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To illustrate the vibration characteristics of a rotating pipe in flow, experiments were conducted for a pipe in flow, a rotating pipe in still water and a rotating pipe in flow. For the pipe in flow without rotation, the trajectory diagram is ‘8’ shaped. For the rotating pipe in still water, a multiple frequency component was induced, and a ‘positive direction whirl’ was found. For the flow and rotation, at a flow velocity of 0.46 m/s, the vibration is dominated by the combination of flow and rotation. With an increase in rotating frequency, the trajectory of the rotating pipe varies from an ‘8’ shape to a circular shape and the ‘reverse direction whirl’ is induced, which is different from ‘positive direction’ in still water. The vibration frequency ratio increases uniformly with flow velocity. At a flow velocity of 1.02 m/s, at which the frequency is close to the theoretical natural frequency, the vibration frequency ratio is f*≈1. Predominantly governed by vortex-induced vibration (VIV), the vibration behavior of a rotating pipe subjected to fluid flow conditions has been found to exhibit complete vanishing of whirl. The vibration characteristics of a rotating pipe in flow are studied by the experiments which is benefit for structural drilling design.

In this paper, the assembly problem of circular-rectangular compound peg and hole parts in automatic assembly is proposed for the first time, and an automatic assembly method based on six-dimensional force sensor is summarized. Firstly, according to the quasi-static equilibrium condition, the contact states are summarized. It is concluded that there are 7 categories of 44 contact states in insertion stage and the forces conditions to maintain each contact state; Secondly, according to the analysis of the force/moment relationship, the jamming diagram is drawn, and the conditions of jamming are analyzed. Thirdly, the assembly strategy is discussed, including contact state recognition strategy, hole searching strategy, and pose adjustment strategy. Finally, combined with impedance control, the assembly theory is verified in ADAMS, and the assembly with minimum clearance of 0.1 mm is achieved.

Floating offshore wind turbines are easily affected by typhoons in the deep sea, which may cause serious damage to their structure. Therefore, it is necessary to study further the dynamic response of wind turbine structures under typhoons. This paper took the 5MW floating offshore wind turbine developed by the National Renewable Energy Laboratory (NREL) as the research object. Based on the motion theory of platforms in waves, a physical model with a scale ratio of 1:120 was established, and a hydraulic cradle was used to simulate the effect of waves on the turbines. The dynamic response characteristics of offshore wind turbines under typhoons are systematically studied. The research results clarified that the turbine structure is mainly affected by wave loads under typhoons, and its motion response reaches its maximum value under the action of extreme wave loads. The research results of this paper can provide reference value for the design of offshore wind turbine structures under typhoons.

Due to the confinement effect, the blast load from a confined space explosion tends to cause more severe damage to structures. When subjected to this type of confined explosion, thermoplastic fibre–metal laminate (TFML) panels would experience repeated shock waves and relatively longer durations of quasi-static pressure. A better understanding of the dynamic response and damage mechanism of TFMLs under confined blast loading can greatly benefit the design of composite structures with improved blast resistance. In the present work, TFMLs with seven different configurations were designed and fabricated. Confined-blast experiments with various masses of trinitrotoluene (TNT) were performed on these TFMLs. The experimental results, including deflection time histories and X-ray computed tomography (CT) images, have been applied to the development of a method for predicting the dynamic response of laminates under confined blast loads. The findings of this work will assist in the rapid assessment of the deformation of fibre–metal laminates and assist in the pre-design of laminate structures in confined explosions.

This paper continues the proposed idea of stability training for legged robots with any number of legs and any size on a motion platform and introduces the concept of a learning-based controller, the global self-stabilizer, to obtain a self-stabilization capability in robots. The overall structure of the global self-stabilizer is divided into three modules: action selection, adjustment calculation and joint motion mapping, with corresponding learning algorithms proposed for each module. Taking the human-sized biped robot, GoRoBoT-II, as an example, simulations and experiments in three kinds of motions were performed to validate the feasibility of the proposed idea. A well-designed training platform was used to perform composite random amplitude-limited disturbances, such as the sagittal and lateral tilt perturbations (±25°) and impact perturbations (0.47 times the robot gravity). The results show that the proposed global self-stabilizer converges after training and can dynamically combine actions according to the system state. Compared with the controllers used to generate the training data, the trained global self-stabilizer increases the success rate of stability verification simulations and experiments by more than 20% and 15%, respectively.

This work reviews the ultimate compressive strength of aluminium plates and stiffened panels. The effect of boundary condition, initial imperfection, welding-induced residual stress and heat-affected zone are discussed. As the effect of manufacturing technology lacks in the literature, this effect is analysed employing the finite element method, considering the technology of welding and integrated extrusion. The numerical analyses have shown that the ultimate strength of the integrated extruded stiffened panel is relatively higher than the one of the traditional welded panel.

Missing data is a major problem in data-driven intelligent transportation systems. This study presents an imputation method, called TrafficMosaic, for effective imputation of lost traffic flow data. If we consider traffic data as a image, then the missing data in it can be regarded as a mosaic. The design of TrafficMosaic is inspired by super resolution techniques. First, a deep neural network (DNN) is employed to recover the lost data by a suite of techniques inspired from image super resolution. This DNN method combines the temporal relevance of historical flow with spatial correlation of current fragmented flow data, and uses the imputation result as input for recursive calculation. Second, a data-driven road network matrixing algorithm is proposed to mine location relations from trajectory data and reconstruct a road network flow into matrixes of road network flow pictures. Convolutional local calculation in a convolutional neural network is introduced to extract local spatial features of the road network, thereby reducing the computational complexity and improving the generalization ability. The final step is to extract the local temporal features of the flow data. Traffic flows at adjacent moments have strong temporal characteristics, and we splice several historical road network traffic pictures in chronological order so that our model can capture temporal information from the sequence. The experimental evaluation used a real automatic number plate recognition dataset for experiments, and the results show the effectiveness of TrafficMosaic for lost data imputation.

Based on the equivalent mechanics model of wire rope, a kinetics modeling method of rope-driven unit for robot rotary joint is proposed, and the kinetics equation of rope-driven unit is derived. The impact resistance of rope-driven unit is analyzed theoretically, including passive compliance and active compliance. The active compliance control is introduced on the basis of tension feedback and position closed-loop controller of joint. According to the signals of tension sensor to judge the impact force, the change of output joint angle of rope-driven unit which the impact force may cause is calculated. Then, it will be substituted into the system kinetics equation to obtain the compensation angle needed by motor, so that rope-driven unit makes the corresponding retrograde motion to achieve the effect of unloading force when it is impacted by the external. Taking FDU-II rope-driven unit developed independently by our laboratory as an example, the system kinetics modeling and impact experimental research are carried out by using the above method. The results show that the active–passive compliance control can effectively improve the impact resistance of FDU-II rope-driven unit. At present, FDU-II rope-driven unit can withstand 3 times of the impact force of the load gravity and achieve 20% of the buffer ability. Compared with the impact experimental results only relying on passive compliance, it has greatly improved and also effectively reduced the period of shock caused by the impact, which provides a theoretical and experimental basis for the future research of biped robot stable walking experiment.

The external loads and structural ultimate strength are two important aspects for the safety of ship hull girder. It may collapse in case the structural capacity is less than the external forces in extreme seas. In the present research, progressive collapse test is performed to investigate the collapse mechanism of ship structure in waves. External load with time history and corresponding structural collapse behavior are measured and discussed to demonstrate the interaction of fluid and structures.

Test on a small scaled model is an effective approach to predict the dynamic response of full scale structure under blast loadings. However, the geometric dimensions of specimens cannot simply comply with complete geometrical similarity due to manufacture or test restrictions. It would result in the difference structural performance between the full and small scaled models. This paper proposed a corrected similarity relationship of the dynamic behaviour between prototype and replica of stiffened plates subjected to blast load, in which both the thickness of the plate and the configuration (cross-sectional shape) of stiffeners are distortedly scaled-down (double distorted geometric scaling factors). Firstly, based on the mesh convergence study and comparing with results from experimental tests, a numerical method in predicting the confined blast load and dynamic response of structure was verified, which provides a reliable means to determine the dynamic behaviour of stiffened plate designed by the corrected similarity criterion of this paper. Then, the influence of altering the stiffener configuration on the dynamic response of stiffened plates was analysed and on the basis of it, a criterion for scaling the stiffener is proposed to help design a stiffener-distorted model from prototype structure. In addition, a method for scaling the double-parameter distortedly small scaled model is proposed to predict the dynamic response of the prototype. Finally, two sets of examples of both the small size and prototype stiffened structures subjected to blast load were analysed by using the presented method. It is shown that the replica developed by applying the present method is able to accurately predict the behaviour of the full-size stiffened plates, even when the thickness of the plate and the configuration of the stiffeners are distortedly scaling down with different factors.

The lethality of a semi-preformed fragment warhead is closely related to the expand velocity and spatial distribution of the fragments from ruptured metal casing. The topic of how to improve the utilization of charge of have been drawing great attention from researchers and designer in this filed. In present paper, in order to investigate the influence of charge initiation manners on the scattering characteristics of semi-preformed fragment warhead, the numerical simulations and experimental test are conducted. Firstly, the influence of grid density on numerical results is investigated, and a proper numerical model with relatively high accuracy and effectiveness is determined. Then, numerical simulations of three kinds of different initiation position of a semi-preformed fragment warhead are carried out. An experimental test of the explosion of a semi-preformed fragment warhead is carried out. By comparing and analyzing the numerical results and experimental data, it is found that the initiation manners have great influence on scattering characteristics of semi-preformed fragment warhead. The researcher work of this paper would provide an effective alternative method to optimize the design of warhead. Keywords: Initiation manners, Semi-preformed fragment warhead, Deformation pattern

The ship motions and wave-induced loads of a new type of river-to-sea ship are investigated experimentally and numerically. A river-to-sea ship is an unconventional type of container ship characterized by high breadth to draft ratio and low length to breadth ratio, which makes it more prone to hydroelasticity than conventional ships of the same size. A segmented model was tested under two loading conditions, namely, ballast and loaded conditions, to determine the vertical motions and wave-induced loads under each condition. Results are compared with numerical simulations in the frequency domain. The wave-induced responses are calculated by a nonlinear time domain code at each time step. The response amplitude operators of vertical ship responses in regular waves are analyzed, and the wave-induced responses are consistent with the experimental results.

In view of lack of a general mechanics model and theoretical calculation formulas for the bending state of a wire rope at present, a new mechanics modeling method for wire rope under bending is put forward. Firstly, the change law of the secondary helix angle is analyzed, and the reasonable assumptions for the mechanics model are put forward. According to the elastic thin rod theory of Love and the conservation of energy principle, the mechanics model of multi-strand wire rope in bending state is established, and the theoretical formulas of bending stiffness and equivalent elastic modulus are derived. Taking 6 × 7 and 6 × 19 wire ropes as examples, theoretical formulas are applied for calculation, meanwhile, the finite element simulation is carried out using ABAQUS and a special deflection measuring device is designed and manufactured to measure the large deformation deflection of the wire ropes. The theoretical calculation results are compared with the finite element simulation results and the measurement results. The contrast results show that the theoretical results are closer to the measurement results than the finite element simulation results. The maximum deformation error of the wire ropes free end between the theoretical results and the measurement results is 11.16%, which verifies the correctness of the mechanics model.

This paper presents the results of experimental and numerical investigations into the response of unstiffened and stiffened steel plates under confined blast loading. Experimental tests were carried out on square mild steel plates with different stiffener configurations under the loading produced by cylindrical TNT charge explored in a specially designed blast chamber. The permanent deformation profiles of specimens were recorded. In general, the plates show large inelastic global deformations with the maximum deflection occurring at the center of the plate. Through the comparison to the impulse in a free air blast with the same charge, the equivalent impulse applied to the plate could increase by up to 4.03–5.63 times in the confined blast cases due to the confinement effect of blast chamber. Besides, numerical simulations are conducted to gain further insight into the deformation modes of plates using ANSYS/AUTODYN. Very good correlation is obtained with regards to midpoint deflections and deformation profiles. The validated numerical models were further used to investigate the influence of the stiffener and vents on deformation modes of stiffened and unstiffened plates under confined blast loading. The results from numerical simulations demonstrate that the maximum plastic deformation decreases greatly with increasing the mass ratio of the stiffener to the steel plate. It was found that the stiffener location (on the side or opposite side of loading) has an insignificant influence on the deformation modes of the stiffened plates under confined blast loading. The numerical results also clearly show that the vents can reduce the degree of confinement of the blast chamber as well as the impulse applied to the plates in the confined blast cases, which results in the decrease of structural deformation.

When SWATH (Small Waterplane Area Twin Hull) ship hulls are exposed to horizontal extreme wave loads, the transverse ultimate strength is critical due to large stress concentrations in the narrow struts and haunches. In this paper, an experiment has been performed to examine the ultimate strength of a one-eighth scaled SWATH ship model subjected to transverse loads. The experimental results are compared with finite element simulations. The structural model, scaled from an actual SWATH ship, is designed with scaling laws and linear static analyses performed by the MSC.Nastran finite element solver. The procedure to design and manufacture the complex structural model is given. The actual ship and its scaled model are analysed numerically to achieve the consistency of the maximum stress and the stress distribution in their corresponding finite element models. The experimentally obtained force-displacement response and shape of the deformation show good agreement with the simulations performed by the implicit MSC.Marc nonlinear finite element solver. The maximum stresses are mainly concentrated around the hull haunches, and the stress distributions at the ship ultimate collapse are presented. The ultimate strength of the actual SWATH ship is evaluated according to scaling laws, and the ship safety margin is analysed. Moreover, the effects of hydrodynamic wave pressure distributions on the ship ultimate strength are investigated.

The dynamic buckling of the main deck grillage would result in the total collapse of the ship hull subjected to a far-filed underwater explosion. This dynamic buckling is mainly due to the dynamic moment of the ship hull when the ship hull experiences a sudden movement under impact load from the explosion. In order to investigate the ultimate strength of a typical deck grillage under quasi-static and dynamic in-plane compressive load, a structure model, in which the real constrained condition of the deck grillage was taken into consideration, was designed and manufactured. The quasi-static ultimate strength and damage mode of the deck grillage under in-plane compressive load was experimentally investigated. The Finite Element Method (FEM) was employed to predict the ultimate strength of the deck grillage subjected to quasi-static in-plane compressive load, and was validated by comparing the results from experimental tests and numerical simulations. In addition, the numerical simulations of dynamic buckling of the same model under in-plane impact load was performed, in which the influences of the load amplitude and the frequency of dynamic impact load, as well as the initial stress and deflection induced by wave load on the ultimate strength and failure mode were investigated. The results show that the dynamic buckling mode is quite different from the failure mode of the structure subjected to quasi-static in-plane compressive load. The displacements of deck edge in the vertical direction and the axial displacements are getting larger with the decrease of impact frequency. Besides, it is found that the dynamic buckling strength roughly linearly decreased with the increase of initial proportion of the static ultimate strength P0. The conclusions drawn from the researches of this paper would help better designing of the ship structure under impact loads.

Due to the influence of strain-rate effect of rate dependent materials, the relations of responses between scale-down model and prototype plates under blast loads cannot assure the satisfaction of the scaling laws, which is known as non-scalability of structure under impact loads. In this paper, by employing the dimensional analytical method, the strain-rate effect involved in blast loaded plates with different scaled values was firstly analyzed, then a corrected equation was established by taking a correction factor of impulse per unit area into consideration. Besides, a set of empirical formulae used to calculate the impulse per unit area is given, in which the relations between the mass of TNT, the stand-off distance and the impulse per unit area is determined. Furthermore, this paper adopted the method presented by Oshiro and Alves [14] to establish the corrected similarity relation between incomplete scale-down models and prototype. On the basis of this, a rapid solution to predict the value of exponent n is proposed, guaranteeing this method could be used more smoothly in practical engineering.

In view of the lack of general mechanics model and theoretical formula for force-deformation calculation of wire rope, a novel modeling method for wire rope mechanics model is presented. The mathematical model of wire rope's secondary helix is established using the Frenet frame and differential geometry. On the basis of that geometrical parameters of secondary helical line is derived from the necessary assumptions and geometrical relationship, using elastic thin rod theory of Love to establish an equivalent mechanics model of wire rope, and the equivalent elastic modulus and equivalent shear modulus calculation formulas are deduced. The deformation and elongation of wire rope under known tension can be calculated by the formulas. The force-deformation calculation of actual wire rope is carried out, and the results show that the maximum deviation of elongation is less than 8% compared with the finite element simulation and experimental measurement. Therefore, the correctness and generality of the model are verified, and it has theoretical and practical significance for the application and analysis of wire rope.

In order to investigate the fatigue damage evolution of typical joints of River-Sea-Going Ship (RSGS) under a repeating two-step variable amplitude (VA) loading condition, and to estimate the influence of the damage of low amplitude load below the fatigue limit and the interaction effect between the high and low amplitude loads on the fatigue life of the structure, a series of fatigue experiments of designed T-type specimen (DTS) under different repeating two-step VA loading conditions were carried out in this work, which are designed according to hull structure characteristics and actual service conditions of RSGS. The experimental results show that the interaction damage value ( D nl ) firstly increases and then decreases with increasing the cycle ratio of low to high amplitude load from 1 to 5. The value of D nl is negative when the cycle ratio is relatively large, not less than 4.5 in the current study, which indicates that the effect of loading interaction not only doesn’t cause damage but has a beneficial effect on the fatigue life of the DTS. The X-ray Diffraction (XRD) analysis was carried out subsequently at the fatigue crack initiation region with the aim of confirming the material characteristic at the microcrack tip changing from work-hardening state to work-softening state with the cycle ratio increasing.

A 3D water entry of a typical bow model of river-to-sea ship is studied experimentally. A large number of systematic experiments have been performed for the bow model with different pitch angles. Considering various pitch angles and impact velocities in the model tests, the slamming pressure distributions on the bottom of the bow are presented and discussed. The measured slamming pressures on the bow are identified in terms of the maximum slamming coefficient. The effects of the pitch angle and impact velocity on slamming pressure are discussed as well, based on the experimental measurements. It is shown that the slamming load on the bottom of the model increases as the pitch angle decreases in most cases. With a higher impact velocity, the coefficient of the maximum slamming pressure is smaller for most of the tested cases.

The blast loading from an explosion of a condensed explosive in a confined space is quite different from that in an open environment. Due to the confinement effect, a confined-blast load usually causes more severe damage. The detonation products from a fuel-rich explosive, such as Trinitrotoluene (TNT), can react with the surrounding air under specific conditions and release additional energy, resulting in a significant increase of reflected shockwaves and quasi-static pressure in a confined space. Mitigation of the confined-blast loading is an effective way to protect structures from destruction. In this paper, a detailed experimental investigation of the influence of water mist on both the mitigation of blast load and dynamic response of the structure is presented. Six cases of experimental tests, with different charge masses of 80, 120 and 160 g of TNT explosive, with and without the presence of water mist, are performed in a confined chamber, with the shock pressure and deflection-time history curves of blast-loaded steel plates being recorded, as well as quasi-static pressure and temperature of the contained gas. By analysing the experimental data, it is found that the water mist decreases the reflected blast wave and quasi-static pressure by restraining the combustion effect and subsequent energy release of detonation products. As a consequence, both the first peak deflection and the residual deformation of the blast-loaded steel plates decrease greatly. Furthermore, based on a non-dimensional analysis of the experimental results for plates with different thickness subjected to different loading conditions, a new empirical relationship between non-dimensional deflection of the plate and a non-dimensional load parameter (for fully confined blast loading) was obtained. By employing this new empirical relation, the mitigation effect of fine water mist on confined blast load was determined quantitatively. The use of water mist is a very good alternative to mitigate the damage of structures subjected to a confined-blast load in the design of anti-blast structures.

The nonlinear synthetic bending moment caused by springing and whipping can be simplified as the superposition of high-frequency load components and low-frequency load components. In order to investigate the influence of this high-low frequency superimposed loading on the fatigue performance of hull structure, the high-low frequency superimposed fatigue tests under different frequency ratios, amplitude ratios and mean stresses were carried out for the time domain response characteristics of nonlinear vertical bending moments in the wave load model test of River-Sea-Going-Ship. Combined with the rain-flow counting method and Goodman correction method, the cumulative damage of small loads under fatigue limit and the effect of high-low frequency coupling damage on the fatigue life were analyzed, a fatigue life prediction model suitable for high-low frequency superimposed loading was proposed. The analysis results show that the high-frequency, small-amplitude loads have a significant impact on the fatigue life of the structure. The threshold that the high-low frequency coupling damage causes the reduction of fatigue life is closely related to the combined effects of the amplitude ratio and the frequency ratio.

The coupled effect of geometric and material nonlinearity existing in the buckling process of the stiffened plates sometimes makes it difficult to evaluate their ultimate load capacity numerically. Therefore, so far, experimental tests are still indispensable in the design process of a complicated structure. However, the experimental methods for predicting the whole buckling process of a stiffened plate subjected to in-plane compressive load are still not well developed. In this paper, the fundamental element in the complicated bearing structures, stiffened plate, was set as the object, and its buckling process was deeply analysed. Then, a set of similarity criteria for the stiffened plate subjected to compressive load were proposed based on the Buckingham's Pi theorem, by which the designed scale models for experimental tests could keep similar to the real structures in the whole loading process. Then, the similarity criteria were verified by numerical simulations and experimental tests with different scale models. The work presenting in this paper may potentially contribute to improving the precision of the experimental prediction of the structural ultimate load capacity and the corresponding optimization works.

T-welded joints are commonly employed in ship and ocean structures. The fatigue failure of structure components subjected to cyclic loading always occurs in T-welded joints because of the metallurgical differences, tensile residual stress fields and stress concentrations. The former researches about T-welded joints fatigue have in common that the boundary condition needs to be taken into account as an influencing parameter to predict the crack propagation during cyclic loading. In this paper, the crack growth behaviour in T-welded joint processed with Q345D steel (Pingxiang Iron & Steel Co., Ltd, Hukou, Jiangxi Province in China) under the fatigue loading was analysed via analytical model and verified via experiment. The results show that the influence of boundary condition should be considered in T-welded joint structure during crack propagation in weld toe area. The correction factor concerning the effect of boundary condition and modified Paris' equation was proposed according to the experimental results and verified by the following repeated experiments.

The large-deflection behavior of the clamped stiffened plates subjected to confined blast load is investigated through experimental tests, theoretical calculation and numerical simulation in this paper. The blast load in confined space lasts longer and has more complex form compared to the shock waves from an open space explosion. The influence of elastic-plastic effect on the dynamic response of blast loaded plate should be taken into account in theoretical prediction of permanent displacement. Besides, evident yield lines, which could change the deformed shape of the plates, can be always found around the clamped edges and the diagonals of plates. The global deformation of a plate cannot be represented by a simple shape function of a smooth surface. In this paper, a series of experimental tests of square stiffened plates under confined blast load was conducted. Based on experimental observation and assumed-modes, an elastic-plastic analytical model for blast loaded stiffened plates is presented, in which the effects of yield line pattern and elastic-plastic deformation are considered. The Lagrange motion equation that contains the total strain energy, potential energy and kinetic energy of stiffened plates and blast load system is established and solved. Numerical simulations are performed to investigate the influence of strain rate effect of material and boundary conditions on the dynamic responses of stiffened plates. By comparing the numerical results, the rationality of hypothetic conditions employed in analytical model is verified. The classical rigid-plastic and elastic-plastic methods were also used to calculate the dynamic response and permanent displacements of test specimens. The comparison results showed that the theoretical calculation model presented in this paper is feasible and of high precision and practicability.

There are two aims in the present paper. The first one is to see and understand the detailed buckling process, especially the interactions between material nonlinearity and geometric nonlinearity on the post-buckling stage, of stiffened panels subjected to in-plane compressive load. The second one is to validate the similarity criteria of designing different sizes of stiffened panels which have the same buckling modes and proportional ultimate strength. These similar relationships make it possible to predict the buckling behavior and ultimate strength of a full-size structure by testing its scale-down model. To these ends, three different sizes of stiffened panels with the same flexural rigidity ratio, plate slenderness and column slenderness, were designed, manufactured and tested. In order to trace and analysis the detailed buckling process, three-dimensional digital image correlation (3D-DIC) method was employed. So, the integrated evolution process of global deformation and strain distribution fields of the stiffened panels were obtained. These data also provide accurate data to verify the numerical or theoretical method in predicting the bulking, especially post-buckling process and ultimate strength of stiffened panel. Results show that the three stiffened panels have reasonable similarity relationships of the buckling failure process. Finally, finite element models with measured initial imperfections were established to reappear the experimental process. The numerical results agree well with the experimental data.

The combination damage induced by mechanical interference, in reality, is more likely to happen. In this paper, numerical models on pipes with combined dent and metal loss in terms of a notch are developed and validated through tests (diameter-to-thickness ratio D / t of test pipes around 21), capable of predicting the residual ultimate strength of pipes in terms of bending moment ( M c r ) and critical curvature ( κ c r ). The effect of residual stress is explored, assuming a linear distribution in the pipe hoop direction. Investigations of damaged pipes with different D / t (15–50) are carried out. Through changing damage parameters in the combinations, i.e. dent depth ( d d ) or metal loss depth ( d m ), the corresponding effects of damage are clarified. Results show that the combined dent and notch damage is a more severe type of damage on pipe strength compared with other damage types (excluding fracture). The dent in combined damage plays a more dominant role on the pipe residual strength. Empirical formulas are proposed to predict residual ultimate strength of damaged metallic pipes ( D / t around 21) with combined dent and metal loss under bending moment, which can be used for practical purposes. The application domain can be expanded to pipes with D / t up to 30 based on simulations.

A shear-deformable beam theory is proposed to model the coupled bending and twisting vibration in a symmetric laminated beam with a rectangular cross section. The warping of the beam cross section and Poisson effect are considered in the formulation. The governing equations of motion for the symmetric laminated beams exhibiting bending–torsional coupling are derived by using the Hamilton’s principle, and the dynamic stiffness matrix is formulated from the exact analytical solutions of the homogeneous governing differential equations. Numerical results of appropriately chosen symmetric laminated beams are presented and compared with the previously published numerical and experimental solutions whenever possible. The influences of Poisson effect, layup, and boundary condition on the natural frequencies of symmetric laminated beams are extensively investigated.

In this paper, a precise transfer matrix method is presented to calculate the structural and acoustic responses of the conical shell. The governing equations of conical shells are written as a coupled set of first order differential equations. The field transfer matrix of the shell and non-homogenous term resulting from the external excitation are obtained by precise integration method. After assembling the field transfer matrixes, the whole matrix describing dynamic behavior of the stiffened conical shell is obtained. Then the structural and acoustic responses of the shell are solved by obtaining unknown sound pressure coefficients. The natural frequencies of the shell are compared with the FEM results to test the validity. Furthermore, the effects of the semi-vertex angle, driving force directions and boundary conditions on the structural and acoustic responses are studied.

A high-order numerical method for three-dimensional hydrodynamics is presented. The present method applies high-order compact schemes in space and a Runge-Kutta scheme in time to solve the Reynolds-averaged Navier-Stokes equations with the k-ε turbulence model in an orthogonal curvilinear coordinate system. In addition, a two-dimensional equation is derived from the depth-averaged momentum equations to predict the water level. The proposed method is first validated by its application to simulate flow in a 180° curved laboratory flume. It is found that the simulated results agree with measurements and are better than those from SIMPLEC algorithm. Then the method is applied to study three-dimensional hydrodynamics in a natural river, and the simulated results are in accordance with measurements.

A hyperbolic shear deformation theory is used for the free vibration analysis of generally layered composite beams with arbitrary boundary conditions. The variationally consistent governing differential equations and boundary conditions are derived by employing Hamilton's principle. The dynamic stiffness method is applied to calculate the vibration frequencies of the laminated beams with the help of Wittrick–Williams algorithm. Examples of application of the hyperbolic shear deformation theory for the free vibration analysis of the laminated beams with a couple of different boundary conditions are presented. The present results are compared to the numerical solutions and experimental results available in the literature.

The main function of a multi-layer protective structure of a combatant ship is to prevent the inner cabins from being destroyed by anti-ship weapons. The damage effect of these weapons on ship structures mainly comes from the blast wave and fragments. The motivation of this study was to investigate the synergistic effect of blast wave and fragment impact loadings on the multi-layer protective structure. A protective structure model with four layers and a metal casing filled with TNT charge (MCTC) which was used to simulate the warhead of an anti-ship weapon were designed and manufactured. An experiment was conducted in which the MCTC exploded inside an empty cabin of the first layer of the multi-layer protective structure. The distribution of fragments and the equivalent bare charge of the MCTC were determined by a numerical method. From experimental results, the failure pattern of the multi-layer protective structure under the synergistic effect of blast wave and fragment impact loadings was presented. The synergistic effect for the stiffened plates was also presented in the experiment by comparing the deformation and the rupture of the air-backed and water-backed stiffened plates. On the other hand, the agreement between numerical results and experimental results validated the numerical method, which enabled the numerical model to be used to predict the response of a full scale structure under loadings of anti-ship weapons. Finally, a discussion of synergistic effects of blast and fragment loadings on a multi-layer structure was presented and suggestions for the design of a protective structure are put forward.

The objective of the paper is to analyze the free vibration of laminated composite beams using a refined higher-order shear deformation theory. The influences of parabolic transverse shear strain, transverse normal strain and Poisson effect are included in the present formulation. The governing differential equations of motion for coupled vibrations of laminated beams are derived using the Hamilton’s principle. In the case of simply supported composite beams, the closed-form solutions for the natural frequency of free harmonic vibration are obtained. The correctness and accuracy of the present theory are validated by comparing the present results with those previously published in the literature and ANSYS solutions.

Extreme waves have caused a lot of ship accidents and casualties. In this paper, a two-dimensional (2D) hydroelastoplasticity method is proposed to study the nonlinear dynamic responses of a container ship in extreme waves. On the one hand, the traditional ultimate strength evaluation is mainly performed using a quasi-static assumption without considering the dynamic wave effect. On the other hand, the dynamic response of a ship induced by a wave is studied based on hydroelasticity theory, which means the ship structural response to large waves is linear. Therefore, a 2D hydroelastoplasticity method that accounts for the coupling between the time-domain wave and ship beam for nonlinear vertical bending moment (VBM) is proposed. In addition, a nonlinear dynamic finite element method (FEM) is also applied for the nonlinear VBM of ship beam. The computational results of the FEM, including the nonlinear VBM and deformational angle, are compared with the results of the 2D hydroelastoplasticity and hydroelasticity. A number of numerical extreme wave models are selected for computations of hydroelasticity-plasticity, hydroelasticity, and FEM. A difference is observed between the nonlinear VBM calculated by FEM and linear VBM calculated by hydroelasticity, and conclusions are drawn.

A new synthetic reagent DPTUHP [diphenyl α-(3-phenylthioureido) hexylphosphonate] containing a hydrocarbon chain nonpolar group, a thioureido, and a phosphonate easter chelating group, has proven to be an effective collector for the flotation of cerussite mineral. The synthetic method utilized the Mannich-type reaction of an N-monosubstituted thiourea, an aldehyde, and triphenyl phosphate in glacial acetic acid solution. The experimental results of flotation of the cerussite mineral show that the collector has stronger collecting ability and higher selectivity in a neutral and a slightly alkaline medium, especially in the pulp of pH=8. Using the measurements by infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) of the cerussite mineral, the collector, as well as the cerussite treated with the collector, the flotation mechanism of cerussite has been discussed. It is concluded that the adsorption of collector on cerussite is a chemical adsorption through the electron donor atoms of the collector chelating the Pb (II) of cerussite to form chelate.

The surface quality is always the crucial element of machined quality in precision ultra-precision metal cutting. A new concept that the surface integrity should include the edge quality of parts is put forward In this paper, the weight value of a series of characteristic parameters of surface integrity are calculated with using analytic hierarchy process, three basic methods of evaluating surface integrity are presented, and the comprehensive evaluation system has been formed which will theoretically play a great important role on rapid development in the precision machining.Copyright © 2007 by ASME

The existence of the metal cutting burr not only reduces the dimension and shape accuracy of the workpiece, but also increases the manufacturing cost. Currently, the burr has been the most troublesome obstruction to high productivity and automation of machining processes. In this paper, the hazard of the burrs is systematically discussed in the precision or ultra-precision machining firstly and then, the formation principle and morphology of burrs in precision turning, planing, drilling and milling are studied. Finally many new technologies and methods of restraining or decreasing burrs have been developed by the cutting experiments.