Study on the integrity detection and evaluation method of damaged pipeline
To detect the integrity of damaged pipeline and accurately evaluate its damaged condition, a CCD image data guided digital automatic ultrasonic testing system was designed to realize the dynamic measurement of a pipeline damaged surface, and extract the characteristic parameter of damaged pipeline. Based on the three-dimensional discrete point set which gathered to describe the integrity of damaged pipeline, we establish a damaged pipeline entity model which is closer to the actual condition, analyze and simulate mechanical properties under the actual load by using the numerical simulation software (ABAQUS), to get the most dangerous region and the trend of stress and displacement. This method provides more reliable reference for integral safety analysis and evaluation of damaged pipeline.
Mechanical Behavior of Spun-Cast Gray Iron Pipe
Past work has made little differentiation between the mechanical properties of pit and spun cast gray iron water pipes. Mechanical tests on coupons from spun and pit cast samples presented here show that spun cast gray iron has mechanical properties that fall between those of pit cast gray iron and ductile iron pipes, often with marked similarities to ductile iron. The properties determined from the mechanical tests were used to examine whether linear elastic analysis can be successfully used to approximate the mechanical behavior of a pipe loaded in bending. Linear elastic analysis was found to produce reasonable approximations to the behavior of undamaged pipes. The effect of corrosion pitting was included in the analysis by determining stress concentration factors for pits of varying depths at different stress levels. Multiplying the stress concentration factors by the results of the linear elastic analysis produced results with an error of no more than 6% from the values produced by a full cast iron p...
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.