Development of an adaptive two-phalanx grip model for robotic manipulators

The aim of the study was to develop a new FEM (finite element method) model of a mandible with the temporal joint, which can be used in the numerical verification of the work of bonding elements used in surgical operations of patients with mandibular fractures or defects. Most of such types of numerical models are dedicated to a specific case. The authors engaged themselves in building a model that can be relatively easily adapted to various types of tasks, allowing to assess stiffness, strength and durability of the bonded fragments, taking into account operational loads and fatigue limit that vary in time. The source of data constituting the basis for the construction of the model were DICOM (digital imaging and communications in medicine) files from medical imaging using computed tomography. On their basis, using the 3D Slicer program and algorithms based on the Hounsfield scale, a 3D model was created in the STL (standard triangle language) format. A CAD (computer-aided design) model was created using VRMesh and SolidWorks. An FEM model was built using HyperWorks and Abaqus/CAE. Abaqus solver was used for FEM analyses. A model meeting the adopted assumptions was built. The verification was conducted by analyzing the influence of the simplifications of the temporomandibular joint in the assessment of mandibular strain. The work of an undamaged mandible and the work of the bonded fracture of the mandible were simulated.

Validation of an automated method of three-dimensional finite element modelling of bone

Electrothermal purification is an effective method for achieving over 99.9 pct purity for graphite particles with minimal environmental impact. However, the lack of a suitable heat and electric resistivity model has hindered the scaling up of electrically heated fluidized bed (EHFB) reactors for graphite purification. In this study, three commercial natural graphite flake populations were tested in a bench-scale fluidized bed reactor at temperatures of up to 1000 °C. The experiments varied key parameters, including the graphite particle size, particle bed temperature, fluidization index, and electrode depth within the particle bed. Controlling the fluidized bed reactor at high temperatures requires an understanding of bed resistivity and how current flows throughout the EHFB system. The results show that fluidized bed resistivity decreases with temperature, with a diminished effect at higher temperatures. Smaller particles exhibit a higher resistance, likely due to a larger number of contact points required to pass current between the electrodes. In this study, a Finite Difference Method (FDM) model was developed using Visual Basic for Applications (VBA) in Excel®. Additionally, a Finite Element Method (FEM) model was created using COMSOL Multiphysics®. The FDM model assumes the current flows only radially, whereas the FEM model accounts for both radial and vertical current flow. The FDM model was validated against experimental data. Additionally, the FDM model was verified through a comparison with the FEM model. The FDM model showed good agreement with experimental resistance data and moderate agreement with power consumption, while the FEM model provided more accurate predictions by accounting for a detailed geometry and heat loss mechanisms. Achieving a uniform temperature distribution within the fluidized bed is influenced by the electrode’s contact area. Deeper immersion of the electrode enhances thermal uniformity and provides results that more closely match experimental observations.

The thermal conductivity of emulsion-polymerized styrene–butadiene rubber (ESBR) composites filled with carbon nanotubes (CNTs), zinc oxide (ZnO) and alumina (Al2O3) was predicted using the finite element method (FEM). Two-dimensional (2D) FEM models, which involved the effects of aspect ratio (AR), shape, orientation and thermal conductivity anisotropy (TCA) of the CNTs, and interfacial thermal resistance (ITR), were used to simulate the microstructure of CNT filled ESBR composites. Also, 2D and three-dimensional (3D) FEM models were developed to simulate the microstructure of Al2O3 or ZnO filled ESBR composites. An increase in the thermal conductivity with increasing Al2O3 or ZnO loadings was predicted by the FEM. The orientation angle (OA) of the CNTs and the ITR strongly affect the thermal conductivity as predicted by the FEM. The TCA of the CNTs also has a prominent effect on the thermal conductivity when CNTs have a relatively small OA. At a given filler loading, the thermal conductivity increased with the increasing intrinsic thermal conductivity of the filler over a certain range for a particular shape of filler. The thermal conductivities predicted by the FEM were compared with those predicted by Agari's models and the experimental results. The trends of the thermal conductivity predicted by the FEM agreed with the experimental data. The thermal conductivity of the ESBR composites predicted by 2D and 3D spherical particle filler (SPF) FEM models as a function of ZnO and Al2O3 loading showed that the 3D SPF FEM model agreed well with the experimental results at low loadings (not higher than 20 phr), while the 2D SPF FEM model agreed well with the experimental results at high loadings (higher than 80 phr). In addition to being used for the analysis of existing composites, the proposed FEM models are useful for the design and optimization of new composite materials, and are expected to provide a more insightful understanding into the thermal conductivity of polymeric composites.

This paper introduces the design of a small-size single-pylon cable-stayed bridge to be built in Xingtai city, China. The main structural members of this bridge including box-girder, stayed cables and pylon were selected to meet the requirement of bearing properties and artistic display. The numerical model for analyzing the static properties of the bridge structure was made by the design software MIDAS/Civil. The distribution and ultimate value of internal forces, stress and displacement of these main members are summarized, which provide the basis for calculating the reinforcement and prestressed strands of the bridge.

Evaluation of the biomechanical effects and stability of titanium and carbon fiber-reinforced polyetheretherketone mini plates in Le Fort I advancement osteotomy fixation using finite element analysis

A study was conducted to analyze the stress distribution of masticatory forces on Zirconia (Kids e), Bioflx (Kids e), and experimental Graphene crowns in primary mandibular molars using finite element analysis (FEA). The research aimed to assess the comparative performance of these materials to better understand their suitability for dental applications. This was an in vitro study conducted using FEA models developed from cone-beam computed tomography (CBCT) images of primary mandibular second molars. The study compared stress distribution on three crown materials: Zirconia, Bioflx, and experimental Graphene. Virtual geometry models (VGMs) of primary second molars, each restored with a Bioflx crown, Graphene crown, and Zirconia crown, were created using CBCT images. The images were processed using specialized software to reconstruct a three-dimensional model of the dentoalveolar structures. These VGMs were then used to perform FEA to evaluate stress distribution under simulated masticatory forces. The crown materials were compared for stress levels. Zirconia crowns exhibited the lowest stress values (368.3 MPa), followed by Bioflx crowns (520.92 MPa) and Graphene crowns (555.69 MPa) showing the highest stress levels. The study also found that glass ionomer cement (GIC) type I posed a higher risk of fracture in Graphene crowns, with a stress value of 130.83 MPa. Zirconia crowns demonstrated superior stress resistance under masticatory forces compared to Bioflx and Graphene crowns in primary mandibular second molars. However, the use of GIC type I with Graphene crowns may increase the risk of fracture, suggesting that material selection and luting agents need careful consideration in clinical practice.

This study aims to investigate the numerical behaviors of the mixed lubrication model in point contact and three-dimensional (3D) line contact based on the non-normalized discretization, in which the dimensional Reynolds equation is discretized according to the full analysis of the pressure balance. The solution is iteratively obtained from an initial value by the analysis of the dry contact and the model is capable of both the steady-state and the time-dependent lubrication in a large range of entrainment velocity. The transient solutions of the startup and shutdown processes in point contacts are compared with those experimentally measured and good consistency is achieved, and effects of the time intervals on lubrication evolution are numerically investigated. The algorithm developed in this study enables its application for the elliptical lubrication without ellipticity parameters specified. The contact of a roller with a flat surface is presented to demonstrate the generality of the point-contact model and the effects of roughness orientation are also revealed. The numerical errors of the 3D-line lubrication brought by the formulation of the solution matrix are then discussed in detail, comparing with the solutions of the two-dimensional (2D) lubrication model. It is concluded that the hydrodynamic effect along the extending direction plays an important role in the lubrication when surfaces with transversely oriented roughness are concerned and the 3D model may provide a more reasonable solution. The 2D lubrication model, nevertheless, may provide a relatively accurate solution along a specified line for the longitudinal roughness while consuming less computational time.

Muscle elasticity strongly relies on the mechanical anchoring of the giant protein titin to both the sarcomere M-band and the Z-disk. Such strong attachment ensures the reversible dynamics of the stretching-relaxing cycles determining the muscle passive elasticity. Similarly, the design of biomaterials with enhanced elastic function requires experimental strategies able to secure the constituent molecules to avoid mechanical failure. Here we show that an engineered titin-mimicking protein is able to spontaneously dimerize in solution. Our observations reveal that the titin Z1Z2 domains are key to induce dimerization over a long-range distance in proteins that would otherwise remain in their monomeric form. Using single molecule force spectroscopy, we measure the threshold force that triggers the noncovalent transition from protein dimer to monomer, occurring at ∼700 piconewtons. Such extremely high mechanical stability is likely to be a natural protective mechanism that guarantees muscle integrity. We propose a simple molecular model to understand the force-induced dimer-to-monomer transition based on the geometric distribution of forces occurring within a dimeric protein under mechanical tension.

A field live load test and a finite element method (FEM) analysis performed on an existing 60° skew, three-span continuous steel girder bridge are presented. The live load testing program with nonstandard truck load was carried out to allow for assessing the adequacy of existing structures and pier support to carry an HS25 standard load. In particular, it was of interest to evaluate the effect of bridge skew on the distribution of reaction forces at interior piers. The measured bridge response under the live load was used to develop and calibrate a FEM model by using the ANSYS computer program. The calibrated FEM model was then used to predict bridge response under an HS25 load. For all load cases investigated, the FEM results showed that distribution of vertical reaction forces on the interior piers was nonuniform. The analysis results indicated that higher reaction forces were experienced by piers on the side of the bridge closer to the obtuse corner than on the side near the acute corner. The importance of using actual field measured test data to develop and calibrate a realistic FEM model is demonstrated.

Nature of stress accommodation in sheared granular material: Insights from 3D numerical modeling

Context:To understand the effect of masticatory and parafunctional forces on the integrity of the prosthesis and the underlying cement layer.Aims:The purpose of this study was to evaluate the stress pattern in the cement layer and the fixed prosthesis, on subjecting a three-dimensional finite element model to simulated occlusal loading.Materials and Methods:Three-dimensional finite element model was simulated to replace missing mandibular first molar with second premolar and second molar as abutments. The model was subjected to a range of occlusal loads (20, 30, 40 MPa) in two different directions – vertical and 30° to the vertical. The cements (zinc phosphate, polycarboxylate, glass ionomer, and composite) were modeled with two cement thicknesses – 25 and 100 μm. Stresses were determined in certain reference points in fixed prosthesis and the cement layer.Statistical Analysis Used:The stress values are mathematic calculations without variance; hence, statistical analysis is not routinely required.Results:Stress levels were calculated according to Von Mises criteria for each node. Maximum stresses were recorded at the occlusal surface, axio-gingival corners, followed by axial wall. The stresses were greater with lateral load and with 100-μm cement thickness. Results revealed higher stresses for zinc phosphate cement, followed by composites.Conclusions:The thinner cement interfaces favor the success of the prosthesis. The stresses in the prosthesis suggest rounding of axio-gingival corners and a well-established finish line as important factors in maintaining the integrity of the prosthesis.

The design of optimized and efficient solar cells is a key factor for the future development of the photovoltaic (PV) technology. This paper focuses on three-dimensional (3D) modeling of a Back Contact-Back Junction (BC-BJ) crystalline silicon (c-Si) solar cells featuring a point contact (PC) scheme in the rear emitter region in order to optimize the efficiency with respect to the use of a conventional linear contact (LC) pattern. A 3D model has been built to ensure a good accuracy in the simulation of the considered solar cell structures. The developed model includes a proper modeling of the series resistance effects related to the implemented contact pattern. The TCAD Sentaurus software provided by Synopsys has been adopted to perform comparative simulations between the considered PC BC-BJ solar cell and its LC counterpart. Our simulation results prove that the adoption of a PC scheme in the emitter region of a BC-BJ solar cell is beneficial to boost its efficiency (up to 22.43%) with respect to the conventional LC cell, while keeping lower the contacted fraction of the emitter region.

Three dimensional analysis of mechanical behavior of lumbar vertebra under impact load and its biomechanical importance

A BE Hyper-singular Formulation for Contact Problems using Non-conforming Discretization