Prediction of Load-Displacement Curve of Flexible Pipe Carcass Under Radial Compression Based on Residual Neural Network

The carcass layer of flexible pipe comprises a large-angle spiral structure with a complex interlocked stainless steel cross-section profile, which is mainly used to resist radial load. With the complex structure of the carcass layer, an equivalent simplified model is used to study the mechanical properties of the carcass layer. However, the current equivalent carcass model only considers the elastic deformation, and this simplification leads to huge errors in the calculation results. In this study, radial compression experiments were carried out to make the carcasses to undergo plastic deformation. Subsequently, a residual neural network based on the experimental data was established to predict the load-displacement curves of carcasses with different inner diameter in plastic states under radial compression.The established neural network model’s high precision was verified by experimental data, and the influence of the number of input variables on the accuracy of the neural network was discussed. The conclusion shows that the residual neural network model established based on the experimental data of the small-diameter carcass layer can predict the load-displacement curve of the large-diameter carcass layer in the plastic stage. With the decrease of input data, the prediction accuracy of residual network model in plasticity stage will decrease.

Method for determining the position of landslide slip-surface with a typical inclinometric curves

In the actual monitoring of deep hole displacement,the identification of slip surfaces is primarily based on abrupt changes observed in the inclinometric curve.In conventional identification methods,inclinometric curves exhibiting indications of sliding can be categorized into three types:B-type,D-type,and r-type.The position of the slip surface is typically determined by identifying the depth corresponding to the point of maximum displacement mutation.However,this method is sensitive to the interval of measurement points and the observation scale of the coordinate axes and suffers from unclear sliding surfaces and uncertain values.Based on the variation characteristics of these diagonal curves,we classified the landslide into three components:the sliding body,the sliding interval,and the immobile body.Moreover,three different generalization models were established to analyze the relationships between the curve form and the slip surface location based on different physical indicators such as displacement rate,relative displacement,and acceleration.The results show that the displacement rate curves of an r-type slope exhibit a clustering feature in the sliding interval,and by solving for the depth of discrete points within the step phase,it is possible to determine the location of the slip surface.On the other hand,D-type slopes have inflection points in the relative displacement curve located at the slip surface.The acceleration curves of B-type slopes exhibit clustering characteristics during the sliding interval,while the scattered acceleration data demonstrate wandering characteristics.Consequently,the slip surface location can be revealed by solving the depth corresponding to the maximum acceleration with cubic spline interpolation.The approach proposed in this paper was applied to the monitoring data of a landslide in Yunnan Province,China.The results indicate that our approach can accurately identify the slip surface location and enable computability of its position,thereby enhancing applicability and reliability of the deep-hole displacement monitoring data.

Determination of ultimate bearing capacity of uplift piles using intact and non-intact load−displacement curve

Based on the field destructive test of six rock-socketed piles with shallow overburden,three prediction models are used to quantitatively analyze and predict the intact load−displacement curve.The predicted values of ultimate uplift capacity were further determined by four methods(displacement controlling method(DCM),reduction coefficient method(RCM),maximum curvature method(MCM),and critical stiffness method(CSM))and compared with the measured value.Through the analysis of the relationship between the change rate of pullout stiffness and displacement,a method used to determine the ultimate uplift capacity via non-intact load−displacement curve was proposed.The results show that the predicted value determined by DCM is more conservative,while the predicted value determined by MCM is larger than the measured value.This suggests that RCM and CSM in engineering applications can be preferentially applied.Moreover,the development law of the change rate of pullout stiffness with displacement agrees well with the attenuation form of power function.The theoretical predicted results of ultimate uplift capacity based on the change rate of pullout stiffness will not be affected by the integrity of the curve.The method is simple and applicable for the piles that are not loaded to failure state,and thus provides new insights into ultimate uplift capacity determination of test piles.

Powell dynamic identification of displacement parameters of indeterminate thin-walled curve box based on FCSE theory

The FCSE controlling equation of pinned thinwalled curve box was derived and the indeterminate problem of continuous thin-walled curve box with diaphragm was solved based on flexibility theory. With Bayesian statistical theory,dynamic Bayesian error function of displacement parameters of indeterminate curve box was founded. The corresponding formulas of dynamic Bayesian expectation and variance were deduced. Combined with one-dimensional Fibonacci automatic search scheme of optimal step size,the Powell optimization theory was utilized to research the stochastic identification of displacement parameters of indeterminate thin-walled curve box. Then the identification steps were presented in detail and the corresponding calculation procedure was compiled. Through some classic examples,it is obtained that stochastic performances of systematic parameters and systematic responses are simultaneously deliberated in dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step size is solved by adopting Fibonacci search method. And the Powell identification of displacement parameters of indeterminate thin-walled curve box has satisfied numerical stability and convergence,which demonstrates that the presented method and the compiled procedure are correct and reliable.During parameters鈥？iterative processes,the Powell theory is irrelevant with the calculation of finite curve strip element（FCSE） partial differentiation,which proves high computation effciency of the studied method.

Dynamic Bayesian estimation of displacement parameters of continuous curve box based on Novozhilov theory

The finite strip controlling equation of pinned curve box was deduced on basis of Novozhilov theory and with flexibility method, and the problem of continuous curve box was resolved. Dynamic Bayesian error function of displacement parameters of continuous curve box was found. The corresponding formulas of dynamic Bayesian expectation and variance were derived. After the method of solving the automatic search of step length was put forward, the optimization estimation computing formulas were also obtained by adapting conjugate gradient method. Then the steps of dynamic Bayesian estimation were given in detail. Through analysis of a Classic example, the criterion of judging the precision of the known information is gained as well as some other important conclusions about dynamic Bayesian stochastic estimation of displacement parameters of continuous curve box.

Parameter Identification Based on Force-Displacement Curves for a Bolted Joint Finite Element Model

In order to identify the uncertain parameters of a bolted joint finite element model,a simple and applicable way of parameter identification is introduced.By utilizing numerical simulation with the Abaqus software and experimental investigation with the MTS material testing system,the tangential force-displacement curves that reflect the characteristics of the bolted joint were acquired.On the basis of this,by employing the response surface methodology（RSM）and genetic algorithms（GAs）,parameters in the FEM model were identified.The force-displacement curves by both virtual and experimental approaches are well correlated at the end.This phenomenon-based parameter identification method may help facilitate precise prediction of complex jointed connection structures.

Combine S-N curve and fracture mechanics for fatigue life analysis of welded structures

Based on the evolution of fatigue cracks in welded structures,the fatigue life of welded structures was defined as the sum of the crack initiation life Ni and the crack propagation life Np.Correspondingly,a fatigue-life analysis method combining S-N curves and fracture mechanics theory was proposed.The equivalent structural stress method and the lower 99%boundary of the master S-N curve were used to evaluate Ni,and cracks at the end of the initiation stage were considered as semi-elliptical surface cracks.Moreover,Paris equation and the stress intensity factor range of the cracks were used to evaluate Np.Furthermore,the fatigue test results obtained from the running girder of cranes were used as a reference for comparison and verification of the results.The results revealed that the equivalent structural stress is a good indicator for the crack initiation behavior of complex welded structures.In addition,the predicted fatigue life corresponded closely to the testing life.

GENERALIZED FATIGUE CONSTANT LIFE CURVE AND TWO-DIMENSIONAL PROBABILITY DISTRIBUTION OF FATIGUE LIMIT

According to the traditional fatigue constant life curve, the concept and the universal expression of the generalized fatigue constant life curve were proposed. Then, on the basis of the optimization method of the correlation coefficient, the parameter estimation formulas were induced and the generalized fatigue constant life curve with the reliability level p was given. From P-S-a-S-m curve, the two-dimensional probability distribution of the fatigue limit was derived. After then, three se, of tests of LY11 CZ corresponding to the different average stress were carried out in terms of the two-dimensional up-down method. Finally, the methods are used to analyze the test results, and it is found that the analyzed results with the high precision may be obtained.

Hardness-Based Non-destructive Method for Developing Location Specific S-N Curves for Fatigue Life Evaluation

This paper first describes the importance of using location specific S-N curves for fatigue damage assessment of existing steel structures. It discusses the existing concepts and methods for developing S-N curves using empirical formulae and monotonic strength parameters, such as the ultimate tensile strength and hardness. It also discusses relationships among these monotonic parameters. Then it presents formulae for developing hardness-based full range S-N curves for medium strength steels. The formulae are verified using experimental data obtained from both monotonic and cyclic testing. Finally, it describes the advantages of these hardness-based formulae for developing location specific S-N curves as hardness testing is a non-destructive test which can be carried out on specific locations in structures.

Research on Fatigue Curves for Pre-corroded Aircraft Structures

To quantitatively evaluate the effects of corrosion during grounding onfatigue life of aircraft structures, a new power equation is proposed using two-variable linearregression method. That the slope is a constant and the logarithmic intercept is a linear functionof pre-corrosion time makes this equation advantageous: it has a simple form, its parameters haveunambiguous technical and geometrical meanings, and it facilitates engineering applications.Three-parameter equations after pre-corrosion are obtained from back-calculation of fatigue limits,which have been successfully used to predict safe life of aircraft structures in corrosiveenvironment.

ASSESSMENT OF LOCAL INFLUENCE IN A GROWTH CURVE MODEL WITH RAO'S SIMPLE COVARIANCE STRUCTURE

The present paper deals with the problem of assessing the local influence in a growth curve model with Rao's simple covariance structure. Based on the likelihood displacement,the curvature measure is employed to evaluate the effects of some minor perturbations on the statistical inference, thus leading to the large curvature direction, which is the most critical diagnostic statistic in the context of the local influence analysis. As an application, the common covariance-weighted perturbation scheme is thoroughly considered.

Determination of Carboplatin Dose by Area Under the Curve in Combination Chemotherapy for Senile Non-small Cell Lung Cancer

To preliminarily determine the appropriate dosage of carboplatin （CBP） at AUC of 5 mg-M1^-1·min^-1 in the combination chemotherapy for Chinese senile patients with non-small cell lung cancer （NSCLC）. Thirty-five Chinese senile patients with NSCLC in advanced stage （Ⅲ/Ⅳ） were given 96 cycles of combination chemotherapy. Chemotherapy schedules included Taxol＋CBP, Gemzar＋CBP and NVB＋CBE The dose of CBP was at 5 mg.mL^-1·min^-1 of area under the concentration-time curve （AUC）. Side effects and quality of life were observed before and after the chemotherapy. Myelosuppression was severe and commonly observed. Grade 3/4 of granulocytopenia was found in 47.9% （46/96） of the patients and grade 3/4 of thrombocytopenia was noted in 28.1% （27/96） of the subjects. However, other side effects were slight. The mean score of quality of life （QOL）, according to the criteria of QOL for Chinese cancer patients had reduced 6.8. At 5 mg.mL^-1·min^-1 by AUC, the hematological toxicity of CBP was severe and it had some negative effects on the QOL. The administration of CBP at 5 mg.mL^-1·min^-1 by AUC may be too high for Chinese senile patients with non-small cell lung cancer.

Classification Study on Relative Permeability Curves

The classification method of relative permeability curves is rarely reported, when relative permeability curves are applied;if the multiple relative permeability curves are normalized directly, but not classified, the calculated result maybe cause a large error. For example, the relationship curve between oil displacement efficiency and water cut, which derived from the relative permeability curve in LD oilfield is uncertain in the shape of low water cut stage. If being directly normalized, the result of the interpretation of the water flooded zone is very high. In this study, two problems were solved: 1) The mathematical equation of the relationship between oil displacement efficiency and water cut was deduced, and repaired the lost data of oil displacement efficiency and water cut curve, which solve the problem of uncertain curve shape. After analysis, the reason why the curve is not available is that relative permeability curves are not classified and optimized;2) Two kinds of classification and evaluation methods of relative permeability curve were put forward, the direct evaluation method and the analogy method;it can get the typical relative permeability curve by identifying abnormal curve.

BUCKLING OF SPATIAL CURVED RODS WITH CIRCULAR CROSS-SECTIONS

Formulae for determining Green strain of an initially curved and twisted rod with circular cross-sections are derived by using the natural (curvilinear) coordinate system. Finite element analyses are performed for the flexural buckling of initially curved and twisted thin rods under simultaneous action of axial force and torque. Numerical examples demonstrate that the given formulae are correcte. Some numerical results are compared with existing analytical solutions and data obtained by commercial FE software. The convergence of the proposed curved element is better than that of elements in the commercial FE software. It is shown that good accuracy and convergency are achieved by solving three-dimensional problems.

Monotricat, Innovative Displacement Hull High Hydrodynamic Efficiency and Energy Recovery, Navigating at Speeds of Planing Hulls on Spray Self-produced

The need to have naval units ever faster pushed the ship design to design hull shapes with increasingly higher performance thanks to the use of lightweight materials such as aluminum, and more powerful engines, etc., but without substantially modifying the traditional forms of hull. The hull patented Monotricat high hydrodynamic efficiency and energy saving it represents an evolution of the traditional architectures of the hulls, as its shape is adapted to recover wave formation engendered from the bow and sprays associated with it so as to reduce the resistance to the benefit of the speed, and navigating in displacement at speeds of planing hulls with an efficiency of about 20%. The patented hull Monotricat represents the overcoming of distinction between displacement and planing hulls, because, unlike previous solutions, the hull conventionally called Monotricat is the first displacement hull that can navigate at both displacement and planning speeds, with a resistance curve almost straight, maintaining the characteristics of a displacement hull, since it combines the characteristics of displacement and planning hull. It presents an innovative architecture that could be defined as a hybrid between a monohull and catamaran, navigating on spray self-produced. The combination of these three types of naval hulls allows it to ensure： safety, comfort navigation, best seakeeping and maneuverability in restricted waters, stability, reduction of resistance to motion, cost management, regularity on the routes even in adverse weather-sea. These characteristics of the hull have been studied, tested and validated by leading research institutes and universities with more ameliorative results in each subsequent experimentation, reported in the present work, which demonstrated a greater hydrodynamic efficiency compared to conventional hulls of 20%.

Study on Prediction Method of Structural Three-parameter Power Function P-S-N Curve

This paper applies weighted least square method to estimate the three-parameter power function equation of the fatigue life curve, and uses comprehensive fatigue life coefficient to correct the equation, and at the same time combines probability statistics method to bring out the prediction method of structure＇s three- parameter power function P-S-N curve, finally applies the prediction method to a ship＇s frame-type elevate, based on the fatigue test data of it＇s material-SA06 aluminium alloy, to obtain it＇s structure＇s three-parameter power function P-S-N curve. Compared with the conventional least square method, the presented method can give

基于断裂力学的腐蚀钢丝疲劳S-N曲线研究

高强冷拔钢丝因其优异的力学性能被广泛应用于缆索承重结构,服役过程中钢丝腐蚀与断裂威胁着结构安全。钢丝腐蚀后表面的蚀坑因应力集中效应易产生疲劳裂纹,因此腐蚀钢丝剩余疲劳寿命主要取决于裂纹的扩展阶段,且裂纹扩展受到腐蚀程度(初始损伤)的显著影响。精确表征腐蚀程度并准确评估服役期钢丝腐蚀后的剩余寿命,仍是亟待解决的维修难题。首先采用蚀坑最大深度表征钢丝腐蚀程度,以应力强度因子幅作为裂纹扩展驱动力指标,基于断裂力学的Paris公式建立受拉钢丝裂纹扩展理论模型,进而推导腐蚀钢丝的疲劳S-N曲线。大量既有的腐蚀钢丝疲劳试验结果与理论预测值的比较验证了所提理论模型及疲劳S-N曲线的合理性和有效性。含多个蚀坑的钢丝裂纹扩展有限元模拟表明,等效单裂纹适用于多腐蚀坑钢丝疲劳寿命的简化分析。参数分析表明,蚀坑深度和腐蚀环境是腐蚀钢丝疲劳强度的关键影响因素,而应力比和疲劳加载频率影响较小,所提出的S-N曲线在钢丝常规服役条件下适用于评估其剩余寿命,可得到合理的预测结果。基于断裂力学所提的理论方法和疲劳S-N曲线可为腐蚀钢丝的疲劳强度和寿命评估提供参考。

高速铁路大跨度钢桁架桥接触网腕臂安装技术研究

高速铁路大跨度钢桁架桥纵向伸缩量大且变位复杂,是影响接触网腕臂偏移等系统能否正常、安全运行的重要因素,如何解决接触网腕臂安装、偏移调整与钢梁伸缩之间的协同配合,目前国内在此方面鲜有研究。通过阐述受导线伸缩影响的腕臂偏移机理和大跨度钢桁架桥梁体纵向伸缩机理,分析在不同接触网锚段布置方式下大跨度钢桁架桥梁体伸缩对腕臂偏移的影响,并采用逐工点分析法总结不同工况下钢梁伸缩与导线伸缩对腕臂偏移影响的相互关系,揭示了接触网腕臂安装曲线在导线伸缩及钢梁伸缩共同作用下的计算方法。结合典型案例计算分析,建议采用不同钢梁跨度下的推荐锚段布置方式能有效降低腕臂偏移量,并提出应重点关注伸缩缝两侧锚段腕臂偏移问题、腕臂偏移为叠加关系时缩小半锚长度、钢梁跨度大于720 m时应重点计算伸缩缝两侧双腕臂间距等优化事项。研究内容及计算公式可为系统性解决高速铁路大跨度钢桁架桥接触网腕臂偏移设计、施工及运营维护等技术难题提供理论支持。

江苏宝华山宝华玉兰种群结构与动态特征分析

为了揭示极危(CR)植物宝华玉兰〔Yulania zenii(W.C.Cheng)D.L.Fu〕野生种群的结构和动态特征,对江苏省句容市宝华山宝华玉兰野生资源进行全面调查,并运用静态生命表、存活曲线和生存分析等方法综合分析宝华玉兰种群结构和动态变化。结果表明:宝华山全境现存宝华玉兰野生开花植株115株,主要分布于宝华山北坡中部。宝华玉兰种群以中树和大树〔10 cm≤胸径(DBH)<25 cm〕为主,占比达66.1%,属于衰退型种群。从静态生命表看,宝华玉兰种群的生命期望随着径级的增加逐渐下降,种群存活曲线趋向于Deevey-Ⅱ型。生存分析结果显示:宝华玉兰种群趋势具有前期锐减、中期稳定、后期衰退的特点。种群动态量化分析结果表明:宝华玉兰种群动态总体呈增长趋势,但增长极为缓慢。基于上述研究结果,建议采取人工播种、补植实生苗等方式加强对宝华玉兰种群的保护和管理,促进其种群的更新和良性发展。

波纹管最大压缩位移及疲劳寿命分析

为解决某GIS母线中波纹管的最大压缩位移和疲劳寿命究竟能否同时满足工程指标的难题,应用工程计算和有限元分析分别加以计算,然后通过两种计算结果和实验验证进行比较,以期获得哪种方法更精确可靠。为达此目的,文中给出了工程计算和有限元建模的详细过程。按工程计算方法得到的最大压缩位移结果无法满足工程指标,而有限元分析计算方法,却可以达到工程指标,且有较大的安全裕度。有限元分析还揭示了满足大压缩位移的机理,计算结果符合某GIS工程同时需要的压缩位移和疲劳寿命。经型式试验也验证了模拟的正确性。充分证明了有限元分析方法是比按工程计算方法更为先进和准确的设计手段。