High Equivalent Stress Research Articles

Topological and lattice-based AM optimization for improving the structural efficiency of robotic arms

The robotic arm is one of the vital components of robot assembly. The purpose of the robotic arm is to transmit power and conduct the desired motion, i.e., translation or rotation. Robotic limbs are designed and constructed to execute certain tasks with a high degree of speed, accuracy, and efficiency. This research focuses on to enhancing the strength-to-weight ratio of robotic arm using certain techniques of additive manufacturing, i.e., topology optimization and lattice structure. Employing the finite element analysis, the impact of weight reduction optimization on structural parameters such as stress and deformation in the current design is assessed using ANSYS R18.1 for FE analysis and Creo parametric 7.0 design software for computer-aided design modeling. Observations reveal that the 0.5 and .4 scale lattice structure designs have deformation of 0.01453mm and 0.01453 mm respectively though the generic design has 0.01043 mm deformation. Notably, the 0.5 scale lattice of the robotic arm exhibits a 31.08% higher equivalent stress than the generic design with 29.3%. reduction in mass of the robotic arm. These findings highlight the efficacy of lattice structures for optimizing the robotic arm’s performance, contributing to advancements in power-efficient robot assembly processes.

Effect of crack on morphology evolution of the precipitates in Nickel-based superalloys under applied stress

Nickel-based superalloys are widely used in turbine blades and aviation engine due to their outstanding mechanical property at elevated temperatures. The superior mechanical property of nickel-based superalloys is highly relevant to the morphology evolution of γ′ precipitates in the γ matrix phase. At high temperature, the directional coarsening of γ′ precipitates may result in rafting behavior under applied stress. In addition, defects such as the cavities, inclusions and micro-cracks introduced during the manufacturing process in superalloys have significant influence on the evolution of the γ′ precipitates. In this work, a phase field model with crack and precipitate as order parameters has been proposed to investigate the effect of crack on the morphology evolution of the γ′ precipitates. The morphology evolution and volume fraction evolution of the γ′ precipitates in the Nickel-based superalloys with different cracks have been investigated under the tensile and shear stresses. It is found that the local high equivalent stress and high elastic strain energy near the crack lead to the migration of solute atoms from the high stress region to the low stress region. The migration of solute atoms results in the disappearance of the γ' phases in the vicinity of cracks, which is consistent with the experimental observation. The disappearance of the γ' phases around the crack reduces the volume fraction of the γ′ precipitates, which will affect the mechanical property of the superalloys.

Mechanical Influence of Edentulous Mandibular Morphology on Peri-implant Bone in Implant Prosthetics: Threedimensional Finite Element Analysis.

The purpose of this study was to examine the mechanical influence of edentulous mandibular morphology on peri-implant bone in implant prosthetics by finite element analysis. Computed tomographic data from 25 patients with edentulous mandibles were selected and the radius of mandibular curvature and the height of the mandible at the midline were measured in order to clarify the morphological characteristics of the mandible. From the measurement, two patients with the smallest and largest radii of the mandible were selected. Two types of three-dimensional finite element models consisting of the edentulous mandible (small and large radius), superstructure (a cantilever bridge), implants, and abutments were created. Four implants were inserted between the right and left mental foramina. The upper surface of the mandibular condyle was constrained, and a vertical load of 100 N was applied on the occlusal surface of the right first molar. Three-dimensional finite element analysis of each model was performed to examine the mechanical influence of the edentulous mandibular morphology on the peri-implant bone. Measurement of mandibular morphology in CT images indicated that the lower the mandibular height was, the larger was the radius of the anterior mandibular curvature. Finite element analysis revealed that a higher equivalent stress was generated in the peri-implant bone of the model with a larger radius of curvature than that of the model with a smaller radius of curvature. The highest equivalent stress in the mandible was generated in the distal margin of the peri-implant bone posterior to the loaded side of the large radius of curvature model. The mandibular morphology had a mechanical influence on the peri-implant bone.

Analysis of mechanical strengths of extreme line casing joint considering geometric, material, and contact nonlinearities

To address the challenges associated with difficult casing running, limited annular space, and poor cementing quality in the completion of ultra-deep wells, the extreme line casing offers an effective solution over conventional casings. However, due to its smaller size, the joint strength of extreme line casing is reduced, which may cause failure when running in the hole. To address this issue, this study focuses on the CST-ZT Φ139.7 mm × 7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint, taking into account the influence of geometric and material nonlinearities. A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load. The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures. Additionally, the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches. The findings reveal that, under axial tensile load, the bearing surface of each thread tooth experiences uneven stress, with relatively high equivalent stress at the root of each thread tooth. The end thread teeth are valuable spots for failure. It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence. Under external pressure, the circumferential stress is highest at the small end of the external thread, leading to yield deformation. The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7% compared to the analytical and experimental values, proving the reliability of the finite element model. The tensile strength of the joint is 3091.9 kN. Moreover, in terms of anti-collapse capability, the joints demonstrate higher resistance to collapse compared to the casing body, which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment. The failure load of the casing body under external collapse pressure is 87.4 MPa. The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.

Effect of flow on heat transfer between a translating plate and gas discharged from multiple inclined slot nozzles

The presented study aims to reveal flow and heat transfer characteristics as a translating aluminum plate is impinged by high-temperature gas discharged from inclined slot nozzles. The computational fluid dynamics (CFD) and the fluid-solid interaction (FSI) techniques were used to simulate the impingement process. A comprehensive comparison of flow, heat transfer, and structural parameters was implemented. The results indicate that twin vortices are produced between the two inclined nozzles. When the velocity ratio increases from 0.1 to 1.0, the vortex at the left expands, while the right one is compressed. Meanwhile, average Nusselt number and the pressure coefficient exhibit opposite variation tendencies. The highest average pressure coefficient of 0.45 arises at a velocity ratio of 0.5. As the plate-nozzle distance increases, characteristic flow structures are developed, and the distributions of temperature and the pressure coefficient are uniformized. The maximum Nusselt number decreases from 473 to 266 when the nondimensional plate-nozzle distance increases from 4 to 8. Large deformation occurs at the middle part of the plate. High equivalent stress is concentrated at the front and rear ends of the plate, which is insensitive to the velocity ratio and the plate-nozzle distance.

Stepwise reduction of bone mineral density increases the risk of cage subsidence in oblique lumbar interbody fusion patients biomechanically: an in-silico study

BackgroundCage subsidence causes poor prognoses in patients treated by oblique lumbar interbody fusion (OLIF). Deterioration of the biomechanical environment initially triggers cage subsidence, and patients with low bone mineral density (BMD) suffer a higher risk of cage subsidence. However, whether low BMD increases the risk of cage subsidence by deteriorating the local biomechanical environment has not been clearly identified.MethodsOLIF without additional fixation (stand-alone, S-A) and with different additional fixation devices (AFDs), including anterolateral single rod screws (ALSRs) and bilateral pedicle screws (BPSs) fixation, was simulated in the L4-L5 segment of a well-validated finite element model. The biomechanical effects of different BMDs were investigated by adjusting the material properties of bony structures. Biomechanical indicators related to cage subsidence were computed and recorded under different directional moments.ResultsOverall, low BMD triggers stress concentration in surgical segment, the highest equivalent stress can be observed in osteoporosis models under most loading conditions. Compared with the flexion-extension loading condition, this variation tendency was more pronounced under bending and rotation loading conditions. In addition, AFDs obviously reduced the stress concentration on both bony endplates and the OLIF cage, and the maximum stress on ALSRs was evidently higher than that on BPSs under almost all loading conditions.ConclusionsStepwise reduction of BMD increases the risk of a poor local biomechanical environment in OLIF patients, and regular anti-osteoporosis therapy should be considered an effective method to biomechanically optimize the prognosis of OLIF patients.

Movement of flexible filter media under pulse-jet filter cleaning conditions

Reverse pulse-jet cleaned bag filters are widely used for the removal of fine particles from gas streams. Based on the material properties of a single fiber, the entire filter medium is modeled which shows an elastic and apparent viscous property mainly due to the restoration of the weaving pattern. Thus, for the pulse-jet cleaning, the actual transient pressure difference can be linked directly to the deflection of the filter medium. The filter medium displacement is simulated for the filtration and cleaning measures by finite element method (FEM) for a clamped filter test sample and the large-scale bag filter situation, respectively. As expected a high curvature of the filter medium coincides with a high equivalent tensile stress which in turn is a pre-curser for the probability for cake breakage.

A Forward Identification Method for High-Temperature Stress–Strain Curves of 7075 Aluminum Alloy Sheet Considering the Necking Stage

The necking phenomenon of metal sheet under high temperatures is serious and continues over a longer duration. It is difficult to describe the high-temperature mechanical properties of materials only on the basis of hardening behavior before necking. To obtain the high-temperature stress–strain curve considering diffuse necking stage, a forward identification method based on strain measurement is proposed in this study. Here, the strain field of the minimum cross-section in the necking region of the specimen is obtained using a DIC (digital image correlation) measurement technique, and the average axial true stress–strain curve is calculated. Then, the average axial true stress–strain curve is modified using the modified Bridgeman formula. Taking 7075 aluminum alloy as an example, the high temperature equivalent stress–strain curve considering the diffuse necking stage is obtained. Compared with the traditional method, the maximum effective strain range is expanded from 0.05 to 0.8 due to the consideration of the necking stage. The obtained curve is characterized by a coupled viscoplastic–damage constitutive model and embedded in ABAQUS through the user subroutine VUMAT to simulate the hot tensile process. The relative error of force–displacement between the simulation and the experiment was 2.4%, validating the ability of the presented method. This study provides theoretical guidance and a scientific basis for the application and forming control of hot stamping processes.

FSI investigation of cooling tower subjected to high gusts

The cooling tower is one of the vital installations of chemical plants, bio-chemical and power generation plants. The cooling towers are located at regions of high gust which may cause structural imbalance. The structural stability of cooling tower is essential for smooth operation of cooling tower. The structural stability of cooling tower depends upon type of material used in the manufacturing of cooling tower. The objective of current research is to investigate the strength of cooling tower subjected to external air flow conditions. The CAD model of cooling tower was developed in Creo design software and CFD simulation was conducted in ANSYS CFX v21 software. The cooling tower is exposed to high air flow conditions with magnitude of 50 m/s. The turbulence model considered in the simulation is K-epsilon. The base columns analyzed in the study was steel and concrete type. The static structural analysis is conducted on the basis of mapped pressure data obtained from the CFD analysis. The critical regions of high stresses and deformation are determined. The research findings have shown higher deformation and stresses for concrete cooling tower as compared to steel cooling tower. The concrete cooling tower generated 13.93% higher equivalent stress as compared to steel cooling tower. Similarly, the shear generated on concrete cooling tower was 16.41%.

Influence of copper anodization on structural and heat transfer characteristic of aluminum piston

The piston transmits force from the combustion gas expansion to the crankshaft through the connecting rod in an engine. The piston head is exposed to tremendous pressure by expanding combustion gases at a greater magnitude and at a high temperature. The piston should withstand these thermal shocks. Today, there are many different technical and industrial techniques available to alter the characteristics of a material to meet the needs of a certain application. Anodization is a surface treatment process that is used exclusively for aluminum and its alloys to increase durability and corrosion resistance. With the capacity to control the factors involved in the anodizing process, it is possible to change some of the characteristics of the finished anodized goods. This article examines the anodizing of aluminum pistons with and without a copper coatings. The purpose of this study is to evaluate if the piston is capable of withstanding high equivalent stress and low heat flux. Static structural analysis and steady state thermal analysis are performed using ANSYS software. The results of this research show that aluminum anodized with copper improves the structural integrity of the aluminum piston while also enhancing its structural and heat transfer properties.

Оценка возможности использования мобильных мостов для преодоления искусственных сооружений специализированными многоосными колесными транспортными средствами

The article provides general information about double-support mobile bridges designed for contactless movement of heavily loaded specialized multi-axle wheeled vehicles on top of man–made structures. Also, recommendations are given on substantiating the possibility of their use for solving specific problems. These recommendations contain expressions obtained by the methods of structural mechanics, on the basis of which it is possible to determine not only the required (minimum) camber of the mobile bridge, which is necessary to ensure the normal passage of the vehicle, but also to assess the stress state of the mobile bridge, as well as to determine the nature of the deformation of the mobile bridge when vehicle moves along it. The presented recommendations allow, at a first approximation, to assess the suitability of the available solutions of a mobile bridge for the passage of specialized multi-axle vehicles over mane–made structures, depending on the required span of the mobile bridge and the load from the vehicle on the mobile bridge. The article also provides an example of solving a specific problem on the basis of these recommendations, in accordance with which, when a mobile bridge is spanned 23.4 m and a working load from one axis of the vehicle is equal to 33.5 tons, the required camber is 400 mm, and the highest equivalent stresses will be about 380 MPa.

Influence of blade leaning on hydraulic excitation and structural response of a reversible pump turbine

Blade leaning is commonly seen in the runner design of reversible pump turbines which operate under varying conditions. However, there is no certain law in determine the leaning mode and level. Considering performance, hydraulic excitation and structural response, five runners with strong rotational (RL+), rotational (RL), strong counter-rotational (CL+), counter-rotational (CL) and without (NL) blade leaning are compared under high-efficiency condition in pump mode and turbine mode. The head, efficiency, internal flow pressure pulsation and runner stress are comparatively studied. Among the five runners, CL+ runner is found has the highest efficiency as pump when RL+ runner has the highest efficiency as turbine. Pressure pulsation results show that the rotor-stator interaction region is the strongest pulsation source especially for runner and blade frequencies. In pump mode, pressure pulsation intensity decreases when blade leaning mode gradually changes from rotational to counter-rotational. In turbine mode, the NL runner has the strongest pressure pulsation intensity in runner and guide vane. Both rotational and counter-rotational leaning will reduce pressure pulsation. Velocity contours indicate that blade leaning will affect the velocity uniformity especially along rotational direction and cause stronger or weaker local hydraulic excitation. Under hydraulic excitation, RL+ runner suffers the highest equivalent stress as pump while CL runner suffers the highest equivalent stress as turbine. From rotational to counter-rotational blade leaning, the maximum stress moves on the crown from low pressure side to high pressure side. Considering hydraulic excitation and structural response, the strong counter-rotational leaning blade is found better in reversible runner design.

Surface roughness analysis of medical grade titanium sheets formed by single point incremental forming

Single point incremental forming (SPIF) process has proven benefits in terms of formability, flexibility, and low cost as compared to conventional sheet forming, although it has some issues such as dimensional accuracy and low quality of surface finish for some materials. The SPIF is considered as a potential method of producing customised medical parts such as craniofacial implants using a titanium sheet. This investigation aims to analyse the overall surface roughness of grade 1 pure titanium along the wall of the hyperbolic truncated cone formed by the SPIF process with different forming parameters (i.e. forming tool diameter, step size, and feed rate). Focus variation microscopy was used to measure the surface roughness experimentally along the wall of the truncated cone. Abaqus/Explicit was used to predict the equivalent stress and equivalent plastic strain along the wall of the truncated cone part from the top to the fractured region to evaluate the relationship between the stress, strain, and roughness distribution. It was found that the surface roughness changes with the deformed part height and rough surface could be produced in the region of high equivalent stress and low equivalent plastic strain. Such a surface roughness and equivalent stress and plastic strain correlation has a clear implication to the design and the surface quality of sheet parts made by SPIF.

Study of Tank Containers for Foodstuffs

In this study, we examined a tank container for foodstuff that is generally used for the transport of foodstuffs. With the aid of the “ANSYS R17.0” program code, a numerical model of the tank container for foodstuffs was realized. Further, to validate the considered model, the tank container considered was submitted to the most important ISO tests concerning both its support frame and the tank. The results obtained from the FEM analysis, in terms of displacement for each test, were compared with those provided by the manufacturer and related to the tank container considered, evaluating the difference between the numerical results with the experimental ones. This allowed us to validate the model examined. Furthermore, the results obtained from each test, in terms of stress, have made it possible to locate the areas with the highest equivalent stress and quantify the maximum value, comparing it with the allowable stress. In this way, a better understanding of the structure was achieved, and it was detected that the most stressed area is that of the connections between the container and the frame. Furthermore, modal analysis was carried out, in which the natural frequencies relating to the most dangerous modes of vibrations were found, that is, with the lowest frequency values. Finally, changes for the considered tank container were examined, and it was found that, by changing parameters, such as the thickness of the plate and skirt, and subsequently acting on the arrangement of the corner supports, the highest value of the stresses generated by the loads related to the ISO tests, it is significantly lowered, resulting in a better distributed stiffening of the structure and a reduction, although minimal, of weight. It is evident that this modeling and validation method, suitably integrated by further calculation modules, can be used in an iterative optimization process.

The deformation and fracture behavior of 316L SS fabricated by SLM under mini V-bending test

In the present study, mini V-bending testing was conducted on 316L stainless steel specimens fabricated by selective laser melting (SLM). In order to analyze the microstructure evolution during the V-bending test, FE-SEM and EBSD techniques were performed along the building (BD) and scanning directions (SD). Microstructure analysis revealed that the as-fabricated SLM specimens contained pores in the surface and subsurface regions, which affected the deformation and fracture behavior during the V-bending process. The effect that these microstructural heterogeneities exerted on the deformation behavior of the SLM specimens is discussed herein with respect to the evolution of the Kernel average misorientation (KAM), grain boundaries (GBs), and Σ3 twin boundaries (TBs). Two-level finite element (FE) simulations were performed to explain the deformation and fracture behaviors during the V-bending process. The first-level FE simulation was done to understand the macroscopic deformation of the specimen during the V-bending process. During the second-level FE simulation, representative volume elements (RVEs) were considered in discussing the evolution of equivalent plastic strain and stress triaxiality at regions near the pores. High equivalent plastic strain and stress triaxiality states at regions near the pores in the surface and subsurface of the specimens made a considerable contribution to the nucleation and propagation of cracks during the V-bending process.

Ulnar collateral ligament dysfunction increases stress on the humeral capitellum: a finite element analysis.

BackgroundRepetitive mechanical stress on the elbow joint during throwing is a cause of ulnar collateral ligament dysfunction that may increase the compressive force on the humeral capitellum. This study aimed to examine the effects of ulnar collateral ligament material properties on the humeral capitellum under valgus stress using the finite element method.MethodsComputed tomography data of the dominant elbow of five healthy adults were used to create finite element models. The elbows were kept at 90° of flexion with the forearm in the neutral position, and the ulnar collateral ligament was reproduced using truss elements. The proximal humeral shaft was restrained, and valgus torque of 40 N·m was applied to the forearm. The ulnar collateral ligament condition was changed to simulate ulnar collateral ligament dysfunction. Ulnar collateral ligament stiffness values were changed to 72.3 N/mm, 63.3 N/mm, 54.2 N/mm, 45.2 N/mm, and 36.1 N/mm to simulate ulnar collateral ligament laxity. The ulnar collateral ligament toe region width was changed in increments of 0.5 mm from 0.0 to 2.5 mm to simulate ulnar collateral ligament loosening. We assessed the maximum equivalent stress and stress distribution on the humeral capitellum under these conditions.ResultsAs ulnar collateral ligament stiffness decreased, the maximum equivalent stress on the humeral capitellum gradually increased under elbow valgus stress (P < .001). Regarding the change in the ulnar collateral ligament toe region width, as the toe region elongated, the maximum equivalent stress of the humeral capitellum increased significantly under elbow valgus stress (P < .001). On the capitellum, the equivalent stress on the most lateral part was significantly higher than that on other parts (P < .01 for all).ConclusionUnder elbow valgus stress with elbow flexion of 90° and the forearm in the neutral position, ulnar collateral ligament dysfunction increased equivalent stress on the humeral capitellum during the finite element analysis. The highest equivalent stress was noted on the lateral part of the capitellum.

Assessment of the Impact of Shot-Peening on the Fatigue Life of a Compressor Blade Subjected to Resonance Vibrations.

This publication presents an assessment of the influence of a surface treatment such as shot-peening on the fatigue life of a compressor blade exposed to resonant vibrations. As part of the work, a geometric model of the blade was developed, and a numerical modal and fatigue analysis were performed. The fatigue analysis was based on the Manson–Coffin–Basquin and Ramberg–Osgood models. Additionally, the location of the highest equivalent stresses was established. Based on the results of the strength analysis, two points were identified where a fatigue crack may potentially occur. As part of the work, the influence of different values of residual stresses on the results of the fatigue life was determined. The obtained results were compared to the literature values of fatigue life for this blade. A secondary objective of the study was to determine the size of the grains at various points of the blade, as well as the thickness of the layer plasticized as a result of peening. The relationship between the location of the highest values of the equivalent stresses and the thickness of the plasticized layer was determined. An explanation of the effect of shot-peening on the increase in the fatigue life of the blade was proposed.

Influence of non-uniformly periodic distribution of fibers in composites on the stress field and effective shear modulus under anti-plane shear

Based on the complex variable techniques combined with the boundary collocation method, a semi-analytical procedure is proposed to explore the anti-plane shear behavior of non-uniformly periodic fibrous composites under uniform remote shear loadings. Specific series with unknown coefficients are introduced to describe the complex potentials of the representative unit cell (RUC) of the composite. The unknown coefficients are determined from the continuity conditions on the interface, the periodic boundary conditions imposed on the edge of the unit cell and the remote loading conditions. Once the complex potentials are determined, the effective moduli of the composite are obtained according to the average-field theory. Extensive numerical examples are provided to investigate the influence of the periodic distribution of the inclusions, the moduli of each component, and the volume fraction of the inclusions on the local stress fields and effective shear moduli of the composite. Numerical results show that the inhomogeneous distribution of the inclusions may induce a continuous area with high equivalent stress in the matrix under certain loadings and material properties of each component. However, we could overcome this disadvantage by changing the components or the periodic arrangement of the inclusions. For the case of a RUC with double inclusions, the two inclusions with the same shear moduli arranged symmetrically in the direction of 45 degrees may induce the transverse isotropy of the composite. Nevertheless, when the two inclusions are horizontally arranged and the volume fraction of the inclusions is large enough (more than 10%), the composite generally shows orthotropic characteristics.

Design Optimization of Car Front Hood for Pedestrian Safety

Nowadays many people deaths in the world were reported from vehicle traffic accidents that involved with pedestrian impact in higher percentage. This percentage may increase if there is no strong attention to the pedestrian safety from automakers and authorities. This study will focus on the analysis of pedestrian head impact on a car hood with different types of materials; also the hood thickness will be analysed with different measurements during the head test impact using the numerical simulation analysis which is available in ANSYS finite element software. The pedestrian head and front hood will be modelled using CAD software. Therefore the simulation will demonstrate the effects on the impact performance for each type of materials with different thickness used in this research. The observation from the numerical analysis showed that aluminium had high deformation as compared to steel and magnesium materials of hood. The steel had lowest deformation but it had higher equivalent stress when compared to aluminium and magnesium. Furthermore the lowest type of thickness produced high deformation and high equivalent stress value for each material type. In general each material had its own characteristic; therefore manufacturers can evaluate the lower material cost or design a safe front hood using the same material but with different thickness that suitable for pedestrian safety.

Mechanical response of the Cr3C2–NiCr coating-substrate system during nanoindentation process

The coating deformation behavior and stress evolution of the plasma sprayed Cr3C2–NiCr coating during nanoindentation process were analyzed by finite element modeling based on its real elastic-plastic properties. The effects of indentation depth and the coating thickness on the mechanical response of the coating were studied. The results show that once the indentation depth exceeded 13% of the coating thickness, the coating material near the indenter was extruded and piled up on the top surface. Meanwhile, high equivalent stress was developed along the coating-substrate interface rather than inside the coating. Even when the indentation depth was smaller than 13% of the coating thickness, the substrate still influences the mechanical behavior of the coating, inducing different reaction force to the indenter.