Fatigue Life Improvement of the High Strength Steel Welded Joints by Ultrasonic Impact Peening

The heat input into the material during welding significantly affects the properties of high-strength steels in the near-weld zone. A zone of hardness decrease forms, which is called the soft zone. The width of the soft zone also depends on the cooling time t8/5. An investigation of the influence of welding parameters on the resulting properties of welded joints can be performed by thermal physical simulation. In this study, the effect of the cooling rate on the mechanical properties of the heat-affected zone of the steel S960MC with a thickness of 3 mm was investigated. Thermal physical simulation was performed on a Gleeble 3500. Three levels of cooling time were used, which were determined from the reference temperature cycle obtained by metal active gas welding (MAG). A tensile test, hardness measurement, impact test with fracture surface evaluation, and microstructural evaluation were performed to investigate the modified specimen thickness. The shortest time t8/5 = 7 s did not provide tensile and yield strength at the minimum required value. The absorbed energy after recalculation to the standard sample size of 10 × 10 mm was above the 27 J limit at −40 °C. The hardness profile also depended on the cooling rate and always had a softening zone.

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“…Compared to mild steels, structures can achieve a comparable or higher fatigue life. This is described inŚlęzak's [6] and Lago's [7] research.…”

Section: Introductionmentioning

confidence: 99%

Effect of the t8/5 Cooling Time on the Properties of S960MC Steel in the HAZ of Welded Joints Evaluated by Thermal Physical Simulation

Mičian

Harmaniak

Nový

et al. 2020

Metals

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“…Several authors [18][19][20][21][22] have studied the problem of fatigue behaviour of HSLA steel welded joints. Works published in this area differ from each other mainly with respect to the type of steel used, the type of stressed joint, the loading method and in light of the welding technology used.…”

Section: Discussionmentioning

confidence: 99%

“…The effect of the heat input value on the changes in the fatigue life of welded joints of steels with yield strengths lower than 550 MPa was investigated by, e.g., Šebestová et al [18] and Moravec et al [19]. The fatigue life of welded joints from steel S700MC and produced using the MAG (Metal Active Gas) method has been studied by Lahtinen et al [20], and the case of steels with higher yield strength has been studied by, e.g., Lago et al [21] and Kim et al [22]. However, all of the abovementioned authors comprehensively evaluated the effect of welding on fatigue life, by determining the S-N curves (stress-life) of the tested welded joints under the conditions defined by the authors.…”

Section: Introductionmentioning

confidence: 99%

Assessment the Partial Welding Influences on Fatigue Life of S700MC Steel Fillet Welds

Moravec

Sobotka

Nováková

et al. 2021

Metals

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Fine-grained steels belonging to the HSLA group (High-Strength Low-Alloy steels) of steels are becoming increasingly popular and are used in both statically and dynamically stressed structures. Due to the method of their production, and thus also the method use to obtain the required mechanical properties, it is really necessary to limit the heat input values for these steels during welding. When applying temperature cycles, HSLA steels in highly heated heat-affected zones (HAZ) reveal intensive grain coarsening and also softening behaviour. This subsequently results in changes in both mechanical and brittle-fracture properties, and the fatigue life of welded joints. While grain coarsening and structure softening have a major effect on the change of strength properties and KCV (Charpy V-notch impact toughness) values of statically stressed welded joints, the effect of these changes on the fatigue life of cyclically stressed welded joints has not yet been quantified. The paper is therefore conceived so as to make it possible to assess and determine the percentage impact of individual aspects of the welding process on changes in their fatigue life. To be more specific, the partial effects of angular deformation, changes that occur in the HAZ of weld, and the notch effect due to weld geometry are assessed.

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“…As an intermittent cutting method, ultrasonic vibration machining (UAM) has been widely discussed for its ability to open the tool-workpiece contact area intermittently. As one of the typical UAM processes, the ultrasonic-assisted milling technique has been widely applied to machine difficult-to-cut alloys for its superiority in expanding tool life, lowering cutting force and delivering better surface quality [18][19][20][21][22][23][24]. In order to obtain the intermittent cutting mode between the tool and the workpiece in UAM, its relative velocity in cutting direction should be controlled as the opposite to the tool rotation direction periodically.…”

Section: Introductionmentioning

confidence: 99%

High-Speed Rotary Ultrasonic Elliptical Milling of Ti-6Al-4V Using High-Pressure Coolant

Zhang

Guo³

et al. 2020

Metals

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High-speed rotary ultrasonic elliptical milling (HRUEM), as a novel ultrasonic vibration cutting method, has been introduced in milling the alloy Ti-6Al-4V. The application of ultrasonic vibration in high-speed milling can help open the cutting contact area intermittently. New cutting effects will happen with full use of the separation effect brought by ultrasonic vibration and the cooling effect brought by a high-pressure coolant (HPC). On the basis of that, this paper firstly introduces HPC into HRUEM of Ti-6Al-4V in the open literature and analyzes the tool-workpiece separation cooling mechanism in HRUEM, including kinematic analysis of tool tip trajectories, tool-workpiece separation principles and high-pressure coolant effects. We have conducted a comprehensive experimental study and the results show when HPC is increased to 200 bar, compared to conventional milling (CM), the tool life in HUREM can be extended by 6.6 times at 80 m/min, 4.2 times at 120 m/min and 2.4 times at 160 m/min. The maximum material removal volume (MRV) for a given new end mill in HRUEM is increased by 657% approximately. When the cutting speed is 80 m/min, the cutting temperature of the workpiece in HRUEM is reduced by 24.1% compared to that of CM. By applying the combination of HPC and tool-workpiece periodic separation, we can significantly enhance the cooling and lubrication efficiency in HRUEM and also inhibit the tool wear mode of adhesive wear typically occurred in CM.

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Fatigue Life Improvement of the High Strength Steel Welded Joints by Ultrasonic Impact Peening

Cited by 27 publications

References 17 publications

Effect of the t8/5 Cooling Time on the Properties of S960MC Steel in the HAZ of Welded Joints Evaluated by Thermal Physical Simulation

Effect of the t8/5 Cooling Time on the Properties of S960MC Steel in the HAZ of Welded Joints Evaluated by Thermal Physical Simulation

Assessment the Partial Welding Influences on Fatigue Life of S700MC Steel Fillet Welds

High-Speed Rotary Ultrasonic Elliptical Milling of Ti-6Al-4V Using High-Pressure Coolant

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