Surface performance of workpieces processed by electrical discharge machining in gas

The surface performance of workpieces processed by electrical discharge machining in gas(dry EDM)was studied in this paper.Firstly,the composition,micro hardness and recast layer of electrical discharge machined(EDMed)surface of 45 carbon steels in air were investigated through different test analysis methods.The results show that the workpiece surface EDMed in air contains a certain quantity of oxide,and oxidation occurs on the workpiece surface.Compared with the surface of workpieces processed in kerosene,fewer cracks exist on the dry EDMed workpiece surface,and the surface recast layer is thinner than that obtained by conventional EDM.The micro hardness of workpieces machined by dry EDM method is lower than that machined in kerosene,and higher than that of the matrix.In addition,experiments were conducted on the surface wear resistance of workpieces processed in air and kerosene using copper electrode and titanium alloy electrode.The results indicate that the surface wear resistance of workpieces processed in air can be improved,and it is related with tool material and dielectric.

Implantable PEKK/tantalum microparticles composite with improved surface performances for regulating cell behaviors,promoting bone formation and osseointegration

Polyetherketoneketone(PEKK)exhibits admirable biocompatibility and mechanical performances but bioinert while tantalum(Ta)possesses excellent osteogenesis and osseointegration but high elastic modulus and density,and processing is too difficult and expensive.In the present study,combining of the advantages of both PEKK and Ta,implantable composites of PEKK/Ta were fabricated by blending PEKK with Ta microparticles of 20 v%(PT20)and 40 v%(PT40)content.In comparison with PT20 and PEKK,the surface hydrophilicity,surface energy,roughness and proteins adsorption as well as mechanical performances of PT40 significantly increased because of the higher Ta particles content in PEKK.Furthermore,PT40 exhibited the mechanical performances(e.g.,compressive strength and modulus of elasticity)close to the cortical bone of human.Compared with PT20 and PEKK,PT40 with higher Ta content remarkably enhanced the responses(including adhesion,proliferation and osteogenic differentiation)of MC3T3-E1 cells in vitro.Moreover,PT40 markedly improved bone formation as well as osseointegration in vivo.In short,incorporation of Ta microparticles into PEKK created implantable composites with improved surface performances,which played key roles in stimulating cell responses/bone formation as well as promoting osseointegration.PT40 might have great potential for bear-loading bone substitute.

Explicit Correlation Model of Multi-source Constraints for Re-design Parts with Complex Curved Surface

In precision machining of complex curved surface parts with high performance, geometry accuracy is not the only constraint, but the performance should also be met. Performance of this kind of parts is closely related to the geometrical and physical parameters, so the final actual size and shape are affected by multiple source constraints, such as geometry, physics, and performance. These parts are rather difficult to be manufactured and new manufacturing method according to performance requirement is urgently needed. Based on performance and manufacturing requirements for complex curved surface parts, a new classification method is proposed, which divided the complex curved surface parts into two categories： surface re-design complex curved surface parts with multi-source constraints（PRCS） and surface unique complex curved surface parts with pure geometric constraints（PUCS）. A correlation model is constructed between the performance and multi-source constraints for PRCS, which reveals the correlation between the performance and multi-source constraints. A re-design method is also developed. Through solving the correlation model of the typical paws performance-associated surface, the mapping relation between the performance-associated surface and the related removal amount is obtained. The explicit correlation model and the method for the corresponding related removal amount of the performance-associated surface are built based on the classification of surface re-design complex curved surface parts with multi-source constraints. Research results have been used in the actual processing of the typical parts such as radome, common bottom components, nozzle, et al., which shows improved efficiency and accuracy of the precision machining for the surface re-design parts with complex curved surface.

Rock excavation using surface miners: An overview of some design and operational aspects

Surface miner, a continuous mining machine, is being manufactured in India and abroad owing to enhanced demand of production in various mining industries like coal, limestone, gypsum, bauxite etc. Different types of surface miners are manufactured today based on cutting drum placement and design specifications. Selective mining without drilling and blasting, high production and small size products are some of the prominent attractive features obtained with these moving marvels. This machine can be used with good efficiency in soft to medium hard rock (100-120 MPa). This paper synthesizes the different applications, equipment models, features offered, operating methods, cutting performance assessment models as well as typical production performance of surface miner in coal and limestone mines of India. Engine hour metre reading, diesel and pick consumptions are linearly influenced by production. The emphasis for future research is also brought out.

Tool wear performance and surface integrity studies for milling DD5 Ni-based single crystal superalloy

Based on the results of slot milling experiments on the DD5 Ni-based single crystal superalloy(001) crystal plane along the [110]crystal direction, in this paper, efforts were devoted to investigate the tool wear process, wear mechanism and failure modes of the physical vapor deposition(PVD)-AlTiN and TiAlN coated tools under dry milling and water-based minimum quantity lubrication(MQL) conditions. The scanning electron microscope(SEM) morphological observation and energy dispersive X-ray spectroscopy(EDX) elements analysis methods were adopted. Moreover, under the water-based MQL condition, the surface integrity such as surface roughness, dimensional and shape accuracy, microhardness and microstructure alteration were researched. The results demonstrated that the tool edge severe adhesion with the work material, induced by the high Al content in the PVD-AlTiN coating caused the catastrophic tool tip fracture. In contrast, the PVD-TiAlN tool displayed a steady and uniform minor flank wear, even though the material peeling and slight chipping also occurred in the final stage. In addition, due to the high effective cooling and lubricating actions of the water-based MQL method, the PVD-TiAlN coated tool demonstrated intact tip geometry; consequently it could be repaired and reused even if the failure criterion was attained. Moreover, as the accumulative milling length and the tool wear increased, all indicators of the surface integrity forehand were deteriorated.

Flight performance and wing morphology in the bat Carollia perspicillata:biophysical models and energetics

Studies on functional performance are important to understand the processes responsible for the evolution of diversity.Morphological trait variation within species influences the energetic cost of locomotion and impacts life history traits,with ecological and evolutionary consequences.This study examined wing morphology correlates of flight performance measured by energetic expenditure in the Seba’s short-tailed bat,Carollia perspicillata.In the flight experiments,nature caught bats(59 females,57 males)were allowed to fly for 3 min in a room.After each flight,thermographic images were taken to measure body temperature,and biophysical models were used to calculate sensible heat loss as a measure of energetic expenditure.Wing morphological traits were measured for each individual and associated with heat loss and power required to fly on performance surfaces.Wing morphological traits explained 7-10%of flight energetic cost,and morphologies with the best performance would save the energy equivalent to 9-30%of total daily requirements.The optimal performance areas within the C.perspicillata morphospace were consistent with predicted selection trends from the literature.A trade-off between demands for flight speed and maneuverability was observed.Wing loading and camber presented sexual dimorphism.These morphological differences are likely associated with more economical but less maneuverable flight in females,leading them to fly more often in open areas along the forest edge.Our findings demonstrate how small scale changes in wing morphology can affect life history strategies and fitness.

Investigation of HDD Ramp Unloading Processes with an Efficient Scheme

Ramp load/unload(L/UL)mechanisms are widely used to rest sliders in hard disk drives(HDDs).Loading/unloading a slider swiftly and smoothly is crucial in a HDD design.A novel,efficient simulation scheme is proposed to investigate the behaviors of a head disk interface(HDI)in ramp unloading processes.A dual scale model is enabled by decoupling the nano-meter scale change of an air bearing and the micro-or milli-meter scale deformation of a suspension.A modified Reynolds equation governing the air bearing was solved numerically.The slider design was characterized with performance functions.Three stages in an unloading process were analyzed with a lumped parameter suspension model.Key parameters for the model were estimated with a comprehensive finite element suspension model.Finally,simulation results are presented for a commercial HDI design.