scholarly journals Fatigue improvement of aluminium welds by means of deep rolling and diamond burnishing

2021 ◽  
Author(s):  
Jan Schubnell ◽  
Majid Farajian
Keyword(s):  
Fatigue Strength ◽  
Treatment Process ◽  
Potential Method ◽  
Fatigue Tests ◽  
Deep Rolling ◽  
Butt Joints ◽  
Diamond Burnishing ◽  
Life Improvement ◽  
Stress States ◽  
Mechanical Surface

AbstractDeep rolling is an industrially widely established mechanical surface treatment process for the modification of roughness and fatigue resistance. However, the process has not been considered as a potential method for the mechanical post welded treatment of welded joints yet. Even, the potential of deep rolling for increasing the fatigue strength is comparably well-known in the case of non-welded components. Therefore, the effect of deep rolling (hydrostatic mounted tool) and diamond burnishing (mechanical mounted tool) to increase the fatigue strength of butt joints was approved in this work for aluminium alloy AlMg4,5Mn0,7 (EN AW 5083). For this purpose, fatigue tests under full tensile loading were performed in as-welded and deep rolled, burnished and ultrasonic impact treated conditions. Different residual stress states as well as work hardening states are determined in deep rolled and burnished condition. However, similar and significant fatigue life improvement was determined for both processes.

Differences in Fatigue Strength Between Arc and Laser Hybrid Welded Joints

2008 ◽  
Vol 24 (03) ◽  
pp. 139-146
Author(s):  
H. Remes ◽  
P. Varsta
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Fatigue Tests ◽  
Notch Depth ◽  
Butt Joints ◽  
Fatigue Design ◽  
Notch Stress ◽  
Notch Geometry ◽  
Laser Hybrid ◽  
Fatigue Endurance

This paper presents the results of fatigue tests, including tests of laser hybrid and arc welded butt joints, for two plate thicknesses, 6 and 12 mm. Pure laser welded joints were also tested. The S-N curves based on nominal stresses for the different welded joints are presented. The results were further analyzed using the notch stress approach, where the fatigue notch factors were determined from the measured geometries of the welded joints. Unexpected differences in the S-N curves based on the notch stresses were found between the laser hybrid and arc welded joints and between the laser hybrid and pure laser welded joints. The reasons for this difference were studied with the help of extensive measurements of weld notch geometries. Significant differences in the geometries were observed. Taking into account the notch geometry and the notch depth, the notch stress approach partially explains the differences between the fatigue endurance limits of the laser hybrid and arc welded joints. The applicability of the notch stress approach to the fatigue design of laser hybrid welded joints is also discussed.

scholarly journals Influence of Weld-Porosity Defects on Fatigue Strength of AH36 Butt Joints Used in Ship Structures

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 444
Author(s):  
Vincenzo Crupi ◽  
Gabriella Epasto ◽  
Eugenio Guglielmino ◽  
Alberto Marinò
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Stress Ratio ◽  
Infrared Camera ◽  
Experimental Tests ◽  
Fatigue Tests ◽  
Butt Joints ◽  
Ship Structures ◽  
Weld Porosity ◽  
Porosity Defects

Experimental tests were carried out to assess the fatigue strength of four types of welded joints, made of AH36 steel and used for ship structures. The joints differ for the presence of weld defects and for the thickness value. Fatigue tests were carried out applying axial cyclic loads at a frequency of 20 Hz and at a stress ratio R = 0.5. The temperature e increment of the specimen surface was detected during the load application by means of an infrared camera. The analysis of the thermographic images allowed the assessment of both the fatigue strength of the welded joints, applying the rapid thermographic method, and the S-N curve by the energy approach. Moreover, 3D computed tomography was used for the analysis of the defective welded joints.

scholarly journals Effect of micro-notches on fatigue strength of electrodeposited nanocrystalline nickel thin films

2018 ◽  
Vol 165 ◽  
pp. 04011
Author(s):  
Keisuke Tanaka ◽  
Yuta Murase ◽  
Hirohisa Kimachi
Keyword(s):  
Thin Films ◽  
Fatigue Strength ◽  
Fatigue Limit ◽  
Stress Ratio ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Fine Grained ◽  
Nickel Thin Films ◽  
Nano Crystalline ◽  
Fictitious Crack

The effect of micro-notches on the fatigue strength of nickel thin films was studied. Two types of thin films with 10 μm thickness were produced by electrodeposition using sulfamate solution without and with brightener: ultra-fine grained film (UFG) with the grain size of 384 nm and nano-crystalline grained film (NCG) with that of 17 nm. Micro-sized notches introduced by FIB had the width of 2 μm and various depths from 8 to 150μm. Fatigue tests were conducted under the stress ratio of 0.1. The fatigue strength decreased with increasing depth of notches. NCG had much higher strength than UFG compared at the same notch depth. Notches as small as 8μm did reduce the fatigue strength of both UFG and NCG. The fatigue limit was controlled by the initiation of cracks and no non-propagating crack was observed in specimens fatigued below the fatigue limit. A model of fictitious crack successfully predicted the reduction of the fatigue limit due to micro-notches. The characteristic crack length of NCG was much smaller than the UFG, while the fatigue strength of defect-free NCG was larger than that of UFG. SEM observation of fracture surfaces was conducted to reveal micromechanisms of fatigue crack initiation.

Fatigue Life Improvement of Welded Elements and Structures by Ultrasonic Impact Treatment

2011 ◽  
Author(s):  
Yuriy Kudryavtsev ◽  
Jacob Kleiman
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Testing ◽  
Highway Bridges ◽  
Surface Layers ◽  
Ultrasonic Impact Treatment ◽  
Stress Relieving ◽  
Life Improvement

The ultrasonic impact treatment (UIT) is relatively new and promising process for fatigue life improvement of welded elements and structures. In most industrial applications this process is known as ultrasonic peening (UP). The beneficial effect of UIT/UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of a material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The UP technique is based on the combined effect of high frequency impacts of special strikers and ultrasonic oscillations in treated material. Fatigue testing of welded specimens showed that UP is the most efficient improvement treatment as compared with traditional techniques such as grinding, TIG-dressing, heat treatment, hammer peening and application of LTT electrodes. The developed computerized complex for UP was successfully applied for increasing the fatigue life and corrosion resistance of welded elements, elimination of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of the surface of materials. The UP could be effectively applied for fatigue life improvement during manufacturing, rehabilitation and repair of welded elements and structures. The areas/industries where the UP process was applied successfully include: Shipbuilding, Railway and Highway Bridges, Construction Equipment, Mining, Automotive, Aerospace. The results of fatigue testing of welded elements in as-welded condition and after application of UP are considered in this paper. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increasing of fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used.

scholarly journals Multiaxial fatigue study on steel transversal attachments under constant amplitude proportional and non-proportional loadings

2018 ◽  
Vol 165 ◽  
pp. 16007
Author(s):  
Martin Garcia ◽  
Claudio A. Pereira Baptista ◽  
Alain Nussbaumer
Keyword(s):  
Fatigue Life ◽  
High Strength ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Life Assessment ◽  
Experimental Program ◽  
Proportional Loading ◽  
Load Carrying ◽  
Stress States ◽  
Experimental Values

In this study, the multiaxial fatigue strength of full-scale transversal attachment is assessed and compared to original experimental results and others found in the literature. Mild strength S235JR steel is used and an exploratory investigation on the use of high strength S690QL steel and the effect of non-proportional loading is presented. The study focuses on non-load carrying fillet welds as commonly used in bridge design and more generally between main girders and struts. The experimental program includes 33 uniaxial and multiaxial fatigue tests and was partially carried out on a new multiaxial setup that allows proportional and non-proportional tests in a typical welded detail. The fatigue life is then compared with estimations obtained from local approaches with the help of 3D finite element models. The multiaxial fatigue life assessment with some of the well-known local approaches is shown to be suited to the analysis under multiaxial stress states. The accuracy of each models and approaches is compared to the experimental values considering all the previously cited parameters.

Influence of Inner Surface Defects on the Fatigue Strength of Pipe Subjected to Cyclic Internal Pressure

1978 ◽  
Vol 100 (4) ◽  
pp. 360-368
Author(s):  
Y. Yazaki ◽  
S. Hashirizaki ◽  
S. Nishida ◽  
C. Urashima
Keyword(s):  
Fatigue Strength ◽  
Internal Pressure ◽  
Test Specimen ◽  
Surface Defects ◽  
Fatigue Crack Initiation ◽  
Internal Surface ◽  
Fatigue Tests ◽  
Inner Surface ◽  
Surface Notch ◽  
Medium Diameter

Cyclic internal oil pressure fatigue tests were carried out on medium-diameter ERW pipes of API 5LX - X60 in an attempt to determine the influence of surface defects on the fatigue strength. Experimental factors investigated were the depth and location of internal surface notch in relation to the axis of pipe. The specimen was subjected to cyclic internal pressure, the cyclic rate being 0.3–0.5 Hz. During the test, Acoustic Emission (AE) techniques were applied to detect the fatigue crack initiation. Along with the aforementioned fatigue tests, pulsating tension fatigue tests were carried out on specimens with the same surface notches as the cyclic internal pressure fatigue test specimen.

The effect on the fatigue strength of bone cement of adding sodium fluoride

2001 ◽  
Vol 215 (2) ◽  
pp. 251-253 ◽  
Author(s):  
C Minari ◽  
M Baleanil ◽  
L Cristofolini ◽  
F Baruffaldi
Keyword(s):  
Fatigue Strength ◽  
Bone Cement ◽  
Sodium Fluoride ◽  
Biomedical Applications ◽  
Cement Mantle ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Bone Cements ◽  
The Novel ◽  
Pmma Bone Cement

New bone cements that include several additives are currently being investigated and tested. One such additive is sodium fluoride (NaF), which promotes bone formation, facilitating implant integration and success. The influence of NaF on the fatigue performance of the cement as used in biomedical applications was tested in this paper. In fact fatigue failure of the cement mantle is a major factor limiting the longevity of a cemented implant. An experimental bone cement with added NaF (12wt%) was investigated. The fatigue strength of the novel bone cement was evaluated in comparison with the cement without additives; fatigue tests were conducted according to current standards. The load levels were arranged based on a validated, statistically based optimization algorithm. The curve of stress against number of load cycles and the endurance limit were obtained and compared for both formulations. The results showed that the addition of NaF (12 wt %) to polymethylmethacrylate (PMMA) bone cement does not affect the fatigue resistance of the material. Sodium fluoride can safely be added to the bone cement without altering the fatigue performance of the PMMA bone cement.

Effect of Processing Layer on Fatigue Strength of Extruded AZ61 Magnesium Alloy

2013 ◽  
Vol 577-578 ◽  
pp. 429-432 ◽  
Author(s):  
Yukio Miyashita ◽  
Kyohei Kushihata ◽  
Toshifumi Kakiuchi ◽  
Mitsuhiro Kiyohara
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Magnesium Alloy ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Crack Growth Resistance ◽  
Az61 Magnesium Alloy

Fatigue Property of an Extruded AZ61 Magnesium Alloy with the Processing Layer Introduced by Machining was Investigated. Rotating Bending Fatigue Tests were Carried out with the Specimen with and without the Processing Layer. According to Results of the Fatigue Tests, Fatigue Life Significantly Increased by Introducing the Processing Layer to the Specimen Surface. Fatigue Crack Initiation and Propagation Behaviors were Observed by Replication Technique during the Fatigue Test. Fatigue Crack Initiation Life of the Specimen with the Processing Layer was Slightly Longer than that of the Specimen without the Processing Layer. Higher Fatigue Crack Growth Resistance was also Observed when the Fatigue Crack was Growing in the Processing Layer in the Specimen with the Processing Layer. the Longer Fatigue Life Observed in the Fatigue Test in the Specimen with the Processing Layer could be Mainly due to the Higher Crack Growth Resistance. it is Speculated that the Fatigue Strength can be Controlled by Change in Condition of Machining Process. it could be Effective way in Industry to Improved Fatigue Strength only by the Cutting Process without Additional Surface Treatment Process.

Fatigue of Autofrettaged Thick Tubes: Closed and Open Ended; As-Received and Honed

1983 ◽  
Vol 105 (3) ◽  
pp. 195-201 ◽  
Author(s):  
W. N. Findley ◽  
R. M. Reed
Keyword(s):  
Fatigue Strength ◽  
Fatigue Tests ◽  
Steel Tubes

Results of fatigue tests are presented for thick tubes of 32.3 mm (1.27 in) ID and wall ratio of 2.5 of SAE 4333 steel. Tubes having both as-received and honed bores were autofrettaged to three different degrees. Results are given for both open-ended and closed-ended autofrettage. Autofrettage increased the fatigue strength as much as 107 percent. Over autofrettage and open-ended autofrettage produced results not much different from closed-ended normal autofrettage. Under autofrettage causing half the change in diameter of normal autofrettage produced 21 percent less fatigue strength than normal autofrettage.

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