The Corrosion Characteristics and Tensile Behavior of Reinforcement under Coupled Carbonation and Static Loading
This paper describes the non-uniform corrosion characteristics and mechanical properties of reinforcement under coupled action of carbonation and static loading. The two parameters, namely area-box (AB) value and arithmetical mean deviation (Ra), are adopted to characterize the corrosion morphology and pitting distribution from experimental observations. The results show that the static loading affects the corrosion characteristics of reinforcement. Local stress concentration in corroded reinforcement caused by tensile stress drives the corrosion pit pattern to be more irregular. The orthogonal test results from finite element simulations show that pit shape and pit depth are the two significant factors affecting the tensile behavior of reinforcement. Under the condition of similar corrosion mass loss ratio, the maximum plastic strain of corroded reinforcement increases with the increase of Ra and load time-history significantly.
Orthogonal Array Approach for Test Case Optimization
In Software Testing, we try to cover all test scenarios and test cases to test an application/product to achieve 100% test coverage. However, most of the times we do not have the leisure of time to test all the test cases (1). In such cases, we have to balance between the specified time and quality so that we achieve maximum test coverage. This becomes a very big challenge for the Software Test Managers. According to Gupta (6), managers adopt multiple strategies to optimize the testing effort and achieve the right balance between Cost, Schedule and Quality. Striking a right balance decides the success or failure of any software solution. In this paper, we have proposed a technique called Orthogonal Array Approach for reducing the number of test cases that needs to be tested for any given software and hence improve the efficiency of testing. With this technique, reduced numbers of test cases are generated automatically. Fewer test cases would reduce time consumption of the testing as a whole and hence the cost of testing will also reduce. The details of the technique are described along with two case studies for illustration. The advantages of the method are clearly brought out with the help of analysis graphs.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME