The study of the physical properties (geophysical methods) of rocks associated with its mechanical properties has recently received lots of attention. Recent studies show that geophysical methods especially the seismic and geoelectric methods are able to estimate the mechanical parameters and recognize their spatial variations, including anisotropy. Meanwhile, electrical and seismic methods are the most used one.Electrical measurement is one of the non-invasive geophysical methods commonly used by engineers working in various fields such as mining, geotechnical, civil, underground engineering as well as oil and gas mineral explorations. This method can be applied both in laboratory and in the field. Numerous scientists have focused on the relation between resistivity and porosity. However, there is a very limited study on the relation between the electrical resistivity and the rock properties apart from porosity.In this paper, changes in the electrical conductivity of rocks during a uniaxial compression test were investigated in laboratory. The uniaxial compressive strength, elastic modulus, and density values of the samples were determined in laboratory. We installed special electrodes on seven nearly saturated core samples in order to measure the resistivity. Core samples had a 52-mm diameter and a 110-mm length. Two-electrode as well as four-electrode arrays were both used in resistivity monitoring in laboratory. Using a four-electrode array minimized the undesirable electrode polarization effects. In the four-electrode array, we used two non-polarizing Ag/AgCl electrodes mounted on the core sample. Our laboratory observations showed that there was not any electrode polarization effect. When we used a two-electrode array, the resistivity changes were less than 5 percent compared to a four-electrode array. In our laboratory investigation, we used different sedimentary core samples including sandstone, fossilioferous limestone and travertine. Maximum resistivity observed for the travertine core sample was less than 12 kohm. During the uniaxial compressive test, deformation measurements were made and the stress–strain curves were plotted. Tangent Young’s modulus values were obtained from stress–strain curves at a stress level equal to 50% of the ultimate uniaxial compressive strength.Sandstone core samples showed a resistivity increase in the whole strain range. On the contrary, the fossiliferous limestone samples (thin section showed that the sample was composed of tiny calcium fossils in a fine aggregate of micrite cementation) showed a resistivity decrease in the whole strain range. Travertine and limestone showed an intermediate behavior (resistivity increased in the lower strain and it decreased in the higher range). In other words, the onset of new crack formation occurs well inside the quasi-linear part of the stress-strain curve. The quasi-linear portion of the stress-strain curve was the result of a competition between closure of one population of cracks, and the growth of new propagation of the existing cracks.Resistivity behavior during a uniaxial compression load is closely related to the pores in the lower strain ranges and then to the new induced fractures in higher strains. Our results showed that the electrical resistivity may be a representative measure of the rock properties. Additionally, the effect of certain minerals on the rock’s resistivity must be taken into account. The results indicated that the rock structure had an important effect on the resistivity behavior during a mechanical loading.

The current study presents a series of tests on steel fiber-reinforced lightweight aggregate concrete (SFRLWAC) cylinders in order to develop a stress-strain model for SFRLWAC subjected to compressive monotonic loading. In this experiment, steel fiber ratios of 0, 0. 5, 1, and 1. 5 percent by volume of the sample were used in the mixtures. The findings show that adding steel fiber to the lightweight concrete has a slight impact on the ascending branch of the stress-strain curve; however, it has a noticeable influence on the descending branch. The peak stress, strain at peak stress, and modulus of elasticity were investigated. To this end, some equations were established. To predict the complete SFRLWAC stress-strain curve, a stress-strain model was introduced and the validity of the model was explored. There was a good agreement between the proposed model data and experimental findings. Using ABAQUS software, numerical simulation of the SFRLWAC beams subjected to monotonic loading was conducted; the simulated results had an acceptable agreement with the experimental data.

This paper deals with studying and developing a proper constitutive model for liver tissue. For this purpose, deformation of liver in uniaxial compression, for two different strain rates, is analytically and numerically studied based on both hyperelastic and hyperviscoelastic constitutive models. Both of the models are based on a polynomial-form energy function. The stress-strain curves, for uniaxial compression obtained from these models have been fitted to the existing experimental data to determine the model coefficients. Moreover, the models are examined in uniaxial tension and pure shear loadings.ABAQUS commercial software, in which both of the models are available, has been used for numerical simulations. Thesn, to evaluate the computational analyses, analytical and numerical results have been compared with each other and also with the existing experimental data. The results show that the presented analytical solution and FE simulation are very close together and also both are accurate enough compared with the experimental data, and an acceptable stability is observed. Furthermore, the effect of friction coefficient between the sample and the compressing plate in uniaxial compression test has been investigated. FE simulation results show that the stress will increase with increasing friction coefficient. This implies that friction coefficient must be carefully selected to accurately describe the tissue’s response. Compared with previously published researches on other tissues, the constitutive models adopted here to predict liver behavior are mathematically more complex due to non-zero material constants. Analytical solution of these constitutive models is, in fact, the main challenge and innovation of this paper.

The rocks in the studied area are prone to deterioration and failure due to frequent exposure to extreme temperature variations and loading conditions. In the context of rock engineering reliability assessment, understanding the energy conversion process in rocks is critical. Therefore, this research work aims to assess the energy characteristics and failure modes of pink and white-black granite subjected to uniaxial compression loading at various temperatures. Samples of pink and white-black granite are heated to a range of temperatures (0 °C, 200 °C, 400 °C, 600 °C, 900 °C, and 1100 °C), and their failure modes and energy characteristics including total energy, elastic energy, and dissipated energy are studied by testing preheated samples under uniaxial compression. The results show that the dissipation energy coefficient initially rises rapidly, and then falls back to its minimum value at the failure stage. The micro-structures of granite rock directly affect its elastic and dissipation energy. Axial splitting failure mode is observed in most of the damaged granite specimens. After heating granite to 600 °C, the effect of temperature on the failure mode becomes apparent.

Improvement of poor soils as an inevitable issue plays an important role in civil engineering projects. In this paper, the effect of adding metakaolin on Atterberg limits and uniaxial compressive strength of sandy clay soil was investigated. For this purpose, uniaxial compressive strength tests have been done on non-stabilized and stabilized soil samples with 5, 10, 15, 20 and 25% of metakaolin at curing times including immediately after mixing, as well as 7, 14 and 28 days. The Atterberg limits test have been also conducted on stabilized soil samples with 5, 15 and 25 at immediately after mixing. The results show that increasing the percentage of metakaolin increases the liquid and plasticity limits of sandy clay. So that the amount of plasticity limit of soil is less than the liquidity and thus the soil plasticity index increase. Stabilized samples with 25% metakaolin increased by 1. 33 and 1. 40 times, respectively, for liquid and plasticity limits, due to the highest change in the Atterberg limits of sandy clay soil. The study of stabilized soil in plasticity chart shows that by adding of metakaolin, the soil's position in this chart is negligible. Also, increasing the percentage of metakaolin and the curing time increases uniaxial compressive strength of the sandy clay. The highest strength rate for 25% of metakaolin occurred at 28 days. Also, studying the failure planes and the failure rate of the tested specimens shows that with increasing metakaolin, the failure of the specimens occurs faster after reaching the final strength.

In this investigation, a series of nickel open-cell structures with cubic geometry were fabricated by electroforming onto stereolithography (SLA) resin 3D-printed templates. The thickness of the electroformed Ni foams was controlled under constant voltage conditions for two days in a warm nickel sulfamate bath. Ni open-cell samples with varying thicknesses and masses were subsequently subjected to uniaxial compression tests, and their deformation behavior was analyzed and modeled using load–displacement curves. The results show that the mass and apparent density of the Ni open-cell samples exhibit a linear relationship with electroforming time at 6 PPI, unlike the Ni thickness. However, the first maximum compressive strength of the samples, measured according to ISO 13314, does not show a linear dependence on thickness. In this work, Ni open-cell foams were successfully fabricated by warm electroforming under controlled temperature and voltage, achieving densities below 0.93 g/cm³, compressive strengths above 7.50 MPa, and energy absorption values exceeding 4.90 J/cm³. These outstanding mechanical properties, particularly the strength-to-density and energy-absorption-to-density ratios at 6 PPI, demonstrate significant potential for advancing the production of nickel open-cell foams.

For prevention of soil compaction, knowledge of allowable compression stress limit (compaction strength) in soil is important. Pre-compaction stress ( spc ) was introduced as soil compaction strength and often used as a criterion for evaluation of soil susceptibility to compaction. In this research, pre-compaction stress was measured for a sandy loam soil with plate sinkage (PST) and confined compression (CCT) tests. To prepare soil samples with different initial compactness, two soil water contents (17 and 19%db) and six pre-loading stresses (0, 25, 50, 100, 150 and 200 kPa) were used. The effects of soil water content and pre-loading stress on estimated pre-compaction stress were studied using a factorial experiment in a completely randomized design with three replications. The spc values were significantly influenced by loading combination and soil water content. For PST, pre-load increase and higher soil water content resulted in higher and lower values of spc , respectively. However, predicted spc value increased with higher soil water content for CCT. The results also showed that the spc predicted with PST was accurate, whereas the values obtained with CCT were 4.5 (at 17 %db) and 8.5 (at 19 %db) times higher than the applied pre-loads. Overall, the findings indicated that spc prediction depends on the compression test, and PST could be a suitable method for soil pre-compaction stress (compaction strength) determination in sustainable soil management, i.e., soil trafficability and tillage. The PST method is also suitable to assess the effect of managing factors on pre-compaction stress.

Delamination is one of the most common failure modes in composite structures. In the case of in-plane compressional loading, delamination of a layered flat structure can cause a local buckling in delaminated area which subsequently affects the overall stiffness of the initial structure. This leads to an early failure of the overall structure. Moreover, with an increase in load, the delaminated area may propagate in the post-buckling mode; and consequently, to predict this behavior, a combination of failure modes will be used to predict failure. In this work, the proposed analysis will predict the delamination shape and load carrying capacity of a composite laminated plate during delamination process in post-buckling mode. For this purpose, it is assumed that the composite laminate contains an initial circular delaminated (defected) area. The analysis is performed through a numerical scheme based on finite element method. Results show that in most cases, the onset of crack growth is affected by the first opening mode while it is well probable that during the delamination growth, the effects of other modes dominate the initial primary opening mode. Consequently, during progression of any delamination which may occur as a result of further loading, a jump in failure mode which is predicted in this analysis, may occur. Moreover, the induced results show that the stacking sequence of the delaminated composite plate has a significant effect on the delamination growth and the load carrying capacity of the overall structure.

The present study's focus is to investigate the influence of loading micro-cracks on the transport properties of self-consolidating concrete (SCC). To have concrete mixtures with distinctly different fracture properties and diffuse damage behaviors, three SCCs were prepared: two SCCs with two different types of aggregates (limestone and siliceous) and one containing steel fibers. The loading micro-cracks were done on the specimens via the application of uniaxial compression up to 70% of the ultimate compressive strength (UCS) with different loading times to propagate damage within mixtures. Accelerated carbonation was applied to undamaged and damaged specimens with a concentration of CO2 of 20% at 20±5°C and humidity at 70±5% in the carbonation chamber to evaluate the transport properties of SCC. The chloride resistance of the SCC was measured using an accelerated chloride migration test. Based on the results, it was concluded that the transport properties in concrete are highly affected by sustained loading time. The SCC-containing steel fibers showed good resistance against diffusion of chloride ions and CO2 gas for two damaged and undamaged state conditions. Also, a correlation was obtained between the intrinsic permeability coefficient and chloride diffusion coefficient in the damaged and undamaged state for each SCC and also between mechanical damages and durability parameters.

Background: Chronic diabetes is substantially associated with circulatory disorders in lower limbs. Vacuum-compression Therapy (VCT) has been commonly used in treatment of peripheral circulatory disorders. VCT is based on intermittent alteration of Positive- Negative pressure phases. The purpose of this study was to determine effects of VCT on diabetic subjects' peripheral blood flow.Methods: In this Before-After and case-series study, 18 type 2 diabetic subjects with diabetic neuropathy and/or peripheral vascular disease (PVD) completed the study. Subjects received 45 min of VCT for 10 sessions three times weekly. Blood flow (calf+foot) was measured via venous occlusion plethysmography.Results: Among Variables of "Arterial Inflow", "Venous Outflow", "Venous Capacity", "Postischemic Reactive Hyperemia" and "Peak Flow of Reactive Hyperemia", only "Venous Outflow" significantly improved after 10 sessions treatment via VCT (P<0.05).Conclusions: Arterial blood inflow, which was the most important determinant evaluated in this study, was not increased via VCT. Additional studies are required to investigate the effective VCT parameters and duration of each session and number of sessions, considering progressive and deteriorative natural history of diabetes.