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文章速递The Effects of Fatigue Cracks on Fastener Loads during Cyclic Loading and on the Stresses Used for Crack Growth Analysis in Classical Linear Elastic Fracture Mechanics Approaches 认领
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作者 Claudiu Gudas 《材料科学与应用期刊(英文)》 2020年第7期505-551,共47页
High strength threaded fasteners are widely used in the aircraft industry, and service experience shows that for structures where shear loading of the joints is significant, like skin splices, fuselage joints or spar ... High strength threaded fasteners are widely used in the aircraft industry, and service experience shows that for structures where shear loading of the joints is significant, like skin splices, fuselage joints or spar caps-web attachments, more cracks are initiated and grow from the edges of the fastener holes than from features like fillets radii and corners or from large access holes. The main causes of this cracking are the stress concentrations introduced by the fastener holes and by the threaded fasteners themselves, with the most common damage site being at the edge of the fastener holes. Intuitively, it is easy to visualize that after the crack initiation, during the growth stages, some of the load transferred initially by the fastener at the cracked hole will decrease, and it will be shed to the adjacent fasteners that will carry higher loads than in uncracked condition. Using currently available computer software, the method presented in this paper provides a relatively quick and quantitatively defined solution to account for the effects of crack length on the fastener loads transfer, and on the far field and bypass loads at each fastener adjacent to the crack. At each location, these variations are determined from the 3-dimensional distribution of stresses in the joint, and accounting for secondary bending effects and fastener tilt. Two cases of a typical skins lap splice with eight fasteners in a two rows configuration loaded in tension are presented and discussed, one representative for wing or fuselage skins configurations, and the second case representative for cost effective laboratory testing. Each case presents five cracking scenarios, with the cracks growing from approx. 0.03 inch to either the free edge, next hole or both simultaneously. 展开更多
关键词 Fasteners Load Transfer Functions Fatigue Life Multi-Site Fatigue Damage Fasteners Modelling Effects of Crack Length on Adjacent Fasteners Secondary Bending Crack Growth Analysis
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Investigation on Fracture Properties of Single-Flawed Tunnel Model Under Medium-to-Low-Speed Impacts 认领
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作者 Lei Zhou Zheming Zhu +3 位作者 Ruifeng Liu Yong Fan Yuqing Dong Peng Ying 《固体力学学报:英文版》 SCIE EI CSCD 2020年第2期205-225,共21页
Dynamic fractures occur frequently in geophysical processes and engineering applications.It is thus essential to study crack and failure behaviors,such as crack time-to-initiation,crack growth rate and arrest period u... Dynamic fractures occur frequently in geophysical processes and engineering applications.It is thus essential to study crack and failure behaviors,such as crack time-to-initiation,crack growth rate and arrest period under dynamic loading.In this study,impact experiments were implemented by utilizing the single-flawed tunnel specimens under drop-hammer impacts.Four brittle materials,i.e.,green sandstone,red sandstone,black sandstone and polymethyl methacrylate,were selected to make single-flawed tunnel specimens.Strain gauges and crack extension gauges were employed to measure the crack extension parameters.The properties of crack growth rate,crack time-to-initiation and arrest period of these four brittle materials were discussed and analyzed.The corresponding numerical simulation was performed by using the commercial software AUTODYN.The numerical results of crack growth rate and crack time-to-initiation agreed with the impact test results.The commercial software ABAQUS was applied to compute the dynamic stress intensity factors.The results show that both the dynamic initiation fracture toughness and the crack growth rate increase with the elastic moduli of these four types of brittle materials under the same loading conditions,whereas the crack time-to-initiation decreases with the increase in elastic moduli of the brittle materials under the same loading conditions. 展开更多
关键词 Single-flawed tunnel Impact loading Crack growth rate Crack time-to-initiation Initiation fracture toughness
Influence of Early Life Stress on Alcohol and Crack Dependents 认领
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作者 Elton Brás Camargo Júnior Maria Neyrian de Fátima Fernandes +3 位作者 Larissa Bessani Hidalgo Gimenez Jaqueline Rodrigues Stefanini Ana Carolina Guidorizzi Zanetti Edilaine Cristina da Silva Gherardi-Donato 《护理学期刊(英文)》 2020年第5期490-512,共23页
Background: Early life stress is a significant public health problem associated with increased rates of psychiatric disorders, especially those related to drug abuse. Objective: To identify the prevalence of early lif... Background: Early life stress is a significant public health problem associated with increased rates of psychiatric disorders, especially those related to drug abuse. Objective: To identify the prevalence of early life stress in drug users, to compare the intensity of trauma in alcohol and crack users, and to relate the power of injury to the severity of drug dependence. Method: Cross-sectional analytical study with a sample of 105 alcohol and crack users treated by an outpatient service. The instruments for data collection were sociodemographic data questionnaire, the Mini-International Neuropsychiatric Interview, and the Severity of Dependence Scale. The categorical variables association was analyzed using the Chi-squared test, considering p Results: High prevalence of early stress and severity of dependence were identified, with higher rates among crack users. The early stress revealed in the Alcohol group high rates of emotional (88.7%) and physical (94.3%) neglect and in the Crack group significant frequency of physical (61.5%) emotional abuse (51.9%), sexual (46.2%), and emotional (78.8%) and physical (90.4%) neglect. Crack users are 2.6 times more likely to have been emotionally abused, and 2.1 times more likely to have been sexually abused during childhood when compared to the alcohol group. Conclusion: Early stress was prevalent with significant intensity in drug users, and evaluation of this problem is essential for a better understanding of these disorders. 展开更多
关键词 CHILDHOOD Trauma ADVERSE CHILDHOOD Experiences Child ABUSE Early Life Stress Substance ABUSE CRACK ALCOHOL
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等速驱动轴中间轴淬火后崩裂原因分析 认领
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作者 崔小毅 《智能城市应用》 2020年第5期99-103,共5页
公司某批次中间轴在中频淬火后发生表层崩裂现象。通过宏观观察、化学成分分析、淬火结果金相检查等方法分析了崩裂产生的原因。结果表明,中间轴崩裂的主要原因为,原材料表层裂纹的存在导致中频淬火时在裂纹处应力集中,产生崩裂。而崩... 公司某批次中间轴在中频淬火后发生表层崩裂现象。通过宏观观察、化学成分分析、淬火结果金相检查等方法分析了崩裂产生的原因。结果表明,中间轴崩裂的主要原因为,原材料表层裂纹的存在导致中频淬火时在裂纹处应力集中,产生崩裂。而崩裂的次要原因为,碳含量偏上限,低温段淬火液冷速又较快,产生了较大的组织拉应力,诱发崩裂。 展开更多
关键词 中间轴 崩裂 表层裂纹 应力集中 组织应力
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裂纹面局部均布荷载下Ⅰ型裂纹有限宽板应力强度因子∗ 认领
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作者 李亚 易志坚 +1 位作者 王敏 苏康 《应用数学和力学》 CSCD 北大核心 2020年第10期1083-1091,共9页
采用应力强度因子的裂纹线求解方法,对裂纹面局部均布荷载作用下的Ⅰ型裂纹有限宽板应力强度因子进行了解析求解.其思路是:直接利用无限宽板裂纹问题应力场的解析解,求得应力分量在裂纹线上的形式,通过合理的修正,提出修正后的应力场在... 采用应力强度因子的裂纹线求解方法,对裂纹面局部均布荷载作用下的Ⅰ型裂纹有限宽板应力强度因子进行了解析求解.其思路是:直接利用无限宽板裂纹问题应力场的解析解,求得应力分量在裂纹线上的形式,通过合理的修正,提出修正后的应力场在裂纹线应满足的条件;进而求解应力强度因子,得出了有限宽板对相应无限宽板的应力强度因子修正系数.当板宽趋于无限大时,得到的应力强度因子与相应的无限宽裂纹板的解答一致. 展开更多
关键词 应力强度因子 有限宽板 裂纹 线场分析方法
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Assessment of Existing Bridge’s Beam Bending Stiffness Using Crack Characteristics 认领
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作者 Donglian Tan 《工程(英文)(1947-3931)》 2020年第2期82-89,共8页
At present, the bearing capacity evaluation is mainly based on load detection, which requires closed traffic and has certain risks. With the increase of service time, the cracks of reinforced concrete beam bridge will... At present, the bearing capacity evaluation is mainly based on load detection, which requires closed traffic and has certain risks. With the increase of service time, the cracks of reinforced concrete beam bridge will gradually develop and the stiffness will reduce, resulting in the decrease of bearing capacity. Therefore, in this paper, the calculation of stiffness reduction coefficient by using crack characteristic parameters, which provides basic data for bearing capacity evaluation, has been studied. In this paper, using regression analysis through fracture characteristics of four model beam observation and test load-displacement curve characteristic parameters, crack flexural rigidity of the beam bridge relationship has been set up. The qualitative assessment based appearance of cracks in the structure of checks has been converted to quantitative assessment. And compared with the test results of a real bridge, comparative results show that the assessment is objective and reliable. It makes the assessment more objective and scientific. A new way of Quantitative assessment of the structural performance has been provided for a large number of existing reinforced concrete beam bridge. 展开更多
关键词 BEAM Bridge CRACK CHARACTERISTICS BENDING STIFFNESS ASSESSMENT
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服役过程中裂纹齿轮时变啮合刚度计算方法研究进展 认领
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作者 徐慧 吴小刚 +2 位作者 刘德权 赵哲 王奕霖 《机械工程与自动化》 2020年第5期221-222,共2页
围绕齿轮系统裂纹故障问题,讨论了裂纹扩展路径及裂纹故障中时变啮合刚度的求解方法,旨在为齿轮系统故障诊断提供帮助。
关键词 裂纹 齿轮传动 时变啮合刚度 裂纹扩展路径 计算方法
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An Extended Dielectric Crack Model for Fracture Analysis of a Thermopiezoelectric Strip 认领
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作者 Xianci Zhong Yuanbo Wu Keshi Zhang 《固体力学学报:英文版》 SCIE EI CSCD 2020年第4期521-545,共25页
An extended dielectric crack model is proposed to capture the effects of the physical properties of crack interior on crack-tip thermoelectroelastic fields.The typical crack-face boundary conditions can be retrieved b... An extended dielectric crack model is proposed to capture the effects of the physical properties of crack interior on crack-tip thermoelectroelastic fields.The typical crack-face boundary conditions can be retrieved by considering the limiting cases of electrical permeability and thermal conductivity inside a crack.Making use of the Fourier transform technique,the problem of a thermopiezoelectric strip weakened by a Griffith crack is investigated and transformed to solve the system of the second kind Fredholm integral equations with Cauchy kernel.The Lobatto-Chebyshev collocation method is used to form a nonlinear system of algebraic equations,which is solved by elaborating on an algorithm.The crack-tip thermoelectroelastic fields are determined by using the approximate solutions.Numerical simulations are carried out to show the variations of the fracture parameters of concern under applied thermoelectromechanical loads,the physical properties of the dielectric medium inside the crack and the geometry of the cracked thermopiezoelectric strip.Some comparisons with the experimental results are reported to reveal the effectiveness of the extended dielectric crack model. 展开更多
关键词 Extended dielectric crack model Thermopiezoelectric strip Fourier transform technique Crack-tip field.Experimental comparison
The Influence of Ceramic Coating on Fatigue Crack Growth Behaviour of X17CrNi15-2 Stainless Steel 认领
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作者 Ran Li Wenshu Wei +13 位作者 Shoubin Li Rui Zhao Hao Liu Jiankai Zhang Jian Ye Huigang Wu Yao Xu Fei Xiao Mengyu Wu Dalong Wang Jingbin Chen Wei Wang Na Gao Rongming Chen 《工程(英文)(1947-3931)》 2020年第2期140-149,共10页
Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some ... Fatigue crack growth tests were carried out on the SEN B3 precracked specimens, with dimensions in accordance with ISO 12108 requirements. The specimens were made of martensitic stainless steel, X17CrNi15-2, and some of them were modified by the ceramic coating deposition surface treatment. The effects of ceramic coating, on the fatigue crack growth behaviour of hollow shaft specimens, were experimentally investigated. Fatigue crack growth rates, da/dN, were characterised, using the power law relationship between da/dN (in mm/cycle) and the stress intensity factor range, ΔK (in MPa&#8729;m0.5). The two constants of the correlation are 7.9768 × 10&#8722;9 and 2.8107 for the parent material, and those for the coated material are 2.4391 × 10&#8722;9 and 3.1990, respectively. Microstructural analyses were carried out on the tested specimens, which shows that the maximum hardness of the ceramic coating is higher than that of substrate by a factor of ~3.2. The dimple fracture dominates the final fracture mechanism for the parent material, and the combination of fatigue, ductile fracture and cleavage dominates the final fracture mechanism for the coated material, based on the SEM analyses. EDS tests’ results reveal that the parent material specimen shows higher levels of C at matrix regions along with Fe- and O-rich regions, compared with the coated material specimen. 展开更多
关键词 Fatigue CRACK Growth SEN B3 Precracked SPECIMEN X17CrNi15-2 CERAMIC Coating DEPOSITION Surface Treatment Corrosion Resistance
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Unveiling the underlying mechanism of forming edge cracks upon high strain-rate rolling of magnesium alloy 认领
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作者 Biwu Zhu Xiao Liu +4 位作者 Chao Xie Jing Su Pengcheng Guo Changping Tang Wenhui Liu 《材料科学技术:英文版》 SCIE EI CAS CSCD 2020年第15期59-65,共7页
In the current study,high strain-rate rolling(≥10 s-1) has been successfully employed to produce Mg-3 A1-1 Zn alloy sheets to a high reduction of 82% with a fine grain structure in a single pass.The underlying mechan... In the current study,high strain-rate rolling(≥10 s-1) has been successfully employed to produce Mg-3 A1-1 Zn alloy sheets to a high reduction of 82% with a fine grain structure in a single pass.The underlying mechanism of forming primary and secondary edge cracks has been investigated.It is found that dynamic recrystallization(DRX) induced by subgrains tends to blunt cracks,while twinning-induced D RX is mainly observed around sharp crack tips.The motion of emitted dislocations from blunted cracks is inhibited by the DRX grain boundaries.This,on one hand,increases local work hardening,and on the other hand,causes stress concentration alo ng grain boundaries especially in the triple junctions leading to the formation of secondary cracks. 展开更多
关键词 Edge crack Secondary crack High strain-rate rolling AZ31 magnesium alloy Dynamic recrystallization
Fractographic analysis of the overload effect on fatigue crack growth in 2024-T3 and 7075-T6 Al alloys 认领
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作者 A.Albedah B.Bachir Bouiadjra +1 位作者 S.M.A.K.Mohammed F.Benyahia 《矿物冶金与材料学报:英文版》 SCIE EI CAS CSCD 2020年第1期83-90,共8页
The effect of single overload on the fatigue crack growth in 2024-T3 and 7075-T6 Al alloys was analyzed.Fatigue tests under constantamplitude loading with overload peak were carried out on V-notched specimens.Fractogr... The effect of single overload on the fatigue crack growth in 2024-T3 and 7075-T6 Al alloys was analyzed.Fatigue tests under constantamplitude loading with overload peak were carried out on V-notched specimens.Fractographic analysis was used as a principal approach to explain the crack growth retardation due to the overload.Scanning electron microscopy(SEM)analyses were conducted on the fractured surface of failed specimens to study the retardation effect.The obtained results show that the overload application generates a plastic zone in both aluminum alloys.The generated plastic zone is three times larger in the case of 2024-T3 compared to 7075-T6,and thus,a significant crack retardation was induced for 2024-T3.The retardation effect due to the overload for 2024-T3 and 7075-T6 lasted for about 10 mm and 1 mm,respectively,from the point of overload application. 展开更多
关键词 fatigue CRACK growth OVERLOAD RETARDATION FRACTOGRAPHY CRACK tip plasticity
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基于扩展有限元法的平板裂纹研究 认领
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作者 赵雪薇 尹大刚 《价值工程》 2020年第5期273-274,共2页
扩展有限元法(XFEM)是一种模拟结构裂纹扩展的有效方法,它保留了有限元方法的许多优点,同时又克服了有限元法的一些缺陷,使裂纹扩展不再局限于单元边界。通过扩展有限元法模拟裂纹在构件中的扩展,分析工程结构构件中孔隙对裂纹扩展路径... 扩展有限元法(XFEM)是一种模拟结构裂纹扩展的有效方法,它保留了有限元方法的许多优点,同时又克服了有限元法的一些缺陷,使裂纹扩展不再局限于单元边界。通过扩展有限元法模拟裂纹在构件中的扩展,分析工程结构构件中孔隙对裂纹扩展路径的影响,研究构件中孔隙对裂纹扩展的影响。 展开更多
关键词 扩展有限元法 裂纹 扩展路径 止裂
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Effects of metallic microstructures on fatigue fracture of Q345 steel 认领
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作者 Han-qing Liu Chun-ming Wang +3 位作者 Hong Zhang Zhi-yong Huang Qing-yuan Wang Qiang Chen 《钢铁研究学报:英文版》 SCIE EI CAS CSCD 2020年第6期702-709,共8页
Effects of high-frequency cyclic loading on the banded ferrite-pearlite steel were analyzed through crack initiation and propagation. Interfaces of ferrite and pearlite colony with a small angle deviation from the loa... Effects of high-frequency cyclic loading on the banded ferrite-pearlite steel were analyzed through crack initiation and propagation. Interfaces of ferrite and pearlite colony with a small angle deviation from the loading axis were verified to be the most potential sites to fabricate the microcracks caused by the high strain gradient. The initial crack extension inside ferrite grain was driven by shear stress in model II along the direction with a 45° angle to the loading axis. Banded pearlite colony and the high-angle grain boundaries were considered as the dominant factors that promote the fatigue resistance of the material through arousing crack deflection in short crack propagation range and crack branching in long crack propagation range to reduce the crack propagation driving force in the crack tip. P-S-N curves were used to quantify the dispersion of fatigue lifetimes and evaluate the effect of elevated volume content of pearlite colony on the fatigue performance of the material. 展开更多
关键词 Ferrite-pearlite steel High-cycle fatigue Crack propagation Crack branching High-angle grain boundary P-S-N curve
Bridge Girder Crack Assessment Using Faster RCNN Inception V2 and Infrared Thermography 认领
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作者 Murad Al Qurishee Weidong Wu +4 位作者 Babatunde Atolagbe Joseph Owino Ignatius Fomunung Said El Said Sayed Mohammad Tareq 《交通科技期刊(英文)》 2020年第2期110-127,共18页
Manual inspections of infrastructures such as highway bridge, pavement, dam, and multistoried garage ceiling are time consuming, sometimes can be life threatening, and costly. An automated computerized system can redu... Manual inspections of infrastructures such as highway bridge, pavement, dam, and multistoried garage ceiling are time consuming, sometimes can be life threatening, and costly. An automated computerized system can reduce time, faulty inspection, and cost of inspection. In this study, we developed a computer model using deep learning Convolution Neural Network (CNN), which can be used to automatically detect the crack and non-crack type structure. The goal of this research is to allow application of state-of-the-art deep neural network and Unmanned Aerial Vehicle (UAV) technologies for highway bridge girder inspection. As a pilot study of implementing deep learning in Bridge Girder, we study the recognition, length, and location of crack in the structure of the UTC campus old garage concrete ceiling slab. A total of 2086 images of crack and non-crack were taken from UTC Old Library parking garage ceiling using handheld mobile phone and drone. After training the model shows 98% accuracy with crack and non-crack types of structures. 展开更多
关键词 Bridge GIRDER CONVOLUTION Neural Network CRACK Detection Structural Health Monitoring Infrared THERMOGRAPHY
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文章速递高速公路改扩建路面检测评价及裂缝处置技术研究 认领
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作者 吴茂军 《建筑技术开发》 2020年第6期94-96,共3页
随着社会经济发展,沥青高速公路改扩建工程势在必行,裂缝病害会对路基结构强度造成影响,对高速公路进行路面检测评价以及裂缝修补技术研究显得尤为重要,通过文献查阅总结、对文献进行理论分析、具体的现场试验,结合现场施工情况总结得... 随着社会经济发展,沥青高速公路改扩建工程势在必行,裂缝病害会对路基结构强度造成影响,对高速公路进行路面检测评价以及裂缝修补技术研究显得尤为重要,通过文献查阅总结、对文献进行理论分析、具体的现场试验,结合现场施工情况总结得出以下结果:总结了路面裂缝的种类;对路面状况进行了检测及评价,路段整体评价较好,且病害以裂缝为主;经过对该路段研究分析,得出了该段路面产生裂缝的原因,根据实际工程状况制订了施工方案,为其他工程提供了经验。 展开更多
关键词 高速公路 路面检测 路面评价 裂缝 裂缝处置
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文章速递常幅和过载下考虑焊接残余应力的裂纹闭合效应研究 认领
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作者 彭子牙 杨平 +1 位作者 胡康 宋月林 《船舶与海洋工程学报:英文版》 CSCD 2020年第2期195-207,共13页
Welding residual stress in the engineering structure has a non-negligible influence on crack propagation,and crack closure is a significant factor affecting the crack propagation.Based on the elastoplastic finite elem... Welding residual stress in the engineering structure has a non-negligible influence on crack propagation,and crack closure is a significant factor affecting the crack propagation.Based on the elastoplastic finite element method and crack closure theory,we studied crack closure and residual compressive stress field of butt-welded plates under constant amplitude loading and overloading regarding the stress ratio,maximum load,overload ratio,and number of overloads.The results show that the welding residual tensile stress can decrease the crack closure because of a decrease in the residual compressive stress in the wake zone,but the effect is gradually reduced with increased stress ratio or maximum load.And the combined effect of welding residual tensile stress and overload can produce a stronger retardation effect on crack propagation. 展开更多
关键词 Welding residual stress Crack closure Overloading Crack propagation Butt-welded plate
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文章速递沥青路面裂缝灌缝施工技术研究 认领
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作者 王建文 《工程建设与设计》 2020年第23期209-210,共2页
灌缝施工能够有效弥补旧沥青路面经过长时间使用而产生的表面裂缝,而且采用灌缝施工对于施工成本的控制也能够达到较好的要求。论文对沥青混凝土路面产生裂缝的类型和原因进行了分析,对沥青混凝土路面裂缝使用灌缝施工技术处理的具体内... 灌缝施工能够有效弥补旧沥青路面经过长时间使用而产生的表面裂缝,而且采用灌缝施工对于施工成本的控制也能够达到较好的要求。论文对沥青混凝土路面产生裂缝的类型和原因进行了分析,对沥青混凝土路面裂缝使用灌缝施工技术处理的具体内容进行了介绍,希望能够帮助有关从业人员在未来面对沥青路面灌缝施工技术时有更详细的认识。 展开更多
关键词 沥青路面 裂缝 灌缝施工技术
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文章速递Experimental Study and Numerical Simulation Using Extended Finite Element Method (XFEM) Combined with Cohesive Zone Model (CZM), of Crack Growth Induced by Non-Explosive Expansive Material on Two Neighboring Circular Holes of A Gneiss Rock 认领
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作者 Frank Ferry Kamgue Tiam Raïdandi Danwe +1 位作者 Noël Konaï Lucien Meva’a 《应用科学(英文)》 2020年第10期592-612,共21页
The Non-explosive expansion material (NEEM) is a method more environmentally friendly than the harmful conventional rock fracturing techniques. However, it is slower and very costly. Thus, any means of economizing the... The Non-explosive expansion material (NEEM) is a method more environmentally friendly than the harmful conventional rock fracturing techniques. However, it is slower and very costly. Thus, any means of economizing their use is very desirable. This paper investigates the crack growth between two neighboring holes of a gneiss rock internally pressurized by NEEM mixed with water with the aim to evaluate the influence of holes spacing (center-to-center distance), on the initiation and growth of cracks. Field experimental results reveal that crack starts earlier and grows faster with increasing ambient temperature. But when the ambient temperature is above 28<span style="white-space:nowrap;">°</span>C, the NEEM is “blown out” of the holes. At these ambient temperatures, the surrounding rocks are hot and cannot dissipate efficiently the heat generated by the hydration reaction. The best filling time was found to be in the evening when the daily hot temperature has drooped. The time to first crack increases as hole diameter decrease<span style="font-family:Verdana;">s</span><span style="font-family:Verdana;">. The 3D numerical modeling and simulation of crack growth between two neighboring holes internally pressurized by NEEM using ABAQUS (XFEM/CZM) software show</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> a good agreement with the theoretical and experimental results.</span> 展开更多
关键词 Crack Growth XFEM Gneiss Holes Spacing
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文章速递Modeling and Simulation of a Cracked Beam with Different Location Using FEM 认领
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作者 Rajib Karmaker Ujjwal Kumar Deb Amrita Das 《水能与环境工程(英文)》 2020年第4期145-158,共14页
Nowadays presence of crack in different engineering structures becomes a serious threat to the performance. Since most of the civil and mechanical structures may be damaged due to material fatigue, mechanical vibratio... Nowadays presence of crack in different engineering structures becomes a serious threat to the performance. Since most of the civil and mechanical structures may be damaged due to material fatigue, mechanical vibration, environmental attack and long-term service. Moreover, dynamical systems of a beam usually possess a non-linear character, which causes practical difficulties on the model-based damage detection techniques. This paper presents a novel approach to detect damage in a simply supported beam. In this study, a numerical simulation using the Finite Element Method (FEM) has been done to determine the frequencies to detect the crack in a concrete beam of length 0.12 m and width 0.015 m. A vibration-based model is employed to simulate the results by using COMSOL Multiphysics. At the tip, by performing the computational analysis it is found that the presence of cracks affects the natural frequencies of the concrete structure. It is observed that after applying load</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> the frequencies of the cracked beam ha</span><span style="font-family:Verdana;">ve</span><span style="font-family:Verdana;"> been changed</span><span style="font-family:Verdana;"> with the variation of the location of the crack for all the modes of vibration. It also found that maximum frequency reserved at the cracked point so it will also help us to detect different hidden defect</span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> in any structure. A comparison is also made with the experimental results. It is also found that the effect of crack is more near the fixed end than at the free end. 展开更多
关键词 Vibration Characteristics Crack Detection Modal Analysis Condition Monitoring FEM
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汽车大梁用500L-Z热轧钢裂纹形成原因分析 认领
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作者 孙成钱 王俊雄 +6 位作者 董毅 时晓光 刘仁东 王越 景鹤 张宇 韩楚菲 《热加工工艺》 北大核心 2020年第3期157-159,162共4页
某汽车大梁用500L-Z钢在冲压过程中出现开裂。采用宏观检验、金相检验和扫描电镜检验对其冲压开裂的原因进行了分析。结果表明:在冲压过程中,切边不平直处发生加工硬化导致开裂,而试样中间的珠光体偏析带也是产生裂纹的原因之一。
关键词 500L-Z钢 热轧 裂纹 夹杂物
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