Experimental and theoretical studies on buckling of thin spherical shells under axial loads

In this paper we present experiments, simulation as well as analysis of the collapse behaviour of thin spherical shells under quasi-static loading. Various aluminium spherical shells with variation in geometrical parameters were manufactured by spinning. Experiments were performed on these shells in a universal testing machine and their load–compression histories were obtained on the machine chart recorder. Three-dimensional numerical simulations were carried out for all the specimens tested under quasi-static loading using ANSYS^®. All the stages of collapse of the shell including non-symmetrical lobe formation were simulated. Material, geometric and contact nonlinearities were incorporated in the analysis. The stress–strain curves of standard samples made from the material were used as input. Piecewise linearity was taken in the plastic region of the material curve. Results thus obtained compared with the experiments well.An analysis was also carried out to study the behaviour of shells under axial compression based on the formation of rolling and stationary plastic hinges. These hinges were also simulated numerically and results match the experiments well.     

烧结机压料装置中轴压厚壁圆筒有限元分析

探讨了130m2烧结机压料装置中轴压厚壁圆筒的计算问题,提出了厚壁圆筒应按强度问题分析.利用ANSYS在载荷和内径不变的情况下对其进行有限元分析,从应力和位移两个角度综合讨论,得出应力分布不均匀使变形复杂,径向位移正负交加可使零件发生局部失稳,这两种情况均不利于零件的正常工作.得出壁厚为5mm圆筒最为合理这一结论.     

Parametric instability of spinning twisted Timoshenko beams under compressive axial pulsating loads

The parametric instability on lateral bending vibrations of a spinning pretwisted beam under compressive axial pulsating forces is investigated. Equations of motion of the twisted beam are derived in the spinning twist coordinate frame using the Timoshenko beam theory and applying the Hamilton’s principle. The finite element method is employed to discretize the equations of motion into time-dependent ordinary differential equations with gyroscopic terms. A set of second-order ordinary differential equations with periodic coefficients of Mathieu-Hill type is formed to obtain the boundary frequencies of instability regimes. The influence of twist angle, spinning speed, static component of axial force, aspect ratio and restraint condition on the instability regions of the spinning twisted Timoshenko beam is discussed.     

编织型复合材料低速冲击损伤及剩余压缩强度研究

通过应用三维逐渐累积损伤理论和分析技术,建立了适用于编织型复合材料板的低速冲击(LVI)及冲击后压缩破坏(CVI)过程的一种全程分析方法.该方法对复合材料板的冲击以及冲击后含损伤板在压缩载荷下损伤扩展的全过程进行分析,分析中把冲击后复合材料板的预测损伤直接用于剩余压缩强度研究,从而提高了最终失效载荷的预测精度,而且避免了为获得冲击后损伤状态参数所进行的大量试验,同时开发了与由MSC.NASTRAN求解器调用执行的模拟程序.     

The effects of non-periodic microstructure and defects on the compressive strength of two-dimensional cellular solids

The utility of unit cell models that assume periodic microstructures may be limited when applied to cellular materials that have non-periodic microstructures. We analyzed the effects of non-periodic microstructure and defects on the compressive failure behavior of Voronoi honeycombs using finite element analysis. Our results indicate that the non-periodic arrangement of cell walls in random Voronoi honeycombs (with cells approximately uniform in size) results in higher strains in a small number of cell walls compared to periodic, hexagonal honeycombs. Consequently, the Voronoi honeycombs were approximately 30% weaker than periodic, hexagonal honeycombs of the same density. The strength difference between the Voronoi and periodic honeycombs depended slightly on density, due to density-dependent interactions between failure modes (i.e. plastic collapse and elastic buckling). Defects, introduced by removing cell walls at random locations, caused a sharp decrease in the effective mechanical properties of both Voronoi and periodic honeycombs (e.g. a 10% reduction in density due to defects caused a 60% reduction in the strength of Voronoi honeycombs). The sensitivity to defects was comparable for thin-walled, elastomeric honeycombs (relative density 0.015) and for thicker walled, plastic honeycombs (relative density 0.15). The properties degraded to zero when 35% of the cell walls were removed, consistent with the percolation limit for a two-dimensional network of hexagonal cells. When four or more adjacent cell walls were removed, the localized band of cell collapse passed through the defect site and the effective strength and modulus were reduced, indicating that even those defects which have a negligible effect on density can alter the failure pattern as well as the effective properties of honeycombs with cells of approximately equal size and strength.     

大吨位自卸车货厢高强度钢板强度等代设计

对大吨位自卸车货厢高强度钢板等代设计问题进行了研究,以弹性力学和板壳理论为基础,推导出利用高强度钢板进行强度等代设计时板厚的计算公式,给出了具体的等代设计流程图,并对大吨位货厢进行了轻量化设计。在不改变货厢原结构情况下,实现了货厢减重1679.757kg,约32.95%,取得了较好的轻量化效果。     

轴心受压高强钢圆管稳定承载性能研究

对770MPa级高强钢管件的初始几何缺陷、残余应力和本构关系进行了测试,完成了66根770MPa级不同规格高强钢管件的轴压极限承载力试验,结合仿真分析,验证了添加初始缺陷的一致模态法分析高强钢管件极限承载力的准确性。     

复杂载荷下传动轴强度与刚度的程序化求解

用传统方法求解有复杂载荷作用的传动轴的强度与刚度,需要十分繁重的计算工作量。利用奇异函数描述轴的弯矩方程、扭矩方程和抗弯截面模量方程,推出在任何载荷作用下传动轴所受应力、转角和挠度的通用方程式,采用一维优化方法,借助计算机技术求解传动轴在复杂载荷作用下的强度与刚度,突破了传统求解方法,便于计算机编程处理,适应范围广,对受不同载荷以及含有不同几何形状的阶梯轴具有通用性,且可提高机械工程设计效率,具有较高的工程实用价值。     

弹性元件对受轴向工作载荷螺纹联接强度的影响

弹性元件作为一种常用的机械元件,经常应用于螺纹联接中。为了深入分析弹性元件对螺纹联接强度的影响,对不同联接方式下的螺栓联接进行了刚度分析和受力分析,从理论上提出弹性元件有增大螺栓相对刚度、增大螺栓受力的作用,由此得出弹性元件削弱螺纹联接强度的观点。同时,应用ANSYS仿真软件对不同联接方式下的螺栓联接进行有限元仿真分析,以螺栓的受力、变形的差异说明理论分析的正确性。将这一正确结果应用在实际工程中,有助于提高螺纹联接的强度。     

普通钢与高强度钢激光拼焊板数值模拟比较研究

为了研究高强度钢激光拼焊板的成形性能,基于LS—DYNA软件,以典型的盒形件为研究对象,从材料流动、最大增厚率、最大减薄率和成形极限图等方面,比较了普通钢和高强度钢激光拼焊板在不同压边方式下的变形情况,得到了高强度钢激光拼焊板的成形性能。研究结果表明,该研究为高强度钢激光拼焊板的实际成形和工艺优化提供了理论依据和指导。     

BR1500HS高强钢板淬火工艺实验研究

以宝钢生产的热轧板BR1500HS为对象,利用加热炉及拉伸试验机等设备对其进行淬火性能实验研究。研究了该钢板在水冷、风冷及空冷条件下淬火后板料的抗拉强度和金相组织。同时,研究了该钢板从炉中取出到开始淬火这段时间板料的温度变化与时间的关系。对于高强钢热冲压成形工艺设计具有很重要的指导意义。     

钻削高强度钢的切屑形态仿真及试验研究

为探究钻削34CrNi3MoV高强度钢时切屑形态的变化规律,一方面,通过运用AdvantEdge有限元仿真软件,通过选取不同的刀具几何参数和切削用量的组合,进行钻削加工过程的仿真,得到不同切削条件下的切屑几何参数及切屑形态;另一方面,在加工中心上进行钻削34CrNi3MoV高强度钢的切削试验,通过试验与仿真结果的对比分析,进一步验证切屑形态仿真结果并分析其原因。研究结果表明,钻削加工高强度钢时,通过改变刀具几何参数和切削用量可以有效地改变切屑形态及切屑几何参数,为实现高效钻削高强度钢的实际应用提供理论基础。     

一种中厚钢板全自动切割设备的环保工艺及装备

介绍氧乙炔焰、等离子弧水下切割中厚钢板工艺及防撞机构的结构特点、工作原理,对解决现场环保问题,有重要的实用意义.     

AOD精炼高强度低合金钢工艺及应用

从AOD工作层砌筑与烘烤、电弧炉熔炼配合、AOD精炼操作过程控制及产品验证等方面进行阐述,证明用AOD与电弧炉双联精炼高强度低合金钢工艺切实可行.     

Tribological properties of hardened high strength Boron steel at combined rolling and sliding condition

The use of hardened high strength steel is found in applications where high wear resistance is required. The wear properties of high strength Boron steel are well known in applications with abrasive wear from stones, ore and other hard material. A unique concept of wear protection of rails is newly presented, a wear resistant cap made of hardened high strength Boron steel.Reducing the wear of rails and wheels and controlling the frictional behavior in the wheel/rail contact are two key issues for railway owners in order to reduce the increasing costs related to higher axle loads, higher speeds, more frequent traffic, etc. Therefore, the aim of this work has been to investigate and compare the tribological properties of Boron steel and UIC 1100 rail steel in contact with Blue Light wheel steel (AAR Class C (69-JDG-8)) under dry and water lubricated conditions in a two-disc tribometer. Advanced analytical instruments including 3D optical surface profiler, micro-hardness indenter, light microscope and SEM/EDS were used to analyze the results.Results from the experiments show that the friction coefficient in tests with Boron steel is more stable both in dry and water lubricated conditions than tests including UIC 1100 rail steel used in todays application. Surface damages seen from water lubricated tests on UIC 1100 rail steel are not seen on the surface of the Boron steel discs. In all tests, the wear decreased when water was added in the contact and friction was slightly decreased.     

CF62低合金高强度钢在严寒地区汽车车架上的应用

研究了CF62低合金高强度钢的机械性能和可焊性，并采取措施对CF62钢的焊接质量进行控制结果表明，其焊缝成形美观，机械性能、低温韧性和焊接性能基本满足严寒地区用汽车车架的要求。     

Plastic mechanism and elastic-analytical approaches applied to estimate the strength of an axially compressed-thin-walled channel steel section beam

This paper presents the study of an analytical model to estimate the strength of a thin-walled channel steel section beam subjected to axial-compressive loads. The model is based on two different methods of analysis, which are performed by analysing a plastic failure mechanism and elastic behaviour of the beam. These analytical methods can be used to establish plastic-unloading and elastic-inclining-theoretical load-deflection behaviour of the beam. Meanwhile, the axial-compressive strength of the beam is estimated by directly measuring the value of load at an intersection point between two different curves of the theoretical load-deflection behaviour. The accuracy of using this analytical model is also verified by comparing its estimated data of the strength to the one obtained from a number of tests on 38 specimens of thin-walled channel steel section under the test loads of axial compression. It is clearly shown that deviation of the analytical data from the experimental one is still scattered within acceptable limits of ±20%. A statistical analysis of the scattered data indicates that its mean value is 1.03 with standard deviation of 0.058. This certainly means that the estimated strength, on average, displaces from the actual one by 3% and mostly tends to be conservative.     

喷丸与激光喷丸强化高强度钢对比试验

为了考察和对比喷丸(SP)和激光喷丸(LSP)2种表面强化技术对金属零件的强化效果,以30CrMnSiNi2A钢为试样,进行喷丸和激光喷丸强化处理试验。试验结果显示,2种强化试样的残余压应力和硬度都有较大的提高。分别测定了喷丸强化和激光喷丸强化试样在同一应力水平下的疲劳寿命,并运用扫描电镜分析了两者的疲劳断口。试验结果表明,激光喷丸强化试样中值疲劳寿命是喷丸强化试样的1.11~2.75倍,激光喷丸强化比喷丸强化在提高金属零件表面性能方面的效果更佳。     

Finite element analysis of the effect of interfacial roughness and adhesion strength on the local delamination of hard coating under sliding contact

The interfacial roughness and the adhesion strength are very important for making a high-quality coating for friction and wear applications. In order to obtain a quantitative understanding concerning the effect of the two factors on the local delamination of hard coatings, finite element analyses concerning the maximum shear stress in a hard coating with various kinds of interfacial roughness and adhesion strength were made under low and high frictional conditions. As a result, local delamination maps for the identification of the local delamination of hard coatings were obtained as a function of the shear strength ratio of coating to substrate and the ratio of coating thickness to half-contact width. Also, the critical contact pressure required to produce local delamination of hard coatings is given.