Twin-Shaft Mixers' Mechanical Behavior Numerical Simulations of the Mix and Phases

In this paper, the mechanical behavior of concrete twin-shaft mixers is analyzed in terms of power consumption and exchanged forces between the mixture and the mixing organs during the mixing cycle. The mixing cycle is divided into two macro phases, named transient and regime phase, where the behavior of the mixture is modeled in two different ways. A force estimation and power consumption prediction model are presented for both the studied phases and they are validated by experimental campaigns. From the application of this model to different machines and by varying different design parameters, the optimization of the power consumption of the concrete twin-shaft mixers is analyzed. Results of this work can be used to increase productivity and profitability of concrete mixers and reduce energy waste in the industries which involve mixing processes

Characterization of finger joints with underactuated modular structure

The characterization of flexible joints of robotic underactuated fingers allows the investigation of the finger flexion trajectories using a tendon-driven actuation. In this paper, the characterization of TPU 3D printed joints used in underactuated robotic fingers, is experimentally and numerically performed. Since the mechanical properties of 3D printed materials are uncertain, this research helps to define the characteristics of robotic fingers in terms of stiffness. The role of the stiffness for the control of fingers’ trajectories is fundamental and the obtained results are very useful for improving the method to track a certain predefined trajectory. Experimental and theoretical results evaluate the stiffness as a function of the infill density percentage of the materia

Do Exostoses Correlate with Contact Disfunctions? A Case Study of a Maxillary Exostosis

A maxillary exostosis is a benign overgrowth of bone that occurs on the outer or facial surface of the maxilla and is usually located near the premolar or molar teeth. This paper investigates the correlation between the presence and growth of jaw exostoses and the oral mechanics of contact. For this purpose, a case study of an upper jawbone exostosis of a female patient was considered. 3D models of the patient’s cranial bones were extracted from 2D computerized tomography (CT) data and were analyzed by proper software. A contact congruence evaluation based on the Winkler contact model was performed, and results were presented in terms of indentation maps and load distributions. Results were correlated with the theory of bone remodelling by Wolff

Metal Transfer evaluation on ceramic biocomponents: a protocol based on 3D Scanners

Titanium signs frequently appear on femoral heads coupled with metal back acetabular components, after dislocation or repositioning of total hip arthroplasties. These metallic deposits, called metal transfer, are a significant clinical phenomenon because they can affect the resistance and tribological performance of the prosthesis. The quantification and the study of position of the metal transfer extent over a prosthesis surface is a scientific problem to be addressed to design more effective replacements. This paper proposes a new protocol to evaluate the metal transfer amount, employing 3D optical scanners, and reverse engineering software. The technique allows the assessment of metal transfer rates, absolute areal coverage, and position of the metal deposits by acquiring the 3D digital colored model of the hip ball surfaces with high-precision 3D scanners, and separating the regions with metallic depositions by 3D mesh processing. Results permit to evaluate effects on the tribological behavior of the synovial biobearing

New Challenges in Tribology: Wear Assessment Using 3D Optical Scanners

Wear is a significant mechanical and clinical problem. To acquire further knowledge on the tribological phenomena that involve freeform mechanical components or medical prostheses, wear tests are performed on biomedical and industrial materials in order to solve or reduce failures or malfunctions due to material loss. Scientific and technological advances in the field of optical scanning allow the application of innovative devices for wear measurements, leading to improvements that were unimaginable until a few years ago. It is therefore important to develop techniques, based on new instrumentations, for more accurate and reproducible measurements of wear. The aim of this work is to discuss the use of innovative 3D optical scanners and an experimental procedure to detect and evaluate wear, comparing this technique with other wear evaluation methods for industrial components and biomedical devices

Wear Distribution Detection of Knee Joint Prostheses by Means of 3D Optical Scanners

The objective of this study was to examine total knee polyethylene inserts from in vitro simulation to evaluate and display—using a 3D optical scanner—wear patterns and wear rates of inserts exposed to wear by means of simulators. Various sets of tibial inserts have been reconstructed by using optical scanners. With this in mind, the wear behavior of fixed and mobile bearing polyethylene knee configurations was investigated using a knee wear joint simulator. After the completion of the wear test, the polyethylene menisci were analyzed by an innovative 3D optical scanners in order to evaluate the 3D wear distribution on the prosthesis surface. This study implemented a new procedure for evaluating polyethylene bearings of joint prostheses obtained after in vitro wear tests and the proposed new approach allowed quantification of the contact zone on the geometry of total knee prostheses. The results of the present study showed that mobile TKPs (total knee prosthesis) have lower wear resistance with respect to fixed TKPs

A Numerical Procedure Based on Orowan’s Theory for Predicting the Behavior of the Cold Rolling Mill Process in Full Film Lubrication

In this paper, a numerical model for predicting the working parameters of the cold rolling mill process in full film lubrication is presented. The model is useful from an industrial point of view, because it can forecast the thickness reduction of the metal sheet and the pressure trend, so that the rolling mill process parameters can be regulated to obtain a specific output thickness. Experimental tests were performed, and results are compared to the theoretical ones resulting from the model. The novelty of the proposed model is that it combines Orowan’s theory for the plastic deformation analysis with the Reynolds equation in full film lubrication and the continuity conditions. The lubricant flow and viscosity are studied, taking in account their dependence on pressure and temperature. The proposed model describing the full film regime is also compared to another one, previously proposed by the authors, based on the well-known slab analysis and sharing with it the representation of the lubrication regime, the mathematical procedure, and the boundary conditions. The results show that the proposed model provides a better prediction of the working parameters with respect to the model based on the slab analysis