Characteristics of an Axial-flux Permanent Magnet Synchronous Machine with Contra-rotating Rotors under Unbalanced Load Condition from 3-D Finite Element Analysis

During recent years,the axial-flus PMSM with contra-rotating rotors has become a hot topic in academic research due to its high efficiency and simple structure.However,its back-EMF may be distorted under the condition of different angular positions.This paper investigates characteristics of the novel motor used for contra-propeller driving.Considering the torque ripple and current oscillation under unbalanced load condition,this paper analyzes the distorted back-EMF of the machine when its two rotors get different angular positions during rotating.The analysis results are validated by transient-magnetic 3-D FEA method,which the 3-D FEA software is used to model this motor and transient simulations are carried out to obtain its magnetic characteristic and main performances.A main focus is put on the back-EMF characteristic with different angular positions between the two rotors.Furthermore,the characteristic of torque production under unbalanced load is investigated.Finally,a prototype motor is fabricated to validate the analyses of this paper.

A multiscale 3D finite element analysis of fluid/solute transport in mechanically loaded bone

The transport of fluid, nutrients, and signaling molecules in the bone lacunar-canalicular system （LCS） is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching （FRAP） approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30-50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis （FEA） approach. An intact murine tibia was first re-constructed from microCT images into a three-dimensional （3D） linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform （FEBio） to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex. Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces （shear and drag forces） for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.

3D Finite Element Analysis of a Man Hip Joint Femur under Impact Loads

Objective: The biomechanical characters of the bone fracture of the man femoral hip joint under impact loads are explored. Methods:A biosystem model of the man femoral hip joint by using the GE (General Electric) lightspeed multi-lay spiral CT is conducted. A 3D finite element model is established by employing the finite element software ANSYS. The FE analysis mainly concentrates on the effects of the impact directions arising from intense movements and the parenchyma on the femoral hip joint on the stress distributions of the proximal femur. Results:The parenchyma on the hip joint has relatively large relaxation effect on the impact loads. Conclusion:Effects of the angle δ of the impact load to the anterior direction and the angle γ of the impact load to the femur shaft on the bone fracture are given;δ has larger effect on the stress and strain distributions than the angle γ, which mainly represents the fracture of the upper femur including the femoral neck fracture when the posterolateral femur is impacted, consistent with the clinical results.

Discrete Element with Flexible Connector for Dynamic Analysis of 3-D Beam Structures

Combined multi-body dynamics with structural dynamics, a new discrete element with flexible connector, which is applicable for 3-D beam structures, is developed in this paper. Both the generalized elastic coefficient matrix of the flexible connector and the mass matrix of discrete element may be off-diagonal in a general case. The zero-length rigid element is introduced to simulate the node at which multiple elements are jointed together. It may also be effective when the axes of adjacent elements are not in the same line. The examples for eigenvalue calculation show that the model is successful. It can be extended to the geometric nonlinear response analysis.

Three dimensional finite element analysis of anatomic distal radius Nitinol memory connector treating distal radius fracture

Objective: To study the memory biomechanical character of anatomic distal radius Nitinol memory connector (DRMC) in treating distal radius fracture. Methods: Establishing three dimensional model and finite element analysis, we calculated the stress in and around the fracture faces when distal radius fracture was fixated with DRMC. Results: Axial holding stress produced by holding part of DRMC on distal radius was 14.66 MPa. The maximum stress of holding part was 40-70 MPa, the minimum stress was 3-7 MPa,and the stress of compression part was 20-40 MPa. Conclusion: The distribution of stress produced by DRMC around the fracture line is reasonable, and axial holding stress can help stabilize fracture during earlier period. The existence of longitudal compression and memory effect can transfer fixated disused section into developed section and enhance fracture healing.

Optimal Design Strategies of Femur Tumor Hyperthermia Based on Finite Element Analysis of Temperature Field

A 3D femoral model was built to obtain the three-dimensional temperature distribution of femur and its surrounding tissues and provide references for clinical applications. According to the relationship between gray-value and material properties,the model was assigned with various materials to make sure that it is more similar to the real femur in geometry and physical properties. 3D temperature distribution is obtained by using finite element analysis software ANSYS 11. 0 on the basis of heat conduction theory,Laplace equation,Pennes bio-heat transfer equation,thermo physical parameters of bone tissues,the boundary condition,and initial conditions. Taken the asymmetry of the 3D distribution of temperature into account,it is necessary to adopt the heating method with multiple heat sources. This method can ensure that the temperature fields match well with the tumor tissues and kill the tumor cells efficiently under the condition of protecting the normal tissues from damage. The analysis results supply important guidance for determining the needle position and the needle number and controlling the intensity of heating.

Biomechanical analysis of an absorbable material for treating fractures of the inferior orbital wall

AIM:To investigate the biomechanical properties and practical application of absorbable materials in orbital fracture repair.METHODS:The three-dimensional(3D)model of orbital blowout fractures was reconstructed using Mimics21.0 software.The repair guide plate model for inferior orbital wall fracture was designed using 3-matic13.0 and Geomagic wrap 21.0 software.The finite element model of orbital blowout fracture and absorbable repair plate was established using 3-matic13.0 and ANSYS Workbench 21.0 software.The mechanical response of absorbable plates,with thicknesses of 0.6 and 1.2 mm,was modeled after their placement in the orbit.Two patients with inferior orbital wall fractures volunteered to receive single-layer and double-layer absorbable plates combined with 3D printing technology to facilitate surgical treatment of orbital wall fractures.RESULTS:The finite element models of orbital blowout fracture and absorbable plate were successfully established.Finite element analysis(FEA)showed that when the Young’s modulus of the absorbable plate decreases to 3.15 MPa,the repair material with a thickness of 0.6 mm was influenced by the gravitational forces of the orbital contents,resulting in a maximum total deformation of approximately 3.3 mm.Conversely,when the absorbable plate was 1.2 mm thick,the overall maximum total deformation was around 0.4 mm.The half-year follow-up results of the clinical cases confirmed that the absorbable plate with a thickness of 1.2 mm had smaller maximum total deformation and better clinical efficacy.CONCLUSION:The biomechanical analysis observations in this study are largely consistent with the clinical situation.The use of double-layer absorbable plates in conjunction with 3D printing technology is recommended to support surgical treatment of infraorbital wall blowout fractures.

A 3-Node Co-Rotational Triangular Finite Element for Non-Smooth,Folded and Multi-Shell Laminated Composite Structures

Based on the first-order shear deformation theory,a 3-node co-rotational triangular finite element formulation is developed for large deformation modeling of non-smooth,folded and multi-shell laminated composite structures.The two smaller components of the mid-surface normal vector of shell at a node are defined as nodal rotational variables in the co-rotational local coordinate system.In the global coordinate system,two smaller components of one vector,together with the smallest or second smallest component of another vector,of an orthogonal triad at a node on a non-smooth intersection of plates and/or shells are defined as rotational variables,whereas the two smaller components of the mid-surface normal vector at a node on the smooth part of the plate or shell(away from non-smooth intersections)are defined as rotational variables.All these vectorial rotational variables can be updated in an additive manner during an incremental solution procedure,and thus improve the computational efficiency in the nonlinear solution of these composite shell structures.Due to the commutativity of all nodal variables in calculating of the second derivatives of the local nodal variables with respect to global nodal variables,and the second derivatives of the strain energy functional with respect to local nodal variables,symmetric tangent stiffness matrices in local and global coordinate systems are obtained.To overcome shear locking,the assumed transverse shear strains obtained from the line-integration approach are employed.The reliability and computational accuracy of the present 3-node triangular shell finite element are verified through modeling two patch tests,several smooth and non-smooth laminated composite shells undergoing large displacements and large rotations.

Stochastic analysis of excavation-induced wall deflection and box culvert settlement considering spatial variability of soil stiffness

In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.

A New Finite Element Model with Manufactured Error for Additive Manufacturing

Additive manufacturing(AM),adding materials layer by layer,can be used to produce objects of almost any shape or geometry.However,AM techniques cannot accurately build parts with large overhangs,especially for the large features close to horizontal,hanging over the void.The overhangs will make the manufactured model deviate from the design model,which will result in the performance of the manufactured model that cannot satisfy the design requirements.In this paper,we will propose a new finite element(FE)analysis model that includes the manufacturing errors by mimicking the AM layer by layer construction process.In such FE model,an overhang coefficient is introduced to each FE,which is defined by the support elements in the lower layer.By mimicking the AM process from the bottom layer to the top layer,all the FE properties are updated based on their overhang coefficients,which makes the computational model be able to predict the manufactured model with manufacturing errors.The proposed model can be used to predict the performance of the AM objects in the design stage,which will help the designers to improve their design by the simulation results.

3D Design and Analysis of Crushing Roller of High-pressure Grinding Roller

Crushing roller is one of the main parts of High-p re ssure Grinding Roller, which is a kind of high efficient ore crushing equipment. A kind of assembled roller, which is more convenient to renovate worn surface b y simply replacing segmented surface of the roller, was developed. The structura l models of assembled roller’s components were designed with SolidWorks softwar e based on feature modeling, these solid models of the roller were virtually ass embled. Through this work, not only was the assemble interference checked out so as to examine validity of the structure design, but also these solid models cou ld be recognized by COSMOS/Works software, through which the finite element an alysis can be done. Then the stress and displacement of the main shaft and sur face segment in two different working states were analyzed and detected quickly according to the analysis results with COSMOS/Works. In conclusion, the optimum clearance of 1.0～2.0 mm between concave-convex studded segments is determined to make the using life of assembled roller longer.

Analysis of the Magnetic Flux Density, the Magnetic Force and the Torque in a 3D Brushless DC Motor

As permanent magnet motors and generators produce torque, vibration occurs through the small air gap due to the alternating magnetic forces created by the rotating permanent magnets and the current switching of the coils. The magnetic force can be calculated from the flux density by finite element methods and the Maxwell stress tensor in cy-lindrical coordinates. In this paper the magnetic flux density, the magnetic force and the torque of a real three dimen-sional brushless DC motor are simulated using Maxwell 3 D V 11.1.

NaF-AlF_(3)体系热导率的有限元数值模拟

固态/液态铝电解质热导率是开展铝电解槽热平衡计算的重要参数,对预测电解槽侧壁上的电解质炉帮厚度变化具有重要意义。本文采取传感器测量与有限元数值模拟相结合的方法,开发研究了一种确定熔盐热导率的新方法。使用ANSYS/Fluent软件中的流体体积模块、离散坐标辐射模块和熔化/凝固模块对传感器冷却过程的热行为进行数值模拟,以测试值和模拟值的残差分析为标准来确定铝电解质的热导率。研究结果表明,该方法对单组元熔盐的热导率和双组元熔盐的热导率的计算都有效。利用该方法,建立了NaF-AlF_(3)体系的固态热导率和熔融态热导率的温度分段函数方程,用于计算该体系随着分子比变化和温度变化的热导率,计算结果与文献数据良好吻合。

Numerical Investigation of Laser Surface Hardening of AISI 4340 Using 3D FEM Model for Thermal Analysis of Different Laser Scanning Patterns

Laser surface hardening is becoming one of the most successful heat treatment processes for improving wear and fatigue properties of steel parts. In this process, the heating system parameters and the material properties have important effects on the achieved hardened surface characteristics. The control of these variables using predictive modeling strategies leads to the desired surface properties without following the fastidious trial and error method. However, when the dimensions of the surface to be treated are larger than the cross section of the laser beam, various laser scanning patterns can be used. Due to their effects on the hardened surface properties, the attributes of the selected scanning patterns become significant variables in the process. This paper presents numerical and experimental investigations of four scanning patterns for laser surface hardening of AISI 4340 steel. The investigations are based on exhaustive modelling and simulation efforts carried out using a 3D finite element thermal analysis and structured experimental study according to Taguchi method. The temperature distribution and the hardness profile attributes are used to evaluate the effects of heating parameters and patterns design parameters on the hardened surface characteristics. This is very useful for integrating the scanning patterns’ features in an efficient predictive modeling approach. A structured experimental design combined to improved statistical analysis tools is used to assess the 3D model performance. The experiments are performed on a 3 kW Nd:Yag laser system. The modeling results exhibit a great agreement between the predicted and measured values for the hardened surface characteristics. The model evaluation reveals also its ability to provide not only accurate and robust predictions of the temperature distribution and the hardness profile as well an in-depth analysis of the effects of the process parameters.

Evaluation of labial versus labio-inferior lines of osteosynthesis using 3D miniplate for fractures of anterior mandible:A finite element analysis with a pilot clinical trial

Purpose:The fractures of anterior mandible are subject to severe torsional forces due to muscles acting in opposite directions.3D miniplate has been suggested as a good alternative by some researchers.However,finite element model(FEM)studies indicate that labio-inferior positioning of two miniplates perpendicular to each other offers better stability as compared to labial positioning.This study aims at combining the advantages of a single 3D miniplate and labio-inferior positioning of two conventional miniplates,which was assessed by finite element analysis along with a pilot clinical trial.Methods:Two FEM models were created using CT data of a 24-year-old patient with Angie class I occlusion:control model with labial plating and study model with labio-inferior plating.The models were processed with MIMICS.(materialise,Leuven,Belgium),CATIA.(Dassault Systemes)and finite element analysis softwares.Parameters adopted for analysis were(1)displacement(mm)of fracture fragments during each screw fixation,(2)lingual splay and post fixation stability of fracture fragments with masticatory load,and(3)stress distribution(MPa)across fracture fragments.Moreover,a pilot clinical trial including five patients with anterior mandible fracture was conducted.The fractures were managed by intraoral open reduction and 3D miniplate fixation in labio-inferior position.Intraoperative interfragmentary gap,post fixation lingual splay and radiographic fracture union and complications were assessed clinically.Results:Labio-inferior plating demonstrated less displacement(mm)of fracture fragments during screw fixation(0.059 vs.0.079)as well as after application of masticatory load(1.805 vs.1.860).Negligible lingual splay and less stress distribution(MPa)across fracture fragments(1.860 vs.1.847)were appreciated in the study group as compared to control group.Clinical trial support the favorable outcome related to intraoperative and postoperative assessment parameters.Conclusion:FEM analysis and clinical trial reveal better results with labio-inferior positioning of 3D miniplate when compared to labial positioning.

3-D Modelling of the Confederation Bridge Using Data of Full Scale Tests

Long-span bridges are special structures that require advanced analysis techniques to examine their performance. This paper presents a procedure developed to model the Confederation Bridge using 3-D beam elements. The model was validated using the data collected before the opening of the bridge to the public. The bridge was instrumented to conduct fullscale static and dynamic tests. The static tests were to measure the deflection of the bridge pier while the dynamic tests to measure the free vibrations of the pier due to a sudden release of the static load. Confederation Bridge is one of the longest reinforced concrete bridges in the world. It connects the province of Prince Edward Island and the province of New Brunswick in Canada. Due to its strategic location and vital role as a transportation link between these two provinces, it was designed using higher safety factors than those for typical highway bridges. After validating the present numerical model, a procedure was developed to evaluate the performance of similar bridges subjected to traffic and seismic loads. It is of interest to note that the foundation stiffness and the modulus of elasticity of the concrete have significant effects on the structural responses of the Confederation Bridge.

硬质相形状对Ti-Al_(3)Ti仿生复合材料断裂行为影响的数值模拟研究

Al_(3)Ti具有低密度、高硬度等特点,然而,由于其具有较高的脆性,导致较小的变形下便会发生破碎。为了提高Al_(3)Ti的应用范围,受生物结构的启发,根据贝壳珍珠层、海螺壳和鱼鳞的几何结构,建立了Ti-Al_(3)Ti仿生有限元计算模型,研究了硬质相形状和加载速度对材料断裂的影响,从断裂行为、裂纹扩展过程和吸能效果等角度分析仿生复合材料的抗断裂机理。定义了形状系数,并对结构进行优化设计。结果表明,在准静态条件下,硬质相形状对仿珍珠层试样的断裂行为有显著影响。长方形硬质相能更好地抑制裂纹向载荷端扩展,从而提高试样的承载能力。形状系数在5.0左右的试样表现出最优的抗断裂能力和吸能效果。在动态冲击条件下,软质相抑制裂纹扩展的能力增强,使长方形试样的抗断裂能力和吸能效果得到进一步提高。

过渡层TiO_(2)含量对2197铝锂合金/Al_(2)O_(3)-TiO_(2)复合涂层等离子喷涂残余应力影响的有限元分析

采用有限元模拟方法,研究了成分分别为Al_(2)O_(3)-10%TiO_(2)、Al_(2)O_(3)-20%TiO_(2)、Al_(2)O_(3)-30%TiO_(2)和Al_(2)O_(3)-40%TiO_(2)的过渡涂层对以2197铝锂合金为基底、NiAl为粘结层和以Al_(2)O_(3)-5%TiO_(2)为陶瓷顶层的整体模型残余应力的影响及其规律。结果表明,随着过渡层TiO_(2)含量的增加,喷涂涂层的等效残余应力急剧增大。过渡层TiO_(2)含量对过渡层与粘结层界面径向残余应力影响最大:随过渡层TiO_(2)含量从10%增加到40%,该区域最大径向残余拉应力由1.74 MPa增加到5.33 MPa。过渡层TiO_(2)含量对过渡层与顶层界面残余应力影响较小。最大径向残余应力出现在陶瓷顶层的轴心位置,最大轴向残余应力集中在涂层结合界面接近边缘的区域。工业上建议使用TiO_(2)含量较少的过渡层以减小喷涂涂层的残余应力,提升喷涂涂层的强度。

超快激光制备高频1-3型PIN-PMN-PT复合材料超声换能器

与其他压电材料相比,1-3型压电单晶复合材料具有优异的压电性能和更匹配的声学特性,更有利于制备出性能优异的超声换能器。该文通过有限元软件COMSOL对复合材料的振动模态及阻抗特性进行了系统的研究,同时采用皮秒激光制备了高频1-3型Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PIN-PMN-PT)铁电单晶/环氧树脂复合材料,并进行了性能表征。该1-3复合材料机电耦合系数为0.65,声阻抗为19.96 MRayls。该复合材料可用于制备高频超声换能器,结果表明,换能器中心频率为17.68 MHz,-6 dB带宽为84.38%,插入损耗为-25.4 dB。

金刚石线锯锯切β-Ga_(2)O_(3)晶体应力场分析

作为典型的硬脆材料,氧化镓晶体(β-Ga_(2)O_(3))加工时易裂解。金刚石线锯是生产β-Ga_(2)O_(3)晶片的主要方式,切片加工过程中会在晶片表面产生微裂纹损伤层,应力作用下微裂纹会发生扩展,导致材料破碎和断裂。本文建立了金刚石线锯多线切割β-Ga_(2)O_(3)(010)晶面的有限元模型,研究了锯切过程中机械应力、热应力和热力耦合应力的分布变化规律,分析了锯丝速度、进给速度和恒速比下不同参数组合对热力耦合应力的影响。结果表明,锯切过程中锯切热产生的热应力占据热力耦合应力的主导地位,锯切力引起的机械应力占比较小,但机械应力会影响热力耦合应力的分布情况,锯丝速度和进给速度的增加会引起热力耦合应力的增加。