铆接铆钉分布压力的计算

分析计算铆接铆钉所需的压力、铆接成型后铆钉对板孔圆柱面上的径向分布压力和铆钉帽对板圆环面上的分布压力 ,对工程实际具有一定的参考价值。同时 ,在对一些具有铆钉连接的板或梁进行有限元分析和计算时 ,解决了其力边界条件的问题     

真空助力器壳体铆接螺栓分布压力的计算

分析计算真空助力器壳体铆接螺栓铆接所需的铆接力和铆接成型后铆钉对真空助力器壳体铆接孔圆柱面上的径向分布压力,对助力器壳体加工制造具有参考价值,在对真空助力器壳体进行有限元分析和计算时,解决了确定边界条件的问题。     

航空结构宽板铆接搭接件承载性能数值研究

为研究飞机蒙皮铆接搭接结构的力学特性,基于ANSYS软件建立宽板三排铆钉搭接件的三维有限元分析模型。考虑物面间的非线性接触、铆钉与板孔间的干涉配合、铆钉预紧力的影响,应用非线性有限元法对宽板铆接搭接件在恒定远端拉伸载荷作用下的承载性能进行计算。通过读取沿预设路径的位移分布数据,获得宽板搭接件产生的次弯曲和第三弯曲的变形趋势。从搭接板等效应力云图可以看出,靠近宽搭接板侧缘的沉头铆钉孔周围应力集中比较严重。计算每个铆钉的钉传载荷,获得宽板搭接件铆钉承载的分布规律。在调整铆钉预紧力和钉孔干涉配合量的情况下,给出三排铆钉载荷传递比的变化情况。针对宽板铆接搭接件的力学特性计算分析,可以为后续的搭接件结构多处损伤裂纹扩展和疲劳寿命研究奠定基础。     

含裂铆接搭接板应力强度因子分析方法

针对工程中广泛存在的铆接搭接结构断裂问题，充分考虑搭接板裂纹通过铆钉后铆钉继续传力的特点，利用位移连续条件，提出裂尖应力强度因子有限元分析模型。计算典型铆接搭接结构应力强度因子曲线，分析所提模型及其计算结果的合理性、正确性。提出的计算方法为铆接搭接结构应力强度因子提供了便捷、有效的分析手段，所得结果可供工程结构损伤容限分析时参考。     

轻量化薄板无铆钉铆接的力学性能及接头断裂机理

轻量化作为汽车节能减排的重要手段,得到世界各国的高度重视。目前车身大都采用多材料混用,而异质材料用传统电阻点焊难以形成可靠连接。无铆钉铆接技术是一种冷成形连接工艺,避免了接头热输入问题,通过材料的机械自锁作用形成有效接头。文章通过控制铆接行程,凸凹模直径等参数对不同材料匹配的铆接试样进行拉剪实验。结合成形过程中力-位移曲线,研究无铆钉铆接接头的力学性能及断裂机理。研究发现,拉剪过程中铆接试样出现三种断裂模式,即上层板铆钉压溃,界面断裂和下层板铆钉塑性变形。其中,发生下层板铆钉塑性变形断裂模式的试样表现出更高的拉剪强度和较好的吸能效果。对于界面断裂、上层板接头颈部发生开裂,接头拉剪强度取决于上层板侧壁厚度。     

摆碾铆接过程数值模拟分析

应用DEFORM-3D有限元分析软件建立碾压铆接有限元模型,对摆碾铆接工艺过程进行数值模拟。分析了其成形过程的三个阶段、应力应变和行程载荷曲线的变化趋势,结果表明最大应力应变都集中在铆钉头部边缘区,边缘区点最先受到旋压力开始变形,最早发生屈服现象并进入弹塑性变形阶段;铆钉在相同行程下达到相同的成形效果时,碾压铆接需要的载荷要远远低于传统铆接的载荷。最后分析了影响碾压铆接质量的几个核心因素,如铆头速度、铆头倾斜角度等,为有效地进行碾压铆接工艺研究提了供理论依据。     

基于超声振动辅助铆接技术研究

针对无人机中铆钉连接难成形问题,提出超声振动辅助铆接技术.通过仿真与试验结合的分析方法,进行了超声振动对铆接压力和干涉量影响的研究.结果表明,超声振动技术能有效降低铆接压力约20％,随着铆接速率的增加,超声振动降低铆接压力的效果逐渐弱化;超声振动辅助铆接技术可以获得较大且分布更均匀的干涉量,提高了铆接件的疲劳寿命.     

大型轴承实体保持架铆接机的设计及支架分析

目前企业在铆接大型轴承实体保持架的过程中由于采用手动铆接技术使得铆接过程经常出现毛刺、对中性差等问题,导致合格率较低。针对上述问题,设计了一种具有找正铆钉功能的新型双头卧式摆碾铆接机。分析了铆接机的工作流程并依据铆钉参数进行了铆接力及动力头参数计算,其中铆钉最大直径为准10mm,最小铆接力大小为F_(min)=11643N。对电机受力进行了计算及有限元静力学分析,结果表明电机支架在铆接力最大应力为σ_(max)=10.895MPa,最大形变量为δ_(max)=0.0408MPa。设备的机械强度设计满足生产要求,机架设计合理可靠。     

考虑钻孔应力的铝合金板铆接变形实验

针对具有多个铆钉连接的铝板这一典型航空结构件,提出了ABAQUS中铆接等效建模方法,探讨了钻孔应力对铝板的变形影响。首先考虑钻孔引入的应力、铆接时铆钉自身膨胀力以及多个铆钉连接的相互耦合作用建立ABAQUS铆接等效模型,并仿真计算得出铝板压铆后的变形结果;然后进行了普通切削和线切割铝板的铆接实验;最后将实验结果与仿真结果对比,证明了钻孔应力对铆接变形的显著影响和仿真方法的有效性。     

一种崭新的铆接工艺——应力波铆接

由于航天科学的高速发展,对材料的要求也越来越高。为了满足某些特殊要求,用高强度、耐高温、耐腐蚀的钛合金来代替铝合金。同时对钛合金的铆接工艺和铆钉材料也提出了相应要求。为此,我们对钛合金铆钉的铆接工艺进行了探索。钛材的屈强比σ_s/σ_b非常接近,手工铆接很难控制压力。当压力低于屈服限σ_8时,铆钉不会成形,而压力稍高时,又会因超过强度限σ_b而产生裂纹(钛合金的应力——应变曲线见图1)。所以用常规压缩空气驱动的气铆,铆接的合格率极低。有的单位为了避     

Effect of hole perpendicularity error and squeeze force on the mechanical behaviors of riveted joints

In the automatic drilling and riveting process, the perpendicular error of the hole is inevitable, which has a great influence on the assembly quality. In the current research, the shear and pull-out behaviors of riveted joints under different perpendicularity errors and squeeze forces were investigated and compared by the quasi-static tests. The fracture of the failed samples was characterized by a scanning electron microscope and the formation process of fracture was discussed. The failure mechanisms of riveted joints were analyzed in detail to guide engineering applications. The test results demonstrated that the shear load and pull-out load of riveted joints increased slightly with the increase of the tilt angle from 0° to 4°. The perpendicularity error did not affect the shear and pull-out failure modes of the riveted joints. However, the squeeze force had a significant effect on the failure modes of the pull-out samples. Fracture analysis showed that the failure of all shear samples occurred at the rivet shaft. Besides, when the squeeze force increased from 15 kN to 23 kN, the failure modes of the pull-out samples changed from the sheet to the rivet itself.     

Experimental and numerical studies of stress/strain characteristics in riveted aircraft lap joints

The fatigue property of riveted lap joint is greatly related to the riveting-induced residual stress, especially the stress distribution on the faying surface. However, an accurate study of the residual stress characteristics in the riveted sheet could be very difficult. In this paper, both numerical and experimental investigations were carried out on the stress/strain characteristics in riveted aircraft lap joints. A special specimen was designed for the test of strain variations on the faying surface of the sheet by microstrain gages. For the numerical simulation, the rivet squeezing process was analyzed using the explicit dynamic finite element (FE) method, whilst a general static FE analysis was employed for the elastic springback after the squeeze force was removed. A comparison of the strain variations between the experimental results and FE simulations shows a general good agreement, although there may be some difference for points measured near the hole surface. The FE analysis reveals that both compressive and tensile residual stresses could be introduced in the riveted sheet. Massive compressive residual stress can be created in the near-surface layer of the hole. However, the stress level is not always increased with increasing the squeeze force, and so is the improvement of fatigue life observed. Further study is still necessary to account for the fatigue life decreasing effect caused by a high squeeze force.

     

Numerical analysis of static performance comparison of friction stir welded versus riveted 2024-T3 aluminum alloy stiffened panels

Most researches on the static performance of stiffened panel joined by friction stir welding（FSW） mainly focus on the compression stability rather than shear stability. To evaluate the potential of FSW as a replacement for traditional rivet fastening for stiffened panel assembly in aviation application, finite element method（FEM） is applied to compare compression and shear stability performances of FSW stiffened panels with stability performances of riveted stiffened panels. FEMs of 2024-T3 aluminum alloy FSW and riveted stiffened panels are developed and nonlinear static analysis method is applied to obtain buckling pattern, buckling load and load carrying capability of each panel model. The accuracy of each FEM of FSW stiffened panel is evaluated by stability experiment of FSW stiffened panel specimens with identical geometry and boundary condition and the accuracy of each FEM of riveted stiffened panel is evaluated by semi-empirical calculation formulas. It is found that FEMs without considering weld-induced initial imperfections notably overestimate the static strengths of FSW stiffened panels. FEM results show that, buckling patterns of both FSW and riveted compression stiffened panels represent local buckling of plate between stiffeners. The initial buckling waves of FSW stiffened panel emerge uniformly in each plate between stiffeners while those of riveted panel mainly emerge in the mid-plate. Buckling patterns of both FSW and riveted shear stiffened panels represent local buckling of plate close to the loading corner. FEM results indicate that, shear buckling of FSW stiffened panel is less sensitive to the initial imperfections than compression buckling. Load carrying capability of FSW stiffened panel is less sensitive to the initial imperfections than initial buckling. It can be concluded that buckling loads of FSW panels are a bit lower than those of riveted panels whereas carrying capabilities of FSW panels are almost equivalent to those of riveted panels with identical geometries. Finite elem     

整体壁板结构纵向连接接头的应力分布研究

纵向连接接头是影响机身整体壁板结构的安全疲劳寿命的关键部位,因此本文设计了一种适用于机身整体壁板纵向连接的阶梯状两台阶铆接接头结构。文中应用ANSYS软件建立阶梯状两台阶铆接接头结构的三维非线性有限元模型,进行静强度有限元分析,得到接头结构上的精确应力分布,确定各铆钉孔边危险点处的应力集中系数,对接头结构的疲劳性能分析有着重要的参考基础,为纵向连接接头的设计及综合验证提供科学依据。     

Effect of rivet die structure on the quality of riveted aircraft structures using slug rivet

The International Journal of Advanced Manufacturing Technology - Slug rivet interference-fit riveting is an advanced connection technology. The quality of riveted aircraft structures can be evolved...     

Microstructure investigation and mechanical property analysis in electromagnetic riveting

Electromagnetic riveting (EMR) is a new joining technology based on high-speed magnetic impulse forming and conventional riveting. EMR experiments were conducted on dual-layered 2A12 aluminum alloy sheets with one 2A10 aluminum alloy rivet. Observation of the microstructure and mechanical properties of rivet heading verified the forming quality of the heading. And, mechanical property tests were performed to evaluate the durability of riveted specimens through shear and pull-out loading. Microstructure observation indicated that adiabatic shear bands, where the deformation was highly concentrated, were an important characteristic of deformed structures in rivet headings under electromagnetic riveting. The distribution law of hardness in rivet headings was obtained. The compressive yield strength of rivet headings increased 70 % over that of the original rivets. Riveted specimens were capable of withstanding shear loads of 23.2 kN and pull-out loads of 35 kN. Ruptures characterized by a scanning electron microscope were found to be due to shear failure.     

基于CAD/CAE计算铆钉连接件疲劳寿命

介绍了航空器铆接结构件模型建立及参数选取情况.采用SOLIDWORKS和COSMOS软件,计算出铆钉孔的应力集中系数Kt.然后,应用诺伯法和应力功恒等法计算出连接件的疲劳寿命.最后结果显示:采用CAD/CAE技术可以简化计算过程;通过对Kt值的修正,可以提高计算疲劳寿命的精度.     

塑件光盘座的冷铆装配工艺

塑料零件采用冷铆装配工艺,因不改变塑料结晶体组织,可以提高铆接强度;室温下铆接,可减少因温差造成的装配变形。文中结合塑件光盘座冷铆装配实例,从理论、试验和铆头设计等方面介绍了光盘座的冷铆装配工艺。