Dynamic experimental studies of a6n01s-t5 aluminum alloy material and structure for high-speed train

In this study, we focus on the dynamic failure property of A6N01S-T5 aluminum alloyusing for high-speed train. The method of SHBT+3D DIC was put forward to figure out the dynamic mechanical properties and dynamic failure strain of A6N01S-T5 aluminum alloy,and on the basis of this, Johnson-Cook model constitutive parameters and dynamic failure strain parameters were obtained through a series of static and dynamic tests.An important character of this methodwas that the sandwich structure from the true high-speed train was used in penetration test,followed by the numerical calculation of the same working condition using LS-DYNA.Then we compare the experimental results with simulation results mentioned above in terms of failure morphology in structure and the bullet speed throughout the entire process to verifythe accuracyof the parameter. The experimental results provide a data basis for the crash simulation model of high-speed trains,in turn to optimize the structural design and whole efficiency.

6N01-T5铝合金焊接接头疲劳断裂分析

为了确定6N01-T5铝合金挤压型材焊接接头发生疲劳断裂的原因,对6N01-T5铝合金型材及其焊接接头分别进行了疲劳试验,获得了它们的S-N曲线及条件疲劳极限.分析了接头的显微组织与力学性能,并对疲劳断口进行分析,得到了6N01-T5铝合金焊接接头的疲劳断口特征.结果表明,接头显微组织为-αAl与-αAl和Mg2Si的伪共晶,主要缺欠为气孔;在热影响区与母材交界处存在一软化区,该软化区会引起静载断裂,但不是构件发生疲劳断裂的主要原因;位于焊缝表面焊接缺欠以及构件的表面状态是影响接头疲劳性能的主要原因.

A6N01-T5铝合金焊接接头的组织与疲劳性能

为了确定A6N01-T5铝合金挤压型材MIG焊接接头发生疲劳断裂的原因,本文采用高频疲劳试验机对A6N01-T5铝合金MIG焊接试样进行低周疲劳拉伸试验,研究了A6N01-T5铝合金焊接接头低周疲劳行为、疲劳裂纹表面和断口表面以及缺陷对疲劳性能的影响。结果表明:在热影响区存在一个明显的软化区,该软化区在疲劳拉伸实验中变形较严重;A6N01铝合金焊接试样的疲劳裂纹源萌生于气孔及夹杂等缺陷产生应力集中处;焊缝近表面的气孔及内部的夹杂是裂纹快速扩展的诱因。

Evolution of residual stress field in 6N01 aluminum alloy friction stir welding joint

Based on the characteristics of friction stir welding( FSW) and Coulomb friction work theory,the residual stresses field of FSW joints of 6 N01 aluminum alloy( T5),which was used in high speed train,were calculated by using the ANSYS finite element software. During the FEM calculation,the dual heat source models namely the body heat source and surface heat source were used to explore the evolution law of the welding process to the residual stress field. The method of ultrasonic residual stress detecting was used to investigate the residual stresses field of the 6 N01 aluminum alloy FSW joints. The results show that the steady-state temperature of 6 N01 aluminum alloy during FSW is about 550 ℃,and the temperature mutates at the beginning and at end of welding. The longitudinal residual stress σ_x is the main stress,which fluctuates in the range of-25 to 242 MPa. Moreover,the stress in the range of shaft shoulder is tensile stress that the maximum tensile stress is 242 MPa,and the stress in the outside of shaft shoulder is compressive stress that the maximum compressive stress is 25 MPa. The distribution of the tensile stress in the welding nugget zone( WNZ) is obviously bimodal,and the residual stress on the advancing side is higher than that on the retreating side. With the increasing of the welding speed,the maximum temperature decreased and the maximum residual stress decreased when the pin-wheel speed kept constant. With the increasing of the pin-wheel speed,the maximum temperature of the joint increased and the maximum residual stress increased when the welding speed was constant. The experimental results were in good agreement with the finite element results.

A6N01-T5铝合金型材力学性能与停放时间的关系

论述了A6N01-T5铝合金型材停放时间与力学性能的关系。铸锭经挤压机挤压成形,在挤压机上在线淬火处理,室温停放不同的时间,随后在相同的时效制度下进行人工时效,其力学性能的变化非常明显。通过对比试验,确定了型材力学性能与停放时间的关系曲线。

国产A6N01铝合金型材MIG焊接头的微观组织与力学性能

利用金相观察、显微硬度测定、拉伸和弯曲性能测试等方法研究了A6N01-T5铝合金型材MIG焊接接头的显微组织和力学性能.结果表明：焊接接头焊缝中心金属为明显的激冷形成的铸态组织,呈等轴晶状;熔合区靠近焊缝侧的结晶形态为沿散热方向排列的柱状晶,邻近熔合区的热影响区晶粒粗化.焊缝中心处具有较高的显微硬度,在距离焊缝中心10~12 mm处的热影响区显微硬度值最低.国产A6N01-T5铝合金型材焊接接头抗拉强度达到欧洲标准DIN EN 288-4的要求.

铝合金表面三嗪二硫醇和硅烷纳米复合薄膜的制备及表征

通过电化学方法,在铝合金表面制备6-N,N-二丁基胺-1,3,5-三嗪-2,4-二硫醇单盐(DBN)的纳米聚合薄膜(PDB),然后采用自组装技术对铝合金表面PDB膜进行十六烷基三甲氧基硅烷化处理,形成疏水性的高分子纳米复合薄膜(CPDB)。通过循环伏安法解释了DBN在铝合金表面的反应及PDB的生长过程,同时分析了CPDB膜的形成机理。借助傅里叶变换红外光谱仪(FT-IR)、X射线光电子能谱仪(XPS)、扫描电子显微镜(SEM)、接触角测量仪对铝合金表面薄膜的特性进行了表征。结果表明,PDB膜形成后铝合金表面的接触角从未镀膜的89.9°上升到124.3°,CPDB膜形成后接触角达135.8°;SEM和XPS测定表明该方法可以有效地在铝合金表面获得均匀致密的高分子纳米复合薄膜。