Thermal Elastic Analysis Research Articles

Hybrid Finite Element Method Based on Polygon-Quadtree Meshes for Heat Transfer and Thermal Elastic Analysis

Hybrid Finite Element Method Based on Polygon-Quadtree Meshes for Heat Transfer and Thermal Elastic Analysis

Three-dimensional thermoelastic analysis of orthotropic laminated cylindrical shells subjected to uniformly localized thermal boundary conditions

Accurate evaluation of three-dimensional (3D) thermal-elastic analysis of laminated cylindrical shells under different loads has a significant impact on their safety design. In this study, we present a 3D thermoelastic solution of laminated orthotropic cylindrical shells subjected to uniformly localized thermal boundary conditions. For a homogeneous orthotropic layer, a thinning layer approach is introduced to deal with the heat conduction equation and the elastic equation. Based on the eigenequation method and pseudo-Stroh formalism, general solutions for physical quantities of a homogeneous layer are derived. The propagator matrix method is used to deal with multilayered media. A closed form solution for the laminated cylindrical shells is obtained. A numerical example of a 3-layered cylindrical shell subjected to convective heat transfer boundary conditions is presented to verify the solutions’ correctness. An excellent convergence of the current approach is found and the physical quantities predicted by the current method agree well with the numerical results by the finite element method. Finally, the numerical solutions of a 3-layered orthotropic cylindrical shell subjected to uniformly localized thermal boundary conditions are obtained by the current method. The closed form solution presented in this article can be used for 3D thermoelastic analysis of laminated cylindrical shells under complex boundary conditions.

Thermal-elastic analysis of laminated plates based on the incompatible generalized partial mixed method

Based on the generalized Hellinger-Reissner (H-R) mixed variational principle, the incompatible generalized partial mixed finite element method (IGPMFEM) is proposed in this paper for the thermomechanical stress analysis of laminated composites and sandwich plates. This method inherits the advantages of the generalized mixed element method, allowing for the simultaneous introduction of displacement and stress boundary conditions, and satisfies the discontinuity of the in-plane stresses at the material interface. Introduction of incompatible displacement mode adds higher-order terms in the polynomial expansion of the exact displacements, effectively improving the bending performance and the element accuracy. Although adding stress components would normally increase the computational effort, we address this issue by the elimination method, considering only the out-of-plane stress variables to reduce the matrix dimensions. The accuracy and effectiveness of the proposed method are evaluated by comparing the numerical results of this method with existing elasticity solutions, while the effect of stress boundary conditions is also investigated.

Study on welding crack sensitivity assessment method based on thermal elastic plastic finite element analysis

This study presents a new welding crack sensitivity assessment method with the equivalent plastic strain increment as an indicator, and the reliability is verified by comparing the computed results and experimental results of bead-on-plate joint under different welding conditions. Then the proposed method is applied to assess the welding crack sensitivity of multi-pass joints in the bridge rehabilitation engineering. The results show that the equivalent plastic strain increment increases with increasing heat input and constraint degree, and decreases with increasing preheat temperature. The equivalent plastic strain increment can be used as an indicator for assessing welding crack sensitivity assessment of joints. With regard to multi-pass welded joints, the welding crack sensitivity decreases with the increase of number of weld passes in terms of equivalent plastic strain increment. The welding crack sensitivity assessment method proposed in this study is reliable and can provide a practical tool for assessing the performance of welded joints.

Aero-thermal-elastic Coupled Simulations of An Air-cooled Turbine with an FDM solver

The aero-thermal-elastic coupled simulations of an air-cooled turbine vane were carried out by a developed coupled solver, HIT3D, employing the finite difference method. The pressure on the vane surface and the temperature in the solid vane were obtained by the coupled heat transfer simulation, then the single-way aero-elastic and thermal-elastic analysis on the turbine vane were performed. It shows that the predicted profile temperature employing the transition model agrees well with the measured one, the blade deformation caused by aerodynamic force is negligible, and that the greater thermal deformation and thermal stress locate at the blade leading edge pressure side and at the blade trailing edge, as the result of the strong temperature gradient and the constraint at the vane endwalls.

On the Simulation of 3D Printing Process by a Novel Meshless Analysis Procedure

ABSTRACTTo evaluate the thermal deformation induced by 3D Printing (Three Dimensional Printing) process, a novel meshless analysis procedure is established. To account for the heat transfer and solidification effects of each printing layer from liquid to solid phase transition, the layer temperature is measured by the implanted thermocouples. Based on the temperature variation measured, the printing layer temperature can be averaged and considered as uniform for thermal analysis. In addition, as observed by the deformation of the printed target through experiment, only linear thermal elastic analysis is performed.A rigorous algorithm for simulating the 3D Printing process is presented herein. Since the interpolation functions are no longer polynomials, a simple integration scheme using uniform integration points is applied to calculate the global stiffness matrix. Thus, the density and location of the integration points can be easily adjusted to fulfill the required accuracy. Further, for practical implementation, the simulation is also carried out by the concept of equivalent layer.Demonstrative cases of printing a rectangular PLA (Polylactic Acid) brick are tackled to prove the accuracy and efficiency of the proposed meshless analysis procedure. The effects of layer thickness, equivalent layer and slenderness ratio on the thermal deformation of the printed brick are also investigated.

Thermal shock resistance of tri‐layer Yb2SiO5/Yb2Si2O7/Si coating for SiC and SiC‐matrix composites

AbstractA new tri‐layer Yb2SiO5/Yb2Si2O7/Si coating was fabricated on SiC, C/SiC, and SiC/SiC substrates, respectively, using atmospheric plasma spray (APS) technique. All coated samples were subjected to thermal shock test at 1350°C. The evolution of phase composition and microstructure and thermo‐mechanical properties of those samples before and after thermal shock test were characterized. Results showed that adhesion between all the 3 layers and substrates appeared good. After thermal shock tests, through microcracks which penetrated the Yb2SiO5 top layer were mostly halted at the Yb2SiO5‐Yb2Si2O7 interface and no thermal growth oxide (TGO) was formed after 40‐50 quenching cycles, implying the excellent crack propagation resistance of the environmental barrier coating (EBC) system. Transmission electron microscopy analysis confirmed that twinnings and dislocations were the main mechanisms of plastic deformation of the Yb2Si2O7 coating, which might have positive effects on crack propagation resistance. The thermal shock behaviors were clarified based on thermal stresses combined with thermal expansion behaviors and elastic modulus analysis. This study provides a strategy for designing EBC systems with excellent crack propagation resistance.

Magnetism aided mitigation of deformation and residual stress in dissimilar joint 316L with EH36

Magnetism aided mitigation of deformation and residual stress was researched in dissimilar joint 316 L with EH36. Application of external magnetic field, microstructure was refined, weld profile was regulated by narrowing upper width and broadening bottom width. A simulation method by integrating image extraction and fitting of actual weld profile into thermal elastic plastic finite element analysis was proposed to evaluate welding deformation and residual stress in the dissimilar joint with an asymmetrical weld shape. Considering the effect of external magnetic field, welding deformation was decreased by ∼34%, the tensile stress was reduced. Mitigation mechanism by external magnetic field was that temperature gradient and cooling rate of the weld pool were decreased by Lorentz force stir with low micro-strain and micro-stress. This work offered an effective method to regulate deformation and residual stress of dissimilar joint in laser welding.

Reduction of Welding Distortion for an Improved Assembly Process for Hatch Coaming Production

The alignment between the hatch coaming top surface and hatch cover is essential to maintain hatch cover water tightness and smooth mechanical operation. An improved assembly process for hatch coaming production is proposed, in which the complete hatch coaming is assembled on the shop floor and then lifted as one part, fitted, and welded to the deck. When this complete hatch coaming is assembled to a ship deck, an irregularly distributed gap is usually found between the lower side of the hatch coaming and the deck. Fitting and welding distortion, in particular longitudinal and transverse shrinkage, influence the dimensional accuracy and consequently the production schedule. In this research, welding pass sequence of a fillet welded joint is improved using thermal elastic plastic analysis and welding distortion of the hatch coaming top surface is predicted using elastic analysis. First, three specimens with different gaps that model the welded joint between the hatch coaming and deck were welded and the changed distance between the measuring equipment and the flange was measured. A three-dimensional thermal elastic plastic finite element analysis was carried out for the same specimens and the computed welding distortion was shown to have good agreement with the measurements. As a result of the possible significant influence of welding pass sequence on transverse shrinkage of a fillet welded joint, the influence of welding pass sequence is studied using the computational approach and improved welding pass sequences are proposed to reduce transverse shrinkage. Finally, elastic analysis using inherent longitudinal and transverse shrinkage deformations evaluated by thermal elastic plastic analysis is used to predict welding distortion of the hatch coaming. In this elastic analysis, the influence of different gaps at different locations between the hatch coaming and the deck is considered.

Reduction of Welding Distortion for an Improved Assembly Process for Hatch Coaming Production

The alignment between the hatch coaming top surface and hatch cover is essential to maintain hatch cover water tightness and smooth mechanical operation. An improved assembly process for hatch coaming production is proposed, in which the complete hatch coaming is assembled on the shop floor and then lifted as one part, fitted, and welded to the deck. When this complete hatch coaming is assembled to a ship deck, an irregularly distributed gap is usually found between the lower side of the hatch coaming and the deck. Fitting and welding distortion, in particular longitudinal and transverse shrinkage, influence the dimensional accuracy and consequently the production schedule. In this research, welding pass sequence of a fillet welded joint is improved using thermal elastic plastic analysis and welding distortion of the hatch coaming top surface is predicted using elastic analysis. First, three specimens with different gaps that model the welded joint between the hatch coaming and deck were welded and the changed distance between the measuring equipment and the flange was measured. A three-dimensional thermal elastic plastic finite element analysis was carried out for the same specimens and the computed welding distortion was shown to have good agreement with the measurements. As a result of the possible significant influence of welding pass sequence on transverse shrinkage of a fillet welded joint, the influence of welding pass sequence is studied using the computational approach and improved welding pass sequences are proposed to reduce transverse shrinkage. Finally, elastic analysis using inherent longitudinal and transverse shrinkage deformations evaluated by thermal elastic plastic analysis is used to predict welding distortion of the hatch coaming. In this elastic analysis, the influence of different gaps at different locations between the hatch coaming and the deck is considered.

Study on the Nonlinear Characteristic Effects of Dielectric on Warpage of Flip Chip BGA Substrate

In this study, both a finite element analysis and an experimental analysis are executed to investigate the mechanical characteristics of dielectric material effects on warpage. Also, viscoelastic material properties are measured by DMA and are considered in warpage simulation. A finite element analysis is done by using both thermal elastic analysis and a thermo-viscoelastic analysis to predict the nonlinear effects. For experimental study, specimens warpage of non-symmetric structure with body size of <TEX>$22.5{\times}22.5$</TEX> mm, <TEX>$37.5{\times}37.5$</TEX> mm and <TEX>$42.5{\times}42.5$</TEX> mm are measured under the reflow temperature condition. From the analysis results, experimental warpage is not similar to FEA results using thermal elastic analysis but similar to FEA results using thermo-viscoelastic analysis. Also, its effect on substrate warpage is increased as core thickness is decreased and body size is getting larger. These FEA and the experimental results show that the nonlinear characteristics of dielectric material play an important role on substrate warpage. Therefore, it is strongly recommended that non-linear behavior characteristics of a dielectric material should be considered to control warpage of FCBGA substrate under conditions of geometry, structure and manufacturing process and so on.

Heat Transfer and Thermal Elastic Deformation Analysis on the Piston/Cylinder Interface of Axial Piston Machines

The piston/cylinder interface of swash plate–type axial piston machines represents one of the most critical design elements for this type of pump and motor. Oscillating pressures and inertia forces acting on the piston lead to its micro-motion, which generates an oscillating fluid film with a dynamically changing pressure distribution. Operating under oscillating high load conditions, the fluid film between the piston and cylinder has simultaneously to bear the external load and to seal the high pressure regions of the machine. The fluid film interface physical behavior is characterized by an elasto-hydrodynamic lubrication regime. Additionally, the piston reciprocating motion causes fluid film viscous shear, which contributes to a significant heat generation. Therefore, to fully comprehend the piston/cylinder interface fluid film behavior, the influences of heat transfer to the solid boundaries and the consequent solid boundaries’ thermal elastic deformation cannot be neglected. In fact, the mechanical bodies’ complex temperature distribution represents the boundary for nonisothermal fluid film flow calculations. Furthermore, the solids-induced thermal elastic deformation directly affects the fluid film thickness. To analyze the piston/cylinder interface behavior, considering the fluid-structure interaction and thermal problems, the authors developed a fully coupled simulation model. The algorithm couples different numerical domains and techniques to consider all the described physical phenomena. In this paper, the authors present in detail the computational approach implemented to study the heat transfer and thermal elastic deformation phenomena. Simulation results for the piston/cylinder interface of an existing hydrostatic unit are discussed, considering different operating conditions and focusing on the influence of the thermal aspect. Model validation is provided, comparing fluid film boundary temperature distribution predictions with measurements taken on a special test bench.

Simulation and experimental study on distortion of butt and T-joints using WELD PLANNER

This paper investigates the capability of linear thermal elastic numerical analysis to predict the welding distortion that occurs due to GMAW process. Distortion is considered as the major stumbling block that can adversely affect the dimensional accuracy and thus lead to expensive corrective work. Hence, forecast of distortion is crucially needed and ought to be determined in advance in order to minimize the negative effects, improve the quality of welded parts and finally to reduce the production costs. In this study, the welding deformation was simulated by using relatively new FEM software WELD PLANNER developed by ESI Group. This novel Welding Simulation Solution was employed to predict welding distortion induced in butt and T-joints with thickness of 4 mm. Low carbon steel material was used for the simulation and experimental study. A series of experiments using fully automated welding process were conducted for verification purpose to measure the distortion. By comparing between the simulation and experimental results, it was found out that this program code offered fast solution analysis time in estimating weld induced distortion within acceptable accuracy.

Crack Propagation in Glass by Laser Irradiation Along Laser Scribed Line

A mechanical breaking process after laser scribing is indispensable to complete the separation of glass substrate since the crack depth induced by the laser scribing is limited. Laser irradiation along the laser scribed line is introduced in this paper as a crack propagation method in depth direction after the laser scribing of a relatively thick glass in order to make the mechanical breaking easier. Since the separating load decreases by propagating the scribed crack deeply, it contributes to the inhibition of glass particle generation. The target of this research is to clarify the mechanism of crack propagation by the laser irradiation along the laser scribed line. Two-dimensional thermal elasticity analysis was conducted by a finite element method based on the experimental results in order to theoretically estimate the laser irradiation condition, which propagates crack. The following results were obtained. Compressive stress is generated on the glass surface and tensile stress is generated inside the glass by the laser irradiation along the laser scribed line. The tensile stress concentrates at the crack tip induced by the laser scribing, and the crack propagates into the depth direction. The condition of crack propagation can be estimated from the maximum surface temperature and the maximum tensile stress of the crack tip in practical processing velocity (200 mm/s or more mm/s).

Influence of thermal expansion coefficient in laser scribing of glass

Aluminosilicate glass, which has a relatively low thermal expansion coefficient, is used as a glass substrate in liquid crystal displays, whereas soda-lime glass is generally used for such items as windows. The aim of this study was to clarify the influence of the thermal expansion coefficient on the glass substrate during laser scribing with crack propagation produced by laser heating and followed by quick quenching. The laser scribe conditions with aluminosilicate glass and fused silica were obtained in laser irradiation experiments to compare the difference of glass materials. Two-dimensional thermal elasticity analysis was then conducted with a finite element method based on the experimental results. The laser scribable condition of aluminosilicate glass can be estimated by combining the upper limit of the maximum surface temperature and the lower limit of the maximum tensile stress in the cooling area. The tensile stress generated in the cooling area decreases as the thermal expansion coefficient decreases. Therefore, fused silica, whose thermal expansion is much lower than aluminosilicate glass, is rarely applicable in laser scribing for separation.

Influence of glass substrate thickness in laser scribing of glass

The thickness of the glass substrate used in liquid crystal displays continues to be decreased from its original thickness of 1.1 mm for the purpose reducing size and weight. The aim of this study was to clarify the influence of the glass substrate thickness during laser scribing with crack propagation caused by laser heating followed by quick quenching. The laser scribe conditions for soda-lime glass substrates with thickness equal to or less than 1.1 mm were obtained in laser irradiation experiments. Two-dimensional thermal elasticity analysis was conducted with a finite element method based on the scribable conditions obtained in the experiment. The laser scribable conditions can then be estimated by the upper limit of the maximum surface temperature, Tmax, and the lower limit of the maximum tensile stress, σtmax, in the cooling area, regardless of the glass substrate thickness. There is a substrate thickness with which the maximum tensile stress σtmax becomes the largest under each scribe condition. The substrate thickness with which σtmax becomes the largest is obtained at a faster scribe velocity for thinner glass substrate and at slower scribe velocity for thicker glass substrate. Owing to these relations, the crack depth also has almost the same tendency as σtmax.

OS0104 ステルスダイシングにおける応力拡大係数を用いたき裂進展解析(弾性数理解析とその応用,オーガナイズドセッション)

In stealth dicing (SD), a permeable nanosecond laser is focused inside a silicon wafer and scanned horizontally. A thermal shock wave is propagated every pulse toward the side to which the laser is irradiated, then a high dislocation density layer is formed inside a wafer after the thermal shock wave propagation. In our previous study, it was supposed that an internal crack whose initiation is a dislocation is propagated when the thermal shock wave by the next pulse overlaps with this layer partially. In this study, a two-dimensional thermal elasticity analysis based on the fracture mechanics was conducted. The internal crack propagation was analyzed by calculating the stress intensity factor at the crack tips and comparing with a threshold of that. As a result, validity of the previous hypothesis was suggested.

Thermal stress analysis on laser scribing of glass

In the laser scribing of glass a thermal stress is introduced into a glass substrate by means of a CO2 laser irradiation. The glass substrate is then rapidly cooled down by water jet immediately after the irradiation. For the purpose of theoretical clarification of the factors ruling the scribable condition and the crack depth, scribable conditions were acquired in laser irradiation experiments using a soda-lime glass substrate having a thickness of 0.7 mm. Furthermore, the crack depth and the crack edge profile were observed for various values of the distance between the heating area and the cooling area. On the basis of the scribable conditions obtained from the experiments results, a thermal elasticity analysis was conducted by a finite element method. The following results were obtained. The scribable condition can be estimated from the maximum tensile stress in the cooling area and the maximum temperature in the heating area. The crack depth in laser scribing depends on the tensile stress in the cooling area and the compressive stress field immediately under the area.

Laser cleaving on glass sheets with multiple laser beams

A multiple laser system consisting of CO 2 line-shaped and Nd-YAG pulsed lasers was applied to cleave a soda-lime glass substrate in this study. Due to an increase of absorption coefficient of the wavelength of 1.06 μm for Nd-YAG laser on the soda-lime glass at high temperatures, the glass sheets were preheated by the CO 2 line-shaped laser and followed with the pulsed Nd-YAG laser to generate a mixture fracture mode on the substrate. The stress distribution on the glass substrate cleaved by the multiple laser beams has been analyzed. An uncoupled thermal–elastic analysis based on the finite-element method (FEM) was made. The numerical results show that the stress field of the fracture region is caused by a complex stress state and the cleavages are significantly affected by the pulsed laser. A clean cut of the soda-lime glass substrate could be obtained due to a large shear stress state on the cutting direction with the pulsed laser radiated on the glass substrate.

D18 ガラスのレーザスクライブにおける予亀裂導入モデルによる熱弾性解析(OS-9 レーザ応用加工(2))

In the laser scribing of a glass, a crack is propagated when the surface is cooled down immediately after CO_2 laser is irradiated. In this process, scribable conditions and the crack depth are influenced depending on various parameters such as laser power, scribe velocity, and the distance between the heating area and the cooling area. Therefore, it is important to estimate the scribable conditions by the analysis. We analyzed crack propagation phenomena by a finite element method, using a model with a pre-crack. The crack depth was evaluated by calculating the stress intensity factor at the crack tip. The obtained conclusions are as follows: By giving a suitable threshold of the stress intensity factor, the crack depth can be estimated by a thermal elasticity analysis. The propagation velocity of a crack shows almost the same tendency, even when the scribe condition is different.