Stress Deformation Research Articles

Co-vulcanization of natural rubber and Eucommia ulmoides gum for mediation of the nonlinear rheology behaviors

Co-vulcanization of natural rubber (NR) and high-moduli Eucommia ulmoides gum (EUG) is promising while the reduction in crystallinity of crosslinked EUG is adverse for developing high-performance materials. Proposed herein is a novel method to prepare high-strength and high-stretchability NR/EUG vulcanizates with rapid vulcanization of EUG into slightly crosslinked particles, followed by further vulcanization of NR to form crosslinked matrix network. Deep eutectic solvents (DESs) are employed to facilitate the vulcanization of EUG during its blending with NR. The two-step vulcanization results in vulcanizates exhibiting superior mechanical properties under shear, tensile, and compressive conditions, significantly exceeding those of vulcanizates prepared by traditional processing methods. The reinforcement mechanism is elucidated by controlling thermomechanical coupling conditions and is supported by comprehensive structural characterizations. It is suggested that the EUG crystalline regions, maintained through the special processing method, work in conjunction with the stress-induced crystallization of the matrix to enhance the vulcanizates, nearly doubling the deformation stress at 800% strain. The crystalline regions can mediate the deformation stress during shear and compression and weaken nonlinear rheological behavior. The established structure-performance relationship is guidable for preparing high-performance NR/EUG blend vulcanizates.

WASTE EGGSHELL AND SAWDUST AS REINFORCEMENTS FOR SUSTAINABLE POLYESTER COMPOSITES: MECHANICAL CHARACTERIZATION AND ENVIRONMENTAL DURABILITY ASSESSMENT

This research endeavor undertakes an experimental investigation into the bending and tensile properties of polyester composites reinforced with waste eggshell powder and sawdust particles at 35 wt.%. Valorizing these waste materials as reinforcements contributes to sustainable practices, waste minimization, and environmental pollution mitigation. Composite samples were fabricated using hand lay-up and compression molding techniques. The effects of environmental exposure to water, acidic, and basic media immersion on the mechanical performance were evaluated to assess durability. Experimental characterization through tensile and three-point bending tests determined mechanical properties, stress-strain behavior, and failure mechanisms. Additionally, finite element analysis (FEA) simulations complemented the experiments by providing insights into stress distributions, deformations, and potential failure initiation sites within the composites under flexural loading. The computational models accurately captured the reinforcing effects of the waste materials and the degradation induced by environmental exposure, validating the experimental trends. Incorporating waste natural fibers significantly enhanced polyester's bending strength by 140% (sawdust) and 75% (eggshell), and tensile strength by 13% (sawdust) and 10% (eggshell). However, environmental exposure degraded properties to varying extents, with water immersion reducing tensile strength by 63% (sawdust) and 3% (eggshell), and flexural strength by 63% (sawdust) and 3% (eggshell). The acidic medium caused 58% (sawdust) and 23% (eggshell) reductions in tensile strength, and similar flexural strength degradations. Strikingly, the basic medium decreased eggshell composite tensile strength by 170% and flexural strength by 6%, while sawdust composite strengths declined by 44%.

Stress Concentration Modelling in Internal Stiffeners of Ship-to-Shore Quay Cranes Legs Due to Structural Heightening

This paper presents a study on the modelling and estimation of stress concentration at the tips of leg stiffeners in ship-to-shore (STS) quay cranes, which is intensified in those on the sea-side leg extensions, which are more prone to crack formation, notably following structural heightening of the cranes. A computer-simulated database was generated, incorporating mechanical parameters and geometric features that impact stress concentration. These variables can then be integrated as inputs into a multiple linear regression model (MLR). This methodology offers an alternative to the finite element method (FEM) for the computation of stress concentration and deformations. At the same time, the statistical significance of the parameters influencing this scenario is determined, ensuring a comprehensive assessment of their impact on the studied phenomenon. The research underscores the importance of incorporating stress concentration and structural geometry considerations into crane design or modification, given their crucial role in preserving the remaining lifecycle of the structure. Crack initiation is significantly intensified in regions characterised by high stress concentrations, particularly in areas where there are geometric changes at the tips of the stiffeners, where local stiffness is altered. All of this is in combination with work cycles under the supported loads.

Model scale tests on the behaviour of single piles in cohesive soils under combined loads

ABSTRACT Model scale tests were conducted to study the influence of combined loads (uplift + compressive, uplift + lateral, lateral + compressive and lateral + uplift) on stress distribution, ultimate capacities and deformations of single piles in Indian black cotton soils, in comparison to pure uplift and lateral loads. Numerical analysis was performed in Plaxis 3D to examine the effect of pile slenderness ratio (L p /d = 15, 20 and 25) on ultimate capacity and pile head displacements. The test results showed that uplift capacity and pile head displacements increased by 35–49% and 30–50% with an increase in staged compressive loads, respectively. Therefore, piles subjected to combined uplift and compressive loads should be designed for pile head displacements rather than uplift capacity. The compressive loads did not affect the stress distribution along the pile–soil interface. However, lateral loads altered stress distribution, resulting in a curved failure plane and a substantial increase of 80–150% in the uplift capacity of piles under combined uplift + lateral loads. The lateral load–deflection curve for 60% and 80% of staged uplift loads showed an elastic response, indicating that the pile and surrounding soil did not yield under the applied lateral loads.

Evaluation and Prediction of Mechanical Properties According to Welding Methods of Ni 825/A516-70N Clad Plates

In this study, the microstructures and mechanical properties of different methods of FCAW (Flux-cored arc welding) + FCAW or FCAW + GTAW (Gas tungsten arc welding) welding on Ni825/A516-70N clad plate were investigated, using a double U groove angle on a laboratory scale. The amount of specimen deformation with FCAW + FCAW welding was ~1.5 mm, and that with FCAW + GTAW welding was ~3.6 mm. In the Vickers hardness tests, the average hardness value of the FCAW + GTAW welding specimens tended to be higher, and the hardness of the steel showed the same value. Also, in the tensile tests, the maximum strength and elongation of the FCAW + GTAW specimens were found to be higher. The SEM analysis of the welding boundaries of each specimen revealed the phenomenon of grain refinement in the specimens with FCAW + GTAW welding. This was due to the slow welding speed of this welding process and the rapid cooling rate caused by the relatively low layer thickness despite the relatively high number of weld passes. The computer simulation of the amounts of deformation were similar, with a value of 1.5 mm for FCAW + FCAW and 3.6 mm for the computer simulation, indicating the credibility of the simulation. In the computational simulation of butt welding, FCAW + GTAW showed high values for both residual stress and angular strain. The L-seam and C-seam of the demo vessel size were welded under the same conditions as the actual welding. The residual stress and angular deformation in the L-seam were 849 MPa and 2.3 mm for the FCAW + FCAW and 852 MPa and 2.9 mm for FCAW + GTAW. The residual stress and angular deformation in the C-seam were 920 MPa and 0.7 mm for FCAW + FCAW and 930 MPa and 0.9 mm for FCAW + GTAW, respectively.

Investigation of support structure configurations for selective laser melting of In718

The Selective Laser Melting (SLM), as a widely used metallic Additive manufacturing (AM) process, relies heavily on support structures. This study investigated the impact of different support structure configurations on the quality of In718 samples fabricated through SLM. On the basis of a comprehensive review of existing support structures configurations from the literature, three typical configurations: block, cone, and lattice, were designed to support cantilever parts for performance comparison. A coupled thermo-structural finite element simulation using ANSYS was performed to evaluate the temperature, deformation, and thermal stress evolution during the printing process of the three supported cantilever structures. The residual stress and deformation of the printed In718 cantilevers with different support structures were measured for validation. The results showed that block support exhibits the best strength and heat dissipation capability, making it the most effective support configuration for the SLM of In718 material. This research provides a fundamental procedure for evaluating the supporting performances among various support structures for the SLM process.

Enhancing efficiency in hot stamping of polymethyl methacrylate foils: computer analysis and modeling

ABSTRACT This work is leading the way in developing a new method to evaluate the efficacy of hot stamping on polymethyl methacrylate (PMMA) foils. The art of hot stamping, which involves stamping, heat, and pressure to produce elaborate images on flexible foil surfaces, has long been prized for its artistry. A thorough examination of the embossing mechanism is complicated by the fact that different process factors might result in different levels of quality for embossed patterns. This study stands out for its creative approach to hot stamping process optimisation. Traditionally, resource-intensive and time-consuming empirical studies are used to determine the ideal process conditions. By using computer analytic techniques, this research, on the other hand, presents a novel way for quickly and precisely determining the most effective process parameters. Furthermore, by exploring the evolution of the embossing phenomena utilising cutting-edge methodologies like the finite element method (FEM) and creative reproduction approaches, this work explores the unexplored area. A thorough analytical model is carefully created, accounting for temperature-specific stress characteristics, strain rates, stress distribution, and the softening characteristics of the elastic foil. The research makes a unique contribution by precisely characterising the stress hardening, deformation, and thermal expansion of PMMA materials. This paves the way for extrusion analysis utilising customised processes.

Finite-element simulation of functional knee sleeves based on three-dimensional modeling of the knee joint

Knee sleeves are one of the most satisfying and widely used items of protective equipment for sports enthusiasts. Achieving an effective balance between functionality and comfort is a key factor in the design of knee sleeves. However, there are still some problems with the knee protection products currently on the market, such as poor thermal and moisture comfort, difficulty in putting on and taking off, slippage during doing sports, and the lack of a timely and effective feedback mechanism that cannot guide the user to actively adjust their movement posture to avoid sports injuries. To improve the function and pressure comfort of the human body after wearing knee sleeves, this study took the knee joint as the research object, established a three-dimensional knee joint model through computed tomography (CT) scanning and Mimics software, and then built a finite-element model under the contact state between the human body and pressure clothing on this basis. Moreover, ABAQUS was used for finite-element simulation to obtain the pressure and displacement distribution of knee joints after wearing knee sleeves. In order to further investigate the stress state and deformation trend of knee joint after wearing knee sleeves, each section of the human body at the knee joint was divided into four regions according to the angle, and the functional relationship between pressure and displacement was obtained by curve fitting. This study has significance for the investigation of the pressure comfort threshold of knee sleeves and the optimization of the design of functional knee sleeves.

Efficient calculation of deformation and FEM stress for substructures of floating wind turbines

Abstract Design tools for floating wind turbines must be able to quantify the effects of elastic substructure flexibility. The implementation in HAWC2 is here validated against a physical model test with a generic floater. Next, the detailed stresses in the substructure require Finite Element Modelling (FEM). When the deformations are small, linear analysis is sufficient and superposition can be utilized. Thus following modest pre-computation, stress time series for any random realization can be achieved efficiently through influence functions and FFT based transfer functions. We present a proof of concept here.

An asymmetric pinching damaged hysteresis model for glubam members: Parameter identification and model comparison

The performance of glue laminated bamboo (glubam) members is governed by the nonlinear response at their joints, where high deformation levels and stress concentrations are developed. Numerous phenomenological models are presently employed to describe the hysteresis behavior of these joints, while these models always have an excessive number of parameters, and the physical interpretation of these parameters is often challenging. Moreover, some hysteresis models cannot capture all hysteresis features such as asymmetry, pinching, and damage. Consequently, this paper introduces a novel phenomenological-based hysteretic model named Asymmetric Pinching Damaged (APD) model, and implemented it in Abaqus by combining connector and spring elements in series or parallel. This model encompasses asymmetry, pinching, and strength degradation for bamboo joint components, with parameters that possess clear physical meanings and are readily comprehensible. This study also presented a parameter identification framework coupling the Parallel Genetic Algorithm (PGA) and Bayesian Neural Network (BNN). By merging the FE modeling and optimizing algorithms with the interactive application of ABAQUS and Python software platforms, the integrated identification framework is capable of performing multi-threaded parallel computation of finite element models considering the BNN-based uncertainty quantification, thus greatly improving the efficiency of parameter identification.

Static analysis of wind blades based on weight loads to the gravitation and the centrifugal forces Using Finite Element

Static analysis of wind turbine blades that convert kinetic energy using wind to electrical power has been analyzed using Ansys model. The geometry was imported in ANSYS workbench 2020R1, where the material was changed to Epoxy E-Glass Wet. The mesh independence that occurred at 800 and 600 element sizes and an element size of 800 was chosen for subsequent static analysis. The static analysis shows that the total deformation and von Mises stress of the wind turbine blade was improved at both the vertical position and the horizontal position by 40.0% and 38.61%, respectively. Besides, the static analysis showed an almost linear mode shape increased from mode lines. Nevertheless, Campbell's diagram showed that resonance vibration occurred at an amplitude of 5.5x106Pa with a corresponding frequency of 5Hz, which gave a rotational speed of 262.4x106 rpm. This shows that the impulse force is better applied in wind turbine blade transient analysis at a lower von Mises stress to attain a quicker damping response steady-state, which favors wind turbine blade analysis. Overall, the wind turbine blade is better designed at a vertical position to allow better deformation stress at a static position. Conversely, the von Mises stress showed 44.64% and 38.61% at horizontal and vertical positions. This also agrees with static total deformation, since stress is better managed at a lower percentage range.

Numerical Analysis of the Bond Behaviour of High-Strength Concrete-Filled Steel Square Columns with Different Shear Connectors

This paper deals with a numerical method of analysis of the performance of shear connectors in transferring load in high-strength concrete-filled steel tube square sections. The novelty of the model is that it considers all the important parameters that affect performance at once: bond strength, the transfer rate of each connector, and the stress distribution and deformation of each element. Four specimens fabricated using different types of connectors were validated using ABAQUS version 2017 software. The deformation of the connectors, concrete damage, and the local instability of the steel tube were extensively investigated. The main parameters considered were the ultimate bond strength and load transfer ratio. The shear connector arrangement consisting of four specimens, namely C1 with 16 studs, a circular rib (C2), a circular rib with 8 studs (C3), and a circular rib with 8 vertical ribs (C4), had a significant influence on the key parameters. Connectors C2, C3, and C4 transferred more than 80% of the total load. The circular rib was more effective in transferring the load and limiting slip than the vertical rib and the studs. The circular rib (C2) transferred the load mainly through the four corners. The deterioration of the concrete and local instability of the steel tube had complex deformations which were influenced by the geometry of the inserted connectors.

Finite-element investigations on the influence of material selection and geometrical parameters on dental implant performance

Abstract Dental implants provide functional and aesthetically pleasing dental replacements, but their longevity depends on biomechanical factors, physical characteristics, and patient variability. The present study used finite-element analysis to reveal the biomechanical response and potential modes of failure of dental implant systems subjected to normal occlusal loads. A generalized comparative assessment was carried out to measure the effect of the choice of crown material with zirconia, porcelain-fused-to-metal, and ceramic crowns. Such simulations showed complex patterns of stress distribution and deformation in the implant assembly with significant variation due to the mechanical properties of the crown material. Stiffer zirconia crowns magnified stress concentrations by 12.6, 10.8, 11.4, and 9.1% in the implant fixture, crown, cortical bone, and cancellous bone, respectively, compared with more compliant ceramic crowns. Furthermore, the maximal deformation of both the cortical and cancellous bone induced by zirconia crowns was higher by 21.1 and 19.2%, respectively, compared with the ceramic crowns. These results emphasize that the crown material properties are significant for controlling and modulation biomechanical load transfer, which plays a decisive role in the long-term durability and resistance to failure mechanisms such as interfacial debonding, bone resorption, and fatigue cracking. This study provides valuable information for optimizing implant designs and material selection that may improve clinical results, positively affecting patient satisfaction with dental implant therapy.

Residual stress and deformation of welded T-joint between low carbon steel and stainless steel

The welded structures between carbon steel and stainless steel are widely used in many sectors such as pedestrian bridges, food industry, chemical industry, petroleum, and thermal power plants, … These composite structures take advantages of each material for different parts of structure. In the welded structures between carbon steel and stainless steel, the structure is made by T-joint that is the most common. The calculation of residual stress and welding strain of the T-joint between low-carbon and stainless steel materials is the basis to evaluate the working ability of this structure. In this study, the residual stress and welding deformation of the T-joint are determined by the imaginary force method. The double-sided weld of T-joint between low carbon steel and stainless steel is welded simultaneously by MIG welding process. The obtained results of residual stress and welding deformation in this case are compared with the case of single-sided weld so that we can find the difference between residual stress and welding deformation in two cases.

Deformation Evolution and Perceptual Prediction for Additive Manufacturing of Lightweight Composite Driven by Hybrid Digital Twins

This paper proposes a deformation evolution and perceptual prediction methodology for additive manufacturing of lightweight composite driven by hybrid digital twins (HDT). In order to improve manufacturing quality of irregular lightweight composite through boosting conceptual design in aeronautic and aerospace engineering, the HDT meaning hybridization of physical and digital domains, including deformation and energy efficiency can be built, where the essential parameters can be perceptually predicted in advance, by virtue of the fusion of physical sensors and digital information. The long short term memory (LSTM) can be employed to void vanishing gradient problem and improve predicting precision via Recurrent Neural Networks, thereby laying a foundation for the HDT. The diverse manufacturing requirements of different regions are integrated into the parameters designing phase by attaching region weights confirmed via empiricism and in-service simulation. The effects of slicing strategy and external support structures on manufacturing quality are considered from the perspective of improving dimensional accuracy. The manufacturing efficiency and comprehensive costs are accounted as consideration factors, which are perceptually predicted via LSTM. The designed manufacturing parameters through HDT were virtually examined by evaluating the deformation and equivalent stress distributions of fabricated lightweight component with composite material through AM process simulation. The physical experiments were conducted to verify the HDT-based pre-designing and optimization method of manufacturing parameters via fused deposition modeling (FDM). The energy consumption of actual manufacturing process was measured via digital power meter and applied to evaluate accuracy of perceptual prediction outcomes. The dimensional accuracy and distortion distribution of the manufactured lightweight prototype made with composite material were measured through the coordinate measuring machine (CMM) and 3D optical scanner. The proposed method demonstrates effectiveness in improving manufacturing quality and accurately predicting energy consumption, which have been verified with a three-way solenoid valve element, in which the maximum deformation was reduced by 39.78% and the mean absolute percentage error for perceptual prediction was 3.76%.

Study of thermal stress deformation in hybrid 3D printing and milling process of PEEK material

Hybrid manufacturing can enable rapid production of personalized artificial bones that are made of Polyether-ether-ketone (PEEK) by integrating 3D printing and milling. A main challenge, however, is the thermal stress deformation that arises from the fused deposition process, leading to warping and shrinkage. As a result, the fabrication accuracy is significantly diminished. This work aims to address this challenge by investigating the thermal stress deformation behavior of PEEK in hybrid manufacturing. The main contributions of this work, therefore, include the development of a model for this thermal deformation behavior, and the identification of key parameters such as cross-section length ( Ls), printed layer thickness ( Lh), and current workpiece height ( He). Further, experiments are conducted based on response surface methodology (RSM) to explore the relationships between temperature variation rate (Δ T), end surface height difference (Δ S), and length shrinkage rate (Δ L) with critical hybrid processing parameters. Optimal parameter combinations are then identified. Our experiments demonstrate that the proposed methods effectively reduce the effects of warping and shrinkage.

A novel model for predicting deformation of thermoplastic composites during heat-pressing process

Carbon fiber/polyetheretherketone (CF/PEEK) thermoplastic composites are widely used in the aerospace industry due to their excellent mechanical properties and high-temperature resistance. However, the research on heat-pressing deformation and residual stress during high-temperature and high-pressure heat-pressing processes in CF/PEEK was relatively deficient. In this paper, a framework coupled with crystallization kinetics, micromechanics and thermodynamics was developed to predict the heat-pressing deformations of CF/PEEK and it was conducted by UMAT, DISP and UEXPAN subroutines. Moreover, the predictive model was verified by experiments effectively. Finally, we compared the difference in residual stress distributions between symmetric and asymmetric lay-ups and found that the melting temperature, thickness, angle and sequence of layers have a significant impact on the heat-pressing deformation. This work provided an effective tool for predicting heat-pressing deformations, which is great of significance in the manufacturing and application of CF/PEEK.

Finite element analysis of rockfall impact on pipelines with different erosion resistant coatings

In this paper, the finite element analysis method is used to extensively study the response of rockfall impact on pipelines with different erosion resistant coating. Based on the numerical results, the safety of the pipeline is comprehensively evaluated. Firstly, through the establishment of detailed pipeline and rockfall models, the impact of different rockfall materials and speeds on the pipeline is simulated. The results of the finite element analysis indicate that rockfall impact can cause significant stress concentration and deformation in the pipelines and damage to the coating. With the increment of impact speed, the damage to the pipeline also increases significantly, and different rockfall materials exhibit varying damage conditions, and it is found that fibreglass reinforced epoxy is better than the polyethylene coating. By comparing the analysis results under different conditions, the safety threshold of the pipeline under various rockfall impact scenarios is obtained. This provides an important theoretical basis and reference for the protection design and safety maintenance of the pipeline. The research in this paper not only aids in deepening the understanding of the mechanism of rockfall impact on pipelines but also serves as a valuable reference for improving the safety and reliability of pipeline engineering.

Investigation of printing turn angle effects on structural deformation and stress in selective laser melting

Additive manufacturing (AM) technology facilitates the creation of complex structures, where the printing path significantly impacts thermal distribution, subsequently influencing stress distribution and structural deformation. The primary challenge in path planning is to determine a printing turn angle that ensures uniform thermal distribution, thereby minimizing structural deformation while maintaining printing efficiency. To address this issue, we propose a composite function, which comprehensively characterizes the effects of the printing turn angle and the length of the printing path on the printing results. Combining a specific cubic porous structure, we calculate the maximum (Pmax) and minimum (Pmin) values of the composite function P, and compare the structural deformation and stress of the Pmax and Pmin paths with those of the typical Pzigzag path. Finite element method (FEM) simulation and experimental validation show that the Pmax path achieves significantly lower structural deformation and residual stress compared to the Pzigzag path and Pmin path.

Strengthening Transformer Tank Structural Integrity through Economic Stiffener Design Configurations Using Computational Analysis

Power transformers play a vital role in adjusting voltage levels during transmission. This study focuses on optimizing the structural design of power transformer tanks, particularly high-voltage (HV) tank walls, to enhance their mechanical robustness, performance, and operational reliability. This research investigates various stiffener designs and their impact on stress distribution and deformation through finite element analysis (FEA). Ten different configurations of stiffeners, including thickness, width, type, and position variations, were evaluated to identify the optimal design that minimizes stress and deflection while considering weight constraints. The results indicate that specific configurations, particularly those incorporating 16 mm thick H beams, significantly enhance structural integrity. Experimental validation through pressure testing corroborated the simulation findings, ensuring the practical applicability of the optimized designs. This study’s findings have implications for enhancing the longevity and reliability of power transformers, ultimately contributing to more efficient and resilient power transmission systems.