Deformable Bodies Research Articles

Research on the slip deformation characteristics and improvement measures of concrete-faced rockfill dams on dam foundations with large dip angles

The pumped storage power station (PSPS) is an important measure to achieve the strategic goal of “dual carbon”. As one of the preferred types for the upper reservoir dams of PSPSs, the concrete-faced rockfill dam (CFRD) often has a dam foundation on a steep transverse slop and is prone to produce slip deformation along the slope, resulting in poor anti-sliding stability of the dam slope. It is dangerous for the operation safety of PSPSs. Therefore, the slip deformation of CFRDs on dam foundations with large dip angles is investigated. The mechanism for the initiation of slip deformation is revealed. The design measures of physical mechanic and geometric structure are proposed to reduce slip deformation. The results show that the larger sliding forces and smaller anti-sliding forces are the fundamental reasons that CFRDs on dam foundations with large dip angles are prone to produce slip deformation. The larger the dip angle of the dam foundation, the larger the slip deformation of the dam body and face slab, and the smaller the safety factor of the dam slope. When the dip angle of the dam foundation is greater than 15°, the safety factor of the dam slope is less than the minimum value of 1.5 required by codes. The addition of pressure slopes can effectively reduce the slip deformation of the dam body or face slab and significantly improve the anti-sliding stability of the dam slope. When the height or width of the pressure slope platform is greater and the cohesion or internal friction angle of the pressure slope is larger, the slip deformations of the dam body and face slab are smaller, and the safety factor of the dam slope is greater. It is recommended that the height and width of the pressure slope platform be 1/2 times the maximum height of the main dam, and the density (cohesion and internal friction angle) of the pressure slope be equivalent to that of the main dam’s rockfill material. The research results can provide theoretical and technical support for the design and construction of CFRDs for the upper reservoir of PSPSs.

Capacitive biophysical stimulation improves the healing of vertebral fragility fractures: a prospective multicentre randomized controlled trial

BackgroundCapacitively coupling electric fields (CCEF) is a method of non-invasive biophysical stimulation that enhances fracture repair and spinal fusion. This multicentre randomized controlled trial aimed to further examine the roles of CCEF in (1) the resolution of vertebral bone marrow oedema (VBME) using a follow-up MRI study and (2) pain relief, analgesic drug consumption and quality of life improvement in stimulated patients who were referred with acute vertebral fragility fractures (VFFs) compared to non-stimulated patients.MethodsBetween September 2016 and December 2019, patients who were referred to the spine centres that participated in this multicentre randomized clinical study with acute VFFs of type OF1 or OF2 were included in the present study. All the VFFs were conservatively managed according to Good Clinical Practice. Moreover, the patients were randomized into two groups: the CCEF group received, as an adjunct to the clinical study protocol, biophysical stimulation with a CCEF device (Osteospine, IGEA) for 8 h per day for 60 days, whereas the control group was treated according to the clinical study protocol. At baseline (T0), the 30-day follow-up (T1), the 60-day follow-up (T2), and the 6-month follow-up (T3), each patient underwent clinical evaluation using the Visual Analogue Scale (VAS) for Pain and the Oswestry Disability Index (ODI). Analgesic therapy with paracetamol 1000 mg tablets for 7 days—or longer, depending on the pain intensity—was performed; patients were required to report their paracetamol consumption on a specific sheet between study day 8 to 180 days of follow-up. MRI studies of the thoracolumbar spine were performed at 0 (T0), 30 (T1) and 60 days of follow-up (T2) using a 1.5-T MRI system in all of the centres that took part in the study. For each VBME area examined via MRI, the vertebral body geometry (i.e. anterior wall height/posterior wall height and vertebral kyphosis) were assessed.ResultsA total of 66 patients (male: 9, 13.63%; mean age: 73.15 years old) with 69 VFFs were included in the present study and randomized as follows: 33 patients were included in the control group and the remaining 33 patients were randomized into the CCEF group. In the CCEF group, good compliance with CCEF therapy was observed (adherence = 94%), and no adverse effects were recorded. In the stimulated patients, faster VBME resolution and significantly less vertebral body collapse during follow-up were observed compared to the control patients. Moreover, in the active group, faster pain reduction and improvement in the ODI mean score were observed. Stimulated patients also reported a significantly lower paracetamol consumption rate from the third follow-up after treatment until the 6-month follow-up. In terms of sex-related differences, in the CCEF group, VBME showed a faster resolution in male patients compared with females.ConclusionBiophysical stimulation with CCEF, as an adjunct to traditional conservative treatment, is a useful tool to hasten the VBME resolution process and prevent vertebral body deformation. These MRI findings also correlate with faster back pain resolution and quality of life improvement. From the third follow-up after treatment untilthe 6-month follow-up, stimulated patients reported a significantly lower paracetamol consumption than control patients, even though back pain and quality of life showed no significant differences between the two groups.Level of evidenceII.Trial Registration Register: ClinicalTrials.gov, number: NCT05803681.

ANALYSIS OF THE RESULTS OF PERCUTANEOUS VERTEBROPLASTY OF COMPRESSION FRACTURES OF BODIES OF CHEST AND LUMBAR VERTEBRAE ON THE BACKGROUND OF OSTEOPOROSIS

It is well known that the most frequent complication of osteoporosis is compression fractures of vertebral bodies. In addition to brittleness of the bones and mechanical stress, more and more evidence approving that compression fractures of vertebral bodies are related to many risk factors, such as aging, sex, concomitant morbidities of cardiovascular and cerebrovascular diseases and lifestyle (chronic smoking and alcohol consumption) are collected. Objective. Analyzing the condition of spines of the patients suffering from compression fractures of vertebral bodies on the background of osteoporosis after the performed Percutaneous vertebroplasty (PV). Methods. 553 patients who underwent hospital treatment at the spine pathology clinic of the Sytenko Institute of Spine and Joint Pathology (2005–2022) and underwent PV were examined. Results. The patients were divided into three groups depending on the number of damaged vertebrae. The 1st group included the patients with compression fractures of one vertebra (185 — 33.4 %); the 2nd group included the patients having 2 or 3 deformed vertebrae (216 — 39 %); and the 3rd group included the patients with 4–5 damaged vertebrae (152 — 27.4 %). Stages of compression of vertebral bodies during the X-ray morphometry was as follows before the surgery: I — 349 (24 %) vertebrae; II — 494 (34 %); III — 552 (38 %); and IV — 58 (4 %). We achieved the reduction of the level of compression of vertebral bodies as a result of PV in 20 % of cases (patients who noticed the manifestation of the pain syndrome within 2 weeks mostly suffered from these deformations). Conclusions. The results of analysis of PV of 553 patients with composite material and bone cement in the near and far future provide us an opportunity to state that this surgical treatment is an efficient and safe treatment method (despite the materials used). 40 (24 %) patients out of 165 patients of the group I, 52 (33 %) patients out of 157 patients of the group II and 54 (44 %) patients our of 133 patients of the group III were diagnosed with repeated compression fractures. Summarizing all the above, we should note that the more compression fractures the patient has, the higher the risk of further augmentation of other deformations of vertebral bodies is.

Accuracy and feasibility of 3D virtual dynamic fit technology

PurposeThe research evaluated the feasibility of 3D dynamic fit utilizing female compression tops by comparatively analyzing the virtual and actual dynamic fit.Design/methodology/approachSix female participants were 3D body-scanned and photographed in compression tops in four types of athletic movements (pull-up, kettlebell swing, circle-crunch and sit-up). Fit measurements, waist cross-sectional areas, waist width, waist depth, numerical simulation of clothing pressure (kPa) and objective pressure measurements (kPa) were collected from 3D virtual animation, 3D fit scan data and actual photos with the four types of athletic motions. The data were comparatively investigated between virtual and actual dynamic fit.FindingsThe 3D-animated body was not reflected with human body deformation because only bone structure was changed while maintaining the constant forms of muscle and body surface in athletic movements. Due to this consistency of virtual dynamic fit, there were significant differences with the actual dynamic fit at the top length, shoulder width and waist cross-sectional areas. Also, the virtual dynamic pressure indicated significantly higher levels than the objective dynamic pressure while presenting no significant correlations at the front neckline, breast, lateral waist, upper back, back armhole and back waist.Originality/valueThis study is the first to verify multiple aspects of virtual dynamic fit using 3D digital technology. This study provided useful information about which aspects of the current virtual animation need to be improved to apply in the dynamic fit evaluation.

Novel hybrid rigid-deformable fetal modeling for simulating the vaginal delivery within the second stage of labor

Background and objectiveThe fetal representation as a 3D articulated body plays an essential role to describe a realistic vaginal delivery simulation. However, the current computational solutions have been oversimplified. The objective of the present work was to develop and evaluate a novel hybrid rigid-deformable modeling approach for the fetal body and then simulate its interaction with surrounding fetal soft tissues and with other maternal pelvis soft tissues during the second stage of labor. MethodsCT scan data was used for 3D fetal skeleton reconstruction. Then, a novel hybrid rigid-deformable model of the fetal body was developed. This model was integrated into a maternal 3D pelvis model to simulate the vaginal delivery. Soft tissue deformation was simulated using our novel HyperMSM formulation. Magnetic resonance imaging during the second stage of labor was used to impose the trajectory of the fetus during the delivery. ResultsOur hybrid rigid-deformable fetal model showed a potential capacity for simulating the movements of the fetus along with the deformation of the fetal soft tissues during the vaginal delivery. The deformation energy density observed in the simulation for the fetal head fell within the strain range of 3 % to 5 %, which is in good agreement with the literature data. ConclusionsThis study developed, for the first time, a hybrid rigid-deformation modeling of the fetal body and then performed a vaginal delivery simulation using MRI-driven kinematic data. This opens new avenues for describing more realistic behavior of the fetal body kinematics and deformation during the second stage of labor. As perspectives, the integration of the full skeleton body, especially the upper and lower limbs will be investigated. Then, the completed model will be integrated into our developed next-generation childbirth training simulator for vaginal delivery simulation and associated complication scenarios.

Modified Overset Method in OpenFOAM for Simultaneous Motion and Deformation: A Case Study of a Flexible Flapping Foil

The influence of wing deformation in animal propulsion and motion is an intriguing phenomenon that has contributed to a growing interest in biomimetics in both academia and industry. The study focuses on developing a robust numerical tool for analyzing the motion of biological systems in fluid flows, crucial to understanding fluid-structure interaction (FSI) phenomena. The research introduces a new mesh deformation solver, dynamicOversetZoneFvMesh, designed to address limitations in OpenFOAM's conventional Overset method. This solver enables the application of both rigid body motion and deformation at specified patches within certain zones, allowing for more complex motion scenarios. Through meticulous verification, parallelization, validation, and mesh convergence studies, the modified Overset solver's reliability is confirmed. Two cases are examined: a rigid-body flapping foil and a flexible foil with leading-edge deformation. Results demonstrate the adapted solver's proficiency in managing complex fluid dynamics and accommodating simultaneous motion and deformation. Furthermore, the study reveals that leading-edge flexibility improves the power extraction efficiency of flapping foils, aligning with previous literature. Overall, the research lays the foundation for advancing FSI simulations and opens avenues for addressing previously challenging problems in the field.

Effect of groove angle on the residual stress and deformation of nuclear waste container cylinder body welded by plasma arc welding

AbstractAs an important barrier for high‐level radioactive waste transportation and deep burial disposal, the welding quality of nuclear waste container is particularly important. At present, nuclear waste container is usually manufactured by plasma arc welding. Therefore, in order to manufacture nuclear waste container parts with high quality, based on the finite element simulation software simufact welding, this paper uses a combination of numerical simulation and experimental verification to simulate the temperature field, stress field and deformation of the longitudinal weld of 316L nuclear waste container cylinder body by selecting different welding groove angles. The test results show that the groove angle of the V‐groove increases, the residual stress distribution and size increase, and the deformation increases. The stress value of the I‐shaped groove is between the V‐shaped groove angle of 30° and 45°, but the deformation is the smallest. In practical engineering applications, residual stress and deformation need to be considered comprehensive. Reasonable groove angle plays an important role in controlling residual stress and deformation after welding.

Effect of sound-induced vibrations of the pinna on head-related transfer functions: Experimental and numerical investigations.

Numerical simulations of head-related transfer functions (HRTFs) conventionally assume a rigid boundary condition for the pinna. The human pinna, however, is an elastic deformable body that can vibrate due to incident acoustic waves. This work investigates how sound-induced vibrations of the pinna can affect simulated HRTF magnitudes. The work will motivate the research question by measuring the sound-induced vibrational patterns of an artificial pinna with a high-speed holographic interferometric system. Then, finite element simulations are used to determine HRTFs for a tabletop model of the B&K 5128 head and torso simulator for a number of directions. Two scenarios are explored: one where the pinna is modeled as perfectly rigid, and another where the pinna is modeled as linear elastic with material properties close to that of auricular cartilage. The findings suggest that pinna vibrations have negligible effects on HRTF magnitudes up to 5 kHz. The same conclusion, albeit with less certainty, is drawn for higher frequencies. Finally, the importance of the elastic domain's material properties is emphasized and possible implications for validation studies on dummy heads 1as well as the limitations of the present work are discussed in detail.

Fluidic undulation effects on carangiform swimmers propelled by internal active bending moments

With different shapes and material properties, fish all achieve undulatory swimming gait under the action of internal active muscle stimulation and external fluid forces. Such locomotion can be decomposed into deformation affected by internal and external forces in the body frame and overall translation and rotation solely determined by fluid forces. In order to revisit the undulatory swimming gait, we investigate the hydrodynamic performance of two-dimensional flexible carangiform swimmers with varying stiffnesses and thicknesses, which are driven by the active internal bending moments, and employ the complex orthogonal decomposition and Fourier decomposition methods to quantitatively measure and analyze the proportion of undulation. It is found that standing wave deformation characteristics are prominently observed along fish-like bodies with high stiffness, whereas traveling wave characteristics are more evident in bodies with lower stiffness. The self-propelled fish body demonstrates lateral oscillation and rotation around its center of mass, namely, the heaving and pitching movement, particularly in specimens with high stiffness. The present analysis shows that the heaving and pitching locomotion induced by the fluid significantly increase the traveling wave proportion by modulating the amplitude and phase of the left and right traveling waves viewed in forward frame. We called it fluidic undulation effects (FUE), which is different from the undulation of body deformation. This effect is more pronounced for large stiffnesses and thin airfoils. The standing wave deformation observed with a large stiffness transforms into a traveling wave propulsion pattern, with its traveling wave index even slightly surpassing that of a small-stiffness pattern. Although the efficiency of the standing wave deformation is low, it facilitates a faster forward speed (body lengths per stroke). The positive impact of the FUE on the swimming performance is also confirmed by restricting the recoil motions of the lateral translation and rotation of the body. Furthermore, we observe that there is no undulatory swimming gait that has both the highest energy efficiency and the highest speed.

Biomechanics as support for forensic expert reports in after pedestrian-car collisions

This paper systematically explores the mechanical properties of facial and cranial bones, aiming to contribute to the understanding of brain and cervical spine injuries from a mechanical/biomechanical perspective. The research also seeks to provide insights applicable in forensic practice, bridging the gap for engineering professionals not typi-cally involved in forensic medicine. Strength and stiffness parameters of facial and cra-nial bones were utilized to analyze forces leading to fractures, proposing a simple analyt-ical approach for determining head velocity upon striking a car windshield. Experimental testing was conducted to examine defects on the windshield resulting from an impactor's crash, simulating head impacts at varying velocities. Two approaches for determining head impact velocity during pedestrian-car collisions were explored. The first, neglect-ing body deformation effects, assumes that the manikin's center of gravity moves at the same speed as the impacting vehicle, resulting in an impact velocity that is approximate-ly twice the car's speed. The second, a more realistic scenario, considers slower move-ment of the body's center of gravity, yielding an impact velocity that is about one and a half times the car's speed, with a specific angle relative to the X-axis. Calculation reveals that head impact velocity decreases with reduced windshield inclination at constant ve-hicle speed. Experimental testing with an adult head impactor monitored impact velocity, acceleration, contact time, and puncture diameter and depth on the vehicle glass. Results align closely with published data, emphasizing higher injury risk near the location of fixation of the windshield to the frame of the vehicle. In forensic investigations, the re-search findings, including newly measured or calculated parameters, offer practical ap-plications. Acknowledging simulation limitations, the study emphasizes the reliance on experimental data for a more realistic understanding. Application of knowledge in expert opinions for car crashes with injuries involves considering windshield defect dimen-sions in relation to speed, minimizing the need for revision by expert opinions. This comprehensive exploration contributes to understanding biomechanical factors influenc-ing injuries, particularly in vehicular accidents, and underscores the importance of em-pirical data in forensic practice. The proposed analytical approach and experimental insights provide valuable tools for forensic professionals and contribute to the broader understanding of injury mechanisms.

ЭНЕРГЕТИЧЕСКИЕ СВОЙСТВА СИММЕТРИЧНЫХ ДЕФОРМИРУЕМЫХ СИСТЕМ

Energy methods for calculating structures, which have become popular for a century, are based on the Lagrange principle and have the meaning of equality of work of external forces and internal forces. Having proved their effectiveness in the overwhelming majority of problems of structural mechanics, they became the dominant approach in formulating the problems of studying solid deformable systems and gave rise to the main methodology for solving problems. As a result, a situation has arisen that the internal potential energy of a deformed body remains insufficiently studied.
 The paper develops an approach to the study of the symmetric structure at critical levels of strain energy. The criterion of critical levels of strain energy, based on the concepts of "self-stress" ("self-balance") of a deformable body. Limiting values of the structure strain energy may get by varying the reactions and deflections in the nodal points. The extreme values of forces and displacements of the rods are calculated in matrix form from the values of nodal reactions (displacements).
 Methodology for studying the energy properties of a system is shown on the examples of the study of symmetric rod systems without involving the concept of external forces. The technique is based on matrix methods of structural mechanics and the mathematical apparatus of eigenvalue problems. The comparison of structural design and structural analysis solution of structural mechanics tasks by traditional methods and with the proposed methodology is carried out.

Co-rotational 3D beam element using quaternion algebra to account for large rotations: Formulation theory and static applications

This paper presents a co-rotational beam element based on quaternion algebra as a means of parameterizing large rotations. This co-rotational framework is based on a decomposition of beam kinematics into a rigid element frame, which follows the element and its pure deformation. Once the decomposition between rigid body motion and deformation is obtained, the principle of virtual work allows calculating the element response projected onto large displacements and rotations. This 3D co-rotational element lies within the framework of incremental formulations. The special feature of this formulation pertains to the decomposition of kinematics to extract the rigid body motion and pure deformations through use of quaternion algebra by solving an internal nonlinear kinematic equation. Thus, from the 2 quaternions defining global rotations and the 2 displacement vectors at the ends of the beam, this method is able to extract: 1 quaternion and 1 displacement vector parameterizing the rigid body motion, plus 2 other quaternions defining the internal rotations and beam elongation. The proposed formulation based on quaternion algebra therefore constitutes an alternative to the literature’s treatment of large-rotation kinematics using a quaternion algebra. The operators are also linearized in order to obtain the algorithmic stiffness operator. Eleven distinct static numerical applications are presented, along with comparisons from the literature in the aim of demonstrating the efficiency of this proposed element.

Relationship between Treatment Choices according to the Modified Osteoporotic Fracture Score and Posttreatment Radiographic Outcomes.

Retrospective observational study. To evaluate the modified osteoporotic fracture (mOF) scores in three treatment groups and compare imaging findings in patients treated and not treated according to the mOF score-based treatment recommendation. The osteoporotic fracture (OF) score was established by the AO Spine to guide therapeutic decisions. To enhance its applicability, a mOF score was recently introduced. Consecutive patients diagnosed with OFs at Fujieda Heisei Memorial Hospital were divided into three groups: nonsurgical therapy, balloon kyphoplasty (BKP), and open surgery groups. The mOF score was calculated, and the levels of independence and posttreatment imaging data were compared between patients treated and not treated according to the mOF score-based treatment recommendation. In total, 118 patients were included (nonsurgical therapy, n=57; BKP, n=48; open surgery, n=13), of whom 100 (85%) received treatment consistent with the mOF score-based treatment recommendation. In the BKP and open surgery groups, the mOF scorebased treatment recommendations were consistent with the actual treatment in 93% of the patients. However, in the nonsurgical group, the mOF score-based treatment recommendation was not consistent with the actual treatment in 25% of the patients. In this group, patients not treated according to the mOF score had significantly shorter vertebral body height, greater local kyphosis, and smaller sacral slope after treatment than patients treated according to the mOF score-based treatment recommendation. In the BKP and open surgery groups, the mOF scores were consistent with actual clinical selection. In the nonsurgical therapy group, patients not treated according to the mOF score-based treatment recommendation exhibited severe vertebral body deformity and a less well-balanced spine shape after treatment. The mOF score may help in selecting suitable treatments for OFs.

2-DOF Woven Tube Plane Surface Soft Actuator Using Extensional Pneumatic Artificial Muscle

Soft actuators, designed for fragile item conveyance and navigation in complex environments, have garnered recent attention. This study proposes a cost-effective soft actuator, created by weaving tubes into twill patterns, capable of transportation and movement. The actuator achieves this by inducing traveling waves on its upper and lower surfaces through sequential pressurization of tubes. Notably, its fabrication does not require specialized molds, contributing to cost efficiency. The single actuator generates traveling waves with two degrees of freedom. Conventional silicone tube-based actuators demonstrate slow transport speeds (3.5 mm/s). To address this, this study replaced silicone tubes with pneumatic artificial muscles, enhancing overall body deformation and actuator speed. Experiments involving both extensional and contractional artificial muscles demonstrated that soft actuators with extensional artificial muscles significantly improved transportation and movement speed to 8.0 mm/s.

Numerical modeling of structural body deformation under free surface flow based on volume of fluid–discrete element method coupling

In this work, we proposed a numerical model based on the coupling of the volume of fluid–discrete element method and bond particle method (BPM). The simulation of particle bonding and the structural body formation process had been presented, and the inter-particle bonding mechanism was introduced. We also tested dam-busting impact elastic and wedge plates at high Reynolds numbers (1.26 × 107 and 2.16 × 106) and compared the results with numerical simulations. The results show that the model has mean errors of 3.9% and 6.5% for the large and the micro-deformations, respectively. It is in perfect agreement with the curve trends of the test and keeps good convergence for different particle sizes. In addition, we also used the model used to study the hydrodynamic changes in underwater box net structures in offshore aquaculture, and the deformation kinematic properties of box nets under different material strengths were evaluated. This numerical model of this study provides the effective theoretical support and engineering guidance for the further study of the behavior of structural bodies under hydrodynamic action.

Study on precursor information and disaster mechanism of sudden change of seepage in mining rock mass

Abstract Changes in the stress field and seepage field of mining unloading are one of the important causes of deformation and destabilization of the rock body of the bottom slab. With the increase of mining intensity and depth, the disaster of water influx on the bottom plate under the dual action of mining unloading and pressurized water has become one of the main problems restricting the efficient and safe mining of coal. Based on the research background of confined water inrush from Ordovician limestone floor in North China Coalfield, the numerical analysis revealed that mining unloading concentrates stresses, increases deformation, and increases the plastic zone and permeability range. Based on laboratory acoustic emission and mechanical tests, it is found that the peak of acoustic emission ringing number can be one of the precursor information of limestone seepage mutation. This study reveals the evolution law of rock body deformation and permeability under the unloading path, and the research obtains the unloading seepage and water gushing disaster mechanism of the subgrade rock body.

Computational design of ultra-robust strain sensors for soft robot perception and autonomy

Compliant strain sensors are crucial for soft robots’ perception and autonomy. However, their deformable bodies and dynamic actuation pose challenges in predictive sensor manufacturing and long-term robustness. This necessitates accurate sensor modelling and well-controlled sensor structural changes under strain. Here, we present a computational sensor design featuring a programmed crack array within micro-crumples strategy. By controlling the user-defined structure, the sensing performance becomes highly tunable and can be accurately modelled by physical models. Moreover, they maintain robust responsiveness under various demanding conditions including noise interruptions (50% strain), intermittent cyclic loadings (100,000 cycles), and dynamic frequencies (0–23 Hz), satisfying soft robots of diverse scaling from macro to micro. Finally, machine intelligence is applied to a sensor-integrated origami robot, enabling robotic trajectory prediction (<4% error) and topographical altitude awareness (<10% error). This strategy holds promise for advancing soft robotic capabilities in exploration, rescue operations, and swarming behaviors in complex environments.

Transient Response of Macroscopic Deformation of Magnetoactive Elastomeric Cylinders in Uniform Magnetic Fields.

Significant deformations of bodies made from compliant magnetoactive elastomers (MAE) in magnetic fields make these materials promising for applications in magnetically controlled actuators for soft robotics. Reported experimental research in this context was devoted to the behaviour in the quasi-static magnetic field, but the transient dynamics are of great practical importance. This paper presents an experimental study of the transient response of apparent longitudinal and transverse strains of a family of isotropic and anisotropic MAE cylinders with six different aspect ratios in time-varying uniform magnetic fields. The time dependence of the magnetic field has a trapezoidal form, where the rate of both legs is varied between 52 and 757 kA/(s·m) and the maximum magnetic field takes three values between 153 and 505 kA/m. It is proposed to introduce four characteristic times: two for the delay of the transient response during increasing and decreasing magnetic field, as well as two for rise and fall times. To facilitate the comparison between different magnetic field rates, these characteristic times are further normalized on the rise time of the magnetic field ramp. The dependence of the normalized characteristic times on the aspect ratio, the magnetic field slew rate, maximum magnetic field values, initial internal structure (isotropic versus anisotropic specimens) and weight fraction of the soft-magnetic filler are obtained and discussed in detail. The normalized magnetostrictive hysteresis loop is introduced, and used to explain why the normalized delay times vary with changing experimental parameters.

Data-Driven Unsteady Aerodynamic Modeling for Fluid–Structure Interaction

The piston theory class of simplified aerodynamic models that link body deformation to localized pressure fluctuation with respect to a mean steady state is attractive for modeling purposes as they constitute a computationally efficient model to calculate the unsteady pressure response on deforming bodies. However, as piston theories are valid for flow regimes where M>1.5, they are inaccurate for modeling the aerodynamic response associated with aeroelastic phenomena in subsonic or low-supersonic flow regimes. Unsteady computational fluid dynamics (CFD) simulations are used to learn the unsteady pressure response, and dynamic mode decomposition (DMD) is applied to the error between the CFD-computed pressure fluctuation and the piston-theory-predicted pressure fluctuation. This process is performed on two-dimensional and three-dimensional flow domains over various flow regimes. For both scenarios, the DMD analysis learns dominant spatial modes in the error that constitute low-order models, which may be used to improve the pressure response and are confirmed to be physically relevant. A method for computing aeroelastic stability with these leading modes is discussed and applied to fluid–structural beam and panel configurations. The results are compared against prior numerical and experimental investigations to quantify the improvement in prediction obtained by the DMD-augmented piston theory.

Body dysmorphic disorder in adult orthodontic treatment candidates according to the index of treatment need

Objectives: Body image perception plays an important role in seeking orthodontic treatment. Body dysmorphic disorder (BDD) is a psychological condition where an individual constantly focuses on flaws in their appearance. This study aimed to assess BDD in adult orthodontic treatment candidates according to the index of treatment need (IOTN) in Qazvin city in 2020. Material and Methods: This descriptive study was conducted on 404 eligible patients over 18 years of age presenting to dental clinics in Qazvin seeking orthodontic treatment. The patients were categorized according to their IOTN (grades 1–5) and filled out the Body Deformation Metacognition Questionnaire (BDMCQ). Data were analyzed by t-test and Analysis of Variance using the Statistical Package for the Social Sciences. Results: Of all the patients, 50.2% were grade 1 (no need for treatment),and 1.5% were grade 5 (very great need for treatment). Furthermore, 54.5% of patients had severe BDD. BDD had no significant correlation with gender or marital status (P &gt; 0.05). BDD was significantly correlated with age, educational level, and IOTN grade (P &lt; 0.05). Conclusion: The present results revealed that over 50% of patients seeking orthodontic treatment did not need treatment, according to the IOTN. Dental clinicians are advised to be more careful in accepting patients with a history of psychological problems and numerous surgical procedures who seek cosmetic treatments.