Equivalent Compliance Research Articles

Numerical determination of the equivalent elastic compliance tensor for fractured rock masses using the distinct element method

Abstract The purpose of this paper is to establish a methodology to determine the equivalent elastic properties of fractured rock masses by explicit representations of stochastic fracture systems, and to investigate the conditions for the application of the equivalent continuum approach for representing mechanical behavior of the fractured rock masses. A series of numerical simulations of mechanical deformation of fractured rock masses at different scales were conducted with a large number of realizations of discrete fracture networks (DFN), based on realistic fracture system information and using the two-dimensional distinct element program, UDEC. General theory of anisotropic elasticity was used for describing the macroscopic mechanical behavior of fractured rock masses as equivalent elastic continua. Verification of the methodology for determining the elastic compliance tensor was conducted against closed-form solutions for regularly fractured rock mass, leading to very good agreements. The main advantage of the developed methodology using the distinct element method is that it can consider complex fracture system geometry and various constitutive relations of fractures and rock matrix, and their interactions. Two criteria for the applicability of equivalent continuum approach were adopted from the investigations: (i) the existence of a properly defined REV (representative elementary volume) and (ii) the existence of an elastic compliance tensor. For the problems with in situ conditions studied in this paper, the results show that a REV can be defined and the elastic properties of the fractured rock mass can be represented approximately by the elastic compliance tensor through numerical simulations.

頭蓋内圧脈波の振動解析に関する研究 ２ シミュレーションによる動物実験データの解析

To understand the relation between arterial pressure (AP) waves and intracranial pressure (ICP) pulse waves, animal experiments using adult cats and computer simulation using linear vibration model are conducted. In animal experiments, hypercapnias are performed. Equivalent compliance and equivalent mass are estimated by computer simulation using AP and ICP wave data measured by animal, experiment. During the increase of ICP at the beginning of experiments, the equivalent compliance decreases to low value and equivalent mass increases to high value. And when ICP returns to the initial low levels, the equivalent compliance and equivalent mass recover to the initial value. However, after several experiments, although ICP returns to low level, the equivalent compliance remains low value but equivalent mass recovers to low one. These results suggest that the compliance estimated by the computer simulation is available for the indicator of pathological changes in intracranial functions. And the increase of the equivalent mass is caused by that the flow rate of cerebrospinal fluid, which flows through narrow crevices in cranium, increases due to the rise of ICP. This phenomenon is verified by a vibration analysis of experimented results based on a dynamic model.

Prediction of crack growth in a tensioned band

An experimental method is developed to predict crack growth, and ultimately failure, in a dynamically fatigued tensioned steel band. The transfer function across the double edge notched crack is measured. The band’s modal response changes as the crack progresses, due to a change in the crack’s equivalent compliance and a reduction in the remaining area of the material. The frequencies of the transfer function are tracked throughout the fatigue cycle, and the changes in frequencies are used in estimating crack growth and failure. A general trend shows that the resonance frequencies drop as the crack grows. When the material starts to approach failure, the frequencies stop dropping, and in some cases rise. This is an indication that failure can occur at any time. Just before failure, the modal frequencies drop rapidly, until the band breaks. Using the general trends in the change in the bar’s frequency response it is possible to predict failure.

Simulation, surreptitious observation and the modification of hypnotizability: two tests of the compliance hypothesis

AbstractIn Experiment 1, two groups of subjects low in hypnotizability were administered the full Carleton Skills Training Package (CSTP) to enhance hypnotizability and two groups were given a partial version of the CSTP, which eliminates information aimed at teaching an active interpretation of suggestions. Half the subjects given the full CSTP and half given the partial CSTP were instructed to fake their way through the training and later hypnotizability post‐tests. Simulators in both the full and partial group exhibited equivalently high post‐test scores, but non‐simulators given the full CSTP attained higher post‐test scores than non‐simulators given the partial CSTP. These findings suggest that the partial and full CSTP contain equivalent compliance demands and that differences between these procedures in enhancing hypnotizability stems from the interpretational skills taught by the full CSTP. In Experiment 2, hypnotic post‐test responding was surreptitiously observed when subjects believed that they were alone. Simulators instructed to fake their way through the CSTP and the post‐test stopped responding when they believed they were alone. CSTP non‐simulators and subjects who attained high hypnotizability without training exhibited high levels of post‐test responding while alone. Together the findings of the two experiments indicate that compliance cannot account adequately for the hypnotizability enhancements induced by skill training. Copyright © 1996 British Society of Experimental and Clinical Hypnosis

Effect of body posture on respiratory impedance.

The effects of posture on the mechanics of the respiratory system are not well known, particularly in terms of total respiratory resistance. We have measured respiratory impedance (Zrs) by the forced random noise excitation technique in the sitting and the supine position in 24 healthy subjects. Spirometry and lung volumes (He-dilution technique) were also measured in both postures. The equivalent resistance (Rrs), compliance (Crs), and inertance (Irs) were also calculated by fitting each measured Zrs to a linear series model. When subjects changed from sitting to the supine position, the real part of Zrs increased over the whole frequency band. The associated equivalent resistance, Rrs, increased by 28.2%. The reactance decreased for frequencies lower than 18 Hz and increased for higher frequencies. Consequently, Crs decreased by 38.7% and Irs increased by 15.6%. All of these parameter differences were significant (P less than 0.001). A covariance analysis showed that a significant amount of the postural change in Rrs and Crs can be explained by the reduction of functional residual capacity (FRC). This indicates that the observed differences on Zrs can in part be explained be a shift of the operating point of the respiratory system induced by the decrease in the FRC.

Nurse-Supervised Education of Patients with Symptomatic Gastroesophageal Reflux

Patient educational programs supervised by non-physicians are becoming popular, but comparison of their effect on outcome with that of physician teaching is limited. We developed a nurse-supervised class for patients with symptomatic gastroesophageal reflux (GER). Primary physicians referred patients to the program. The patient's initial knowledge and the program's excellent cognitive effect were unrelated to demographic and symptom data. One hundred twelve consecutive patients were alternately given appointments either with the class or with a gastroenterologist. Although failed appointments and inappropriate referrals excluded some patients, the remainder of the two groups were similar with regard to demographic and symptom data and their return rate of follow-up questionnaires. They reported equivalent symptomatic improvement and therapeutic compliance after 2 weeks and 2 months. The program's success prompts us to continue this form of patient education.

Crack propagation with quasistatic energy analysis

In the application of quasistatic energy analysis, the P-u-A diagram has been found a valuable supplement in illustrating the characteristics of crack propagation. The diagram is useful not only for evaluating fracture toughness under quasistatic conditions, but also for representing important fracture parameters such as stability criteria, crack speed, strain rate, fatigue, environmental effects, etc. A general method of characterizing these parameters in the form of a P-u-A diagram is presented for both linear and non-linear load-displacement relationships at constant crack area. This was achieved by polynomial representation of the diagram. The analysis was extended to cover crack propagation under multiple-loading conditions. By introducing a complementary strain-energy function, equivalent load and compliance, a method of solution has been devised to avoid the laborious computations which may otherwise be required if the loadings become numerous and complex. The computed values of fracture toughness from the numerically represented P-u-A diagram, and the displacements evaluated with the equivalent compliance concept, compare well with those obtained experimentally.