几种钎钢材料的冲击疲劳性能

通过冲击疲劳试验,研究了几种材料不同热处理的冲击疲劳性能。结果表明．40Cr正火高温回火热处理的冲击疲劳寿命高于淬火低温回火和正火低温回火的冲击疲劳寿命。30CrNi4Mo钢正火低温回火的冲击疲劳裂纹形成寿命高于淬火低温回火和淬火高温回火的冲击疲劳裂纹形成寿命,淬火高温回火的冲击疲劳总寿命高于正火及淬火低温回火热处理的冲击疲劳寿命。新型贝氏体钢正火低温回火热处理的冲击疲劳寿命高于淬火低温圆火热处理的冲击疲劳寿命。文中分析了多次冲击疲劳裂纹扩展的行为及不同热处理工艺下冲击疲劳寿命提高的原因。     

WK-75型挖掘机动臂的裂纹萌生寿命分析

疲劳破坏是WK-75型挖掘机动臂的主要破坏形式。疲劳寿命主要有两部分组成:裂纹萌生寿命,裂纹扩展寿命。工程实际中通常将疲劳寿命等同于裂纹萌生寿命。为研究动臂的裂纹萌生寿命,首先通过有限元法对处于危险工况下的动臂做静力学分析,接着对挖掘机挖掘物料的过程做刚体动力学分析,获得动臂上相应位置的载荷谱。最后,通过疲劳分析软件fe-safe对静力学分析结果与刚体动力学分析结果进行处理,获得使动臂产生裂纹的疲劳载荷谱,最终估算出动臂的裂纹萌生寿命。     

提升钢丝绳的微动损伤实验研究

微动磨损是造成钢丝绳寿命降低的主要原因之一。本文以6×19点接触式钢丝绳为研究对象，对钢丝绳中钢丝进行实验室摸型化，设计并制作了钢丝微动磨损试验机，对钢丝试件进行大量的激动磨损实验。把磨损后的试件从侧向磨损缺口拍摄成SEM照片，由照片上的磨损尺寸计算磨损深度，并以此评定钢丝试件在载荷、循环次数、错动位移变化时，磨损深度的变化趋势     

构件疲劳破坏的数值模拟分析

简单介绍了基于有限元分析结果进行疲劳寿命估算的基本理论和思路 ,运用ANSYS程序对一典型构件进行有限元数值模拟 ,得到应力强度因子 ,并进行了疲劳寿命估算。得出不同裂纹长度的应力强度因子幅值、裂纹扩展率和疲劳寿命。分析结果与用解析法的计算结果基本相近 ,同时体现了有限元法在构件疲劳寿命评估和“损伤容限”设计领域的优越性和可靠性     

塔式起重机起重臂疲劳裂纹扩展的机理分析

塔式起重机起重臂下弦杆疲劳裂纹影响因素多,裂纹形成过程复杂。从塔式起重机起重臂的工作载荷和焊接残余应力特征出发,应用断裂力学理论分析了起重臂疲劳裂纹萌生点和疲劳裂纹的扩展过程。针对塔式起重机承受随机载荷的特点,应用时间循环法估算塔式起重机起重臂的疲劳裂纹扩展寿命。研究结果表明:疲劳裂纹在下弦杆与腹杆焊接处萌生;疲劳裂纹扩展的主要原因是交变应力与变幅小车循环次数的累积作用,并为现役塔机的安全评定提供了理论分析依据。     

自冲铆接中微动的研究概况

介绍了自冲铆接技术及自冲铆接,微动的破坏机制,在受到循环载荷的作用下,自冲铆接连接表面易产生微动磨损。可从结构、增加材料接触表面强度、降低摩擦系数和材料匹配等方面提高铆接材料的抗微动损伤能力,降低微动损伤。     

夹杂物尺寸对汽车车轮用钢疲劳寿命的影响

采用MTS858电液伺服疲劳实验机研究了高强度车轮用钢的疲劳寿命, 并用Quanta 600环境扫描电子显微镜对疲劳断口形貌进行了观察。通过对实验数据分析, 计算得出了夹杂物的临界尺寸, 并根据正态分布理论对车轮钢的疲劳寿命进行了预测。研究结果表明, 疲劳裂纹均是从内部或者亚表面的夹杂物处萌生; 能谱分析表明: 夹杂物的成分主要是钙铝的氧化物, 测量所得裂纹源处夹杂物尺寸大部分超过了临界尺寸。     

提升机闸盘碟形簧疲劳保护和疲劳信号的改进

<正> 新近安装或改造的提升绞车中,一般都增设闸盘碟形簧疲劳保护和疲劳信号显示装置。由于一般的手册资料对闸盘的磨损保护和磨损信号显示有介绍,而对闸盘碟形簧的疲劳保护和疲劳信号显示的介绍则少见。我局楼梯沟矿副井于1991年4月改造一台苏式2 BM (3000)╱(1500)-2的老式绞车,将角移式制动改为闸盘剥动。在厂家提供的制动设备中,在其闸盘座上共设了8个闸瓦磨损微动开关和8个碟形簧疲劳微动开关。安     

航空2024铝合金VIC-3D静载分析和疲劳试验

通过VIC-3D技术测量静态拉伸全场二维应变及应力,基于航空载荷谱进行动态载荷疲劳试验,利用扫描电子显微镜对试件断口进行观察,研究航空2024铝合金的力学性能。结果表明,利用Y方向应变随时间变化云图,可以探究裂纹出现及发展规律,疲劳试样在第34周循环,总第169 973次循环后发生疲劳断裂。疲劳断口可观察到疲劳源区、疲劳裂纹扩展区及瞬时断裂区,并呈扇形向外扩展。疲劳裂纹萌生于试件表面,裂纹扩展区二次长裂纹方向和裂纹扩展方向垂直,并存在疲劳辉纹,瞬时断裂区呈现出塑性断裂韧窝状形貌,局部存在冲击面形貌。     

35CrNiMo圆柱齿轮齿根弯曲疲劳裂纹扩展分析及寿命预测

基于断裂力学理论,利用有限元软件Abaqus和FRANC3D对产生裂纹的齿轮进行疲劳裂纹扩展。在齿轮上预置一定形状的裂纹,利用有限元软件计算裂纹前端的应力情况,并计算得出裂纹前端应力强度因子和扩展角度等;并进行下一步的扩展,预测裂纹扩展的轨迹,计算裂纹疲劳扩展速率,以此预测含有裂纹齿轮的剩余寿命。     

Influence of HVOF coating on the HCF of 300M low alloy steel

1IntroductionLanding gear is easily worn due to its action with ground during landing and takeoff,and traditionalabrasive-resistance methodis the Cr electroplating technology.Cr is deposited owing to the oriented move-ment of Cr2O7-to the cathode of D.C.where electrochemical reactions take place.The technology is fea-tured as si mplicity,lowcost,high hardness,good abrasion-and corrosion-resistance andis widely appliedin many industries.However,Cr electroplating technique will let off carcin…     

Influence of HVOF coating on the HCF of 300M low alloy steel

The ultimate methods for solving the contamination of Cr6+ is to replace the Cr electroplating with other techniques, thermal spray provides one of the best choices among those alternative techniques. The influence of coatings upon the fatigue performance of substrate, however,should be labeled as an important factor at some high level applications. The effects of both coatings manufactured by HVOF and Cr electroplating respectively on the fatigue performance of substrate are investigated in this article. These results show that the fatigue limit strength at P= 50 ,of thermal spray coating is 750 MPa in comparing with fatigue limit 726 MPa for substrate, and the fatigue life increase 25,- 150, when comparing with fatigue life of substrate at different stress levels. The fatigue life increases in the stress scope of 750-850 MPa even the area of thermal spray coating is subtracted. Cr eleetroplating coating reduces the fatigue life by 70,- 95, and the fatigue limit is only 600 MPa. Fracture analysis reveals that the main fracture is initiated at the subsurface, which is 0.2-0.5 mm away from substrate surface. The analysis also observes that the crack in the Cr electroplating propagates through the interface and finally into the substrate which hastens the formation of crack origin and the extension of crack in the substrate, however, the crack in the thermal spray coating deflects at the interface, spreads along the interface, as a result,the crack forming in the coatings has no negative influence on the main crack initiator and crack extension in the substrate.     

Influence of HVOF coating on the HCF of 300M low alloy steel

The ultimate methods for solving the contamination of Cr6+ is to replace the Cr electroplating with other techniques, thermal spray provides one of the best choices among those alternative techniques. The influence of coatings upon the fatigue performance of substrate, however,should be labeled as an important factor at some high level applications. The effects of both coatings manufactured by HVOF and Cr electroplating respectively on the fatigue performance of substrate are investigated in this article. These results show that the fatigue limit strength at P= 50 %of thermal spray coating is 750 MPa in comparing with fatigue limit 726 MPa for substrate, and the fatigue life increase 25%- 150% when comparing with fatigue life of substrate at different stress levels. The fatigue life increases in the stress scope of 750-850 MPa even the area of thermal spray coating is subtracted. Cr eleetroplating coating reduces the fatigue life by 70%- 95% and the fatigue limit is only 600 MPa. Fracture analysis reveals that the main fracture is initiated at the subsurface, which is 0.2-0.5 mm away from substrate surface. The analysis also observes that the crack in the Cr electroplating propagates through the interface and finally into the substrate which hastens the formation of crack origin and the extension of crack in the substrate, however, the crack in the thermal spray coating deflects at the interface, spreads along the interface, as a result,the crack forming in the coatings has no negative influence on the main crack initiator and crack extension in the substrate.     

矿井提升机卷筒结构有限元静力及疲劳强度分析研究

针对矿井提升机卷筒工作中常见的筒壳纵向轴向均开裂、筒壳径向开裂等故障,对卷筒的结构静力及疲劳强度作了有限元分析,按照卷筒实际工况施加载荷和约束,名义应力值经历1 000 000次循环,在2倍缩放因子下名义应力值再循环1 000 000次,得到卷筒的应力分布云图、强度安全系数云图、疲劳安全系数云图及疲劳寿命云图,直观地显示出卷筒在出现裂纹之前结构可承受的循环加载的持续时间。     

机械设备焊接结构的疲劳寿命研究

以某厂桥式起重机主梁的危险可见裂纹的研究为例,介绍了一种将断裂力学和有限元分析相结合,对机械设备焊接结构进行疲劳寿命研究的新方法。     

基于FRANC3D的三维疲劳裂纹扩展的数值模拟

介绍了三维断裂分析软件FRANC3D(Fracture Analysis Code in 3 Dimensions)以及相关原理,详细说明了FRANC3D对于复合型裂纹断裂的判定依据、断裂后新裂纹前缘面的形成过程以及软件进行疲劳裂纹扩展计算的一个完整过程。最后,由应用实例验证了FRANC3D预测疲劳裂纹扩展路径及构件寿命的准确性。     

激光标刻、电解标刻对GH4169疲劳性能的影响北大核心

对GH4169合金进行激光标刻和电解标刻处理,研究了两种标刻工艺后GH4169合金的高周疲劳性能及其断裂机理。结果表明,激光标刻、电解标刻后试样的抗拉强度下降幅度很小,几乎不影响合金的抗拉强度,与未标刻的GH4169合金疲劳寿命相比,激光标刻后合金疲劳寿命下降19.2%,电解标刻后疲劳寿命下降16.0%。从标刻截面处观察发现激光标刻后的形貌较为尖锐,电解标刻的陷坑形貌较为圆滑。通过观察裂纹源区形貌发现未标刻试样裂纹从合金表面处萌生,激光标刻试样缺口处产生了高应力集中,加快了裂纹的萌生速率。电解标刻位置存在呈灰暗色的化学蚀刻层,进而引起裂纹的萌生和扩展,综合比较下航空用电解标刻工艺所标刻的试样比激光标刻工艺疲劳性能更优。