轮胎-路面三维力解析模型的建立与简化方法

研究轮胎-路面之间的三维作用力,对预测路面早期损坏、优化道路设计具有指导作用,同时也是分析车辆动力学性能、研制和改进整车控制系统的有效手段.文中利用ABAQUS有限元仿真软件,建立了轮胎与路面之间相互作用力与胎冠相对轮辋中心位移之间的力-位移多元非线性回归模型;该模型通过分析在三维力作用下轮胎不同位置处节点的变形和位移,实现了不同节点处的轮胎与路面之间作用力的求解,并通过改变充气断面尺寸、不同载荷下沉量等指标使模型有效性得到了验证,为设计并优化位移传感器的布局、提高测量结果的可信度,提供了理论依据.采用带有二次项的多元非线性回归模型对11.00R20载重子午线轮胎进行仿真计算.结果表明,在接地中心角θ不超过±15°范围内,回归模型的三维力预测值相对于预设值的误差不超过±2%.为在兼顾回归模型准确度的前提下,提高该模型的解算效率、降低由位移解算力过程的繁琐性,通过分析完整模型中各子项对力预测结果的贡献度,进一步提出了简化回归模型;当θ≤±15°时,各个节点处完整模型与简化模型均方根误差(RMSE)的最大值相差0.43 kN;当θ≤±9°时,两者差值减小至0.27 kN.分析结果表明,通过对安装在轮胎上的位移传感器所采集的数据进行处理,完整模型和简化模型均能实现轮胎与路面间相互作用三维力的预测和计算,但简化模型的适用范围比完整模型要窄.

重力坝坝基稳定三维地质力学模型试验研究

采用三维地质力学模型运用超载与强度储备相结合的研究方法进行了坝基稳定破坏试验 ,获得了坝基失稳破坏过程、破坏形态和破坏机理 ,经分析得到两个坝段的综合稳定安全度K为 3.3。同时提出了对坝基相应部位进行灌浆和提高灌浆质量以及对下游蚀变带和F6断层加深混凝土塞等加固处理建议。

一个评估髋关节生物力学属性的三维静力模型

为了评估人体髋关节生物力学属性,通过建立一个三维静态人体髋关节生物力学普适模型,并以人体单足静立状态为例,计算和分析了髋关节处的峰值应力、承载区域、应力分布等生物力学属性;通过与文献比较,显示本模型具有较好的可靠性;所建立的人体髋关节生物力学普适模型,可有效地应用于临床髋关节生物力学分析,从而为揭示骨盆骨性几何参数与髋关节接触力与应力分布间的本质关系、为临床治疗髋关节疾病等提供科学的理论依据.

代表/参与——三维领导力模型的新构面

领导力理论是管理理论的重要组成部分。本文回顾了西方领导力模型的发展,讨论了这些模型在西方和亚洲国家使用的局限性。针对文化因素的缺失,提出了“代表/参与”构面,建立了一个新的领导力三维模型。新的三维领导力模型与文化管理的模式相适应,丰富和发展了企业文化的内涵。原文作者乔治·费舍尔是澳大利亚国立大学的讲师,他的研究方向集中在国际化管理,国际背景下的领导力,电子商务的人力资源等。

数字乡村建设中县级党组织数字治理能力研究

数字乡村建设是新时代我国实施乡村振兴战略的重要方向。在借鉴国内外研究的基础上,以“三维九力”理论模型,构建资源—过程—目标三要素分析框架。资源要素维度的数字治理能力包括数字基础能力、数字人才能力和数字素养能力;过程要素维度的数字治理能力包括数字统领能力、数字规范能力和数字服务能力;目标要素维度的数字治理能力包括数字赋能能力、数字创新能力和数字包容能力。同时,县级党组织数字治理能力具有目标价值的多元性、能力结构的层级性以及数字技术的依赖性等特征,能够为数字乡村建设提供有效支撑。

服装PVC(利、量、持续力)模型管理的企业表现分析

基于PVC(利、量、持续力)三维模型,通过对服装企业管理中的财务、商务流程等主要元素的分析,结合案例剖析的形式,依据企业现状结合内外环境制定战略目标、实施计划进行企业表现(竞争力)和PVC系统因果链分析,力求为服装企业提供可持续发展管理方案,提高企业的市场竞争力.

基于力学模型的同心鼓动态调整策略

本文是对2019年全国大学生数学建模竞赛B题的解答和进一步研究.本文对排球撞击鼓面过程进行受力分析,并建立受力模型,给出了进行同心鼓游戏的最优策略.该策略结合实际情况,确定了队员的站位策略,拉力组合策略,及在球偏离竖直平面时的动态调整策略.在问题一中,在不产生人为失误的情况下,以人在同等体能下,能连续颠起更多的球为优化目标;通过受力分析,给出队员站位策略.在问题二中,考虑队员失误的情况,利用题目给定的数据集,计算不同情况下队员失误产生的鼓面倾斜角.在问题三中,结合现实情况下失误的情况,对问题一的策略进行调整,给出具有容错性的动态调整策略.在问题四中,给出在球偏移竖直方向时,为使球回到竖直方向的颠球策略.

基于TESSYS技术下14岁青少年脊柱L4~5节段椎间孔成形术后有限元分析

目的建立14岁青少年正常脊柱L3~L5节段三维有限元模型,分析不同程度腰椎间孔成形术后腰椎生物力学变化情况,为青少年椎间孔成形术改良提供参考。方法选择1名既往无腰椎病史的14岁女性志愿者,收集腰椎(L)CT影像数据导入Mimics 16.0软件建立模型,利用ABAQUS软件进行有限元模型受力分析。在正常脊柱L3~L5节段模型M的基础上建立M1(磨除L5左上关节突面积1/4)、M2(磨除L5左上关节突面积1/3)、M3(磨除L5左上关节突面积1/2)模型。在中立位及前屈、后伸等6种加载工况下测定相应节段关节突关节应力并进行比对分析。结果建立的三维有限元模型有效,方差分析模型有效。模型M1中,L5左上关节突在后伸、右旋转工况加载下应力值与模型M中应力值对比差异有统计学意义(P<0.05);模型M2中,L4左上关节突在左侧屈、工况加载下应力值与模型M中应力值对比差异有统计学意义(P<0.05);模型M3中,L4左上关节突在后伸工况,L5左上关节突在左侧屈、右侧屈、右旋转工况,L4右上关节突在右侧屈、右旋转工况,L5右上关节突在后伸、左侧屈、左旋转工况加载下应力值与模型M关节突应力值对比差异有统计学意义(P<0.05)。结论青少年椎间孔成形时,切除腰椎单侧单节段上关节突内侧面积1/2及以上时明显破坏腰椎生物力学稳定性,临床应慎重切除超过1/2以上的关节突关节面,以免导致腰椎不稳。

条带开采中条带煤柱塑性区宽度分析

根据煤的变形破坏特点，对煤变形采用弹塑性应变软化模型，根据条带开采的特殊性，用三维受力单元模型来分析。通过数学运算推导出条带煤柱塑性区应力及宽度的表达式。最后，对影响塑性区宽度的几个主要因素作了分析。

INCLINED LAMINAL COMBINATION MODEL OF 3D BRAIDED COMPOSITES

As an advanced composite material, the 3D braided composite has received more and more attention in foreign countries. However, it has received less attention in China. The geometric unit cell which can describe the basic structure and the relationship between the braiding angle and geometric parameters of the fabric and fiber volume ratio are given in this paper based on two 3D braiding processes, namely, the four-step and the twostep ones. Several existing mechanical models to predict groperties of the 3D braided comPOsites are discussed and their shortcomings are pointed out herein. Then a new model called the inclined laminal combination model is proposed, which is based on the classical laminated plate theory and can predict the basic mechanical behavior of the two 3D braided composites with four-step or two-step braid. In the model, each yarn in the unit cell is regarded as an inclined laminate and then a 3D analysis is performed. It is found that the predicted mechanical properties of the 3D braided composites by the proposed model are compared well with the experimental data.

Modeling transportation of suspended solids in Zhujiang River estuary, South China

A three-dimensional transportation model for suspended solids (SS) in Zhujiang (Pearl) River estuary, South China, was developed by coupling with a three-dimensional hydrodynamic model. The model was validated using hourly measured data of sediment contents during 25–26, July 1999. The results showed that modeled contents matched well with measured ones and that the modeled top layer distribution agreed with the remotely sensed image of suspended solids in summer. The modeled results showed clearly the layers of sus- pended solids in depth, with larger sediment contents in lower layers though in the interface between salt water and freshwater the lowest contents appeared in middle layer. In overall, the suspended solids inflow from 8 rivers, transport southwestward, and carried by strong coastal flow in Zhujiang River estuary. Contours of sediment contents in the estuary spread further to the open sea during ebb tide rather than flood tide which reflects that the suspended solids in the estuary are land sourced.

Simulated circulations off the Changjiang (Yangtze) River mouth in spring and autumn

The circulations off the Changjiang mouth in May and November were simulated by a three dimension numerical model with monthly averaged parameters of dynamic factors in this paper. The area covers the East China Sea (ECS), Yellow Sea and Bohai Sea. Simulated results show that the circulation off the Changjiang mouth in spring and autumn is mainly the Changjiang runoff and Taiwan Warm Current (TWC). The Changjiang discharge is much larger in May than in November, and the wind is westward in May, and southward in November off the Changjiang mouth. The runoff in May branches in three parts, one eastward flows, the other two flow northward and southward along the Subei and Zhejiang coast respectively. The Changjiang diluted water expands eastward off the mouth, and forms a strong salinity front near the mouth. Surface circulation in autumn is similar to that in winter, the runoff southward flows along the coast, and the northward flowing TWC becomes weaker compared to that in spring and summer. The bottom circulations in May and November are mainly the runoffnear the mouth and the TWC offthe mouth, and the runoff and TWC are greater in May than in November.

Theoretical analysis of characteristics of acoustic emission in rock failure based on statistical damage mechanics

Based on statistical damage mechanics,the constitutive model of a rock underthree-dimensional stress was established by the law that the statistical strength of rockmicro-element obeys Weibull distribution.The acoustic emission (AE) evolution model ofrock failure was put forward according to the view that rock damage and AE were consistent.Moreover,in the failure process of rock under three-dimensional stress,the change inrelationship between stress condition parameter and the characteristic parameters of AE,such as the event number and its change rate,were studied.Also,the rock AE characteristicunder uniaxial compression was analyzed in theory and verified with examples.Theresults indicate that the cumulative event number and change rate of AE in rock failure aredetermined by stress state parameter F.Along with the gradual increase of F,first the cumulativeevent number increases gradually,then rapidly,and then slowly after the stresspeak.The form of change rate of an event by increasing F is consistent with the distributionform of rock micro-element strength.The model explained the phenomenon that a relativelyquiet period of AE appears before rock rupture that is observed by many researchersin experiments.Verification examples indicate that the AE evolution model is consistentwith the test results,so the model is reasonable and correct.

Reliability analysis for seismic stability of tunnel faces in soft rock masses based on a 3D stochastic collapse model

A new horn failure mechanism was constructed for tunnel faces in the soft rock mass by means of the logarithmic spiral curve. The seismic action was incorporated into the horn failure mechanism using the pseudo-static method. Considering the randomness of rock mass parameters and loads, a three-dimensional (3D) stochastic collapse model was established. Reliability analysis of seismic stability of tunnel faces was presented via the kinematical approach and the response surface method. The results show that, the reliability of tunnel faces is significantly affected by the supporting pressure, geological strength index, uniaxial compressive strength, rock bulk density and seismic forces. It is worth noting that, if the effect of seismic force was not considered, the stability of tunnel faces would be obviously overestimated. However, the correlation between horizontal and vertical seismic forces can be ignored under the condition of low calculation accuracy.

Number Concentration of Cylindrical Particles in a Fluidized Bed

In this study, a three-dimensional model based on RANS, slender-body theory and Newton-Euler dynamics is established to study the number concentration, one of the most important fluidization characteristics of cylindrical particles. Also, the effects of interaction between cylindrical particles are taken into account by introducing the rigid collision dynamics. To validate the model, the fluidization experiments of cylindrical particles in a cold-state fluidized bed are carried out. The number concentration characteristics of cylindrical particles are obtained from computational fluid dynamics (CFD) simulation. It is found that cylindrical particles arriving at the exit of the riser the earliest come from the near-wall regions, the horizontal transfer of so many cylindrical particles from the radial centre regions to the near-wall regions is evident. Meanwhile, there is no distinct relationship between the number concentration and inlet wind velocity.

LUMBAR SPINAL STENOSIS: A REVIEW OF BIOMECHANICAL STUDIES

Objective. To investigate the biomechanical aspects of etiology,pathology, clinical manifestation, diagnosis and surgical treatment of the lumbar spinal stenosis. Methods’ A series of biomechanical methods, such as three-dimensional finite element models. three-dimensional kinematic measurement, cadeveric evaluation, and imaging assessment was applied to correlate lumbar biomechanics and lumbar spinal stenosis. Surgery of lumbar spinal stenosis has been improved. Results. The stresses significantly concentrate on the posterolateral part of the annulus fibrosus of disc, the posterior surface of vertebral body, the pedicle, the interarticularis and the facet joints. This trend is intensified by disc degeneration and lumbar backward extension. Posterior element resection has a definite effect upon the biomechanical behavior of lumbar vertebrae. The improved operations proved satis- factory. Conclusion. Stress concentration in the lumbar vertebrae is of importance to the etiology of degenerative lumbar spinal stenosis, and disc degeneration is the initial key of this process. Then these will be aggravated by backward extension. Functional radiography and myelography are of assistance to the diagnosis o f the lumbar spinal stenosis. For the surgical treatment of the lumbar spinal stenosis, destruction of the posterior element should be avoid as far as possible based upon the thorough decompression. Maintaining the lumbar spine in flexion by fusion after decompression has been proved a useful method. When developmental spinal stenosis is combined with disc herniation, discectomy through laminotomy is recommend for decompression.

Nonlinear finite element analysis of effect of seismic waves on dynamic response of Shiziping dam

Many high earth-rockfill dams are constructed in the west of China. The seismic intensity at the dam site is usually very high, thus it is of great importance to ensure the safety of the dam in meizoseismal area. A 3D FEM model is established to analyze the seismic responses of Shiziping earth-rockfill dam. The nonlinear elastic Duncan-Chang constitutive model and the equivalent viscoelastic constitutive model are used to simulate the static and dynamic stress strain relationships of the dam materials, respectively. Four groups of seismic waves are inputted from the top of the bedrock to analyze the dynamic responses of the dam. The numerical results show that the calculated dynamic magnification factors display a good consistency with the specification values. The site spectrum results in larger acceleration response than the specification spectrum. The analysis of relative dynamic displacement indicates that the displacement at the downstream side of the dam is larger than that at the upstream side. The displacement response reduces from the center of river valley to two banks. The displacement responses corresponding to the specification spectrum are a little smaller than those corresponding to the site spectrum. The analysis of shear stress indicates that a large shear stress area appears in the upstream overburden layer, where the shear stress caused by site waves is larger than that caused by specification waves. The analysis of dynamic principal stress indicates that the minimum dynamic stresses in corridor caused by specification and site waves have little difference. The maximum and minimum dynamic stresses are relatively large at two sides. The largest tensile stress occurs at two sides of the floor of grouting corridor, which may result in the crack near the corridor side. The numerical results present good consistency with the observation data of the grouting corridor in Wenchuan earthquake.

CONFINING PRESSURE EFFECT ON ACOUSTIC EMISSIONS IN ROCK FAILURE

Based on the phenomenon that acoustic emissions (AE) generated by rock mass increase suddenly because of underground excavation, time sequence of AE rate in rock failure has been discussed by using statistical damage theory. It has been demonstrated that how the influence of confining pressure on the deformation behavior and AE characteristics in rocks can be inferred from a simple mechanics model. The results show that loading confining pressure sharply brings out increasing of AE. On the other hand, few AE emits when confining pressure is loaded sharply, and AE occurs again when axial pressure keeps on increasing. These results have been well simulated with computer and show close correspondence with directly measured curves in experiments.

Modelling and simulation of contact force in cold rotary forging

Cold rotary forging is an advanced and complex metal forming technology with continuous local plastic deformation.Investigating the contact force between the dies and the workpiece has a great significance to improve the life of the dies in cold rotary forging.The purpose of this work is to reveal the contact force responses in cold rotary forging through the modelling and simulation.For this purpose,a 3D elastic-plastic dynamic explicit FE model of cold rotary forging is developed using the FE code ABAQUS/Explicit.Through the modelling and simulation,the distribution and evolution of the contact force in cold rotary forging is investigated in detail.The experiment has been conducted and the validity of the 3D FE model of cold rotary forging has been verified.The results show that: 1) The contact force distribution is complex and exhibits an obvious non-uniform characteristic in the radial and circumferential directions; 2) The maximum contact force between the upper die and the workpiece is much larger than that between the lower die and the workpiece; 3) The contact force evolution history is periodic and every period experiences three different stages; 4) The total normal contact force is much larger than the total shear contact force at any given time.

3D Numerical Modeling of Wave Forces on Tandem Fixed Cylinders Using the BEM

In this paper a 3D numerical model was developed to study the complicated interaction between waves and a set of tandem fixed cylinders.The fluid was considered to be inviscid and irrotational.Therefore,the Helmholtz equation was used as a governing equation.The boundary element method（BEM） was adopted to discretize the relevant equations.Open boundaries were used in far fields of the study domain.Linear waves were generated and propagated towards tandem fixed cylinders to estimate the forces applied on them.Special attention was paid to consideration of the effect on varying non-dimensional cylinder radius and distance between cylinders,ka and kd on forces and trapped modes.The middle cylinder wave forces and trapped modes in a set of nine tandem cylinders were validated utilizing analytical data.The comparisons confirm the accuracy of the model.The results of the inline wave force estimation on n tandem cylinders show that the critical cylinder in the row is the middle one for odd numbers of cylinders.Furthermore the results show that the critical trapped mode effect occurs for normalized cylinder radiuses close to 0.5 and 1.0.Finally the force estimation for n tandem cylinders confirms that force amplitude of the middle cylinder versus normalized separation distance fluctuates about that of a single cylinder.