Thermal Deformation Model Research Articles

Processing correlations of laser direct energy deposited Inconel718 based on multi-field numerical simulation

Laser direct energy deposited (LDED) Inconel718 always have problems of non-uniform temperature distribution because of the complex flow of molten pool and layer-by-layer fabrication characterization which directly affected the microstructure and mechanical properties of materials. In this work, Inconel718 revealed a refined grains and a weave structure exhibiting excellent mechanical properties which were superior to those of the conventional casting process were successfully fabricated by adopt a high-precision and intelligent coaxial powder feeding system during the LDED processing. Moreover, based on multi-field numerical simulation method, a two-phase flow model and a transient thermal mechanical deformation model were established to simulate the LDED processing, while takes into account the evaporated mass loss of the inconel718 alloy. The morphology prediction of laser directed energy deposition by multi-physics numerical simulation, the relationship among the laser process parameters, i.e., the laser power, scanning speed and the amount of powder feeding, the temperature filed and the microstructure and mechanical properties of Inconel718 alloy during LDED were investigated and established. The simulated results consistent well with the experimental results. Results shown that the relative density of sample was sensitive to the laser power, the precision and stability of the powder feeding rate. With increasing laser power, the grain size of Inconel718 is refined, and the microhardness and tensile properties of the materials increased. The optimized LDED processing parameters were determined. Evaluating the mechanical properties of the materials LDEDed at a laser power of 600W and a scanning speed of 8.5mms-1 exhibited a high tensile strength of 944±5 MPa and a good elongation of 29 ± 0.5 %. This work suggests that the processing parameters can be optimized to prepare densified materials with excellent mechanical properties.

Thermomechanical modeling in elastic body with corotated total Lagrangian SPH

In this paper, we propose a novel thermal deformation formulation for elastic bodies' thermomechanical simulation with total Lagrangian smoothed particle hydrodynamics (TLSPH), which employing fixed reference configuration. We utilize implicit corotated TLSPH as a base methodology to address tensile instability and enhance the robustness of simulation. The reference configuration of heat transfer model is updated, but the reference configuration of thermal deformation model is fixed like TLSPH. As particle's temperature is changed, the inter-particle distance in reference configuration is updated by using linear thermal expansion theory. Validation involved two basic cantilever beam loading cases and a thermomechanical analysis with heat-induced thermal deformation on a cantilever beam. The TLSPH simulation results were compared against Finite Element Method simulations and analytical solutions, demonstrating equivalent accuracy across all tests. This study indicates the potential for conducting a wide array of simulations involving thermal deformation using the TLSPH method, which efficiently supports parallel computing on an individual particle basis.

A Novel Thermal Deformation Self-Stabilization Flexible Connection Mechanism

In micro-LED chip repair, a nanopositioner is commonly used to adjust the positioning of the LED chip. However, during the bonding process, the heat generated can cause the positioning system to deform, leading to inaccurate alignment and poor-quality chip repair. To solve this issue, a novel flexible connection structure has been proposed that can eliminate thermal deformation. The principle of this novel flexible connection structure is that the thermal distortion self-elimination performance is achieved via three flexible connection modules (FCM) so that the thermal stress is automatically eliminated. First, the paper introduces the principle of thermal deformation elimination, and then the design and modeling process of the proposed structure are described. A heat transfer model is then developed to determine how temperature is distributed within the structure. A thermal deformation model is established, and the size of the FCM is optimized using a genetic algorithm (GA) to minimize the thermal deformation. Finite element analysis (FEA) is used to simulate and evaluate the thermal distortion self-elimination performance of the optimized mechanism. Finally, experiments are conducted to verify the reliability and accuracy of the simulation results. The simulations and experiments show that the proposed structure can eliminate more than 38% of the thermal deformation, indicating an excellent thermal deformation self-eliminating capability.

Modeling and improvement for the thermal stability of ring-shaped workpieces with shape boundary constraints

Ring-shaped workpieces are commonly utilized in high-precision measuring instruments, and their thermal deformation affects the instruments’ measuring accuracy. A novel method for establishing the thermal deformation model of ring-shaped workpieces is proposed in this article. The mechanism of thermal deformation caused by shape boundaries is investigated using the principle of molecular dynamics. A mathematical model between deformation degree and height, diameter ratio, or temperature is created using a large-scale atomic/molecular massively parallel simulator. The established model is verified by measuring the thermal deformation of ring-shaped workpieces. The model is used to optimize laser collimation systems, and stability experiments for laser collimation systems in different sizes are performed. The stability of optimized systems can be improved by 50%, 50%, and 48% with temperature increases of 10 °C, 20 °C, and 30 °C, respectively. The experimental results indicate the obtained model can be utilized to improve the stability of instruments.

Prediction of Thermal Deformation and Real-Time Error Compensation of a CNC Milling Machine in Cutting Processes

This study constructs a prediction model of thermal deformation with an artificial neural network and implements the real-time error compensation for a three-axis vertical CNC milling machine in cutting processes to improve the thermal error of the workpiece. There are 32 PT-100 thermal sensors installed in key parts of the machine in order to measure the temperature of key machine parts in actual cutting conditions. Pearson’s correlation coefficients are used to select crucial temperature sensors for building the prediction model of thermal deformation. The reduced number of crucial temperature sensors in model construction can simplify the model complexity and speed up the response time of prediction. This study constructs a long short-term memory (LSTM) neural network model to predict the thermal error of the machine in cutting processes. This prediction model of thermal deformation can be further used in real-time error compensation of the workpiece in cutting processes. In an 8 h cutting experiment, the dimensions of the workpiece show that, with real-time error compensation, the thermal error in X-axis decreases from 7 µm to 3 µm, the thermal error in Y-axis decreases from 74 µm to 21 µm, and the thermal error in Z-axis decreases from −64 µm to −20 µm. The results indicate that the prediction model of thermal deformation and the real-time error compensation can significantly reduce the thermal error and improve the dimensional accuracy of the workpiece.

THEORETICAL MODELING OF THE NUCLEATION OF INTERNAL LATENT THERMAL DEFECTS IN A BITUMINOUS MEDIUM WITH RUBBER INCLUSIONS

The current state and progress of the technology and science associated with the reuse and recycling of the tyre rubber worldwide in the road industry compels to study more thoroughly high and low temperature performance of the road bitumen modified with rubber crumbs, permitting to understand influence of the temperature, rubber grain size and mixture bitumen-rubber modification on the composite strength and sustainability. Below, these issues are studied taking into account the peculiarities of the thermomechanical properties of rubber associated with its low rigidity when changing shape, practical incompressibility when changing volume, and low (zero or even negative) coefficient of linear thermal expansion. The purpose of the study is to determine the reasons leading to a violation of the strength of asphalt concrete materials with admixtures of rubber crumb. For this purpose, the influence of the incompatibility of thermomechanical characteristics (moduli of elasticity, Poisson's ratios and coefficients of thermal expansion) of bitumen and rubber on the concentration of additional internal thermal stresses in the system caused by seasonal and daily temperature changes is analyzed. Using the relations of the theory of thermoelasticity, a mathematical model of thermal deformation of crumb rubber in a bitumen medium has been constructed. With the possibility of complete and surface modification of rubber with bitumen, solutions for three-phase media are constructed, which make it possible to trace the influence of the parameters of each phase on the thermal stress fields in the system. It has been established that additional thermal stresses in bitumen, due to the thermomechanical incompatibility of the physical parameters of the phases, are concentrated in the zone of its contact with the surface of the rubber crumb and can cause defects and chippings in it. The influence of the effect of modifying rubber crumb with bitumen and of the depth of its penetration into crumb of different sizes on reducing thermal stresses in the system and increasing its sustainability is considered.

Spatially discretised compensation method for coordinate transformation in large-scale metrology under nonuniform temperature field

Temperature-variation-induced error compensation plays a pivotal role in large-scale metrology, in which the nonuniform temperature field would greatly influence the coordinate transformation process between different systems. This paper proposes a novel analytical thermal deformation compensation method with spatial discretisation modelling among 2D distributed enhanced reference system points to reduce the thermal influence on the coordinate transformation process. First, the analytical thermal deformation model based on the spatial discretisation is established with the plane thermal elastic mechanics and the Finite Difference Method. Then the nonuniform temperature field model is developed based on Ordinary Kriging spatial interpolation. Finally, a compensation method for the coordinate transformation process is proposed based on the actual measurement data and the proposed thermal deformation model. The experimental results illustrate the existence and significance of the nonuniform feature of the temperature field. By the proposed compensation method, the coordinate transformation error is reduced by 47.13% and 76.67% in the x and y directions, respectively. The method is applicable to diminish the influence of thermal deformation under a nonuniform temperature field on the coordinate transformation of large-scale metrology.

Modeling of nonuniform thermal deformation and high thermal stability design method for precision instruments

Structural deformations caused by environmental temperature changes are the main reason affecting the accuracy of high-precision instruments. A model of nonuniform thermal deformation is established. In addition, a new high thermal stability design method based on the developed model is proposed in this paper. The mechanism of nonuniform thermal deformation is investigated based on the principle of molecular dynamics. A mathematical model of nonuniform thermal deformation is established through the Large-scale Atomic/Molecular Massively Parallel Simulator. The proposed design method is applied to a laser collimation system. Stability contrast experiments for the original as well as the optimized laser collimation systems are also carried out. The stability of the optimized laser collimation systems is improved by approximately 60% with a temperature change of 10 °C. The experimental results indicate that the established model of nonuniform thermal deformation and the high thermal stability design method are effective and inexpensive, and can be applied to improve the thermal stability of other precision instruments.

Thermal Stress Characteristics of Dissimilar Joints Joining Ti-64 and CCM via Linear Friction Welding

Linear Friction Welding (LFW) is a unique welding process which enables dissimilar materials to be welded without filler material. In this study, bi-metallic Ti-64-CCM joints were manufactured utilizing LFW and subsequently analyzed. A coupled thermal-deformation model was created to accurately model both thermal and deformation profiles along the weld interface. Ti-64 and CCM stock were machined in accordance with ASTM standards for tensile testing. Temperature distribution of the two material surfaces were measured using an IR camera. Tensile testing was then performed to analyze weldability and bonding strength. A transient decoupled thermomechanical simulation model was generated to simulate the LFW process. The simulation model produced results within 5% error of both experimental results. The tensile testing results indicate that successful bonding of Ti-64 to CCM is possible for an oscillation amplitude of 2 mm under large forging pressure. The results also show that parameter optimization is essential for successful LFW, as the decrease in percent error from test set 1 to test set 4 was 62.5%. From the tensile testing and thermal data collected, it was concluded that bonding of Ti-64 to CCM via LFW is possible but further research into the necessary process parameters is needed.

Thermal Deformation Modeling for Phased Array Antenna Compensation Control.

Thermal compensation control can correct errors caused by the thermal deformation of phased array antenna (PAA) panels. Thermal deformation of the panel is needed to calculate the compensation value. While the PAA is working, thermal deformation is unconditional to measure, but predicting it by temperature is feasible. However, thermal deformation is also affected by other factors, such as the structural shape, assembly method, and material parameters, and it is difficult to measure these parameters of PAA because of the complex structure. In contrast, the measurement method of the temperature and thermal deformation of the PAA in the laboratory is much easier. Therefore, a comprehensive influence parameters (CIPs)-finite element method (FEM) method was proposed in this study, it can extract the influence of above parameters on thermal deformation from temperature and thermal deformation measurement data and build a thermal deformation prediction model. Experiments have verified that the CIPs-FEM can greatly reduce the difficulty of thermal deformation modeling and have a high prediction accuracy.

Thermal analysis of the laser-induced thermal deformation of a diffractive optical element in a single-aperture coherent beam combining system

Diffractive optical element (DOE) is a critical device for combining multiple laser beams into a single beam in a coherent beam combining (CBC) architecture. This study proposes a determination method for calculating the intrinsic absorption rate of the DOE, and the corresponding experimental system is established. We present a theoretical thermal deformation model of the laser-irradiated DOE based on the thermoelastic equation and thermal conduction theory. The temperature and thermal deformation of the DOE are simulated using different parameters, including the laser power density, substrate size, substrate material, laser incident time, and clamping method. The simulations indicated that the thermal deformation is directly proportional to substrate area and inversely proportional to substrate thickness. The thermal deformation of the DOE can also be decreased by using a two-surface fixing method, and the maximum decrease is 4.4%. The quantitative discussion and analysis of the DOE temperature field and thermal deformation are important for designing a DOE to increase the combining efficiency and improve the combined beam quality of a practical DOE-based CBC system.

Study of static thermal deformation modeling based on a hybrid CNN-LSTM model with spatiotemporal correlation

Study of static thermal deformation modeling based on a hybrid CNN-LSTM model with spatiotemporal correlation

Hot compression deformation behavior and constitutive model of 2050 Al-Li alloy

Isothermal compression experiments of 2050 AL-Li alloy were carried out by Gleeble-3800 thermal-mechanical simulator. Hot compression deformation behavior of the alloy under the conditions of deformation temperature of 300~500 °C and strain rate of 0.01~10 s-1 was studied. The constitutive model of thermal deformation was established. Results indicate that there is an obvious rheological steady state in the isothermal compression process of 2050 aluminum alloy. The microstructure shows that the alloy has recrystallization. 2050 aluminum alloy is a positive strain rate sensitive material. At constant temperature, the steady state flow stress increases with the increase of strain rate. Arrhenius constitutive model can accurately predict the rheological behavior of 2050 aluminum alloy. The average absolute relative error (AARE) of the relative error between the experimental value and the predicted value is 8.59%.

Development of a thermal compensator based on PLC for Fanuc CNC system

To improve the machining accuracy and stability of CNC machine tools, the lead screw is divided into several segments, and the action law of single section thermal deformation is analyzed, then the thermal deformation model of lead screw base on subsection processing is established. Then the relative relation of thermal deformation of each segment, the cumulative thermal drift of thermal deformation of each segment itself, the total thermal deformation of the free end of lead screw, and the relationship between them are obtained. Then, a segmented thermal compensator based on PLC for CNC system is developed. The thermal error of each segment of the lead screw is detected and compensated separately, and then the thermal error of the segment where the machine tool worktable moves to the different segment of the lead screw is compensated. Tests show that the segmented thermal compensator has achieved good actual compensation effect, so that the positioning error caused by thermal deformation of each shaft can be reduced by more than 50%.

Study on seepage and deformation characteristics of coal microstructure by 3D reconstruction of CT images at high temperatures

To study the seepage and deformation characteristics of coal at high temperatures, coal samples from six different regions were selected and subjected to computed tomography (CT) scanning studies. In conjunction with ANSYS software, 3D reconstruction of CT images was used for the establishment of fluid-solid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal. In addition, the structure of coal was studied in 2D and 3D perspectives, followed by the analysis of seepage and deformation characteristics of coal at high temperatures. The results of this study indicated that porosity positively correlated with the fractal dimension, and the connectivity and seepage performances were roughly identical from 2D and 3D perspectives. As the porosity increased, the fractal dimension of coal samples became larger and the pore-fracture structures became more complex. As a result, the permeability of coal samples decreased. In the meantime, fluid was fully heated, generating high-temperature water at outlet. However, when the porosity was low, the outlet temperature was very high. The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension. The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.

Simulation and experimental study of laser-induced thermal deformation of spectral beam combination grating.

The multilayer dielectric (MLD) grating is a critical device for combining multiple laser beams into a single beam in a spectral beam combining (SBC) system. We established a theoretical thermal deformation model of the laser-irradiated MLD grating. Thermal deformation on the surface of the grating is simulated according to a series of parameters including the laser irradiation time, laser power density, and substrate size. To verify the model, we exposed a 960 l/mm, 50×50×1.5 mm3 grating to a laser power density of 3.61 kW/cm2 and observed the temperature change. We used a Twyman-Green interferometer to measure the interference fringes on the grating surface. Based on the Fourier-transform method and a Zernike polynomial fitting method, the real-time grating surface profile is reconstructed. The results show that substrate thickness increase or area decrease can reduce thermal deformation, the average decreases are 18.3% and 19.9%, respectively. The discussion and analysis of the grating thermal deformation are potentially valuable for designing grating to decrease the thermal deformation and improve the combined beam quality of a SBC system.

Environmental Temperature Considerations in Development of High-Precision Meso Deep Drawing Tool

Design and manufacturing of the high-precision meso deep drawing tools, especially in the low mesoscale range, demands close tolerance and high positional accuracy. Variation in environmental temperature affects the dimensions of individual components and final assembly due to thermoelastic deformation. This paper describes an approach to estimate the thermal deformation and positional errors of the tool components using finite element simulation. A shift of 52.74 and 61.79 μm with reference to central plane is observed for the guide push holes on left-hand and right-hand sides, respectively, at 42 °C. The thermal deformation along X-direction is validated through a dedicated measurement system with an expanded uncertainty of 2.8594 µm m−1. Based on thermal error estimation, CNC program is reconstructed to compensate dimensionally during the manufacturing of relevant tool components. A dimensional chain analysis reveals a maximum offset of 18 μm between punch and die axes in the tool assembly. Using the developed meso deep drawing tool, cups of 5.5 mm diameter are deep drawn from 0.8-thick sheet of IS513 low-carbon steel. This paper discusses the thermal deformation modeling, development of software system and experimental results in detail. The increased positional accuracy with desired clearances enhances the quality of the drawn parts, thereby ensuring improvement in the tool performance and its life. The proposed approach can be applied in the development of micro-deep drawing and other forming tools.

Thermal Deformation Test and Modeling of Main Spindle of Numerical Control Vertical Machining Center

Thermal error is the main factor affecting the manufacturing accuracy of the numerical control vertical machining center. The thermal deformation of the machine spindle is the main source of machine tool thermal error. In view of the deficiency of single factor modeling of thermal deformation of spindle of traditional machine tools, it is measured in this paper the temperature rise and Z-axis thermal deformation of a vertical machining center under several rotating speed conditions, the test data is analyzed and processed, and the relationship curves of thermal deformation of the spindle relative to time and temperature rise under several working conditions are drawn. Binary linear regression analysis model and artificial neural network model for thermal deformation of the spindle are presented. By comparing the residual error of these two modeling methods, the error for binary regression modeling is from −7.5μm to 10μm, however, the error for neural network modeling is from −5.5μm to 8.1μm, it is shown that neural network modeling is superior to binary regression modeling.

Investigating the Causes of the Emergency Shutdown of the Gas Turbine Unit

The development and causes of the emergency shutdown of a gas turbine unit as part of a CCPP are analyzed. Based on visual and baroscopic inspection of the gas turbine unit, chemical analysis of the metal of the compressor and turbine parts, analysis of archive data of the gas turbine unit and thermal deformation modeling, the causes of gas turbine shutdown were identified and measures to improve the reliability of the gas turbine were developed.

The fractal leakage model of contact mechanical seals considering wear and thermal deformation

At present, the effects of seal surface morphology, wear and thermal deformation on leakage are neglected in most studies about the contact mechanical seals, and the influence of surface topography is not considered from the microscopic perspective. In this paper, based on fractal theory, the contact between surfaces of dynamic and static rings is simplified to the contact between the rough surface and the ideal rigid plane. The leakage model, wear model and thermal deformation model of the contact mechanicals seal are established, and the fractal leakage model considering wear and thermal deformation is established by taking them all into consideration. Finally, according to the established model, the effects of fractal parameters, specific load and material parameters on the leakage are analyzed to obtain the conclusion that the fractal leakage model of contact mechanical seals considering wear and thermal deformation is of great significance for predicting the safe operation of contact mechanical seals. And the accuracy of the model is verified by comparing the model data with the experimental data.