scholarly journals Dynamic Behavior and Energy Evolution Characteristic of Deep Roadway Sandstone Containing Weakly Filled Joint at Various Angles

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Qinyong Ma ◽  
Qingqing Su ◽  
Pu Yuan
Keyword(s):  
Plastic Deformation ◽  
Energy Release ◽  
Elastic Deformation ◽  
Joint Angle ◽  
Deformation Modulus ◽  
Peak Strain ◽  
Energy Evolution ◽  
Absorbed Energy ◽  
Filled Joint ◽  
Dynamic Compressive Strength

Dynamic impact tests were carried out by implying split-Hopkinson pressure bar (SHPB) apparatus under three-dimensional stress state to investigate the influences of weakly filled joint at seven kinds of angles on dynamic behavior and energy evolution characteristic of deep roadway sandstone (985 m below the surface). The results indicated that rebound strain phenomenon was obvious and the growth rate of stress was in two kinds of phased variations. Dynamic peak strain was inversely proportional to joint angle under three different strain rates. Dynamic compressive strength, elastic deformation modulus, and plastic deformation modulus were in similar variable tendencies with incremental joint angles, showing firstly decrease to minimum value at joint angle of 45° and then increase to maximum value at joint angle of 90°. Moreover, the sensitivity of plastic deformation modulus to joint angle was obviously inferior to that of elastic deformation modulus when joint angle increased from 0° to 45°. Furthermore, both elastic deformation modulus and plastic deformation modulus were independent of strain rate, which was contrary to dynamic compressive strength and dynamic peak strain. Additionally, absorption energy release rate was introduced and defined to describe energy release and conversion characteristics of joint specimens. The changed trend of energy reflection coefficient was completely opposite to that of energy transmission coefficient and absorbed energy release rate. Absorbed energy density was linearly decreased with incremental joint angle and was increased with the increase of strain rate.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

Effect of Plastic Deformation on the Strain Energy Release Rate in a Centrally Notched Plate Subjected to Uniaxial Tension

1966 ◽  
Vol 88 (1) ◽  
pp. 82-86 ◽  
Author(s):  
R. G. Forman
Keyword(s):  
Plastic Deformation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Uniaxial Tension ◽  
Correction Factor ◽  
Release Rate ◽  
Strain Energy ◽  
Strain Energy Release Rate ◽  
Strain Energy Release ◽  
Linear Elastic

This paper presents theoretical studies on the effect of plastic deformation on the strain energy release rate, G, of a plate under uniaxial tension with a central propagating crack. The linear elastic fracture mechanics solution for G is improved by using the Dugdale model for the crack and yielded region to obtain the axial rigidity of the plate. The axial rigidity is then used to obtain the solution for the strain energy release rate as the crack propagates. It is found that plastic deformation has a pronounced effect on G. A correction factor is presented for correcting the linear elastic solution for the strain energy release rate. The correction factor is found to depend upon the nominal (gross) stress to material yield stress ratio and the crack length to plate width ratio.

PALEO: Plastically Annealed Lamina Emergent Origami

2018 ◽  
Author(s):  
Yves Klett
Keyword(s):  
Plastic Deformation ◽  
Elastic Deformation ◽  
Deformation Potential ◽  
Flat Sheet

Origami is usually folded from a flat sheet of material. Folding mostly works by introduction of plastic deformation into that sheet, resulting in a permanently altered region, viz., the crease. Lamina emergent mechanisms also start by definition from the flat state, but make use of compliant elements to provide mobility by elastic deformation. We introduce a combination of origami tessellations with LEM elements that are annealed in a (partially) collapsed state and retain this shape afterwards, while still offering the elastic deformation potential in the annealed shape. A number of such Plastically Annealed Lamina Emergent Origami structures or PALEOs have been successfully designed and tested.

scholarly journals Achievements in Micromagnetic Techniques of Steel Plastic Stage Evaluation

2020 ◽  
Vol 20 (1) ◽  
pp. 16-55 ◽  
Author(s):  
M. F. de Campos
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Elastic Deformation ◽  
Magnetic Measurements ◽  
Soft Magnetic Materials ◽  
Hysteresis Curve ◽  
Hole Drilling ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
The Difference

AbstractThe investigation of plastic deformation and residual stress by non-destructive methods is a subject of large relevance for the industry. In this article, the difference between plastic and elastic deformation is discussed, as well as their effects on magnetic measurements, as hysteresis curve and Magnetic Barkhausen Noise. The residual stress data can be obtained with magnetic measurements and also by the hole drilling method and x-ray diffraction measurements. The residual stress level obtained by these three different methods is different, because these three techniques evaluate the sample in different depths. Effects of crystallographic texture on residual stress are also discussed. The magnetoelastic term should be included in micromagnetic methods for residual stress evaluation. It is discussed how the micromagnetic energy Hamiltonian should be expressed in order to evaluate elastic deformation. Plastic deformation can be accounted in micromagnetic models as a term that increases the coercive field in soft magnetic materials as the steels are.

scholarly journals Связь макроскопических характеристик твердого тела с энергией связи иона в решетке металлов

2021 ◽  
Vol 63 (7) ◽  
pp. 825
Author(s):  
К.М. Ерохин ◽  
Н.П. Калашников
Keyword(s):  
Binding Energy ◽  
Elastic Deformation ◽  
Sound Speed ◽  
Simple Formula ◽  
Characteristic Temperature ◽  
Deformation Modulus ◽  
Debye Characteristic Temperature ◽  
Individual Atom ◽  
The Relationship ◽  
Macroscopic Parameters

Abstract: The paper examines the relationship between the macroscopic parameters, such as the Young's modulus in the Hooke's law, the sound speed and the Debye characteristic temperature, with the binding energy of an individual atom. A formula for calculating the elastic deformation modulus is proposed. A simple formula is obtained to calculate the sound speed in a metal rod. It is suggested that the Debay characteristic temperature is connected with the binding energy of the ion in the solid lattice.

Experimental evaluation of fracture properties of bovine hip cortical bone using elastic–plastic fracture mechanics

2021 ◽  
pp. 1-10
Author(s):  
Waseem Ur Rahman ◽  
Rafiullah khan ◽  
Noor Rahman ◽  
Ziyad Awadh Alrowaili ◽  
Baseerat Bibi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Fracture Mechanics ◽  
Cortical Bone ◽  
Elastic Deformation ◽  
Compact Tension ◽  
J Integral ◽  
Elastic Plastic ◽  
American Society ◽  
Fracture Specimens

BACKGROUND: Understanding the fracture mechanics of bone is very important in both the medical and bioengineering field. Bone is a hierarchical natural composite material of nanoscale collagen fibers and inorganic material. OBJECTIVE: This study investigates and presents the fracture toughness of bovine cortical bone by using elastic plastic fracture mechanics. METHODS: The J-integral was used as a parameter to calculate the energies utilized in both elastic deformation (Jel) and plastic deformation (Jpl) of the hipbone fracture. Twenty four different types of specimens, i.e. longitudinal compact tension (CT) specimens, transverse CT specimens, and also rectangular unnotched specimens for tension in longitudinal and transverse orientation, were cut from the bovine hip bone of the middle diaphysis. All CT specimens were prepared according to the American Society for Testing and Materials (ASTM) E1820 standard and were tested at room temperature. RESULTS: The results showed that the average total J-integral in transverse CT fracture specimens is 26% greater than that of longitudinal CT fracture specimens. For longitudinal-fractured and transverse-fractured cortical specimens, the energy used in the elastic deformation was found to be 2.8–3 times less than the energy used in the plastic deformation. CONCLUSION: The findings indicate that the overall fracture toughness measured using the J-integral is significantly higher than the toughness calculated by the stress intensity factor. Therefore, J-integral should be employ to compute the fracture toughness of cortical bone.

Ductile deformation and microstructures

2021 ◽  
pp. 58-85
Author(s):  
Jean-Luc Bouchez ◽  
Adolphe Nicolas
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Elastic Deformation ◽  
Applied Stress ◽  
Deformation Mechanism ◽  
Chemical Elements ◽  
Shear Zones ◽  
Ductile Deformation ◽  
Deformation Mechanisms ◽  
Solid Materials

In contrast to the elastic deformation, which is reversible, usually neglected by field geologists but important for geophysicists working in seismology, ductile deformation is irreversible. This chapter is restricted to solid materials. Materials containing a melt fraction will be examined in Chapter 7. In the geological literature, ‘ductile’ is often used as a synonym for ‘plastic’. The latter is rather used, and will be used to specify deformation mechanisms that dominantly involve the action of dislocations. In contrast to brittle deformation, which by essence is discontinuous and highly localized (see Chapter 3), ductile deformation is generally continuous and affects large volumes of rock. However, ductile deformation may be concentrated into restricted rock volumes (or domains). Such localization is common in shear zones and/or when superplastic deformation mechanism is involved. Plastic deformation mechanisms naturally depend on temperature, magnitude of the applied stress, mineral nature and grain-size of the rocks. In upper parts of the crust, fluids are able to carry chemical elements over large distances and influence the deformation mechanisms. Micrographs of several microstructural types as well as deformation maps for olivine and calcite are given at the end of this chapter.

scholarly journals Blasting-Induced Permeability Enhancement of Ore Deposits Associated with Low-Permeability Weakly Weathered Granites Based on the Split Hopkinson Pressure Bar

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Lei Yan ◽  
Wenhua Yi ◽  
Liansheng Liu ◽  
Jiangchao Liu ◽  
Shenghui Zhang
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Deformation Modulus ◽  
Constant Speed ◽  
Initial Porosity ◽  
Peak Strain ◽  
Variable Speed ◽  
Hopkinson Pressure Bar ◽  
Impact Compression ◽  
Split Hopkinson ◽  
Pressure Bar

By utilizing the improved split Hopkinson pressure bar (SHPB) test device, uniaxial, constant-speed cyclic, and variable-speed cyclic impact compression tests were conducted on weakly weathered granite samples. By combining nuclear magnetic resonance (NMR) and triaxial seepage tests, this study investigated the change laws in the mechanical properties, porosity evolution, and permeability coefficients of the samples under cyclic impacts. The results showed that in constant-speed cyclic impacts with increasing impact times, deformation modulus decreased, whilst porosity firstly decreased and then increased. Furthermore, dynamic peak strength firstly increased and then decreased whereas peak strain constantly increased before failure of the samples. In the variable-speed cyclic impacts, as impact times increased, deformation modulus firstly increased and then declined with damage occurring after four impact times. The compaction process weakened and even disappeared with increasing initial porosity. Three types of pores were found in the samples that changed in multiscale under cyclic loading. In general, small pores extended to medium- and large-sized pores. After three variable-speed cyclic impacts, the porosity of the samples was larger than the initial porosity and the permeability coefficient was greater than its initial value. The results demonstrate that the purpose of enhancing permeability and keeping the ore body stable can be achieved by conducting three variable-speed cyclic impacts on the samples.

scholarly journals Research on the Dynamic Mechanical Properties and Energy Dissipation of Expansive Soil Stabilized by Fly Ash and Lime

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Sheng-quan Zhou ◽  
Da-wei Zhou ◽  
Yong-fei Zhang ◽  
Wei-jian Wang ◽  
Dongwei Li
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Expansive Soil ◽  
Dynamic Mechanical Properties ◽  
Test Results ◽  
Absorbed Energy ◽  
Dynamic Mechanical ◽  
Stabilized Soil ◽  
Dynamic Compressive Strength

To probe into the dynamic mechanical properties of expansive soil stabilized by fly ash and lime under impact load, the split-Hopkinson pressure bar (SHPB) test was carried out in this study. An analysis was made on the dynamic mechanical property and final fracture morphology of stabilized soil, and the failure mechanism was also explored from the perspective of energy dissipation. According to the test results, under the impact pressure of 0.2 MPa, plain soil and pure fly ash-stabilized soil exhibit strong plasticity. After the addition of lime, the stabilized soil shows obvious brittle failure. The dynamic compressive strength and absorbed energy of stabilized soil first increase and then decrease with the change of mix proportions. Both the dynamic compressive strength and the absorbed energy reach the peak value at the content of 20% fly ash and 5% lime (20% F + 5% L). In the process of the test, most of the incident energy is reflected back to the incident bar. The absorbed energy of stabilized soil increases linearly with the rise of dynamic compressive strength, while the absorbed energy is negatively correlated with the fractal dimension. The fractal dimension of pore morphology of the plain soil is lower than that of the fly ash-lime combined stabilized soil when it comes to the two different magnification ratios. The test results indicate that the modifier content of 20% F + 5% L can significantly improve the dynamic mechanical properties of the expansive soil.

scholarly journals Effect of Heating Rate on the Dynamic Compressive Properties of Granite

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Ronghua Shu ◽  
Tubing Yin ◽  
Xibing Li
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Heating Rate ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Quadratic Function ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Compressive Properties ◽  
Dynamic Compressive Strength

Variation in the heating rate due to different geothermal gradients is a cause of much concern in underground rock engineering such as deep sea and underground tunnels, nuclear waste disposal, and deep mining. By using a split Hopkinson pressure bar (SHPB) and variable-speed heating furnace, the dynamic compressive properties of granite were obtained after treatments at different heating rates and temperatures; these properties mainly included the dynamic compressive strength, peak strain, and dynamic elastic modulus. The mechanism of heating rate action on the granite was simultaneously analyzed, and the macroscopic physical properties were discussed. The microscopic morphological features were obtained by scanning electron microscopy (SEM), and the crack propagation was determined by high-speed video camera. The experimental results show that the dynamic compressive strength and elastic modulus both show an obvious trend of a decrease with the increasing heating rate and temperature; the opposite phenomenon is observed for the peak strain. The relationships among the dynamic compressive properties and temperature could be described by the quadratic function. The ductility of granite is enhanced, and the number and size of cracks increase gradually when the heating rate and temperature increase. The microstructure of rock is weakened by the increased thermal stress, which finally affects the dynamic compressive properties of rock.

Sign in / Sign up

Export Citation Format

Share Document