Youd’s method is a widely adopted standard penetration test based approach for evaluation of liquefaction potential. This method was established by pooling the post-earthquake survey data collected from different regions of the world, and its accuracy may vary when applied in different regions. This paper investigates the inter-region variability associated with the accuracy of Youd’s method using a Bayesian model. It is found that Youd’s method is on average biased towards conservatism, and there does exist the inter-region variability associated with the uncertainty of the model bias factor. Nevertheless, the inter-region variability associated with the model uncertainty of Youd’s method is less significant than the intra-region variability. Due to the existence of inter-region variability, the same factor of safety (FOS) may imply different levels of liquefaction probabilities in different regions. If the inter-region variability is not considered, the obtained FOS—failure probability relationship may lead to underestimation or overestimation of the liquefaction potential when applied in different regions. A verification method is proposed to compare the predicted number of liquefied cases with the actual number of liquefied cases in each region. An illustrative example for assessing the liquefaction potential is used to demonstrate the application of the proposed method.
Boriding of the surface of a tool steel using boron powder and the plasma transferred arc process was investigated. It was shown that this method is an easy and effective technique in producing uniform alloyed layers with a thickness of about 1.5 mm and a hardness between 1000 and 1300 HV.The microstructure of the borided surfaces consists of primary Fe2B-type borides and a eutectic mixture of borides and martensite. Some cracks are observed in the eutectic regions but they do not seem to critically affect the behaviour of the coatings in sliding wear.The wear rate of pin on disc tests is primarily affected by the applied load and it lies between 10−5 mm3/m for low loads and 10−2 mm3/m for high loads. Two distinct regimes of mild and severe wear are obtained separated by a critical load. Mild wear is due to the load supporting effect of borides and severe wear is due to their breakage above a critical load. The wear rate is not significantly affected by the sliding velocity and is consistent with the friction coefficient.The friction coefficient varies from 0.13 to 0.23 and depends strongly on the oxidation status of the wear track. The sliding velocity affects the sliding distance where the coefficient of friction reaches equilibrium. 相似文献