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[Objectives] This paper aims to study the influence of welding defects on fatigue life of aluminum alloy plate frame.[Methods] Firstly,use X-ray to detect the welds of the test aluminum alloy plate frames with two gusset joints,and then select two plate frames with and without welding defects respectively. Then obtain main types of the welding defects through the analysis on the X-ray images. Then,carry out fatigue tests for these two plate frames with and without welding defects under different loads,so as to obtain the fatigue life of the plate frames. Finally,establish local FE models for the test plate frames with three types of welding defects by using ABAQUS software,and analyze and reveal the failure mechanism of the plate frames with welding defects.[Results] The test results show that,the failure of the test plate frame with welding defects is caused by the fracture on the longitudinal web due to the extension of the crack in the welding defect at the end of the weld;the failure of the test plate frame without welding defects,which is related to the gusset joint,is caused by the fracture on the longitudinal web due to the extension of the fatigue crack generated under the cyclic loads on the longitudinal web.[Conclusions] This study results can provide a reference for the assessment of the fatigue life and for the influence of the welding defects on the fatigue life.

With the global temperature continuing to rise, the Arctic ice is melting. The development of the Arctic route and exploitation of Arctic resources are drawing the wide attention of international society. Many countries are starting a new round of the construction of polar ships. In recent years, domestic and foreign researchers have begun to focus on the numerical study of ice loads on structure. However, the current commercial finite element software lacks a specialized element used for simulating the mechanical properties of sea ice. This lack increases the difficulty of the numerical study of ice loads on structure. In this paper, based on Reinicke and Remer's elliptic failure criteria and Winkler's elastic foundation, an element has been developed to simulate the bending failure of isotropic granular ice. The ice loads of typical marine structures, such as slope structure and conical structure, are calculated through the direct analysis method with the developed element. A comparison between the results of the direct analysis method and analytical method show good agreement. In brief, the proposed direct analysis method may provide tools and certain references for structural design in an ice environment.

Composite double-arrow auxetic structures were designed and fabricated. The local impact experiments were carried out on the auxetic structures to explore the dynamic responses and failure modes. The effects of relative density and impulse level on the impact properties were analyzed and discussed. As the relative density increased, the local deformation of the auxetic structures and the damage of the core layer decreased, and the overall response of the auxetic structure increased. The finite element model was used to simulate the impact responses of the auxetic structures, and the numerical simulation results were in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

[Objectives] A concept named ‘component contribution rate’ is proposed to solve problems concerning the influence of ship structure components on ship structure performance.[Methods] First, a hierarchical structure is elaborated and mapped from structural components to structural performance. Second, the component contribution rate is defined in order to describe the contribution rate for a component in structural performance to fulfill its structural purpose. Next, the grey target theory is applied to quantify the component contribution rate.[Results] Finally, the application of the proposed method is demonstrated through a SWATH case study.[Conclusions] This method can be applied in the evaluation of the ship structural schemes,in order to support the optimal design of ship structure.

Due to the wave and hydrodynamic interaction between two ships advancing parallel on the ocean, their six-degrees-of-freedom motions are much more complex during replenishment. The seakeeping performance of two vessels is analyzed with AQWA. On the basis of the RAO functions of the two parallel vessels, spectrum analysis and time-domain analysis were carried out, and the significant amplitudes were obtained using the computed time-history and correlation function method. The significant amplitudes are compared with the results of the spectrum analysis and good agreement is observed. It is found that hydrodynamic interaction between two ships has a great impact on the process of replenishment. Depending on the results of the analysis, dangerous conditions during the replenishment process could be avoided, thereby ensuring the safety of supply work.

High long-term stress on the plantar fascia (PF) is the main cause of plantar fasciitis. Changes in the midsole hardness (MH) of running shoes are an important factor leading to the alteration of the PF. This study aims to establish a finite-element (FE) model of the foot–shoe, and investigates the effects of midsole hardness on PF stress and strain. The FE foot–shoe model was built in ANSYS using computed-tomography imaging data. Static structural analysis was used to simulate the moment of running push and stretch. Plantar stress and strain under different MH levels were quantitatively analyzed. A complete and valid 3D FE model was established. With an increase in MH from 10 to 50 Shore A, the overall stress and strain of the PF were decreased by approximately 1.62%, and the metatarsophalangeal (MTP) joint flexion angle was decreased by approximately 26.2%. The height of the arch descent decreased by approximately 24.7%, but the peak pressure of the outsole increased by approximately 26.6%. The established model in this study was effective. For running shoes, increasing the MH reduces the stress and strain of PF, but also imposes a higher load on the foot. [ABSTRACT FROM AUTHOR]

Deck structures subjected to drop-weight low-velocity impact are critical safety elements for ships and offshore structures. Therefore, the aim of the present study is to propose experimental research on dynamic responses of deck structures composed of stiffened plates subjected to drop-weight impact of a wedge impactor. The first step was to fabricate a conventional stiffened plate specimen and a strengthened stiffened plate specimen, as well as a drop-weight impact tower. Then, drop-weight impact tests were carried out. Test results show that local deformation and fracture occurred in the impact area. A sharp wedge impactor caused premature fracture, even under relative low impact energy; the permanent lateral deformation of the stiffened plate was reduced by 20–26% by the strengthening effect of a strengthening stiffer; residual stress and the stress concentration of the cross-joint caused by welding may cause undesired brittle fracture. The present investigation provides useful insight for improving the crashworthiness design of the deck structure of ships and offshore structures. [ABSTRACT FROM AUTHOR]