Friction behaviors in the metal cutting process:state of the art and future perspectives

Material removal in the cutting process is regarded as a friction system with multiple input and output variables.The complexity of the cutting friction system is caused by the extreme conditions existing on the tool–chip and tool–workpiece interfaces.The critical issue is significant to use knowledge of cutting friction behaviors to guide researchers and industrial manufacturing engineers in designing rational cutting processes to reduce tool wear and improve surface quality.This review focuses on the state of the art of research on friction behaviors in cutting procedures as well as future perspectives.First,the cutting friction phenomena under extreme conditions,such as high temperature,large strain/strain rates,sticking–sliding contact states,and diverse cutting conditions are analyzed.Second,the theoretical models of cutting friction behaviors and the application of simulation technology are discussed.Third,the factors that affect friction behaviors are analyzed,including material matching,cutting parameters,lubrication/cooling conditions,micro/nano surface textures,and tool coatings.Then,the consequences of the cutting friction phenomena,including tool wear patterns,tool life,chip formation,and the machined surface are analyzed.Finally,the research limitations and future work for cutting friction behaviors are discussed.This review contributes to the understanding of cutting friction behaviors and the development of high-quality cutting technology.

Partial Surface Damper to Suppress Vibration for Thin Walled Plate Milling

The material removal rate and required work- piece surface quality of thin-walled structure milling are greatly limited due to its severe vibration, which is directly associated with the dynamic characteristics of the system. Therefore, the suppression of vibration is an unavoidable problem during milling. A novel partial surface damping method is proposed to modify the mode of the thin walled cantilever plate and to suppress vibration during milling. Based on classical plate theory, the design criterion is analyzed and configuration of the partial surface damper is introduced, in which viscoelastic plate and constraining plate are attached to the surface of the plate to increase the system＇s natural frequency and loss factor. In order to obtain the energy expression of the cutting system, the Ritz method is used to describe the unknown displacements. Then, with Lagrange＇s equation, the natural frequency and loss factor are calculated. In addition, the plate is divided into a finite number of square elements, and the regulation of treated position is studied based on theoretic and experimental analysis. The milling tests are conducted to verify its damping performance and the experimentalresults show that with treatment of partial surface damper, the deformation of the hare plate is reduced from 0.27 mm to 0.1 mm, while the vibration amplitude of the bare plate is reduced from 0.08 mm to 0.01 mm. The proposed research provides the instruction to design partial surface damper.

Multiscale design and biomechanical evaluation of porous spinal fusion cage to realize specified mechanical properties

Backgrou nd Dense titanium(Ti)fusion cages have been commonly used in transforaminal lumbar interbody fusion.However,the stiffness mismatch between cages and adjacent bone endplates increases the risk of stress shielding and cage subsidence.Methods The current study presents a multiscale optimization approach for porous Ti fusion cage development,including microscale topology optimization based on homogenization theory that obtains a unit cell with prescribed mechanical properties,and macroscale topology optimization that determines the layout of framework structure over the porous cage while maintaining the desired stiffness.The biomechanical performance of the designed porous cage is assessed using numerical simulations of fusion surgery.Selective laser melting is employed to assists with fabricating the designed porous structure and porous cage.Results The simulations demonstrate that the designed porous cage increases the strain energy density of bone grafts and decreases the peak stress on bone endplates.The mechanical and morphological discrepancies between the as-designed and fabricated porous structures are also described.Conclusion From the perspective of biomechanics,it is demonstrated that the designed porous cage contributes to reducing the risk of stress shielding and cage subsidence.The optimization of processing parameters and post-treatments are required to fabricate the designed porous cage.The present multiscale optimization approach can be extended to the development of cages with other shapes or materials and further types of orthopedic implants.

Three‑dimensional Modeling and Simulation of Muscle Tissue Puncture Process

Needle biopsy is an essential part of modern clinical medicine.The puncture accuracy and sampling success rate of puncture surgery can be effectively improved through virtual surgery.There are few three-dimensional puncture(3D)models,which have little significance for surgical guidance under complicated conditions and restrict the development of virtual surgery.In this paper,a 3D simulation of the muscle tissue puncture process is studied.Firstly,the mechanical properties of muscle tissue are measured.The Mooney-Rivlin(M-R)model is selected by considering the fitting accuracy and calculation speed.Subsequently,an accurate 3D dynamic puncture model is established.The failure criterion is used to define the breaking characteristics of the muscle,and the bilinear cohesion model defines the breaking process.Experiments with different puncture speeds are carried out through the built in vitro puncture platform.The experimental results are compared with the simulation results.The experimental and simulated reaction force curves are highly consistent,which verifies the accuracy of the model.Finally,the model under different parameters is studied.The simulation results of varying puncture depths and puncture speeds are analyzed.The 3D puncture model can provide more accurate model support for virtual surgery and help improve the success rate of puncture surgery.

Chatter suppression techniques in milling processes:A state of the art review

Chatter in the machining system can result in a decrease in tool life,poor surface finish,conservative cutting parameters,etc.Despite many review papers promoting the understanding and research of this area,chatter suppression techniques are generally discussed within limited pages in the framework of comprehensive chatter-related problems.In recent years,the developments of smart materials,advanced sensing techniques,and more effective control strategies have led to some new progress in chatter suppression.Meanwhile,the widely used thin-walled parts present more and more severe machining challenges in their milling processes.Considering the above deficiencies,this paper summarizes the current state of the art in milling chatter suppression.New classifications of chatter suppression techniques are proposed according to the working principle and control target.Based on the new classified framework,the mechanism and comparisons of different chatter suppression strategies are reviewed.Besides,the current challenges and potential tendencies of milling chatter suppression techniques are highlighted.Intellectualization,integration,compactness,adaptability to workpiece geometry,and the collaboration of multiple control methods are predicted to be important trends in the future.

A novel stability prediction approach for thin-walled component milling considering material removing process

The milling stability of thin-walled components is an important issue in the aviation manufacturing industry, which greatly limits the removal rate of a workpiece. However, for a thin-walled workpiece, the dynamic characteristics vary at different positions. In addition, the removed part also has influence on determining the modal parameters of the workpiece. Thus,the milling stability is also time-variant. In this work, in order to investigate the time variation of a workpiece＇s dynamic characteristics, a new computational model is firstly derived by dividing the workpiece into a removed part and a remaining part with the Ritz method. Then, an updated frequency response function is obtained by Lagrange＇s equation and the corresponding modal parameters are extracted. Finally, multi-mode stability lobes are plotted by the different quadrature method and its accuracy is verified by experiments. The proposed method improves the computational efficiency to predict the time-varying characteristics of a thin-walled workpiece.

Osteogenic and antibacterial ability of micro-nano structures coated with ZnO on Ti-6Al-4V implant fabricated by two-step laser processing

The biological performance of Ti-6Al-4V implant is primarily determined by their surface properties.However,traditional surface modification methods,such as acid etching,hardly make improvement in their osseointegration ability and antibacterial capacity.In this study,we prepared a multi-scale composite structure coated with zinc oxide(ZnO)on Ti-6Al-4V implant by an innovative technology of two-step laser processing combined with solution-assistant.Compared with the acid etching method,the physicochemical properties of surface significantly improved.The in vitro results showed that the particular dimension of micro-nano structure and the multifaceted nature of ZnO synergistically affected MC3T3-E1 osteogenesis and bacterial activities:(1)The surface morphology showed a‘contact guidance'effect on cell arrangement,which was conducive to the adhesion of filopodia and cell spreading,and the osteogenesis level of MC3T3-E1 was enhanced due to the release of zinc ions(Zn^(2+));(2)the characterization of bacterial response revealed that periodic nanostructures and Zn^(2+)released could cause damage to the cell wall of E.coli and reduce the adhesion and aggregation of S.aureus.In conclusion,the modified surface showed a synergistic effect of physical topography and chemical composition,making this a promising method and providing new insight into bone defect repairment.

Doped, conductive SiO_(2) nanoparticles for large microwave absorption

Although many materials have been studied for the purpose of microwave absorption,SiO_(2) has never been reported as a good candidate.In this study,we present for the first time that doped,microwave conductive SiO_(2) nanoparticles can possess an excellent microwave absorbing performance.A large microwave reflection loss(RL)of−55.09 dB can be obtained.The large microwave absorption originates mainly from electrical relaxation rather than the magnetic relaxation of the incoming microwave field.The electrical relaxation is attributed to a large electrical conductivity that is enabled by the incorporation of heterogeneous(N,C and Cl)atoms.The removal of the magnetic susceptibility only results in a negligible influence of the microwave absorption.In contrast,the removal of the heterogeneous atoms leads to a large decrease in the electrical conductivity and microwave absorption performance.Meanwhile,the microwave absorption characteristics can be largely adjusted with a change of the thickness,which provides large flexibility for various microwave absorption applications.

Fiber orientation effects on grinding characteristics and removal mechanism of 2.5D C_(f)/SiC composites

Carbon fiber reinforced silicon carbide(C_(f)/SiC)composites are widely used in aerospace for their excellent mechanical properties.However,the quality of the machined surface is poor and unpredictable due to the material heterogeneity induced by complex removal mechanism.To clarify the effects of fiber orientation on the grinding characteristics and removal mechanism,single grit scratch experiments under different fiber orientations are conducted and a three-phase numerical modelling method for 2.5D C_(f)/SiC composites is proposed.Three fiber cutting modes i.e.,transverse,normal and longitudinal,are defined by fiber orientation and three machining directions i.e.,MA(longitudinal and normal),MB(longitudinal and transverse)and MC(normal and transverse),are selected to investigate the effect of fiber orientation on grinding force and micro-morphology.Besides,a three-phase cutting model of 2.5D C_(f)/SiC composites considering the mechanical properties of the matrix,fiber and interface is developed.Corresponding simulations are performed to reveal the micro-mechanism of crack initiation and extension as well as the material removal mechanism under different fiber orientations.The results indicate that the scratching forces fluctuate periodically,and the order of mean forces is MA>MC>MB.Cracks tend to grow along the fiber axis,which results in the largest damage layer for transverse fibers and the smallest for longitudinal fibers.The removal modes of transverse fibers are worn,fracture and peel-off,in which normal fibers are pullout and outcrop and the longitudinal fibers are worn and push-off.Under the stable cutting condition,the change of contact area between fiber and grit leads to different removal modes of fiber in the same cutting mode,and the increase of contact area results in the aggravation of fiber fracture.

Microwave absorption of aluminum/hydrogen treated titanium dioxide nanoparticles

Interactions between incident electromagnetic energy and matter are of critical importance for numerous civil and military applications such as photocatalysis,solar cells,optics,radar detection,communications,information processing and transport et al.Traditional mechanisms for such interactions in the microwave frequency mainly rely on dipole rotations and magnetic domain resonance.In this study,we present the first report of the microwave absorption of Al/H2 treated TiO_(2) nanoparticles,where the A_(l)/H_(2) treatment not only induces structural and optical property changes,but also largely improves the microwave absorption performance of TiO_(2) nanoparticles.Moreover,the frequency of the microwave absorption can be finely controlled with the treatment temperature,and the absorption efficiency can reach optimal values with a careful temperature tuning.A large reflection loss of
58.02 dB has been demonstrated with 3.1mm TiO_(2) coating when the treating temperature is 700℃.The high efficiency of microwave absorption is most likely linked to the disordering-induced property changes in the materials.Along with the increased microwave absorption properties are largely increased visiblelight and IR absorptions,and enhanced electrical conductivity and reduced skin-depth,which is likely related to the interfacial defects within the TiO_(2) nanoparticles caused by the Al/H2 treatment.

Constrained layer damping treatment of a model support sting

In transonic wind tunnel tests,the pulsating airflow is prone to induce the first order resonance of the sting support system.The resonance limits the wind tunnel test envelope,makes the test data inaccurate,and brings potential security risks.In this paper,a model support sting with constrained layer damping(CLD)treatment is proposed to reduce the first order resonance response.The CLD treatment mainly consists of material selection and geometric optimization processes.The damping performance of the optimized CLD sting is compared with an AISI 1045 steel sting with the identical diameter in laboratory.The frequency response curves of the CLD sting support system and the AISI 1045 steel sting support system are obtained by sine sweep tests.The test results show that the first order resonance response of the CLD sting support system is 37.3%of that of the AISI 1045 steel sting support system.The first order damping ratios are calculated from the frequency response curves by half power point method.It is found that the first order damping ratio of the CLD sting support system is approximately 2.6 times that of the AISI 1045 steel sting support system.

Efficiency Enhancement of Cu(In,Ga)Se_2 Solar Cells by Applying SiO_2-PEG/PVP Antire flection Coatings

An effective approach was presented to enhance photoelectric conversion efficiency of Cu(In,Ga)Se2 (CIGS) solar cells by using modified SiO2 antireflection coatings(ARCs) to harvest more incident sunlight.Polyethylene glycol(PEG) and polyvinyl pyrrolidone(PVP) used as additives were introduced into silica sols to prepare SiO2-PEG and SiO2-PVP coatings in the sol-gel dip-coating process,respectively. The different effects of PEG and PVP additives on SiO2 coatings were analyzed and the antireflection performance of SiO2-PEG and SiO2-PVP coatings was investigated. The transmittance over 97% ranging from 450 nm to 700 nm with a maximum transmittance over 99.40% at about 550 nm was achieved for both SiO2-PEG2000A and SiO2-PVP0.5 coatings. The relative efficiencies of CIGS solar cells coated with SiO2-PEG2000A and SiO2-PVP0.5 ARCs were increased by 7.27% and 8.33%,respectively. The modified SiO2 ARCs possessed the advantages of the low manufacturing cost,good adhesion,superior antireflective performance and the feasible method for large area fabrication.