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International audience; Friction dampers are classically used in turbomachinery for bladed disks to control the levels of vibrations at resonance and limit the risk of fatigue failure. It consists of small metal components located under the platforms of the blades, which dissipates the vibratory energy through friction when a relative displacement between the blades and the damper appears. It is well known that the shape of such component has a strong influence on the damping properties and should be designed with a particular attention. With the arrival of additive manufacturing, new dedicated shapes for these dampers can be considered, determined with specific numerical methods as topological optimisation (TO). However, the presence of the contact nonlinearity challenges the use of traditional TO methods to minimise the vibration levels at resonance. In this work, the topology of the damper is parametrized with the Moving Morphable Components (MMC) framework, and optimised based on meta-modelling techniques: here kriging coupled with the Efficient Global Optimisation (EGO) algorithm. The level of vibration at resonance are computed based on the harmonic balanced method augmented with a constraint to aim directly for the resonant solution. It corresponds to the objective function to be minimised. Additionally, a mechanical constraint based on static stress analysis is also considered to propose reliable damper designs. Results demonstrate the efficiency of the method and show that dampers geometries that meet the engineers' requirements can be identified.

This paper investigates model-order reduction methods for geometrically nonlinear structures. The parametrisation method of invariant manifolds is used and adapted to the case of mechanical systems expressed in the physical basis, so that the technique is directly applicable to problems discretised by the finite element method. Two nonlinear mappings, respectively related to displacement and velocity, are introduced, and the link between the two is made explicit at arbitrary order of expansion. The same development is performed on the reduced-order dynamics which is computed at generic order following the different styles of parametrisation. More specifically, three different styles are introduced and commented: the graph style, the complex normal form style and the real normal form style. These developments allow making better connections with earlier works using these parametrisation methods. The technique is then applied to three different examples. A clamped-clamped arch with increasing curvature is first used to show an example of a system with a softening behaviour turning to hardening at larger amplitudes, which can be replicated with a single mode reduction. Secondly, the case of a cantilever beam is investigated. It is shown that the invariant manifold of the first mode shows a folding point at large amplitudes which is not connected to an internal resonance. This exemplifies the failure of the graph style due to the folding point, whereas the normal form style is able to pass over the folding. Finally, A MEMS micromirror undergoing large rotations is used to show the importance of using high-order expansions on an industrial example.

The analysis of whole engine rotor-dynamic models is an important element in the design of aerojet engines. The models include gyroscopic effects and allow for rubbing contact between rotor and stator components such as bladed discs and casing. Due to the non-linearities inherent to the system, bifurcations in the frequency response may arise. Reliable and efficient methods to determine the bifurcation points and solution branches are required. For this purpose a multi-harmonic balance approach is presented that allows a numerically efficient detection of bifurcation points and the calculation of both continuous and isolated branches of the frequency response functions. The method is applied to a test-case derived from a commercial aero-engine. A bifurcation structure with continuous and isolated solution branches is observed and studied in this paper. The comparison with time-marching based on simulations shows both accuracy and numerical efficiency of the newly developed approach

The aim of this paper is to study the effects of mistuning on fan flutter. The computations are based on a three-dimensional, whole assembly, timeaccurate, viscous, finite-volume compressible flow solver. The unsteady flow cases are computed as Reynolds-averaged Navier–Stokes, with the basic assumption that the frequencies of interest are sufficiently far away from the frequencies of turbulent flow structures. The overall solution method is implicit, with second-order accuracy in space and time. A rig wide-chord fan blade, typical of modern civil designs, was used as the benchmark geometry for this study. There are 20 blades in the fan assembly. A random pattern frequency mistuning was used in most of analysis undertaken in this paper. The 1F mode shapes are the same for all mistuned blades. The objectives of this work are: 1. To check if the introduction of mistuning would bring the experimental and computed flutter boundaries closer 2. To explain how mistuning provide stability 3. Establish a relationship between mistuning and damping 4. Provide a data base which can be used in future for testing simple mistuning models

Colloque avec actes et comité de lecture. Internationale.; International audience; This paper presents an application of the harmonic balance method for modelling the blade-tip casing interaction. A new nonlinear element has been implemented in the in-house code FORSE in order to take into account the contact with friction that can occur when blade tip touches the abradable coating of the casing. This approach permits to efficiently calculate the frequency response of the blade excited by the contact of the casing. Numerical results presented in this paper agree with other observations proposed in the literature both numerical and experimental.

International audience; The reaction of MoO3 [or «WO3.H2O»], aqueous H2O2 (30 wt%) with R2Si(OR')2 in alkaline hydrogen peroxide-ethanol mixtures followed by treatment with PPh4+Cl- affords the corresponding salts of the previously unknown dioxotetraperoxodi(molybdenum or tungsten) heteropolyanion, [PPh4]2[R2SiO2{M2O2(Μ-O2)2(O2)2}] in 75-80% isolated yields (R2=(CH3)2, (i-C4H9)2 or (CH3)(CH2Cl); R'=CH3 or C2H5; M=Mo(VI) or W(VI)). These results are unequivocally established by a combination of elemental analysis, IR, 1H and 13C NMR spectroscopy and complete X-ray crystal structure analysis of the three molybdenum complexes. There is good evidence that the tungsten analogues are isostructural compounds. The O–O bonds are in the 1.464–1.483 Å range, typical of peroxo complexes with Η2-O22- and Μ2-Η2:Η1-O22- groups. These complexes represent a type of silicon-based polyoxoperoxo species which are models of moieties that are obtained by grafting on silica surfaces and also in the preparation of organic inorganic mesophases to synthesize MOx–SiO2–MCM-41 or MOx–SiO2–SBA-15. These materials, after calcination, have a highly dispersed MoOx/SiO2 structure and lead to leach-resistant catalysts.

Lactones are efficiently oligomerized by heteropolyacids H3[PM12O40]·aq with M=Mo or W, “H3+n[PMo12−nVnO40]·aq” (HPA-n) and molybdenum(VI) acetylacetonate, vanadium(V) sulfate initiators in the presence of dioxygen. The resulting linear oligomers display relatively low polydispersity (≤1.7) and high monomer conversion (≥99%), and are obtained with relatively short reaction times (1–24 h, 20–60 ◦C). The products were analysed by various physicochemical methods: size-exclusion chromatography (SEC) (to determine the molecular weight properties); IR; 1H and 13C NMR; matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOFMS). Lactone oligomerization is proposed to proceed by a coordination-insertion mechanism via cationic species (VO2 + and/or MO2 2+; M=Mo orW) with chain growth involving acyl-oxygen bond cleavage and an activated monomer. Br¨onsted acids catalyse the reaction. These reactions are the first examples of the ring-opening oligomerization of lactones catalysed by heteropolyacids and the inexpensive “VOSO4·xH2O/THF–H2O/O2” system.

When peroxotetramolybdophosphate, [(n-C4H9)4N]3[PO4{Mo2O2(µ-O2)2(O2)2}2], denoted (NBu4)3PMo4, and its tungsten(VI) analogue, (NBu4)3PW4, are mixed in acetonitrile at room temperature, redistribution occurs with the formation of three mixed-addenda species [PO4{Mo4–xWxO20}]3–(x= 1–3). The temperature dependence of the phosphorus-31 NMR spectra of a 1 1 mixture and of the pure salts, (NBu4)3PMo4 or (NBu4)3PW4, shows that {MO(O2)2} species are in chemical exchange, as are the {MOp} units of certain heteropolyacids (e.g. H3[PMo12O40]·aq and H3[PW12O40]·aq). However, there is no chemical exchange between free phosphate and {MO(O2)2} species in these systems; but there is fluxional behaviour involving PMo2W2, PMo4 and PW4. This is attributed to the rapid equilibrium between isomers (PMo2W2) and to equilibrium between anionic structures with tridentate (µ-2:1-O22–) and bidentate (2-O22–) modes of coordination for the two peroxo groups of the {M2O2(µ-O2)2(O2)2} moieties.

Estudou-se o ciclo evolutivo da mariposa oriental Grapholita molesta (Busck, 1916), em dieta artificial, em temperaturas constantes (20, 23, 26 e 30°C), umidade relativa de 75+10% e fotofase de quatorze horas, com o objetivo de determinar as necessidades termicas das diferentes fases de desenvolvimento, e estimar o numero de geracoes anuais e durante o ciclo vegetativo do pessegueiro na localidade de Pelotas, RS. A determinacao da temperatura-base inferior e o valor da constante termica em graus-dia (GB) foram feitos utilizando-se o metodo da hiperbole. As temperaturas-bases inferiores foram de 6,47°C (ovo), 9,04°C (lagarta), 50,16°GD (pre-pupa), 6,61°C (pupa) e 8,99°C (ciclo evolutivo). As constantes termicas foram de 64,79 GD (ovo), 223,63 GD (lagarta), 50,16 GD (pre-pupa), 155,46 GD (pupa) a 482,00 GD (ciclo evolutivo). Atraves da temperatura-base do ciclo evolutivo estimou-se que nessa localidade podem desenvolver-se de seis a sete geracoes anuais de G. molesta, e de quatro a cinco, sobre o ciclo vegetativo do pessegueiro. Made available in DSpace on 2011-04-09T12:16:28Z (GMT). No. of bitstreams: 1 pab04jul92.pdf: 351621 bytes, checksum: 3d1dda938152b014d995b0e7b1723acd (MD5) Previous issue date: 2001-09-03

Trichopoda pennipes parasitization had a strong negative effect on Nezara viridula adult longevity, fecundity and feeding. A parasitized female lived half the time of an unparasitized one and for a parasitized male this reduction in longevity was even greater. Unparasitized females laid four times more eggs than parasitized one. Parasitization had no significant effect on egg fertility. Feeding intensity by N. viridula is reflected by the number of punctured soybean seeds. Caged plants exposed to unparasitized adults produced only one half as many unpunctured seeds compared to cages with parasitized adults. The percentage of normal seeds (with commercial value) was 31.1% higher in cages with parasitized adults. Made available in DSpace on 2011-04-09T12:16:25Z (GMT). No. of bitstreams: 1 pab02jul92.pdf: 388240 bytes, checksum: 3b1bd49f053be50e5451c8cb17d89c1e (MD5) Previous issue date: 2001-08-31

Eggs of Trichopoda pennipes were found on Nezara viridula host bodies at all sample sites. Supernumerary oviposition was found to be common on both male and female, and males had a higher incidence of tachinid eggs and more eggs/individual. Males consistently had higher parasitization levels. Tachinid eggs were found virtually on the whole body surface of Nezara viridula. The highest concentration was on the thorax, followed by the abdomen and head. The largest number was laid on the ventral surface of the thorax, while very few on the appendages. A significant relationship between number of tachinid eggs on the host body and level of parasitization was found. More tachinid eggs per host were directly related to a higher probability of parasitization for individuals with three eggs or less. When two tachinid eggs were present on a host, only 0.95 were truly parasitized With three eggs or more, 0.99 were truly parasitized, and larger number of tachinid eggs on the host does not improve chances for being parasitized. Made available in DSpace on 2011-04-09T12:17:54Z (GMT). No. of bitstreams: 1 pab06jan91.pdf: 403423 bytes, checksum: f997ea279b6e2020b23678ab48a3843f (MD5) Previous issue date: 2001-09-13

Neste estudo foram testados à nível de laboratório, dezenove formulações de produtos disponíveis no mercado nacional, sobre Anastrepha fraterculus, quanto à ação de contato ou ação tópica; ação de ingestão; e ação de profundidade ou larvicida. Made available in DSpace on 2022-07-05T20:19:21Z (GMT). No. of bitstreams: 1 Hortisul-1990-v1-n3-p10.pdf: 619819 bytes, checksum: 046ddae5b43692f4f85bf8b29ce3b00a (MD5) Previous issue date: 1990

Visando verificar as cultivares de milho (Zea mays L.) selecionadas para maior prolificidade poderiam compensar a reducao na produtividade de graos em decorrencia da diminuicao da populacao de plantas, tanto em monocultivo como em consorcio com o feijao (Phaseolus vulgaris L.), foram conduzidos tres experimentos. Dois deles foram realizados no Centro Nacional de Pesquisa de Milho e Sorgo (CNPMS), Sete Lagoas, MG, nos anos agricolas de 1983/84 e 1984/85 e o outro na Escola Superior de Agricultura de Lavras (ESAL), Lavras, MG, ano agricola 1984/85. Os tratamentos foram as cultivares de milho, e combinacao de tres populacoes de plantas (20, 40 e 60 mil plantas/ha), em monocultivo e em consorcio com o feijao. No sistema consorciado, a semeadura foi simultanea na mesma linha. A produtividade de graos do feijao respondeu linearmente a diminuicao na populacao de milho. A produtividade media de graos de milho na populacao de 20 mil plantas/ha foi de 20% inferior a obtida na populacao de 40 mil plantas/ha quando se considerou a media dos tres locais e os sistemas de plantio. O indice de espiga, porem, foi 30,8% superior, na menor populacao, quando comparado ao da maior populacao. As cultivares utilizadas apresentaram, de modo geral, desempenho semelhante, e foram igualmente afetadas pela presenca do feijao e pelas alteracoes nas populacoes de plantas. Quando se avaliou a producao combinada de graos de milho e feijao, observou-se que a maior producao de feijao nas menores populacoes compensou a reducao na produção de feijão nas menores populações compensou a redução na produção de grãos de milho observada nesta condição. Made available in DSpace on 2021-12-13T12:04:24Z (GMT). No. of bitstreams: 1 Utilizacao-cultivares.pdf: 6588849 bytes, checksum: 12f3ca83cb5b508a079b615e781c09ee (MD5) Previous issue date: 1987