Search

This paper presents a methodology for determining the uniaxial and triaxial compressive strength of heterogeneous material composed of dacite (D) and altered dacite (AD). A zone of gradual transition from altered dacite to dacite was observed in the rock mass. The mechanical properties of the rock material in that zone were determined by laboratory tests of composite samples that consisted of rock material discs. However, the functional dependence on the strength parameter alteration of the rock material (UCS, intact UCS of the rock material, and mi) with an increase in the participation of “weaker” rock material was determined based on the test results of uniaxial and triaxial compressive strength. The participation of altered dacite directly affects the mode and mechanism of failure during testing. Uniaxial compressive strength (σciUCS) and intact uniaxial compressive strength (σciTX) decrease exponentially with increased AD volumetric participation. The critical ratio at which the uniaxial compressive strength of the composite sample equals the strength of the uniform AD sample was at a percentage of 30% AD. Comparison of the obtained exponential equation with practical suggestions shows a good correspondence. The suggested methodology for determining heterogeneous rock mass strength parameters allows us to determine the influence of rock material heterogeneity on the values σciUCS, σciTX, and constant mi. Obtained σciTX and constant mi dependences define more reliable rock material strength parameter values, which can be used, along with rock mass classification systems, as a basis for assessing rock mass parameters. Therefore, it is possible to predict the strength parameters of the heterogeneous rock mass at the transition of hard (D) and weak rock (AD) based on all calculated strength parameters for different participation of AD.

The soil-rock mixture (S-RM) is widely used as a kind of geotechnical material in some construction engineering. When analyzing the stability of the engineering, the strength properties of S-RM are used as crucial input parameters. In this paper, to improve the understanding of strength properties of S-RM, a series of large-scale direct shear tests were conducted on S-RM with two volumetric rock block contents (VBCs), each with three types of block lithology. The particle breakage after each test and its relationship with strength properties were also analyzed. The results reveal that the influences of VBC and block lithology on particle breakage are slight when VBC is low, while significant as VBC increases. Compared with the traditional M-C strength criterion, a modified M-C nonlinear strength criterion is more suitable for the S-RM. When VBC is low, the influences of VBC and block lithology on the strength properties are slight. However, when VBC is high, their impacts will become greater, especially on the nonlinear strength parameter Δφ. The nonlinear strength characteristics become more obvious with an increase in relative breakage index Br, which are mainly caused by the particle breakage during the shearing process.

In view of phenomenological observations, the anisotropic state variable accounting for the effect of inherent fabric anisotropy, which can describe the microstructural characteristics of sand, is thought to influence the critical state of sand. Based on revised forms of the anisotropic state variable, the form for the anisotropic critical state line function is revised and the non-monotonically anisotropic effects are incorporated into the strength parameter in the re-adjustment of the elements of the model. The anisotropic plasticity model parameters of Toyoura sand are re-calibrated with triaxial compression and extension tests having various deposition directions. In comparison to the experiments on Toyoura sand, it is shown that the model can simulate the anisotropic stress-strain relationship reasonably well. Then, bifurcation analyses are conducted to predict the onset of strain localization with the corresponding non-coaxial anisotropic model. The results show that the modeling of shear band formation based on the non-coaxial model is in agreement with the tests considering the anisotropic characteristic.

The fatigue crack growth (FCG) process is usually accessed through the stress intensity factor range, ΔK, which has some limitations. The cumulative plastic strain at the crack tip has provided results in good agreement with the experimental observations. Also, it allows understanding the crack tip phenomena leading to FCG. Plastic deformation inevitably leads to micro-porosity occurrence and damage accumulation, which can be evaluated with a damage model, such as Gurson–Tvergaard–Needleman (GTN). This study aims to access the influence of the GTN parameters, related to growth and nucleation of micro-voids, on the predicted crack growth rate. The results show the connection between the porosity values and the crack closure level. Although the effect of the porosity on the plastic strain, the predicted effect of the initial porosity on the predicted crack growth rate is small. The sensitivity analysis identified the nucleation amplitude and Tvergaard’s loss of strength parameter as the main factors, whose variation leads to larger changes in the crack growth rate.

A deep understanding of the behavior and specifications of grouting materials between soil particles is required to increase the applications of various grouting technologies. Out of the different ...

Based on laboratory testing of bedded specimens made of artificial geomaterial, meta-siltstone and schist subjected to uniaxial compression and triaxial compression by the Karman scheme, the deformation and strength characteristics of the materials are determined as functions of the bedding angle. The elasticity properties and strength are estimated in accordance with the theoretical model by Salamon and Tien and the Hoek–Brown criterion. For the layered artificial geomaterial, the theoretical model by Salamon and Tien ensures a well-contended estimate of elastic properties. The strength parameter obtained based on the Hoek–Brown criterion is independent of the level of the lateral pressure applied.

Drained triaxial tests have been performed to explore the effect of particle loss on shearing behaviour and critical states in granular mixtures. The mixtures comprise Leighton Buzzard sand (d50 = 0.8 mm), to which was added 15% by mass of salt particles of different nominal sizes: 0.063 mm, 0.25 mm and 0.5 mm. Shearing behaviours before and after particle loss (by dissolution) were compared. A good fit is observed between the test data and a stress-dilatancy relationship for the post-dissolution tests, highlighting the ability of the stress-dilatancy analysis as a means to interpret the effects of particle loss on shearing. It was noted that critical state strength parameter M is determined by the post-dissolution grading regardless of size of removed particle. However, the duration of contractant volumetric strain increased with the larger removed particles (0.25 mm & 0.5 mm) even when initial specific volumes were virtually identical. It is suggested that a loose volumetric state is reached if the sand particle network is initially disrupted by the amount and/or size of salt particles, which following dissolution results in structural or fabric phenomena that are not reflected in scalar volumetric measures such as specific volume.

Measurement of tensile strength of soil by direct methods can be challenging due to difficulties in sample preparation and in fixing the specimen while applying uniaxial tension forces. However the tensile strength of soil samples can be measured by indirect tests, such as the Brazilian and double punch tests, assuming that tensile stress is distributed uniformly on the failure plane. In this study, the tensile strength of statically-compacted sand bentonite and cement-enhanced sand bentonite mixtures is measured in varying curing time periods using the “double punch” test. The compressive strengths of samples are also measured using the unconfined compression test, and the correlation between tensile and compressive strength is discussed in relation to curing time. A simple method is also applied to determine the undrained cohesion and internal friction angle of samples through the Mohr-Coulomb circle method, using the double punch tensile strength and unconfined compressive strength. The results show that cohesion increases in both sand bentonite and sand bentonite-cement samples along with curing time.

The strength parameter D, ideal glass transition temperature T0, and fragility parameter m are vital parameters and frequently used to analyze significant problems in various glass-forming liquids. It is found that parameters D, T0 and m will have great difference when these values for the same glass-forming liquid are obtained by fitting the measured viscosity data in different temperature ranges near glass transition temperature Tg. In order to obtain accurate parameters (T0, D and m), the temperature dependences of viscosity in different temperature ranges are studied. The results show that in the temperature range 0.97Tg~1.16Tg, the fitting viscosity data obtained by the measured data in temperature ranges (f)~(k) and Plazek's expression are close to the measured viscosity data. However, there are still great difference between the minimum and maximum values for fluctuant T0 and D values, which are 28.61 K and 24.91, respectively. The study further finds that parameters obtained using the measured viscosity data in temperature ranges (g)~(i) and (k) by VFT relation are more accurate and the maximal fluctuations of T0 and D parameters are decreased to 10.57 K and 10.79, respectively. Furthermore, parameters obtained by the measured data in (g) are the most accurate than those obtained by the measured data in any temperature range.

Rock fracture process is associated with the degradation and mobilization of the mechanical and strength properties of rock. A number of true triaxial cyclic loading and unloading tests were carried out on three types of hard rocks (i.e., granite, marble and sandstone) to investigate the evolution of the rock properties as a function of accumulated damage. In addition to stress and strain measurements, acoustic emission (AE) signals were monitored and used to associate different stages of crack development with different stages of the mechanical and strength parameter evolution. Young's modulus and five strain increment ratios were calculated from the measured increments of stresses and strains in each cycle. It was found that hard rocks exhibited profound deformation anisotropy and directional dilation. A general trend of decreasing volumetric strain reversal stress and peak stress with increasing plastic strains was observed for all the tested specimens. The evolution of the strength properties of rock under true triaxial compression was investigated using a linear 3D hard rock failure criterion and was found to be generally consistent with the cohesion weakening and frictional strengthening concept. The influence of the intermediate principal stress on the evolution of the rock properties was also discussed.

We present a plausible explanation for the scaling issue in the penetration of concrete targets by rigid projectiles, as manifested by the different penetration efficiency of projectiles with various sizes. Our analysis uses the empirically-based size effect for the unconfined compressive strengths of concrete specimens, according to which larger specimens have lower strengths. We define a new (effective) strength parameter for the concrete target, which depends also on the diameter of the projectile. The analysis results in a monotonic relation between the resistance to penetration of a given projectile/concrete pair and the effective compressive strength of this pair. With this relation one can predict the penetration depth of a rigid projectile into a given concrete target, for any impact velocity. We also introduce the concept of equivalent aluminum targets, in order to obtain useful information about penetrations in concrete targets without the complexities involved in their constitutive relations.

Herein, measured and ideal glass transition temperatures of glass-forming liquids have been investigated. The value of T0/Tg increases with increasing fragility parameter m or decreasing strength parameter D (where Tg and T0 are the measured and ideal glass transition temperatures, respectively). We utilize T0/Tg values to classify various glass-forming liquids into three broad categories, which are strong, metallic glass-forming (intermediate) and fragile liquids. The result reveals that strong liquids with 15.25

Considering the difficulty in measuring the model I fracture toughness of rocks, this study aims to develop a quantitative relationship between model I fracture toughness and strength parameters such as the tensile strength, the uniaxial compressive strength, and the Hoek-Brown (H-B) strength parameter m i . Based on the collected experimental data from the literature, a relationship between model I fracture toughness and tensile strength is derived statistically. The rock tensile strength can be determined using a closed-form relationship from the uniaxial compressive strength and the H-B strength parameter m i , which can be easily measured. Combining the two relationships, a new method is proposed to determine the model I fracture toughness conveniently. Finally, collected experimental data is used to validate the proposed estimating method.

The criterion Δɛ = ɛ(AX) − ɛ(BX) enabling the systematization of structures in terms of symmetry categories was proposed for the classification of three-element ionic halides by complex/double type. The adequacy of this approach was verified by the structure maps plotted using the generalized strength parameter. The crystal-chemical properties of the structures of ABX2, ABX3, and ABX4 halides were predicted.

Through the permeability leach test,this paper analyzed the change rule of the strength parameters of the saline soil with salt content. The results show that the more salt the saline soil had before leached,the more cohesive force and internal friction angle is reduced after it was leached, and the relationship between them can be explained through hyperbolic function.According to the soil shear strength theory, deduced the calculation formula of the strength after leached. Through the verification, the calculation values of the strength parameter and measured values were very close. Shear strength calculation formula offers a theoretical basis for the design and the foundation stability calculation of buildings in saline soil areas.

We study defect modes in optically induced one-dimensional lattices in photovoltaic-photorefractive crystals. These defect modes exist in different bandgaps due to the change of defect intensity. For a positive defect, defect mode branches exist not only in the semi-infinite bandgap, but also in the first and second bandgaps. When the defect mode branch is fixed, the confinement of defect modes increases with the defect strength parameter. For a negative defect, defect mode branches exist only in the first and second bandgaps. For a given defect mode branch, the strongest confinement of the defect modes appears when the lattice intensity at the defect site is not the smallest in its branch. On the other hand, when the defect strength parameter is fixed, the most localized defect modes arise in the semi-infinite bandgap for the positive defect and in the first bandgap for the negative defect.

Miniature specimen techniques viz. small-punch tests (SPT) have been carried out at room temperature in order to correlate the microstructural degradation of 2.25Cr-1Mo steel with that of SPT parameters. Microstructural degradation of this steel has been introduced as a result of thermal ageing corresponding to Larson-Miller parameters (LMP) values of 33,012, 35,402, 37,846 and 38,374. SPT parameters viz. total area and area under the region of plastic instability of the load-displacement curve have been found to decrease with an increase in LMP values. A strength parameter viz. UTS obtained using uniaxial tensile tests has also been found to decrease with an increase in LMP values. The results indicated that miniature specimen techniques viz. small-punch test could be successfully used to assess the degradation of microstructures in 2.25Cr-1Mo steel generated due to their exposure to high temperatures.

The rock mass deformation properties of unloading is very different from loading.The physical and mechanical properties of structural plane can bring a very great influence to rock’s unloading behavior. The lower the strength parameter of joint plane and the greater the angle of joint, the lower the unloading modulus of deformation. The greater the connectivity of joint,the faster the unloading modulus of deformation descend. In any case unloading amount is near linear relation with descend amount of unloading deformation modulus.

This article deals with the classification of glassy and polymer electrolytes for lithium-ion batteries into the so-called “strong/fragile” scale, by the means of the bond-strength-coordination number fluctuation model. We have evaluated the strength parameter, which plays a key role in the understanding of the relaxation phenomena, of each lithium-ion conductor under consideration. We have derived a relationship that not only describes accurately the experimental results, but also provides important details on the interrelation between the strength parameter, the bond strength of the structural unit, the binding energy, the coordination number and the glass transition temperature.

Current research and development of high performance concrete, together with study of phenomena that are pertinent to impact resistance, have lead to a new generation of barriers with improved properties to resist impact loads. The paper reviews major properties and mechanisms that affect impact resistance of concrete barriers as per criteria that characterize the resistance. These criteria are the perforation limit, penetration depth and the amount of front and rear face damage. From the long-known, single strength parameter that used to represent the barriers` impact resistance, more of the concrete mix ingredients are now considered to be effective in determining it. It is shown that the size and hardness of the aggregates, use of steel fibers and micro-silica have different effects on performance under impact and on the resistance. Additional pertinent phenomena, such as the rate and size effects, confinement and local versus global response, are pointed out with their reference to possible future developments in the design of impact resisting concrete barriers.

Dependencies of creep and strength parameters on physical properties and temperatures are exposed on the basis of experiments conducted in triaxial compression for frozen clayey soils exhibiting marine-like salinity.

WOS: 000237060100008, The effects of Ag2O addition on electromagnetic properties in a Bi2223 superconductor have been investigated by means of AC susceptibility measurements and theoretical analysis. Intergranular critical current density was found to be decreased with increased amount of Ag2O addition (0, 15, 30 wt.%). The effective volume fractions of the grains were estimated as a function of Ag2O amount. The field and temperature dependence of the intergranular critical current density for each sample has been accounted by the function J(cm) (T) = (J(0)/B-n) (1 - T/T-cm)(P), where alpha(0) denotes the pinning strength parameter at T = 0. The field exponent n, temperature exponent p, and maximum intergranular loss peaks, which are determined from the comparison of the experimental and calculated curves, increased with increasing amount of Ag2O addition. Experimental isothermal hysteresis losses as a function of field amplitude are also seen to adequately be reproduced by model calculation using the same fitting parameters as for AC susceptibility chi(n)(T) data. (c) 2006 Elsevier B.V. All rights reserved.

Molecular dynamics simulations of the Lennard-Jones model are used to study phase transitions at a smooth surface. Our motivation is the observation that the existence of an attractive wall facilitates crystallization. To investigate how this wall influences phase transitions, the strength of wall-particle interaction is varied in our studies. We find that the phase behavior depends on the strength parameter α, i.e., the ratio between wall-particle and the particle-particle attraction strength. Three critical values of the ratio, namely, αp, αw, and αc, are used to define the qualitative nature of the phase behaviors at a smooth surface. Some interesting phenomena due to the increase of α are observed. First, a set of close-packed planes, i.e., {111} planes in fcc structures or {0001} planes in hcp structures, are "rotated" from intersecting to parallel to the wall when α = αp; second, the layering phase transition close to the wall antecedes that of the bulk when α = αw. Finally, the first-order phase transition in the first two layers is supplanted by a continuous phase transition when α = αc, which to some extent can be treated as a quasi-two-dimensional process. We find that bulk freezing always discontinuously occurs through a first-order phase transition, and seems to be isolated from the freezing process occurring close to the attractive surfaces. Moreover, during the heating process, we observe minimal dependence at a strongly attractive surface.

Transient magnetic fields (TF) have been measured for oxygen ions with the 16 O(3 − ) state as probe traversing thin layers of crystalline Fe and amorphous Fe 80 B 20 compounds. The TF associated with polarized 1s electrons have strengths of B TF (Fe) = 412 (38) T in Fe and B TF (FeB) = 368 (62) T in FeB implying degrees of polarization of p 1s (Fe) = 0.13 (1) and p 1s (FeB) = 0.14 (3), respectively. The strength parameter a = 12.1 (2.3) T deduced for FeB agrees very well with other data rendering it highly suitable for TF measurements.

The emission spectra of the Eu3+ ion in GdOBr:Eu3+ were measured in the range of pressure from 0 GPa to 12.4 GPa. The energy level schemes established from the spectra show that the splittings of the 7F1, 7F3 and 5D1 multiplets decrease obviously with increasing pressure. The crystal-field parameters Bqk and the crystal-field strength parameter S versus Bqk were determined at different pressures. With pressurization S reduces and the J-mixings of the state functions for the Eu3+ ion decrease, which is in agreement with the decrease of the multiplet-splittings. This shows that for Eu3+ in REOX: Eu3+ the diminution of the crystal-field strength with pressure, the authenticity of which is under suspicion for several years, is certain.

Triaxial compression tests following stress paths of constant σ 1 were conducted to determine the shear strength of five processed scrap tire products having different gradations and particle shapes. The interparticle frictional component was separated from the total shear strength according to the energy correction concept proposed by researchers. The experimental results show that all five tire chip products have ultimate internal friction angles of 45° to over 60°. The interparticle frictional component of the strength was fully mobilized and nearly reached a constant value after approximately 5% axial strain. The experimental results confirmed that the strength parameter obtained with constant σ 1 was more reasonable. This finding is supported by field observation in which the tire chips have an angle of repose ranging from 37° to 43° (loosely stock piled) and up to 85° (compacted). The engineering applications of the experimental results are discussed.

In order to ensure reliable products, electronic, as well as mechanical, properties of thin chips must also be characterised. In particular, the strength of silicon devices is an important key for improvement of the yield and avoidance of the fracture of silicon chips and devices in manufacturing and application, respectively. This chapter discusses strength parameter in detail and how strength of thin silicon chips can be analysed. Besides theoretical relations, examples of strength behaviour of thin silicon chips are presented regarding different manufacturing steps.

A method of construction of the effective strength surface of matrix composites based on the properties of their components taking into consideration the arbitrary anisotropy of the strength, elastic, and geometric parameters of these composites has been developed. The method is based on use of determinations of the first and second moments of the tensors of stresses in the components of composite materials.

This paper briefly summarizes several promising new mechanical as well as thermal means for initiating the debonding of a fiber in a matrix or a metal film on a substrate of a composite structure. Also described are quantitative electrical and acoustic (ultrasonic) techniques for monitoring the failure of this interface and for recovering an interfacial strength parameter. The focus is on practical bond strength measurement techniques which are accurate, reproducible and reasonably simple to carry out.

The method developed permits considering the random character of the components of an applied stressed state and makes it possible to analytically predict the reliability of a three-directional LRP. The possibility of optimization of the material was demonstrated and the corresponding method was developed based on an analysis of the effect of the structure (geometry of the structure of the RES, number of layers), scattering of the loading and strength parameters on the reliability of LRP. The criterion for optimization of the structure of LRP in application to the actual conditions of random loading can be used both for a given loading level and for a required reliability level. Use of the method developed can also be promising in the case of the effect of combined loads.

Limit load solutions obtained by elastic-perfectly plastic finite element analysis (EPP-FEA) are compared to results of tests of low-alloy steel perforated plate geometries loaded to full plastic collapse. Results are given for two plastic-collapse tests of flat circular disks with circular penetrations arranged in a triangular pattern and drilled normal to the surface of the plate. The ligament efficiency (minimum distance between holes divided by the distance between the centers of the holes) of the pattern is 0.32 and the plate thickness is 2.39 inches (60.7 mm). The tests were designed so that a transverse load generated plastic collapse in the outer row of penetrations due to a combination of transverse shear and in-plane bending. Limit-load solutions were obtained using EPP-FEA with small-strain, small-deflection linear geometry assumptions. Two FEA models are used: one where the perforated region is modeled using an equivalent solid plate (EQS) representation and another where each hole is explicitly modeled by FEA. The results presented in this paper demonstrate that the deformation patterns produced by the EPP-FEA solutions match exactly with the deformation patterns produced by the test. The EQS-EPP FEA solution is about 15% lower than the explicit-hole EPP-FEA solution. Using one-third the actual ultimate strength of the material as the strength parameter in the limit load calculation produces a calculated limit load that is greater than a factor of three less than the mean measured plastic-collapse load obtained in the tests. This paper adds to the qualification of the use of limit-load solutions obtained using small-strain, small deflection EPP-FEA programs for the calculation of the limit load for perforated plates.Copyright © 2002 by ASME

Weibull’s method of analysis was used for fracture data obtained from the testing of dental composite restorative materials.

We computationally investigate the compression-induced reversible stripe rearrangement process, which is experimentally observed for the spontaneously formed pattern of microwrinkles on a Pt-sputtered elastomer surface. We propose a rough model for the wrinkles in a small bending regime considering the pattern memory of the neutral state with the strength parameter s, which should be attributable to the degree of material flow during initial pattern formation. The original pattern recovers after a compressive perturbation within finite time periods above the specific value of s. The simulated stripe rearrangement process shows qualitative agreement with the experimental results. In particular, the hysteretic behavior is reproduced and discussed in relation to s.

Rubbing is a simple but reliable method used to homogeneously align liquid crystal. It is widely used in the actual production of liquid crystal displays. However, this technology is mainly based on experience, and the relationship between rubbing strength and surface anchoring strength has not been clarified. Therefore, the authors have studied the relationship between the surface anchoring strength and the rubbing strength parameter L which is defined by the authors. Consequently, it has been determined that the anchoring strength is proportional to L, and that the memory effect of the surface orientation exists when there is weak anchoring strength.

The problem of the expansion of an initially thick-walled cylinder due to an internal pressure under conditions of plane strain is considered. The cylinder is composed of an elasto-plastic, Tresca material with an associated flow rule. No restriction is placed on the magnitude of the deformation or on the magnitude of the material parameters. Solutions are presented for a particular initial (stress free) geometry and it is shown that the maximum value of the internal pressure is a function of the deformation to strength parameter ratio.

Orthotropic materials such as unidirectional composites have a high degree of directionality in their strength. For example, most modern composite materials have longitudinal strength ten to twenty times that of the transverse and shear strengths. Under the imposed combined stresses or strains, the failure criteria must be more exact than that required for isotropic materials. One strength parameter such as the uniaxial tensile strength will suffice for the description of the behavior of the isotropic material under combined stresses such as the von Mises criterion.

The mechanisms of cold working of very pure steel with 0.005 up to 0.2 % C were investigated with and without deformation under various temperature-time conditions. Some mechanical properties of these alloys were determined such as yield point, Petch-Parameter “σy” and “σl”. The critical deformations of the amplitude curves describing the micro-plastic strength parameter during internal friction were also found out. Investigations were conducted on the ageing precipitations (such as composition, geometry and topography, particles and segregations) occurring in several stages of development.