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1
YAMAUCHI, TATSUO. "Fracture toughness testing methods for paper materials." Sen'i Gakkaishi 53, no. 10 (1997): P330—P333. http://dx.doi.org/10.2115/fiber.53.10_p330.
Повний текст джерела
2
Díaz, Pedro-J., Jenny-M. Carvajal, and Miguel-Fernando Palencia-Muñoz. "Double torsion testing machine to determine the subcritical fracture index in rocks." CT&F - Ciencia, Tecnología y Futuro 4, no. 3 (May 24, 2011): 37–46. http://dx.doi.org/10.29047/01225383.237.
Повний текст джерелаАнотація:
This paper discusses the design methodology applied to build a testing machine to determine the sub-critical fracture index in a rock, based on double torsion testing in order to characterize naturally fractured formations such as those located in the Colombian Llanos Foothill Basin . These formations have been subjected to cyclic loads over time, causing fractures that trend to spread at sub-critical stress intensity values. Similarly, it presents the results of testing conducted on nine specimens of the Tambor Formation from 2 different outcrops to establish the testing traceability in the equipment.
3
Liu, Xue-wei, Quan-sheng Liu, Shi-bing Huang, Lai Wei, and Guang-feng Lei. "Fracture Propagation Characteristic and Micromechanism of Rock-Like Specimens under Uniaxial and Biaxial Compression." Shock and Vibration 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/6018291.
Повний текст джерелаАнотація:
This paper presents a set of uniaxial and biaxial compression tests on the rock-like material specimens with different fracture geometries through a rock mechanics servo-controlled testing system (RMT-150C). On the basis of experimental results, the characteristics of fracture propagation under different fracture geometries and loading conditions are firstly obtained. The newly formed fractures are observed propagating from or near the preexisting crack tips for different specimens, while the propagation paths are affected by the loading condition obviously. Then, by adopting acoustic emission (AE) location technique, AE event localization characteristics in the process of loading are investigated. The locations of AE events are in good agreement with the macroscopic fracture propagation path. Finally, the micromechanism of macroscopic fracture propagation under uniaxial and biaxial compression conditions is analyzed, and the fracture propagation can be concluded as a result of microdamage accumulation inside the material. The results of this paper are helpful for theory and engineering design of the fractured rock mass.
4
PARUCHURU, SATYA PRASAD, ANUJ JAIN, and XIAODU WANG. "SIZE REQUIREMENTS OF COMPACT SANDWICH SPECIMEN FOR TESTING OF BONE." Journal of Mechanics in Medicine and Biology 07, no. 04 (December 2007): 419–31. http://dx.doi.org/10.1142/s0219519407002406.
Повний текст джерелаАнотація:
It is well understood that bone quality deteriorates due to aging, disease, etc., and may be affected by factors at different length scales due to its hierarchical microstructure. Fracture toughness is one of the properties that assess bone quality. The compact sandwich (CS) specimen gives a better choice of bone sample size, and therefore suits a wide variety of fracture toughness testing needs and constraints. Reliable and statistically valid overall CS specimen size requirements are established in this paper; these serve as guidelines for choosing the CS specimen size. Finite element analysis (FEA) is used for simulating fracture toughness tests. Experimental fracture toughness tests are carried out to verify the FEA results. The experimental results are verified qualitatively by performing scanning electron microscopy (SEM) on the fractured specimen surfaces.
5
Wojtanowicz, A. K., and D. Zhou. "Borehole Failure Resulting From Formation Integrity (Leak-Off) Testing in Upper Marine Sediments Offshore." Journal of Energy Resources Technology 120, no. 2 (June 1, 1998): 111–17. http://dx.doi.org/10.1115/1.2795020.
Повний текст джерелаАнотація:
This paper presents the results of a theoretical study, supported with the finite element analysis, into potential loss of external integrity around a casing shoe resulting from leak-off testing (LOT) in upper marine sediments (UMS). Three types of possible failures from LOTs were considered: vertical fracture, horizontal fracture, and a channel outside cemented annulus. It is proved in the paper that vertical fracture is the most unlikely failure of the three. The other two types of failure can be distinguished by different values of propagation pressures. Although horizontal fractures are initiated at low pressure in the plastic zone around the wellbore, they cannot propagate beyond the plastic zone until wellbore pressures exceed overburden pressures. Annular channels, on the other hand, may propagate upwards at pressures lower than overburden pressure. The paper shows that these channels are initiated at pressures equal to the contact stress between cement and rock and their propagation pressures are on average 3.5-fold greater than contact stress. It is also explained how to identify the UMS with high risk of annular channeling during LOTs.
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Anghel, S., and D. Márton. "The Loss of Correction in Thoracolumbar Burst Fracture Treated by Surgery. Can We Predict It?" Acta Medica Marisiensis 60, no. 3 (June 1, 2014): 99–101. http://dx.doi.org/10.2478/amma-2014-0020.
Повний текст джерелаАнотація:
Abstract Objective: This paper aims to differentially depict potential patterns of the loss of correction in surgically treated thoraco-lumbar burst fractures. These may eventually serve to foreseeing and even forestalling loss of correction. Methods: The study focused on 253 patients with surgically treated thoraco-lumbar fractures. This cohort of patients was clustered in four subgroups according to the fracture spine segment (T11-L1 or L1-L2) and surgery type (short segment fi xation or anterior approach). Relevant recorded and processed data were the fracture level, post-operative (Kpo) and last follow-up (Kf) kyphosis angle values. Correlation, regression and determination testing were performed for the last follow-up kyphosis angle and post-operative kyphosis angle, and regression equations were determined for each subgroup of patients. Results: The patterns of loss of correction were described through the following equations: Kf = 0.95*Kpo + 3.2° for the T11-L1 level fractured vertebrae treated by posterior short segment fixation; Kf = 0.98*Kpo + 3.4° for the L1-L2 level fractured vertebrae treated by posterior short segment fixation; Kf = 1.1*Kpo + 1.6° for the T11-L1 level fractured vertebrae treated by anterior approach; and Kf = 0.7*Kpo + 2.8° for the L1-L2 level fracture vertebrae treated by anterior approach. Conclusions: The loss of correction may be predicted, to a certain extent, for thoraco-lumbar fractured vertebrae treated surgically. The bestfit equations depicted for both type of surgery (short segment fixation and anterior approach) and both spinal segments (T11-L1 and L2-L3) are significantly different than the equations delineated for the collapse of non-surgically treated fractures.
7
Andrews, R. M. "Measurement of the Fracture Toughness of Glacier Ice." Journal of Glaciology 31, no. 108 (1985): 171–76. http://dx.doi.org/10.1017/s0022143000006420.
Повний текст джерелаАнотація:
AbstractFracture-toughness testing of both fresh-water and sea ice has used specimen geometries designed for metals. These designs are too large and difficult to manufacture for testing material cored from a glacier. This paper presents an alternative specimen, a radially cracked ring fractured by internal pressure. Tests using this specimen on the Bersærkerbræ, a valley glacier in the Stauning Alper, north-east Greenland, gave a mean fracture toughness of 58. This is half the value typically obtained by other workers in laboratory tests. The results are compared with other data and the reasons for the disagreement discussed.
8
Andrews, R. M. "Measurement of the Fracture Toughness of Glacier Ice." Journal of Glaciology 31, no. 108 (1985): 171–76. http://dx.doi.org/10.3189/s0022143000006420.
Повний текст джерелаАнотація:
AbstractFracture-toughness testing of both fresh-water and sea ice has used specimen geometries designed for metals. These designs are too large and difficult to manufacture for testing material cored from a glacier. This paper presents an alternative specimen, a radially cracked ring fractured by internal pressure. Tests using this specimen on the Bersærkerbræ, a valley glacier in the Stauning Alper, north-east Greenland, gave a mean fracture toughness of 58 . This is half the value typically obtained by other workers in laboratory tests. The results are compared with other data and the reasons for the disagreement discussed.
9
Manikandan, Periyasamy, and Gin Boay Chai. "Mode-I Metal-Composite Interface Fracture Testing for Fibre Metal Laminates." Advances in Materials Science and Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/4572989.
Повний текст джерелаАнотація:
The main contribution of the present paper is the determination of the mode-I fracture of metal-composite interface region for fibre metal laminates (FMLs). A hybrid DCB configuration is proposed to investigate the mode-I fracture between metal-composite interface using experimental and numerical approaches. A computationally efficient and reliable finite element model was developed to account for the influence of metal plasticity on the measured fracture energy. The results of the experimental and numerical studies showed that metal plasticity increases the fracture energy of the metal-composite interface as the fracture event progresses. The applied energy truly utilized to propagate metal-composite interface fracture was predicted numerically by extracting the elastic strain energy data. The predicted true fracture energy was found to be approximately 50% smaller than the experimentally measured average propagation energy. The study concluded that metal plasticity in hybrid DCB configuration overpredicted the experimentally measured fracture energy, and this can be alleviated through numerical methodology such as the finite element approach as presented in this paper.
10
Das, Sreekanta, J. J. Roger Cheng, and David W. Murray. "Behavior of wrinkled steel pipelines subjected to cyclic axial loadings." Canadian Journal of Civil Engineering 34, no. 5 (May 1, 2007): 598–607. http://dx.doi.org/10.1139/l06-165.
Повний текст джерелаАнотація:
Full-scale laboratory tests were carried out at the University of Alberta to investigate the post-wrinkling ultimate behavior of steel pipelines. The pipe specimens exhibited extreme ductile behavior and did not fail in fracture under monotonically increasing axisymmetric compressive axial loads and displacements. Fractures developed at the wrinkled region, however, when a wrinkled pipe specimen was subjected to cyclic strain reversals due to unloading and loading of primary loads. This paper presents test procedures, complete post-wrinkling behavior, fracture limit strain values, and fracture configurations obtained from full-scale tests on wrinkled pipe specimens under cyclic and monotonic axial loadings. Key words: steel pipeline, laboratory testing, cyclic axial loading, wrinkling, post-wrinkling behavior, accordion failure, strain reversals, fracture.
11
Wu, Yonghui, Linsong Cheng, Sidong Fang, John E. Killough, Shijun Huang, and Pin Jia. "A Novel Edge-Based Green Element Method for Simulating Fluid Flow in Unconventional Reservoirs with Discrete Fractures." SPE Journal 25, no. 02 (December 31, 2019): 842–66. http://dx.doi.org/10.2118/195342-pa.
Повний текст джерелаАнотація:
Summary The boundary-element method (BEM) is widely used in modeling fluid flow in fractured reservoirs. However, the computation is extremely expensive when real heterogeneity and large numbers of fractures are modeled. This paper presents a novel edge-based Green element method (GEM) (eGEM) for this problem, and two significant modifications are made to the classical GEM. An edge-based discretization scheme is proposed to improve accuracy of the GEM. The eGEM technique is further enriched for simulating discrete fractures. The mathematical model is transformed into the Laplace domain, which makes it convenient to incorporate multiporosity models because the form of the boundary integral equation is the same. The matrix is meshed using Cartesian grids, and discrete fractures are handled flexibly by embedding into the matrix grids. In eGEM, the matrix/matrix flow is coupled at the common edge, so the unknown flux can be eliminated by using the edge-based scheme. In each matrix block, the matrix/fracture flow is modeled by treating the fracture elements as sources or sinks, as with BEM. The finite-difference method (FDM) is used to handle the fracture/fracture flow. In this paper, we tested the numerical accuracy and computational efficiency of the eGEM using several cases. First, the technique was shown to have higher accuracy than the classical corner-based GEM for transient problems in the petroleum industry. This shows the advantage of the edge-based discretization approach in handling the unknown flux of each solution point. The ability of the eGEM to handle discrete fractures was validated with the several models for transient-flow problems. The computation of the proposed eGEM is much less expensive than that for BEM in modeling the transient behavior of fractured media. Compared with the commercial numerical simulator in handling discrete fractures, the eGEM is shown to be less grid sensitive and to maintain a relatively high precision even with coarse grids near the discrete fractures. A detailed grid-sensitivity analysis was performed. The fracture grids are recommended to be refined to capture the early-time-flow behavior in pressure-transient analysis, especially in modeling low-conductivity fractures. For the first time, an efficient edge-based discretization scheme for GEM is presented, which handles the unknown flux of each solution point and at the same time uses eGEM to enrich simulation of discrete-fracture networks. This method serves as a new efficient approach for reservoir simulation and numerical well testing. Because of the high precision of eGEM with coarse grids, it would be efficient in larger field applications.
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Yang, Binbin, and Yong Liu. "Application of Fractals to Evaluate Fractures of Rock Due to Mining." Fractal and Fractional 6, no. 2 (February 10, 2022): 96. http://dx.doi.org/10.3390/fractalfract6020096.
Повний текст джерелаАнотація:
Fractures caused by mining are the main form of water inrush disaster. However, the temporal and spatial development characteristics of fractures of the rock mass due to mining are not clearly understood at present. In this paper, two geometric parameters, namely, fractal dimension and fracture entropy, are proposed to determine the spatial and temporal states of rock mass fractures caused by mining. The spatial and temporal structure characteristics of fractures in the rock mass due to mining are simulated with physical scale model testing based on digital image processing technology. A spatiotemporal model is created to examine the spatial and temporal patterns of hot and cold spots of the fractures based on a Geographic Information System (GIS). Results indicate that the fractal dimensions and entropy of the fractures network in the rock mass increase and decrease with the progression of mining, respectively, which can be examined in three stages. When the fractal dimension of the fractures in rock mass rapidly increases, the conductive fracture zone has a saddle shape. The fracture entropy of fracture has periodic characteristics in the advancing direction of the panel, which reflects the characteristics of periodic weighting. The fractal dimension and fracture entropy of fractures of the rock mass increase with time, and the rock mass system undergoes a process of increasing entropy. When the fractal dimension and fracture entropy of the fractures increase, the spatiotemporal state of fractures in rock mass caused by mining is initiated. When the fractal dimension and fracture entropy of the fractures decrease, the spatiotemporal state of fractures in rock mass is closed.
13
Man, Ke, Xiao Li Liu, Ju Wang, Rui Su, and Yong Qiang Zhu. "Double Fracture Systems of Rock Flow for Geological Disposal of the High-Level Radioactive Waste." Applied Mechanics and Materials 361-363 (August 2013): 912–16. http://dx.doi.org/10.4028/www.scientific.net/amm.361-363.912.
Повний текст джерелаАнотація:
Based on the diagenesis, classification and its physical, mechanical, and hydromechanical properties of fractured rock, this paper describes the current status of the fractured rock seepage models and their characteristics. Especially from the point of the safety assessment of the geological disposal of the high level radioactive waste, the discrete fracture network model, the equilibrium continuous medium model and the double media continuous model have been elaborated, and has been analyzed and compared with each other. Furthermore, the double fracture systems for rock flow have been introduced as the much better suitable seepage model for the geological disposal of the high level radioactive waste. In the double fracture systems seepage model, the seepage flow is described and reflected by the main fracture system, and the water store property is given by the subordinate fracture system. The appropriate seepage model for the geological disposal of the high level radioactive waste can be achieved through the double fracture systems, combined with the hydrological testing data in site and other geological information.
14
Słowik, Marta. "The role of aggregate granulation on testing fracture properties of concrete." Frattura ed Integrità Strutturale 15, no. 58 (September 25, 2021): 376–85. http://dx.doi.org/10.3221/igf-esis.58.27.
Повний текст джерелаАнотація:
Concrete is a porous material containing aggregate of different sizes, hardened cement matrix with air pores, microcracks and water. Concrete internal structure is different from that of other engineering materials. Furthermore concrete is described as quazi-brittle material. Fracture processes in it form in a way that does not fit within classical theories. Therefore, to describe failure of concrete structures nonlinear fracture mechanics is often applied with success. Basic concrete parameters, like compressive and tensile strength, and modulus of elasticity, are not enough to analyze fracture processes in concrete structures. Additional fracture properties should be tested, among them fracture energy, complete diagram of stress-deformation under axial tension and the width of fracture process zone. Recognizing and testing fracture parameters is of paramount importance when analysing fracture process in concrete structures. The correct data of material’s properties and the adequate fracture model applied in numerical simulations influence final results. In the paper the findings reported in the professional literature are summarized and obtained results of the own numerical simulation are reported in order to give a deeper knowledge on the role of aggregate on fracture properties of concrete.
15
Chuluunbat, Turbadrakh, Cheng Lu, Andrii Kostryzhev, and Kiet Tieu. "Influence of Loading Conditions during Tensile Testing on Acoustic Emission." Key Engineering Materials 626 (August 2014): 121–26. http://dx.doi.org/10.4028/www.scientific.net/kem.626.121.
Повний текст джерелаАнотація:
The Acoustic Emission (AE) monitoring technique is widely used in mechanical and material research for detection of plastic deformation, fracture initiation and crack growth. However, the influence of AE features (such as signal amplitude, frequency, rise time and duration) on the fracture parameters (such as brittle or ductile mode of propagation and fracture propagation speed) is not completely understood. In this paper, the effect of loading conditions on fracture behavior was studied using AE monitoring during tensile testing of an aluminum alloy specimen. The fracture development was observed using a high speed video camera and was analyzed using the finite element method. The hardware and software produced by Physical Acoustics Corporation (USA) was used. Variations in AE parameters were analyzed and correlated to the stress-strain curves obtained during testing. It is shown that the strain rate and the presence of a crack (modeled by a notch on the sample), affect the fracture mode (brittle or ductile) and a relative amount of the mode dependent AE signatures.
16
Kuchuk, Fikri, Denis Biryukov, and Tony Fitzpatrick. "Fractured-Reservoir Modeling and Interpretation." SPE Journal 20, no. 05 (October 20, 2015): 983–1004. http://dx.doi.org/10.2118/176030-pa.
Повний текст джерелаАнотація:
Summary Fractures are common features of many well-known reservoirs. Naturally fractured reservoirs (NFRs) consist of fractures in igneous, metamorphic, and sedimentary rocks (matrix). Faults in many naturally fractured carbonate reservoirs often have high-permeability zones and are connected to numerous fractures with varying conductivities. In many NFRs, faults and fractures frequently have discrete distributions rather than connected-fracture networks. Because faulting often creates fractures, faults and fractures should be modeled together. Accurately modeling NFR pressure-transient behavior is important in hydrogeology, the earth sciences, and petroleum engineering, including groundwater contamination to shale gas and oil reservoirs. For more than 50 years, conventional dual-porosity-type models, which do not include any fractures, have been used for modeling fluid flow in NFRs and aquifers. They have been continuously modified to add unphysical matrix-block properties such as matrix skin factor. In general, fractured reservoirs are heterogeneous at different length scales. It is clear that even with millions of gridblocks, numerical models may not be capable of accurately simulating the pressure-transient behavior of continuously and discretely NFRs containing variable-conductivity fractures. The conventional dual-porosity-type models are obviously an oversimplification; their serious limitations for interpreting well-test data from NFRs are discussed in detail. These models do not include wellbore-intersecting fractures, even though they dominate the pressure behavior of NFRs for a considerable length of testing time. Fracture conductivities of unity to infinity dominate transient behavior of both continuously and discretely fractured reservoirs, but again, dual-porosity models do not contain any fractures. Our fractured-reservoir model is capable of treating thousands of fractures that are periodically or arbitrarily distributed with finite- and/or infinite conductivities, different lengths, densities, and orientations. Appropriate inner-boundary conditions are used to account for wellbore-intersecting fractures and direct wellbore contributions to production. Wellbore-storage and skin effects in bounded and unbounded systems are included in the model. Three types of damaged-skin factors that may exist in wellbore-intersecting fracture(s) are specified. With this highly accurate model, the pressure-transient behavior of conventional dual-porosity-type models are investigated, and their limitations and range of applicability are identified. The behavior of the triple-porosity models is also investigated. It is very unlikely that triple-porosity behavior is caused by the local variability of matrix properties at the microscopic level. Rather, it is caused by the spatial variability of conductivity, length, density, and orientation of the fracture distributions. Finally, we have presented an interpretation of a field-buildup-test example from an NFR by use of both conventional dual-porosity models and our fractured-reservoir model. A substantial part of this paper is a review and discussion of the earlier work on NFRs, including the authors’ work.
17
Kim, J. S., Young Jin Kim, and S. M. Cho. "Finite Element Analyses for Thickness Effects on J-Integral Testing using Non-Standard Testing Specimens." Key Engineering Materials 261-263 (April 2004): 693–98. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.693.
Повний текст джерелаАнотація:
This paper compiles solutions of plastic η factors for standard and non-standard fracture toughness testing specimens, via detailed three-dimensional (3-D) finite element (FE) analyses. Fracture toughness testing specimens include a middle cracked tension (M(T)) specimen, SE(B), single-edge cracked bar in tension (SE(T)) and C(T) specimen. The ligament-to-thickness ratio of the specimen is systematically varied. It is found that the use of the CMOD overall provides more robust experimental estimation than that of the LLD, for all cases considered in the present work. Moreover, the estimation based on the load- CMOD record is shown to be insensitive to the specimen thickness, and thus can be used for testing a specimen with any thickness.
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Kremenetsky, Mikhail I., Andrey I. Ipatov, Alexander A. Rydel, Kharis A. Musaleev, and Anastasija N. Nikonorova. "Risk decreasing of water waste through spontaneous fracturing in injectors by integrated well-testing and production logging." PROneft’. Proffessional’no o nefti 6, no. 4 (December 24, 2021): 92–105. http://dx.doi.org/10.51890/2587-7399-2021-6-4-92-105.
Повний текст джерелаАнотація:
Background. When creating an effective reservoir pressure maintenance system, unstable spontaneous hydraulic fractures can be created in injection wells. This can both negatively and positively affect hydrocarbon production. First, fracture improves reservoir connectivity, which increases injection efficiency. On the other hand, unstable fractures can cause behind-the-casing flows and unproductive injection into off-target layers or fingering.
Goal. The paper is devoted to the analysis of well testing (PTA) and production logging (PLT) improvement for the diagnosis of unstable fractures in injection wells.
Materials and methods. The analysis is based on the results of modeling the pressure in the reservoir system, describing the penetration reservoirs by an unrestricted conductivity unstable fracture. It is taken into account that the fracture can cross both the perforated formation and the thickness not penetrated by the perforation, and can grow with increasing overbalance.
The modeling results made it possible both to assess the potential informative capabilities of well testing and to substantiate recommendations for the practical use of the obtained results.
Conclusions. The proposed approaches to the technology of well testing and production logging and the interpretation of their results make it possible to estimate the additional thicknesses of the reservoirs connected by the spontaneous hydraulic fracturing to injection, the proportion of nonproductive injection in the total volume of the well. The research technology used by the authors is based on continuous measurements of pressure and flow rate during cyclic change of pressure and assessment of the effective transmissibility of the formation system at different heights of unstable fractures.
The role of the PLT is to determine the effective production thickness of the reservoirs. When assessing the injectivity profile when penetrating the injector with the spontaneous hydraulic fracturing, the key role belongs to non-stationary temperature logging. In this case, it is necessary to take into account the specific features of temperature relaxation in the wellbore after the injection cycle, related to hydraulic fracturing, primarily the increase in the relaxation rate with increasing fracture length.
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Carpenter, Chris. "Machine-Learning Upscales Realistic Discrete Fracture Simulations." Journal of Petroleum Technology 73, no. 11 (November 1, 2021): 65–66. http://dx.doi.org/10.2118/1121-0065-jpt.
Повний текст джерелаАнотація:
This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203962, “Upscaling of Realistic Discrete Fracture Simulations Using Machine Learning,” by Nikolai Andrianov, SPE, Geological Survey of Denmark and Greenland, prepared for the 2021 SPE Reservoir Simulation Conference, Galveston, Texas, 4–6 October. The paper has not been peer reviewed. Upscaling of discrete fracture networks to continuum models such as the dual-porosity/dual-permeability (DP/DP) model is an industry-standard approach in modeling fractured reservoirs. In the complete paper, the author parametrizes the fine-scale fracture geometries and assesses the accuracy of several convolutional neural networks (CNNs) to learn the mapping between this parametrization and DP/DP model closures. The accuracy of the DP/DP results with the predicted model closures was assessed by a comparison with the corresponding fine-scale discrete fracture matrix (DFM) simulation of a two-phase flow in a realistic fracture geometry. The DP/DP results matched the DFM reference solution well. The DP/DP model also was significantly faster than DFM simulation. Introduction The goal of this study was to evaluate the effect of different CNN architectures on prediction accuracy for the DP/DP model closures and on the accuracy of DP/DP simulations in comparison with fine-scale DFM simulations. As a starting point, two CNN configurations were considered that have achieved breakthrough performance in image-classification tasks. The author adopted these architectures to the problem of learning the mapping between pixelated fracture geometries and the DP/DP model closures and indicated several key features in the CNN structure that are crucial for achieving high prediction accuracy. Mapping of fracture geometries requires significant effort, which limits the possibilities for creating large training data sets with realistic fracture geometries. The author, therefore, used the synthetic random linear fractures’ data set to train the CNNs and the fracture geometry from the Lägerdorf outcrop for testing purposes. It was demonstrated that an optimal CNN configuration yielded the DP/DP model closures such that the corresponding DP/DP results matched well the two-phase DFM simulations on a subset of the Lägerdorf data. The run times for the DP/DP model were a fraction of the time needed to accomplish the DFM simulations. Problem formulation is presented in a series of equations in the complete paper.
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Hosseini Mehrab, Alireza, Seyedmahdi Amirfakhrian, and M. Reza Esfahani. "Fracture characteristics of various concrete composites containing polypropylene fibers through five fracture mechanics methods." Materials Testing 65, no. 1 (January 1, 2023): 10–32. http://dx.doi.org/10.1515/mt-2022-0210.
Повний текст джерелаАнотація:
Abstract This paper investigates and compares the experimental results of fracture characteristics in various polypropylene fiber-reinforced concretes (high strength concrete, lightweight concrete, and engineered cementitious composite) on 90 three-point bend (notched and un-notched) beams. Five widely used fracture mechanics testing methods, such as work of fracture method, stress-displacement curve method, size effect method, J integral method, and ASTM E399, were used to investigate the fracture behavior. Results have demonstrated that fracture energy and fracture toughness improved as the dosage of polypropylene fibers increased in concretes. However, this improvement was different in concretes owing to various results of fracture mechanics testing methods and different properties of each concrete. Aggregates played significant role in the performance of polypropylene fibers on the fracture behavior of concretes. Among testing methods, the ASTM E399 showed the lowest values for the fracture toughness of concretes. Both work of fracture and stress-displacement curve methods exhibited appropriate results for the fracture energy of polypropylene fiber-reinforced concrete composites. The accuracy of size effect method was acceptable for determining size-independent fracture parameters of plain high strength and lightweight concretes. Furthermore, the J integral method showed more relevant results for the fracture toughness of polypropylene fiber-reinforced engineered cementitious composite.
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Fett, T., D. Munz, and G. Thun. "Fracture Toughness Testing on Bars Under Opposite Cylinder Loading." Journal of Engineering for Gas Turbines and Power 126, no. 1 (January 1, 2004): 50–54. http://dx.doi.org/10.1115/1.1639003.
Повний текст джерелаАнотація:
Bars loaded by opposite concentrated forces via rollers are appropriate test specimens for the determination of the fracture toughness, KIc, and the crack resistance curve (R-curve) of ceramic materials. In this paper stress solutions for the proposed test specimens are provided, as well as the stress intensity factor and the T-stress solutions. As practical applications, R-curves are determined for a soft PZT ceramic and several alumina ceramics.
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Hu, Hui, Yu Peng Cao, and Pei Ning Li. "Study on Fracture Toughness Prediction of Non Power Law Hardening Material by Using Local Approach." Advanced Materials Research 197-198 (February 2011): 1640–46. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.1640.
Повний текст джерелаАнотація:
A new method of fracture toughness K1C prediction of non power law hardening material by using cleavage fracture local approach is proposed in this paper. The fracture toughness of A508-Ⅲ 16MnR at different cleavage fracture probability are predicted by using the method. To most of pressure vessel carbon-manganese steels, cleavage fracture is likely to occur at the load corresponding to 62% cleavage fracture probability. Hence, the fracture toughness corresponding to the load is the most possible fracture toughness of the steels. The values of fracture toughness corresponding to 62% cleavage fracture probability is close to that of testing fracture toughness. The work of this paper expends the application of Beremin cleavage fracture model in predicting fracture toughness.
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Yamauchi, Tatsuo, and Hironobu Hirano. "Examination of the onset of stable crack growth under fracture toughness testing of paper." Journal of Wood Science 46, no. 1 (February 2000): 79–84. http://dx.doi.org/10.1007/bf00779558.
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Xing, Hai Yan, Da Bo Wu, Li Hong Zhang, and Min Qiang Xu. "Steam Turbine Blade MMM Testing and Failure Analysis." Advanced Materials Research 139-141 (October 2010): 2561–64. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.2561.
Повний текст джерелаАнотація:
Metal magnetic memory (MMM) method, based on the magneto-elasticity and mechanical effect theory, is a new nondestructive testing technology. This paper aims at the material property and failure analysis for steam turbine blade with MMM method. The failure blade and its fracture face are tested with MMM technology at workshop. It has been found that the MMM signal variation gradient of the crack transition zone in the fracture face is minimal, that of the crack initiation zone is in the middle, and that of the tear fracture zone is maximal. MMM testing results reflect material behavior degradation of the failure blade. In order to proof the MMM results, the dynamic stress of the steam turbine blade under the operation loading is calculated by WESTHOMES software and analyzed theoretically. It has proved the validity of the MMM method applied on material property evaluation and failure analysis for steam turbine blade.
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Apostol, Dragoş Alexandru, Dan Mihai Constantinescu, Liviu Marsavina, and Emanoil Linul. "Mixed-Mode Testing for an Asymmetric Four-Point Bending Configuration of Polyurethane Foams." Applied Mechanics and Materials 760 (May 2015): 239–44. http://dx.doi.org/10.4028/www.scientific.net/amm.760.239.
Повний текст джерелаАнотація:
Many efforts have been made recently to determine the fracture toughness of different types of foams in static and dynamic loading conditions. Taking into account that there is no standard method for the experimental determination of the fracture toughness of plastic foams, different procedures and specimens were used. This paper presents the polyurethane foam fracture toughness results obtained experimentally for three foam densities. Asymmetric four-point bending specimens were used for determining fracture toughness in mode I and in a mixed one, and also the influence of the loading speed and geometry of the specimen were investigated.
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Liu, Yue Hua, Hui Ping Yu, Wei Wei Wang, Xiao Yang Li, and Shu Jun Chen. "Experimental Research on Tensile-Shear Behavior of Spot-Welded Lap Joints of Ultra-High Strength Steel." Applied Mechanics and Materials 226-228 (November 2012): 1720–24. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.1720.
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The ultra-high strength quenched 22MnB5 steel is researched in this paper, the intermediate frequency inverter & electric servo welding gun system is used to weld the sheets, experiments included of tensile-shear with synchronous electrical testing, microstructure of the material and fractures analysis and the Vickers-Hardness testing. The results point out that the maximum hardness is located at weld nugget, and the minimum hardness is appeared in heat affected zone (HAZ). Fracture is formed under the combined effects of shear stress and normal stress, the shear stress contributes to interfacial fracture, and leads to rupture. Non-uniformity of the microstructure caused by spot welding, changed the property of the material in nugget, stress-strain relationship of this area is nonlinear. The results also show that the conventional weld size guidance of 4√t is not sufficient to produce nugget pullout failure mode for 22MnB5 UHSS spot welds.
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Wu, Zhongwei, Chuanzhi Cui, Zhen Wang, Yingfei Sui, Peifeng Jia, and Wenhao Tang. "Well Testing Model of Multiple Fractured Horizontal Well with Consideration of Stress-Sensitivity and Variable Conductivity in Tight Gas Reservoirs." Mathematical Problems in Engineering 2018 (September 6, 2018): 1–13. http://dx.doi.org/10.1155/2018/1693184.
Повний текст джерелаАнотація:
Multiple fractured horizontal wells have been widely used to develop unconventional tight gas reservoirs. Currently, many well testing models were established to study the performance of fractured horizontal wells in tight gas reservoirs. However, none of these models thoroughly takes stress-sensitivity of natural fractures and variable conductivity of artificial fractures into consideration. Based on the consideration of stress-sensitivity of natural fractures and variable conductivity of artificial fractures, a novel well testing model for fractured horizontal well in tight gas reservoirs is proposed. And the semianalytical solution of this new model is obtained by dividing the artificial fracture into different segments under the integrative methods of Laplace transformation, point source function, perturbation theory, superposition principle, and Stehfest numerical inversion. After validation, the semianalytical solution is consistent with that of Zerzar’s model (2004). Also, typical pressure and pressure derivative curves are plotted. According to typical curves, seven regimes can be derived, namely, bilinear flow, linear flow, early-time pseudoradial flow, biradial flow, intermediate-time pseudoradial flow, and pseudo-steady state interporosity flow, and late-time pseudoradial flow can be identified. In addition, this paper analyzes the impact on pressure and pressure derivative curves exerted by variable conductivity and stress-sensibility. The results show that variable conductivity mainly affects the early flow regimes, including bilinear flow, linear flow, and early-time radial flow, while the stress-sensitivity mainly affects the later flow regimes, including intermediate-time pseudoradial flow, pseudo-steady state interporosity flow, and late-time pseudoradial flow. The typical curves will ascend with the increasing of stress-sensitivity coefficient. The research provides a method for precise prediction of formation parameters and has a significant impact on the tight gas reservoir development.
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Taleghani, A. Dahi, M. Ahmadi, W. Wang, and Jon E. Olson. "Thermal Reactivation of Microfractures and Its Potential Impact on Hydraulic-Fracture Efficiency." SPE Journal 19, no. 05 (February 20, 2014): 761–70. http://dx.doi.org/10.2118/163872-pa.
Повний текст джерелаАнотація:
Summary Core studies have revealed the presence of abundant cemented microfractures in many tight formations. Further independent studies have revealed the opening of some of these microfractures on the wall surface of main hydraulic fractures. In addition, early-production well-testing analysis in some of these cases provides estimates for the hydraulically-induced-fracture surface area, which is much larger than fracture dimensions estimated in fracturing design or provided by the location of microseismic events. Opening of small-sized fractures could be a possible reason for this discrepancy. In this paper, we show to what extent thermal stresses induced by temperature difference between fracturing fluid and formation fluid could provide the driving force to open a portion of these small, cemented natural fractures lying on the surface of hydraulic fractures. Moreover, through combination of stress analysis and empirical fracture-distribution models obtained from outcrops, we calculate the increase of total reservoir/fracture contact surface under the condition of microfracture activation. Our thermoelasticity analysis reveals the effect of the pump rate and temperature of the fracturing fluid on the number of activated microfractures. The results show that the volume of the microfractures varies depending on the length of the microfracture, rock properties, and time. At the end of the paper, through an example, we show that activation of only a small portion of these microfractures can increase the total fracture/formation contact area considerably and, consequently, increase initial production. Reservoir-pressure changes caused by production might partially close or reopen these microcracks during production; hence, the effectiveness of these microfractures could be mainly restricted to the early life of the reservoirs.
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Čamagić, Ivica, Nemanja Vasić, Predrag Živković, Aleksandar Radović, Tamara Sedmak, Meri Burzić, and Zijah Burzić. "Compatibility of Endurance Limit and Fatigue Crack Growth Parameters in Evaluation of Low Alloyed Steel Welded Joint Behaviour." Advanced Materials Research 1111 (July 2015): 121–26. http://dx.doi.org/10.4028/www.scientific.net/amr.1111.121.
Повний текст джерелаАнотація:
Analysis of fracture toughness of high-strength low alloyed steel, Nionikral-70, welded joint constituencies, subjected to variable load is given in this paper, using two parameters. Crack initiation resistance is determined by testing of endurance limit and by designing of Wöhler curves. Crack propagation resistance is determined by testing of crack growth rate, and accordingly determination of Paris equation parameters. Analysis of fracture toughness is given based on testing results, comparing obtained values for base metal, weld metal and heat affected zone.
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Trajkovic, Isaak, Milos Milosevic, Milan Travica, Marko Rakin, Goran Mladenovic, Ljudmila Kudrjavceva, and Bojan Medjo. "Novel method for measurement of pipeline materials fracture resistance-examination on selective laser sintered cylindrical specimens." Science of Sintering 54, no. 3 (2022): 373–86. http://dx.doi.org/10.2298/sos2203373t.
Повний текст джерелаАнотація:
This paper presents a part of development of a non-standard method for testing of cylindrical test specimens for measurement of fracture properties of pipeline materials. This method for testing of cylindrical structures working under pressure is based on determining of fracture mechanics parameters on SENT (Single Edge Notched Tension) specimens and new PRNT (Pipe Ring Notched Tension) specimens. In this work, both types of specimens required for this testing were manufactured from polyamide PA12 by using SLS (selective laser sintering) additive manufacturing method. Testing of the specimens is performed on the universal device for testing of mechanical properties of materials Shimadzu, AGS-X 100 kN. The tensile testing is accompanied by GOM Aramis 2M system, used for digital image correlation. By using these two systems, test results are obtained for ring-shaped and SENT specimens, including forces, displacements and fracture mechanics parameters CMOD (Crack Mouth Opening Displacement) and CTOD-?5 (Crack Tip Opening Displacement obtained by ?5 technique), as well as crack growth. Repeatability of this process, along with valid result consistency, represent the basis for further development of the new method, including the determining of energy-based fracture mechanics parameters: J integral and stress intensity factor.
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Bertorello, Argüelles, Mollón, Bonhomme, Viña, and Viña. "Use of a LHFB Device for Testing Mode III in a Composite Laminate." Polymers 11, no. 8 (July 26, 2019): 1243. http://dx.doi.org/10.3390/polym11081243.
Повний текст джерелаАнотація:
The present paper studies the fatigue delamination behaviour of an epoxy/carbon composite material under mode III loading using a longitudinal half fixed beam (LHFB) device initially designed for mode III static tests of composite materials formed by the stacking of plies. For this purpose, a series of tests was carried out at different levels of loading representative of the fatigue behaviour of the material, from the crack onset phase through the delamination phase to final fracture. The experimental results were treated statistically, obtaining the values of the fatigue limit for probabilities of fracture of 5% and 50%. Finally, a fractographic analysis of the fracture surfaces was performed which allowed us to identify the same characteristic patterns of static mode III fracture, namely broken fibres, cusps and saw-teeth, in addition to a new morphology consisting of the formation of agglomerations of resin produced by the friction between the lips of the specimen in the fracture zone that point to dynamic mode III fracture. These agglomerations eventually crack and become detached from the fibres, leaving these free of resin.
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Yang, Dayong, Hamid Reza Karimi, and Mohammad Reza Mohammad Aliha. "Comparison of Testing Method Effects on Cracking Resistance of Asphalt Concrete Mixtures." Applied Sciences 11, no. 11 (May 31, 2021): 5094. http://dx.doi.org/10.3390/app11115094.
Повний текст джерелаАнотація:
As an inherent characteristic of materials, the fracture toughness is an important parameter to study the cracking behavior of asphalt concrete mixtures. Although material compositions and environmental conditions have a significant effect on the fracture toughness, for a certain material and testing environment, the test condition including the specimen configuration and loading type may also affect the obtained fracture toughness. In this paper, the effect of specimen configuration and applied loading type on the measured pure mode-I fracture toughness (KIc) is investigated. In order to achieve this purpose, using a typical asphalt mixture, four different test specimens including Semi-Circular Bend (SCB), Edge Notch Disc Bend (ENDB), Single Edge Notch Beam (SENB) and Edge Notch Diametral Compression (ENDC) disc are tested under pure mode I. The mentioned specimens have different shapes (i.e., full disc, semi-disc and rectangular beam) and are loaded either with symmetric three-point bending or diametral compressive force. The tests were performed at two low temperatures (−5 °C and −25 °C) and it was observed that the critical mode-I fracture toughness (KIc) was changed slightly (up to 10%) by changing the shape of the test specimen (i.e., disc and beam). This reveals that the fracture toughness is not significantly dependent on the shape of the test specimen. However, the type of applied loading has a significant influence on the determined mode I fracture toughness such that the fracture toughness determined by the disc shape specimen loaded by diametral compression (i.e., ENDC) is about 25% less than the KIc value with the same geometry but loaded with the three-point bending (i.e., ENDB) specimen. In addition, the fracture toughness values of all tested samples were increased linearly by decreasing the test temperature such that the fracture toughness ratio (KIc (@−25 °C)/KIc (@−5 °C)) was nearly constant for the ENDB, ENDC, SCB and SENB samples.
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Lukáč, Pavel, and Zuzanka Trojanová. "The Effect of Grain Size on the Deformation Behaviour of Selected Mg Alloys." Materials Science Forum 567-568 (December 2007): 85–88. http://dx.doi.org/10.4028/www.scientific.net/msf.567-568.85.
Повний текст джерелаАнотація:
The mechanical properties and deformation behaviour of magnesium alloys are significantly influenced by the testing temperature, texture and grain size. The paper gives an overview on the influence of the grain size on the mechanical properties of Mg and Mg-2Al alloys at various temperatures. The yield stress and the fracture stress increase with decreasing grain size. It was shown that the elongation to fracture increases with inverse square root of grain size. The effect of grain size on the tensile strength and the elongation to fracture is influenced by the testing temperature. The observed grain size dependence of the elongation to fracture is explained by the activity of non-basal slip systems.
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Akram, Amanda. "Size effect at testing strength properties of concrete." Budownictwo i Architektura 20, no. 4 (December 29, 2021): 037–46. http://dx.doi.org/10.35784/bud-arch.2821.
Повний текст джерелаАнотація:
Various strength characteristics of concrete are considered as fracture parameters. The compressive strength of concrete is of paramount importance when designing concrete structures, whereas tensile strength of concrete is the basic property when estimating cracking resistance of a structure and analysing fracture processes in concrete. When testing the compressive strength of concrete, the results are dependent on the shape and dimensions of used specimens. Some findings reported in the literature suggest that size effect exists also when testing such fracture properties of concrete as tensile strength. Unfortunately this problem is much less recognized and described compared to size effect in compressive test results. In this paper, the experimental investigation is presented on how the length of cylindrical specimens influences the tensile splitting strength of concrete obtained by means of the Brazilian method. Additional variable parameters were: type of aggregate (natural gravel and crushed granite) and cement-water ratio (C/W = 1.8 and C/W = 2.6). In conducted laboratory experiments a higher splitting tensile strength of concrete was noted for all specimens with nominal dimensions of 150×150 mm, compared to specimens 150×300 mm in size, regardless of type of aggregate or cement-water ratio.
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Zhou, Jing, and Linsheng Huo. "Computer Vision-Based Detection for Delayed Fracture of Bolts in Steel Bridges." Journal of Sensors 2021 (November 9, 2021): 1–12. http://dx.doi.org/10.1155/2021/8325398.
Повний текст джерелаАнотація:
The delayed fracture of high-strength bolts occurs frequently in the bolt connections of long-span steel bridges. This phenomenon can threaten the safety of structures and even lead to serious accidents in certain cases. However, the manual inspection commonly used in engineering to detect the fractured bolts is time-consuming and inconvenient. Therefore, a computer vision-based inspection approach is proposed in this paper to rapidly and automatically detect the fractured bolts. The proposed approach is realized by a convolutional neural network- (CNN-) based deep learning algorithm, the third version of You Only Look Once (YOLOv3). A challenge for the detector training using YOLOv3 is that only limited amounts of images of the fractured bolts are available in practice. To address this challenge, five data augmentation methods are introduced to produce more labeled images, including brightness transformation, Gaussian blur, flipping, perspective transformation, and scaling. Six YOLOv3 neural networks are trained using six different augmented training sets, and then, the performance of each detector is tested on the same testing set to compare the effectiveness of different augmentation methods. The highest average precision (AP) of the trained detectors is 89.14% when the intersection over union (IOU) threshold is set to 0.5. The practicality and robustness of the proposed method are further demonstrated on images that were never used in the training and testing of the detector. The results demonstrate that the proposed method can quickly and automatically detect the delayed fracture of high-strength bolts.
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Aliha, M. R. M., R. Ashtari, and Majid R. Ayatollahi. "Mode I and Mode II Fracture Toughness Testing for a Coarse Grain Marble." Applied Mechanics and Materials 5-6 (October 2006): 181–88. http://dx.doi.org/10.4028/www.scientific.net/amm.5-6.181.
Повний текст джерелаАнотація:
A series of fracture toughness tests have been conducted on a type of coarse grain marble. The tests were carried out either in pure mode I or in pure mode II conditions by using the cracked chevron notched Brazilian disc (CCNBD) specimen. A total number of 44 CCNBD specimens were tested, half in pure mode I and the rest in pure mode II, to obtain reliable values for mode I and mode II fracture toughness (KIc and KIIc) of the tested marble. The average value of KIc for this marble was approximately about 1.12 MPa m showing a good agreement with those reported for similar coarse grain marbles. The mode II fracture toughness was found to be 2.25 MPa m in average which is approximately twice the mode I fracture toughness. However, the conventional fracture criteria suggest that the mode I fracture toughness should be higher than the mode II fracture toughness, (KIc>KIIc). According to these criteria, the ratio of KIIc / KIc is a figure typically between 0.63 and 0.96. It is shown in this paper that enhanced mode II fracture toughness of CCNBD specimen could be due to the effects of highly negative T-stress when the specimen is subjected to mode II. It is also shown that an improved prediction for the ratio KIIc / KIc can be achieved when the effect of T-stress is taken into account.
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Zarrabi, K., A. Karpour, and A. K. Hellier. "Experimental Investigation of PMMA Fracture under Mixed-Modes I, II and III Loading." Advanced Materials Research 275 (July 2011): 7–10. http://dx.doi.org/10.4028/www.scientific.net/amr.275.7.
Повний текст джерелаАнотація:
Fracture studies of components involving mode III loading are rare. This paper concentrates on mixed-modes I, II and III fracture testing of brittle PMMA material and summarises an extensive experimental investigation. Karpour and Zarrabi have developed a special pair of grips for which they have received a patent. These grips allow the application of various mixtures of modes, including mode III, using a universal testing machine. To measure the three-dimensional crack-tip opening and sliding displacements, Karpour and Zarrabi have also developed a novel stereo machine vision system whose description is included in the paper. The measured critical crack-opening displacements presented in normalised format with potential of being used to assess the integrity of any component against elastic fracture and they compare well with limited pertinent data available from literature.
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Cicero, S., V. Madrazo, and I. A. Carrascal. "Estimation of Fracture Toughness by Testing Notched Fracture Specimens and Applying the Theory of Critical Distances." ISRN Materials Science 2012 (September 17, 2012): 1–8. http://dx.doi.org/10.5402/2012/689386.
Повний текст джерелаАнотація:
This paper applies a methodology that allows the fracture toughness of a given material to be estimated by testing notched fracture toughness specimens and applying the Theory of Critical Distances, which requires the elastic stress field at the notch tip to be determined by finite elements simulation. This methodology, which is not intended to substitute any standardised fracture characterisation procedure, constitutes an alternative in those situations where pre-cracking processes may be too time-consuming, too expensive or, simply, cannot be performed. It comprises testing two notched specimens with different notch radii, defining the corresponding stress fields at fracture by using finite elements analysis, and applying the Theory of Critical Distances in order to calibrate the material’s critical distance and to apply the corresponding apparent fracture toughness formulation. The methodology has been applied to two different materials, PMMA and Al7075-T651, and the results have proven that, as long as the Theory of Critical Distances has been applied within its validity range, the fracture toughness estimations are highly accurate.
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Chuluunbat, Turbadrakh, Andrii G. Kostryzhev, and Olexandra Marenych. "Investigation of X80 Line Pipe Steel Fracture during Tensile Testing Using Acoustic Emission Monitoring." Key Engineering Materials 794 (February 2019): 21–27. http://dx.doi.org/10.4028/www.scientific.net/kem.794.21.
Повний текст джерелаАнотація:
The acoustic emission (AE) monitoring technique is widely used in mechanical and materials research for detection of plastic deformation, fracture initiation and crack growth. However, the quantitative dependences of the AE signal parameters on material fracture parametersare not completely understood. This paper presents recent research results on AE monitoring of the fracture behavior of X80 line pipe steel, a critically important material for the oil and gas transportation industry.Fracture of this steel was studied using tensile testing of small scale specimens coupled with AE monitoring and high speed video camera. The dependence of fracture behavior and AE parameters on loading conditions (strain rate and presence or absence of a notch) was investigated. The AE parameters were analyzed using the “Average Hit” features and “Wave Form and Power Spectrum” methodologies. The fracture surface was characterized using scanning electron microscopy and a dependence of the AE parameters on the average void size has been obtained.
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Wang, Zhide, Zuyao Ma, Yuanyou Xia, Xiong Zhou, Manqing Lin, Jie Li, and Jinyuan Wang. "Testing Method for the Range of Fracture Zone of Rock Slope under Blasting Load." Shock and Vibration 2021 (June 4, 2021): 1–12. http://dx.doi.org/10.1155/2021/5574696.
Повний текст джерелаАнотація:
In engineering blasting, the determination of the range of rock blasting fracture zone has important guiding significance for blasting construction. This paper proposes a method that can accurately and directly obtain the range of rock blasting fracture zone. Based on the theory of elastic wave propagation, test rods which are made of appropriate material are selected and prepared. A certain number of boreholes are drilled for subsequent insertion of the test rods along the direction perpendicular to the free surface of the excavation at a certain distance from the blast hole. Based on the field blasting test results, the deepest fracture position of the test rod is used as the boundary of the blasting fracture zone, and the range of the rock blasting fracture zone is obtained. A numerical analysis model is established according to the Mohr–Coulomb constitutive relationship and the Von Mises yield criterion. Then, the range of the fracture zone and the maximum horizontal radius of the fracture zone are analyzed and obtained. The numerical analysis results are compared with the field measured data. It is demonstrated that the range of the fracture zone obtained by the numerical simulation is in good agreement with the blasting test results of the pre-embedded test rods. The research results can provide references for the safety control of blasting and excavation of rock slopes.
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Wagoner, Michael P., William G. Buttlar, Glaucio H. Paulino, and Philip Blankenship. "Investigation of the Fracture Resistance of Hot-Mix Asphalt Concrete Using a Disk-Shaped Compact Tension Test." Transportation Research Record: Journal of the Transportation Research Board 1929, no. 1 (January 2005): 183–92. http://dx.doi.org/10.1177/0361198105192900122.
Повний текст джерелаАнотація:
In recent years the transportation materials research community has focused a great deal of attention on the development of testing and analysis methods to shed light on fracture development in asphalt pavements. Recently it has been shown that crack initiation and propagation in asphalt materials can be realistically modeled with cutting-edge computational fracture mechanics tools. However, much more progress is needed toward the development of practical laboratory fracture tests to support these new modeling approaches. The goal of this paper is twofold: ( a) to present a disk-shaped compact tension [DC(T)] test, which appears to be a practical method for determining low-temperature fracture properties of cylindrically shaped asphalt concrete test specimens, and ( b) to illustrate how the DC(T) test can be used to obtain fracture properties of asphalt concrete specimens obtained from field cores following dynamic modulus and creep compliance tests performed on the same specimens. Testing four mixtures with varied composition demonstrated that the DC(T) test could detect the transition from quasi-brittle to brittle fracture by testing at several low temperatures selected to span across the glass transition temperatures of the asphalt binder used. The tendency toward brittle fracture with increasing loading rate was also detected. Finally, the DC(T) test was used in a forensic study to investigate premature reflective cracking of an isolated portion of pavement in Rochester, New York. One benefit of the DC(T) test demonstrated during testing of field samples was the ability to obtain mixture fracture properties as part of an efficient suite of tests performed on cylindrical specimens.
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Haberfield, C. M., and I. W. Johnston. "Determination of the fracture toughness of a saturated soft rock." Canadian Geotechnical Journal 27, no. 3 (June 1, 1990): 276–84. http://dx.doi.org/10.1139/t90-038.
Повний текст джерелаАнотація:
Although the literature provides a reasonable range of information concerning the fracture toughness of relatively hard rocks, there is virtually no data for saturated soft rocks of uniaxial compressive strengths less than about 10 MPa. To gain some insight into the plane strain fracture toughness of such a soft rock for use in the numerical modelling of crack propagation during pressuremeter testing, a large number of laboratory tests were conducted. The material used in these tests was a synthetic soft rock that modelled soft mudstone rocks reasonably accurately. This paper describes the test techniques adopted and the results obtained. The variation of fracture toughness with loading rate and with size and shape of the test specimens is presented and discussed. On the basis of these results, guidelines are suggested for the determination of plane strain fracture toughness of a soft rock. Key words: fracture mechanics, fracture toughness, laboratory testing, soft rock, weak rock.
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Prokić Cvetković, Radica, Olivera Popović, Ljubica Radović, Aleksandar Sedmak, and Ivana Cvetković. "Fracture Behavior of AlMg4.5Mn Weld Metal at Different Temperatures under Impact Loading." Sustainability 15, no. 2 (January 13, 2023): 1550. http://dx.doi.org/10.3390/su15021550.
Повний текст джерелаАнотація:
This paper deals with a three-component aluminum alloy AlMg4.5Mn that was welded using a GTAW process in the shielded atmosphere of Ar+70%He+0.015%N2. The weld-metal toughness was evaluated at three different temperatures using instrumental Charpy pendulum impact testing to measure not only the total energy, but also the crack initiation energy and the crack growth energy. Fractographic analysis of the fracture surfaces and EDS analysis of large second-phase particles on fractured surfaces at each temperature were also carried out. Fractographic analysis at different temperatures indicated a clearly distinguishable fracture mechanism. It was inferred that the absorbed energy was closely correlated with the fracturing of surfaces. Moreover, it was concluded that with decrease in the amount of microscopic voids and dimples, the total energy absorbed also decreased.
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Cai, Li Xun, Lei Jin, and Chen Bao. "On Fracture Mechanics Testing Technique Based on Compliance of Specimens." Key Engineering Materials 385-387 (July 2008): 293–96. http://dx.doi.org/10.4028/www.scientific.net/kem.385-387.293.
Повний текст джерелаАнотація:
Based on compliance testing of a straight-notch compact tensile (SN-CT) or a single edge bending (SEB) specimen, this paper present a formula with increment form to calculate plastic part of J-integral, two formulas for a SN-CT specimen and a SEB specimen to transform crack mouth opening displacement (CMOD) v0 to the crack opening displacement (COD) q along load line, and simplified formulas to estimate crack length a and effective young’s modulus E. Furthermore, the relation between v and q of the SN-CT specimens of 45 steel and SEB specimens of 30Cr steel were investigated. The results show that the formulas to describe the relation between the ratio v/q and the dimensionless crack length a/w of the specimens accord with the testing results better.
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Wong, Lydia Chwang Yuh, Wing Kong Chiu, Matthias Russ, and Susan Liew. "Experimental Testing of Vibration Analysis Methods to Monitor Recovery of Stiffness of a Fixated Synthetic Pelvis: A Preliminary Study." Key Engineering Materials 558 (June 2013): 386–99. http://dx.doi.org/10.4028/www.scientific.net/kem.558.386.
Повний текст джерелаАнотація:
Monitoring the healing of long bones has been studied extensively to reduce the period of encumbrance and unnecessary pain for patients suffering from fractured bones. This is more critical for unstable fractures in the pelvis as the patients can bedridden for up to 12 weeks to allow proper healing to take place. Current methods employed to monitor long bone healing are insufficient for applications in the pelvis as the human pelvis presents a significant change in geometry which demands a different approach. This paper explores an approach where vibration analysis is used to provide in-situ monitoring of a healing fracture in a human pelvis. Experimental tests were conducted on 4th generation synthetic pelvises instrumented with an array of PZT sensors. The synthetic pelvises were cut at the sacrum to simulate a fractured pelvis followed by the application of araldite epoxy to simulate healing by allowing the epoxy to cure. Measurements were collected from the sensor array over the curing period to obtain the transfer functions (TFs) for various excitations. An impact hammer was utilised to obtain powerful broadband excitations while the PZT sensors were used to detect the response in the synthetic pelvis as a results of these excitation signals. A comparison of TF against cure time (healed amount) indicates the presence of a significant relationship with the stiffness recovery of the epoxy at the cut of the synthetic model.
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Ghiban, Brândușa, Nicoleta Elisabeta Pascu, Iulian Vasile Antoniac, Gabriel Jiga, Claudia Milea, Gabriela Petre, Cristina Gheorghe, Corneliu Munteanu, and Bogdan Istrate. "Surface Characterization of Fracture in Polylactic Acid vs. PLA + Particle (Cu, Al, Graphene) Insertions by 3D Fused Deposition Modeling Technology." Coatings 11, no. 6 (May 25, 2021): 633. http://dx.doi.org/10.3390/coatings11060633.
Повний текст джерелаАнотація:
Polylactic acid (PLA) is one of the most extensively used biodegradable aliphatic polyester produced from renewable resources, such as corn starch. Due to its qualities, PLA is a leading biomaterial for numerous applications in medicine as well as in industry, replacing conventional petrochemical–based polymers. The purpose of this paper is to highlight the fracture behavior of pure PLA specimens in comparison with PLA particle insertions, (copper, aluminum and Graphene), after evaluation the mechanical properties, as well as the influence of filament angle deposition on these properties. In order to check if the filling density of the specimen influences the ultimate tensile stress (UTS), three different filling percentages (60%, 80%, and 100%) have been chosen in the experimental tests. A hierarchy concerning elongation / fiber heights after tensile testing was done. So, the highest elongation values were for simple PLA (about 4.1%), followed by PLA + Al insertion (3.2%–4%), PLA + graphene insertion (2.6%–4%) and the lowest values being for PLA with copper insertion (1.8%–2.7%). Regarding the fiber heights after fracture, the hierarchy was: the highest values was for PLA, then PLA + Al, PLA + grapheme and PLA + Cu. Finally, a correlation between fracture surfaces appearance and mechanical properties were established, being formulated the mechanism of fracture in according with filament angle deposition. Also, it was proposed a new method of evaluation of the fractured surface by measuring the dimensions of the filaments after printing Fused Deposition Modeling (FDM) and tensile testing.
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Chen, Peng Chao, Hong Zhang, and Hong Ju Wang. "Studies on MAaximum Hydrostatic Testing Pressure for New Pipeline." Applied Mechanics and Materials 117-119 (October 2011): 162–66. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.162.
Повний текст джерелаАнотація:
Hydrostatic testing is an important step in pipeline construction. This test ensures the integrity of newly-constructed pipelines. Testing pressures used by Chinese construction contractors are lower than that in foreign countries. Nowadays, higher testing pressure is considered safer for pipeline operation. But what is testing pressure we should apply? Basing on fracture mechanics theory, this paper addresses the effects of testing pressure on pipeline materials, and calculates the maximum safe testing pressure. Also, experiments validate the theoretic conclusions.
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Holušová, Táňa, Stanislav Seitl, and Alfonso Fernández Canteli. "Comparison of Fracture Energy Values Obtained from 3PB, WST and CT Test Configurations." Advanced Materials Research 969 (June 2014): 89–92. http://dx.doi.org/10.4028/www.scientific.net/amr.969.89.
Повний текст джерелаАнотація:
Modeling of concrete failure under fatigue loading is becoming a field of interest. Possible alternative testing solutions are now being searched. In this paper, the fracture energy for a certain concrete, resulting from three traditional fracture tests, namely three point bending test, wedge-splitting test and modified compact tension test, is investigated.
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Hu, Shao Wei, Jun Lu, and Xiaoqing Zhong. "Study on Characteristics of Acoustic Emission Property in the Normal Concrete Fracture Test." Advanced Materials Research 189-193 (February 2011): 1117–21. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.1117.
Повний текст джерелаАнотація:
This paper first elaborates the domestic and foreign study and applying current situation in terms of the concrete testing field regarding to acoustic emission technology, especially the study progress in the large dam concrete field. By improving the current test device and updating and reforming the measuring equipment, the task team introduces the acoustic emission testing system into the concrete double-K fracture parameter test. The new device can not only accurately control the loading velocity in the test, but also correctly judge the time and property of cracking, instability and damage of specimen. This paper establishes the acoustic emission criterion for concrete fracture according to the recognition features of acoustic emission of concrete in fracture critical state. The test result presents that the cracking time of specimen can be correctly judged by using feature parameters of acoustic emission, which properly matches the cracking time measured by the traditional strain method, and this judging is more direct and convenient for on-site operation, providing theoretical and technical support for application in the concrete fracture parameter test by acoustic emission technology.
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Bartsch, Marion, Bernd Baufeld, Serdar Dalkiliç, and Iulian Mircea. "Testing and Characterization of Ceramic Thermal Barrier Coatings." Materials Science Forum 492-493 (August 2005): 3–8. http://dx.doi.org/10.4028/www.scientific.net/msf.492-493.3.
Повний текст джерелаАнотація:
This paper gives a short overview of tests applied for the investigation of long term behaviour of thermal barrier coating systems. A variety of tests has been conducted on an exemplary material system with the coatings applied by electron beam physical vapour deposition. Damages and damage evolution in different tests are compared. Since the observed damage mechanisms are different, it is proposed to design laboratory tests as realistic as possible, especially if the test data are used for lifetime assessment. In order to get reasonable testing times, the damage accumulation has to be described as a function of loading history, long time before failure. For the case of final failure by spallation of the ceramic top coat, it is proposed to use the apparent interfacial fracture toughness as damage parameter. Several methods for measuring the apparent fracture toughness of brittle coatings are discussed with respect to their application to thermal barrier coating systems.