储气库注采气井管柱优选研究

随着储气库建设工作逐步展开，对注采井管柱优选是储气库安全运行的重要保证。通过对气藏注采方案下不同管径的注采能力、携液和冲蚀情况进行分析，优选出挂采井管柱管径；同时，通过对比直井注／采过程油管的受力计算，和对丝扣连接强度校核、抗内压强度和抗外挤强度校核，并考虑到温度和压力的作用，计算出管柱受力情况，进而优选出管柱级别。基于该方法优选的储气库注采管柱在储气库注采井得到采用，效果良好。     

基于疲劳寿命计的桥梁载荷谱识别研究

疲劳寿命计是结构承载过程中理想的疲劳状态监测元件，其电阻产生的不可逆变化反映了结构的疲劳加载历程。首先比较分析了普通应变片和疲劳寿命计在实际应用中的优劣，然后在采用恒幅加载实验研究其基本测试性能的基础上，通过多级加载实验进一步证实了疲劳寿命计电阻响应规律的正确性，由此研究分析了桥梁等大型结构在实际的瑞利分布载荷作用下的疲劳加载历程，并对其使用寿命和剩余寿命进行预测。     

超长寿命疲劳破坏行为的可靠性研究

为了进行超长寿命疲劳破坏行为的可靠性研究,对GCr15钢超长寿命疲劳S-N试验数据进行了统计评估,采用Bansqun模型描述了其S-N曲线关系,建立了其概率S-N曲线模型,并采用SEV方法和Murakami方程分别预测了钢中最大夹杂尺寸和其相对应的疲劳强度。结果表明:其超长寿命疲劳S-N数据能较好地服从三参数威布尔分布,其概率S-N曲线形式都呈现持续下降的趋势;在验证了最大夹杂尺寸服从Gumbel分布的基础上,SEV方法预测的最大夹杂尺寸随着钢体积的增大而线性增加,Murakami方程预测的结果揭示了其概率S-N曲线呈现持续下降的原因。     

高强度钢30Cr3SiNiMoVA的疲劳特性研究

为了获得超高强度钢30Cr3SiNiMoVA的疲劳设计数据,对该材料进行了疲劳性能实验。分别对该材料的抛光和未抛光试样进行轴向拉压疲劳实验。用升降试验法测定材料的条件疲劳极限,用成组实验法在四级应力水平下测试其疲劳寿命。结合升降法所得的条件疲劳极限值和成组法实验数据,采用双参数最小二乘法拟合S-N曲线,运用概率方法求得P-S-N曲线。通过对两种试样的S-N曲线分析可知:未抛光试样的疲劳寿命要低于抛光试样的疲劳寿命,并且疲劳载荷级越低,两类试样之间的疲劳寿命差越大,抛光试样的疲劳极限大约是未抛光试样的1.4倍。相关实验现象表明30Cr3SiNiMoVA的疲劳寿命对试样表面粗糙状态非常敏感,建议该类材料在应用过程中要采取有效措施改善构件的表面状态。文中实验数据可为该材料的工程应用提供参考。     

Ⅱ型加载条件下疲劳裂纹扩展试验研究

对４种金属材料在Ⅱ型加载条件下的疲劳裂纹扩散行为进行的试验研究表明：在Ⅱ型加载条件下，裂纹可能仍沿Ⅱ型方向继续扩展，亦可能发生分支转变成Ⅰ型甚至Ⅰ＋Ⅱ型扩展，主要取决于材料本身的性质和它们的微观结构以及应力水平。当裂纹仍沿Ⅱ型方向扩展时，其扩展速率比相当应力水平的Ⅰ型裂纹扩展速率要大得多。     

TNM-Ti Al合金室温高周疲劳性能研究

采用升降法与成组法对TNM-TiAl合金试样进行了应力比R=-1的室温拉压疲劳和R=0.1的室温拉伸疲劳试验,得到TNM-TiAl合金的P-S-N曲线,并对断口进行了分析。结果表明:TNM-TiAl合金对应力十分敏感,R=-1和R=0.1时的曲线整体呈较为平直的斜线,R=-1时的疲劳极限为414.7 MPa,R=0.1时的疲劳极限为285.6 MPa。R=0.1的S-N曲线远低于R=-1的S-N曲线;R=-1时,应力幅与疲劳寿命的关系满足Basquin方程。疲劳试件宏观断口较为粗糙,静态拉伸宏观断口平整,两者差异较大。拉伸断口整体分为裂纹萌生区与扩展区,其中起裂源均位于试样表面或板状试件的边角棱线处,起裂源区域包括γ相的解理断裂面、片层团的沿层解理面以及β₀相平整的穿晶断裂平面等特征。疲劳断口整体分为裂纹萌生区、扩展区与瞬断区,其中裂纹萌生区分为表面沿层起裂和γ相起裂。TNM-TiAl合金的疲劳断裂为脆性断裂,主要体现在扩展区上大量的片层团穿层断裂、扭折撕裂、γ相解理断裂和β₀相穿晶断裂。同寿命量级下,R=-1的断口与R=0.1的断口断裂类型...     

汽车发动机曲轴弯曲疲劳试验方法研究

目的研究两种常用的疲劳试验加载原理对疲劳试验结果的影响,为曲轴选材、设计和制造的各阶段开展弯曲疲劳试验提供技术支持。方法在两种加载方式下采用同批次曲轴进行弯曲疲劳试验,利用成组法得到疲劳试验结果,针对试验加载原理和试验数据开展分析和讨论。结果电液伺服加载方法的试验精度更准确,而电磁谐振加载方法可以大幅度缩短试验周期。电液伺服加载和电磁谐振加载试验的疲劳极限分别为1140.4 N·m和1189.4 N·m。两种加载方法下,曲轴的失效情况均为连杆颈辊压槽处断裂。结论两种加载方法对曲轴弯矩的加载效果相同,试验结果的相对误差为4.3%。在曲轴的仲裁试验中或有争议的情况下使用,推荐使用电液伺服加载方法。在使用电磁谐振加载方法时须严格控制标定误差。曲轴连杆颈辊压槽是曲轴的薄弱环节,应严格控制辊压槽的机加工质量。     

疲劳裂纹扩展试验载荷谱加重方法研究

为探索缩短疲劳裂纹扩展试验周期的载荷谱处理方法,对多种裂纹扩展模型进行了综述,概括出一种通用的裂纹扩展预测模型表达式。提出了一种将峰谷值同时等比例放大的载荷谱加重方法,并推导出加重前后裂纹扩展寿命的转换关系。用一种随机谱和两种块谱的基准谱及对应四种比例加重谱进行了LY12CZ中心裂纹板裂纹扩展试验,用常幅载荷谱及其1.1倍加重谱进行了典型机身壁板结构裂纹扩展试验。试验结果表明载荷谱等比例加重方法可以有效缩短疲劳裂纹扩展试验周期而不改变结构破坏模式,而分析结果表明由该方法预测的裂纹扩展寿命与试验结果的误差在15%以内,满足工程精度要求。     

瓦楞纸板承载能力疲劳损伤曲线研究

瓦楞纸板在使用的过程中,随着振动、冲击次数的增加,其性能会不同程度的衰减下降,出现疲劳现象.对A型瓦楞纸板进行疲劳振动试验,获得瓦楞纸板不同振动加速度下的疲劳损伤次数,得出疲劳破损曲线N-A,并进行两级应力振动疲劳累积效应分析,为瓦楞纸板承载功能的实现提供有价值的参考.     

碳纤维束疲劳损伤失效试验

为了解碳纤维束的疲劳特性及疲劳加载后剩余强度的变化, 为建立碳纤维复合材料疲劳性能的细观力学分析模型提供必要的基础数据, 研究设计了碳纤维束静载力学性能及疲劳特性试验方案, 并进行了试验。采用最小二乘法拟合得到了单束碳纤维的应力-寿命(S-N)曲线。对经过预疲劳的碳纤维束试验件进行了剩余强度试验, 采用最小二乘法拟合得到了碳纤维束疲劳加载剩余强度模型。试验结果表明: 试验所用碳纤维束的条件疲劳极限为静拉伸强度的80.47%; 碳纤维束经历一定循环次数的拉-拉疲劳可以提高其强度, 其剩余强度随着疲劳加载循环次数的增加先增加后减小。     

大尺寸储气库套管抗挤强度影响因素试验研究

根据大尺寸储气库套管受到外挤载荷时的受力及变形特点,通过室内全尺寸试验分析套管椭圆度、钢级、径厚比等因素对大尺寸储气库套管抗挤强度的影响,并利用试验数据对现有的套管抗挤计算公式进行修正。将套管变形分为弹性和塑性变形两个阶段,建立套管弹、塑性变形受力计算模型,利用能量平衡方程推导出套管抗挤强度计算公式,分析初始椭圆度、套管钢级和径厚比对大尺寸储气库套管抗挤强度的影响,将修正前后的计算结果与试验结果进行对比分析。研究结果表明:利用本文建立的套管挤毁受力模型能够很好地预测带有初始椭圆度的大尺寸储气库套管抗挤强度,计算公式简单、准确,适用于不同椭圆度、屈服强度和径厚比的套管抗挤强度计算,能够弥补现有大尺寸储气库套管规范的不足及缺失;套管的抗挤强度随着初始椭圆度和径厚比的增加而降低,随着套管钢级的增加而增加;内、外椭圆度对大尺寸储气库套管抗挤强度影响具有耦合作用,在制造过程中要严格控制椭圆度及其跳跃性,建议制订相应的储气库大尺寸套管内壁椭圆度控制规范以满足相应套管的需求。     

Microstructure based fatigue analysis of cast components under variable amplitude loading

Reliable numerical fatigue life analyses are becoming increasingly important given the need to reduce the time and costs for product development and the need to evaluate large and single components. Stress‐based approaches as well as the local strain approach and its fracture mechanics based extension (P_J model) are in use for that. Both the local strain approach and the P_J model require the supply of pure material data. This requirement for input data that are not component‐specific makes such approaches interesting for widespread application. The accuracy of numerical fatigue life analyses is an essential criterion for the acceptance and the spread in industrial application. In the local strain approach, accuracy is determined on one hand by the transferability of material data for the fatigue life analysis of components and on the other by the damage accumulation rule. In this paper, the local strain approach and the P_J model are used to analyse fatigue life under both constant and variable amplitude loading. These analyses are based on the experimental results obtained from tests of a commercial vehicle component made of nodular cast iron EN‐GJS‐400‐15. Aspects of transferability and damage accumulation are considered. Results obtained from using an elastic‐plastic fracture mechanics based approach to estimate a P_SWT‐N curve, taken into account the inhomogeneities in the microstructure of the cast iron, are also presented.     

Inclusion of fatigue effects in human reliability analysis

The effect of fatigue on human performance has been observed to be an important factor in many industrial accidents. However, defining and measuring fatigue is not easily accomplished. This creates difficulties in including fatigue effects in probabilistic risk assessments (PRA) of complex engineering systems that seek to include human reliability analysis (HRA). Thus the objectives of this paper are to discuss (1) the importance of the effects of fatigue on performance, (2) the difficulties associated with defining and measuring fatigue, (3) the current status of inclusion of fatigue in HRA methods, and (4) the future directions and challenges for the inclusion of fatigue, specifically sleep deprivation, in HRA.     

温室气体提高采收率的资源化利用及地下埋存

全球气候变化是人类迄今面临的既重大又复杂的环境问题,由于温室气体大量排放而引起的全球气候变暖问题日趋严峻,正在严重地威胁着人类赖以生存的环境,国际社会必须采取积极有效措施.2006年中国国家科技部批准国家"九七三"项目--温室气体提高石油采收率的资源化利用及地下埋存研究.建立适合中国国情的CO2高效利用和埋存体系;实现CO2减排的社会效益和CO2高效利用的经济效益;发展适合中国国情的CO2埋存地下理论、多相多组分相态理论、多相多组分非线性渗流理论和CO2捕集与储运理论.通过上述基础研究,形成具有自主知识产权的CO2地质埋存和高效利用的综合技术,使中国CO2安全埋存一高效利用研究处于国际水平.必将为全球资源和环境的高水平、高效益开发和可持续发展提供理论及实践依据.     

Multiaxial notch fatigue life prediction based on the dominated loading control mode under variable amplitude loading

A new calculation approach is suggested to the fatigue life evaluation of notched specimens under multiaxial variable amplitude loading. Within this suggested approach, if the computed uniaxial fatigue damage by the pure torsional loading path is larger than that by the axial tension–compression loading path, a shear strain‐based multiaxial fatigue damage parameter is assigned to calculate multiaxial fatigue damage; otherwise, an axial strain‐based multiaxial fatigue damage parameter is assigned to calculate multiaxial fatigue damage. Furthermore, the presented method employs shear strain‐based and axial strain‐based multiaxial fatigue damage parameters in substitution of equivalent strain amplitude to consider the influence of nonproportional additional hardening. The experimental data of GH4169 superalloy and 7050‐T7451 aluminium alloy notched components are used to illustrate the presented multiaxial fatigue lifetime estimation approach for notched components, and the results reveal that estimations are accurate.     

The effect of periodic-random loading on fatigue crack growth

A theory of fatigue crack growth based on the concept of damage accumulation is presented which takes some account of the effect of periodic-random loading. The Dugdale model of plasticity is used to calculate the distribution of the energy dissipated during stress cycling in the plastic zones of a crack embedded in a material sample of infinite extent. It is shown how to calculate the damage accumulated by decomposing the random group of stress levels into significant complete stress cycles of various amplitudes. A simple short numerical algorithm is presented which performs this decomposition. A crack growth law is derived having a very simple form which automatically incorporates the condition for catastrophic failure.

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Résumé On présente une théorie sur la croissance des fissures de fatigue basée sur le concept du dommage cumulatif, et tenant compte de l'effet de mise en charges aléatoires. On recourt au modèle de plasticité de Dugdale pour le calcul de la distribution de l'énergie dissipée lors du cycle de contrainte dans les zônes plastiques d'une fissure noyée dans un matériau de dimension infinie.On montre comment calculer le dommage cumulatif en décomposant les blocs de contraintes de niveau aléatoire en collectifs de contraintes cycliques d'amplitudes variables. Un algorithme numérique simple est présenté pour effectuer cette décomposition. On en tire une loi de propagation de la fissure dont la forme est très simple et qui comporte automatiquement les conditions susceptibles de conduire à une rupture brutale.

     

Influence of the loading path on fatigue crack growth under mixed-mode loading

Fatigue crack growth tests were performed under various mixed-mode loading paths, on maraging steel. The effective loading paths were computed by finite element simulations, in which asperity-induced crack closure and friction were modelled. Application of fatigue criteria for tension or shear-dominated failure after elastic–plastic computations of stresses and strains, ahead of the crack tip, yielded predictions of the crack paths, assuming that the crack would propagate in the direction which maximises its growth rate. This approach appears successful in most cases considered herein.     

Case analysis of catastrophic underground pipeline gas explosion in Taiwan

This study is related to underground pipeline gas explosions that occurred in the southern region of Taiwan in July 2014. This disaster, which resulted in substantial numbers of fatalities and injuries in addition to about 6 km of damaged roads, was the largest petroleum catastrophe in Taiwan's history.Because pipeline gas explosions of such a large extent are rare, the Kaohsiung District Prosecutors Office and Kaohsiung Fire Department launched an investigation in which an author of this paper participated. The aim of this paper is to explore the causes of the explosions, thereby contributing to the prevention of similar cases in the future.First, the causes of the large explosions are thoroughly investigated. Second, metallographic studies are conducted on the ruptured pipelines. Finally, the results are summarized, and conclusions are drawn.     

Rossini型气体热量计电校正实验与分析

Rossini型气体热量计是目前测量准确度最高的气体热值测定装置,在研制过程中,量热容器的当量热容是实验装置的一个重要参数,采用电校正方法能够准确地测量其当量热容。为保证电校正实验与燃烧实验的一致性,实验中要做到电加热功率与燃烧功率完全相同,之后通过测量燃烧器周围吸热介质的温升分析得到量热容器的当量热容。实验结果表明:在电加热功率与燃烧功率一致的情况下,两种实验中燃烧器周围吸热介质的温升曲线完全吻合,测得量热容器的当量热容为19 023 J/K,当量热容测量不确定度为28 J/K,其相对不确定度为0.15%。