金属结构的疲劳损伤有限元分析研究

金属材料的疲劳损伤是工程界早已发现的问题,金属结构的疲劳破损问题正日益突出.为了较好地预测金属结构和构件的剩余疲劳强度与疲劳寿命,必须建立疲劳损伤有限元分析模型,来完整描绘其应力场、应变场以及损伤场的变化全过程.针对金属材料的特点,从损伤力学的基本原理出发,通过切实可行的疲劳损伤演化规律实现损伤理论与有限元软件的结合,建立适用于金属结构的疲劳损伤有限元分析模型.最后通过疲劳试验结果与理论计算比较,对模型进行了分析与评价.

基于弹塑性有限元分析的电镀铜薄膜缺口疲劳断裂特性研究

对11.5μm厚中间缺口电镀铜薄膜的单向拉伸疲劳断裂特性进行研究。试件采用准LIGA(lithographie,gal-vanformung,abformung,光刻、电铸、塑铸的完美结合)工艺制作。试验观测发现,多数电镀铜薄试件断裂发生在缺口根部,断裂表面与缺口Y向对称轴线夹角约成12°,以沿晶断裂为主。利用弹塑性有限元分析,模拟得到断裂危险区域为缺口根部;连接危险区域边界点与缺口曲率中心的边界线,与缺口Y向对称轴线的夹角约成±14.2°范围内,与试样断裂情况相符;缺口根部断裂主要受拉伸应力控制。用Neuber方法所得结果与有限元分析结果进行对比,间接验证有限元分析结果的合理性。

铝合金材料A356疲劳寿命试验研究优化CAE有限元分析

产品开发前期的CAE有限元可靠性寿命分析,只用软件固有的材料性能参数,不能得到较准确的分析结果。因为相同材料的不同热处理等加工工艺,其应力-寿命曲线数据会有很大的差异。文章主要研究如何对特定加工工艺材料的不同结构产品进行置信度较高的有限元疲劳寿命分析。首先对特定材料的多根棒材静态拉伸后进行一定比例的不同载荷下的多项疲劳试验。再将试验后的数据进行威布尔分布统计分析得到该特定材料的应力-寿命曲线数据,并将其用于CAE分析软件数据库的数据优化。进而用优化后的CAE分析软件对某种结构件的分析结果与该结构件实际台架试验结果进行比对验证。两种结果的误差范围在可接受的范围内时,数据库优化后的CAE分析软件就可以在产品开发前期对该特定材料的不同结构产品、不同受力试验项目进行置信度较高的疲劳寿命分析。

75kg/m钢轨12号高锰钢辙叉受力有限元分析

针对重载铁路上75 kg/m钢轨12号高锰钢辙叉出现水平裂纹、竖直裂纹及垂磨等病害问题,分别建立既有线上、中铁山桥改进型、中铁宝桥改进型高锰钢辙叉的有限元受力分析模型,计算分析三种辙叉在极限荷载和疲劳荷载作用下的受力性能,并对高锰钢辙叉改进前后力学性能进行对比分析,为重载铁路高锰钢辙叉结构设计提供参考。

越野轮胎起重机车架的疲劳计算

本文采用I-DEAS软件对某越野轮胎起重机车架进行三维建模,把三维模型导入HyperWorks软件进行有限元模型的建立,然后用Ansys软件对车架进行静强度分析,最后进行疲劳计算。

一种冲击器钎头体的疲劳强度分析

冲击器在工作过程中,由于岩屑等固态物质进入其内腔造成了冲击器卡滞、冲击无力等故障.为了排除这些故障,我们对现有冲击器钎头进行了局部优化改进.通过对冲击器的原钎头体和改进后的钎头体分别进行疲劳强度分析,对比结果得出改进后的钎头体的疲劳寿命满足设计要求.

42CrMo硬齿面齿轮虚拟全寿命的试验与分析

在完成42CrMo材料硬齿面齿轮大样本全寿命成组试验的基础上,通过试验数据处理获得了定寿命下极限应力概率分布和R S N曲线。提出有限元疲劳寿命预测法的研究策略和实施方法,采用虚拟技术得到了42CrMo齿轮应力寿命曲线,与实际试验齿轮S N曲线较为接近。

Finite element simulation and optimal analysis of surfacing on steel orthotropic bridge deck

To analyze the stress state of steel orthotropic deck pavement and provide reference for the design of the overlay, the inner stress state and strain distribution of surfacing under the load of the deformation of the whole bridge structure and tyre load are analyzed by the finite element method of submodeling. Influence of surfacing modulus on the strain state of the overlay is analyzed for the purpose of the optimal design of the overlay structure. Analysis results show that the deformation of the whole bridge structure has no evident influence on the stress state of the overlay. The key factor of the overlay design is the transverse tensile strain in the overlay above the upper edge of web plate of rib. The stress state of the overlay is influenced evidently by the modulus of rigidity transform overlay. And the stress state of the overlay can be optimized and lowered by increasing the modulus and thickness of rigidity transform overlay, The fatigue test has been done to evaluate the fatigue performance and modulus of different deck pavement materials such as epoxy asphalt, SBS modified asphalt, rosphalt asphalt which can provide reference for deck pavement structure design.

Computation of the Fatigue Life of Road Wheel with Double-Layer Rubber Flange

In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.

RESEARCH ON COLD EXPANDED HOLE WITH FEM

Because of the generated residual stress after applying cold expanded technique with split sleeve, fatigue life of joint hole in aircraft can be distinguishedly prolonged. To study residual stress around cold expanded hole, some hypothesises such as small deformation in radial symmetry, plane stress, plane strain, uniform distribution pressure have been presented in most papers. However, accurate result cannot be gained based on these hypothesises. In order to overcome the shortage, a 3 dimensional model is proposed which takes into consideration of the effect on split sleeve and the different distribution pressure along thick direction of specimen. The stress distributions of cold expanded hole with split sleeve under loading or unloading, as well as under fatigue tension have been stu died. To reveal the advantage of cold expanding process with split sleeve, the expansion without split sleeve has also been studied and compared with the former.

塔机驾驶室专用电梯及控制系统设计

为提高塔机司机在攀爬过程中的安全性与舒适性,降低司机坠落事故频率,本文基于人因工程学设计出一种安装于塔机标准节内部的司机攀登驾驶室专用电梯。为验证装置的安全性和可靠性,基于SolidWork软件建立三维数字模型,对装置的疲劳及模态进行静力学仿真有限元分析。结果表明:在循环荷载作用50000次周期后,疲劳所引起的破坏才覆盖到整个装置,装置的使用周期完全满足正常使用,在规定的时间和荷载条件下,载人结构的整体消耗研究对象寿命的2%。模态分析得到装置前5阶频率,为其共振问题提供了数据支撑,避免因共振问题出现事故。基于PLC控制程序开发装置的智能化控制系统,拟定出装置的控制方案流程和梯形图,实现对速度、高度、载重量、倾斜角等参数的适时反馈与控制,实现对危险因素的动态智能预防。

基于离散元素法的矿石码头转料溜筒优化设计

散货码头的皮带机转运站,通常是故障率和维修率较高的场所,尤其矿石码头因其物料的特殊性,转料溜筒磨损快,出料皮带及缓冲托辊等组件磨损或疲劳破坏严重。本文利用基于离散元素法的仿真软件EDEM,对江苏太仓某矿石码头BC3A转运站的转料溜筒的现状进行模拟,找出了问题所在,并对结构进行优化改进。在不改变绝大部分结构,充分考虑制作、安装和维护便利性的情况下,对溜筒结构进行优化设计,并改善溜筒内的扬尘情况。同时,对缓冲托辊容易磨损的部位,利用ANSYS有限元分析软件进行强度和疲劳分析,并提出优化改进方案。

Finite element analysis of contact fatigue and bending fatigue of a theoretical assembling straight bevel gear pair

The aim of this work is to propose a 3D FE model of a theoretical assembling straight bevel gear pair to analyze the contact fatigue on the tooth surface and the bending fatigue in the tooth root. Based on the cumulative fatigue criterion and the stress-life equation, the key meshing states of the gear pair were investigated for the contact fatigue and the bending fatigue. Then, the reliability of the proposed model was proved by comparing the calculation result with the simulation result. Further study was performed to analyze the variation of the contact fatigue stress and the bending fatigue stress under different loads. Furthermore, the roles of the driving pinion and the driven gear pair were evaluated in the fatigue life of the straight bevel gear pair and the main fatigue failure mode was determined for the significant gear. The results show that the fatigue failure of the driving pinion is the main fatigue failure for the straight bevel gear pair and the bending fatigue failure is the main fatigue failure for the driving pinion.

Fatigue and mechanical properties of dental implant with zirconia pile

In order to investigate the effect of piles on tooth restoration and their service life, micro-computed tomography （CT） was used to scan the first maxillary canines by establishing a three-dimensional finite element model for pile restoration. The stress distributions after tooth restoration with different pile materials were analyzed using a 100 N bite force. Then, the S-N fatigue characteristic curve of zirconia material was obtained using experimental data. The fe-safe fatigue analysis software was used to study the service life of zirconia piles in teeth. The static analysis results demonstrate that when fiber piles are used to repair, the stress from the dentin neck is larger than that by zirconia piles, but the stress from the apical of the dentin is smaller than that by zirconia piles. Besides, the stress exerted by fiber piles is lower than that by zirconia piles. Furthermore, the fatigue analysis results indicate that under normal conditions, zirconia piles can be used in teeth for over 20 years. Compared with fiber piles, zirconia piles have a better effect on the repair of tooth defects.

Effects of surface finish and treatment on the fatigue behaviour of vibrating cylinder block using frequency response approach

This paper presents the effects of surface finish and treatment on the high cycle fatigue behaviour of vibrating cylinder block of a new two-stroke free piston engine at complex variable amplitude loading conditions using frequency response approach. Finite element modelling and frequency response analysis was conducted using finite element analysis software Package MSC.PATRAN/MSC.NASTRAN and fatigue life prediction was carded out using MSC.FATIGUE software. Based on the finite element results, different frequency response approach was applied to predict the cylinder block fatigue life. Results for different load histories and material combinations are also discussed. Results indicated great effects for all surface finish and treatment. It is concluded that polished and cast surface finish conditions give the highest and lowest cylinder block lives, respectively; and that Nitrided treatment leads to longest cylinder block life. The results were used to draw contour plots of fatigue life and damage in the worst or most damaging case.

Fatigue fracture analysis of gear teeth using XFEM

Gear teeth in gear transmission systems suffer seriously from fatigue failure during service. In this work, a 2 D double-tooth model was constructed with periodic boundary conditions. The fatigue fracture behavior of gear teeth was analyzed using the extended finite element method(XFEM), with emphases on the impacts of initial crack geometries and cyclic load factors. The results suggested that the shortest fatigue life is expected for 0° orientation cracks initiating at the maximum principal stress. Cracks that initiate closer to the bottom land of gear tooth are relatively safe. Moreover, to evaluate the fatigue load conditions, load ratio, load range, and mean load should be all taken into considerations. Further XFEM simulation for material selection was performed to guide the gear design. Among various material parameters, the material constant C and tensile strength are the most significant ones in determining the fatigue life.

Stress distribution and fatigue life of built-up sleeved backup roll

The advantage of built-up sleeved backup roll was described. Based on the stress distribution analysis and simulation for the built-up sleeved backup roll by using finite element method, the effects of roll sleeve thickness and shrink range on the stress-strain field were studied. Finally, based on the methodology and strategy of the fatigue analysis, fatigue life of backup roll was estimated by using the stress-strain data obtained through finite element simulation. The results show that roll sleeve thickness and shrink range have a great influence on sleeve stress distribution of built-up sleeved roll. Under the circumstance of ensuring transferring enough torque, the shrink range should be kept small. However, thicker roll sleeve has longer roll service life when the shrink range is constant.

Finite Element Simplified Fatigue Analysis Method for a Non-tubular Joint of an Offshore Jacket Platform

This paper proposes the finite element simplified fatigue analysis method for fatigue evaluation of the composite non-tubular joint structure of an offshore jacket subjected to wave loads. The skirt pile sleeve of the offshore jacket, which had been in service, was taken as an example of the non-tubular joint structure. SACS software was used for global analysis of multi-directional wave loads for the jacket platform, and ALGOR software was used to build a finite element model, perform finite element analysis, post-process stress results for acquiring the stress range, and perform fatigue evaluation. The analysis results indicate that the extreme stress range is within the allowable stress range and meets the requirements of DNV code. That means the simplified fatigue analysis method is effective and can be used in fatigue design for the non-tubular joint structure of an offshore jacket.

Analysis and Comparison of Safety and Fatigue Comfort of Postal Bicycles Based on Finite Element Method and sEMG

The safety and the fatigue comfort were compared between a domestic and a Japanese postal bicycle. Firstly, the fatigue comfort of these two kinds of bicycles was evaluated by surface electromyographic signal (sEMG) experiment, in which human lower limb muscle groups were research objects, and the average EMG (AEMG) index and median frequency (MF) were chosen as the evaluation indexes. Secondly, the safety of these two kinds of bicycle frames was analyzed and compared by using the finite element analysis. The results show that the riding fatigue comfort of the Japanese postal bicycle is better, and the Japanese postal bicycle frame is more safe and reasonable although both the postal bicycles meet the requirement for strength. Finally, based on the above analysis, the frame structure and related parameters of the domestic postal bicycle were improved with reference to the Japanese postal bicycle and biomechanics theory.

Numerical simulation and experimental study on constant amplitude fatigue behavior of welded cross plate-hollow sphere joints

In order to reveal the constant-fatigue fracture form and mechanism of the welded cross plate-hollow sphere joints(WCPHSJs)and establish its formula,the WCPHSJs were fatigue tested.A total of 19 specimens were tested under constant amplitude fatigue loads using a specially designed test rig.The joint was analyzed statically by t e finite element analysis(F3A),and metallographic analysis of fatigue fracture was done by the electron scanning microscope.Numerical simulation and experimental results show that the hot-spot of WCPHSJ lies at the weld toe location where severe stress is concentrated.Fatigue cracks initiate at the weld toe and then propagate circumferentially around the sphere with a diameter equivalent to the width of the cross plate up to the fatigue facture.The initial welding defects and constructional detail constitute the main factor of fatigue failure.The S-N curves for the joints were developed through a linear regession analysis of fatigue data.A formula for calculating constant amplitude fatigue,base on the concept of the hot spot stress amplitude,is proposed.