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.

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.

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.

Cutting Behavior of Cortical Bone in Different Bone Osteon Cutting Angles and Depths of Cut

Cortical bone is semi-brittle and anisotropic,that brings a challenge to suppress vibration and avoid undesired fracture in precise cutting process in surgeries.In this paper,a novel analytical model is proposed to represent cortical bone cutting processes.The model is utilized to predict the chip formations,material removal behavior and cracks propagation under varying bone osteon cutting angles and depths.Series of orthogonal cutting experiments were conducted on cortical bone to investigate the impact of bone osteon cutting angle and depth of cut on cutting force,crack initialization and propagation.The observed chip morphology highly agreed with the prediction of chip formation based on the analytical model.The curly,serrated,grainy and powdery chips formed when the cutting angle was set as 0°,60°,90°,and 120°,respectively.Cortical bone were removed dominantly by shearing at a small depth of cut from 10 to 50μm,and by a mixture of pealing,shearing,fracture and crushing at a large depth of cut over 100μm at different bone osteon angles.Moreover,its fracture toughness was calculated based on measured cutting force.It is found that the fluctuation of cutting force is suppressed and the bone material becomes easy to remove,which attributes to lower fracture toughness at bone osteon cutting angle 0°.When the cutting direction develops a certain angle to bone osteon,the fracture toughness increases then the crack propagation is inhibited to some extent and the fluctuation of cutting force comparatively decreases.There is a theoretical and practical significance for tools design and operational parameters choice in surgeries.

FORMING PRINCIPLE OF TWO SIDE-DIRECTION BURR AND IT'S PREDICTION IN METAL CUTTING

The burr is one of the common phenomena occurring i n metal cutting operations The mathematical mechanical model of two side dir ection burr formation and transformation is established with plane stress strain theory,based on the orthogonal cutting The main laws of formation and change of the burr are revealed,and it is confirmed by experiment result,which first realizes prediction of the forming and changing of the two side direction burr in metal cutting operation.

Cutting force model and damage formation mechanism in milling of 70wt%Si/Al composite

High-mass fraction silicon aluminium composite(Si/Al composite) has unique properties of high specific strength, low thermal expansion coefficient, excellent wear resistance and weldability. It has attracted many applications in terms of radar communication, aerospace and automobile industry. However, rapid tool wear resulted from high cutting force and hard abrasion, and damaged machined surfaces are the main problem in machining Si/Al composite. This work aims to reveal the mechanisms of milling-induced damages of 70wt% Si/Al composites. A cutting force analytical model considering the characteristics of both the primary silicon particles and the cutting-edge radius was established. Milling experiments were conducted to verify the validity of the model. The results show that the analytical model exhibits a good consistency with the experimental results, and the error is about 10%. The cutting-edge radius has significant effects on the cutting force, surface roughness and damage formation. With the increase in the cutting-edge radius, both the cutting force and the surface roughness decrease firstly and then increase. When the cutting-edge radius is 27 μm, the surface roughness(Sa) reaches the minimum of 2.3 μm.Milling-induced surface damages mainly contain cracks, pits, scratches, matrix coating and burrs.The damage formation is dominated by the failure mode of primary silicon particles, which includes compressive breakage, intragranular fracture, particle pull-out, and interface debonding. In addition, the high ductility of aluminium matrix leads to matrix coating. This work provides guidance for tool selection and damage inhibition in high-efficiency and high-precision machining of high mass fraction Si/Al composites.

Finite element modeling of chip separation in machining cellular metals

Cellular metals and metal foams belong to a young material group. Although it is desired to manufac- ture near-net-shape parts of cellular metals by primary shaping processes, additional secondary machining opera- tions are often unavoidable to obtain the required geome- tries and quality demands. Nevertheless, conventional machining of cellular metals leads to undesirable surface damage and poor precision. Furthermore, the chip forma- tion and the mechanism description of the surface damage are still unclear. A mesoscopic finite element model was developed to simulate the chip formation process in machining cellular metals. Experimental data of orthogonal machining tests were used to validate the finite element model. The cutting and thrust forces, as well as the images of the chip formation process of both experiments and simulations were compared and analysed. The model enabled the analysis of the chip formation and the surface defect mechanisms. The rake angle and cutting conditions affected the chip formation process, but the cell arrange- ment was detected as a decisive factor in the chip forma- tion and the resulting surface damage.

Cooperative energy transfer in Tm^(3+)and Yb^(3+) co-doped phosphate glasses

An efficient near-infrared （NIR） quantum cutting （QC） in Tm3＋ and Yb3＋ co-doped phosphate glasses was demonstrated, which involved the emission of two NIR photons from an absorbed visible photon via a cooperative energy transfer （CET） from Tm3＋ to Yb3＋ ions. Judd-Ofelt （J-O） theory was used to calculate the intensity parameters （ 2 , 4 , 6 ）, the radiative transition rates （Ar ）, and radiative transition lifetime （τ rad ） of Tm3＋ . Based on Inokuti-Hirayama＇s model, the energy transfer processes were studied and results indicated that the energy transfer of the electric dipole-dipole （Edd） was dominant in this system. Quantum efficiency related to Yb 3＋ concentration was calculated, and the maximum QE efficiency reached 169.8%.