Disc Deformation Research Articles

Deformation and failure of thin domed-scored metallic disc under impulsive loading

This paper presents the structural deformation and failure of a thin domed-scored metallic disc (SMD) applied at the bottom of a pressurized rocket silo which needs to withstand a storage pressure and undergo instantaneous rupture under an impulsive pressure. Initially, the large deformation and rupture of a flat-thin SMD subjected to a pressure impulse is numerically studied and validated with experimental results. Subsequently, the behavior of a domed-thin SMD is investigated for the aforementioned loadings in the rocket silo. The influence of loading rates [Formula: see text], score depth and width-to-disc thickness ratio ( t 1/ t and b/ t), diameter-to-disc thickness ratio ( D/ t), dome height-to-disc diameter ratio ( H/ D), score length-to-disc radius ratio ( l/ R), score pattern, and score geometry on the deformation and failure response of the domed-thin SMD is investigated. The studies demonstrate that (1) the failure initiation point shifts from 1/4th radius to the disc center for loading rates > 10 MPa/s; (2) under impulse loading, the responses are (i) sensitive to the loading rates up to 100 MPa/s, (ii) sensitive to score’s depth, only up to half the disc thickness and insensitive to score’s width, (iii) unaffected for number of scores N > 6, (iv) stabilized for l/R > 0.4, and (vii) almost the same for semi-circular, rectangular and triangular score geometries; (3) the failure do not initiate and propagate along all scores for N > 10 in the disc; and (4) behavior of the domed SMD approaches to that of a spherical dome for H/D > 0.3.

On the Effects of Disc Deformation on the Tilting-Induced Vibration of a Spline-Guided Spinning Disc with an Axial-Fixed Boundary

This paper investigates the effects of disc deformation on the tilting-induced vibration of a splined spinning disc with axial-fixed boundaries.The purpose is to provide an intuitive interpretation of the vibration variance of the wet clutch system with different deformed discs. First, tilting models of flat and deformed discs are derived by introducing distinctive shape functions. Additionally, the inner spline interface is chosen as the friction boundary. Then, an impact model between friction pairs and the rigid boundary is established by adopting Hertz’s contact theory. Finally, the dynamic equations are solved via numerical methods, and the responses are analyzed in both time and frequency domains. The deformation can increase the nonlinearity of the dynamic response of the spinning disc. Moreover, the effects of increasing the impulse force and reducing the boundary distance are quite similar; they both increase the motion intensity.

Investigation of geometric deformations of the lumbar disc during axial body rotations

BackgroundQuantitative data on in vivo vertebral disc deformations are critical for enhancing our understanding of spinal pathology and improving the design of surgical materials. This study investigated in vivo lumbar intervertebral disc deformations during axial rotations under different load-bearing conditions.MethodsTwelve healthy subjects (7 males and 5 females) between the ages of 25 and 39 were recruited. Using a combination of a dual fluoroscopic imaging system (DFIS) and CT, the images of L3–5 segments scanned by CT were transformed into three-dimensional models, which matched the instantaneous images of the lumbar spine taken by a double fluorescent X-ray system during axial rotations to reproduce motions. Then, the kinematic data of the compression and shear deformations of the lumbar disc and the coupled bending of the vertebral body were obtained.ResultsRelative to the supine position, the average compression deformation caused by rotation is between + 10% and − 40%, and the shear deformation is between 17 and 50%. Under physiological weightbearing loads, different levels of lumbar discs exhibit similar deformation patterns, and the deformation patterns of left and right rotations are approximately symmetrical. The deformation patterns change significantly under a 10 kg load, with the exception of the L3–4 disc during the right rotation.ConclusionThe deformation of the lumbar disc was direction-specific and level-specific during axial rotations and was affected by extra weight. These data can provide new insights into the biomechanics of the lumbar spine and optimize the parameters of artificial lumbar spine devices.

Lumbar intervertebral disc diurnal deformations and T2 and T1rho relaxation times vary by spinal level and disc region.

Magnetic resonance imaging (MRI) is routinely used to evaluate spine pathology; however, standard imaging findings weakly correlate to low back pain. Abnormal disc mechanical function is implicated as a cause of back pain but is not assessed using standard clinical MRI. Our objective was to utilize our established MRI protocol for measuring disc function to quantify disc mechanical function in a healthy cohort. We recruited young, asymptomatic volunteers (6 male/6 female; age 18-30years; BMI < 30) and used MRI to determine how diurnal deformations in disc height, volume, and perimeter were affected by spinal level, disc region, MRI biomarkers of disc health (T2, T1rho), and Pfirrmann grade. Lumbar discs deformed by a mean of -6.1% (95% CI: -7.6%, -4.7%) to -8.0% (CI: -10.6%, -5.4%) in height and -5.4% (CI: -7.6%, -3.3%) to -8.5% (CI: -11.0%, -6.0%) in volume from AM to PM across spinal levels. Regional deformations were more uniform in cranial lumbar levels and concentrated posteriorly in the caudal levels, reaching a maximum of 13.1% at L5-S1 (CI:-16.1%, -10.2%). T2 and T1rho relaxation times were greatest in the nucleus and varied circumferentially within the annulus. T2 relaxation times were greatest at the most cranial spinal levels and decreased caudally. In this young healthy cohort, we identified a weak association between nucleus T2 and the diurnal change in the perimeter. Spinal level is a key factor in determining regional disc deformations. Interestingly, deformations were concentrated in the posterior regions of caudal discs where disc herniation is most prevalent.

Association of progressive optic disc tilt with development of retinal nerve fibre layer defect in children with large cup-to-disc ratio

Background/aimsWhereas myopic optic disc deformation has been posited as a risk factor for glaucomatous damage, longitudinal studies evaluating their association have been sparse. We investigated whether the optic nerve head...

Automated segmentation of articular disc of the temporomandibular joint on magnetic resonance images using deep learning

Temporomandibular disorders are typically accompanied by a number of clinical manifestations that involve pain and dysfunction of the masticatory muscles and temporomandibular joint. The most important subgroup of articular abnormalities in patients with temporomandibular disorders includes patients with different forms of articular disc displacement and deformation. Here, we propose a fully automated articular disc detection and segmentation system to support the diagnosis of temporomandibular disorder on magnetic resonance imaging. This system uses deep learning-based semantic segmentation approaches. The study included a total of 217 magnetic resonance images from 10 patients with anterior displacement of the articular disc and 10 healthy control subjects with normal articular discs. These images were used to evaluate three deep learning-based semantic segmentation approaches: our proposed convolutional neural network encoder-decoder named 3DiscNet (Detection for Displaced articular DISC using convolutional neural NETwork), U-Net, and SegNet-Basic. Of the three algorithms, 3DiscNet and SegNet-Basic showed comparably good metrics (Dice coefficient, sensitivity, and positive predictive value). This study provides a proof-of-concept for a fully automated deep learning-based segmentation methodology for articular discs on magnetic resonance images, and obtained promising initial results, indicating that the method could potentially be used in clinical practice for the assessment of temporomandibular disorders.

Deformability of discs in turbulence

The aim of this study is to investigate experimentally the transition from a rigid regime to a deformed regime for flexible discs freely advected in turbulent flows. For a given disc, the amplitude of the deformation is expected to increase when its bending modulus decreases or when the turbulent kinetic energy increases. To quantify this qualitative argument, experiments are performed where the deformation of flexible discs is measured using three cameras. The amplitude of the deformation has been characterised by the eigenvalues of the moment of inertia tensor. Experimental results exhibit a transition from a rigid regime to a deformed regime that depends on the size, the density and the flexibility of the disc and the turbulent kinetic energy. The modelling of this transition is a generalisation and an extension of the previous models used to characterise the deformation of flexible fibres in turbulent flows.

Spectral Galerkin method for solving Helmholtz boundary integral equations on smooth screens

Abstract We solve first-kind Fredholm boundary integral equations arising from Helmholtz and Laplace problems on bounded, smooth screens in three dimensions with either Dirichlet or Neumann conditions. The proposed Galerkin–Bubnov methods take as discretization elements pushed-forward weighted azimuthal projections of standard spherical harmonics onto the unit disk. By exactly depicting edge singular behaviors we show that these spectral or high-order bases yield super-algebraic error convergence in the corresponding energy norms whenever the screen is an analytic deformation of the unit disk. Moreover, we provide a fully discrete analysis of the method, including quadrature rules, based on analytic extensions of the spectral basis to complex neighborhoods. Finally, we include numerical experiments to support our claims as well as appendices with computational details for treating the associated singular integrals.

Abnormal deformation and negative pressure of a hard magnetic disc under the action of a magnet

Intelligent robots are widely used in a wide spectrum of areas, but the underlying mechanism on the operation of actuated structures has not been fully uncovered. In the present study, we have made a comprehensive investigation on the mechanical behaviors of a hard magnetic disc under the action of a magnet. A new technique for preparing the hard magnetic disc is presented. The configurations of the disc after deformation are recoded, which are consistent with the analytical solutions and the numerical simulation results, and the maximum axial displacement of the disk is up to 2.7 mm. The contact force between the disc and the substrate is also calculated, which matches the experimental result very well. The negative pressure of the disc can cause the rise of water column linked with a reservoir (~9.3 mm), which can be explained by the theoretical model. These findings have important implications in such areas as controllable devices, robotics and high-precision measurement.

A comparative study of the effects of the anterior disc displacement with reduction and without reduction on the components of the temporomandibular joint by using magnetic resonance imaging – A Retrospective study

Background: Internal derangement of the temporomandibular joint (TMJ) results in anterior disc displacement with reduction (ADDR), the disc is ante- riorly displaced in the closed position whereas in the opened position the disc returns to its normal location. In anterior disc displacement without reduction (AD- DWR), the disc is anteriorly displaced in the closed po- sition but does not return to its original location in the opened position. Here we studied and compared the effects of the ADDR and the ADDWR on the components of the TMJ by using the magnetic resonance imaging technique (MRI). Methods and materials: From the archival MRI records, 214 joints from 107 patients were included. The selec- tion criteria for the patients complaints as TMJ pain, clicking, limited mouth opening, headache, jaw tenderness and difficulty in eating. MRI records with sequences Proton Density (PD), PD FAT SAT and T2* gradient in the closed position and T2* gradient echo in the opened position. Data analysis and frequency distribution of explanatory variables by disc position in the open state was performed using chi-square test Results: Statistically significant differences were observed between the variables such as the joint space (closed position), disc morphology (closed position) and range of movement (opened position) among the ADDR and the ADDWR. In ADDWR, 20.3% demonstrated narrowed joint space and 1.6% with widened joint space, while in ADDR, 2.5% of joints had narrowed joint space and 0% widened joint space. Same was observed with abnormal disc morphology and rang of movement. Conclusion: The disc deformity is more in ADDWR compared to ADDR which can be seen as an alteration in the signal intensity. The malaligned disc could lead to the narrowing of the joint space and decreased range of movement in the ADDWR affected individuals.

Load bearing analysis on Lumbosacral Disc in Pre-operative and Post-operative Thoracic Scoliosis Patient

Scoliosis is a musculoskeletal disorder seen all around the world. It affects both the alignment of the vertebra and intervertebral disc. Scoliosis can be treated conservatively with a cast and brace or surgically with spinal instrumentation. During planning for surgical instrumentation, several factors need to be considered. Among those, biomechanical changes in the non-scoliotic vertebrae and discs are important. This is vital in determining the future degenerative changes of the spine. For this reason, this study was conducted with a finite element model of the lumbosacral joint using CT scan files to find the total deformation and equivalent static strain of the lumbosacral disc between pre and post-operative thoracic scoliosis patient. From the results, it is evident that there is a biomechanical change in the lumbosacral disc and structural change in the vertebral alignment followed immediately after corrective surgery. The correction in the alignment of the scoliotic spine brings changes to the biomechanical functionality and load-bearing capacity of the lumbosacral intervertebral disc before and after surgery.

Development of a new piezoelectric galvanometer scanner: fabrication, operation, and measurements

Our objective in this study was to overcome the size and complexity of existing galvanometers by developing a direct-drive galvanometer based on the deformation of a double-layer ceramic piezoelectric disc with mirrored surface. The resulting device is extremely compact (0.41 mm), light weight, and highly responsive. The performance of the galvanometer was evaluated using an electronic speckle interferometer to characterize vibration mode characteristics. The voltage and input frequency can be adjusted to match the vibration amplitude and vibration mode required for practical galvanometer operations. Using a position sensitive detector, we recorded changes in the position of a light spot generated by a single-point laser by which to track changes in the optical path imposed by the galvanometer. Experiments using graphics drawn by an open-loop control system verified the performance of the device.

The Verification of Human Lumbar Vertebrae and Intervertebral Disc Finite Element Models under Mechanical Forces

Bone, being nonhomogeneous in nature need a complicated and time-consuming process to undergo computed simulation like finite element analysis. To overcome this hurdle, assuming a nonhomogeneous model as homogeneous could be a solution. The objective of this study is to focus on developing a homogeneous human lumbar finite element models and verify them under mechanical force by measuring disc stress, disc strain, disc deformation, total strain, and total deformation. Experimental and geometrical analysis were performed before verifying the lumbar model. To verify the models’ reliability, nonhomogeneous lumbar models were also developed. Five different static structural simulations were performed on four lumbar segments, and twenty parameters were measured. Numerically, out of twenty, eighteen parameters showed very less or no significant difference between homogeneous and nonhomogeneous models of the intervertebral discs and lumbar vertebrae. At the same time, proper caution to be provided while examining the results. With this validation procedure, researchers can process artifact images to get more information which enables them to contribute to the patient’s well-being.

MRI-Based Assessment of Masticatory Muscle Changes in TMD Patients after Whiplash Injury.

Objective: to investigate the change in volume and signal in the masticatory muscles and temporomandibular joint (TMJ) of patients with temporomandibular disorder (TMD) after whiplash injury, based on magnetic resonance imaging (MRI), and to correlate them with other clinical parameters. Methods: ninety patients (64 women, 26 men; mean age: 39.36 ± 15.40 years), including 45 patients with symptoms of TMD after whiplash injury (wTMD), and 45 age- and sex-matched controls with TMD due to idiopathic causes (iTMD) were included. TMD was diagnosed using the study diagnostic criteria for TMD Axis I, and MRI findings of the TMJ and masticatory muscles were investigated. To evaluate the severity of TMD pain and muscle tenderness, we used a visual analog scale (VAS), palpation index (PI), and neck PI. Results: TMD indexes, including VAS, PI, and neck PI were significantly higher in the wTMD group. In the wTMD group, muscle tenderness was highest in the masseter muscle (71.1%), and muscle tenderness in the temporalis (60.0%), lateral pterygoid muscle (LPM) (22.2%), and medial pterygoid muscle (15.6%) was significantly more frequent than that in the iTMD group (all p < 0.05). The most noticeable structural changes in the masticatory muscles occurred in the LPM with whiplash injury. Volume (57.8% vs. 17.8%) and signal changes (42.2% vs. 15.6%) of LPM were significantly more frequent in the wTMD group than in the iTMD group. The presence of signal changes in the LPM was positively correlated with the increased VAS scores only in the wTMD group (r = 0.346, p = 0.020). The prevalence of anterior disc displacement without reduction (ADDWoR) (53.3% vs. 28.9%) and disc deformity (57.8% vs. 40.0%) were significantly higher in the wTMD group (p < 0.05). The presence of headache, sleep problems, and psychological distress was significantly higher in the wTMD group than in the iTMD group. Conclusion: abnormal MRI findings and their correlations with clinical characteristics of the wTMD group were different from those of the iTMD group. The underlying pathophysiology may differ depending on the cause of TMD, raising the need for a treatment strategy accordingly.

Research on plastic deformation law and forming technology of rotary forging with multi-cone rolls

With the development of industrial technology, the application of large diameter-thickness ratio integral discs in various high precision vessels is becoming more and more important. At present, the forming processes of large-diameter disc mainly includes welding and multiple local upsetting, but these processes exhibit large defects and cannot meet the requirements of industry. Therefore, a new metal plastic forming technology, namely rotary forging with multi-cone rolls (MCRs) is proposed to integrally form large diameter and ultra-thin discs. The forming process was simulated by DEFORM-3D finite element analysis software, and the deformation characteristics of MCRs disc were revealed. The results show that the axial plastic deformation of disc can be divided into three stages. In the first stage, the plastic deformation area was basically symmetrical, and the deformation was relatively stable. In the second stage, the plastic deformation area on both sides was different, which was in the unstable stage and easy to produce defects. In the third stage, the plastic deformation area was approximately symmetrical for a long time, and the plastic deformation was stable. At the same time, the influence of process parameters on the form characteristics of MCRs, the main defects in the deformation process and the preventive measures were studied. The research results are helpful to better understand the metal plastic forming technology of MCRs and promote the further development of MCRs.

Experimental study on the wear and damage of wheel-rail steels under alternating temperature conditions

The objective of this study is to investigate the wear and rolling contact fatigue (RCF) damage of wheel and rail materials under alternating temperature conditions. Two series of rolling-sliding tests were performed: (1) at 20 °C for 75,000 cycles, and then continued at −40 °C for 10,000, 30,000, and 75,000 cycles, respectively; (2) at −40 °C for 75,000 cycles, and then continued at 20 °C for 10,000, 30,000, and 75,000 cycles, respectively. The results indicated that the decrease in the temperature would alleviate the wheel wear due to the formation of wear debris layer. Both the rising and dropping of the environmental temperature during the tests could lead to the increase in the rail wear. Besides, the decrease in the temperature could increase the plastic deformation and work hardening of wheel and rail discs. In addition, the crack initiation was correlated with the behaviour of plastic flow on the wheel. At 20 °C, long single cracks initiated and propagated along the highly deformed ferrite boundaries. At −40 °C, white-etching layer (WEL) was observed only on the wheel surface, which was mainly attributed to the severe plastic deformation. Then, the refined ferrites and WELs were the main crack initiation sources on the wheel.

Presenting a novel higher-order bounded convection scheme for simulation of multiphase flows and convection heat transfer

The primary aim of the current study is to enhance the stability and accuracy of the Volume-Of-Fluid (VOF) method for modeling free-surface flows with large topological changes and high density ratio. For accurate capturing of fluid interfaces, a novel higher-order bounded convection scheme is first constructed based on the total variation diminishing (TVD) concept and is then employed for the discretization of convection terms in Navier-Stokes, energy and transport equations. In the second step, the classical PISO algorithm is modified according to the two-step projection method (Chorin's model) and the combined model (PISOC) is then applied for the treatment of the pressure-velocity coupling. Moreover, the second-order accurate piecewise-linear interface reconstruction technique (PLIC-ELVIRA) is used for determining the normal direction and curvature of the interface. The robustness and accuracy of the proposed models in handling multiphase flows with interface rupture and coalescence are verified against several experimental and numerical benchmark solutions such as: dam break, Rayleigh-Taylor instability, bubble rising, rotation of a slotted disk (Zalesak's problem), deformation of a 2D disk and pure convection of a step profile. The results show that, the proposed third-order TVD flux-limiter scheme can considerably reduce the false-diffusion errors and ensure the boundedness of the volume fraction while retaining the sharpness and shape of the interface. Furthermore, it is found that the proposed PISOC algorithm has strong stability and convergence characteristics in strongly coupled multiphase problems and is less susceptible to divergence when larger pressure under-relaxation factor is used. The performance and effectiveness of the proposed modifications are further demonstrated by analyzing transient entropy generation due to conjugate natural convection heat transfer in two different canonical test cases (i.e. Differentially Heated Cavity and Rayleigh-Bénard Convection) and good agreements are found with previously published works.

Increasing BMI increases lumbar intervertebral disc deformation following a treadmill walking stress test

High body mass index (BMI) and obesity have been implicated as risk factors for lumbar degenerative disc disease and low back pain. Despite this, there is limited in vivo data to quantify how obesity influences the mechanical function of intervertebral discs (IVD) in response to activities of daily living. Recently, our lab has developed methodologies to non-invasively measure in vivo IVD deformation resulting from activities of daily living using magnetic resonance (MR) imaging and solid modeling techniques. This pilot study expands on these methodologies to assess how BMI influences IVD deformation following treadmill walking in eight asymptomatic individuals. Ordinary least squares regression analyses revealed a statistically significant relationship between BMI and compressive deformation (strain (%)) in the L5-S1 IVD (R2 = 0.61, p < 0.05). This relationship was weaker in the L3-L4 (R2 = 0.28, p > 0.05) and L4-L5 IVDs (R2 = 0.28, p > 0.05). Importantly, no relationship between pre-exercise disc height and BMI was identified (p > 0.05). Therefore, the results of this study suggest that BMI may alter the mechanical response of lumbar spine IVDs, particularly at the L5-S1 level. Furthermore, the observed relationship between increased BMI and IVD compressive deformation, in the absence of a detected relationship between pre-exercise disc height and BMI, suggests that changes in IVD mechanical function may be more sensitive to alterations in disc health than static clinical imaging alone. This finding highlights the importance of quantifying disc mechanical function when examining the relationship between BMI and IVD degeneration.

Correlation between optic disc deformation and retinal vasculature in non-pathological high myopia.

The aim of the current study was to investigate the correlation between optic disc deformation and retinal vasculature in high myopia. A total of 130 eyes with non-pathological high myopia were included in the current cross-sectional study. β-zone parapapillary atrophy (β-PPA), optic disc tilt ratio, and horizontal and vertical disc diameters were analyzed using fundus color photography. A 3x3 mm grid and a 4.5x4.5 mm grid were used to scan parafoveal and peripapillary regions, respectively, using optical coherence tomography angiography. Vessel flow density (VFD) and fractal dimension of the retina, as well as the foveal avascular zone (FAZ), were analyzed and quantified using en face projection images. Optic disc parameters that were associated with vascular changes were determined using multiple linear regression analysis. The results from the multivariate analysis revealed that β-PPA was negatively correlated with the VFD of the superficial retinal plexus (R=-2.805; P=0.006), deep retinal plexus (R=-2.801; P=0.006), radial parapapillary capillaries (R=-3.936; P<0.001) and enhanced-depth imaging of the fovea (R=-2.161; P=0.034). Additionally, FAZ was not significantly correlated with any factors in the current study. Age was negatively correlated with the VFD of the retina (R=-4.234; P<0.001), while the optic tilt ratio (R=-2.291; P=0.025) was negatively correlated with three sectors in the deep layer. Overall, the present results demonstrated that optic disc deformation was negatively correlated with the retinal microvasculature in non-pathological high myopia, particularly in the radial peripapillary capillaries and the deep retinal plexus. Therefore, optic disc deformation may be used to predict the retinal vasculature in high myopia.

Forces in Axial Flux Magnetic Gears with Integer and Fractional Gear Ratios

This paper presents a comparison of two variants of an axial flux magnetic gear (AFMG), namely, with integer and fractional gear ratios. Based on calculations derived with the use of three-dimensional numerical models, the torque characteristics of the analyzed AFMGs are computed and verified on a physical model. The greatest emphasis is put on the detailed decomposition and analysis of local forces in modulator pole pieces (also used in the structural analysis) within the no-load and maximal load conditions. The authors also describe the unbalanced magnetic forces (UMF) in the axial and radial directions resulting from the construction of the considered AFMGs variants, and their possible effects in the context of the use of additive manufacturing (AM) in prototypes. The paper also proposes an effective method for limiting the axial strain by using the asymmetry of the air gaps, which slightly reduces the torque transmitted by AFMGs. Finally, a static strength analysis was presented that allows us to assess the effects of local forces in the form of modulator disc deformation for selected cases of air gap asymmetry.