Modeling Of Residual Stresses Research Articles

Development of residual stress model of orthotropic steel decks using measurements

Orthotropic steel decks are widely used in the bridge engineering practice due to light weight, high performance and high ultimate strength-to-weight ratio. Purpose of the current paper is developing the first residual stress model for orthotropic steel decks (OSDs) with U-shaped stiffeners based on residual stress measurement results. The proposed simplified residual stress model is valid for OSDs with single-bevel butt welds, manufactured from steel grade up to S355. Distribution and magnitude of manufacturing-induced residual stresses due to hot rolling, thermal cutting, cold-forming, welding, etc. are determined using contour method with thin-plate smoothing spline. It makes it possible to interpret two-dimensional full-map residual stresses, instead of conventional pointwise residual stress measurement techniques, resulting in higher spatial resolution. Longitudinal residual stress patterns are evaluated in representative cross-sections clearly indicating high stress peaks near the welds, even exceeding yield strength of the base material, while the influence of thermal cutting and cold-forming can be addressed as well. Statistical evaluation of measurement results is carried out, which resulted in mean standard deviation of 22 MPa and 34 MPa in the stiffener and deck plate, respectively, which is comparable with the accuracy of other measurement techniques, e.g., X-ray diffraction method or hole-drilling technique.

3D residual stress modelling in turning of AISI 4140 steel

3D residual stress modelling in turning of AISI 4140 steel

Three-dimensional analytical model for residual stress in the weld of thick plates by friction stir welding

Three-dimensional analytical model for residual stress in the weld of thick plates by friction stir welding

A Review on Thermal Modelling of Residual Stresses during Additive Manufacturing

Additive Manufacturing (AM) has received interest since it is simpler to manufacture complicated 3D component without the requirement for casting moulds than convective fabrication. AM has a lot of significance in fields like aerospace, medicine, and more to make parts of any kind of complex shape. Since the finished products are subjected to repeated cycles of heating and cooling, there will always be some residual stresses present in them. During layer-over-layer deposition, the large difference in temperature between the layers causes residual stresses, which hurt the performance of the products. As far as the author’s knowledge, there is no thorough review of the thermal modelling of residual stress in AM. In this review paper, the goal is to first get a good understanding of how residual stresses are developed, and then to look at how different models measure them. So, residual stresses can be seen as a key factor in controlling costs, performance, and quality standards of the finished component. This paper does a thorough review of the field to give engineers and researchers up-to-date information and advice about residual stresses.

7075 aluminum alloy induced by ultrasonic surface rolling: grain refinement and residual stress model analysis and evaluation

7075 aluminum alloy induced by ultrasonic surface rolling: grain refinement and residual stress model analysis and evaluation

Residual stresses in circular steel tubular columns repaired by laser-cladding additive manufacturing

This paper presents a study that investigates the magnitude and distribution of residual stress (RS) in laser cladding (LC) repaired circular steel tubular columns. The study involves experimental tests and numerical simulation. The familiar blind-hole method is employed in the experimental investigation for two RS measurement tests, while the finite element method is used for numerical thermal-mechanical analysis to obtain the temperature field and RS field. The results indicate the presence of residual tensile stress in the LC sheet and its surrounding area. The RS in the LC sheet area and in the vicinity of the LC sheet-substrate boundary is much greater than that in the substrate area located far away from the LC sheet. Additionally, the RS in the LC sheet along the scanning direction is larger than that perpendicular to the scanning direction. Nevertheless, the RS values in both the LC sheet and substrate are less than their respective yield strength values. The temperature-time cooling curves obtained from the finite element analysis, which simulate the laser cladding process for repairing the circular steel tubular column, are used to develop a theoretical model for predicting the RS in the LC sheet. A simplified RS model is proposed based on the thermal-mechanical theory, utilising the linear-exponential two-stage cooling curve. Comparisons between the experimental results and the theoretical results that are predicted using the proposed simplified RS model show both results to be in good agreement. Therefore, the simplified RS model proposed in this paper is suitable for efficiently and accurately predicting the RS in LC sheet for circular steel tubular columns repaired by LC.

Data-driven surrogate modelling of residual stresses in Laser Powder-Bed Fusion

ABSTRACT In order to enable the industrialization of additive manufacturing, it is necessary to develop process simulation models that can rapidly predict part quality. Although multi-physics simulations have shown success at predicting residual stress, distortion, microstructure and mechanical properties of additively manufactured parts, they are generally too computationally expensive to be directly used in applications, such as optimization, controls, or digital twinning. In this study, a critical evaluation is made of how data-driven surrogate models can be used to model the residual stress of parts fabricated by Laser Powder-Bed Fusion. Residual stress data is generated by using an inherent-strain based process simulation for two families of part geometries. Three different models using varying levels of sophistication are compared: a multilayer perceptron (MLP), a convolutional neural network (CNN) based on the U-Net architecture, and an interpolation-based method based on mapping geometries onto a reference. All three methods were found to be sufficient for part design, providing mechanical predictions for a CPU time below 0.2 s, representing a runtime speed-up of at least 3900 × . Neural network-based models are significantly more expensive to train compared to using interpolation. However, the generality of models based on the U-Net architecture is attractive for applications in optimization.

COMPUTATIONAL MODELING OF A LAYERED AORTIC MEDIAL WALL CONSIDERING EFFECTIVE RESIDUAL STRESSES

We previously developed a simplified finite element (FE) “unit” model to reproduce the mechanical interaction between the smooth muscle layer and elastic lamina (EL) in the aortic media. Nevertheless, whether this simplified FE model can represent the structure of a real medial wall and whether its modeling technique can help in developing a highly sophisticated and structure-based aortic FE model should be determined. Therefore, this study aimed to computationally represent EL buckling in the aortic medial ring at an unloaded state based on the integrated unit models and reproduce transmural variations in EL waviness across the vascular wall. We confirmed that the inner and outer layers of the medial wall were relatively subjected to compressive and tensile residual stresses, respectively, at the unloaded state, implying that the ring model will open spontaneously when it is radially cut. In addition, the residual stresses computed under such a stress-free condition were comparable to the analytically estimated values, partially supporting the validity of our modeling approach. Although further study is still required, the information obtained in this study will greatly improve the understanding of basic aortic physiology and pathophysiology and provide a basis for performing more sophisticated computational modeling of the aortic wall.

Establishment and experimental verification of a three-dimensional finite element model for residual stress in surface processing of Inconel 718 alloy by laser cladding

The local load and residual stress changes of conventional forged Inconel 718 alloy can be simulated in a two-dimensional (2D) cutting simulation model, but the type and distribution of global residual stress field of the alloy cannot be predicted during laser cladding layer cutting. To address the shortcomings of conventional 2D cutting simulation models for forging Inconel 718 alloy, this paper proposed a 3D closed-loop finite element model, and taking the dry-side milling process of Inconel 718 alloy laser cladding layer as an example, the generation mechanism and distribution of residual stress are predicted during the machining process. Further testing of surface, near-surface, and subsurface residual stresses was conducted to analyze the specific distribution of residual stresses in the workpiece. The results indicated that the uneven distribution of cutting stress and temperature on the workpiece had a significant non-stationary thermal-mechanical effect on the surface of the machined workpiece; the distribution of surface residual stress was uneven, with the significant tensile residual stress at the workpiece boundary. As the depth increases, the influence of mechanical effects dominated, and the compressive residual stress was generated on the subsurface of the workpiece. Residual stress testing was conducted on the surface/near-surface, and the experimental results were consistent with the simulation results of the closed-loop simulation model. In the subsurface, residual stress showed a similar trend of change. This study compensated for the shortcomings of conventional finite element simulation and provided the reference value for the application of three-dimensional finite element simulation in laser cladding materials.

Proposed residual stress model for hot‐rolled wide flange steel cross sections

AbstractResidual stresses in hot‐rolled wide flange steel cross sections may lead to premature yielding, accelerated corrosion and brittle fracture of steel members. The above phenomena lead to a loss of a steel member's stiffness and resistance under mechanical loading. Available residual stress models are mostly based on residual stress measurements that date back to 1950s. Some of the drawbacks of these models relate to the lack of consistency in the considered parameters that affect the residual stress development within a steel cross section. Motivated by this, this paper proposes a new residual stress model for hot‐rolled wide flange steel cross sections. The proposed residual stress model relies on a dataset of 80 experiments that are complemented by additional measurements done as part of the present study. A parabolic residual stress distribution, which is deduced from a constraint optimization problem, is fitted to the assembled data. The proposed residual stress distributions are generalized with the aid of rigorous statistical analyses. The results suggest that the residual stress model is highly dependent on the cross‐sectional area and the depth‐to‐width ratio of a hot‐rolled wide flange steel cross section. The proposed residual stress model reduces the error, on average, by 60‐70% compared to available residual stress models (e.g., European Convention for Constructional Steelwork model), regardless of the cross‐sectional geometry of the hot‐rolled cross section.

Finite element based 3-D modelling of residual stress in high vacuum actively brazed diamond/Ni-Cr filler/C45 steel joint

In active brazing of diamonds, high brazing temperature and difference in the thermo-mechanical properties of the diamond grain, filler alloy, and substrate lead to the development of unfavorable residual stresses in the bonding region. This residual stress can potentially cause initiation of cracks within the interfacial reaction layer formed between diamond and filler-alloy, weakening the joint. Since the diamond particles used in diamond grinding tools are micro-sized and complex in shape, it is experimentally difficult to measure residual stress at the grit-filler interface. In the present investigation, a coupled thermo-mechanical three-dimensional finite element model has been developed to predict, map, and analyse the formation of residual stresses in diamond-bond-substrate systems. The presented model uniquely differs from those in literature, which are mostly 2-D type and did not consider the presence of interfacial reaction layer between diamond and filler. A Ni-Cr-Fe-B active brazing alloy has been selected as the filler and C45 steel as the substrate in the current simulation. Chromium carbide has been considered to be the interfacial compound. The numerical simulation suggests that the maximum value of residual stresses, predominantly tensile in nature, gets shifted from the diamond to the intermetallic zone at the bond level when the interfacial reaction compound is introduced between the diamond and filler. It also establishes that orientations of diamond during its placement on substrate for brazing have significant influence on the magnitude of induced residual stress. Approximately 40 % reduction has been observed in case of hexagon-base brazed diamonds when compared to that (1620 MPa) developed on square-base brazed diamonds. Raman spectral analysis of brazed specimen was conducted to experimentally validate the numerical simulation results. Residual stress was estimated from the peak shift of D-band in the spectra. The numerically computed residual stresses were found to deviate within the range of 3–15 % of the experimentally determined values.

Residual stress modeling of mitigated fused silica damage sites with CO2 laser annealing

A numerical model based on measured fictive temperature distributions is explored to evaluate the residual stress fields of CO2 laser-annealed mitigated fused silica damage sites. The proposed model extracts the residual strain from the differences in thermoelastic contraction of fused silica with different fictive temperatures from the initial frozen-in temperatures to ambient temperature. The residual stress fields of mitigated damage sites for the CO2 laser-annealed case are obtained by a finite element analysis of equilibrium equations and constitutive equations. The simulated results indicate that the proposed model can accurately evaluate the residual stress fields of laser-annealed mitigated damage sites with a complex thermal history. The calculated maximum hoop stress is in good agreement with the reported experimental result. The estimated optical retardance profiles from the calculated radial and hoop stress fields are consistent with the photoelastic measurements. These results provide sufficient evidence to demonstrate the suitability of the proposed model for describing the residual stresses of mitigated fused silica damage sites after CO2 laser annealing.

A novel correlation models for predicting stress intensity factor of semi-elliptical crack in welded pipelines under cyclic internal pressure based on Bézier base XIGA

Pipelines are strategic infrastructures that are used for energy transfer in the world. Cracks in the residual stress field are the common defects in welded pipelines. These defects with cyclic internal pressure cause crack growth and decrease the fatigue life of pipelines. In this study, a novel correlation model is proposed to predict the stress intensity factor (SIF) of the semi-elliptical crack front in welded steel pipeline subjected to cyclic internal pressure. For this purpose, the Bézier extraction base extended isogeometric method is applied for numerical analysis and preparing a database of results based on the thermo elastic-plastic equation. Taguchi standard L25 orthogonal array was used as the analysis design to create the simulations. New correlations were proposed for SIF prediction using the multivariate linear regression method. These correlations were obtained based on a parametric study that included three parameters. These parameters are dimensionless crack geometry (a/c), pipe geometry (D/t), and loading (P/Pb) or (σres/E). The R-Square (R2) values of the presented model for the welding residual stress and cyclic internal pressure were obtained as 0.989 and 0.992, respectively. The results of FEM analysis with similar conditions were compared to the results of XIGA and correlation models to validate the presented method. The maximum difference between them is approximately 3.71% for the cyclic internal pressure, and 2.94% for the welding residual stress. RMSD for the cyclic internal pressure model is 0.49, and for the welding residual stress model is 0.51. Therefore, the proposed correlation models have acceptable accuracy in predicting the SIF and fatigue crack propagation rate of the semi-elliptical crack in the steel pipes.

Welding process optimization for blast furnace shell by numerical simulation and experimental study

At cold temperatures, the stress after welding a blast furnace shell is not completely released because of the fast cooling speed, which results in cracks. To solve this problem, an integrated method combining gray relational analysis, back propagation (BP) neural network, and genetic algorithm-BP (GA-BP) was proposed in this study. Its aim was to analyze the dominant mechanism of residual stress in multi-layer and multi-pass welding process under the heating of ceramic sheet and achieve super-objective collaborative optimization of residual stress. GRA indicated that through the correlation analysis of welding parameters, residual stress, maximum temperature of characteristic point, and deformation, welding speed was determined to be an all-important factor affecting welding quality. A BP prediction model of residual stress was established. The predicted value was in good agreement with the experimental value, and the maximum error was 8.75%. The influence of each factor on the quality of welding seam is not a single, but a complex mechanism of mutual influence. GA-BP determined the combination of low level welding speed 28 mm/min, medium level welding current 210A and medium and low level welding voltage 21V as the optimal solution of low residual stress. The maximum prediction error of residual stress was 13.76%. The experimental results show that the maximum prediction error of residual stress is 4.4%, and the optimized weld has better macro and micro structure, which proves the feasibility of the multi-objective optimization method. Most importantly, the proposed method can effectively identify the optimal welding parameters, which can provide a reliable theoretical basis for engineering practice.

Effects of shot peening residual stresses on fatigue crack propagation behavior of 316L

To study the influence of shot peening residual compressive stress on the fatigue crack propagation behavior of 316L austenitic stainless steel, a three-dimensional finite element model of the compact tensile specimen based on abaqus software and an initial stress simulation model of a shot peening residual stress imported through the re-development of the SIGINI subroutine are established. The fatigue crack propagation behavior under the combined effect of the shot peening residual stress field and external cyclic loading is investigated using the extended finite element method. The results show that the crack propagation path and fatigue life obtained by the finite element method are in good agreement with the experimental results, and the error of the fatigue life is only about 4.05%. When the crack propagates into the shot peening region, the shot peening residual compressive stresses imported on the specimen surface and subsurface enhance the crack closure effect and suppress the crack propagation behavior. The impact of shot peening in the double side peened samples is higher than that in the single side peened samples. For 19 mm crack lengths, double side shot peened specimens presented a 1.2 times increase in fatigue life, compared to single side shot peened specimens (1.1 times).

Residual stress assessment for dissimilar metal welds in nuclear power plant

The European Network on Neutron Techniques Standardization for Structural Integrity (NeT) aims to develop experimental and numerical techniques and standards for the reliable characterization of residual stresses in structural welds. NeT has developed over 20 years and involves over 30 organizations including industrial, academic, and research facilities around the world. The network tackled each specific problem by creating a dedicated Task Group (TG), which undertakes both measurement and modelling studies. NeT TG8 follows on from the successful TG1 and TG4 benchmarks, which studied the dissimilar metal welds (DMW) between 18MnD5 and Alloy 52. The material properties characterization, residual stress measurements and modelling have been conducted for NeT TG8. This paper only presents the NeT TG8 benchmark residual stress measurement in the as welded condition and preliminary simulation results.

Assessment of residual stresses in welded T-joints using contour method

Welded T-joints are commonly used in manufacturing of stiffened panels or crossbeams. However, welding of web-to-flange joint induces residual stresses and distortions resulting in significant challenges during both manufacturing and service. These issues can ultimately impact the structural performance, including fatigue and stability, and lifetime of the weldment. The purpose of current paper is determining the distribution and magnitude of manufacturing-induced longitudinal residual stresses in welded T-joints. Influence of hot rolling, thermal cutting, prestressing, welding, etc. are all included using the so-called contour method. Deformed surfaces are measured using coordinate measuring machine after wire electrical discharge machining of specimens. An inverse linear elastic finite element analysis is carried out for assessing residual stresses after data smoothing. Two-dimensional longitudinal residual stress patterns are evaluated in representative cross-sections clearly indicating high stress peaks near the welds, even exceeding yield strength of the base material. In addition, longitudinal membrane residual stresses are determined based on through-thickness stresses. In addition, a simplified residual stress model, satisfying the requirement for equilibrium of internal forces and bending moments, is developed for welded T-joints with double-sided fillet welds based on contour method results.

Experiments and proposed model for residual stresses in hot-rolled wide flange shapes

This paper proposes a new residual stress model for hot-rolled wide flange steel cross sections. For this purpose, a dataset of 85 residual stress measurements is first assembled. The dataset is comprised of prior measurements available in the literature that are complemented by additional ones as part of the present study. A constrained optimization problem is then formulated by assuming parabolic residual stress distributions for both the flanges and the web of hot-rolled wide flange cross sections. The parameters of the developed residual stress model are inferred from the results of the optimization method and from rigorous statistical analyses. The results demonstrate that the cross-sectional area and the depth-to-width ratio strongly influence the residual stress distributions in the flanges and the web of a hot-rolled wide flange profile. The results suggest that there is no evidence that the yield strength of the material influences the developed residual stresses within a cross section. Contrary to available residual stress models in the literature that may be applicable for a limited range of cross-sectional geometries, the proposed model reduces the mean error between all available measurements and predictions by 60%–70%. The variance of the error is also reduced by a factor of two to four across all known cross-sectional properties.

Impact of the fabrication process on the lateral–torsional buckling of welded I-section beams

The buckling behaviour of a steel member is greatly dependent on the residual stress distribution, which is affected by the fabrication process. Indeed, residual stresses in welded steel members are significantly influenced by possible flame-cuts at the flange tips commonly used in practice. However, the Eurocode 3 rules do not account for the beneficial effects of the flame-cuts. Experimental data on commonly used slender members are limited, and therefore to gain further insight an experimental test campaign involving eight slender welded members is carried out. The influence of the flange dimensions and fabrication process was investigated. A new residual stress model is proposed for welded I-sections made of flame-cut flanges integrating results from the literature. Moreover, the actual buckling behaviour of welded members made of flame-cut flanges and/or with a cross section that is not uniform and doubly symmetric is studied. A literature overview of past experimental works highlights the lack of results on common mono-symmetric and/or tapered members, especially for welded members made of flame-cut flanges. An experimental study was thus conducted including lateral–torsional buckling tests on four beams: two uniforms and two tapered. Both types of beams comprised a doubly symmetric and a mono-symmetric I-section. The benefits resulting from tapering and/or increasing the compression flange thickness of an I-section beam are highlighted. The experimental results validate the use of a finite element model for studying the impact of the flange fabrication process on the lateral–torsional buckling resistance. Flame-cuts present at both flange ends increase the ultimate resistance.

Modeling and validation of residual stresses induced by heat treatment of AA 7075-T6 samples toward the prediction of part distortion

Residual stresses distributions induced by heat treatment of AA 7075-T6 alloy were modeled and simulated. Models of quenching followed by tempering were developed and simulated using the Finite Element Method (FEM). To determine the convection coefficients used in these models, an inverse method coupled with optimization algorithms was developed. The simulated residual stresses distributions were validated by comparing these stresses with those determined experimentally using layer removal and contour methods. The layer removal method consisting into remove successive layers of material by milling was also modeled and simulated using FEM to predict not only the residual stresses, but also part distortion. The predicted part distortion was close to that measured experimentally, which proves the hypothesis that the residual stresses induced by the layer removal method do not affect part distortion. The contour method was used to validate the residual stresses determined by layer removal, and to evaluate the effects of the temperature gradient on the residual stress distribution.