Study on Characteristics of Energy for Hard Roof Fracture in Island Workface

2013 ◽  
Vol 734-737 ◽  
pp. 694-697
Author(s):  
Xu Feng Pang ◽  
Ke Xue Zhang
Keyword(s):  
Strain Energy ◽  
Typical Case ◽  
Energy Characteristics ◽  
Hard Roof ◽  
Coal Bump ◽  
Bending Strain ◽  
Before And After ◽  
Mechanical Models

According to the characteristics of the island workface with hard roof, various mechanical models of hard roof in island workface are established, to analyze energy characteristics of hard roof before and after the first fracture in island workface with all round gobs, derived their simplified formulas of bending strain energy for hard roof before and after the first fracture, and using these formulas to estimate the bending strain energy for the typical case of coal bump, reveals the energy cause of coal bump and verify the validity of these formulas.

Helical Domain Patterns in Tube Configurations: Effect of Geometry Length Scales

2011 ◽  
Vol 172-174 ◽  
pp. 1090-1095 ◽  
Author(s):  
R.H. Zhou ◽  
Qing Ping Sun
Keyword(s):  
Strain Energy ◽  
Optical Measurement ◽  
Strong Support ◽  
Martensite Phase ◽  
Helical Domain ◽  
Self Organized ◽  
Bending Strain ◽  
Strain Martensite ◽  
Tube Geometry

Superelastic NiTi polycrystalline tubes, when subjected to quasi-static stretching, transform from an initial austenite phase to a high-strain martensite phase by the formation and growth of a macroscopic self-organized helical domain as deformation progresses. This paper performed an experimental study on the effects of the externally applied stretching and tube geometry (length L, wall-thickness h and tube radius R) on the martensitic helical domains in the tubes under very slow (isothermal) stretching. The evolution of the helical domains with the applied strain in different tube geometries are quantified by in-situ optical measurement. We demonstrate that the shape of the self-organized helical domain and its evolution are governed by the competition between bending strain energy and domain front energy in minimizing the total energy of the tube system. The former favors a long slim helical domain, while the latter favors a short fat helical domain. The experimental results provide a strong support to the recently developed theoretical relationship.

Infrastructure Sustainability

2011 ◽  
pp. 186-201
Author(s):  
Hoi Wai Shih ◽  
David Thambiratnam ◽  
Tommy Chan
Keyword(s):  
Energy Method ◽  
Strain Energy ◽  
Health State ◽  
Modal Strain Energy ◽  
Structural Health ◽  
Modal Strain Energy Method ◽  
Modal Flexibility ◽  
Before And After ◽  
Composite Bridges ◽  
Strain Energy Method

Assessing the structural health state of urban infrastructure is crucial in terms of infrastructure sustainability. This chapter uses dynamic computer simulation techniques to apply a procedure using vibration-based methods for damage assessment in multiple-girder composite bridges. In addition to changes in natural frequencies, this multi-criteria procedure incorporates two methods, namely, the modal flexibility and the modal strain energy method. Using the numerically simulated modal data obtained through finite element analysis software, algorithms based on modal flexibility and modal strain energy change, before and after damage, are obtained and used as the indices for the assessment of structural health state. The feasibility and capability of the approach is demonstrated through numerical studies of a proposed structure with six damage scenarios. It is concluded that the modal strain energy method is capable of application to multiple-girder composite bridges, as evidenced through the example treated in this chapter.

Multistable Behavior of Compliant Kaleidocycles

2015 ◽  
Author(s):  
Thomas A. Evans ◽  
Brett G. Rowberry ◽  
Spencer P. Magleby ◽  
Larry L. Howell
Keyword(s):  
Strain Energy ◽  
Stable Equilibrium ◽  
Compliant Mechanisms ◽  
Neutral Stability ◽  
Energy Characteristics ◽  
Continuous Rotation

We present an analysis of the compliant kaleidocycle, a mechanism which, unlike other compliant mechanisms, may undergo continuous rotation. We analyze the strain energy characteristics of this mechanism during its motion and show that by varying the stiffness and orientation of the flexures, kaleidocycles may be designed to achieve customizable multistable behavior. These devices may be designed to include up to four distinct stable equilibrium positions and may also include regions of neutral stability.

Structural Multi-Damage Identification Based on Modal Strain Energy Equivalence Index Method

2014 ◽  
Vol 14 (07) ◽  
pp. 1450028 ◽  
Author(s):  
Hui Yong Guo ◽  
Zheng Liang Li
Keyword(s):  
Energy Dissipation ◽  
Structural Damage ◽  
Strain Energy ◽  
Damage Identification ◽  
Index Method ◽  
Modal Strain Energy ◽  
Energy Equivalence ◽  
Before And After ◽  
Accurate Expression ◽  
Equivalence Theory

In order to solve structural multi-damage identification problems, a damage detection method based on modal strain energy equivalence index (MSEEI) is presented. First, an accurate expression of modal strain energy (MSE) before and after damage occurs is given. Then, according to the energy equivalence theory that the change in MSE caused by the damage should be equivalent to the energy dissipation caused by the same damage, an energy equivalence equation is deduced. Finally, four roots of the energy equivalence equation are found and a MSEEI is obtained from the four roots. Simulation results demonstrate that the proposed MSEEI method can identify structural damage locations and extent with good accuracy. Identification precision of the proposed method is clearly better than that of the modal strain energy dissipation ratio index (MSEDRI) method.

Damage Detection of Surface Crack in Composite Quasi-Isotropic Laminate Using Modal Analysis and Strain Energy Method

2006 ◽  
Vol 306-308 ◽  
pp. 757-762 ◽  
Author(s):  
Hui Wen Hu ◽  
Bor Tsuen Wang ◽  
Cheng Hsin Lee
Keyword(s):  
Damage Detection ◽  
Modal Analysis ◽  
Surface Crack ◽  
Strain Energy ◽  
Differential Quadrature Method ◽  
Damage Index ◽  
Mode Shapes ◽  
Cutting Machine ◽  
Before And After ◽  
Energy Formula

This paper presents a damage detection of surface crack in composite laminate. Carbon/epoxy composite AS4/PEEK was used to fabricate a quasi-isotropic laminate [0/90/±45]2s. Surface crack was created by using laser cutting machine. Modal analysis was performed to obtain the mode shapes of the laminate before and after damage. The mode shapes were then adopted to compute the strain energy, which was used to define a damage index. Consequently, the damage index successfully predicted the location of surface crack in the laminate. Differential quadrature method (DQM) was introduced to calculate the partial differential terms in strain energy formula.

scholarly journals Stressing State Analysis on a Single Tube CFST Arch Under Spatial Loads

2019 ◽  
Vol 9 (23) ◽  
pp. 5039
Author(s):  
Kangkang Yang ◽  
Jian Yuan ◽  
Jun Shi ◽  
Kaikai Zheng ◽  
Jiyang Shen
Keyword(s):  
Strain Energy Density ◽  
Strain Energy ◽  
Characteristic Curve ◽  
Arch Model ◽  
Average Strain ◽  
Bending Strain ◽  
Strain Data ◽  
Internal Forces ◽  
Arch Structures ◽  
Behavior Characteristics

This paper analyzes the stressing state characteristics of a concrete-filled steel tubular (CFST) arch model under spatial loads, using the method of modeling structural stressing state and the thin plate simulating interpolation (TSI) method. Firstly, the parameter-generalized strain energy density (GSED) is applied to model the stressing state of the arch. Then, the normalized GSED sum at each load plots the characteristic curve. The characteristic loads P (66 kN) and Q (85 kN) in the curve are distinguished by the Mann–Kendall (M–K) criterion. To characterize structural axial and bending stressing states, the parameters of the sectional average strain and generalized bending strain are proposed as stressing state submodes. Finally, the TSI method is used to interpolate strain data for deep analysis of internal forces. By modeling the structural stressing state, the working behavior characteristics of arch structures are greatly revealed in a particular view and the results could provide a reference for the development of bridge design.

Fracability evaluation of lacustrine shale by integrating brittleness and fracture toughness

2019 ◽  
Vol 7 (2) ◽  
pp. T363-T372
Author(s):  
Cheng Huang ◽  
Chao Yang ◽  
Feng Shen
Keyword(s):  
Fracture Toughness ◽  
Plastic Strain ◽  
Strain Energy ◽  
Evaluation Method ◽  
Peak Stress ◽  
Brittleness Index ◽  
Before And After ◽  
Lacustrine Shale ◽  
The Difference ◽  
The Impact

Rock brittleness and fracture toughness are important parameters for evaluating rock fracability. The stress-strain curves indicate that the lacustrine shale is strongly brittle. Brittle failure occurs rapidly when the stress of the lacustrine shale reaches its peak value. In addition, the lacustrine shale has different plastic strains before and after peak stress; this can relax the stress concentration of the crack tips. Therefore, the plastic strain that occurs before and after the peak stress can cause decreasing brittleness, which can be used to distinguish the brittleness and fracability in the formation of the lacustrine shale clearly. Moreover, this further enlarges the difference in the brittleness index. Based on the influence of plastic strain on brittleness, we have developed a new brittleness evaluation method that uses the ratio of linear elastic strain energy to the total strain energy before complete rock failure, which can indicate the difference of the lacustrine shale clearly. Fracture toughness is another important parameter that impacts the fracture extension and influences fracability. Based on the impact of brittleness and fracture toughness on the fracability, we have developed a new fracability evaluation method. The brittleness index increases with increases in the quartz content, and it decreases with increases in the albite feldspar and calcite contents. The fracture toughness decreases with increases in the quartz and clay contents, and it increases with increases in the siderite content. In addition, we established an empirical formula that can evaluate the brittleness index and the fracture toughness using mineral contents obtained from elemental logging. Using the new fracability evaluation method to optimize the fracturing stage, the preliminary field test indicates that the new approach was effective in the lacustrine shale formation.

Post-Buckling Analysis of a Uniform Self-Weight Beam with Application to Catenary Riser

2019 ◽  
Vol 19 (04) ◽  
pp. 1950047 ◽  
Author(s):  
Ong-Art Punjarat ◽  
Somchai Chucheepsakul
Keyword(s):  
Axial Force ◽  
Strain Energy ◽  
Equilibrium Configuration ◽  
Virtual Work ◽  
Beam Theory ◽  
Energy Functional ◽  
Arc Length ◽  
Bending Strain ◽  
Highly Nonlinear ◽  
Post Buckling

This paper focused on a simply supported beam under uniform self-weight, subjected to an axial force at the roller end. The principle of virtual work-energy was used to formulate the equation for the nonlinear deformation of the beam, which involves the bending strain energy, the virtual work due to self-weight, and the virtual work of the axial force applied at the free-sliding roller end. The work–energy functional was expressed in terms of the arc-length coordinate. The functional vanished, yielding the static equilibrium configuration of the beam — a highly nonlinear problem. Finite element and Newton–Raphson iterative methods were used to solve the problem. The beam theory was extended to large sag analysis of a catenary riser. With this, some interesting features of the various configurations of the catenary riser under various end forces were evaluated.

Enhanced production of magnesium silicates from strained magnesia

1965 ◽  
Vol 35 (269) ◽  
pp. 177-188 ◽  
Author(s):  
W. F. Bush ◽  
W. O. Williamson
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Strain Energy ◽  
Free Energies ◽  
Hydrated Silica ◽  
Enhanced Production ◽  
Before And After ◽  
Magnesium Silicates ◽  
The Difference

SummaryMechanically strained, in contrast to annealed, MgO produced greater yields of forsterite and protoenstatite by solid-state reaction with a quartz–cristobalite mixture at 1200–1400° C. The specific surfaces of the strained and of the annealed MgO were similar. The strained MgO was more hygroscopic and similarity of the surface free energies was thus unlikely. The difference in the amounts of silicates produced from the two types of MgO decreased as the temperatures of synthesis increased. This was ascribed to loss of strain energy by unavoidable annealing before and after these temperatures had been reached.Similar results were obtained when hydrated silica was substituted for the quartz-eristobalite mixture, but more forsterite was produced.

scholarly journals Analysis of Mudstone Fracture and Precursory Characteristics after Corrosion of Acidic Solution Based on Dissipative Strain Energy

2021 ◽  
Vol 13 (8) ◽  
pp. 4478
Author(s):  
Dong Xu ◽  
Yu Wu ◽  
Kewang Cao ◽  
Naseer Muhammad Khan ◽  
Sajjad Hussain ◽  
...  
Keyword(s):  
Strain Energy ◽  
Acidic Solution ◽  
Ph Value ◽  
Rate Of Change ◽  
Chemical Solution ◽  
Solution Ph ◽  
Energy Characteristics ◽  
Chemical Corrosion ◽  
Rock Samples ◽  
Failure Precursor

The deformation and failure of rock materials are closely related to the strain energy characteristics during the loading process. These strain energy characteristics and rock properties are greatly affected when the rock is subjected to the acidic solution. To study the effects of chemical solutions with different pH on the mechanical properties and strain energy mechanism of mudstone, the chemical corrosion mudstone samples are subjected to a uniaxial loading testing machine (CN64 electro-hydraulic servo). The corrosive effects of the acidic solution on the porosity, strain energy characteristics, and failure mode of mudstone samples were thoroughly investigated. The findings of this research indicate that: (1) The rate of change in the porosity and chemical damage coefficient of rock samples after chemical corrosion decreases, which is closely linear with the increase of solution pH; (2) The total strain energy, elastic strain energy, and dissipative strain energy decrease with the increase of pH, and, as a result, it is proposed that the observed turning point of the proportion curve of dissipated strain energy from decline to rise is used as a precursor point of the rock failure; (3) The stress value of the failure precursor point increases and the strain value decreases with the increase in pH value. However, the ratio of the stress value of the failure precursor point to the peak stress hardly changes with pH value, and its value is about 0.883; and (4) Rock samples soaked in a weak acidic chemical solution (pH 7.3 and 5.3) are damaged by tensile crack, while rock samples soaked in a strong acidic chemical solution (pH 3.3 and 1.3) are mainly damaged by the combination of tensile and shear. The findings of this study can be used to provide an experimental and theoretical foundation for monitoring rock engineering disasters such as slope, tunnel, and coal mine failures.

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