FLOW STRESS MODELING FOR AERONAUTICAL ALUMINUM ALLOY 7050-T7451 IN HIGH-SPEED CUTTING

The high temperature split Hopkinson pressure bar （SHPB） compression experiment is conducted to obtain the data relationship among strain, strain rate and flow stress from room temperature to 550 C for aeronautical aluminum alloy 7050-T7451. Combined high-speed orthogonal cutting experiments with the cutting process simulations, the data relationship of high temperature, high strain rate and large strain in high-speed cutting is modified. The Johnson-Cook empirical model considering the effects of strain hardening, strain rate hardening and thermal softening is selected to describe the data relationship in high-speed cutting, and the material constants of flow stress constitutive model for aluminum alloy 7050-T7451 are determined. Finally, the constitutive model of aluminum alloy 7050-T7451 is established through experiment and simulation verification in high-speed cutting. The model is proved to be reasonable by matching the measured values of the cutting force with the estimated results from FEM simulations.

A Decision-Making Framework Model of Cutting Fluid Selection for Green Manufacturing and the Case Study

Pursuing the green manufacturing (GM) of products i s very beneficial in the alleviation of environment burdens. In order to reap such benefits, green manufacturing is involved in every aspect of manufacturing proc esses. During the machining process, cutting fluid is one of the main roots of e nvironmental pollution. And how to make an optimal selection for cutting fluid f or GM is an important path to reduce the environmental pollution. The objective factors of decision-making problems in the traditional selection of cutting flu id are usually two: quality and cost. But from the viewpoint of GM, environmenta l impact (E) should be considered together. In this paper, a multi-object d ecision-making model of cutting fluid selection for GM is put forward, in which the objects of Quality (Q), Cost(C) and Environmental impact (E) are considered together. In this model, E means to minimize the environmental impact, Q means to maximize the quality and C means to minimize the cost. Each objective is anal yzed in detail too. A case study on a decision-making problem of cutting fluid selection in a gear hobbing process is analyzed, and the result shows the model is practical.

A Real-time Cutting Model Based on Finite Element and Order Reduction

Telemedicine plays an important role in Corona Virus Disease 2019(COVID-19).The virtual surgery simulation system,as a key component in telemedicine,requires to compute in real-time.Therefore,this paper proposes a realtime cutting model based on finite element and order reduction method,which improves the computational speed and ensure the real-time performance.The proposed model uses the finite element model to construct a deformation model of the virtual lung.Meanwhile,a model order reduction method combining proper orthogonal decomposition and Galerkin projection is employed to reduce the amount of deformation computation.In addition,the cutting path is formed according to the collision intersection position of the surgical instrument and the lesion area of the virtual lung.Then,the Bezier curve is adopted to draw the incision outline after the virtual lung has been cut.Finally,the simulation system is set up on the PHANTOM OMNI force haptic feedback device to realize the cutting simulation of the virtual lung.Experimental results show that the proposed model can enhance the real-time performance of telemedicine,reduce the complexity of the cutting simulation and make the incision smoother and more natural.

Assessing cutter-rock interaction during TBM tunnelling in granite:Large-scale standing rotary cutting tests and 3D DEM simulations

The widespread utilisation of tunnel boring machines(TBMs)in underground construction engineering requires a detailed investigation of the cutter-rock interaction.In this paper,we conduct a series of largescale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method(DEM)to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses.The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters.More specifically,the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius.In contrast,the side force decreases as the cutting radius increases.Additionally,the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases.The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius.Consequently,an optimal penetration is identified,leading to a low boreability index and specific energy.A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations,whereby an improved CSM(Colorado School of Mines)model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model.The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations.The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.

Predictive Modeling and Parameter Optimization of Cutting Forces During Orbital Drilling

To optimize cutting control parameters and provide scientific evidence for controlling cutting forces,cutting force modeling and cutting control parameter optimization are researched with one tool adopted to orbital drill holes in aluminum alloy 6061.Firstly,four cutting control parameters(tool rotation speed,tool revolution speed,axial feeding pitch and tool revolution radius)and affecting cutting forces are identified after orbital drilling kinematics analysis.Secondly,hybrid level orthogonal experiment method is utilized in modeling experiment.By nonlinear regression analysis,two quadratic prediction models for axial and radial forces are established,where the above four control parameters are used as input variables.Then,model accuracy and cutting control parameters are analyzed.Upon axial and radial forces models,two optimal combinations of cutting control parameters are obtained for processing a13mm hole,corresponding to the minimum axial force and the radial force respectively.Finally,each optimal combination is applied in verification experiment.The verification experiment results of cutting force are in good agreement with prediction model,which confirms accracy of the research method in practical production.

A flexible multi-body model of a surface miner for analyzing the interaction between rock-cutting forces and chassis vibrations

The discontinuous nature of rock cutting can easily cause unwanted vibrations in the structure of a surface miner.If these vibrations are not properly addressed,the related stress cycles can gradually damage the chassis resulting in fatigue failures.These events can seriously undermine the safety of operators and digging operations may be stopped for days,with an obvious economic impact.This work presents an analysis of the dynamics of a surface miner,focusing on the interaction between cutting machine dynamics and cutting forces,which is a new approach for this type of machine.For this purpose,the authors developed a numerical model of the cutting process made up of(1)a multi-body model of the cutting machine,which takes into account the chassis's flexibility;(2)a model of the rotating cutting head;and(3)a model of the interaction between the cutting head and rock,based on Shao's model.The model was compared with experimental results and then used to investigate the effects of cutting speed and cutting depth on the machine dynamics.

Numerical simulations on cutting of frozen soil using HJC Model

Numerical simulation is known as an effective method for mechanical properties during frozen soil excavation.In order to reveal the development of cutting force,effective stress and cutting fragments in frozen silt during the cutting process,we introduce an explicit finite element program LS-DYNA to establish a two-dimensional numerical model of the frozen soil cut.We also use the Holmquist-Johnson-Cook(HJC)damage constitutive model for simulating the variation of soil mechanical properties according to the strong dependence between the cutting tool and frozen silt during the process with different cutting depths,angles and velocities.Meanwhile,a series of experimental results are acquired of frozen silt cutting to prove the application of the HJC model during simulation of cutting force variations.The result shows that the cutting force and fragment size are strongly influenced by cutting depths and cutting velocities increased,and the maximum effective stress at points where the tool contacts frozen soil during the cutting process.In addition,when the cutting angle is 52°,the cutting force is the smallest,and the cutting angle is optimum.Thus,the prediction of frozen soil mechanical properties on the cutting process by this model is conducive to selecting machinery equipment in the field.

Force Modeling for Ultrasonic-assisted Wire Saw Cutting SiC Monocryatal Wafers

The advantages, such as a small cutting force, narrow kerf and little material waste make wire saw cut- ting suitable for machining precious materials like SiC, Si monocrystal and a variety of gem. As regards wire saw cutting fo wafer, however, in traditional wire saw cutting process, the cutting efficiency is low, the wear of wire saw is badly, the surface roughness of wafer is poor etc, which have a seriously impact on the cutting process stability and the use of wafers. Ultrasonic-assisted machining method is very suitable for processing a variety of non-conduc- tive hard and brittle materials, glass, ceramics, quartz, silicon, precious stones and diamonds, etc. In this paper, the force model of ultrusonic-assisted wire saw cutting of SiC monocrystal wafer, based on the kinematic and experi- mental analysis were established. The single factor and orthogonal experimental scheme for different processing pa- rameters such as wire saw speed, part rotation speed of and part feed rate, were carried out in traditional wire saw and ultrasonic-assisted wire saw cutting process. The multiple linear regression method is used to establish the static model among the cutting force, processing parameters and ultrasonic vibration parameters, and the model signifi- cance is verified. The results show, as regards ultrasonic-assisted wire saw cutting of SiC monicrystal wafer, both the tangential and normal cutting forces can reduce about 24. 5%-36% and 36. 6%-40%.

A MECHANICAL MODEL FOR THE CHIP SIDE DEFORMATION IN ALUMINIUM ALLOY CUTTING

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Research on Cutting Force Modeling and Surface Qualityin the Transition Area of the Mosaic Mold

Aiming at the problem of tool wear and breakage, the low accuracy of machined surface duringthe milling process of automobile panel splicing dies, the cutting force modeling of micro element is carriedout. The cutting chip thickness of each cutting cycle is built as a function of the cutting angle and the shearforce according to the different hardness of machining materials, and a plow force model are obtained underng angles. By introducing a single degree of freedom italic collision model, the Hopkinsontest is used to obtain the elastic deformation δ of the tool workpiece impact under different spindle speeds,sults showforce on the tool in the transition area is obtained. Combining above models together,of milling force in the transition area can be obtained. Experiment and simulation reconslstendirections is studied. Fromcythto prove the accuracy of the model. The surface quality under different feede analysis results of machined surface quality, surfacedifference between workpieces, it is concluded that better surface quality can be obtaineness and heightness and low hardness workpiece. The results provide theoretical support for the optimizationing process in the splicing die of the automobile panel highof the milling process in the splicing die of the automobile panel.

Oblique Cutting Based Mechanical Model for Insertion Torque of Dental Implant

The insertion torque of a dental implant is an important indicator for the primary stability of dental implants.Thus,the preoperative prediction for the insertion torque is crucial to improve the success rate of implantation surgery.In this present research,an alternative method for prediction of implant torque was proposed.First,the mechanical model for the insertion torque was established based on an oblique cutting process.In the proposed mechanical model,three factors,including bone quality,implant geometry and surgical methods were considered in terms of bone-quality coefficients,chip load and insertion speeds,respectively.Then,the defined bone-quality coefficients for cancellous bone with the computed tomography(CT)value of 235–245,345–355 and 415–425 Hu were obtained by a series of insertion experiments of IS and ITI implants.Finally,the insertion experiments of DIO implants were carried out to verify the accuracy of developed model.The predicted insertion torques calculated by the mechanical model were compared with those acquired by insertion experiments,with good agreement,the relative error being less than 15%.This method allows the insertion torque for different implant types to be quickly established and enhances prediction accuracy by considering the effects of implants’geometries and surgical methods.

Hydraulic modeling and optimization of jet mill bit considering the characteristics of depressurization and cuttings cleaning

A jet mill bit(JMB)is proposed to increase the drilling efficiency and safety of horizontal wells,which has the hydraulic characteristics of depressurization and cuttings cleaning.This paper fills the gap in the hydraulic study of the JMB by focusing on the hydraulic modeling and optimization of the JMB and considering these two hydraulic characteristics.First,the hydraulic depressurization model and the hydraulic cuttings cleaning model of the JMB are developed respectively.In the models,the pressure ratio and efficiency are chosen as the evaluation parameters of the depressurization capacity of the JMB,and the jet hydraulic power and jet impact force are chosen as the evaluation parameters of cuttings cleaning capacity of the JMB.Second,based on the hydraulic models,the effects of model parameters[friction loss coefficient,target inclination angle,rate of penetration(ROP),flow ratio,and well depth]on the hydraulic performance of the JMB are investigated.The results show that an increase in the friction loss coefficient and target inclination angle cause a significant reduction in the hydraulic depressurization capacity,and the effect of ROP is negligible.The flow ratio is positively related to the hydraulic cuttings cleaning capacity,and the well depth determines the maximum hydraulic cuttings cleaning capacity.Finally,by combining the hydraulic depressurization model and hydraulic cuttings cleaning model,an optimization method of JMB hydraulics is proposed to simultaneously maximize the jet depressurization capacity and the cuttings cleaning capacity.According to the drilling parameters given,the optimal values of the drilling fluid flow rate,backward nozzle diameter,forward nozzle diameter,and throat diameter can be determined.Moreover,a case study is conducted to verify the effectiveness of the optimization method.

Mathematical Model and Simulation of Cutting Layer Geometry in Orthogonal Turn⁃Milling with Zero Eccentricity

Orthogonal turn-milling is a high-efficiency and precision machining method.Its cutting layer directly affects chip formation,cutting forces,and chatter,and further affects tool life,machining quality,etc.We studied The cutting layer geometry(CLG)in orthogonal turn-milling with zero eccentricity(OTMZE)is studied to explore orthogonal turn-milling cutting layer formation process.OTMZE principles of motion and formation processes are analyzed statically without considering kinetic influences.Mathematical models of the entrance and exit angles,cutting thickness,and cutting depth are established.In addition,these models are validated experimentally and some influences of cutting parameters on the tool cutting layer are analyzed.The results show that OTMZE cutting layer formation can be divided into two stages,chip shapes are nearly consistent with the simulated CLGs,and the most influencial parameter in affecting the cutting layer is found to be the tool feed per revolation of workpiece fa,followed by the ratio of the tool and workpiece speedsλand the cutting depth ap.These models and results can provide theoretical guidance to clarify formation processes and quantitatively analyze changes in cutting layer geometry during OTMZE.In addition,they offer theoretical guidelines for cutting forces and chatter.

Parameter estimation of cutting tool temperature nonlinear model using PSO algorithm

In cutting tool temperature experiment, a large number of related data could be available. In order to define the relationship among the experiment data, the nonlinear regressive curve of cutting tool temperature must be constructed based on the data. This paper proposes the Particle Swarm Optimization (PSO) algorithm for estimating the parameters such a curve. The PSO algorithm is an evolutional method based on a very simple concept. Comparison of PSO results with those of GA and LS methods showed that the PSO algorithm is more effective for estimating the parameters of the above curve.

Cutting edge curve models for equal pitch cutters and their applications

A mathematic model is established using infinitesimal geometry for the cutting edge design of special milling cutters which use equal lead helix as cutting edges; equations are given for front-end and proclitic surface of revolution of ball pillar milling cutters, ball taper milling cutters and angularly conical milling cutters; and corresponding models are established for the continuity cutting edge curves of milling cutters. Typical examples are given to illustrate the applications of mathematic models, which prove the correctness and applicability of these geometric models.

Mathematical Modelling of Cutting Force as the Most Reliable Information Bearer on Cutting Tools Wearing Phenomenon

Being one of their prominent exploitative characteristics, cutting tools durability depends on the character, intensity and the speed of wearing. Identification of tool wearing is of great significance for the purpose of avoiding sooner or later replacement of tools. The parameters of tool wearing can be measured by out-process and in-process-measuring systems. Given the extremely limiting role of the former in modern production lines, development of the latter （the indirect measuring systems） has gained prominence, The basis of indirect measuring systems comprises a set of various signals originating from the units of the system under treatment which stand in certain correlations with the wearing parameters. The paper presents mathematical models of axial force designed on the basis of experimental research in drilling tempered steel by twist drills made of high-speed steel manufactured by powder metallurgy.

A Cutting Parameter Optimization System Design Based on Mathematical Models and Databases of Parameters

To solve the problem of difficulty in selecting NC cutting parameters by the redundancy technique, a method is put forward to optimize cutting parameters based on a revolutionary mathematical model and a revolutionary cutting parameters database. By use of fuzzy inference rules, it can not only make the method itself evolved and updated, but also ensure data to be correct and feasible from the two optimization routes. Practical running and testing proved that this method can facilitate for the user to select parameters and greatly improve the processing efficiency.

Modeling of Transient Thermal Conditions in Cutting

The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality of the work piece. This in particular applies for manufacturing processes like milling, drilling and turning for high-value turbomachinery components like impellers, combustion engines and compressors of the aerospace and automotive industry as well as energy generation, which play a major role in modern societies. However, numerous analytical and experimental efforts have been conducted in order to understand the thermal conditions in metal cutting, yet many questions still prevail. Most models are based on a stationary point of view and do not include time dependent effects like in intensity and distribution varying heat sources, varying engagement conditions and progressive tool wear. In order to cover such transient physics an analytical approach based on Green＇s functions for the solution of the partial differential equations of unsteady heat conduction in solids is used to model entire transient temperature fields. The validation of the model is carried out in orthogonal cutting experiments not only punctually but also for entire temperature fields. For these experiments an integrated measurement of prevailing cutting force and temperature fields in the tool and the chip by means of high-speed thermography were applied. The thermal images were analyzed with regard to thermodynamic energy balancing in order to derive the heat partition between tool, chips and workpiece. The thus calculated heat flow into the tool was subsequently used in order to analytically model the transient volumetric temperature fields in the tool. The described methodology enables the modeling of the transient thermal state in the cutting zone and particular in the tool, which is directly linked to phenomena like tool wear and workpiece surface modifications.

New Virtual Cutting Algorithms for 3D Surface Model Reconstructed from Medical Images

This paper proposes a practical algorithms of plane cutting, stereo clipping and arbitrary cutting for 3D surface model reconstructed from medical images. In plane cutting and stereo clipping algorithms, the 3D model is cut by plane or polyhedron. Lists of edge and vertex in every cut plane are established. From these lists the boundary contours are created and their relationship of embrace is ascertained. The region closed by the contours is triangulated using Delaunay triangulation algorithm. Arbitrary cutting operation creates cutting curve interactively. The cut model still maintains its correct topology structure. With these operations, tissues inside can be observed easily and it can aid doctors to diagnose. The methods can also be used in surgery planning of radiotherapy.

A MECHANICS MODEL FOR CIRCULAR FORM TOOL CUTTING

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