scholarly journals Impact of Moisture Content on the Dynamic Failure Energy Dissipation Characteristics of Sandstone

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Aihong Lu ◽  
Shanchao Hu ◽  
Ming Li ◽  
Tianzhu Duan ◽  
Bing Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Energy Dissipation ◽  
Surface Energy ◽  
Moisture Content ◽  
Rock Masses ◽  
Moisture Contents ◽  
Dry Conditions ◽  
Moisture Conditions

Rockburst frequently occurs in deep underground engineering, which poses a threat to safety and causes economic losses. Water injection into surrounding rock masses is an effective method for preventing rockburst, and the moisture content of rocks is significant for assessing the probability of rockburst. However, the majority of studies focus on the relationship between the macromechanical properties of rock masses under static loads and the moisture content of rock masses and seldom explore the impact of moisture variation (under dynamic loads) on the mechanical properties and energy dissipation. In this paper, the mechanical properties and energy dissipation of sandstone with different moisture contents have been experimentally investigated by the split Hopkinson pressure bar (SHPB) test. The test results indicate that the peak strength, dynamic elastic modulus, and unloading elastic modulus of sandstone in dry conditions are considerably larger than those in moisture conditions, and the three parameters linearly decrease as the moisture content increases from 0% to 2.58%. The distribution law of sandstone fragments with different moisture contents has been investigated by sieving test fragments with different grain sizes of grading sieves. The results show that the percentage of large grain size fragments incrementally decreases, and the percentage of small grain size fragments incrementally increases with moisture contents from 0% to 2.58%. When the moisture content ranges from 2.01%∼2.58%, the fractal dimension linearly increases, which indicates that the higher the moisture content is, the larger the dimension of the broken sandstone is. The calculation results for energy indicate that the sandstone energy attains the peak value with 0% moisture content. When the moisture content ranges from 2.01%∼2.58%, the reflected energy increases, and the transmitted energy and dissipated energy linearly decrease. In addition, the surface energy of the sandstone with different moisture contents has been investigated by converting fragments into spheres with the corresponding size. The results indicate that the smallest surface area of sandstone is obtained in dry conditions, but its surface energy in dry conditions is larger than that in moisture conditions. When the moisture ranges from 0% to 2.58%, due to 3% illite and 2% chlorite clay minerals reacting with different proportions of moisture, the surface areas of sandstone fragments linearly increase and the surface energy of sandstone linearly decreases.

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 Mechanical Properties of Grains Sorghum Subjected to Compression at Different Moisture Contents

2019 ◽  
Vol 11 (4) ◽  
pp. 279
Author(s):  
Gabrielly B. Rodrigues ◽  
Osvaldo Resende ◽  
Daniel E. C. de Oliveira ◽  
Lígia C. de M. Silva ◽  
Weder N. Ferreira Junior
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Uniaxial Compression ◽  
Deformation Modulus ◽  
Grain Sorghum ◽  
Parallel Plates ◽  
Compression Force ◽  
Moisture Contents ◽  
Rest Position ◽  
Different Temperatures

This study aimed to evaluate the influence of drying at different temperatures on the mechanical properties of grains of grain sorghum subjected to compression at the natural rest position. Grains dried at temperatures of 60, 80 and 100 °C with different moisture contents (0.515; 0.408; 0.315; 0.234; 0.162 and 0.099 (d.b.)) were subjected to uniaxial compression between two parallel plates, applied at their natural rest position, at a rate of 0.001 m s-1. The force required to rupture in grains of grain sorghum increased as their moisture contents decreased, with values of 47.17 to 78.44 N, 61.81 to 69.66 N and 52.07 to 70.89 N for the temperatures of 60, 80 and 100 °C, respectively. The compression force required to deform grain sorghum decreased with the increment in moisture content, and the proportional deformation modulus increases with moisture content reduction. Within the studied range of moisture content, the values were 87 × 10-7 to 354.99 × 10-7 Pa, 132.63 × 10-7 to 465.98 × 10-7 Pa and 80.18 × 10-7 to 429.85 × 10-7 Pa for the temperatures of 60, 80 and 100 °C, respectively.

scholarly journals Direct Correlations among the Grain Size, Texture, and Indentation Behavior of Nanocrystalline Nickel Coatings

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 188 ◽  
Author(s):  
Lu Feng ◽  
Yong-Yue Ren ◽  
Yan-heng Zhang ◽  
Shibin Wang ◽  
Linan Li
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Elastic Anisotropy ◽  
Texture Coefficient ◽  
Process Conditions ◽  
Nickel Coatings ◽  
Fundamental Relationship ◽  
Underlying Mechanisms ◽  
First Time

By using nc-Ni coatings as a model system, systematic experiments were designed to evaluate the interaction between the microstructural and mechanical properties tailored by electrodeposition conditions. A direct correlation between grain size and texture was established for the first time. The grain size of the (111) crystalline plane decreases with the texture coefficient (RTC) regardless of the process conditions, and that of the (220) plane has different trends. Then, a peculiar phenomenon is revealed that the dependence of hardness on grain size is accurately described by the Hall-Petch relationship when changing the temperature or pH, but with different slopes, while it deviates from such a relationship with changing current density, denoting more underlying mechanisms related to texture. Finally, a surprising degree of influence of texture on hardness and elastic modulus is also presented, with the overall trend of hardness increasing with texture; and when the RTC of (111) exceeds 40%, the elastic modulus increases with texture, implying a fundamental relationship between modulus and texture. Texture predominates over the other factors on the elastic modulus, revealing the importance of elastic anisotropy. Significantly, the present work suggests a useful tailoring routine to fabricate high quality nc-Ni coatings with the desired structure and mechanical properties.

Evaluating Mechanical Properties of Cement Materials by Depth-Sensing Indentation Method

2010 ◽  
Vol 44-47 ◽  
pp. 2587-2591
Author(s):  
Xiu Fang Wang ◽  
Yi Wang Bao ◽  
Kun Ming Li ◽  
Yan Qiu ◽  
Xiao Gen Liu
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Energy Dissipation ◽  
Engineering Application ◽  
Calculated Data ◽  
Absorption Capacity ◽  
Cement Industry ◽  
Depth Sensing ◽  
Indentation Method ◽  
Recovery Resistance

The energy consumption of crushing is directly affected by the mechanical properties of cement materials. The elastic modulus, energy dissipation, recovery resistance and other mechanical properties of cement materials are evaluated based on the depth-sensing indentation method in this work. It is significant and efficient for engineering application. In results, the calculated elastic modulus is close to that measured by dynamic method, being used to verify the correctness of the calculated data. And the calculated energy dissipation of clinker is higher than that of limestone and granite, which can partially be used to explain why the grinding of clinker consumes a lot of energy in cement industry. The recovery resistance of clinker is almost identical to that of granite, more than that of limestone. It is found that the clinker, in contrast to granite and limestone, exhibits better plasticity and greater energy absorption capacity.

Influence of Annealing on the Microstructure and Mechanical Properties of Electrodeposited Nanocrystalline Nickel

2011 ◽  
Vol 683 ◽  
pp. 103-112 ◽  
Author(s):  
B. Yang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Grain Boundary ◽  
Boundary Structure ◽  
Boundary State ◽  
Microstructure And Mechanical Properties ◽  
Grain Boundary Structure ◽  
Average Grain Size ◽  
Different Grain Size

The evolution of the microstructure and mechanical properties of electrodeposited nanocrystalline Ni with different annealing procedures was studied systematically. For the annealed specimens hardness decreases with increasing average grain size but the dependence changes at different grain size ranges. The specimens annealed at a low temperature show higher hardness compared to the as-deposited nanocrystalline Ni, despite an increased measured average grain size. In association with this hardening an increase in elastic modulus and a decrease in microstrain was observed after annealing. With increasing annealing temperature both the tensile strength and the fracture strain were observed to decrease, this is companied with a transition from ductile to brittle in the fracture surfaces. These results indicated that the mechanical behaviour of nanocrystalline Ni depends not only on the average grain size but also on the grain boundary structure. A change in the grain boundary state arising from annealing may be responsible for the observed increase in hardness and elastic modulus as well as the deterioration of tensile properties.

Moisture Sorption Behavior, and Effect of Moisture Content and Sorbitol on Thermo-Mechanical and Barrier Properties of Pectin Based Edible Films

2007 ◽  
Vol 3 (4) ◽  
Author(s):  
Neda Maftoonazad ◽  
Hosahalli S. Ramaswamy ◽  
Michele Marcotte
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Moisture Content ◽  
Moisture Sorption ◽  
Water Vapor Permeability ◽  
Edible Films ◽  
Vapor Permeability ◽  
Sorption Behavior ◽  
Intermediate Water ◽  
Moisture Contents

The moisture sorption behavior of pectin films formulated with different sorbitol content was evaluated and films with different equilibrium moisture contents were obtained. Different models were used to describe the moisture sorption isotherms (MSI) of pectin films, sorbitol and pectin powder. Based on changes observed in MSI, sorbitol was found to strongly interact with pectin polymers. Incorporation of sorbitol in pectin films resulted in lower equilibrium moisture contents at low to intermediate water activities (aw), but much higher moisture contents at aw > 0.53. Estimates of monolayer moisture values (1.53 – 3.81 g H2O kg-1 solids) were obtained by the application of Guggenheim-Anderson-DeBoer (GAB) model. A differential mechanical analyzer (DMA) was used for mechanical properties of formulated films while a differential scanning calorimeter (DSC) was used for thermal properties and glass transition temperature (Tg). With both DMA and DSC tests, the strong plasticizing action of water and sorbitol was evident. Tg vs. moisture content data were successfully fitted to the Fox empirical model. Multi-frequency DMA measurements provided estimates for the apparent activation energy (Ea) of the second glass transition in the range of 131-184 kJ/mol; the values for Ea decreased with increasing sorbitol concentration. Water vapor permeability (WVP) and mechanical properties of the films were also analyzed under varying sorbitol and moisture contents. Increasing moisture or addition of sorbitol to pectin films increased the elongation at break, but decreased the tensile strength, modulus of elasticity and Tg, and increased WVP of the films.

Some Physical and Mechanical Properties of Sugarcane Trash Relating to the Criteria Design of a Sugarcane Trash Chopping Machine

2014 ◽  
Vol 931-932 ◽  
pp. 1574-1581
Author(s):  
Nirattisak Khongthon ◽  
Somposh Sudajan
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Coefficient Of Friction ◽  
Physical And Mechanical Properties ◽  
Unit Weight ◽  
Shearing Force ◽  
Moisture Contents ◽  
The Mean ◽  
Static Coefficient Of Friction ◽  
Static Coefficient

The physical and mechanical properties of sugarcane leaves were necessary for the design consideration of the relating storage, handling and processing equipment. The sugarcane trash at moisture contents of 23.40 and 73.91 % w.b. were used for this study. The mean length and unit weight of sugarcane trashes were 168.63 cm and 65.87 grams respectively. The average number of leaf of each sample was 4. The mean diameter of the thrash top, width and thickness increased with the increase of moisture from 23.40 and 73.91 % w.b.. The average leaf angles (β) relative to the horizontal plane of the first left leaf, second left leaf, first right leaf and second right leaf were 65.10, 73.36, 71.07 and 78.26 degrees for 73.91 % w.b., and 66.33, 73.50, 67.50 and 75.83 degrees for 23.40 % w.b. respectively. When the moisture content increased from 23.40 to 73.91% w.b., the static coefficient of friction increased from 0.30 to 0.43, 0.38 to 0.41, 0.30 to 0.37 and 0.54 to 0.66 for plywood, mild steel, galvanized iron and rubber plate respectively. The least static coefficient of friction occurred on the galvanized iron plate. The results from experimenting on mechanical properties showed that the maximum shearing force increased with the increase in moisture content from 23.40 to 73.91% w.b. respectively. The maximum shearing force was 360.15 and 457.32 N for moisture contents of 23.40 and 73.91% w.b.. The maximum tensile force decreased toward upper region of the leaf for both 23.40 and 73.91% w.b.. The results of this study would be useful for the design and optimization of the equipment associated with harvesting, threshing, chopping and processing.

Effect of Microstructure on Mechanical Properties and Wear Characteristics of Cemented Tungsten Carbides

2009 ◽  
Vol 76-78 ◽  
pp. 609-612 ◽  
Author(s):  
H.Q. Sun ◽  
Rudy Irwan ◽  
Han Huang ◽  
Gwidon W. Stachowiak
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Friction Coefficient ◽  
Tungsten Carbide ◽  
Removal Rate ◽  
Tungsten Carbides ◽  
Removal Rates ◽  
Wear Characteristics ◽  
Effect Of Microstructure

The effect of microstructure of cemented tungsten carbide materials on their mechanical properties and wear characteristics was investigated using nanoindentation and nanoscratch methods. The results indicated that the variation in grain size insignificantly affected the hardness, elastic modulus and friction coefficient of the work materials, but considerably influenced their removal rates. The carbide with coarser grains exhibited a much higher removal rate was obtained during scratching.

Correlation of the Coefficient of Adhesion With Various Physical and Mechanical Properties of Metals

1963 ◽  
Vol 85 (2) ◽  
pp. 279-285 ◽  
Author(s):  
M. E. Sikorski
Keyword(s):  
Crystal Structure ◽  
Mechanical Properties ◽  
Elastic Modulus ◽  
Surface Energy ◽  
Work Hardening ◽  
Physical And Mechanical Properties ◽  
Atomic Volume ◽  
Recrystallization Temperature ◽  
Bonding Method

The coefficients of adhesion determined by a modification of the twist-compression bonding method are compared with the following properties of metals: crystal structure, hardness, surface energy, elastic modulus, work-hardening properties, recrystallization temperature, purity, and atomic volume. Conclusions are reached regarding the desirable characteristics of metals, or combinations of metals, for antifriction applications.

scholarly journals Mechanical Properties of Gelcast Cerium Dioxide From 23 to 1500 °C

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Stephen J. Sedler ◽  
Thomas R. Chase ◽  
Jane H. Davidson
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Elastic Modulus ◽  
Flexural Strength ◽  
Cerium Dioxide ◽  
Porous Ceramic ◽  
Specimen Size ◽  
Strength Data ◽  
Lower Porosity ◽  
Solid Area

This work reports the elastic modulus and four-point flexural strength of a gelcast ceramic, cerium dioxide (ceria), with a microporosity of nominally 20% and a grain size of 11 μm from 23 to 1500 °C. The data augment the sparse data published for ceria and extend previous results by 150 °C. The ceria tested is representative of that constituting the ligaments of a reticulated porous ceramic. The elastic modulus decreases from 90 GPa at 23 °C to 16 GPa at 1500 °C. The flexural strength is 78 MPa below 900 °C and then decreases rapidly to 5 MPa at 1500 °C. These trends are consistent with data reported for other ceramics. Comparing the measured elastic modulus to prior data obtained for lower porosity shows the minimum solid area (MSA) model can be used to extend the modulus data to other porosities. Similarly, the flexural strength data agree with prior data when the effects of specimen size, porosity, and grain size are taken into account.

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