Search

This paper concerns the simulation of Mode I fracture with a local concrete damage model in explicit finite element code LSDYNA. A reliable modeling of fracture is essential in the analysis of tension-dominated problems, as well as the prediction of concrete damage due to cracking. A special focus of this paper is placed on an effective representation of the tensile localization in finite element modeling while generalized macro material properties are employed to modeling meso-scale problems. An investigation into the use of a typical damage plasticity concrete model within LSDYNA Explicit, based on the crack band theory, is described in detail. The main focus of the current paper is on the tensile softening branch.

Transmission lines pass through various types of regions in China and some of that are corrosive. The foundation concrete of transmission lines in corrosive environments had shown serious deterioration, which usually caused by concrete deterioration, rebar corrosion, degradation of bond strength between rebar and concrete due to various corrosive effects. There are salt lake areas in west China where some power transmission channels pass through. Field tests are carried out in Golmud area to research the durability of foundation concrete of transmission lines. And test results show that the concrete strength in the air is higher than underground and the carbonation depth of the foundation concrete decreases with the increase of concrete compressive strength.

Aiming at the disadvantage of existing equipment maintenance accessibility evaluation method, this paper studied the project of equipment maintenance accessibility evaluation. a method of equipment maintenance accessibility evaluation in the virtual environment is put forward based on Matrices Permanent and index correlation degree , at last an example is given. It is significant for developing maintainability verification and increasing Equipment Maintainability in the course of equipment digital mock-up designing.

Aiming at the disadvantage of existing equipment MTTR demonstration method, this paper studied the project of equipment maintainability demonstration Based on Virtual Simulation, and put forward a method of equipment MTTR demonstration in the virtual environment, at last power system of equipment is verified as an example. It is significant for developing maintainability demonstration and increasing Equipment maintainability in the course of equipment digital mock-up designing.

Aiming to lack for the verification method of equipment maintainability quantitative requirements, this paper researched the verification method of average replacement time through virtual simulation technology, and proposed the mathematical model of average replacement time, which can lay the foundation for maintainability virtual verification.

Aiming at the disadvantage of existing materiel maintainability quantitative requirements demonstration method, this paper studied the project of the materiel maintainability qualitative requirement demonstration Based on virtual simulation, in order to determine the materiel maintainability qualitative requirement, the accessibility and visibility as an example to illustrate the virtual demonstration method. It is significant for developing maintainability demonstration and increasing materiel maintainability in the course of materiel digital mock-up designing.

Al-Li alloy 2198-T8 was used in the fuselage application. Integral fuselage panels were joined by double friction stir welds. Fatigue tests were conducted in the R=0.1. Notch was made between two welds. Residual stresses were measured and analyzed in the test samples with double welds. Cracks grew from the centre of two welds and across the two welds were observed, and crack growth rates were measured and compared with parent material. It is shown that crack growth rates are lower between double welds, and it is close to parent material after cross the two welds. The virtual crack closure technique (VCCT) method was used to calculate stress intensity factor from residual stress (Kres) in aim to explain the experimental findings.

In this work, Compact-Tension (C(T)) specimens with transverse welds in the sample centre were designed. The residual stress distributions were measured parallel and perpendicular to the weld nugget. Fatigue crack growth (FCG) rates were measured in the lab air. It is shown that compressive residual stresses around notch have significant effect on FCG rates and the effect deceases with crack growing. FCG rate is lower in the nugget than in parent material. Effects of residual stress were studied with crack growing. The lower crack growth rate in nugget is believed to be linked in part to compressive residual stress, but also in part to a microstructure effect present when crack grows in the recrystallized nugget.

In this work, CrN/NbN nanometer multi-layers were deposited on the metal substrates by a dual-target DC reactive magnetron sputtering system. X-ray diffraction, Scanning Electron Microscope and Energy Dispersive Spectrometer were used to analysis the phase composition, crystal structure, surface morphology, fracture morphology and elemental composition of thin films. Micro Hardness Tester and wear-resistant experiments were used to test the hardness and wear properties of the films.