Measuring of thickness of the asphalt pavement with Use of GPR
The results of development, tests and application of the GPR for measurement of the road asphalt layers thickness are presented in the paper. Main necessary improvements providing the possibility of use the GPR as a measuring device are described as well as some results of application of the GPR for inspection of the road structure after reparation the road. It was achieved accuracy of layers thickness measurement better than 0.5 cm.
Measurements of antenna properties in time domain
The authors of this work have designed, manufactured, tested and applied an ultra-wideband measurement system (MS) for investigating characteristics of antennas in the operating frequency band of up to 2 GHz. The synamic range of the measured signals is at least 80 dB. The use of fairly strong signals for excitation of radiating antenna extends the power budget by 40 dB else. The absence of reflections from interfering objects in the test signal enabled us to utilize the entire dynamic range. In the paper; features of instrumentation are briefly described, and an example of measurement results is presented.
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