全自动集装箱码头装卸系统质量管理

全自动集装箱码头装卸系统集成了当今世界各项先进技术,在研发、制造、调试过程中,都要坚持质量第一、安全第一的原则,确保各项技术参数可靠,设备运行稳定。在总结国内几个全自动码头装卸系统的质量管理方法与经验的基础上,结合自动化码头自身特点,给出全自动集装箱码头装卸系统主要质量管理方法,进一步丰富发展自动化码头装卸系统建造过程中的“不欠债离岸”质量管理理念。     

Evaluation of different modelling conditions in the cohesive zone analysis of single-lap bonded joints

Cohesive Zone Models (CZM) are widely used for the strength prediction of adhesive joints. Different simulation conditions, such as damage initiation and growth criteria, are available for use in CZM analyses to provide the mixed-mode behaviour. Thus, it is highly relevant to understand in detail their influence on the simulations’ outcome. This work studies the influence of different conditions used in CZM simulations to model a thin adhesive layer in single-lap joints (SLJ) under a tensile loading, for an estimation of their influence on the strength prediction under diverse geometrical and material conditions. Validation with experimental data is considered. Adhesives ranging from brittle to highly ductile and overlap lengths (L_O) between 12.5 and 50 mm were considered. Different studies were considered: Variation of the elastic stiffness of the cohesive laws, different mesh refinements, study of the element type, and evaluation of several damage initiation and growth criteria. The analysis carried out in this work confirmed the known suitability of CZM for static strength prediction of bonded joints and pointed out the best set of numerical conditions for this purpose. Inaccurate results can be obtained if the choice of the modelling conditions is not the most suitable for the problem.     

下沟煤矿本煤层预抽钻孔合理封孔长度研究

封孔长度的合理性对于煤层预抽钻孔的抽采质量影响较大，当封孔长度较大时，不利于封孔段瓦斯的抽采，同时封孔成本增加，反之当封孔段长度较小时，若未封孔部分与煤壁裂隙导通，钻孔发生漏气又影响钻孔抽采质量。为确定合理的封孔长度，针对下沟煤矿302工作面特定的地质条件，采用单孔声波发射对巷道卸压区和应力集中区范围进行了研究，通过分析卸压区范围，确定了合理的封孔长度，并结合试验孔周边的预抽钻孔抽采数据，进行了验证分析，得出该工作面的合理封孔深度为8 m。     

Fracture Mode of Martensite-Austenite Constituents Containing Multiphase Steel Controlled by Microstructural and Micromechanical Aspects

The fracture mode in different M-A constituents containing multiphase steels under impact load was examined considering their microstructural and micromechanical aspects. The results showed that a ductile fracture develops in the fine-grained bainitic ferrite/M-A multiphase by microvoids initiation and coalescence, while cleavage develops in the coarse-grained polygonal ferrite/M-A multiphase by microcracks initiation and propagation, due to their diversities in morphologies of microstructural components and microhardness difference between phases.     

Bayesian model selection and parameter estimation for fatigue damage progression models in composites

A Bayesian approach is presented for selecting the most probable model class among a set of damage mechanics models for fatigue damage progression in composites. Candidate models, that are first parameterized through a Global Sensitivity Analysis, are ranked based on estimated probabilities that measure the extent of agreement of their predictions with observed data. A case study is presented using multi-scale fatigue damage data from a cross-ply carbon–epoxy laminate. The results show that, for this case, the most probable model class among the competing candidates is the one that involves the simplest damage mechanics. The principle of Ockham’s razor seems to hold true for the composite materials investigated here since the data-fit of more complex models is penalized, as they extract more information from the data.     

Multilevel approach to lifetime assessment of steam turbines

This paper presents a multilevel methodology for a steam turbine lifetime assessment based on the damage calculation, probabilistic analysis and fracture mechanics considerations. Creep-fatigue damage calculations serve as a basis for evaluating the current lifetime expenditure and for defining additional steps of analysis. The need for the use of probabilistic analysis results from the inherent uncertainty in estimating the lifetime expenditure primarily caused by scatter in material properties. Fracture mechanics considerations are helpful in determining additional safety margins for components containing cracks. This methodology has been illustrated using an example of the lifetime calculations of a high-temperature steam turbine rotor. The calculations were based on the results of 2D numerical simulations performed for steady state and transient operating conditions.     

Failure response of fiber-epoxy unidirectional laminate under transverse tensile/compressive loading using finite-volume micromechanics

The transverse damage initiation and extension of a unidirectional laminated composite under transverse tensile/compressive loading are evaluated by means of Representative Volume Element (RVE) presented in this paper based on an advanced homogenization model called finite-volume direct averaging micromechanics (FVDAM) theory. Fiber, fiber-matrix interface and matrix phases are considered within the RVE in determining fiber-matrix interface debonding and matrix cracking. The simulated fracture patterns are shown to be in good agreement with experimental observations.     

A methodology for the estimation of transverse failure strength of an oxidized lamina from isothermal aging studies

Surface oxidation and ensuing damage substantially decrease the service life of High Temperature Polymer Matrix Composite (HTPMC) structures. Oxidative degradation behavior of composites is strongly dependent on the coupling between chemical and mechanical responses of the material. In a composite lamina, the onset of damage and subsequent coupled acceleration of both damage and oxidation are controlled by the transverse failure strength of the oxidized regions. The direct measurement of this strength from experimentation is challenging and cumbersome. A model-based methodology for estimating the mean transverse failure strength of the oxidized regions of a unidirectional composite is described in this paper. As the strength of the oxidized region is expected to show a high-degree of spatial variability, the estimated mean is shown to be relatively insensitive to the effect of strength variance. The developed methodology is illustrated with isothermal aging data available for a typical high-temperature composite system.     

Damage mapping with a degrading elastic modulus using piezospectroscopic coatings

The development of piezospectroscopic (PS) composites has enabled the creation of a non-destructive evaluation (NDE) technique which integrates piezospectroscopy, digital image correlation (DIC) and analytical multi-scale mechanics to map the elastic modulus of a coated material. The measured elastic modulus was represented as a normal distribution with a mean value (32.2 GPa) which is within 8% of the conventionally recorded modulus (35 GPa). Damage mechanics are applied to map elastic degradation in situ mechanical loading with an average uncertainty (~10 GPa) that was sufficient in observing subsurface, progressive damage patterns which are unique to the coated material.     

Energy dissipation capacity of fibre reinforced concrete under biaxial tension–compression load. Part I: Test equipment and work of fracture

The objective of this research was to analyse the differences in the dissipated energy under uniaxial tension and biaxial tension–compression load of fibre reinforced concretes using the Wedge Splitting Test. Under biaxial load the specimens were subjected to compressive stress ratios from 10% to 50% of the concrete compressive strength perpendicular to the direction of the tensile load.Under biaxial tension–compression load the energy dissipation capacity of the specimens decreases compared to the uniaxial tension load case on average 20–30%. It is believed that the decrease is a result of the damage mechanism of the concrete matrix and deterioration of the fibre–matrix and/or aggregate–cement paste interfaces in case the section is additionally loaded with compression stresses. This indicates that dimensioning of concrete elements under biaxial stress states using material parameters obtained from tests conducted on specimens under uniaxial tensile load is unsafe and could potentially lead to a non-conservative design.In the second part of this paper the extent of the fracture process zone under uniaxial tension and biaxial tension–compression load will be examined with the Acoustic Emission technique and the reasons for decrease of the energy dissipation capacity under biaxial load will be further discussed.