Plasticity of Workpieces Processed by Deforming Broaching with Through Deformations

modifying the thickness and mechanical properties of the ingot crust. However, this often leads to the formation and development of surface cracks, especially edge, reticular, and transverse cracks. Thus, by selecting different cooling rates, the temperature gradient and the temperature stress and strain at the outer surface and solidification front may be adjusted, and the brittleness range may be avoided. A compromise value must be sought here, since increasing the temperature gradients is favorable in terms of compressive stress and strain at the center of the billet but also tends to increase the tensile stress and strain at the outer surface. At most Russian metallurgical enterprises, quality requirements are formulated in terms of axial porosity, axial chemical inhomogeneity, internal cracks (perpendicular to the broad or narrow faces, axial cracks, pitlike cracks), and external cracks (longitudinal, transverse, edge, and reticular). The appearance of such cracks is due to complex factors, most notably the derivatives of the thermal stress and stress-strain state with respect to the mechanical loads. Manufacturers of continuous-casting machines employ different approaches to cooling.

The most common method of treating of the congenital funnel-shaped chest is thoracoplasty method by D. Nuss. During this surgery, a significant mechanical effect is created on the ribs, sternum, spinal column, which act instantly and continuously for a long time and create new biomechanical conditions for the «chest – rib – spine» system. Objective. To construct a functional model of the chest with a spinal column, which takes into account the movements in the costal-vertebral joints, it allows modeling the funnel-shaped deformation in conditions close to the reality, its operative correction, predicting the results and choosing the optimal parameters of thoracoplasty. Methods. Normal and funnel-shaped chest models based on the articular connection of the ribs to the spine were created using SolidWorks. The main calculations were made using the ANSYS program. To estimate the stress-strain state (SSS), stresses are selected by Mises. Results. The created dynamic mathematical model of the chest makes it possible to conduct a reliable analysis of the biomechanical interaction of the plate with the chest, to analyze the stress-strain state of the constructed models in the norm, with and without taking into account the movements in the costal-vertebral joints. In addition, it allows to simulate the operation by D. Nuss and to study the biomechanical changes in conditions close to reality, occurring in the «chest – rib – spine» system, to determine the areas of maximum loads and safety boundaries. Conclusions. The reproduction of articular ribs rotation in the dynamic model changes the picture of the SSS distribution. In the case of modeling the correction of funnel-shaped deformation of the chest by the method by D. Nuss, the largest zone of stress concentration was found on the outer posterior surface of the sixth pair of ribs. The most tense vertebrae were ThV– ThVI, but the maximum values did not exceed the permissible values. In the case of a lower plate conduction, the correction is achieved with better SSS values in the higher elements of the «chest – ribs – spine» system.

The work aim is the mathematical modeling of the austenitic steel pipes sink drawing process to establish the effect of the pipe wall thickness on the material stress-strain state and to predict the martensitic transformation development. The drawing process was simulated for thin-walled and thick-walled pipes by the finite element method using the DEFORM-2D software package. There are determined the shape change and deformations distribution, the deformations intensity and the average normal stress for seven variants of pipes with different wall thickness ratios and diameter are determined. Distribution patterns for two extreme variants are shown. The difference is shown in the stress state at the drawing process of thin-walled and thick-walled pipes. The change in the average normal stress in time t of a particle passage through the deformation zone for the outer and the inner surfaces for a thin-walled and extra thick-walled pipe is given. In either case, the compression stresses up to –400 MPa for the inner surface and tensile stresses for the outer surface up to +200 MPa are prevail at the entrance to the deformation zone. Inside the deformation zone, a thin-walled pipe is characterized by the presence of approximately equal compressive stresses both on the outer surface and on the inner one. However, the stresses are close to zero outside and reach –600 MPa inside for a thick-walled pipe. The deformation zone numerical simulation in the sink drawing made of austenitic steel showed that there are differences in the stress-strain state in the case of processing thin-walled and thick-walled pipes. The performed calculations and comparison with the literature data on the stress state influence on the cold martensitic transformation process made it possible to predict the development of this transformation in the drawing process. It was revealed that during thin-walled pipes drawing process are created more favorable conditions for the phase transition development.This work was performed with partial financial support of Resolution No. 211 of the Government of the Russian Federation, contract No. 02.A03.21.

We propose the Ni–W plating film as a mold material for the hot embossing of borosilicate glass. The lifetime of a Ni–W plating mold is important from a practical perspective. However, there have been no previous reports on the life of a mold. Contact angle has been reported as a parameter for the comparative assessment of wettability. In this report, we identified the components of borosilicate glass reacted with a Ni–W film by elemental analysis together with a wettability test. In the wettability test, increasing temperature caused a decrease in of contact angle, which is caused by the chemical reaction at the center of glass. In the results of the elemental analysis of the Ni–W film in contact with glass, Zn, a constituent of the glass, was not detected in the noncontact zone, but was detected in the contact zone. There is no binary alloy phase diagram of W–Zn. It is considered that W does not form an alloy with Zn. Results from the reaction of Zn on Ni indicated an increase in the wettability of borosilicate glass for the Ni–W plating film.

Purpose. Establishment of dependencies of a stress-strain state in a rubber-cable tractive element with a broken structure considering a nonlinear dependency of shear modulus on rubber shell deformations. Research methodology. Construction by methods of the theory of composite materials and analytical solution of a rubber-cable rope model with a broken structure and a rubber shear modulus nonlinearly dependent on deformations. Findings. Analytical dependencies are constructed that allow determining the indicators of a stress-strain state in a rubber-cable rope with a broken structure and a rubber shear modulus depending on rubber deformation. An algorithm for determining a stress-strain state of a rubber-cable rope with a broken structure and a rubber shear modulus dependent on deformation of elastic layers is formulated. A mechanism for changing a stress-strain state of a rubber-cable rope is established, taking into account the nonlinear deformation-dependent shear modulus of rubber. The obtained expressions make it possible to determine the internal loading forces on cables and their displacements, which allow calculating tangential stresses in the elastic shell material located between the cables, which are directly proportional to the tangent of the angle of its displacement. Scientific novelty. The character of change for parameters of a stress-strain state in a rubber-cable rope with a broken structure considering a nonlinear dependency of shear modulus on rubber shell deformations is determined. Practical significance. Taking into account a non-linearly dependent shear modulus of rubber makes it possible to specify the dependencies of main parameters of a stress-strain state of rubber-cable rope and allows considering the effect of this phenomenon on rope strength, as well as to clarify the prediction of a stress state in a rope with a cable continuity breakage and to ensure a possibility of increasing the operational safety of rubber-cable ropes, in particular by using as stay ropes in capital structures.

Stress analysis in contact zone between the segments of telescopic booms of hydraulic truck cranes

Thin films of polystyrene (PS) are bonded to copper grids and crosslinked with electron irradiation. When the films are strained in tension regions of local plastic deformation, either crazed or plane stress deformation zones (DZs), nucleate and grow from dust particles. the nature of the local deformation, as well as the local extension ration λ, is determined by transmission electron microscopy. The behavior of the PS glass is consistent with its being a network of molecular strands of total density v = vE + vX, where vE is the entangled strand density inferred from melt elasticity measurements of uncrosslinked PS and vX is the density of crosslinked strands determined from the ratio of the applied electron dose to the electron dose for gelation. when v is less than 4 × 1025 m−3 (<1.3vE), only crazes are observed whose microstructure is similar to those in uncrosslinked PS. As v increases from 4 × 1025 to 8 × 1025 m−3 (from 1.3vE to 2.5vE) shear deformation begins to compete with crazing. As v increases above 8 × 1025 m−3, only shear DZs are observed, the strain in which becomes progressively more diffuse as v increases. The λ in the crazes and DZs correlate well with λmax, the maximum extension ratio of a strand in a network of density v computed using the Porod×Kratky model. For crazes ln(λ) ≃ 0.9 ln(λmax) and for DZs ln(λ) ≃ 0.55 ln(λmax). The strain at which crack nucleation is first observed increases as v increases from <5% in uncrosslinked PS with v = 3.3 × 1025 m−3 to >20% in PS with v = 33 × 1025 m−3 (v = 10vE); crosslinking to still higher crosslink densities, e.g., v = 14vE, results in cracks which propagate in a catastrophic manner at low applied strains. An optimum v thus exists, one not too high to suppress local shear ductility but high enough to suppress crazes which can act as crack nucleation sites. these results are compared with previous results on a variety of linear homopolymers, copolymers, and polymer blends that are characterized by a wide range of v (v = vE). The transitions from crazing to crazing plus shear and from crazing plus shear to shear only take place at almost identical values of v. In addition the correlation between λ in the crazes and DZs and λmax for a single network strand is the same for both classes of polymers. This agreement implies that chain scission is the major mechanism by which strands in the entanglement network are removed in forming fibril surfaces. Craze suppression, by either increasing v in the crosslinked polymer or vE in the uncrosslinked ones, is due to the extra energy required to break more main‐chain bonds to form these surfaces.

The elastic-plastic deformation, limiting states and supercritical behavior of cylindrical shells under tension and combined loading by internal pressure and tension to failure are studied theoretically and experimentally. This problem is characterized by the occurrence of large strains, shape changes and, as a result, an inhomogeneous stress-strain state. In the numerical solution of such problems, the problem arises of constructing true stress-strain curves of materials. In this regard, to study the deformation and strength properties of materials, it is important to use an experimental-computational approach, which makes it possible to take into account the non-uniaxiality and inhomogeneous of the stress-strain state without accepting simplifying hypotheses. The paper presents a new efficient algorithm for constructing a true stress-strain curve, which is based on the procedure of nonlinear extrapolation of the curve. Such an algorithm, in the process of direct numerical solution of the problem, consistently constructs a stress-strain curve without using repeated direct calculations, which significantly (at times) increases its efficiency. Based on the experimental-computational approach, the true stress-strain curves for solid rods and shells made of 10KhSND and 10G2FBYu steels were determined under tension and combined loading by internal pressure and tension to failure. The failure of shells under tension occurs at lower (at times) values of true strain than solid rods. Significant differences in true stresses and strains at the moment of failure are due to different localization of deformation of solid rods and shells after the loss of stability of plastic deformation in tension. It is shown numerically and experimentally that after loss of stability of plastic deformation according to Considerer in tension, the cylindrical shell contains two forms of loss of stability until the moment of failure. The first form of loss of stability, as in solid rods, is characterized by localization of deformations along the diameter of the sample in the form of a neck, and the second form is characterized by localization of deformations along the thickness of the sample, which determines the final stage of failure. Under the action of internal pressure on the shell, the first form of loss of stability of plastic deformation degenerates with the formation of a neck inside the shell, and only the form of loss of stability is observed, caused by the localization of deformations along the thickness of the shell.

Using the method of mathematical modeling, as well as the laws of thermodynamics, analytical dependences were obtained to study the stress-strain state of spherical tanks depending on the different surface temperatures of this structure. The calculations performed showed that the radial stresses are insignificant compared to the tangential ones, which act on tension. The greatest absolute value of tangential stresses is taken on the inner surface of the spherical structure, acting in tension and on the outer surface – compression. The investigation results are presented graphically. Explosive and toxic substances are a major component of military bases stored in special-purposes tanks, namely spherical tanks, which are one of the most common. As a result of sabotage or arson of these tanks, there is a leak of toxic substances and the formation of steam and gas clouds which can lead to an explosion, significant thermal radiation, and the possibility of infection of military equipment, territory, and various objects in the vicinity of the accident, including personnel, which makes it impossible to conduct hostilities for a long time. Analyzing the experience of accidents at similar facilities, several types of accidents of spherical gasholders during their depressurization are possible, namely: explosion, flare, fireball, fire of toxic substances and the presence of a saturated explosive cloud. Analyzing the extraordinary accidents in the places of storage of toxic, explosive substances and fuels and lubricants, which are related to the violation of their storage and exploitation, allows us to conclude that this is a global problem of today. Therefore, to prevent explosion and fire hazards, the strength of engineering structures that contain toxic and explosive substances are quite high requirements. One of the main tasks in the general problem of explosion and fire safety is the ability to timely warn or prevent accidental explosions on building, military or explosion-proof structures, as well as personnel nearby. Therefore, the impact of temperature on special-purpose tanks due to sabotage, natural factors and abnormal cases on the strength characteristics of engineering structures of this type are important, both theoretically and practically.

The chapter presents influence of boundary conditions on mechanical and thermal stresses of an oil cooled piston in diesel engine Scania DC09074A and its deformation due to high combustion pressure and changeable temperature. Due to different fixing of the pin in the piston hub the deformation of the piston shape and von Misses stresses differ at the same boundary conditions. The piston is an indirect element in heat exchange in combustion engines, because it transfers the heat from the gas to cylinder walls by piston rings and some part of heat is transferred from the bottom surfaces of the piston to the gas inside the crankcase. Calculations of the piston loads were carried out by using 0D mathematical model at assumption of the Wiebe combustion model and the Woschni heat transfer model for homogenous mixture. For precise determination of the gas temperature in the combustion chamber the CFD technique was used and for that case the simulation of compression, combustion and expansion processes was carried out by using the program Fluent. The numerical calculations were done for two kinds of fuel: diesel oil and CNG. For proper work of CNG engine the compression ratio was decreased. This was done by reducing the volume of the combustion chamber. Calculations done in the program Ansys showed that the modification of the piston do not influence significantly on the total stresses. The chapter shows the differences of the total stresses and piston deformation at fastened piston hub and at “floating” piston pin. Most calculations are made at assumption that the piston hubs are fixed, but it is not right assumption. In summary the paper gives indications how to set boundary conditions for “floating” piston pin. Due to different fixing of the pin in the piston hub the deformation of the piston shape and von Misses stresses differ at the same boundary conditions The analysis has shown that FEM calculations of the piston should be done together with the pin for giving the engineers right information how to design the piston shape, usually “barrel-oval”, in order to enable a proper clearance between the piston and cylinder walls particularly at high loads.

The temperature fields and stress-strain state during the thermomechanical straightening of a terminal bend in surface-hardened rails are calculated. The distribution of temperature fields was determined using integral identity with allowance for energy balance, and the stress-strain state was determined as the stepwise minimization of the strain-energy functional. The optimal heating time, and the intensity of the thermal flux were determined in conformity with a flow chart. It is demonstrated that the terminal bend can be reduced by the thermal effect of an induction heater along, if the initial bend does not exceed 2 mm, and by the combined use of thermal straightening and a pressure roller in the case of a large initial bend.

The formulation of the problems of thermoelasticity is demonstrated, taking into account the nonlinear temperature dependence of thermal expansion at finite strains. In the framework of this formulation, a significant effect of the thermal expansion of elastomers on the stress-strain state is shown. As an example, the isothermal deformation of a round elastomeric cylindrical sleeve with the potential energy of the Mooney—Rivlin strain subjected to longitudinal shear forces on the inner and outer side surfaces is considered. Further, the deformed sleeve is placed in a uniform temperature field in which it expands freely.

Objective. The study aims to develop a mathematical model to predict the stress-strain state (SSS) of rocks during interaction with drilling tools, enabling optimization of drilling parameters and enhancing wellbore efficiency in oil, gas, and mining industries. Methodology. The research combines theoretical, numerical, and experimental approaches. The theoretical framework is based on continuum mechanics equations describing stress and strain distribution in rocks, accounting for their heterogeneity and anisotropy. Numerical simulations employ the Finite Element Method (FEM) in ANSYS software to model complex tool-rock contact geometry and dynamic loads. Contact interaction is simulated using no-slip conditions and the Coulomb-Amonton friction law. Experimental data from laboratory tests on rock samples (sandstone, limestone, shale) are used to determine mechanical properties (Young’s modulus, Poisson’s ratio, strength limits) and validate the model. The model incorporates drilling parameters such as axial load (50–150 kN), rotational speed (60–180 RPM), and tool type (roller-cone or PDC bit) to assess their impact on SSS. Results. The study yielded a mathematical model predicting stress and strain distribution in heterogeneous and anisotropic rocks. The model demonstrated prediction accuracy for maximum stress (σmax) within 5–10% for sandstone/limestone and 6–15% for shale compared to experimental data (±5% deviation). A linear stress dependence on axial load was observed, with increases of 144% (limestone) and 150% (shale) when load rose from 50 to 150 kN. The model identifies potential failure zones, particularly in shales, where stresses concentrate along bedding planes. Numerical results align with experimental data, confirming stress distribution at the contact zone. The model also revealed sensitivity to drilling parameters; e.g., 180 RPM exacerbates fracture initiation in anisotropic rocks. Novelty. The proposed model integrates rock heterogeneity and anisotropy via an elastic modulus tensor and spatially variable mechanical properties. Unlike existing models that often simplify rocks as isotropic, this work accounts for dynamic effects (vibrations, rotation) and their SSS impact. The novelty lies in the adaptive numerical algorithm for complex geological conditions, enabling high-accuracy failure zone prediction. Practical Significance. The model optimizes drilling regimes (e.g., 100 kN axial load and 120 RPM for limestone) to maximize rate of penetration (ROP) and minimize tool wear. It enhances wellbore stability by identifying collapse-prone zones, reducing operational risks. Results can improve tool design (e.g., cutter geometry) to mitigate localized stresses. Future integration into real-time drilling control systems may lower costs and boost economic efficiency.

An elastic-plastic contact law that incorporates local permanent deformation in the contact zone has been used to investigate the efficacy of the momentum balance method in transverse impact problems. The momentum balance solution is compared to the numerical solution of the same equations using the contact law. It is shown that the momentum balance method gives very good results for the post impact behavior of both the impacter and the beam. In certain cases, it is also shown to yield satisfactory results for the dynamic behavior during contact. It is demonstrated that the momentum balance method with an appropriate coefficient of restitution obtained from the contact law, is physically the same as using the contact law itself, with the difference that the local deformation is neglected.

We present the results of application of a physical criterion of yield in the complex stress-strain state to the description of plastic deformation at the crack tip. Unlike the von Mises criterion, the proposed criterion enables one to take into account the characteristics of plastic deformation of bcc metals at low temperatures. We simulated the process of loading of a platelike specimen (400×1600 mm) containing a central crack under conditions of plane deformation. It is shown that the drop of shear resistance under the action of normal tensile stresses observed in the process of low-temperature plastic deformation of bcc metals and alloys strongly affects the parameters of the stress-strain state of the metal at the crack tip. Thus, it leads to the enlargement of the zone of local plastic strains, promotes an increase in the maximum level of plastic strains at the crack tip, and affects the relationship between the tangential and normal stresses in the plastic zone. It is demonstrated that the physical criterion of yield can be efficiently used for the numerical analysis of the stress-strain state at the crack tip in bcc metals and alloys at low temperatures by the finite-element method.