Influence of Fastener Flexibility on the Prediction of Load Transfer and Fatigue Life for Multiple-Row Joints

2008 ◽  
pp. 221-221-30 ◽  
Author(s):  
H Huth
Keyword(s):  
Fatigue Life ◽  
Load Transfer

scholarly journals Fatigue Life Enhancement of Welded Steel-Steel Composite during Crack Growth from Weak to Strong Steel: An Experimental Validation

2009 ◽  
Vol 417-418 ◽  
pp. 825-828
Author(s):  
Sunil Bhat ◽  
Vijay G. Ukadgaonker
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Load Transfer ◽  
Electron Beam Welding ◽  
Fatigue Testing ◽  
Crack Tip ◽  
Compact Tension ◽  
Welded Steel ◽  
Maraging Steels ◽  
Bimetallic Composite

Strength mismatch effect across weld interfaces, generated by welding weak and strong steels, influences fatigue and fracture properties of a welded bimetallic composite. Advancing fatigue crack tip in weak parent steel is shielded from the remote load when it reaches near the interface of ultra strong weld steel. Entry of crack tip plasticity into weld steel induces load transfer towards weld which dips crack growth rates thereby enhancing the fatigue life of the composite. A computational model for fatigue life prediction of strength mismatched welded composite under K dominant conditions is validated by experimental work in this paper. Notched bimetallic compact tension specimens, prepared by electron beam welding of weak alloy and strong maraging steels, are subjected to fatigue testing in high cycle regime.

Methods to Increase the Fatigue Life of Friction Stir Lap Welds in No-load Transfer Coupons Using a Retractable Pin Tool

2012 ◽  
Vol 9 (5) ◽  
pp. 103899 ◽  
Author(s):  
Farzad Baratzadeh ◽  
Christian A. Widener ◽  
Hamid M. Lankarani ◽  
Dwight A. Burford
Keyword(s):  
Fatigue Life ◽  
Load Transfer ◽  
Friction Stir

Fatigue of Cold Expanded Open Hole Coupons with Pre-Existing Cracks

2014 ◽  
Vol 891-892 ◽  
pp. 69-74 ◽  
Author(s):  
Pud S. Baburamani ◽  
Rob Ogden ◽  
Qian Chu Liu ◽  
P. Khan Sharp
Keyword(s):  
Fatigue Life ◽  
Load Transfer ◽  
Fatigue Crack Initiation ◽  
High Stress ◽  
Cost Effective ◽  
Fatigue Loading ◽  
Experimental Program ◽  
Cold Expansion ◽  
Open Hole ◽  
Life Improvement

Fastener holes have a high stress concentration at the edge of the hole and are primary sources of fatigue crack initiation, resulting in widespread fatigue damage leading to fatigue failures in airframe structures. The split-sleeve cold expansion (SsCx) technology is a simple and cost-effective way to improve the fatigue resistance of fastener holes by the introduction of compressive residual stresses around the holes. An investigation was carried out by DSTO to quantify the effectiveness of this technology, in terms of fatigue life improvement factors on a typical airframe aluminium alloy. Open hole (zero load transfer) coupons were tested to failure in non-cold expanded and cold expanded conditions. Coupons were also pre-cracked to specified crack lengths at the open hole, and cold expanded or left non-cold expanded, and tested to failure. This paper will present the results of the initial phases of the experimental program, involving constant amplitude fatigue loading of open hole coupons with and without cracks. The fatigue life improvement achieved by the use of hole cold expansion technology will be presented.

scholarly journals EFFECT OF THE RIVET-HOLE TOLERANCE ON THE STRESS-SEVERITY FACTOR

2021 ◽  
Vol 55 (2) ◽  
pp. 237-242
Author(s):  
Jiří Běhal ◽  
Roman Růžek
Keyword(s):  
Fatigue Life ◽  
Load Transfer ◽  
Research Centre ◽  
Hole Filling ◽  
Molybdenum Disulphide ◽  
Severity Factor ◽  
Transfer Factors ◽  
Riveted Joints ◽  
Riveted Joint ◽  
Initial Clearance

This work is focused on a quantitative procedure for estimating the generally unfavourable effects that incorrectly drilled holes, characterized by the initial clearance between a rivet and a hole, have on the fatigue life of riveted joints. The solution is based on an analytical approach using the stress-severity-factor concept. An experimental programme with riveted-joint specimens characterized by low-load transfer factors was realized in the Czech Aerospace Research Centre (VZLU) test lab under constant amplitude loading. The holes for rivet joints with 4-mm diameters were prepared with the clearance in a range of 0.0–0.16 mm. Force-controlled riveting was applied using a constant pressure force to form the driven head. To prevent fretting events between the joined parts, their anodized contact surfaces were lubricated with MOLYKA, plastic grease with molybdenum disulphide and graphite. The experimental data showed that the load-transfer factor and the fatigue life depend on the initial clearance between a rivet and a hole. The presented procedure introduced the hole-filling factor, integrated in the stress-severity-factor concept as a function of the initial clearance between a rivet and a hole.

Applicability of Empirical Formulae for the Fatigue Notch Factor to Estimate Riveted Lap Joint Fatigue Strength

2014 ◽  
Vol 224 ◽  
pp. 81-86
Author(s):  
Tomasz Machniewicz ◽  
Małgorzata Skorupa ◽  
Andrzej Skorupa ◽  
Adam Korbel
Keyword(s):  
Fatigue Life ◽  
Load Transfer ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Lap Joints ◽  
Riveted Joints ◽  
Riveted Joint ◽  
Fatigue Notch Factor ◽  
Riveted Lap Joints ◽  
Semi Empirical

A semi-empirical fatigue life prediction model under development by the present authors for riveted lap joints used in aircraft structures is outlined. In contrast to existing models, it will account for the influence of the rivet squeeze force on the fatigue life of riveted joints. To determine the effect of rivet-hole interference on the fatigue behaviour of a riveted joint, a series of fatigue tests on filled hole coupons with different amounts of interference will be carried out under loading conditions representing the bypass load, transfer load and secondary bending. These experiments will allow evaluating of the dependency of the fatigue notch factors on rivet hole expansion. Preliminary results obtained so far are presented in this paper.

scholarly journals АНАЛІЗ КОНСТРУКТИВНИХ ОСОБЛИВОСТЕЙ З'ЄДНАНЬ СИЛОВИХ ЕЛЕМЕНТІВ КРИЛА ЛІТАКІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 139-151
Author(s):  
Дмитрий Юрьевич Жиряков
Keyword(s):  
Fatigue Life ◽  
Load Transfer ◽  
Construction Materials ◽  
Local Stress ◽  
Cost Effective ◽  
Aviation Industry ◽  
Structural Element ◽  
Prefabricated Structure ◽  
Structural Parts ◽  
High Level

Ensuring the fatigue life of the aircraft structure is a requirement for flight safety, and for a cost-effective aircraft. A plane with a long lifetime can perform more flights, reduce routine maintenance costs and increase airline profits. Market trends in the aviation industry show the interest of airlines in long life aircraft. Structural elements of the wing are joined by fasteners. The wing structure fatigue is determined by the endurance of regular zones. Regular zones include longitudinal, transverse joints. The fatigue life of the wing irregular zones should be no less than the fatigue life of the regular zone. The article provides an analysis of the design features of the wing structural element joints performing short and medium flights, ANTONOV and Boeing, which have reached a high level in this field of research. Structural schemes of the wings, location and execution of the joints of the wing structural parts using facilities that improve take-off and landing characteristics (such as ailerons, flaps, slats and spoilers) are analyzed. The types, diameters and materials of fasteners that vary within the wing limits are considered. Attention was focused on such important indicators as the edge tolerance, distance between the fasteners (spacing), wing and fastener construction materials. The wing is made of a prefabricated structure, to ensure safety requirements for permissible destruction. In turn, this leads to an increase in the amount of fasteners. Since fatigue life is affected not only by the kinds of materials, parameters of fasteners, rated stresses, but also the degree of load transferring between parts. The constructive execution of the longitudinal and transverse connections of the load-bearing elements was analyzed to further study the degree of load transfer in a difficult - stressed state. The materials of the article provide an opportunity for further in-depth research on the general and local stress-strain state of the wing.

Life enhancement of fatigue-aged fastener holes using the cold expansion process

2000 ◽  
Vol 214 (5) ◽  
pp. 281-293 ◽  
Author(s):  
J Gaerke ◽  
X Zhang ◽  
Z Wang
Keyword(s):  
Fatigue Life ◽  
Experimental Test ◽  
Load Transfer ◽  
Test Results ◽  
Expansion Process ◽  
Cold Expansion ◽  
Final Failure ◽  
Low Load ◽  
Open Hole ◽  
Life Enhancement

This paper examines the benefits of cold expanding fastener holes at various stages of the fatigue life in a 2024-T351 low-load transfer joint. The specimens were pre-cycled to 25, 50 and 75 per cent of the baseline fatigue life of a non-expanded specimen and then cold expanded prior to cycling to final failure. The experimental test was designed to provide a close comparison with standard maintenance practices for aircraft structures and used the FALSTAFF spectrum which was derived from actual flight loading. The test results have indicated that part-life cold expansion can provide substantial improvements in fatigue life, but the actual benefit is dependent upon the degree of precycling and he length of existing cracks when the specimen is cold expanded. Additionally, tests on open hole specimens of the same material and thickness were also carried out, with attempts being made to predict the crack growth lives of these specimes.

Numerical Modelling of the Biaxial Fatigue Test of Aluminium Wheels

2020 ◽  
Author(s):  
Federico Ballo ◽  
Giampiero Mastinu ◽  
Giorgio Previati ◽  
Massimiliano Gobbi
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Load Transfer ◽  
Experimental Tests ◽  
Contact Forces ◽  
Biaxial Test ◽  
Interface Surface ◽  
Biaxial Fatigue ◽  
Wheel Rim ◽  
Wheel Model

Abstract The paper is devoted to the numerical simulation of fatigue life of lightweight aluminium wheels subject to biaxial fatigue test. A numerical model based on finite elements is developed for the scope. The model receives as input the test load sequences and outputs the fatigue life of wheel. Two different methods for modelling the load transfer mechanism of the tyre have been analysed, i.e. how the tyre-drum contact forces are transferred to the wheel rim. The first method consists of a simple cosine loading function acting on a fixed arch of the wheel rim. The second method relies on a physical model of the tyre that is fixed at the tyre-rim interface surface; the computed reaction forces are fed as input to the wheel model. The fatigue life of the wheel is estimated by using the Palmgrem-Miner approach. Both the Sines fatigue criterion and the Papadopoulos critical plane with gradient effect criterion are used and the results are compared. Experimental tests have been performed on an actual wheel mounted on the biaxial test bench for a preliminary validation of the method.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

1992 ◽  
Vol 50 (1) ◽  
pp. 158-159
Author(s):  
Warren J. Moberly ◽  
Daniel B. Miracle ◽  
S. Krishnamurthy
Keyword(s):  
Thermal Stresses ◽  
Load Transfer ◽  
Coefficient Of Thermal Expansion ◽  
Hot Isostatic Pressing ◽  
Matrix Composites ◽  
Ongoing Research ◽  
Aerospace Applications ◽  
Sic Fiber ◽  
The Matrix ◽  
Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

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