共查询到20条相似文献,搜索用时 15 毫秒
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Yi-tao Yang Wei Luo Meng Chen Guang-jie Shao 《Frontiers of Materials Science in China》2009,3(3):301-305
To quantitatively analyze the main reasons of common crack in the surface of alloy steel ingot with 5% Cr during production
and to propose the direction of improvement, a physical model system, which consisted of steel ingot mold, casting, riser
of heat insulation, slag layer, sprue pipe, and runner, was primarily established by three-dimensional CAD software. The joint
simulation method concerned with pouring, solidification, temperature field, and cast stress was determined by using ADSTEFAN
cast simulation software. The stress distribution of casting and the quantitative effect of shake-out timing were analyzed
in detail. An effective plan of decreasing stress was proposed in cooling mode. 相似文献
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Development of a new software for adaptive crack growth simulations in 3D structures 总被引:1,自引:0,他引:1
M Schöllmann 《Engineering Fracture Mechanics》2003,70(2):249-268
A new software system called ADAPCRACK3D has been developed by the authors to predict fatigue crack growth in arbitrary 3D geometries under complex loading by the use of the finite element method. The main focus of ADAPCRACK3D is on the determination of 3D crack paths and surfaces as well as on the evaluation of components' lifetimes as a part of the damage tolerant assessment. Throughout the simulation of crack propagation an automatic adaptive mesh adaption is carried out in the vicinity of the crack front nodes. The fracture mechanical evaluation is based on a new criterion recently developed by the authors. 相似文献
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带阻尼台叶片多向模锻过程场量分布规律研究 总被引:1,自引:0,他引:1
为了提高带阻尼台叶片的综合机械性能,采用多向模锻技术来实现带阻尼台叶片的精净成形,通过确定带阻尼台叶片多向模锻分模形式及分模面位置,基于UG建立了带阻尼台叶片多向模锻模具的几何实体模型;在此基础上,采用DEFORM3D建立了该类叶片多向模锻过程的三维有限元模型,确定了模具的加载方式和加载顺序,实现了带阻尼台叶片多向模锻过程有限元模拟,获得了该成形过程中不同加载方式下坯料的速度场、等效应变场和温度场分布规律及载荷-行程曲线,揭示了带阻尼台叶片多向模锻过程中金属充填模具型腔的情况及温度场、应变分布以及载荷随行程的变化规律.该成果可应用于带阻尼台叶片的实际生产过程中,对采用多向模锻工艺来实现带阻尼台叶片的精锻具有指导作用. 相似文献
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30CrNi2MoV钢是一种中碳合金钢,常用于制造高强韧性的大型锻件,广泛用于制造火电、核电等电站装备和大型冶金、矿山和运输装备中的承力和传动结构部件.为提高30CrNi2MoV钢的低温冲击韧性和室温强度,本文采用金相显微镜、扫描电子显微镜、拉伸机和硬度仪等方法对其进行组织观测、断口形貌分析和力学性能测试,研究了不同锻造方式对30CrNi2MoV钢的组织与力学性能的影响.结果表明:经过2次镦粗的30CrNi2MoV钢再经1次镦粗或1次镦粗+1次拔长两种锻造方式后能够有效细化且均匀晶粒,提高晶粒等轴性;与2次镦拔工艺的30CrNi2MoV钢相比,再经过1次镦粗或1次镦粗+1次拔长后其抗拉强度、延伸率和冲击韧性分别由1 043.6 MPa、35.65%和40.33 J提高至1 161.6和1 157.4 MPa、37.80%和36.13%、103和87 J.数据表明,30CrNi2MoV钢经过2次镦拔+1次镦粗工艺后,其组织与力学性能达到最好状态. 相似文献
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Silvio José Gobbi Vagner João Gobbi Gustavo Reinke Palloma Vieira Muterlle Daniel Monteiro Rosa 《Materials Science & Technology》2013,29(11):1355-1364
Ultra-low-temperature process treatments could raise tool steel wear resistance through microstructural change that occurs on the material, enhancing, that way, tools and dies lifetime. To investigate the tool steel wear resistance impact, micro-abrasive wear tests were carried out and an analysis based on the Archard’s law was considered, evaluating specimen mass loss by laser interferometry. Micro-hardness, X-ray diffractometry, scanning and optical microscopy and carbides quantitative evaluation were carried out aiming to material characterisation. Results demonstrated a micro-hardness improvement, ranging from 0.9–4.7% for the cryogenically treated specimens, when compared to the bulk material. This effect is related, mainly, to the retained austenite transformation and to the increase of fine secondary carbides dispersed amount in the martensitic matrixes cryogenically treated. 相似文献
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A mathematical methodology for analyzing void closure in the forging process of steel ingot with a large size was proposed from the view of strain function. A numerical simulation of the forging process was established to describe the distribution field of compressive strain within deformed steel ingot. Then the analytic function of compressive strain distribution was given by mathematical fitting on the basis of Gaussian function (including the models without and with void). And finally the quantitative relationship between void closure and compressive strain, namely mathematical expressions of the criterion for central and non-central void closure, was presented by derivation and calculation of this function. The criterion for central and non-central void closure was verified by finite element simulation for a typical steel ingot. This new methodology gives an acute prediction in terms of elimination of void defects, where the deviation is less than 7%. 相似文献
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利用现阶段国内外流行的岩土数值分析软件FLAC3D,模拟分析了圆形隧道围岩不同阶段的应力和位移,并把数值解和理论解析解进行了对比;分析了剪胀性对于隧道围岩应力位移的影响,对隧道工程的设计和施工有指导作用和参考价值。 相似文献
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Jixi Zhang 《Engineering Fracture Mechanics》2009,76(3):315-2911
The mechanics of high cycle fatigue crack nucleation (formation of a stable crack that can grow away from the influence of the notch root of the inclusion) at subsurface primary inclusions in carburized and shot-peened martensitic steel subjected to cyclic bending is investigated using three-dimensional (3D) finite element (FE) analysis. FE models are constructed using a voxellation technique to address the shape, size, and distribution of primary inclusions within clusters. The critical depth for fatigue crack nucleation is predicted considering the gradient in material properties arising from carburization, prestrain and compressive residual stress distribution due to shot peening, and the gradient of applied bending stress. The influence of inclusion shape and interface condition (intact or debonded) with the matrix on the driving force for fatigue crack nucleation is examined. It is observed that the inclusion shape has minimal influence on the predicted results while the effect of the interface condition is quite significant. For partially debonded interfaces, the predicted critical depth from surface for fatigue crack nucleation agrees qualitatively with experimental observations. 相似文献
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The influence of the 3D frictional crack surface interaction on the fracture mechanical parameters as well as on the crack path is numerically investigated. For the solution of the boundary value problem the 3D dual boundary element method in terms of the discontinuous formulation is utilized. This method is especially suited for contact problems because it directly deals with the discontinuities at the crack surfaces. The contact problem is solved by the application of the penalty method. Coulomb’s frictional law is utilized for the consideration of the dissipative nature of friction. For discrete steps within one load cycle the stress intensity factors are determined by an extrapolation procedure from the stress field. Based on the analysis of a load cycle, the cyclic stress intensity factors are obtained. For the simulation of crack propagation an implicit time integration scheme of a crack propagation law implemented in terms of a predictor-corrector scheme is applied. The influence of the crack surface roughness on the crack path is shown by numerical examples. 相似文献
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《Virtual and Physical Prototyping》2013,8(2):160-174
ABSTRACTWith the number of 3D printed concrete structures rapidly increasing, the demand for concepts that allow for robust and ductile printed objects becomes increasingly pressing. An obvious solution strategy is the inclusion of fibers in the printed material. In this study, the effect of adding short straight steel fibers on the failure behaviour of Weber 3D 115-1 print mortar has been studied through several CMOD tests on cast and printed concrete, on different scales. The experiments have also been simulated numerically. The research has shown that the fibers cause an important increase in flexural strength, and eliminate the strength difference between cast and printed concrete that exists without fibers. The post-peak behaviour, nevertheless, has to be characterised as strongly strain-softening. In the printed specimens, a strong fiber orientation in the direction of the filament occurs. However, this has no notable effect on the performance in the tested direction: cast and printed concrete with fibers behave similarly in the CMOD test. For the key parameters, no scale effect was found for the specimens with fibers, contrary to the ones without. Numerical modelling of the test by using the Concrete Damage Plasticity material model of Abaqus, with a Thorenfeldt-based constitutive law in compression and a customised constitutive law in tension, results in a reasonable fit with the experimental results. 相似文献
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ANSYS是通常用于分析和设计声学换能器的有限元软件之一,通过实例给出分析声学换能器的处理过程,包括建模、施加载荷、设置求解选项、使用后处理器、以及获得换能器振动辐射参数的一般过程,并涉及宽带换能器、矢量换能器的发射与接收问题,对ANSYS有限元软件模拟换能器的一些经常遇到的问题细节的处理方法做了较全面的概括。还简要讨论了流体中结构模态分析的一般处理方法,对结果数据进行数学运算操作并获得换能器的特性参数等等。 相似文献
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Shot peening has been widely applied in industrial design to improve fatigue durability of high loaded machine components. The compressive residual stress induced by shot peening is in general assumed to be responsible for the improvement of material fatigue strength. In the present work a cyclic cohesive zone model is extended to analyze three-dimensional fatigue crack growth in shot-peened specimens. Fatigue crack growth behaviors in both unpeened and peened specimens are investigated using 3D finite element analysis. The parameters of the cohesive zone model have been identified in 2D unpeened specimens and are applied to predict peened specimens directly. The results indicate that shot peening strongly affects crack initiation time and crack profiles, but has little effect on crack propagation rate. It implies that the shot peening will hardly change Paris’ law used for the damage tolerant design. 相似文献
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As concrete freezes and thaws cracks may develop. These cracks can provide a path for water and ionic species to penetrate the concrete. This may reduce the service-life of the concrete element. In this study, X-ray computed tomography (CT) was used as a non-destructive technique to characterize the microstructure of mortar samples that were exposed to different levels of freeze-thaw damage by varying degree of saturation in the samples (75, 90, 95, and 100% degrees of saturation). Acoustic emission (AE) experiments were performed during freezing and thawing to investigate sample cracking behavior. The volume of cracks present within the mortar samples after freezing and thawing were determined using X-ray CT and compared to passive acoustic emission data. The location/source of cracks was also determined using X-ray CT. The crack sources (i.e., void, aggregate, interfacial transition zone, or paste) were determined using X-ray CT and were related to AE activities during cracking. Crack volumes were found to increase with increased levels of saturation, and visual observations of cracking were found to correlate with AE signatures of various crack sources. 相似文献
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This paper deals with the numerical simulation of a stable crack propagation experiment at in a 16MND5 steel. At this temperature, the material is viscoplastic. A cohesive zone model is formulated in order to simulate the rupture of a CT specimen. A large displacement 3D cohesive element with eight nodes is implemented in the finite element code ABAQUS. The associated traction-separation law is of Tvergaard and Hutchinson type, in which an hardening slope has been added. This hardening simulates the material strengthening associated to the increasing strain rate in front of the crack tip when crack tip starts to propagate.We show that in this case the form of the cohesive law has great impact on the simulated propagation velocity. 相似文献
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目的研究剪板机压料油缸缸体闭塞热精锻成形工艺的可行性。方法制定闭塞热精锻成形工艺,运用DEFORM-3D软件对缸体单元成形过程进行有限元模拟分析,得到了金属流动规律、金属流线、挤压力载荷、合模力载荷随挤压行程变化的结果。结果模拟结果表明,锻件金属流线分布合理,无明显交叉、断裂情况,整个过程中挤压力与合模力载荷也维持在一个较低水平。对合模力大小进行了计算,计算结果与模拟的误差为8.4%,最后结合工艺进行了工业性试制。结论成形后的锻件无飞边,尺寸精度高,力学性能良好,无明显缺陷。 相似文献