Experimental study on rock-breaking mechanism of micro-coring PDC bit

In this paper, in order to study the rock-breaking mechanism of the micro-coring PDC bit, a series of unit breaking experiments containing 2 breaking forms (static-pressure breaking and fracture breaking) are conducted on core columns of sandstone, limestone, and granite. Besides, a full-sized micro-coring PDC bit with a diameter of 152.4 mm is designed and manufactured and is used to conduct an indoor experiment on multiple sized sandstone core columns. The unit breaking experiment results show that ROP (rate of penetration) of the fracture breaking is higher than the static-pressure breaking. The indoor experiment results of the full-sized bit show that ROP of the micro-coring PDC bit is 49–112% higher than the conventional bit and that the diameter of core column shows greater influence on ROP, while the height of the column shows smaller. Moreover, the micro-coring PDC bit realizes volumetric fracture on all of the three types of rock samples. Since volumetric fracture produces large rock debris, the rock-breaking efficiency and ROP of the micro-coring PDC bit will be improved significantly.

Seismic performance of new adobe bricks masonry: Design and experiment

At present, adobe houses with traditional characteristics are still widely used in rural areas in western China, but their seismic performance is relatively poor, and they often suffer serious damage under earthquake. To improve the seismic performance of traditional adobe buildings while retaining the characteristics of residential buildings, the mechanical properties of compressed earth blocks (CEB) were tested in this study, and the microstructure characteristics of CEB after failure were analyzed by electron microscope. On this basis, six adobe wall specimens were designed and tested by quasi-static loading to investigate the influence of core columns and different types of bricks on its seismic performance. The results show that the core column can improve the bearing capacity and shear capacity of hollow CEB, and it can also significantly increase the bearing capacity, energy dissipation capacity, and ductility of CEB wall. In general, the adobe wall with core columns shows excellent seismic performance, which can provide a new choice for improving the seismic performance of the adobe house.

Calculation Model of Shear Capacity of Multiple Composite Core Column Joints Based on Softened Tension-Compression Bar Model

This paper aims to study the seismic performance of multiple composite core column joints. The influence of the stress mechanism, axial compression ratio, and shear span ratio on the failure mode, hysteretic performance, and shear capacity of the multiple composite core column joints was studied through the low-reversed cyclic loading tests of three specially designed and manufactured multiple composite core column joints. The angle ratio method is used to calculate the effective area of the vertical tie bar, and based on the mechanism of the softening tension-compression bar, the formula for calculating the shear capacity of the joint with multiple composite core column is established. In addition, it is also verified by the test data in this paper. The experimental results show that when the axial compression ratio increases from 0.26 to 0.45, the number and width of cracks at the beam end decrease. When the shear span ratio increases from 1.67 to 2.22, the number and width of cracks at the joint beam end increase. The average value and standard deviation of the ratio between the measured value and the calculated value of the shear capacity are 0.97 and 0.16, indicating that the proposed calculation method has a high agreement with the actual value and strong engineering application.

Nonlocal Mean Filtering Algorithm for Low Contrast Images and its Application

High background noise, cracks, fuzzy boundaries image containing the chromatism, etc are the common problems faced in the low contrast image recognition, this paper takes the core fracture identification of two-dimensional section as an example, and highlight the point, simplify the problem, this paper only considering the three dimensional images of two-dimensional cross section along the direction perpendicular to the core shaft, focusing on the identification of disc core cracks within the dark grey. Each voxel based on 3D digital images corresponds to a gray value. The smaller the value, the blacker the corresponding voxel will be. The larger the value, the whiter the corresponding voxel is. By fine-tuning the background color difference, filtering and denoising, marking the non-crack area, secondary denoising by graphics method and other algorithm methods, the identification efficiency of the crack area in the two-dimensional cross-section diagram of the core column is effectively improved. This method can also be used as a solution to other problems in similar scenes.

Efficacy of Different C18 HPLC Analytical Columns in the Analysis of Fumonisins B1 and B2 in Different Matrices

Fumonisins B1 and B2 are carcinogenic and commonly contaminate corn and corn-based products. Analysis of such toxins using C18 HPLC column is officially accredited but still unknown if all column types can effectively separate FB1 and FB2 or not. The present study evaluated the efficiency of 5 analytical columns with different dimensions, particle sizes, and porosities to determine these toxins in both agar cultures of Fusarium verticillioides and cornflakes. Interestingly, the traditional column 150mm of length with 5µm porous particles had close retention times to those of the short-fused core column 75mm of length with 2.7 µm reflecting in time and solvents saving. Using Sep-Pack C18 for clean-up played an important role in enhancement the limit of quantification (LOQ) for cornflake samples (5-13.7 and 16.1-39 µg kg-1 for FB1 and FB2, respectively). However, it was relatively higher for fungal culture samples that were not passed through the cleaning-up step (11.5-16 and 28.1-46.3 µg kg-1 for FB1 and FB2, respectively). Overall, the lowest LOQ was obtained using the shorter fused core column. Finally, using such clean-up in the extraction of FB1 and FB2 from spiked cornflakes samples gave good recoveries (>80%) using all tested columns.

Finite Element Analysis applied to Electromagnetic Forces calculation on Power Transformers

High electromagnetic forces on power transformers windings may cause the equipment unavailability, resulting in technical and financial losses. To ensure its reliability, transformers must withstand the mechanical stresses demanded by the operation conditions. Once forces measurement and determination have a high degree of complexity, it is needed tools that support forces calculation and analysis accurately. This paper presents the Finite Element Analysis (FEA) applied to determine the electromagnetic forces and its distribution on transformer windings. A complete and close to the practice modeling is done, considering the magnetic core and lateral phases presence in a 3D and 3-phase configuration. The total, radial and axial forces over the windings, as well as its distribution around the core column and along its height are determined on the three phases. With precision and versatility, FEA may be widely applied by industry, contributing for more reliable transformers designs and in cost reduction.

PENGARUH VARIASI MUTU JAKET BETON DAN PENAMBAHAN TULANGAN LATERAL TERHADAP KAPASITAS AKSIAL KOLOM BUJUR SANGKAR

Many researches have been carried out regarding concrete jacketing, such as the addition of stirrup reinforcement and enlargement of dimensions with the quality of the concrete jacket that is equal or exceeds the quality of the core column concrete. To determine the effect of concrete jacket quality and the addition of stirrup reinforcement to the axial column capacity, in this study, the core column (K25) with 25 MPa quality and the quality of the concrete jacket varied 20 MPa, 25 MPa, 30 MPa, with the addition of stirrup reinforcement (KJs column) and without the addition of stirrup reinforcement (KJ column) in each variation of the quality of concrete jackets. It made 3 colomn for each type of treatment. The core column has a square shape with dimensions 80 x 80 x 320 mm and a concrete reinforcement jacket is given with dimensions 160 x 160 x 300 mm. The column is given concentric axial load and the shortening is calculated using a dial gauge for every 20 kN load. The results of this study indicate the addition of jacket and stirrup reinforcement concrete can increase axial capacity and column ductility. As for the increase in axial capacity that occurs in the KJ20, KJ25, KJ30 column, the K25 column is respectively 17.4%; 34.0%; 34.7%. While the axial capacity increase in the KJs20, KJs25, KJs30 columns, for the K25 column is 54.9%; 62.5%; 71.5%. The reinforcement column with the addition of stirrup reinforcement, has a shorter value and greater axial capacity than the core column and reinforcement column without accompanying the addition of stirrups. The increase in axial capacity that occurs also increases along with the increase in the concrete compressive strength of the jacket which is used as reinforcement. Keywords: quality variation, axial capacity, concrete jacketing.

High Temperature Performance of a prefabricated concrete sandwich panel

The innovative sandwich wall panel studied in this paper can be used as the load-bearing member of the structure. In addition to the traditional sandwich panel structure, the new panel system also has the characteristics of spiral stirrups along the section of the core column, 650mm column spacing, foam concrete for insulation layer and self-compacting concrete for outer layer. In addition, in order to improve the overall strength and stiffness of the panel, a unique wire system consisting of two vertical wire mesh connected by a short horizontal steel bar is adopted in the concrete layer. In order to study the mechanical properties of the new panel system at high temperature, ABAQUS simulation was carried out. The simulation results show that the new precast concrete sandwich wall system has good resistance to high temperature and still has good bearing capacity after high temperature.

Study on Seismic Behavior of Concrete-filled square steel tube column with core column-Steel Beam Joints

This paper has carried out the quasi-static tests of five specimens of FRP-UHPC column-steel beam joints with core columns, and the extensive parameter analysis of the joints by numerical simulation. The results show that the Concrete-filled square steel tube column with core column -Steel Beam Joints have strong bearing capacity. It has excellent deformability, stiffness and energy dissipation capacity, and works well under the condition of high axial compression ratio. The bearing capacity of the replacement beam specimen does not deteriorate significantly, which indicates that the Concrete-filled square steel tube column with core column -Steel Beam Joints is replaceable.