To investigate the mechanical properties of tunnel lining concrete under different moderate-low strain rates after high temperatures, uniaxial compression tests in association with ultrasonic tests were performed. Test results show that the ultrasonic wave velocity and mass loss of concrete specimen begin to sharply drop after high temperatures of 600°C and 400°C, respectively, at the strain rates of 10‒5s‒1 to 10‒2s‒1. The compressive strength and elastic modulus of specimen increase with increasing strain rate after the same temperature, but it is difficult to obtain an evident change law of peak strain with increasing strain rate. The compressive strength of concrete specimen decreases first, and then increases, but decreases again in the temperatures ranging from room temperature to 800°C at the strain rates of 10‒5s‒1 to 10‒2s‒1. It can be observed that the strain-rate sensitivity of compressive strength of specimen increases with increasing temperature. In addition, the peak strain also increases but the elastic modulus decreases substantially with increasing temperature under the same strain rate.
The paper presents a method of measuring deformations of cylindrical samples on the testing machine for free tube hydroforming experiments. During experiments a sample made of a thin-walled metal tube is expanded by the internal pressure of the working liquid and additionally subjected to axial compression. This results in a considerable circumferential deformation of the tube and its shortening. Analysis of the load cases and their impact on the deformations can be helpful in determining e.g. tube material properties or general limiting conditions in the tube hydroforming process. In connection with the above, the value of deformations and knowledge of their course during experiment has become one of the most important problems related to the issue described above.
Coal ash produced from thermal power plants as a substitute for conventional construction material has increased considerably in recent years. In the past, studies on partial replacement of soil were carried out with a single type of ash. Because of the insufficient evidence, limited research has been initiated on the productive usage of Fly and Bottom Ashes. This paper aims to study the properties of these materials and investigate their efficacy in road construction. Laboratory investigations were conducted to assess chemical and physical properties and mechanical performance to evaluate both ash types in pavement construction. The rutting factor is calculated for various combinations of coal ash materials with the addition of polypropylene fiber as a reinforcement in increments of 0.1% of its total weight with an aspect ratio of 200. The analytical tool ANSYS is used to validate the service life, vertical strain and quality of reinforced ash materials.
The main objective of this study is to develop an echocardiographic model of the left ventricular and numerical modeling of the speckles- markers tracking in the ultrasound (ultrasonographic) imaging of the left ventricle. The work is aimed at the creation of controlled and mobile environment that enables to examine the relationships between left ventricular wall deformations and visualizations of these states in the form of echocardiographic imaging and relations between the dynamically changing distributions of tissue markers of studied structures.
Mechanical properties of the pipeline samples that had been cut in annular and axial directions were investigated. The methodology of modeling and calculation of the real stress-strain state was described. The stable state during in the deformation process was defined. The results of the experimental researches were used as a test variant during examination of pipe strength.
The brake linkage of a hoisting machine is a very important component determining the safety of
the hoisting machine’s entire braking system. It is subject to weekly inspections. However, an efficiency
test of brake performance is carried out every 6 months. Once every 3 years, a test must be carried out by
an appraiser who pays particular attention to the executive and control components of the brakes as well
as the strain - brake system and brake release components. The legal provisions regulating the testing
of braking system linkages are not precise. So far, the control has been based on random measurement
of strains using electrical resistance strain gauges stuck to the surface of the linkage. A new method
for measuring the strains of the linkage has been proposed in the work. It is based on fibre optic strain
sensors with Fibre Bragg Gratings (FBG). They are mounted using specially designed and tested holders
for mounting on the brake linkage. They provide quick assembly and the measurement of strain in the
direction parallel to the axis of the linkage. The structure of the holder also allows for the measurement
in 4 positions turned every 90 relative to one another. Such a measurement enables a comprehensive
analysis of strains and stresses in the brake linkage. In the work, it was shown that there is a complex
state of strain and stress in the brake linkage. The previous procedures for linkage testing are inadequate
in relation to this condition. An experimental and numerical method was proposed to assess the state
of linkage stress. It should constitute the basis for the decision of the appraiser to allow the linkage for
further use. The method proposed in the work also allows for continuous measurements of linkage strains
as well as dynamic braking tests.
A number of micromechanical investigations have been performed to predict behaviour of composite interfaces, showing that the detailed behaviour of the material at these interfaces frequently dominates the behaviour of the composite as a whole. The interfacial interaction is an extremely complex process due to continuous evolution of interfacial zones during deformation and this is particularly true for carbon nanotubes since the interfacial interaction is confined to the discrete molecular level. The atomic strain concept based upon Voronoi tessellation allows analyzing the molecular structure atom by atom, which may give a unique insight into deformation phenomena operative at molecular level such as interface behaviour in nanocomposites.
Single point incremental forming process is a most economical Die-less forming process. The major constraint of it is that it is a time consuming process. In this work, a new attempt was made in incremental forming process using Multipoint tool for SS430 sheets to increase the formability and to reduce forming time. Fractography analysis was made to study the size of voids that were formed during fracture. The forming limit diagrams were drawn and compared for single point incremental forming and the multipoint incremental forming of SS430 sheet. It was proved that the formability of SS430 sheet in the multipoint forming was better than the formability of that in single point forming and the time consumed was reduced. The strain distribution in both processes had also been studied along with surface roughness.
An optimal sensor placement methodology is implemented and herein proposed for SHM model-assisted design and analysis purposes. The kernel of this approach analysis is a genetic-based algorithm providing the sensor network layout by optimizing the probability of detection (PoD) function while, in this preliminary phase, a classic strain energy approach is adopted as well established damage detection criteria. The layout of the sensor network is assessed with respect to its own capability of detection, parameterized through the PoD. A distributed fiber optic strain sensor is adopted in order to get dense information of the structural strain field. The overall methodology includes an original user-friendly graphical interface (GUI) that reduces the time-to-design costs needs. The proposed methodology is preliminarily validated for isotropic and anisotropic elements.
Reliable evaluation of stress-strain characteristics can be done only in the laboratory where boundary conditions with respect to stress and strain can be controlled. The most popular laboratory equipment is a triaxial apparatus. Unfortunately, standard version of triaxial apparatus can reliable measure strain not smaller than 0.1 %. Such accuracy does not allow to determine stiffness referred to strain range most often mobilized in situ i.e. 10-3 ÷ 10-1%, in which stiffness distribution is highly nonlinear. In order to overcome this problem fundamental modifications of standard triaxial apparatus should be done. The first one concerns construction of the cell. The second refers to method of measurement of vertical and horizontal deformation of a specimen. The paper compares three versions of triaxial equipment i.e. standard cell, the modified one and the cell with system of internal measurement of deformation. The comparison was made with respect to capability of stiffness measurement in strain range relevant for typical geotechnical applications. Examples of some test results are given, which are to illustrate an universal potential of the laboratory triaxial apparatus with proximity transducers capable to trace stress-strain response of soil in a reliable way.
Therapeutic and surgical applications of focused ultrasound require monitoring of local temperature rises induced inside tissues. From an economic and practical point of view ultrasonic imaging techniques seem to be the most suitable for the temperature control. This paper presents an implementation of the ultrasonic echoes displacement estimation technique for monitoring of local temperature rise in tissue during its heating by focused ultrasound The results of the estimation were compared to the temperature measured with thermocouple. The obtained results enable to evaluate the temperature fields induced in tissues by pulsed focused ultrasonic beams using non-invasive imaging ultrasound technique
Among the full-field optical measurement methods, the Digital Image Correlation (DIC) is one of the techniques which has been given particular attention. Technically, the DIC technique refers to a non-contact strain measurement method that mathematically compares the grey intensity changes of the images captured at two different states: before and after deformation. The measurement can be performed by numerically calculating the displacement of speckles which are deposited on the top of object’s surface. In this paper, the Two-Dimensional Digital Image Correlation (2D-DIC) is presented and its fundamental concepts are discussed. Next, the development of the 2D-DIC algorithms in the past 33 years is reviewed systematically. The improvement of 2DDIC algorithms is presented with respect to two distinct aspects: their computation efficiency and measurement accuracy. Furthermore, analysis of the 2D-DIC accuracy is included, followed by a review of the DIC applications for two-dimensional measurements.