Theoretical and experimental methods for obtaining and investigating effective thermomechanical characteristics - residual stresses and deformation in panels made of nanomodified materials with ...asymmetrical reinforcement scheme have been developed in this paper. The study of the residual stress-strain state of structural elements made of carbon plastic using the values of thermoelastic characteristics of composite monolayers identified on the basis of the developed methods meade it possible to reveal the possibility of reducing the residual stress-strain state in structures with asymmetric reinforcement schemes.
Актуальность. В статье рассматривается проблема строительства и эксплуатации трубопроводов на участках распространения пучинистых грунтов. Рассматриваемая проблема является актуальной, поскольку ...одной из основных причин, осложняющих процесс прокладки трубопроводных систем в северных районах, является морозное пучение, заключающееся в многократном увеличении объема влажных грунтов при замерзании. Металл труб подземных магистральных трубопроводов при их эксплуатации на участках распространения пучинистых грунтов подвергается существенным деформациям, происходящим из-за неконтролируемых подвижек грунта вследствие процесса морозного пучения. Данное силовое взаимодействие подземного трубопровода и мерзлого грунта может стать причиной возникновения аварийных ситуаций. Цель: создать 3D-модель взаимодействия трубопровода с мерзлым пучинистым грунтом для того, чтобы имитировать процесс пучения грунта и выявить графическую зависимость напряжений и деформаций, возникающих в трубопроводе, от перемещения грунта. Объекты: участок трубопровода, проложенный на участках распространения пучинистых грунтов. Методы. В процессе исследования была изучена литература и нормативные документы по строительству и эксплуатации сооружений в многолетнемерзлых грунтах и проведен анализ влияния пучинистых грунтов на здания и сооружения, а также проведено моделирование в программном комплексе Ansys. В работе анализируется процесс взаимодействия многолетнемерзлых грунтов с подземным трубопроводом в программном комплексе AnsysWorkbench. Результаты. Авторами выполнено моделирование процесса пучения грунта и проведена оценка напряженно-деформированного состояния трубопровода, проложенного на участках распространения пучинистых грунтов, в программном комплексе AnsysWorkbench. С помощью разработанной модели получены и проанализированы значения напряжений и полных деформаций стенки трубы при контакте с мёрзлым грунтом, построена графическая зависимость наблюдаемых величин при усилении процесса пучения и увеличении участка пучения.
Introduction: The research is aimed to identify the vulnerable areas of quarry slopes through the creation of a stress-strain state model for the rock mass at the Vostochny quarry, East Saryoba field ...of the Zhi-landy Group of cupriferous sandstones, as well as their subsequent strengthening. Methods: The research is based on the development of a database containing information on mining-geological, geophysical, geodetic and aerospace surveys. The authors of the research use modern geodetic, aerospace and geophysical technologies for scientifically based predicting of technogenic disasters and the rock mass stress-strain state modeling to ensure safe and optimal mining of fields in difficult mining-geological conditions. Results: The results obtained show that the strengthening of weakened quarry slopes based on the rock mass stress-strain state modeling contributes to the scientific-practical profitability of field mining and provides safe mining in difficult mining-geological conditions. Discussion: Novelty is in the scientific substantiation of the method for strengthening quarry slopes, which is based on the rock mass stress-strain state modeling. The research is of great practical importance, as the rock mass stress-strain state modeling increases the reliability of predicting the rock mass state during its mining. Strengthening of quarry slopes using the proposed method reduces risks and increases safety and economic efficiency of mining the solid mineral deposits in difficult mining-geological conditions.
The stress-strain state of ZrB2-SiC ultra-high-temperature ceramics, produced using commercial powders with different impurity levels, was investigated by X-ray diffraction. Upon analysis of ZrB2 and ...SiC diffraction lines shift, the level of thermal stresses (strains) of the different phases was determined. An increase of internal stresses in ceramics with rising viscous-brittle transition temperatures, Tve, was attributed to increased grain boundary strength. Ceramics, for which high Tve and high level of internal stresses were estimated, exhibited high strength, up to 700 MPa at 1400 °C. A field of compressive thermal stresses in the matrix phase resulted to be necessary for achieving high strength at low-temperatures. On the contrary, the presence of low-melting impurities at the grain boundaries negatively impacted on the stress level in ZrB2 boundaries in the high temperature regime.
Significant changes in the stress-strain state cause a change in the soil profile of the massif, which is affected by various physical and chemical factors. In particular, groundwater filtration, ...mass transfer, heat transfer, dissolution and leaching of soil masses. This can lead to various types of accidents. Therefore, the study of the stress-strain state of the soil massif is an important topic. Nonlinear dependences in the form of polynomials of the modulus of deformation and Lame coefficients on the concentration of salt solutions and their temperature have been received in this research based on experimental research and their statistical processing. This allowed improving the mathematical model of the stress-strain state of the soil taking into account the nonlinear deformation processes occurring in the soil masses under the presence and filtration of saline solutions in non-isothermal conditions.
Znaczące zmiany stanu naprężeniowo-odkształceniowego powodują zmianę profilu glebowego masywu, na który wpływają różne czynniki fizyczne i chemiczne. W szczególności filtracja wód gruntowych, przenikanie masy, przenoszenie ciepła, rozpuszczanie i wymywanie mas glebowych. Może to prowadzić do różnego rodzaju wypadków. Dlatego ważnym tematem jest badanie stanu naprężeniowo-odkształceniowego masywu glebowego. W niniejszych badaniach otrzymano nieliniowe zależności w postaci wielomianów modułu odkształcenia i współczynników Lame’a od stężenia roztworów soli i ich temperatury w oparciu o badania eksperymentalne i ich obróbkę statystyczną. Pozwoliło to na udoskonalenie modelu matematycznego stanu naprężeniowo-odkształceniowego gruntu uwzględniającego nieliniowe procesy odkształceń zachodzących w masach gruntu pod wpływem obecności i filtracji roztworów soli w warunkach nieizotermicznych.
Surface faulting along active faults poses a threat to the facilities that might be affected. It is especially important for lifelines, trunk pipelines in particular, that, unlike other structures ...that can be just replaced, often cannot be retraced to avoid crossing with active faults able to produce surface faulting associated with large earthquakes. Pipelines' damage may produce significant economic, social and ecological losses. Pipelines, however, can sustain significant offsets that was demonstrated successfully by the Trans-Alaska oil pipeline during the 2002 Denali Fault earthquake. The critical point is that, estimating the design displacement that might occur during anticipated earthquake, researchers and engineers have to deal with significant uncertainties produced by combination of several factors: (1) significant and hardly predictable slip variability along fault strike; (2) very large, up to 1-2 orders of magnitude, scatter of maximal displacement of surface ruptures with the specified rupture length and during earthquakes with certain magnitude; (3) lack of data on the displacement values consistency at a particular fault section during successive rupturing events. Amount of fieldwork required to get such information is, usually, too large to be performed during site investigations for a particular lifeline project. Moreover, traces of older events are poorly recognizable and can be hardly characterized quantitively in the same way as those of modern surface ruptures. The pipeline design solutions, however, are "discrete" – i.e. they are appropriate for some range of the design displacement values. Stress-strain state of the pipeline strongly depends not only on fault displacement value, but also on fault kinematics, on relative orientation of a pipeline and fault at their crossing point, on the shape of a trench, backfill properties, pipe diameter and material. The preliminary analysis of all these factors and the numerical modeling of the pipeline-fault crossing can provide threshold displacement values which excess requires change of the crossing design. Thus, the main task of site investigation is to find if the anticipated displacement will exceed such threshold or not. If not – there is no need to waste time and efforts trying to specify the exact offset value and work can be concentrated on specifying fault kinematics, exact position of the anticipated fault plane, etc. Close cooperation of geologists and engineers at the earliest stages of pipeline projects implementation will help selection of optimal design solutions and optimization of the site investigations program.
Hypotheses and prerequisites for modelling the stress-strain state of the normal cross-section of wooden elements for subsequent calculation using the deformation method are proposed. Stages of the ...stress-strain state of solid and glued wood elements are presented. The concept of the “design cross-section” with a fold in the compressed zone of the element is proposed.
Based on previously performed calculations of the load-bearing capacity for the ultimate and serviceability limit states, an experimental design of a rafter arch was developed. New results from ...experimental studies on the stress-strain state of its components were obtained, specifically for the semi-arches, ties, and struts under the influence of symmetrical and asymmetrical loads. According to the proposed methodology, a full-scale sample of a steel arch structure was studied in accordance with the loading schemes that are possible in practice. As a result, the actual stresses in all elements were determined, considering both the inclusion and exclusion of preliminary stress. The main theoretical prerequisites for the calculation of the rafter arch, proposed by the authors under the methodology, have been validated. The research objectives were formulated for the subsequent experimental and theoretical investigations of continuous perforated elements. The focus is on establishing effective structural solutions for intermediate supports based on various factors, including size, nature (static or dynamic), type (concentrated, evenly distributed, combined), load action scheme, material strength (standard or high-strength steels), span size, and geometric parameters of the section. Distinct variations are considered concerning the presence or absence of stiffeners along the axis of the intermediate support and the inclusion of welded or non-welded perforation holes on the left and right of the support. It was determined that the stress distribution in the calculation points of characteristic cross-sections with holes of the bearing part of the non-separated perforated beam near the intermediate support significantly differs from the stress distribution in the span part, since the sign of the bending moment curve changes from positive in the span to negative at the support.
