The study of adiabatic shear band instability in a pearlitic 4340 steel using a dynamic punch test

The formation of adiabatic shear band instabilities in a pearlitic 4340 steel using a dynamic punch test has been studied. The dynamic punch-impact test produced white-etching adiabatic shear bands. The average strain of 0.5 was sufficient to produce adiabatic shear bands in this steel at an average strain rate of 18,000 s⁻¹. Nanohardness variations found across the adiabatic shear band are thought to be caused by the fragmentation and spheroidization of the Fe₃C and the overall deformation and work hardening of the pearlitic microstructure. The cracks formed at the termination of the adiabatic shear band caused the sample to fracture in a ductile mode.     

连铸方坯感应补热过程的有限元分析

根据电磁感应理论及传热基本原理,利用大型工程软件ANSYS对连铸方坯的感应补热过程进行了多物理场耦合的有限元模拟,并对铸坯断面上的温度梯度、磁场分布等进行了分析.模拟结果与实测结果一致.     

PQF轧管机连轧过程芯棒温度场有限元分析

芯棒是PQF(Premium Quality Finishing,高质量精轧机)的主要加工设备之一,其温度的分布和变化情况是研究芯棒磨损和缺陷产生的依据.采用有限元法分析PQF生产28CrM057钢管过程中芯棒各阶段温度场和温度随连轧时间的变化曲线.结果表明,表面节点一直处于较高温度,而芯棒内部的各取样点温度几乎保持在初始温度;芯棒表层温度变化剧烈,在1#机架和2#机架间时温降速率超过160 K/s;芯棒整体平均温度在第一机架轧制时升高最快,在以后的各阶段温升迅速减慢.结合轧制过程芯棒温度变化规律和失效机理,提出了延长芯棒寿命的建议.     

Finite element analysis of the temperature profile of rolls

The thermal conditions during hot rolling operations can adversely affect the rolls’ service life and the quality of the rolled product. Analysis of the temperature profile of the rolls is an essential step towards the development of precise cooling systems to minimise their surface deterioration and thermal bending or camber. This paper makes an attempt at developing a finite element model for analysing the steady state temperature profile of rolls of varying dimensions. Rolls of large surface area exhibit greater differences in temperature between the surface and the interior as compared to those having smaller surface area and therefore make greater demands on the cooling system.     

Finite element analysis of formability of a few kinds of special steel sheets

Deep drawing processes of various special steel sheets are simulated by the rigid-plastic finite element method. To predict the forming limit a criterion for ductile fracture is applied. From the histories of stress and strain in each element calculated by the finite element simulation, the fracture initiation site and the critical stroke are predicted by means of the ductile fracture criterion. The predictions so obtained are compared with experimental observations. The results show that the finite element analysis combined with the ductile fracture criterion is useful to predict the forming limit in a wide range of sheet steels.     

夹钳自动开启装置性能的有限元分析

某钢铁厂使用40 t重力式自动板坯夹钳几年来,其中的自动开启装置经常发生断裂现象。通过有限元软件,分析了该装置发生断裂的原因,并给予改进的措施。     

喷雾阀嘴多步成形有限元分析

喷雾阀嘴是喷雾罐的关键部件,其成形过程复杂、难度较大。采用三维光学扫描仪检测喷雾阀嘴各步成形件的三维尺寸,推导模具方案进行逆向建模。同时采用有限元技术分析喷雾阀嘴成形过程特点,探索材料性能对其成形质量的影响。结果表明,模型实现了精确分析喷雾阀嘴复杂的多步成形过程,可分析喷雾阀嘴任一时刻、任一位置的成形状态和成形质量状况。同时得出,MR T3-BA材料或比其屈服强度更高的材料容易出现成形质量问题。     

Finite element stress analysis of a new design of synthetic leaflet heart valve

This paper presents a parametric finite element analysis of the stresses in the leaflets of a new design of polyurethane heart valve in the closed position. The alpharabola geometry of the valve has previously been reported by Leat and Fisher (1) and has been shown to demonstrate good opening characteristics. The effects of variations in leaflet offset parameter, g, length, h, and local thickening have been determined for a valve where the frame is assumed rigid. A spherical leaflet geometry has also been analysed for comparative purposes. Results have shown that the alpharabola leaflet geometry can reduce the maximum principal tensile stress to 60 per cent of that for a spherical valve of the same mesh density.     

H型钢万能轧制过程中金属流动的有限元分析

采用显示动力学有限元软件LS-DYNA,结合生产实际,对H型钢万能轧制进行了仿真计算.在仿真结果的基础上,根据轧制平面内的节点位移矢量分布情况,分析了轧件断面内金属流动规律.仿真结果显示轧件断面内在立辊和平辊压下方向上存在\     

底卸式环冷机热机耦合变形有限元分析

炼铁过程中,烧结矿的冷却及余热回收工艺主要依靠环冷机实现。烧结矿初入环冷机时温度可达520℃,经环冷机回转1周冷却后,温度降低至120℃以下。明显的温度梯度导致环冷机的不均匀热变形,严重时会引起运行失稳、卡轨等问题。因此,对常见的底卸式环冷机作业过程中的温度场及热机耦合变形的分析具有重要的工程意义。首先采用流场分析软件,对环冷机内烧结矿的冷却过程进行分析,将烧结矿温度场施加于环冷机有限元模型中,计算环冷机整体结构的温度场和热机耦合变形。为了验证有限元分析结果,对现场运行的环冷机表面温度场进行了实时测量,测量结果表明有限元的温度场分析结果较为准确。数值仿真结果表明,底卸式环冷机的整体温度较高,隔温效果差。由于鼓风冷却作用,温度自上至下呈递减趋势,同一高度上的局部区域内温度变化不大。环冷机热机耦合变形明显,最大变形发生于高温区的内圈侧轨处,总位移达到91 mm,水平位移达22 mm。底卸式环冷机的工作温度高,热变形明显,需要进行进一步的优化改进,实施更新换代。     

底卸式环冷机热机耦合变形有限元分析

炼铁过程中,烧结矿的冷却及余热回收工艺主要依靠环冷机实现。烧结矿初入环冷机时温度可达520 ℃,经环冷机回转1周冷却后,温度降低至120 ℃以下。明显的温度梯度导致环冷机的不均匀热变形,严重时会引起运行失稳、卡轨等问题。因此,对常见的底卸式环冷机作业过程中的温度场及热机耦合变形的分析具有重要的工程意义。首先采用流场分析软件,对环冷机内烧结矿的冷却过程进行分析,将烧结矿温度场施加于环冷机有限元模型中,计算环冷机整体结构的温度场和热机耦合变形。为了验证有限元分析结果,对现场运行的环冷机表面温度场进行了实时测量,测量结果表明有限元的温度场分析结果较为准确。数值仿真结果表明,底卸式环冷机的整体温度较高,隔温效果差。由于鼓风冷却作用,温度自上至下呈递减趋势,同一高度上的局部区域内温度变化不大。环冷机热机耦合变形明显,最大变形发生于高温区的内圈侧轨处,总位移达到91 mm,水平位移达22 mm。底卸式环冷机的工作温度高,热变形明显,需要进行进一步的优化改进,实施更新换代。     

Finite element analysis of trabecular bone structure: a comparison of image-based meshing techniques

OBJECTIVE: To report a qualitative evaluation of the Partnerships in Health Care/EMS Project between Poland and the United States. The goal of the partnership was to strengthen the emergency medical services (EMS) system in three Polish cities, Krakow, Bialystok, and Lodz. METHODS: The Polish participants were interviewed in Poland approximately eight months after a U.S.-based training program. They were asked to evaluate the effectiveness of the partnership project and discuss their experiences incorporating U.S. emergency medicine (EM) knowledge and technology in the Polish EMS system. RESULTS: The Polish physicians identified three major factors that had the greatest impact on the implementation of U.S. EM knowledge in Poland. These factors were the substantive differences between Polish and U.S. EM knowledge and technology, staffing differences in Polish and U.S. ambulances, and the differing role the EMS system plays in the delivery of primary care in the two countries. CONCLUSIONS: The Polish physicians succeeded in training EM providers in the three cities, thus strengthening clinical skills of EMS providers. They also were able to adapt the principles of U.S. EM that they had learned to fit the specific circumstances that characterize Polish emergency care. As in the United States, the health care system in Poland is inseparable from the social, political, and economic realities of the nation.     

轧制边线形成过程的有限元分析

利用有限元软件对空冷后具有一定温度梯度的板坯的轧制过程进行数值模拟计算,研究分析两种不同高温力学特性的钢种在轧制时边角部金属的位移、应变及应力情况,分析边部线状缺陷起源的褶皱的形成过程并通过轧制试验予以验证。分析结果表明,边线形成与变形温度范围内变形抗力的不连续变化具有明显相关性,变形抗力随温度连续变化的钢种轧制过程角部金属不会形成褶皱;变形抗力随变形温度不连续变化的钢种,当板坯角部金属进入两相区时,由于轧制过程两相区变形抗力出现谷值,易出现褶皱并最终演变为边部线状缺陷。     

Finite element analysis of static loading in donkey hoof wall

A finite element model of donkey hoof wall was constructed from measurements taken directly from the hoof capsule of the left forefoot. The model was created with a 2 mm mesh and consisted of 11,608 nodes. A linear elastic analysis was conducted assuming isotropic material properties in response to a 375 newton (N) load, to simulate static loading. The load was applied to the wall via 400 laminae in order to simulate the way in which the pedal bone is suspended within the donkey hoof capsule. Displacement, stress concentration, principal strain, and force distribution across the hoof wall were evaluated. The hoof wall model revealed loading responses that were in broad agreement with previously reported in vivo and modelled observations of the equid hoof. Finite element analysis offers the potential to model hoof wall function at the macroscopic and microscopic level. In this way, it could help to develop further our understanding of the functional relationship between the structural organisation and material properties of the hoof wall.     

铁水罐应力场有限元分析

在大型铁水罐的设计校核过程中,准确确定铁水罐各处的应力分布对铁水罐的安全可靠运行具有十分重要的意义.针对包钢集团设计的120 t铁水罐的使用特点,对铁水罐在吊起、倾翻和返回铁水罐车上3种状态下各种应力的分布、数值和方向,即应力场进行了有限元校核分析,分析结果与铁水罐的实际运行情况相符.此分析方法简单、可靠、合理,可为铁水罐设计时的校核分析提供理论依据.     

泡沫铜压缩屈服强度有限元计算方法

以超声波辅助电沉积工艺制备得到的泡沫铜为研究对象,利用X射线显微计算机断层扫描(computed tomography,micro-CT)技术和数字图像处理技术,实现了对泡沫铜结构的三维重构,并通过有限元软件建立了与电沉积泡沫铜的真实三维结构相一致的有限元简化模型—十四面体三棱柱模型。基于十四面体三棱柱模型,开展了对泡沫铜压缩屈服强度的有限元计算方法研究,深入探讨了十四面体三棱柱单胞模型引起的应力分布变化,建立了屈服强度与孔隙率之间的定量关系。通过对模型进行主动设计,提出了力学性能更为优异的十四面体圆柱模型,为3D打印制备高性能泡沫金属提供了模型参考。     

预应力叠合梁斜截面抗剪性能有限元分析

在国内外学者研究的基础上,从理论上分析了预应力叠合梁的受力性能,运用ANSYS有限元软件对预应力叠合梁和普通叠合梁分别进行了非线性有限元模拟分析,对比分析得出预应力对叠合梁斜截面抗剪性能的有利贡献是客观存在的,ANSYS能较好的模拟预应力叠合梁的受力特点,且模拟结果与理论分析能较好的吻合.     

Finite element analysis of defibrillation fields in a human torso model for ventricular defibrillation

In order to optimize defibrillation electrode systems for ventricular defibrillation thresholds (DFTs), a Finite Element Torso model was built from fast CT scans of a patient who had large cardiac dimensions (upper bound of normal) but no heart disease. Clinically used defibrillation electrode configurations, i.e. Superior Vena Cava (SVC) to Right Ventricle (RV) (SVC-RV), left pectoral Can to RV (Can-RV) and Can + SVC-RV, were analyzed. The DFTs were calculated based on 95% ventricular mass having voltage gradient > 5 V/cm and these results were also compared with clinical data. The low voltage gradient regions with voltage gradient < 5 V/cm were identified and the effect of electrode dimension and location on DFTs were also investigated for each system. A good correlation between the model results and the clinical data supports the use of Finite Element Analysis of a human torso model for optimization of defibrillation electrode systems. This correlation also indicates that the critical mass hypothesis is the primary mechanism of defibrillation. Both the FEA results and the clinical data show that Can + SVC-RV system offers the lowest voltage DFTs when compared with SVC-RV and Can-RV systems. Analysis of the effect of RV, SVC and Can electrode dimensions and locations can have an important impact on defibrillation lead designs.     

Finite element stress analysis of stress distribution endodontic posts at shoulder

Pancreatic tuberculosis is rare and may present differential diagnostic problems, specially with cancer of the pancreas. An immunocompetent patient with a pancreatic tuberculous abscess whose clinical manifestations were epigastric pain and a toxic syndrome of one month of evolution is presented. A cystic mass was detected on computerized axial tomography in the tail of the pancreas suggestive of irresectable carcinoma because of vascular invasion with negative percutaneous cytologic puncture for malignant cells. The patient was surgically treated with no histologic confirmation of malignancy. A second laparotomy was performed at 6 months since spontaneous size reduction, external pancreatic fistula with miliary peritoneal dissemination and biopsy compatible with tuberculous granulomas was found. Staining for resistant acid-alcohol bacilli were always negative. Medical treatment achieved complete disappearance of the pancreatic tumor in one year.