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101.
航空航天领域广泛存在着振动疲劳问题,严重危及飞行器结构的安全可靠性。本文首先设计了激振器直接作用于试件的力激励振动疲劳试验系统,并提出了跟踪结构共振频率的频带激励共振疲劳寿命测试方法;而后利用试件进行了频带激励下的定应变共振或定载荷共振结构振动疲劳试验;最后针对试验结果分析与讨论了可能影响结构振动疲劳寿命的各种因素。结论表明,试验结构件的边界条件、初始条件以及结构动力学特性等都可能是影响振动疲劳寿命的关键因素。频带激励共振疲劳试验方法为振动疲劳寿命曲线的测试积累了经验。 相似文献
102.
The effect of frequency and sample shape on fatigue behaviors of DZ125 superalloy are systematically studied. The results show that fatigue fracture still occurs above the cycle of 108 for tests carried out at the frequency of f = 20 kHz and stress ratio R = ?1, so the traditional fatigue limit at cycle of 107 is not appropriate for fatigue design. Fatigue fracture surfaces are perpendicular to stress axis for cylindrical and plate specimens, and the fatigue cracks originate from the extra surface of the specimens. Fatigue crack is apt to propagate from cutting direction to forward direction, which occurs mainly in the second propagation stage at higher stress amplitude. There is an obvious frequency effect for DZ125 superalloy. The higher the test frequency is, the more serious the effect of frequency on fatigue behaviors of the alloy. After the frequency correction, the ultra-high cycle fatigue S-N curve well coincide with the traditional fatigue S-N curve. 相似文献
103.
Introduction Thefatiguedestructionisoneofthemaintypesofthemetaldamage.Therelationcurve betweenthefatiguecrackgrowthrateda/dNandthestressstrengthfactoramplitudeΔKisthe importantdatiumoffatiguecapabilityindesigningthemetaldamagetolerantlimitsandpredicting thelifeofmetalcomponentparts.Duetovariabilityofthefatiguecrackgrowthrate,alarge amountoftestsamplesareusuallyrequiredtoderiveahighlyreliableda/dN_ΔKcurve. However,inmostactualengineeringpractice,itishardtofindmultiplespecimenswithvery simil… 相似文献
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Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-Ⅰand model-Ⅱstress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris's fatigue equation. Further, parameters (C and m) of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing. 相似文献
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108.
V. M. Tikhomirov 《Journal of Applied Mechanics and Technical Physics》2008,49(5):864-871
Crack propagation under alternating loading is investigated. Relations between the growth rate of a fatigue defect and loading
parameters and the expression for the stress intensity factor are derived for compression of a cracked solid taking into account
the possible contact of the crack faces. A model for the deformation of a small region near the crack tip is proposed which
allows one to formulate the conditions of residual opening of a growing fatigue crack. The experimental data obtained in tests
of steel samples are compared with the results of calculation using the developed procedure.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 5, pp. 190–198, September–October, 2008. 相似文献
109.
A. V. Zheldubovskii A. D. Pogrebnyak V. V. Kasperskaya 《International Applied Mechanics》2008,44(3):313-319
The paper studies the fatigue resistance of metallic samples subjected to high-cycle loading and microhardness measurement.
The fatigue damage of materials during loading is identified as decrease in the thickness of the barrier surface layer, which
prevents fatigue failure. It is shown that the thickness of this layer is independent of the plastic characteristics of the
material and the level of stress. A method to evaluate accumulated fatigue damage is developed. Kinetic curves of damage accumulation
are analyzed. Methods to predict fatigue characteristics are proposed
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Translated from Prikladnaya Mekhanika, Vol. 44, No. 3, pp. 86–95, March 2008. 相似文献
110.
孔周弹塑性变形与疲劳循环次数的相关性 总被引:2,自引:1,他引:1
应用白光散斑相关技术研究了孔周弹塑性变形与疲劳循环次数的相关性,以便探索疲劳寿命的预测方法.疲劳实验在单边带缺口的拉伸板状试件上进行,试件由GH4169材料制成,试件表面上喷涂了白光散斑图.疲劳加载采用0→Pmax→0的循环加载方式,加载波形为正弦波,加载频率为10Hz.实验中,按一定的疲劳循环周次在零载及最大载荷两种状态下停机、采图.应用数字图像相关技术求出孔周附近的残余位移场,并应用逐点最小二乘法求出应变场.实验中获得了一些对于疲劳寿命研究很有意义的结果. 相似文献