Thermal Cracking Meso-Characteristic of LuHui Granite

2010 ◽  
Vol 34-35 ◽  
pp. 355-359
Author(s):  
Yuan Zhang ◽  
Yang Sheng Zhao
Keyword(s):  
Quantitative Analysis ◽  
Narrow Range ◽  
Thermal Cracking ◽  
Thermal Crack ◽  
Rock Crystal ◽  
Thermal Cracks ◽  
Micro Cracks ◽  
Crystal Grains

Rock macro mechanic character is decided by rock composite and meso configuration. LuHui granite minerals composite, micro configuration and the rock thermal cracking in differ temperature are observed by micro-photometer in meso. LuHui granite is composited by kinds of minerals, and its minerals’ inhomogeneity is visible, the change of cementation among rock crystal grains, dislocation and micro cracking in crystal is produced in crystal grains under temperature. By means of experiment, the development of granite micro cracks and interior configuration, and change laws of micro cracks were observed. The quantitative analysis of the micro mechanism and laws of granite thermal crack was made, granite cracks number increases acutely in 240-260 degree C after a narrow range fluctuation in 80 degree C. Finally, the thermal cracks threshold of granite was determined primarily.

scholarly journals Restraint of Thermal Crack on Rake Face of Cermet Tool in Intermittent Cutting

2013 ◽  
Vol 7 (3) ◽  
pp. 263-269
Author(s):  
Akira Mizobuchi ◽  
◽  
Masahiro Masuda ◽  
Teruo Nogami ◽  
Hitoshi Ogawa ◽  
...  
Keyword(s):  
Feed Rate ◽  
Cutting Temperature ◽  
Good Effect ◽  
Rake Face ◽  
Thermal Crack ◽  
Machining Processes ◽  
Thermal Cracks ◽  
Micro Cracks ◽  
Machining Lines ◽  
Intermittent Cutting

Thermal cracks due to heating-cooling cycles in intermittent cutting in the machining processes of bearing production play an important role in tool life. This paper discusses restraint in the tool failure of TiC cermet used in actual machining line. The purpose of this study is to investigate two effects the appearance of the rake face and variation in the feed rate in thermal cracks on machining lines and to examine the thermal crack mechanism. As a result, we found that tools with some micro cracks were easily damaged. Removing some cracks on the rake face delays thermal crack generation time and reduces the number of cracks. Slightly decreasing the feed rate has a good effect on restraining the occurrence of cracks due to lowering of the cutting temperature.

scholarly journals The problem of temperature cracking in concrete gravity dams

Vestnik MGSU ◽  
2020 ◽  
pp. 380-398
Author(s):  
Nikolay A. Aniskin ◽  
Nguyen Trong Chuc
Keyword(s):  
Thermal Stress ◽  
Stress State ◽  
Crack Formation ◽  
Thermal Cracking ◽  
Mass Concrete ◽  
Thermal Stress State ◽  
Research Projects ◽  
Thermal Crack ◽  
Gravity Dams ◽  
Concrete Gravity Dams

Introduction. The concreting of solid structures, such as concrete dams, bridge constructions, foundations of buildings and structures, is accompanied by exothermic heating, caused by cement hydration. Heat, emitted by mass concrete blocks, slowly leaves constructions. A substantial temperature difference frequently arises between the solid concrete centre and its surface. If this temperature difference reaches a critical value, thermal cracking occurs, which destroys structural continuity. Temperature problems and those associated with thermal stress state should be resolved to pre-assess and prevent potential cracking. This problem has enjoyed the attention of specialists, and it has been the subject of numerous research projects. Materials and methods. The overview is based on the information about implemented research projects focused on the thermal cracking of mass concrete dams and its prevention. Computer modeling techniques were applied to develop a mathematical model capable of projecting and assessing the potential cracking of mass concrete. Results. The co-authors have compiled an overview of advanced approaches to the assessment of potential thermal crack formation, contemporary problem-solving methods and selected research findings obtained using the finite element method. The co-authors offer a thermal behaviour/thermal stress state projection methodology for solid concrete, as well as a thermal crack formation assessment methodology. Conclusions. The thermal cracking problem has not been solved yet. The proposed methodology and a projection-oriented numerical model can be used as a reference by civil engineers in the process of designing and constructing concrete gravity dams. It may help to reduce cracking probability caused by heat evolution in cement.

scholarly journals Analysis of Flexural Fatigue Damage in Woven Glass-Polyester Composites

1997 ◽  
Vol 6 (2) ◽  
pp. 096369359700600 ◽  
Author(s):  
R. Elleuch ◽  
A. Chateauminois ◽  
Ch. Bradai
Keyword(s):  
Quantitative Analysis ◽  
Fatigue Damage ◽  
Fatigue Behaviour ◽  
Fiber Bundles ◽  
Flexural Fatigue ◽  
Three Point Bending ◽  
Micro Cracks ◽  
Polyester Composite ◽  
Longitudinal Fiber ◽  
Polyester Composites

The monotonic and fatigue behaviour of a woven glass/polyester composite has been investigated under three-point bending conditions. Microscopic observations of the fatigue specimens revealed that the damage was mainly related to the early nucleation of transverse micro-cracks and delaminations along the longitudinal fiber bundles. From the quantitative analysis of the length and the orientation of these defects, it was possible to derive a lifetime criterion which was associated to a transition in damage mechanisms.

scholarly journals XFEM for Thermal Crack of Massive Concrete

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Guowei Liu ◽  
Yu Hu ◽  
Qingbin Li ◽  
Zheng Zuo
Keyword(s):  
Cooling System ◽  
Concrete Structures ◽  
Thermal Cracking ◽  
Pipe System ◽  
Degree Of Hydration ◽  
Thermal Cracks ◽  
Massive Concrete ◽  
Cooling Pipe ◽  
Equivalent Equation ◽  
Viscoelastic Constitutive Model

Thermal cracking of massive concrete structures occurs as a result of stresses caused by hydration in real environment conditions. The extended finite element method that combines thermal fields and creep is used in this study to analyze the thermal cracking of massive concrete structures. The temperature field is accurately simulated through an equivalent equation of heat conduction that considers the effect of a cooling pipe system. The time-dependent creep behavior of massive concrete is determined by the viscoelastic constitutive model with Prony series. Based on the degree of hydration, we consider the main properties related to cracking evolving with time. Numerical simulations of a real massive concrete structure are conducted. Results show that the developed method is efficient for numerical calculations of thermal cracks on massive concrete. Further analyses indicate that a cooling system and appropriate heat preservation measures can efficiently prevent the occurrence of thermal cracks.

Low-Temperature Stresses and Fracture Analysis of Asphalt Overlays

1996 ◽  
Vol 1539 (1) ◽  
pp. 132-139
Author(s):  
A. Shalaby ◽  
A. O. Abd El Halim ◽  
S. M. Easa
Keyword(s):  
Three Dimensional ◽  
Thermal Cracking ◽  
Multiple Cracks ◽  
Element Analysis ◽  
Thermal Cracks ◽  
Balance Principle ◽  
Thermoelastic Response ◽  
Transient Thermal ◽  
Asphalt Overlays ◽  
Pavement Reinforcement

Thermal cracking of asphalt overlays is a leading cause of pavement deterioration. The thermoelastic response of a multilayered pavement structure is modeled using a transient thermal analysis followed by a quasi-static stress analysis at discrete time intervals using finite element analysis. Numerical analysis of two- and three-dimensional cracking problems is performed. Based on a fracture mechanics approach, the potential of thermal cracks to propagate through the overlay is examined using both a displacement formula and an energy-balance principle. The interaction between multiple cracks and the effect of bond between layers on crack propagation are examined. The proposed numerical methods for analysis of pavement thermal cracking provide a means to characterize and optimize different evolving materials and innovative pavement reinforcement techniques.

Research about the Influence of Loading History on the Rock’s Thermal Cracking Fracture

2013 ◽  
Vol 631-632 ◽  
pp. 740-746
Author(s):  
Wei Hong Xie ◽  
Nan Zhou ◽  
Hai Feng Shen ◽  
Feng Zhang
Keyword(s):  
Fatigue Testing ◽  
Thermal Cracking ◽  
Testing System ◽  
Thermal Fracture ◽  
Loading History ◽  
Thermal Crack ◽  
Damage And Fracture ◽  
History Of ◽  
Different Order ◽  
Theory And Experiment

The research on the history of load and temperature to the influence of rock’s damage and fracture is rare. Commonly, it takes no account of the order of load and temperature and despite how the load’s history which arose its damage of thermal fracture is, the process of damage evolvement and the intensity of fracture is same as long as adds of carry is similar to temperature value. However, the thermal influenced by the history of adds of temperature and the result will be different under different order of adds of carry. This paper carries through meso-structure experiment of different order of adds of carry and temperature by the numbers, observe the process of limestone’s thermal crack damage under the different order of adds of temperature and carry on real time with instrument such as DaoJin High Temperature Fatigue Testing System with Scanning Electron Microscope. In the view of the rock’s tiny crack growth, compute its crack tip energy release rate under different order of adds of carry. The result of theory and experiment indicate that the fracture of rock’s thermal cracking are intensively influenced by the history of adds of carry.

scholarly journals Thermal cracking characteristics and mechanism of sandstone after high-temperature treatment

2021 ◽  
Author(s):  
Weijing Xiao ◽  
Guo Yu ◽  
Haitao Li ◽  
Dongming Zhang ◽  
Shujian Li ◽  
...  
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Thermal Cracking ◽  
Temperature Treatment ◽  
Outer Edge ◽  
High Temperature Treatment ◽  
Thermal Fracture ◽  
Thermal Cracks ◽  
Heterogeneous Rock ◽  
Cracking Characteristics

To study the thermal cracking characteristics and mechanism of sandstone after high-temperature treatment, the pore size distribution and micromorphology of sandstone were observed by nuclear magnetic resonance and scanning electron microscopy. Then, based on the Weibull distribution theory, a thermal elastic mechanical model of random heterogeneous rock was established for the rock unit, the thermal stress distribution characteristics of sandstone were analysed, and the thermal fracture mechanism of rock was discussed. The results show that the porosities of the samples increased with increasing temperature, and the proportion of large pores increased significantly when exceeded 400 °C. Particularly when reached 1000 °C, thermal cracking was distributed in a complex network. Additionally, different rock units are in different thermal stress states, which leads to the regional differences in the distribution of rock thermal fracture. When exceeded 400 °C, there were obvious thermal cracks near the outer edge that weakened the mechanical properties of rock.

scholarly journals Thermal Cracking Analysis during Pipe Cooling of Mass Concrete Using Particle Flow Code

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Liang Li ◽  
Xinghong Liu ◽  
Vinh T. N. Dao ◽  
Yonggang Cheng
Keyword(s):  
Thermal Cracking ◽  
Numerical Approach ◽  
Two Dimensions ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Mass Concrete ◽  
Concrete Gravity Dam ◽  
Thermal Cracks ◽  
Thermal Fields ◽  
Good Agreement

Pipe cooling systems are among the potentially effective measures to control the temperature of mass concrete. However, if not properly controlled, thermal cracking in concrete, especially near water pipes, might occur, as experienced in many mass concrete structures. In this paper, a new numerical approach to simulate thermal cracking based on particle flow code is used to shed more light onto the process of thermal crack propagation and the effect of thermal cracks on thermal fields. Key details of the simulation, including the procedure of obtaining thermal and mechanical properties of particles, are presented. Importantly, a heat flow boundary based on an analytical solution is proposed and used in particle flow code in two dimensions to simulate the effect of pipe cooling. The simulation results are in good agreement with the monitored temperature data and observations on cored specimens from a real concrete gravity dam, giving confidence to the appropriateness of the adopted simulation. The simulated results also clearly demonstrate why thermal cracks occur and how they propagate, as well as the influence of such cracks on thermal fields.

scholarly journals Thermal Cracking Analysis of Microbial Cemented Sand under Various Strains Based on the DEM

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Yang Tang ◽  
Guobin Xu ◽  
Yue Yan ◽  
Dengfeng Fu ◽  
Chunlai Qu ◽  
...  
Keyword(s):  
Ground Improvement ◽  
Thermal Cracking ◽  
Heating Process ◽  
Cemented Sand ◽  
X Ray ◽  
Thermal Cracks ◽  
Temperature Load ◽  
Calibration Algorithm ◽  
Improvement Method ◽  
Strength And Stiffness

Microbial-induced calcite precipitation (MICP) is a novel ground improvement method to increase the strength and stiffness of sand. However, the influences of temperature load on the internal microstructure of microbial cemented sand (MCS) material under the experimented strain have always been a key concern for the extensive application. Three kinds of experiments, X-ray diffraction (XRD), X-ray computed tomography (XCT), and scanning electron microscopy (SEM), were conducted to explore the composition, shape, and bonding characteristics of physical assemblies in this paper. A precision DEM modelling of MCS, mainly composed of irregular particle modelling and a mesoparameter calibration algorithm, has been proposed for the thermal cracking analysis under various strains (i.e., 1.0‰–3.0‰). Research results indicate that three kinds of bonding (that is sand-calcite, calcite-calcite, and sand-sand) are present in the MCS material. The application of temperature has a superposition effect on the damage of MCS material with increasing strain. Moreover, as the heating duration gradually increases, the effect of thermal rupture produces a distinct quiet period. The length of thermal cracks in the transverse direction increases throughout the heating process.

scholarly journals Network of thermal cracks in meteorites due to temperature variations: new experimental evidence and implications for asteroid surfaces

2020 ◽  
Vol 500 (2) ◽  
pp. 1905-1920
Author(s):  
Guy Libourel ◽  
Clément Ganino ◽  
Marco Delbo ◽  
Mathieu Niezgoda ◽  
Benjamin Remy ◽  
...  
Keyword(s):  
Thermal Cracking ◽  
Temperature Variations ◽  
Hydrous Minerals ◽  
Thermal Cracks ◽  
Temperature Cycles ◽  
Rapid Temperature ◽  
Thermal Fracturing ◽  
Cracking Process ◽  
Near Earth Asteroids ◽  
Highly Porous

ABSTRACT In recent years, several studies have shown the importance of thermal fracturing of rocks due to temperature variations, on The Earth and Mars. Rock thermal cracking might also be a process at play on the lunar surface. These temperature variations as well as change rates can reach important amplitude on bodies without an atmosphere, in particular on those that reach small perihelion distances such as near-Earth asteroids. On the other hand, the formation, geometry, and extension of cracks on these bodies have not been fully investigated yet. Here, we show results of thermal cracking laboratory experiments on chondrite meteorites, which develop networks of cracks when subjected to rapid temperature cycles with amplitudes similar to those experienced by asteroids with low perihelion distances. The depth of the cracks can reach a few hundred of microns in some hundreds of temperature cycles, in agreement with theoretical studies. We find that dehydration of hydrous minerals enhances the cracking process. The formation of crack networks increases the porosity both at the surface and in the sub-surface of our specimens. We propose that this process could help explaining the recent finding of the very highly porous surfaces of most of the boulders on the asteroids Ryugu and Bennu.

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