共查询到17条相似文献,搜索用时 62 毫秒
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利用极大似然法测试疲劳寿命曲线,研究未熔透尺寸对十字接头疲劳强度的影响。应用有限元方法,可确定疲劳裂纹的开裂位置(焊根或焊趾)。经疲劳试验表明,极大似然法实用性及曲线拟合理性较好,而且十字焊接接头存在一个临界未熔透尺寸,低于临界值,承受轴向载荷作用的焊接接头疲劳强度不会受到影响。 相似文献
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根据部分熔透搭接激光焊工艺特点和结合不锈钢车体侧墙结构,采用不同规格厚度及表面加工类型组合不锈钢进行部分熔透搭接激光焊,焊后对试样进行腐蚀和疲劳试验,以研究其疲劳性能。试验结果表明:疲劳裂纹均启裂于下板上表面的热影响区,并向下板内部扩展;在试样的宽度方向上,裂纹从下板一侧启裂,向另一侧扩展。疲劳断口扫描电镜分析发现,所有断口整个断裂界面比较粗糙,未观察到明显韧窝和腐蚀引起的点腐。在相同疲劳循环次数的条件下,激光焊部分熔透搭接接头疲劳强度随厚度增加而提高。腐蚀疲劳试验结果表明,在高载荷条件下,腐蚀时间对接头疲劳性能的影响较小;随着疲劳循环次数的增加,腐蚀对接头疲劳性能的影响逐渐增大。 相似文献
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采用焊条电弧焊的方法对7N01铝合金焊接试板进行TIG熔修,对熔修前后的试件进行疲劳寿命测试,并对焊接接头的显微硬度变化进行测试,采用扫描电镜对疲劳断口进行显微形貌分析,并对疲劳源区缺陷进行XRD成分检测.结果表明,TIG熔修对焊趾应力集中的降低有限,还可能引入新的焊接缺陷成为疲劳裂纹源;同时TIG熔修使得焊接区域经受二次加热,沉淀强化相的形态和重新分布造成接头组织弱化,降低了焊接接头抵抗疲劳裂纹扩展的能力,多方面作用的结果是:经TIG熔修后铝合金焊接接头疲劳寿命略有降低,所以对于7N01高强铝合金对接接头单纯采用焊趾TIG熔修的方法提高疲劳性能不具备可行性. 相似文献
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采用MTS landmark 370型液压伺服动静疲劳拉伸试验机研究了应力比(R=σmin/σmax)为0.1时X80大应变管线钢焊接接头的拉拉疲劳寿命;并采用显微硬度计和扫描电镜对焊接接头的硬度及疲劳断口进行了分析。结果表明:焊接接头的疲劳寿命显著低于母材;疲劳裂纹均萌生在焊缝熔合线处;裂纹沿热影响区向内扩展,当裂纹扩展到一定程度时,裂纹沿热影响区快速开裂。焊缝金属咬边所形成的夹杂物、焊缝的应力集中及热影响区性能恶化是疲劳裂纹萌生及快速扩展的原因。 相似文献
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Kiyotaka Nakashima Hiroshi Shimanuki Tetsuro Nose Tadashi Ishikawa 《Welding International》2013,27(5):343-349
It has been generally recognized that the fatigue life of welded joints is little influenced by the strength of steels owing to the high-stress concentration and the tensile residual stress near the weld toe. In this paper, improvement of the fatigue life of welded joints using steel with high resistance to fatigue crack growth (ferrite/martensite (F/M) steel) is investigated. F/M steel has a microstructure with an elongated and banded martensite phase distributed in a ferrite matrix and a fatigue crack growth rate of about one-half to one-tenth in the thickness direction, compared with conventional steel. As a result, the fatigue life of an out-of-surface gusset-welded joint increases with the decrease of the fatigue crack growth rate. The fatigue life of welded joints using F/M steel with the highest resistance to fatigue crack growth increases to about twice that of joints using conventional steel. Whereas the fatigue crack growth rate decreases significantly, the fatigue life of welded joints increases only slightly. This can be attributed to the stress ratio independent of the fatigue crack growth rate. In other words, the fatigue crack growth rate of F/M steel increases with the increase of the stress ratio, approaching that of conventional steel. In the case of welded joints, even if a fatigue test is carried out at a low-stress ratio, the region near the weld toe is under a high-stress ratio due to tensile residual stress. Therefore, improvement of the fatigue life of welded joints becomes comparatively small so that the effect of fatigue crack retardation of F/M steel decreases. 相似文献
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为了明确不同强度残余压应力场对裂纹扩展速率及寿命的影响,采用埋弧自动焊通过不同焊接热输入控制不同焊缝宽度,从而在制备标准CT试样时通过机械加工时的残余应力释放得到各组不同强度残余压应力场的各组焊接接头,并根据裂纹闭合原理,提出基于Elber的三参数分段公式,根据分段公式条件从MTS试验机采用柔度法获得的试验数据中提取、归纳数据,利用断裂力学方法和数理统计方法进行分析,得出结论,裂尖存在的焊接残余压应力场在一定程度上可以明显降低裂纹扩展速率,提高裂纹扩展寿命,对焊接接头裂纹扩展有着关键性作用。 相似文献