Fatigue damage in spline couplings: numerical simulations and experimental validation

Abstract Spline couplings are often over dimensioned concerning fatigue life, but they are subjected to wear phenomena. For as concerns fatigue life, standard design methods consider only a part of the spline teeth to be in contact and this brings to underestimate the components life, so a better understanding about component fatigue behavior may allow to a weight reduction and a consequent increasing of machine efficiency. On the other hand, wear damage may cause spline coupling run outs; this phenomenon is generally caused by the relative sliding between engaging teeth; the sliding may be due to kinematic conditions (angular misalignment between shafts) of teeth deflection. In order to obtain component optimization, both fatigue and wear behavior have to be taken into account. Standard spline coupling design methods do not properly consider wear damage and they evaluate fatigue life with big approximations. In this work fatigue damage are experimentally and numerically investigated while wear damage has been experimentally evaluated. Experimental results have been obtained by a dedicated test rig. Fatigue tests have been performed by means of a special device connected to a standard fatigue machine. Tests have been done by varying the most important working parameters (torque and misalignment angle). Experimental results have been compared with standard design methods to evaluate if and how they may over dimension the components. Results show that concerning the fatigue life, the actual component life is higher respect to that calculated by standard methods. Regarding wear behavior, results shows that whenever a relative motion between engaging teeth is present, wear damage appears

methodology development to design a representative test specimen for wear damage in spline couplings

Abstract Aim of this paper is to develop a new methodology in order to design a representative test specimen for wear damage characterisation in spline couplings. In other words, real component and test specimen (same material) have been considered having a common target that is an isodamage condition reached after an established number of working (testing) cycles.Influence parameters chosen for this aim are, under the hypothesis of equal friction coefficient, hertzian pressure due to the load entity (torque) and the corresponding slidings. Slidings have been determined referring to two different working conditions, traditional fatigue testing with variable torque (aligned conditions) and wear testing in misaligned conditions. Specimen geometry has been firstly stated following DIN 5480 requirements, then profile micro geometries have been varied to tune the established target parameters and the corresponding FEM simulations have been carried on. Hertzian pressure values and corresponding contact areas have been verified by classical formula.A preliminary experimental activity has been done in order to verify the specimen design related to isodamage dimensioning aspects

experimental investigation about tribological performance of grapheme nanoplatelets as additive for lubricants

Abstract Graphene has received a great interest by researchers in a wide field of applications. Referring to tribological aspects, graphene has been considered as an additive in lubricants, in order to reduce components friction and machine losses. Some papers are available in literature about graphene utilized as additive in solids or liquid lubricants. Despite the big potential of graphene in this field, its use as a lubricant or a lubricant additive on macro-meso scale remains relatively unexplored. In particular, the literature is lacking about specific applications of graphene added lubricants on mechanical systems. In this paper, the effect graphene added to a standard lubricants to create high performance compounds has been investigated. Firstly, the Coefficient of Friction (CoF) of different compositions of lubricant-graphene compounds has been experimentally evaluated. In particular, a commercial grease and two commercial oils have been chosen to be used as base lubricants. Results in terms of Coefficient of Friction values of all compounds have been compared each other. Finally, characterization results of graphene added grease have been related to that available from previous studies performed on a mechanical component (a spline coupling), commonly used in many industrial applications, lubricated by the same graphene-grease compounds. Results show that graphene added to viscous lubricants generally reduces the coefficient of friction, in both materials and components

Update on the fluorometric measurement of enzymatic activities for Lysosomal Storage Disorder detection: The example of MPS VI

Lysosomal Storage Disorders (LSD) are rare diseases that as a whole havea combined incidence ranging from 1:1500 to 1:7000 live births. One of suchdiseases is Mucopolysaccharidosis VI (MPS VI), or Maroteaux Lamy Syndrome.MPS VI patients undergo devastating and irreversible skeletal alterations andmultisystemic failure as from early childhood due to reduced Arylsulfatse B(ARSB) enzyme activity.Reaching a final diagnosis is not always a short cut path, but rather a yearslongbattle against uncertainty and unnecessary medical interventions. Ouraim is to contribute from the bench table with different approaches that couldserve as alternatives to pre-existing assays for screening and diagnosing MPSVI and other LSD.The present work is based on our research article authored by Franco etal.1 where we studied the effect of blood-derived hemoglobin, and other bloodcomponents, on the fluorescence of 4-Methylumbelliferone when measuringARSB enzyme activity from dried blood spot (DBS) samples.Our experience indicates that to date there are plenty of differentapproaches for measuring ARSB enzyme activity, although the sample typerequired or the assay in itself often make them more adaptable for either highthroughput screening or small scale diagnostics.As a whole, the fluorometric determinations seem to be the mostaccessible to low budget laboratories with equally valuable performancesas a sophisticated mass spectrometry analysis for this disease. Furthermore,the DBS serves as an attractive sample type for screening the disease in largepopulations.Fil: Franco, Paula Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Quimica Biologica. Cátedra de Química Biológica Patológica; ArgentinaFil: Adamo, Ana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Quimica Biologica. Cátedra de Química Biológica Patológica; ArgentinaFil: Mathieu, Patricia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Quimica Biologica. Cátedra de Química Biológica Patológica; ArgentinaFil: Perez, Maria Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Quimica Biologica. Cátedra de Química Biológica Patológica; ArgentinaFil: Setton, Clara Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Quimica Biologica. Cátedra de Química Biológica Patológica; ArgentinaFil: Silvestroff, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Quimica Biologica. Cátedra de Química Biológica Patológica; Argentin

All-order waveforms from amplitudes

Waveforms are classical observables associated with any radiative physical process. Using scattering amplitudes, these are usually computed in a weak-field regime to some finite order in the post-Newtonian or post-Minkowskian approximation. Here, we use strong field amplitudes to compute the waveform produced in scattering of massive particles on gravitational plane waves, treated as exact nonlinear solutions of the vacuum Einstein equations. Notably, the waveform contains an infinite number of post-Minkowskian contributions, as well as tail effects. We also provide, and contrast with, analogous results in electromagnetism.Comment: 14 pages + references, 1 figur

Response of Venice storm gates to incident waves

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (p. 103).For the prevention of flooding of Venice a system of gates to close the inlets of the lagoon has been designed. Each system is composed of a series of 20 hollow gates hinged at the bottom. In the present work a linear theory is developed first to study the motions of the gates forced by a monochromatic incident wave. The gates are assumed to be vertical and the fluid domain is approximated to a channel of infinite length on the Adriatic side and to a semi infinite space on the lagoon side. Several theorems based on Green's formula are developed to get a deeper understanding of the physics of the problem and to check both the theory and the numerical computations performed. In particular, the law of energy conservation is derived. The amplitude of gates motion, added mass and radiation damping are reported for a large interval of periods. Synchronous resonance of the gates is found and the occurrence of negative added masses is reported and discussed.by Andrea Adamo.S.M

Membrane-Based, Liquid–Liquid Separator with Integrated Pressure Control

We describe the development and application of an improved, membrane-based, liquid–liquid separator. Membrane-based separation relies on the exploitation of surface forces and the use of a membrane wetted by one of the phases; however, successful separation requires accurate control of pressures, making the operation and implementation cumbersome. Here we present an improved separator design that integrates a pressure control element to ensure that adequate operating conditions are always maintained. Additionally, the integrated pressure control decouples the separator from downstream unit operations. A detailed examination of the controlling physical equations shows how to design the device to allow operation across a wide range of conditions. Easy to implement, multistage separations such as solvent swaps and countercurrent extractions are demonstrated. The presented design significantly simplifies applications ranging from multistep synthesis to complex multistage separations.Novartis-MIT Center for Continuous ManufacturingUnited States. Defense Advanced Research Projects Agency (Grant N66001-11-C-4147

Effect of Implant Surface Roughness and Macro- and Micro-Structural Composition on Wear and Metal Particles Released

Background: Considerations about implant surface wear and metal particles released during implant placement have been reported. However, little is known about implant surface macro- and microstructural components, which can influence these events. The aim of this research was to investigate accurately the surface morphology and chemical composition of commercially available dental implants, by means of multivariate and multidimensional statistical analysis, in order to predict their effect on wear onset and particle release during implant placement. Methods: The implant surface characterization (roughness, texture) was carried out through Confocal Microscopy and SEM-EDS analysis; the quantitative surface quality variables (amplitude and hybrid roughness parameters) were statistically analyzed through post hoc Bonferroni's test for pair comparisons. Results: The parameters used by discriminant analysis evidenced several differences in terms of implant surface roughness between the examined fixtures. In relation to the observed surface quality, some of the investigated implants showed the presence of residuals due to the industrial surface treatments. Conclusions: Many structural components of the dental implant surface can influence the wear onset and particles released during the implant placement