Equivalent Stress Research Articles

Study the Influence of Impact on the Filled Tube of Aluminum 6082-T6 Alloy by Consideration of Temperature using FEM

In this study, a numerical analysis of the impact behavior of a hollow tube made of aluminum 6082-T6 alloy in accordance with ISO 13314-2011 was conducted using FEM. ANSYS was utilized to execute the simulation procedure utilizing the Explicit Dynamic tool. The geometry of the present study consists of a 900 mm-long tube with a diameter of 60 x 2 mm, which was designed using SpaceClaim in Ansys. The model has meshed with a sweep-type mesh utilizing local coordinates. As a result, quadratic elements were utilized to simulate every impactor effect. The convergence of the mesh was determined in accordance with the equivalent strain analysis. The scope of the inquiry is limited to the mechanical behavior and energy conservation that occurs after the impact technique. The energy that is responsible for each and every sort of energy has been recognized. Instability was observed in both the internal and kinetic energies, with the latter reaching a maximum value of three electro-megajoules. Within each of the three axes, the directional deformation of the tube has been outlined. For a period of forty millimeters, the parallel axis of the impactor has undergone the greatest degree of maximum deformation that it has ever encountered. The equivalent stress, also known as von Mises, was measured in combination with the length of the tube, and it was discovered that it reached its highest point at 450 millimeters at the site of impact with 950 megapascal stresses.

Small fatigue crack behavior of CP-Ti in thin-walled cruciform specimens under biaxial loading

This study investigates the small fatigue crack propagation behavior of commercially pure titanium (CP-Ti) using thin-walled cruciform specimens under in-plane biaxial loading, considering the effects of biaxial ratio and phase angle. Increasing phase angle results in more secondary cracks merging with main cracks perpendicular to the rolling direction (RD) and transverse direction (TD), a phenomenon attributed to the rise in shear stress that accelerates main crack growth. Higher loading biaxiality or a lower phase angle leads to decreased crack propagation rates and increased biaxial fatigue life. Electron backscatter diffraction (EBSD) analysis reveals that when the maximum normal stress aligns with the RD, prismatic slip primarily governs crack propagation, thereby accelerating crack propagation rates. Conversely, alignment with the TD reduces prismatic slip activity and crack propagation rates. Under equi-biaxial loading, prismatic slip activity decreases further, and crack propagation is dominated by multiple slip and twinning, consequently resulting in the slowest propagation rates. Additionally, a higher proportion of prismatic slip under high phase angle also accelerates crack propagation. Finally, incorporating Findley equivalent stress into the Chapetti model, which considers the crack length-dependent threshold effect, a highly accurate biaxial small fatigue crack propagation rate model is proposed.

Three-dimensional finite element analysis of stress distribution on different complex macro designs in commercially available implants: An in-vitro study

ObjectiveThis study aimed to investigate the effects of different commercially available complex implant macro designs on stress distributions using Finite element analysis. The experiment is done under varying simulated bone conditions to provide reference for clinical application. Materials and methodsThe study employed the Finite Element Analysis (FEA) method to compare four commercially available complex implant macro designs on a Computer-Aided Design (CAD) model of a maxillary bone segment. The three-dimensional geometrical model of the implants was reconstructed from computed tomography (CT)-slices in Digital Imaging and Communications in Medicine (DICOM) format and contact condition between the implant and the bone was considered as ‘Bonded’, implying perfect osseointegration. All materials used in the models were assumed to be isotropic, homogeneous, and linearly elastic. The Finite element simulations employed load of 400 N under both axial and non-axial conditions Stresses were analysed under different bone conditions. ResultsAverage values of von Mises stresses were used for comparing stress levels between implant designs. There was a definite increase in the equivalent stress values from higher density(D1)to lower density (D4) bone conditions for all implants. The percentage of increase ranged from 23.63 to 49.39 on axial loading and 20.39 to 57.19 when subjected to non-axial loading. The equivalent stress values resulted from non-axial loading were 1.78–2.94 times higher than that of axial loading for all implants under all bone densities. Among the complex designs Equinox Myriad Plus implant exhibited the least stress under axial loading (12.749–19.046 MPa) and (37.462–49.217 MPa) for non-axial loading. The stress on the crestal module was higher (1.49–2.99 times) than the overall stress on the implant regardless of the loading direction or bone conditions. ConclusionsData from the present study shows Equinox Myriad Plus implant generating the least equivalent stress and this can be taken as indicator in the biomechanical performance of the design.

Comparative Analysis of Boron-Al Metal Matix Composite and Aluminum Alloy in Enhancing Dynamic Performance of Vertical-Axis Wind Turbine

This study aims to assess the dynamic performance of the vertical-axis wind turbine (VAWT) with the help of conventional aluminum (Al) and the boron Al metal matrix composite (MMC). The simulations were conducted using ANSYS software and involved natural frequencies, mode shapes, a mass participation factor, and Campbell plots. The results of static structural analysis show that the boron Al MMC is vastly superior to the aluminum alloy because there is a 65% reduction of equivalent stress with a 70% reduction of deformation compared to the aluminum alloy. These results show that boron Al MMC can withstand higher loads with lesser stress; the structure remains compact and rigid in its working conditions. From the findings, it can be ascertained that employing boron Al MMC improves VAWT power, efficiency, and robustness. However, the critical speed that was established in the dynamic analysis of boron Al MMC requires extraordinary control and the use of dampening systems, thereby avoiding resonance. Overall, boron Al MMC contributes to significant enhancements in the VAWTs’ mechanical and operational characteristics; however, the material’s complete potential can be achieved only with proper maintenance and employing the correct damping techniques. Information about these two materials will allow for a better understanding of their comparative efficacy and their potential application in the further development of VAWTs.

Design and Testing of a Crawler Chassis for Brush-Roller Cotton Harvesters

In China’s Yangtze River and Yellow River basin cotton-growing regions, the complex terrain, scattered planting areas, and poor adaptability of the existing machinery have led to a mechanized cotton harvesting rate of less than 10%. To address this issue, we designed a crawler chassis for a brush-roller cotton harvester. It is specifically tailored to meet the 76 cm row spacing agronomic requirement. We also conducted a theoretical analysis of the power transmission system for the crawler chassis. Initially, we considered the terrain characteristics of China’s inland cotton-growing regions and the current cotton agronomy practices. Based on these, we selected and designed the power system and chassis; then, a finite element static analysis was carried out on the chassis frame to ensure safety during operation; finally, field tests on the harvester’s operability, stability, and speed were carried out. The results show that the inverted trapezoidal crawler walking device, combined with a hydraulic continuously variable transmission and rear-drive design, enhances the crawler’s passability. The crawler parameters included a ground contact length of 1650 mm, a maximum ground clearance of 270 mm, a maximum operating speed of 6.1 km/h, and an actual turning radius of 2300 mm. The maximum deformation of the frame was 2.198 mm, the deformation of the walking chassis was 1.0716 mm, the maximum equivalent stress was 216.96 MPa, and the average equivalent stress of the entire frame was 5.6356 MPa, which complies with the physical properties of the selected material, Q235. The designed cotton harvester crawler chassis features stable straight-line and steering performance. The vehicle’s speed can be adjusted based on the complexity of the terrain, with timely steering responses, minimal compaction on cotton, and reduced soil damage, meeting the requirements for mechanized harvesting in China’s inland small plots.

Numerical simulation of the creep of a turbine blade made of a monocrystalline alloy

The article is devoted to the creep model of a monocrystalline alloy and the development of a methodology for identifying material parameters based on the results of physical experiments. A finite element analysis of the creep of a gas turbine engine blade was performed. Creep is one of the most dangerous types of deformation in the operating conditions of turbine blades. In the process of studying the problems of assessing the strength of turbine blades of aircraft engines and power plants, special attention should be paid to the study of stress redistribution during creep. The characteristics of the crystallographic structures of modern turbine blades have a very significant influence on the progress of the crack development process during engine operation. To date, turbine blades are manufactured by the method of single-crystal casting. This type of blade material structure is characterized by orthotropic mechanical properties. This study considers the steady-state creep model of an anisotropic heat-resistant single-crystal alloy with cubic symmetry. The authors carried out a numerical simulation of the material parameters using the well-known literary creep properties of single crystals. An algorithm is described that allows you to determine some creep characteristics of single crystals. The parameters of the given ratios can be obtained after conducting direct experiments, or based on micromechanical analysis, using the example of composite materials. The authors calculated the creep constants of a typical heat-resistant monocrystalline alloy as a result of the approximation of its creep curves, which were obtained experimentally. Based on the Norton-Bailey equation and using the Maple Release 2021.0 calculation complex, a graph of the dependence of the rate of creep deformation on the level of load applied to the material was plotted, and the minimum rate of deformation and creep constants were also determined. The results of the calculations were used for finite-element simulation of creep on the example of a solid-state model of a high-pressure turbine blade. Several series of calculations were carried out on the basis of the ANSYS Workbench complex, in particular, the calculation of the elastic problem when the blade is loaded by centrifugal forces, as well as the accumulation of creep deformations at different exposure times. Graphs of the change in equivalent stresses and creep deformations as a function of time are plotted.

Base joint hysteresis model for reinforced concrete assembly columns with post-pouring area

In response to the problem of uncontrollable grouting quality of traditional grouting sleeves in the connection between prefabricated components, a column base joint with post pouring area connected by grouting sleeves (PCGS) is proposed. Both the sleeve and post pouring area could cause differences in hysteresis characteristics between prefabricated and cast-in-place components. In order to investigate the hysteresis model of PCGS column base joint, the cyclic load tests and finite element parametric analysis of PCGS column base joint were conducted. The theoretical calculation method for load and displacement of PCGS column base joint at yield, peak, and ultimate characteristic points was established based on equivalent rectangular stress and plastic hinge length in joint area. The average ratios of theoretical calculations to test results for load and displacement at the above three characteristic points are 0.997, 0.983, and 0.983, and 1.020, 1.041, and 0.970, respectively, indicating that the theoretical calculation method can accurately predict the strength and deformation of PCGS column base joint. The dimensionless skeleton curve model with double broken lines in the elastic and strengthening stages, and exponential function in descending stage has been established based on the test and simulated results. The degradation behavior of unloading stiffness and bearing capacity was quantitatively described using the regression fitting method, and the hysteresis rule was defined. The established hysteresis model can effectively reflect the strength and stiffness degradation under cyclic loading, which can provide guidance for the elastic-plastic seismic response analysis of PCGS column base joint.

Study on the structural behavior and reinforcement design of openings in subway station floor slabs

This paper investigates the structural behavior of openings in subway station floor slabs through model experiments and finite element simulation. The study analyzes the effects of the opening's aspect ratio, dimensions, and position on the stress characteristics of various structural components. Based on the stress levels and failure characteristics at different locations in the station structure, three reinforcement schemes are proposed: adding corner fillets, installing buttress columns, and adding ring beams. Comparative analysis with the original structure's internal forces and displacement patterns reveals the effectiveness of each reinforcement scheme. The results show that openings reduce the moment of inertia of the floor slab cross-section, weakening the slab's stiffness and making the area around the openings and slab-column joints prone to local damage. Increasing the aspect ratio of the opening, enlarging its dimensions, or closely arranging multiple openings diagonally reduces the local load-bearing capacity of the structure. Adding corner fillets can reduce the maximum equivalent stress in the slab by more than 15 %, alleviating stress concentration caused by the openings. Buttress columns and ring beams increase the stiffness of the side walls, distribute the lateral forces causing wall bending moments, and enhance the structure's resistance to lateral displacement.

Multi-Objective Optimization of the Forming Process Parameters of Disc Forgings Based on Grey Correlation Analysis and the Response Surface Method

This paper introduces a multi-objective optimization problem (MPO) for the forming process parameters of disc forgings using grey relational analysis (GRA) and the response surface methodology (RSM). Firstly, an experimental design based on the Box–Behnken design (BBD) principle was established, and simulations were performed in Deform to obtain response data. Secondly, GRA was used to transform the MPO into a grey relational degree (GRD) problem, and the entropic weight method was integrated to ascertain the influence weights of each variable on GRD. Then, a quadratic polynomial prediction model based on the RSM was constructed, and its accuracy was ensured through model validation. Finally, the optimal process parameter combination was determined through the particle swarm optimization algorithm, which included a friction coefficient of 0.3, an initial temperature of 1250 °C, and a downward pressing speed of 7.5 mm/s. The results of the experimental investigation indicate that optimized process parameters significantly reduce the forming load, equivalent stress, and damage value, effectively enhancing the overall quality of forged parts.

Research on fracture prediction and control of UHSS thin-walled component with complex section in roll forming process

Aiming at the fracture of an ultra-high-strength steel (UHSS) thin-walled component with complex section in the roll forming process, the three-dimensional finite element model was established. It is found that the stress triaxiality and equivalent plastic strain are the main factors affecting the fracture behaviour of the UHSS thin-walled component with complex section, and the influence laws of forming strategies and process parameters on the fracture behaviour were discussed. The results show that the damage value, equivalent plastic strain and stress triaxiality at the fracture position are reduced by increasing the inter-distance and roll diameter, decreasing friction coefficient and forming velocity. The mathematical model of the UDP comprehensive measure with the forming strategies and process parameters was established by the response surface method. The numerical simulation and industrial test verify the effectiveness of the UDP comprehensive measure, which provides a theoretical and practical basis for the fracture prevention control.

Seismic Response of Foundation Settlement for Liquid Storage Structure in Collapsible Loess Areas

To investigate the impact of foundation settlement in loess areas on the dynamic response of liquid storage structure (LSS) under seismic motion, a finite element analysis model of the liquid–solid coupling of LSS was established using ADINA V9.6 software. By analyzing the dynamic response patterns of LSS under seismic motion with foundation failure, this study examines the effects of foundation failure and the direction of seismic wave incidence on the equivalent stress, maximum shear stress, wall displacement, and liquid sloshing wave height of the structure. The results indicate that among the three foundation failure scenarios, foundation failure at the center of the tank bottom has the least impact on the structural dynamic response. In contrast, foundation failure affecting one-fourth of the tank base has the greatest impact. Furthermore, compared to seismic motion along the X-axis, the dynamic response of the structure is more significantly affected when seismic motion co-occurs along the X-Z-axis.

A Comparison of Free and Mapped Meshes for Static Structural Analysis

Abstract This study addresses the challenge faced by Finite Element Analysts when choosing between free and mapped meshes, especially in terms of convergence stability and solution accuracy. The investigation focuses on 3D solid models under static structural loading, analyzed using Ansys® and MSC Patran®. Both free and mapped mesh types, employing equivalent 3D solid elements, are used to assess an aircraft structural component under design load conditions, with fixed boundaries. For free meshes, Tet10 elements in Patran (equivalent to Solid 72 in Ansys) are used, whereas for mapped meshes, CPENTA / CHEXA elements in Patran (equivalent to Wed6 / Hex8 in Ansys) are employed. Mesh convergence studies ensure that discretization does not affect the numerical solution. Notably, a significant stress increase is observed with successive refinement of free meshes, while mapped meshes achieve mesh independence at coarser refinement levels. Comparison of fringe plots indicates the same location for maximum deformation and equivalent stress in both free and mapped mesh models. The findings demonstrate that free meshes tend to underpredict maximum deformation and equivalent stress compared to mapped meshes, with both meshes showing deformation and stress at consistent locations. The findings underscore the importance of carefully choosing the appropriate mesh type, particularly when analyzing critical structural components, to ensure reliability and accuracy in FEA simulations.

Mechanical analysis of modified femoral neck system in the treatment of osteoporotic femoral neck fractures

BackgroundDespite the explicit biomechanical advantages associated with FNS, it is currently inconclusive, based on the existing literature, whether Femoral Neck System (FNS) outperforms Cannulated cancellous screws (CSS) in all aspects. Due to variances in bone morphology and bone density between the elderly and young cohorts, additional research is warranted to ascertain whether the benefits of FNS remain applicable to elderly osteoporosis patients. This study aimed to investigate the biomechanical properties of FNS in osteoporotic femoral neck fractures and propose optimization strategies including additional anti-rotation screw.MethodsThe Pauwels type III femoral neck fracture models were reconstructed using finite element numerical techniques. The CSS, FNS, and modified FNS (M-FNS) models were created based on features and parameterization. The various internal fixations were individually assembled with the assigned normal and osteoporotic models. In the static analysis mode, uniform stress loads were imposed on all models. The deformation and stress variations of the femur and internal fixation models were recorded. Simultaneously, descriptions of shear stress and strain energy were also incorporated into the figures.ResultsFollowing bone mass reduction, deformations in CSS, FNS, and M-FNS increased by 47%, 52%, and 40%, respectively. The equivalent stress increments for CSS, FNS, and M-FNS were 3%, 43%, 17%, respectively. Meanwhile, variations in strain energy and shear stress were observed. The strain energy increments for CSS, FNS, and M-FNS were 4%, 76%, and 5%, respectively. The shear stress increments for CSS, FNS, and M-FNS were 4%, 65% and 44%, respectively. Within the osteoporotic model, M-FNS demonstrated the lowest total displacement, shear stress, and strain energy.ConclusionModified FNS showed better stability in the osteoporotic model (OM). Using FNS alone may not exhibit immediate shear resistance advantages in OM. Concurrently, the addition of one anti-rotation screw can be regarded as a potential optimization choice, ensuring a harmonious alignment with the structural characteristics of FNS.

Influence of hot forging on grain formation in Al0.35CoCrFeNi high-entropy alloy: numerical simulation, microstructure and mechanical properties

One-step (F100) and three-step (F30-60-40) hot forging of Al0.35CoCrFeNi alloy was investigated to achieve a uniform equiaxed grain structure. In the as-cast and forged state, only a single-phase face-centered cubic structure was observed. The formation of twins, recrystallized and partially recrystallized grains in the volume of the samples was observed depending on used forging process. To predict uniform grain-size formation numerical simulation of the hot-forging process was used. The numerical model was calibrated and validated by means of measured compression experimental data of as-cast Al0.35CoCrFeNi alloy before forging. Thermal analysis using finite element analysis was used to simulate cooling of sample during the relocation from the furnace on the lower die. Simulations were run under different thermo-mechanical conditions and the regions for the formation of dynamically recrystallized grains were predicted. Room temperature mechanical properties were evaluated after F100 and F30-60-40 hot-forging process. The F30-60-40 hot forging optimized the grain size, which was evident in the very small dispersion of the room temperature mechanical properties in tension. Elongation after F30-60-40 hot forging increased by 17%. The correlation between temperature, equivalent stress, equivalent plastic strain, microstructure, tensile properties, and strain-hardening behavior is discussed.

Stress triaxiality and Lode angle parameters driven phase field coupled finite deformation plasticity formulation of ductile fracture

The effect of stress triaxiality and Lode angle parameters on crack initiation and propagation is investigated using the phase field coupled elasto-plasticity formulation. To accomplish this, a multi-invariants, i.e., first invariant of stress tensor and second and third invariants of deviatoric stress tensor, dependent finite deformation hyperelasto-plasticity is coupled with phase field theory of ductile fracture. The novel ideas include a proposition of a phase field coupled multi-invariants dependent yield function by including the Hosford equivalent stress in the Drucker–Prager yield function in order to accurately predict the ductile response of the material prior to initiation of the failure and the postulation of the threshold energy in the phase field evolution equation defining a measure of the ductility of materials. The measure of ductility is reported in the form of damage initiation surface in terms of threshold plastic energy as a function of stress triaxiality and normalized Lode angle parameters using the Mohr–Coulomb fracture initiation criterion. The model parameters are calibrated based on the available experimental results in the literature considering the stress triaxiality and Lode angle parameters dependent responses of different specimens. The crack initiation and propagation paths predicted by the proposed model under the different states of stress triaxiality and Lode angle parameters, such as axisymmetric tension, plane strain condition, and axisymmetric compression, match with those predicted experimentally in the literature.

Fluid-Solid coupling analysis of PTFE impeller in hydraulic turbines for sewage resource utilization

Abstract Hydraulic turbines, vital energy-saving devices, convert pressure energy from liquid fluids into mechanical energy. As wastewater resource utilization and zero discharge industries proliferate, relevant research is of great interest. In order to design a suitable medium and low pressure hydraulic turbine for industrial water treatment, we conducted a study analyzing the stress and strain characteristics of a PTFE turbine impeller by means of bi-directional fluid-structure coupling numerical simulation. Our findings suggest that the impeller’s maximum equivalent stress and maximum deformation fall within acceptable material limits, with stress concentration at the blade-cover plate interface. The blade experiences maximum deformation at its midpoint due to high liquid pressure on the volute periphery. Fluid solid coupling reduces the maximum equivalent stress of the impeller by about 1.65MPa and the maximum deformation of the blade by about 0.05mm. The equivalent stress at the sampling point fluctuates periodically, with a significant change in stress amplitude at the sampling point of the cover plate on one side of the support surface, increasing susceptibility to fatigue damage.

Deformation and Stress Prediction of Tank under Uneven Settlement

Abstract The differential settlement of crude oil tank foundations can lead to deformation and stress concentration, posing significant risks to the safe operation of storage tanks. This study developed a finite element model for a large crude oil storage tank subjected to harmonic settlement to address the issue of non-uniform settlement around the tank. The model systematically varied the tank’s diameter-to-thickness ratio, height-to-diameter ratio, and the wind beam’s relative bending stiffness. The research examined the impact of these three factors on the maximum dimensionless radial displacement at the tank top and the maximum equivalent stress at the tank bottom. A predictive method was proposed for estimating the radial displacement at the tank top and the equivalent stress at the tank bottom under uneven settlement, offering valuable insights for assessing the integrity of large tanks in such conditions.

Welding residual stress analysis based on ABAQUS direct coupling

Abstract Taking the welded joints of the drive axle shell and half shaft casing as the research object, based on the ABAQUS engineering software and its DFLUX subroutine, numerical simulation of the residual stresses of the welded joints before and after the heat treatment is carried out by adopting the direct coupling of temperature-displacement and the method of birth-death unit, to analyze the improvement effect of post-weld heat treatment on the residual stress of welded joints. The results show that the heat treatment process significantly reduces the equivalent peak stress of welded joints, from the original 195.25 MPa to 145.21 MPa, with a decrease of 25.6%. The axial peak stress of the welded joints decreased from 170.94 MPa to 130.84 MPa, with a decrease of 23.5%.

Research on mechanical properties of HTPB propellants

Abstract Slat propellants with different sizes and shapes are designed to investigate the strength criteria of HTPB propellants. According to the calculation and simulation results, with the increase of multiple, the designed size slat specimens can achieve equivalent biaxial tensile stress ratios of 1:2, 1:2.5, 1:3, 1:3.5, and 1:4 under uniaxial tensile conditions. The biaxial mechanical properties of the slab with a stress ratio of 1:2 were tested at low temperatures (25°C, −30°C, −50°C, and 0.4 s−1, 4.0 s−1, 14.29 s−1, 42.86 s−1). It was found that as the temperature and the strain rate rise, an increase is observed in the maximum tensile strength and the initial modulus, a decrease is observed in the maximum elongation of the propellant, and the strength envelope is constructed according to the typical mechanical parameters: the strength envelope of HTPB propellant increases as the temperature decreases. The research findings are expected to provide statistical support for the analysis of the structural integrity of HTPB propellants under low-temperature ignition.

Improved black-winged kite algorithm and finite element analysis for robot parallel gripper design

This paper presents a comprehensive study on the design optimization of a robotic gripper, focusing on both the gripper modeling and the optimization of its parallel mechanism structure. This study integrates the Black-winged Kite Algorithm (BKA), Finite Element Analysis (FEA), Backpropagation Neural Network (BPNN), and response surface optimization techniques. The Good Point Set (GPS), nonlinear convergence factor, and adaptive t-distribution method improve BKA, which enhances exploration and exploitation performance, convergence speed, and solution quality. Subsequently, the parallel mechanism structure is designed to minimize the total mass, total deformation, and maximum equivalent stress. The central composite design (CCD) method was used to design the FEA experiment and establish the BKA-BPNN regression prediction model. The RMSE of this model’s training set and test set are 0.001615 and 0.0029328. A response surface optimization model is constructed to determine the best design solution. The optimized design achieves a 33.12% reduction in maximum equivalent stress, a 1.47% decrease in total mass, and a 0.16% reduction in maximum total deformation. This study provides valuable insights into the design optimization process for robotic grippers, showcasing the effectiveness of the proposed methodologies in enhancing performance while reducing mass and improving structural integrity.