Search

Focusing on the issue of thermal deformation in dry hobbing machine tools, the mechanisms of temperature change and the characteristics of temperature rise are thoroughly investigated. By analyzing heat generation through the energy conversion of various heterogeneous forms, including electrical, mechanical, and hydraulic energy, a comprehensive heat transfer model is developed to elucidate the complex thermal processes within the dry hobbing machine tool. The temperature at critical points of the machine tool during the dry hobbing of automotive gears is measured using a combination of infrared thermal imaging and online sensor technology. Experimental data are processed using Python to generate the machine tool's temperature rise curve. Based on this analysis, the temperature rise characteristics of the dry hobbing machine tool are further explored. The findings provide valuable insights for controlling thermal deformation and designing thermal balance systems for dry hobbing machine tools. [ABSTRACT FROM AUTHOR]

The mechanical behavior of pure Pt at elevated temperatures is critical for its high-temperature processing and applications. To understand its thermal deformation behavior and reach better processing control, thermal compression deformation was conducted for pure Pt in this work with a strain rate of 0.01 s−1 and temperatures ranging from 500 to 700 °C, followed by microstructure characterization by using electron backscatter diffraction (EBSD) technique. The results indicate that the grain size, fraction of low-angle grain boundaries, and dislocation density are generally reduced with increasing temperature. An analysis combining true stress–strain curves and microstructural characteristics indicates that dynamic recovery based on dislocation cross-slip/climb is always a main softening mechanism of pure Pt during thermal deformation. Continuous dynamic recrystallization and geometric dynamic recrystallization also occur when the deformation temperature exceeds 650 °C, which will effectively improve the microstructural homogeneity of pure Pt. [ABSTRACT FROM AUTHOR]

The pandemic of highly infectious diseases like COVID-19 has highlighted the vulnerabilities of public transportation. In particular, railways are more vulnerable due to their dense environment, and the heating system used in winter is a major factor in increasing the transmission and risk of the virus. To improve the existing heating system, a study was conducted to develop a resistive heating composite capable of radiant heating. In this study, the applicability of heating elements, heating performance, and internal thermal deformation factors of laminated panels and sandwich panels used as rail vehicle components were analyzed in detail to consider the actual application of this technology in the railway industry. The experimental results confirmed that both types of panels effectively heated above the target temperature (120℃) in the heating element layer, demonstrating uniform heating characteristics. Additionally, sandwich panel is more affected by thermal deformation compared to the laminate panel. These experimental results are expected to serve as essential foundational data for the effective utilization, safety, and reliability considerations of resistive heating composite materials in real industrial environments. [ABSTRACT FROM AUTHOR]

Fundamentally, the heat source in the ball screw feed system accounts for the thermal behavior of ball screw. Due to the fact that cooling resources are not always sufficient, the main objective of this paper is to allocate cooling resources for multiple heat sources. The network model of ball screw thermal deformation and temperature at the heat source is constructed based on wavelet neural network (WNN). Combined with the mathematical analysis results, the explicit mathematical expression of thermal deformation and heat source under this working condition is deduced, and the explicit mathematical expression of heat source contribution is further obtained. After that, keeping the total heat source contribution constant under this working condition, the particle swarm optimization (PSO) algorithm is used to determine the heat source contribution distribution that can minimize the thermal deformation of the ball screw. Finally, through the design of the ball screw cooling system, the minimum thermal deformation of various heat sources at different cooling ratios under constant cooling flow is explored. The contribution of heat source is basically consistent with the optimal cooling ratio, which not only verifies each other, but also shows that the uniform cooling of heat source can best inhibit thermal deformation. [ABSTRACT FROM AUTHOR]

To further investigate the properties of Incoloy825/P110 bimetallic composite seamless pipes, thermal deformation analysis was conducted on their billets. The thermal deformation and dynamic recrystallization (DRX) behavior of Incoloy825/P110 bimetallic composite materials were studied through hot compression tests at deformation temperatures (850–1150 °C) and strain rates (0.01–10 s−1). A constitutive relationship was established, and compensation and correction were made based on the differences in materials corresponding to different strain states. The hot processing map was established based on the thermal deformation behavior of bimetallic materials. In addition, the evolution of microstructure was also studied to verify the feasibility of the established hot processing map. The results show that the strain compensated Arrhenius can accurately predict the flow stress. By analyzing the microstructure using EBSD, it can be found that DRX behavior has a significant impact on the thermal processing properties of composite materials. This study provides an important theoretical basis for the production of Incoloy825/P110 bimetallic composite seamless pipes in the future. [ABSTRACT FROM AUTHOR]

Tolerance allocation is one of the prominent tools to achieve the optimal manufacturing cost and the best performance for mechanical assemblies. Variations in dimensions and geometry shape due to different working temperatures for various components within an assembly can make initially assigned tolerances ineffective. Therefore, it is necessary to consider the component's deformation caused by thermal gradients during the tolerance design. In this paper, a new method is presented for optimal tolerance allocation of mechanical assemblies under thermal deformation. First, the system's temperature working conditions and tolerance design goals are specified, followed by the finite element simulation of the assembly at the desired working temperature. Then, the assembly equation is determined according to the complexity of the problem by using analytical methods and some machine learning (ML) algorithms such as XGBoost. The optimal tolerance design is formulated into a constrained multi-objective optimization problem. Then, to obtain the Pareto front of optimal tolerances, the multi-objective optimization is solved by the NSGA-II algorithm. Finally, to illustrate the capability of the proposed method, two case studies are considered, and obtained results from the presented method and conventional approaches are compared. [ABSTRACT FROM AUTHOR]

The hot forming-quenching integrated process (HFQ®) organically combines the deformation and heat treatment, which can improve the forming performance of aluminum alloy while ensuring the final strength of formed parts. Thermal deformation in HFQ® has a non-negligible influence on precipitation behavior in subsequent artificial aging treatment and affects the mechanical properties of the formed parts. In this study, the relationship between the precipitation behavior and thermal deformation ratios was investigated. Results indicated that the formation temperatures of η′ and η decreased with an increasing deformation ratio; however, the former decreased more than the latter. The activation energy of η′ precipitation decreased linearly with increasing deformation ratio. Additionally, the phase transition fraction of η′ increased with the deformation ratio, leading to shorter times required to reach equivalent phase transition fractions. Deformation accelerated the phase transition of η′, and greater deformation resulted in a shorter transition time. The aging time required for peak Vickers hardness decreased with increasing deformation ratio, reflecting the promotion of precipitated phase formation and transformation by introduced dislocations. Consequently, peak hardness and yield strength were achieved in shorter aging times. In terms of industrial applications, this discovery offers significant advantages for shortening the production cycle of the hot stamping process and reducing production costs. [ABSTRACT FROM AUTHOR]

The control of MnS inclusions is crucial in developing high‐quality nonquenched and tempered steel. Single‐pass compression experiments are conducted on F40MnVS steel using a Gleeble‐3800 thermomechanical simulation testing machine, and the hot deformation behaviors of MnS inclusions at temperatures of 950–1150 °C and strain rates of 0.01 s−1 are investigated. Based on the experimental results of hot deformation, the steel is isothermally homogenized after forging to study the effect of holding time on the morphology and characteristics of MnS. Results indicate that at a lower deformation temperature of 950 °C and increased deformation, the relative plasticity of MnS diminishes, reducing the aspect ratio from 3.38 to 1.44 and primarily causing MnS fragmentation. At 1150 °C, as deformation increases, the relative plasticity of MnS also increases, with the aspect ratio rising from 1.46 to 2.01, leading to the growth of MnS. Under either low temperature and high deformation conditions or high temperature and low deformation, MnS fragmentation is more pronounced, resulting in more spherical MnS. With extended homogenization time, elongated MnS fractures, progressively transforming into spheroidal or ellipsoidal shapes before enlarging. The diffusion of S primarily controls the fracture and growth of MnS during isothermal heating. [ABSTRACT FROM AUTHOR]

With the continuous advancement of high-resolution satellite technology, the impact of thermal deformation on the performance of star cameras is becoming more significant, particularly in relation to installation conditions and orbital environments. To address this challenge, an in-depth investigation of the thermal design of a star camera is conducted in this study. The thermal deformation of this camera is evaluated systematically through simulation analysis, thermal balance tests, and on-orbit temperature measurements. In addition, a simulation analysis is used to identify and quantitatively evaluate the thermal deformation error sources that affect the spatial attitude measurement accuracy of the star camera. The results indicate that thermal deformations of the optical system, the mounting surface of the star camera, and the support significantly impact on-orbit measurement accuracy. Ultimately, the limit error attributable to on-orbit thermal deformation is determined to be 0.62″. In the thermal balance experiments, the maximum absolute difference between the test results and the thermal simulation analysis results is under 1.8 °C. Additionally, analysis of the orbital temperature data reveals that the maximum absolute difference between the orbital results and the thermal simulation results is 1.18 °C, while the attitude accuracy of the star sensor is better than 0.54″. These findings validate the effectiveness of the thermal design and the accuracy of the thermal simulation analysis. The analysis of error sources presented in this paper offers crucial insights for effectively controlling the thermal deformation errors of star cameras and lays the groundwork for optimizing overall thermal design. [ABSTRACT FROM AUTHOR]

The article demonstrates the effectiveness of the mechanochemical activation of a cement-ash binder by increasing the specific surface area of the ash and introducing a sodium fluorosilicate additive (Na2SiF6). It has been experimentally proved that the introduction of a Na2SiF6 additive makes it possible to increase the degree of cement hydration, as well as the intensity of free CaO binding when heating the cement-ash binder in the range of 500 °C to 800 °C. Mechanochemical activation prevents a decrease in the strength of the preheated cement-ash binder. During cyclic heating and cooling of slag mortars based on the activated cement-ash binder, an improvement in the set of basic properties was observed: compressive strength, flexural strength, water absorption, dynamic modulus of elasticity, and conditional elongation. Experimental design was carried out to obtain experimental–statistical models of mortar properties based on composition, heating temperature, and number of heating–cooling cycles. These models made it possible to develop quantitative relationships for predicting mortar properties at elevated temperatures and to rank the factors in order of importance. The optimal values for the dosage of fly ash, sodium silicofluoride additive, and the binder's specific surface area were established. It was demonstrated that the activator has a positive effect on the thermal deformation of mortars. [ABSTRACT FROM AUTHOR]

Additive manufacturing, particularly laser powder bed fusion (L-PBF), is an emerging method for fabricating complex parts in various industries. However, it faces the persistent challenge of thermal deformation, a significant barrier to its wider application and reliability. Current strategies, while partially effective, do not fully address the intricate thermal dynamics of the process, indicating a clear research gap in optimizing manufacturing techniques for better thermal management. This study focuses on understanding and mitigating thermal deformation in L-PBF using Genetic Algorithms (GAs). The application of GAs as a 'black-box' approach is explored to gain insights into the complex physics of L-PBF. A comprehensive investigation into the optimization of island sequencing within L-PBF processes is presented, employing GAs to systematically reduce thermal deformation. Various island sequences in a bilayered block structure are analyzed to assess the effectiveness of GAs in minimizing deformation, including scenarios such as variations in block sizes and interlayer rotation angles. Statistical tools such as silhouette scores and probability density distribution plots are utilized to provide a thorough analysis of deformation patterns and their respective thermal behaviors. The results show GA's remarkable efficiency in enhancing thermal management, achieving a significant reduction in thermal deformation within a range of 12–15% across the examined scenarios. This achievement highlights GA's capability in rapid optimization of scan sequences for better thermal deformation control. The findings enhance the understanding of thermal dynamics in L-PBF and consequently open new avenues for improving the quality and reliability of other metal additive manufacturing processes as well. [ABSTRACT FROM AUTHOR]

An experimental study of thermal deformation of a polymer film exposed to laser radiation of different intensity was carried out. The dependence of the radius of curvature of the deformed film on the duration of laser exposure and on the power of radiation was established. The temperature of the laser spot area was measured and the relative change in the film volume was calculated. The coefficient of volumetric expansion of the film material was determined from the obtained data. [ABSTRACT FROM AUTHOR]

In this investigation, the effects of different deformation passes—namely, single pass and multipass—on the microstructural evolution and deformation mechanisms in the Ti–6.5Al–2Zr–1Mo–1V alloy are analyzed. It is observed that following a single‐pass hot compression, the extent of lamellar α phase spheroidization enhances as the temperature increases. During multipass hot compression, there is a gradual reduction in the size and concentration of equiaxed α phase, alongside an increase in spheroidization. Dislocation density escalates to 15.88%, while the proportion of high‐angle grain boundaries (HAGBs) diminishes to 75.24%. Static recrystallization occurring during the holding process facilitates dislocation annihilation. The dynamic phase transformation mechanism manifests through interfacial permeation at the primary α phase. Strain localization at the boundaries or sub‐boundaries of the primary α phase, which exhibit minimal curvature, induces elevated shear stress, thereby promoting the shearing of the primary α phase and reducing its presence. Texture components predominantly observed are <‐12‐10>//Z0 and <0001>//Z0, transitioning from <‐12‐10> to <0001> with increasing strain. [ABSTRACT FROM AUTHOR]

The thermal environment in a geostationary orbit is more complicated than a low orbit. Thermal deformation is a primary factor to deteriorate geometric quality of remote imaging of geostationary optical satellites. The on-orbit geometric quality testing of the SDLT-1 satellite of China shows that the light of sight (LOS) deformation in longitude and latitude are 26 pixels and 14 pixels, respectively, which do not meet the accuracy requirements. Therefore, a novel on-orbit geometric calibration method based on star observation is proposed to improve the geometric deformation. The imager embodied stars are employed as sources to evaluate the developed method and compared with the traditional procedure based upon landmarks. The results show that the geometric accuracy of the new approach is 3.2 pixels which is improved compared to traditional calibration method. [ABSTRACT FROM AUTHOR]

This paper presents the design and optimization of a composite flexible support structure aimed at addressing the challenges associated with maintaining the positional accuracy and surface integrity of large-aperture cryogenic infrared lenses with long focal lengths. The primary objective of the structure is to maintain precise lens alignment while preserving the surface shape under operational conditions. The design complexities and underlying principles of the flexible support structure are systematically explored. A mechanical model of the flexible support structure was derived based on its structural characteristics, and the equilibrium equation was established to ensure the lens meets thermal deformation requirements in various directions. Optimization of key design parameters was conducted for a lens operating at 200 K, measuring 304 mm × 230 mm. The gravitational deformation of the optimized lens exhibited a root mean square (RMS) surface accuracy of 7.72 nm in the X direction, 7.08 nm in the Y direction, and 9.60 nm in the Z direction for lens surface 1. For lens surface 2, RMS values were 8.62 nm in the X direction, 8.41 nm in the Y direction, and 9.64 nm in the Z direction. At 200 K and lower temperatures, the RMS values of lens surfaces 1 and 2 were 2.41 nm and 2.74 nm, respectively, with a first-order mode frequency of 143.37 Hz. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Errors affect the actual meshing process of gears, alter the actual wear pattern of the tooth profile, and may even impact the overall service life of machinery. While existing research predominantly focuses on individual errors or a narrow set of factors, this study explores the combined effects of multiple errors on tooth profile wear. A comprehensive gear wear prediction model was developed, integrating the slice method, lumped mass method, Hertz contact model, and Archard's wear theory. This model accounts for initial tooth surface topography, thermal deformation, dynamic effects, and wear, establishing strong correlations between gear wear prediction and key factors such as tooth surface morphology, temperature, and vibration. Experimental validation demonstrated the model's high accuracy, with relatively small deviations from the observed wear. Initial profile errors (IPEs) at different positions along the tooth width result in varying relative sliding distances, leading to differences in wear depth despite a consistent overall trend. Notably, large IPEs at the dedendum and addendum can influence wear progression, either accelerating or decelerating the wear process over time. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Turning and milling machines (TMMs) have diverse and complex heat sources, which pose challenges to understanding their thermal behavior and thermal critical regions. Methods: A comprehensive procedure was proposed to explore the thermal characteristics of TMMs and identify thermally critical components. This study employed a Taguchi-FEM approach along with sensitivity analysis to evaluate the significant contributing boundary conditions of TMMs to tool center point (TCP) deformation in the X-, Y-, and Z-directions. An ANOVA-driven search was further proposed to identify thermal key points significantly impacting TCP deformation across directions and time intervals. Integrating both methods facilitated the identification of the TMM thermal critical regions. Results: The spindle TCP's thermal critical regions were most significantly influenced by the spindle component, followed by the milling cutter shaft component and then the right side of the base bed. Similarly, for the sub-spindle TCP, the highest impact came from the sub-spindle components, followed by the right side of the base bed and the milling cutter shaft components. Conclusions: The proposed procedure identified the significant regions for assisting evaluation in TMMs and reduced the number of required temperature monitoring points while optimizing their placements to minimize measurement costs. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The loading and friction of the elastoplastic line contact in boundary lubrication is studied by accounting for the contact thermal deformation effect. When the contact is mainly in the elastic deformation, the contact thermal deformation has significant influences on both the contact width and contact friction coefficient for a given load, and it reduces their values; However when the contact is mainly in the plastic deformation, the effect of the contact thermal deformation is weak or even negligible. Owing to the contact thermal deformation, the critical load for the initiation of the contact plastic deformation is also reduced. [ABSTRACT FROM AUTHOR]

6061 aluminum alloy is characterized by good comprehensive using properties and thermal processing performance. Traditional numerical simulation of 6061 aluminum alloy's thermal deformation is mostly limited to macroscopic deformation degree, stress-strain field, and deformation temperature field, which hinders accurately analyzing such microscopic phenomena as grain morphology change and dynamic recrystallization (DRX), thus affecting the precise quality control of the final parts. In order to simulate the dynamic recrystallization behavior during thermal deformation effectively, the hot compression experimental data were analyzed to establish the constitutive equation of flow stress and the critical equation of DRX. Then, the thermal deformation microstructure of 6061 aluminum alloy was numerically simulated based on Microstructure module of DEFRORM software, and the influencing laws of deformation amount, strain rate, and deformation temperature on the dynamic recrystallization were examined, followed by a comparative analysis with the deformation force, electron backscatter diffraction(EBSD)-based grain morphology, and transmission electron microscope (TEM)-based microstructure acquired in the hot compression experiment. Finally, the accuracy of the established models was verified. Results reveal that, as the deformation amount increased, the average grain size decreased; as the strain rate increased at a certain temperature, the size of the grains formed by dynamic recrystallization decreased, and the DRX volume fraction declined; as the temperature rose at a specific strain rate, the DRX volume fraction increased and the average grain size decreased. This study provides an important basis for optimizing the thermal deformation for 6061 aluminum alloy and regulating its structural performance. [ABSTRACT FROM AUTHOR]

Selective laser melting (SLM) is crucial for fabricating complex geometries, such as the tibial component of an artificial knee joint. However, its inherent high-temperature gradients often induce thermal defects and deformations, compromising product accuracy. This study addressed these challenges by using a multifaceted approach in which finite element method (FEM) simulations, Taguchi method analysis, and deep neural network (DNN) prediction were combined. Initially, a transient thermal model was developed using the FEM to analyze the thermal behavior of a tibial component during and after SLM; the model was then validated through experiments. Subsequently, the Taguchi method was employed to evaluate the thermal influence of various SLM parameters on deformation and stress. Furthermore, a K-means-based exploration method was developed and used to identify critical thermal areas affecting a component's size and quality. Finally, a DNN model was developed for rapid prediction of thermal deformation by leveraging an FEM proxy modeling methodology to facilitate efficient monitoring in a digital-twin framework. The FEM analysis revealed average deformation errors of 3.26% during SLM and 0.05 mm after SLM. The optimal SLM parameters for minimizing thermal deformation and stress for a tibial component were identified. The DNN model, trained on the proxy database, achieved error margins of only 5.47% and 4.62% in comparison with the FEM and experimental results, respectively, but took substantially less computation time than did the FEM. This study integrated FEM simulations, the Taguchi method, and DNN prediction to enhance the accuracy of SLM manufacturing of tibial components. [ABSTRACT FROM AUTHOR]

The aluminium heat block affects the dual nozzles of the folded additive manufacturing device, causing thermal deformation, and resulting in relative positional deviation that affects printing accuracy. The amount of thermal deformation of the print heads also varies when printing different materials, making it difficult to control printing accuracy. Using polyvinyl alcohol (PVA) and polyether ether ketone (PEEK) as examples, this study analysed the temperature field distribution and positional deviation of dual nozzles under different materials and combinations using the Steady-State Thermal module of Ansys Workbench. Experiment was also conducted to verify the simulation results. The study demonstrates that resetting the nozzle position in advance based on the derived deviation data through the built-in algorithm of the additive manufacturing device can significantly reduce the positional deviation caused by thermal deformation of the dual nozzles and improve printing accuracy. [ABSTRACT FROM AUTHOR]

The anisotropic characteristics of thermal deformation of ultrapure 2,4-dinitroanisole (2,4-DNAN) crystals were determined by the methods of powder thermorentgenography of the internal standard. The points of structural changes are registered in increments of 10 K, and in the melting region of 2 and 1 K. Calculations of powder X-ray diffraction data are performed by methods of full-profile analysis with a cycle of quantum modeling of the structure of molecules integrated into the algorithm. The Pauli, Le Bail (WPPD), Rietveld (WPPF) and WPPM methods were used as reference methods for full-profile analysis. The main crystallographic axes and characteristic surfaces of the thermal deformation tensor α and β-2,4-DNAN are determined. At atmospheric pressure, the main coefficients of linear (α) and volumetric (β) thermal deformation (expansion) were at 293 K for α-2,4-DNAN with α1(293) = 11,516 x 10-5 K-1, α2(293) = - 0,120 x 10-5 K-1, α3(293) = 5,098 x 10-5 K-1, β(293) = 16,333 x 10-5 K-1; at 293 K for β-2,4-DNAN with α1(293) = 13,217 x 10-5 K-1, α2(293) = 0,494 x 10-5 K-1, α3(293) = -8,6504 x 10-5 K-1, β(293) = 6,8191 x 10-5 K-1; at 260 K for β'-2,4-DNAN with α1(260) = 25,214 x 10-5 K-1, α2(260) = -5,823 x 10-5 K-1, α3(260) = 7,741 x 10-5 K-1, β(260) = 27,112 x 10-5 K-1. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Anhui University of Technology (Natural Science) is the property of Anhui University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)