Computer vision-aided DEM study on the compaction characteristics of graded subgrade filler considering realistic coarse particle shapes

The compaction quality of subgrade filler strongly affects subgrade settlement.The main objective of this research is to analyze the macro-and micro-mechanical compaction characteristics of subgrade filler based on the real shape of coarse particles.First,an improved Viola-Jones algorithm is employed to establish a digitalized 2D particle database for coarse particle shape evaluation and discrete modeling purposes of subgrade filler.Shape indexes of 2D subgrade filler are then computed and statistically analyzed.Finally,numerical simulations are performed to quantitatively investigate the effects of the aspect ratio(AR)and interparticle friction coefficient(μ)on the macro-and micro-mechanical compaction characteristics of subgrade filler based on the discrete element method(DEM).The results show that with the increasing AR,the coarse particles are narrower,leading to the increasing movement of fine particles during compaction,which indicates that it is difficult for slender coarse particles to inhibit the migration of fine particles.Moreover,the average displacement of particles is strongly influenced by the AR,indicating that their occlusion under power relies on particle shapes.The dis-placement and velocity of fine particles are much greater than those of the coarse particles,which shows that compaction is primarily a migration of fine particles.Under the cyclic load,the interparticle friction coefficientμhas little effect on the internal structure of the sample;under the quasi-static loads,however,the increase inμwill lead to a significant increase in the porosity of the sample.This study could not only provide a novel approach to investigate the compaction mechanism but also establish a new theoretical basis for the evaluation of intelligent subgrade compaction.

Effect of brazing temperature on microstructure and tensile strength ofγ-TiAl joint vacuum brazed with micro-nano Ti−Cu−Ni−Nb−Al−Hf filler

A novel micro-nano Ti−10Cu−10Ni−8Al−8Nb−4Zr−1.5Hf filler was used to vacuum braze Ti−47Al−2Nb−2Cr−0.15B alloy at 1160−1220℃ for 30 min.The interfacial microstructure and formation mechanism of TiAl joints and the relationships among brazing temperature,interfacial microstructure and joint strength were emphatically investigated.Results show that the TiAl joints brazed at 1160 and 1180℃ possess three interfacial layers and mainly consist of α_(2)-Ti_(3)Al,τ_(3)-Al_(3)NiTi_(2) and Ti_(2)Ni,but the brazing seams are no longer layered and Ti_(2)Ni is completely replaced by the uniformly distributed τ_(3)-Al_(3)NiTi_(2) at 1200 and 1220℃ due to the destruction of α_(2)-Ti_(3)Al barrier layer.This transformation at 1200℃ obviously improves the tensile strength of the joint and obtains a maximum of 343 MPa.Notably,the outward diffusion of Al atoms from the dissolution of TiAl substrate dominates the microstructure evolution and tensile strength of the TiAl joint at different brazing temperatures.

Influence of filler characteristics on particle removal in fluid catalytic cracking slurry under an alternating electric field

The characteristics of the packing material under an alternating electric field are an important factor in the removal of FCCS particles.In this study,the electric field distribution of a separation unit consisting of packed spheres under an alternating electric field is simulated,and the movement mechanism of catalyst particles is analysed.An"effective contact point"model is derived to predict the adsorption of filler contact points on catalyst particles under the alternating electric field,and the model is validated by simulations and experiments.The numerical calculation and experimental results indicate that the electrical properties of the filler spheres,the filler angleθ,and the frequency f of the alternating electric field affect the adsorption of catalyst particles.As the frequency of the electric field increases,the particle removal efficiency of the high-conductivity filler(silicon carbide)increases and then settles,and the separation efficiency of the low-conductivity filler(glass,zirconia)is not sensitive to the change in electric field frequency.

Basic Characteristics of an Appropriate Waste Fillers for Solvent Free and Water-Borne Industrial Polymer Floors and Their Utilization

Recently the manufacture of epoxy coating and flooring materials begun to be under strong pressure to use more environmentally friendly raw materials in its composition.First tendency to reduce of solvents and diluents contained in the materials appeared at the end of 90´s.This situation was supported by the Council of Europe in 2004 to reduce VOC emissions to zero till 2020.Solvent materials were thus largely replaced by solvent free materials from which the volatile substances are not released into the air.But pressure continued to increase,and over the past decade began to take centre stage water-based epoxy.On the Czech market solvent based material is still occasionally used,but predominant are solvent free materials.There are no commonly used materials containing wastes as fillers in new water-borne and solvent-free epoxy materials.Characteristics identification of the waste material as a potential filler is a set of properties that determine the limits of secondary raw materials or waste as a filler.This paper describes the basic characteristics which must be selected to meet the requirements,to affect negatively the workability,sedimentation,properties and behavior of the final floor system.Some materials must comply with special requirements,such as resistance to chemicals,etc.Next part of paper talks about utilization of polymer floors and their mechanical properties.

Development of Al-12Si-xTi system active ternary filler metals for Al metal matrix composites

To improve the wettability of Al metal matrix composites（Al-MMCs） by common filler metals,Al-12Si-xTi（x=0.1,0.5,1,3.0;mass fraction,%） system active ternary filler metals were prepared.It was demonstrated that although the added Ti existed within Ti（Al1-xSix）3（0≤x≤0.15） phase,the shear strength and shear fracture surface of the developed Al-12Si-xTi brazes were quite similar to those of traditional Al-12Si braze due to the presence of similar microstructure of Al-Si eutectic microstructure with large volume fraction.So,small Ti addition（～1%） did not make the active brazes brittle and hard compared with the conventional Al-12Si braze.The measured melting range of each Al-12Si-xTi foil was very similar,i.e.,580-590 ℃,because the composition was close to that of eutectic.For wettability improvement,with increasing Ti content,the interfacial gap between the Al2O3 reinforcement and filler metal（R/M） could be eliminated,and the amount of the remainder of the active fillers on the composite substrate decreased after sessile drop test at 610 ℃ for 30 min.So,the wettability improvement became easy to observe repeatedly with increasing Ti content.Additionally,the amount and size of Ti（AlSi）3 phase were sensitive to the Ti content（before brazing） and Si content（after brazing）.

Microstructure and properties of Cu/Al joints brazed with Zn-Al filler metals

The mechanical properties and microstructural distribution of the Cu/A1 brazing joints formed by torch-brazing with different Zn-A1 filler metals were investigated. The microstructure of the Zn-A1 alloys was studied by optical microscopy and scanning electron microscopy, and the phase constitution of the Cu/A1 joints was analyzed by energy dispersion spectrometry. The results show that the spreading area of the Zn-A1 filler metals on the Cu and A1 substrates increases as the A1 content increases. The mechanical results indicate that the shear strength reaches a peak value of 88 MPa when A1 and Cu are brazed with Zn-15AI filler metal. Microhardness levels from HV122 to HV515 were produced in the three brazing seam regions corresponding to various microstructure features. The Zn- and Al-rich phases exist in the middle brazing seam regions. However, two interface layers, CuZn3 and A12Cu are formed on the Cu side when the A1 content in the filler metals is 2% and more than 15%, respectively. The relationship between intermetallic compounds on Cu side and Zn-xA1 filler metals was investigated.

Characterization on Surface and Interfacial Properties of Nitramine Crystal Fillers and Polymeric Bonding Agents

The surface and interfacial properties of polymeric bonding agents and nitramine crystal fillers were studied. The surface free energy and adhesion work of polymeric bonding agents and nitramine fillers were calculated by using Kaeble′s equations. It was observed that the hydroxyl values of neutral polymeric bonding agents (NPBA) correlate well with the polar components of surface free energies. On the basis of the measurements of swelling ratio and initial modulus, the interfacial bonding through highly crosslinked polymeric shell formation around the nitramine particles and generating interfacial reinforcement were rationalized. The application of Tapping Mode AFM (atomic force micro scope) to observing the surface morphology of NPBA reveals that methyl acrylate monomer appears to play a role for aiding the formation of network like structure when nanometer scale images of NPBA are created.

Effect of different fillers on oxidation behavior of low-temperature chromizing coating

Three different chromizing coatings were produced on Ni substrate using a conventional pack-cementation method with Al2O3,Al2O3＋CeO2 and CeO2 acting as filler,respectively,at a greatly decreased temperature（700 ℃）.Effects of different fillers on the isothermal and cyclic oxidation resistance of chromizing coating in air at 850 ℃ were comparably investigated.Microstructure results show that the addition of CeO2 into the filler significantly retards the grain growth of the chromizing coating.Oxidation results indicate that the chromizing coating using CeO2 as filler exhibits somewhat increased oxidation resistance than the normal chromizmg coating,while the chromizing coating using Al2O3＋CeO2 as filler exhibits much better oxidation resistance.The effects of different fillers on the oxidation behaviors were discussed in detail.

Effects of germanium additions on microstructures and properties of Al-Si filler metals for brazing aluminum

A series of Al?Si?Ge filler metals were studied for brazing aluminum. The microstructures and properties of the filler metals were investigated systematically. The results show that the liquidus temperature of Al?Si?Ge filler metals drops from 592 to 519 °C as the content of Ge increases from 0 to 30% (mass fraction). As the content of Ge increases, bright eutectic Ge forms. However, as the Ge content exceeds 20%, the aggregation growth of the eutectic structure tends to happen and coarsened primary Si?Ge particle forms, which is detrimental to the properties of alloys. The Al?10.8Si?10Ge filler metal has good processability and wettability with the base metal Al. When this filler metal is used to braze 1060 aluminum, the complete joint can be achieved. Furthermore, the shear strength test results show that the fracture of brazed joint with Al?10.8Si?10Ge filler metal occurs in the base metal.

基于Hole-Filler模型的XML流数据剪切分片技术

对基于Hole-Filler模型的XML流数据剪切分片问题,首先利用XML文档的Document Object Model(DOM)结构,根据节点扇出度提出了基于DOM的XML流数据剪切分片策略及其算法.然后,在此基础上,对标签结构进行剪切以确定文档的剪切点,提出了基于标签的XML流数据剪切分片算法,有效地减少了节点扇出度与阈值的比较次数.最后,提出了优化的剪切策略,根据阈值与节点扇出度的比值对XML子树加以整合,以减少碎片的产生.实验结果表明,XML剪切算法在剪切时间、分片粒度等方面都有较好的性能.

基于Hole-Filler模型的XML数据流上的SLCA算法

与传统数据库对XML数据的处理不同,对XML数据流的处理不仅受实时性的约束,还受存储空间的限制.在XML片段无序传送的广播模型中,考虑在XML数据流上进行高效的关键字查询,进而首次提出近似SLCA算法.SLCA算法利用结构Hash表和LCA表对关键字进行匹配并计算SLCA,从而避免冗余操作.同时,SLCA算法可以对匹配结果立即输出而不必等到数据流传输结束.实验结果表明,基于Hole-Filler模型的XML数据流上的SLCA算法在节省时间和空间开销方面均表现出较好的性能.

Effects of carbonaceous conductive fillers on electrical and thermal properties of asphalt-matrix conductive composites

The relationship between thermal/electrical conductivity enhancement in asphalt-matrix mixtures and the properties of filling conductive particles is studied. The thermal properties with filling the carbon fiber, graphite conductive particles in asphalt-matrix mixtures are investigated. Based on the generalized effective medium theory （ EMT ）, the effective thermal and electrical conductivity of carbon fiber/asphalt and graphite/asphalt composites are theoretically elucidated. The theoretical results are found to be in reasonably well agreement with the experimental data. Moreover, the theoretical and experimental results show that the large-aspect-ratio shape of particles can help to achieve a large enhancement of effective conductivity, and the use of disk-like high conductivity particles can limit the additive contents for preserving the volumetric properties and mechanical properties of asphalt composites. The generalized effective medium theory model can be used for predicting the thermal and electrical properties of asphaltmatrix composites, which is still available for most of the thermal/electrical modifications in two-phase composites.

Advancements and Challenges in Organic–Inorganic Composite Solid Electrolytes for All‑Solid‑State Lithium Batteries

To address the limitations of contemporary lithium-ion batteries,particularly their low energy density and safety concerns,all-solid-state lithium batteries equipped with solid-state electrolytes have been identified as an up-and-coming alternative.Among the various SEs,organic–inorganic composite solid electrolytes(OICSEs)that combine the advantages of both polymer and inorganic materials demonstrate promising potential for large-scale applications.However,OICSEs still face many challenges in practical applications,such as low ionic conductivity and poor interfacial stability,which severely limit their applications.This review provides a comprehensive overview of recent research advancements in OICSEs.Specifically,the influence of inorganic fillers on the main functional parameters of OICSEs,including ionic conductivity,Li+transfer number,mechanical strength,electrochemical stability,electronic conductivity,and thermal stability are systematically discussed.The lithium-ion conduction mechanism of OICSE is thoroughly analyzed and concluded from the microscopic perspective.Besides,the classic inorganic filler types,including both inert and active fillers,are categorized with special emphasis on the relationship between inorganic filler structure design and the electrochemical performance of OICSEs.Finally,the advanced characterization techniques relevant to OICSEs are summarized,and the challenges and perspectives on the future development of OICSEs are also highlighted for constructing superior ASSLBs.

Influences of different filler metals on electron beam welding of titanium alloy to stainless steel

Electron beam welding experiments of titanium alloy to stainless steel were carried out with different filler metals, such as Ni, V, and Cu. Microstructures of the joints were examined by optical microscopy, scanning electron microscopy and X-ray diffraction analysis. Mechanical properties of the joints were evaluated according to tensile strength and microhardness. As a result, influences of filler metals on microstructures and mechanical properties of electron beam welded titanium-stainless steel joints were discussed. The results showed that all the filler metals were helpful to restrain the Ti-Fe intermetallics. The welds with different filler metals were all characterized by solid solution and interfacial intermetallics. For each type of the filler metal, the type of solid solution and interfacial intermetallics depended on the metallurgical reactions between the filler metals and base metals. The interfacial intermetallics were Fe2Ti＋Ni3Ti＋NiTi2, TiFe, and Cu2Ti＋CuTi＋CuTi2 in the joints welded with Ni, V, and Cu filler metals, respectively. The tensile strengths of the joints were dependent on the hardness of the interfacial intermetallics. The joint welded with Ag filler metal had the highest tensile strength, which is about 310 MPa.

Microstructures of brazing zone between titanium alloy and stainless steel using various filler metals

Titanium alloy (Ti-Al-V alloy) substrate was brazed with stainless steel (STS304) using filler metal.At an optimized brazing condition,various filler metals were used.Microstructures were observed at each condition.Filler metals were titanium based 40Ti-20Zr-20Cu-20Ni,silver based Ag 5Pd,and nickel based Ni-7Cr-3.1B-4.5Si-3Fe-0.06C (BNi2) and Ni-14Cr-10P-0.06C (BNi7).To select a good filler metal for brazing process,wetting test was performed at 880-1050 °C.It was not brazed using silver based filler metals,but at the conditions using titanium and nickel based filler metals had brazed zone between titanium alloy and stainless steel.However,titanium alloy was eroded during brazing using titanium based filler metals.Nickel based filler metal has a good brazed zone between titanium alloy and stainless steel among the filler metals.

Effect of filler wire on the joint properties of AZ31 magnesium alloys using CO_2 laser welding

Laser welding with filler wire of AZ31 magnesium alloys is investigated using a CO2 laser experimental system. The effect of three different filler wires on the joint properties is researched. The results show that the weld appearance can be effectively improved when using laser welding with filler wire. The microhardness and tensile strength of joints are almost the same us those of the base metal when ER AZ31 or ER AZ61 wire is adopted. However, when the filler wire of ER 5356 aluminum alloy is used, the mechanical properties of flints become worse. For ER AZ31 and ER AZ61 filler wires, the microstructure of weld zone slws small dendrite grains. In comparison, for ER 5356 filler wire, the weld shows a structure of snowy dendrites and many intermetallic compounds and eutectic phases distribute in the dendrites. These intermetallic constituents with low melting point increase the tendency of hot crack and result in fiagile joint properties. Therefore, ER AZ31 and ER AZ61 wire are more suitable filler material than ER 5356 for CO2 laser welding of AZ31 magnesium alloys.

Effects of Ga and In on the properties of cadmium-free Ag-Cu-Zn filler metal

Melting temperature, spreadability, mechanical properties and the microstructures of joints brazed with silver-base filler metals including different amounts of Ga and/or In were studied respectively in this paper, and the results show that the melting temperature of the silver-base filler metals is decreased, spreadability of the silver-base filler metals is improved, and the microstructures of silver-base filh, r metals are refined obviously with the addition of Ga and/or In. Using copper and brass plates as base metal and brazing with flame method, the mechanical properties of the lap-joint and butt joint were also examined and analyzed respectively, and the results indicate that the fracture position of two kinds of brazed joints occurred on the base metal, except for the lap-joint of brass, which shows better mechanical properties of the joints brazed with the silver- based filler metals including Ga. For the lap-joint of brass, the tensile strength gradually increased with the increase of Ga content, while the addition of In has little effect on mechanical properties. It is also found that the best comprehensive properties of cadmium-free Ag-Cu-Zn filler metals are obtained when Ga content is about 3.0 wt. % and In content is between 1.5 wt. % and 2. 0 wt. %.

Brazing of Ti_2 AlNb Based Alloy with Amorphous Ti-Cu-Zr-Ni Filler

Amorphous Ti-Cu-Zr-Ni filler foils with low melting point of 1 133 K were synthesized using a melt-spinning method in argon atmosphere. A Ti2A1Nb based alloy was brazed at 1 153-1 223 K for 600-3 000 s. The effects of brazing temperature （Tb） and time （tb） on the shear strength of the joints were investigated. The results showed that the joint strength was significantly affected by the reaction layer thickness. The optimum brazing parameters can be determined as follows： Tb=l 173 K, and tb=600 s. The maximum tensile strength of the joint obtained can reach 260 MPa. Furthermore, the activation energy Q and the growth velocity A0 of the reaction layer in the brazed joints were calculated to be 161.742 kJ/mol and 0.213 m2/s, respectively. The growth of the reaction layer （y） could be expressed by the expression： ya =0.213exp（-19 454/Tb）tb.

Brazing 6061 aluminum alloy with Al-Si-Zn filler metals containing Sr

Al-6.5Si-42Zn and Al-6.5Si-42Zn-0.09Sr filler metals were used for brazing 6061 aluminum alloy. Air cooling and water cooling were applied after brazing. Si phase morphologies in the brazing alloy and the brazed joints were investigated. It was found that zinc in the Al-Si filler metals could reduce the formation of eutectic Al-Si phase and lower the brazing temperature at about 520℃. Adding 0.09wt% Sr element into the Al-6.5Si-42Zn alloy caused a-Al phase refinement and transformed acicular Si phase into the finely fiber-like. After water cooling, Zn element dissolved into the Al-Si eutectic area, and η-Zn phase disappeared in the brazed joints. Tensile strength testing results showed that the Sr-modified filler metal could enhance the strength of the brazed joints by 13% than Al-12Si, while water-cooling further improved the strength at 144 MPa.

Effects of Al2O3-Particulate-Contained Composite Filler Materials on the Shear Strength of Alumina Joints

Al2O3l2O3 joints were brazed with a new kind of filler materials, which were formed by adding AI203 particulates into Ag-Cu-Ti active filler metal. The results showed that the material parameters (the Ti content, Al2O3 particulate volume fraction) of the composite filler materials affected the shear strength of brazed joints. When the Ti content was 2 wt pct in the filler metal, the shear strength of brazing joints decreased with the increasing the volume ratio of Al2O3 particulate. When the Ti content was 3 wt pct in the filler metal, the shear strength of joints increased from 93.75 MPa(AI203p 0 vol. pct) to 135.32 MPa(AI203p 15 vol. pct).