Cruciform specimens for biaxial fatigue tests: An investigation using finite-element analysis and photoelastic-coating techniques

1971 ◽  
Vol 6 (1) ◽  
pp. 27-37 ◽  
Author(s):  
I H Wilson ◽  
D J White
Keyword(s):  
Finite Element ◽  
Central Region ◽  
High Strain ◽  
Fatigue Tests ◽  
Surface Strain ◽  
Element Analysis ◽  
Biaxial Fatigue ◽  
Photoelastic Coating ◽  
Endurance Range ◽  
Transition Radius

The results are presented of investigations made on four cruciform biaxial fatigue specimens, each of which had a differently designed central region. This central region consisted of a reduced section of uniform thickness t over a circular area of diameter d which was connected by a transition radius to the full thickness of the cruciform. Equal tensile and compressive forces were applied alternately along one pair of arms only and the distribution of surface strain was studied by photoelastic-coating techniques after elastic cycling and then plastic cycling. To assess the fatigue performance of the specimens further cycling was carried out until cracks developed. Under elastic conditions, strains uniform over the thickness were calculated by finite-element techniques. For conventional fatigue tests in the high-endurance range the specimen with d/t = 12.5 is recommended. For high-strain low-endurance fatigue investigations the specimen with d/t = 5 is preferred. The recommended designs are free from problems of buckling and are such that an area of uniform strain is produced at the centre of the specimen.

Low Cycle Fatigue Tests and Simulations on Steel Elbows

2013 ◽  
Author(s):  
Patricia Pappa ◽  
George E. Varelis ◽  
Spyros A. Karamanos ◽  
Arnold M. Gresnigt
Keyword(s):  
Finite Element ◽  
Low Cycle Fatigue ◽  
Local Strain ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Out Of Plane ◽  
Strain Gauge Measurements ◽  
Number Of Cycles

In this paper the low cycle fatigue behaviour of steel elbows under strong cyclic loading conditions (in-plane and out-of-plane) is examined. The investigation is conducted through advanced finite element analysis tools, supported by real-scale test data for in-plane bending. The numerical results are successfully compared with the experimental measurements. In addition, a parametric study is conducted, which is aimed at investigating the effects of the diameter-to-thickness ratio on the low-cycle fatigue of elbows, focusing on the stress and strain variations. Strain gauge measurements are compared with finite element models. Upon calculation of local strain variation at the critical location, the number of cycles to fracture can be estimated.

Effect of Interosseous Membrane on Load Transfer in Rat Forelimb Using Finite Element Analysis

2004 ◽  
Author(s):  
A. E. Tami ◽  
G. Suresh ◽  
R. B. Patel ◽  
M. L. Knothe Tate
Keyword(s):  
Finite Element ◽  
Strain Distribution ◽  
Load Transfer ◽  
Complex Geometry ◽  
Lateral Displacement ◽  
Surface Strain ◽  
Interosseous Membrane ◽  
Distribution Data ◽  
Element Analysis ◽  
Element Mesh

Due to the curvature of the ulna and the complex geometry of the ulna and radius as well and their interaction with and possible transfer of load through the interosseous membrane that joins them, an understanding of the loading situation is not trivial. The IOM might counteract the bending effect resulting from the curvature of the ulna, therefore stabilizing the lateral displacement of the ulna and decreasing the ratio between bending and compression. Thus, in order to understand the mechanisms underlying effects of the mechanical stimulation applied using the end-loading model of the ulna, it is necessary to have a fundamental understanding of the loading mechanics and strain distribution. Hence, the goals of this study were: i) to develop a three dimensional finite element mesh of a mature rat ulna, ii) to measure experimental surface strain values of rat forelimbs with intact and non-intact interosseous membranes, iii) to compare experimental and computational strain distribution data, and iv) to analyze for the first time the effect of the radius and interosseous membrane on axial load distribution through the ulna.

Fatigue Prediction Verification of Fiberglass Hulls

2001 ◽  
Vol 38 (04) ◽  
pp. 278-292
Author(s):  
Paul H. Miller
Keyword(s):  
Finite Element ◽  
Fatigue Tests ◽  
Boiling Water ◽  
Tensile Failure ◽  
Analytical Models ◽  
Ship Motions ◽  
Long Term Effects ◽  
Element Analysis ◽  
Design Factor

The growing use of marine composite materials has led to many technical challenges and one is predicting lifetime durability. This analysis step has a large uncertainty due to the lack of data from in-service composite vessels. Analytical models based on classical lamination theory, finite-element analysis, ship motions, probability and wind and wave mechanicswere used in this project to predict hull laminate strains, and fatigue tests were used to determine S-N residual stiffness properties of coupons. These predictions and test data were compared against two cored fiberglass sisterships having significantly different fatigue histories and undamaged laminates representing a new vessel. Strains were measured while underway and good correlation was achieved between predictions and measurements. Fatigue damage indicators were identified which could be used in vessel inspection procedures. Endurance limits were found to be near 25% of static failure load, indicating that a fatigue design factor of four is required for infinite service with this material. Standard moisture experiments using boiling water were compared with long-term exposure. Results indicated the boiling water test yielded significantly conservative values and was not a reliable means of predicting long-term effects. Panel tests were compared with a combined coupon and finite-element procedure. Results indicated the proposed procedure was a viable substitute, at least for the materials studied. A rational explanation for using thicker outer skin laminates in marine composites was identified through single-sided moisture flex tests. These showed that the reduced strength and stiffness due to moisture of the outer hull skin laminate could be compensated by increased thickness. Although the resulting unbalanced laminate is not ideal from a warping standpoint, the approach leads to consistent tensile failure of the inner skin when subjected to normal loads. Permeability considerations make this desirable for hull laminates.

Finite-element analysis of stresses in shafts due to interference-fit hubs

1969 ◽  
Vol 4 (2) ◽  
pp. 105-114 ◽  
Author(s):  
D J White ◽  
J Humpherson
Keyword(s):  
Finite Element ◽  
Tensile Stress ◽  
Maximum Tensile Stress ◽  
Stress Distributions ◽  
Local Pressure ◽  
Element Analysis ◽  
Interference Fit ◽  
Axial Tensile ◽  
Stress Relieving ◽  
Transition Radius

Stress distributions in shafts due to interference-fit hubs are presented for shafts with various hub-seat features. For the calculations axisymmetric finite-element computer programmes were used. In a plain shaft there is a high local pressure just inside the hub face and a high axial tensile stress just outside it. These stresses are relieved by features, such as fillets or grooves in the shaft, arranged to give a raised or isolated hub seat and, of the two, a raised seat with a transition radius is more effective than a stress-relieving groove. Hubs fitted on either side of a groove reduce the maximum tensile stress compared with a single hub, while overhung hubs produce no significant change compared with flush hubs. Methods of fitting which promote axial constraint between the hub and shaft should be avoided since this leads to an increase in tensile stress in the shaft.

Development of Steel Dual-Core Self-Centering Braces: Quasi-Static Cyclic Tests and Finite Element Analyses

2015 ◽  
Vol 31 (1) ◽  
pp. 247-272 ◽  
Author(s):  
Chung-Che Chou ◽  
Ying-Chuan Chen
Keyword(s):  
Finite Element ◽  
Low Cycle Fatigue ◽  
Design Procedure ◽  
Fatigue Tests ◽  
Finite Element Analyses ◽  
Axial Deformation ◽  
Cyclic Tests ◽  
Element Analysis ◽  
Core Self ◽  
Dual Core

This work presents mechanics, tests, and finite element analyses of a novel steel dual-core self-centering brace (SCB) with flag-shaped re-centering responses. The axial deformation capacity of the brace is doubled with respect to the SCED brace by serial deformations of two sets of parallel tensioning elements when both braces use the same tensioning elements. The mechanics of the brace is first explained; six tensioning elements and four dual-core SCBs are tested to evaluate their cyclic performance. The braces exhibit excellent performance up to a drift of 2% with a maximum axial force around 1,400 kN. The braces also survive 15 low-cycle fatigue tests at a drift of 1.5%. Tensioning elements fail when the braces are overloaded to 2.5–3% drift. Finite element analysis is conducted to further verify hysteretic responses of the dual-core SCB in cyclic tests. A design procedure for the proposed dual-core SCB is also included in the paper.

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