Equipment of type DSO for fatigue testing in repeated impact and harmonic loading with various stress ratios

“…The specimens were tested with a DSO-2 unit in three-point bending [11] at the pulse cycle of their strain-controlled loading. The specimen was mounted in the immovable supports ( Fig.…”

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Strain-Gauge Method of Detecting Subcritical Fatigue Cracks in Low-Carbon Steel Welds

2015

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A. O. Lukashevich, V. A. Leonets', UDC 621.791.052 and L. M. Chaus Detection of subcritical fatigue cracks in low-carbon steel welds with the strain-gauge nullindicator method based on the amplitude difference and phase difference procedures was investigated. It was established that a marked growth of the difference in strain amplitudes pointed to the origin of a main crack 1 mm long near the weld. An initial increase in strain amplitude differences reveals fatigue damage much earlier in comparison with the visual crack detection. The phase difference procedure cuts down the time of fatigue damage detection in low-carbon steel welds tens of times from the visual method.

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“…To determine the optimal treatment conditions from the fatigue life criterion, three series of hardened specimens were subjected to fatigue tests on a DSO-2 test machine [8,9] with pulsating harmonic-loading cycle under plane bending conditions. Then a 40 40 14´mm template (Fig.…”

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Effect of High-Frequency Mechanical Peening Conditions on Increase in the Fatigue Resistance of Butt-Welded Joints

Degtyarev

Gopkalo

2014

Strength Mater

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A procedure is proposed for the determination of the endurance limit of butt-welded joints of low-carbon steels under different high-frequency mechanical peening conditions from the maximum depth value of plastically deformed layer using experimental microhardness measurement data.Keywords: endurance limit, groove depth, high-frequency mechanical peening velocity, depth of plastically deformed layer, welded joint, microhardness.Introduction. At the present stage of development of technological methods of increasing the fatigue resistance of welded metallic structures and extending their service life, much attention is given to high-frequence mechanical peening (HFMP) [1]. This is due to the fact that HFMP can provide the maximal improvement of the fatigue resistance of products and increase in their life [2,3], at low climatic temperatures as well. However, the large-scale introduction of HFMP is limited by the absence of the reliable control criterion of its efficiency, insofar as the criterion now in use, which is based on the velocity of working tool movement along the weld, which is 0.5 m/min [2], does not ensure the required increase in fatigue resistance and treatment efficiency control both in the manufacture of welded metallic structures and in repair and restoration works.In [4] it was proposed to use as a HFMP efficiency criterion the depth of the groove formed after the peening of the zone of fusion of weld and base metal. The optimal depth value was determined to be 0.14 mm, and HFMP velocity parameters as a function of working tool vibration amplitude were proposed. However, the effect of different treatment conditions on the fatigue resistance of welded joints remains unstudied up to now. Since carrying out a series of full-scale experimental investigations is a rather expensive and long-term procedure, which involves high material consumption, the computational estimation of the fatigue resistance of butt-welded joints appears to be the most reasonable solution of the problem in comparison with individual experimental data.The purpose of this work is to computationally assess the effect of HFMP conditions on increase in the endurance limit of butt-welded joints from the results of microhardness measurement at the different depth of plastically deformed layer.Equipment, Materials, and Test Procedure. The object of investigations was a butt-welded joint of St. 3sp plate steel, which was made by semiautomatic carbon dioxide shielded welding. The test specimens were prepared at several stages.At the first stage, a previously butt-welded plate (Fig. 1a) was cut into 40 400 14´mm specimens with a transverse weld. This allowed us to greatly reduce the residual stresses occurring after welding the plate.At the second stage, specimens were subjected to HFMP along the line of fusion of weld and base metal (Fig. 1b) with a USP-300 ultrasonic tool [6] with a vibration frequency of 22 kHz, whose deforming mechanism was a four-striker head with built-in rods 3 mm in diameter. Specimens were treated along the fus...

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Equipment of type DSO for fatigue testing in repeated impact and harmonic loading with various stress ratios

Cited by 12 publications

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Life extension of the stiffening ribs of VL60 electric locomotive truck frames

Life extension of the stiffening ribs of VL60 electric locomotive truck frames

Strain-Gauge Method of Detecting Subcritical Fatigue Cracks in Low-Carbon Steel Welds

Effect of High-Frequency Mechanical Peening Conditions on Increase in the Fatigue Resistance of Butt-Welded Joints

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