COMPARISON OF THE CRACK-GROWTH METHOD AND THE CRACK STRESS WHITENING ZONE METHOD FOR THE FRACTURE-TOUGHNESS DETERMINATION OF PHENOLPHTHALEIN POLY(ETHER KETONE)

Fracture toughness values of phenolphthalein poly(ether ketone) (PEK-C) at 190 degrees C were determined by two different methods, i. e. the conventional crack growth method and the crack stress whitening zone method, which show consistent results. This indicates that the crack stress whitening zone method can be used to determine the crack initiation of some polymers for which the blunting line concept is unsuitable.

THE FRACTURE-BEHAVIOR OF PHENOLPHTHALEIN POLYETHER ETHER KETONE AT ELEVATED-TEMPERATURE FOR LONG TERMS

The fracture behavior of phenolphthalein polyether-ether ketone (PEK-C) affected by physical aging at 200 degrees C was studied by tensile experiments, scanning electron microscopy, and differential scanning calorimetry observations. The ductile-brittle fracture transition (DBT) caused by physical aging can be considered as a competition between fracture mechanisms of crazing and shear yielding. The aging time required for the DBT is found to be around 400 h, based on the morphological studies and tensile experiments. The shear yielding component of the mechanical deformation could erase the aging effect, thus a deaging phenomenon occurs. We found that the deaging phenomenon has an intrinsic relationship with the extent of aging in the specimen and as a result of the fracture behavior. (C) 1995 John Wiley and Sons, Inc.

TEMPERATURE RATE DEPENDENCE OF YIELD AND FRACTURE-BEHAVIOR OF PHENOLPHTHALEIN POLY(ETHER KETONE)

The rate/temperature dependence of yield stress, tensile modulus and crack opening displacement of phenolphthalein poly(ether ketone) (PEK-C) has been investigated. The rate/temperature dependence of crack opening displacement and the correlation establis

INTERLAMINAR FRACTURE OF CARBON THERMOPLASTIC POLYIMIDE COMPOSITES

Mode I interlaminar fracture of a novel amorphous thermoplastic polyimide reinforced with unidirectional carbon fibre has been studied experimentally using double cantilever beam specimens and scanning electron microscopy. Three kinds of composite were ma

FRACTURE-TOUGHNESS AND MORPHOLOGY OF PHENOLPHTHALEIN POLY(ETHER SULFONE) THERMOTROPIC LIQUID-CRYSTALLINE POLYMER BLENDS

Blends of a new phenolphthalein poly (ether sulfone) (PES-C) and a thermotropic liquid crystalline polymer (LCP) were prepared by melt-blending in a twin-screw extruder. Rheological properties, fracture toughness, K(IC), and morphology of the blends were

ON THE ANALYSIS OF THE END-NOTCHED FLEXURE SPECIMEN FOR MEASURING MODE-II FRACTURE-TOUGHNESS OF COMPOSITE-MATERIALS

This paper deals with the correction of mode II strain energy release rate, G(II), of composite laminates measured with the end-notched flexure (ENF) specimen. A derivation is given of the expressions for compliance and strain energy release rate, in whic

DETERMINATION OF INITIATION VALUE OF MODE-I INTERLAMINAR FRACTURE-TOUGHNESS OF UNIDIRECTIONAL POLYMER COMPOSITES

The use of interlaminar fracture tests to measure the delamination resistance of unidirectional composite laminates is now widespread. However, because of the frequent occurrence of fiber bridging and multiple cracking during the tests, it leads to artificially high values of delamination resistance, which will not represent the behavior of the laminates. Initiation fracture from the crack starter, on the other hand, does not involve bridging, and should be more representative of the delamination resistance of the composite laminates. Since there is some uncertainty involved in determining the initiation value of delamination resistance in mode I tests in the literature, a power law of the form G(IC) = A.DELTA alpha(b) (where G(IC) is mode I interlaminar fracture toughness and DELTA alpha is delamination growth) is presented in this paper to determine initiation value of mode I interlaminar fracture toughness. It is found that initiation values of the mode I interlaminar fracture toughness, G(IC)(ini), can be defined as the G(IC) value at which 1 mm of delamination from the crack starter has occurred. Examples of initiation values determined by this method are given for both carbon fiber reinforced thermoplastic and thermosetting polymers.

EFFECT OF REPTATION ON FRACTURE-MECHANICS OF RUBBER NETWORKS

End-linked hydroxyl-terminated polybutadiene containing unattached linear polybutadiene was used to study the effect of reptating species on the fracture mechanics of rubber networks. The concentration of reptating species in the networks ranged from 0 to 100%. The fracture mechanics of the networks was described using the critical strain energy release rate in mode III testing, i.e. the tearing energy. The tearing energy was measured at room temperature using a 'trouser' specimen at a strain rate spanning five logarithmic decades. When the strain rate was as low as 10(-4) s-1, the tearing energy of the networks increased with reduction in reptating species. In this case the reptating species did not contribute to the tearing energy of the networks due to relaxation. Hence, the tearing energy increased with the number of crosslinked chains per unit volume in the networks. At a strain rate ranging from 10(-3) to 10(-1) s-1, the tearing energy of the networks was governed by local viscosity. The tearing energies of the networks containing various amounts of reptating species were superimposed to give a master curve based on the Williams-Landel-Ferry equation.

SEM STUDY ON FRACTURE-BEHAVIOR OF ETHYLENE/PROPYLENE BLOCK COPOLYMERS AND THEIR BLENDS

The toughening effect of the separate phases of ethylene/propylene block copolymers and their blends was studied by scanning electron microscopy (SEM). The results obtained show that the interfacial adhesion between separate phases and the isotactic polypropene (iPP) matrix in ethylene/propylene block copolymers is strong at room temperature, but poor at low temperature; specimens exhibit tearing of separate phases during fracture at room temperature, but interfacial fracture between separate phases and the iPP matrix at low temperature. From the characteristics of fractographs of ethylene/propylene block copolymers and their blends, it could be concluded that the separate phases improve the toughness of specimens in several ways: they promote the plastic deformation of the iPP, and they can be deformed and fractured themselves during the fracture process. However, it was shown that the plastic deformation processes, such as multiple-crazing, shear yielding, etc. of the matrix are the dominant mechanisms of energy absorption in highly toughened ethylene/propylene block copolymers and their blends. The deformation and fracture of separate phases are only of secondary importance.

胜利勘探数据中心及勘探辅助决策系统研究

In the paper through extensive study and design, the technical plan for establishing the exploration database center is made to combine imported and self developed techniques. By research and repeated experiment a modern database center has been set up with its hardware and network having advanced performance, its system well configured, its data store and management complete, and its data support being fast and direct. Through study on the theory, method and model of decision an exploration decision assistant schema is designed with one decision plan of well location decision support system being evaluated and put into action. 1. Study on the establishment of Shengli exploration database center Research is made on the hardware configuration of the database center including its workstations and all connected hardware and system. The hardware of the database center is formed by connecting workstations, microcomputer workstations, disk arrays, and those equipments used for seismic processing and interpretation. Research on the data store and management includes the analysis of the contents to be managed, data flow, data standard, data QC, data backup and restore policy, optimization of database system. A reasonable data management regulation and workflow is made and the scientific exploration data management system is created. Data load is done by working out a schedule firstly and at last 200 more projects of seismic surveys has been loaded amount to 25TB. 2. Exploration work support system and its application Seismic data processing system support has the following features, automatic extraction of seismic attributes, GIS navigation, data order, extraction of any sized data cube, pseudo huge capacity disk array, standard output exchange format etc. The prestack data can be accessed by the processing system or data can be transferred to other processing system through standard exchange format. For supporting seismic interpretation system the following features exist such as auto scan and store of interpretation result, internal data quality control etc. the interpretation system is connected directly with database center to get real time support of seismic data, formation data and well data. Comprehensive geological study support is done through intranet with the ability to query or display data graphically on the navigation system under some geological constraints. Production management support system is mainly used to collect, analyze and display production data with its core technology on the controlled data collection and creation of multiple standard forms. 3. exploration decision support system design By classification of workflow and data flow of all the exploration stages and study on decision theory and method, target of each decision step, decision model and requirement, three concept models has been formed for the Shengli exploration decision support system including the exploration distribution support system, the well location support system and production management support system. the well location decision support system has passed evaluation and been put into action. 4. Technical advance Hardware and software match with high performance for the database center. By combining parallel computer system, database server, huge capacity ATL, disk array, network and firewall together to create the first exploration database center in China with reasonable configuration, high performance and able to manage the whole data sets of exploration. Huge exploration data management technology is formed where exploration data standards and management regulations are made to guarantee data quality, safety and security. Multifunction query and support system for comprehensive exploration information support. It includes support system for geological study, seismic processing and interpretation and production management. In the system a lot of new database and computer technology have been used to provide real time information support for exploration work. Finally is the design of Shengli exploration decision support system. 5. Application and benefit Data storage has reached the amount of 25TB with thousand of users in Shengli oil field to access data to improve work efficiency multiple times. The technology has also been applied by many other units of SINOPEC. Its application of providing data to a project named Exploration achievements and Evaluation of Favorable Targets in Hekou Area shortened the data preparation period from 30 days to 2 days, enriching data abundance 15 percent and getting information support from the database center perfectly. Its application to provide former processed result for a project named Pre-stack depth migration in Guxi fracture zone reduced the amount of repeated process and shortened work period of one month and improved processing precision and quality, saving capital investment of data processing of 30 million yuan. It application by providing project database automatically in project named Geological and seismic study of southern slope zone of Dongying Sag shortened data preparation time so that researchers have more time to do research, thus to improve interpretation precision and quality.

小湾电站坝基岩体卸荷工程地质力学研究

Dam is the key main works in the construction of water power. The success or failure of the construction of the dam mainly depends on the stability of the dam foundation. The double curvature arch dam-XiaoWan Dam is the highest one among the dams with the same type in the world, and the water thrust acted on it reaches ton, so the rock bearing capacity of dam foundation becomes more important. Because of the high and steep valley-side slope, the large scale of excavation and the complex body type of excavation, it is prominent that the problem of stress release of the rock mass in dam foundation. More great attentions should be paid for the stability and the degraded of rock properties of rock mass induced by the stress release. In this paper, the phenomena of stress release of rock mass in XiaoWan Dam foundation and its mechanisms were analyzed based on the collection of data, the detailed field engineering investigations, measurement of the rock mass and the 2D numerical calculations. The rock mass under the foundation is weak-weathered to intact, the quality of which is good. After excavation of the foundation, the rock mass near the slope surface occurred extend, stretch and stick-slip along original textures till the new fracture surface formed. Then platy structure of the rock mass takes on. The rock mass in the dam foundation occur resilience due to stress release towards free faces with the characteristics of time effect and localized deformation. In-situ measurements show that the rock mass near the surface are degraded. The stress release induced by excavation is a process of the interaction between engineering structures and geologic body. The stress release of rock mass in dam foundation is related to the changed degree of geometrical conditions. The rock near excavation surface failed nearly under uniaxial stresses. The bending-breaking mechanism of plate girder can interpret the failure model of the rock mass with platy structure in dam foundation slope. In essence, the stress release is the change of stress field including the change of directions and magnitudes of stress induced by excavation, which can induce the comedown of the safety margin. In this paper, the inducing conditions of stress release were calculated by numerical analyses. Moreover, from the point of view that the change of stress field, the coefficient of K, i.e. the variable load coefficient was proposed. Then the law of the change of it is interpreted. The distributional characteristics of fracture zone were expressed by the coefficient. The stress release of hard rock has the characteristic of localization. The measuring technique of sound wave can not reflect the small cracks in this kind of rock mass due to stress release. So, the spectral analysis method was proposed. At the same time, the application foreground in engineering of the Stockwell Time-Frequency- Spectrum method was discussed with a view to the limitation of it.

基于窗口精细结构描述的岩体质量评价及力学参数综合优选

This thesis bases on horizontal research project “The research about the fine structure and mechanical parameters of abutment jointed rock mass of high arch dam on Jinping Ⅰ Hydropower Station, Yalong River” and “The research about the fine structure and mechanical parameters of the columnar basalt rock mass on Baihetan Hydropower Station, Jinsha River”. A rounded system about the fine structure description and rock mass classification is established. This research mainly contains six aspects as follow: (1) Methods about fine structure description of the window rock mass; (2) The window rock mass classification about the fine structure; (3) Model test study of intermittent joints; (4) Window rock mass strength theory; (5) Numerical experimentations about window rock mass; (6) The multi-source fusion of mechanical parameters based on Bayes principle. Variation of intact rock strength and joint conditions with the weathering and relaxation degree is studied through the description of window rock mass. And four principal parameters: intact rock point load strength, integration degree of window rock mass, joint conditions, and groundwater condition is selected to assess the window rock mass. Window rock mass is classified into three types using the results of window rock mass fine structure description combined with joints develop model. Scores about intact rock strength, integrality condition, divisional plane condition and groundwater conditions are given based on window rock mass fine structure description. Then quality evaluation about two different types of rock mass: general joint structure and columnar jointing structure are carried out to use this window rock mass classification system. Application results show that the window rock mass classification system is effective and applicable. Aimed at structural features of window structure of “the rock mass damaged by recessive fracture”, model tests and numerical models are designed about intermittent joints. By conducting model tests we get shear strength under different normal stress in integrated samples, through samples and intermittent joints samples. Also, the changing trends of shear strength in various connectivity rates are analyzed. We numerically simulate the entire process of direct shear tests by using PFC2D. In order to tally the stress-strain curve of numerical simulation with experimental tests about both integrated samples and through samples, we adjust mechanical factors between particles. Through adopting the same particle geometric parameter, the numerical sample of intermittent joints in different connective condition is re-built. At the same time, we endow the rock bridges and joints in testing samples with the fixed particle contacting parameters, and conduct a series of direct shear tests. Then the destructive process and mechanical parameters in both micro-prospective and macro-prospective are obtained. By synthesizing the results of numerical and sample tests and analyzing the evolutionary changes of stress and strain on intermittent joints plane, we conclude that the centralization of compressive stress on rock bridges increase the shear strength of it. We discuss the destructive mechanics of intermittent joints rock under direct shear condition, meanwhile, divide the whole shear process into five phases, which are elasticity phase, fracture initiation phase, peak value phase, after-peak phase and residual phase. In development of strength theory, the shear strength mechanisms of joint and rock bridge are analyzed respectively. In order to apply the deducted formulation conveniently in the real projects, a relationship between these formulations and Mohr-Coulomb hypothesis is built up. Some sets of numerical simulation methods, i.e. the distinct element method (UDEC) based on in-situ geology mapping are developed and introduced. The working methods about determining mechanical parameters of intact rock and joints in numerical model are studied. The operation process and analysis results are demonstrated detailed from the research on parameters of rock mass based on numerical test in the Jinping Ⅰ Hydropower Station and Baihetan Hydropower Station. By comparison，the advantages and disadvantages are discussed. Results about numerical simulation study show that we can get the shear strength mechanical parameters by changing the load conditions. The multi-source rock mass mechanical parameters can be fused by the Bayes theory, which are test value, empirical value and theoretical value. Then the value range and its confidence probability of different rock mass grade are induced and these data supports the reliability design.

锦屏电站地下厂房卸荷岩体参数研究

It is a basic work to ascertain the parameters of rock mass for evaluation about stability of the engineering. Anisotropism、inhomogeneity and discontinuity characters of the rock mass arise from the existing of the structural plane. Subjected to water、weathering effect、off-loading, mechanical characters of the rock mass are greatly different from rock itself, Determining mechanical parameters of the rock mass becomes so difficult because of structure effect、dimension effect、rheological character, ‘Can’t give a proper parameter’ becomes one of big problems for theoretic analysis and numerical simulation. With the increment of project scale, appraising the project rock mass and ascertaining the parameters of rock mass becomes more and more important and strict. Consequently, researching the parameters of rock mass has important theoretical significance and actual meaning. The Jin-ping hydroelectric station is the first highest hyperbolic arch dam in the world under construction, the height of the dam is about 305m, it is the biggest hydroelectric station at lower reaches of Yalong river. The length of underground factory building is 204.52m, the total height of it is 68.83m, the maximum of span clearance is 28.90m. Large-scale excavation in the underground factory of Jin-ping hydroelectric station has brought many kinds of destructive phenomenon, such as relaxation、spilling, providing a precious chance for study of unloading parameter about rock mass. As we all know, Southwest is the most important hydroelectric power base in China, the construction of the hydroelectric station mostly concentrate at high mountain and gorge area, basically and importantly, we must be familiar with the physical and mechanical character of the rock mass to guarantee to exploit safely、efficiently、quickly, in other words, we must understand the strength and deformation character of the rock mass. Based on enough fieldwork of geological investigation, we study the parameter of unloading rock mass on condition that we obtain abundant information, which is not only important for the construction of Jin-ping hydroelectric station, but also for the construction of other big hydroelectric station similar with Jin-ping. This paper adopt geological analysis、test data analysis、experience analysis、theory research and Artificial Neural Networks （ANN） brainpower analysis to evaluate the mechanical parameter, the major production is as follows: (1)Through the excavation of upper 5-layer of the underground powerhouse and the statistical classification of the main joints fractures exposed, We believe that there are three sets of joints, the first group is lay fracture, the second group and the fourth group are steep fracture. These provide a strong foundation for the following calculation of and analysis; (2)According to the in-situ measurement about sound wave velocity、displacement and anchor stress, we analyses the effects of rock unloading effect，the results show a obvious time-related character and localization features of rock deformation. We determine the depth of excavation unloading of underground factory wall based on this. Determining the rock mass parameters according to the measurement about sound wave velocity with characters of low- disturbing、dynamic on the spot, the result can really reflect the original state, this chapter approximately the mechanical parameters about rock mass at each unloading area; (3)Based on Hoek-Brown experienced formula with geological strength index GSI and RMR method to evaluate the mechanical parameters of different degree weathering and unloading rock mass about underground factory, Both of evaluation result are more satisfied; (4)From the perspective of far-field stress, based on the stress field distribution ideas of two-crack at any load conditions proposed by Fazil Erdogan (1962)，using the strain energy density factor criterion (S criterion) proposed by Xue changming(1972)，we establish the corresponding relationship between far-field stress and crack tip stress field, derive the integrated intensity criterion formula under the conditions of pure tensile stress among two line coplanar intermittent jointed rock，and establish the corresponding intensity criterion for the exploratory attempt; (5)With artificial neural network, the paper focuses on the mechanical parameters of rock mass that we concerned about and the whole process of prediction of deformation parameters, discusses the prospect of applying in assessment about the parameters of rock mass，and rely on the catalog information of underground powerhouse of Jinping I Hydropower Station, identifying the rock mechanics parameters intellectually，discusses the sample selection, network design, values of basic parameters and error analysis comprehensively. There is a certain significance for us to set up a set of parameters evaluation system，which is in construction of large-scale hydropower among a group of marble mass.

龙游石窟洞室群稳定性分析及最佳旅游路线选择

The large ancient underground rock caverns in Longyou is an important component of grotto cultural. Current task facing the long-term preservation of these unmovable cultural relics is arduous and challenging. The deformation failure of the caverns' surrounding rock is deteriorating. The weathering velocity of these caverns is accelerating. With the strength of caverns' surrounding rock worsening, critical rocks were generated in local regions of the caverns' vault and posing a threat to the security of people passing by. Selection of a maximum-security route and construction a aisle in the caverns might be an efficient way to ensure the security of tourists and reach the target of long-term preservation. The deformation and destruction of the ancient underground caverns is primarily dominated by geological conditions and the special structure of caverns. Based on field investigation, several fundamental conditions for deformation and failure are recognized, and nine deformation and fracture patterns of the Longyou grotto are proposed. In order to judge the stability of caverns’ surrounding rock, the element safety coefficient method is presented. An explicit explanation for the meaning of the method is deduced using Mohr-Coulomb strength criterion. Numerical analyses are carried out in the dissertation through FLAC3D code. Through numerical analysis, the stress distribution regularities of the caverns’ roofs, piles and public side wall are analysed, and the stability properties of caverns’ surrounding rock are also assessed. At the same time, the element safety coefficient method is introduced to contrast the stability degree of different regions in caverns. The above analyses are bases for choosing the optimal tourism routes in the caverns of Longyou grotto. The impact of surface load on the stability of shallow buried cavities in Longyou grotto is evaluated, the results show that building load has significant influence on the stability of the No.1 cavern’s roof, pile and public side wall between the No.1 cavern and the No.2 cavern, pedestrian load has less impact on the stability of surrounding rock than building load. The principles for choosing the optimal tourism routes in the caverns are discussed. With these principles, the dissertation makes a systematic research on the geological analytic method, numerical analytic method and meeting tourism requirements method, which are used in selecting the optimal tourism routes in the caverns. In order to achieve the best effect in the process of tourism routes selection, the above three method are integrated through Theory of Engineering Geomechanics Meta-system(EGMS). According to field investigations, numerical analyses, tourism requirements and expert experiences, the optimal tourism routes through No.1 to No.5 cavern are determined preliminarily. The obtained results from the research work are useful for the security aisle's construction, they also have reference value to other projects in practice.