Abstract: When a patient is undergoing a total knee arthroplasty, the proximal tibia is cut with a certain depth for tibial tray mounting. Moreover, the proximal tibia plateau is then drilled distally to create a hole where the tibial tray stem is inserted. Due to the existence of tibial tray stem stuck into the central part of the proximal tibia, the development of stress around the stem becomes the interesting parameter to be investigated, especially in the cement. For this purpose, a simplified two-dimensional finite element model has been created. The focus of the result analysis was fixed only on the knee bend activity load due to the highest von Mises stress occurred in this activity. The highest von Mises stress of 52.80 MPa occurred in the tibial tray, and then followed by the cortical bone, cement, central cancellous bone, and edge cancellous bone with von Mises stresses were 34.56, 5.40, 1.41, and 1.26 MPa, respectively. In the field of displacement and true strain in the cement, the highest resultant of displacement of 0.2mm occurred in the top section of the cement. Around the posterior tip, the cement experienced the tensile strain of 0.02 and around the anterior tip the strain was the compressive strain with similar value.
Abstract: The paper presents a complex material model which covers the elastic-plastic behavior, material deterioration and ductile fracture. The calibration of such model was conducted for Aluminum Alloy (AA) 2024-T351 using specimens with various geometries and loading which covers various stress states. The model was then applied to the simulations of tensile test of plates. The computations were carried out in Abaqus/Explicit using the user subroutine Vectorized User MATerial (VUMAT), where the crack initiation and subsequent propagation was realized using the element deletion technique. The results were compared to the experimental observation in the end.
Abstract: The downtime problem of wind turbine increases due to fatigue damage of wind turbine blades, which is even more crucial in the larger blades. One of the critical failure modes is the blade trailing edge failure, which can result in the trailing edge joint cracked. In this paper, we experienced that abnormal sound was happened in the trailing edge at the cross-section in the max chord during fatigue testing of a 2 MW full-scale wind turbine blade according to IEC61400-23. Through the conditional monitoring of the trailing edge, the delamination between GFRP and balsa wood is caused by stress concentration. The abnormal sound is happened due to GFRP beat the balsa wood when the blade vibrates in the edgewise direction. Moreover, the sound is amplified because the introduction of air due to the delamination. The local stress distribution and stability factors are computed through FEM methods, the program that increasing the core materials in the trailing edge is proposed. Therefore the structure reliability in the trailing edge is improved.
Abstract: This study aims to investigate the quasi-static response of linear viscoelastic Kirchhoff plates of uniformly varying cross-section subjected to time-dependent loads. Four-parameter solid model is used for defining the linear viscoelastic material behavior. Through an efficient systematic procedure based on the Gâteaux Differential (GD), a functional has been constructed for the analysis. For the analysis, mixed finite element (MFE) method in transformed Laplace-Carson space is used. For transformation of the solutions obtained in the Laplace-Carson domain to the real time domain, Dubner & Abate (D&A) numerical inverse transform technique is employed.
Abstract: Ultra-high molecular weight polyethylene (UHMWPE) is a tough semi-crystalline polymer employed widely as a bearing material in total joint replacements. The micromechanical model has been presented that predicts stiffness of UHMWPE as an aggregate of crystalline inclusions (lamellae) embedded in a rubbery matrix of amorphous polymer chains. The differential scheme was chosen for its ability to represent the interaction between an inclusion and the matrix. Numerical simulations show that increasing lamellar thickness results in less stiffness, less shear stress imposed on the lamellae, indicates that thick lamellae are desirable for UHMWPE materials utilized in total joint replacement bearings.
Abstract: The paper focuses on the analysis of the eccentricity effect in the measurement of the hole-drilling residual stress. Relaxed strains were evaluated by computational simulation of the hole-drilling experiment using the finite element method. Errors induced by eccentricity were estimated for elastic and elastic-plastic states in area around the drilled hole due to the stress concentration. The invariance of the stress change with depth was assumed. The correction of eccentricity and plasticity effects in evaluation of residual stresses was realized within the EVAL 7 software (SINT Technology). The analysis shows that in elastic state the eccentricity and angular position of the drilled hole have a significant effect on relative residual stress errors. Correction according to the HDM method is very effective in this case. If the relative error of 5 % is allowed, which is in engineering practice acceptable, eccentricity of ±0.05 mm could be accepted without correction. When the combination of eccentricity and plasticity occurs, the correction of plasticity is more important in method 13-EXT-UN.
Abstract: The paper reviews stress and deformation analysis of the thin coating. The coating covers a surface of a contact component of the trapeziometacarpal joint replacement which serves as a surgical treatment of a hand joint disease called rhizarthrosis. Motivation for this study consists mainly in the fact of occasional damage of some parts of the replacement in practice . It emerged that the thin coating breaks in the location of contact which opens an effort to explore stress states of such a location depending on various input parameters. Better awareness of detailed contact conditions could lead to improvement of the replacement design and, thus, prevention from necessary reoperation.
Abstract: Soft solid undergoes large deformation under external loading. In order to understand the mechanical characteristics of soft solid, a quantitative evaluation of the deformation behavior is necessary. In the previous study, a strain distribution on the surface of soft solid during an indentation (penetration) test was obtained by evaluating the deformation behavior using isoparametric finite element. However, three-dimensional deformations including out-of-plane deformation was neglected. In this study, the deformation behavior of the soft solid was analyzed using a stereo camera system and binocular disparity method. The out-of-plane deformation of the soft solid was then reconstructed three-dimensionally. Analysis result showed that this study was able to reconstruct the out-of-plane deformation in the area below the indenter. In addition, the displacements of specific points located on the deformed surface could also be estimated. Under the indentation loading condition, the out-of-plane displacements of points in the area below the indenter were estimated to be between 5.9 and 9.9 mm. However, the accuracy of the estimation should be validated by other measurement techniques in the future.
Abstract: The present study is performed for investigation of the correlation between UPV value and strength of rubber-concrete. Compressive and splitting tensile strengths of concrete containing waste tire-rubber particles by four different volume contents were investigated using ultrasonic pulse velocity (UPV) test and direct destructive tests. Test results showed that ultrasonic pulse velocity test can be successfully estimated to the strength of rubber-concrete as used in normal concrete.
Abstract: In order to let fresh concrete react with carbon dioxide sufficiently, the carbon dioxide was added to mixing concrete. The study used three water cement ratio (0.55, 0.65, 0.75), three CO2 pressures (0.2, 0.4, 0.6 MPa), and two CO2 concentration (50% and 100%) to make concrete samples, and observed the effect of carbon dioxide adsorption in the above parameters. Finally, the compressive strength and carbonation degree of concretes were tested after three curing time (7, 14 and 28 days). The research showed that concrete could be more efficient to absorb carbon dioxide by using this pressure method. The results found that the mixing concrete react with carbon dioxide in a short time, and shorten the initial setting time of concrete. But this method would greatly reduce the workability of concrete after mixing with carbon dioxide and it might be enhanced by water or superplasticizer. The bond of cement matrix might cut down after reacting with carbon dioxide. Based on the above, the compressive strength of concrete which was mixed with carbon dioxide would be impaired. The proposed CO2-mixing method has the capacity to uptake 9.5% carbon dioxide based on water cement ratio and CO2 pressure.