Vibratory Stress Relief Research Articles

The Vibratory Stress Relief of Drill Pipe

Drill pipe is made from 35CrMnMo. The used drill pipes were curved, when they were aligned and deformed, there is high macro residual stress in the aligned used drill pipe. In active service, the macro residual stress releases and thus causes considerable deformation of the aligned used drill pipe. The vibratory stress relief is introduced to the aligned used drill pipe. The vibratory stress relief of the aligned used drill pipe was carried out. The mechanical properties of the aligned used drill pipe were measured before and after vibration. Seven points vibratory stresses were measured. The macro residual stress was measured before and after vibration. The macro residual stress decreased notably. The mechanical properties changed slightly. The vibratory wave is standing wave. The vibratory stress relief is valid for macro residual stress relieving of the aligned used drill pipe. The aligned used drill pipes were steady in latter active service. The mechanism of the macro residual stress relieving by vibration on the aligned used drill pipe is discussed. The “double-dynamic mechanism” is introduced to explain the course of macro residual stress relieving in the test.

Technology of quantitative analysis on vibratory stress relief based on ultrasonic time-of-arrival method

The effect of vibratory stress relief (VSR) is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method (UTM), which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.

Vibratory Stress Relief in Manufacturing the Rails of a Maglev System

To reduce the welding induced residual stress in the rails of a magnetic levitation (maglev) transport system, the procedure of vibratory stress relief (VSR) is applied and discussed in this paper. Suitable welding sequence for the rails is introduced to keep the residual stress low. Qualitative analysis with scanning curve shows that the peak of acceleration becomes higher after the procedure of VSR and the resonant frequency becomes lower. It means that the procedure of VSR is effective according to the JB/T5926-91 standard. The residual stress in the rail was measured before VSR and after VSR, using hole-drilling method, and the result shows that the average principal stresses was reduced by about 30% after VSR.

The vibratory stress relief of a marine shafting of 35 # bar steel

The marine shafting is made from a 35 # bar steel. The 35 # bar steel is named based on PR China national standard GB 699-88, “Quality carbon structure steel technical requirements,” the 35 # bar steel corresponds to 060A35, B.S. The bar steel was hot rolled, piled and air cooled; hot rolling, cooling and microstructure transformation formed macro residual stress in the bar steel. There is high macro residual stress in the 35 # (060A35, B.S.) bar steel. Worker shaped the bar steel into marine shafting with lathe. During machining, the macro residual stress releases and thus causes considerable deformation of the marine shafting. The vibratory stress relief is introduced to the bar steel that was shaped into marine shafting. The vibratory stress relief of the bar steel of the marine shafting was carried out. The tensile properties of the bar steel were measured before and after vibration. While the bar steel was vibrating, six different location axial surface vibratory stresses were measured with dynamic strain gauge; the axial surface vibratory stresses distributive curve is obtained. The macro residual stress was measured with X-ray stressmeter before and after vibration. The macro residual stress decreased notably by about 48%. The tensile properties changed slightly. The vibratory wave is a standing wave. The vibratory stress relief is valid for macro residual stress relieving of the bar steel of the marine shafting. The mechanism of the macro residual stress relieving by vibration on the bar steel of marine shafting is discussed. The “double-dynamic mechanism” is introduced to explain the course of macro residual stress relieving in the test.

Effect of residual stress on thermal fatigue in a type 420 martensitic stainless steel weldment

This paper aimed at the investigation of the effect of residual stress on thermal fatigue in martensitic stainless steel. In this study, a submerged arc welding was utilized. In order to obtain the different magnitude of residual stresses, the parallel heat welding, vibration stress relief, shot peening, and controlled low temperature stress relief processes were used for reduction of residual stresses due to welding. During welding, the thermal cycle of different locations in weldment were recorded. The residual stresses were determined by using the hole-drilling strain-gage method of ASTM standard E837. The retained ferrite content was determined with a digital optical microscope and image process software. The experimental results showed that the residual stresses decrease with increase of thermal fatigue cycle number. This is because that the formation of crack relieves residual stresses of specimen. Because of solidification structure difference, at low thermal fatigue cycle, the density of cracks on near fusion line is the higher than centerline. At high thermal fatigue cycle, the density of crack from near fusion line is lower than centerline, but very longer crack is found easily. The retained ferrite content and thermal fatigue crack tendency exist a critical value. The retained ferrite less than about 31.5 vol.% will increase crack propagation tendency. The retained ferrite become a harmful factor for crack propagation tendency when the retained ferrite more than this critical content. It is because that too much ferrite content in martensitic matrix may result in a lower strength structure and crack can propagate easily. In addition, the dual phase structure may introduce more harmful interior stress due to different volume shrinkage between retained phase and matrix.

The Influence of Vibratory Treatment on the Fatigue Life of Welds: A Comparison with Thermal Stress Relief

Abstract: A comparison has been made between the fatigue lives of welded specimens a) in the as welded condition b) after heat treatment, and c) after post‐weld vibration. By comparison with the as‐welded specimens, the fatigue lives of the thermally relieved specimens were found to decrease by 43%, while the vibration treated specimens showed an increase of between 17% and 30%. While these findings are interesting in that they offer a way of extending the fatigue lives of welded joints, they confirm the view that the mechanism of residual stress relieving in the vibratory stress relief (VSR) method, and its relationship with fatigue life is poorly understood.

Vibratory stress relief—an investigation of the torsional stress effect in welded shafts

In this study the effect of torsional vibration on residual stresses was investigated. Three types of shaft specimen were processed, namely (a) a homogeneous shaft, (b) a shaft welded on a circumferential line and (c) a spot-welded shaft. The first two types of shaft showed some redistribution in the residual stresses under applied torsional loads. On the spot-welded shafts the residual stresses were found to decrease significantly at a very low level of vibration induced stress.

Modification of residual stress by post-weld vibration

Previous studies have suggested that welding residual stresses can be reduced by the application of controlled vibration. In the present study welded specimens were processed after being cooled to room temperature, with varying amplitude of applied stress and time of vibration. An increase in the applied stress led to a significant decrease in the residual stresses. The effect of time of vibration was found to be very small for a lower range of applied stresses (<230 MPa); an increase in the time of vibration had no influence on residual stresses. At higher applied stresses (>230 MPa), the residual stresses were found to redistribute with increasing time of vibration. It is shown that the energy concept of the vibratory stress relief mechanism was not validated.

Reduction of Residual Stress for Welding Joint Using Ultrasonic Vibrational Load.

Welding is widely used for construction of many structures. The residual stresses created in a structure by a welding operation may influence the mechanical behavior of the structure in several ways. Hence, reduction of the residual stress caused by welding is very important. Stress relief may be accomplished by heating operation. However, processing by heat treatment requires much electric energy, processing time and so on. While, low frequency vibratory stress relief process has been reported as an effective method. However, this process has a limitation in applicability for high rigid parts such as dies and thick plates. In this paper, a new method for reduction of welding residual stress and its analytical model are proposed. The new method is carried out using ultrasonic vibrational loading which is applied during the welding operation. The proposed method is applicable to not only a structure consist of plate but also a massive block. An experiment was carried out for single-pass butt-welding of steel plates and single-pass repair welding of steel blocks. It is confirmed that the peak residual stress on the bead is significantly reduced. Furthermore, reduction of residual stress is examined by an analytical method using a mechanical model considering local plastic deformation.

Evaluating the effectiveness of vibratory stress relief by a modified hole-drilling method

In this paper, a modified through hole-drilling method is developed to evaluate the effectiveness of the application of vibratory stress relief (VSR). The principal residual stresses at any specified point before and after the treatment of VSR are measured by this method with the same cemented commercially available three-element strain gauge rosette. By comparing the magnitude of the measured results, the effectiveness of the treatment of VSR can thus be determined. Thin butt-welded specimens are prepared to verify the accuracy of the modified hole-drilling method compared to that of the conventional hole-drilling method. The experimental results show that the percentages of the relative errors between these two methods are all within 2.9%. Therefore, this modified method shows good accuracy in the determination of residual stresses before and after VSR. Meanwhile, the maximum principal residual stresses at the measured points are effectively reduced by about 5.8% to 27% after the application of VSR, and the minimum principal residual stresses at the measured points are effectively reduced by about 9.6% to 31%.

Fatigue damage in two step loading of 316L steel. I. Evolution of persistent slip bands : Polák, J., Vasek, A. and Obrtlik, K. Fatigue Fract. Eng. Mater. Struct. (1996) 19 (2–3), 147–155

The work reported in this paper is a summary of the results obtained from several projects run over a five year period. A number of thrusts were encompassed in the project scope, which was to examine the fatigue strength of extruded 6261-T6 I-beams with centrally located, welded cover plates under constant amplitude (CA) and variable (two-level repeated block) amplitude (VA) loading. The CA part of the work examined the effect of cover plate geometry, specimen size, thermal and vibratory stress relief, and differences in fabrication quality on fatigue performance. A number of cases were identified which gave rise to cross-overs in performance in moving from shorter to longer fatigue lives. The aim of the VA part of the work was to identify situations which might give rise to fatigue lives shorter than predicted by linear damage summation models, such as Miner's rule. Two such cases were identified: specimens which had been subjected to vibratory stress relief; and specimens in which weld `quality' (as assessed by profile, heat affected zone hardness, extent and microstructure) varied. Explanations for these observations are proposed and supported by interpretation of a two-level block of small fatigue crack growth.

Dislocation substructures at fatigue crack tips of 304 stainless steel cycled in air or vacuum : McEvily, A.J., Gonzalez, J.L. and Hallen, J.M. Scripta Materialia (1996) 35, 761–765

The work reported in this paper is a summary of the results obtained from several projects run over a five year period. A number of thrusts were encompassed in the project scope, which was to examine the fatigue strength of extruded 6261-T6 I-beams with centrally located, welded cover plates under constant amplitude (CA) and variable (two-level repeated block) amplitude (VA) loading. The CA part of the work examined the effect of cover plate geometry, specimen size, thermal and vibratory stress relief, and differences in fabrication quality on fatigue performance. A number of cases were identified which gave rise to cross-overs in performance in moving from shorter to longer fatigue lives. The aim of the VA part of the work was to identify situations which might give rise to fatigue lives shorter than predicted by linear damage summation models, such as Miner's rule. Two such cases were identified: specimens which had been subjected to vibratory stress relief; and specimens in which weld `quality' (as assessed by profile, heat affected zone hardness, extent and microstructure) varied. Explanations for these observations are proposed and supported by interpretation of a two-level block of small fatigue crack growth.

Crystallographic preferred orientation induced by cyclic rolling contact loading : Voskamp, A.P. and Mittemeijer, E.J. Metall. Mater. Transact. A (1996) 27A (11), 3445–3465

The work reported in this paper is a summary of the results obtained from several projects run over a five year period. A number of thrusts were encompassed in the project scope, which was to examine the fatigue strength of extruded 6261-T6 I-beams with centrally located, welded cover plates under constant amplitude (CA) and variable (two-level repeated block) amplitude (VA) loading. The CA part of the work examined the effect of cover plate geometry, specimen size, thermal and vibratory stress relief, and differences in fabrication quality on fatigue performance. A number of cases were identified which gave rise to cross-overs in performance in moving from shorter to longer fatigue lives. The aim of the VA part of the work was to identify situations which might give rise to fatigue lives shorter than predicted by linear damage summation models, such as Miner's rule. Two such cases were identified: specimens which had been subjected to vibratory stress relief; and specimens in which weld `quality' (as assessed by profile, heat affected zone hardness, extent and microstructure) varied. Explanations for these observations are proposed and supported by interpretation of a two-level block of small fatigue crack growth.

Fatigue performance of 6261-T6 aluminium alloy – constant and variable amplitude loading of parent plate and welded specimens

The work reported in this paper is a summary of the results obtained from several projects run over a five year period. A number of thrusts were encompassed in the project scope, which was to examine the fatigue strength of extruded 6261-T6 I-beams with centrally located, welded cover plates under constant amplitude (CA) and variable (two-level repeated block) amplitude (VA) loading. The CA part of the work examined the effect of cover plate geometry, specimen size, thermal and vibratory stress relief, and differences in fabrication quality on fatigue performance. A number of cases were identified which gave rise to cross-overs in performance in moving from shorter to longer fatigue lives. The aim of the VA part of the work was to identify situations which might give rise to fatigue lives shorter than predicted by linear damage summation models, such as Miner's rule. Two such cases were identified: specimens which had been subjected to vibratory stress relief; and specimens in which weld `quality' (as assessed by profile, heat affected zone hardness, extent and microstructure) varied. Explanations for these observations are proposed and supported by interpretation of a two-level block of small fatigue crack growth.

Constant and variable amplitude loading of 6261 aluminium alloy I-beams with welded cover plates—Influence of weld quality and stress relief

A study of the constant amplitude and variable amplitude (VA) fatigue performance of 6261-T6 aluminium 1-beams with a welded rectangular cover plate is reported. The test programme involved >100 specimens and considered the effects of weld ‘quality’ (in terms of weld toe angle, leg length and heat input), and thermal and vibratory stress relief on stress-life curves under simple repeated two-level ] block loading. The number of high-to-low amplitude cycles in a single VA block was varied from 1/20, through 10/20 to 1/1000 and 1/50,000. Load amplitude increase percentages of 25%, 75% and 150% were considered. Observed fatigue lives were compared with the predictions of Miners rule and explanations are proposed for situations where Miners rule is non-conservative.

Vibratory Stress Relief—An Investigation of the Underlying Processes

The use of vibration to reduce residual stress levels in fabrications is potentially an attractive alternative to thermal annealing. The application of the process has hitherto been limited by the lack of coherent theory of operation. In this study, residual stresses were introduced into a low-alloy steel EN3b by rolling. It was shown that prolonged low-amplitude vibration at 100 Hz induced a stress relaxation of as much as 40 per cent, where the original level was close to yield. A model has been developed to explain the diverse effects resulting from low-amplitude vibration; the model involves the motion of dislocations under the influence of the combined residual and external cyclic stress fields. This model, which has been validated by detailed X-ray line profile analysis and elasticity measurements, is an extension to the currently available explanation for VSR (vibratory stress relief). The standard model, which assumed the need to exceed the local yield stress, only comes into operation at the higher levels of applied stress amplitude. The development of accurate and validated methods for the application of VSR may now be contemplated.

Vibratory stress relief of welded components

Vibratory stress relief of welded components

Vibratory Stress Relief: A Fundamental Study of Its Effectiveness

Techniques have been devised for inducing consistent residual stress distributions into cantilever beams and for measuring their variation through the section. Commercial vibratory stress relief procedures have been simulated using a laboratory shaker, and it has been shown that resonant vibration techniques are capable of producing almost complete surface stress relief in specimens of hot rolled mild steel, cold drawn mild steel, and an aluminium alloy. The variables involved in the process are examined and conclusions are reached regarding cyclic strain amplitudes, cycle numbers, and frequency and fatigue effects.