Disc Deformation Research Articles

A theoretical model for predicting the wax breaking force during pipeline pigging

Pipeline pigging is a major conventional wax remediation technique for waxy crude oil transportation. Predicting the wax breaking force, a decisive parameter for pigging arrangements, however still remains an open question, primarily due to the ambiguities in wax removal physics as well as a lack of methods. To address this issue, here we propose a new theoretical wax breaking model to explain the wax removal mechanism and predict the wax breaking force, allowing the no empirical parameters or correction factors. It is met by introducing orthogonal cutting in wax removal explanation and employing slip-line field theory in wax breaking force calculation. Scraping disk deformation is incorporated in this model. An indirect trial method is adopted for the wax-disk frictional angle determination. To check its correctness, we conducted verification experiments with 29-mm-ID and 50-mm-ID pipes. Good agreement between the predicted and measured wax breaking forces has been observed with the maximum and average relative deviations being 21.98% and 8.85% respectively. Moreover, case study suggests this model can potentially enable applications in pig design. Recommendations on pig geometry are accordingly given in detail. On the whole, calculating the wax breaking force, this presented model benefits in optimizing the pig design. In a broader perspective, it further helps to avoid pig stall.

Changes in Intervertebral Disk Mechanical Behavior During Early Degeneration.

Intervertebral disk (IVD) degeneration is commonly described by loss of height and hydration. However, in the first stage of IVD degeneration, this loss has not yet occurred. In the current study, we use an ex vivo degeneration model to analyze the changes in IVDs mechanical behavior in the first phase of degeneration. We characterize these changes by stretched-exponential fitting, and suggest the fitted parameters as markers for early degeneration. Enzymatic degeneration of healthy lumbar caprine IVDs was induced by injecting 100 μL of Chondroïtinase ABC (Cabc) into the nucleus. A no-intervention and phosphate buffered saline (PBS) injected group were used as controls. IVDs were cultured in a bioreactor for 20 days under diurnal, simulated-physiological loading (SPL) conditions. Disk deformation was continuously monitored. Changes in disk height recovery behavior were quantified using stretched-exponential fitting. Disk height, histological sections, and water- and glycosaminoglycan (GAG)-content measurements were used as gold standards for the degenerative state. Cabc injection caused significant GAG loss from the nucleus and had detrimental effects on poro-elastic mechanical properties of the IVDs. These were progressive over time, with a propensity toward more linear recovery behavior. On histological sections, both PBS and Cabc injected IVDs showed moderate degeneration. A small GAG loss yields changes in IVD recovery behavior, which can be quantified with stretched-exponential fitting. Parameters changed significantly compared to control. Studies on disk degeneration and biomaterial engineering for degenerative disk disease (DDD) could benefit from focusing on IVD biomechanical behavior rather than height and water-content, as a marker for early disk degeneration.

Focal Lamina Cribrosa Defect in Myopic Eyes With Nonprogressive Glaucomatous Visual Field Defect

To investigate focal lamina cribrosa (LC) defect that spatially correspond to the nonprogressive glaucomatous visual field defect (VFD) in myopic subjects. Case-control study. We included 159 myopic eyes with glaucomatous VFD under treatment and followed up for 7 years. Serial enhanced-depth imaging spectral-domain optical coherence tomography B-scans of the optic discs were acquired at the end of the follow-up and reviewed for the LC defect. Nonprogressive VFD was defined as having ≤1 progressing point of Humphrey visual field, with a slope calculated using pointwise linear regression worse than -1.0 dB/year at P < .01. Eyes were classified as having either progressive or nonprogressive VFD, and associating factors were evaluated. Sixty-four subjects (40.3%) exhibited nonprogressive VFD with mean deviation change -0.06 ± 0.22 dB/year. Multivariate logistic regression analysis revealed that presence of LC defect was significantly associated with nonprogressive VFD (odds ratio, 3.96; P= .002). The location of LC defect corresponded spatially to the location of VFD. Nonprogressive eyes with LC defect exhibited lower baseline intraocular pressure (IOP) (16.6mm Hg vs 21.0mm Hg, P= .0030) and smaller percentage of IOP change (12.9% vs 30.5%, P < .0001) than those without LC defect, but greater myopic optic disc deformation (10.1 degrees vs 1.2 degrees in torsion angle, P < .0001). When the eyes with LC defect had higher baseline IOP, they exhibited progressive VFD. In myopic eyes, there are specific patters of LC defect that are suggested to be associated with nonprogressive glaucomatous VFD.

A magnetic resonance imaging framework for quantifying intervertebral disc deformation in vivo: Reliability and application to diurnal variations in lumbar disc shape

Low back pain is a significant socioeconomic burden in the United States and lumbar intervertebral disc degeneration is frequently implicated as a cause. The discs play an important mechanical role in the spine, yet the relationship between disc function and back pain is poorly defined. The objective of this work was to develop a technique using magnetic resonance imaging (MRI) and three-dimensional modeling to measure in vivo disc deformations. Using this method, we found that disc geometry was measurable with precision less than the in-plane dimensions of a voxel (≈100 µm, 10% of the MRI pixel size). Furthermore, there was excellent agreement between mean disc height, disc perimeter, disc volume and regional disc height measurements for multiple trials from an individual rater (standard deviation <3.1% across all measurements) and between mean height, perimeter, and volume measurements made by two independent raters (error <1.5% across all measurements). We then used this measurement system to track diurnal deformations in the L5-S1 disc in a young, healthy population (n = 8; age 24.1 ± 3.3 yrs; 2 M/6F). We measured decreases in the mean disc height (−8%) and volume (−9%) with no changes in perimeter over an eight-hour workday. We found that the largest height losses occurred in the posterior (−13%) and posterior-lateral (−14%) regions adjacent to the outer annulus fibrosus. Diurnal annulus fibrosus (AF) strains induced by posterior and posterior-lateral height loss may increase the risk for posterior disc herniation or posterior AF tears. These preliminary findings lay a foundation for determining how deviations from normal deformations may contribute to back pain.

Magnetic Resonance Imaging-Based Prediction of the Relationship between Whiplash Injury and Temporomandibular Disorders.

Whiplash injury can cause internal derangement of the temporomandibular joint (TMJ) and lead to temporomandibular disorders (TMDs). Our aim was to evaluate whether the initial clinical findings in TMD patients with whiplash injury are correlated with their magnetic resonance imaging (MRI) characteristics. This case-control study involved 219 patients (135 women, 84 men; mean age: 37.84 years) who visited our orofacial pain clinic with TMD; TMD was diagnosed using the diagnostic criteria for TMD Axis I. Patients were categorized into three groups based on the presence and type of macrotrauma: in the "wTMD" group, patients had suffered whiplash injury; patients in the "pTMD" group had post-traumatic TMD; the "iTMD" group comprised patients who had presented with TMD symptoms and had sustained no macrotrauma. We investigated the presence of disk displacement, effusion, disk deformity, and condylar degeneration, and changes in the lateral pterygoid muscle (LPM). To evaluate the severity of TMD pain and objectively analyze symptoms, we used a visual analog scale (VAS), palpation index (PI), neck PI, dysfunction index, and craniomandibular index (CMI). The VAS scores, and the severity indexes of the TMD including PI, neck PI, and CMI were highest in the wTMD patients. Atrophy of the LPM was most commonly seen in the wTMD group, as was disk deformity. In wTMD patients only, VAS score was significantly correlated with stress; it was correlated with headache in wTMD and iTMD patients. The clinical symptoms of TMD were not correlated with MRI findings in the wTMD group. However, alterations in the LPM were strongly correlated with disk displacement. If clinicians recognize alterations in the LPM and disk displacement in the TMJ, they will better understand the clinical symptoms and pathophysiology of TMD with whiplash injury. Whiplash injury may lead to TMD via different mechanisms from other macrotraumas.

Air Core Transformer Winding Disk Deformation: A Precise Study on Mutual Inductance Variation and Its Influence on Frequency Response Spectrum

It is well-known that the deformation of transformer winding can produce detectable changes to the frequency response spectrum compared with a referenced past measurement. To interpret such changes for diagnostic purposes, main causes of the trace deviation need to be recognized precisely. In addition, it is useful that the interpretation of transformer frequency response is classified in a way that IoT-based techniques can be developed in the near future to analyze the transformer mechanical integrity. This paper has specifically concentrated on the inductance and capacitance variation due to the axial and radial disk deformation of transformer winding. Analytical analyses on self- and mutual-inductance variations are discussed and capacitance variation is studied in detail for symmetrical and asymmetrical transformer disk deformations. A numerical example is provided to establish the analytical approach and compare inductance and capacitance variation. The analytical approach is finally examined through the experimental study of disk deformation in a 66 kV transformer winding.

Consideraciones para el diseño de un sistema diagnóstico de frenos de disco en un vehículo particular

El presente artículo describe los aspectos en el proceso de frenado de un vehículo particular, para determinar la viabilidad de un sistema diagnóstico que establezca su estado actual en tiempo real, disminuyendo los índices de accidentalidad establecidos por la ANSV (Agencia Nacional Seguridad Vial). Por otra parte, se relacionan investigaciones respecto al tema de sistemas de frenos de disco y cómo aportan al diseño del sistema diagnóstico, mediante simulaciones con software ANSYS (Swanson Analysis Systems, Inc.) y sistemas de frenos de disco utilizados comúnmente como los ABS (Sistema antibloqueo de ruedas), teniendo en cuenta los antecedentes de estos sistemas. En consecuencia, como resultado del análisis realizado a las diferentes variables del sistema de freno de disco, se deter­minó que la temperatura es una de las fuentes que más afecta el desempeño del sistema de frenado, ocasionando desgastes en pastillas de freno, mecanismos del mismo y deformaciones en el disco.

A thermo-elasto-hydrodynamic model for air foil thrust bearings including self-induced convective cooling of the rotor disk and thermal runaway

A 3D thermo-elasto-hydrodynamic model for air foil thrust bearings (AFTBs) is presented. A detailed shell model is applied for the foils. The deformation of the rotor disk is modeled by axisymmetric Navier-Lamé equations taking into account thermal expansion effects. The pressure in the lubricating gap of the AFTB is calculated by the Reynolds equation and the temperature by a 3D energy equation. Particular emphasis is put on detailed thermal submodels for the bearing parts. An analytic formula is presented for the effective thermal resistance of the bump foil incorporating thermal contact resistances between the bump foil and the top foil as well as between the bump foil and the base plate. The self-induced cooling flow at the backside of the rotor disk is modeled by appropriate boundary layer equations including an eddy viscosity turbulence model. The heat flux through the tight gap between the outer part of the disk and the housing is accounted for as well. The presented model is used to reveal thermal features of AFTBs. The main finding is that load capacity increases with rotor speed only up to a critical value, above which load capacity is even found to decrease with increasing speed. This thermal runaway is proved to originate from a thermally induced bending of the disk that leads to an unfavorable gap function. Furthermore, experimentally observed beneficial effects on unit load capacity of AFTBs - as for example a forced cooling flow and a reduced number of pads - are successfully reproduced by the presented model. Finally, the relative magnitude of the different heat fluxes occurring in AFTBs is analyzed in detail.

62 - Investigation of Cervical Disc Deformation Using Weight-Bearing and Non–Weight-Bearing References

BACKGROUND CONTEXT: Investigation of in-vivo cervical disc deformation is critical for understanding the cervical function and pathology as well as for improvement of treatment of cervical diseases. However, it is a challenge to determine a cervical spine position that could be used as a reference position to calculate the cervical disc deformation. Supine and weight-bearing standing positions have been used in literature as references for calculation of disc deformation, but no data have been reported on the differences of disc deformation calculated using different spinal reference positions.

Study on the free edge effect on finite line contact elastohydrodynamic lubrication

Abstract This paper incorporated a recently developed algorithm, which directly gives the elastic deformation of loaded quarter-space (QS) bodies, into a finite line contact elastohydrodynamic lubrication (EHL) analysis. Half-space (HS) and QS models were adopted in the analysis and the results were compared with the data obtained from conventional optical EHL tests of steel rollers on a glass disc. This study found that contact deformation was dominated by glass disc deformation. Thus, the use of a steel roller on a glass disc in conventional optical EHL technique is not appropriate for studying the free edge surface effect. Free edge surfaces reduce the magnitude of pressure spikes near the ends of contact. Rollers with different end profiles were also evaluated.

Modelling of Magneto-Elastic Phenomena in Inductive Dynamic Drive

Inductive dynamic drives (IDD) are ultra rapid actuators where the moving part (disc) is subjected to impulse force. This paper presents the second model of inductive dynamic drive – a mechanical model where analytic- numerical approach was applied. The magnetic pressure, which was determined on the basis of the results obtained in the electrodynamic model, becomes the input data for mechanical model. Research with application of the mechanical model is necessary in order to determine the proper disc oscillation frequency and to obtain the stress state control for drive elements to be designed. Also, the selection of drive parameters to keep the disc deformation insignificant (while oscillating) is a condition under which these models do not need to be coupled together.

Ranges of Cervical Intervertebral Disc Deformation During an In Vivo Dynamic Flexion-Extension of the Neck.

While abnormal loading is widely believed to cause cervical spine disc diseases, in vivo cervical disc deformation during dynamic neck motion has not been well delineated. This study investigated the range of cervical disc deformation during an in vivo functional flexion-extension of the neck. Ten asymptomatic human subjects were tested using a combined dual fluoroscopic imaging system (DFIS) and magnetic resonance imaging (MRI)-based three-dimensional (3D) modeling technique. Overall disc deformation was determined using the changes of the space geometry between upper and lower endplates of each intervertebral segment (C3/4, C4/5, C5/6, and C6/7). Five points (anterior, center, posterior, left, and right) of each disc were analyzed to examine the disc deformation distributions. The data indicated that between the functional maximum flexion and extension of the neck, the anterior points of the discs experienced large changes of distraction/compression deformation and shear deformation. The higher level discs experienced higher ranges of disc deformation. No significant difference was found in deformation ranges at posterior points of all the discs. The data indicated that the range of disc deformation is disc level dependent and the anterior region experienced larger changes of deformation than the center and posterior regions, except for the C6/7 disc. The data obtained from this study could serve as baseline knowledge for the understanding of the cervical spine disc biomechanics and for investigation of the biomechanical etiology of disc diseases. These data could also provide insights for development of motion preservation surgeries for cervical spine.

Clinical value of MRI in treatment choice of anterior disc displacement with reduction

Objective To investigate the clinical value of MRI in treatment choice of anterior disc displacement with reduction. Methods 1.5 T superconducting MR was used to scan bilateral temporomandibular joints in 72 consecutive patients who were diagnosed by MRI as unilateral (66 patients) /bilateral(6 patients) anterior disc displacement with reduction at closed and open mouth. MRI sequences included oblique sagittal T2 weighted image and proton density weighted image, and 78 joints' images were acquired. According to the severity of clinical symptoms, all joints were divided into severe symptom group (45 joints) and mild symptom group (33 joints). Treatment was performed in severe symptom group, while follow up was conducted in mild symptom group. Disk position(angle between posterior margin of the disc and the condyle vertical line), disk morphology(biconcave, biplanar, biconvex, rounded, folded, thick posterior band), and joint effusion (none effusion, mild effusion, moderate effusion, marked effusion) were evaluated by two radiologists. The observer agreement for image evaluation was calculated using Kappa statistics. Group difference in disk position was compared using t-test and Chi-square test was used to compare group difference in disk morphology and joint effusion. Results The Kappa value between two radiologists were 0.816 and 0.832 (P<0.01) on evaluation of disk morphology and joint effusion. Statistical results indicated that the angles between posterior margin of the disc and the condyle vertical line in severe symptom group (54.2±10.9)° were larger than those in mild symptom group (46.4±9.0)° (t=3.37, P<0.05). There was no significant difference in disc deformation incidence between the two groups (χ2=1.18, P=0.277). The common deformation in sever symptom group was thick posterior band (χ2=5.65, P<0.05), and in mild symptom group was biplanar (χ2=5.67, P<0.05). No statistical difference in joint effusion incidence was observed(χ2=1.02, P=0.312). Moderate and marked effusion were more common in sever symptom group than that in mild symptom group (χ2=6.55, P<0.05). Conclusions MRI is a useful tool for making treatment choice in anterior disc displacement with reduction. Treatment should be given when the following occurred on MRI: moderate anterior disc displacement, disc deformation (excepting for biplanar), moderate or marked joint effusion. Key words: Temporomandibular joint dysfunction syndrome; Temporomandibular joint disk; Magnetic resonance imaging; Anterior disc displacement with reduction

Association of Myopic Deformation of Optic Disc with Visual Field Progression in Paired Eyes with Open-Angle Glaucoma.

PurposeThe influence of myopia on glaucoma progression remains unknown, possibly because of the multifactorial nature of glaucoma and difficulty in assessing a solo contribution of myopia. The purpose of this study is to investigate the association of myopia with visual field (VF) progression in glaucoma using a paired-eye design to minimize the influence of confounding systemic factors that are diverse among individuals.MethodsThis retrospective study evaluated 144 eyes of 72 subjects with open-angle glaucoma, with similar intra-ocular pressure between paired eyes, spherical equivalent (SE) ≤ -2 diopter (D), and axial length ≥ 24 mm. Paired eyes with faster and slower VF progression were grouped separately, according to the global VF progression rate assessed by automated pointwise linear regression analysis. The SE, axial length, tilt ratio and torsion angle of optic discs, Bruch’s membrane (BM) opening area, and gamma zone parapapillary atrophy (PPA) width were compared between the two groups. Factors associated with faster VF progression were determined by logistic regression analysis.ResultsThe mean follow-up duration was 8.9 ± 4.4 years. The mean value of SE and axial length were -6.31 ± 1.88 D and 26.05 ± 1.12 mm, respectively. The mean global visual field progression rate was -0.32 ± 0.38 dB/y. Tilt ratio, BM opening area, and gamma zone PPA width were significantly greater in the eyes with faster VF progression than those with slower progression. In multivariate analysis, these factors were significantly associated with faster VF progression (all P < 0.05), while SE and axial length were not associated with it.ConclusionIn myopic glaucoma subjects, tilt of the optic disc and temporal shifting and enlargement of the BM opening were associated with faster rate of VF progression between paired eyes. This suggests that myopia influences VF progression in glaucomatous eyes via optic disc deformations rather than via refractive error itself.

Biomechanical analysis of combining head-down tilt traction with vibration for different grades of degeneration of the lumbar spine

In recent years, a combination of traction and vibration therapy is usually used to alleviate low back pain (LBP) in clinical settings. Combining head-down tilt (HDT) traction with vibration was demonstrated to be efficacious for LBP patients in our previous study. However, the biomechanics of the lumbar spine during this combined treatment is not well known and need quantitative analysis. In addition, LBP patients have different grades of degeneration of the lumbar spinal structure, which are often age related. Selecting a suitable rehabilitation therapy for different age groups of patients has been challenging. Therefore, a finite element (FE) model of the L1–L5 lumbar spine and a vibration dynamic model are developed in this study in order to investigate the biomechanical effects of the combination of HDT traction and vibration therapy on the age-related degeneration of the lumbar spine. The decrease of intradiscal pressure is more effective when vibration is combined with traction therapy. Moreover, the stresses on the discs are lower in the “traction+vibration” mode than the “traction-only” mode. The stress concentration at the posterior part of nucleus is mitigated after the vibration is combined. The disc deformations especially posterior disc radial retraction is improved in the “traction+vibration” mode. These beneficial effects of this therapy could help decompress the discs and spinal nerves and therefore relieve LBP. Simultaneously, patients with grade 1 degeneration (approximately 41–50 years old) are able to achieve better results compared with other age groups. This study could be used to provide a more effective LBP rehabilitation therapy.

해양시추선용 경량수밀댐퍼 설계

This study has designed and evaluated the safety of watertight damper for Offshore Rigs. The watertight damper is an improved design for conventional DN 350 butterfly valve. Numerical analysis has been performed to investigate the safety factor and seat leakage of the designed 3-type disk dampers. The structure analysis results present the deformations, the equivalent stresses and the safety factor. It was confirmed that the designed disk, rib-disk and streamlined disk of watertight damper are safe enough in maximum operating pressure of 0.98MPa. The results show that the disk damper had the smallest maximum deformations and stress among 3-type disk dampers and the safety factor was 4.3. Therefore it is confirmed that the disk damper has the most excellent strength. Also linear static structural analysis was individually conducted for disk and body. The results show that the maximum disk deformation was larger than the body deformation, Therefore the disk damper is causes no seat leakage.

Coupled Thermo‐Mechanical and Wear Effects on the Analysis of High Speed Railway Brake Systems

AbstractThe high speed railway brakes transfer a large amount of kinetic energy into heat. The temperature during a brake operation could reach values higher than 90 °C. The dynamics of the brake system is rather complicated with respect to the multiphysical phenomena. In this paper, the thermo‐mechanical coupling are investigated combined with the loos of brake material due to wear. The coupled model is discretized by conventional finite element method. Different coupled algorithms have been tested. Various scenarios have been simulated and shown reasonable results. The temperature and deformation on pad and disc, especially the thermal deformation of disc the so–called coning effect can also be prescribed with this coupled multiphysics model. Furthermore, the tapered wear on brake pads is also discussed as a requirement of railway brake design in terms of durability. Thereby, the Ehlers's model is normally used to minimize tapered wear by selecting an adequate point of applied braking force. An extended Ehlers's model is also presented here, which concerns wear effect based on Archard's model. (© 2016 Wiley‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

P20 - Ranges of Cervical Intervertebral Disc Deformation during an In Vivo Dynamic Flexion-Extension of the Neck

P20 - Ranges of Cervical Intervertebral Disc Deformation during an In Vivo Dynamic Flexion-Extension of the Neck

Failure Mechanism of Foamed Concrete Made with/without Additives and Lightweight Aggregate

It has been reported that owing to a densification of the internal structure of concrete, adding mineral admixtures leads to a more brittle behaviour. Therefore, with the intention of modifying (increasing the strength of) foamed concrete to make it suitable for structural purposes by means of admixtures and lightweight aggregate addition, the effect of these additions on the failure mechanism under compressive and tensile loading using different techniques is evaluated and discussed in this paper. Eight different mixes, made using a pre-formed foam, were investigated with varying density (different foam volumes), nominally 1300, 1600 and 1900 kg/m3, without/with admixtures (silica fume, fly ash and superplasticizer) and lightweight aggregate. The Digital Image Correlation (DIC) technique was adopted to measure the deformations and strains on the surface of a specimen under uniaxial compressive load. Meanwhile, a Video Gauge technique was used to measure the horizontal deformation of discs during a splitting tensile test. From elasticity, fracture and fractal points of view, it was found that, for the same density, brittleness increases with many of the additives while it reduces with inclusion of lightweight aggregate. However, for all mixes, the lower the density (higher added foam volume), the higher the ductility.

Effects of Cervical Extension on Deformation of Intervertebral Disk and Migration of Nucleus Pulposus

BackgroundWe theorized that active cervical extension should influence the position of the nucleus pulposus (NP) within the intervertebral disk (IVD) in the sagittal plane. Although several studies on the lumbar IVD have been conducted, there are no quantitative data for in vivo positional changes of the NP in the cervical IVD. ObjectiveTo evaluate the influence and mechanism of cervical extension on the deformation and migration of IVD and NP in the sagittal plane and understand underlying mechanisms of the extension maneuver. DesignAsymptomatic subjects underwent magnetic resonance imaging while supine with their cervical spines in neutral and extended positions. SettingAcademic medical center. ParticipantsTen young, healthy male participants (age range 19-30 years; mean 22.4 ± 1.64 years). MethodsT2-weighted sagittal images from C3-C4 to C6-C7 of subjects in both neutral and extension positions were analyzed. Main Outcome MeasurementsDeformation of IVD and positional change of NP were quantified and compared between neutral and extension positions. Intersegmental angles between vertebrae, horizontal positions of anterior and posterior IVD and NP margins, IVD outer and inner heights, and sagittal morphology of NP were quantified and compared between the neutral and extension positions. Correlations between the measured parameters and segmental extension angle were also investigated. ResultsAnterior and posterior IVD margins moved posteriorly with respect to the vertebral body in extension. Both NP margins remained unchanged relative to the vertebral body but moved anteriorly with respect to the IVD. IVD outer and inner heights in the anterior region increased in extension, and morphological changes of the NP were less noticeable when compared with its relative migration within the IVD. Most of the intradiskal changes were linearly correlated with the segmental extension angle. ConclusionsCervical extension induces anterior migration of the NP away from the posterior disk margin and may have a clinical effect on diskogenic neck pain resulting from internal disk disruption. Level of EvidenceNot applicable.