Containment of high-speed rotating disk fragments

Disk burst accidents sometimes happen in aeroengines. To avoid tragic consequences, aeroengine casings must have sufficient containment capability. Experiments and simulations need to be conducted to study the impact, distortion, and perforation caused by disk burst and which may give important clues to potential failure mechanisms. This paper presents some containment tests of high-speed rotating disk fragments, in which the original disks were burst into three equal fragments within a predetermined rotating speed range. The failure modes of the containment casing varied significantly with the thickness of the containment casing. Shearing, tearing, tensile fracture, and large plastic stretching deformation occurred in a thin-walled containment casing, while a thick-walled casing could contain disk fragments and withstand large plastic deformation. Numerical simulations were carried out to study the impact process and failure modes further. Good agreement was found between the results of the simulations and the tests.     

钢轨波磨处高速轮轨滚动接触行为与波磨发展的模拟研究

研究目的：为求解钢轨（短波）波磨处的高速轮轨瞬态滚动接触建立有限元模型,研究影响高速钢轨波磨发展的重要因素。削新要点：1．求解不同牵引条件下轮轨间的瞬态法和切向滚动接触问题,并考虑真实轮轨几何和钢轨波磨,最高模拟速度达500km／h;2．基于模拟结果,解释了中国高速线路上发现的钢轨波磨很快稳定下来的现象。研究方法：1．详细分析钢轨波磨处高速轮轨瞬态滚动接触的法、切向解以及由此导致的V-M等效应力和摩擦功沿轨面的波动;2．变化波磨波长、波深及重要滚动参数如速度和牵引系数等,研究它们对波磨处滚动接触行为的影响;3．对比上述有限元模型与传统多体动力模型在波磨处的法向轮轨力结果。重要结论：1．法、切向轮轨力及法、切向接触应力均随着波磨几何呈周期性波动,但相位略有差异,V-M等效应力和摩擦功的波动形式接近切向接触应力;2．牵引系数越大,波磨处V-M等效应力和摩擦功的波动范围越大;3．名义参数下,对于所研究高铁系统,波长为80mm左右、速度为250-300km／h时波磨的动态响应最大,这与现场观测相符;4．传统多体动力模型会高估钢轨波磨激励的法向轮轨力;5．钢轨波磨会逐渐稳定下来,通过速度越高进入稳定越快。     

基于边界摩擦的碟簧隔振器力学性能(英文)

为研究边界摩擦对碟簧隔振器力学性能的影响,基于能量守恒定律推导了在考虑边界摩擦时碟簧隔振器的载荷位移迟滞曲线公式.通过有限元分析与静载试验验证了该公式的正确性.在此基础上研究了边界摩擦对碟簧隔振器承载能力的影响,并通过动载试验研究了边界摩擦对碟簧隔振器的动态性能的影响.试验结果表明:边界摩擦可提供较大的阻尼,使得碟簧隔振器具有良好的阻尼特性,其阻尼比可达0.23;隔振器的耗能、动刚度和阻尼特性对加载幅值更为敏感,而对加载频率敏感度较小.该研究成果对碟簧隔振器设计具有重要的指导意义.     

铝型材拉弯成形数值模拟及工艺优化

针对汽车行李架铝型材拉弯成型问题,运用ABAQUS 有限元分析软件,建立型材拉弯成形过程的有限元模型,通过对A6043 铝型材结构件进行拉弯成形正交数值试验,研究预拉量、包覆拉伸量、补拉量和摩擦系数等拉弯成形关键工艺参数对型材回弹量的影响规律,结果表明:在一定拉伸范围内,回弹量随预拉量、包覆拉伸量、补拉量的增大而减少,随摩擦系数的增大先减小后增大?工艺参数中包覆拉伸量对回弹结果的影响最大,达到3%,回弹量趋于稳定?当预拉量为1%、包覆拉伸量为3%、补拉量为1%、摩擦系数为0.1 的工艺参数下,不规则铝型材汽车行李架拉弯成形后的回弹量最小。     

基于ANSYS挤出过程中数值模拟的探索

本文根据聚合物流变学理论,以有限元软件Ansys、Polyflow和Flow2000为平台,采用数值模拟的方法对挤出模具材料一次性摩擦的影响后对模具的温度场、应力场进行数值模拟,从而给出了塑料异型材挤出模具高速稳定设计的数值模拟及优化方法。这样即可节约设计时间,又可节约成本,同时提高了产品的设计质量和精度。     

Explicit finite element analysis and experimental verification of a sliding lead rubber bearing

Based on the explicit finite element (FE) software ANSYS/LS-DYNA, the FE model for a sliding lead rubber bearing (SLRB) is developed. The design parameters of the laminated steel, including thickness, density, and Young’s modulus, are modified to greatly enlarge the time step size of the model. Three types of contact relations in ANSYS/LS-DYNA are employed to analyze all the contact relations existing in the bearing. Then numerical simulations of the compression tests and a series of correlation tests on compression-shear properties for the bearing are conducted, and the numerical results are further verified by experimental and theoretical ones. Results show that the developed FE model is capable of reproducing the vertical stiffness and the particular hysteresis behavior of the bearing. The shear stresses of the intermediate rubber layer obtained from the numerical simulation agree well with the theoretical results. Moreover, it is observed from the numerical simulation that the lead cylinder undergoes plastic deformation even if no additional lateral load is applied, and an extremely large plastic deformation when a shear displacement of 115 mm is applied. Furthermore, compared with the implicit analysis, the computational cost of the explicit analysis is much more acceptable. Therefore, it can be concluded that the proposed modeling method for the SLRB is accurate and practical.     

高速列车车轮多边形对车内噪声的影响

研究目的：研究高速列车车轮多边形特征对轮轨噪声和车内噪声的影响规律,讨论目前国内高速列车车轮镟修指标的不足,为高速列车车轮镟修方法的优化改进提供科学依据。创新要点：系统分析高速列车车轮多边形阶次、幅值和相位等参数对车内噪声的影响规律;提出车轮镟修中仅考虑车轮径跳作为限值是不够的。研究方法：1．基于线路试验,初步分析高速列车车轮多边形状态对车内噪声的影响,进而对车轮多边形特征进行剖析;2．基于带通滤波和快速傅里叶变换,使用MATLAB程序生成不同阶次、幅值和相位的车轮多边形粗糙度数据;3．基于TWINS轮轨噪声原理,使用HWTNS预测含有不同车轮多边形特性的轮轨噪声;4．基于混合有限元-统计能量分析（FE—SEA）方法,建立高速列车客室端部车内噪声预测模型,预测车内噪声;5．通过分析车轮多边形参数、车轮径跳和车内噪声之间的相互关系,研究目前的高速列车车轮镟修指标是否合适。重要结论：1．高速列车车轮径跳值相同,但车轮多边形状态不同时,轮轨噪声与车内噪声有明显差异;2．当车轮多边形幅值相同时,高阶多边形可以引起更高的轮轨噪声和车内噪声;3．改变车轮多边形的相位,可以获得不同的车轮径跳值,但是对轮轨噪声和车内噪声几乎没有影响。     

Large eddy simulation for wind field analysis based on stabilized finite element method

In this paper, a stabilized finite element technique, actualized by streamline upwind Petrov-Galerkin (SUPG) stabilized method and three-step finite element method (FEM), for large eddy simulation (LES) is developed to predict the wind flow with high Reynolds numbers. Weak form of LES motion equation is combined with the SUPG stabilized term for the spatial finite element discretization. An explicit three-step scheme is implemented for the temporal discretization. For the numerical example of 2D wind flow over a square rib at Re=4.2×10⁵, the Smagorinsky’s subgrid-scale (SSGS) model, the DSGS model, and the DSGS model with Cabot near-wall model are applied, and their results are analyzed and compared with experimental results. Furthermore, numerical examples of 3D wind flow around a surface-mounted cube with different Reynolds numbers are performed using DSGS model with Cabot near-wall model based on the present stabilized method to study the wind field and compared with experimental and numerical results. Finally, vortex structures for wind flow around a surface-mounted cube are studied by present numerical method. Stable and satisfactory results are obtained, which are consistent with most of the measurements even under coarse mesh.     

Mesh size effect in numerical simulation of blast wave propagation and interaction with structures

Numerical method is popular in analysing the blast wave propagation and interaction with structures.However,because of the extremely short duration of blast wave and energy trans-mission between different grids,the numerical results are sensitive to the finite element mesh size.Previous numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case,even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accu-rate numerical results.Therefore,both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with structures.Based on the numerical results and their comparison with field test re-sults and the design charts in TM5-1300,a numerical modification method was proposed to correct the influence of the mesh size on the simulated results.It can be easily used to improve the accu-racy of the numerical results of blast wave propagation and blast loads on structures.     

Response of Box-Type Structures Under Internal-Blast Loading

The tests of box-type structures under internal-blast loading are carried out. Then a numerical analysis of the test structures is done using a fully coupled numerical finite element model. The break-up process of the structure is simulated. The failure modes of the simulated structure agree well with the experimental results. The effects of the size of the reinforcing bars and the detailing of connections among the rebars in the concrete on the throw velocity of the fragments are discussed.     

Reinforcement Efficiency Analysis of Geosynthetic-Reinforced Embankment with Different Soil Properties

The use of high strength geosynthetic in the base ofembankments constructed over soft soil layers is a commonpractice.Those embankments are called geosynthetic-rein-forced embankments (GRE) . Geosynthetic reinforcementcanimprove stability,decrease lateral and vertical soil de-formations under working conditions , and allow embank-ments to be constructedto greater height[1].However ,the effectiveness of geosynthetic reinforce-mentin GREvaries greatlyin different cases .Despitethereare many s…     

Reinforcement Efficiency Analysis of Geosynthetic-Reinforced Embankment with Different Soil Pronerties

Based on finite element (FE) method, an analysis program of geosynthetic-reinforcement embankments (GRE) is proposed. The improvement of stress field of surface layer of GRE after reinforcement can be indicated by this program. The comparison of failure area ratio of foundation soil before and after reinforcement is made, so that the efficiency of geosynthetic reinforcement under different soft soil properties can be shown. The embankment soil is simulated with Duncan-Chang model in this program, while reinforcement is modeled with linear elastic model and interface of reinforcement-soil by Goodman elements. Parameters about foundation soil, such as cohesion, inner friction angle and unit weight are considered, as well as three Duncan-Chang model parameters: modulus coefficient, bulk modulus coefficient and break ratio. The relationship between those soil parameters and failure area ratio indicate the reinforcement efficiency of GRE. The results show the cohesion and inner friction angle are the most important parameters for reducing the failure area,while modulus coefficient and bulk modulus coefficient, have little effect on the calculation results; the reinforcement efficiency is low if the cohesion and inner friction angle of foundation soil are too small or too big; different foundation soil will get different conclusions. The selection of model parameter is an important procedure for accurate modeling of GRE by numerical method.     

消音小锯片振动特性研究

采用有限元分析软件ANSYS,对轧钢厂金属小锯片的固有特性进行了系统研究。通过对锯片在打孔、开槽情况下固有频率及振型的计算分析发现:打孔对锯片固有频率无太大影响,但对降噪影响较大;开环形槽对五阶以上固有频率影响相对明显。     

Equivalent Kelvin Impact Model for Seismic Pounding Analysis of Bridges

Based on Hertz contact theory, a method to determine the parameters of Kelvin impact model for seismic pounding analysis of bridges is proposed. The impact stiffness of Kelvin model is determined by the ratio of maximum impact force to maximum contact deformation, which is calculated based on Hertz contact theory with considering the vibration effect. The restitution coefficient which has great influence on the damping coefficient of Kelvin impact model is investigated by numerical analysis. Numerical results indicate that the impact stiffness of Kelvin impact model increases with the increment of the Hertz contact stiffness, approaching velocity or the length ratio of short to long girders. Vibration effect has remarkable influence on the impact stiffness and cannot be neglected. The restitution coefficient decreases when approaching velocity increases or the length ratio of short girder to long girder decreasing. The practical ranges of impact stiffness and restitution coefficient are obtained as 3×108-6×108 N/m and 0.6-0.95 respectively.     

Finite element analysis of internal gear in high-speed planetary gear units

The stress and the elastic deflection of internal ring gear in high-speed spur planetary gear units are investigated. A rim thickness parameter is defined as the flexibility of internal ring gear. Six evenly spaced linear springs are used to describe the fitting status between internal ring gear and the gearcase, The finite element model of the whole internal ring gear is established by means of Pro/E and ANSYS. The loads on meshing teeth of internal ring gear are applied according to the contact ratio and the load-sharing coefficient. With the finite element analysis （FEA）, the influences of flexibility and fitting status on the stress and elastic deflection of internal ring gear are predicted. The simulation reveals that the principal stress and deflection increase with the decrease of rim thickness of internal ring gear. Moreover, larger spring stiffness helps to reduce the stress and deflection of internal ring gear. Therefore, the flexibility of internal ring gear must be considered during the design of high-speed planetary gear transmissions.     

盲孔法中释放系数的有限元标定研究

基于有限元方法,研究了盲孔法在测量残余应力时释放系数的标定方法。提出了一种新的对释放系数进行标定的有限元模拟办法。运用新的有限元数值模拟方法对ASTM标准中的释放系数值进行了标定。结果表明,有限元标定结果与ASTM标准推荐值有较好的一致性。     

大型自移式破碎站钢结构落料冲击系数研究

基于虚拟样机技术及有限元法,提出了破碎站钢结构的力学模型等效及落料冲击系数的数值模拟方法,采用理论公式对单块物料冲击钢结构的动载系数进行计算,并将其与数值模拟分析结果对比。分析表明,1m3大小的正方体煤岩物料从5m高度下落直接冲击钢结构,其冲击系数的理论计算及刚体动力学分析结果均为123,而柔体动力学分析结果为125,三者误差约1.6%,表明提出的数值模拟方法及钢结构等效模型有效,分析方法可为破碎站的性能评估及结构优化提供基础。     

混凝土坝裂纹扩展算法(英文)

混凝土建筑物中的裂纹扩展追踪计算是确定结构安全度的重要手段。本文提出用虚拟裂纹单元及断裂力学准则(应变强度因子)追踪和模拟裂缝初始断裂、扩展并最终导致破坏的过程,给出一条逐段扩展的裂纹线,本方法计算结果与某些混凝土坝实测资料及模型试验结果吻合较好。     

一类二维变系数椭圆方程数值求解

利用有限元法求解了二维变系数椭圆方程边值问题,得到了相应的误差分析,并进行了数值模拟。结果表明解此类问题时有限元法具有程序简单,计算精度高的优点。     

方管截面铝合金轴心受压构件力学性能研究

通过有限元软件ANSYS构建非线性数值模型,并利用现有试验数据进行模型准确性验证。分析了板件宽厚比、截面尺寸效应以及是否约束某一主轴方向位移对构件稳定承载力的影响,发现三者影响均可不予考虑。在大规模参数分析的基础上,本文建议对于6061-T6,几何缺陷系数中的两个参数分别取和,对于6061-T4建议取和。对比中、欧规范计算结果发现,该建议与试验及参数分析结果具有更好的吻合性,满足计算精度和安全度的工程设计要求。