An Experimental Study on Constant Current Load Test of Reinforced Concrete based on 3D Paraffin Isolation

Aiming at the complex corrosion degradation factors of reinforced concrete and clearing the deterioration mechanism in the constant stress state,a new type of constant current accelerated corrosion method in the saline soil environment was developed.The three-dimensional paraffin isolation specimens and the three-dimensional penetration specimens were taken as the research objects,and the Cl−content and AC impedance Bode diagram were measured.The macro morphology and micro analysis were also used to evaluate the corrosion degradation laws of the two groups of specimens.A constant current three-factor system accelerated model was established for the current acceleration factor,chloride ion,and sulfate ion acceleration factor.The experimental results show that,in the constant stress test of the saline soil environmental conditions,the paraffin isolation layer can effectively isolate corrosive chloride ions,which is a brand-new research method of single factor variable control in the constant stress test.According to the basic corrosion data,the law of constant current acceleration test is summarized and divided into five corrosion degradation stages,and each stage has significant changes in the accelerated corrosion efficiency.The corrosion degradation of a constant stress test is the combined effect of constant current,positive and negative penetration of chloride ions and sulfate ions.

EVALUATION OF ADHESION AND PLASTICITY OF PVD FILMS

Evaluation of adhesion of PVD Ti and TiN films on steel A_3 was carried out with constant rate pulling test(CRPT)at 0.05 mm/min under simultaneous SEM observation. As a criterion,the critical elongations of the film/substrate system for the initial cracking and spelling of the film may be applied to evaluate the plasticity and adhesion of the film to substrate.The conventional scratch test was also made for evaluation of the adhesion for the same systems.Both methods give the coordinate assessment for all the systems. In addition,the influence of the films on the ultimate yield strength of the substrate was discussed and another criterion of conherent work was proposed for the evaluation.

Statistical analysis of dependent competing risks model in constant stress accelerated life testing with progressive censoring based on copula function

In this paper, we consider the statistical analysis for the dependent competing risks model in theconstant stress accelerated life testing (CSALT) with Type-II progressive censoring. It is focusedon two competing risks from Lomax distribution. The maximum likelihood estimators of theunknown parameters, the acceleration coefficients and the reliability of unit are obtained by usingthe Bivariate Pareto Copula function and the measure of dependence known as Kendall’s tau.In addition, the 95% confidence intervals as well as the coverage percentages are obtained byusing Bootstrap-p and Bootstrap-t method. Then, a simulation study is carried out by the MonteCarlo method for different measures of Kendall’s tau and different testing schemes. Finally, a realcompeting risks data is analysed for illustrative purposes. The results indicate that using copulafunction to deal with the dependent competing risks problems is effective and feasible.