Evaluation of the conditions of drill pipes failure during tripping operations

The experimental evaluation of the power criterion for the metal fracture of the reserve and the long operated drill pipes was carried out. The conditions under which, during tripping operations, the failure of explored drill pipes, containing external or internal transverse annular cracks are possible. An interrelation between the depth of critical external or internal transverse annular cracks in drill pipes with the weight of the drilling string is considered, taking into account the influence of dynamic loads during tripping operations. It is shown that internal transverse annular cracks in lowering operating drilling strings at depths of more than 1400 m are more dangerous than external ones, while at depths up to 1400 m, external cross-sectional circular cracks are more dangerous.

Analysis and Study on Crack Characteristics of Highway Tunnel Lining

Lining cracks are one of the most common diseases in highway tunnels, and the existence of lining cracks directly affects the overall stability and durability of tunnels, which has an important impact on the safe operation of tunnels, and it is necessary to analyze and study the characteristics of tunnel lining cracks. Combining with the detection data of multiple highway tunnels in the field, the different types of tunnel cracks are divided, and the classification numerical statistics method is used to obtain that the number and length of annular cracks in highway tunnel cracks are significantly higher than those of the other two kinds of cracks, and the longitudinal cracks in tunnel crack cracking degree are greater than the circumferential cracks and the inclinded cracks. The influence degree of cracks on the safety of tunnel structure longitudinal cracks are relatively the largest, the inclinded cracks are second only to longitudinal cracks, and the influence of cyclic cracks is relatively small. It provides reference for tunnel engineering design, construction, operation management and comprehensive improvement work.

Evaluation of the dynamic loads impact on the conditions of drill string failure during tripping operations

The conditions of drill string failure during tripping operations with external or internal transverse annular cracks were defined. At the same time, considering the experimental evaluation of the force criterion for failure of metal of backup and operated drill string pipes, the interrelationship between the depth of the critical external or internal transverse annular cracks in drill string pipes with the weight of the drill string was established, considering the effect of dynamic loads during tripping operations. It was determined that dynamic loads during run-in-hole operations are more dangerous at depths of more than 3.7 km, while at lower depths, the dynamic loads occurring during pulling out of string are considered more dangerous. It was demonstrated that, when pulling out operated drill strings, internal transverse annular cracks at depths exceeding 1.1 km, are more dangerous than external ones, while at depths up to 1.1 km the external transverse cracks are more dangerous.

Taxonomy of the corticolous, shrubby, esorediate, neotropical species of Usnea Adans. (Parmeliaceae) with an emphasis on southern Brazil

Seventeen corticolous shrubby apotheciate Usnea species without vegetative propagules are reported from Brazil, including five species that are new to science: Usnea aurantiaca-parvula A. Gerlach & P. Clerc (characterized by an orange medulla and lageniform spinulose fibrils), U. cirrosa Motyka, U. cladocarpa Fée (syn. nov.: U. ramillosa Motyka), U. concinna Stirton (lectotype designated here, syn. nov. U. radiata Stirton, U. florida var. scabrosa Zahlbr.), U. cristatula Motyka, U. erinacea Vain., U. fleigiae A. Gerlach & P. Clerc (characterized by large spores and a thin, lax medulla), U. grandispora A. Gerlach & P. Clerc (characterized by large spores, a black base and protocetraric or salazinic acids in the medulla), U. kalbiana P. Clerc & A. Gerlach (characterized by a vitreous cortex and annular cracks in the basal part), U. lunaria Motyka, U. meridionalis Zahlbr. (syn. nov.: U. michauxii I. I. Tav.), Usnea cf. moreliana Motyka, U. parvula Motyka, U. steineri Zahlbr, U. subelegans (Vain.) B. de Lesd. (lectotype designated here), U. subparvula A. Gerlach & P. Clerc (characterized by spinulose fibrils and protocetraric acid in the medulla) and one as yet unidentified species (named Usnea sp. 1). Usnea cirrosa, U. cristatula and U. erinacea are new records for Brazil. A full description with morphological, anatomical (CMA and ascospores) and chemical features (TLC), as well as geographical distribution, is provided for each species along with an identification key to all species reported. Molecular data from the ITS rDNA, RPB1 and Mcm7 markers are present for most taxa, except for U. concinna, U. cristatula, U. kalbiana, U. lunaria, U. cf. moreliana and U. subelegans.

Enhanced Mechanical Performance of Electrospun Graphene/Polyacrylonitrile (PAN) Composite Microfibrous Yarns via Post-Processing

The graphene/Polyacrylonitrile (PAN) composites have drawn increased attention due to their significant improvements in mechanical and physical properties. A post treatment, enhancing the mechanical properties of the electrospun graphene/PAN fibrous yarns, was investigated in this study. The yarns obtained by this post treatment showed increased average strength and decreased elongation, which demonstrated that the as-reported method was an effective way to prepare higher performance electrospun graphene/PAN yarns. The method has potential application in preparation of micro ropes and self-assembled 3D electrospun fibrous yarns. Moreover, it is an innovation to apply dyeing during the investigation of the electrospun fibers under tension condition to analyze the tensile mechanism of yarns. The annular cracks were observed, which was recognized as the immediate cause for the yarns lengthening. Furthermore, according to its growth and fracture, the tensile mechanism of electrospun fibrous yarns was revealed.