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

Znaleziono wyników: 273

Liczba wyników na stronie
first rewind previous Strona / 14 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  finite element analysis
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 14 next fast forward last
EN
The article deals with the stress-strain state of the cutters used in the mills of a new design for the restoration of the working surfaces of locomotive wheels. A comparative analysis of stresses in the cutters was carried out using the finite element method, which showed a significant advantage of the new technical solution, the novelty of which is confirmed by the patent.
EN
In coastal regions, earthquakes caused severe damage to marine structures. Many researchers have conducted numerical investigations in order to understand the dynamic behavior of these structures. The most frequently used model in numerical calculations of soil is the linear-elastic perfectly plastic model with a Mohr-Coulomb failure criterion (MC model). It is recommended to use this model to represent a first-order approximation of soil behavior. Therefore, it is necessary to accommodate soil constitutive models for the specific geotechnical problems. In this paper, three soil constitutive models with different accuracy were applied by using the two-dimensional finite element software PLAXIS to study the behavior of pile-supported wharf embedded in rock dike, under the 1989 Loma Prieta earthquake. These models are: a linear-elastic perfectly plastic model (MC model), an elastoplastic model with isotropic hardening (HS model), and the Hardening Soil model with an extension to the small-strain stiffness (HSS model). A typical pile-supported wharf structure with batter piles from the western United States ports was selected to perform the study. The wharf included cut-slope (sliver) rock dike configuration, which is constituted by a thin layer of rockfill overlaid by a slope of loose sand. The foundation soil and the backfill soil behind the wharf were all dense sand. The soil parameters used in the study were calibrated in numerical soil element tests (Oedometer and Triaxial tests). The wharf displacement and pore pressure results obtained using models with different accuracy were compared to the numerical results of Heidary-Torkamani et al.[28] It was found that the Hardening Soil model with small-strain stiffness (HSS model) gives clearly better results than the MC and HS models. Afterwards, the pile displacements in sloping rockfill were analyzed. The displacement time histories of the rock dike at the top and at the toe were also exposed. It can be noted that during the earthquake there was a significant lateral ground displacement at the upper part of the embankment due to the liquefaction of loose sand. This movement caused displacement at the dike top greater than its displacement at the toe. Consequently, the behavior of the wharf was affected and the pile displacements were important, specially the piles closest to the dike top.
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.
EN
The axial crushing behaviour of tubes of different section shapes has been extensively investigated as they have an excellent energy absorption, but the thin walled corrugated tube structures have been designed to further improve their energy absorption performance. The study aims to analyze the effect of sinusoidal corrugations along cross section of the tube on peak force, energy absorption and specific energy absorption. In the present work the response surface methodology (RSM) using central composite design (CCD) has been used and simulation work is performed by using ANSYS workbench to explore the effects of geometrical parameters on the responses of constructing models.
5
Content available Dynamic analysis of the aortic valve functioning
EN
The aim of the paper was to recognize the influence of mechanical factors on the movement of the leaflets. Mechanical stimuli may have a positive effect on remodeling the leaflet material to adapt its structure to a changing load. A model of the valve functioning process was developed. A geometric model similar to the construction of a natural valve was adopted. The hybrid process of the liquid-solid interaction problem was described. The interaction process was modeled. The problem was formulated with the Galerkin FEM method. Numerical analyses of a single valve work cycle and the calcification process of aortic valve bioprostheses were performed.
EN
Motor coolers are operated with the coupling of temperature and pressure fields, in which the change rule is affected by multiple factors. In this study, the thermal resistance of the motorcooler was examined using the velocity coefficient method to reveal the influence of heat transfer and wind resistance. The temperature and pressure fields were analyzed using the finite element method based on the hydrodynamics and momentum theorem. By varying the heat transfer and wind resistance coefficients to reflect temperature and pressure characteristics, wind and water velocities were determined. Results demonstrate that the total convective heat transfer and wind resistance coefficients of the cooler model are sensitive to variations in face-to-face wind velocity, but not to those of the cooling water flow rate. When wind velocity increases from 0.8 to 5.19m/s, the total convective heat transfer increases by 1.85 times and wind resistance increases by 18.74 times. Variations in cooling water velocity has little effect on the Nusselt numberon the air side and the Euler number of the single row tube, which are multiplied with the increase of the Reynolds number. When the Reynolds number increases from 1020 to 6345, the Nusselt number increases by 2.05 times and the Euler numer decreases by 2.29 times. The results provide references for the design and performance testing of high-power motor coolers.
EN
Purpose: The purpose of this study is to investigate the ultimate bearing capacity of the rectangular footing resting over layered sand using finite element method. Design/methodology/approach: Finite element analysis was used to investigate the dimensionless ultimate bearing capacity of the rectangular footing resting on a limited thickness of upper dense sand layer overlying limitless thickness of lower loose sand layer. The friction angle of the upper dense sand layer was varied from 41° to 46° whereas for the lower loose sand layer it was varied from 31° to 36°. Findings: The results reveal that the dimensionless ultimate bearing capacity was found to increase up to an H/W ratio of about 1.75 beyond which the increase was marginal. The results further reveal that the dimensionless ultimate bearing capacity was the maximum for the upper dense and lower loose sand friction angles of 46° and 36°, while it was the lowest for the upper dense and lower loose sands corresponding to the friction angle of 41° and 31°. For H/W = 0.5 and 2, the dimensionless bearing capacity decreases with the increase in the L/W ratio from 0.5 to 6 beyond which the dimensionless ultimate bearing capacity remains constant for all combinations of parameters. The results were presented in nondimensional manner and compared with the previous studies available in literature. Research limitations/implications: The analysis is performed using a ABAQUS 2017 software. The limitation of this study is that only finite element analysis is performed without conducting any experiments in the laboratory. Further the study is conducted only for the vertical loading. Practical implications: This proposed numerical study can be used to predict the ultimate bearing capacity of the rectangular footing resting on layered sand. Originality/value: The present study gives idea about the ultimate bearing capacity of rectangular footing when placed on layered sand (dense sand over loose sand) as well as the effect of thickness of top dense sand layer on the ultimate bearing capacity. The findings could be used to calculate the ultimate bearing capacity of the rectangular footing on layered sand.
EN
In the present research, a physical-geometric-feature of continuous yarn in a plain woven fabric was created and its FE model was analysed by considering the two key issues of woven fabric, the crimp and inter-yarn friction. The basic parameters of Young’s modulus of single yarn and the inter-yarn friction coefficient were investigated for practical fabrics in tensile and pull-out tests. FE analysis indicated that the stress-strain curves of the FE model were effective in evaluating the equivalent modulus of a woven fabric by comparing with a tensile experiment on Twaron CT® Plain Woven Fabric. In addition, a simplified three dimensional model of the unit cell of plain woven fabric (UCPW) was employed to quantitively investigate two important fabric characteristics – the crimp rate of the yarn and inter-yarn friction-to determine their influence on the mechanical properties of the fabrics. Furthermore, we used FE analysis to evaluate how the crimp rate and inter-yarn friction affected the mechanical properties by determining the equivalent modulus of single yarn and UCPW in both uniaxial and biaxial tensile loading. The stresses at representative nodal points and the mechanical interaction between yarns were also investigated from a microscopic perspective, and their deformation mechanisms were also analysed and discussed.
PL
W pracy stworzono fizyczno-geometryczną cechę przędzy ciągłej w gładkiej tkaninie i przeanalizowano jej model FE, biorąc pod uwagę dwa kluczowe zagadnienia tkaniny: karbikowatość i tarcie między przędzami. Zbadano podstawowe parametry: moduł Younga przędzy pojedynczej oraz współczynnik tarcia między przędzami. Analiza FE wykazała, że krzywe naprężenie-odkształcenie modelu FE były przydatne w ocenie tkaniny przez porównanie z eksperymentem rozciągania tkaniny Twaron CT® Plain Woven. Ponadto zastosowano uproszczony trójwymiarowy model komórki elementarnej z gładkiej tkaniny (UCPW) do ilościowego zbadania dwóch ważnych cech tkaniny: szybkości fałdowania przędzy i tarcia między przędzami – w celu określenia ich wpływu na właściwości mechaniczne tkaniny. Ponadto wykorzystano analizę FE, aby ocenić, w jaki sposób szybkość fałdowania i tarcie między przędzami wpłynęły na właściwości mechaniczne. Dokonano tego poprzez określenie równoważnego modułu pojedynczej przędzy i UCPW zarówno przy jednoosiowym, jak i dwuosiowym obciążeniu rozciągającym. Naprężenia w reprezentatywnych punktach węzłowych i mechaniczne interakcje między przędzami zbadano również z perspektywy mikroskopowej, a także przeanalizowano i omówiono ich mechanizmy deformacji.
9
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
Through silicon via (TSV) has become one of the key emerging trends of three-dimensional (3D) packages, as it can realize vertically interconnect between stacked-dies. Due to large mismatch in thermal expansion coefficients (CTE) between the copper via and the silicon, significant mechanical stresses are induced at the interfaces when TSV structure is subjected to thermal stresses, which would greatly affect the reliability and electrical performance of TSV 3D device. In this paper, the relationship between the state of stresses and failure of TSV had been explored by combining finite element model simulation (FEM) and failure physical analysis. The position of the maximum stress of the TSV structure was obtained by FEM analysis. The relationship of stress and displacement change with temperature was also studied. And a thermal cycling experiment was conducted to validate the simulation results. Physical failure analysis after thermal cycling experiment was used to verify the degradation mechanism predicted by thermo-mechanical simulation.
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.
13
Content available remote Deflection of an eccentric crack under mixed-mode conditions in an SCB specimen
EN
Crack propagation under mixed-mode (I + II) conditions has been investigated in a semicircular disc where various levels of mixed-mode can be achieved by means of different geometry configurations. The research has been performed on a novel cementitious material, alkali-activated concrete. Its main advantage is that it is environment-friendly. On the other hand, its fracture mechanical properties, as of yet, have not been described sufficiently. Therefore, a fracture analysis has been performed. The crack deflection under three point bending conditions has been investigated numerically as well as experimentally. The numerical approach is based on a combination of the common finite element analysis and a multi-parameter form of the maximum tangential stress criterion. This generalized method is suitable especially for materials with specific (elasto-plastic, quasi-brittle etc.) fracture behaviour. The over-deterministic method together with the Williams expansion is applied to approximate selected stress tensor components around the crack tip. In this work, the influence of the eccentric crack is also discussed. In the conclusions, several recommendations about using single-parameter/multi-parameter fracture mechanics are stated.
EN
Most current concrete design codes include provisions for punching shear of reinforced concrete slabs supported on columns with L, T, and cruciform shapes. Reference studies verifying the accuracy of these code provisions are typically not provided. Empirical data of punching failures of slabs supported on columns with L, T, and cruciform shapes are limited due to the cost and time required to test specimens with slab thicknesses and column sizes commonly used in practice. In this paper, the punching shear behaviour of five interior L-shaped slab-column connections, one without a slab opening and four with slab openings, subjected to static concentric loading are analyzed using a plasticity-based nonlinear finite element model (FEM) in ABAQUS. The FEM is similar to models previously calibrated at the University of Waterloo and are calibrated considering nine slabs that are tested to study the impact of column rectangularity on the punching shear behaviour of reinforced concrete slabs. The finite element analysis results indicate that shear stresses primarily concentrate around the ends of the L, and that current code predictions from ACI 318-19 and Eurocode 2 may be unconservative due to the assumed critical perimeters around L-shaped columns.
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
In this paper we aim to improve the understanding of the relationship between unilateral-uniplanar external fixator design parameters and their influences on fixator performance. Stability and strength of bone-fixator construct as well as the quality of healing were defined as our major concerns in order to evaluate the performance of fixator. The roles of six key design parameters were assessed during the early stage of healing by using finite element models. Tissue differentiation within the callus was predicted through the implementation of a mechanoregulation theory of bone healing. Taguchi and ANOVA methods were used to achieve optimal design sets for outputs and to determine contribution percentage of each design parameter on outputs. For improving overall fixator performance, optimal set of design parameters consisting of 2 mm, 8 mm, 120 mm, 20 GPa, 50 mm and 20 mm were determined by Taguchi for pin diameter, rod diameter, rod elevation, fixator Young's modulus, distance of the nearest pin to fracture site and distance between adjacent pins, respectively. Also, results of ANOVA revealed that rod elevation is the most important design parameter, with 43 % effectiveness on overall fixator performance, which was followed by fixator material and pin diameter with 28 % and 19 %, respectively. Results of this study can assist orthopedic surgeons to achieve an optimal fixator device with respect to the patient's condition and give insight into the importance of different design parameters.
EN
To find the relationships between internal fixation parameters and biomechanical indexes with least number of runs, a regression orthogonal approach is proposed to establish surrogate models of different biomechanical indexes. Firstly, a simplified model of transverse femoral shaft fracture is built, and varieties of geometric sizes for plates and screws configurations are combined based on orthogonal array. Next, the biomechanical indexes of different combinations are calculated through finite element analysis (FEA). Furthermore, surrogate models are developed with the aid of regression orthogonal analysis. Finally, with comparison of biomechanical indexes obtained from the surrogate models and FEA results, highly coincident results validate the surrogate models. The number of combinations is greatly reduced compared with that arranged by comprehensive regression analysis. The surrogate models show acceptable results for predicating biomechanical indexes, whose relative deviation is less than 9%. Moreover, the results obtained by the surrogate models suggest that working length and thickness of the plate are the significant parameters on the maximum plate stress and maximum intra-fragmentary movement respectively, which complies with previous studies. The regression orthogonal method presented in this study can greatly reduce the number of experimental runs for investigating the biomechanics of internal fixation for femoral shaft fracture. The method can also be applied to other scenarios of fractures or even the other biomedical fields to provide a comprehensive insight into biomedical relationships with least number of trials.
EN
Three-dimensional angle-interlock woven composites (3DAWCs) are widely used for their excellent mechanical properties. The most significant feature is the existence of the undulated warp yarns along the thickness direction, which makes it interesting to study the mechanical properties in the warp direction. The quasi-static tensile behavior of a layer-to-layer 3DAWC along the undulated warp direction was studied by experimental and finite element analysis (FEA) methods. Based on the experimental results, the typical failure mode involving fibers, resin, and their interfaces was found. According to the FEA results, the stress concentration effect, key structural regions, and microstructural (yarn and resin) damage mechanism were obtained, which provided effective guidance for structural optimization design of the 3DAWC with stronger tensile resistance performance. In addition, the three-step progressive failure process of the 3DAWC under quasi-static tensile load was also described at the “yarn–resin” microstructural level.
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.
first rewind previous Strona / 14 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.