An Innovative Finite Element Geometric Modeling of Single-Layer Multi-Bead WAAMed Part

Finite element (FE) coupled thermal-mechanical analysis is widely used to predict the deformation and residualstress of wire arc additive manufacturing (WAAM) parts. In this study, an innovative single-layermulti-bead profilegeometric modeling method through the isosceles trapezoid function is proposed to build the FE model of theWAAMprocess. Firstly, a straight-line model for overlapping beads based on the parabola function was establishedto calculate the optimal center distance. Then, the isosceles trapezoid-based profile was employed to replace theparabola profiles of the parabola-based overlapping model to establish an innovative isosceles trapezoid-basedmulti-bead overlapping geometric model. The rationality of the isosceles trapezoid-based overlapping model wasconfirmed by comparing the geometric deviation and the heat dissipation performance index of the two overlappingmodels. In addition, the FE-coupled thermal-mechanical analysis, as well as a comparative experiment of thesingle-layer eight-bead deposition process show that the simulation results of the above two models agree with theexperimental results. At the same time, the proposed isosceles trapezoid-based overlappingmodels are all straightlineprofiles, which can be divided into high-quality FE elements. It can improve the modeling efficiency andshorten the simulation calculation time. The innovative modeling method proposed in this study can provide anefficient and high-precision geometricmodelingmethod forWAAMpart FE coupled thermal-mechanical analysis.

An ultrasound-guided percutaneous electrical nerve stimulation regimen devised using finite element modeling promotes functional recovery after median nerve transection

Percutaneous electrical nerve stimulation of an injured nerve can promote and accelerate peripheral nerve regeneration and improve function.When performing acupuncture and moxibustion,locating the injured nerve using ultrasound before percutaneous nerve stimulation can help prevent further injury to an already injured nerve.However,stimulation parameters have not been standardized.In this study,we constructed a multi-layer human forearm model using finite element modeling.Taking current density and activated function as optimization indicators,the optimal percutaneous nerve stimulation parameters were established.The optimal parameters were parallel placement located 3 cm apart with the injury site at the midpoint between the needles.To validate the efficacy of this regimen,we performed a randomized controlled trial in 23 patients with median nerve transection who underwent neurorrhaphy.Patients who received conventional rehabilitation combined with percutaneous electrical nerve stimulation experienced greater improvement in sensory function,motor function,and grip strength than those who received conventional rehabilitation combined with transcutaneous electrical nerve stimulation.These findings suggest that the percutaneous electrical nerve stimulation regimen established in this study can improve global median nerve function in patients with median nerve transection.

Effect of surface retaining elements on rock stability:laboratory investigation with sand powder 3D printing

This study aims to investigate the benefcial efects of surface retaining elements (SREs) on the mechanical behaviors of bolted rock and roadway stability. 3D printing (3DP) technology is utilized to create rock analogue prismatic specimens for conducting this investigation. Uniaxial compression tests with acoustic emission (AE) and digital image correlation techniques have been conducted on 3DP specimens bolted with diferent SREs. The results demonstrate that the strength and modulus of elasticity of the bolted specimens show a positive correlation with the area of the SRE;the AE characteristics of the bolted specimens are higher than those of the unbolted specimen, but they decrease with an increase in SRE area, thus further improving the integrity of the bolted specimens. The reinforcement efect of SREs on the surrounding rock of roadways is further analyzed using numerical modelling and feld test. The results provide a better understanding of the role of SREs in rock bolting and the optimization of rock bolting design. Furthermore, they verify the feasibility of 3DP for rock analogues in rock mechanics tests.

滇西保山地块金厂河Fe-Cu-Pb-Zn矽卡岩型多金属矿床黑柱石成因及地质意义

黑柱石是一种矽卡岩型铅锌及铁矿床中少见的矿物,与铅锌矿体、磁铁矿体关系密切。为查明黑柱石成矿过程中与铅锌铁铜多金属成矿作用的关系,本文对金厂河Fe-Cu-Pb-Zn多金属矿床中的黑柱石产状、矿物共生组合、化学成分、分带性等开展了研究。根据电子探针数据计算可得,金厂河矿区黑柱石的化学式为:Ca_(0.95-1.08)(Fe_(0.87-1.97)Mn_(0.08-0.36)Mg_(0.01-0.06))^(2+)_((1.89-2.03))(Fe_(0.82-1.04)Al_(0.01-0.03))^(3+)_((0.88-1.15))[Si_(1.94-2.08)O_(7)]O(OH)。结合矿物组合类型、产状、分带特征等,推测矿床内矽卡岩由内带逐渐向外带交代的趋势。金厂河矿区主要有3种矿物共生组合:黑柱石+磁铁矿组合,黑柱石+磁铁矿+黄铁矿+黄铜矿组合,黑柱石+方铅矿+闪锌矿+黄铜矿组合,分别对应三个不同的蚀变阶段:晚期矽卡岩阶段(代表组合Ⅰ),以石榴子石的分解为主,形成大量的黑柱石;退蚀变阶段(代表组合Ⅱ),以阳起石、黄铜矿、黄铁矿发育为主;石英-硫化物阶段(代表组合Ⅲ),以发育大量的方铅矿、闪锌矿为主,同时这一阶段内黑柱石分解,形成阳起石、方解石、磁铁矿等。此外,黑柱石的稀土元素配分模式与石榴子石的类似,一定程度上保留了石榴子石的稀土元素特征。研究认为:黑柱石是早期石榴子石退化分解的产物,矿床自内向外逐渐交代,形成了铅锌铜矿体中以锰质黑柱石为主,而磁铁矿体、铜矿体中以含锰黑柱石为主的分带特性。锰质黑柱石有利于铅锌矿的形成,而对于磁铁矿有贫化的影响,同时也可为矿区揭露中酸性岩体和深部找矿提供重要科学意义。

基于纳米压痕反向分析的Fe-32Ni超因瓦合金介观尺度弹塑性本构关系

采用纳米压痕技术和电子背散射衍射分析技术对Fe-32Ni超因瓦合金不同取向的晶粒进行了测试,得到了材料在(001)、(101)和(111)取向下的弹性模量和硬度。同时基于量纲分析提出了一种改进的反向算法,并结合有限元仿真对Fe-32Ni超因瓦合金的纳米压痕过程进行了反向分析和计算,通过纳米压痕实验曲线与仿真曲线的对比,最终获得材料在(001)、(101)和(111)取向下的应力应变关系,结果表明:(001)取向下晶粒的屈服强度最高,(101)取向下晶粒的屈服强度最低。此外,(101)和(111)取向的晶粒屈服后的应力-应变曲线变化趋势较为一致,而(001)取向下的应力-应变曲线变化较为平缓,材料在不同取向下的力学响应具有明显的各向异性。

The Effect of Ligament Modeling Technique on Knee Joint Kinematics: A Finite Element Study

Finite element (FE) analysis has become an increasingly popular technique in the study of human joint biomechanics, as it allows for detailed analysis of the joint/tissue behavior under complex, clinically relevant loading conditions. A wide variety of modeling techniques have been utilized to model knee joint ligaments. However, the effect of a selected constitutive model to simulate the ligaments on knee kinematics remains unclear. The purpose of the current study was to determine the effect of two most common techniques utilized to model knee ligaments on joint kinematics under functional loading conditions. We hypothesized that anatomic representations of the knee ligaments with anisotropic hyperelastic properties will result in more realistic kinematics. A previously developed, extensively validated anatomic FE model of the knee developed from a healthy, young female athlete was used. FE models with 3D anatomic and simplified uniaxial representations of main knee ligaments were used to simulate four functional loading conditions. Model predictions of tibiofemoral joint kinematics were compared to experimental measures. Results demonstrated the ability of the anatomic representation of the knee ligaments (3D geometry along with anisotropic hyperelastic material) in more physiologic prediction of the human knee motion with strong correlation (r ≥ 0.9 for all comparisons) and minimum deviation (0.9° ≤ RMSE ≤ 2.29°) from experimental findings. In contrast, non-physiologic uniaxial elastic representation of the ligaments resulted in lower correlations (r ≤ 0.6 for all comparisons) and substantially higher deviation (2.6°≤ RMSE ≤ 4.2°) from experimental results. Findings of the current study support our hypothesis and highlight the critical role of soft tissue modeling technique on the resultant FE predicted joint kinematics.

Discrete Element Modelling of Damage Evolution of Concrete Considering Meso-Structure of ITZ

The mechanical properties of interfacial transition zones(ITZs)have traditionally been simplified by reducing the stiffness of cement in previous simulation methods.A novel approach based on the discrete element method(DEM)has been developed for modeling concrete.This new approach efficiently simulates the meso-structure of ITZs,accurately capturing their heterogeneous properties.Validation against established uniaxial compression experiments confirms the precision of thismodel.The proposedmodel canmodel the process of damage evolution containing cracks initiation,propagation and penetration.Under increasing loads,cracks within ITZs progressively accumulate,culminating in macroscopic fractures that traverse themortarmatrix,forming the complex,serpentine path of cracks.This study reveals four distinct displacement patterns:tensile compliant,tensile opposite,mixed tensile-shear,and shear opposite patterns,each indicative of different stages in concrete’s damage evolution.The widening angle of these patterns delineates the progression of cracks,with the tensile compliant pattern signaling the initial crack appearance and the shear opposite pattern indicating the concrete model’s ultimate failure.

Influence of Various Earth-Retaining Walls on the Dynamic Response Comparison Based on 3D Modeling

The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement concrete facing panels,and gravity-type earth-retaining walls.The finite element(FE)simulations utilized a 3D plane strain condition to model full-scale ER walls and numerous nonlinear dynamics analyses.The seismic performance of differentmodels,which includes reinforcement concrete panels and gravity-type and hollowprecast concrete ER walls,was simulated and examined using the FE approach.It also displays comparative studies such as stress distribution,deflection of the wall,acceleration across the wall height,lateral wall displacement,lateral wall pressure,and backfill plastic strain.Three components of the created ER walls were found throughout this research procedure.One is a granular reinforcement backfill,while the other is a wall-facing panel and base foundation.The dynamic response effects of varied earth-retaining walls have also been studied.It was discovered that the facing panel of the model significantly impacts the earthquake-induced displacement of ER walls.The proposed analytical model’s validity has been evaluated and compared with the reinforcement concrete facing panels,gravity-type ER wall,scientifically available data,and American Association of State Highway and Transportation Officials(AASHTO)guidelines results based on FE simulation.The results of the observations indicate that the hollow prefabricated concrete ER wall is the most feasible option due to its lower displacement and high-stress distribution compared to the two types.The methodology and results of this study establish standards for future analogous investigations and professionals,particularly in light of the increasing computational capabilities of desktop computers.

Implementation of a particle-in-cell method for the energy solver in 3D spherical geodynamic modeling

The thermal evolution of the Earth’s interior and its dynamic effects are the focus of Earth sciences.However,the commonly adopted grid-based temperature solver is usually prone to numerical oscillations,especially in the presence of sharp thermal gradients,such as when modeling subducting slabs and rising plumes.This phenomenon prohibits the correct representation of thermal evolution and may cause incorrect implications of geodynamic processes.After examining several approaches for removing these numerical oscillations,we show that the Lagrangian method provides an ideal way to solve this problem.In this study,we propose a particle-in-cell method as a strategy for improving the solution to the energy equation and demonstrate its effectiveness in both one-dimensional and three-dimensional thermal problems,as well as in a global spherical simulation with data assimilation.We have implemented this method in the open-source finite-element code CitcomS,which features a spherical coordinate system,distributed memory parallel computing,and data assimilation algorithms.

考虑材料参数空间变异性的SBFEM开裂模拟

论文建立了基于比例边界有限元法(scaled boundary finite element methods,SBFEM)框架的非局部宏微观损伤模型,考虑材料细观物理参数的空间变异性,探讨了材料参数的空间变异性对结构开裂过程的影响。结果表明:考虑材料参数空间变异性后,裂纹扩展路径具有不确定性,建议的模型能够很好地反应材料内在的随机性;随着结构受力情况的复杂化和结构本体缺陷的增多,裂纹开裂模式的变异性也会增大。自相关长度和参数变异系数对结构开裂分析结果有重要影响。

Finite Element Analysis in Combination with Perfectly Matched Layer to the Numerical Modeling of Acoustic Devices in Piezoelectric Materials

The characterization of finite length Surface Acoustic Wave (SAW) and Bulk acoustic Wave (BAW) resonators is addressed here. The Finite Element Analysis (FEA) induces artificial wave reflections at the edges of the mesh. In fact, these ones do not contribute in practice to the corresponding experimental response. The Perfectly Matched Layer (PML) method, allows to suppress the boundary reflections. In this work, we first demonstrate the basis of PML adapted to FEA formalism. Next, the results of such a method are depicted allowing a discussion on the behavior of finite acoustic resonators.

Hip Fracture Risk Assessment Based on Different Failure Criteria Using QCT-Based Finite Element Modeling

Precise evaluation of hip fracture risk leads to reduce hip fracture occurrence in individuals and assist to check the effect of a treatment.A subject-specific QCT-based finite element model is introduced to evaluate hip fracture risk using the strain energy,von-Mises stress,and von-Mises strain criteria during the single-leg stance and the sideways fall configurations.Choosing a proper failure criterion in hip fracture risk assessment is very important.The aim of this study is to define hip fracture risk index using the strain energy,von Mises stress,and von Mises strain criteria and compare the calculated fracture risk indices using these criteria at the critical regions of the femur.It is found that based on these criteria,the hip fracture risk at the femoral neck and the intertrochanteric region is higher than other parts of the femur,probably due to the larger amount of cancellous bone in these regions.The study results also show that the strain energy criterion gives more reasonable assessment of hip fracture risk based on the bone failure mechanism and the von-Mises strain criterion is more conservative than two other criteria and leads to higher estimate of hip fracture risk indices.

Contribution to the Full 3D Finite Element Modelling of a Hybrid Stepping Motor with and without Current in the Coils

The paper presents our contribution to the full 3D finite element modelling of a hybrid stepping motor using COMSOL Multiphysics software. This type of four-phase motor has a permanent magnet interposed between the two identical and coaxial half stators. The calculation of the field with or without current in the windings (respectively with or without permanent magnet) is done using a mixed formulation with strong coupling. In addition, the local high saturation of the ferromagnetic material and the radial and axial components of the magnetic flux are taken into account. The results obtained make it possible to clearly observe, as a function of the intensity of the bus current or the remanent induction, the saturation zones, the lines, the orientations and the magnetic flux densities. 3D finite element modelling provide more accurate numerical data on the magnetic field through multiphysics analysis. This analysis considers the actual operating conditions and leads to the design of an optimized machine structure, with or without current in the windings and/or permanent magnet.

高Ce含量RE-Fe-B烧结磁体元素分布与磁性能研究

为了开发具有商业价值的高Ce含量RE-Fe-B磁体,提高高丰度稀土Ce的利用率,对不同Ce替代量RE-Fe-B磁体的磁性能和微观结构进行了研究。实验结果表明,Ce/(Ce+Nd)质量分数达到40%的双主相磁体仍保持着优良的磁性能,剩磁Br达到1.31 T,最大磁能积(BH)_(max)达到310.56 kJ/m^(3)。在Ce替代量为40%的单、双主相磁体中,Nd和Ce元素的置换行为存在差异,单、双主相磁体中Nd元素均偏向于进入主相晶粒,Ce元素则趋于聚集在晶界相或主相晶粒表层,且在双主相磁体中形成贫Ce主相和接近名义成分的(Nd_(0.6)Ce_(0.4))_(30.5)(Fe,M)_(bal)B_(0.97)主相。通过观察磁畴翻转分析了单、双主相磁体的磁化行为,研究了双主相磁体矫顽力增强机制:贫Ce主相的高各向异性场对富Ce主相的磁矩起到了钉扎作用。Nd和Ce元素扩散行为的研究为制备高Ce含量、高磁性能的商业化RE-Fe-B磁体提供了依据。

Modeling the 3D Terrain Effect on MT by the Boundary Element Method

A numerical method is put forward in this paper, using the boundary element method (BEM) to model 3D terrain effects on magnetotelluric (MT) surveys. Using vector integral theory and electromagnetic field boundary conditions, the boundary problem of two electromagnetic fields in the upper half space (air) and lower half space (earth medium) was transformed into two vector integral equations just related to the topography: one magnetic equation for computing the magnetic field and the other electrical equation for computing the electrical field. The topography integral is decomposed into a series of integrals in a triangle element. For the integral in a triangle element, we suppose that the electromagnetic field in it is the stack of the electromagnetic field in the homogeneous earth and the topography response which is a constant; so the computation becomes simple, convenient and highly accurate. By decomposition and computation, each vector integral equation can be calculated by solving three linear equations that are related to the three Cartesian directions. The matrix of these linear equations is diagonally dominant and can be solved using the Symmetric Successive Over-Relaxation (SSOR) method. The apparent resistivity curve of MT on two 3D terrains calculated by BEM is shown in this paper.

Cr元素掺杂对Fe-C-Mn-Al系轻质钢的影响研究进展

Fe-C-Mn-Al系轻质钢具有良好的耐腐蚀性、低密度和优异的综合力学性能,在钢中添加合金元素会显著影响相变热力学与动力学,进一步影响并决定组织形貌的演化过程.添加Cr元素会对Fe-C-Mn-Al系轻质钢微观组织产生显著作用,重点对添加不同含量的Cr元素后,对κ-碳化物、β-Mn和DO_(3)等相生长、晶粒尺寸变化及晶界角度的改变,促进Al_(2)O_(3)及含Cr氧化物的生成,以及提高Fe-C-Mn-Al系轻质钢抗拉强度、耐腐蚀性和抗氧化性等性能的情况进行分析.并归纳总结了Cr元素的加入及不同含量的Cr元素给Fe-C-Mn-Al系轻质钢带来的优势,同时对当前的发展趋势进行展望.

Rapid Modeling and Finite Element Analysis of Missile Stiffener

Stiffener is the important missile structure to ensure the structural strength of the missile. In order to improve the design efficiency and the quality of the missile stiffener, the methods of missile stiffener rapid modeling and analysis are proposed. First, the problems of traditional manual modeling of the stiffener are analyzed. According to the problems and actual requirement of modeling, volume decomposition method is used to divide the stiffener into the upper section, the lower section and the web in order for feature analysis and parameter extraction. Then based on the parameters the basic unit decomposed above is created for Boolean operation to establish the stiffener. Finally, a rapid stiffener modeling and analysis program were developed based on UG Open API, the modeling and analysis result validates the feasibility of the method.

XFEM和修正剑桥模型模拟高聚物劈裂注浆方法研究

针对自膨胀高聚物材料在土体中劈裂扩散仿真手段尚不完备的现状,初步建立了一种模拟高聚物对土体劈裂压密作用的仿真方法。该方法采用扩展有限元离散求解区域土体介质,用修正剑桥模型描述土体力学特性,利用高聚物密度-围压关系迭代计算作用于裂缝面的浆液膨胀压力,实现了对土体劈裂缝扩展过程的数值模拟,通过与试验结果的对比验证了该方法的适用性。算例分析表明,应用该方法能够模拟膨胀力作用下土体裂缝启裂过程、扩展走向和浆脉厚度变化,获得裂缝周围土体变形模量、孔隙比、应力场和密度场分布特征,为深入研究膨胀性高聚物注浆材料对土体劈裂压密机制奠定了基础。

基于GP14.3运动学混合震源模型和SPECFEM 3D谱元法的宽频地震动模拟

基于确定性物理模型的全过程地震动模拟是现代地震工程的重要发展方向.然而受限于合理震源模型和计算资源需求,目前模拟的有效频率还多处于低频范围,难以满足工程结构敏感频带(5~10 Hz或更高)需求.本文即借助运动学混合震源模型能激发宽频地震波和谱元法空间高精度及计算收敛快的优势,首先将确定性的凹凸体震源模型与GP14.3随机震源模型结合得到有限断层运动学混合震源模型,进而将上述混合震源模型开发到SPECFEM 3D谱元法开源代码中,实现了基于谱元法和运动学混合震源模型的全过程宽频带地震动模拟.将方法首先应用于一维波速结构模型0~10 Hz地震动模拟,通过与频率波数域(FK)方法结果进行比较,验证了方法的精度;进而应用于2021年5月21日云南漾濞6.4级地震0.1~5 Hz地震动模拟,通过与4个台站的时程记录和相应反应谱的比较,以及与NGA-West2地震动衰减方程在频率0.1~5 Hz的反应谱的比较,检验了方法的适用性;最后给出了漾濞地区的地震动峰值加速度(PGA)和峰值速度(PGV)云图,分析了漾濞地震下近场强地面运动的空间分布特征.结果显示,震中PGA接近400 cm·s-2,PGV达到45 cm·s^(-1),烈度达到Ⅸ度,且受局部地形起伏影响,大理以及洱海西侧位置出现高烈度异常区.

AUTOMATIC FINIT EELEMENT MODELING OF A WING

研究了建立机翼有限元模型的自动化。用行列法标识结构的部件（肋、梁、蒙皮、立柱），并用简单明了的表格界面来输入所有部件的几何、网格密度、材料、载荷、边界条件等参数。设计并用ＰＣＬ（ＰＡＴＲＡＮｃｏｍｍａｎｄｌａｎｇｕａｇｅｕｎｄｅｒＰＡＴＲＡＮ６．０）编制了相应的自动化建立整个机翼有限元模型的用户化程序模块。作为算例建立了ＶＦＷ６１４机翼的有限元模型并用ＮＡＳＴＲＡＮ６８进行了计算。结果表明，本方法有效和高效。