Improving Fatigue Life of Riveted Joints by Rivet Hole Sizing

2014 ◽  
Vol 598 ◽  
pp. 141-146
Author(s):  
Adam Lipski ◽  
Zbigniew Lis
Keyword(s):  
Fatigue Life ◽  
Fold Increase ◽  
Fatigue Tests ◽  
Aviation Industry ◽  
Lap Joint ◽  
Riveted Joints ◽  
Riveting Process ◽  
The Difference ◽  
Structural Connection ◽  
The Impact

The aim of this paper is to assess the impact of the rivet hole sizing process on the fatigue life based on the example of the structural connections characteristic for riveted joints used in aviation industry. Test specimens reflected the structural connection consisting in a riveted lap joint of an airplane plating stiffened with a T-bar. Connected plates and the T-bar are made of D16CzATW aluminum alloy. 3 mm diameter oval head solid rivets for aviation-related purposes were made of PA24 aluminum. During fatigue tests, individual specimens with non-sized holes and with sized holes were subjected to uniaxial, one-sided, fixed-amplitude loading (R = 0). It can be concluded from the fatigue life comparison that introduction of an additional operation in the riveting process, i.e. the hole sizing, results in significant, about two-fold increase of the fatigue life of the riveted structural connection, even at slight sizing degree. The difference of the specimen damage nature was observed between specimens with sized and non-sized holes.

Effects of Continuous Strain Rate Changing on Environmental Fatigue for Stainless Steels in PWR Environment

2010 ◽  
Author(s):  
Yuichiro Nomura ◽  
Seiji Asada ◽  
Takao Nakamura ◽  
Masakazu Tanaka
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Water Environment ◽  
Sine Wave ◽  
Fatigue Tests ◽  
Integral Model ◽  
Strain Rates ◽  
Test Results ◽  
Approach Method ◽  
The Difference

The strain rates in actual transients of operating plants are not constant and changing momentarily. A large number of fatigue tests under stepwise strain rate changing conditions were performed to develop a method for evaluating fatigue life under varying strain rate conditions. Based on these test results, a strain base integral model known as the named the modified rate approach method was developed and verified. However it was reported recently that in the case of sine wave fatigue tests in BWR environment, the fatigue life was two to six times longer than the fatigue life predicted by the modified rate approach method. For this paper, in order to confirm whether the same tendency is observed in PWR environment, fatigue tests of sine wave were performed of SS316 in simulated PWR water environment. As the result, the difference of fatigue life by sine wave test reported in BWR environment was not observed between experimental and predicted life in PWR environment and the modified rate approach method was applicable under continuous strain rate changing condition.

Effect of Interference-Fit on Fatigue Life for Composite Lap Joints

2014 ◽  
Vol 939 ◽  
pp. 39-46 ◽  
Author(s):  
Hong Qian Xue ◽  
Qian Tao ◽  
Emin Bayraktar
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Tests ◽  
Lap Joints ◽  
Finite Element Simulations ◽  
Cyclic Loads ◽  
Lap Joint ◽  
Interference Fit ◽  
3D Finite Element ◽  
Double Shear

The aim of this study is to examine the effect of the clearance and interference-fit on the fatigue life of composite lap joints in double shear, 3D finite element simulations have been performed to obtain stress (or strain) distributions around the hole due to interference fit using FEM package, Non-linear contact analyses are performed to examine the effects of the clearance and interference for titanium and composite lap joint. Fatigue tests were conducted for the titanium and composite lap joints with clearance fit and interference fit with 0.5, 1, and 1.5% nominal interference fit levels at different cyclic loads. The results shows that interference fit increases fatigue life compared to clearance fit specimens, the titanium and composite lap joint with 1% interference fit level has the better fatigue life.

scholarly journals The Analysis of the Influence of Riveting Parameters Specified in Selected Riveting Instructions on Residual Stresses

2014 ◽  
Vol 2014 (6) ◽  
pp. 63-71
Author(s):  
Wojciech Wronicz ◽  
Jerzy Kaniowski
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Numerical Simulations ◽  
Western Europe ◽  
Point Of View ◽  
Industry Standards ◽  
Riveted Joints ◽  
Aerospace Companies ◽  
The Impact

Abstract The riveting parameters strongly affect residual stresses induced during riveting, which in turn have an impact on the fatigue life of riveted joints. Since rivets are established as critical from the fatigue point of view, the fatigue life of riveted joints often determines the life of the whole structure. The authors were able to become acquainted with three riveting instructions (process specifications) used by the aerospace companies from western Europe. This work presents the analysis of the riveting parameters' influence on residual stresses around the rivets. The impact of the clearance between a rivet shank and a hole as well as driven head dimensions and a rivet length were investigated based on the numerical simulations. The aim of the analysis was to determine the range of stresses variation when the requirements of the riveting instructions are fulfilled. For the purposes of comparison, the calculations were performed also with the parameters as specified in the Polish industry standards. For all calculations, the geometry of the universal rivet MS20470 was used. The results show that residual stresses can vary strongly depending on the parameters in the instructions and standard requirements.

A new model of multiaxial fatigue life prediction with the influence of different mean stresses

2019 ◽  
Vol 28 (9) ◽  
pp. 1323-1343 ◽  
Author(s):  
Bowen Liu ◽  
Xiangqiao Yan
Keyword(s):  
Fatigue Life ◽  
Equivalent Stress ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Stress Effect ◽  
Mean Stress ◽  
New Model ◽  
Von Mises ◽  
The Impact ◽  
Mean Stresses

In this paper, based on the thought of Modified Wöhler Curve Method (MWCM), a new general model for predicting multiaxial fatigue life with influence of mean stress is presented. Different from the MWCM, the expressions of multiaxiality effect and mean stress effect are located separately in the proposed fatigue equation, so that the new model can consider the impact of both axial and torsional mean stresses, and the equation form possesses excellent extendibility and variability. The wildly used von Mises equivalent stress is adopted as the fatigue parameter to improve computational efficiency. Finally, in conjunction with the Itoh criterion, the model can be trivially extended to perform non-proportional fatigue prediction with different mean stresses. Some representative fatigue tests published in the previous literature are used to verify this study.

Analysis of the Local Phenomena during Riveting Process

2014 ◽  
Vol 224 ◽  
pp. 255-260
Author(s):  
Jerzy Kaniowski ◽  
Wojciech Wronicz ◽  
Krystyna Pietrzak
Keyword(s):  
Residual Stress ◽  
Electron Microscope ◽  
Fatigue Life ◽  
Point Of View ◽  
Cold Welding ◽  
Lap Joint ◽  
Metal Parts ◽  
Riveting Process ◽  
New Phenomena ◽  
Scanning Electron

The riveting still remains the most popular and basic method of joining metal parts in airframes. At the same time, the rivets are critical from the fatigue point of view. The paper presents the selected investigations of local phenomena during the riveting process. At the beginning, some results from the literature, concerned on the riveting process influence on fatigue of the three-row lap joint were shown. The analysis of these results leads to the conclusion that the increase in fatigue life caused by higher riveting force is so high that the more beneficial residual stress cannot be the only explanation, but the new phenomena in riveting process occurs and it is a reason of huge increase in fatigue life. The working hypothesis has been assumed that during the riveting process adhesive joint (called cold welding) were formed between the rivet shank and the sheets. Several microstructure tests were conducted in order to verify this hypothesis. The tests include riveting the specimens for various configurations and analyses of the microsection of selected specimens with the use of optical and scanning electron microscope. In the case of several specimens the punctual and linear welding between rivet shank and sheets were observed. The paper presents the investigation and selected results. The authors are going to continue presented researches.

scholarly journals The impact of compound library size on the performance of scoring functions for structure-based virtual screening

2020 ◽  
Author(s):  
Louison Fresnais ◽  
Pedro J Ballester
Keyword(s):  
Virtual Screening ◽  
Fold Increase ◽  
Scoring Functions ◽  
Compound Library ◽  
Library Size ◽  
Compound Libraries ◽  
Docking Tool ◽  
The Difference ◽  
High Level ◽  
The Impact

Abstract Larger training datasets have been shown to improve the accuracy of machine learning (ML)-based scoring functions (SFs) for structure-based virtual screening (SBVS). In addition, massive test sets for SBVS, known as ultra-large compound libraries, have been demonstrated to enable the fast discovery of selective drug leads with low-nanomolar potency. This proof-of-concept was carried out on two targets using a single docking tool along with its SF. It is thus unclear whether this high level of performance would generalise to other targets, docking tools and SFs. We found that screening a larger compound library results in more potent actives being identified in all six additional targets using a different docking tool along with its classical SF. Furthermore, we established that a way to improve the potency of the retrieved molecules further is to rank them with more accurate ML-based SFs (we found this to be true in four of the six targets; the difference was not significant in the remaining two targets). A 3-fold increase in average hit rate across targets was also achieved by the ML-based SFs. Lastly, we observed that classical and ML-based SFs often find different actives, which supports using both types of SFs on those targets.

Investigating Machining Impact on Fatigue Variance: A Machining Quality Perspective

2004 ◽  
Vol 127 (3) ◽  
pp. 492-502 ◽  
Author(s):  
Xiaoping Yang ◽  
C. Richard Liu
Keyword(s):  
Fatigue Life ◽  
Data Center ◽  
Room Temperature ◽  
Fatigue Tests ◽  
Machining Processes ◽  
Case Scenario ◽  
Bending Fatigue ◽  
Machining Quality ◽  
Four Point Bending ◽  
The Impact

Fatigue life of nominally identical structures under nominally identical loading conditions can scatter widely. This study has investigated the impact of machining processes on such scatters. After Ti 6Al-4V samples were surface ground and face turned, they were subject to constant amplitude four-point bending fatigue tests under room temperature. The best-case scenario of process capability ratios of fatigue for these samples were evaluated with assumed tolerances of fatigue life. Based on these ratios, the numbers of nonconforming parts were estimated. Under the machining conditions from the Machining Data Handbook (Machining Data Center, Cincinnati, 1980), up to 39% of samples due to one process are expected to be nonconforming, whereas only up to 0.6% of samples due to the other process are expected to be nonconforming. The ramifications in terms of cost for machining quality control due to the different capability ratios have been discussed. The current findings indicate an urgent need to further the study of this issue in a scientific manner.

scholarly journals Fracture Areas Quantitative Investigating of Bending–Torsion Fatigued Low-Alloy High-Strength Steel

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1620
Author(s):  
Wojciech Macek
Keyword(s):  
Fatigue Life ◽  
Surface Topography ◽  
High Strength ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Void Volume ◽  
Variation Method ◽  
Rupture Area ◽  
The Impact ◽  
Maximum Stresses

In this study, the impact of pseudo-random non-proportional bending-torsion fatigue loadings proportion on the fatigue life and the fracture surface topography was analyzed. Investigation was carried out for 24 specimens made of S355J2 steel with 11 different ratios of maximum stresses λ. For these cases, after the fatigue tests, the surface topography measurements were carried out using an optical profilometer, using the focus variation method. Three fracture zones were analyzed for each specimen: (1) total; (2) propagation; (3) rupture, taking into account the root average square height Sq and void volume Vv parameters. The results pointed that ratio of maximum stresses λ is the most influenced on volume surface parameters represented by void volume at a given height Vv, in the rupture area. A new fatigue loading parameter P was used, depending on fatigue life T and ratio of maximum stresses λ, which shows very good correlation in 4th degree type of fit, to void volume Vv parameter for the rupture area.

scholarly journals Local Phenomena During Riveting Process

2014 ◽  
Vol 2013 (5) ◽  
pp. 66-78
Author(s):  
Jerzy Kaniowski ◽  
Wojciech Wronicz
Keyword(s):  
Fatigue Life ◽  
Numerical Study ◽  
Numerical Models ◽  
Stress System ◽  
Strain Effect ◽  
Fe Model ◽  
Force Increase ◽  
Riveted Joints ◽  
Riveting Process ◽  
Strain Signal

Abstract The paper presents experimental and numerical study of the local phenomena during the riveting process. It is commonly accepted that technological factors of the riveting process has a strong influence on the fatigue life of riveted joints. The authors analysed the papers concerned the experimental researches of the riveting force influence on fatigue life. The magnitude of the life increase caused by the riveting force increase suggests the authors that this is not only the result of beneficial stress system but the change of the joint formation mechanism has taken place. This was an inspiration to undertake more detailed researches of the riveting process. The strain progress during the riveting process has been experimentally investigated for four types of aluminium rivets used in airframes. Measurements confirm very high strains near the driven head. For some types of rivets the reversal strain signal has been recorded. Several FE model has been use to investigate the riveting process. The axisymmetric and solid models were used. The agreement of experimental and numerical results in some cases were good, in other cases the numerical models demand further development. In any calculations, the reversal strain effect has not been obtained, This suggest that it is result of the phenomenon which has not been taken into account in numerical modelling. The working hypothesis has been assumed that during the riveting process adhesive joints (called cold welding) were formed and destroyed during the process, what was the reason of the observed reversal strain signal. The authors are going to continue this investigation.

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.

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