Local Stress-strain State Research Articles

Effect of Cr and Ni on mechanical response and microstructural evolution of nanocrystalline ferrite: A molecular dynamics study

Microalloying plays a critical role in improving the mechanical properties of steel. To offer a better theoretical guide for experimental research at the atomic level, this paper investigated the synergistic mechanism of adding trace amounts of alloy Cr and Ni and the microstructure evolution of nanocrystalline ferrite during the mechanical response process. First-principles calculations were implemented to investigate electronic properties. Hybrid molecular dynamics and Monte Carlo simulations were employed to explore the deformation mechanism under uniaxial tension and scratching. Specifically, comprehensive differences between doped and pure nanocrystalline ferrites were explored regarding local stress-strain state, dislocation evolution, twin expansion, and grain boundary activity. The results show that Cr- and Ni-doped nanocrystalline ferrite has higher strength and better wear resistance. The potential mechanism is that the addition of Cr and Ni enhances the atomic bonding strength with Fe atoms, hinders the movement of dislocations caused by lattice distortion, and suppresses grain boundary slip and migration, thereby improving the resistance to plastic deformation and grain boundary stability. Theoretical calculations based on microstructure indicate that compared to solid solution strengthening, Ni-induced grain boundary strengthening plays a dominant role in improving yield strength. Under large deformation, the trend of mechanical response is reversed. The suppression of dislocation motion by Cr reduces the dislocation density and dislocation entanglement, resulting in flow stress and local scratch force being smaller than that of pure samples. However, the formation of more nanoscale twins and twin-dislocation interactions enhances strain-hardening ability during tensile. Finer nanostructured subgrains are formed under scratching. These results provide valuable insights into the understanding of the strengthening mechanism and plastic deformation mechanism of Cr-Ni system low alloy steel under dynamic loading.

On the strength of many-layer fiber-reinforced plates

In Kolpakov and Rakin (2021), the concept of a representative model for multilayer plates was introduced. It was shown that a three-layer representative plate model provides us with complete information about the local stress-strain state (SSS) in a multilayer plate formed from an arbitrary number of layers. In this paper, it is shown that for a many-layer plate (the number of layers is more than 300), the periodicity cell problems (PCPs) corresponding to in-plane (tension/shear) make the main contribution to the local SSS. On one hand, it is a similarity with the uniform plate. On another hand, the solutions to the PCPs corresponding to in-plane (tension/shear) for fiber-reinforced plate are very different from the solutions corresponding to uniform plate.If the number of layers is less than 60, it is necessary to take into account the solutions to the bending/torsion cell problem. In both cases, it is necessary to take into account the skin-boundary layers (which occurs both in tension/shear and bending/torsion PCPs).Using the idea of a representative model, we construct a homogenized strength criterion (HSC) for fiber reinforced plates. As a result of the complex form of the local stress-strain stale in the components of composite, the HSC is built as a computer procedure. Since the representative model is low-dimension one, the procedure is fast.In general, the failure surface is a 5-dimensional surface in 6-dimensional space. For a multilayer plate, the strength criterion depends on three variables (three combinations of tension/shear and bending/torsion). In this case, the failure surface is a 2D surface in 3D space and can be visualized. In multilayer plates, we find many similarities with the classical theory of plates, but at the same time we clearly see quantitative and qualitative differences between multilayer plates and classical information plates. In particular, we see that the maximum of the local stress in composite plate occurs not at the top/bottom surfaces of the plate, but in the deep of the plate.

Effect of Inhomogeneous Mechanical Properties on the Stress-Strain Field at the Crack Tip and Crack Growth Direction in Dissimilar Metal Welded Joints

In the failure analysis and safety assessment of dissimilar metal welded joints, the mechanical heterogeneity of local regions is usually ignored and limited sampling locations are selected. The mechanical behavior of the crack tip region is the main variables affecting the environmentally assisted cracking behavior, and it is crucial for understanding the impact of mechanical heterogeneity on the local stress-strain state at the crack tip in welded joints. In this study, the effect of mechanical heterogeneity on the local mechanical behavior at the crack tip and on the stress-strain condition at the crack tip front for different crack sizes was investigated through finite-element simulations based on user-defined material subroutines. The local mechanical behavior of an interface region and crack propagation direction with mechanical heterogeneity and a series of initial crack locations were analyzed. The results show that mechanical heterogeneity has a significant effect on the mechanical condition and growth path of cracks at different sampling locations. The interaction between the mechanical heterogeneity around the crack and the crack depth determines the stress and plastic strain in front of the crack tip, which causes a substantial change in the crack growth path. The interface cracks have high stress and plastic strain; thus, the interface is often the weak position where damage occurs. To guarantee a reliable integrity assessment of cracks in mechanically heterogeneous interface regions, local mechanical properties related to crack locations should be determined and utilized.

A New Energy Approach to Predicting Fracture Resistance in Metals

To ensure the reliability and durability of structural elements, modern approaches require data characterizing the local stress-strain state of the material in risk zones. In order to predict the fracture resistance of structural elements, a theoretical-experimental method based on the damage accumulation model using the energy approach is proposed. One of the unique characteristics of the proposed approach is that it uses local parameters of the stress-strain state, which are determined using a highly accurate and easy-to-use noncontact method of optical-digital image correlation (ODIC). This can be used both in laboratory conditions and for structural elements under real operating conditions. The proposed method of plotting stress-strain curves makes it possible to determine the true stresses near the concentrators in structural elements under a complex load. Using these diagrams in calculations and the finite element method (FEM), a study of local strain not only of the surface, but also of the internal volumes of the material was carried out. The damage parameter is introduced as the ratio of the elastoplastic strain energy of the local volume to its critical value. It is confirmed that the damage of the sample material starts from its centre. It was established that the damage parameter in the centre of the sample is 25-35% higher than its value on the surface of the sample.

Compositional undulation induced strain hardening and delocalization in multi-principal element alloys

Multi-principal element alloys (MPEAs) exhibit outstanding mechanical properties due to their unconventional compositions and chemical structures. Rational design of element distribution in such alloys promises for achieving an unprecedented combination of superior properties. Here, using hybrid molecular dynamics and Monte-Carlo simulation method, atomistic models with compositional periodicity and chemical short-range order (SRO) are designed to investigate the effect of compositional undulation on the tensile behavior of CoCrNi medium-entropy alloy (MEA). Specifically, the differences between MEAs with and without compositional undulation in the evolution of defects, local stress-strain state, dislocation nucleation, slip, and its interaction with planar defects are explored. The results reveal that compositional undulation in MEAs can improve the elastic limit and achieve a strong lattice distortion effect which can enhance the dislocation glide resistance. In addition, obvious strain hardening and stress/strain delocalization are observed in the MEA with compositional periodicity, which promotes strength-plasticity synergy. More interestingly, there are formation of many hcp microbands consists of stacking faults, hcp-like structures and nanotwins owing to the compositional undulation. Such structures induced delocalized activation of slip systems which improves the strength/plasticity and strain hardening ability. The proposed compositional design can further optimize the comprehensive mechanical properties in addition to SRO, which provides a feasible approach to design novel MPEAs with exceptional performance.

A New Microstructural Approach to the Strength of an Explosion Weld.

In this paper, the local stress-strain state in an explosion weld was investigated and the local strength of the welded materials near the weld analyzed. It follows from the experimental data that the explosion weld at the microlevel looks like a wavy line. In the first approximation, this wavy line may be assumed to be periodic. We used the two-scale method to analyze the corresponding interface elasticity problem. We carried out numerical computations for three of the most referenced types of weld geometry: the symmetric wave, the asymmetric wave, and the wave with crest. We found that the wave geometry of the weld leads to increase in local stress in the weld zone. The stress concentration varied from 20% to 200% in dependence on the weld geometry and the macroscopic loading. Explosion welding is accompanied by strain hardening of the materials in the welding zone. In some cases, the strain hardening may compensate for the increasing local stress. As a result, the weld may be both stronger and weaker than the welded materials.

Local stresses in the reinforced plate with orthogonal systems of fibers. The homogenized strength criterion

In [1], the method of computation of local stress–strain state in the fiber-reinforced plate was presented. It was introduced the notion of the representative model for the multi-layer plates. It was demonstrated that the three-layer plate provides us with complete information about the local stress–strain state in the multi-layer plate formed of an arbitrary number of layers.In this paper, we construct the homogenized strength criterion (HSC) for the fiber-reinforced plates. In the general case, HSC is constructed in the form of a computer procedure. We develop the corresponding computer program. For the pure in-plane tension/shift or pure bending/torsion, 3-D failure surfaces may be drawn. We present the failure surface for the case of pure bending/torsion.

The Effect of Technological Damage on the Properties and Reliability of Construction Materials and Structures

The effect of the quantitative and qualitative composition of mixed binders on the physical and mechanical properties of cement compositions has been experimentally established. A cement stone with a different amount and dispersion of mineral fillers was considered. The research results showed that the plastic strength of the hardening system depends on its initial composition. The defects embedded in the material during its technological processing into the product determine the local stress-strain state of the structure, the nature of cracking and the fracture surface. The effect of technological damage on the mechanical characteristics and the nature of cracking of cement compositions are shown. The possibility of reducing the material consumption of construction materials by 15-21 wt.% due to the use of fillers that are optimal in appearance and quality composition has been proved.

A fiber optic conjugate stress sensor for instantaneous tangent modulus detection targeting prognostic health monitoring applications

In this work, a surface-mounted fiber optic conjugate stress sensor (FOCSS) is developed, fabricated, and experimentally demonstrated to accurately evaluate the instantaneous tangent modulus of various metals, thus allowing measurement of the elastic-plastic stress–strain behavior of the host material. The originally proposed embedded version of the conjugate stress (CS) sensor measured the deformations experienced in two fully embedded, ellipsoidal, collocated sensors of significantly different stiffnesses, and related those sensor deformations to host modulus via Eshelby’s equivalent inclusion method. In contrast, the current experimental study focuses on a surface-mounted implementation of the CS sensor. As Eshelby’s analysis is not applicable in this case, a simplified lumped-element spring model is developed to instantaneously relate the deformations in the CS sensor to the local stress–strain state of the host. Therefore, tangent modulus of the host can be estimated from the output of the FOCSS, which can serve as an important damage precursor in structural and prognostic health monitoring for a prominent set of failure mechanisms, including mechanical overstress, fatigue, and corrosion. In this study, the FOCSS data is used in conjunction with the lumped-element spring model to measure the elastic modulus of three different materials of significantly different stiffness: aluminum, copper, and steel. Additionally, as validation of instantaneous tangent modulus tracking, the elastic-plastic stress–strain curves of copper and steel are reconstructed from the FOCSS outputs during uniaxial tensile tests (with a goodness of fit R 2 > 0.98). The results demonstrate the ability of the FOCSS to detect instantaneous modulus as materials experience plastic deformation.

Effects of temperature and microstructure on low cycle fatigue behaviour of a PM Ni-based superalloy: EBSD assessment and crystal plasticity simulation

The macro and mesoscale deformation and damage of the PM nickel-based superalloy FGH4098 under low cycle fatigue loading at elevated temperatures were investigated using both SEM/EBSD characterization and crystal plasticity finite element (CPFE) simulations. The results indicate that higher temperature leads to more severe macroscale damage i.e. larger areas of hysteresis loops and shorter fatigue life with transgranular failure mode at both 650 °C and 750 °C. The misorientation parameters derived from EBSD characterization show similar deformation at both temperatures, but more intense localized deformation in the crack initiation region at 750 °C. Based on the accumulated shear-strain energy dissipation density and Fatemi-Socie fatigue indicator parameter, the distribution and evolution of fatigue damage are shown to be strongly affected by local stress–strain state and temperatures, and more severe and homogeneous damage is found at 750 °C. The CPFE simulation results also show higher damage propensity, as indicated by the fatigue indicator parameters used here, in the vicinity of annealing twin boundaries with high difference in elastic modulus.

The influence of material microstructural characteristics on the strength of porous or composite ceramic coatings

This paper is a follow-up study to our earlier research that identified several types of preferred stress concentration regions in a material with a porous coating and suggested certain microstructural factors to induce them (Zinoviev et al., 2020). This study takes a closer look at each of the factors indicated earlier, examining their effects on the deformation and fracture of a coating and a coated material as a whole. Porosity, including a pore distribution, size, number, and distance between them, elastic property difference in a composite coating, curvilinear coating-substrate interface, and thickness of the pore-free coating layer are among the causative factors analyzed in microstructure-based mechanical simulations. It is found that the pore distribution controls the crack-initiation strain and first crack location while having a low effect on the elastic modulus. A dimensionless parameter is proposed to characterize the effect of the pore size and minimum distance between them on the local stress–strain state of a coating. The research findings provide insights for the choice of filler materials to be induced in a polymer-derived ceramic coating, suggesting the material resulting in the highest strength properties of the coated material among the considered ones. Analysis of the non-porous layer effect suggests that cracks form either at the coating-substrate interface or pore surface, and defined the layer thickness when the location of crack initiation changes. The insights gained from this study may be of assistance for coating design and engineering.

АНАЛІЗ СИЛ ФУНКЦІОНУВАННЯ ВІД’ЄМНОЇ ЧАСТИНИ КРИЛА ЛІТАКА ТРАНСПОРТНОЇ КАТЕГОРІЇ

Each experimental design department has experience in determining design and operational loads for a given type of aircraft. The reliability of the data on the loading of a particular structural element determines the success of the aircraft being created. This is often confidential information. Much work has been investigated to improve the fatigue life of wing structural elements. With the development of integrated design methods, aircraft structure design can be performed in the shortest time, and with high technical excellence. In most cases, the fatigue life of wing elements is determined from the nominal stresses in the element. For a longitudinal structure set, it is customary to perform fatigue calculations directly using normal stresses in the element. For a more detailed specification of the fatigue life, it is necessary to have a general and local stress-strain state of a given structure. A feature of the work is to analyze the spectrum of loads acting on the wing console during a typical flight. The influence of high-lift devises (slats, flaps) on the shear forces and torque moment of the wing was analyzed. It has been shown that with the extensions high-lift devices, there is a significant increase in torque. These articles will make it possible to obtain the stress distribution of the detachable part of the wing under all operating modes. This, in turn, leads to a more thorough prediction of fatigue life. Since some operating loads can significantly change the distribution of the stress-strain state in the design element, and in turn change the fatigue life. The structural elements of the wing, in particular the attachment points for the high-lift devices, operate in a complex-stressed state. This complicates the process of predicting the fatigue life of these elements. To obtain a competitive aircraft, it is necessary to develop new methods of wing design with widespread use of integrated systems. This will contribute to obtaining a more optimal and perfect wing design

Local stresses in the reinforced plate with orthogonal sytems of fibers

We discuss the methods of computation of local stress–strain state (SSS) in the reinforced plate with orthogonal systems of fibers. Although the problem seems similar to fiber-reinforced solids [1], the final results are more different rather than similar. The main differences between the solids and plates are related to the top and the bottom surfaces of the plate and bending/torsion deformation of the plate. We investigate local stresses corresponding to the basic macroscopic deformations of plate: macroscopic in-plane strain/shift and bending/torsion. Investigation of the boundary layer (BL) near the top and the bottom of the plate demonstrates that the boundary layer thickness is less than the thickness of one structural layer. On this basis, we introduce a new notion of the representative model of a multi-layer plate. Namely, we demonstrate that the three-layer plate provides us with complete information about the local SSS in the multi-layer plate formed of an arbitrary number of layers. This fact allows drastically reduces the dimension of the problems of the calculation of multi-layer fiber-reinforced plates. We discuss the application of these results to the construction of the homogenized strength criterion (HSC) for the fiber-reinforced plates.

The Numerical study of the influence of a two-scale pore structure on the dynamic strength of water-saturated concrete

Many infrastructural concrete facilities, such as dams, bridge footings, foundations of port facilities and offshore drilling platforms, operate in a permanent contact with water. The permeable fractured-porous structure of concrete determines the water-saturated state of the surface layers of such concrete elements. Under dynamic contact loading, the pore fluid is capable of exerting a significant mechanical influence on the local stress-strain state and strength characteristics of the surface layers of concrete. This has to be taken into account when assessing the wear intensity of surface layers and predicting a concrete element’s service life. The aforesaid determines the relevance of the study aimed at identifying the influence of the pore fluid and characteristics of the concrete pore structure on the strength and fracture pattern under quasistatic and dynamic compressive loading. The present work is devoted to the theoretical study and generalization of the laws of mechanical influence of the pore fluid on the dynamic strength of high-strength concrete with a two-scale pore structure. The emphasis in the study is on analyzing the contributions of each of the pore subsystems to the integral mechanical effect of the fluid. To carry out such an analysis, a coupled hydromechanical model is developed. It takes into account the compositional structure of concrete, the presence of a pore space in a cement stone of two different scales, the interaction of a pore liquid and a solid-phase skeleton based on the Bio poroelasticity model, as well as fluid filtration in a pore space. By using the developed model were performed the numerical studies of the dependence between the compressive strength of the representative concrete volumes of the mesoscopic scale on the strain rate, the sample size, the pore fluid viscosity, and pore structure parameters. The simulation results showed the possibility of combining the obtained dependencies into a generalized (master) curve in terms of a combined dimensionless parameter, which has the meaning similar to the Darcy number. We identified two key factors that control the type and parameters of the concrete master curve of the dynamic strength. The first factor is the mobility of the pore fluid in the network of the capillary pores. It determines the rate of stress equalization in the porous skeleton due to fluid flow. The second factor is the interconnection of large micropores with the network of the small capillary pore channels. It determines the magnitude of the decrease in stress concentration in micropores by filtering the excess pore fluid into the capillary pore network. It is shown that the contributions of these two factors to the amplitude of variation of the dynamic strength of the water-saturated concrete are additive, and their total contribution reaches 25 %.

Analysis of the Seismic Moment Tensor of Acoustic Emission: Granite Fracture Micromechanisms During Three-Point Bending

An experimental study of granite fracture micromechanisms during three-point bending based on reconstruction of the seismic moment tensor components for acoustic emission events has been carried out. An original three-stage algorithm for refining and rejecting solutions for the seismic moment tensor of acoustic emission events is proposed, based on a hybrid iterative algorithm and the jackknife resampling method. After the formation of a catalog of acoustic emission events with a stable solution, their mechanisms were analyzed. It is shown that in the case of three-point bending of granite, acoustic emission events are localized in the zone of formation of the future main crack. It has been found that granite bending is accompanied by the formation and development of normal opening cracks with an additional shear component of varying intensity. The kinematics of the found mechanisms of acoustic emission events corresponds to the configuration of loads applied to the sample. The shear component is caused by the microstructural inhomogeneity of the sample. Variations in the orientations of the axes of maximum deviatoric compression (P-axis) and tension (T-axis) are determined, which are associated with the variability of the local stress-strain state of the material near acoustic emission sources. It is shown that the instantaneous magnitudes of acoustic emission events obey the Gutenberg–Richter law.

Features of the stress-strain state in the corner zones of structures

Corner regions of structures are characterized by a complex stress-strain state (SSS), caused by both the shape of the boundary or the “geometric factor”, and the finite rupture of the specified forced deformations, mechanical properties that go to the contact surface of the elements of composite structures. The relevance of the work consists in the analysis of local SSS in the corner zone of the region boundary with various study approaches: theoretical, experimental. For the theoretical analysis of the SSS of the region, we consider the resolving system of equations of the problem of the theory of elasticity in the zone of the cutout of the boundary and elements of the similarity theory; the photoelasticity method is used for experimental studies. An experimental solution was obtained on polymer composite models with an angle cut of the boundary under the action of forced deformations in one of the regions. The analysis of possibilities of theoretical, experimental approaches of SSS studies in zones with irregular point of border allows to reveal zones of applicability of solutions of linear elasticity problem.

Numerical and experimental assessment of the long-operated drill pipes destruction conditions

The cause of failures in the elements of the drill string when drilling deep wells is the occurrence and development of crack-like defects in the cross section. The generalized data of defectoscopy of long-term operated drill pipes conducted at the Ukrburgaz drilling rigs from 2015 to 2017, as well as numerous literature data show that such defects are formed at the bottom of corrosion ulcers that occur during operation under the influence of workloads and drilling fluids, in particular during tripping operations, both on the inner and outer surfaces of the drill pipe. During the tripping operations, under the influence of tensile loads, they being developed go up to the surface of the drill pipe, forming scouring, which ultimately leads to the destruction of the pipe. Using known analytical solutions, the stress state in the vicinity of the semieliptic crack located on both the outer and inner surfaces of the hollow cylinder under axial load was estimated and the corresponding stress intensity coefficients at the crack tip of these defects were determined. To predict the limit state of a drill pipe with a semieliptic crack, the analysis of crack parameters reflecting the local stress-strain state near the crack tip is performed. Using the finite-element method, the stress state around the vertex of the semieliptic crack was determined and on this basis the characteristics of fracture mechanics were calculated: J – integral and stress intensity coefficients. Diagrams of fracture risk assessment in the coordinates "depth of crack-like defect - depth of drilling - stress intensity factor" are offered, which make it possible to estimate the safe depth of both internal and external semieliptic crack-like defects detected by technical diagnostics taking into account results of experimental investigations of critical crack resintance. The admissible sizes of the studied defects depending on the depth of drilling are determined.

Методика расчета на прочность волноводов для обеспечения улучшенных массогабаритных параметров

This paper presents a calculation procedure for designing waveguides with iproved mass-dimensional parameters, which ensures the required strength and stiffness characteristics under static, dynamic and deformational loads. The procedure is based on the analysis of methods for determining the stress-strain state of the waveguide-and-distribution systems of spacecraft. The first stage of the procedure involves modelling the waveguide-and-distribution systems in a general formulation by a rod structure with equivalent loading and fixing conditions and determining the stress-strain state of such a system. At the second stage, local areas with the maximum stress-strain state values are selected for a further refined analysis in the rod system. An evaluation of the influence of the waveguide wall thickness on the general stress-strain state is performed. It is shown that when the waveguide wall thickness varies in the range of 0.25 – 2.50 mm, the strength and stiffness of its sections under static loads basically follow the linear law. It is established that under dynamic loading the wall thickness has almost no effect on the resultant stress-strain state of the waveguide arising under the influence of forced fluctuations and quasi-static loading owing to its dependence on the ratios of mass, moments of inertia and resistance, which for some standard sizes of the waveguides will be almost constant. The equations obtained for the rod system cannot be used for evaluating the influence of the wall thickness on local stress-strain state in the form of wall deflection, local loss of stability, etc. In view of this, at the second stage of modelling local areas of interest are selected and transformed into 3D thin-walled structures, with translation into finite element method programs for a more exact analysis. In the future, the proposed technique can be used to solve connected problems of interrelation and the influence of cross-sectional deformations in local zones of the waveguide on the changes in electromagnetic fields with the formation of parasite waves. This will significantly improve the quality of radio engineering characteristics of the waveguide and distribution systems while ensuring their strength, stiffness and minimal mass-dimensional parameters.

АНАЛІЗ КОНСТРУКТИВНИХ ОСОБЛИВОСТЕЙ З'ЄДНАНЬ СИЛОВИХ ЕЛЕМЕНТІВ КРИЛА ЛІТАКІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

Ensuring the fatigue life of the aircraft structure is a requirement for flight safety, and for a cost-effective aircraft. A plane with a long lifetime can perform more flights, reduce routine maintenance costs and increase airline profits. Market trends in the aviation industry show the interest of airlines in long life aircraft. Structural elements of the wing are joined by fasteners. The wing structure fatigue is determined by the endurance of regular zones. Regular zones include longitudinal, transverse joints. The fatigue life of the wing irregular zones should be no less than the fatigue life of the regular zone. The article provides an analysis of the design features of the wing structural element joints performing short and medium flights, ANTONOV and Boeing, which have reached a high level in this field of research. Structural schemes of the wings, location and execution of the joints of the wing structural parts using facilities that improve take-off and landing characteristics (such as ailerons, flaps, slats and spoilers) are analyzed. The types, diameters and materials of fasteners that vary within the wing limits are considered. Attention was focused on such important indicators as the edge tolerance, distance between the fasteners (spacing), wing and fastener construction materials. The wing is made of a prefabricated structure, to ensure safety requirements for permissible destruction. In turn, this leads to an increase in the amount of fasteners. Since fatigue life is affected not only by the kinds of materials, parameters of fasteners, rated stresses, but also the degree of load transferring between parts. The constructive execution of the longitudinal and transverse connections of the load-bearing elements was analyzed to further study the degree of load transfer in a difficult - stressed state. The materials of the article provide an opportunity for further in-depth research on the general and local stress-strain state of the wing.

Experimental study of wind impact on multilevel industrial scaffolding

In the article, the local stress-strain state of structures and constructions is investigated, various variants for the design of the boundary are taken into account: special lines, points. The acting forced deformations don’t satisfy the compatibility conditions. They have a finite discontinuity along the contact line (surface) of the domains, including the irregular point of the boundary, causing stresses. The subject of article is stress concentrators the singularity of the stress-strain state of structures and constructions exhibiting “constructive heterogeneity” and discontinuous forced deformations determined on polymer models of photoelasticity and defrosting of deformations. A complex theoretical-numerical-experimental approach, for obtaining and analyzing the stress state in the neighborhood of the irregular point of the plane domain boundary, is proposed to extrapolate reliable experimental data to a domain where the fringe contour is not readable.