scholarly journals Effects of Ultrasonic Impact Treatment on the Stress-Controlled Fatigue Performance of Additively Manufactured DMLS Ti-6Al-4V Alloy

2019 ◽  
Vol 9 (22) ◽  
pp. 4787 ◽  
Author(s):  
Walker ◽  
Malz ◽  
Trudel ◽  
Nosir ◽  
ElSayed ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Surface Defects ◽  
Mechanical Design ◽  
Hydrostatic Stress ◽  
Fatigue Performance ◽  
Surface Porosity ◽  
Ultrasonic Impact Treatment ◽  
Ship Hulls ◽  
Before And After

Additive manufacturing (AM) offers many advantages for the mechanical design of metal components. However, the benefits of AM are offset to a certain extent by the poor surface finish and high residual stresses resulting from the printing process, which consequently compromise the mechanical properties of the parts, particularly their fatigue performance. Ultrasonic impact treatment (UIT) is a surface modification process which is often used to increase the fatigue life of welds in ship hulls and steel bridges. This paper studies the effect of UIT on the fatigue life of Ti-6Al-4V manufactured by Direct Metal Laser Sintering (DMLS). The surface properties before and after the UIT are characterized by surface porosity, roughness, hardness and residual stresses. Results show that UIT enhances the fatigue life of DMLS Ti-6Al-4V parts by suppressing the surface defects originating from the DMLS process and inducing compressive residual stresses at the surface. At the adopted UIT application parameters, the treatment improved the fatigue performance by 200%, significantly decreased surface porosity, reduced the surface roughness by 69%, and imposed a compressive hydrostatic stress of 1644 MPa at the surface.

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.

Effects of Ultrasonic Deep Rolling on Fatigue Performance of Pre-Corroded 7A52 Aluminum Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 897-900 ◽  
Author(s):  
Xiong Lin Ye ◽  
You Li Zhu ◽  
Dong Hu Zhang
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Aluminum Alloys ◽  
Residual Stresses ◽  
Fatigue Behavior ◽  
Fatigue Performance ◽  
Deep Rolling ◽  
Fatigue Crack Nucleation ◽  
7A52 Aluminum Alloy ◽  
Compressive Residual Stresses

The effects of ultrasonic deep rolling (UDR) on the fatigue behavior of pre-corroded 7A52 aluminum alloys were investigated. By means of X-Ray diffraction stress measurements and scanning electron microscopy (SEM), residual stress and fractograph of 7A52 aluminum alloys with and without UDR treatment were analyzed. The results indicated that the UDR produced compressive residual stresses with depth approaching 1mm. UDR treatment can extend the fatigue life of the pre-corroded 7A52 specimens to a large extent, depending on the level of corrosion and UDR parameter. For the slightly corrode specimens, the UDR treatment changed the fatigue crack nucleation site from surface to the transition zone between the compressive residual stresses and tensile stresses, resulted in a much longer fatigue life. For the severely corrode specimens, the crack still nucleated by intergranular cracking, however, due to the compressive residual stresses introduced and the closure of the corrosion pits and corrosion micro-crocks, UDR treatment still improved fatigue performance of the pre-corroded 7A52 aluminum alloy substantially.

scholarly journals Fatigue improvement of welded elements by ultrasonic impact treatment

2020 ◽  
Vol 65 (4) ◽  
pp. 179-190
Author(s):  
Yuir Kudryavtsev
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Large Scale ◽  
Fatigue Testing ◽  
Fatigue Improvement ◽  
Surface Layers ◽  
Ultrasonic Impact Treatment ◽  
Stress Relieving

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 tensile residual stresses and introducing of compressive residual stresses into surface layers of a material. The secondary factors in fatigue improvement by UIT/UP are decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. Fatigue testing of welded specimens showed that UIT/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 UIT/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 results of fatigue testing of large-scale welded specimens in as-welded condition and after application of UIT/UP are considered in this paper. It is shown that UIT/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.

Characterization of TC17 Titanium Alloy Treated by Square-Spot Laser Shock Peening

2013 ◽  
Vol 652-654 ◽  
pp. 2378-2383 ◽  
Author(s):  
Zi Wen Cao ◽  
Shui Li Gong ◽  
Yu Gao
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Stress Gradient ◽  
Laser Shock Peening ◽  
Fatigue Performance ◽  
Specimen Thickness ◽  
Laser Shock ◽  
Shock Peening ◽  
Square Spot

Laser shock peening (LSP) is widely known as a cold-worked surface treatment, and this technology has been to greatly improve the fatigue life of many metallic components. Our works focused on laser shock peening with Nd: glass laser system (pulse duration 30ns) and square laser spot size of 4mm×4mm for TC17 titanium alloy. Surface morphology, residual stresses and fatigue performance had been studied for TC17 alloy specimens and blades processed by LSP treatment. The results show that plastic strains in shocked dents become more homogeneous than ones produced by original circle spot with gaussian energy distribution. Surface residual stresses which measured using x-ray diffraction method showed different characteristic as varying specimen thickness, and LSP with overlapping ratio of 8% provided uniform residual stresses on peened surface. Low fluence peening which was implemented at borderline of peened surface was effective to diminish the stress gradient. Compared with mechanical shot peening, LSP attained smoother surface, lower microhardness and better fatigue performance. In a word, Square-spot LSP is an excellent way to improve fatigue life of titanium blade.

scholarly journals Investigation on Influence of Ultrasonic Impact Treatment (UIT) on Fatigue Life for Aluminium Alloy 2017-T4

2018 ◽  
Vol 21 (1) ◽  
pp. 141 ◽  
Author(s):  
Hussain J. M. Alalkawi ◽  
Aseel A. Alhamdany ◽  
Marib R. Abdul Hassan
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Ambient Temperature ◽  
Aluminium Alloy ◽  
Mechanical Design ◽  
Fatigue Tests ◽  
Strong Tendency ◽  
Ultrasonic Impact Treatment ◽  
Variable Amplitude

Improving fatigue life is one of the most important issues in mechanical design; an investigation has been conducted on Al 2017-T4. Group of samples have been machined and prepared, some of specimens have been treated using the ultrasonic impact treatment (UIT) with one line peening. The fatigue tests were carried out under constant and variable amplitude (R=-1) at ambient temperature, in order to find out the fatigue life S-N curve and strength after treatment. It has been found significant increasing in strength after it was treated by (UIT).  The fatigue strength is improved after treatment up to 4.16% at 107 cycles, enhancement are present with 24% and 18.78% for the cumulative fatigue lives low-high and high–low respectively.  These results also show a strong tendency of increasing of fatigue strength after application of (UIT) with increase in mechanical properties of material used.

scholarly journals Cumulative Fatigue damage of AA7075-T6 under Shot Peening and Ultrasonic Surface Treatments

2021 ◽  
Vol 14 (1) ◽  
pp. 1-10
Author(s):  
Marwa S. Mahammed ◽  
Hussain J. Alalkawi ◽  
Saad T. Faris
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Shot Peening ◽  
Endurance Limit ◽  
Mechanical Design ◽  
Ultrasonic Impact Treatment ◽  
Sample Group ◽  
Cumulative Fatigue Damage ◽  
Fatigue Endurance

One of the important aspects of mechanical design is improving fatigue life.; In this work, the effect of Ultrasonic impact treatment (UIP) and shot peening (SP)on constant cumulative fatigue life and fatigue strength of AA7075-T6 were studied; The sample group was machined and primed, and some specimens were treated using ultrasonic impact therapy (UIT) with one line of peening. Fatigue experiments were conducted under constant and variable amplitude (R=-1) at ambient temperature to determine the fatigue life of the S-N curve and fatigue strength during treatment 3.46% and 8.57% at 107 cycles for (UIT) and (SP). Cumulative fatigue damage testing was carried out for two steps loading it is observed that the fatigue life for SP and UIP treated specimens was improved compared to the unpeeled results. The fatigue endurance limit was enhanced by 35% for UIT and 54% for SP. The fatigue life for both treatments was much improved compared to as-received metal. These results also show a strong tendency of increasing fatigue strength after application of (UIT) and (SP) with an increase in mechanical properties of the material used.

Fatigue of High Quality Girth Welds

2011 ◽  
Author(s):  
Oddvin O¨rjasaeter ◽  
Sigmund Aas ◽  
Per J. Haagensen ◽  
Ba˚rd Wathne Tveiten
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Wall Thickness ◽  
Nickel Content ◽  
Welding Process ◽  
Fatigue Performance ◽  
High Quality ◽  
Weld Root ◽  
Girth Welds

Several studies on fatigue strength of high quality girth welds are summarized and discussed. The fatigue performance of such welds is consistently above the common design classes, as long as key set of influencing parameters are controlled. Fatigue life and crack initiation depend on loading mode, and weld defects, weld geometry, residual stresses, and degree of weld distortions. The welding method, especially for the root, has also proven to be important, e.g. TIG and high quality STT are often superior to Cu-backed roots. In practice the most important factor will be the surface breaking flaws as root LOP, etc. Such flaws are rarely found at the cap side. Thick pipe walls will also reduce the fatigue capacity, e.g. a 45mm wall thickness with 25mm reference, will reduce the with the same amount as above. High fatigue performance requires absence of any weld discontinuity above certain critical sizes which may be a challenge for the accuracy and resolution of NDT systems. In the present study, some important factors that influence the fatigue strength are examined. Based on results and theoretical calculations, the effects of the various crack-like discontinuities are described and compared to current design standards. The geometrical misalignment of the joint (hi/lo) will also influence the fatigue capacity. In bending, the weld cap toe and the weld root are the critical locations. The residual stress distribution in the welded region may, however, alter this. With pipe wall thickness larger than ∼25mm residual stresses can be beneficial to the weld root area. However, due to the scatter in the measurements it is difficult to assess the influence on fatigue life exactly. FE modeling of the welding process is therefore used to supplement this discussion. Improvement methods are available to suppress the critical influence of surface cracks/discontinuities. Grinding of the cap weld toe has in many cases shown significant improvements of girth welds. Also, TIG-dressing, high quality STT, or fillers with high nickel content, have potential for improving the root performance.

Low-Cycle Fatigue Performance of Buckling Restrained Braces and Assessment of Cumulative Damage under Severe Earthquakes

2018 ◽  
Vol 763 ◽  
pp. 867-874
Author(s):  
Yu Shu Liu ◽  
Ke Peng Chen ◽  
Guo Qiang Li ◽  
Fei Fei Sun
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Structural Reliability ◽  
Low Cycle Fatigue ◽  
Engineering Application ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Buckling Restrained Braces ◽  
Energy Dissipation Devices

Buckling Restrained Braces (BRBs) are effective energy dissipation devices. The key advantages of BRB are its comparable tensile and compressive behavior and stable energy dissipation capacity. In this paper, low-cycle fatigue performance of domestic BRBs is obtained based on collected experimental data under constant and variable amplitude loadings. The results show that the relationship between fatigue life and strain amplitude satisfies the Mason-Coffin equation. By adopting theory of structural reliability, this paper presents several allowable fatigue life curves with different confidential levels. Besides, Palmgren-Miner method was used for calculating BRB cumulative damages. An allowable damage factor with 95% confidential level is put forward for assessing damage under variable amplitude fatigue. In addition, this paper presents an empirical criterion with rain flow algorithm, which may be used to predict the fracture of BRBs under severe earthquakes and provide theory and method for their engineering application. Finally, the conclusions of the paper were vilified through precise yet conservative prediction of the fatigue failure of BRB.

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