Fatigue Life Of Welded Structures Research Articles

Estimation of fatigue life of welded structures incorporating importance analysis of influence factors: A data-driven approach

The fatigue life prediction of welded joints with different specifications under different conditions was a challenging issue due to the quite complex influence. Specifically, the current fatigue life prediction methods lacked comprehensive analysis of multiple influence factors and reasonable incorporation of physical models. So, the analysis of factors influencing the fatigue life of welded joints and the fatigue life prediction were critical to the safety and reliability of engineering structures. In this study, a prediction approach for fatigue performance was proposed based on influence factor analysis using data-driven methods. The fatigue performance dataset was processed via physical models to realize the physics-based analysis of the factors affecting fatigue performance. The weights of the physics-informed influence factors on the fatigue life were analyzed using the extreme gradient boosting (XGBoost) algorithm and verified by cross-validation. The prediction results extracted from the SN curves predicted by the deep convolutional neural network (DCNN) model incorporating the weight analysis of influence factors exhibited better accuracy and stability than direct prediction and other existing prediction models. Because of the advantages of DCNN in avoiding over fitting and local optimization, the proposed approach can better describe and estimate the fatigue performance of welded structures.

Determination of Residual Fatigue Life of Welded Structures at Bucket-Wheel Excavators through the Use of Fracture Mechanics

This paper presents a methodological approach for the assessment of service life of vital welded structures of a bucket-wheel excavator Sch Rs 650/5x24 (’Thyssen Krupp’, Germany) boom, subjected to cyclic loading with a variable amplitude through the use of experimental tests carried out in order to determine operational strength and growth of a fatigue crack. Realized researches and results presented in this paper offer great possibilities for the analyses of behaviour of vital welded structures of the bucket-wheel boom. By the application of the measurement device with 8 channels for registration and processing of electric signals HBM Spider 8 and measurement tapes HBM 6/350xXY31 deformations were measured at vital welded structures of the boom in the area of the bucket-wheel, made of steels St 37.2 and St 52.3 in accordance with standard DIN 17100, or steels S235J2G3 and S355J2G3 in accordance with standard EN 10025-2. The objective of the test is to determine if there is a possibility of occurrence of plastic deformations or initial cracks due to fatigue at vital welded structures. Tests that refer to the growth of the fatigue crack located at the welded joint have been carried out by bending at three points with asymmetric load R = 0.5 (R = σmin / σmax) at the specimen with a single edge notch. Tests were performed through the use of controlled force, ranging between Fmax and Fmin at the high-frequency pulsator ‘Cracktronic’, while obtainment of data regarding the crack growth was carried out through the use of measurement gauge ARM A-10.

Effect of Post Weld Toe Treatments on Fatigue Life of Welded Structures using FEA

Welding joints is the weak region for the components of all earth-moving machines as they are exposed to the repeated fluctuating stresses which cause fatigue cracks at the toe and throat of welded joints due to the metallurgical imperfections. This is why welded joints must be fully understood to improve the fatigue and service life of the earth-moving machines. Here failure at throat can be minimized by achieving optimum strength but problem of weld toe cracking only be eliminated by reducing stress concentration at weld toe. To do this, R & D work has been initiated by preparing set of five T-joint weld samples having 6mm (sample A to E) throat thickness with one as-welded sample i.e. E (without post weld toe treatment) using GMAW welding process. As per IIW guidelines, samples A to D has post weld toe treated with cylindrical & hemispherical burr tool, cutter (A24PBF) and flap disc grinder respectivelyto reduce the stress concentration at weld toe by making smooth transition at weld toe with undercut of 0.5mm. Fatigue analysis shows that, sample “B” with 8mm weld size post weld toe treated with hemispherical burr tool has given maximum optimization in fatigue life of 76.22% as compared to as-welded samples i.e. E.Validation carried out by hardness testing at Heat affected zone (HAZ) of etched samples.

Comparison for the Test Methods of Fatigue Life of Welded Structures

Taking the local parts of high-speed training service as the research object, the static form of the finite element model is established, and the dangerous parts of the stress distribution under different load form corresponding to loading and displacement conditions applied in experimental test is calculated. Fatigue life of the same welding parts of the different forms due to the state of the uniaxial tensile and the bending is respectively tested in the lab, the life distribution and characteristics of their statistics are obtained; Compared to the stress distribution of dangerous parts and data of the test, analysis that the similar parameters of life and failure forms can be received if it choose the reasonable load parameters in different form and loading in the test.

Fully Dynamic Numerical Simulation of the Hammer Peening Fatigue Life Improvement Technique

This paper presents the results of the development process for a Finite Element Analysis of the Hammer Peening Fatigue Life Improvement Technique. The Fatigue Life of welded structures is still in need for improvement. The sheer number of Fatigue Live Improvement Techniques parameters leads to the need of simulating and predicting their results. For this study, two different materials were used, an Austenitic Stainless Steel and a Duplex Stainless Steel. Non-load carrying cruciform weld joints were produced and fatigue tested, with and without the Hammer Peening treatment. Finally a FEA code (ABAQUS®) was used to simulate the Hammer Peening technique. A fully dynamic model was used, combined with the Chaboche Kinematic-hardening material model and different Hammering parameter experimentally determined. Alongside the residual stresses introduced by the Hammer Peening Technique, the predicted Fatigue Life using the FEA model were compared with the experimental results, showing a very good agreement between them. Also the effect of several parameters, like the hammering impact load, the hammer positioning or the number of hammering passages, were analysed as a way to validate the FEA model. The most important result was of course the Fatigue Strength Gain factor, for the Hammer Peening Technique, that in both cases was found to be superior to 1.3.