Improvement of Harvesters for Tires by Means of Multi-Physics Simulation

Author(s):  
Alberto Doria ◽  
Cristian Medè ◽  
Daniele Desideri ◽  
Alvise Maschio ◽  
Federico Moro

The specific working conditions of piezoelectric harvesters for scooter tires are analyzed. Calculated and experimental results show that the excitation of the harvester can be considered a series of separated impulses. Harvester response to an ideal impulse is analyzed with a single-mode model. An optimal ratio between impulse duration and natural period of the harvester that maximizes harvester excitation is found. A numerical finite element (FE) model of a bimorph cantilever harvester is developed in COMSOL and validated by means of experimental tests. The validated FE model is used for showing that an actual harvester excited by road impulses generates a large voltage only if there is a specific relation between impulse duration and natural period of the harvester. Starting from the validated FE model, small harvesters suited to tires are developed and analyzed. Also these harvesters show the best performance for a specific range of impulse durations, which corresponds to the highest speeds of the speed range of the scooter (50–80 km/h) and to high levels of acceleration.

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 632 ◽  
Author(s):  
Ahmed M. Sayed

The perforated steel sheets have many uses, so they should be studied under the influence of the uniaxial tensile load. The presence of these holes in the steel sheets certainly affects the mechanical properties. This paper aims at studying the behavior of the stress-strain engineering relationships of the perforated steel sheets. To achieve this, the three-dimensional finite element (FE) model is mainly designed to investigate the effect of this condition. Experimental tests were carried out on solid specimens to be used in the test of model accuracy of the FE simulation. Simulation testing shows that the FE modeling revealed the ability to calculate the stress-strain engineering relationships of perforated steel sheets. It can be concluded that the effect of a perforated rhombus shape is greater than the others, and perforated square shape has no effect on the stress-strain engineering relationships. The efficiency of the perforated staggered or linearly distribution shapes with the actual net area on the applied loads has the opposite effect, as it reduces the load capacity for all types of perforated shapes. Despite the decrease in load capacity, it improves the properties of the steel sheets.


2010 ◽  
Vol 22 (2) ◽  
pp. 171-195
Author(s):  
Gerardo Meil

The aim of this paper is to analyse, differentiated by gender, the effects that high geographical job mobility has on parenthood decisions. In particular, in a first part we will examine whether job mobility fosters childlessness and/or postponement of childbearing and if mobility implies a lower family size. In a second part we will analyse how the specific working conditions of mobile people and their resources for balancing working and private lives affect childlessness and postponement of parenthood. The analysis will be based on a representative survey of people aged 25 to 54, performed in six European countries (Germany, France, Spain, Poland, Switzerland and Belgium) in 2007, oversampling mobile people in order to get enough cases to analyse. Results show that the impact of high job mobility on the timing and quantum of parenthood is important, both for men and women, but stronger for the latter. Besides gender, the strength of the impact depends on the duration of job mobility and when it takes place in the lifecycle. Resources for promoting a better balance of working and private lives such as flexitime and teleworking have no clear impact on parenthood decisions, but having a supportive employer facilitates family development of mobile employees. A greater involvement of men in unpaid work does not seem to facilitate fertility decisions of mobile women. Zusammenfassung In diesem Beitrag wird der Frage nachgegangen, inwieweit hohe berufsbedingte räumliche Mobilität negative Folgen auf die Familienentwicklung hat. Im ersten Teil des Aufsatzes wird getrennt nach Geschlecht analysiert, ob Mobilität Kinderlosigkeit fördert, eine Verschiebung des Geburtenkalenders verursacht und ob sie eine Reduktion der Familiengröße zur Folge hat. Darüber hinaus wird in dem zweiten Teil analysiert, welchen Einfluss bestimmte Arbeitsbedingungen sowie die Ressourcen, die Familien zur Verfügung stehen, um Familie und Beruf zu vereinbaren, auf die Entscheidungen bezüglich Elternschaft ausüben. Die Analyse stützt sich auf eine repräsentative Umfrage in sechs europäischen Ländern (Deutschland, Frankreich, Spanien, Polen, Schweiz und Belgien) mit Personen im Alter zwischen 25 und 54 Jahren. Die Daten wurden in 2007 erhoben. Mobile Erwerbstätige wurden überproportional erhoben, um eine ausreichende Fallzahl zu gewährleisten. Die Ergebnisse zeigen, dass die Auswirkung der Mobilität auf die Familienentwicklung von Bedeutung ist, wobei sich Mobilität von Frauen stärker auswirkt. Darüber hinaus ist von Bedeutung, wann im Lebenslauf Mobilität und Elternschaft stattfinden und wie lange die Phase der mobilen Arbeit andauert. Flexible Arbeitszeiten oder die Möglichkeit, einen Teil der Arbeit zu Hause zu leisten, haben keinen eindeutigen Einfluss auf die Entscheidungen zur Elternschaft von mobilen Erwerbstätigen, wohl aber die Unterstützung durch den Arbeitgeber. Unterstützung seitens des Partners scheint die Entscheidung mobiler Frauen für Kinder nicht zu fördern.


2020 ◽  
Vol 18 (Suppl.1) ◽  
pp. 315-322
Author(s):  
Iv. Prokopov ◽  
M. Legurska ◽  
V. Mircheva

The present study explains the cause of "burnout" among teachers and offers the author's model for its diagnosis. Burnout syndrome can easily be called a "modern teacher's disease" due to the fact that it mainly affects the professional group of teachers. In the present study we aim to present a brief analysis of the problem and to offer a methodology for diagnosing and self-diagnosing "burnout" among teachers. The relevance of the research is related to the teachers` high workload of and the problem of the aging teachers, who often complain of exhaustion, lack of motivation, unwillingness to work. This raises the question of the specific working conditions that lead to diseases of the professional group of teachers. For this reason it is necessary to periodically take measures for the prevention of "burnout" syndrome.


2008 ◽  
Vol 109 (1) ◽  
pp. 100-107 ◽  
Author(s):  
Shahan Momjian ◽  
Denis Bichsel

Object The mechanism of ventricular dilation in normal-pressure hydrocephalus remains unclear. Numerical finite-element (FE) models of hydrocephalus have been developed to investigate the biomechanics of ventricular enlargement. However, previous linear poroelastic models have failed to reproduce the relatively larger dilation of the horns of the lateral ventricles. In this paper the authors instead elaborated on a nonlinear poroplastic FE model of the brain parenchyma and studied the influence of the introduction of these potentially more realistic mechanical behaviors on the prediction of the ventricular shape. Methods In the proposed model the elasticity modulus varies as a function of the distension of the porous matrix, and the internal mechanical stresses are relaxed after each iteration, thereby simulating the probable plastic behavior of the brain tissue. The initial geometry used to build the model was extracted from CT scans of patients developing hydrocephalus, and the results of the simulations using this model were compared with the real evolution of the ventricular size and shape in the patients. Results The authors' model predicted correctly the magnitude and shape of the ventricular dilation in real cases of acute and chronic hydrocephalus. In particular, the dilation of the frontal and occipital horns was much more realistic. Conclusions This finding suggests that the nonlinear and plastic mechanical behaviors implemented in the present numerical model probably occur in reality. Moreover, the availability of such a valid FE model, whose mechanical parameters approach real mechanical properties of the brain tissue, might be useful in the further modeling of ventricular dilation at a normal pressure.


Author(s):  
José Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman ◽  
George C. Campello

This work focuses on the structural analysis of a damaged 9.13″ flexible pipe to pure and combined axisymmetric loads. A set of experimental tests was carried out considering one up to ten broken wires in the outer tensile armor of the pipe and the results obtained are compared to those provided by a previously presented finite element (FE) model and a traditional analytical model. In the experimental tests, the pipe was firstly subjected to pure tension and, then, the responses to clockwise and anti-clockwise torsion superimposed with tension were investigated. In these tests, the induced strains in the outer armor were measured. Moreover, the axial elongation of the pipe was monitored when the pipe is subjected to tension, whilst the twist of the pipe was measured when torsion is imposed. The experimental results pointed to a slight decrease in the stiffness of the pipe with the increasing number of broken wires and, furthermore, a redistribution of forces among the intact wires of the damaged layer with high stress concentration in the wires close to the damaged ones. Both theoretical models captured these features, but, while the results obtained with the FE model agreed well with the experimental measurements, the traditional analytical model presented non-conservative results. Finally, the results obtained are employed to estimate the load capacity of the pipe.


Author(s):  
Hisham Kamel ◽  
Omar Harraz ◽  
Tamer Attia

Abstract This paper presents the results of an investigative study on the development of an affordable and functional prosthetic foot for below knee amputees. A prototype was successfully manufactured using 3D printing technology. This continuously evolving technology enables the rapid production of prosthetics that are individually customized for each patient. Our prototype was developed after conducting a topology optimization study that interestingly converged to the shape of the biological human foot. Afterwards, a design was envisioned where a simple energy storage and release mechanism was implemented to replace the Achilles tendon, which minimizes the metabolic energy cost of walking. Our mechanism can successfully manage 70% of the energy compared to a normal person during each walking step. A finite element (FE) model of the prosthetic was developed and validated using experimental tests. Then, this FE model was used to confirm the safe operation of the prosthetic through simulating different loading scenarios according to the ISO standard. Our study clearly showed that customizable prosthetics could be produced at a fraction 1/60 of the cost of the commercially sold ones.


2013 ◽  
Vol 549 ◽  
pp. 529-534 ◽  
Author(s):  
Kimmo Illikainen ◽  
Kalle Holappa ◽  
Kari Mäntyjärvi

This study focuses on quality assurance in a laser welded axisymmetric sandwich structure that functions as the body of an electric machine. The manufacturing quality of the structure was measured using destructive testing and visual inspection. The destructive tests included both fatigue and static tests in addition to a macrographic examination. The visual inspection comprised ocular estimates of the laser welded seams as well as their requirements. Compared with the real working conditions of the machine, the experimental tests were exhaustive. Nevertheless, in the tests, the bodies held up very well which shows the great strength of the structure.


Author(s):  
Massimiliano Gobbi ◽  
Giorgio Previati ◽  
Giampiero Mastinu

An off-road motorcycle frame has been analyzed and modified to optimize its fatigue life. The fatigue life of the frame is very important to define the service life of the motorcycle. The strain levels on key parts of the frame were collected during experimental tests. It has been possible to locate the areas where the maximum stress level is reached. A finite element (FE) model of the frame has been developed and used for estimating its fatigue life. Static test bench results have been used to validate the FE model. The accuracy of the finite element model is good, the errors are always below 5% with respect to measured data. The mission profile of the motorcycle is dominated by off-road use, with stress levels close to yield point, so a strain-life approach has been applied for estimating the fatigue life of the frame. Particular attention has been paid to the analysis of the welded connections. A shell and a 3D FE model have been combined to simulate the stress histories at the welds. Two reference maneuvers have been considered as loading conditions. The computed stresses have been used to assess the life of the frame according to the notch stress approach (Radaj & Seeger). The method correlates the stress range in a idealized notch, characterized by a fictitious radius in the weld toe or root, to the fatigue life by using a single S-N curve. New technical frame layouts have been proposed and verified by means of the developed finite element model. The considered approach allows to speed up the design process and to reduce the testing phase.


1976 ◽  
Vol 98 (3) ◽  
pp. 988-998 ◽  
Author(s):  
J. M. Tessarzik ◽  
R. H. Badgley ◽  
D. P. Fleming

Experimental tests have been conducted to further demonstrate the ability of the Influence Coefficient Method to achieve precise balance of flexible rotors of virtually any design for operation through virtually any speed range. Four distinct practical aspects of flexible-rotor balancing were investigated in the present work: (1) Balancing for operation through multiple bending critical speeds; (2) balancing of rotors mounted in both rigid and flexible bearing supports, the latter having significantly different stiffnesses in the horizontal and vertical directions so as to cause severe ellipticity in the vibration orbits; (3) balancing of rotors with various amounts of measured vibration response information (e.g., numbers of vibration data sets, and numbers and types of vibration sensors), and with different number of correction planes; (4) balancing of rotors with different (though arbitrary) initial unbalance configurations. Tests were made on a laboratory quality machine having a 122-cm (48-in.) long rotor weighing 50 kg (110 lb) and covering a speed range up to 18,000 rpm. The balancing method was found in every instance to be effective, practical, and economical, permitting safe rotor operation over the full speed range covering four rotor bending critical speeds.


2013 ◽  
Vol 461 ◽  
pp. 50-56
Author(s):  
Qiang Zhang ◽  
Lu Lu Yu ◽  
Hong Lei Jia ◽  
Xian Jun Liu ◽  
Li Zhang

Based on study of morphology of animal claws and subsoiling characteristics of subsoiler, a bionic hook-shape subsoiler is designed to decrease its operating resistance and to improve the terrain surface morphology. Design concepts and the structure scheme of the subsoiler are presented. The influences of tillage depth and operating speed on the operating resistance of bionic hook-shape subsoiler are examined in soil bin experimental tests by compared with a standard arc-shape subsoiler regulated by national standard (JB/T 9788-1999). It is proved by experiment results that the bionic hook-shape subsoiler when the operating speed range is 4-5km / h, compared with the standard arc-shape subsoiler, showed much lower operating resistance and power requirement against soil. The resistance-decrease index of the bionic hook-shape subsoiler is 24.1%, 24.4% and 26.5% at 300, 350 and 400mm cutting depth, respectively.


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