Numerical Study of Welding Residual Stresses in Blisk Repairs by Patching

2020 ◽  
Author(s):  
Ricarda Berger ◽  
Benedikt Hofmeister ◽  
Cristian G. Gebhardt ◽  
Raimund Rolfes
Keyword(s):  
Residual Stresses ◽  
Numerical Study ◽  
Welding Process ◽  
Element Model ◽  
Parent Material ◽  
Heat Transfer Analysis ◽  
High Tech ◽  
Compressor Blades ◽  
Repair Procedure ◽  
Patch Repairs

Abstract Patching is a high-tech repair procedure that is very adequate for compressor blisks with larger damages. This repair concept has the advantage that the added patch provides the same mechanical strength as the parent material of the blade and the initial aerodynamic contour of the blade is fully restored. However, the welding process locally induces stresses in the heat affected zone at the patch-to-blisk interface. These welding residual stresses influence the fatigue life of the repaired blade and have to be considered during the design phase of patch repairs. In this work, we contribute to the design of patch repairs by introducing a numerical simulation to predict weld-induced stresses in repaired compressor blades. Therefore, a finite element model is developed that includes sequential thermal and mechanical analyses of blisk blades. The temperature field caused by the welding torch is determined by performing a transient heat transfer analysis. The model also reflects the changes in the geometry due to the additional patch material and subsequent re-contoured patch. Different patch geometries are evaluated and compared in terms of their resulting stress levels. Basically, two kinds of patch geometries with long and short welding seams are studied. The stationary stress distribution of the repaired blade results from the superposition of residual stresses with steady stresses due to rotational and pressure forces. Thus, we provide the basis for a new fatigue assessment of the repaired blade considering the residual stress level in the patch-to-blisk interface.

Numerical Modeling of AA2024-T3 Friction Stir Welding Process for Residual Stress Evaluation, Including Softening Effects

2014 ◽  
Vol 611-612 ◽  
pp. 1675-1682 ◽  
Author(s):  
Mads Rostgaard Sonne ◽  
Pierpaolo Carlone ◽  
Gaetano S. Palazzo ◽  
Jesper Henri Hattel
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Welding Process ◽  
Element Model ◽  
Transverse Cross Section ◽  
Heat Transfer Analysis ◽  
Contour Method ◽  
Friction Stir ◽  
Longitudinal Residual Stress ◽  
Numerical Finite Element

In the present paper, a numerical finite element model of the precipitation hardenable AA2024-T3 aluminum alloy, consisting of a heat transfer analysis based on the Thermal Pseudo Mechanical model for heat generation, and a sequentially coupled quasi-static stress analysis is proposed. Metallurgical softening of the material is properly considered and included in the calculations by means of the Myhr and Grong model, implemented as a user subroutine in ABAQUS. Numerical outcomes are compared with experimental results, highlighting the intriguing predictive capabilities of the model for both temperatures and residual stresses. The contour method is employed to map the longitudinal residual stress distribution on a transverse cross section of the joint. The influence of the applied boundary conditions and of the release of the clamping system on residual stresses is also assessed.

Evaluation by FEM of the Influence of the Preheating and Post-Heating Treatments on Residual Stresses in Welding

2014 ◽  
Vol 627 ◽  
pp. 93-96 ◽  
Author(s):  
Raffaele Sepe ◽  
Enrico Armentani ◽  
Giuseppe Lamanna ◽  
Francesco Caputo
Keyword(s):  
Temperature Distribution ◽  
Residual Stresses ◽  
Gas Metal Arc Welding ◽  
Welding Process ◽  
Element Model ◽  
Butt Joint ◽  
Temperature Fields ◽  
Heating Process ◽  
Butt Weld ◽  
Metal Arc Welding

During the last few years various experimental destructive and non-destructive methods were developed to evaluate residual stresses. However it is impossible to obtain a full residual stress distribution in welded structures by means of experimental methods. This disadvantage can be solved by means of computational analysis which allows to determine the whole stress and strain fields in complex structures. In this paper the temperature distribution and residual stresses were determined in a single-pass butt joint welded by GMAW (Gas Metal Arc Welding) process by finite element model (FEM). A 3D finite parametric element model has been carried out to analyze temperature distribution in butt weld joints and thermo-mechanical analyses were performed to evaluate resulting residual stresses. Temperature fields have been investigated by varying an initial preheating treatment. Moreover the technique of “element birth and death” was adopted to simulate the process of filler metal addition The high stresses were evaluated, with particular regard to fusion zone and heat affected zone. The influence of preheating and post-heating treatment on residual stresses was investigated. The residual stresses decrease when preheating temperature increases. The maximum value of longitudinal residual stresses without pre-heating can be reduced about 12% and 38% by using the preheating and post-heating process respectively.

Numerical Study of the Tool Rake Angle Effect on the Material Flow in Friction Stir Welding Process

2007 ◽  
Author(s):  
Hosein Atharifar ◽  
Radovan Kovacevic
Keyword(s):  
Friction Stir Welding ◽  
Material Flow ◽  
Numerical Study ◽  
Welding Process ◽  
Rake Angle ◽  
Heat Transfer Analysis ◽  
Tool Geometry ◽  
Friction Stir ◽  
Tool Pin ◽  
Welding Processes

Minimizing consumed energy in friction stir welding (FSW) is one of the prominent considerations in the process development. Modifications of the FSW tool geometry might be categorized as the initial attempt to achieve a minimum FSW effort. Advanced tool pin and shoulder features as well as a low-conductive backing plate, high-conductive FSW tools equipped with cooling fins, and single or multi-step welding processes are all carried out to achieve a flawless weld with reduced welding effort. The outcomes of these attempts are considerable, primarily when the tool pin traditional designs are replaced with threaded, Trifiute or Trivex geometries. Nevertheless, the problem remains as to how an inclined tool affects the material flow characteristics and the loads applied to the tool. It is experimentally proven that a positive rake angle facilitates the traverse motion of the FSW tool; however, few computational evidences were provided. In this study, numerical material flow and heat transfer analysis are carried out for the presumed tool rake angle ranging from −4° to 4°. Afterwards, the effects of the tool rake angle to the dynamic pressure distribution, strain-rates, and velocity profiles are numerically computed. Furthermore, coefficients of drag, lift, and side force and moment applied to the tool from the visco-plastic material region are computed for each of the tool rake angles. Eventually, this paper confirms that the rake angle dramatically affects the magnitude of the loads applied to the FSW tool, and the developed advanced numerical model might be used to find optimum tool rake angle for other aluminum alloys.

Residual Stresses in Butt Welding of Two Circular Pipes: An Experimental and Numerical Investigation

2014 ◽  
Author(s):  
Gurinder Singh Brar
Keyword(s):  
Finite Element Method ◽  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Finite Element Model ◽  
Welding Process ◽  
Diffraction Method ◽  
Element Model ◽  
X Ray Diffraction ◽  
X Ray

Welding is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Welding is carried out with a very complex thermal cycle which results in irreversible elastic-plastic deformation and residual stresses in and around fusion zone and heat affected zone (HAZ). A residual stress due to welding arises from the differential heating of the plates due to the weld heat source. Residual stresses may be an advantage or disadvantage in structural components depending on their nature and magnitude. The beneficial effect of these compressive stresses have been widely used in industry as these are believed to increase fatigue strength of the component and reduce stress corrosion cracking and brittle fracture. But due to the presence of residual stresses in and around the weld zone the strength and life of the component is also reduced. To understand the behavior of residual stresses, two 10 mm thick Fe410WC mild steel plates are butt welded using the Metal Active Gas (MAG) process. An experimental method (X-ray diffraction) and numerical analysis (finite element analysis) were then carried out to calculate the residual stress values in the welded plates. Three types of V-butt weld joint — two-pass, three-pass and four-pass were considered in this study. In multi-pass welding operation the residual stress pattern developed in the material changes with each weld pass. In X-ray diffraction method, the residual stresses were derived from the elastic strain measurements using a Young’s modulus value of 210 GPa and Poisson’s ratio of 0.3. Finite element method based, SolidWorks software was used to develop coupled thermal-mechanical three dimension finite element model. The finite element model was evaluated for the transient temperatures and residual stresses during welding. Also variations of the physical and mechanical properties of material with the temperature were taken into account. The numerical results for peak transverse residual stresses attained in the welded plates for two-pass, three-pass and four-pass welded joint were 67.7 N/mm2, 58.6 N/mm2, and 48.1 N/mm2 respectively. The peak temperature attained during welding process comes out to be 970°C for two-pass weld, 820.8°C for three-pass weld and 651.9°C for four-pass weld. It can be concluded that due to increase in the number of passes during welding process or deposition weld beads, the residual stresses and temperature distribution decrease. Also, the results obtained by finite element method agree well with those from experimental X-ray diffraction method.

Numerical Study of Welding with Trailing Heat Sink Considering Phase Transformation Effects

2014 ◽  
Vol 875-877 ◽  
pp. 2118-2122
Author(s):  
Shirish R. Kala ◽  
N. Siva Prasad ◽  
G. Phanikumar
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Material Properties ◽  
Heat Sink ◽  
Numerical Study ◽  
Gaussian Model ◽  
Welding Process ◽  
Source Model ◽  
Element Analysis

Welding process with trailing heat sink for 2 mm mild steel plates has been analyzed to estimate distortion and residual stresses using a finite element modeling software Sysweld. The material properties used for the analysis are both temperature dependent and phase dependent. A transient thermal analysis is carried out using Goldak double ellipsoidal heat source model and heat sink as Gaussian model with negative heat flux. The finite element analysis (FEA) is conducted by considering the material properties of all phases of steel as well as without phase transformation i.e. by considering properties of only ferrite phase. Temperature distribution, distortion and residual stresses are calculated and compared for four cases: without phase without cooling, without phase with cooling, with phase without cooling and with phase with cooling. It is found that FEA without phase transformation effects overestimates the residual stresses in the fusion zone (FZ) and heat affected zone (HAZ). It is also found that a trailing heat sink reduces transverse compressive residual stresses thus minimizing the possibilities of buckling.

Residual Stresses in Dissimilar Friction Stir Welding of AA2024 and AZ31: Experimental and Numerical Study

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Z. Hou ◽  
J. Sheikh-Ahmad ◽  
F. Jarrar ◽  
F. Ozturk
Keyword(s):  
Friction Stir Welding ◽  
Residual Stresses ◽  
Numerical Study ◽  
Stress Component ◽  
Weld Zone ◽  
Element Model ◽  
Maximum Temperature ◽  
Friction Stir ◽  
Tool Offset ◽  
Dissimilar Friction Stir Welding

Thermal history and residual stresses in dissimilar friction stir welding (FSW) of AA2024 and AZ31 were studied under different tool offsets using a coupled Eulerian–Lagrangian (CEL) finite element model and a mechanical model. Welding experiments and residual stresses' measurements were conducted to validate the models. Comparisons between the experimental and numerical results indicated good agreement. The maximum temperature in the welded zone was predicted to be slightly lower than 400 °C, regardless of offset, and that its location shifted with tool offset from the advancing side (AS) to the retreating side (RS). Longitudinal residual stresses changed from tensile under the tool shoulder to compressive beyond this region and it appeared to be the dominant stress component. The transverse stresses were tensile and of lower magnitude. Both the longitudinal and transverse residual stresses have their maximum values within the weld zone near the end of the weld length. For both peak temperatures and residual stresses, higher values were obtained at the AS with no tool offset and 1 mm offset to the AS, and at the RS with 1 mm offset to the RS. Lower residual stresses and better weld quality were obtained with tool offset to the aluminum side.

A Numerical Study on Mock-Up Downsizing to Predict Residual Stresses at CRDM Welds

2010 ◽  
Author(s):  
Ik-Joong Kim ◽  
Jae-Uk Jeong ◽  
Jae-Boong Choi ◽  
Young-Jin Kim ◽  
Sung-Woo Kim ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Nuclear Power ◽  
Power Plants ◽  
Numerical Study ◽  
Welding Process ◽  
Piping System ◽  
Experimental Conditions ◽  
Control Rod ◽  
Set Up

Since several defects caused by PWSCC (Primary Water Stress Corrosion Cracking) have been observed at the piping system of nuclear power plants, during the last two decades, lots of analytical and experimental researches have been performed to find out the relationship between the residual stress and PWSCC initiations. The present research deals with prediction of the residual stress at welding parts of CRDM (Control Rod Drive Mechanism). Especially, numerical investigations are carried out to support relevant experimental set-up because it is not easy to prepare large-sized mock-ups comparable to real geometry. First, preliminary examination was performed to establish an optimized welding process simulation procedure to accurately predict weld residual stresses. Then, detailed parametric FE analyses were carried out to examine effects of varying geometries and experimental conditions. Key findings were obtained from the FE analyses, which were used for finalizing the configuration of mock-up, are fully discussed in this manuscript.

Analysis of Arc Welded Thin-Walled Cylinders to Investigate the Effects of Welding Process Parameters on Residual Stresses

2008 ◽  
Vol 575-578 ◽  
pp. 763-768
Author(s):  
Afzaal M. Malik ◽  
Ejaz M. Qureshi ◽  
Naeem Ullah Dar
Keyword(s):  
Residual Stresses ◽  
Process Parameters ◽  
Arc Welding ◽  
Research Work ◽  
Three Dimensional ◽  
Welding Process ◽  
Welding Current ◽  
Element Model ◽  
Welding Parameters ◽  
Thin Walled

The research work presents a computational methodology based on three-dimensional finite element model to simulate the gas tungsten arc welding (GTAW) of thin-walled cylinders. The aim was to study the effects of two basic welding parameters (welding speed and welding current) on weld induced residual stresses. The complex phenomenon of arc welding was numerically solved by sequentially coupled transient, non-linear thermo-mechanical analysis. The accuracy of the numerical model was validated through experiments for temperature distribution and residual stresses. The results reveals that the present simulation strategy can be used as a proper tool to get the optimized welding process parameters and minimize the in service failures of thinwalled structures due to residual stresses.

Application of SPH for Modelling Heat Transfer and Residual Stress Generation in Arc Welding

2010 ◽  
Vol 654-656 ◽  
pp. 2751-2754 ◽  
Author(s):  
Raj Das ◽  
Paul W. Cleary
Keyword(s):  
Heat Transfer ◽  
Arc Welding ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Welding Process ◽  
Parent Material ◽  
Stress Generation ◽  
Heat Transfer Analysis ◽  
Structural Behaviour ◽  
Mechanical Responses

An approach for three-dimensional modelling of thermo-mechanical responses in an arc welding process is developed using the Smoothed Particle Hydrodynamics (SPH) method. It is demonstrated for a simple arc welding configuration by solving the fully coupled three-dimensional elastoplastic and heat transfer analysis. The temperature distribution of the metal in the weld pool and the surrounding parent material are analysed using SPH, and the resulting residual thermal stresses are evaluated. This work establishes the capability of SPH as a tool for simulating the long-term thermo-mechanical responses, including heat transfer and residual stresses in a welded joint, and gaining insights into post-welding structural behaviour of joints during cooling stages.

Effect of welding residual stresses on local behavior of rectangular hollow section joints/Einfluss der Schweißeigenspannungen auf die Tragfähigkeit von Rechteck-Hohlprofil-KnotenTeil 1: Entwicklung eines numerischen Modells

Bauingenieur ◽  
2018 ◽  
Vol 93 (04) ◽  
pp. 152-159 ◽  
Author(s):  
M. Garifullin ◽  
B. Launert ◽  
M. Heinisuo ◽  
H. Pasternak ◽  
K. Mela ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Structural Engineering ◽  
Experimental Studies ◽  
Welding Process ◽  
Element Model ◽  
Structural Behavior ◽  
Initial Stiffness ◽  
Hollow Section ◽  
Tubular Joints ◽  
Thermomechanical Simulation

Welded tubular joints are widely used in structural engineering due to their excellent resistance and stiffness in contrast to open sections, as well as simpler end preparation. Welding residual stresses that occur in these joints after the welding process can affect their structural behavior. Some recent experimental studies have shown that this effect can be considerable. This study numerically evaluates the influence of welding residual stresses on the behavior of rectangular hollow section T joints. The paper consists of two parts. Part I develops and validates a finite element model for the joints directly taking into account welding residual stresses by means of an upstream thermomechanical simulation of the welding process. It is proven that particular attention needs to be paid to the discretization of the model, the material properties and the adequate description of the weld heat input. The validation with experimental results shows that the developed numerical model properly captures the local structural behavior of tubular joints and can be efficiently used for further investigations. Part II employs the constructed model to investigate the effect of welding residual stresses on the resistance and initial stiffness of the considered joints.

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