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Intenzivna plastična deformacija u procesima višefaznog sabijanja materijala / Severe Plastic Deformation in Material Multi-stage Upsetting ProcessesVilotić Marko 06 November 2015 (has links)
<p>Predstavljena je nova metoda intenzivne plastične deformacije – višefazno sabijanje V-alatom. Koristeći ovu metodu, sabijanjem u osamnaest faza, unapređene su mehaničke osobine niskougljeničnog čelika Č.1221 – tvrdoća, čvrstoća i deformabilnost. Za ispitivanje mikrostrukture korišćeni su svetlosni, skening i transmisioni mikroskop. Prosečna veličina kristalnog zrna početnog materijala od 19 mikrometara je smanjena na 250 nanometara nakon dvanaest faza sabijanja. Nakon osamnaest faza sabijanja na čelu uzorka ostvarena je ukupna deformacija u iznosu od 3,38.</p> / <p>A new severe plastic deformation method has been presented - multistage upsetting by V-shape dies. By using this method, in eighteen upsetting stages, mechanical propreties (hardness, strenght and formability) of C15E low carbon steel has been improved. For microstructure analysis light, scanning and transmission microscopes have been employed. Initial average grain size of 19 μm has been reduced to 250 nm after twelve upsetting stages. After eighteen upsetting stages, total effective deformation at the sample forehead of 3,38 has been obtained.</p>
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The Quest for Maternal Survival in Rwanda : Paradoxes in Policy and Practice from the Perspective of Near-Miss Women, Recent Fathers and Healthcare ProvidersPåfs, Jessica January 2016 (has links)
Rwanda has made significant progress in decreasing the number of maternal deaths and increasing the number of antenatal care visits and childbirths at health facilities. This thesis seeks to illuminate potential barriers for Rwanda’s goal for maternal survival. The studies explore the bottom-up perspective of policies and practices in regards to maternal care in Kigali. Semi-structured interviews were conducted between 2013 and 2016 with women who nearly died (‘near-miss’) during pregnancy, their partners, and with other recent fathers and community members, as well as healthcare providers who work within abortion care. The framework of naturalistic inquiry guided the study design and data collection. Analysis was conducted using framework analysis, thematic analysis and naturalistic inquiry. The findings identify paradoxical outcomes in the implementation of maternal care policies. Despite recent amendments of the abortion law, safe abortion was identified as being non-accessible. Abortion-related symptoms continue to carry a criminalized and stigmatized label, which encourages risk-taking and clandestine solutions to unwanted pregnancies, and causes care-seeking delays for women with obstetric complications in early pregnancy. Healthcare providers had limited awareness of the current abortion law, and described tensions in exercising their profession due to fear of litigation. The first antenatal care visit appeared to require the accompaniment of a male partner, which underpinned women’s reliance on men in their care-seeking. Men expressed interest in taking part in maternal care, but faced resistance for further engagement from healthcare providers. Giving birth at a health facility was identified as mandatory, yet care was experienced as suboptimal. Disrespect during counseling and care was identified, leading to repeated care-seeking and may underpin the uptake of traditional medicine. An enhanced implementation of the current abortion law is recommended. Reconsideration of policy is recommended to ensure equitable and complete access to antenatal care: women should be able to seek care accompanied by their person of choice. These findings further recommend action for improved policy to better address men’s preferred inclusion in maternal health matters. The findings of this thesis promote continued attention to implementing changes to strengthen quality, and trust, in public maternal care.
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Der Einfluss des Blutglukosespiegels auf den frühen intensivmedizinischen Verlauf und der Benefit einer intensivierten Insulintherapie bei Patienten mit mittelschwerem und schwerem Schädel-Hirn-TraumaBötel, Martina 29 March 2017 (has links) (PDF)
Seit Veröffentlichung der Studien von G. Van den Berghe et al. im Jahre 2001 galt es die strikte Blutzuckereinstellung in normoglykämische Bereiche bei Schwerverletzten anzustreben. Die intensivierte Insulintherapie wurde daraufhin von verschiedensten Fachgesellschaften in Leitlinien und Therapieregimen integriert, so auch auf der neurochirurgischen ITS der Universitätsklinik Leipzig. Kurze Zeit später erschienen große multizentrische Studien, die den Benefit der intensivierten Insulintherapie in Frage stellten und sogar von einer signifikant höheren Letalität bei strikt normoglykäm eingestellten Patienten berichteten.
Daher wird in dieser Studie die zwiespältige aktuelle Datenlage zum Anlass genommen, die Beziehungen zwischen Blutzuckereinstellung und ITS-Regime sowie die Auswirkungen hyperglykämischer Stoffwechselsituationen und mögliche Bedeutung des Blutglukosespiegels respektive der intensivierten Insulintherapie speziell für Patienten mit isoliertem mittelschwerem und schwerem Schädel-Hirn-Trauma zu evaluieren.
Mit Hilfe der Integration wird erstmalig ein Verfahren zur Blutglukosedarstellung verwendet, dass durch die Flächenberechnung (Area under the Curve (AUC-BG)) ein Abbild von Höhe und Dauer der Hyperglykämie schafft.
Es konnte gezeigt werden, dass die Blutzuckereinstellung mit dem klinischen Verlauf, krankheitsspezifischen Therapiekonzepten, Komplikationen und dem Outcome der Patienten korreliert und positiv Einfluss nimmt. Von besonderem Interesse war die Auswirkung auf den Hirndruck und die Notwendigkeit von Dekompressionskraniektomien, als auch auf Infektionsereignisse, die kontrollierte Beatmung, Ernährungsform und das Outcome.
Nach Einführung der intensivierten Insulintherapie wurde ein Vergleich mit konventionell therapierten Patienten herbeigeführt. Es wurden vergleichende Analysen zwischen der retrospektiven (n = 65, konventionelle Insulintherapie, Blutzucker < 10,0 mmol/l [< 180 mg/dl]) und prospektiven Gruppe (n = 65, intensivierte Insulintherapie, Blutzucker 4,4 – 6,1 mmol/l [80 – 110 mg/dl]) bezüglich Blutzuckerfläche, Intensivverlauf und Outcome durchgeführt. Nach 1:1-Matching hinsichtlich Alter und Geschlechterzugehörigkeit waren die beiden Therapiegruppen homogen und es zeigten sich keine Unterschiede bezüglich der Aufnahmecharakteristik. Schädelhirntraumatisierte Patienten profitierten von einer intensivierten Insulintherapie im Vergleich zur Kontrollgruppe, auch wenn es nicht gelang, den Blutzuckerspiegel entsprechend der initiierten Therapierichtlinie signifikant hin zur Normoglykämie zu senken. Die positiven Effekte zeigten sich deutlich in Bezug auf die Infektionsrate und Ernährungsform. Die intensivierte Insulintherapie senkte den Hirndruck und die Rate risikobehafteter Dekompressionskraniektomien mit einem deutlicheren Trend zu besseren Outcomemesswerten. Vor allem Patienten mit einem besseren initialem GCS und Nicht-Diabetiker scheinen von einer guten Blutzuckereinstellung zu profitieren. Hypoglykämien (Blutzucker ≤ 3 mmol/l) traten entgegen der Vermutung dabei nicht gehäuft auf und stellten somit kein Gegenargument einer derartigen Therapie dar.
Die Senkung des Blutzuckers in einen moderaten, therapeutischen Bereich sollte das Mindestziel in der Gesamttherapie von Patienten mit einem mittelschweren und schweren Schädel-Hirn-Trauma sein, wobei ein Konsens über den optimal therapeutischen Blutzuckerzielbereich bisher noch nicht gefunden wurde und somit weitere Untersuchungen gerechtfertigt sind.
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Étude exploratoire des réflexions et dilemmes éthiques auxquels sont confrontés les psychiatres, au regard de la problématique du consentement éclairé aux soins des patients souffrant de troubles mentaux gravesGrou, Christine 12 1900 (has links)
La problématique du consentement éclairé en santé mentale demeure au coeur des préoccupations des cliniciens, médecins spécialistes et médecins experts. Le travail auprès des cérébrolésés ou des patients souffrant de troubles mentaux graves, tout comme les questions qui me sont adressées depuis près de 20 ans par les médecins spécialistes, juristes ou résidents en psychiatrie, m’ont amenée à y réfléchir davantage. J’ajouterais que le constat personnel d’une compréhension des comportements, attitudes, motivations et jugements des patients vulnérables qui s’est modifiée au fil des ans, et le constat de l’importance de la notion du consentement vs le flou de sa définition et la fragilité des paramètres établis pour l’évaluer et la définir ont ravivé cette réflexion.
La présente étude n’a aucunement pour but d’élaborer quelque règle de conduite que ce soit, ni de définir ce que devrait être le consentement éclairé en psychiatrie, mais plutôt d’explorer les dilemmes éthiques et les questionnements cliniques auxquels sont confrontés les médecins psychiatres afin de raviver une réflexion éthique qui semble s’estomper au profit de procédures juridiques et administratives. / In the mental health field, the topic of informed consent has always been among the most important problems to address for clinicians and psychiatrists. My clinical work with head injured patients and patients with severe mental health disorder, as well as all the questions addressed by physicians, residents or lawyers for the last decade lead me to think about it more deeply. Moreover, the personal observation of cognitively impaired patients and the fact that the concept of informed consent is so present compared to the lack of parameters to assess it has lead me to think about it otherwise.
This study does not pretend to lead the actions or clinical behaviour, nor as it pretend to find a better definition of the concept of informed consent. It is only a way to explore some aspects of the complexity and clinical difficulties over the legal and administrative frame in which the medical field is evolving.
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Mateřství žen s těžkým zrakovým postižením / Motherhood of Women with Heavy Visual DisabilityViktorová, Šárka January 2014 (has links)
In my work, I deal with motherhood from the perspective of mothers with severe visual impairment. I focused especially on parenthood planning, on the period of pregnancy, childbirth and stay in the maternity ward and on the care for the child from birth to the age of three. I was interested to find out, whether visually impaired mothers encounter prejudices on part of the well-sighted people, whether they were worried that they could give birth to a handicapped child, what are the difficulties that severely visually impaired mothers come across most often in the individual period of development of the child, if and how education of children is different from the perspective of visually impaired parents from the perspective of well-sighted parents and also whether the child growing up in a family with at least one visually impaired parent is deprived of something or whether, on the contrary, this family situation has any advantages for such child. The objective of my diploma thesis is to map out various aspects of life of visually impaired mothers with small children in the greatest detail, directly from the point of view of those women. I attempted to achieve this objective by means of a qualitative method research, in particular in the form of a structured interview with six visually impaired mothers.
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Verbundprojekt WASA-BOSS: Weiterentwicklung und Anwendung von Severe Accident Codes – Bewertung und Optimierung von Störfallmaßnahmen; Teilprojekt B: Druckwasserreaktor-Störfallanalysen unter Verwendung des Severe-Accident-Code ATHLET-CDJobst, M., Kliem, S., Kozmenkov, Y., Wilhelm, P. 09 March 2017 (has links) (PDF)
Innerhalb des Vorhabens wurde ein ATHLET-CD-Eingabedatensatz für einen generischen deutschen DWR vom Typ KONVOI entwickelt. Das ATHLET-CD-Modell wurde für die Simulation schwerer Störfälle aus den Störfallkategorien Station Blackout (SBO) und Kühlmittelverluststörfällen mit kleinen Lecks (SBLOCA) eingesetzt. Dabei ist die vollständige Störfalltransiente für den Zeitbereich zwischen dem einleitenden Ereignis bis zum Versagen des Reaktordruckbehälters (RDB) abgedeckt und alle wesentli-chen Phänomene schwerer Störfällen werden abgebildet: Beginn der Kernaufheizung, Spaltproduktfrei-setzung, Aufschmelzen von Brennstoff- und Absorbermaterialien, Oxidationsprozesse mit Freisetzung von Wasserstoff, Verlagerung von geschmolzenem Material, Verlagerung in das untere Plenum, Schä-digung und Versagen des RDB. Das Modell wurde für die Analyse möglicher präventiver und mitigativer Notfallmaßnahmen für SBO und SBLOCA angewandt. Dafür wurden die Notfallmaßnahmen primärseitige Druckentlastung (PDE), primärseitiges Einspeisen mit mobilen Pumpensystemen sowie für SBLOCA das verzögerte Einspeisen der kaltseitigen Druckspeicher untersucht und die Eigenschaften und Einleitekriterien der Maßnahmen variiert. Es wurden die Zeitverläufe der Unfallszenarien analysiert und die verbleibenden Zeitspannen für die Einleitung zusätzlicher Maßnahmen ermittelt. Für ein SBO-Szenario mit PDE wurde für die Frühphase der Transiente (bis zum Beginn der Kernschmelze) eine Unsicherheits- und Sensititvitätsanalyse durchgeführt. Zusätzlich wurde für ein SBLOCA-Szenario ein Code-zu-Code-Vergleich zwischen ATHLET-CD und dem Störfallcode MELCOR erarbeitet.
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The singular case of SARS : medical microbiology and the vanishing of multifactoralityAttenborough, Frederick Thomas January 2010 (has links)
This thesis is about the politics and the possibilities of aetiology. Firstly, the possibilities. Does an infectious disease have one, single pathogenic cause or many, interacting causes? In the medical microbiological sciences, there is no definitive answer, one way or another, to this question: there, the conditions of aetiological possibility exist in a curious tension. Ever since the birth of the 'germ theory of disease' and the concomitant birth of the singular aetiological object, these conditions have allowed for the co-existence of a very different, and far less well understood kind of object: the multifactorial object. That SARS was caused by one, singular viral agent, a coronavirus (CoV), is now entrenched as microbiological fact. And yet, the curious thing about SARS is that the history of the 2003 outbreak is littered with moments at which the possibility of the multifactorial object presented itself to, and was actively considered by, medical microbiologists. So how did we get here - to SARS-CoV, an infectious disease that could be understood and storied in this, the most singular of ways? And what happened along the way to deny the multifactorial aetiological object any kind of existence at all? In an attempt to grapple with these questions, the thesis seeks to recover the possibility of the multifactorial object through a deep, ethnomethodological reading of the moments at which it flared up precise/y as a possibility for medical microbiologists investigating the outbreak. What emerges from that recovery operation is a sense that the multifactorial object was never actually ruled out or disproved in any way, but rather, was vanished. Put another way, the suggestion is that various medical microbiological practices and interventions, whilst establishing singularity, were serving, at the same time, to create an illusion of multifactorality's non-existence; an illusion behind which the issue of multifactorality, its possibility, could be discarded without ever having to be resolved, one way or the other. In the closing sections of this thesis a move is made towards suggesting that SARS-Co V, the singular disease, was the product of a choice-, a choice that was made to explore one aetiological possibility at the expense of another. And that is where the politics comes in. For if politics, the realm of the political, can be taken to arise in situations where various possibilities exist but not all possibilities can be chosen, then it follows that what this thesis provides is an opportunity to foreground the politics bound up with the practical doing of aetiology. As a result, and based on the experience of attempting to recover the vanished multifactorial object from the 2003 SARS outbreak, the thesis concludes with an attempt to inhabit the present in such a way as to make it possible to think, in a little more detail, about where aetiology, as understood by medical microbiologists, might be heading in the future: might recent shifts in practical, everyday, seemingly innocuous microbiological technique, have begun to make it easier to coax the multifactorial object out into a space of visibility? Might those shifts actually herald the crossing of an epistemological threshold in the medical sciences? And might the conditions of aetiological possibility be changing, and changing in ways that would drastically alter what it meant to speak of a 'disease', an 'infection' and a 'pathogen'?
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Desenvolvimento de equações preditivas de composição corporal para obesos graves: uso da bioimpedância elétrica / Development of body composition prediction equations for severely obese patients: the use of bioelectrical impedanceHorie, Lilian Mika 26 September 2008 (has links)
INTRODUÇÃO: A obesidade grave dificulta fisicamente a avaliação da composição corporal. OBJETIVO: Desenvolver equações para estimativa de gordura corporal (GC) em obesos grau III. MÉTODOS: Adultos obesos graves tiveram a GC estimada por bioimpedância elétrica (BIA impedância de 5, 50, 100 e 200kHz) e por método de referência (pletismografia de deslocamento aéreo - PDA). Avaliaram-se os limites de concordância e seu coeficiente de correlação (CCC). Novas equações preditivas foram desenvolvidas por análise de regressão multivariada. RESULTADOS: A GC estimada por BIA e PDA foi similar para a população estudada (64,8 ± 15kg vs 65,6 ± 16kg, p>0,05). Ambas tiveram boa acurácia, precisão e CCC, porém a sua comparação teve amplos limites de concordância que variaram de -10,4 a 8,8kg. A equação residente de BIA aplicada em mulheres superestimou a GC (-1,3 kg; p<0,05) e em homens subestimou a GC (5,6 kg; p<0,05). Novas equações preditivas de GC foram criadas, para BIA de freqüência de 50kHz, Horie-Waitzberg & Barbosa-Silva1: GC1 (kg) = 23,25 + (0,13 × idade) + (1,00 × peso atual) + (0,09 × Resistência 50kHz) (0,80 × altura) e para BIA de frequência de 100kHz, Horie-Waitzberg & Barbosa-Silva2: GC2 (kg) = 23,97 + (0,10 × Impedância 100kHz) + (0,11 × idade) + (0,99 × peso atual) - (0,80 × altura). CONCLUSÕES: A equação residente no aparelho de BIA foi inadequada para estimar a GC em pacientes obesos grau III. As equações desenvolvidas especialmente para esta população forneceram estimativas de GC mais precisas (melhores limites de concordância, precisão, acurácia e CCC). / RATIONALE: Severe obesity limits physically the body composition assessment. AIM: To develop equations of body fat (BF) estimative in severe obesity. METHODS: Severely obese adults had BF estimated by bioelectrical impedance (BIA impedance of 5, 50, 100 and 200kHz) and reference method (air displacement plethysmography - ADP). The limits of agreement and of concordance correlation coefficient (CCC) of the data were evaluated. New predictive equations were developed by multivariate regression analysis. RESULTS: The BF estimations from BIA and ADP were similar for the studied population (64.8 ± 15kg vs 65.6 ± 16.4kg, p>0.05). Both had good accuracy, precision, and CCC, but their comparison had wide limit of agreement with range from -10.4 to 8.8kg. The home BIA equation overestimated BF in women (-1.3 kg, p<0,05) and underestimated BF in men (5.6 kg; p <0.05). BF new predictive equations were generated, for BIA with 50kHz frequency, Horie- Waitzberg & Barbosa-Silva1: BF1 (kg) = 23.25 + (0.13 × age) + (1.00 × current weight) + (0.09 × Resistance 50kHz) (0.80 × height) and for BIA with 100kHz frequency, Horie-Waitzberg & Barbosa-Silva2: BF2 (kg) = 23.97 + (0.10 × Impedance 100kHz) + (0.11 × age) + (0.99 × current weight) - (0.80 × height). CONCLUSIONS: The home equation on BIA was inadequate for estimating BF in severely obese patients. Equations developed especially for this population provides more accurate BF estimative (better limits of agreement accuracy, precision and CCC).
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Evolução dos valores de saturação venosa central de oxigênio, lactato e déficit de base em cães com sepse grave e choque séptico submetidos à ressuscitação volêmica precoce / Evolution of central venous saturation oxygen, lactate and base deficit in severe sepsis and septic shock patients submitted to early volemic resuscitationPatara, Andreza Conti 10 December 2009 (has links)
A sepse é uma síndrome clínica que promove alterações características na microcirculação, dificultando a avaliação da perfusão tecidual. No homem, estudos demonstram a importância de estabelecer a terapia baseando-se nas avaliações clínicas rotineiras, bem como nas variáveis de oxigenação e de perfusão tecidual como saturação venosa central de oxigênio, o lactato e a diferença de base. Assim, o objetivo deste estudo foi avaliar a evolução desses parâmetros durante as seis primeiras horas de reposição volêmica, buscando identificar o valor destas variáveis como marcadores de prognóstico. Foram incluídas 30 cadelas com sepse grave e choque séptico submetidas à reposição volêmica com 40 ml/kg/hora de solução cristalóide durante as seis primeiras horas de tratamento intensivo. Durante este período, a pressão arterial sistólica, o débito urinário, a pressão venosa central, o lactato, o déficit de base e a saturação venosa central de oxigênio foram monitorados a cada 90 minutos. A prevalência de algumas características clínicas dos animais, analisando a relação destas características com o desfecho (alta ou óbito) foi realizada através do teste de qui-quadrado ou teste exato de Fisher. A saturação venosa central de oxigênio, o déficit de base e o lactato foram comparados entre os sobreviventes e não- sobreviventes utilizando análise de variância com dois fatores. Foi considerada estatística significativa com p< 0,05. A taxa de mortalidade foi de 36,7%. Os sobreviventes apresentaram valores de saturação venosa central acima de 70% quando comparados aos não sobreviventes (p<0,001). Níveis séricos de lactato mais elevados também foram observados no grupo de não sobreviventes (p<0,001), bem como os valores de déficit de base também foram mais elevados no grupo de sobreviventes quando comparado aos animais que vieram a óbito (p<0,001). O suporte intensivo aos animais com sepse grave é fundamental na redução da mortalidade desses animais. Os valores de lactato, saturação venosa central de oxigênio e de déficit de base podem ser considerados bons marcadores de prognóstico. A utilização destes parâmetros como metas da reposição volêmica durante as seis horas iniciais do atendimento parece reduzir a mortalidade, no entanto, estudos multicêntricos são necessários para definir esta relação. / Sepsis is a clinical syndrome that causes changes in the microcirculation characteristics, making the assessment of tissue perfusion. In humans, studies have shown the importance of establishing a therapy based on routine clinical assessments and the variables of oxygenation and tissue perfusion and central venous saturation of oxygen, lactate and base deficit. The aim of this study was to evaluate the evolution of these parameters during the first six hours of resuscitation in order to identify the value of these variables as prognostic markers. We included 30 dogs with severe sepsis and septic shock underwent replacement with 40 ml / kg / hour of crystalloid solution during the first six hours of intensive care. During this period, the systolic blood pressure, urine output, central venous pressure, lactate, base deficit, and central venous saturation of oxygen were monitored every 90 minutes. The prevalence of some clinical characteristics of the animal, analyzing the relationship of these characteristics with the outcome (discharge or death) was performed using chi-square or Fisher\'s test. The central venous saturation of oxygen, base deficit and lactate were compared between survivors and nonsurvivors using analysis of variance with two factors. It was considered statistically significant with p <0.05. The mortality rate was 36.7%. The survivors had values of central venous oxygen saturation above 70% when compared to non-survivors (p <0.001). Serum lactate higher were also observed in the non survivors (p <0.001), and the values of base deficit were also higher in the group of survivors compared to animals that eventually died (p <0.001). The intensive support to animals with severe sepsis is essential to reduce the mortality of these animals. The values of lactate, central venous saturation of oxygen and base deficit can be considered good markers of prognosis. Using these criteria as goals of resuscitation during the initial six hours of care appears to reduce mortality; however, multicenter studies are needed to define this relationship.
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Estudo da transição do regime de desgaste moderado para o desgaste severo a seco e sob o regime de lubrificação limítrofe. / Study of the mild and severe wear transition in dry wear and boundary lubricated wear.Rovani, Ane Cheila 11 June 2014 (has links)
Os mecanismos do desgaste e atrito que ocorrem durante o desgaste por deslizamento, bem como, a transição do regime do desgaste moderado para o desgaste severo, são influenciados pela força aplicada, rugosidade, temperatura e umidade, sendo estas variáveis frequentemente estudadas. Entretanto, a avaliação da remoção de debris durante o deslizamento e a influência do aditivo lubrificante, em regime limítrofe/quase seco (e.g. Ácido Esteárico C18H32O2) ainda são necessários maiores entendimentos sobre os mecanismos de desgaste e também a força na qual ocorre a transição do regime do desgaste moderado para o desgaste severo durante o deslizamento. Para os testes a seco, com e sem a remoção dos debris, foram realizados ensaios tribológicos convencionais com as duas durezas de disco, 435 e 530 HV30. Os resultados mostraram que a transição do regime de desgaste é influenciada pela dureza e pela remoção dos debris. A influência da dureza é observada apenas quando os ensaios convencionais são realizados, nos quais foi observado que o aumento da dureza do contra corpo estende a transição do desgaste moderado para o severo em forças maiores. A remoção dos debris aumenta a extensão da força para ocorrer a transição moderado/severo. Para os testes lubrificados, foram realizados ensaios com a dureza de disco de 530 HV, variando a concentração do ácido esteárico. Os resultados mostram que o aumento da concentração do aditivo e da força normal aplicada são varáveis determinantes para a redução do coeficiente de atrito. A ação do aditivo lubrificante é fundamental nas forças baixas, sendo que nas forças elevadas apenas o aumento da força normal é suficiente para manter o baixo coeficiente de atrito. Adicionalmente, para as elevadas forças aplicadas, o filme lubrificante falha em função do tempo de deslizamento, e maiores concentrações de aditivo são necessárias para manter o coeficiente de atrito constante. / The wear and friction mechanisms that occur during the sliding wear, as well as the transition from mild to severe wear regimes are influenced by the normal load applied, roughness, temperature and humidity, the variables more frequently studied. However, the assessment of debris removal during the sliding wear and oil influence with lubricant additive (e.g. Stearic Acid C18H32O2) in the boundary/dry lubrication needs further understanding of the mechanisms and the load that occur a wear transition from mild to severe wear. The aim in this work is the characterization and evaluation the contact surface without debris in sliding surface (cleaning of the wear track) and the wear surface in boundary lubrication tests. The materials studied are: the pin AISI 4140 - 435 HV30 steel and the disc AISI H13 - 435 e 530 HV30 steel. Firstly were made conventional tribological tests with two disc hardness. Then, tests with the cleaning of the wear track were made. The results showed that the hardness and the absence of debris influence in the wear transition regime. The hardness influence is observed only when the conventional tests were made. When the counter body hardness increased, the transition from mild to severe wear extends to greater loads. The debris influence was evidenced in tests with the cleaning of the wear track, and showed that greater loads are needed from mild to severe wear transition. For the lubricated tests, the hardness of the disk was 530 HV. The results shown that the concentration of the lubricant additive and the normal load applied are determinant variables to decreasing the friction coefficient. The lubricant additive action is critical in low loads, and in high loads only the increasing of the load is needed to maintain the low friction. In addition, in the high load applied, the failure of the lubricant film occurs with the increase of the sliding time, and higher additive concentrations are needed to maintain constant the friction coefficient.
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