共查询到18条相似文献,搜索用时 62 毫秒
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综合了中国科学院金属研究所高温合金和金属间化合物研究组在高温合金蠕变研究方面的主要成果:蠕变和断裂规律及其机理,蠕变-环境交互作用及其机理,蠕变阻力模型以及疲劳-蠕变-环境交互作用规律及其机理。 相似文献
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气缸盖在工作中受到低周热疲劳损伤、高周热疲劳损伤和蠕变损伤,其寿命和可靠性是发动机的重要指标。用热瞄构顺序耦合分析方法计算了气缸盖的温度场和应力场,分析了气缸盖上危险点在10个启动-工作-停车循环的弹性应变、塑性应变和蠕变应变,从理论上证明了影响气缸盖寿命的主要因素是低周热疲劳损伤,启动次数是其最主要的寿命指标。蠕变不影响低周热疲劳的应力幅,只是使循环中的平均应力增加。高温下松弛与蠕变同时发生,降低了平均应力的增长速度。经历有限个循环,平均应力基本稳定。因此,把发动机气缸盖的蠕变-低周热疲劳等效为一定应力幅和平均应力的热-机械疲劳,并用标准试样的热-机械疲劳试验预测了发动机气缸盖的使用寿命(可承受的最大启动次数)。 相似文献
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从应变范围区分法(SRP),应变能区分法(SEP)的有关概念出发,研究DD3单晶镍基合金拉—拉应力状态下的蠕变—疲劳性能和保持时间的影响,并对其进行了定量计算;同时,用应变能区分法的数值法(SEP—NCM)实现对拉—拉应力状态下蠕变—疲劳的寿命预测。 相似文献
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研究了GH4049镍基高温合金在700℃,±0.45%应变控制条件下的疲劳-蠕变行为。发现合金在循环初始阶段呈硬化趋势,随后呈软化趋势,利用透射电镜观察了合金在疲劳-蠕变不同阶段的形变结构,利用会聚束电子衍射技术研究了合金γ/γ相错配度在疲劳-蠕变中的变化规律,结果表明,γ/γ相的共格性在形变过程中未受到损失均匀形变区内,基体位错密度迅速增加,导致合金2形变初始硬化,随形变进行,形变带内γ相也发生 相似文献
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对一种新型第3代粉末高温合金A3在700℃、应变范围0.6%~1.4%试验条件下的低周疲劳性能进行了研究,分析了材料的循环滞后回线、Massing特性、循环应力应变响应、应变-寿命关系等特性。采用Manson-Coffin模型、拉伸滞回能模型、三参数能量模型对疲劳寿命数据进行拟合预测,结果表明Manson-Coffin模型的寿命预测精度最高,在3倍分散带以内。用扫描电子显微镜对疲劳源区观察,结果表明:低应变时疲劳源数量上呈现单源,高应变时呈多源特征;随应变量增大,疲劳源位置趋向于试样表面,裂纹扩展区面积减小,瞬断区面积增大。疲劳断口典型的3个区域观察结果表明:疲劳源四周存在较多河流状线,其为裂纹扩展方向,裂纹扩展区存在较多二次裂纹,瞬断区出现韧窝与解理断裂特征。A3合金的断裂模式主要为穿晶断裂。 相似文献
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晶粒尺寸对GH720Li镍基合金蠕变-疲劳寿命的影响 总被引:1,自引:0,他引:1
胡殿印 《稀有金属材料与工程》2018,47(8):2386-2391
为探明晶粒尺寸对涡轮盘材料—GH720Li镍基高温合金的蠕变-疲劳寿命的影响机理,开展了650℃下不同晶粒尺寸的GH720Li高温合金圆棒蠕变-疲劳试验研究。GH720Li高温合金的蠕变-疲劳寿命随着晶粒尺寸的减小而降低。而后,通过断口的SEM分析研究晶粒尺寸对GH720Li高温合金的蠕变-疲劳损伤影响机制。其失效机制主要为晶界的氧化起裂,而晶界长度随晶粒尺寸变小而增加。最后,对基于迟滞能量的损伤方程和机械功密度2种方法进行了修正,GH720Li合金的蠕变-疲劳寿命预测与试验结果吻合较好,验证了方法的准确性。 相似文献
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Y.Noguchi M.Miyahara 《金属学报(英文版)》2004,17(4):355-360
A new method was proposed for the multiaxial creep-fatigue life evaluation under proportional loadings. Because this method was derived from the strain range partitioning method with a multiaxiality factor, it was possible to consider the influence of both creep-fatigue interaction and multiaxial stress state on fatigue life. In order to predict the combined axial-torsional fatigue life the damage under combined loading was defined as linear summation of the damages under axial loading and torsional loading. Axial-torsional creep-fatigue tests were carried out using tubular specimens of 316LC austenitic stainless steel and the ferritic rotor steel. This rotor steel was developed for the permanent magnet type eddy current retarder in heavy trucks. Experimentally obtained lives of both steels were well corresponded with the lives predicted by the proposed method. It was found that the proposed method was effective in multiaxial fatigue life evaluation under proportional creep-fatigue Ioadings. 相似文献
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M.F. Geng 《金属学报(英文版)》1997,10(6):495-500
1.IntroductionSuperalloysareirreplaceableinengines[llandenginesundergostaticandcyclicloading[2].Thereforeitisimportanttostudycrackgrowthbehaviorofsuperalloysundercreepfatigueconditions.Itisnoticedthattheeffectofcyclicloadingoncrackgrowthisconsiderablel3'4],butdifferentatalowstresslevelfromthatatahighoneIS'6].Itisfoundthattheyieldstrengthofmaterialsisanimportantparameterinstudyingfatiguepropertiesl7,8]andcrackgrowthic,lo].Soitisofmuchimportancetocorrelatecrackgrowthbehaviorandfracturefeaturew… 相似文献
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N. Wang B.S. Zhou Z.D. Wang D.D. Wu College of Mechanical Engineering East China University of Science Technology Shanghai China 《金属学报(英文版)》1999,12(1):31-35
1.IntroductionAlotofequipmentworksunderelevatedtemperatureandhighpresureenvironmentinpetrochemicalindustry.Notonlyplasticand... 相似文献
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A new life prediction function based on a model formulated in terms of stress relaxation during hold time under creep-fatigue
conditions is proposed. From the idea that reduction in fatigue life with hold is due to the creep effect of stress relaxation
that results in additional energy dissipation in the hysteresis loop, it is suggested that the relaxed stress range may be
a creep-fatigue damage function. Creep-fatigue data from the present and other investigators are used to check the validity
of the proposed life prediction equation. It is shown that the data satisfy the applicability of the life relation model.
Accordingly, using this life prediction model, one may realize that all the Coffin-Manson plots at various levels of hold
time in strain-controlled creep-fatigue tests can be normalized to make one straight line. 相似文献
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铸造镍基高温合金的蠕变阻力 总被引:6,自引:0,他引:6
在对颗粒强化理论和位错蠕变理论进行回顾、评价基础上,发展了一个位错蠕变阻力模型,认为蠕变阻力是影响铸造镍基高温合金蠕变机制的重要因素。当施加应力足以使位错切入γ′相时,主要蠕变机制是位错切割γ′相过程,蠕变阻力就是位错切入γ′相的临界门槛应力。在低施加应力区,位错只能借助于热激活攀移过程通过γ′相。蠕变阻力包括两部分:第一项是位错攀移临界门槛应力,与施加应力无关;第二项是与施加应力有关的阻力项,代表了其他强化机制的贡献。位错攀移机制蠕变阻力的上限是切割机制门槛应力。在3种铸造镍基高温合金中(定向凝固DZ17G合金,IN100合金和IN738合金),对上述模型进行了验证,理论计算应用了SL强化理论,与实测值符合较好。 相似文献
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燃气涡轮用单晶高温合金的成本因素 总被引:7,自引:0,他引:7
介绍了单晶合金研制和应用中的成本考虑因素。通过降Re和Ru的合金成分的调整可以提高合金的长时组织稳定性,大幅降低合金的成本。适量C,B,Hf能提高合金可靠性,有利于提高单晶叶片的成品率、重新因溶处理可有效的延长单晶合金的使用寿命。应用计算材料学可大大缩短合金的研制周期,返回料的应用既降低了成本,又符合环保要求。 相似文献
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In-Soo Kim Trevor A. Brown Jong-Taek Yeom Nho-Kwang Park 《Metals and Materials International》2000,6(5):407-413
Hysteresis loops of strain controlled LCF tests for Waspaloy were characterized within the temperature range of 350°C and
600°C. Materials deformation behaviors under symmetric and asymmetric loading conditions were assessed using Chaboche’s viscoplasticity
model. The strain hardening and stress relaxation occurring in the loading cycles were estimated. Hardening plays an important
role at an early stage of loading, but the stress relaxation becomes dominant at a later stage. The observed change in the
slope of hysteresis loops between the first cycle and the second cycle and mean stress relaxation under asymmetric loading
conditions may be explained by the evolution of the kinematic hardening variable which depends on the inelastic strain range.
The effect of creep on the cyclic shake down is expected to be limited. 相似文献