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A novel SiC coating with a relatively high crack resistance property (crack extension force (GC): 12.0 J·m−2) and outstanding thermal shock resistance was achieved merely by pack cementation. Compared with the conventional SiC coating with Al2O3 addition (AOSC2), SiC coating with Al–B–C additions (ABSC2) possesses refined and denser microstructure owing to different effects in promoting SiC densification under different additions. Therefore, the improvement in microstructures results in superior mechanical capabilities, antioxidation performance (900 °C), and thermal shock resistance (between 1500 °C and room temperature).

The effect of the content of silicon carbide whiskers and the sintering temperature on the physicomechanical and thermophysical properties of samples of a ceramic composite material (CCM) of the SiC–SiCw–B4C–AlN system with weight content of silicon carbide whiskers (SiCw) 10, 30, and 50%, obtained by spark plasma sintering. Introducing silicon carbide whiskers SiCw into CCM of the SiC–B4C–AlN system increased the bending strength and crack resistance, and at SiCw weight content 30 and 50% the strength and crack resistance of the CCM were at the same level.

In this paper, the impact of electromagnetic stirring (EMS) on the gas metal arc welding (GATW) of an MAR-M247 superalloy was investigated. Results revealed that, without electromagnetic stirring, it was easy for carbides in the heat-affected zone (HAZ) of the weld bead to liquefy during welding, leading to weld bead cracks. Electromagnetic stirring refined the grains in the HAZ and the weld bead, leading to grain strengthening and subsequently resulting in the effective improvement in the hardness of the weld bead. In addition, electromagnetic stirring significantly facilitated the formation of the weld bead by the removal of large inclusions which in turn effectively improved crack resistance at the joint. It also accelerated the floating up of gas holes thereby reducing the generation of gas hole defects.

Phase-field models of fracture allow the prediction of crack propagation and crack patterns. In this contribution, externally driven fracture processes in linear and finite elasticity are investigated. Different approaches to consider pneumatic pressure and materials with non-isotropic crack resistance are studied, combined, and examined in detail. The versatility of the proposed models is proven by a series of numerical simulations in two and three dimensions.

Objective: Solving the problem of determining the conditions for the onset and development of unstable fracture, which is extremely important for the development of methods for calculating the limiting states of structural elements, improving the dynamic testing schemes of materials and classifying steels according to their ability to resist fracture. Methods: Analytical methods for assessing the limiting state of structural elements are used. Results: A brief overview of the available test methods for structural steels for dynamic strength and crack resistance is given. The experience accumulated by domestic and foreign practices in testing steels for strength and crack resistance under high-speed loading is analyzed. The disadvantages of the existing methods for assessing the indicators of dynamic strength and resistance to brittle fracture are indicated. Practical importance: It is shown that along with the traditional methods for assessing strength based on safety factors, it is necessary to develop and apply new methods for assessing the limiting state of structural elements, including by the criteria of crack resistance

The safety of reliable operation of aircraft and their durability essentially depend on the strength of the glazing, which is a critical structural element. There are a number of different requirements for glazing. To provide the necessary parameters, high-strength silicate glass is widely used, and special technologies for its strengthening are used. The analysis of the problem showed that the insufficient strength of aircraft glazing elements and the complexity of methods for monitoring the state of glass during production and operation due to the presence of microscopic surface defects, as well as the need for a reliable assessment of residual stresses, require that there be used new approaches and technical solutions for the development of modern technologies for creating structures. Ion exchange is one of the glass strengthening mechanisms, which makes it possible to reduce the negative effect of surface defects by artificially creating residual compressive stresses and reducing the thickness of the damaged layer. Computational studies, under bending strains, of the crack resistance of ion-exchange strengthened sheet glass were carried out using an in-house FEM-based software package developed to study the thermally stressed states of structures. The results obtained showed that the strength of real sheet glass fracture due to tensile stresses in bending is determined by crack-like surface defects. The creation of residual compressive stresses on the glass surface by ion exchange strengthening provides an increase in bending strength. With an increase in residual stresses and the depth of their distribution, the effect of ion-exchange treatment increases. If the depth of the zone of compressive stresses due to ion-exchange strengthening is much less than the depth of the surface crack, then the strength of the glass depends little on the maximum compressive stresses on the surface. The effect of ion-exchange strengthening increases significantly in the case of a decrease in the depth of the surface crack. The expediency of further research and comparison of calculation results with experimental data are shown. The developed technique will make it possible to solve important practical problems in studying the strength of the aircraft multilayer glazing and determining the optimal methods for eliminating defects.

In this study, monolayer TiN and multilayer TiN/Ti coatings involving different modulation ratios were deposited on Ti–6Al–4V substrate. Ti interlayers in the multilayer TiN/Ti coatings were prepar...

Based on analysis of mechanical test the results a search is completed for the optimum content of the main alloying elements of maraging steels (MS) based on Fe–Cr–Ni–Mo that provides a combination of increased strength properties, impact strength, and static crack resistance. A multiple regression model that determines the dependence of the mechanical properties of steel on the alloying elements contained within them is proposed. It is shown that the optimization task is multi-factorial with conflicting criteria and can be effectively resolved using an “ideal point” method.

Compact ceramic materials based on the Ti–B system modified with 5 wt.% of nanosize Si3N4 particles are prepared by the SHS-extrusion method. Results of studying structure, phase composition, and physical and mechanical properties of the materials obtained are presented. It is shown that addition of Si3N4 promotes formation of new phases, in particular titanium diboride and nitride in the final product. It is found that introduction of modifying nanosize Si3N4 particles into an initial charge leads to an increase in hardness and microhardness by 15 – 20 %, as well as to an increase in crack resistance by a factor of 1.5 compared with unmodified samples.

A procedure for calculation of the fracture force for a compressed composite plate with initial delamination is suggested. The fracture criterion of the J-integral forms the basis of evaluation of crack resistance. To facilitate calculation of the J-integral, an original procedure for expansion of initial loading into two states is suggested, so that the main section would not be loaded for the first system of loadings and the curvature values of sections would be identical for the second system and the system would be safe in the context of crack resistance. In order to determine the fracture force, the system of two transcendent equations is derived. The results of the calculation of the fracture force are compared for laminated plates made from carbon fiber-reinforced plastic and glass-reinforced plastic with various values of the initial delamination prepared according to the suggested procedure for the experimental data (the calculation error of the fracture force is less than 10% as compared to the experimental data).

One of the major factors affecting the life span of a Reactor Pressure Vessel (RPV) is the Pressurised Thermal Shock (PTS). PTS is a thermo-mechanical load on the RPV wall due to steep temperature gradients and structural load created by internal pressure of the fluid within the RPV. Safe operating life of a nuclear power plant is ensured by carrying out fracture analysis of the RPV against thermal shock. Carrying out fracture tests on RPV/large scale components is not always feasible. Hence, studies on laboratory level specimens are necessary to validate and supplement the prototype results. This paper aims to study the fracture behaviour of standard Compact Tension [C(T)] specimens, made of RPV steel 20MnMoNi55, subjected to thermal shock through experimental and numerical investigations. Fracture tests have been carried out on the C(T) specimens subjected to thermal transient load and tensile load to quantify the effect of thermal shock. Crack resistance curves are obtained from the fracture tests as per ASTM E1820 and compared with those obtained numerically using XFEM and a good agreement was found. A quantitative study on the crack tip plastic zone, computed using cohesive segment approach, from the numerical analyses justified the experimental crack initiation toughness.

Beams of a trapezoidal cross-section with a wide upper edge with prestressed reinforcement combine positive qualities in terms of strength, crack resistance, deformability and resource saving, which allows them to cover significant spans of multi-storey buildings. To develop a method for calculating the moment of cracking in these structures, a nonlinear deformation model was adopted, which includes equilibrium equations, conditions for the linear distribution of relative deformations along the height of the element section, and refined deformation diagrams of concrete and reinforcement. Concrete state diagrams are assumed to be nonlinear without a falling branch. To describe the deformation diagrams of high-strength and conventional reinforcement, a universal dependence is adopted, consisting of one linear and two nonlinear equations, in which the calculation of individual parameters is performed using different formulas. For the initial stage of the crack formation process, a design scheme is presented, in accordance with which the necessary equations and ratios are drawn up in relation to the considered prestressed reinforced concrete beam of a trapezoidal cross-section. The purpose of the study, in addition to developing a calculation methodology, was also the development of an algorithm and a computer calculation program. To obtain and analyze the results, a numerical experiment was carried out, the results of which are presented in tabular form. Due to the fact that the calculation method was built without involving empirical dependencies, the possibility of its application to determine the crack resistance of prestressed reinforced concrete beams of trapezoidal cross-section for any class of concrete and reinforcement was confirmed.

The article provides information about the stress state protective and decorative coatings during aging. The influence of the discrete nature of the substrate on the change in the stress state of the coatings from the action of the wind load is considered. It was revealed that for each type of coating there is its own critical value of the pore size (unfilled paint), the excess of which leads to cracking of the coatings. A method is proposed for selecting the optimal coating thickness.

This paper presents an analytical method for calculating the cracking moment of concrete beams reinforced with fiber reinforced polymer (FRP) bars, which considers the non-linear behavior of concrete in the tension zone and the contribution of FRP reinforcement. Theoretical cracking moments obtained by the proposed method were verified with the experimental results and the theoretical results calculated according to ACI 440.1R-15. The comparison results show good agreement between theoretical and experimental data. A parametric study on the effect of longitudinal FRP reinforcement ratio and elastic modulus of FRP on the cracking moment of FRP reinforced concrete beams also were done by using the proposed method. The parametric study results show that both longitudinal reinforcement and modulus of elasticity of FRP significantly affect the cracking moment of FRP reinforced concrete beams. Moreover, parametric study results also clarify the weakness of ACI 440.1R-15 in determining the cracking moment of concrete beams reinforced with a large amount of FRP reinforcement ratio and with high modulus of elasticity of FRP.

This study evaluated the effects of the types (MFL and acetate anti-icing filler) and the replacement rate of anti-icing additives on the performance of asphalt mixtures. Additionally, the road performance as well as ice inhibition capacity between environmental (acetate anti-icing filler) and conventional (MFL) anti-icing materials were compared. The equivalent volume displacement method was applied to determine the amount of anti-icing filler in asphalt mixture. In this paper, the high-temperature stability, low-temperature bending properties, water stability, ice inhibition properties and anti-icing persistence of the mixture were investigated in the laboratory. The results show that the ice inhibitor has negative effects on the rutting resistance, crack resistance and moisture sensitivity of the asphalt mixture. Additionally, the adverse effects become more obvious as the replacement rate increases. There was a similar trend in the mixtures with three kinds of ice inhibition filler in general. The tests also proved that the anti-icing fillers can effectively delay and inhibit the occurrence of road icing, weaken the bonding force between pavement surface and the ice layer and make the ice layer easy to be removed. It is found that the comprehensive performance of traditional ice inhibitors is better. Moreover, the high-temperature stability, anti-icing capacity and ice inhibition persistence of environmentally friendly anti-icing additives need to be improved.

Information on the stress state of protective and decorative coatings during the curing process, in particular on the cohesive state of destruction, is given. The influence of the type of substrate on the change in internal stresses in the coating is considered. It was revealed that the greatest value of shear stresses is observed in coatings on a heavyweight concrete substrate. The subsequent increase in temperature after curing to 50°C leads to an increase in the value of the normal stresses. The probability of cracking of coatings during thermal aging is estimated. It was revealed that during aging there is an exponential decrease in the cohesive strength of coatings and an increase in internal stresses. Aging tends to increase the likelihood of cracking of coatings. The change in stresses in coatings as a result of seasonal fluctuations in air temperature is considered.

Fusion weld is a portable and economical joining and repairing method of metals. However, weld cracks often occur during the fusion weld of Ni-base superalloys, which hinder the applications of fusion weld on this kind of materials. In this work, the effects of microstructures of grain boundaries (GBs) of the prototype M951 superalloy on its weldability were investigated. The precipitated phases, the elemental segregations on GBs, and the morphologies of GBs can be largely altered by regulating the cooling rates of pre-weld heat treatments. With decreasing the cooling rate, chain-like M23X6 phase precipitates along the GBs, accompanying segregations of B, and GBs becomes more serrated in morphology. During fusion weld, the engineered GBs in the M951 superalloy with a low cooling rate favor the formation of the continuous liquid films on GBs, which together with the serrated GB morphology significantly prevents the formation of weld cracks. Our findings imply that the weld-crack resistance of the superalloys can be ameliorated by engineering GBs.

Specimens of armco iron and steels 09GS and 37G2S possessing strongly different load-extension diagrams are studied. The σ = f (δ) curves are divided into regularly alternating periods, i.e., linear, power within the uniform stage, and I, II, III in the lumped stage. Each period is characterized by the yielding parameter (YP), plasticity components (elongation δi), initial stress σi, and rate of growth/decrease of the stress (∆σ/δ∆)i. Analysis of the YP is used to compare the periods in differently hardened specimens. It is shown that the combination of these periods is responsible for the standard mechanical properties of the specimens. The values of the YP are used to trace the relation between the ductility and the crack resistance and to show that the stress σII and the elongation $$ {\updelta}_{\mathrm{l}}^{\mathrm{IIs}} $$ at the start of period II of the concentrated stage may be treated as criteria of crack resistance.

This article presents a literature review into the current state of the theory and practice of spraying complex titanium and zirconium nitride on steel P6M5, as well as a study of the effect of spraying time on the structural and mechanical characteristics of the applied coating. With the help of microstructural analysis and the measurement of the mechanical properties of the sprayed layers, it was found that the size of the voids and their number per unit surface area decreases with the spraying time. The highest values of hardness and crack resistance of the coating were obtained during the technological process – 15 minutes. It was found that the duration of vacuum-condensation spraying with Ti-Zr-N alloy significantly increases the wear resistance of structural steels, and the best results among the considered parameters showed a sample with a spraying time of 15 min, this figure can be considered optimal.

In this paper, the brittleness coefficient, elastic modulus-to-strength ratio, drying shrinkage and autogenous shrinkage and cracking sensitivity were used to investigate the effect of styrene-acrylic emulsion (SAE) on crack resistance of cement-based materials under ultralow water binder ratio (0.22). Then the pore structures, hydration products and surface morphology were also studied to explore the mechanism of SAE on improving the crack resistance of cement-based materials. Results show that, the addition of SAE significantly reduces the elastic modulus, brittleness coefficient, elastic strength ratio, drying shrinkage and autogenous shrinkage of the specimen. The cracking susceptibility is also decreased by the incorporation of SAE and when the dosage of SAE was 5%, the initial cracking time would be extended by 43 hours. In addition, incorporation of SAE can reduce the amount of pores that have an adverse effect on shrinkage, refine the microstructure and decrease the calcium hydroxide formation and microcracks of cement-based materials. Such results would be expected to provide guidance on enhancing the anti-cracking ability of high-performance cementitious materials by the dosage of SAE under low water-binder ratio in practical engineering.

This paper aims to study the temperature control of mass concrete, and to understand concrete pouring of hydration heat temperature field and temperature stress distribution. The influence of relevant parameters on reducing the temperature difference between inside and outside and the concrete temperature control and crack resistance measures are put forward. Taking Fuma Yangtze River Bridge as the engineering background, the combining of engineering measurement, theoretical calculation, and ANSYS numerical simulation is adopted. Results show that the use of ANSYS simulation for the mass concrete casting process is feasible. Furthermore, it is concluded that the cracks of mass concrete are prone to appear at the corner of the surface, and the influences of t input temperature, mixing ratio on reducing the internal and external temperature difference are also studied.

In order to solve the problem of workability and durability of concrete caused by poor particle shape and morphology of manufactured sand and high content of stone powder, which leads to crack problems of concrete, the tensile strength, elastic modulus, shrinkage performance and adiabatic temperature rise performance of manufactured sand concrete were studied in this paper. And the cracking risk factor (the reciprocal of the anti cracking safety factor) of the concrete with the special admixtures and the crack resistant functional materials was calculated by according to GB 50496-2018. The experimental results show that the elastic modulus and tensile strength at the age of 28 d of the test concrete are increased from 31.0 GPa to 34.6 GPA and 2.91 MPa to 4.23 MPa, respectively. The shrinkage performance and adiabatic temperature rise of the concrete are reduced from 98 με to 65 με and 38.9°C to 38.4°C, respectively. The risk factors of surface and center crack resistance of mass concrete floor are 0.52 and 0.75, so the concrete under inspection will not crack.

The influence of calcium microalloying on the texture of aluminum Al–Mg–Li and Al–Mg–Si–Cu alloys is studied. The paper considers the mechanical properties at static and dynamic loads, the fatigue characteristics, the crack resistance, and the high-temperature strength of V1341 alloy sheets with a regulated recrystallized structure in state T1. The properties of the sheets are also determined after long-term heating at 100–150°C for 10–1000 h. The results of service and corrosion tests of the sheets are presented.

The occurrence of crack-like defects is a common phenomenon in the operation of vertical steel tanks (VST). Such defects can occur both at the beginning of the operation of the tanks, which may be associated with a violation of the manufacture conditions or the installation procedures of the tank elements and during operation. Over time, such defects increase significantly and turn into cracks. Existing regulations prohibit the operation of VST with cracks. At the same time, the organization that operates the tank does not always have the opportunity to perform repairs immediately. There are cases of trouble-free operation of tanks with non-through surface cracks at the stage of sustainable growth, which are confirmed by model calculations are known from practical experience. The analysis of crack resistance of the VST-5000 tank with a semi-elliptical crack under the action of hydrostatic pressure is carried out in the work. The level of filling the tank with petroleum products is 95% of its height. The semi-elliptical crack is located on outside surface of the wall panel in lower row of cladding. Determination of crack resistance of a tank with a crack is performed on the basis of stress intensity factors (SIF). Direct and energy methods were used to SIF calculation. Determination of the stress-strain state is performed on the basis of the semi-analytical finite element method (SFEM). The SIF distribution along the crack front obtained using SFEM by both direct and energy methods almost coincides and agrees well with the values of SIF calculated by the direct method when using three-dimensional FEM. The obtained values of SIF differ along the crack front by 50%: the minimum value of SIF acquires at the point of the front, which is located on the outer surface of the tank, the maximum one - at the point of the front inside the wall that is furthest from the outer surface. The obtained results show the quite uneven SIF distribution along the crack front, so that the calculation of such problems requires the spatial setting of problem.

The article considers modern perspectives and directions of using fast – hardening high – strength concretes for protection against striking factors of action of different types of weapons. It is shown that the use of concrete materials in weapons and military equipment is one of the important components of defense structures and protective fortifications during hostilities as platoons and bases, and structures for the protection of civilians. The possibility of obtaining such concretes for the creation of special purpose fortifications is shown. Developed concrete structures have increased strength and impact resistance to high-speed impact. Due to the reinforcement of the concrete structure with mineral and chemical additives and ultrafine fibers, high rates of early strength, viscosity, crack resistance and impact resistance are achieved. The paper presents the main indicators of water consumption, strength and impact resistance of high-strength concrete. The results of the experimental study of samples of the destroyed concrete elements are presented and the corresponding conclusions concerning the use of various types of fibers for reinforcement of such concretes and increase of their crack resistance by basalt fibers are made. It is shown that a high-strength concrete with high construction and technical performance can be successfully used to create protective fortifications and fortifications for special purposes.

Operation reliability of a pipeline depends on many factors, including conditions of pipe forming, and a type of structure of pipe steel. Results of study of mechanical properties, impact toughness, crack resistance of pipe steel variation as a result of deformation aging depending on modes of pipe production and type of steel structure state presented. It was shown that standard mechanical properties practically don’t depend on the place of sampling in most extreme sections of pipe circumference and method of deformation at their manufacturing. Most favorable variation of impact toughness parameters and crack resistance was discovered for pipe metal, obtained by deformation schemes in rolls and UOE-forming, where increasing of their characteristics is observed. At the step forming JCOE a considerable scatter of impact toughness values over section of a pipe workpiece was noted, which decreased in the finished pipe. It was shown that deformation aging results in a decrease of deformation ability of the metal, cold resistance, crack resistance, which is most typical for steel with bainite structure. It was established that deformation aging of bainite steel to a greater extent decreases the crack resistance (the work of initiation, the work of propagation of a crack, its critical opening) at static tests for bending, than that of ferrite-perlite steel. Therefore, as a result of deformation aging, the destruction resistance of pipe steels with bainite structure decreases to a greater extent.

At present, rutting and cracking have become serious issues in asphalt pavement, especially in the areas of summer heat and winter cold. Nanomodifier has been widely used in recent years due to its unique properties in improving the characteristics of asphalt binders. To make better use of nanomodifier to solve the problem of rutting and cracking of pavement, a compressive review on the high- and low-temperature performance of nanomodified asphalt is performed. The results indicate that for high- and low-temperature performance of asphalt binder, the effectiveness of nanomodification is found to be strictly influenced by the combination of original asphalt type, nanomodifier type, nanomodifier dosage, nanoparticle size, and preparation of nanomodified asphalt, and the high-temperature antirutting performance and low-temperature crack resistance of final blends are various with the combination. Chemical composition, microstructure, dispersion, and compatibility of final blends were the possible reason causing the difference. The rational selection of the combination can improve the high-temperature rutting resistance and the low-temperature cracking resistance of asphalt binder. So far, there is a lack of systematic investigation in this regard. Therefore, it is very necessary to study systematically the original asphalt, nanomodifier, nanomodifier dosage, nanoparticle size, and preparation of nanomodified asphalt effect on the high and low performance of nanomodified asphalt, especially in the modification mechanism in the future.

Fracture toughness of syntactic composites with various degrees of filling with hollow glass microspheres is studied. It is shown that the “area method” can be employed for calculation of the crack resistance of syntactic composites.

The paper presents results of studies on technological defectiveness, structural and mechanical heterogeneity and crack resistance characteristics of welded joints from lowcarbon and low alloy stee...

Mechanical properties as well as crack resistance and stress corrosion cracking (SCC) resistance parameters of ultralow-carbon martensite steels (ULMS) type 05H2G2B and HSLA pipe steel 10G2FB with a different structures depending on processing are investigated. It is shown that despite a higher strength level, SCC resistance of ULMS steel is 25–30% higher than for HSLA steel with ferrite-perlite structure and close to that for this steel subjected to quenching and tempering.

This paper presents the experimental testing of eccentrically compressed reinforced concrete columns. There are experimental results of crack resistance of non-strengthened (control) and strengthened RC columns in the tension zone. The columns were strengthened by carbon fiber reinforced polymers (CFRP). As a result of experimental studies with the columns strengthened by CFRP, we obtain that the width of their crack decreased by an average of 33%. The eccentric compression load of the crack’s appearance increased from 40 kN to 60 kN for strengthened columns.

The versions of nonlinear defining relations and characteristics of nonlinear fracture mechanics controlling and simulating the service life, survivability, and durability of parts of modern power and energy structures operating at low, cryogenic temperatures are investigated.

The article presents the results of a study of the relationship between strength and performance (temperatures of ductile-brittle transition Tdb and zero plasticity NDT, critical opening at the crack tip CTOD at a test temperature of —40°C) on the structure parameters of thick plate products made of low-carbon low-alloy steels with different contents of basic alloying and microalloying elements.

The development of tensile stress can cause desiccation cracks, further increasing infiltration and inducing instability in green infrastructure (slopes and landfill liners). Recent research has promoted the use of biochar (i.e., stable carbon with a life period of more than 500 years) as an eco-friendly material that can provide simultaneous benefits in reducing tensile stresses and crack development, aiming to enhance landfill cover longevity. However, there is a lack of guidelines and criteria for selecting biochar (feedstock type and particle size) as landfill cover material. This study aims to investigate the effects of biochar particle size and feedstock type on cracking of soil. Two contrasting feedstock types (i.e., pig manure-based and wood-based) have been selected for amendment on lean clay soil. Laboratory experiments were conducted to monitor the cracks. The results show that wood biochar (WB) is more efficient in crack reduction than pig manure biochar (PMB). Moreover, it has been observed that fine-grained biochar is more suspectable to cracks formation regardless of biochar type. The cohesion and internal friction angle of biochar are dependent on the surface morphology of biochar. WB has more angularity and sharp edges, which can increase interlocking in soil, thereby enhancing shear resistance and, hence, soil stability. The comprehensive study can help narrow down the selectivity of biochar and its specifications to mitigate cracks and enhance the strength of landfill cover.

This article analyzes the resistance against destruction of C0.65Mn and C0.60Si2 steels characterized by different structure and phase composition depending on thermal treatment for the purpose of improving the crack resistance of springs. Two types of specimens have been tested: with crack and with round notch. It has been demonstrated that the parameters of crack resistance of bainite steels determined on the specimens with crack are lower and on the specimens with round notch are higher in comparison with troostite steels.

The results of experimental and theoretical researches of crack resistance, development and growth of cracks of a fragment of a reinforced concrete multi-storey frame of a monolithic building with prestressed beams for a special emergency impact caused by a sudden removal of one of the load-bearing elements are presented. Removal of the middle column of the frame was considered as an emergency impact. Analysis of the pattern cracking in the frames with a prestressed beam before and after a special impact is carried out against the pattern cracking in an unstressed frame structure. Based on the increments of cracks width in the beam, the coefficient of dynamic additional loading in prestressed frame structures from a special impact was calculated. The obtained results of experimental and theoretical researches of the crack resistance of frame structures in considered influences can be used in the development of methods for protecting the frames of monolithic multi-storey buildings against progressive collapse.

In order to restore worn parts during repair work, it is often used to press the repair bushings. While assembling joints, cracks may form in the spanning part (bushing), as it may have surface and structure defects. Therefore, an urgent task is to increase the crack resistance of joints with tension during its assembly. The paper examines the influence of the geometry of the spanning part on the process of cracking. To assess the effect of defects on the crack formation, the method of modeling defects with a surface crack of a semi elliptical shape was used. The crack resistance is estimated using the force criterion of fracture mechanics – the stress intensity coefficient. As a result, it was found that the ratio between the wall thickness of the enclosing sleeve and its outer diameter has a significant effect on the crack resistance of the joint with tension, which allows reducing the origin probability and crack development during its pressing by varying these parameters. While assembling joints, the following methods are often used: mechanical-using a press and thermal with heating of the covering part. When the method of joint with cooling of the covered part, the greatest strength of the joint is achieved, but the probability of cracking increases. This is because when the temperature of the enclosing sleeve decreases in contact with the cooled shaft, the critical stress intensity coefficient (fracture toughness), which is a mechanical characteristic of crack resistance, decreases. To reduce the effect of cooling the sleeve, you can use a combined method of assembling the joint, in which the covered part is cooled and the covering part is heated. It is shown that to assess the fracture resistance at low temperatures, it is optimal to conduct full-scale tests, where the cooling and heating temperatures of the press joint parts are the experimental factors.

A finite-element method is proposed for predicting crack initiation and development when laser shock processing are applied to materials with linear and V-shaped cracks. The optimal shock-wave treatment for minimal speed of crack propagation is determined.

The paper examines the effect of some operational factors on the cyclical crack resistance of the beam with an inner transverse crack of the circular shape. The beam with the cross-section of an uneven I-beam joist is positioned on a solid elastic foundation and is subjected to repeated loading by concentrated force. The temperature dependence of the number of loading cycles required for the defect to grow to a given size is established. In addition, on the basis of the principle of the independence of the forces, the residual resource of the beam is assessed in the case of an arbitrary system of forces. The proposed calculation scheme is used to assess the durability of rails.

Helix concrete consists of twisted steel wires of star shape and size approximately 1 mm2 areas with 25 mm, 35 mm, 50 mm, 65 mm & 80 mm long added to cement concrete. Replacing the rebar to some extent is to achieve higher crack resistance and structural strength throughout the concrete mass in all directions. In the present research, the analytical studies have been carried-out using MSC Nastran. The analytical studies have been carried-out on star cross sections of helix. It was observed that the shape and number of twists of steel wires maximizes the bond between the steel and cement based concrete matrix. Helix steel wire, with its twisted profile is a more superior reinforcement and is a substantial improvement over fibers of any time. When concrete is stressed or bent the fibers which are straight will slide out smoothly with minimal possible friction, so the force required to pullout is generally small. Adding deformation like a hooked end or corrugations adds friction and increases pullout force substantially.

The effect of additional heat treatment at elevated temperatures on the physicomechanical characteristics of unidirectional epoxy organoplastics has been studied. It has been shown that long exposure (24 h) at temperatures of 120 and 180°C leads to a significant decrease in crack resistance, as well as in the bending and shear characteristics of the composites under study. Infrared spectroscopy has revealed a tendency towards the formation of carbonyl groups after holding at 120°C. Possible reasons for the observed changes are discussed.

Alternating current accelerates stress corrosion cracking of grade X70 pipe steel in electrolytes of various compositions: 3.5% NaCl solution (pH 7), citrate buffer (pH 5.5), and a mixture of NS4 solution with borate buffer (pH 7). The increase in crack growth rate upon static load and deterioration of steel crack resistance during constant extension rate testing correlate with an increase in the metal corrosion rate.

A method is proposed for identifying diamond-grinding conditions that ensure crack stability of silicon-carbide plates, with satisfactory productivity, taking account of the tensile stress in subsequent manufacturing operations. By that means, the waste in the production of semiconductor instruments may be decreased.

The use of local brittle fracture criteria for predicting the crack resistance of low-alloy steels is a generally accepted approach. The paper analyzes the possibility of its use for experimental melts of highstrength low-alloy steel sheets with yield strength of about 1000 MPa, the structural state of which was previously studied. Cylindrical specimens with an annular notch of three types differing in the stress-strain state in the net cross-section were tested. It is found that the use of the simplest formulation of such a criterion in the form of an energy condition for the propagation of microcracks through structural barriers (large-angle grain boundaries) gives acceptable results for notched specimens made of metal with different grain sizes, and allows linking these results with the crack resistance of the studied materials.