81 research outputs found
fitri andri yana 165100001
No full textTeknologi merupakan sebuah perusahaan yang bergerak dibidang distribusi. Dalam aktivitas pembukuuan mereka menggunakan aplikasi untuk memudahkan proses acunting. Dalam penggunaannya untuk mempermudah pencatatan pembukuan perusahaan dan juga untuk menghindari kehilangan data. Tujuannya dari dilakukannya audit pada perusahaan ini adalah mengidentifikasi tingkat efektivitas dan efiensi dari aplikasi yang digunakan pada perusahaan,dan meneliti apakah implementasi aplikasi sudah memenuhi visi misi perusahaan ini atau belum. Manfaat dari audit ini adalah menjadi pedoman bagi perusahaan untuk mengevaluasi sistem kinerja dari aplikasi.
Kata Kunci : sistem audit data perusahaa
Properties of multifunctional composite materials based on nanomaterials: a review
No full textComposite materials are being used for high-end applications such as aviation technology, space ships, and heavy equipment manufacturing. The use of composite materials has been observed in recent advancements in the field of multifunctional composite materials (MFCMs). There is continuous progress related to improvements, innovations, and replacement of metals inspite of rigorous destructive and non-destructive testing, proving the toughness and lifelong durability of such materials. The present study aims to review the topics relevant to modern multifunctional composite materials. The reviewed articles mostly cover the field of MFCMs based on nanomaterials. The structural functions emphasize on the mechanical properties such as fracture toughness, strength, thermal stability, damping, stiffness, and tensile strength. The non-structural properties include biodegradability, thermal conductivity, electrical conductivity, and electromagnetic interference (EMI) shielding. The study has concluded that the applications of multifunctional nanoparticle-based composite materials and structures include durable but light-weight aircraft wings, components and structures of electric self-driving vehicles, and biomedical composite materials for drug delivery
Definition of a new predictor for multiaxial fatigue crack nucleation in rubber
No full textInternational audienceFrom an engineering point of view, prediction of fatigue crack nucleation in automotive rubber parts is an essential prerequisite for the design of new components. We have derived a new predictor for fatigue crack nucleation in rubber. It is motivated by microscopic mechanisms induced by fatigue and developed in the framework of Configurational Mechanics. As the occurrence of macroscopic fatigue cracks is the consequence of the growth of pre-existing microscopic defects, the energy release rate of these flaws need to be quantified. It is shown that this microstructural evolution is governed by the smallest eigenvalue of the configurational (Eshelby) stress tensor. Indeed, this quantity appears to be a relevant multiaxial fatigue predictor under proportional loading conditions. Then, its generalization to non-proportional multiaxial fatigue problems is derived. Results show that the present predictor, which is related to the previously published predictors, is capable to unify multiaxial fatigue data
Effect of the hysteretic response of elastomers on the fatigue life
No full textInternational audienceElastomers are widely used in automotive anti-vibration systems (AVS). This chapter considers the qualitative relationship between hysteretic response and fatigue life prediction of elastomers. It discusses the effect of hysteretic response of elastomers on the fatigue life. The chapter presents a general derivation of constitutive equations for a simple non-linear phenomenological three-parameter model in order to simulate a stabilized hysteretic response. In order to derive the constitutive relations, a stress-stretch curve of carbon black-filled natural rubber is considered. This curve was obtained from uniaxial cyclic test interrupted by relaxation steps at different stretching levels. The chapter provides a brief analysis of the fatigue life criterion. The criterion value increases until a certain limit of minimum stretch is reached before it decreases with the increase of minimum stretch. This limit (minimum stretch) is likely independent of the stretch amplitude
Définition d'une nouvelle grandeur prédictive pour la durée de vie en fatigue des matériaux élastomères
No full textCes dernières années, de nombreux progrès ont été faits dans le domaine de la simulation numérique de pièces en élastomère. Ces avancées sont en grande partie motivées par la nécessité d'améliorer les délais et les coûts de conception dans des domaines industriels fortement compétitifs, et notamment pour les pièces anti-vibratoires automobiles. Dans ce contexte, si les logiciels classiques de type éléments finis sont capables de prédire efficacement l'histoire des déformations et des contraintes au sein des pièces, la prédiction de la durée de vie de celles-ci en fatigue reste un problème ouvert. Le processus de rupture par fatigue dans les élastomères se fait en deux phases : une premère phase d'initiation durant laquelle des micro-fissures apparaissent au sein du matériau, puis une phase de propagation durant laquelle ceux-ci croissent jusqu'à la rupture. Des travaux récents ont démontré que la première phase est prédominante pour la fin de vie des pièces anti-vibratoires. Ainsi, la construction d'une grandeur prédictive effcace doit être capable de déterminer les zones propices à l'apparition de micro-défauts au sein d'une pièce. Les trois grandeurs prédictives classiquement utilisées pour estimer la durée de vie en fatigue des élastomères sont la déformation principale maximale, la contrainte principale maximale et l'énergie de déformation. Si celles-ci s'avèrent effcaces pour des cas de chargement uniaxiaux, leur utilisation pour des cas de chargement multiaxiaux pose problème. Afin de prédire la rupture en fatigue des pièces élastomères en service, une grandeur prédictive efficace dans le domaine mul-tiaxial est nécessaire. Celle-ci doit être indépendante du mode de déformation, motivée par la physique des phénomènes mis en jeu, théoriquement bien fondée et finalement aisément implantable dans les outils numériques. La présente thèse propose de construire une telle grandeur. Des observations expérimentales réalisées préalablement et permettant de comprendre les phénomènes physiques mis en jeu nous ont conduit à considérer le tenseur des contraintes configurationnelles établi par Eshelby en 1951. Dans le domaine élastique, le nouveau prédicteur proposé est la plus petite valeur propre de ce tenseur, la direction propre associée étant la direction normale au plan d'ouverture de la fissure. L'extension de ces travaux au cas inélastique est aussi développée. Afin de vérifier le bien-fondé de cette théorie, des données expérimentales classiques de la bibliographie ont été utilisées ; les résultats obtenus démontrent l'efficacité de notre approche notamment pour unifier les résultats multiaxiaux en fatigue.The last decade has experienced a major advance in the development of finite element based tools for the simulation of a wide range of industrial rubber parts. This is mainly motivated by the need to improve time and cost efficiencies in highly competitive industries particularly in automotive Anti-Vibration Systems (AVS) industry. While the basic concept of finite element method capable of predicting stress and strain histories has been well established, the use of these histories to estimate fatigue life of rubber parts in service remains a critical issue. Typically, the fatigue failure process involves a period during which cracks nucleate in regions that were initially free of observed cracks, followed by a period during which nucleated cracks grow to the point of failure. For AVS, the former is the most important one. The three most widely used predictors for rubber crack nucleation are the maximum principal stretch, the maximum principal stress and the strain energy density. However, they fail to give satisfying prediction for multiaxial problems. In order to prevent fatigue failure of rubber parts in service, an efficient and well-defined multiaxial fatigue life predictor is required, i.e. independent of deformation state, physically motivated, theoretically well-formulated and easy to implement into finite element software. Thus, the purpose of this study is to develop a new fatigue life predictor which can meet these requirements. Experimental observations were conducted to understand physical phenomena which take place during fatigue crack nucleation and growth in rubber. Based on these observations, we consider that the configurational stress tensor introduced by Eshelby in 1951 is an appropriate continuum mechanics quantity to develop a relevant fatigue life predictor. In elasticity, the new predictor is given by the smallest eigenvalue of this tensor and the normal of the crack plan is the eigenvector associated with the smallest eigenvalue. An extension to the case of inelasticity is also proposed. To verify its efficiency, experimental data issued from the literature are considered. Results demonstrate that the proposed predictor is capable of unifying multiaxial fatigue data.NANTES-BU Sciences (441092104) / SudocNANTES-Ecole Centrale (441092306) / SudocSudocFranceF
Някои аспекти на защитата от дискриминация при упражняване правото на труд – проблеми и тенденции
Get PDFThe report analyses some of the aspects of discrimination in Bulgaria in practicing of the right of work. Based on the actual normative analysis and related to the practice of the SPD the author makes conclusions and summaries. Considering prevention of discrimination in the labour law the author develops the contemporary tendencies and makes recommendations for improvement of the legislation
Prediction of fatigue life improvement in natural rubber using configurational stress
No full textInternational audienceTo some extent, continua can no longer be considered as free of defects. Experimental observations on natural rubber revealed the existence of distributed microscopic defects which grow upon cyclic loading. However, these observations are not incorporated in the classical fatigue life predictors for rubber, i.e. the maximum principal stretch, the maximum principal stress and the strain energy. Recently, Verron et al. considered the configurational stress tensor to propose a fatigue life predictor for rubber which takes into account the presence of microscopic defects by considering that macroscopic crack nucleation can be seen as the result of the propagation of microscopic defects. For elastic materials, it predicts privileged regions of rubber parts in which macroscopic fatigue crack might appear. Here, we will address our interest to a broader context. Rubber is assumed to exhibit inelastic behavior, characterized by hysteresis, under fatigue loading conditions. The configurational mechanics-based predictor is modified to incorporate inelastic constitutive equations. Afterwards, it is used to predict fatigue life. The emphasis of the present work is laid on the prediction of the well-known fatigue life improvement in natural rubber under tension-tension cyclic loading
Нормативни гаранции за опазване данните от електронните документи в трудовото досие на работника или служителя
Get PDFThe paper examines the normative measures, guaranteeing the security of the data from the electronic documents in the employees work file. Based on the analysis the author makes conclusions and recommendations for guaranteeing the security of the data
Recent advances on fatigue of rubber after the literature survey by Mars and Fatemi in 2002 and 2004
No full textSubjected to multiaxial mechanical loading and hostile environment, rubber experiences degradation over a period of time. Therefore, it is of utmost importance to prevent failure of rubber components during the service. As highlighted in Mars and Fatemi [Mars, W.V, Fatemi, A., 2002. A literature survey on fatigue analysis approaches of rubbers. Int. J. Fatigue 24, 949–961; Mars, W.V, Fatemi, A., 2004. Factors that affect the fatigue life of rubber: A literature survey. Rubber Chem. Technol. 77, 391–412], a large number of works focused on the durability of rubber. Furthermore, it has been expanding rapidly until today. For this reason, the present work focuses on collecting and analyzing the vast amount of works on fatigue of rubber conducted in the last 15 years since the review of Mars and Fatemi in 2002 and 2004. To this end, three bibliographic databases are consulted: Google Scholar, Scopus and Web of Science. The collected works are analyzed with the objective to identify the current and future trends and needs in the study of rubber fatigue
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