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In the electric vehicles studied, the driven wheels and the differential, which are responsible for the transfer of power and rotational motion, are connected by half-shafts. The failure of two half-shafts in the rear gearbox of a three-wheeled electric vehicle, popularly known as a Tuk Tuk, is examined and evaluated in this research. Therefore, the primary goal of this work is to look at the factors that contribute to the failure of the aforementioned components. Visual examination and fractographic analysis were performed utilizing optical and scanning electron microscopes to investigate the half-shafts’ mode of failure. Samples from both half-shafts were obtained for tensile testing, metallographic examination, chemical composition analysis, and fracture surface analysis. According to visual examination, reversed bending fatigue, occurring simultaneously with torsion loading, caused the fracture in the half-shaft to the left of the differential (rear view). Analysis of the fracture surface of the half-shaft to the right of the differential revealed that it resulted mainly from bending fatigue loading. Moreover, regarding the mechanical design safety of the half-shafts, calculations were performed considering different trajectories, limit speeds, and different design criteria. Finally, some recommendations are drawn to improve the design safety of this mechanical component.

The purpose of this study was to evaluate the retentive forces over time of removable partial denture clasps fabricated by the digital method. Occlusal rest seats were fabricated on three premolar teeth fixed in acrylic blocks (9 × 20 × 40 mm). Digitization of the teeth was performed using a laboratory scanner (Zirkonzahn Scanner S600 GmbH, Gais, Italy). After the analysis and determination of the insertion axis, two types of clasps with mesial occlusal rests were designed per tooth: the back-action and the reverse back-action clasps, using the Partial Planner Zirkonzahn program. The file was sent for fabrication of six metal clasps from a cobalt-chromium SP2 alloy in the EOSINT M270 system by a direct laser sintering process. The Instron 5544 universal testing machine was used to perform 20,000 cycles of clasp insertion and removal in the corresponding tooth with a load cell of 100 N and a speed of 2.5 mm/s. The retentive force was recorded for each of the 1000 cycles, and the change in retention over time was calculated. Statistical analysis was performed using the nonparametric Mann–Whitney test and a significance level of 5%. At 16,000 cycles, a maximum change in retention of 3.74 N was recorded for the back-action clasps and a minimum of −24.28 N at 1000 cycles for the reverse back-action clasps. The reverse back-action clasps exhibited statistically significant lower change in retention than the reverse-action clasps at 4000 and 5000 cycles. No differences were observed in the remaining cycles. During the 20,000 cycles, the change in retention was low regardless of the type of clasp. For most cycles, there were no differences in the change in retention between the two types of clasps.

The Forest Fire Fighting Vehicle (FFFV) is one of the most important pieces of equipment in direct firefighting; therefore, its maintenance is strategic to guarantee high levels of reliability. The history of interventions is essential to support the increase in the quality of maintenance, namely with regard to the specificity of each equipment, in its actual operating conditions. In the absence of previous information, it is important to resort to complementary tools that allow for overcoming this gap where usually the knowledge of maintenance held by professionals and users is structuring and very helpful. In this perspective, data were collected from several fire brigades. The analysis and decisions were possible using fuzzy logic, following the Mamdani model and the centroid method for the defuzzification phase. Subsequently, a Failure Modes, Effects and Criticality Analysis (FMECA) was carried out to identify which would be the most severe failures, the possible cause of each failure and the respective maintenance action. Through the results obtained, it was possible to identify a set of elements of the FFFV where maintenance should pay additional attention so that the vehicle guarantees the desired levels of reliability and propose a maintenance program with added value compared to what is currently practised.

Under strain control tests and cyclic loading, extruded magnesium alloys exhibit a special mechanism of plastic deformation (“twinning” and “de-twining”). As a result, magnesium alloys exhibit an asymmetric material behavior that cannot be fully characterized with the typical numerical tools used for steels or aluminum alloys. In this sense, a new phenomenological model, called hypo-strain, has been developed to correctly predict the cyclic stress–strain evolution of magnesium alloys. On this basis, this work aims to accurately describe the local cyclic elastic–plastic behavior of AZ31B-F magnesium alloy under multiaxial cyclic loading with Abaqus incremental plasticity. The phenomenological hypo-strain model was implemented in the UMAT subroutine of Abaqus/Standard to be used as a design tool for mechanical design. To evaluate this phenomenological approach, the results were correlated with the uniaxial and multiaxial proportional and non-proportional experimental tests. In addition, the estimates were also correlated with the Armstrong–Frederick nonlinear kinematic hardening model. The results show a good correlation between the experiments and the phenomenological hypo strain approach. The model and its implementation were validated in the strain range studied.

In this work, the magnesium alloy AZ31BF subjected to proportional and non-proportional loads has been studied. For this purpose, a series of experimental multiaxial fatigue tests were carried out according to the ASTM E466 protocol. The main objective was to determine the relationship between the multiaxial fatigue strength of this alloy under these two different types of loading. The results showed that the AZ31BF magnesium alloy has different fatigue strengths depending on the loading type. Based on these results, it was found that the ratio between proportional and non-proportional damage in AZ31BF magnesium alloy varies depending on the number of loading cycles. To represent this variation, parameter Y was used to modulate the non-proportional damage of AZ31BF. In this way, two Y functions were considered, one for the normal stress component and the other for the shear stress component. The results obtained for the non-proportional parameter Y are of particular interest since the multiaxial fatigue models do not distinguish between these two types of loading when evaluating fatigue life. In this sense, the results of this study can be used in these models to overcome this limitation.

Wind power technologies are being used as a mean of harvesting the energy from the wind with low carbon impact and with great potential to contribute to a new energy paradigm. Great benefits may arise from the use of offshore turbines, such as having a reduced visual impact, if far enough from the coast, or being able to produce more energy due to the use of bigger turbines. Current challenges for these technologies include producing a stable and profitable platform that allow turbines to be installed in deep waters, meaning that these solutions need to be of floating type. An example of such structure is the foundation developed by the DeepCWind consortium, which is evaluated for its structural integrity on this document. The evaluation consists of modal and static/transient analyses, according to a selected Design Loading Case, which is defined for the certification of wind turbines’ offshore foundations. The objective is to observe how this structure would perform when subjected to a simulated real life loading. The DeepCWind foundation exhibited great difficulties enduring the applied loads. Therefore, a structurally improved platform was design with the aim of successfully passing the load case.

Additive Manufacturing (AM) has carved a significant leap in mechanical design history, offering an almost infinite geometric freedom. It enables complex geometries with lower weight and enhanced behaviour, like topology optimisation. AM material mechanical properties is under continuous research due to the ever-increasing available materials, methods and an overall higher number of influential variables, such as printing parameters and powder shape and size (associated with metal AM). A rough and low quality-built surface is obtained from most AM methods. It has been proven to have a far from neglectable influence on the final mechanical properties and fatigue strength. Different post-treatment methods have shown a positive impact on correcting the rough surface impact on fatigue strength. In this work, the Ti6Al4V titanium alloy additively manufactured by Selective Laser Melting (SLM) is placed under Ultrasonic Fatigue Testing (UFT) within the Very High Cycle Fatigue (VHCF) regime. Ti6Al4V is widely applied in the aerospace industry due to its high strength, low-density relation. This work aims to evaluate the influence of surface roughness, defect size and location on fatigue strength. Several non-heat treated Ti6Al4V specimens were manufactured in one printing session. The present defect type, size and density, were quantified, and their tension, ductility and fatigue life properties evaluated. Tensile UFT were conducted with R =-1 to as-built and polished mirror-like specimens. The resulting fatigue fracture showed surface crack initiation for as-built specimens and sub-surface in polished specimens. A significant fatigue strength increase accompanied the crack initiation change. Sub-surface crack initiation occurred on the most common AM present defects, gas pores and smooth facets. Their location in respect to the surface appeared to influence fatigue resulting life directly.

Additive manufacturing technologies have been in continuous growth due to their advantages over traditional manufacturing. The iro3d is a powder deposition machine designed to build metal parts. This research work proposed the adaptation of the iro3d selective powder deposition process to allow the production of glass-ceramic parts using recycled glass powders. Various specimens were produced using different deposition strategies such as build orientation and sintering holding times. Specimens were evaluated in terms of geometric distortions (shrinking and warping) and in terms of mechanical performance (flexural behavior and hardness). Two geometrically complex test parts were also produced to infer the minimum feature size capabilities of the process. The results denoted parts that displayed significant geometrical deviations, which could be correlated with some of the tested parameters. Through the addition of sand to the tested specimens, we demonstrated that distortions could be mitigated with proper control of the powder’s coalescence. In the end, the specimens’ fracture surfaces were examined, and the presence of porosities was correlated with their mechanical properties. The results demonstrated that the iro3d SPD process could be used to produce additively manufactured glass parts.

The destruction caused by forest fires generates social impacts, environmental impacts, and extremely important economic impacts caused by the destruction of a wide range of infrastructures and essential goods. Therefore, as it is impossible to remove all the infrastructures from the forest and wildland–urban interface, the design of protection systems is essential. The main objective of this work is the development of a low-cost protection system, with rigid panels, requiring a simple installation, in order to protect outdoor infrastructures such as telecommunications stations, shelters, roadside enclosures, power cabinets, and other structures. A study was carried out on panels that could be used for protection in order to determine whether the protective material would be more appropriate. Taking into account the fire resistance behavior, thermal and structural properties and cost, the panels selected were the magnesium oxide fiberglass reinforced. The protection was constructed, installed on a telecommunication cabinet, and experimentally laboratory tested in a wind combustion tunnel. To collect the data InfraRed and video cameras, heat flux sensors, and thermocouples were used to determine the fire propagation, heat flux, and temperatures, respectively. The experimental data show that the low-cost protection is effective for protecting telecommunication cabinets and similar infrastructures against forest fires.

Não tenho do meu curso de História, na época de 1960 a 1966, ano em que defendi a tese de licenciatura, uma imagem essencialmente positiva, conforme já o disse num livro, História… Que História?, publicado pela editora Temas e Debates em 2015. A nossa ciência era então vista de uma forma “narrativista” e “acontecimental”. As cadeiras que estimulavam a minha reflexão crítica —aprendida no liceu com Alberto Martins de Carvalho — fui buscá-las particularmente à Filosofia e à História da Cultura, em que ensinavam professores, de diversas concepções, oriundos de outras áreas: Sílvio Lima (em 1935 demitido por Salazar, mas que pudera regressar nos anos 40), o qual reflectia, nas suas lições inesquecíveis, sobre os princípios da teoria da História

Wildland fires are frequent events worldwide, particularly in the European-Mediterranean region, USA, and Australia. These fires have been more frequent and intense in recent years due to climate changes and may cause significant damage, especially when reaching the Wildland-Urban Interface (WUI) areas. The presence of liquefied petroleum gas (LPG) cylinders may cause severe events in WUI areas, as occurred in Portugal during the large wildfires of 2017, which could have been avoided if the cylinders were protected. Devices for protecting the parts of houses under WUI fire were previously presented, but a protective device for cylinders was not. In this work, a protective device for LPG cylinders made with a thin fabric with an aluminum coating on the external face was tested in laboratory and field conditions. The cylinder and the fabric were equipped with thermocouples and heat flux sensors attached to their surfaces. The tests showed that the device gave effective protection to the cylinder, decreasing the radiative heat flux that reaches it and keeping it in a safe condition when exposed to a fire; consequently preventing extreme behavior such as an explosion.

O “Estado Novo”, vulgarmente chamado “fascismo à portuguesa”, sistema corporativo com ideologia única e com “partido único”, teve a sua polícia política que foi tratando os diversos casos em função da ideologia de cada um, do estrato social a que pertencia ou da sua importância pessoal. Os “intelectuais”, na sua grande maioria, exerceram desde sempre uma acção de oposição em defesa da liberdade, tendo sido, porém, objecto de repressão diferente, por exemplo, conforme eram simplesmente liberais ou comunistas, de acordo com as críticas que faziam ao regime ou a sua importância literária. Ferreira de Castro era um escritor consagrado nacional e internacionalmente. Assim, olhando o seu processo, verifica-se que, apesar de ter participado em quase todas as acções pacíficas contra o Estado Novo (que iam sendo descritas e vigiadas pela polícia), não foi vítima de uma repressão demasiado violenta, como a prisão, a tortura ou a perda de direitos políticos.

National holidays have both a civic and religious significance. Under the Estado Novo (1930-1974) — a kind of “Portuguese-style” fascism – civil law or secular policy was followed for quite some time, in line, in fact, with the idea of “separation” of Church and State adopted by the First Republic (1910-1926), albeit more moderate (“second separation”). Indeed, it was only after the Concordat (1940) was signed between the State and the Catholic Church that the meaning of the religious spirit (until then only taken advantage of by the State) was revealed, when some politicians attempted to create a “Catholic State”. But it never came to pass. It was from 1948, but more so from 1952, that religious holidays were observed. The State started adapting the national holidays from the First Republic to its ideology of authoritarian nationalism and a “one-party” regime.

With the introduction of new materials and advances in medical science, the endodontic files have changed since the early days of root canal treatments. In the late days, we have seen an increasing use of Nickel-Titanium (NiTi) alloys, to the detriment of more conventional alloys. At body temperature, NiTi alloys present a superelastic behaviour, which allows to be more effective in the removal of the tooth pulp tissue, and in the protection of the tooth structure. Anyhow, these NiTi instruments will eventually fracture, usually without any visual signal of degradation. Thus, there is a need of studying these alloys, as they present a high hysteresis cycle and non-linearities in the Elastic domain. Currently, there is no international standard to test NiTi endodontic files, so various authors have attempted to design systems that can test them under fatigue loads, usually based on empirical setups. Following a systematic approach, this work presents the results of rotary fatigue tests for two Alfa Aesar® Nitinol wires with different diameters (0.58mm and 0.25mm).The formulation is presented, where the material strength reduction can be quantified from the determination of the strain and the number of cycles until failure, as well numerical FEM simulation to verify the analytical model predictions.

https://doi.org/10.14195/2183-8925_37

Pseudomonas syringae pv. actinidiae (Psa) is a phytopathogen responsible for bacterial canker in kiwifruit plants and can be disseminated through pollen. This study aimed to evaluate the effectiveness of antimicrobial photodynamic therapy (aPDT) in the inactivation of Psa on kiwifruit pollen using New Methylene Blue (NMB) and Methylene Blue (MB) in the presence/absence of potassium iodide (KI). Pollen germination assays were also performed to evaluate if it was affected by aPDT. Higher reduction of Psa was achieved using NMB (5.0 μM) combined with KI (100 mM) in vitro (ca. 8 log CFU mL−1 after 90 min of irradiation), while NMB alone promoted a lower reduction (3.7 log CFU mL−1). The most efficient NMB concentration with KI was used to study the photodynamic efficiency of MB (5.0 μM). MB with KI photo-inactivated Psa more efficiently than NMB, causing the same bacterial reduction (ca. 8 log CFU mL−1) in half the irradiation time (45 min). Therefore, MB was selected for the subsequent ex vivo aPDT assays in pollen. Almost all the Psa cells added artificially to the pollen (3.2 log CFU mL−1) were photo-inactivated (3.1 log CFU mL−1), whereas aPDT had a low effect on pollen natural microorganisms. When KI was added, a significant increase in aPDT effectiveness was observed (4.5 log CFU mL−1). No negative effects were observed in the pollen germination after aPDT. The results show aPDT is an effective and safe method to Psa inactivation on kiwifruit pollen, and MB use is a promising alternative in the control of Psa transmission.

Fatigue is one of the main causes for in service failure of mechanical components and structures. With the development of new materials, such as high strength aluminium or titanium alloys with different microstructures from steels, materials no longer have a fatigue limit in the classical sense, where it was accepted that they would have ‘infinite life’ from 10 million (107) cycles. The emergence of new materials used in critical mechanical parts, including parts obtained from metal additive manufacturing (AM), the need for weight reduction and the ambition to travel greater distances in shorter periods of time, have brought many challenges to design engineers, since they demand predictability of material properties and that they are readily available. Most fatigue testing today still uses uniaxial loads. However, it is generally recognised that multiaxial stresses occur in many full-scale structures, being rare the occurrence of pure uniaxial stress states. By combining both Ultrasonic Fatigue Testing with multiaxial testing through Single-Input-Multiple-Output Modal Analysis, the high costs of both equipment and time to conduct experiments have seen a massive improvement. It is presently possible to test materials under multiaxial loading conditions and for a very high number of cycles in a fraction of the time compared to non-ultrasonic fatigue testing methods (days compared to months or years). This work presents the current status of ultrasonic fatigue testing machines working at a frequency of 20 kHz to date, with emphasis on multiaxial fatigue and very high cycle fatigue. Special attention will be put into the performance of multiaxial fatigue tests of classical cylindrical specimens under tension/torsion and flat cruciform specimens under in-plane bi-axial testing using low cost piezoelectric transducers. Together with the description of the testing machines and associated instrumentation, some experimental results of fatigue tests are presented in order to demonstrate how ultrasonic fatigue testing can be used to determine the behaviour of a steel alloy from a railway wheel at very high cycle fatigue regime when subjected to multiaxial tension/torsion loadings.

Monopiles for offshore wind are the most used foundations by farm operators due to their low production costs, when compared to other bottom-fixed or floating foundations. In this research, a monopile foundation for offshore wind power was evaluated for its soil interaction and grout behavior, and an appropriate numerical model for the structural analysis of the foundation and tower was developed. FAST 8, an aero-hydro-servo-elastic numerical code developed by NREL, was used to obtain the loads applied on the supporting structures. These loads were pre-processed before they were inputted on the finite element model, developed using the finite element software ANSYS. The considered conical grout connection, which connects the monopile to the transition piece through friction, was modeled under a changing-status nonlinearity condition. To model the soil–pile interaction, a p-y model was applied using the ANSYS APDL commands. Static, modal, and transient structural analyses were produced to study the structure suitability for its use on offshore environments. Different soil interactions were modeled, and their results were then compared within the transient and modal analysis, indicating that the angle of the grout connection strongly affects the loading conditions on the grout. Moreover, scouring affects the dynamic behavior of the overall supporting structures, thus protection against this phenomenon is suggested.

The history of the University in Portugal lives a moment of great relevance in the transition to democracy in the decade 1970-1980. Under the Marcello Caetano government (1968-1974) –the continuation of the New State of Salazar, the «fascism of the professorship»– there were some internal reforms, state reform experiences (with the creation of new universities and schools of higher education) and important struggles of students against the dictatorship; after the «Carnation Revolution» of April 25, there was also a poorly planned and not achieved attempt to draw a «political university» of Marxist influence, with the intention to accompany the extreme phase of the revolution. With the 1976 Constitution, based on a democratic nature of Occidental countries, and the first constitutional governments, higher education has been consolidated in our binary system, made by university and polytechnic. However, there is also evidence of the trend towards a neoliberal education system, announcing the foundation of many universities and particular institutes. In order to discuss this complex evolution, the article exceeds the decade of the 70s of the XX century, even to the current XXI century, characterized by the crisis of the universits, which leads us to ask: Which University? How to reference this article Torgal, L. R. (2015). A Universidade em Portugal em período de transição para a democracia e para o neoliberalismo. Espacio, Tiempo y Educación, 2(2), 155-171. doi: http://dx.doi.org/10.14516/ete.2015.002.002.008

Os autores apresentam um caso raro de choque em doente sem antecedentes pessoais significativos, admitido na unidade de terapia intensiva por suspeita de choque séptico. Inicialmente, foi tratado com fluidoterapia sem melhoria, tendo sido aventada a hipótese de síndrome de hiperpermeabilidade capilar, após confirmação de hipoalbulinemia paradoxal grave, hipotensão e hemoconcentração exuberante - tríade característica da doença. Os autores discutiram o diagnóstico diferencial e ainda realizaram uma revisão do diagnóstico e do tratamento da doença.

Evocar um autor pode supor uma análise histórica objetiva e um recurso à memória, ou seja, ao testemunho pessoal do autor. Foi isso que se pretendeu fazer, ao escrever este artigo sobre José Sebastião da Silva Dias. Assim, analisou-se Silva Dias como ideólogo, que foi passando de uma perspetiva católica e integralista, com um lastro social, para uma perspetiva socialista democrática. Mas também se tentou mostrar que Silva Dias chegou a essa ideologia, através de uma análise objetiva da História, em que se interligava o conhecimento do documento com a reflexão filosófica. Acima de tudo, como modernista e como contemporaneísta (neste caso mais como orientador de investigação) deve-se-lhe uma «escola» ou «escolas». No fundo renovou a historiografia, lançando as bases, desde os anos de 1960, dos estudos científicos da História Contemporânea.

O presente artigo, elaborado para conferência de encerramento do XV Encontro Regional de História da ANPUH-RJ – “Ofício do Historiador: Ensino e Pesquisa” –, ocorrido em 2012, aborda a História da História, demarcando o entendimento da História como Ciência, numa preocupação em delimitar os problemas oriundos dos campos da pesquisa e do ensino nos dias atuais, com ênfase especial para a atuação do profissional de história no cenário português. São postas em questão as influências da ideologia e da memória na produção histórica, sobretudo nos desdobramentos da crise atual, tanto na educação básica quanto na educação superior.

RESUMO: As fístulas broncopleurais (FBP) constituem um problema clínico frequente mas de resolução complicada, sobretudo em doentes sob ventilação mecânica. O manejo destas situações envolve um controlo adequado.dos sistemas de drenagem torácica e do suporte ventilatório. A terapêutica cirúrgica é habitualmente reservada para as situações em que as medidas médicas falham, mas muitos doentes internados em UCI são péssimos candidatos a uma cirurgia torácica major. Nos últimos anos têm sido descritas várias técnicas para reparação endobrônquica de FBP envolvendo o uso de materiais selantes, tais como derivados do cianoacrilato ou fibrina. Descrevemos uma nova técnica de reparação de FBPs por oclusão brônquica selectiva com catéter de Swan-Ganz. Esta técnica foi aplicada com sucesso num doente ventilado, com internamento prolongado em UCI (mais de 3 meses) por múltiplas fistulas distais de alto débito que condicionavam insuficiência respiratória grave e impossibilidade de desmame do ventilador. SUMMARY: The medical therapy of bronchopleural fistulas (BPF) in the mechanically ventilated patient continue to present a formidable challenge. Management includes adequate control of chest tubes, drainage systems and ventilator support. Most patients in ICU are poor surgical candidates so nonoperative therapy was develloped.in last years. These modalities include endobronchial occlusion with cyanoacrylatebased agents and fibrin agents. We present a new technique by selective bronchial occlusion with a Swan-Ganz catheter. This technique was successfully applied in a ventilated patient with long-standing permanence in ICU by multiple peripheral high-flow BPF and serious respiratory failure with ventilator dependence. Palavras-chave: Broncofibroscopia, fistula broncopleural, oclusão brônquica, Key-Words: fiberoptic bronchoscopy, bronchopleural fistula, bronchial occlusion

RESUMEN: El concepto de “intelectual” es difícil de definir y sin duda se debate constantemente. Sin embargo, es importante reflexionar sobre él a fin de comprender su significado y los problemas que implica. Sea como fuere, a un Estado autoritario “moderno” se le supone una única ideología que tiene que difundirse por medio de una propaganda bien organizada, proceso en el que los intelectuales desempeñan un papel significativo. El “Nuevo Estado” de Salazar encaja en esta categoría y sin duda el conocimiento acerca de sus “intelectuales” es fundamental. En este artículo, el objetivo es proporcionar algunos ejemplos interesantes de “intelectuales” o de simples “funcionarios políticos” con inclinación intelectual a fin de indicar el sentido y complejidad de un estudio con una dimensión distinta sobre este asunto. A este fin han sido seleccionadas tres personalidades responsables de la actividad ideológica y cultural de gran relieve en el Estado de Salazar: António Ferro, João Ameal y Costa Brochado. Palabras clave: Estado Novo; Authotitarianism; Salazar, António de Oliveira; Intellectuals; Ferro, António; Brochado, Idalino da Costa; Ameal, João. ABSTRACT: The concept of the “intellectual” is difficult to define and undoubtedly constantly debated. It is nevertheless important to reflect on it in order to understand its meaning and the problems involved with it. Be that as it may, a “modern” authoritarian State presumes a single ideology which has to be diffused by means of well-organised propaganda, in which process “intellectuals” play a significant role. Salazar’s “New State” fits this category and, undoubtedly, knowledge about its “intellectuals” is fundamental. The objective in this article is to provide some interesting examples of “intellectuals” or simple “political functionar- ies” with an intellectual bent so as to indicate the sense and complexity of a study of a different magnitude on this topic. To this end, three personalities responsible for ideological and cultural activity of great salience in Salazar’s State have been selected: António Ferro, João Ameal and Costa Brochado. Keywords: Estado Novo; Autoritarismo; Salazar, António de Oliveira; Intelectuais (intelectuais); Ferro, António; Brochado, Idalino da Costa; Ameal, João.

RESUMO A ressuscitação hídrica do paciente em falência circulatória aguda tem como um de seus objetivos aumentar o volume sistólico e, consequentemente, o débito cardíaco, para melhor oxigenação dos tecidos. Contudo, isso não se verifica em cerca de metade dos pacientes, que são considerados não respondedores a fluidos. A avaliação da resposta a fluidos antes de sua administração pode selecionar os pacientes que devem ter benefício e evitar o risco de sobrecarga nos restantes. Os parâmetros dinâmicos de avaliação da resposta a fluidos têm se revelado promissores enquanto fatores preditores. Entre estes, a medição ecocardiográfica da variação respiratória do diâmetro da veia cava inferior é um método de fácil aplicação, que tem sido difundido na avaliação hemodinâmica em unidades de cuidados intensivos. No entanto, a aplicabilidade desta técnica tem muitas limitações, e os estudos, até à presente data, são heterogêneos e pouco consistentes em alguns grupos de pacientes. Realizamos uma revisão sobre a utilização da variação respiratória do diâmetro da veia cava inferior, medida por ecocardiografia transtorácica, na decisão de administrar fluidos ao paciente em falência circulatória aguda, em cuidados intensivos, incluindo potencialidades e limitações da técnica, de sua interpretação e a evidência existente.