Combined Action Of Temperature Research Articles

Experimental study on creep-fatigue damage of hot central plant recycling asphalt mixture containing high RAP

The objective of this study is to delve into the nonlinear damage evolution mechanism of hot central plant recycling asphalt mixture under the influence of creep-fatigue interaction. A predictive model for lifespan, considering the interaction of temperature and load, was developed. Dynamic creep tests were conducted at different temperatures to assess the creep effect of the asphalt mixture under actual road temperature conditions. The investigation began by acknowledging the material's viscoelastic properties, thereby deriving the loss compliance value - a key indicator of temperature effects - using an equivalent conversion factor and a viscoelastic mechanics model. This allowed for the incorporation of creep behavior into the load system. Furthermore, to analyze the nonlinear damage mechanism and fatigue prediction mechanism, direct tensile fatigue tests were performed at different temperatures and different stress levels. The fatigue damage evolution law of hot central plant recycling asphalt mixture containing high RAP considering the creep effect was revealed, and the fatigue life evaluation method under the combined action of temperature and stress level was proposed. The results show that the fitting degree of the time-temperature conversion equation and the viscoelastic mechanics model to the test data is more than 0.9, and the derived loss compliance value better captures the creep effect. Based on the nonlinear creep-fatigue damage model, the damage law of high-RAP hot central plant recycling asphalt mixture was identified. The optimized fatigue life prediction model fully considers the combined effect of temperature and stress level and analyzes the influence parameters of the real state of pavement fatigue. The prediction accuracy is within the requirements of engineering applications. The model's predictive accuracy meets the criteria for engineering applications, enhancing the multifaceted damage coupling analysis approach for hot central plant recycling asphalt mixture and predict the service life of recycled pavements under complex conditions, establishing a groundwork for the prediction and assessment of long-lasting recycled pavements.

Hot-pressure acid leaching changes grain boundaries to deeply remove impurities in quartz sand

High-purity quartz sand is a crucial raw material for advanced industries such as photovoltaics. However, due to the limited availability of high-quality ore sources, there is currently no method to prepare high-purity quartz sand using alternative minerals, leading to a shortage of high-purity quartz sand resources. This study aims to explore the mechanism of efficiently purifying quartz sand through a comparative analysis of hot-pressure acid leaching (HPAL) and atmospheric-pressure acid leaching (APAL), providing a theoretical foundation for preparing high-purity quartz sand using alternative minerals. The results indicate that, during the HPAL process, the combined action of temperature and pressure transforms closed grain boundaries (CGBs) into open grain boundaries (OGBs), increasing the degree of openness of OGBs. The opening of CGBs provides additional channels for the leaching agent to penetrate the quartz, exposing it to more internal impurities. Under conditions of hydrochloric acid (HCl) concentration (3 M), liquid-to-solid ratio (5:1), stirring speed (450 rpm), and holding time (2 h), elemental contents of iron (Fe), aluminum (Al), potassium (K), and sodium (Na) after APAL (363 K, atmospheric pressure) were reduced to 63.9 μg/g, 58.7 μg/g, 21.3 μg/g, and 7.3 μg/g, respectively. However, after HPAL (473 K, 1.5 MPa), these values decreased significantly to 4.7 μg/g, 30.9 μg/g, 3.6 μg/g, and 4.9 μg/g. This paper elucidates the mechanism of HPAL efficiently removing impurities in quartz sand through grain boundaries (GBs), providing a new direction and theoretical basis for the preparation of high-purity quartz sand.

Structural Response of a Cement Concrete Pavement with a Buffer Layer to Temperature and Moving-Load Effects

The main issues associated with cement concrete pavements are cracks and broken plates that affect driving comfort and road service life. To ensure sustainable use of the cement concrete, a buffer layer (AC-10) can be introduced between the base and the cement concrete panel. In this study, the interlayer shear test was performed, and the interlayer bonding coefficient under different temperature conditions was determined. The creep test of the buffer layer was also conducted, and the four parameters (E1, E2, η1, and η2) of the Burgers model of the buffer layer were analyzed using regression. According to the parameters obtained from the test, the finite-element model was established, and the moving load was applied to analyze the structural model response under high-, medium-, and low-temperature conditions. The results show that the (1) temperature stress is mainly concentrated in the buffer layer and regions above the structural layer. At low temperatures, the maximum stress at the top of the surface layer is 2.16 MPa, and the vertical strain decreases as a function of depth. (2) Under the combined action of temperature and moving load, the variation ranges of tensile and compressive stresses at the top of the surface layer are the largest; the variation range of the buffer layer and the subsequent structure is small; the maximum warpage deformation of the surface layer is 0.453 mm under high-temperature conditions; and the maximum compression deformation is 0.219 mm under low-temperature conditions. (3) The comprehensive coefficient kc of the fatigue equation was modified, and the comprehensive coefficient kc of the fatigue equation under different vehicle speeds was proposed. This study provides a reference for the sustainable development of cement concrete pavements with buffer layers.

Structural layer applicability of semi-flexible material for rutting resistance: A coupled temperature-mechanical approach.

Semi-flexible material (SFM) is produced by pouring cement grouting material into the asphalt concrete skeleton. It exhibits both characteristics of cement and asphalt, increasing structural stiffness and reducing rutting. Extensive studies have shown that the temperature load coupling effect is one of the leading causes of road rutting. However, few researchers focused on the anti-rutting impact and structural layer applicability of SFM under this effect. Thus, a coupled temperature-mechanical approach was developed based on the finite element (FE) method to simulate the rutting of SFM at different pavement layers and times of the day. During simulation, both standard load and overload were applied to the FE model of pavement. Asphalt mixture and SFM specimens were prepared for essential road performance and dynamic modulus testing. The mechanical properties of SFM and asphalt mixtures at different temperatures were obtained based on the measured data. The structural layer applicability of SFM was revealed by simulating the response of the pavement structure under the combined action of temperature and load. An accelerated pavement test (APT) based validation indicated that the simulation results were accurate. The results show that traditional asphalt pavement and pavement with SFM at the surface and bottom layers tend to exhibit dilative heave adjacent to the wheel load. Using SFM at the middle layer shows a compacted rutting mode, and the pavement has a minimum rise of 51% in rutting depth under the double overloading compared with the pavements with SFM in other layers. It implies that using SFM in the middle layer gives optimal resistance to overload. Considering the depth, form, and resistance of rutting, the SFM in the middle layer of pavement can functionally exert its anti-rutting characteristic.

Assessment of the stressed-strained state of a reinforced transport pipe under the combined effect of ambient temperature and static loads

The object of this study is a reinforced three-layer transport pipe, which is subjected to the joint action of ambient temperature and static loading of the road subgrade soil. The analytical model for assessing the stressed-strained state of reinforced three-layer pipes, under the combined action of temperature and static loads, has been improved using the theory of elasticity. The stressed-strained state of the reinforced pipe was assessed taking into account the values of the joint action of temperature and loads from vehicles, the physical and mechanical parameters of structural materials, and the geometric parameters of the pipe. As a result of the calculation of the reinforced multilayer pipe, it was found that the maximum movements that occur on the outside of the defective pipe are 0.64 mm, the metal pipe – 0.75 mm, and in the concrete mortar (fine-grained concrete) – 0.69 mm. It was established that under the combined action of ambient temperature and static loads from the road subgrade soil, ring stresses are maximum. They are 151 MPa. Axial stresses are also high – 141 MPa. At the same time, the maximum radial stresses are the smallest – 37.4 MPa. It has been established that a small difference in displacements occurs on the contact of structural materials of the reinforced pipe. However, the magnitude of the stresses is high. The maximum difference in ring stresses was 73 MPa, while the difference in radial and axial stresses was up to 1.0 MPa. It has been established that to restore the bearing capacity of damaged reinforced concrete pipes, it is possible to use the repair technology by the method of "sleeving". It involves pulling a metal pipe into the middle of the layer damaged with concrete mortar remaining between the concrete defective and the new metal pipes.

Experimental and numerical study on the behavior of single-layer spherical reticulated shells under the combined action of temperature and impact load

The long-span spatial single-layer reticulated shell with welded hollow spherical joints is often exposed to impact loads and extreme temperatures, which may cause the failure of local joints and parts or the collapse of the whole structure. Research results have shown that the joints should be considered rigid when analyzing the mechanical properties of single-layer reticulated shells. The welded spherical joints in the actual form, however, are not entirely stiff, and the lack of stiffness of these critical joints may cause a dynamic failure of the reticulated shells. For this paper, through experiment and numerical simulation, the dynamic behavior of welded spherical joints and reticulated shells under the combined action of impact load and temperature is studied. Five sets of welded spherical full-scale joint specimens with different diameters and wall thicknesses and a reduced-scale specimen of reticulated shell were tested on an impact device designed by ourselves. Three deformation modes of joint models are defined. The experimental results indicate that increasing the stiffness by reducing the diameter of the welded hollow ball or increasing its wall thickness can increase the stiffness of the joint, and this enhanced impact resistance. The time history curves of displacement, acceleration, and strain obtained from the experiment and the deformation process of the reticulated shell photographed by high-speed camera reveal the mechanism of dynamic failure of the reticulated shell. The finite element models of five joint specimens and reticulated shell specimens are established in ANSYS/LS-DYNA software to simulate the dynamic behavior under the same conditions as the test. The numerical simulation results are consistent with the experimental results. A parametric study was subsequently conducted to study the influence of temperature on the dynamic response of joints and reticulated shells and the effect of impact energy on the collapse mode of reticulated shells. The numerical results show that the impact force and energy dissipation are greatly affected by temperature, and that, the impact energy has a great influence on the collapse mode of the reticulated shell. The distribution position of failing parts of the collapsed reticulated shell adheres to specific principle.

Performance zoning method of asphalt pavement in cold regions based on climate Indexes: A case study of Inner Mongolia, China

Asphalt pavements are environmentally sensitive, and their service performance is affected by the local climate. This study aims to classify asphalt pavements into specific regional zones based on their performance in the adverse environments of Inner Mongolia, which is located in Northeast China. Firstly, in view of the environmental exposure effects of premature failure of asphalt pavements in Inner Mongolia, such as temperature, precipitation, frozen soil and freeze–thaw, different performance zoning indexes of asphalt pavement layers and subgrade were proposed. Secondly, the proposed indexes were calculated based on the climate data of 36 meteorological stations in the past ten years, and spatially interpolated using the kriging interpolation method. The spatial distribution map of the zoning indexes was drawn based on the ArcGIS platform. Thirdly, the service performance of the asphalt pavement was calculated based on the performance prediction equations. The rationality of the proposed zoning indexes was verified by comparing the similarity of spatial distribution characteristics between the zoning indexes and pavement service performance. Finally, pavement performance zoning was studied using cluster analysis and layer overlay methods, and the established performance zoning was verified using historical pavement field performance detection data to better represent the performance distribution characteristics of asphalt pavements in Inner Mongolia. Consequently, different primary and secondary performance zones for asphalt pavement layers and subgrade were developed in Inner Mongolia. It was observed that different environmental factors have adverse effects on asphalt pavement layers and subgrade in different zones, and an appropriate pavement design scheme needs to be selected to adapt to the local environment of Inner Mongolia. The adverse effects on asphalt pavement layers and subgrade were observed as low-temperature frost heave, high-temperature permanent deformation, potholes formed by the combined action of high temperature and precipitation, and frost boiling caused by the combined action of temperature and precipitation. In summary, the zoning method proposed in this study can provide guidance for asphalt pavement design under the local climatic conditions of Inner Mongolia, and for the performance zoning of other regions with different climatic environments.

Damage Simulation Analysis of Canal Concrete Lining Plates Based on Temperature-Stress-Water Load Coupling

Forming an important component of water conservation infrastructure, canal concrete linings are often subjected to damage to different degrees under the combined action of many factors (temperature, stress, water load, etc.) during construction or later operation. Here we explore the temperature and stress changes in the lining plate under different temperatures and water loads and determine the most unfavorable position (where the stress is more concentrated or the stress value is the largest) of the whole canal lining plate to provide guidance for the subsequent design, construction, and maintenance of canal linings. This paper takes a large irrigation district canal lining project in Henan Province, China as an example and uses ABAQUS finite element software to simulate the temperature and stress fields of the canal concrete lining plate under the combined actions of temperature, stress and water load. The results show that under both conditions of no water or water load, the temperature distribution is more uniform in the middle area of the canal bottom slab, and the temperature of the sunny side slope is higher than that of the shady side slope. The stress values of the lining plate and the bottom plate at the slope foot of the canal are large. Under the action of water load, the maximum stress of the right slope foot of the canal concrete lining plate reaches 2.38 MPa. Furthermore, the validity of the model is verified by comparing the error values, and parameters such as the elastic modulus and Poisson’s ratio were found to have a large influence on the sensitivity of the model. The results can be used as a reference for further research on canal concrete lining construction quality control.

Analysis of Interfacial Mechanical Properties of Steel Beams Strengthened with CFRP Sheets under Temperature and Creep.

Under the combined action of temperature and creep of CFRP (Carbon Fiber Reinforced Polymer) sheet, the interface between CFRP sheet and steel beams which are strengthened with CFRP sheet will produce relative slip. This slip will affect the interface interaction, reduce the bearing capacity and stiffness of members as well as increase the deformation. In this paper, the elastic method is used to introduce the creep effect of CFRP sheet and the temperature effect of steel beam. The calculation formulas of interface slip between CFRP sheet and steel beam, CFRP sheet tension and steel beam deformation under the combined action of temperature and CFRP creep are established. The accuracy of the analytical formula is verified by finite element analysis using the software ABAQUS. The results show that the CFRP sheet tension is smallest at the beam end while largest at the middle of the span. When the stiffness reaches about 3 ka, CFRP sheet tension basically does not change. When the temperature increases by 5 °C, the tensile force of CFRP sheet increases by about 3.7 kN, 1.8 kN and 2.3 kN, respectively. The increase of stiffness under creep has little effect on the change of CFRP sheet tension. The deformation is largest in the middle of the span while smallest at the beam end. Stiffness, temperature (5–25 °C), CFRP thickness and stiffness under creep have little effect on deformation. When the load increases by 5 kN under creep, the deformation increases by about 2.2 × 10−7 mm, 1.8 × 10−6 mm and 9.4 × 10−7 mm, respectively.

Study on Mechanical Properties of Simply Supported Girder Bridge after Jointless

The jointless bridges includes integral bridges, semi-integral bridges and extended deck bridges. The integral bridges adopts an integral abutment, and its main girder, abutment and pile under abutment are fixed together to bear the force together. The expansion joint and expansion device are cancelled, and the integrity, durability and driving comfort of the bridge are improved. In this paper, a simply supported girder bridge in Fujian Province of China is taken as the research background, and it is transformed into an integral bridge. Midas/Civil software is used to establish the finite element models of the original bridge and the integral bridge, and the mechanical properties of the main girder and the pile under the combined action of dead load and overall temperature rise of 25 °C are analyzed. The results show that due to the consolidation of the main girder and abutment of the integral bridge, the internal force at the girder end under the combined action of temperature and dead load is greater than that of the simply supported beam bridge. The pile deformation of the integral bridge is significant under the combination of temperature and dead load. With the increase of the height-to-thickness ratio of the abutment of integral bridge, the bending moment at the girder end and the mid-span are increasing. Different abutment height-to-thickness ratio has little influence on the horizontal displacement of the girder end of integral bridge. With the increase of height-to-thickness ratio of the abutment of integral bridge, the deformation of pile decreases. The flexible abutment with large height-to-thickness ratio can improve the mechanical properties of pile and achieve the purpose of protecting the pile.

Dynamic Mechanical Characteristics of Impact Rock under the Combined Action of Different Constant Temperatures and Static and Dynamic Loads

The complex mechanical environment of deep coal and rock masses leads to obvious changes on their dynamic mechanical properties. However, there are few reports on the dynamic mechanical properties of rocks under the combined action of medium temperature (normal temperature ∼100°C) and static and dynamic loads. In this paper, a dynamic load and temperature combined action Hopkinson pressure bar experimental system is used to experimentally study the impact type of a fine sandstone under temperature conditions of 18°C, 40°C, 60°C, 80°C, and 100°C, an axial static load of 3 MPa, a gas chamber pressure of 0.06 MPa, and a constant temperature time of 4 h. The dynamic characteristics of the change law of the fine sandstone and the energy dissipation characteristics of the load process are analyzed, and the characteristic law of the fine sandstone surface response is analyzed using digital image correlation technology. Our results indicate the following. (1) Under conditions in which the other experimental conditions remain unchanged, the dynamic stress-strain of the fine sandstone presents a bimodal shape with a “rebound” phenomenon. Increasing temperature causes the peak strength of the fine sandstone to increase; however, the relative strength can increase or decrease. The relative increase in the strength is 1.14 MPa (°C) when the temperature increases from 40°C to 60°C, 0.15 MPa (°C) when the temperature increases from 60°C to 80°C, and 0.62 MPa (°C) when the temperature increases from 80°C to 100°C. (2) The digital image correlation results show that, under the action of a dynamic load stress wave, the fine sandstone experiences a displacement vector change on the sample surface; furthermore, under the combined action of the temperature and dynamic and static loads, the fine sandstone experiences macroscopic shear failure. The surface strain in the propagation direction of the stress wave is obviously higher and can even reach values of more than 10 times that of the strain in other directions. (3) From the perspective of energy dissipation, the incident energy, reflected energy, and dissipated energy of the fine sandstone under an impact load have the same change law. After being affected by a dynamic load, the energy rapidly increases to a certain value and then remains relatively stable. The transmitted energy is relatively small and can be approximated as a horizontal line. As the temperature increases, the incident energy, reflected energy, and dissipated energy tend to first decrease and then increase, and most of the incident energy in the fine sandstone is dissipated in the form of reflected waves.

Tetrazene-Characterization of Its Polymorphs.

The reinvestigation of tetrazene single crystalline material by means of X-ray methods resulted in a slightly different structure when compared to previously published data. Reaction conditions responsible for different crystalline modification formation were investigated. Newly described C form was found to be the primary reaction product and the combined action of temperature and the presence of water over time is required for the transition to the A form. Both forms were described by X-ray powder diffraction. Tetrazene was also subjected to infrared and Raman spectroscopy, which allowed differentiating between the forms. The molecule was isotopically labeled with 15N atoms at two different locations (ring and nitrogen sidechain) and employed in assigning vibrational modes to the resulting bands. Differences between sensitivities to mechanical stimuli of the two modifications were investigated and found industrially insignificant. In the same vein, the performance of either modification in primer composition and primer was identical.

Exploring the coupling relationship between hydrocarbon generation of continental shale and nanopore structure evolution\u2014A case study of Shahejie formation in Bohai Bay Basin

The nano-scale pore structure of shale is closely related to the self-generated and self-accumulated shale oil and gas. The Bohai Bay Basin is a crucial oil-bearing basin in eastern China, and the Paleogene Shahejie Formation is the most important source rock section in this area. In order to study the internal relationship between hydrocarbon generation evolution and pore structure characteristics of source rocks, we conducted hydrocarbon generation simulation tests with a closed gold tube system, and heated up original rocks from Shahejie Formation in Laizhou Bay Sag, southern Bohai Bay Basin, from 290 °C to 440°C at different heating rates. Besides, we carried out low-temperature N2 adsorption experiments on sample residues, and measured their pore structure characteristic parameters. The results show that with the increase of simulated temperature, the specific surface area and pore volume of nano-pores below 10 nm (which are mainly organic pores) decrease first and then increase, while those of nano-pores above 10 nm increase all the way. The evolution trend of total specific surface area and pore volume is mainly controlled by pores below 10 nm which are mainly organic pores, especially micropores below 2 nm. There are two main factors affecting the development of inorganic pores: (1) Dissolution of organic acids produced by pyrolysis of organic matter in hydrocarbon-generation evolution; (2) Deformation of crystal structure of mineral components under the combined action of temperature and pressure. The experimental results at different heating rates demonstrate that rapid settlement under geological conditions is not conducive to the development of nano-pores, especially micro-pores composed of organic pores.

Application of BP Neural Network in Cross- Sensitivity Solution of Temperature and Strain of FBG Sensor

Fiber Bragg grating (FBG) sensor has the advantages of long transmission distance and less channel occupied by data acquisition instrument, so it can be used for strain measurement of power engineering and electronic engineering and so on. FBG is sensitive to both strain and temperature, that is, both changes can change the central wavelength of the grating. In structural health monitoring, the load on the tested part is complicated, and the temperature also changes greatly in the long-term monitoring process. If the FBG sensor is fixed on the tested component, it will inevitably be affected by the combined action of temperature and strain at the same time, making the test result produce error or deviation. In this paper, the temperature compensation of FBG strain sensor is analyzed and studied. Based on the calibration data, the FBG strain sensor temperature compensation is realized by BP Neural Network Algorithm. The research results of this paper can be used as a reference for health monitoring of large-scale structures using FBG sensors.

MECHANICAL CHARACTERIZATION OF PA 12 AND HDPE PIPES BEFORE AND AFTER AGING IN WATER AT TWO DIFFERENT TEMPERATURES

Polymer pipes are being widely used by many industrial segments. Although not affected by corrosion, the mechanical performance of these pipes can be reduced due to exposure to temperature, UV radiation and by contact with various fluids. Depending on the deterioration process, embrittlement or plasticization may occur, and the service life of the pipe can be severely reduced. In this work, the combined action of temperature and water upon the mechanical performance of polyamide 12 and high-density polyethylene pipes is evaluated. Destructive and non-destructive techniques were used and the performance of both materials was compared. Both polymers were platicized by the effect of water. However, for high density polyethylene the effect of temperature was more relevant than for polyamide. This behavior was attributed to the dependence of the free volume with the markedly different glass transition temperature of the polymers and the temperatures of testing.

Interaction of elements in carbon-graphite—Al—Mg—Zn—Cu melt system under combined action of temperature and pressure

Redistribution of chemically active elements is established on its inner surface of pores and at the interface with the alloy when impregnating carbon-graphite framework with Al—Mg—Zn—Cu alloy at temperature of 800 °C under pressure of up to 3 MPa. In this case, change in the solubility of melt elements in aluminum is possible as result of the combined action of temperature and pressure in the impregnation process, created due to the difference in the coefficients of thermal and thermal expansion of the matrix alloy, and the material of the impregnation device during impregnation. Titanium compounds are found in the pores filled with metal that are not added to the matrix alloy, but are formed as result of the contact of the matrix alloy melt with the walls of the impregnation device.

Ageing Tests of Samples of Glass-Epoxy Core Rods in Composite Insulators Subjected to High Direct Current (DC) Voltage in a Thermal Chamber

In this article, we presented the results of the tests performed on three sets of samples of glass-reinforced epoxy (GRE) core rods used in alternating current (AC) composite insulators with silicone rubber housing. The objective of this examination was to test the aging resistance of the rod material when exposed to direct current (DC) high voltage. We hypothesized that the long-term effects of the electrostatic field on the GRE core rod material would lead to a gradual degradation of its mechanical properties caused by ionic current flow. Further, we hypothesized that reducing the mechanical strength of the GRE core rod would lead to the breakage of the insulator. The first group of samples was used for reference. The samples from the second group were subjected to a temperature of about 50 °C for 6000 h. The third group of samples were aged by temperature and DC high voltage for the same time. The samples were examined using the 3-point bending test, micro-hardness measurement and microscopic analysis. No recordable degradation effects were found. Long-term temperature impact and, above all, the combined action of temperature and DC high voltage did not reduce the mechanical parameters or change the microstructure of the GRE material.

Experimental System of Hydrodynamic Action of Dunhuang Mogao Grottoes under Temperature-Humidity-Mechanical (THM) Coupling

In order to thoroughly investigate the weathering mechanism of the murals in Dunhuang Mogao Grottoes, based on the independently developed hydrodynamic test system of the surrounding rocks under the combined action of temperature, humidity, and stress, this study performed the liquid water adsorption test and gaseous water adsorption test of the surrounding rocks of the support body of Dunhuang Mogao Grottoes, as well as the softening test of the strength of liquid water adsorbed by the rock samples. The experimental results are as follows: (a) Q–t curve and lnw–lnt curve of the three types of black sandstone rock samples obtained by analyzing the nonpressure water absorption experiment data indicate that the Q–t curve of the rock samples showed a similar trend with time, with the initial curve being steep and rapid increase in the water absorption; the double logarithmic curve of water absorption is convex and tends to be saturated. (b) The absorbing water softening test analysis was carried out for four types of siltstone specimens with intensity of pressure; bibulous rate was found to vary with time, and sample parameters such as compressive strength and elastic modulus decreased linearly with increasing water absorption at different times of uniaxial compression test. (c) Through the summer and winter and cave surrounding rock within the sample, the gas adsorption of water simulation was combined with the adsorption curve analysis, indicating that the adsorption characteristics of the surrounding rock and the correlation of larger sample depend on season. These research results provide a reliable theoretical basis and technical support for the protection of the murals in the Mogao Grottoes of Dunhuang and the prevention and control by salt damage.

Design of surface profile of pairs of friction unit

To control the processes of friction and wear in the working pairs of the friction unit, it is necessary to study the behavior of the materials of the friction unit during contact interaction, accompanied by the combined action of temperature and dynamic loads. Numerous studies are devoted to the study of the influence of the chemical composition on the friction process of friction units, as well as the creation of new materials for brake units. There are practically no works devoted to the influence of nanogeometry of the surfaces of contact pairs of friction units on contact pressure. In this case, from an uneven distribution of contact pressure over the friction surface, strong heating can occur, which results in the formation of burns, thermal spots and foci of microcracks.

Multidisciplinary design optimization analysis of pin fins based on the Monte Carlo simulation

For aero-engines, pin fins improve the heat exchange efficiency of blades but increase their mass. To reduce the mass of blades, three types of pin fin models (diamond, elliptical, and rectangular) were used in this paper to analyze the stress distribution under the combined action of temperature and centrifugal force. The maximum stress was used as the constraint condition in these models. With the aim of mass optimization, these models were subjected to the multidisciplinary design optimization based on the Monte Carlo simulation. After the optimization via diamond, elliptical, and rectangular models, the pin fin mass was reduced by 15.42, 19.42, and 16.03%, respectively.