AXICRP — Finite element computer code for creep analysis of plane stress, plane strain and axisymmetric bodies

Fracture behavior in nickel-titanium (NiTi) shape memory alloys (SMAs) subjected to mode-I, isothermal loading is studied using finite element analysis (FEA). Compact tension (CT) SMA specimen is modeled in Abaqus finite element suite and crack growth under displacement boundary condition is investigated for plane strain and plane stress conditions. Parameters for the SMA material constitutive law implemented in the finite element setup are acquired from characterization tests conducted on near-equiatomic NiTi SMA. Virtual crack closure technique (VCCT) is implemented where crack is assumed to extend when the energy release rate at the crack-tip becomes equal to the experimentally obtained material-specific critical value. Load-displacement curves and mechanical fields near the crack-tip in plane strain and plane stress cases are examined. Moreover, a discussion with respect to the crack resistance R-curves calculated using the load-displacement response for plane strain and plane stress conditions is presented.

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

The Journal of Strain Analysis for Engineering Design ◽

10.1177/03093247211007662 ◽

2021 ◽

pp. 030932472110076

Author(s):

Levi Mallin ◽

Simon Barrans

Keyword(s):

Permanent Magnet ◽

Plane Strain ◽

Plane Stress ◽

High Speed ◽

Electric Machines ◽

Mechanical Transmission ◽

Element Analysis ◽

Theoretical Approaches ◽

Rotor Design ◽

Stress Plane

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.

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On Systematic Errors of Two-Dimensional Finite Element Modeling of Right Circular Planar Flexure Hinges

Journal of Mechanical Design ◽

10.1115/1.1898341 ◽

2004 ◽

Vol 127 (4) ◽

pp. 782-787 ◽

Cited By ~ 29

Author(s):

B. Zettl ◽

W. Szyszkowski ◽

W. J. Zhang

Keyword(s):

Finite Element ◽

Plane Strain ◽

Plane Stress ◽

Compliant Mechanisms ◽

Three Dimensional ◽

Systematic Errors ◽

Plane Stress State ◽

3D Analysis ◽

Two Dimensional ◽

Flexure Hinges

This paper discusses the finite element method (FEM) based modeling of the behavior of typical right circular flexure hinges used in planar compliant mechanisms. Such hinges have traditionally been approximated either by simple beams in the analytical approach or very often by two-dimensional (2D) plane stress elements when using the FEM. The three-dimensional (3D) analysis presented examines these approximations, focusing on systematic errors due to 2D modeling. It is shown that the 2D models provide only the lower (assuming the plane stress state) or the upper (assuming the plane strain state) limits of the hinge’s stiffness. The error of modeling a particular hinge by 2D elements (with either the plane stress or the plane strain assumptions) depends mainly on its depth-to-height ratio and may reach up to about 12%. However, this error becomes negligible for hinges with sufficiently high or sufficiently low depth-to-height ratios, in which either the plane strain or stress states dominate respectively. It is also shown that the computationally intensive 3D elements can be replaced, without sacrificing accuracy, by numerically efficient 2D elements if the material properties are appropriately manipulated.

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