模具工艺参数对自冲铆接工艺过程及铆接质量的影响

通过对6063铝合金板料自冲铆接过程的实验和数值模拟,分析了自冲铆接工艺过程中半空心铆钉和板料的变形和受力.对比研究了铆接过程中铆钉载荷与位移的关系曲线,探讨了模具的深度、模具凸台高度和模具圆角半径对铆接质量的影响.研究表明,计算机模拟与实验结果吻合良好,自冲铆接工艺参数的探讨为提高铆接质量提供了理论依据.     

Study of the impact of riveting sequence, rivet pitch, and gap between sheets on the quality of riveted lap joints using finite element method

Sheet metal parts are widely used in the assembly of aircraft. The most common method of joining sheet metal parts is through riveting. There are many parameters associated with a riveting process that affect the quality of rivets and the integrity of the final assembled product. This paper presents a study on the effect of some controllable process parameters in riveting (i.e., the sequence of riveting, distance between rivets (pitch), and gap between sheets) on the quality of riveted lap joints and the formed rivets. The study is performed on a one eight-inch nominal diameter flat head Tinner rivet and 0.064-in.-thick aluminum sheet. Finite element simulation is used as a means of modeling and analysis of the riveting process. Statistical design of experiment is employed to analyze the simulation data. A good combination of riveting process parameters is found which minimizes the residual stress in sheets and rivets, bulging and material growth in sheets, and which reduces the chances of postriveting clearance in a riveted lap joint.     

Durability of riveted joints of the fuselage skin

Experimental studies of the fatigue and durability of panels forming a longitudinal lap joint of the fuselage skin are considered. Correction factors for calculating strain intensities, panel durability until crack formation, the duration of the process of fatigue crack growth until damage to panels, and criteria of their residual strength are given.     

铆接工艺参数分析

为了充分了解铆接后铆钉及被连接件的残余应力分布状态,以及精确分析残余应力和铆接工艺参数之间的关系,采用非线性有限元分析软件ABAQUS建立了铆钉连接的参擞模型,通过准静态方式模拟了铆钉连接时铆钉和被连接件的变形过程.根据分析结果建立了残余应力和铆钉钉杆长度及钉孔间隙之间的关系式和关系曲面.结果表明,残余应力随着钉杆长度的增加而增大,而随着钉孔间隙的增大而减小,增加钉杆长度或减小钉孑乙间隙可有效增大残余应力,为实际的铆钉连接工艺过程提供了有益的指导.     

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.     

Effect of riveting process parameters on the local stress field of a T-joint

Rotorcraft airframes are complex structures designed to satisfy different goals; fatigue life represents one of the most critical issues, which must be guaranteed throughout the design and the construction phase. In this scenario riveted joints play an important structural role especially because of the variable loads they are subjected to. Their fatigue behaviour is strictly influenced by the local stress fields left very near to the holes during riveting manufacturing operations. Therefore, with the aim to improve design awareness, the effects of the different parameters involved during the riveting process are herein investigated. The effects of the squeeze force, the clearance, the rivet length and the clamping angle in the stress field of the joints are considered by means of numerical models. Detailed finite elements models (including rivet forming formation) are validated through experimental tests. These models are aimed at obtaining an accurate stress–strain field in the most stressed zone including the residual stress in the holes. Finally, using the literature fatigue data of Al8090-T81 and the Crossland multiaxial fatigue criterion, the influence of the riveting parameters on the fatigue strength is evaluated for optimisation purposes.     

Static and dynamic behaviour of composite riveted joints in tension

The tensile response and failure of composite riveted joints are studied experimentally in the present paper. Seven joint configurations for aircraft application are tested at quasi-static, 4 and 8 m/s nominal loading rates. Joint specimens are made of CFRP in a number of lay-ups of unidirectional tapes and woven fabrics. A dynamic tensile test method is designed to give reliable test results. It is shown that the variation of tensile strength with loading rate is negligible for the tested composite riveted joints. However, for most of the tested specimens, the average total energy absorption of the composite joint increases with increasing loading rate. Various failure modes are identified for various joint designs and it was found that joint failure modes can change with varying loading rates.     

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...     

Evaluation of the health of riveted joints with active and passive structural health monitoring techniques

Many active and passive structural health monitoring (SHM) techniques have been developed for detection of the defects of plates. Generally, riveted joints hold the plates together and their failure may create accidents. In this study, well known active and passive methods were modified for the evaluation of the health of the riveted joints between the plates. The active method generated Lamb waves and monitored their propagation by using lead zirconate titanate (PZT) disks. The signal was analyzed by using the wavelet transformations. The passive method used the Fiber Bragg Grating (FBG) sensors and evaluated the spectral characteristics of the signals by using Fast Fourier Transformation (FFT). The results indicated that the existing methods designed for the evaluation of the health of individual plates may be used for inspection of riveted joints with software modifications.     

轻型车身自冲铆接头拉伸剪切实验的研究

自冲铆接是一种很有潜力的连接工艺,尤其对于轻型材料(轻合金、复合材料等)的连接。文中对2 mm厚铝合金板5052的自冲铆连接试件进行了研究,分析了整个铆接过程;采用有限元分析软件ANSYS分析了自冲铆接结构;利用AG-IS力学实验机对铆接试件进行了拉伸剪切实验,通过8组实验数据分析对比,分析了铆接试件的断裂形式;客观地评价了自冲铆连接技术对汽车轻量化制造的重大意义。     

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.

     

浪形保持架特殊铆合模的设计及工艺改进

针对浪形保持架54等分铆合模等分球窝无法加工的问题,增加了工艺孔,减少了不必要模具的制造,节约了成本,缩短了生产周期。     

铆接过程中进给速度对轮毂轴承性能的影响

第三代轮毂轴承单元在加工过程中普遍使用铆接加工方法,铆接时的进给速度会对轮毂轴承的性能带来很大影响。通过试验方法测得不同的进给速度下铆接对芯轴的塑性变形而产生的应变,计算出因为变形而引起的卡紧力大小和内圈的压缩量,再利用ANSYS Workbench进行有限元仿真,分析由于变形对轮毂轴承性能的影响,从而可以得到合适的进给速度,为加工过程中控制铆头的进给速度提供参考。     

车床尾座故障对零件加工质量的影响分析

车床尾座故障是影响零件加工质量的重要因素之一,探讨分析其对零件加工质量影响对机床维护、精密加工等具有重要意义.在分析车床尾座内锥面磨损、位置偏移等主要故障基础上,探讨了其对零件加工质量的影响关系.     

Effect of process parameters on the cutting quality in lasox cutting of mild steel

Samples of mild steel have been cut on a CO₂ laser machine using the principle of laser assisted oxygen cutting (LASOX). The combined effects of input process parameters (cutting speed, gas pressure, laser power and stand off distance) on cut quality (heat affected zone (HAZ) width, kerf width and surface roughness) have been studied. Regression analysis has been used to develop models that describe the effect of the independent process parameters on cut quality. Using the developed model, we attempted to optimize the input parameters that would improve the cut quality (minimization of HAZ width, kerf width and surface roughness), increase the productivity and minimize the total operation cost. We found from the study that the gas pressure and cutting speed had pronounced effect on cut quality. Low gas pressure produces lower HAZ width, lower kerf width and good surface finish whereas increase in speed results in higher HAZ width, lower kerf width and good surface finish.     

基于焊点虚拟成形技术的SMT焊点质量保证技术研究

基于焊点形态理论和焊点虚拟成形技术的表面组装技术焊点质量检测与控制技术的基本思想是,将利用图像获取及处理技术得到的实际焊点形态,与通过焊点虚拟成形技术形成的合理焊点形态进行比较,根据比较的差异,通过智能鉴别得出实际焊点组装故障的类型与产生主因,然后形成调整组装工艺参数的反馈信息对相关组装工艺进行调整控制,以达到提高和保证焊点组装质量的目的。在阐述其基本思想和原理的基础上,结合实例介绍了该技术的实现方法与步骤,对其中焊点图像的获取与处理、焊点质量的分析评价等主要内容与关键技术进行了研究和探讨,并对结果进行了分析验证。     

电流辅助对铆钉压铆过程及连接性能的影响

钛合金铆钉在塑性成型过程中存在变形抗力大、变形不均匀等问题。在铆接过程中引入电流辅助铆接技术可有效提升钛合金铆钉的铆接质量,其原理为通过在铆接过程中施加电流,改善金属铆钉塑性,提高铆钉的可加工性。以TA2M航空用铆钉为研究对象,研究了6种电流密度水平下铆钉的温升过程与成型效果,并开展拉伸试验与疲劳试验研究铆接件的力学性能。研究发现,通电会在较短时间内产生显著的焦耳热效应,这对难变形的钛合金铆钉来说是一种有效的热软化手段;通电带来的铆钉软化效应极大降低了加工难度,改善了镦头的成型效果;当通以电流密度为26 A/mm²的电流时,压铆力降低了24.69%,且镦头直径增大了6.80%,高度降低了14.04%,更加接近标准所要求的尺寸;电流辅助铆接技术对钛合金板连接件静态拉伸强度的影响不显著,但可有效提升连接件的疲劳寿命。     

Effect of process induced variations on machining characteristics of a model epoxy resin system

The present work aims to understand the effect of process induced variation on mechanisms of failure, deformation and damage mechanisms in a model epoxy resin system during machining. Process variations have been introduced for a 5052 Huntsman epoxy resin system by considering three post-cure temperature and cycles, viz., 50°C for 15 h, 80°C for 8 h and 100°C for 4 h. Detailed orthogonal cutting experiments have been carried out at different cutting speeds, rake angles and uncut chip thicknesses. Studies of chip formation characteristics, cutting force signatures and fractography indicate a significant brittle-like behavior with increasing post-cure temperature resulting in discontinuous chips that became more pronounced for a positive rake angle. Concurrently, extensive mechanical characterization under different strain rates and temperatures has been carried out using dynamic mechanical analyzer for the epoxy specimens. In addition, standard tensile tests have also been conducted that indicate a correlation between mechanical properties and post-cure temperature cycles. Results are indicative of a strong correlation between post-cure variations and associated failure, fracture characteristics during machining that can be used as a tool for assessing the in-situ cure characteristics in a composite structure.     

点焊接头设计对车身质量的影响

基于有限元分析方法,探讨了点焊三种接头形式对车身力学性能和尺寸精度的影响,指出了车身点焊要用不同的接头形式时应重点考虑的问题。