On the Analytical Determination of the Nominal Stresses in Dovetail Attachments

2020 ◽  
Author(s):  
Glenn Sinclair
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Contact Region ◽  
Essential Elements ◽  
Contact Stresses ◽  
Physical Models ◽  
Analytical Determination ◽  
Bending Stress ◽  
Attachment Model

Abstract Simple physical models are developed for the nominal contact stresses in dovetail attachments. These nominal stresses include the pressure, the shear traction, and the bending stress in the contact region, both during loading up and unloading. The models furnish closed-form expressions for these stresses. For a specific dovetail attachment, model values are compared with verified finite element values. As a result of the simplifications introduced to make the models tractable, model values only approximately equal finite element values. Nonetheless, the models capture the essential elements of the response of nominal stresses in dovetail attachments.

Determination of critical angle of circumferential throughwall crack for structurally distorted 90° pipe bends under bending moment with and without internal pressure

2017 ◽  
Vol 233 (5) ◽  
pp. 817-830 ◽  
Author(s):  
S Sumesh ◽  
AR Veerappan ◽  
S Shanmugam
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Closed Form ◽  
Bending Moment ◽  
External Loading ◽  
Element Analysis ◽  
Critical Crack ◽  
Structural Distortions ◽  
Internal Pressures

Throughwall circumferential cracks (TWC) in elbows can considerably minimize its collapse load when subjected to in-plane bending moment. The existing closed-form collapse moment equations do not adequately quantify critical crack angles for structurally distorted cracked pipe bends subjected to external loading. Therefore, the present study has been conducted to examine utilizing elastic-plastic finite element analysis, the influence of structural distortions on the variation of critical TWC of 90° pipe bends under in-plane closing bending moment without and with internal pressure. With a mean radius ( r) of 50 mm, cracked pipe bends were modeled for three different wall thickness, t (for pipe ratios of r/ t = 5,10,20), each with two different bend radius, R (for bend ratios of R/r = 2,3) and with varying degrees of ovality and thinning (0 to 20% with increments of 5%). Finite element analyses were performed for two loading cases namely pure in-plane closing moment and in-plane closing bending with internal pressure. Normalized internal pressures of 0.2, 0.4, and 0.6 were applied. Results indicate the modification in the critical crack angle due to the pronounced effect of ovality compared to thinning on the plastic loads of pipe bends. From the finite element results, improved closed-form equations are proposed to evaluate plastic collapse moment of throughwall circumferential cracked pipe bends under the two loading conditions.

Constraint Solutions for Cracked Plates and Cylinders

2016 ◽  
Author(s):  
Caroline Meek ◽  
Marius Gintalas ◽  
Andrew H. Sherry ◽  
Robert A. Ainsworth
Keyword(s):  
Finite Element ◽  
Stress Field ◽  
Biaxial Loading ◽  
Analytical Determination ◽  
Plastic Collapse ◽  
Finite Element Analyses ◽  
Elastic Plastic ◽  
Cracked Plates ◽  
Computing Effort

There is little advice in fitness for service procedures for assessing constraint parameters T (elastic) and Q (elastic plastic) for biaxially loaded plates and cylinders. This paper presents the analytical determination of T stresses for biaxially loaded plates and the determination of Q for plates and cylinders using finite element analyses. It demonstrates the extent to which T can be used to conservatively predict Q and how, near collapse, Q can be estimated from the stress field corresponding to plastic collapse, enabling a significant reduction in computing effort. The effect of biaxial loading of plates and cylinders on these parameters is discussed as well as the differences found when comparing the values for plates and cylinders.

Finite Element Analysis of Rolling Contact Problems Using Minimum Dissipation of Energy Principle

1998 ◽  
Vol 65 (1) ◽  
pp. 271-273 ◽  
Author(s):  
S. K. Rathore ◽  
N. N. Kishore
Keyword(s):  
Finite Element ◽  
Contact Region ◽  
Contact Problems ◽  
Rolling Contact ◽  
Element Analysis ◽  
Energy Principle ◽  
Dissipation Of Energy ◽  
Rolling Surface ◽  
Strain Stress

In steady rolling motion, the loads and the fields of strain, stress, and deformations do not change with time at the contact region, as the contact region is continuously being formed by a new rolling surface. The principle of minimum dissipation of energy and the concept of traveling finite elements are made use of in solving such problems and the determination of micro-slips. The conditions of contact are discovered by use of the kinematic constraints and the Coulomb’s law of friction. A two-dimensional plane-strain finite element method along with the iterative procedure is used. The results obtained are in good agreement with expected behavior.

scholarly journals A closed-form formulation for the conformal articulation of metal-on-polyethylene hip prostheses: Contact mechanics and sliding distance

2018 ◽  
Vol 232 (12) ◽  
pp. 1196-1208 ◽  
Author(s):  
Ehsan Askari ◽  
Michael S Andersen
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Contact Mechanics ◽  
Contact Pressure ◽  
Contact Point ◽  
Contact Stresses ◽  
Computational Time ◽  
Physiological Loading ◽  
Sliding Distance ◽  
Inertia Forces

Using Hertz contact law results in inaccurate outcomes when applied to the soft conformal hip implants. The finite element method also involves huge computational time and power. In addition, the sliding distance computed using the Euler rotation method does not incorporate tribology of bearing surfaces, contact mechanics and inertia forces. This study, therefore, aimed to develop a nonlinear dynamic model based on the multibody dynamic methodology to predict contact pressure and sliding distance of metal-on-polyethylene hip prosthesis, simultaneously, under normal walking condition. A closed-form formulation of the contact stresses distributed over the articulating surfaces was derived based upon the elastic foundation model, which reduced computational time and cost significantly. Three-dimensional physiological loading and motions, inertia forces due to hip motion and energy loss during contact were incorporated to obtain contact properties and sliding distance. Comparing the outcomes with that available in the literature and a finite element analysis allowed for the validation of our approach. Contours of contact stresses and accumulated sliding distances at different instants of the walking gait cycle were investigated and discussed. It was shown that the contact point at each instant was located within the zone with the corresponding highest accumulated sliding distance. In addition, the maximum contact pressure and area took place at the stance phase with a single support. The stress distribution onto the cup surface also conformed to the contact point trajectory and the physiological loading.

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