Solution model of nonlinear integral adjustment including different kinds of observing data with different precisions

1　INTRODUCTIONInthedataprocessoftheconstructionofdigitalcityanddigitalnationandthemoderndeformationmonitoring ,manykindsofmeasurementswithdifferentprecisionscontaininggeometricandphysicaldataarecaptured .Thedistribu tiontypesofthesedatacanbedividedintothenormaldistribution ,theLaplace’sdistribution ,thenormalmixeddistribu tionandsoon .Meantimetherelationsbetweentheseobservingdataandtheunknownparametersarenonlinearinmostofthecases .Sofardifferentkindsofobservingdatawithdifferentprecision…     

Welding characteristics in different laser-TIG hybrid manners

An experiment for determining the laser-TIG hybrid welding characteristics was carried oat in three kinds of hybrid methods: CO2 laser-TIG coaxial hybrid, CO2 laser-TIG paraxial hybrid and Nd: YAG laser-TIG paraxial hybrid. The experimental results indicate that hybrid welding has two welding mechanisms in CO2 laser-TIG hybrid welding: deep penetration welding and heat conduction welding. As the effect of the laser-induced keyhole, the arc root is condensed, the current density and penetration depth increase significantly, the welding characteristic is apt to deep penetration welding.When current increases to some degree, the keyhole induced by laser disappears, which produces a shallow penetration and wide bead. The weld exhibits heat conduction welding characteristics. Furthermore, the arc images and weld bead crosssections of three kinds of hybrid manners were also compared and analyzed at different welding currents, which established the foundation for understanding the welding characteristics of laser-TIG hybrid welding comprehensively.     

Failure modes of PDC cutters under different loads

The capability of several types of flat PDC cutters to withstand combined loads were tested and evaluated by the impact and cutting of single PDC cutter on granite in a linear impact-cutting table.The primary failure modes of PDC cutters withstanding different combined loads were investigated and analyzed.The suggestions of enhancing PDC cutters to be suitable for drilling very hard rock have been made.     

Electro-oxidation behavior of tungsten carbide electrode in different electrolytes

The electrochemical activity and stability of tungsten carbide gas diffusion electrode in different electrolytes were determined by galvanostatic charge method. It is shown that WC exhibits good electrocatalytic activity and stability for hydrogen oxidation in acidic solutions when the electrode potential is below about 800 mV (vs DHE), WC is firstly oxidized to an unstable blue tungsten oxides at 800-900mV which are closed to a composite stoichiometry of W2O5 in H2 SO4 solution and W8O23 in HCl solution calculated by charge consumed. Furthermore,the generated intermediate tungsten oxides can be further oxidized into WO3 at higher potentials. While in alkali solution, WC can not be used as anodic catalyst for its poor stability and catalytic activity due to the fact that WC will be directly oxidized into WO3.     

High-temperature wear behaviors of MoSi2 under different loads

MoSi2 was prepared by SHS, pressed at room-temperature and then vacuum sintered at 1 500 ℃ for 1 h. The tribological properties of MoSi2 against Al2O3 were investigated by using an XP-5 type High Temperature Friction and Wear Tester. Micrographs and phases of the worn surface of MoSi2 were observed by SEM with EDS and X-ray diffraction. The results show that the wearing process of MoSi2 at high temperature exists three stages： running-in, interim and steady periods. MoSi2 exhibits preferable wear resistance when the load is lower than 50 N. Adhesion and oxidation wear exists widely at elevated temperature; however besides these, with increasing the load, the main wear mechanisms of MoSi2 could be changed from adhesion, plastic forming to fatigue fracture in turn.     

Comparisons between different models for thermal simulation of GTAW process

0IntroductionIn arc welding processes,final microstructure andmechanical properties of the weldments mainly depend onthe thermal cycle undergoing during the heating and cool-ing process.The accurate analysis of the welding thermalprocess is the foundation…     

Chemical behaviors of different arsenic-bearing sulphides bio-oxidated by thermophilic bacteria

1INTRODUCTION Arsenic bearinggoldoreiswidelydistributedinprovincesofYunnan,Guizhou,Sichuan,Guan gxi,Guangdong,Hunan,Jiangxi,Liaoning,Jilin,Hebei,Shanxi,Gansu,Qinghai,Xinjiang,etc.Withtheprocessdevelopmentofbacteriummetal lurgy[1,2],suchgoldoreresourcemaybereasona blyutilized,however,arsenicintheseoresishigh lytoxictotheleachingbacteriaandbecomesthe researchfocus.Arsenicisacomplexandvitalele mentofarsenic bearingmineralswiththeelectronconfigurationof4s34p3[3].WhenAslosesthree electro…     

Effect of different incidence angles on bonding performance in cold spraying

The deformation behaviour of spray particles impacting upon a substrate under the oblique impact condition in cold spraying was investigated using finite element analysis(FEA)method.The effect of incidence angle of particle on the deformation of particle and substrate was examined.It is found that the contact area between the deformed particle and substrate decreases and the crater depth in the substrate reduces with increasing the tilting angle at the same impact velocity.The normal component of impact velocity takes an important role in the impacting process and formation of bonding.     

Effect of strain rate on solidification crack susceptibility of different metals

In this paper,a slow bending speed varestraint test method with con-tinuously adjustable deformation rate for testing hot cracking sensitivity is de-veloped and its working principle is described.From great amounts of tests,itis known that strain rate affects the sensitivity of solidification crack because ofits influnce on material ductility in BTR directly.The smaller the strain rate,the better the ductility and the lower the solidification crack sensitivity.The ex-tent of this effect varies with different materials,for LF-6 aluminum alloy,it isgreat,but for 16Mn,19Mn5 and 20G steels,it is small.Through systematicinvestigation,it is concluded that strain rate of a metal during welding can belowered and the resistance to solidification crack can be enhanced by reducingstructrual restraint and by adjustment of welding parameters.     

Mechanical properties of WC–Co coatings with different decarburization levels

In this study, two kinds of WC–Co coatings with different decarburization levels were deposited by high-velocity oxy-fuel(HVOF) spraying using the ultrafine WC–Co composite powder and commercial micronsized powder, respectively. The hardness and elastic modulus were measured on the top surface and cross sections of the prepared coatings by the nanoindentation method. The results show that the ultrafine-structured coating has much higher density and inhibited decarburization than the conventional coating, which thus results in higher hardness and elastic modulus values than the micronsized coating. The wear resistance of thermal-sprayed cermet coatings greatly depends on the cross-sectional hardness and elastic modulus which reflects the bond strength between splats to some extent. Based on the analysis, a better understanding of the microstructure and properties in cermet coating materials was obtained.     

Tribological properties of nickel-graphite composite against different counterfaces at elevated temperatures

Nickel-based graphite-containing composites were prepared by powder metallurgy method. The effect of graphite addition on mechanical properties of nickel-based alloy was investigated and the tribological properties from room temperature to 600 ℃ were tested by a pin-on-disk tribometer with alumina, silicon nitride and nickel-based alloy as counterfaces. The microstructure was analyzed by X-ray diffraction（XRD） and scanning electron microscope （SEM） attached with energy dispersive spectroscopy（EDS）. The worn surfaces at high temperature were observed by optical microscope and SEM. The results show that the tensile strength and hardness of composites decrease after adding graphite, while the friction and wear properties are all improved by adding 12%（mass fraction） graphite. Compared with the counterface of alumina and silicon nitride, the friction coefficients and wear rates are lower when the composite rubs against nickel-based alloy containing molybdenum disulfide.     

Properties of Fe-Mn-Al alloys with different Mn contents using density functional theory

The chemical stability,electronic structures,mechanical properties and Debye temperature of Fe-MnAl alloys were investigated using first-principles calculations.The formation enthalpy and cohesive energy are negative for Fe-Mn-Al alloys,showing that they are thermodynamically stable.FeAl has the lowest formation enthalpy,indicating that FeAl is the most stable alloy in the Fe-Mn-Al system.The partial density of states,total density of states and electron density distribution maps were used to an...     

Warm compaction behaviors of iron-based powder lubricated by different kinds of graphite

1　INTRODUCTIONConventionalpowdermetallurgy(PM ) process ingcanproduceiron basedPM partswithadensitylessthan 7.1g/cm3(arelativedensityofapproxi mately 90 % ) .Theirmechanicalpropertiesaresub stantiallylessthanthoseoftheirfulldensitycounter part.IncreasingdensityisthebestwaytoincreasetheperformanceofthePM parts .Therearemanyprocessesthatcanproduceiron basedPM partswithhighdensitysuchaspowderforging ,doublepress/doublesinter(DP/DS)andCuinfiltration ,butwarmcompactionisthemosteconomical…     

Hydrogen absorption of slurry system composed of different MgNi alloy and benzene

The hydrogen absorption amount and kinetics of the slurry formed by suspending the MgNi alloy powder in liquid benzene were studied.It is discovered that hydrogen is absorbed by both the solid phase(alloy) and liquid phase(C6H6)and the hydrogen absorption rate varies with the temperature and the content of the Mg-Ni in the slurry.Most hydrogen absorption curves of the slurry fall into two regions.in which the mechanism of hydriding reaction in the slurry system is different.In the former region,the hydriding of the alloy proceeds with hydrogen diffusing through C6H6.The part in the second region is the outcome of the hydrogenation of C6H6.At 548K and under the hydrogen pressure of 4.5MPa saturation capacity for the slurry of 80% C6H69mass fraction) 20%Mg Ni(mass fraction)is 5.9%(mass fraction)hydrogen,which is 97% of the theoretic capacity of the slurry system. The hydride of the alloy MgNi,which is only the hydride of Mg2 Ni phase,Mg2NiH4,is an efficent catalyst for the hydrogenation of C6H6into C6H12(C6H6 3H2→C6H12)in the slurry system.     

Succession law of Nd–Fe–B alloys with different coercivities

In order to establish a succession law of every phase in sintered Nd–Fe–B magnets marked as 38/38H/38SH/38 UH, four alloys of Nd33-xDyxAl0.7Nb0.6Cu0.1B1.05 Fe bal.(at%) were investigated after smelting processing, sintering processing, high-temperature tempering processing, and highand low-temperature tempering processing. It is found that the four phases: the Nd2Fe14B matrix phase, Nd-rich phase,B-rich phase, and defect phase can be inherited by means of the subsequent processing. These phases might have the special constitution and appearance in the different states.Magnetic properties also have succession law. In every processing except smelting one, the values of remanence and maximum energy product hardly alter, but the value of coercive force increases gradually.     

Effects of different tempers on precipitation hardening of 6000 series aluminium alloys

By means of Vickers hardness,mechanical property and formability tests,the effects of different tempers on precipitation hardening of 6000 series aluminium alloys for automotive body sheets were investigated.The results indicate that the short-time pre-aging at 170℃makes for subsequent artificial aging precipitation hardening.With the increase of pre-aging time,the artificial aging hardenability increases.The aging hardening rate reaches the maximum when pre-aging time is up to 10 min,and then it decreases.The short-time pre-aging at 170℃benefits sheets to obtain lower strength under delivery condition and consequently to improve stamping formability of automotive body sheets.The effects of different tempers on precipitation hardening are much more obvious than those of the alloying elements.It is a good treatment schedule to perform pre-aging for 5 min at 170℃right after solution treatment.     

Deformation behavior ofAZ31 magnesium alloy at different strain rates and temperatures

The deformation behavior of AZ31 was examined by compression and tension testes over a wide strain rate and temperature range, strain rate from 10^-3 to 10^3 s^-1, temperature from 300 to 623 K. Analysis of flow behavior and microstructural observations indicate that in tension tests dislocation glide is the most important deformation mechanism in the test strain rate and temperature range, while in compression tests twinning deformation mechanism is important at lower temperature when the strain rate ranges from 10^-3 to 10 s^-1. At 10^3 s^-1 strain rate, dislocation glide and twinning are present at the same time. At the strain rate of 2 964 s^-1, adiabatic shear band can be found easily, even at the strain rate of 1 537 s^-1 adiabatic shear localization zone can be found. In adiabatic shear localization zone, there are fine recrystallization grains. But in adiabatic shear band, the grains cannot be identified by optical microscopy.