In hypoelastic constitutive models, an objective stress rate is related to the rate of deformation through an elasticity tensor. The Truesdell, Jaumann, and Green–Naghdi rates of the Cauchy and ...Kirchhoff stress tensors are examples of the objective stress rates. The finite element analysis software ABAQUS uses a co-rotational frame which is based on the Jaumann rate for solid elements and on the Green–Naghdi rate for shell and membrane elements. The user subroutine UMAT is the platform to implement a general constitutive model into ABAQUS, but, in order to update the Jacobian matrix DDSDDE in UMAT, the model must be expressed in terms of the Jaumann rate of the Kirchhoff stress tensor. This study aims to formulate and implement various hypoelastic constitutive models into the ABAQUS UMAT subroutine. The developed UMAT subroutine codes are validated using available solutions, and the consequence of using wrong Jacobian matrices is elucidated. The UMAT subroutine codes are provided in the “Electronic Supplementary Material” repository for the user’s consideration.
Stadnyk, M, Sepehri, M, Cook, M, Adeeb, S, and Westover, L. Quantifying asymmetry and performance of lower limb mechanical muscle function in varsity athletes-using non-countermovement jumps. J ...Strength Cond Res 37(1): 98-106, 2023-The ability to automatically quantify jump performance and lower limb muscle function in athletes would be beneficial for both training and rehabilitation purposes. Countermovement jumps (CMJs) and non-CMJs (NCMJs) are simple, quick, and require relatively inexpensive equipment to effectively and reliably monitor lower limb function. In a previous study, CMJ characteristics were assessed across different varsity sports. This study is a follow-up study to incorporate NCMJs into assessing jump characteristics of the same sports and investigate the additional information provided by the complementary jump type. The main objective of this study was to look at a means of quantifying the lower limb mechanical muscle function automatically to provide information for rehabilitation and performance purposes in athletes of specific sports. Male and female varsity athletes from 4 different sports completed 5 trials of an NCMJ on dual force plates. An analysis program was developed using Wolfram Mathematica to analyze force-time jump data. Various parameters of interest were generated, including peak force, force-time curve shape classification, jump phase lengths, phase-specific kinetic impulse, asymmetry index, takeoff velocity, jump height, phase-specific center of mass displacements, and reactive strength index modified. Results obtained indicate that similar jump characteristics to the CMJ study can be quantified, which can be used for performance enhancement or injury rehabilitation. Additional data found, such as the ability of an athlete to hold a steady squat during an NCMJ, could also be meaningful in aiding trainers to design programs tailored for athletes.
Customized talus implants have been regarded as a better treatment alternative to talus avascular necrosis than traditional surgical fusion because of its ability to maintain joint mobility while ...ameliorating pain. Despite the use of ankle hemiarthroplasty clinically, the cartilage contact characteristics of adjacent bones remain unclear. This study aims to use finite element modeling to evaluate the contact characteristics of three types of cobalt-chrome talus implants in three postures, in four subjects. This study also compared the contact area, contact pressure, and peak contact pressure of the implant models with a reference biological model. Among the various biological and implant models, our results showed that the biological models generally had the largest contact areas and smallest peak contact pressures, whereas the implant-type models had smaller contact areas and relatively larger peak contact pressure. Moreover, among the three implant types, customized-scale models showed a larger total contact area than that of the SSM-scale and universal-scale models, but their variation was relatively limited. The results from this study can have significance in future endeavors into ankle joint modeling, as well as being able to improve implant design to enhance recovery outcomes for patients who may benefit from talar replacement.
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Simulation studies, such as finite element (FE) modeling, provide insight into knee joint mechanics without patient involvement. Generic FE models mimic the biomechanical behavior of the tissue, but ...overlook variations in geometry, loading, and material properties of a population. Conversely, subject-specific models include these factors, resulting in enhanced predictive precision, but are laborious and time intensive. The present study aimed to enhance subject-specific knee joint FE modeling by incorporating a semi-automated segmentation algorithm using a 3D Swin UNETR for an initial segmentation of the femur and tibia, followed by a statistical shape model (SSM) adjustment to improve surface roughness and continuity. For comparison, a manual FE model was developed through manual segmentation (i.e., the de-facto standard approach). Both FE models were subjected to gait loading and the predicted mechanical response was compared. The semi-automated segmentation achieved a Dice similarity coefficient (DSC) of over 98% for both the femur and tibia. Hausdorff distance (mm) between the semi-automated and manual segmentation was 1.4 mm. The mechanical results (max principal stress and strain, fluid pressure, fibril strain, and contact area) showed no significant differences between the manual and semi-automated FE models, indicating the effectiveness of the proposed semi-automated segmentation in creating accurate knee joint FE models. We have made our semi-automated models publicly accessible to support and facilitate biomechanical modeling and medical image segmentation efforts ( https://data.mendeley.com/datasets/k5hdc9cz7w/1 ).
Overtime, continuous research efforts have been devoted to investigating the effects of permanent ground deformation (PGD) on buried pipelines. These efforts have faced major uncertainties in the ...ground movement patterns that impose displacement-controlled loads on pipelines. This study presents a systematic review of the PGD patterns available in the literature for the analysis of buried pipelines, with particular emphasis on the PGD directions relative to pipeline axes. Depending on the directions, PGD patterns are divided into three groups: longitudinal, transverse and oblique. The relevant literature is organized into four main categories: experimental, numerical, analytical and probabilistic. Seven different PGD patterns (block, ramp, step, ridge, sinusoidal, asymmetric ridge, and asymmetric sinusoidal) available in the literature are discussed in this study. All these PGD patterns, except asymmetric sinusoidal, were applied in the longitudinal direction. In contrast, only three (block, sinusoidal and asymmetric sinusoidal) were applied transversely, which indicates a potential gap considering the randomness of PGD relative to pipeline axes. Besides, one additional PGD pattern (trapezoidal) is suggested in the present study based on the literature review. The findings of the present study show that 84 % of the reviewed cases considered either block or sinusoidal PGD pattern, while only 16 % considered the other PGD patterns (ramp, step, ridge, asymmetric ridge, and asymmetric sinusoidal). Almost all these 16 % reviewed cases assumed pipelines primarily as linear elastic materials. Based on these observations, the present study recommends a comprehensive study on the effects of all the mentioned PGD patterns on pipelines in all three directions.
How reduced femoral neck anteversion alters the distribution of pressure and contact area in Hip Resurfacing Arthroplasty (HRA) remains unclear. The purpose of this study was to quantitatively ...describe the biomechanical implication of different femoral neck version angles on HRA using a finite element analysis. A total of sixty models were constructed to assess the effect of different femoral neck version angles on three different functional loads: 0°of hip flexion, 45°of hip flexion, and 90° of hip flexion. Femoral version was varied between 30° of anteversion to 30° of retroversion. All models were tested with the acetabular cup in four different positions: (1) 40°/15° (inclination/version), (2) 40°/25°, (3) 50°/15°, and (4) 50°/25°. Differences in range of motion due to presence of impingement, joint contact pressure, and joint contact area with different femoral versions and acetabular cup positions were calculated. Impingement was found to be most significant with the femur in 30° of retroversion, regardless of acetabular cup position. Anterior hip impingement occurred earlier during hip flexion as the femur was progressively retroverted. Impingement was reduced in all models by increasing acetabular cup inclination and anteversion, yet this consequentially led to higher contact pressures. At 90° of hip flexion, contact pressures and contact areas were inversely related and showed most notable change with 30° of femoral retroversion. In this model, the contact area migrated towards the anterior implant-bone interface along the femoral neck. Femoral retroversion in HRA influences impingement and increases joint contact pressure most when the hip is loaded in flexion. Increasing acetabular inclination decreases the area of impingement but doing so causes a reciprocal increase in joint contact pressure. It may be advisable to study femoral neck version pre-operatively to better choose hip resurfacing arthroplasty candidates.
Three dimensional (3D) markerless asymmetry analysis was developed to assess and monitor the scoliotic curve. While the developed surface topography (ST) indices demonstrated a strong correlation ...with the Cobb angle and its change over time, it was reported that the method requires an expert for monitoring the procedure to prevent misclassification for some patients. Therefore, this study aimed at improving the user-independence level of the previously developed 3D markerless asymmetry analysis implementing a new asymmetry threshold without compromising its accuracy in identifying the progressive scoliotic curves.
A retrospective study was conducted on 128 patients with Adolescent Idiopathic Scoliosis (AIS), with baseline and follow-up radiograph and surface topography assessments. The suggested "cut point" which was used to separate the deformed surfaces of the torso from the undeformed regions, automatically generated deviation patches corresponding to scoliotic curves for all analyzed surface topography scans.
By changing the "cut point" in the asymmetry analysis for monitoring scoliotic curves progression, the sensitivity for identifying curve progression was increased from 68 to 75%, while the specificity was decreased from 74 to 59%, compared with the original method with different "cut point".
These results lead to a more conservative approach in monitoring of scoliotic curves in clinical applications; smaller number of radiographs would be saved, however the risk of having non-measured curves with progression would be decreased.
Ground movements caused by continuous freezing and thawing of the ground in arctic regions can potentially lead to pipeline failures. There are many factors such as internal pressure, pipeline ...geometry, pre-crack, corrosion, and pre-existing dents that can expedite the failure processes. There exist several methods to predict the failure in pipelines and study the abovementioned factors and their influences. These methods include experiments, analytical models, finite element method (FEM), and extended finite element method (XFEM). For predicting crack propagation in pipelines, XFEM has recently been proposed by researchers as the most efficient among the available methods. The purpose of our work is to conduct a systematic literature review of the available studies that attempted to use XFEM to predict failure due to crack propagation in pipelines and the effect of the abovementioned factors on failure. Articles are summarized according to the performed experiments, the pipeline material grade, failure material model, the investigated effect of various parameters on failure such as internal pressure or defect size, and methods for results verification. The number of articles in the literature using the XFEM for prediction of failure in pipelines was 23 to the best knowledge of the authors. However, in this systematic literature review, all these articles are categorized and investigated. The reviewed articles in general agree that XFEM simulations compare well with experiments, can accurately predict crack propagation in pipelines, and can be used efficiently to study the effect of various parameters on pipeline crack propagation for a wide range of materials.
In this study a methodology is developed and implemented in Python for fatigue crack growth prediction in pipelines, by leveraging measurement data and fatigue growth model predictions. Specifically, ...Particle Filter (PF) algorithm, Paris law, and the stress intensity factor (SIF) model in API 579 are integrated into a tool to use noisy crack size measurements for estimating the current crack size and fatigue model parameters, also known as joint state-parameter estimation. For illustration purpose, pseudo-data set for crack size measurements is generated considering additive Gaussian white noise of two different noise levels, aiming to mimic crack size data obtained from In-line Inspection (ILI) tools. It is found that the crack state can be reliably estimated compared to noisy measurements and initial model predictions, and the true model parameters can be updated with good accuracy. As such, the current crack size estimated and model parameters updated can be used in the fatigue growth model (i.e., Paris law) to predict the future trajectory of the fatigue crack growth. As more measurement data becomes available, the developed tool more reliably estimates the future crack growth trajectory.
Dent defects can decrease the life span of oil and gas pipelines. Therefore, they need constant monitoring and maintenance to ensure the pipeline’s safety and integrity. Subsequently, this paper ...performs a strain-based reliability analysis on pipe dent defects using a response surface method (RSM) with a quadratic response surface (RS), including the interaction terms between the RS variables. The analyses are performed to determine the factors controlling the dent defects’ probability of failure (POF). Different pipe configurations, pipe lengths, indenter sizes, and dent depths are considered in this study. A suitable finite element (FE) model for the reliability analysis was developed for this study using the FE analysis software ABAQUS. The uncertainties in the pipe wall thickness, the dent depth, the yield strength of the pipe material, and the strain capacity are considered for the reliability analysis. The first-order reliability method (FORM) is used in the RSM as the reliability method to calculate the POF and the most probable point (MPP). The POFs of several dent defects were calculated. It has been found that the POF, which is highly related to the nominal value of the maximum equivalent plastic strains generated in the dent defect, is not only related to the indentation depth or the size of the indenter. Thus, the dent depth criterion used in the engineering practice can lead to inconsistent reliability levels in dented pipes.
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