Coeval development of extensional and contractional features along transform margins: insights from the Diaz Marginal Ridge

The Diaz Marginal Ridge (DMR), on the southern transform margin of South Africa, is a bathymetric feature parallel to the Agulhas Falkland Fracture Zone (AFFZ) that has long been considered an archetype marginal ridge; and yet its origin and evolution remains unconstrained. Using recently acquired seismic data we present a new structural interpretation of the DMR and its association with the evolution of both the AFFZ and the Southern Outeniqua Basin. In contrast to previous scenarios invoking thermo-mechanical explanations for its evolution, we observe a more straightforward structural model in which the genesis of the DMR results from the structural inversion of a Jurassic rift basin. This inversion resulted in the progressive onlap of latest Valanginian-Hauterivian aged stratigraphic units, important for the formation of stratigraphic plays of the recent Brulpadda discovery.Paradoxically, this contraction is contemporaneous with renewed extension observed in the inboard normal faults. The orientation of the DMR and inboard structures have been demonstrated to be controlled by the underlying Cape Fold Belt (CFB) fabric. The onset of motion across the AFFZ shear system led to east-west orientated maximum stress and north-south orientated minimum stress. We propose this stress re-orientation resulted in strain partitioning across existing structures whereby in addition to strike-slip on the AFFZ there was coeval extension and contraction, the nature of which was determined by fault orientation. The fault orientation in turn was controlled by a change in orientation of the underlying CFB. Our model provides new insights into the interplay of changes in regional stress orientation with basement fabric and localised magmatism along an evolving transform. The application of horizontal strain partitioning can provide an explanation of similar features observed on other transform margins.

Reliability improvement of steel storage tanks for phosphoric acid

The paper describes the one-sided welding method for steel structures based on the rational choice of the inverse angle of butt-welded elements of Belgian steel for the manufacture of tank bottom elements of intended for phosphoric acid storage in a construction site. It is shown that the most expedient method for ensuring the design geometry of the tank with a minimum stress of 1.4507 of the material structure, is the bottom sheets preset for welding at a reverse angle of 12 degrees.The proposed method improves the tank reliability for storing aggressive products, its trouble-free and technical safety during the operation. The need is shown for studying the replacement of imported steel by Russian steel to manufacture tanks from alternative nonmetallic materials.

The Staircase Drive—A Novel Actuator Design Optimised for Daisy-Chaining and Minimum Stress Load Coupling

This work presents a novel type of actuator that improves over the standard cantilever by permitting daisy-chaining while minimising stress to the joint connecting to the load. A detailed structural and functional comparison of the proposed device against the cantilever actuator as a baseline is given, led by a brief revision of the cantilever actuator as the state-of-the-art that highlights its limitations with respect to daisy-chaining and the stress it inherently creates within the joint connecting to the load when attempting out-of-plane displacement without rotation. Simulations of both devices’ performance confirm that the newly proposed device yields the targeted displacement profile that both enables the daisy-chaining of such a device into a higher-order actuator for increased displacement and reduce stress in the joint with the load. This comes at the cost of reduced maximum displacement compared to the cantilever, which can be overcome by daisy-chaining. The proposed device’s performance is further evaluated on the basis of manufactured prototypes measured by means of a laser scanning vibrometer. The prototype was manufactured on a 150m alumina substrate, and both electrodes and piezoelectric layer were deposited in a thick-film printing process.

Determination of horizontal stress orientation in the areas of the Tomsk region

Introduction. The World Stress Map project proves that horizontal stress orientation determination is a global task essential for the majority of geomechanical calculations. However, there is scant data on stress orientations in the territory of Russia at the moment. The task is therefore highly relevant. Research objective is to determine the orientations of maximum and minimum horizontal stresses by separate areas of the Tomsk region and build a map of horizontal stresses. Method of research. The basis for determining the orientations of horizontal stresses is the theory of drilling-induced fracture and borehole breakouts occurrence. The maximum stress orientation coincides with the drilling-induced fracture orientation, whereas the minimum stress orientation coincides with the borehole breakouts orientation or is perpendicular to the maximum stresses. Results. Research results are compiled in a summary table containing mean orientations of horizontal stresses by areas and a map of horizontal stress orientations. Conclusions. A summary map of maximum horizontal stress strike azimuths has been constructed. The stresses are of similar orientation in every well under consideration, except for a well in the North-Shingin area. The average value of maximum horizontal stress orientation has made up 337° northwest and 157° southeast.

Optimal hole shape for arrest of longitudinal shear crack

Рассматривается задача об отыскании оптимальной формы отверстия в вершине трещины продольного сдвига. Искомая форма отверстия удовлетворяет условию минимальной концентрации напряжений на его контуре. Исследуется влияние отверстия оптимальной формы на торможение трещины. Дается критерий и метод решения задачи по предотвращению хрупкого разрушения тела, ослабленного прямолинейной трещиной продольного сдвига. Используется минимаксный критерий. Получено условие хрупкого разрушения. The problem of finding optimal hole shape at the tip of a longitudinal shear crack is considered. The desired hole shape satisfies the condition of the minimum stress concentration on the contour. The effect of the optimal hole shape on deceleration of a crack is studied. A criterion and solution method for the problem of preventing brittle fracture of the solid weakened by rectilinear longitudinal shear crack is given. The minimax criterion is used. The brittle fracture condition is obtained.

DFIT: An Interdisciplinary Validation of Fracture Closure Pressure Interpretation Across Multiple Basins

Recent papers on pre-frac tests have proposed fracture closure pressure interpretation methodologies that lead to an earlier, higher stress estimation than the ones estimated from well-established practices. These early time estimations based on the fracture compliance method lead the practitioner to utilize unrealistic permeability, stress, and fracture pressure models. This, in turn, has a severe impact on the modeled fracture geometries which hinders the hydraulic fracture optimization process. A multi-basin analysis of pre-frac tests from the North Sea, Europe, Russia, North Africa and South America is presented to support traditional closure estimation techniques. The validity of traditional minimum stress interpretation techniques will be reinforced through multiple case histories by comparing permeability estimates from the time required for the fracture to achieve closure during diagnostic injections, after-closure analysis, core, pressure build up and rate transient analysis. Results will be supported further by fiber optics and production logging tool (PLT) driven flow allocation, fracture geometry assessment through micro seismic and sonic anisotropy, and diagnostic injections numerical inversions.

Experimental Analysis & Optimization with Validation of Ball Valve Body of WCB Material

The ball valves are used in place of pipelines where the flow of fluid is needed. Ball valves have been mostly used for high temperature and high pressure valves which requires high quality products with confidentiality, reliability and durability. The ball has a bore or passage through the middle, so that when the port is in line with both ends of the valve, the flow of fluid will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and the flow is closed. The ball valve can revolve 90°, which has large size and weight, but it has not only an enormously more excellent confidentiality than other valves in the severely high temperature and high pressure environment When the ball valve is in closed condition the pressure exerted on the ball valve body due to that high pressure fatigue stresses and strain develop on the body of valve. Because of the high pressure and temperature on the ball valve body leakage of body take place which cause safety issue and ball valve failure. By this research stress strain analysis of ball valve body obtains and identifies the maximum and minimum stress and strain produced on the body of ball valve. The Max stress by parts was confirmed through thermal-structural coupled field analysis of major parts to evaluate safety. The objective of this research is to examine the effect of pressure and temperatures on valve components its analysis and optimization

Shear joints and its relations with subsurface structures in Batu Melintang, Jeli, Kelantan, Malaysia

Shear joint is the common rock deformation structures formed in Batu Melintang, Jeli due to its location within Bentong-Raub Suture zone. The structural analysis of shear joint can give information about the direction of maximum and minimum stress exerted on a rock while undergoing deformation as the effect of stress fields in the study area. The subsurface structural analysis is done by using the geophysical resistivity method. It displays the subsurface structure in the area for confirmation of the structure found on the surface whether it is highly fractured, moderately fractured or low fractured. The research area was divided into six grids for systematic field measurement. The shear joints orientation were taken while conducting geological mapping and recorded using rose diagram analysis; while the geophysical resistivity method was carried out with a varied length of survey lines set at 200/100m and 1.25/2.5/5m electrode spacing. The subsurface depth of penetration for each survey line is varied, ranging from 0m to 50m. The data is processed in RES2DINV software to obtain the pseudosection profile of the subsurface. The study area principal stress was identified; the maximum stress force ?1 was directed in NW-SE in direction of S107°E and N287°W, while minimum stress ?3 was directed in NE-SW in direction of N17°E and S197°W. The pseudosection subsurface image also displayed a correlation between surface shear joint structures and subsurface structures. The subsurface investigation; according to the pseudosection found that the study area consists of highly fractured structure displayed as several weak zones and fractures of bedrock.

Stress Distribution in Implant-Supported Overdenture and Peri-Implant Bone Using Three Attachment Systems: A Finite Element Analysis

Background: This finite element analysis (FEA) evaluated stress distribution in implant-supported overdenture (ISO) and peri-implant bone using one extracoronal (ball) and two intracoronal (locator and Zest Anchor Advanced Generation (ZAAG)) attachment systems. Methods: In this in vitro study, the mandible was modelled in the form of an arc-shaped bone block with 33 mm height and 8 mm width. Two titanium implants were modelled at the site of canine teeth, and three attachments (ZAGG, locator, and ball) were placed over them. Next, 100 N load was applied at 90° and 30° angles from the molar site of each quadrant to the implants. The stress distribution pattern in the implants and the surrounding bone was analyzed, and the von Mises stress around the implants and in the crestal bone was calculated. Results: While minimum stress in peri-implant bone following load application at 30° angle was noted in the mesial point of the locator attachment, maximum stress was recorded at the distal point of the ball attachment following load application at 90° angle. Maximum stress around the implant following load application at 90° angle was noted in the lingual point of the ball attachment while minimum stress was recorded in the lingual point of the locator attachment following load application at 90° angle. Conclusions: According to the results, the locator attachment is preferred to the ZAAG attachment, and the ball attachment should be avoided if possible.