Supporting characteristics analysis of constant resistance bolts under coupled static-dynamic loading

To study the tensile mechanical properties of constant resistance bolts, the RFPA(Rock Failure Process Analysis) statics software is used to perform a uniaxial tensile test on a constant resistance bolt. The numerical test results show that the plastic strain value is 12 times the magnitude of the elastic strain. During plastic deformation, the fluctuation in the stress magnitude is relatively stable, indicating that the bolt has good constant resistance characteristics. The numerical test results are in good agreement with the laboratory test results of M.C. He, and the accuracy and reliability of the numerical test method are verified. Therefore, the RFPA software with coupled static-dynamic loading is further adopted to study the supporting effects of traditional bolts and constant resistance bolts under coupled staticdynamic loading. The numerical comparison of the test results show that the constant resistance bolts can effectively control the deformation amount and rate of the laneway surrounding rock, reduce the total and rate of increase in the accumulated acoustic emissions,decrease the stress on the units in the model and protect the stability of the laneway. This paper verifies that a constant resistance bolt has better impact resistance mechanical properties than those of a traditional bolt and provides an effective way to control rock burst and soft rock that is prone to large deformation damage.

Dent Resistance for Automobile Body Panels

Dent resistance of automobile body panels is an important property for automobile design and manufacture, but the study on this aspect is not still profound. This study is to summarize the testing methods and physical significations of static and dynamic dent resistance of automobile body panels combined with the author＇s study, and to analyze the dent behaviors in the round. Several influence factors on dent resistance are expatiated including the mechanical properties of materials, stress states after forming, bake hardening ability, modulus, methods of testing, and structure of specimens and so on. The automotive lightweight and application of high strength steel sheets and aluminum alloys sheets are analyzed, and the significance of testing of dent resistance, especially for dynamic dent resistance of auto-panels, and the finite element simulation analysis are emphasized. To explain the physical phenomenon of dent behaviors, the latest and concerned study results are also discussed. According to this study, a dent resistance test and evaluation standard of Society of Automotive Engineers of China for automotive body panel is presented and is being carried out, and an industry conference is hold to discuss the working-out of the standard, a primary schedule of this standard is confirmed now. The study can guide the further testing and study of dent resistant of auto-panels.

Finite element analysis of stiffness and static dent resistance of aluminum alloy double-curved panel in viscous pressure forming

The static dent resistance performance of the aluminum alloy double-curved panel formed using viscous pressure forming (VPF)was studied by finite element analysis,which mainly considers the forming process conditions.The whole simulation consisting of three stages,i.e.,forming,spring-back and static dent resistance,was carried out continuously using the finite element code ANSYS.The influence of blank holder pressure(BHP)and the drawbead on the stiffness and the static dent resistance of the panels formed using VPF was analyzed.The results show that the adequate setting of the drawbead can increase the plastic deformation of the double-curved panel,which is beneficial to the initial stiffness and the static dent resistance.There is an optimum BHP range for the stiffness and the static dent resistance.

Wear Resistance and Indentation Behavior of Equiatomic Superelastic TiNi and 60NiTi

Indentation and reciprocating wear tests are carried out to study dent and wear resistance of superelastic Ti-Ni alloys. The effect of loading rate on the superelastic behavior of TiNi under indentation loading is investigated and compared to a new generation of shape memory alloys, i.e., 60NiTi. Only limited amount of work has been done to investigate the dependency of superelasticity on loading rate of TiNi under localized compressive loads, but much work is directed towards understanding the effect of strain rate on tensile properties. Understanding the superelastic behavior helps to employ superelastic alloys in applications where high impact loading is expected as in bearings and gears. In the present study, it is found that dent resistance of Ti-Ni alloy is not significantly affected by loading rate (within the employed loading conditions). It has also been found that new-generation 60NiTi alloy exhibits superior wear and dent resistance, as well as higher hardness compared to equiatomic TiNi.

Research on dent resistance of lightweight three-piece cans

An experimental apparatus and a numerical simulation model were built for investigating the dent resistance of lightweight three-piece cans.The dent resistance of raw materials 0.19 mm T4 and 0.17 mm DR7M was compared.It was found that when the thickness reduced from 0.19 to 0.17 mm,the dent resistance became about 80％ of that before thinning.This provides a guidance for the continuous thinning of three-piece cans.

New Methodology for Evaluating Toughness of Composite Laminates-Investigation of Damage Resistance

The existing problems in toughened resin evaluation technology, particularly the disadvantage of the toughened resin identification method by CAI, is pointed out based on the point of view of composite structure design. It is proposed to evaluate the toughness of composites by both damage resistance and damage tolerance. Seven different toughness composites are investigated by impact and quasi\|static indentation tests. Based on experimental data analysis, the parameter that is most sensitive to the damage resistance is determined as the damage parameter. The parameter to evaluate the damage resistance and its measuring method are proposed.

基于厚度和应变映射方法的成形和抗凹性能联合仿真

为提升汽车板抗凹性能仿真精度,开展了成形和抗凹性能仿真研究。首先,利用模具将HC180BD+Z板料冲压成两种应变量的试样,然后利用半球形钢制压头以10 mm/min速度对试样进行加载,获得试样初始刚度和失稳凹陷载荷;其次,利用Ls⁃dyna进行成形和抗凹性能仿真,不考虑成形因素的影响下,初始刚度和失稳凹陷载荷仿真误差<10%,通过采用厚度和应变映射方法后,初始刚度和失稳凹陷载荷仿真误差<5%;最后,对比分析了厚度和应变映射对初始刚度和失稳凹陷载荷仿真结果的影响。研究表明:初始刚度与材料厚度相关,而失稳凹陷载荷与材料厚度和屈服强度相关;通过采用厚度和应变映射方法,能有效提升抗凹性能仿真分析精度;各向同性硬化模型高估了失稳凹陷载荷,采用各向同性和随动混合硬化模型能获得更好的仿真结果。

汽车覆盖件抗凹性能研究进展

随着汽车轻量化和个性化的发展,汽车车身材料更多的选择铝合金等轻质材料,因此,对于汽车外覆盖件的抗凹性提出了更高和更严苛的要求。主要总结了汽车外覆盖件静态和动态抗凹性能的影响因素,以及在预测分析和评估方面的研究进展,并阐述了为满足实际应用和技术支持的需要,抗凹性测试的设备设计与测试方法的最新进展。

汽车钢板抗凹性试验研究

汽车零件,尤其是外覆盖件的制造过程中选择钢材等级和规格的重要依据之一是抗凹性.以实验评估为基础介绍抗凹性评估相关参量的物理意义及测量原理,并对数种钢板在不同加工硬化和应变硬化状态下的静态抗凹性行为进行分析.研究表明,本抗凹性评估方法合理,可应用于薄板材料的抗凹性研究.

汽车钢板抗凹性试验方法及其应用

通过对汽车钢板抗凹性试验方法的研究 ,表明基于一定预变形下的胀形件载荷 -挠度曲线而提出的抗凹性指标。局部凹陷抗力、抗凹刚度和起伏载荷 ,反映了胀形件抵抗变形、保持形状的能力。同时测定的不同强度钢板抗凹性试验结果 。

基于Autoform的汽车用钢抗凹性模拟研究

基于板料成形模拟的专用软件Autoform,以武钢材料真实数据库进行材料定义,建立了抗凹性数值分析模型,分析了不同材料的抗凹性,总结了材料厚度和屈服强度等指标对于材料抗凹性的影响。研究表明,用有限元模拟方式研究汽车用钢抗凹性具有较高的准确度和可靠性;选择屈服强度较高、厚度较大的材料可提高覆盖件的抗凹性能,但同时需兼顾材料的冲压成形性能,以达到最佳效果。

汽车板材动态抗凹性数值模拟研究

运用有限元数值模拟方法对汽车板材胀形试件的胀形过程及其动态抗凹变形过程进行了模拟 ,研究了胀形试件的动态凹痕变形机理 ,得到了不同参数对胀形试件动态抗凹性能的影响规律 。

基于预变形的静态抗凹性模拟分析

本文用ABAQUS准静态算法对基于胀形预变形试件的静态抗凹性进行了模拟 ,分析了预变形量及板材类型对静态抗凹性能的影响 。

车身覆盖件抗凹性试验方法及系统

针对实际汽车车身外覆盖件的特点,建立了其静态抗凹性试验评估方法;并以试验方法为基础,设计开发了覆盖件抗凹性自动化试验机系统.试验机系统通过集成"5个运动轴+1个加载轴",保证了加载压头的空间调整能力和可靠加载;基于可编程多轴运动控制器(PMAC,Programmable Multi-Axis motion Controller),通过建立"PC+运动控制器"的控制系统并开发相应的软件系统,实现了对6轴试验机系统运动调整及加载的精确控制;利用近似方法,求解了覆盖件上试验点的法向矢量,并基于机器人运动学原理计算了试验机加载压头由初始位置调整到试验点法方向的运动参数,实现了加载压头的自动法向调整.通过对试验机进行计量并应用,表明试验机系统稳定可靠.

各向同性钢与烘烤硬化钢的烘烤硬化性和抗凹陷性

研究了烘烤温度、烘烤时间和预拉伸应变量对罩式炉退火工艺生产的各向同性钢的烘烤硬化性的影响,并与力学性能相当的冷轧烘烤硬化钢进行了对比。结果表明,在不同的烘烤条件下,各向同性钢的烘烤硬化值均低于同样强度级别的烘烤硬化钢。抗凹陷性测试结果表明,各向同性钢的抗凹陷性低于烘烤硬化钢。汽车外板实物分析结果表明,两种钢冲压成形后再烘烤,其屈服强度几乎没有提高。

汽车覆盖件抗凹性实验评估及测量装置设计

对汽车覆盖件抗凹性的评估指标和实验方法进行了介绍,并综合运用机械装置和Lab VIEW程序,设计出一套抗凹性测量装置。该装置简单、实用,可供机械设计师参考。

铝合金板材抗凹性能研究

通过力学性能测试、烘烤硬化性能测试和抗凹性能测试,研究了用于制备汽车覆盖件的6016铝合金板材的抗凹性能以及抗凹性与材料力学性能和烘烤硬化性能之间的关系。结果表明:6016铝合金板材经两年自然时效后,其强度略有增加,加工硬化指数n值和延伸率增大;板材在不同温度条件下经30 min烘烤后强度增加,烘烤硬化值随着温度升高而显著增加,表现出良好的烘烤硬化性能;板材的抗凹性能与烘烤工艺有关,烘烤温度越高,烘烤后材料的屈服强度越高,板材的抗凹性能越好。

车顶覆盖件抗凹和抗雪压性能分析与评价

本文中运用有限元数值模拟研究了车身顶盖的抗凹性能和抗雪压性能。首先建立了车身顶盖结构有限元模型,确定了载荷工况和边界条件,进行了车身顶盖覆盖件抗凹性和抗雪压性分析。接着将FMVSS216压溃试验标准、GB26134—2010抗压强度标准和企业使用的典型评价准则相结合,提出了适用于CAE分析的车身顶盖抗凹性能和抗雪压性能评价方法,最后通过某一车身顶盖的分析验证了所提出方法的合理性,为车身顶盖抗凹性设计提供了参考。

B180H1钢板成形性能研究

高强度烘烤强化(BH)钢是汽车覆盖件用的高强度钢板。本文通过试验对汽车用高强度钢板B180H1的力学性能、成形性能、烘烤硬化性能和抗凹陷性能进行了全面的研究,并与DC04钢板的各项性能进行了比较。使用NADDRG模型对B180H1钢的成形极限进行了预测。试验结果表明,与DC04钢相比,B180H1钢的屈服强度提高了40.8%,抗拉强度提高了18.4%,延伸率下降了15.6%,且B180H1的塑性应变比和应变硬化指数也高于DC04钢。这说明B180H1的力学性能优于DC04,成形性能不低于DC04,且B180H1的烘烤硬化性能及抗凹陷性能方面均优于DC04。

外覆盖件抗凹性能的模拟仿真研究(英文)

在汽车外覆盖件成形过程中,对于各种冲压缺陷都必须进行分析、评估。文章采用静力显示有限元算法对汽车外覆盖件的静态抗凹性能进行了数值模拟研究,分别研究了覆盖件的抗凹性能与材料、成形条件及面板曲率的关系。结果显示,高强钢能够提高覆盖件的抗凹性能,面板的抗凹性能随着面板的厚度和压边力的增大而增加,而且覆盖件曲率越小,其静态抗凹性能则越高。