Rotational Deformity Research Articles

Oblique anterior pelvic external fixator for intraoperative reduction of rotationally unstable pelvic ring injuries.

Incomplete sacroiliac joint injuries are often associated with external rotation and extension deformities on the injured hemipelvis. To appropriately correct this deformity, an oblique reduction force from caudal to cranial and lateral to medial is helpful. These injuries are often associated with traumatic disruption of the pubic symphysis. However, in injuries without traumatic disruption to the pubic symphysis, a two-pin oblique anterior external fixator can be used to obtain and maintain reduction of the sacroiliac joint, while percutaneous fixation is subsequently placed. Through a small case series and three specific patient examples, we demonstrate that the oblique anterior external fixator frame is a simple and effective strategy with the reduction and stabilization process of these multiplanar hemipelvis deformities.

Melt‐Extruded Thermoplastic Liquid Crystal Elastomer Rotating Fiber Actuators

AbstractUntethered soft fiber actuators are advancing toward next‐generation artificial muscles, with rotating polymer fibers allowing controlled rotational deformations and contractions accompanied by torque and longitudinal forces. Current approaches, however, are based either on non‐recyclable and non‐reprogrammable thermosets, exhibit rotational deformations and torques with inadequate actuation performance, or involve intricate multistep processing and photopolymerization impeding scalable fabrication and manufacturing of millimeter‐thick fibers. Here, the melt‐extrusion and drawing of a 50 m long thermoplastic liquid crystal elastomer fiber with a ≈1.3 mm diameter on a large scale is reported. With the responsive thermoplastic material, rotating actuators are fabricated via easily exploited programming freedom resulting in large, reversible rotational deformations and torques. The actuation performance of the twisted fibers may be controlled by the programmed twisting density without complicated preparation steps or photocuring being required. The thermoplastic behavior enables fabrication of plied fibers, demonstrated as a triple helical twisted rope constructed from individual rotating fibers delivering up to three times as great rotational and longitudinal forces capable of reversibly opening and lifting a screw cap vial. Besides the programmability, the thermoplastic material employed lends itself to be completely reprocessed into other configurations with self‐healing properties in contrast to thermosets.

Experimental study and numerical simulation on the transverse force transmission mechanism of discretely connected precast RC floor

An innovative discretely connected precast RC floor (DCPCF) is presented, in which precast flat slabs (solid slab, sandwich slab or hollow slab) and spandrel beams (walls) are the basic components that connected by distributed mechanical connectors. The experimental program consisting six full-scaled DCPCF specimens and two cast-in-situ slab (CIS) specimens were conducted to evaluate the influence of slab joint structure on force transmission mechanism of DCPCF in orthogonal slab laying direction (OSLD), which in terms of the failure mode, deflection, strain development, etc. The results revealed that the slab joint connectors of DCPCF had good force transmission performance in OSLD, which can effectively transmit the flexural moment and connect the adjacent precast slab. Compared with CIS specimens, DCPCF specimens had no obvious plastic stage and entered elastoplastic stage earlier. The deflection of DCPCF in OSLD was mainly caused by the opening deformation of the slab joint and the rotational deformation of the precast slabs. For DCPCF specimens, the more connectors in each slab joints or the fewer slab joints, the greater the flexure stiffness in OSLD. Based on the test results, finite element models (FEMs) were developed to simulate force transmission mechanism of DCPCF in OSLD, and the accuracy was confirmed by the test results. Finally, it was verified that increasing the number of anchor bars and increasing the diameter of diagonal anchor bars can effectively enhance the anchoring measures of slab joint connectors to achieve replaceability of perforated steel plates.

Multiple hazards vibration control of jacket offshore wind turbines equipped with amplifying damping transfer systems: Winds, waves, and earthquakes

This paper investigated the vibration control problem of jacket offshore wind turbines (JOWTs) caused by multi-hazards including winds, waves, and earthquakes through amplifying damping transfer system (ADTS), which transfers the rotation of upper turbine tower to the jacket platform, making it convenient to install viscous dampers to dissipate external energy. Moreover, ADTS significantly amplifies the rotation deformation to fully drive the viscous damper. Different from traditional tuned mass damper (TMD) which may lose its effectiveness for higher modes, ADTS provides additional damping to both fundamental and higher modes of JOWT, resulting in better performance in resisting multiple hazards. For example, the displacements of turbine tower in JOWTs subjected to winds, waves, and earthquakes are mitigated by about 23.05%, 63.41%, and 48.96%, respectively; in the meantime, the turbine accelerations subjected to those hazards are also reduced by about 34.28%, 62.72%, and 35.27%. Moreover, ADTS also provides considerably response reduction effect to the supporting jacket of JOWTs.

Comparative study on failure mechanism of multi-storey planar composite frames with RC beams to CFST columns subjected to compartment fire

This paper presents a theoretical study of the failure mechanism of planar composite frames composed of reinforced concrete (RC) beams to concrete-filled steel tubular (CFST) columns subjected to compartment fire. The numerical analyses on the planar composite frames with multiple stories and spans are meant to reproduce the conditions of framed members in multi-storey composite structures in real buildings. A refined finite element model is established and calibrated against the thermal and mechanical results from physical testing and shows good reliability in general. Using this model, this study proposes comparative analyses on the failure mechanisms of three typical composite frames, and discusses the effects of two significant parameters: the beam-to-column linear stiffness ratio and the fire protection thickness of the composite column. The responses of the heated composite frames, including the rotational deformation and stiffness degradation of framed joints, the internal force redistribution within framed members, and the failure mode of framed structures are investigated and discussed. The results indicate that there are two important parameters should be considered in the design of composite frames in fire.

Influences of various parameters on shear stiffness of bolted joints subjected to shear load

Parameters which affect shear stiffness characteristics of bolted joints subjected to shear load should be elucidated in order to design mechanical structures for functionality focusing not only on their strength and self-loosening but also on their shear stiffness. In this study, we have both experimentally and analytically investigated the behaviors of a bolted joint subjected to shear load and primary parameters which determine the shear stiffness characteristics of bolted joints. The experiments have been conducted applying the shear load four times repeatedly on clamped plates of a bolt/nut assembly with washers. We measured the shear stiffness of bolted joints and the shear load at which the slippage started to occur between the clamped plates. Four types of washers were used in the experiments with different contact areas on the clamped plates in order to reveal the effect of contact area of washers. We also conducted FE analysis under the same conditions. As the results, it was seen that the shear stiffness slightly increased with an increase in the clamp force of bolted joint. The shear stiffness was not influenced by the number of loading cycles. It was also seen that the amount of rotational deformation in the bolted joint depended on the slippage between the clamped plates. Although the rotation deformation was very small until the slippage occurrence, the rotational deformation remarkably increased after the slippage occurred. In general, it is well-known that the joining portion of lap jointed plates by spot welding, for example, slightly and rotationally deformed, but it has never been elucidated that the inclination angle due to the rotational deformation depends on the slippage between the clamped plates in the bolted joint. It was also seen that the shear stiffness until the slippage occurrence increased with an increase in the contacting surface area between the clamped plates. Although we investigated the effect of surface roughness of the clamped plates only in the experiments, we cannot clearly reveal its effect on the shear stiffness. But it is seen from the FE analysis result that the friction coefficient between clamped plates had a slight influence on the shear stiffness. The result shows that the shear stiffness of bolted joint mainly depends not only on the slip resistance between the clamped plates but also on increase of the contact surface between the washers and clamped plates. The results can be applied in order to control the shear stiffness of lap-jointed plates by spot welding and so on.

A Pathway to Hallux Valgus Correction: Intra- and Interexaminer Reliability of Hallux Alignment

Hallux Valgus is an orthopedic deformity of the forefoot region characterized by a lateral deviation of the first toe by more than 15 degrees with a medial deviation of the first metatarsal, often associated with a rotational deformity of the hallux phalanges. The work presented here is part of a broader study. To assess the (mis)alignment of the hallux, computerized photogrammetry was performed with Kinovea® software. Scientific articles about the reliability of photogrammetry for the (mis)alignment of a hallux evaluation are unknown. The main objective of this work is to verify the reliability of intra- and interexaminer evaluations in the assessment of a hallux (mis)alignment using computerized photogrammetry. For the intrarater evaluation, one examiner analyzed an aleatory sample of 40 feet to measure the (mis)alignment of the hallux, repeating the analysis five or fourteen days later. For the interrater evaluation, two examiners analyzed an aleatory sample of 20 feet. An intraclass correlation coefficient (ICC) and paired samples t-test were applied with a significance level of 0.05. Both inter- and intraexaminer-reliability analyses were rated as excellent (ICCs > 0.7), indicating yet another way to assess hallux (mis)alignment by nonradiological means, avoiding the radiation exposure associated with radiographs and the cost associated with the equipment acquisition.

Poster 214: The Effect of Femoral Retroversion on Hip Range of Motion – A 3D Computational Analysis

Objectives: A subset of patients undergoing hip arthroscopy suffers from persistent pain and dysfunction which can be secondary to a number of factors. Femoral rotational deformities are often overlooked and/or providers are unsure when to address femoral deformities. Currently, there is limited to no data guiding surgeons when to consider a femoral osteotomy at the time of hip arthroscopy for FAI. Through previously validated computer-assisted 3D modeling software, this study sought to answer two questions: 1) How much femoral retroversion is too much to render cam femoroplasty ineffective in improving range of motion (ROM)? 2) In the setting of an osteotomy, what degree of femoral version correction would be sufficient to improve impingement free ROM? Methods: Ten patients were selected with symptomatic focal cam impingement lesions who underwent hip arthroscopy and had pre- and post-operative computed tomography (CT) scans. These patients were screened for normal acetabular morphology and demonstrated no radiographic signs of osteoarthritis. Pre- and post-operative 3D modeling of the involved hip was performed and subsequently dynamized with the femoral version set at (15, 5, -5 and -15 degrees) to define the impingement free ROM and location of impingement with maximum hip flexion and maximum hip internal rotation (IR) at 90 degrees of hip flexion. Results: Mean alpha angle pre and post cam resection were 66°±7.6 ° and 44°±4.9° respectively and were significantly different (p=0.003). Location of impingement shifted during hip flexion from the medial to anterior femoral neck with decreasing femoral version while the IR impingement location remained on the anterior femoral neck and was unaffected by femoral version. Kruskal-Wallis testing demonstrated decreasing femoral version significantly decreased hip flexion and IR ROM in both the pre and post cam resection groups (p<0.0003). Impingement free ROM, as defined by hip flexion and IR greater than 90° and 10° respectively, was only identified in the 5 and 15 degree femoral anteversion models irrespective of whether cam femoroplasty had been performed. In the post cam resection group, hip IR ROM was significantly less with any level of decreasing femoral version (p<0.002) while hip flexion ROM was significantly less with any level of decreased femoral version when compared to 15 degrees of anteversion (p<0.04). When assessing the degree of change in ROM between the pre and post cam resection groups, femoral version had contrasting effects on hip ROM with decreasing femoral version showing less improvement with hip IR ROM while the femoral retroversion models had significantly greater improvements in hip flexion ROM when compared to the 15 degree anteversion model (p=0.02). Conclusions: Decreasing femoral version demonstrates significantly decreased hip flexion and IR both in the presence and absence of a CAM lesion. After cam femoroplasty, any level of decreased femoral version has a significant effect on hip ROM when compared to normal femoral anteversion. Femoral version seems to be the predominant factor in determining the amount of hip IR ROM in flexion and to a certain extent hip flexion ROM irrespective of the cam FAI. Impingement free ROM was only identified within the femoral anteversion models even after cam femoroplasty suggesting that recurrent mechanical collision and intra-articular damage seen with FAI may still be present with any level of true femoral retroversion. This study provides insight into the changes in hip flexion and IR that can be expected following both cam resection and simulated femoral osteotomy. [Table: see text]

Comparison of Habitual Versus Recurrent Patellar Dislocation in Children and Adolescents: Differences in Radiological Features.

Recurrent patellar dislocation (RPD) and habitual patellar dislocation (HPD) in flexion are frequently encountered in children and adolescents. To compare the radiological features of RPD and HPD in children and adolescents. Cross-sectional study; Level of evidence, 3. Imaging data were collected from patients aged 9 to 15 years who received surgical treatment for HPD or RPD at a single institution between June 2015 and September 2020. The prevalence of trochlear dysplasia, tibial tubercle lateralization, and lower limb rotational deformity was assessed through hip/knee/ankle computed tomography (CT) using the following quantitative indicators: trochlear depth index, lateral trochlear inclination, sulcus angle, tibial tubercle-trochlear groove (TT-TG) distance, ratio of TT-TG distance to femoral width, TT-TG angle, femoral anteversion angle, and tibial external rotation angle. The morphology of trochlea and patella were graded on knee CT using the Dejour and Wiberg classification. The Insall-Salvati index and Caton-Deschamps index were used to evaluate the height of the patella on lateral view radiographs. To evaluate lower limbs malalignment, the mechanical lateral distal femoral angle and medial proximal tibial angle were measured on weightbearing full-length radiographs. The collected data were analyzed and compared between the HPD and RPD groups. Enrolled were 15 patients (21 knees) diagnosed with HPD and 18 patients (22 knees) diagnosed with RPD. The age of first dislocation was significantly younger in the HPD group (7.6 ± 3.4 vs 11.2 ± 1.4 years; P = 0.003). Knees in the HPD group had a significantly higher proportion of Dejour type C dysplasia (57.1% vs 4.5%; P < .005) and Wiberg type 3 patella (66.7% vs 9.1%; P < .001). There were statistically significant differences between the groups in the trochlear depth index (HPD vs RPD: 1.1 ± 1.7 vs 2.2 ± 1.5 mm; P = .039), sulcus angle (170.3° ± 13.7° vs 157.3° ± 16.0°; P = .007), Insall-Salvati index (1.1 ± 0.2 vs 1.3 ± 0.2; P = .034), and tibial external rotation angle (31.3° ± 7.8° vs 38.4° ± 8.5°; P = .009). Patients in the HPD group presented with poorer trochlear and patellar development, lower patellar height, and less tibial external rotation compared with patients in the RPG group.

Multi-stage hydraulic fracture monitoring at the lab scale

We introduce a novel experimental and modeling approach to perform lab-scale multistage hydraulic fracturing in Poly-Methyl-Meth-Acrylate (PMMA) and study pressure-based methods to monitor hydraulic fracturing. The approach combines an internal circular V-notch method for fracture initiation with a method for creating hydraulic isolation between subsequent stages. Using high-resolution models of fracturing experiments with injection and monitoring wells, we present novel results of displacement, pressure, and stress evolution around the wells. We identify injection-induced rotational deformation in the domain and asymmetric growth of the hydraulic fracture. We quantify the role of the monitoring well on the rotational deformation and the fracture asymmetry. We analyze the role of undrained deformation in generating the monitor well’s pressure response to individual fracture stages at the injection well. Our results show that lab-scale multistage hydraulic fracturing can be a useful tool to estimate the geometry and property of a hydraulic fracture using pressure data from offset wells in the field.

General assembly rules for metamaterials with scalable twist effects

Metamaterials with twist effects can exhibit remarkable rotational deformation under tension or compression, a behavior that is uncommonly observed in conventional materials. Despite its promise in achieving complex engineering functionalities, the twist effect is unscalable and will quickly diminish as the number of unit cells increases, which is the major restriction for practical applications. In this study, we use screw theory to rigorously analyze the relationship between microscale geometries and twist effects, unraveling the mechanism underlying the loss of scalability. We further propose a general assembly rule for metamaterial crystals to achieve scalable effects. A simplified analytical model is developed to characterize the scalability of the twist. Through simulation, analytical models, and physical experiments, we demonstrate the flexibility and superiority of the proposed assembly rules in enabling scalable twist effects for various unit-cell designs, different strain levels, and even twists around multiple axes. This constitutes an important step towards scaling up the twist effects for real applications.

PrintShear

Most touch-based input devices, such as touchscreens and touchpads, capture low-resolution capacitive images when a finger touches the device's surface. These devices only output the two-dimensional (2D) positions of contacting points, which are insufficient for complex control tasks, such as the manipulation of 3D objects. To expand the modalities of touch inputs, researchers have proposed a variety of techniques, including finger poses, chording gestures, touch pressure, etc. With the rapid development of fingerprint sensing technology, especially under-screen fingerprint sensors, it has become possible to generate input commands to control multiple degrees of freedom (DOF) at a time using fingerprint images. In this paper, we propose PrintShear, a shear input technique based on fingerprint deformation. Lateral, longitudinal and rotational deformations are extracted from fingerprint images and mapped to 3DOF control commands. Further DOF expansion can be achieved through recognition of the contact region of the touching finger. We conducted a 12-person user study to evaluate the performance of PrintShear on 3D docking tasks. Comparisons with other input methods demonstrated the superiority of our approach. Specifically, a 19.79% reduction in completion time was achieved compared with conventional touch input in a full 6DOF 3D object manipulation task.

Correcting intervertebral rotation and scoliosis simultaneously by oblique lumbar interbody fusion: a 3D analysis of EOS images.

With advancements in minimally invasive techniques, oblique lumbar interbody fusion (OLIF) has gained widespread acceptance and is now commonly performed for adult degenerative scoliosis (ADS). The objective of this research paper is to evaluate three-dimensional (3D) intervertebral motions in EOS models before and after surgery and subsequently assess the efficacy of the 3D correction achieved through staged OLIF. In this retrospective study, 29 consecutive patients diagnosed with ADS were included, with a mean age of 63.6 years, who underwent staged OLIF surgery between 2018 and 2021. Spinopelvic parameters were assessed using EOS images, and 3D models were reconstructed to measure intervertebral motion angles (IMAs) in 70 surgical intervertebral segments, comprising wedge, lordosis, and axial rotation angles. Regression analysis was conducted to compare IMAs in different planes before and after the staged OLIF surgery. Significant three-dimensional correction was observed in 70 intervertebral segments following the first-stage OLIF. The wedge angles decreased from 5.2°± 4.2° to 2.7°± 2.4° (P < 0.001). The lordosis angles increased from 5.1°± 5.9° to 7.8°± 4.6° (P = 0.014), while the axial rotation angles decreased from 3.8°± 2.6° to 2.3°± 2.1° (P < 0.001). Linear regression analysis revealed a positive correlation between wedge angles and axial angles preoperatively (P < 0.001, r = 0.43), as well as between corrected wedge angles and corrected axial angles (P < 0.001, r = 0.42). This study demonstrated that intervertebral motions had a correlation between coronal and axial planes in lumbar degenerative scoliosis. First-stage OLIF was efficient at correcting segmental scoliosis by inserting cages while correcting rotation deformity simultaneously, as well as improving the sagittal spinopelvic parameters.

The effect of functional calibration methods on gait kinematics in adolescents with idiopathic rotational deformity of the femur

BackgroundDue to anatomical deviations, assumptions of the conventional calibration method for gait analysis may be violated in individuals with rotational deformities of the femur. Functional calibration methods were compared with conventional methods in this group for 1) localization of the hip joint center and orientation of the knee axis, and 2) gait kinematics. MethodsTwenty-four adolescents with idiopathic rotational deformity of the femur underwent gait analysis and a CT scan. During standing, distance between hip joint centers and knee axis orientation were compared between calibration methods, with CT serving as reference for hip joint center estimation. Gait kinematics were compared using statistical parametric mapping. FindingsThe conventional calibration method estimated the hip joint center closer to the CT reference (4±12 mm more lateral) than the functional calibration method (26 ± 20 mm more lateral). Orientation of the knee joint axis was 2.6° less internal in the functional calibration method. During gait, statistical parametric mapping revealed significantly more hip flexion, less external hip rotation during the swing phase, less knee varus-valgus motion, and larger knee flexion angles when applying the functional method. InterpretationFunctional calibration methods were less accurate in determining the hip joint center location than the conventional calibration method and resulted in a knee joint axis that was less internally rotated. Importantly, there was less knee joint angle crosstalk during gait when using the functional method. Although differences between methods on gait kinematics were within clinically acceptable limits for the sagittal plane, relatively larger differences on transversal hip kinematics may hold clinical importance.

Cardiac Pulsatile Helical Deformation of the Thoracic Aorta Before and After Thoracic Endovascular Aortic Repair of Type B Dissections.

Type B aortic dissections propagate with either achiral (nonspiraling) or right-handed chiral (spiraling) morphology, have mobile dissection flaps, and are often treated with thoracic endovascular aortic repair (TEVAR). We aim to quantify cardiac-induced helical deformation of the true lumen of type B aortic dissections before and after TEVAR. Retrospective cardiac-gated computed tomography (CT) images before and after TEVAR of type B aortic dissections were used to construct systolic and diastolic 3-dimensional (3D) surface models, including true lumen, whole lumen (true+false lumens), and branch vessels. This was followed by extraction of true lumen helicity (helical angle, twist, and radius) and cross-sectional (area, circumference, and minor/major diameter ratio) metrics. Deformations between systole and diastole were quantified, and deformations between pre- and post-TEVAR were compared. Eleven TEVAR patients (59.9±4.6 years) were included in this study. Pre-TEVAR, there were no significant cardiac-induced deformations of helical metrics; however, post-TEVAR, significant deformation was observed for the true lumen proximal angular position. Pre-TEVAR, cardiac-induced deformations of all cross-sectional metrics were significant; however, only area and circumference deformations remained significant post-TEVAR. There were no significant differences of pulsatile deformation from pre- to post-TEVAR. Variance of proximal angular position and cross-sectional circumference deformation decreased after TEVAR. Pre-TEVAR, type B aortic dissections did not exhibit significant helical cardiac-induced deformation, indicating that the true and false lumens move in unison (do not move with respect to each other). Post-TEVAR, true lumens exhibited significant cardiac-induced deformation of proximal angular position, suggesting that exclusion of the false lumen leads to greater rotational deformations of the true lumen and lack of true lumen major/minor deformation post-TEVAR means that the endograft promotes static circularity. Population variance of deformations is muted after TEVAR, and dissection acuity influences pulsatile deformation while pre-TEVAR chirality does not. Description of thoracic aortic dissection helical morphology and dynamics, and understanding the impact of thoracic endovascular aortic repair (TEVAR) on dissection helicity, are important for improving endovascular treatment. These findings provide nuance to the complex shape and motion of the true and false lumens, enabling clinicians to better stratify dissection disease. The impact of TEVAR on dissection helicity provides a description of how treatment alters morphology and motion, and may provide clues for treatment durability. Finally, the helical component to endograft deformation is important to form comprehensive boundary conditions for testing and developing new endovascular devices.

Growth and transtensional reactivation of a basin-bounding fault: Chengbei Sag, Bohai Bay Basin, East China

Models of extensional fault systems are predominantly based on examples where extension is approximately orthogonal to rift boundaries and deformation can be regarded as plane strain. In contrast, extensional faults in transtensional or strike-slip settings present complex geometric and kinematic features due to rotational deformation, and distinct rift and post-rift phases may be difficult to separate. Well-constrained 3D seismic data from the Bohai Bay Basin, East China reveal the growth history and transtensional reactivation of a basin-bounding fault (Chengbei Fault). During the syn-rift phase, the Chengbei Fault reached its near-final length within ∼24 Ma via the propagation and linkage of six initial fault segments, accompanied by the accumulation of 26% of its total displacement; in the following ∼18.7 Ma of the Paleogene, it accumulated the remaining 74% of displacement without an obvious increase in fault length. Following a phase of relative quiescence in the early Neogene, the Chengbei Fault was reactivated at ∼12 Ma, associated with the enhanced activity of a continental-scale strike-slip fault. At least 17 fault segments developed quickly and linked vertically to the lower fault system of the Chengbei Fault. The plan-view en-echelon and horse-tail configuration, and the flower structure seen in section views of the fault system, indicate that the post-rift activity of Chengbei Fault has had both dip-slip and strike-slip components. A calculation of the rotational deformation using fault heaves and orientations indicates that the tectonic reactivation occurred in a strike-slip-dominated transtensional setting accompanied by an increasing extension component with time. In basins affected by strike slip, kinematic analyses that consider rotational deformation can provide more detailed and convincing information on the tectonic setting.

Research on the evolving yielding behaviour and micro-mechanism in biaxial deformation of DP1180 sheet based on crystal plasticity finite element model

Dual-phase steels (DP steels) consist of ferrite and hard martensitic phase. For the high strength and good formability, they are widely used in automotive applications. Compared with the DP steels with lower strength, DP1180 is more special for the volume fraction of martensite is higher than that of ferrite. In this paper, the evolving plastic yielding behaviours and insight into their microscale mechanisms of DP1180 were studied by biaxial tension experiments and crystal plasticity finite element method. The representative volume element (RVE) model of DP1180 taking the dual phase fraction, grain size and texture into consideration is established and the relevant parameters of crystal plasticity are reverse calibrated by the uniaxial tensile test stress strain curve. The simulated biaxial tension tests were conducted by the established RVE model to investigate the yielding micro-mechanisms of DP1180 steel, and the obtained yield loci matches well with the test results. The simulation results show that the texture has a significant effect on the contours of the yield loci. The soft ferrite grains weaken the kinetic constraints to the polycrystalline matrix and further free the rotation and plastic deformation of the neighbouring grains. This study thus provides a comprehensive understanding of the effect of the microstructure (crystal structure, texture and dual phase fraction) on the yielding behaviour of DP1180 steel as well as a method of virtual experiment to get the yield loci of metallic materials.

Linear theory of micropolar media with internal nonlocal potential interactions

AbstractThis paper proposes a mathematical model that can be used to quantify the effects of a polarized electric field on the mechanical properties of a polar dielectric in the framework of mechanics of deformable solids. The physical essence of the phenomenon is known. However, its direct use in practical calculations may cause difficulties due to the complexity of the composition and structure of materials used in the design and manufacture of specific products whose operation regimes are based on polarization effects. A continuum description of the polarization phenomenon makes it possible to circumvent these difficulties.The basis of the generalized model is a micropolar linearly elastic medium. The generalization consists in taking into account the initial stress state of the material, as well as cross effects under the mutual influence of translational and rotational deformations, the possibility to calculate the characteristics of micropolar material properties based on a special nonlocal model of micropolar media with internal nonlocal potential interactions. It takes into account translational and rotational potential interactions of particles of a continuous medium at finite distances. The kinematic characteristics of the material are the same as those used by the traditional model of a micropolar elastic medium ‐ the gradients of translational displacements of the medium's particles, their rotations independent of the medium's rotation and rotations of the particles relative to the medium. Generalized forces performing work on these generalized displacements are volumetrically and surface‐distributed forces and moments. To determine the values of the parameters of the interparticle potentials of the nonlocal model, a method is proposed using data from experiments to determine the material constants of isotropic linearly elastic materials and the dispersion law for plane acoustic waves of high frequency. The paper considers and quantifies the effects of anisotropy in an initially isotropic material, as well as anharmonic effects that cause dielectric heating by a periodically changing polarizing field. The results are compared qualitatively and quantitatively with known experimental data and physical notions of the phenomena in question.

Imaging Methods to Quantify the Chest and Trunk Deformation in Adolescent Idiopathic Scoliosis: A Literature Review.

Background context: Scoliosis is a three-dimensional deformity of the spine with the most prevalent type being adolescent idiopathic scoliosis (AIS). The rotational spinal deformation leads to displacement and deformation of the ribs, resulting in a deformity of the entire chest. Routine diagnostic imaging is performed in order to define its etiology, measure curve severity and progression during growth, and for treatment planning. To date, all treatment recommendations are based on spinal parameters, while the esthetic concerns and cardiopulmonary symptoms of patients are mostly related to the trunk deformation. For this reason, there is a need for diagnostic imaging of the patho-anatomical changes of the chest and trunk in AIS. Aim: The aim of this review is to provide an overview, as complete as possible, of imaging modalities, methods and image processing techniques for assessment of chest and trunk deformation in AIS. Methods: Here, we present a narrative literature review of (1) image acquisition techniques used in clinical practice, (2) a description of various relevant methods to measure the deformity of the thorax in patients with AIS, and (3) different image processing techniques useful for quantifying 3D chest wall deformity. Results: Various ionizing and non-ionizing imaging modalities are available, but radiography is most widely used for AIS follow-up. A disadvantage is that these images are only acquired in 2D and are not effective for acquiring detailed information on complex 3D chest deformities. While CT is the gold standard 3D imaging technique for assessment of in vivo morphology of osseous structures, it is rarely obtained for surgical planning because of concerns about radiation exposure and increased risk of cancer during later life. Therefore, different modalities with less or without radiation, such as biplanar radiography and MRI are usually preferred. Recently, there have been advances in the field of image processing for measurements of the chest: Anatomical segmentations have become fully automatic and deep learning has been shown to be able to automatically perform measurements and even outperform experts in terms of accuracy. Conclusions: Recent advancements in imaging modalities and image processing techniques make complex 3D evaluation of chest deformation possible. Before introduction into daily clinical practice, however, there is a need for studies correlating image-based chest deformation parameters to patient-reported outcomes, and for technological advancements to make the workflow cost-effective.

Analysis and Verification of Load–Deformation Response for Rocking Self-Centering Bridge Piers

Rocking self-centering (RSC) bridge piers were proposed based on the bridge seismic resilience design theory, pushing the development of bridge sustainability. To develop a seismic design method for RSC bridge piers, a clear understanding of their behavior under earthquakes is essential. This study analyzed the whole lateral force–displacement response of RSC piers, taking into account both rotational and flexural deformation, which resulted in a clearer understanding of their behavior under seismic actions. In this study, the whole loading process was simplified into three statuses, and a calculation method was developed to determine the relationship between lateral force and displacement of both single-column and double-column RSC bridge piers. The accuracy of the proposed method was verified by comparing the calculated results with experimental data for six single-column and two double-column RSC bridge piers. The results show that the proposed calculation method predicts the initial stiffness, yield and peak loads, and yield and peak displacements well for RSC bridge piers. The method offers valuable insights into the seismic response of RSC bridge piers, which can serve as a reference for future research, promoting the safety and stability of these structures.