Cruciform specimens’ experimental analysis in ultrasonic fatigue testing

In this work, two special aluminium cruciform specimens are designed and tested in an ultrasonic fatigue machine. They were designed based on Single-Input-Multiple-Output (SIMO) modal analysis to induce in-plane biaxial stress combinations (in-phase T-T and out-of-phase C-T) when at resonance at 20 kHz. The geometries were subjected to both numerical analysis and experimental testing to understand if they can indeed create the intended biaxial state of stresses. Both numerical and experimental results showed an impact of nearby resonant modes of non-interest on the correct functioning of the specimens, especially regarding the T-T specimen where a large deviation from the mode of interest was measured. This means that future work includes re-designing T-T specimens taking into account these mode shapes. Only out-of-phase specimens demonstrated to work properly and tests until failure were conducted. The first failure results showed to be consistent with literature when out-of-phase biaxial stress is applied cyclically

Review of Multiaxial Testing for Very High Cycle Fatigue: From ‘Conventional’ to Ultrasonic Machines

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).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.Peer reviewedFinal Published versio

Ultrasonic fatigue experiments with biaxial cruciform specimens

Fatigue studies of materials in simple or complex loading systems for any given lifetime is object of continuous research. This is due to the advancements on mechanical and structural components, as well as for new and innovative materials, which implies the knowledge of a materials response to all dynamic loads. The fatigue failure regime beyond what was once considered to be the fatigue limit (infinite life) is characterized between 107 and 109, known as Very High Cycle Fatigue regime. Due to the time consuming and energy wide consumption of conventional fatigue testing for such regime, fatigue tests under ultrasonic actuators are being used, capable of applying the dynamic loads at around 20 kHz. Nowadays, several variants of ultrasonic fatigue tests were already proposed and tested but it is still a somewhat limited fatigue test if compared to the conventional servo-hydraulic fatigue testing machines of general use. In this study, biaxial in plane stresses are induced in specially designed cruciform specimens with ultrasonic fatigue testing resonant principals. Two geometries were numerically analysed, manufactured and experimentally tested, the in-phase tension-tension (T-T) specimen and the out-of-phase compression-tension (C-T) specimen. All specific designed geometries go under a thorough numerical and several experiments analysis for their validation. The specimens showing a correct and as intended behaviour are led to failure

Adenoid Cystic Carcinoma of the nasal cavity and paranasal sinuses - Restrospective review of 20 years

Objectivo: Analisar as características clinico-patológicas, tratamento e prognóstico do carcinoma adenóide quístico (CAQ) das fossas nasais e seios perinasais. Material e Métodos: Estudo retrospetivo de doentes com diagnóstico de CAQ de fossas nasais e seios perinasais do Instituto Português de Oncologia de Lisboa desde 1997 até 2016. Resultados: Foram obtidos 30 doentes, sendo 60% do sexo feminino. A idade média foi de 65 anos. O sintoma mais frequente foi obstrução nasal e o sinal mais comum foi tumefacção do palato duro. 63% dos doentes apresentavam tumor localmente avançado. O seio maxilar foi o mais atingido (87%). A invasão óssea foi a mais frequentemente identificada. Todos os doentes realizaram cirurgia com radioterapia adjuvante. Os doentes que apresentaram recorrência (50%) foram maioritariamente tratados com radioterapia. Conclusão: O CAQ das fossas nasais e seios perinasais apresenta habitualmente mau prognóstico. O tratamento cirúrgico é limitado pela recorrência local comum e tardia.info:eu-repo/semantics/publishedVersio

Experimental methodology and analytical solution for cruciform ultrasonic fatigue Testing

As transportation and general machinery demand higher working speeds, reliability, and life spans [1], a higher life span characterisation method was required. In the middle of the 20th century, Mason devised a new fatigue testing method very different from the established ‘conventional’. The designated ultrasonic fatigue machine utilises resonance principles to achieve a considerably higher testing frequency. With Mason’s generally accepted 20 kHz standard reaching a billion cycles was made reliable. To make ultrasonic fatigue machines accessible and accepted, a trusted deterministic experimental methodology is necessary. Claude Bathias, the ultrasonic fatigue pioneer [1], brought ultrasonic fatigue testing (UFT) to the fatigue research world. His book details UTF methodology extensively for all uniaxial loading conditions [2]. Bathias et al. [3] have also shown piezoelectric fatigue testing machines in high and low temperatures, with R≠ -1 stress ratios and fretting. Considerable worldwide research has followed Bathias well described and methodically presented methodologies [4]–[6]. The first ‘conventional’ fatigue machines focused on pure uniaxial cyclical load, meaning one single direction load. Multiaxial stresses were later recognised as the leading dynamic stress state in machines and structures [7]. Thereafter, several different multiaxial testing methods came to fruition over the years, replicating the different cyclic loads. Just as ‘conventional’ fatigue transposed from uniaxial to multiaxial testing mechanisms, UFT developments will follow the same trend. Palin Luc et al. [8] induced a biaxial bending stress state with a carefully shaped disk. P. Costa et al. [9] created an altered ultrasonic setup capable of inducing a specimen in a tension-torsion stress state. In this study, a detailed methodology description with a proposed analytical solution is made to the already proven and working cruciform specimens created by D. Montalvão et al. [10]. Due to the cruciform deformation complexity, finite element analysis (FEA) was used to adjust Bathias analytical concepts

Malignant schwannoma of the soft palate: a case report

Os Schwannomas são tumores benignos das células de Schwann das bainhas dos nervos periféricos. Podem ter origem em diferentes tipos de nervos e podem ser encontrados na porção intra, extra, ou transcraniana. Uma local ização rara é a cavidade oral. O prognóstico do schwannoma é bastante favorável e a remoção cirúrgica conservadora é o tratamento de eleição. A transformação maligna de schwannomas benignos é rara e apesar de indicada a quimioterapia e radioterapia pósoperatória, o schwannoma maligno é geralmente resistente a ambos. Os autores apresentam o caso clínico de schwannoma maligno, do palato mole, num doente de 43 anos com historia de disfagia e disfonia com 1 ano de evolução. Foi submetido a remoção cirúrgica seguida de radioterapia pós-operatória. Após 1 ano não se registam sinais de recorrência. A relevância deste caso reside no diagnóstico raro de um schwannoma maligno do palato mole com um comportamento aparentemente benigno

Neoplasms of minor salivary gland - Retrospective study

Objectivos: Análise descritiva dos casos de neoplasias das glândulas salivares minor tratados no serviço de Otorrinolaringologia do IPO de Lisboa, e comparação dos resultados com o que está descrito na literatura. Metodologia: Análise retrospectiva de todos os casos com diagnóstico histológico de neoplasia das glândulas salivares minor das cavidade nasal, cavidade oral, laringe e faringe, que ocorreram durante o período entre Outubro de 1992 a Novembro de 2015, tratados no serviço de Otorrinolaringologia do Instituto Português de Oncologia de Lisboa, Francisco Gentil. Resultados : Foram documentados 58 casos de neoplasia das glândulas salivares minor, 60% ocorreram em indivíduos do sexo feminino e 40% ocorreram no sexo masculino, com um média de idades de 57 anos. O sintoma mais frequente na cavidade nasal foi a obstrução nasal, na cavidade oral a presença de úlcera ou tumefacção, e na orofaringe a dor. Os tipos histológicos mais comuns foram o carcinoma adenoide quístico (33%), o adenocarcinoma polimórfico (24%) e o carcinoma mucoepidermóide (22%). A orofaringe foi o local mais comum destas neoplasias. A cirurgia foi o tratamento de 1ª linha em 93% dos casos e 52% realizaram radioterapia adjuvante. A recidiva ocorreu em 20% dos casos. A mortalidade relacionada com o tumor foi de 7%. Conclusões: As neoplasias das glândulas salivares minor são pouco frequentes, sendo as mais comuns o carcinoma adenoide quístico, o adenocarcinoma pleomórfico e o carcinoma mucoepidermóide. O tratamento cirúrgico é efetivo isoladamente em muitos casos. A mortalidade está relacionada com o estadio e com o tipo histológico do tumor.info:eu-repo/semantics/acceptedVersio