scholarly journals Mechanical Characteristics and Energy Dissipation Trends of Coal-Rock Combination System Samples with Different Inclination Angles under Uniaxial Compression

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhen Wei ◽  
Ke Yang ◽  
Xiang He ◽  
Xiaolou Chi ◽  
Xinyuan Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Energy Dissipation ◽  
Contact Surface ◽  
Mechanical Characteristics ◽  
Damage Growth ◽  
Deformation And Failure ◽  
Combination System ◽  
Inclination Angles ◽  
Coal Rock ◽  
The Difference

Coal mines are composed of multiple complex rock strata with different mechanical characteristics and energy accumulation and release performances. This implies uneven energy distribution in the coal-rock combination system (CRCS). To explore the effect of the included angle between the loading direction and the coal-rock contact surface on the mechanical properties, crack propagation mode, and energy evolution characteristics of the CRCS, the uniaxial compression tests were carried out on the CRCS samples with zero and 30° inclination angles. The obtained mechanical properties and energy dissipation trends of the tested samples were similar to those of the pure (raw) coal and rock ones but strongly depended on the inclination angles. The impact energy index of the CRCS samples was smaller than those of the pure coal and pure rock samples, and its impact tendency was less pronounced. The deformation and failure of the CRCS samples occurred in the coal part, the rock part inhibiting the development and deformation of the coal. According to the deformation and failure characteristics of the CRCS, the coal support far away from the contact surface should be strengthened in engineering practice to avoid the rock mass failure caused by the expansion and evolution of cracks in the coal part. At a 30° inclination angle, the CRCS sample was tensioned at the coal-rock contact surface, and the original cracks and pores were gradually compacted under the stress component perpendicular to the contact surface. With an increase in the inclination angle, the difference between the total energy accumulated before the peak and the released energy after the peak was reduced, and the difference between the total energy accumulated before the peak and the dissipated energy increased gradually. CRCS samples with different inclinations exhibited three damage stages: initial damage, stable damage growth, and rapid damage growth. The results obtained are considered instrumental in rockburst preventing, monitoring, and early warning under different stress environments.

scholarly journals The deformation rate, atomic mobility and mechanical properties of metals

2021 ◽  
Vol 97 (1) ◽  
pp. 28-37
Author(s):  
D.S. Gertsriken ◽  
◽  
A.M. Husak ◽  
V.F. Mazanko ◽  
S. Ye. Bogdanov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Diffusion Coefficients ◽  
Mechanical Characteristics ◽  
Radioactive Isotopes ◽  
Diffusion Welding ◽  
Magnetic Pulse ◽  
Layer By Layer ◽  
Self Diffusion ◽  
Wide Range ◽  
The Difference

The dependences of diffusion coefficients in metals with different crystal lattice (b.c.c., f.c.c., h.c.p., b.c.t.), subjected to pulse effects by different types of processing in a wide range of strain rates (10-2 - 106 s-1) without heating and at T < 0,5 Tpl. studied by m ethods based on the use of radioactive indicators 55Fe, 95Nb, 60Co, 65Zn, 63Ni, 26Al, 44Ti (layer-by-layer radiometric analysis of residual integral activity, macro- and microautoradiography). Used such types of processing as ultrasonic shock treatment, diffusion welding, shock load, magnetic pulse processing, etc. On the same materials subjected to the same types of processing, mechanical characteristics (impact strength, microhardness, tensile strength, etc.) were determined. In addition, literature data related to the determination of some mechanical characteristics in the deformation of metals at different speeds were used. It turned out that with increasing the rate of plastic deformation there is not only an increase in the mobility of atoms, but also a decrease in differences in the values of the diffusion coefficients of intrinsic atoms and other diffusers in different metals. Despite the large difference in melting temperatures, in particular zinc and niobium, their self-diffusion coefficients in the migration of atoms without heating at a rate of 106 s-1 differ only 1.5 times, while at 1 s-1 the difference in the mobility of atoms is 4 orders of magnitude. It is shown that the velocity dependences of diffusion and mechanical characteristics can be rectilinear, have extremum or inflection, but they will be approximately the same for diffusion coefficients and parameters that characterize the mechanical properties of metals under impulse loads. Establishing the type of velocity dependences for diffusion and mechanical characteristics makes it possible to determine intermediate and extrapolated values for both characteristics, as well as on the schedule of one dependence to predict the shape of the other with a certain accuracy. Keywords: radioactive isotopes, self- and heterodiffusion, pulse loads, strain rate, mechanical characteristic.

scholarly journals Study on Mechanical Properties and Energy Dissipation of Frozen Sandstone under Shock Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Lei Wang ◽  
Yue Qin ◽  
Haibin Jia ◽  
Hongming Su ◽  
Shiguan Chen
Keyword(s):  
Mechanical Properties ◽  
Energy Dissipation ◽  
Phase Change ◽  
Strain Rate ◽  
Impact Loading ◽  
Strengthening Effect ◽  
Red Sandstone ◽  
Water Ice ◽  
The Difference ◽  
Ice Phase

In order to understand the mechanical properties and energy dissipation law of frozen sandstone under impact loading, the cretaceous water-rich red sandstone was selected as the research object to conduct impact tests at different freezing temperatures (0°C, −10°C, −20°C, and −30°C). The test results suggested the following: (1) the peak stress and peak strain of frozen sandstone are positively correlated with strain rate and freezing temperature, and the strain rate strengthening effect and the low-temperature hardening effect are obvious. (2) The strain rate sensitivity of dynamic stress increase factor (DIF) is negatively correlated with temperature. Water-ice phase change and the difference in the cold shrinkage rate of rock matrix under strong impact loading will degrade the performance of rock together, so DIF is less than 1. (3) In the negative temperature range from −10°C to −30°C, DEIF is always greater than 1. The energy dissipation rate of red sandstone specimens fluctuated between 10% and 25% under the impact loading, and the data are discrete, showing obvious strain rate independence. The failure form changes from tensile failure to shear and particle crushing failure. (4) Combined with the micromechanism analysis, the difference in dynamic mechanical properties of red sandstone at different temperatures is caused by the water-ice phase change and the different cold shrinkage rates of the frozen rock medium. When the temperature drops from 0°C to −2°C, water migrates to the free space of the pore of frozen rock and freezes into ice crystal, resulting in frozen shrinkage. At −30°C, the expansion of ice dominates and the migration of water will stop, leading to frost heave.

Mechanical Properties and Energy Dissipation Characteristics of Coal–Rock-Like Composite Materials Subjected to Different Rock–Coal Strength Ratios

2021 ◽  
Vol 30 (3) ◽  
pp. 2179-2193
Author(s):  
Yongchen He ◽  
Pengxiang Zhao ◽  
Shugang Li ◽  
Chun-Hsing Ho ◽  
Sitao Zhu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Energy Dissipation ◽  
Coal Rock ◽  
Coal Strength

scholarly journals Rolling of Flat Aluminum Strips with Tailored Mechanical Properties

2016 ◽  
Vol 854 ◽  
pp. 87-92
Author(s):  
Olexandr Grydin ◽  
Serhii Bondarenko ◽  
Mykhailo Stolbchenko ◽  
Mirko Schaper
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Cold Rolling ◽  
Cross Section ◽  
Experimental Analysis ◽  
Work Hardening ◽  
Mechanical Characteristics ◽  
Tensile Tests ◽  
The Difference

In this study, the possibility of producing of flat aluminum strips with tailored mechanical properties across their width by means of rolling was examined. The aim of the work was an experimental analysis of the effect of cold rolling of the strips with a pre-profiled cross-section in flat rolls. Because of different work hardening of the various elements of the pre-profiled strips a characteristic profile of mechanical properties over the strips cross-section was created. The performed tensile tests and hardness measurements proved the possibility of setting of tailored properties in flat strips by means of rolling. The difference between the mechanical characteristics of various strip’s elements for the selected aluminum alloy can reach 40%.

Effect of silver nitrate on some mechanical properties of heat polymerizing acrylic resins

2019 ◽  
Vol 14 (1) ◽  
pp. 110
Author(s):  
Assiss. Prof. Dr. Sabiha Mahdi Mahdi ◽  
Dr. Firas Abd K. Abd K.
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Silver Nitrate ◽  
Surface Hardness ◽  
Mechanical Tests ◽  
Hardness Tester ◽  
Acrylic Resins ◽  
The Difference

Aim: The aimed study was to evaluate the influence of silver nitrate on surfacehardness and tensile strength of acrylic resins.Materials and methods: A total of 60 specimens were made from heat polymerizingresins. Two mechanical tests were utilized (surface hardness and tensile strength)and 4 experimental groups according to the concentration of silver nitrate used.The specimens without the use of silver nitrate were considered as control. Fortensile strength, all specimens were subjected to force till fracture. For surfacehardness, the specimens were tested via a durometer hardness tester. Allspecimens data were analyzed via ANOVA and Tukey tests.Results: The addition of silver nitrate to acrylic resins reduced significantly thetensile strength. Statistically, highly significant differences were found among allgroups (P≤0.001). Also, the difference between control and experimental groupswas highly significant (P≤0.001). For surface hardness, the silver nitrate improvedthe surface hardness of acrylics. Highly significant differences were statisticallyobserved between control and 900 ppm group (P≤0.001); and among all groups(P≤0.001)with exception that no significant differences between control and150ppm; and between 150ppm and 900ppm groups(P>0.05).Conclusion: The addition of silver nitrate to acrylics reduced significantly the tensilestrength and improved slightly the surface hardness.

Weldability - Behavior of Welded Reinforcement

2019 ◽  
Vol 70 (10) ◽  
pp. 3469-3472
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Mechanical Characteristics ◽  
Mechanical Performance ◽  
Current Work ◽  
Carbon Equivalent ◽  
Work Process ◽  
Ultimate Limit

Weldability involves two aspects: welding behavior of components and safety in operation. The two aspects will be reduced to the mechanical characteristics of the elements and to the chemical composition. In the case of steel reinforcing rebar’s, it is reduces to the percentage of Cech(carbon equivalent) and to the mechanical characteristics: the yielding limit, the ultimate limit, and the elongations which after that represent the ductility class in which the re-bars is framed. The paper will present some types of steel reinforcing rebar’s with its mechanical characteristics and the welding behavior of those elements. In the current work, process-related behavior of welded reinforcement, joint local and global mechanical properties, and their correlation with behavior of normal reinforcement and also the mechanical performance resulted in this type of joints. Keywords: welding behavior, ultimate limit, reinforcing rebar’s

scholarly journals Goldmann Tonometry and Corneal Biomechanics

2021 ◽  
Vol 11 (9) ◽  
pp. 4025
Author(s):  
Dario Messenio ◽  
Marco Ferroni ◽  
Federica Boschetti
Keyword(s):  
Mechanical Properties ◽  
Anterior Chamber ◽  
Pressure Transducer ◽  
Pearson Correlation ◽  
Corneal Thickness ◽  
Applanation Tonometry ◽  
In Vitro Tests ◽  
Goldmann Tonometry ◽  
The Difference

Glaucoma is the second cause of irreversible blindness in the world. Intraocular pressure (IOP) is a recognized major risk factor for the development and progression of glaucomatous damage. Goldmann applanation tonometry (GAT) is internationally accepted as the gold standard for the measurement of IOP. The purpose of this study was to search for correlations between Goldmann tonometry and corneal mechanical properties and thickness by means of in vitro tests. IOP was measured by the Goldmann applanation tonometer (GIOP), and by a pressure transducer inserted in the anterior chamber of the eye (TIOP), at increasing pressure levels by addition of saline solution in the anterior chamber of enucleated pig eyes (n = 49). Mechanical properties were also determined by inflation tests. The GAT underestimated the real measurements made by the pressure transducer, with most common differences in the range 15–28 mmHg. The difference between the two instruments, highlighted by the Bland–Altman test, was confirmed by ANOVA, normality tests, and Mann–Whitney’s tests, both on the data arranged for infusions and for the data organized by pressure ranges. Pearson correlation tests revealed a negative correlation between (TIOP-GIOP) and both corneal stiffness and corneal thickness. In conclusion, data obtained showed a discrepancy between GIOP and TIOP more evident for softer and thinner corneas, that is very important for glaucoma detection.

scholarly journals Experimental and Numerical Analysis of the Mechanical Properties of a Pretreated Shape Memory Alloy Wire in a Self-Centering Steel Brace

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 80
Author(s):  
Bo Zhang ◽  
Sizhi Zeng ◽  
Fenghua Tang ◽  
Shujun Hu ◽  
Qiang Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Energy Dissipation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Loading Rate ◽  
Effective Elastic Modulus ◽  
Maximum Energy ◽  
Numerical Results ◽  
Energy Dissipation Capacity

As a stimulus-sensitive material, the difference in composition, fabrication process, and influencing factors will have a great effect on the mechanical properties of a superelastic Ni-Ti shape memory alloy (SMA) wire, so the seismic performance of the self-centering steel brace with SMA wires may not be accurately obtained. In this paper, the cyclic tensile tests of a kind of SMA wire with a 1 mm diameter and special element composition were tested under multi-working conditions, which were pretreated by first tensioning to the 0.06 strain amplitude for 40 cycles, so the mechanical properties of the pretreated SMA wires can be simulated in detail. The accuracy of the numerical results with the improved model of Graesser’s theory was verified by a comparison to the experimental results. The experimental results show that the number of cycles has no significant effect on the mechanical properties of SMA wires after a certain number of cyclic tensile training. With the loading rate increasing, the pinch effect of the hysteresis curves will be enlarged, while the effective elastic modulus and slope of the transformation stresses in the process of loading and unloading are also increased, and the maximum energy dissipation capacity of the SMA wires appears at a loading rate of 0.675 mm/s. Moreover, with the initial strain increasing, the slope of the transformation stresses in the process of loading is increased, while the effective elastic modulus and slope of the transformation stresses in the process of unloading are decreased, and the maximum energy dissipation capacity appears at the initial strain of 0.0075. In addition, a good agreement between the test and numerical results is obtained by comparing with the hysteresis curves and energy dissipation values, so the numerical model is useful to predict the stress–strain relations at different stages. The test and numerical results will also provide a basis for the design of corresponding self-centering steel dampers.

scholarly journals Investigation of Color Reproduction on Linen Fabrics when Printing with Mimaki TX400-1800D Inkjet with Pigment TP250 Dyes

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 354
Author(s):  
Tim Tofan ◽  
Rimantas Stonkus ◽  
Raimondas Jasevičius
Keyword(s):  
Mechanical Properties ◽  
Color Reproduction ◽  
Related Effect ◽  
Color Characteristics ◽  
Fabric Density ◽  
Different Types ◽  
The Difference ◽  
Printing Parameters ◽  
Linen Fabric

The aim of this research is to investigate related effect of dyeability to linen textiles related to different printing parameters. The study investigated the change in color characteristics when printing on linen fabrics with an inkjet MIMAKI Tx400-1800D printer with pigmented TP 250 inks. The dependence of color reproduction on linen fabrics on the number of print head passes, number of ink layers to be coated, linen fabric density, and different types of linen fabric was investigated. All this affects the quality of print and its mechanical properties. The change in color characteristics on different types of linen fabrics was determined experimentally. We determine at which print settings the most accurate color reproduction can be achieved on different linen fabrics. The difference between the highest and the lowest possible number of head passages was investigated. The possibilities of reproducing different linen fabric colors were determined.

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