Papers by Keyword: Damage Parameter

Abstract: The splitting test for concrete specimens in four different dimensions were carried out in order to build the relative even micro-crack damage fields. The real-time whole-field displacements of concrete surface were measured omni-directionally by DSCM(Digital Speckle Correlation Method). Through analyzing the obtained experimental data, two kinds of micro-crack damage parameter are established :one is damage area based on the MCOD (Micro-Crack Opening Displacement) and another is damage variable based on the weighting-damping elastic modulus, which provides a new index and method for characterization of concrete micro-crack damage.

Abstract: In this paper, the analysis work is conducted for simulating the experimental study on the energy absorption columns performed previously. The software ABAQUS is used for fulfillment of the research. The concrete damage plasticity model is adopted for the calculation of the macro-synthetic fiber-reinforced concrete material used in the columns. The viscosity coefficient and the damage factore of concrete are discussed, and the results analyzed agree with experimented.

Abstract: Micro-crack defects in concrete can affect the Chloride ion permeability of concrete in a certain extent. In the paper, the splitting experiments of concrete specimens from the four different dimensions are carried out in order to build the even damage fields. The displacements of the concrete specimens’ surface are analyzed through DSCM (Digital Speckle Correlation Method). Therefore damage parameters are determined that are damage area based on the MCOD (Micro-Crack Opening Displacement) and damage variable DE based on the weighting-damping elastic modulus. At the same time, Clˉ permeation of concrete specimens before and after the splitting test are studied by NEL method, and Clˉ diffusion coefficients D are recorded in detail. Further relationships between damage parameters and diffusion coefficients of Clˉ are discussed.

Abstract: The research of structural vulnerability analysis is mostly based on the Cornell theory. Using other methods to do seismic fragility analysis is relatively rare. In this paper, beta probability density function is used to continuously fit the probability distribution of damage levels for a frame structure under given seismic intensities. It gets the probability density distribution of the structure under different intensities. The results show that, based on beta probability density function, it can get comparatively accurate solution for structural seismic vulnerability analysis. This method is not only simple and fast, but also the damage state is expressed by continuous damage parameter. The research provides the reference for future earthquake damage prediction and the elaborate calculation about economic loss of earthquake insurance.

Abstract: Nickel-based creep resisting alloys (strengthened by γ´) are the basic materials for high-temperature constructional parts in aircraft engines and energy units. These parts are exposed to combined effects of mechanical stresses, high temperature and dioxide-corrosion conditions. The microstructure changes of cast polycrystalline Ni-based superalloy IN713LC after creep exposure were studied. Three specimens with three different diameters were used for creep tests. The degradation stage (damage parameter π) was determined for all parts of specimens. Individual parts of specimens were metallographic observed and analyzed by image analysis after rupture. The results were compared with model of stress distribution in the specimen with potential damage in the centre of the specimen.

Abstract: The fatigue crack growth experiment was carried out at room temperature for the standard SEB(3) specimens of 40Cr steel, the distribution of the surface magnetic field of the specimen under same load and different cycle numbers (N) was studied. By analyzing relations between the magnetic signals and the crack propagation life, a new damage parameter model has been established by magnetic signals. According to this model, we can evaluate the residual life of ferromagnetic components excellently. This belong to basic research on early damage inspecting and residual life assessment for ferromagnetic materials, it confirmed that residual life assessment and safety estimating for ferromagnetic components based on metal magnetic memory technology is feasible.

Abstract: Little work has been published concerning the transferability of Gurson’s ductile damage model parameters in specimens tested at different strain rates and in the rolling direction of a Grade A ship plate steel. In order to investigate the transferability of the damage model parameters of Gurson’s model, tensile specimens with different constraint level and impact Charpy specimens were simulated to investigate the effect of the strain rate on the damage model parameters of Gurson model. The simulations were performed with the finite element program ABAQUS Explicit [1]. ABAQUS Explicit is ideally suited for the solution of complex nonlinear dynamic and quasi–static problems [2], especially those involving impact and other highly discontinuous events. ABAQUS Explicit supports not only stress–displacement analyses but also fully coupled transient dynamic temperature, displacement, acoustic and coupled acoustic–structural analyses. This makes the program very suitable for modelling fracture initiation and propagation. In ABAQUS Explicit, the element deletion technique is provided, so the damaged or dead elements are removed from the analysis once the failure criterion is locally reached. This simulates crack growth through the microstructure. It was found that the variation of the strain rate affects slightly the value of the damage model parameters of Gurson model.

Abstract: In this paper, 3-dimension finite element model was applied to analyze the commercial pure Ti billet subjected to four-pass equal channel angular extrusion process at 400°C with Bc route. The effective strain distribution and the damage within up to four-pass were described with friction conditions in 3D. The propensity for cracks was predicted, which did correlate approximately to the experiment.

Abstract: Strategies for time-economic lifetime assessment of thermal barrier coatings (TBC) in service are described and discussed on the basis of experimental results, achieved on material systems with coatings applied by electron beam physical vapour deposition. Service cycles for gas turbine blades have been simulated on specimens in thermo-mechanical fatigue tests, accelerating the fatigue processes by an increase of load frequency. Time dependent changes in the material system were imposed by a separate ageing, where the samples were pre-oxidized prior to the fatigue test. Results of thermo-mechanical fatigue tests on pre-aged and as-coated specimens gave evidence of interaction between fatigue and ageing processes. An alternative approach is used, which is focused on the evolution of a failure relevant damage parameter in the TBC system. The interfacial fracture toughness was selected as a damage parameter, since one important failure mode of TBCs is the spallation near the interface between the metal and the ceramic. Fracture mechanical experiments based on indentation methods have been evaluated for monitoring the evolution of the interfacial fracture toughness as a function of ageing time. It was found that the test results were influenced by both changes of the interface (which is critical in service) and changes in the surrounding material.