Numerical Simulation and Experimental Study of Residual Stresses in Compression Molding of Precision Glass Optical Components

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Yang Chen ◽  
Allen Y. Yi ◽  
Lijuan Su ◽  
Fritz Klocke ◽  
Guido Pongs
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
High Volume ◽  
Compression Molding ◽  
Optical Components ◽  
Shape Precision ◽  
Important Quality ◽  
Near Net Shape ◽  
Glass Lenses

Compression molding of glass optical components is a high volume near net-shape precision fabrication method. Residual stresses incurred during postmolding cooling are an important quality indicator for these components. In this research, residual stresses frozen inside molded glass lenses under different cooling conditions were investigated using both experimental approach and numerical simulation with a commercial finite element method program. In addition, optical birefringence method was also employed to verify the residual stress distribution in molded glass lenses. Specifically, optical retardations caused by the residual stresses in the glass lenses that were molded with different cooling rates were measured using a plane polariscope. The measured residual stresses of the molded glass lenses were compared with numerical simulation as a validation of the modeling approach. Furthermore, a methodology for optimizing annealing process was proposed using the residual stress simulation results.

Numerical Simulation Assisted Curve Compensation in Compression Molding of High Precision Aspherical Glass Lenses

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Fei Wang ◽  
Yang Chen ◽  
Fritz Klocke ◽  
Guido Pongs ◽  
Allen Y. Yi
Keyword(s):  
Numerical Simulation ◽  
High Volume ◽  
Compression Molding ◽  
Quality Parameter ◽  
Experimental Results ◽  
Geometrical Shape ◽  
Molding Process ◽  
Curve Change ◽  
Aspherical Lenses ◽  
Glass Lenses

Compression molding is an effective high volume and net-shape fabrication method for aspherical lenses and precision glass optical components in general. Geometrical deviation (or curve change as often referred to in industry) incurred during heating, molding, and cooling processes is a critically important manufacturing quality parameter. In the compression glass molding process, there are many factors that could lead to curve change in final products, such as thermal expansion, stress and structural relaxation, and inhomogeneous temperature distribution inside the molding machine. In this research, an integrated numerical simulation scheme was developed to predict curve change in molded glass aspherical lenses. The geometrical deviation in the final lens shape was analyzed using both an experimental approach and a numerical simulation with a finite element method program. Specifically, numerical simulation was compared with experimental results to validate the proposed manufacturing approach. The measurements showed that the difference between numerical simulation and experimental results was less than 2 μm. Based on the comparison, the mold curve was revised using numerical simulation in order to produce more accurate lens shapes. The glass lenses molded using the compensated molds showed a much better agreement with the design value than the lenses molded without compensation. It has been demonstrated in this research that numerical simulation can be used to predict the final geometrical shape of compression molded precision glass components. This research provided an opportunity for optical manufacturers to achieve a lower production cost and a shorter cycle time.

Finite Element Analyses of Residual Stresses in Typical Welded Joints Used in Nuclear Power Plants and Comparisons With Experiments

2010 ◽  
Author(s):  
Dean Deng ◽  
Kazuo Ogawa ◽  
Nobuyoshi Yanagida ◽  
Koichi Saito
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Welded Joints ◽  
Nuclear Power ◽  
Power Plants ◽  
Butt Joint ◽  
Welding Residual Stress ◽  
Dissimilar Metal ◽  
Water Reactors

Recent discoveries of stress corrosion cracking (SCC) at nickel-based metals in pressurized water reactors (PWRs) and boiling water reactors (BWRs) have raised concerns about safety and integrity of plant components. It has been recognized that welding residual stress is an important factor causing the issue of SCC in a weldment. In this study, both numerical simulation technology and experimental method were employed to investigate the characteristics of welding residual stress distribution in several typical welded joints, which are used in nuclear power plants. These joints include a thick plate butt-welded Alloy 600 joint, a dissimilar metal J-groove set-in joint and a dissimilar metal girth-butt joint. First of all, numerical simulation technology was used to predict welding residual stresses in these three joints, and the influence of heat source model on welding residual stress was examined. Meanwhile, the influence of other thermal processes such as cladding, buttering and heat treatment on the final residual stresses in the dissimilar metal girth-butt joint was also clarified. Secondly, we also measured the residual stresses in three corresponding mock-ups. Finally, the comparisons of the simulation results and the measured data have shed light on how to effectively simulate welding residual stress in these typical joints.

Welding Residual Stress's Numerical Simulation and Relieving of Guyed Mast Earplate Joint Substructure

2011 ◽  
Vol 216 ◽  
pp. 218-222 ◽  
Author(s):  
Wen Li Wang ◽  
Wei Lian Qu ◽  
Jie He
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Temperature Field ◽  
Stress Field ◽  
Residual Stresses ◽  
Welding Residual Stress ◽  
Welding Stress ◽  
Welding Temperature ◽  
Joint Properties ◽  
Guyed Mast

The dynamic stress-strain and welding residual stress during welding are the significant factors which lead to welded cracking and debasement of the joint properties. Therefore, the welding residual stresses are still very importang problems.A large number of guyed mast accidents study shows that the welded joints of earplate and shaft were easily to be destroyed. Therefore, the accurate assessment of the guyed maste earplate joint substructure’s welding residual stress is of great significance. The theory and method of simulation of the welding temperature field and welding stress field by finite element method is first introduced, and then the earplate substructure refine model is established which was up to the welding numerical simulation. Based on ANSYS software’s APDL language to apply the welding heat source load, we can get and save the welding temperature field results at each time. Conversing the thermal analysis element into structure element to finish the caculation of the welding stress field. Eventually by adopting the elimination remnant technology to remove the part of welding residual stresses, we can got the final welding residual stress in different relieving proportion.

Numerical Simulation of Residual Stresses Induced from Shot Peening with Finite Element Method

2013 ◽  
Vol 433-435 ◽  
pp. 1898-1901
Author(s):  
Li Juan Cao ◽  
Shou Ju Li ◽  
Zi Chang Shangguan
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Residual Stress ◽  
Surface Layer ◽  
Residual Stresses ◽  
Shot Peening ◽  
Target Material ◽  
Residual Stress Field ◽  
State Of Stress ◽  
Compressive Residual Stresses

Shot peening is a manufacturing process intended to give components the final shape and to introduce a compressive residual state of stress inside the material in order to increase fatigue life. The modeling and simulation of the residual stress field resulting from the shot peening process are proposed. The behaviour of the peened target material is supposed to be elastic plastic with bilinear characteristics. The results demonstrated the surface layer affected by compressive residual stresses is very thin and the peak is located on the surface.

Assessment of the Crack Compliance Method and the Introduction of Residual Stresses by Shot Peening Using the Finite Element Method

2009 ◽  
Vol 15 ◽  
pp. 109-114 ◽  
Author(s):  
G. Urriolagoitia-Sosa ◽  
E. Zaldivar-González ◽  
J.M. Sandoval Pineda ◽  
J. García-Lira
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Stress Field ◽  
Residual Stresses ◽  
Shot Peening ◽  
Working Life ◽  
The Finite Element Method ◽  
Residual Stress Field ◽  
Main Effect

The interest on the application of the shot peening process to arrest and/or delay crack growth is rising. The main effect of the shot peening technique is to introduce a residual stress field that increases the working life of mechanical components. In this paper, it is presented the numerical simulation (FEM) of the shot peening process and the effect of introducing a residual stress field. Besides, the consequence of changing the sizes of the impacting ball is analyzed. This work also used the Crack Compliance Method (CCM) for the determination of residual stresses in beams subjected to a numerical simulation of a shot peening process. The numerical results obtained provide a quantitative demonstration of the effect of shot peening on the introduction of residual stresses by using different sizes of impacting balls and assess the efficiency of the CCM.

Annealing of Compression Molded Aspherical Glass Lenses

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Bo Tao ◽  
Peng He ◽  
Lianguan Shen ◽  
Allen Yi
Keyword(s):  
Refractive Index ◽  
Residual Stresses ◽  
Aspherical Surface ◽  
Refractive Index Variation ◽  
Index Variation ◽  
Before And After ◽  
Important Quality ◽  
Glass Lens ◽  
Optical Applications ◽  
Glass Lenses

Residual stresses and refractive index of molded glass lenses are important quality indicators of their optical performance. In this research, the control of residual stresses and refractive index variation of molded glass lenses were experimentally investigated by postmolding annealing. Residual stresses were quantitatively measured using a circular polariscope. Refractive index was reconstructed and calculated by an optical setup based on Mach–Zehnder interferometer. In addition, geometry of the aspherical surface of lens was also evaluated before and after annealing. The comparison between the measured results before and after annealing showed that residual stresses and refractive index variation were well controlled and the shape of the aspherical surface was largely retained. This comprehensive experimental study demonstrated a suggestion to improve quality of the compression molded glass lens by postmolding annealing for high-precision optical applications.

scholarly journals Prediction and numerical simulation of residual stress in multi-pass pipe welds

2021 ◽  
Author(s):  
Mahmood Hasan Al-Hafadhi ◽  
Gyorgy Krallics
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Hardness Test ◽  
Element Model ◽  
Good Prediction ◽  
Two Dimensional ◽  
Residual Welding Stress ◽  
Welding Stress ◽  
Simulation Results

AbstractA numerical simulation procedure is presented to predict residual stress states in multi-pass welds in oil transportation pipes. In this paper, a two-dimensional thermo-mechanical finite element model is used to calculate the temperature distribution, hardness, and the distribution of residual stresses during multi-pass welding of pipes of dissimilar metals and varying thicknesses. In this model, the temperature dependence of the thermal and mechanical properties of the material was considered. The present model was validated using the hardness measurement. Good agreement was found between the measurement and the numerical simulation results. The simulated result shows that the two-dimensional model can be effectively used to simulate the hardness test and predict the residual stress in the pipe weld. The simulation results and measurements suggest that the model with moving heat source can obtain a good prediction of residual welding stress. Both the two-dimensional and the three-dimensional modeling can be used to estimate the residual stresses in different weld regions and help saving time.

scholarly journals Evaluation of the Impact of Residual Stresses in Crack Initiation with the Application of the Crack Compliance Method Part I, Numerical Analysis

2010 ◽  
Vol 24-25 ◽  
pp. 253-259 ◽  
Author(s):  
G. Urriolagoitia-Sosa ◽  
B. Romero-Ángeles ◽  
Luis Héctor Hernández-Gómez ◽  
G. Urriolagoitia-Calderón ◽  
Juan Alfonso Beltrán-Fernández ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Numerical Analysis ◽  
Stress Field ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Main Concern ◽  
Residual Stress Field ◽  
Set Up ◽  
The Impact

The understanding of how materials fail is still today a fundamental research problem for scientist and engineers. The main concern is the assessment of the necessary conditions to propagate a crack that will eventually lead to failure. Nevertheless, this kind of analysis tends to be more complicated, when a prior history in the material is taken into consideration and it will be extremely important to recognize all the factors involved in this process. In this work, a numerical simulation of the introduction of residual stresses, which change the crack initiation conditions, in a modified compact tensile specimen to change the condition of crack initiation is presented. Four numerical analyses were carried out; an initial evaluation was performed in a specimen without a crack and it was used for the estimation of a residual stress field produced by an overload; three more cases were simulated and a crack was introduced in each specimen (1 mm, 5 mm and 10 mm, respectively). The overload was then applied to set up a residual stress field into the component; furthermore, in each case the crack compliance method (CCM) was applied to measure the induced residual stress field. By performing this numerical simulation, the accuracy of the crack compliance method can be evaluated. On the other hand, elastic-plastic finite element analysis was utilized for the residual stress estimation. The numerical analysis was based on the mechanical properties of a biocompatible material (AISI 316L). The obtained results provided significant data about diverse factors, like; the manner in which a residual stress field could modify the crack initiation conditions, the convenient set up for induction of a beneficial residual stresses field, as well as useful information that can be applied for the experimental implementation of this research.

Numerical Modelling of Repair Welding Using a Temper Bead Process: Application to Dissimilar Metal Welds

2011 ◽  
Author(s):  
Florence Gommez ◽  
Vincent Robin ◽  
Denis Pont ◽  
Stephan Courtin
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Residual Stresses ◽  
Heat Affected Zone ◽  
Stress Measurement ◽  
Hole Drilling ◽  
Narrow Gap ◽  
Viscous Effects ◽  
Pressurized Water ◽  
Dissimilar Metal

For nuclear reactor applications, AREVA NP has to perform junctions between ferritic low alloy steel heavy section components and austenitic stainless steel piping systems. For Gas Tungsten Arc Welding (GTAW) of dissimilar metal weld (DMW) narrow gap, AREVA NP has developed special manufacturing procedures guaranteeing high quality standards and resistance in service. Since a decade, AREVA NP is developing the numerical simulation of welding to have a better understanding of involved physical phenomena and to predict residual stresses. In spite of the large thickness of Pressurized Water Reactor (PWR) components, the distortion issue may also be important. Narrow gap welding requires indeed a close control of the groove width. This paper presents numerical simulations performed by AREVA NP on 14″ narrow gap DMW mock-ups as part of a research project carried out internally. The simulations focus on the predictions of microstructure and residual stress distribution. The analysis simulates the main steps of the mock-up manufacturing procedure. Multi pass welding simulation reproduces the deposit of each bead by thermo-metallurgical and mechanical calculations. A special attention has been paid on the buttering of the ferritic side. Generally a post weld heat treatment (PWHT) is carried out after the buttering of the ferritic side in order to relieve residual stresses. For some repair operations, a PWHT is not feasible. Thus a temper bead process can be used. During this process, a large part of the previous heat affected zone is tempered to guarantee a limited hardness and to reduce the risk of cold cracking. The results in terms of microstructure and stress obtained with the two techniques are compared. With the temper bead process, the final level of hoop stresses in the heat affected zone (HAZ) of the buttering remains significant as stresses are not relieved by viscous effects implied during PWHT. Nevertheless the temper bead process has a positive effect on the material hardness as the proportion of tempered phase is higher. One of the objectives of this task is to compare the numerical results with measurements. This comparison is not only a validation of numerical simulation of welding but also a way to investigate the relevance of residual stress measurement by Deep Hole Drilling (DHD). Calculated stresses are globally in good agreement with measurements made by DHD. A comparison with axial shrinkage is also made for validation of the modelling methodology.

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