Mechanical Finite Element Model Research Articles

Residual stress relief strategy in thick steel weldments via local induction heat treatment: Simulation and neutron diffraction experiment

This study investigated the effect of local induction post-weld heat treatment (PWHT) on residual stress relief in thick submerged arc welded steel plates. A combination of numerical and neutron diffraction methods was used to examine the effect of various PWHT parameters, such as annealing temperature and holding time, on the relief of residual stress in welded plates with various thicknesses. A sequentially coupled thermal–mechanical finite element model was used to calculate the residual stress distribution in welded AH36 steel plates before and after PWHT. The model was validated by comparing its predictions with the experimental measurements, and the results showed good agreement. The residual stress of the thick welded plates was effectively reduced via PWHT with local induction. The primary mechanism for this stress release was identified as stress relaxation caused by creep strain. Furthermore, a process map was established considering the PWHT conditions and plate geometry. This map provides a means of determining the optimal PWHT conditions to achieve desired stress reduction levels.

Superior Polyurethane-Based Seamless Expansion Joints for Bridges: Mechanical Properties, Full-Scale Test, and Finite Element Modeling

Superior Polyurethane-Based Seamless Expansion Joints for Bridges: Mechanical Properties, Full-Scale Test, and Finite Element Modeling

A computational modelling tool for prediction of head reshaping following endoscopic strip craniectomy and helmet therapy for the treatment of scaphocephaly

BackgroundEndoscopic strip craniectomy followed by helmet therapy (ESCH) is a minimally invasive approach for correcting sagittal craniosynostosis. The treatment involves a patient-specific helmet designed to facilitate lateral growth while constraining sagittal expansion. In this study, finite element modelling was used to predict post-treatment head reshaping, improving our comprehension of the necessary helmet therapy duration. MethodSix patients (aged 11 weeks to 9 months) who underwent ESCH at Connecticut Children's Hospital were enrolled in this study. Day-1 post-operative 3D scans were used to create skin, skull, and intracranial volume models. Patient-specific helmet models, incorporating areas for growth, were designed based on post-operative imaging. Brain growth was simulated through thermal expansion, and treatments were modelled according to post-operative Imaging available. Mechanical testing and finite element modelling were combined to determine patient-specific mechanical properties from bone samples collected from surgery.Validation compared simulated end-of-treatment skin surfaces with optical scans in terms of shape matching and cranial index estimation. ResultsComparison between the simulated post-treatment head shape and optical scans showed that on average 97.3 ± 2.1 % of surface data points were within a distance range of −3 to 3 mm. The cranial index was also accurately predicted (r = 0.91). ConclusionsIn conclusion, finite element models effectively predicted the ESCH cranial remodeling outcomes up to 8 months postoperatively. This computational tool offers valuable insights to guide and refine helmet treatment duration. This study also incorporated patient-specific material properties, enhancing the accuracy of the modeling approach.

Design, fabrication, and characterization of kinetic-inductive force sensors for scanning probe applications.

We describe a transducer for low-temperature atomic force microscopy based on electromechanical coupling due to a strain-dependent kinetic inductance of a superconducting nanowire. The force sensor is a bending triangular plate (cantilever) whose deflection is measured via a shift in the resonant frequency of a high-Q superconducting microwave resonator at 4.5 GHz. We present design simulations including mechanical finite-element modeling of surface strain and electromagnetic simulations of meandering nanowires with large kinetic inductance. We discuss a lumped-element model of the force sensor and describe the role of an additional shunt inductance for tuning the coupling to the transmission line used to measure the microwave resonance. A detailed description of our fabrication is presented, including information about the process parameters used for each layer. We also discuss the fabrication of sharp tips on the cantilever using focused electron beam-induced deposition of platinum. Finally, we present measurements that characterize the spread of mechanical resonant frequency, the temperature dependence of the microwave resonance, and the sensor's operation as an electromechanical transducer of force.

Distribution and Characteristics of Residual Stresses in Super Duplex Stainless Steel Pipe Weld

This paper explores the distribution and features of residual stresses formed by super duplex stainless steel pipe welding. Experimental investigations, which encompass an elevated temperature tensile test and metallographic observation along with a hardness test and residual stress measurement, were first conducted to obtain the mechanical properties at high base metal temperatures and to confirm whether or not the duplex stainless steel undergoes martensitic phase development during the welding process. Finally, experiments were performed to scrutinize the residual stress evolution through the metallurgical phase transformation in the weld region and its vicinity. A sequentially coupled 3D thermal, mechanical and metallurgical finite element (FE) model capable of incorporating the experimental consequences was established next. A 3D FE simulation of the girth welding process was conducted, and the axial and hoop residual stress profiles along the girth were evaluated. The results substantiate that martensitic phase evolution occurs in the process of cooling during the welding of super duplex stainless steel, and they also highlight the significance of taking the metallurgical phase transformation into account in the numerical reproduction of the girth welding process for the accurate expression of weld-induced residual stresses, which is especially important for precisely predicting hoop residual stresses.

Circular recycled aggregate concrete-filled stainless steel tube stub columns after exposure to fire: Experiments, simulations, and design

This paper presents experimental and numerical investigations into the post-fire cross-section compressive behaviour and resistances of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. Twelve stub column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating and cooling of specimens, cylinder tests and post-fire tensile coupon tests and stub column tests. The test results, including load–end shortening curves, failure loads and failure modes, were fully reported and the initial compressive stiffnesses and confinement effect were discussed. The numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data. Given the absence of design codes for stainless steel–recycled aggregate concrete composite structures after exposure to fire, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as set out in the European code, Australia/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to circular RACFSST stub columns after exposure to fire, based on the test and numerical data. The assessment results generally revealed that the European code and the Australian/New Zealand standard led to an acceptable level of design accuracy and consistency, while the American specification resulted in rather conservative and scattered post-fire cross-section compression resistance predictions.

Post-fire behaviour and resistances of square recycled aggregate concrete-filled stainless steel tube stub columns

Experimental and numerical studies on the cross-section compressive behaviour and residual resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns after exposure to fire are reported in this paper. An experimental programme was firstly carried out on twelve stub column specimens with three recycled coarse aggregate replacement ratios (0%, 35% and 70%) after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The test results, including load–end shortening curves, failure loads and failure modes, were presented, with the initial compressive stiffness and confinement effect analysed. The experimental programme was followed by a numerical modelling programme, where thermal and mechanical finite element models were developed and validated against the test results and afterwards used to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions. Based on the test and numerical data, the relevant design rules for square natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as specified in the European code, Australia/New Zealand standard and American specification, were evaluated, using post-fire material properties, for their applicability to square RACFSST stub columns after exposure to fire. The evaluation results generally revealed that the European code and Australian/New Zealand standard led to a good level of design accuracy, while the American specification resulted in slightly conservative post-fire cross-section compression resistance predictions.

Research on casing damage mechanism and prevention and control under creep behavior of salt-gypsum layer

As a good cap rock, the salt-gypsum layer often contains abundant oil and gas resources, but it has strong plastic flow and creep properties, resulting in frequent casing damage problems. Therefore, a new method is proposed to prevent and control casing failure in creep formation by using solid expandable tubular (SET). Based on the Heard model, the creep behavior of formation was described. The expansion experiment of the SET, the material tensile experiment of casing and SET with different expansion rates were carried out. The three-dimensional mechanical model and finite element model of casing-cement sheath- (SET) -formation were established. Numerical simulation of creep behavior of salt-gypsum layer under non-uniform in-situ stress was carried out. Comparative study of casing damage mechanism in two cases with or without SET prevention and control. The influence of sensitive factors such as SET wall thickness and expansion rate on the failure behavior of casing prevented and controlled by SET were analyzed. The results show that (1) In the direction of the maximum horizontal in-situ stress, the stress on the outer surface of the casing is large. In the direction of the minimum horizontal in-situ stress, the stress on the inner surface of the casing is the largest, and the material yield failure occurs first at this position of the casing. The compression deformation of casing is greater than the tensile deformation. The casing is oval after deformation. (2) By increasing steel grade and wall thickness of casing, the service time of the casing under creep behavior of salt-gypsum layer can be prolonged. However, while increasing cost and reducing diameter, it has not played a role in preventing casing failure. (3) By using the method of SET prevention and control, the casing stress is more evenly distributed, the maximum stress is effectively reduced, the stress growth rate is slowed down, and the external collapse resistance ability is significantly enhanced. The maximum stress of the casing is reduced by up to 24.96 %. The larger the wall thickness of the SET, the better the prevention and control effect, and the longer the service time of the casing. The increase of the ultimate wall thickness of the SET with high expansion rate can effectively make up for its poor prevention and control effect. (4) The new method of adding the SET between salt-gypsum layer and cement sheath has the advantages of increasing casing inner diameter, optimizing wellbore structure, reducing cost and wellbore risk. The research results can provide some reference value for the prevention and control of casing failure in creep salt-gypsum layer.

Artificial neural network surrogate modeling for uncertainty quantification and structural optimization of reinforced concrete structures

AbstractOptimization approaches are important to design sustainable structures. In structural mechanics, different design objectives can be defined, for example, to minimize the required construction material or to maximize the structural durability. In this paper, the durability of a reinforced concrete (RC) structure is assessed by advanced finite element (FE) models to simulate the cracking behavior and the chloride transport process. The corrosion initiation time is used as durability measure to be maximized within an optimization approach, where the concrete cover is defined as design variable. The variability of structural loads and material parameters and unavoidable construction imprecision leads to a probabilistic reliability and durability assessment, where aleatory as well as epistemic uncertainties are quantified by random variables, intervals and probability‐boxes. The FE simulation models cannot directly be applied to structural analyses and optimizations with polymorphic uncertain parameters and design variables because of the high computational demand of the multi‐loop algorithm (Monte Carlo simulation, interval analysis, global optimization). In this paper, a new surrogate modeling strategy is presented, where artificial neural networks are trained sequentially to speed‐up the coupled mechanical and transport simulation FE models. The new approach is applied to the uncertainty quantification and the structural durability optimization of a RC structure.

Exploring the Biomedical Potential of PLA/Dysprosium Phosphate Composites via Extrusion-Based 3D Printing: Design, Morphological, Mechanical, and Multimodal Imaging and Finite Element Modeling.

The present investigation demonstrates the feasibility of dysprosium phosphate (DyPO4) as an efficient additive in polylactide (PLA) to develop 3D printed scaffolds through the material extrusion (MEX) principle for application in bone tissue engineering. Initially, uniform sized particles of DyPO4 with tetragonal crystal setting are obtained and subsequently blended with different concentrations of PLA to extrude in the form of filaments. A maximum of 20 wt % DyPO4 in PLA matrix has been successfully drawn to yield a defect free filament. The resultant filaments were 3D printed through material extrusion methodology. The structural and morphological analysis confirmed the successful reinforcement of DyPO4 throughout the PLA matrix in all of the 3D printed components. All of the PLA/DyPO4 composites exhibited magnetic resonance imaging and computed tomography contrasting properties, which were dependent on the dysprosium content in the PLA matrix. The detailed mechanical evaluation of the 3D printed PLA/DyPO4 composites ensured good strength accomplished by the reinforcement of 5 wt % DyPO4 in PLA matrix, beyond which a gradual decline in the strength is noticed. Representative volume elements models were developed to realize the intrinsic property of the PLA/DyPO4 composite, and finite element analysis under both static and dynamic loading conditions has been performed to account for the reliability of experimental results.

Modeling and Control of a 5-DOF Parallel Continuum Haptic Device

In this article, we propose a new continuum robotics approach for haptic rendering and comanipulation. This approach is illustrated using a robotic interface with six motorized fixed axes connected by deformable beams, in parallel, to an end effector with 5 degrees of freedom. Apart from the rotation of the motors, this design has no articulation, and the motion of the end effector is achieved by deformation of the beams. The flexible beams are equipped with bending sensors, and the motors have encoders. We use a nonlinear finite element mechanical model of the robot based on a mesh of beam elements that is computed in real time at 20 Hz. The bending sensors are incorporated into the model, which allows us to obtain an accurate estimate of the force exerted by the user on the end effector. The model enables a new methodology for calculating the workspace of the continuum haptic device. The model also is propagated to a higher frequency loop (500 Hz), which performs sensing and control of the robot at high rates, using an admittance-type control to command new positions of the actuators. We show that this control methodology allows haptic rendering of virtual walls that are stiffer than the natural stiffness of the robot. Finally, we demonstrate the use of the device for simple comanipulation tasks.

Virtual Design of 3D-Printed Bone Tissue Engineered Scaffold Shape Using Mechanobiological Modeling: Relationship of Scaffold Pore Architecture to Bone Tissue Formation.

Large bone defects are clinically challenging, with up to 15% of these requiring surgical intervention due to non-union. Bone grafts (autographs or allografts) can be used but they have many limitations, meaning that polymer-based bone tissue engineered scaffolds (tissue engineering) are a more promising solution. Clinical translation of scaffolds is still limited but this could be improved by exploring the whole design space using virtual tools such as mechanobiological modeling. In tissue engineering, a significant research effort has been expended on materials and manufacturing but relatively little has been focused on shape. Most scaffolds use regular pore architecture throughout, leaving custom or irregular pore architecture designs unexplored. The aim of this paper is to introduce a virtual design environment for scaffold development and to illustrate its potential by exploring the relationship of pore architecture to bone tissue formation. A virtual design framework has been created utilizing a mechanical stress finite element (FE) model coupled with a cell behavior agent-based model to investigate the mechanobiological relationships of scaffold shape and bone tissue formation. A case study showed that modifying pore architecture from regular to irregular enabled between 17 and 33% more bone formation within the 4-16-week time periods analyzed. This work shows that shape, specifically pore architecture, is as important as other design parameters such as material and manufacturing for improving the function of bone tissue scaffold implants. It is recommended that future research be conducted to both optimize irregular pore architectures and to explore the potential extension of the concept of shape modification beyond mechanical stress to look at other factors present in the body.

Biomechanical properties of artificial bones made by Sawbones: A review.

Biomedical engineers and physicists frequently use human or animal bone for orthopaedic biomechanics research because they are excellent approximations of living bone. But, there are drawbacks to biological bone, like degradation over time, ethical concerns, high financial costs, inter-specimen variability, storage requirements, supplier sourcing, transportation rules, etc. Consequently, since the late 1980s, the Sawbones® company has been one of the world's largest suppliers of artificial bones for biomechanical testing that counteract many disadvantages of biological bone. There have been many published reports using these bone analogs for research on joint replacement, bone fracture fixation, spine surgery, etc. But, there exists no prior review paper on these artificial bones that gives a comprehensive and in-depth look at the numerical data of interest to biomedical engineers and physicists. Thus, this paper critically reviews 25 years of English-language studies on the biomechanical properties of these artificial bones that (a) characterized unknown or unreported values, (b) validated them against biological bone, and/or (c) optimized different design parameters. This survey of data, advantages, disadvantages, and knowledge gaps will hopefully be useful to biomedical engineers and physicists in developing mechanical testing protocols and computational finite element models.

Physics-based corrosion reliability analysis of miter gates using multi-scale simulations and adaptive surrogate modeling

Stress corrosion cracking (SCC) initiation is usually simulated at the mesoscale, and these computations are usually expensive. This is made more computationally challenging or impossible when such simulations are coupled with a macroscale structural model required for reliability analysis, due to the sources of uncertainty from both scales. This paper tackles this computational barrier to perform physics-based corrosion reliability analysis of large structures using mesoscale simulations via a novel, adaptive surrogate modeling framework. A global surrogate model of the structure is first constructed from a finite element (FE) mechanical model to propagate various sources of input uncertainty at the macroscale to the local stress responses. After that, a mesoscale surrogate model is constructed from phase-field (PF) simulations to predict the failure probability of a given location by accounting for uncertainty in both the macroscale and mesoscale models. In order to guarantee the accuracy of the mesoscale surrogate model and reduce the number of PF simulations, an adaptive surrogate modeling method is proposed using importance sampling (IS) and active learning to refine iteratively the surrogate model in critical regions. Corrosion reliability analysis of a miter gate structure is adopted to demonstrate the efficacy of the proposed method. The result shows that the proposed framework can efficiently and accurately generate a failure probability map for a large structure like a miter gate based on computationally expensive mesoscale PF simulations. In addition, the proposed method is more accurate and converges faster than existing surrogate model-based reliability analysis algorithms.

Comparative study of thermal breakage of annealed and tempered glazing with different thicknesses under uniform radiation conditions

Glass façades are extensively used in high-rise buildings; however, glass panes may break and fall out when subjected to transient heating from a fire, likely altering the fire dynamics both within and outside the building. This work tested annealed glass (non-tempered) and fully tempered glazing with different thicknesses of 6, 10, 12, 15 and 19 mm under uniform incident radiation of 50 kW/m2. Parameters measured included glass surface temperature, breakage time, fracture behaviour, and incident heat flux to study the different phenomena between annealed and tempered glass. A finite element method (FEM) thermal and mechanical model of annealed and tempered glass considering the glass prestress field was developed to deepen the understanding of the coupling between the internal prestress and thermal stresses under uniform radiation conditions. The simulated glass surface temperature distributions are in reasonable agreement with the measured values, with relative errors of 1.8% (annealed glass) and 2.2% (tempered glass) in terms of breakage times, thus partially validating the glazing heat transfer model. A sequential thermal-mechanical method was then used to predict the glass breakage times, with average relative errors of 10.5% and 12.2% between the predicted and measured results for the annealed and tempered glasses, respectively, regardless of glazing thicknesses. It was established that maximum tensile stresses were located at the edge's centre on the radiation-exposed-side surface for annealed glass; for tempered glass, the maximum stresses were in a region approximately 0.3 of the thickness from the heated side surface, where the cracks are prone to initiating. The time needed to overcome the compressive prestress with thermal tensile stress resulting from transient heating is considered the primary reason for the enhanced ability of tempered glazing to resist fracture, which was approximately double that of annealed glass under the conditions studied in this work.

Adaptive Neuro-Fuzzy-Based Models for Predicting the Tribological Properties of 3D-Printed PLA Green Composites Used for Biomedical Applications.

Tribological performance is a critical aspect of materials used in biomedical applications, as it can directly impact the comfort and functionality of devices for individuals with disabilities. Polylactic Acid (PLA) is a widely used 3D-printed material in this field, but its mechanical and tribological properties can be limiting. This study focuses on the development of an artificial intelligence model using ANFIS to predict the wear volume of PLA composites under various conditions. The model was built on data gathered from tribological experiments involving PLA green composites with different weight fractions of date particles. These samples were annealed for different durations to eliminate residual stresses from 3D printing and then subjected to tribological tests under varying normal loads and sliding distances. Mechanical properties and finite element models were also analyzed to better understand the tribological results and evaluate the load-carrying capacity of the PLA composites. The ANFIS model demonstrated excellent compatibility and robustness in predicting wear volume, with an average percentage error of less than 0.01% compared to experimental results. This study highlights the potential of heat-treated PLA green composites for improved tribological performance in biomedical applications.

Failure analysis of overheated coil leakage in ethylene cracking furnace

The ethylene cracking furnace is the core equipment of ethylene production plants. The safe and efficient operation of the furnace is essential for the production of ethylene and other raw materials. This article analyses the finned tube cracking failure on the convection portion of the ethylene cracking furnace. In order to find out the radical causes of the failure, Metallography, microcracking, chemical composition, mechanical property testing, hardness testing, and finite element modeling were adopted. The original fracture shows a characteristic of columnar crystal cracks with the presence of discontinuous fatigue striations, which is consistent with corrosion fatigue cracks. The fracture area at the tip of the crack shows a dimple fracture pattern, which is a characteristic of plastic cracking. At the same time, a large amount of chromium carbide precipitates at grain boundaries, indicating the presence of intergranular corrosion. Moreover, it worked under conditions of thermal stress and corrosive media. These indicate that corrosion fatigue and intergranular corrosion lead to the cracking of the finned tubes.

Study on the vertical bearing performances of piles on karst cave

Caves affected the load transfer mechanism of bridge pile foundation, and then the safety of the bridge was threatened. This study was to investigate the effect of karst cave under bridge pile foundations on the vertical bearing characteristics of bridge pile foundations by static load test, finite element analysis and mechanical model. The settlement of the pile was measured by displacement meter, and the axial force were measured by stress gauges in the test. The load-settlement, the axial force, the unit skin friction and the ratios of side and tip resistances were compared with the result of the simulation. Then sixteen conditions were selected in finite element analysis, one of them was a conventional pile not on cave. The others were about five kinds of height, five kinds of span and six kinds roof’s thickness of the cave. The simply supported and fixed wide beam were established to calculate the allowance roof thickness. The results reveal that when the cave span is greater than 9 m × 9 m or the roof thickness is less than 2 D (pile diameter), the stress and deformation of piles are significantly affected.

Fracture toughness of fibrin gels as a function of protein volume fraction: Mechanical origins.

The mechanical stability of blood clots necessary for their functions is provided by fibrin, a fibrous gel. Rupture of clots leads to life-threatening thrombotic embolization, which is little understood. Here, we combine experiments and simulations to determine the toughness of plasma clots as a function of fibrin content and correlate toughness with fibrin network structure characterized by confocal and scanning electron microscopy. We develop fibrin constitutive laws that scale with fibrin concentration and capture the force-stretch response of cracked clot specimens using only a few material parameters. Toughness is calculated from the path-independent J* integral that includes dissipative effects due to fluid flow and uses only the constitutive model and overall stretch at crack propagation as input. We show that internal fluid motion, which is not directly measurable, contributes significantly to clot toughness, with its effect increasing as fibrin content increases, because the reduced gel porosity at higher density results in greater expense of energy in fluid motion. Increasing fibrin content (1→10mg/mL) results in a significant increase in clot toughness (3→15N/m) in accordance with a power law relation reminiscent of cellular solids and elastomeric gels. These results provide a basis for understanding and predicting the tendency for thrombotic embolization. STATEMENT OF SIGNIFICANCE: Fibrin, a naturally occurring biomaterial, is the major determinant of the structural and mechanical integrity of blood clots. We determined that increasing the fibrin content in clots, as in some thrombi and fibrin-based anti-bleeding sealants, results in an increase in clot toughness. Toughness corresponds to the ability to resist rupturing in the presence of a defect. We couple bulk mechanical testing, microstructural measurements, and finite element modeling to capture the force-stretch response of fibrin clots and compute toughness. We show that increased fibrin content in clots reduces porosity and limits fluid motion and that fluid motion drastically alters the clot toughness. These results provide a fundamental understanding of blood clot rupture and could help in rational design of fibrin-containing biomaterials.

Topology optimization of single and double panels for improved sound insulation in specific frequency bands

Single and double panels are commonly employed in noise control, e.g., as partitioning elements between rooms and to enclose noisy machines. In presence of narrowband disturbances, related for example to rotating machines, further improvements in sound insulation can be obtained by properly distributing the material within the area of the panels. This allows maximizing the sound Transmission Loss (TL) in the frequency band of interest by controlling structural resonances and antiresonances. In order to achieve this goal, in this work, we apply numerical topology optimization to find the optimal material thickness distribution for single and double panels. In the iterative design process, single panels are schematized through a simple mechanical Finite Element (FE) model, while double panels are modelled considering the vibroacoustic coupling between the two mechanical plates and the internal acoustic air cavity. The sound insulation properties of the designed solution are evaluated by TL computations through hybrid Finite Element-Statistical Energy Analysis (FE-SEA) simulations. The method is applied targeting different frequency bands in the audible range and focusing on practically relevant design cases, such as single and double PMMA and glazing panels.