共查询到19条相似文献，搜索用时 154 毫秒
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复杂飞机结构裂纹萌生寿命确定的工程方法 总被引：1，自引：0，他引：1
采用静拉伸应变测量试验的方法,确定了典型飞机复杂结构在载荷作用下的应变分布,并准确判断出其疲劳危险部位。对典型飞机复杂结构模拟件进行了等幅加载疲劳试验,并在疲劳试验过程中采用着色探伤方法测得了疲劳裂纹扩展数据。在此基础上,提出并建立了一种适用于确定复杂结构疲劳裂纹萌生寿命的工程方法,包括疲劳裂纹萌生寿命反推法和含有不确定寿命样本的统计推断方法。根据该方法对试验样本疲劳数据进行处理得出了裂纹萌生中值寿命及其在95%置信水平下的单侧置信下限。 相似文献
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对GH4169镍基高温合金制成的薄壁圆管试样的多轴循环相关特性进行了研究。试验在MTS809-250 kN/2000 Nm电液伺服拉-扭低周疲劳试验机上进行,采用恒幅总应变控制,对称加载,轴向应变与扭转应变的加载采用三种不同相位(0°、45°和90°),其加载频率分别为0.1 Hz和0.2 Hz,试验温度为650℃.通过对薄壁圆管高温多轴比例和非比例循环加载试验,研究了该材料在多轴循环载荷下的应力-应变响应和循环相关特性。试验结果表明,GH4169合金在试验温度下不通加载路径下均呈现为循环软化现象,其循环软化程度与等效应变和轴向与剪切方向之间的相位差密切相关。 相似文献
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《实验室研究与探索》2013,(12)
对低碳钢材料带孔薄壁圆管试样采用逐级加载试验方法,得出其在室温下的单轴循环应力-应变本构关系。利用有限单元法对圆管试样进行弹塑性分析,采用Von Mises屈服准则、多线性随动强化模型,并结合试验获得的本构关系来定义材料的弹塑性特性。拉扭应变载荷加载在柱坐标下进行,采用一端固定,另一端加轴向位移与周向位移的方式。分别在纯拉、纯扭以及拉-扭比例加载下计算出应力应变场,获得不同受力情况下不同孔径尺寸试样在缺口处的应力应变分布。计算结果为多轴加载疲劳试验和复杂应力状态下工程零部件的疲劳寿命预测与分析提供基本数据。 相似文献
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为实现飞机机身气动载荷的自动分载,采用VB进行软件开发,输入为气动专业提供的机身总载和机身气动载荷分布形态参数,输出为静强度专业加载所用的机身各个框站位所分的集中载荷。软件操作方便,有效提升了机身气动载荷分载的效率和质量。 相似文献
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对于航空航天结构中承受耦合载荷的螺栓，国内外尚未形成标准的测试及强度校核方法。为此，提出了一种耦合受力连接螺栓强度试验方法。根据连接螺栓工作状态，设计了试验加载工装，利用偏心加载的方式实现螺栓耦合受力。结合试验和有限元方法，对耦合承载螺栓连接结构的强度行为进行研究。结果表明，耦合受力显著降低了螺栓的承载能力，在极端偏心加载工况下螺栓破坏载荷仅为标定载荷的44.0%。 相似文献
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飞机主起落架支柱结构中主承力零件包括外筒、活塞杆和上、下扭力臂等,静强度校核是对其承载能力和结构安全性进行考核的关键环节。首先通过载荷分析获取各零件所受外载,然后采用10节点四面体单元对各零件进行有限元建模和计算,结果证明外筒、活塞杆和上、下扭力臂在给定载荷工况SLD下满足静强度要求。传载路线清晰,计算方法可靠,能有效保证飞机主起落架支柱结构的安全。 相似文献
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大骨料混凝土在双轴压应力状态下的变形和强度试验研究 总被引：1，自引：0，他引：1
利用大连理工大学自行研制改造的液压伺服静、动态三轴试验系统对不同骨料级配和尺寸的混凝土试件在双向压荷载作用下的变形和强度特性进行了试验研究.试验所用试件有3种:采用大坝原级配最大骨料粒径为80 mm的立方体试件以及相应的湿筛混凝土试件,尺寸分别为250mm×250mm×250 mm,150 mm×150 mm×150 mm和100 mm×100 mm×100 mm.试验过程中,测得了所有试件两个加载方向的应力和应变,以及未加载方向上的侧向变形,并根据试验结果,系统地探讨了不同级配混凝土的双轴抗压强度、极限变形、应力-应变曲线以及破坏形态的变化规律,发现大骨料混凝土在双轴压作用下的极限强度和变形能力要比相应的湿筛小骨料混凝土提高的更多,最后分别在主应力空间和主应变空间建立了不同级配混凝土的破坏准则,这为水工大体积混凝土按多轴强度理论进行设计提供了试验依据. 相似文献
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为研究FRP(fiber reinforced plastics)加固在役混凝土柱轴压性能的试验方法,采用后张预应力法对混凝土柱施加初始应力,然后采用附加刚性千斤顶加载法进行模拟FRP加固混凝土柱轴压加载试验,得到应力-应变全曲线。研究结果表明,该试验方法能较好地实现FRP加固在役混凝土柱轴心受压试验。 相似文献
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《实验室研究与探索》2018,(9)
钢筋混凝土及预应力混凝土结构在长期和短期荷载作用下的结构行为是评价结构安全性和长期使用性能的重要指标。研制了一种反拉式多功能加载装置,采用了模块化设计,该系统不但可以满足短期静载试验要求,而且在长期加载状态下,加载系统能够保持荷载恒定,满足梁式结构徐变试验技术要求。开展了3m钢筋混凝土试验梁的短期循环荷载试验和长期徐变变形试验,试验结果表明,该加载装置的性能稳定和加载过程安全可靠,满足相关科研与教学使用要求。 相似文献
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采用周期浸润加速腐蚀试验的方法,对某型飞机42框横梁模拟件分组进行了不同时间的加速预腐蚀试验,并通过随机载荷谱下的疲劳试验获得了预腐蚀后模拟件的疲劳寿命。结果表明,在加速腐蚀时间不大于300小时的情况下,预腐蚀对42框横梁结构模拟件疲劳寿命的影响不明显。 相似文献
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A significant temperature raise within hydrogen vehicle cylinder during the fast filling process will be observed, while the strength and fatigue life of the cylinder will dramatically decrease at high temperature. In order to evaluate the strength and fatigue of composite hydrogen storage vessel, a 70-MPa fatigue test system using hydrogen medium was set up. Experimental study on the fatigue of composite hydrogen storage vessels under real hydrogen environment was performed. The experimental results show that the ultimate strength and fatigue life both decreased obviously compared with the values under hydraulic fatigue test. Furthermore, fatigue property, failure behavior, and safe hydrogen charging/discharging working mode of onboard hydrogen storage vessels were obtained through the fatigue tests. 相似文献
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在轴向承载十字焊接头疲劳试验的基础上,用一种新的有限元数值计算模型,并考虑多种影响因素的情况下拟合了两种裂纹类型的应力强度因子表达式,从而为焊接件的疲劳强度研究提供了有益的途径． 相似文献
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Fatigue tests were conducted on tapered plain concrete prism specimens under triaxial constant-amplitude tension-compression cyclic loading. The low stress of the cyclic loading was taken as 0.2fc and the upper stress ranged from 0.20ft to 0.65ft. Three constant lateral pressures were 0.1fc, 0.2fc and 0.3fc respectively. Based on the results, the three-stage evolution nile of the fatigue stiffness, maximttm(minimum) longitudinal strain and damage were analyzed, and a unified S-N curve to calculate fatigue strength factors was worked out. The results show that the fatigue strength and fatigue life under triaxial constant-amplitude tension-compression cyclic loading are smaller than those under uniaxial fatigue condition. Moreover, the secondary strain creep rate is related to the fatigue life, a formula for describing their relation was derived. The investigation of this paper can provide information for the fatigue design of concrete structures. 相似文献
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INTRODUCTION A number of experimental fatigue studies were conducted on plain concrete as well as on steel fibre reinforced concrete (SFRC) beams of different sizes under different loading conditions. Murdock and Kesler (1958) investigated the effect of stress ratio on the fatigue strength of plain concrete. Batson et al.(1972) reported fatigue strength of 74% and 83% of the first crack static flexural strength at 2 million cycles of complete reversed and not-reversed loads respectively… 相似文献
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Jungil Cho 《International Journal of Science Education》2013,35(10):1021-1035
This study looks at the effects of a science-technology-society (STS) in-service programme, designed to change teachers' awareness and practice of STS/constructivist approaches, while also focusing on students' understandings and changes of perceptions of the constructivist learning environments. The STS in-service programme was developed to achieve the following features: teacher-oriented, teaching in a social context, emphasis on a 'constructivist' approach, developing STS units and their use in classrooms. A total of 20 middle and high school science teachers participated in the in-service programme in 1998; and three of the middle school teachers were selected to gain information from their implementation of a Reactions of Acids and Bases unit in their respective classrooms. The Science Education Reform Inventory was administered to all the teachers at both the opening and the end of the programme. One hundred twenty-five students of the three teachers experienced about 16 class hours of lessons comprising the new STS unit. At the beginning and the end of the unit, they completed the Constructivist Learning Environment Survey. In order to assess student understanding, teachers administered the creativity test before and after the unit; and the concept acquisition test and the application test after the unit. Students obtained at average 48% of the 35 key concepts and 6.6 additional non-key concepts after the unit was finished. Students made more relevant and creative responses on unfamiliar situations on the post-test than on the pre-test. Through several tasks including a short essay, students showed their abilities to apply various concepts related to acids and bases to daily life situation. It was found that the STS programme improved the teachers' awareness and practices of the science education reforms characterized by STS and constructivism. The middle school science teachers could develop STS units which they implemented in their own classrooms. They could work together in developing units and reflecting on their teachings through video recordings of science classes. They were willing to assess various aspects of learning such as creativity, application and concept acquisition. Students perceived that the classroom environments improved in terms of personal relevance of contents, scientific uncertainty and student participation. The results showed that the STS in-service programme was effective and could be implemented successfully with Korean science teachers. 相似文献
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A combined cycle fatigue （CCF） testing system with ultrasonic frequency component was developed toevaluate the CCF properties of S350 steel welded joints in this study. The fatigue testing results indicated that the S-Ncurves of CCF did not have fatigue limit, which agreed with those of pure high frequency fatigue of welded joints. TheS-N curves showed that the CCF strength of welded joints dropped greatly with the increasing interaction between highand low frequency fatigue loading. An approximation design method of CCF was presented using amplitude envelopeas the stress range. 相似文献
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对某耐腐蚀铝合金在飞机结构上应用的可行性进行了试验研究,选取飞机某部位全尺寸结构进行了静强度试验鉴定,结果表明,该新研耐腐蚀铝合金结构能够满足飞机设计使用要求,从而为新材料在飞机上的替代给出了可靠的试验依据。 相似文献