Comparison of theoretical approaches to determine the stresses in surface mounted permanent magnet rotors for high speed electric machines

High-speed electrical machines (HSEMs) are becoming more popular in applications such as air handling devices. Using surface-mounted permanent magnet (PM) rotors manufactured from rare earth metals, they provide benefits over their mechanical transmission counterparts. However, these PMs have low tensile strength and are prone to failure under large centrifugal loads when rotating. Therefore, retaining sleeves are used to hold the PMs in compression to eliminate tensile stress and reduce failure risk. The magnets are also often held on a back iron or carrier, forming an assembly of three cylinders. The ability to predict these stresses is extremely important to rotor design. Current published work shows a lack of exploration of analytical methods of calculating these stresses for three-cylinder assemblies. This paper shows the development of plane stress, plane strain and generalised plane strain (GPS) theories for three cylinders. For a range of rotor designs, these theories are compared with finite element analysis (FEA). GPS is shown to be more accurate than plane stress or plane strain for the central region of long cylinders. For short cylinders and for the ends of cylinders, all three theories give poor results.

Decomposition of healing tensor: In continuum damage and healing mechanics

The decomposition of the healing variable (in the case of scalars) and the healing tensor (in the case of tensors) is carried out systematically and consistently. In this respect, the classical linear healing model is adopted in this work. The decomposition of healings includes the healing variable/tensor of cracks and the healing variable/tensor for voids. A third defect type is considered wherever mathematically possible. Thus a complete treatment of the decomposition of the healing tensor is presented covering both the one-dimensional and three-dimensional aspects. As an illustrative example, the case of plane stress, plane damage, and plane healing is solved. In this case, it is concluded that two distinct decomposition equations are obtained as well as one single coupling formula. The coupling equation is an expression that relates the various healing tensor components and damage tensor components for cracks and voids Furthermore; it is shown that there is no coupling in the one-dimensional case.

Modeling of Stiffness and Strength of Bone at Nanoscale

Two distinct geometrical models of bone at the nanoscale (collagen fibril and mineral platelets) are analyzed computationally. In the first model (model I), minerals are periodically distributed in a staggered manner in a collagen matrix while in the second model (model II), minerals form continuous layers outside the collagen fibril. Elastic modulus and strength of bone at the nanoscale, represented by these two models under longitudinal tensile loading, are studied using a finite element (FE) software abaqus. The analysis employs a traction-separation law (cohesive surface modeling) at various interfaces in the models to account for interfacial delaminations. Plane stress, plane strain, and axisymmetric versions of the two models are considered. Model II is found to have a higher stiffness than model I for all cases. For strength, the two models alternate the superiority of performance depending on the inputs and assumptions used. For model II, the axisymmetric case gives higher results than the plane stress and plane strain cases while an opposite trend is observed for model I. For axisymmetric case, model II shows greater strength and stiffness compared to model I. The collagen–mineral arrangement of bone at nanoscale forms a basic building block of bone. Thus, knowledge of its mechanical properties is of high scientific and clinical interests.

MODIFICATIONS OF A SIMPLE I-BEAM AND ITS EFFECTS ON THE STRESS STATE

The motivation for this work is a desire for a deeper understanding of the structural failures in a composite glider wing, which has been tested in the laboratories of the Institute of Aerospace Engineering, Faculty of Mechanical Engineering, Brno University of Technology. To understand the causes of the encountered failures, one has to consider the effects of all the stages in the design, manufacturing and testing of the wing. This paper focuses only on the design stage. The presented facts were obtained from a finite element analysis. The geometry used for the analysis is that of the tested specimens. This allows validating the results by the comparison of the deformation and strains measured during the laboratory tests. The analysis starts with a simple I-beam loaded by three-point-bending. In the next step a cantilever is added. Several more modifications follow, changing the I-beam to the wing. The case evaluation considers the interaction between normal (material direction 1) and inter-laminar shear stresses in the upper flange. The goal of this paper is to quantify the effect of each design change in the wing structure and loading on the stress plane σ1-τ31.

Ternary Constituents Are a Consequence of Mora Sluicing

While ternary rhythm exists, ternary feet do not, not even indirectly by means of recursion. We propose that ternary rhythm arises from mora sluicing, the phenomenon whereby moras can be excluded from the stress plane to satisfy an instance of NO-CLASH in a model that conceives metrical prominences as headed constituents. We demonstrate that the notion of mora sluicing has high explanatory power: it is necessary on independent grounds to explain otherwise unrelated phenomena such as uneven trochee-creating processes in Mohawk and Central Slovak, and opaque stress-epenthesis interactions in Mohawk. One fundamental move derived from the metrical model sketched in this paper is the relation between what we call line1 constituents (phonological syllables) and phonetic syllables (namely CV or CVC sequences), which is not one-to-one anymore, as it is in standard syllable theory.

The Validation of Computational FE Software for Creep Damage Mechanics

The preliminary validation of in-house finite element analysis software for creep damage mechanics is reported. The Finite Element Analysis Method and the programme strcuture for creep damage problem were reported elsewhere and the validation conducted so far include plane stress, plane strain, and axisymmetric cases. Furture work is also outlined.

Influence of Fluctuation Frequency on Stress Corrosion Cracking of X70 Pipeline Steel Welding Joint

Influence of the fluctuation frequency on stress corrosion cracking (SCC) behavior of X70 pipeline steel welding joint was studied in the cathode potential under nearly neutral medium by fluctuant slow strain rate test (F-SSRT). SCC sensitive parts occurs in overheated zone of X70 pipeline steel welding joint under cathode potential nearly neutral medium. SCC crack can be produced from the material surface micro holes and expanding their range up the main stress plane extension, when the load fluctuation frequency increases to a certain degree, SCC crack propagate along 45° maximum shear stress plane.