Research on Interlayer Bonding Quality Control Method of Dam Concrete Based on Equivalent Age

Interlayer bonding quality is the key to the stability and durability of dam concrete. In this study, interlayer splitting tensile strength, relative permeability coefficient, and electric flux of dam concrete at different temperatures were tested. The relationships between equivalent age and strength coefficient, relative permeability coefficient ratio, and electric flux ratio were established. Meanwhile, a comprehensive early-warning and control system of dam interlayer bonding quality based on the above relationships was proposed. The results showed that the interlayer mechanical properties, impermeability, and anti-chloride ion permeability of dam concrete decreased with the increase of temperature. Moreover, the equivalent age was linearly correlated with strength coefficient, relative permeability coefficient ratio, and electric flux ratio of concrete. The correlation coefficients were 0.986, 0.973, and 0.924, respectively. In addition, the interlayer bonding quality of dam concrete can be effectively controlled by the early-warning system established according to the relationship between equivalent age and interlayer properties parameters.

Strength coefficient estimation by indirect methods

Introduction. In exploration, construction, and mining operations it is necessary to assess the physical and mechanical properties of rocks. However, laboratory rock tests are expensive, time-consuming, and require a large number of quality rock samples. There is a problem of rapid evaluation of physical and mechanical properties by indirect, non-destructive methods. The problem is considered on the example of one of the basic properties, the strength coefficient according to Protodiakonov's scale. Research methodology included the analysis of the main indirect methods of determining the strength coefficient based on strength, elastic and acoustic properties of rocks on the grounds of statistical empirical relationships of V. V. Rzhevskii, G. Ia. Novik, L. I. Baron; K. L. Ter-Mikaelian, A. I. Beron, and M. M. Protodiakonov. The most promising methods based on non-destructive laboratory tests of modulus of elasticity and longitudinal wave velocity are selected. Results and conclusions. The strength coefficient was calculated by several methods on the example of siliceous sandstones, selected from the exploration well of the gas-bearing field. The results were compared with each other and with cadastral references and materials. The most optimal for calculations were the dependences of V. V. Rzhevskii, G. Ia. Novik, and L. I. Baron when evaluating the strength coefficient by the modulus of elasticity, and the dependences of A. I. Beron and L. I. Baron when calculating based on acoustic characteristics.

Springback Behavior of High Strength Titanium Tube after Bending under Variations of Material Property Parameters

In order to reveal the springback behavior of high strength TA18 tube after numerical control (NC) bending under the variations of material property parameters, the finite element (FE) model of the whole process for the high strength TA18 tube during NC bending was established under ABAQUS code and its stability was evaluated. Then, using the model, the springback behavior after tube bending under the variations of material property parameters was studied, and the significance of material property parameters on springback was revealed. The results show that the springback angle decreases with the increase of the Young’s modulus, hardening exponent and thickness anisotropy exponent or with the decrease of the strength coefficient and yield stress. The significance of material property parameters on springback of the high strength TA18 tube after NC bending from high to low are the yield stress, Young’s modulus, strength coefficient, thickness anisotropy exponent and hardening exponent.

Research on the Properties and Low Cycle Fatigue of Sc-Modified AA2519-T62 FSW Joint

The aim of this research was to examine the mechanical and fatigue properties of friction stir welded Sc-modified 5 mm thick AA2519-T62 extrusion. The joint was obtained using the following parameters: 800 rpm tool rotation speed, 100 mm/min tool traverse speed, 17 kN axial, and MX Triflute as a tool. The investigation has involved microstructure observations, microhardness distribution analysis, tensile test with digital image correlation technique, observations of the fracture surface, measurements of residual stresses, low cycle fatigue testing, and fractography. It was stated that the obtained weld is defect-free and has joint efficiency of 83%. The failure in the tensile test occurred at the boundary of the thermo-mechanically affected zone and stir zone on the advancing side of the weld. The residual stress measurements have revealed that the highest values of longitudinal stress are localized at the distance of 10 mm from the joint line with their values of 124 MPa (the retreating side) and 159 MPa (the advancing side). The results of low cycle fatigue testing have allowed establishing of the values of the cyclic strength coefficient (k′ = 504.37 MPa) and cyclic strain hardening exponent (n′ = 0.0068) as well as the factors of the Manson–Coffin–Basquin equation: the fatigue strength coefficient σ′f = 462.4 MPa, the fatigue strength exponent b = −0.066, the fatigue ductility coefficient ε′f = 0.4212, and the fatigue ductility exponent c = −0.911.

Influence of inclusions on bending fatigue strength coefficient the medium carbon steel melted in an electric furnace

The parameters of high-grade steel are influenced by a combination of factors, including chemical composition and production technology. The impurity content is also a key determinant of the quality of high-grade steel. Inclusions may also play an important role, subject to their type and shape. Inclusions may increase the strength of steel by inhibiting the development of micro-cracks. The analyzed material was one grade of medium-carbon structural steel. The study was performed on 6 heats produced in an industrial plant in 140 ton electric furnaces. The experimental variants were compared in view of the five heat treatment options. The results were presented to account for the correlations between the fatigue strength coefficient during rotary bending, the diameter of and spacing between impurities. The relationship between the fatigue strength and hardness of high-grade steel vs. the quotient of the diameter of impurities and the spacing between impurities was determined. The proposed equations contribute to the existing knowledge base of practices impact of impurities with various diameters and spacing between non-metallic inclusion on fatigue strength.

Using the strength coefficient(SC) to evaluate the most number of publications in research affiliations involving COVID-19 till April 14, 2020: A bibliometric analysis

Background: When the COVID-19 outbreak spreads to the world, many articles related to it have been published in academics. Since the largest quantity of confirmed cases was reported in China till April 14, 2020, whether the number of Chinese articles of research associated with the COVID-19 topped globally is required to be examined. Thus, an objective measure determining the dominant role in a group should be defined. This study aims to propose an index (strength coefficient, SC) to evaluate the most influential research affiliations in publications of COVID-19. Methods: We simulated data to verify the separation index that can be viable in use for determining the dominant one that has the absolute advantage in a group. We selected 4,369 articles as of April 14, 2020, with abstracts from the Pubmed Central (PMC) based on the keywords COVID-19 or 2019-nCOV. An author-weighted scheme (AWS) was applied to quantify coauthor credits in the article byline. Social network analysis incorporated with SC(from 0 to 1.0 and cutoff=0/70) was applied to display the influential (1) article types, (2)countries, (3)medical subject headings(MeSH terms), and (4) research affiliations. Visual dashboards were created for displaying the results on Google Maps. Results: We observed that the top one(SC) in each topic consists of (1) journal article(0.81), (2) China(0.61),(3) Acad Radol, (4) betacoronavirus (0.66), and (5) Hazhong University of Science and Technology(0.77) in article types, countries, journals, MeSH terms, and research affiliations, respectively. Conclusion: We applied the SC to identify the strength of the top one over the next two. The SC was useful and viable in verifying the dominant role in a group. The implementation and application are worthy of further studies in the future.

Estimating the coupling strength of a Hamiltonian with four different measurement strategies

In this paper, we compare different measurement strategies for estimating coupling strength of a Hamiltonian. In particular, we estimate the coupling strength coefficient when the Hamiltonian couples the pointer (measuring device) momentum to an observable of the system. We compare the performance of the estimations via four different measurement strategies: measuring the position or the momentum of the pointer with or without postselection of the system state. Without postselection, it turns out that all the information of the coupling strength can be extracted by measuring the position of the pointer. As a contrast, no information of the coupling strength can be extracted if the momentum is measured without postselection. Hence, measuring the position is a better choice if postselection is not allowed. However, when postselection is employed, we find that no matter which observable is measured, one can always achieve a great amplification of the measurement outcome, which can be larger than the initial standard deviation of the pointer observable under certain circumstances, at an acceptable cost of losing a little accuracy for the estimation of the coupling strength. With postselection, the better choice of the observable to be measured depends on the characteristic of the measurement devices.

Cryogenic Material Properties of Polycaprolactone

In pursuit of research to create a synthetic tissue scaffold by a micropunching process, material properties of Polycaprolactone (PCL) in liquid nitrogen were determined experimentally. Specimens were prepared using injection molding and tested under compression to determine the stress-strain relationship of PCL below its glass transition temperature. Cryogenic conditions were maintained by keeping the PCL specimens submerged in liquid nitrogen throughout the loading cycle. Specimens of two different aspect ratios were used for testing. Yield Strength, Strength Coefficient, and Strain Hardening Exponent were determined for different specimen aspect ratios and extrapolated for the case with zero diameter to length ratio. Material properties were also determined at room temperature and compared against results available in the literature. Results demonstrate that PCL behaves in a brittle manner at cryogenic temperatures with more than ten times increase in Young’s modulus from its value at room temperature. The results were used to predict punching forces for the design of microscale hole punching dies and for validation of a microscale hole punching model that was created with a commercially available finite element software package, DEFORM 3D. The three parameters Yield Strength, Strength Coefficient, and Strain Hardening Exponent used in Ludwik’s equation to model flow stress of PCL in DEFORM 3D were determined to be 94.8 MPa, 210 MPa, and 0.54, respectively.