Local temperature fields varying over the thickness for relaxing residual stresses in nonhomogeneous cylindrical shells

1975 ◽  
Vol 9 (2) ◽  
pp. 189-192
Author(s):  
Ya. I. Burak ◽  
L. P. Besedina
Keyword(s):  
Residual Stresses ◽  
Cylindrical Shells ◽  
Temperature Fields ◽  
Local Temperature

Finite Element Simulation of Laser Beam Welding Induced Residual Stresses and Distortions in a T-Joint Configuration for Aeronautic Structures

2009 ◽  
Author(s):  
Muhammad Zain-ul-abdein ◽  
Daniel Ne´lias ◽  
Jean-Franc¸ois Jullien ◽  
Dominique Deloison
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Laser Beam ◽  
Boundary Conditions ◽  
Laser Beam Welding ◽  
Temperature Fields ◽  
Heat Transfer Analysis ◽  
Small Scale ◽  
Joint Configuration ◽  
Simulation Results

Laser beam welding has found its application in the aircraft industry for the fabrication of fuselage panels in a T-joint configuration. However, the inconveniences like distortions and residual stresses are inevitable consequences of welding. The effort is made in this work to experimentally measure and numerically simulate the distortions induced by laser beam welding of a T-joint with industrially used thermal and mechanical boundary conditions on the thin sheets of aluminium 6056-T4. Several small scale experiments were carried out with various instrumentations to establish a database necessary to verify the simulation results. Finite element (FE) simulation is performed with Abaqus and the conical heat source is programmed in FORTRAN. Heat transfer analysis is performed to achieve the required weld pool geometry and temperature fields. Mechanical analysis is then performed with industrial loading and boundary conditions so as to predict the distortion and the residual stress pattern. A good agreement is found amongst the experimental and simulation results.

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.

scholarly journals A Semianalytical Model for the Determination of Bistability and Curvature of Metallic Cylindrical Shells

2019 ◽  
Vol 3 (1) ◽  
pp. 22
Author(s):  
Pavlo Pavliuchenko ◽  
Marco Teller ◽  
Markus Grüber ◽  
Gerhard Hirt
Keyword(s):  
Residual Stresses ◽  
Shell Thickness ◽  
Cylindrical Shells ◽  
Model Verification ◽  
Experimental Results ◽  
Steel Shell ◽  
Diffraction Measurement ◽  
Stable States ◽  
Forming Process ◽  
Specific Distribution

Bistable metal shells with a fully closed unfolded geometry are of great interest as lightweight construction parts which could be transported without housing and unfolded at the construction place. In order to achieve the effect of bistability in metallic shells, residual stresses with a specific distribution along the shell thickness are necessary. These residual stresses can be introduced in bending processes. The tools with specific bending radii are used to influence the curvature of the shell in the different stable states and thus determine whether a completely closed profile can be achieved. In addition to the forming process, the shell thickness and the shell material have an effect on the achievable geometries and stability. In order to manufacture bistable metallic cylindrical shells from different materials and shell thicknesses, it is necessary to be able to determine a promising process sequence and corresponding bending radii in advance. For this reason, this article presents a semianalytical model for the calculation of bistability and final curvatures. This model is applied to an incremental die-bending process using two bending operations with bending radii of 6 to 12 mm and a 0.2 mm thick steel shell of grade 1.1274 (AISI 1095). The calculation results show that bistability cannot be reached for all combinations of the two bending radii. Moreover, the model indicates that a bistable and fully closed shell is only achieved for a bending radii combination of R1 = 6 mm and R2 = 6 mm. With the aim of model verification, experiments with a closed-die incremental bending tool were performed. Calculated and experimental results show good correlation regarding bistability and curvature. In addition, X-ray diffraction measurement of the residual stresses shows a good qualitative agreement regarding the calculated and experimental results.

Reconstructing the surface temperature fields of the Last Glacial Maximum and mid-Pliocene Warm Period using climate models and data.

2021 ◽  
Author(s):  
James Annan ◽  
Julia Hargreaves ◽  
Thorsten Mauritsen
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Warm Period ◽  
Temperature Fields ◽  
Local Temperature ◽  
Model Simulations ◽  
Last Glacial ◽  
Wide Range ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>We present new reconstructions of global climatological temperature fields for the Last Glacial Maximum and the mid-Pliocene Warm Period.</p><p>The method is based on an Ensemble Kalman Smoother which combines globally complete modelled temperature fields, with sparse proxy-based estimates of local temperature anomalies. This ensures spatially coherent fields which respect physical principles and which are also tied closely to observational estimates. </p><p>For the Last Glacial Maximum, we use the full set of PMIP2/3/4 model simulations, and we combine this with a wide range of proxy-based SST and SAT estimates of local temperature to ensure the best possible global coverage. Our reconstruction has a global mean surface air temperature anomaly of -5.3 +- 0.9C relative to the pre-industrial climate, and thus lies roughly half-way between the estimates of Annan and Hargreaves (2013) and Tierney et al (2020). We examine the reasons for these differences and discuss their implications.</p><p>For the mid-Pliocene Warm Period, we use the PlioMIP 1 and 2 model simulations and the PRISM proxy estimates for the 3.2 Ma time slice. These data are considerably more sparse and uncertain than for the LGM and our reconstruction is correspondingly more uncertain. We obtain an estimate of 5.6 +- 1.6C which is considerably warmer than most previous estimates, suggesting a significant discrepancy between the models and the data. We investigate the reasons for this and discuss the implications.</p>

Experimental and Computational Flow and Temperature Fields in a Heat Exchanger Crystallizer Geometry for Validation and Implementation of a Novel Process Sensor

2010 ◽  
Author(s):  
Marcos R. Pascual ◽  
Herman J. M. Kramer
Keyword(s):  
Heat Exchanger ◽  
Liquid Crystals ◽  
Temperature Distribution ◽  
Flow Field ◽  
Computational Simulation ◽  
Temperature Fields ◽  
Local Temperature ◽  
Hydrodynamic Characteristics ◽  
Strong Impact ◽  
Monitoring And Control

During crystallization processes the control and effective distribution of heat transfer from the heat exchanger to the solution plays an important role. The turbulent flow field and the temperature variations in the solution determine the local supersaturation profiles and the spatial particle distribution. Thus they have a strong impact on the final product quality, production capacity and efficiency of the process. In this sense, a sensor able to determine in situ the local process variables to get better insight in the process behavior, would be required. The recently proposed Smart moving Process Environment Actuators and Sensors (Smart PEAS) is a promising initiative to achieve a more efficient process control. In this PEAS system a network of floating sensors is integrated using Ultra Wide Band (UWB) wireless technology to form a monitoring and control system. As a first phase in the development of the Smart PEAS, the research is focused on the accurate measurements of the flow field and local temperature distribution in a reactor. The hydrodynamics of the Smart PEAS are very important to achieve the necessary accurate process information. In order to determine the hydrodynamic characteristics of the Smart PEAS and to validate and compare the obtained results, laternative non intrusive techniques are used to investigate them in this work. Microencapsulated liquid crystals are used as a measurement technique to study the local temperature and flow field in a heat exchanger crystallizer geometry. To measure the 3D flow and temperature fields the microencapsulated liquid crystals are recorded in a sheet of light plane inside the crystallizer by two digital color cameras in a stereoscopic position. The images of the liquid crystals are correlated to obtain the three velocity components (3C), while from the colors of the microencapsulated liquid crystals the local temperature can be deduced after appropriate calibration. Parallel experiments are done to investigate the three dimensional trajectories of different sensor geometries in the equipment by direct visualization of the sensors. Computational fluid dynamics simulations are performed to calculate the flow field, temperature distribution and sensor trajectories. The results are compared with the experimental results for validation. The validation of the computational simulation results with the experiments gave the necessary confidence to predict flow fields in new crystallizer designs. On the basis of the analysis the Smart PEAS sensor design and the reliability of the measurements obtained can be compared and implemented.

Finite-Element Simulation of Temperature Fields and Residual Stresses in Butt Welded Joints and Comparison With Experimental Measurements

2014 ◽  
Author(s):  
Enrico Armentani ◽  
Angela Pozzi ◽  
Raffaele Sepe
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Base Plate ◽  
Element Model ◽  
Temperature Fields ◽  
Structural Members ◽  
Temperature Dependent ◽  
Welding Temperature ◽  
Element Simulation ◽  
Surrounding Areas

Welding is used in fabrication of structures ranging from small components to large and important structures. One of the important problems associated with welded structures is development of residual stresses and deformations due to welding temperature. In fact when structures are manufactured by welding, a non-uniform temperature distribution is produced. This distribution initially causes a rapid thermal expansion followed by a thermal contraction in the weld and surrounding areas, thus generating inhomogeneous plastic deformation and residual stresses in the weldment when it is cooled. High residual stresses in regions close to the weld may promote brittle fracture, fatigue, or stress corrosion cracking. Meanwhile, distortion in base plate may reduce the buckling strength of structural members. Therefore estimating the magnitude and distribution of welding residual stresses and distortion are necessary for achieving the safest design. In the present work an elastic-plastic finite element model considering temperature dependent mechanical properties is used to evaluate residual stresses. In this study a parametric model is adopted and the elements birth and death are used in single-pass butt welded joint to simulate the weld filler variation with time. Then numerical results are compared with experimental data.

scholarly journals Additive Manufacturing of Complex Components through 3D Plasma Metal Deposition—A Simulative Approach

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 574 ◽  
Author(s):  
Khaled Alaluss ◽  
Peter Mayr
Keyword(s):  
Temperature Field ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Field Distribution ◽  
Base Material ◽  
Metal Deposition ◽  
Temperature Fields ◽  
Experimental Investigations ◽  
Temperature Field Distribution ◽  
Elastic Plastic

This study examines simulative experimental investigations on the additive manufacturing of complex component geometries using 3D plasma metal deposition (3DPMD). Here, complex contour surfaces for a cross-rolling tool were produced from weld metals in multilayer technology through 3DPMD. As a consequence of the special features of 3DPMD with large-weld metal volumes, greatly differing properties between base material/deposited material and asymmetrical heat input, the resulting shrinkage, deformation and residual stresses are particularly critical. These lead to dimensional and form deviations as well as the formation of cracks, which has a negative influence on the quality of the plasma deposition-welded component structures. By means of the thermo-elastic-plastic simulation model, the temperature field distribution, deformation, and residual stresses occurring during additive 3DPMD of tool contours were predicted and analyzed. The temperature field distribution and its gradients were determined using the ellipsoid heat-source model for the 3DPMD process. On this basis, a coupled thermo-elastic-plastic structural–mechanical analysis was performed. Accordingly, the results achieved were used for the production of almost-net-shaped tool contour surfaces with predefined layer properties. The acquired simulation results of the temperature fields, deformation, and residual stress condition show good alignment with the experimental results.

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