Maximum Equivalent Stress Research Articles

Research on stress performance of universally wrapped assembled joints of lattice wind power tower with concrete-filled steel tube

With the control parameters of the wall thickness of the ball table and the thickness of the pressure plate of the ball table, four universal wrapped assembled joint models were designed for the research of stress performance via static loading test. The failure mode of the joint, the axial force–displacement curve of the web member, the equivalent stress distribution of the ball table and the pressure plate of the ball table were analyzed, and the ABQAUS finite element software was used for the analysis of parameter expansion of the specimen. The research results show that the failure modes of universally wrapped assembled joints can be divided into the buckling failure of the ball table and the strength failure of the material. The wall thickness of the ball table is the key parameter affecting the failure mode of the joints, and the thickness of the pressure plate of the ball table is the crucial parameter influencing the ultimate bearing capacity of the joints. The maximum equivalent stress of the pressure plate and the ball table at compression zone for all the joints is occurred at the side squeezed by the bolt ball, and the growth rate of the equivalent stress for the ball table at compression zone is more uniform than that at tension zone. According to the finite element analysis results, when the wall thickness of the ball table is greater than 7 mm, the thickness of the pressure plate of the ball table is greater than 16 mm, the growth rate of the ultimate bearing capacity of the joint is significantly decreased, therefore, it is recommended to use the wall thickness of 7 mm and the pressure plate thickness of 16 mm in the actual design of the project.

Biomechanical analysis of different fixation methods for Rorabeck II supracondylar femoral fractures after total knee arthroplasty

BackgroundLocking plate (LP) and retrograde intramedullary nailing (RIMN) are widely used to fix Rorabeck II supracondylar femoral fractures after total knee arthroplasty (TKA). The biomechanical properties of the implant used for treatment influence its longevity. Therefore, we aimed to evaluate the biomechanical stability of different fixations using finite element analysis. MethodsSeven finite element models (FEMs) were established, including LP groups (short LP, long LP, and double LP), RIMN groups (short RIMN and long RIMN), and mixed groups (long LP with short RIMN and long LP with long RIMN). The stress of the implants around the fracture area was calculated to evaluate the biomechanical stability under loads. ResultsStress was mainly distributed around the fracture area in all models. The stress-shielding phenomenon was most evident in the short LP. The trend in maximum equivalent stress values of implants around the fracture area for the seven internal fixations was: short LP (324.63 MPa) > short RIMN (306.37 MPa) > long LP (275.06 MPa) > long RIMN (262.74 MPa) > double LP (203.19 MPa) > long LP with short RIMN (124.42 MPa) > long LP with long RIMN (112.41 MPa). We found that the double LP can better disperse the stress than a single LP, and a long LP with long RIMN can prevent stress concentration and make the stress distribution more uniform. ConclusionFrom the perspective of biomechanics, long LP with long RIMN can stabilize fractures and avoid stress concentration in Rorabeck II supracondylar femoral fractures after TKA.

The Effect of Cooling Layer Thickness and Coolant Velocity on Crystal Thermodynamic Properties in a Laser Amplifier.

Laser diode pumped solid-state lasers (DPSSLs) have been widely used in many fields, and their thermal effects have attracted more and more attention. The laser diode (LD) side-pumped amplifier, as a key component of DPSSLs, is necessary for effective heat dissipation. In this paper, instead of the common thermal analysis based only on a crystal rod model, a fluid-structure interaction model including a glass tube, cooling channel, coolant and crystal rod is established in numerical simulation using ANSYS FLUENT for the configuration of an LD array side-pumped laser amplifier. The relationships between cooling layer thickness, coolant velocity and maximum temperature, maximum equivalent stress, inlet pressure and the convective heat transfer coefficient are analyzed. The results show that the maximum temperature (or maximum equivalent stress) decreases with the increase in the coolant velocity; at low velocity, a larger cooling layer thickness with more coolant is not conductive enough for improved heat dissipation of the crystal rod; at high velocity, when the cooling layer thickness is above or below 1.5 mm, the influence of the cooling layer thickness on the maximum temperature can be ignored; and the effect of the cooling layer thickness on the maximum equivalent stress at high velocity is not very significant. The comprehensive influence of various factors should be fully considered in the design process, and this study provides an important reference for the design and optimization of a laser amplifier and DPSSL system.

Determination of thickness parameters of detonation shell and safety performance analysis

AbstractOn the premise of security, it is necessary to ensure good operational performance and technical indicators for nonlethal weapons such as flash detonation bombs. To make the weight of a flash detonation grenade more convenient for hand throwing and material costs save, the outer dimensions of the grenade body are fixed, and the optimal parameters of outer shell thickness of the vertigo grenade are explored. Based on the maximum deformation energy theorem, the strength of the shell with the obtained maximum thickness of 8 mm is checked, and then the optimal shell thickness under the ideal air explosion condition is obtained by reducing the thickness; Then check the thread strength to obtain the inner casing fracture, shock wave, and sound pressure level. The fragmentation performance test, detonation test, and sound pressure level test were carried out for the projectiles involving the shell thickness of 4 and 5 mm, and the simulation results were verified from three aspects of sound intensity, shell strength, and fragments. The results show that the maximum equivalent stress is 232.6 MPa and the maximum deformation is 1.07 × 10−4 mm when the outer shell thickness of the vertigo grenade is 5 mm, which is less than the material failure strength standard and no plastic deformation could occur. The structural connection strength of the missile body meets the standard. Most of the fragments are trapped in the cavity. The average sound pressure level at 1.5 m can reach 159.7 dB. The relative error between the sound pressure level at 3 m and the live ammunition test results is 4.8%, which meets the expected operational technical indicators and has good safety performance. The results of the numerical simulation can provide a reference for the design optimization and performance evaluation of similar vertigo grenades.

Multi-Lane Traffic Load Clustering Model for Long-Span Bridge Based on Parameter Correlation

Traffic loads are the primary external loads on bridges during their service life. However, an accurate analysis of the long-term effect of the operating traffic load is difficult because of the diversity of traffic flow in terms of vehicle type and intensity. This study established a traffic load simulation method for long-span bridges based on high authenticity traffic monitoring data, and an improved k-means clustering algorithm and Correlated variables Sampling based on Sobol sequence and Copula function (CSSC) sampling method. The monitoring traffic data collected through a weigh-in-motion (WIM) system was processed to generate a multi-lane stochastic traffic flow. The dynamic response of a prototype suspension bridge under a traffic load was analyzed. The results show that the traffic load can be divided into clusters with identical distribution characteristics using a clustering algorithm. Combined with CSSC sampling, the generated traffic flow can effectively represent daily traffic and vehicle characteristics, which improves the accuracy of the assessment of the loads long-term effect. The dynamic response of the bridge to different traffic flows varied significantly. The maximum and minimum vertical displacement of the main girder was 0.404 m and 0.27 m, respectively. The maximum and minimum bending stresses of the short suspender were 50.676 MPa and 28.206 MPa, respectively. The maximum equivalent bending stress and axial stress were 16.068 MPa and 10.542 MPa, respectively, whereas the minimum values were 9.429 MPa and 8.679 MPa, respectively. These differences directly influence the short and long-term evaluation of bridge components. For an accurate evaluation of the bridge operation performance, the traffic flow density must be considered.

Characterization and mechanism of cutter parameters in tubing milling

Downhole string milling is becoming increasingly difficult due to the increasing complexity of oilfield development technology and material quality advances, especially for downhole tubing milling. In this paper, a Lagrangian modeling approach is used to investigate the mechanism and effects of cutting parameters on tubing milling characteristics. The cemented carbide cutter parameters, including the cutting angle, lateral angle, weight on cutter, and rotating speed, are determined to obtain the maximum cutting rate. A cutting tool is designed, manufactured, and tested. The simulation results are in good agreement with the test results, yielding the maximum equivalent stress generated by the cutter of 1163 MPa, which is much higher compared to the tubing yield strength. The tubing cutting volume and mass increased with the cutting angle, up to 12.5°, while the maximum value obtained using the lateral angle is 5°. With an increase in weight on cutter, the maximum von Mises equivalent stress and equivalent strain generated by the cutter also increased. Furthermore, the cutting volume and mass increase rapidly with the rotational speed at the start, followed by a slow increase when the rotational speed is above 70 rpm. The cutter mainly generated continuous chips. Finally, industrial tests are successfully carried out, confirming the milling efficiency increase of 40.1% compared to the traditional milling methods.

Mechanical property and sealing performance analysis of the diaphragm compressor cylinder head for the hydrogen refueling station under the mutation impact load

Abstract: Under the combined action of structure-process -load, the stiffness and stress distribution at the sealing interface of the ultra-high pressure diaphragm compressor cylinder head exhibit significant nonlinear and uncertain characteristics, resulting in damage to the sealing interface, diaphragm and sealing ring. This paper first establishes a finite element numerical model considering assembly process parameters based on sudden impact load conditions, and analyzes the dynamic characteristics under different assembly process parameters. It is found that some modal frequencies transition with bolt loosening. Then, the mechanical characteristics of the assembly interface of the compressor sealing system under sudden impact load were studied. The maximum equivalent stress at the assembly interface was 298.9 MPa, and the maximum deformation at the top of the air chamber was 0.167mm. Finally, the nonlinear effects of sealing ring compression rate, sealing ring diameter, and sealing groove structure on contact stress and sealing performance were obtained. The results show that as the compression ratio increases by 20% and 25%, the contact pressure at the sealing interface increases by 42.0% and 77.5%, respectively; When the compression rate is 25%, the width of the sealing groove increases by 0.5mm, and the maximum contact pressure decreases by 8.1%. The research on the dynamic characteristics and sealing performance of diaphragm compressors provides technical support for the structural optimization design of diaphragm compressors cylinder head.

Evaluation possibility of the turbine disks using of converted aircraft engines of the NK family

The article examines the possibility of using converted aircraft engines for gas pumping units using the example of the main parts of the GTE - the disks of the NK-8-2U aircraft engine and the NK-16ST and NK-16-18ST ground engines. For all disks of the second stage of low-pressure turbines of three engines, the stress-strain state calculation was performed using the boundary integral equations method (BEM) and using the FEM in the Ansys program. For three disk stress concentrators, the theoretical stress concentration coefficient was determined and the maximum equivalent stresses were calculated. During long-term operation, the main parameters of engine operation change due to degradation changes (wear, erosion and corrosion, development of seals, contamination and resizing of flow parts). As a result, the main parameters of engine operation change, in particular, the rotation speed of the rotors and the gas temperature in the turbine, which determine the stress-strain state, which must be taken into account when predicting durability. The compliance of the results of the calculated study of the stress-strain state of turbine disks with their real load was confirmed by the data of their metallurgical study after prolonged operation. Using the Manson formula for the disks of three engines, their cyclic durability was determined before the formation of a crack of low-cycle fatigue. Using the linear damage summation hypothesis, the total damage rates (under static loading and under fatigue loading) for the disks of three engines were calculated. It is established that after the conversion of aircraft engines that have spent their life in flight operation, it is advisable to continue the use of turbine disks on ground-based GTU.

Numeric simulation of steel twin disc system under rolling-sliding contact

Various mechanical parts come into high-load rolling and sliding contact at the contact surface. Even with technological advancements, mechanical failures still occur. Rolling-sliding mechanical contact issues are the primary cause of over 90 % of surface and subsurface metallic failures and they are only becoming worse. Using discretised continuum 2D finite element methods (FEM), this research investigates the parametric contact effect of a steel twin disc system subjected to rolling-sliding contact at varied surface friction and comprehensive load condition. The equivalent von Mises stress distribution, contact pressure distribution and shift position of maximum subsurface stress on the contour region are all influenced by changes in compressive load and coefficient of friction, according to a numerical surface-to-surface contact simulation performed with Abaqus at mean Hertzian pressure. The maximal equivalent stress, for a given load, reaches a peak in the subsurface and moves farther away from the surface when the coefficient of friction decreases and comes close to the contact surface when the coefficient of friction increases. Consistency is shown by the analytical and numerical results.

Polyetherketoneketone Mesh for Alveolar Bone Augmentation: Geometric Parameter Design and Finite Element Analysis.

To evaluate the mechanical properties of porous polyetherketoneketone (PEKK) meshes with different thicknesses, pore sizes, and porosities through finite element analysis to provide an optimal PEKK design for alveolar bone augmentation in the posterior mandibular region. A three-dimensional evaluation model of severe alveolar bone defects in the mandibular posterior was constructed based on cone beam computerized tomography (CBCT) data. Then, PEKK meshes with different structural designs were obtained. Two key parameters were set with different values: five levels of thickness (0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 0.6 mm) and three levels of pore size (1 mm, 2 mm, and 3 mm) with a corresponding porosity of 19.18%-42.67%. A 100 N physiological force was simultaneously loaded by finite element analysis (FEA), and the deformation and stress data were outputted for further analysis. The deformation and stress of the PEKK meshes are negatively correlated with the changes in thickness and positively correlated with the changes in pore size. The FEA results show that the maximum deformation, equivalent stress, and maximum principal stress of the PEKK meshes are 0.168 mm-0.478 mm, 49.243 MPa-124.890 MPa, and 31.549 MPa-104.200 MPa, respectively. The PEKK mesh group with a thickness of 0.2 mm, pore size of 3 mm, and porosity of 42.67% is in danger of plastic deformation or even fracture during use. According to the FEA results, the PEKK meshes with larger thicknesses and smaller pore sizes and porosities behave better. In consideration of reducing soft tissue stimulation and promoting bone regeneration, an ultrathin porous PEKK mesh with a pore size of no more than 3 mm, porosity of no more than 42.67%, and thickness of 0.2 mm can be used clinically to meet the mechanical performance requirements of the guided bone regeneration (GBR) structure.

Numerical simulation of the stress and deformation of the chute during the charging process of blast furnace by coupling finite element and discrete element

The chute is one of the most important parts of the blast furnace. The chute operates in a harsh environment and is continuously subjected to high temperature gas and particles. In this paper, for the working environment of chute, numerical simulation method is adopted to analyze the stress and deformation of the chute in the idle stage and the burden stage respectively. The results of the calculations are as follows: during the idle stage, the stress in the lower part of the chute are higher, with a maximum equivalent stress of 267 MPa. The lengthwise displacement of the chute outlet is the largest, with a value of 19.4 mm; the outlet sidewalls extend to both sides. The distribution of stress and deformation in the burden stage is similar to that in the idle stage, mainly affecting the inner wall of the chute. The temperature distribution and charge particles have a huge influence on the chute stress and deformation distribution. The research holds immense significance in enhancing the service life of the chute, refining its structural process, and ensuring the stable of the blast furnace.

Analysis Of Stress And Deformation In Parametric Furniture Using The Finite Element Method

One method of designing furniture is to use parametric design. Parametric design method is a design method in which design uses certain patterns. With the parametric design method, furniture that is very good in shape and aesthetics is produced, one of which is parametric TV table furniture. TV table is a type of furniture that has the function of placing a TV, multimedia supporting tv, mini library, and storage of other mini equipment. To carry out its function, furniture must also be tested for strength, one of which uses the finite element method with the help of ANSYS software version 18.1. The analysis aims to determine the stress and deformation. The simulation results with loads of 400N, 600N, 800N and 1.000N are maximum equivalent stress of 7,05x10-5 Pa, 1,05x106 Pa, 1,41x10-6 Pa, and 1,76x10-6 Pa. The highest maximum principal stress is equal to 1,16x10-5, 1,75x10-5, 2,33x10-5, and 2,92x10-5. Total deformation of 8,27x10-6m, 1,24x10-5m, 1,65x105m, and 2,06x10-5m. The conclusion of this study shows that the results of stress and deformation analysis have no change in shape and failure in load bearing. This shows that parametric TV table furniture can perform its function by being able to withstand TV loads and other furniture until 100Kg (1.000N) with safety factor 1,8.

Evaluation of the packed state of catalyst pellets in the gas phase reactor (Effect of catalyst pellet shape on its packed state)

In this paper, we propose a simulation method to evaluate the packed state of catalyst pellets in a pipe reactor for gas phase reaction. This simulation method is based on dynamic explicit FEM (finite element method) and consists of three steps. Specifically, first, the catalyst pellets freely fall under gravity and flow into a packing hose with a hopper-like inlet. Then, after the catalyst pellets reach the bottom of the pipe reactor, the packing hose is pulled up to create a random packing of the catalyst pellets in the pipe reactor. Finally, the bulk density and stress distribution of the catalyst pellets randomly packed in the pipe reactor are calculated, and the packed state of the catalyst pellets is evaluated. Using this simulation method, we simulated the packing of cylindrical catalyst pellets into the pipe reactor and evaluated the packed state of the catalyst pellets in the pipe reactor. As a result, it is clarified that the maximum equivalent stress generated at the bottom of the catalyst pellets packed in the pipe reactor approaches a constant value as the ratio of the packed height of the catalyst pellets to the diameter of the pipe reactor increases. In addition, the effects of the shape of the catalyst pellets on the bulk density and average equivalent stress of the catalyst pellets in the pipe reactor are elucidated, and the optimal shape of the catalyst pellets that can increase the bulk density and reduces the stress is found. The optimally shaped catalyst pellets are expected to improve their packed state in the pipe reactor, extend the durability of the catalyst pellets and increase the efficiency of production. In this paper, it is assumed that the packed state and durability of the catalyst pellets are evaluated based on the bulk density and stress distribution of the catalyst pellets in the pipe reactor.

ANALISIS KEKUATAN FRAME SEPEDA LISTRIK NGEBUTS MENGGUNAKAN METODE ELEMEN HINGGA

Three hundred and ten million people are affected by global climate change caused by carbon dioxide gas. The internal combustion engine that dominates the transportation fleet is one of the contributors to the amount of carbon dioxide in the atmosphere. Research related to environmentally friendly vehicles, in this case, electric vehicles, needs to continue to be carried out followed by downstream research results in the industry. The hope is to reduce the amount of greenhouse gas emissions produced by internal combustion engine vehicles. This study aims to determine the strength of the electric bicycle frame by conducting a stress analysis using the finite element method. The geometry modeling, inputs (data of material properties, geometry, loads, boundary conditions), mesh, solve, and validation are the steps that are passed in this research. The results show that the maximum equivalent stress (von Mises) of 98.31 MPa occurs at the joint between the Seat Tube and Seat Stay, while the minimum stress of 0.01 MPa occurs at the top of the Head Tube. The maximum deformation that occurs at the top of the Seat Tube is 0.15 mm. The minimum safety factor value on the frame is 2.39. Based on this value, the electric bicycle frame can be said to be strong enough to withstand the load of the rider and the battery.

Research into the loading of a removable module for transportation of long freight in a combined train by the train ferry

The article presents the results of determination of the loading of a removable module for transportation of long freight in a combined train by the train ferry. The article describes the results of the mathematical modelling of the dynamic loading on a removable module placed on the flat car during rolling motion of the train ferry. It suggested that the flat car was rigidly fastened and displaced together with the deck. The displacements of the removable module relative to the flat car frame and the freight relative to the removable module were neglected. The mathematical model was solved with the method of variation of constants and confirmed by means of calculation in Mathcad. It was found that the maximum value of acceleration to the flat car with the removable module was about 2.35 m/s2 (0.24g). The value of acceleration obtained was included in the strength calculation for the removable module. The calculation was based on the finite element method and realized in SolidWorks Simulation with the Mises criterion. The finite element model was formed with spatial isoparametric tetrahedrons. The results of the calculation demonstrated that the maximum equivalent stresses were in the contact area between the vertical posts and the fittings; they amounted to 284.7 MPa. The stresses obtained were lower than the allowable values by 17.5%. The yield strength of the structural material was taken as the allowable stress. The equilibrium stability factor for the removable module was also determined. The strength of the removable module on the flat car without proper displacements and with the long freight inside was provided at the roll angles of the train ferry up to 25°. The results of the research will be of value for those who are dealing with development of transport facilities with better operational efficiency for combined transportation.Key words: removable module, dynamic loading, strength, equilibrium stability, train ferry transportation.

Study of the stress-strain state of the brake lever transmission of the 18-100 carriage model

The object of research is the brake lever transmission of the 18-100 freight car carriage.
 The investigated problem: the destruction of the elements of the triangle, which leads to the occurrence of failures during the car operation. As a result of such refusals, total losses for the railway infrastructure of Ukraine during freight transportation amount to hundreds of thousands of hryvnias.
 The main scientific results: the strength of the brake lever transmission of the freight car carriage is investigated and the most loaded components of its structure are identified. It is proposed to improve the triangle string by making it from a round pipe filled with energy-absorbing material. Aluminum foam is used as an energy-absorbing material.
 To justify the proposed solution, a calculation of the strength of the brake lever transmission is performed using the finite element method. The calculation results show that the maximum equivalent stresses that occur in the string do not exceed the allowable ones.
 The peculiarity of the obtained results is that the proposed improvement of triangle elements can be applied not only at the stage of designing the mechanical brake system, that is, during the manufacture of car assemblies at car-building plants. It is advisable to apply the proposed solutions when carrying out depot or capital type repairs at car repair enterprises.
 The field of practical use of the results is car-building and car-repair enterprises of railway transport of Ukraine.
 Innovative technological product: the improvement of triangle elements will increase the efficiency of the braking systems of freight rolling stock, increase the speed of cars, reduce the time for the delivery of goods, reduce operating costs due to the failure of freight car units in operating conditions, and guarantee the level of safety of traffic on the railway. Also, the conducted research will contribute to the creation of developments in improving the reliability of the braking systems of modern rolling stock.
 The scope of application of the innovative technological product: the fleet of freight cars of JSC "Ukrzaliznytsia", as well as its own industrial transport cars

INVESTIGATION OF LOADING STRUCTURE OF HYPER-HOPPER TWO-SECTION CARRIER DURING CARRIAGE BY RAILWAY

To increase the efficiency of operation of the hopper car, it is proposed to improve it by dividing the body into two separate sections, which facilitates the possibility of transporting different types of cargo. In order to adapt the hopper car for transportation on railway ferries in international traffic, it is proposed to install on its pivot beams knots for fastening chain ties. Determination of the dynamic load of the load-bearing structure of the hopper car was performed by mathematical modeling. The case of the on-board rocking of the railway ferry is taken into account. The solution of the mathematical model is implemented in the MathCad software package. The total amount of acceleration acting on the supporting structure of the hopper car was 2.4 m/s2 (0.24 g). The obtained value of acceleration is taken into account when calculating the strength of the load-bearing structure of the hopper car. The calculation was performed by the finite element method in the SolidWorks Simulation software package. The results of the calculations established that the maximum equivalent stresses are 312.3 MPa and occur in the node for fixing. However, they do not exceed the allowable values. The conducted researches will promote increase of efficiency of operation of hopper cars, and also creation of developments concerning designing of their perspective designs.

Comparative Biomechanical Analysis of Ankle Arthrodesis Techniques: Experimental Study

Background. Despite the existing significant number of various techniques for ankle arthrodesis, a number of authors point to certain technical difficulties of these operations, the loss of the talus and tibia position during ankylosing, nonunion. The problem of the ankle arthrodesis technique improving requires new solutions.
 The aim of the study was to compare the stability of various fixation systems in ankle arthrodesis by the finite element method.
 Methods. The finite element method was used to evaluate the biomechanical characteristics of three variants of ankle arthrodesis systems: three cancellous screws, the originally designed plate combined with two cancellous screws, when the screw in the proximal plates hole is cortical, and the same plate combined with two cancellous screws, when the screw in the proximal plates hole with angular stability. The stresses and strains under the application of various types of loads are studied.
 Results. In the anterior plate ankle fixation model combined with two cancellous screws and a proximal cortical screw, the implants and the talus experienced the least stresses compared to the other two models. Thus, the maximum equivalent stress in implants in the second variant was 68-124 MPa, in the first variant 92-147 MPa, in the third variant 130-331 MPa. The equivalent stress in the talus in the second version of fixation ranged from 20 to 46 MPa, in the first and third versions 28-58 MPa and 47-65 MPa, respectively. The indicators of maximum contact pressure at the border of the tibia and talus turned out to be the highest in the first variant compared to the other two models (34 MPa, 31 MPa and 31 MPa, respectively).
 Conclusions. Among the studied ankle fixation systems for arthrodesis, an anterior plate combined with two cancellous screws and a proximal cortical screw is the most preferable in terms of biomechanics.

The method of fictitious discrete models in calculations of composite bodies

As is known, the calculation of the static strength of elastic composite bodies (CB) is reduced to finding the maximum equivalent stresses for these bodies. The finite element method (FEM) is widely used for the analysis of the stress state of CB. The basic discrete models (BM), which take into account the inhomogeneous structure of bodies in the framework of a micro-approach, have a high dimension. To reduce the dimension of discrete models, multigrid finite elements (MgFE) are effectively used. However, there are BM CB (for example, BM bodies with a micro-homogeneous structure), which have such a high dimension that the implementation of FEM for such BM using MgFE, due to limited computer resources, is difficult. To solve this problem, it is proposed to use fictitious discrete models whose dimensions are less than the dimension of the BM CB. In this paper, we propose a method of fictitious discrete models (MFDM) for calculating the strength of elastic bodies with an inhomogeneous, micro-homogeneous regular structure. The proposed method is implemented using FEM with the use of MgFE and adjusted strength conditions that take into account the error of approximate solutions. The method is based on the position that the solutions that meet the BM CB differ little from the exact ones. The calculation of CB according to MFDM is reduced to the construction and calculation of the strength of fictitious discrete models (FM), which have the following properties. The FM reflects: the shape, characteristic dimensions, attachment, loading and type of the inhomogeneous structure of the CB, and the distribution of elastic modulus corresponding to the BM CB. The FM dimension is less than the BM dimension of the CB. The sequence consisting of FM converges to BM, i.e. the limiting FM coincides with BM. The convergence of such a sequence ensures uniform convergence of the maximum equivalent voltages of the FM to the maximum equivalent voltage of the BM. Two types of FM are considered. The first type of FM consists of scaled discrete models, the second type consists of FM with variable characteristic dimensions. Calculations show that the implementation of FEM for FM using MgFE leads to a large saving of computer resources, which allows the use of MFDM for bodies with a micro-homogeneous regular structure. The calculation of the strength of CB according to MFDM requires times less computer memory than a similar calculation using BM CB, and does not contain a procedure for grinding BM. The use of adjusted strength conditions allows us to use approximate solutions with a large error in the calculations of CB for strength, which leads to an increase in the efficiency of MFDM. The given example of calculating the strength of a beam with an inhomogeneous regular fibrous structure according to MFDM shows its high efficiency.

Dynamic stress characteristics and fatigue life analysis of a slanted axial-flow pump

The shaft of the slanted axial-flow pump device is inclined, so, the stress on the impeller is complex, which leads to the prominent problem of structural reliability. In order to study the mechanical characteristics and fatigue life of the slanted axial-flow pump, the stress-strain characteristics and variation law of impeller under different flow rate conditions are analyzed by fluid-structure interaction method, at the same time, the stress-strain characteristics of impellers with geometrically similar and five different structural sizes when nD value is equal are solved, finally, the fatigue analysis of blades is carried out based on Miner’s linear fatigue cumulative damage theory to predict the fatigue life of impellers. The results show that under different flow rate conditions, the maximum equivalent stress of the impeller blade is concentrated at the blade root and gradually attenuates to the blade flange. The maximum deformation of the blade is located at the blade rim and moves from the inlet side to the outlet side with the increase of flow rate. When the nD value is constant, the maximum equivalent stress and maximum deformation displacement of the blade increase with the increase of the impeller size. Under various flow rate conditions, the service life of the impeller reaches 108, and the safety factor of each part of the blade is greater than 15, when operating within the working condition range of 0.8 Qbep∼1.2 Qbep, the impeller can operate continuously for 14 years without fatigue damage.