Ograniczanie wyników
Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 258

Liczba wyników na stronie
first rewind previous Strona / 13 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  finite element analysis
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 13 next fast forward last
EN
The synchronous reluctance motor design process is usually considering objectives that are in direct or indirect relationship with the rotor magnetic saliency ξ. The magnetic saliency is defined as the ratio of direct (d) Ld and quadrature (q) inductances Lq. Both inductances and their dependence on the dq-axis current plane are investigated with a non-linear analytical model in this paper. With the non-linear analytical model linked to the analysis procedures is also possible to determine the synchronous reluctance motor cross-saturation effect.
PL
W artykule analizowano asymetrię magnetyczną (saliency) wirnika silnika reluktancyjnego. Zastosowano model nieliniowy uwzględniający tę asymetrię i umożliwiający określenie efektu nasycenia.
2
Content available remote Lightweighting of wishbone finite element analysis
EN
This paper focuses on lightweighting of wishbone structure for ordinary 5-seated commercial vehicle. Typically, the wishbone structure is made of high carbon steel and the aim is to investigate if the composite materials, such as E-Glass/Epoxy, Carbon/Epoxy and Boron/Epoxy, can achieve the lightweighting purpose without compromising material strength. The study is carried out through finite element package (Siemen NX) with the consideration of three different loading conditions, namely, lateral braking force, vertical and longitudinal braking force. Throughout the study, it is found that both Carbon/Epoxy and Boron/Epoxy composites is able to reduce the weight of the component by 46% while maintaining the required strength.
EN
Momentum wheels are the key components of the inertial actuators in the satellites, and the momentum wheel bearings are weak links of momentum wheels as they operate under harsh conditions. The reliability estimation for momentum wheel bearings are helpful to guarantee the mission successes for both momentum wheels and satellites. Hence, this paper put emphasis into reliability estimation of a momentum wheel bearing considering multiple coupling operating conditions and frictional heat by using the finite element analysis. The stress-strength interference model is employed to calculate the reliability of the momentum wheel bearing. A comparative analysis for reliability estimation with and without frictional heat of the momentum wheel bearing is conducted. The results show that the frictional heat cannot be ignored in the reliability analysis of momentum wheel bearings.
PL
Koła zamachowe są kluczowymi elementami składowymi siłowników bezwładnościowych w satelitach. Ich łożyska stanowią słaby punkt podczas pracy w trudnych warunkach. Ocena niezawodności łożysk kół zamachowych pozwala zapewnić powodzenie misji zarówno w odniesieniu do samych kół zamachowych, jak i satelitów. Dlatego też niniejszy artykuł poświęcono zagadnieniu oceny niezawodności łożyska koła zamachowego z wykorzystaniem analizy metodą elementów skończonych przy uwzględnieniu wielu sprzężonych warunków pracy oraz ciepła tarcia. Do obliczenia niezawodności łożyska koła zamachowego zastosowano model obciążeniowo-wytrzymałościowy. Przeprowadzono także analizę porównawczą oceny niezawodności łożyska koła zamachowego z uwzględnieniem lub bez uwzględnienia ciepła tarcia. Wyniki pokazują, że w analizie niezawodności łożysk kół zamachowych nie można pominąć ciepła tarcia.
EN
The paper evaluates the causes related to the fatigue damage in a conveyor slide plate, exposed to high-frequency cyclic loads. The plate was made of 1.4301 acid-resistant steel. The fractography showed that the plate failure was caused by fatigue crack. A nonlinear analysis of plate deformation was conducted using the finite element method (FEA) in LS-Dyna software. The maximum normal stresses in the plate fracture were used in further analysis. A “fatigue limit” calculated initially using a FITNET procedure was above the maximum stress calculated using FEA. It indicates that the structural features of the plate were selected correctly. The experimental test results for 1.4301 acid-resistant steel were described using a probabilistic Weibull distribution model. Reliability was determined for the obtained S-N curve at 50% and 5% failure probability allowing for the selected coefficients (cycle asymmetry, roughness, variable load) and the history of cyclic loading. Cumulative damage was determined using the Palmgren-Miner hypothesis. The estimated fatigue life was similar to the actual value determined in the operating conditions for the S-N curve at 5% failure probability. For engineering calculations, the S-N curve at max. 5% failure probability is recommended.
EN
Bone is a nonlinear, inhomogeneous and anisotropic material. To predict the behavior of bones expert systems are employed to reduce the computational cost and to enhance the accuracy of simulations. In this study, an artificial neural network (ANN) was used for the prediction of displacement in long bones followed by ex-vivo experiments. Three hydrated third metacarpal bones (MC3) from 3 thoroughbred horses were used in the experiments. A set of strain gauges were distributed around the midshaft of the bones. These bones were then loaded in compression in an MTS machine. The recordings of strains, load, load exposure time, and displacement were used as ANN input parameters. The ANN which was trained using 3,250 experimental data points from two bones predicted the displace-ment of the third bone (R2 ≥ 0.98). It was suggested that the ANN should be trained using noisy data points. The proposed modification in the training algorithm makes the ANN very robust against noisy inputs measurements. The performance of the ANN was evaluated in response to changes in the number of input data points and then by assuming a lack of strain data. A finite element analysis (FEA) was conducted to replicate one cycle of force-displace-ment experimental data (to gain the same accuracy produced by the ANN). The comparison of FEA and ANN displacement predictions indicates that the ANN produced a satisfactory outcome within a couple of seconds, while FEA required more than 160 times as long to solve the same model (CPU time: 5 h and 30 min).
EN
Different stabilization devices have been used for treating lumbar spine disorders, including fusion, dynamic stabilization devices, flexible rods etc., which possess a different level of limitations. A simple experimental procedure is developed using a prototype lumbar spine specimen (L1-S), to evaluate the biomechanical performance of the lumbar spine. The range of motions (ROM) are tested for pedicle screw made of stainless steel (SS) fixation, using Teflon rod, ultra high molecular weight poly ethylene (UHMWPE) rod, poly ether ether ketone (PEEK) rod and SS flexible rod device (FRD). SS pedicle screw is used for fixation on the prototype lumbar spine. Experimental results are validated and compared with finite element (FE) results. It is observed that, in both flexion and extension, reduction in ROM is higher for Teflon and UHMWPE as compared to PEEK and FRD system. Differences between experimental and numerical results are found to be within an acceptable limit of 5–11%. For flexibility study, both numerical and experimental results support that PEEK rod plays an effective and important role among all the semi-rigid rods. The FRD devices are found to preserve the flexibility of the segment considerably better than PEEK rod.
EN
The paper aims was assessing risks of mandible fractures consequent to impacts or sport accidents. The role of the structural stiffness of mandible, related to disocclusion state, was evaluated using the finite element method. It has been assumed, that the quasi-static stress field, due to distributed forces developed during accidents, could explain the common types of mandibular fractures. Mandibular condyles were supposed jammed in the maxillary fossae. The force of 700 N, simulating an impact on mandible, has been sequentially applied in three distinct areas: centrally, at canine zone and at the mandibular angle. Clinically most frequent fractures of mandible were recognized through the analysis of maximal principal stress/strain fields. It has been shown that mandibular fracture during accidents can be analyzed at satisfactory level using linear quasi-static models for designing protections.
EN
Recently, new materials have been developed in the field of bridge design, one of which is FRP composite. To investigate this topic, the Polish National Centre for Research and Development has founded a research project, whose objectives are to develop, manufacture and test a typical FRP bridge superstructures. Two innovative ideas of FRP composite girder-deck structural systems for small and medium span bridges have been proposed. This paper describes the demonstrative bridges and presents the research results on their development and deployment. The finite element analysis and design procedure, structural evaluation in the laboratory and some results of the proof tests carried out on both bridge systems have been briefly presented.
PL
Kompozyty polimerowe wzmocnione włóknami (z ang. FRP) są stosowane w inżynierii mostowej na całym świecie ze względu na ich doskonałą wytrzymałość, wagę i trwałość, a także możliwość dostosowania ich właściwości do indywidualnych wymagań np. aplikacji o złożonym kształcie. Od 2007 r. Polska stała się wiodącym krajem europejskim pod względem rozwoju sieci autostrad, a także liczby funduszy unijnych wydanych na budowę i/lub modernizację sieci autostrad. Dlatego przy budowie nowych mostów powstaje pytanie, czy tradycyjne materiały, takie jak beton i stal, są nadal najlepszym wyborem, zarówno pod względem argumentów inżynieryjnych, jak i ze względów utrzymaniowych. Aby poszerzyć wiedzę w tym temacie, Polskie Narodowe Centrum Badań i Rozwoju zainicjowało projekt badawczy, którego celem jest opracowanie, produkcja i testowanie typowych przęseł mostów FRP do zastosowania w mostach drogowych w celu osiągnięcia optymalnego rozwiązania konstrukcyjnego z punktu widzenia kosztów w całym cyklu życia konstrukcji. Zaproponowano dwa innowacyjne pomysły kompozytowych systemów konstrukcyjnych FRP dla mostów o małej i średniej rozpiętości: przęsła czysto kompozytowe oraz hybrydowe, kompozytowo-betonowe. W tym artykule opisano oba mosty demonstracyjne i przedstawiono wyniki badań dotyczących ich rozwoju i wdrażania. Krótko przedstawiono analizę z wykorzystaniem elementów skończonych i procedurę projektowania, proces produkcji samych elementów kompozytowych i całych obiektów oraz niektóre wyniki próbnych obciążeń przeprowadzonych na obu typach mostów. Zaprezentowane prace dowodzą, że przęsła małych i średnich rozpiętości wykonane z kompozytów FRP spełniają warunki nośności i sztywności według wytycznych krajowych i europejskich. Jednocześnie obserwacje prowadzone w czasie badań laboratoryjnych wskazują na potrzebę monitorowania stanu technicznego tego rodzaju prototypów, w których zastosowano nowatorskie rozwiązania konstrukcyjne i materiałowe. Oczekuje się, że taki system nie tylko zapewni inżynierom i administracji drogowej cenne narzędzie do monitorowania stanu technicznego nowatorskich przęseł mostów FRP, ale także dostarczy ważnych informacji związanych z trwałością, kryteriami projektowymi i długoterminowym zachowaniem się kompozytu FRP. Ponadto, w miarę jak wytyczne projektowe ulegają poprawie i stają się coraz bardziej rozpowszechnione, a inżynierowie budownictwa zdobywają doświadczenie i zaufanie do kompozytów FRP, prawdopodobne jest, że upowszechni się wykorzystanie elementów kompozytowych FRP w inżynierii mostowej.
9
Content available remote Noise and vibration analysis of a distribution transformer
EN
Transformer noise is a significant contribution to unwanted ambient noise, especially in the vicinity of the electrical transmission facility. It is therefore very important to get to know the mechanism of noise generation of the distribution transformer. As outcomes of this work, a finite element based multiphysics model is presented which provides a convenient and efficient toolchain for simulating the transformer sound emission mechanism. Finally, the operation of modelling chain is presented on a 200kVA distribution transformer simulation.
PL
Hałas transformatora ma znaczący wpływ na niepożądany hałas otoczenia, zwłaszcza w pobliżu instalacji przesyłowej prądu elektrycznego. Z tego powodu ważnym jest poznanie mechanizmu generowania szumu transformatora rozdzielczego. Jako wynik tej pracy przedstawiono model transformatora rozdzielczego 200 kVA oparty na analizie elementów skończonych, który zapewnia wygodny i wydajny zestaw narzędzi do symulacji mechanizmu emisji dźwięku z analizowanego urządzenia.
10
Content available remote Comparison of two constructions of hybrid magnetic bearings
EN
The paper presents a comparative analysis of two various constructions of the hybrid magnetic bearings. For this purpose, the basic parameters of the magnetic bearings were defined. Additionally, new parameters are proposed in order to estimate nonlinearity of the magnetic force and cross-coupling between axes. Comparison of the magnetic bearing constructions was performed using 3 dimensional simulation models.
PL
W artykule przedstawiono analizę porównawczą dwóch różnych konstrukcji hybrydowych łożysk magnetycznych. W tym celu, zdefiniowano podstawowe parametry wykorzystywane do opisu łożysk magnetycznych. Dodatkowo, zaproponowano nowe parametry w celu oszacowania nieliniowości siły magnetycznej oraz sprzężenia między osiami. Porównanie konstrukcji łożysk magnetycznych wykonano w oparciu o analizę 3 wymiarowych modeli symulacyjnych.
EN
The research conducted at Poznan University of Technology with cooperation the Tele- and Radio Research Institute deals with finite element analysis of six-phase, dual star permanent magnet synchronous motor. To reduce eddy current losses in the rotor of the machine the rotor back iron segments have been made of soft magnetic composite (SMC). SMC are composites of iron powder particles separated with an electrically insulated layer. This technology has many advantages in relation to classical laminated core solutions; among other lower manufacturing costs due to simpler technology and reduced eddy current losses out of order times lower conductivity. The mathematical model of machine utilizes field circuit approach assuming planar symmetry of the machine. The magnetic properties of the applied SMC material have been introduced into the model basing on BH curves and unit losses vs. frequency characteristics measured at Tele- and Radio Research Institute. Accuracy of developed numerical model has been verified by measurements of the machine performance under normal and drive fault conditions tested on the elaborated research stand.
PL
Prezentowane badania, prowadzone na Politechnice Poznańskiej we współpracy z Instytutem Tele- i Radiotechnicznym dotyczą analizy i weryfikacji eksperymentalnej sześciofazowego silnika synchronicznego z magnesami stałymi. W celu ograniczenia strat związanych z występowaniem prądów wirowych w obwodzie magnetycznym wirnika maszyny jego segmenty wykonano z miękkiego kompozytu magnetycznego (SMC). W stosunku do powszechnie stosowanych rdzeni laminowanych technologia proszkowych materiałów SMC posiada wiele zalet. Między innymi dzięki znacznie większej rezystywności materiały te pozwalają ograniczyć straty wiroprądowe w rdzeniu, a dzięki uproszczeniu technologii wytwarzania możliwe jest ograniczenie kosztów produkcji. W polowo obwodowym modelu maszyny założono symetrię płaszczyznową obwodu magnetycznego maszyny oraz uwzględniono magnetyczne właściwości zastosowanego materiału SMC na podstawie krzywych BH oraz charakterystyk stratności zmierzonych w Instytucie Tele- i Radiotechnicznym. Dokładność opracowanego modelu numerycznego została zweryfikowana poprzez pomiary wybranych parametrów testowanej maszyny przeprowadzone na opracowanym stanowisku badawczym.
12
Content available Modal Analysis of Medium Calibre Barrels
EN
The paper deals with modal analysis of the two different medium calibre barrel weapons. At present time PC software which are based on FEM modal analysis enable not only create a new design but also check old design how be up to standard on the fire accuracy. Also at this time is big boom to make new armour personal carriers which are equipped with the medium weapon calibre systems. Many of them use standard design of bedding the barrel to the weapon case, however also they are created in new weapon design. The modal analysis is powerful method to describe their vibration properties which have the cardinal influence on the accuracy of fire. The barrels were modelled as 3-D objects with next configuration with aim to obtain right results and their mutual comparison. Figure 1-3 show design of the solved barrels. Modal analysis was performed by LS-DYNA software using iterative Lanczos method. In Tables 1-5, the natural frequencies for these barrels and their modifications and their corresponding own shapes are listed. Next Figures 4, 7-10, 12 show the courses natural frequencies versus modes. In Figure 11 are shown the modal shapes of the modified cylindrical weapon barrel with the armature.
EN
Analysis of cracked cruciform specimens under biaxial loading conditions is very important and closer to reality in the study of behavior of marine, naval, aeronautical and railway structures. The aim of this work is to examine the evolution of fracture parameters in a combined mixed mode of an aluminum alloy A6082-T6 cruciform specimen as a function of the biaxial loading with different ratios. To this end, the effects of main parameters, such as load ratio, crack length, crack orientation and non-proportional loading coefficient have been analyzed and discussed in order to highlight fracture toughness of the studied material. The results show that the finite element method is a useful tool for calculation of crack characteristics in the mechanics of biaxial fracture. According to the obtained results, a non-proportional evolution of the fracture parameters, namely, the SIFs KI and KII , T-stress, and the biaxiality parameter was observed. Indeed, the latter depends considerably on the crack length, the angle of crack orientation and the applied biaxial loading. Detailed concluding remarks are presented at the end of this work.
EN
Delamination crack growth is a major source of failure in composite laminates under static and fatigue loading conditions. In the present study, damage mechanics based failure models for both static and fatigue loadings are evaluated via UMAT subroutine to study the delamination crack growth phenomenon in Glass Fiber Reinforced Plastic (GFRP) composite laminates. A static local damage model proposed by Allix and Ladev`eze is modified to an non-local damage model in order to simulate the crack growth behavior due to static loading. Next, the same classical damage model is modified to simulate fatigue delamination crack growth. The finite element analysis results obtained by the proposed models are successfully compared with the available experimental data on the delamination crack growth for GFRP composite laminates.
EN
A new micromechanical model for predicting the failure locus of long fiber composites under combined axial compression and in-plane shear is proposed. The model is based on a periodic unit cell with centrally located imperfections. Predictions of the compressive behavior for various biaxial loading ratios are made. The role of distribution of fiber imperfections in predicting the biaxial strength is discussed. The failure locus calculated from the new model is found to be in good agreement with experimental data available in the literature and less conservative than that from the periodic model with uniform imperfections.
EN
This research aims to study the fastening rotation behavior of cold-formed steel screw connections by experimental testing and analytical modelling. Both the experimental test and finite element results showed the failure modes of tilting and bearing failure. The rotation failure mode of the screw connection was studied by an analytical method using a spring model with screw-plate stiffness which included the bending and shear stiffness of the screw and the bearing stiffness of the screw and plates. Variation in the screw thread diameter, plate thickness, and plate thickness ratio are assigned to the spring model for the parametric study. The screw rotation or tilting was primarily controlled by the plate thickness. Presented results show that to decrease the effect of tilting failure, the end of the screw should be embedded within the thickest side of the cold-formed steel parts.
EN
An ancient forging device in Spain has been studied, namely the forge with a waterwheel and air-blowing tube or hydraulic trompe, found near the village of Santa Eulalia de Oscos (province of Asturias, Spain). Three procedures using ad hoc methods were applied: 3D modelling, finite element analysis (FEA), and computational-fluid dynamics (CFD). The CFD results indicated the proper functioning of the trompe, which is a peculiar device based on the Venturi effect to take in air. The maximum air volume flow rate supplied to the forge by the trompe was shown to be 0.091 m3/s, and certain parameters of relevance in the trompe design presented optimal values, i.e. offering maximum air-flow supply. Furthermore, the distribution of stress over the motion-transmission system revealed that the stress was concentrated most intensely in the cogs of the transmission shaft (a kind of camshaft), registering values of up to 7.50 MPa, although this value remained below half of the maximum admissible work stress. Therefore, it was confirmed that the oak wood from which the motion system and the trompe were made functioned properly, as these systems never exceeded the maximum admissible working stress, demonstrating the effectiveness of the materials used in that period.
EN
Anisotropic rotor configurations influenced by the presence of a large number of geometrical parameters in a permanent magnet assisted synchronous reluctance (PMASR) motor pose design challenges in obtaining a robust geometry satisfying the requirements of reduced torque ripple and high torque density. Therefore, the purpose of this work is to perform detailed geometrical sensitivity analysis of a 36 slot/4 pole permanent magnet assisted synchronous reluctance (PMASR) motor using h-indexing and level sensitivity analysis in order to specify a guideline for designers to prioritize the design variables for optimization. Systematic multi-level design optimization for multiple objectives is implemented by an NSGA-II algorithm aided by the finite element analysis tool, hardware prototyping and experimental validation. The optimized designs also exhibit better structural and thermal characteristics.
EN
Estimation of thermal response of tumoral tissue to the hyperthermia treatment is an important factor for increasing the effectiveness of therapeutic method. In this study, focused ultrasound (FU) is used to produce irreversible thermal damage for the treatment of benign thyroid tumor. To this end, a multi-layer model of the neck including internal organs from the skin toward the thyroid gland is exposed to ultrasound irradiation at powers of 3 W, 5 W, and 7 W and at the frequency of 3 MHz. It is observed that the acoustic pressure is noticeably increased by considering different neck's internal organs. The temperature profile is obtained by taking into account the non-Fourier thermal response for the thyroid gland. The thermal wave model and dual phase lag model are utilized along with the traditional Pennes bio-heat transfer model. Studying the temperature profile at 3 W power by non-Fourier thermal models illustrates that the maximum temperature with time delays of 11.32, 5.66 and 2.86 s is 20.51%, 14.1% and 8.65% lower than the corresponding value by the Fourier model. Deviation from the Fourier results is increased for higher powers of transducer. It is also inferred that in the presence of time delays, temperature variation in the focal area becomes smoother. Effect of non-Fourier heat transfer is studied on the area of necrotic tumoral region. It is concluded that region with irreversible thermal damage shrinks by considering the phase lags in the way that in 3 W power and 5.66 s time delay, no necrosis of the thyroid nodule is observed.
EN
In this work, effects of various parameters, including regularity of sewing, distance of holes from the edge of the tissue (D), distance between holes (L), suturing pattern, and material and size of the suture on the leakage of human large intestine anastomosis site were investigated, using finite element method (FEM). The effects of various parameters of suturing on leakage were investigated in four different steps: 1. regularity of suturing; 2. variations in D (small, medium and large), and L (small, medium and large); 3. suturing pattern; and 4. material and size of the suture. The models mimicked two sides of human large intestine tissue, sewn together. By considering a 50 mm displacement on right-side free edge of tissue, the surface areas of the gaps created around the holes were calculated, and a gap surface area equals to, or greater than 0.07 mm2 was considered as the leaking specimen. Results showed that in the case of irregular suturing, compared to the regular one, the likelihood of leakage increases. Additionally, in the cases with large D and medium L, the likelihood of leakage decreases. It was found that zigzag pattern has less leakage probability compared with simple continuous and interrupted patterns. Furthermore, by increasing the diameter and elastic modulus of the suture, the likelihood of leakage will increase. Results of this study are in agreement with experimental evidences.
first rewind previous Strona / 13 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.