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ID:33672526
大小:1.64 MB
页数:62页
时间:2019-02-28
《非比例载荷下钛合金bt9低周疲劳特性及寿命预测》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、佳木斯大学硕士学位论文摘要许多研究表明,零构件疲劳寿命预测精度的提高必须以材料疲劳微观结构、损伤机理分析作为理论基础,才能真正解释疲劳破坏的微观本质。然而,国内外疲劳界对非比例循环载荷下材料失效微观机理的分析还处于起步阶段,得出的寿命预测模型缺乏明确的微观物理意义。本文通过对材料微观结构的分析,研究了非比例载荷低周疲劳特性,得出了物理意义明确的多轴低周疲劳寿命预测模型。对钛合金BT9进行了比例、非比例载荷低周疲劳试验研究。比例载荷试验结果表明,YonMises等效应变法简单地将单轴低周疲劳寿命的估算方法应用于多轴
2、比例加载,忽略了应变轨迹方向角对疲劳损伤的影响。提出了新的比例载荷寿命预测模型,该模型计入了应变轨迹方向角对疲劳损伤的影响,使得预测精度进一步提高。非比例载荷试验研究表明:非比例载荷相位角对材料疲劳寿命有很大影响。相同等效应变强度下,疲劳寿命随着相位角的增大而降低。对材料疲劳损伤的微观分析表明,在同一等效应变强度下,位错自由运动间距随载荷非比例度增大而减小。给出了基于疲劳位错自由运动间距均值的非比例参量和具有明确微观物理意义的疲劳损伤参量。文中给出了一种新的低周疲劳寿命预测方法。该模型以应变轨迹方向角及载荷非比例
3、参量作为材料疲劳寿命主要影响因素,不但适用于比例载荷的疲劳寿命预测,且使得非比例载荷寿命预测精度显著提高。关键词:钛合金BT9;低周疲劳;寿命预测;相位角佳木斯大学硕士学位论文CharacteristicsandLifePredictionofTitaniumAlloyBT9underNon—proportionalLCFLoadingAbstractTheresultsofmajorityresearchshowthatenhancingprecisionoffauguelifepredictionksbase
4、donmicroscopicstructureanddamagemechanism,fatiguefailuremicroscopicessenceisexplained.However,theresearchoffaugueisstillinstartstageaboutanalysisofthemulUaxlalnon-proportionalloadingmicroscopicmechanism,thefatiguelifemodelwlthouttheclearmaerophysicalmeaning.T
5、herefore,wehasstudiedonlowcyclefatiguebehaviorundernon-proportionalloadingandgainedtheclearmierophysicalme.1ingmultiaxiallowcyclefatiguelifepredictionmodelthroughanalysisthematerialmicrostmctures.ThelowcyclefatiguetestsofTitaniuma110yBT9underproportionalandno
6、n-proportionalloadlIlgwerecarriedout.Undertheproportionalexperimentalresultsshowthatequivalentstrainapproachisthatlifepredictionmethodunderuniaxialthelowcyclefatiguesimplyapplythemultiaxialproportionalloading.Anewproportionalfanguelifepredielaonmodelconsidere
7、dorientationangleofslrampathinfluencefatiguefadureWaSproposed.Moreover;theprecisioninfatiguelifepredictionishasbeenfurtherimproved.Underthenon-proportionalexperimentalstudy,itisobservedthatphaseangleofnon-proportionalloadinghasamoregreatlyinfluencethematerial
8、fatiguelife;thefauguelifealwaysdecreases鞴,出increasingphaseangleunderthesarfleequivalentswainintensity.Theresultindicatesthatunderthesalllcequivalentstrainintensity,meandistancewithinwhich
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