Asymmetric deformation of near hemispherical diaphragm under uniform surface load

The asymmetric deformation and eccentricity problems of near hemispherical diaphragm under the uniform surface load are quantitatively characterized in the paper. The analysis is based on a 3D finite element analysis (FEA) model established according to elastic-plasticity and large displacement nonlinear finite element method. Besides, the deformation experiments are taken to validate the reliability of FEA model which shows that the simulation results are in good agreement with the experimental results. Then, three angle parameters, deflection angle β, circumvolving angle θ and distributing angle γ, are introduced and expressed to characterize the asymmetric deformation and eccentricity quantitatively. According to the angle parameters, the inversion processes of uniform thickness diaphragm and varying thickness diaphragm are calculated respectively. The inversion process of varying thickness diaphragm is much steadier than that of uniform thickness diaphragm. The present results show that the asymmetric deformation process can be characterized by curve of three angle parameters (β, θ, γ) exactly, the degrees of eccentricity can be indicated by the final value of deflection angle and the eccentricity position can be characterized by the final values of the three angle parameters.     

Mechanical behavior of tubular T-joint after fire

This paper presents experimental results of the post-fire behavior of tubular T-joints. The research aims at the failure modes and the residual strengths of the T-joints after fire. Three tests of full-scale tubular T-joints are conducted. The first one is carried out to study the mechanical behavior of T-joints under ambient temperature. The other two tests are performed to study the influence of pre-load, heating and cooling phase on residual load-bearing capacity of the tubular T-joints. The test results show that the sustained axial load on the brace has remarkable influence on the residual deflection of the T-joints which is cooled down to room temperature. The results of the experiments also indicate that the axial load level and heating and cooling history have more significant effects on the compressive stiffness of the T-joints than the residual strength. In the numerical study, the result of finite element model agrees well with the test result. The work in this paper provides a basis for further parametric analysis and theoretical study on the structural evaluation after fire.     

Numerical study for turbulent flow of drag and flow noise with wavy wall

In this paper, a numerical simulation of flow-induced noise by the low Mach number turbulent flow with a sinusoidal wavy wall was presented based on the unsteady incompressible Navier-Stokes equations and Lighthill’s acoustic analogy. Large eddy simulation (LES) was used to investigate the space-time flow field and the Smagorinsky sub-grid scale (SGS) model was introduced for turbulence model. Using Lighthill’s acoustics analogy, the flow field simulated by LES was taken as near-field sound sources and radiated sound from turbulent flow was computed by the Curle’s integral formulation under the low Mach number approximation. Both spanwise wavy wall and streamwise wavy wall with various wall wave amplitudes were discussed to investigate their effects on reducing the drag and flow noise. The relationship between flow noise and drag on the wavy wall is also studied.     

Research on mechanical properties of 22MnB5 steel quenched in a steel die

22MnB5 is one of the most typical hot stamping boron steels. In order to study the effect of austenitizing temperature and holding time on the mechanical properties of hot stamping boron steel 22MnB5, a series of quenching process are done. The tensile strength and hardness of 22MnB5 samples are measured. The results show that 22MnB5 has a good quenching performance, and the tensile strength and hardness of samples quenched in a water-cooled steel die are similar to those of water quenching. The higher tensile strength and HRC hardness are achieved when austenitizing at temperatures of 880–910 °C. Holding at 910 °C for 5 min and then quenching gives rise to a better combination of tensile strength, hardness and ductility.     

Wrinkle analysis of the space inflatable paraboloid antenna

The presence of wrinkles in the membrane is the main factor to induce the reflector surface inaccuracy of the space inflatable antenna. Based on the commercial finite element package ABAQUS, a numerical procedure for membrane wrinkle analysis was set up and used to analyze a space inflatable antenna which was under inner pressure to evaluate its wrinkle characteristics. First, the inner pressure effect on the reflector’s wrinkle pattern was studied thoroughly. As inner pressure increases, both the number and the amplitude of the wrinkles decrease, but the total deformation of the whole reflector surface increases much. Second, the influence of the interactions between antenna’s parts was investigated comprehensively. Any kind of unwanted interaction deteriorates reflector’s wrinkle characteristics. The works are valuable to the development and research of the space inflatable antenna.     

Numerical study on bank effects for a ship sailing in shallow channel

A numerical study on bank effects in shallow channels is carried out by using a first-order Rankine source panel method. A container ship sailing along a vertical bank and a sloping bank at different forward speeds, different water depths and different distances between the bank and the ship hull is taken as example. The sway force and yaw moment acting on the hull are calculated and the influences of the speed, water depth and distance between the bank and ship hull on the hydrodynamic force and moment are analyzed. This study can provide insight into the bank effects, as well as to give guidance on ship manoeuvring and control in restricted waterways, which is helpful to the navigation safety.     

Climate change and the prospects of increased navigation in the Canadian Arctic

There is wide recognition that the process of climate change may be affecting the Arctic region at a faster pace than other regions. What is uncertain is the full impact of climate change on ice cover, and in particular whether there will be a significant decrease of summer ice from the current three months to a longer period and accompanied by navigation conditions suitable and safe for commercial shipping. New international navigation routes through the Canadian and Russian Arctic sectors could significantly reduce the length of sea voyages from Asia to North America and Europe. However, on the basis of what is known to date, there are significant differences of view as to the feasibility of international commercial navigation in the Northwest Passage.     

Essentials of general average: A synoptic overview of an ancient maritime law

This article provides a synoptic overview of the concept of general average which is one of the saving acts in maritime law. Its principles were entrenched in the Roman law which acknowledged its origins being rooted in the Sea Law of Rhodes. Its evolution as customary law through the medieval maritime codes of the Mediterranean region is also traced in the article. The reader is then brought into the modern era of the international regime of general average through the advent of the York-Antwerp Rules. The basic principles of general average loss, including expenditures and sacrifices, and general average contributions are introduced through references to a number of leading cases. The current status of this ancient law and practice and debates over its future are briefly addressed in conclusion.     

Life-style and travel demand

(Added to the original text) A fundamental solution to the issue of congestion cannot be reached without addressing the question of life-style. This paper reviews the definitions of life-style found in the literature, and identifies variables that have been commonly associated with life-style. Using US consumer expenditure data, life-styles are analyzed longitudinally (examining trends during the 1953–1983 time frame) and cross-sectionally (comparing segments of the population stratified by income, life-cycle stage, and age), and likely relationships to travel behavior are noted. The usefulness of existing empirical findings to long-range forecasting is explored by speculating on shifts of behavioral units across life-style segments, and on shifts in the behavioral patterns within each life-style segment.     

A co-integration approach to forecasting container carriers’ time charter rates

A vector autoregressive model was developed for a sample of container carrier time charter rates.Although the series of time charter rates are themselves found non-stationary, thus precluding the use of manymodeling methodologies, evidence provided by co-integration tests points to the existence of stable long-termrelationships between the series. An assessment of the forecasts derived from the model suggests that the spec-ification of these long-term relationships does not improve the accuracy of long-term forecasts. These resultsare interpreted as a corroboration of the efficient market hypothesis.