Combination of musculoskeletal and wear models to investigate the effect of daily living activities on wear of hip prostheses

Numerical wear predictions are gaining increasing interest in many engineering applications, as they allow to simulate complex operative conditions not easily replicable in the laboratory. As far as hip prostheses are concerned, most of the wear models in the literature are based on the simulation of gait (recommended also in experimental wear tests), since gait is considered the most frequent and important motor task to recover after arthroplasty. However, since joint prostheses have been increasingly implanted in younger people, high loads and potentially severe conditions, e.g. due to sporting activities, should also be considered for a more reliable wear assessment of these implants. In this study, we propose a profitable combination of musculoskeletal and analytical wear modelling for the prediction of wear caused by common daily activities in metal-on-plastic hip arthroplasties. Several motion analysis data available in the literature (walking, fast walking, lunge, squat, stair negotiation) were selected and the effects of such motor tasks on prosthesis wear were investigated, both separately and in combination. Additionally, for comparative purposes, wear prediction for simplified gait conditions prescribed by the ISO 14242 standard, were also considered. Results suggest that this latter case produces lower wear depth and volume with respect to a relatively demanding combination of the selected daily activities. The preliminary results of the present study represent a first step towards the auspicious goal of validating the proposed procedure for in silico trials of hip arthroplasties.

Mathematical Standard-Parameters Dual Optimization for Metal Hip Arthroplasty Wear Modelling with Medical Physics Applications

Total hip metal arthroplasty (THA) constitutes an important proportion of the standard clinical hip implant usage in Medical Physics and Biomedical Engineering. A computational nonlinear optimization is performed with two commonly metal materials in Metal-on-Metal (MoM) THA. Namely, Cast Co-Cr Alloy and Titanium. The principal result is the numerical determination of the K adimensional-constant parameter of the model. Results from a new more powerful algorithm than previous contributions, show significant improvements. Numerical standard figures for dual optimization give acceptable model-parameter values with low residuals. These results are demonstrated with 2D and 3D Graphical/Interior Optimization also. According to the findings/calculations, the standard optimized metal-model parameters are mathematically proven and verified. Mathematical consequences are obtained for model improvements and in vitro simulation methodology. The wear magnitude for in vitro determinations with these model parameter data constitute the innovation of the method. In consequence, the erosion prediction for laboratory experimental testing in THA adds valuable information to the literature. Applications lead to medical physics improvements for material/metal-THA designs.

Predictive Modelling and Technical Design Application into Effective Casing Wear Operational Management Plan

Predicting casing wear has often been regarded as an empirical art as there are many influencing factors, including but not limited to the sizes and grades of the drill pipe and casing, type of hardbanding, drilling fluid properties, rate of penetration, trajectory and formation properties. Formations present in offshore Western Australia often contain loose and friable sands which produce highly abrasive cuttings which, when suspended and circulated in drilling fluid, are known to exacerbate casing wear. Casing wear is considerably worse in deviated and multilateral (ML) wells; Woodside's experience drilling ML wells has involved costly non-productive time (NPT) due to the subsequent requirement for remedial tieback systems to maintain well integrity. In 2018 and 2019 three tri-lateral wells were drilled as part of the larger Greater Enfield Project drilling campaign. Each of the multilateral wells were progressively longer and more challenging with regard to casing wear. Previous experience on nearby wells in analogous fields identified casing wear as a significant risk for the project. Further to this, an opportunity was identified to design the longest tri-lateral well as a quad-lateral well, which would allow increased recovery if reservoir quality was poorer than expected. The Drilling and Completion Engineering team were challenged with proving that casing wear could be effectively evaluated and managed during operations to allow a quad-lateral well design if required. Several key areas were investigated in order to effectively manage casing wear. These included: Assessment and measurement of casing manufacturing tolerances;Predictive casing wear modelling using well offsets in conjunction with casing wear software;Casing connection finite element analysis and mechanical hardbanding testing;Full length ultra-sonic testing of casing for wall thickness benchmarking;Hardbanding management plan (which formed part of the overall drill pipe fatigue management plan);Casing wear management plan based on well offsets and casing wear software modelling results, including additional controls such as 'krev' and swarf monitoring;Planning and execution of casing wear logging;Post well evaluation. The casing wear operational plan was effective in monitoring and limiting the amount of wear. It provided confidence to the management team that successful execution of a quad-lateral well was feasible. This paper will describe the steps taken to minimise casing wear, discuss comparisons between the predicted wear and the actual measured casing wear, and provide a recommended workflow for predicting casing wear in future wells where casing wear is a critical factor.

CBN-Kornverschleißmodellierung/Numerical modeling of CBN grain wear during single grain engagement – CBN-grain wear modelling

Dieser Beitrag stellt die numerische Modellierung des CBN-Kornverschleißes beim Einkorneingriff mit der Finite-Elemente-Methode vor. Es wird erstmalig eine dreidimensionale Verschleißsimulation unter Verwendung realer CBN- Korngeometrien im Korn-Werkstückkontakt durchgeführt. Dazu werden drei reale Korngeometrien simuliert, um die Verschleißmechanismen des realen Korneingriffs abzubilden. Abschließend werden die Simulationsergebnisse mit empirischen Untersuchungen verglichen.   This article is about the numerical modeling of CBN grain wear in single grain engagement using the finite element method. A three-dimensional wear simulation using real CBN grain geometries in grain-workpiece contact is conducted for the first time. For this purpose, three real grain geometries are simulated to represent the wear mechanisms of the real grain engagement. Finally, the simulation results are compared with empirical investigations.

Finite Element Study of the Effect of Load Sequence on the Fretting Wear

Understanding the effect of load sequence is important in the context of a blade-disc dovetail joint in an aero-engine and many other such applications where, the mating surfaces undergo fretting wear under variable slip amplitude loading conditions. In the present work, a two-dimensional finite element analysis is carried out for a cylinder-on-plate configuration. The cylinder is modeled as deformable whereas the plate is modelled as rigid. An incremental wear modelling algorithm is used to model the wear of cylindrical pad while the plate is assumed as un-worn. This simulates a practical scenario where, generally one of the mating surfaces is sufficiently hardened or an interfacial harder/sacrificial element is inserted to restrict the wear to only one of the surfaces. A Fortran-based ABAQUS® subroutine UMESHMOTION is used to simulate the wear profile for the cylinder. A constant extrapolation technique is used to simulate 18000 cycles of fretting. The finite element analysis results are validated with the analytical solutions and literature data. The fretting wear modelling is carried out for two different slip amplitudes viz., 25 μm and 150 μm, to simulate the low and high slip amplitude loading respectively. Two blocks of alternate low and high slip amplitudes are applied to understand the influence of load sequence. Important contact parameters viz., contact pressure, contact stresses and contact slip are extracted. A comparison is made between the low-high and high-low load sequence based on the contact tractions and worn out profiles.