel's end face and subsequent grinding actions.Experimental validation using SiC_(p)/Al demonstrated that cylindrical residues create distinct ring-shaped wear marks,significantly increasing cutting forces,whereas discshaped residues result in hat-shaped wear marks and higher cutting forces when the first grain's protrusion is insufficient.Additionally,inadequate lubrication and chip removal can lead to chip adhesion starting from the absence zone.These findings enhance the theoretical framework of helical grinding/milling and provide valuable insights for precision machining of micro-holes in nonconductive ceramics.展开更多
To address the challenges of poor surface quality and high energy consumption in marble cutting,this study introduces an auxiliary abrasive jet cutting technology enhanced by the use of polyacrylamide(PAM)as a dragred...To address the challenges of poor surface quality and high energy consumption in marble cutting,this study introduces an auxiliary abrasive jet cutting technology enhanced by the use of polyacrylamide(PAM)as a dragreducing additive.The effects of feed rate(50-300 mm/min),polymer concentration(0-0.5 g/L),and nozzle spacing(4-12 mm)on kerf width and surface roughness are systematically investigated through an orthogonal experimental design.Results reveal that feed rate emerges as themost significant factor(p<0.01),followed by PAM concentration and nozzle spacing.The optimal set of parameters,comprising a 200 mm/min feed rate,0.3 g/L PAM concentration,and 6mmnozzle spacing,achieves the narrowest kerf width(0.867 mm)and the lowest surface roughness(10.220μm).Analysis of the underlying mechanisms demonstrates that PAMenhances the energy efficiency of the jet by suppressing turbulent pulsations and increasing fluid viscoelasticity,thereby minimizing energy loss during the cutting process.展开更多
Aluminum alloys are widely used in industry due to their light weight.These alloys are generally exposed to abrasive wear,which diminishes their effective lifespan.The wear resistance of these alloys is enhanced by ad...Aluminum alloys are widely used in industry due to their light weight.These alloys are generally exposed to abrasive wear,which diminishes their effective lifespan.The wear resistance of these alloys is enhanced by adding various reinforcements,however,this enhancement comes at the cost of reduced fracture toughness.This paradox of increased wear resistance versus decreased fracture toughness in aluminum alloys can be resolved by using functionally graded materials (FGMs).This study focuses on the abrasive wear behavior of functional graded aluminum matrix composites reinforced with Al_(3)Ti particles.The wear properties of the composites were investigated by considering the characteristics of the composite such as matrix type and various composite zones,as well as the wear parameters such as abrasive particle diameter,load,sliding speed and distance.Taguchi method was used in the abrasive wear tests in order to get more reliable results in a timeefficient manner.Experiment recipes were created based on the L_(27)(3^(6)) orthogonal series.As a result of the study,it is observed that the wear resistance of the composites increases with an increase in Al_(3)Ti reinforcement content and hardness of the matrix.In addition,the size of abrasive particles and the applied load are significant factors affecting abrasive wear.展开更多
Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integr...Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.展开更多
Radial jet drilling(RJD)technology is expected to be a technology for the efficient exploitation of geothermal resources.However,the low rock-breaking efficiency is the major obstacle hindering the development of RJD ...Radial jet drilling(RJD)technology is expected to be a technology for the efficient exploitation of geothermal resources.However,the low rock-breaking efficiency is the major obstacle hindering the development of RJD technology.The flow field characteristics and rock breaking ability of cone-straight abrasive jet,rotary abrasive jet,and straight-rotating mixed abrasive jet are analyzed by numerical simulations and experiments.Results show that the axial velocity of the cone-straight abrasive jet is high,the tangential velocity is basically zero,the radial velocity is also small,and the jet impact area is concentrated in the center.A deep hole with a diameter of only 25 mm is formed when the cone-straight abrasive jet breaks the granite.Due to the presence of the guiding impeller,the rotary abrasive jet basically has no axial velocity and has the highest tangential and radial velocity,so it can break the granite to form a hole with a diameter of about 55 mm and a central bulge.The straight-rotating mixed abrasive jet has a large axial/tangential/radial velocity at the same time,so it can break the granite to form a hole with a diameter of about 52 mm with a low bulge.The results show that the straight-rotating mixed abrasive jet combines the advantages of the cone-straight jet and the rotary jet,and is more suitable for the RJD technology.The research results can provide reference for the development of efficient rock-breaking and hole-forming technology,and promote the development of RJD technology in the field of geothermal development.展开更多
Epoxy resins are extensively employed in the construction,electronics,automotive,and aerospace industries owing to their outstandingmechanical strength,chemical resistance,and electrical insulation.However,their intri...Epoxy resins are extensively employed in the construction,electronics,automotive,and aerospace industries owing to their outstandingmechanical strength,chemical resistance,and electrical insulation.However,their intrinsic flammability,poor wear resistance,and hydrophilicity significantly restrict broader applications.To address these challenges,a novel multifunctional coating(CEOS-DOPO-PDMS)has been designed and fabricated via an NPGLIDE approach.The system integrates 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)as a reactive phosphorus-based flame retardant,epoxy-terminated polydimethylsiloxane(EP-PDMS)as a hydrophobic segment,and cycloaliphatic epoxy-functionalized oligosiloxanes(CEOS)as a cross-linking co-reactant.The resulting CEOSDOPO-PDMS hybrid precursor was blended with bisphenol A diglycidyl ether(DGEBA)in N-methyl-2-pyrrolidone(NMP)and subsequently cured to form epoxy-based NP-GLIDE coatings.The optimized coating exhibits superior integrated performance,including high hydrophobicity(water contact angle up to 109.6°),outstanding abrasion resistance(5H pencil hardness),and excellent flame retardancy(resisting combustion at 500℃ for 30 s).These enhancements originate from the cooperative effects of the Si-O-Si framework,low-surface-energy PDMS chains,and phosphorus-containing DOPOmoieties,which together provide stable thermal protection,surface roughness-induced hydrophobicity,and durable mechanical integrity.An effective strategy for constructing multifunctional epoxy-based coatingswith simultaneously enhanced flame retardancy,wear resistance,andwater repellency is presented.The CEOSDOPO-PDMS system holds great promise for advanced protective applications in construction,transportation,and aerospace engineering.展开更多
The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This ...The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters （i.e. wheel speed, workpiece speed and depth of cut） on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride （CBN） abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardhess and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 ℃ is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm^3. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the bum-free and crack-free ground surface.展开更多
In dealing with abrasive waterjet machining（AWJM） simulation,most literatures apply finite element method（FEM） to build pure waterjet models or single abrasive particle erosion models.To overcome the mesh distorti...In dealing with abrasive waterjet machining（AWJM） simulation,most literatures apply finite element method（FEM） to build pure waterjet models or single abrasive particle erosion models.To overcome the mesh distortion caused by large deformation using FEM and to consider the effects of both water and abrasive,the smoothed particle hydrodynamics（SPH） coupled FEM modeling for AWJM simulation is presented,in which the abrasive waterjet is modeled by SPH particles and the target material is modeled by FEM.The two parts interact through contact algorithm.Utilizing this model,abrasive waterjet with high velocity penetrating the target materials is simulated and the mechanism of erosion is depicted.The relationships between the depth of penetration and jet parameters,including water pressure and traverse speed,etc,are analyzed based on the simulation.The simulation results agree well with the existed experimental data.The mixing multi-materials SPH particles,which contain abrasive and water,are adopted by means of the randomized algorithm and material model for the abrasive is presented.The study will not only provide a new powerful tool for the simulation of abrasive waterjet machining,but also be beneficial to understand its cutting mechanism and optimize the operating parameters.展开更多
The effect of processing parameters such as hot rolling and heat treatment on microstructure and mechanical properties was investigated for a new 0.27mass% C and Ni, Mo-free low alloy martensitic abrasion resistant st...The effect of processing parameters such as hot rolling and heat treatment on microstructure and mechanical properties was investigated for a new 0.27mass% C and Ni, Mo-free low alloy martensitic abrasion resistant steel. The three-body impact abrasive wear behavior was also analyzed. The results showed that two-step controlled rolling besides quenching at 880 ℃ and tempering at 170 ℃ could result in optimal mechanical property., the Brinell hardness, tensile strength, elongation and --40 ℃ impact toughness were 531, 1530 MPa, 11.8% and 58 J, re- spectively. The microstructure was of fine lath martensite with little retained austenite. Three-body impact abrasive wear results showed that wear mechanism was mainly of plastic deformation fatigue when the impact energy was 2 J, and the relative wear resistance was 1.04 times higher than that of the same grade compared steel under the same working condition. The optimal hardness and toughness match was the main reason of higher wear resistance.展开更多
The Pangolin, a soil-burrowing animal, is covered with scales. These scales are often abraded by soil and rock and their surface is corrugated. The abrasive wear of the surface of the scales was examined. The scales w...The Pangolin, a soil-burrowing animal, is covered with scales. These scales are often abraded by soil and rock and their surface is corrugated. The abrasive wear of the surface of the scales was examined. The scales were taken from a pangolin that had died of natural causes. The tests were run on a rotary disc abrasive wear tester. The abrasive material was quartz sand （96.5 wt.%） and bentonite （3.5 wt.%）. The morphology of the abraded surfaces and the abrasion were examined by stereoscopic microscopy and scanning electron microscopy. The concepts are proposed of ＂Guiding-Effect＂ and ＂Rolling-Effect＂ on the textured surfaces under free abrasive wear conditions and the critical dimensions of the ＂Rolling-Effect＂ are discussed.展开更多
文摘The abrasive waterjet (AWJ) is now widely used in the advanced cutting processes of polymers,metals,glass,ceramics and composite materials like thin multiple-layered material (TMM).Various research and development efforts have recently been made to understand the science of AWJ.However,the interaction mechanism between a workpiece and high-velocity abrasive particles still remains a complicated problem.In this work,the material removal mechanisms of AWJ such as micro penetration and micro dent were experimentally investigated.In addition,a new computer simulation model considering high strain rate effect was proposed to understand the micro impact behavior of high-velocity micro-sized abrasives in AWJ cutting.
基金supported by a grant-in-aid for the National Core Research Center Program from the Ministry of Education Science & Technologythe Korea Science & Engineering Foundation (No.R15-2006-022-01001)
文摘Silicon carbide (SiC) is highly wear resistant with good mechanical properties, including high temperature strength, excellent chemical resistance, and high thermal conductivity and thermal shock resistance. SiC molds, which can be produced with diverse microstructural features, are now widely used in glass molding owing to their excellent characteristics, and also have potential applicability in IT industries. SiC molds are traditionally fabricated by silicon micromachining or dicing. The fabrication cost of silicon micromachining is very high, however, because several expensive masks are needed. Furthermore, the fabrication time is very long. Meanwhile, it is difficult to make micro-patterned molds with arbitrary shapes using dicing saws. Abrasive water jet (AWJ) is widely applied to cut and drill very brittle, soft and fibrous materials. It offers high energy density, the absence of a heat affected zone(HAZ), high performance, and an environment friendly process. In spite of these advantages, micro-hole drilling via conventional AWJ processing suffers from notable shortcomings. We proposed a new abrasive supplying method of AWJ. The proposed method reduces frosting phenomena, and provides micro-machining of AWJ. The characteristics of a hole machined was investigated by the proposed AWJ process according to the ratio of water and abrasives. With the optimal experimental conditions, 3×3 array SiC molds with the diameter of 700 μm and depth of 900 μm were successfully manufactured.
基金supported by the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20233326)the Chongqing Science Fund for Distinguished Young Scholars(Grant No.CSTB2022NSCQJQX0028)the National Natural Science Foundation of China(Grant Nos.U23A20597,52274112).
文摘An abrasive water jet(AWJ)is commonly used to develop deep geothermal resources,such as drilling in hot dry rock(HDR).The influence of rock mineral properties,such as mineral types,mineral contents,and grain size,on the formation of perforation by AWJ is unclear yet.In this study,we investigate AWJ impacts on three types of granite samples with different mineral fractions using a polarizing microscope and scanning electron microscope(SEM).The results show that when the grain size is doubled,the perforation depth increases by 16.22%under the same type of structure and properties.In general,fractures are more likely to be created at the position of rough surfaces caused by abrasive impact,and the form of fractures is determined by the mineral type.In addition,microstructure analysis shows that transgranular fractures typically pass through large feldspar particles and quartz removal occurs along mineral boundaries.The longitudinal extension of perforation depends mainly on the strong kinetic energy of the jet,while the lateral extension is controlled by the backflow.The results contribute to a better understanding of the process involved in the breaking of hard rock by abrasive jets during deep geothermal drilling.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-Ⅳ-002-001 and P2023-B-Ⅳ-003-001)+3 种基金the Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology(No.JSKL2223K01)the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the Henan Science and Technology Public Relations Project(No.212102210445).
文摘The undeformed chip thickness and grinding force are key parameters for revealing the material removal mechanism in the grinding process.However,they are difficult to be well expressed due to the ununiformed protrusion height and random position distribution of abrasive grains on the abrasive wheel surface.This study investigated the distribution of undeformed chip thickness and grinding force considering the non-uniform characteristics of abrasive wheel in the grinding of K4002 nickel-based superalloy.First,a novel grinding force model was established through a kinematic-geometric analysis and a grain-workpiece contact analysis.Then,a series of grinding experiments were conducted for verifying the model.The results indicate that the distribution of undeformed chip thickness is highly consistent with the Gaussian distribution formula.The increase in the grinding depth mainly leads to an increase in the average value of Gaussian distribution.On the contrary,the increase in the workpiece infeed speed or the decrease in the grinding speed mainly increases the standard deviation of Gaussian distribution.The average and maximum errors of the grinding force model are 4.9%and 14.6%respectively,indicating that the model is of high predication accuracy.
基金National Natural Science Foundation of China(U1804124)Key Scientific and Technological Project of Henan Province(202102210014)。
文摘The TZM alloys with different contents of ZrO_(2)were prepared by powder metallurgy and rolling,and the grain size,hardness,and abrasive wear resistance of TZM alloy were studied.The abrasive wear test of TZM alloy was conducted under the conditions of 10,15,and 20 N and abrasive particle sizes of 7,11,18,and 38μm.The results show that the added ZrO_(2)particles in TZM alloy are mainly distributed at the grain boundaries.The grains of TZM alloy containing 1.5wt%ZrO_(2)are significantly refined,and the hardness is increased by 16%.The wear test results show that TZM alloy containing 1.5wt%ZrO_(2)has the lowest mass loss rate and excellent wear resistance under all loads and abrasive sizes,and the wear performance is improved by 12%.The ZrO_(2)with high hardness becomes the main bearer of the load,and as the second-phase,it hinders the abrasive particles from entering the matrix and effectively resists the scratch of the abrasive particles,which is the main reason for the excellent wear resistance.
文摘As a non-contact ultra-precision machining method,abrasive water jet polishing(AWJP)has signi-ficant application in optical elements processing due to its stable tool influence function(TIF),no subsurface damage and strong adaptability to workpiece shapes.In this study,the effects of jet pressure,nozzle diameter and impinging angle on the distribution of pressure,velocity and wall shear stress in the polishing flow field were systematically analyzed by computational fluid dynamics(CFD)simulation.Based on the Box-Behnken experimental design,a response surface regression model was constructed to investigate the influence mech-anism of process parameters on material removal rate(MRR)and surface roughness(Ra)of fused silica.And experimental results showed that increasing jet pressure and nozzle diameter significantly improved MRR,consistent with shear stress distribution revealed by CFD simulations.However,increasing jet pressure and impinging angle caused higher Ra values,which was unfavorable for surface quality improvement.Genetic algorithm(GA)was used for multi-objective optimization to establish Pareto solutions,achieving concurrent optimization of polishing efficiency and surface quality.A parameter combination of 2 MPa jet pressure,0.3 mm nozzle diameter,and 30°impinging angle achieved MRR of 169.05μm^(3)/s and Ra of 0.50 nm.Exper-imental verification showed prediction errors of 4.4%(MRR)and 3.8%(Ra),confirming the model’s reliabil-ity.This parameter optimization system provides theoretical basis and technical support for ultra-precision polishing of complex curved optical components.
基金Supported by National Natural Science Foundation of China(Grant No.52175401)Hunan Provincial Postgraduate Scientific Research Innovation Project(Grant No.QL20230244)+1 种基金Enterprise Innovation and Development Joint Program of National Natural Science Foundation of China(Grant No.U20B2032)Hunan Provincial Science and Technology Innovation Program(Grant No.2022RC1050).
文摘Because the grinding temperature is high when grinding using conventional disordered grinding wheels,the grinding quality improvement is limited when using single abrasive ordered grinding wheels,and the wheel preparation process is complex and costly when using microstructured grinding wheels,abrasive groups ordered grinding wheels are widely investigated.However,there is a paucity of systematic analyses and comprehensive reviews focused on abrasive groups ordered grinding wheels.Therefore,this paper defines abrasive groups ordered grinding wheels and classifies them,based on their unique characteristics,into groups such as abrasive blocks ordered grinding wheel,fine grain structured grinding wheel,abrasive clusters ordered grinding wheel,and abrasive fibers ordered grinding wheel.We provide an overview of the latest advances in wheel structures,preparation methods,and abrasive selection for various types of abrasive groups ordered grinding wheels.Furthermore,we conduct a comparative analysis of the existing types,significant advantages,and challenges associated with the four types of abrasive groups ordered grinding wheels.Looking ahead,given the potential of abrasive groups ordered grinding wheels in reducing grinding force and temperature,we recommend further exploration of their application in combination with special processing techniques.This could pave the way for the development of machining processes that are more environmentally friendly,energy-efficient,and precise.
基金supported by the Korea Agency for Infrastructure Technology Advancement(KAIA)grant funded by the Ministry of Land,Infrastructure and Transport(Grant No.RS-2023-00245334)。
文摘The use of abrasive waterjets(AWJs)for rock drilling offers advantages in urbanized areas,locations that are vulnerable to damage,and piling operations.However,the overall operational cost of AWJ systems remains high compared to that of conventional drilling methods,which constrains the long-term industrial application of AWJs.For instance,the abrasive costs account for over 60%of the total process cost,but the recycling of abrasives remaining after drilling could significantly reduce machining costs.In this study,the post-impact characteristics of abrasives were explored,aiming to enhance their recyclability.The physical properties and particle distribution of used abrasives vary depending on the jet energy,ultimately affecting their recyclability and recycling rate.The particle properties of used abrasives(particle size distribution,particle shape,and mean particle size)were compared under different waterjet energy variables(standoff distance(SOD)and water pressure)and test conditions(dry and underwater).Furthermore,the collision stages of the abrasive particles within a waterjet system were classified and analyzed.The results revealed that abrasive fragmentation predominantly occurred due to internal collisions within the mixing chamber.In addition,an attempt was made to optimize the waterjet parameters for an economical and efficient operation.The findings of this study could contribute to enhancing the cost-effectiveness of AWJ systems for rock drilling applications.
基金financial support to the Application Foundation Frontier Project of the Major Program(JD)of Hubei Province(2023BAA019-4)the National Natural Science Foundation of China(U20A20279,12072245,52071238)+2 种基金the Science and Technology Program of Guangxi Province(AA22068080)the Key Research and Development Program of Hubei Province(2021BAA057)the Taishan Industry-Leading Talent Project Special Funding and Subject Innovation and Talent Introduction Program in Colleges and Universities(111 programs No.D18018)。
文摘Medium-manganese steel exhibits excellent strength and toughness,which are essential features in wear resistance applications.This study examines the impact of annealing temperature on impact abrasive wear.The results have indicated that samples annealed at different temperatures display plowing and fatigue wear effects.In the initial wear stage,the hightemperature annealed steel outperforms samples annealed at a lower temperature in terms of anti-plowing wear performance.This phenomenon is mainly due to the lower initial hardness of the samples subjected to low-temperature annealing.However,with prolonged wear time,the low-temperature annealed samples exhibit improved plowing wear performance,which is ascribed to a refinement of the lamellar microstructure and an increased residual austenite(RA),which enhances the work hardening effect,improving the hardness of the worn surface.The low-temperature annealed samples consistently delivered superior fatigue wear performance when compared with samples annealed at the higher temperature.The latter effect may be attributed to two factors.Firstly,the finer lamellar microstructure in the low-temperature annealed samples,coupled with greater RA,results in transformation-induced plasticity or twin-induced plasticity effect that hinders crack formation and propagation.Secondly,the low-temperature annealed samples form nanoscale equiaxed grains near the worn surface during the wear process.These grains can withstand crack driving forces in fine-grained regions,suppressing the formation and propagation of cracks.
基金Supported by Jiangsu Provincial Natural Science Foundation(Grant No.BK20231497)Jiangsu Provincial Post Graduate Research&Practice Innovation Program(Grant No.KYCX25_2982)+2 种基金China University of Mining and Technology Graduate Innovation Program(Grant No.2025WLKXJ094)National Natural Science Foundation of China(Grant No.51975573),National Key R&D Program of China(Grant No.2022YFC2905600)Priority Academic Program Development of Jiangsu Higher Education Institute of China.
文摘During the excavation process of deep hard rock tunnels,precutting rock with an abrasive water jet can weaken their strength and improve the efficiency of mining machinery.However,owing to the complex geological environment,abrasive jets cannot fully utilize their rock-cutting performance.To fully exploit the advantages of high-pressure abrasive water jets,five orthogonal experiments were designed for rocks with significant differences in strength.Experimental research has been conducted on the performance of rotating abrasive waterjet-cutting rocks.Moreover,a neural network prediction model for predicting rock-cutting characteristics is established by comprehensively considering rock mechanics parameters and abrasive water jet parameters.The results show that the cutting depth of rocks with different strengths increases nonlinearly with increasing work pressure of the abrasive water jet.The cutting depth decreases exponentially with increasing cutting velocity.The cutting depth first increases and then decreases with increasing target distance,and the best target distance is between 4 mm and 6 mm.The effect of the target distance on the cutting width of rock is the most significant,but the cutting width of high-strength rock is not sensitive to changes in the working parameters of the abrasive water jet.The average relative errors of BP(backpropagation)neural networks optimized by global optimization algorithms in predicting rock cutting depth and width are 13.3%and 5.4%,respectively.This research combines the working characteristics of mining machinery to study the performance of abrasive waterjet rotary cutting of rocks and constructs a predictive model for the performance of abrasive waterjet cutting of rocks that includes rock strength factors.This provides a new solution for quickly adjusting the working parameters of abrasive water jets according to mining conditions.
基金supported by the National Natural Science Foundation of China(No.U1737201)。
文摘Manufacturing micro-holes in non-conductive ceramics presents significant challenges in precision machining,particularly due to the absence of central abrasive grains in micro-grinding wheels.This study investigates helical grinding under conditions where the central abrasive grain is absent,focusing on the formation of undeformed chips.It was observed that nearly all microgrinding wheels,regardless of their manufacturing process or grain size,exhibit a central grain absence,with larger grain sizes leading to more extensive absence areas.Analysis revealed that residual patterns at the bottom of machined holes depend on the ratio of the absence zone diameter to the wheel's eccentricity.Analytical models were developed to describe the heights of cylindrical and disc-shaped residues,which were subsequently validated through kinematic simulations.The removal mechanisms for these residues differ;cylindrical residues,which cannot be removed by grinding,cause interference and should be avoided,while disc-shaped residues removal depends on the protrusion height of the first grain,influencing contact with the wheel's end face and subsequent grinding actions.Experimental validation using SiC_(p)/Al demonstrated that cylindrical residues create distinct ring-shaped wear marks,significantly increasing cutting forces,whereas discshaped residues result in hat-shaped wear marks and higher cutting forces when the first grain's protrusion is insufficient.Additionally,inadequate lubrication and chip removal can lead to chip adhesion starting from the absence zone.These findings enhance the theoretical framework of helical grinding/milling and provide valuable insights for precision machining of micro-holes in nonconductive ceramics.
基金supported by the National Natural Science Foundation of China(grant number:52006061)the Key R&D Program of Hunan Province(grant number:2024AQ2001)+2 种基金Scientific Research Program of Hunan Provincial Department of Education(grant number:22B0840)Natural Science Foundation of Hunan Province(grant number:2023JJ50483)Hunan University of Humanities,Science and Technology Graduate Student Research and Innovation Program(ZSCX2024Y06,ZSCX2024Y01).
文摘To address the challenges of poor surface quality and high energy consumption in marble cutting,this study introduces an auxiliary abrasive jet cutting technology enhanced by the use of polyacrylamide(PAM)as a dragreducing additive.The effects of feed rate(50-300 mm/min),polymer concentration(0-0.5 g/L),and nozzle spacing(4-12 mm)on kerf width and surface roughness are systematically investigated through an orthogonal experimental design.Results reveal that feed rate emerges as themost significant factor(p<0.01),followed by PAM concentration and nozzle spacing.The optimal set of parameters,comprising a 200 mm/min feed rate,0.3 g/L PAM concentration,and 6mmnozzle spacing,achieves the narrowest kerf width(0.867 mm)and the lowest surface roughness(10.220μm).Analysis of the underlying mechanisms demonstrates that PAMenhances the energy efficiency of the jet by suppressing turbulent pulsations and increasing fluid viscoelasticity,thereby minimizing energy loss during the cutting process.
基金financially supported by the Scientific Research Project Coordinatorship (BAP) of Yildiz Technical University (YTU) (Project No: FYL-2021-3825)。
文摘Aluminum alloys are widely used in industry due to their light weight.These alloys are generally exposed to abrasive wear,which diminishes their effective lifespan.The wear resistance of these alloys is enhanced by adding various reinforcements,however,this enhancement comes at the cost of reduced fracture toughness.This paradox of increased wear resistance versus decreased fracture toughness in aluminum alloys can be resolved by using functionally graded materials (FGMs).This study focuses on the abrasive wear behavior of functional graded aluminum matrix composites reinforced with Al_(3)Ti particles.The wear properties of the composites were investigated by considering the characteristics of the composite such as matrix type and various composite zones,as well as the wear parameters such as abrasive particle diameter,load,sliding speed and distance.Taguchi method was used in the abrasive wear tests in order to get more reliable results in a timeefficient manner.Experiment recipes were created based on the L_(27)(3^(6)) orthogonal series.As a result of the study,it is observed that the wear resistance of the composites increases with an increase in Al_(3)Ti reinforcement content and hardness of the matrix.In addition,the size of abrasive particles and the applied load are significant factors affecting abrasive wear.
基金financially supported by the National Key Research and Development Project,China(Nos.2018YFA0703300,2022YFB4600019)the National Natural Science Foundation of China(Nos.52275148,52405154)+2 种基金the Innovation Program Phase II of AECC Commercial Aircraft Engine Co.Ltd,China(No.HT-3RJC1053-2020)support by the Postdoctoral Fellowship Program of CPSF,China(No.GZB20240219)the Shanghai Sailing Program,China(No.24YF2708100).
文摘Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.
基金funded by the National Natural Science Foundation of China(No.52374018)Science Foundation of China University of Petroleum,Beijing(No.2462021YJRC009)。
文摘Radial jet drilling(RJD)technology is expected to be a technology for the efficient exploitation of geothermal resources.However,the low rock-breaking efficiency is the major obstacle hindering the development of RJD technology.The flow field characteristics and rock breaking ability of cone-straight abrasive jet,rotary abrasive jet,and straight-rotating mixed abrasive jet are analyzed by numerical simulations and experiments.Results show that the axial velocity of the cone-straight abrasive jet is high,the tangential velocity is basically zero,the radial velocity is also small,and the jet impact area is concentrated in the center.A deep hole with a diameter of only 25 mm is formed when the cone-straight abrasive jet breaks the granite.Due to the presence of the guiding impeller,the rotary abrasive jet basically has no axial velocity and has the highest tangential and radial velocity,so it can break the granite to form a hole with a diameter of about 55 mm and a central bulge.The straight-rotating mixed abrasive jet has a large axial/tangential/radial velocity at the same time,so it can break the granite to form a hole with a diameter of about 52 mm with a low bulge.The results show that the straight-rotating mixed abrasive jet combines the advantages of the cone-straight jet and the rotary jet,and is more suitable for the RJD technology.The research results can provide reference for the development of efficient rock-breaking and hole-forming technology,and promote the development of RJD technology in the field of geothermal development.
基金supported by the Undergraduate Training Programs for Innovations by NEFU(grant number 202410225370)funded by Large-Scale Instrument and Equipment Sharing Service Platform of College of Chemistry,Chemical Engineering and Resource Utilization,NEFU.
文摘Epoxy resins are extensively employed in the construction,electronics,automotive,and aerospace industries owing to their outstandingmechanical strength,chemical resistance,and electrical insulation.However,their intrinsic flammability,poor wear resistance,and hydrophilicity significantly restrict broader applications.To address these challenges,a novel multifunctional coating(CEOS-DOPO-PDMS)has been designed and fabricated via an NPGLIDE approach.The system integrates 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)as a reactive phosphorus-based flame retardant,epoxy-terminated polydimethylsiloxane(EP-PDMS)as a hydrophobic segment,and cycloaliphatic epoxy-functionalized oligosiloxanes(CEOS)as a cross-linking co-reactant.The resulting CEOSDOPO-PDMS hybrid precursor was blended with bisphenol A diglycidyl ether(DGEBA)in N-methyl-2-pyrrolidone(NMP)and subsequently cured to form epoxy-based NP-GLIDE coatings.The optimized coating exhibits superior integrated performance,including high hydrophobicity(water contact angle up to 109.6°),outstanding abrasion resistance(5H pencil hardness),and excellent flame retardancy(resisting combustion at 500℃ for 30 s).These enhancements originate from the cooperative effects of the Si-O-Si framework,low-surface-energy PDMS chains,and phosphorus-containing DOPOmoieties,which together provide stable thermal protection,surface roughness-induced hydrophobicity,and durable mechanical integrity.An effective strategy for constructing multifunctional epoxy-based coatingswith simultaneously enhanced flame retardancy,wear resistance,andwater repellency is presented.The CEOSDOPO-PDMS system holds great promise for advanced protective applications in construction,transportation,and aerospace engineering.
基金National Basic Research Program of China (2009CB724403)Program for Changjiang Scholars and Innovative Research Team in University (IRT0837)Program for New Century Excellent Talents in University from Ministry of Education of China (NCET-07-0435)
文摘The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters （i.e. wheel speed, workpiece speed and depth of cut） on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride （CBN） abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardhess and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 ℃ is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm^3. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the bum-free and crack-free ground surface.
基金supported by Shandong Provincial Natural Science Foundation of China (Grant No. Y2007A07)
文摘In dealing with abrasive waterjet machining（AWJM） simulation,most literatures apply finite element method（FEM） to build pure waterjet models or single abrasive particle erosion models.To overcome the mesh distortion caused by large deformation using FEM and to consider the effects of both water and abrasive,the smoothed particle hydrodynamics（SPH） coupled FEM modeling for AWJM simulation is presented,in which the abrasive waterjet is modeled by SPH particles and the target material is modeled by FEM.The two parts interact through contact algorithm.Utilizing this model,abrasive waterjet with high velocity penetrating the target materials is simulated and the mechanism of erosion is depicted.The relationships between the depth of penetration and jet parameters,including water pressure and traverse speed,etc,are analyzed based on the simulation.The simulation results agree well with the existed experimental data.The mixing multi-materials SPH particles,which contain abrasive and water,are adopted by means of the randomized algorithm and material model for the abrasive is presented.The study will not only provide a new powerful tool for the simulation of abrasive waterjet machining,but also be beneficial to understand its cutting mechanism and optimize the operating parameters.
基金Item Sponsored by National Basic Research Program of China(2010CB630801)
文摘The effect of processing parameters such as hot rolling and heat treatment on microstructure and mechanical properties was investigated for a new 0.27mass% C and Ni, Mo-free low alloy martensitic abrasion resistant steel. The three-body impact abrasive wear behavior was also analyzed. The results showed that two-step controlled rolling besides quenching at 880 ℃ and tempering at 170 ℃ could result in optimal mechanical property., the Brinell hardness, tensile strength, elongation and --40 ℃ impact toughness were 531, 1530 MPa, 11.8% and 58 J, re- spectively. The microstructure was of fine lath martensite with little retained austenite. Three-body impact abrasive wear results showed that wear mechanism was mainly of plastic deformation fatigue when the impact energy was 2 J, and the relative wear resistance was 1.04 times higher than that of the same grade compared steel under the same working condition. The optimal hardness and toughness match was the main reason of higher wear resistance.
基金National Natural Science Foundation of China （Grant No.50675087, 50275037） National Science Fund for Distinguished Young Scholars of China （Grant No. 50025516） ＂Project 985＂ of Jilin University.
文摘The Pangolin, a soil-burrowing animal, is covered with scales. These scales are often abraded by soil and rock and their surface is corrugated. The abrasive wear of the surface of the scales was examined. The scales were taken from a pangolin that had died of natural causes. The tests were run on a rotary disc abrasive wear tester. The abrasive material was quartz sand （96.5 wt.%） and bentonite （3.5 wt.%）. The morphology of the abraded surfaces and the abrasion were examined by stereoscopic microscopy and scanning electron microscopy. The concepts are proposed of ＂Guiding-Effect＂ and ＂Rolling-Effect＂ on the textured surfaces under free abrasive wear conditions and the critical dimensions of the ＂Rolling-Effect＂ are discussed.
