非均质焊接接头中J主导的云纹干涉法实验研究(英文)

采用云纹干涉法研究了焊接接头中应用J积分作为裂纹尖端塑性奇异性参量的可行性.结果表明,在所研究的大多数情形下,u场与v场中的J主导无效.因此,采用J积分作为用来预测焊接结构安全性的控制参量是不正确的.     

Uncertainty evaluation for bearing fatigue property of CFRP double-lap,single-bolt joints

The considerable uncertainty in mechanical properties of composite bolted joints not only prevents advanced composite materials from efficient applications, but also threatens the safety and reliability of the aircraft structures. In this paper, the uncertainty in bearing fatigue properties of a CFRP double-lap, single-bolt joint was evaluated by combing a Progressive Fatigue Damage Model(PFDM) with the interval analysis method. In the PFDM, a residualstrain-based gradual material degradation mo...     

宽直线连接的处理方法

宽直线广泛应用于工程制图、PCB板图绘制等方面,宽直线的效果直接影响着最终输出图形的质量。宽直线的生成涉及许多问题[1],线接头是宽直线生成过程中必须要处理的问题之一,通过使用本文所介绍的两种方法,能有效解决宽直线圆连接和斜切连接的问题,并能获得所希望的效果。     

复合材料径向和轴向螺栓连接失效预测方法及失效模式分析

大型火箭舱段间的复合材料端框连接主要由径向螺栓连接和轴向螺栓连接组成,设计了不同铺层和几何尺寸的连接试验件,并通过试验获得了失效载荷和失效形式。然后,选择了3种渐进损伤方法进行了连接结构的失效预测,并将预测结果与试验结果进行比较,结果表明：采用基于细观力学的复合材料渐进损伤方法,15组径向连接试验件失效载荷计算误差最大为17.3%;4组轴向连接失效载荷计算误差最大7.4%;预测的失效形式与试验结果接近,为连接结构确定了合适的失效预测方法。采用数值分析结果揭示了复合材料单向层的主要失效模式。为复合材料端框连接的设计研究提供了可用的失效预测方法及详细的失效模式分析结果。     

咬边缺陷对超声冲击处理焊接接头疲劳性能的影响

结合国产1 6Mn低合金中强钢,进行了使用超声冲击法提高含咬边缺陷的十字型焊接接头疲劳强度、延长其疲劳寿命的研究。结果表明:咬边等焊接缺陷降低焊接接头疲劳强度(与不含明显上述缺陷的试件相比)约10%～20%左右;超声冲击处理后,含咬边缺陷的(焊趾处)1 6Mn钢十字接头的疲劳强度提高66%,疲劳寿命提高10～40倍;与不含焊接缺陷的焊态试件相比,提高疲劳强度32%,提高疲劳寿命2～7倍;咬边缺陷对冲击处理后焊接接头的疲劳性能仍有不利的影响。     

固体发动机燃烧室壳体／绝热层界面脱粘类型及解决的技术途径

界面粘接是固体发动机装药结构完整性的重要条件、通过对发动机燃烧室壳体／绝热层界面粘接进行的研究，指出燃烧室在绝热层整体粘贴中常见的四种脱粘类型。对各类脱粘原因通过抽样色谱分析、无损检测或解剖作了验证，提出解决脱粘问题的具体技术途径。研究结果表明，这些技术措施在发动机装药研制中取得较好的效果。     

力学不均匀性对焊接接头疲劳裂纹扩展影响的研究

本文将焊接接头简化为夹层材料裂纹体模型，通过实验及弹塑性有限元方法研究了均匀材料和具有力学不均匀性的夹层材料裂纹体中心裂纹试件中疲劳裂纹的扩展规律。发现疲劳裂纹的扩展不但取决于裂纹尖端处材料的性质，而且还受裂纹尖端附近材料力学不均匀性的严重影响；不均匀体裂纹尖端的塑性区、应力应变场与均匀材料裂纹体显著不同；力学不均匀性对疲劳扩展寿命影响的本质在于力学不均匀性对疲劳裂纹闭合的影响     

复合材料平尾接头力学性能研究

针对某平尾中央翼与外翼前梁连接接头,设计了复合材料接头试验件。根据平尾接头实际载荷工况及试验件构型,设计了特定的试验夹具,确定了静力试验方案。通过静力试验,得到了试验件在实际载荷工况下的静力极限载荷和破坏模式。并采用ABAQUS有限元软件,对中央翼前梁接头、外翼前梁接头试验件进行静力分析,有限元预测结果和试验结果吻合较好,证明了有限元模型的准确性。数值计算结果表明：接头在静力载荷工况下,孔边产生应力集中,导致孔边纤维破坏并向周围扩展,最终失去承载能力。     

由摩擦阻尼铰实现桁架结构的被动减振研究

研究利用一种摩擦力随振动幅值的增大而增大的阻尼铰进行结构振动的被动控制。首先分析了含干摩擦约束铰结构单体梁的振动特性,并给出了系统随振动幅值变化的等效固有频率和粘性阻尼的定量表达式,然后建立了在桁架结构中设置此种摩擦铰的振动方程,分析了系统的动力特性,由计算结果发现,这种摩擦铰具有良好的阻尼特性;通过这种非线性元件,不仅通过滑移时消耗能量,而且可以将能量由低阶模态转移到高阶模态来加速振动衰减。     

Mechanical behaviour of adhesively single lap joint under buckling conditions

Adhesive Single Lap Joints have been subjected to tensile and bending investigations by many researchers. However, the joint is also likely to experience buckling loading in some aerospace applications. The aim of this work is to investigate the joint behaviour under quasi-static buckling conditions. For this purpose, the joints with three different adherend thicknesses and 25 mm overlap length were tested using two different types of adherends and an adhesive film. They were modelled using a non-linear Finite Element Method via the ABAQUS Explicit package programme. Load to failure and stress distributions in the joints were predicted and compared with the experimental results, which were found in a good agreement. The adhesive layer in the joint was assumed to experience shear stresses under the buckling mode, similar to that in tensile loading, yet, the stress concentrations at the ends of the overlap, the main cause of the failure, resulted in different effects on the joint performance; for the buckling mode the critical stresses were in compression but for the tensile case in peeling. Unlike the latter, the former was found to prevent failure of the layer depending on the adherend thickness, causing different failure mechanisms. There were two different failure modes of the joints; a complete failure in the adhesive layer and large plastic deformation of adherends which could be a good source for crashworthiness situations. Mechanical properties of the adherends were found to play important roles on the joint performance.