Thermal Stress Relief Research Articles

Investigating the Effects and Mechanisms of Thermal–Vibration-Coupled Stress Relief Treatment on Residual Stress in SiC/Al Composites

Aluminum matrix composites reinforced with particles (PRAMCs) frequently develop considerable residual stresses post-quenching, which can negatively affect fatigue life and dimensional accuracy. Traditional stress relief methods for aluminum alloys are only partially effective. This study examined thermal stress relief (TSR), vibratory stress relief (VSR), and a combined thermal–vibratory stress relief (TVSR) approach for SiC/Al composites. All treatments proved successful in diminishing residual stresses, with the most significant reduction along the direction of peak dynamic stress. Additionally, this study analyzed micro-residual stresses via a macro–micro-residual stress finite element model to understand differences in stress relief outcomes. Optimizing the TVSR process could be key to more effectively reducing residual stresses in SiC/Al composites.

Comparison of the thermal and vibrational stress relief methods in terms of mechanical and metallurgical aspects of rolled AA2024 specimens

Comparison of the thermal and vibrational stress relief methods in terms of mechanical and metallurgical aspects of rolled AA2024 specimens

The effect of in situ-synthesized Y2SiO5 on the thermal shock resistance of Y2O3 ceramic materials

Y2O3 ceramics are increasingly recognized for their excellent vacuum stability and high-temperature chemical stability in the field of functional materials research. However, their poor thermal shock resistance renders them susceptible to spalling and damage during use, thus restricting further applications. To address this issue, the low thermal expansion coefficients of Y2SiO5 materials were leveraged. Through an in situ reaction between SiO2 and Y2O3, a Y2SiO5 phase was generated that induced a thermal expansion mismatch with Y2O3, thereby enhancing the thermal shock resistance of the ceramic. Using Y2O3 fine powder as the primary material, silica sol and nano-SiO2 were selected as reactive silicon sources to prepare Y2O3–Y2SiO5 composite ceramics at 1750 °C. The impact of the different silicon sources and Y2SiO5 phase content on the microstructure, mechanical, and thermal properties of the composite ceramics was studied. The results demonstrated that the in situ formation of Y2SiO5 significantly improved the thermal shock resistance of the composite ceramic. Specifically, increasing the SiO2 content led to a gradual rise in the volume fraction of Y2SiO5 formed between Y2O3 grains, thereby increasing the residual flexural strength and enhancing the hardness and elastic modulus. The low thermal expansion coefficient of Y2SiO5 reduced the overall thermal expansion coefficient of the composite material, thereby improving the thermal shock resistance. Moreover, the thermal expansion coefficient mismatch between the Y2O3 and Y2SiO5 phases induced numerous microcracks within the material, providing thermal stress relief within the microcracks and markedly improving the resistance of the ceramic to thermal shock.

Exploring hydrogen storage safety research by bibliometric analysis

The application of hydrogen energy is affected by the safety of hydrogen storage system. To grasp the current status of research and application in the research field of hydrogen storage safety and explore its research development trend, data analysis techniques, such as co-occurrence, co-citation, and burst detection, were adopted to conduct bibliometric analysis of the relevant literature. The study results show that the research hotspots of hydrogen storage safety mainly concentrate on six aspects: the stability of metal hydride hydrogen storage materials, the study of thermal management and stress relief in metal hydride reactors, the safety analysis of hydrogen fuel cells and hydrogen leakage monitoring, the analysis of leakage and explosion risks in hydrogen refueling stations, the study of filling pressure and temperature distribution in hydrogen storage tanks, and the study of safety issues in underground hydrogen storage. Mg-based hydride stability and underground hydrogen storage risk analyses are current research frontiers in hydrogen storage safety.

Analysis of the effect of vibrational stress relief process parameters on 2024Aluminium alloy

In principle, after all manufacturing processes are performed, a set of residual stresses occur in the product that have their particular distribution given the manufacturing process performed. The residual stresses must be removed to achieve the desired dimensional accuracy and quality. Among stress-relieving processes performed for a piece following the manufacturing process, we can refer to thermal and vibratory stress relief (VSR). Both methods perform the same function as they enter a part or all of a piece into the plastic phase, causing a fracture of residual stresses to be released with local plastic deformations. The process is as follows: The stress induced by thermal or vibratory loads is added to the residual stresses and exceeds the yield stress. This research, which is focused on VSR, aims to evaluate the effect of the main parameters of the VSR method, including load amplitude or amount, load application frequency, and cycle numbers. The general trend of the problem is that the VSR process is performed for a piece with residual stress, and the effect of the abovementioned parameters on reducing its residual stresses is evaluated.

Analysis of Vibratory Stress Relief (VSR) Parameters on Mechanical and Metallurgical Properties of AISI 1008

Analysis of Vibratory Stress Relief (VSR) Parameters on Mechanical and Metallurgical Properties of AISI 1008

REDUCING RESIDUAL STRESSES USING CRYOGENIC THERMAL TREATMENT

This work deals with the reduction of residual stresses using cryogenic thermal treatment as all alternative to normal thennal treatment .The work was performed on a solid z-shaped model component. Ihe models were fabricated from two difl'erent types of materials (alloy steel & alumin:tm). If any residual stresses exist in a manufactured cornponent, then these residual stresses will have an effect on the natural frequency of that component. A new type of measurement method was used to measure the level of residual stresses present. The nahral frequency of the models at a stress fiee state was used as a reference. This method was also used to find the extent of the residual stress relief and percentage of reduction. Residual stresses were incluced by flame heating with different boundary conditions and at different rates of cooling. They were stress relieved by the use of liquid nitrogen (-198uC) and at different various treatment times. This rvas done to find the effect of time on the treatment. Reduction in residual stress level reached 92.38yo.'firis reduction was compared with a normal thermal stress relief. Also a comparison was macie between the two types of material that were stress relieved. It was found that over treatment tends to re-stress the models.

Thermal performance investigation of membrane-assisted radiant cooling system for localised outdoor cooling hub

Heat waves pose increasing threats to human well-being, especially in urban areas, and staying safe beyond comfort during heat waves is a crucial issue. Localised cooling hubs may provide thermal stress relief in the outdoor environment. For outdoor cooling applications, conventional air conditioning systems are not effective but energy-intensive, and the membrane-assisted radiant cooling system can be a potential alternative, which directly treats the radiant loads while minimising the convective heat loss to the ambient. In the present study, a numerical model is developed to analyse the heat transfer behavior of membrane-assisted radiant cooling for outdoor applications, considering the effect of solar and long-wave radiation and wind parameters. As the transmissivity of the membrane material plays a crucial role in reducing the amount of solar heat, the performances of three types of membranes, i.e., non-selective, mid-infrared selective, and sky-window selective, were compared and analysed at different times on a typical summer day in Hong Kong. The results indicate that the sky-window selective membrane, which allows only transmission of infrared in the 8–15 µm wavelength range, saves energy up to 44 % and 47% compared with mid-infrared selective and non-selective membranes, respectively. In the outdoor application, the equivalent convective heat transfer coefficient of the cooling panel can be reduced in the range of 2.2 W/m2K to 2.6 W/m2K. It is observed that, when the panel is not exposed to direct solar radiation, there is no advantage in using the mid-infrared selective membrane over the non-selective membrane. However, under direct solar radiation, a non-selective membrane-assisted cooling panel demonstrates poor performance, absorbing solar heat flux 2.27 times higher compared to MIR-selective membrane-assisted panel.

Design of Thermal Stress-relief Mechanism Available for DREAM

Design of Thermal Stress-relief Mechanism Available for DREAM

Continuum damage mechanics of cyclic viscoplasticity using asymptotic numerical method

Conscious efforts on reduction of greenhouse gas emissions have led to an energy transition to renewable energy, however uncertainties of renewable energy production have resulted in higher thermal cycling demands from conventional power plants. Thermal load cycling at high temperature regions of steam turbine components leads to enhanced creep-fatigue damage accumulation. It is well established that such damage mechanism is numerically best predicted by unified constitutive modeling including damage as a variable as per the formalism of continuum damage mechanics at an expense of considerable computational efforts using finite element analysis. In this paper, the non-iterative Asymptotic Numerical Method (ANM), currently limited to partial cycle analysis with linear hardening plasticity model, is proposed for the first time to address cyclic viscoplasticity problems including damage capable of handling multiple cycles and most generalized loading conditions. Regularization techniques additionally necessary to implement loading-unloading-reloading criteria and advanced constitutive models etc. are presented. The constitutive model chosen for the formulation includes the non-linear multiple back stress variable modified Chaboche model to include damage combined with modified Chaboche-Rousselier isotropic hardening model to include damage, power law for viscoplasticity, Lemaitre’s damage potential and Kachanov-Rabotnov’s creep damage law. The method is verified with defined error measures and then applied to two high pressure steam turbine rotors, one with and another without thermal stress relief groove (TSRG) at the inlet under service type loading conditions to study the beneficial effect of the TSRG on creep-fatigue damage evolution. The accumulated errors of the proposed ANM and computational time are compared to a conventional Newton-Raphson solution.

Multimaterial Additively Manufactured Metamaterials Functionalized with Customizable Thermal Expansion in Multiple Directions.

Metamaterials functionalized with customizable multidirectional coefficient of thermal expansion (CTE) are urgently needed for advanced shape control or dimensional stability under temperature variations. The currently reported metamaterials still lack the development of diverse base material systems and exploration of the multimaterial fabrication process. Especially, the reported range of customizable CTEs for metamaterials in multiple directions is limited within [-68.1, 56.4] ppm/°C. Here, this work explicitly proposes a strategy for closely linking base materials, additive manufacturing (AM) process, architecture, and CTE tunability, in order to provide a general guideline for the design or customization of such metamaterials. In detail, first, we systematically identify the key process parameters and related performance for additive manufacturing of polymers and propose various multimaterial systems such as polypropylene-polycarbonate (PP-PC). Then, six types of metamaterials have been fabricated with high quality by the established multimaterial additive manufacturing. By measuring the effective CTEs in multiple directions, the CTE tunability of metamaterials, including large positive values (+523.36 ppm/°C) and large negative values (-230.61 ppm/°C), far beyond the literature-reported CTE range, has been experimentally verified. Further, we have developed a bidirectional requirement-solution strategy here that acts as a bridge between design and fabrication. This work opens advanced avenues for metamaterials with multidirectionally customizable and extensive CTE tunability for a variety of engineering applications such as actuators, thermal stress relief, and improved structural stability.

Numerical Simulation and Experiment of Stress Relief and Processing Deformation of 2219 Aluminum Alloy Ring

Large aluminum alloy ring forgings are the core components of heavy-duty rocket fuel storage tanks, and the large residual stress inside the rings leads to poor shape accuracy of large thin-walled parts. The initial stress of the 2219 aluminum alloy ring blank was tested using the drilling method, and the creep constitutive coefficient of the 2219 aluminum alloy was determined through stress relaxation tests. The numerical simulation processes of thermal stress relief (TSR), vibration stress relief (VSR), and thermal–vibration stress relief (TVSR) were compared and established. Through the correlation analysis between the actual measurement results of residual stress and the simulation results, it can be seen that the strong correlation in three directions at each measurement point accounts for over 37.5%, and the moderate correlation accounts for over 62.5%. This indicates that the numerical simulation model of 2219 aluminum alloy ring containing initial residual stress can accurately reflect the size and distribution of residual stress inside the actual ring. The simulation results show that the derived constitutive model can describe the stress relaxation process of TVSR by combining a single thermal time effect stress relaxation constitutive theory with a VSR plastic deformation material model. The simulation models established above were used to calculate the residual stress homogenization ability of three types of aging. The results showed that VSR, TSR, and TVSR can homogenize and reduce the residual stress field inside the ring, improve the distribution of residual stress inside the ring, and have a better overall homogenization ability of TVSR. The VSR control has a certain effect on reducing and homogenizing residual stress, but compared with TSR and TVSR, the reduction and homogenization ability of residual stress control is limited. The homogenization control effect TVSR > TSR > VSR, and the maximum equivalent stress homogenization rates of VSR, TSR, and TVSR are 52.8%, 80.6%, and 82.2%, respectively. Then, numerical simulation technology was used to study how the initial residual stress in the blank causes the deformation of the ring during the thin-walled machining process. The roundness error theory of the minimum containment area method was applied to evaluate the deformation degree during the thin-walled numerical machining process, and the TVSR method was used for stress regulation. The deformation law of the thin-walled machining of the ring under different aging parameters was studied.

Experimental study and simulation analysis of thermal-vibratory stress relief treatment of Al-Cu-Mg alloy plate

The considerable uneven residual stress (RS) induced by the quenching process of aluminum (Al) alloys causes dimensional instability and deformation. RS relief is essential to enhance the performance of the Al alloys. Thermal vibration stress relief (TVSR), which integrates conventional thermal stress relief (TSR) and vibration stress relief (VSR), has been shown to effectively reduce and homogenize the RS of Al alloys. To date, the detailed processes and mechanisms of TVSR have yet to be studied. Therefore, TVSR experiments considering the coupling rules of TSR and VSR were conducted on the Al-Cu-Mg alloy. Coupled creep-mechanical finite element (FE) models considering the heat preservation time, vibration time, and vibration sequence was devised to predict the residual stress evolution during TVSR treatment. The TVSR simulation results are in good agreement with the experimental results. The results show that TVSR treatment with a heat preservation time of 110 min followed by vibration for 10 min had the optimal stress relief effect, with a stress relief rate 81.7 % higher than that of TSR. Different TVSR processes had little impact on the Vickers hardness and metallographic structure. The TVSR treatment mechanism was also analyzed.

Research on Residual Stresses and Microstructures of Selective Laser Melted Ti6Al4V Treated by Thermal Vibration Stress Relief

The efficient and cost-effective residual stress control method is of great significance for the application of additive manufacturing (AM) technology. In this work, thermal-vibration stress relief (TVSR) with different temperatures and dynamic stresses was performed on Ti6Al4V samples prepared by selective laser melting (SLM), the stress relief effects of TVSR and its influence on phase and microstructure were investigated and compared with thermal stress relief (TSR) and vibration stress relief (VSR), and the stress relief mechanisms of these methods are discussed. It was found that the residual stress relief rate can reach 86.76% after TVSR treatment at a temperature of 380 °C and a dynamic stress of 400 MPa, which increased by 63.63% compared with VSR under the same dynamic stress. The efficiency is increased by 76% compared with TSR at 580 °C and the residual stress relief rate is almost the same. After TVSR, VSR and TSR treatments, the grain morphology, size and phase content of samples were basically unchanged, and low-angle grain boundaries (LAGBs) were increased after TVSR and VSR treatments and decreased after TSR treatment. The results confirm that the TVSR method has the ability to control the residual stress of selective laser melted Ti6Al4V with low time and cost consumption, and are helpful for engineering applications of TVSR.

Fatigue behavior and damage analysis of PIP C/SiC composite

In this work, we study the fatigue behavior of a C/SiC composite produced by several cycles of polymer infiltration and pyrolysis (PIP). Fatigue tests were performed with maximum stresses corresponding to 60–90% of the tensile strength of the composite. During the fatigue tests, acoustic emission (AE) monitoring was performed and the measured AE energy was utilized to quantify the damage and distinguish possible damage mechanisms. Most of the fatigue damage in the form of matrix cracking, interface damage and fiber breakage occurs in the first cycle. As loading cycles proceeded, damage in form of matrix crack re-opening and interfacial friction constantly accumulates. Nevertheless, all samples survived the run-out of 1,000,000 cycles. After the fatigue tests, an increase of the tensile strength is observed. This phenomenon is associated with the relief of process-induced internal thermal stresses and the weakening of the fiber-matrix interface. In general, the studied material shows very high relative fatigue limit of 90% of its tensile strength.

Residual stress and microstructure of Ti6Al4V treated by thermal-vibratory stress relief process

The stress relief processes, such as thermal stress relief (TSR) and vibratory stress relief (VSR), are generally applied to decrease and control the residual stress in the manufacturing process. Thermal-vibratory stress relief (TVSR) is a novel stress relief method developed in recent years, which has significant advantages over traditional methods. The stress relief mechanism of TVSR and stress evolution under the coupling effect of heat and vibration still need further investigation. In this study, TSR, VSR and TVSR with different process parameters are compared to study their stress relief effect on Ti6Al4V, and corresponding FEM simulations are performed to calculate the stress evolution. The residual stress is measured using X-ray diffraction method. EBSD and TEM characterizations are carried out to investigate the influences on the phase, crystal grain and dislocation. Results show that both TVSR and TSR can eliminate over 90% of residual stress of Ti6Al4V, but the efficiency of TVSR is 4.2 times as that of TSR. The stress relief rate of TVSR is 45.04% higher than that of VSR with the same dynamic stress. Finally, the quantitative relationship between TVSR parameters and residual stress is established, and the stress relief mechanism and effective parameter region of TVSR are analyzed.

Residual stress relief mechanisms of 2219 Al–Cu alloy by thermal stress relief method

Abstract Monolithic thin-wall components of 2219 Al–Cu alloy are widely used in aerospace and military fields, and usually treated with solution and quenching to improve their comprehensive performance. However, a high magnitude residual stress is introduced into the components during the quenching process, which is unfavorable to the subsequent manufacturing process and service performance. Therefore, residual stress relief is essential to enhance the performance of the components. A conventional effective method is thermal stress relief (TSR). However, the underlying mechanisms of TSR still remain unclear and lack a quantitative interpretation. In the present work, the evolution and distribution laws of the residual stresses, tensile properties, Vickers hardness, dislocations, precipitated phases, and metallography during TSR were investigated. Based on the experimental results, dislocation theory and strengthening mechanisms were applied to reveal the underlying mechanisms of the residual stress relief by TSR. The results showed that the circumferential and axial residual stress relief rates can reach 86.37 and 85.77% after TSR, respectively. The residual stress relief after TSR is attributed to the dynamic evolution of dislocation configuration and density. The improvement in the mechanical properties mainly depends on the precipitated phases and is also affected by the stress orientation effect caused by the residual stress.

Interfacial thermal stress relief in Ag–SnO2 composites by in situ formation of CuO nanoparticles additive on SnO2

Interfacial thermal stress is induced by the large differences in the thermal expand coefficients between SnO2 and the Ag matrix in the Ag–SnO2 composite, resulting in the initiation and propagation of microcracks during service. In this study, the in situ formation of CuO nanoparticle additive on SnO2 reinforcements was used to relieve interfacial thermal stress in Ag–SnO2 composites and the electrical contact performances were systematically evaluated. The CuO nanoparticles formed at the interface between SnO2 and the Ag matrix effectively inhibited the initiation and propagation of cracks in the Ag–SnO2 material during the arc erosion process. The arc erosion resistance of the prepared material was significantly improved, accompanied by a significant decrease in the arc energy. The thermal stress concentrated around the SnO2 phase was noticeably relieved by the CuO nanoparticles formed in situ, which is superior to that of the general CuO additive. Moreover, the electrical conductivity of the Ag–CuO@SnO2 composite increased by 41% and the contact resistance was quite stable. This work provides theoretical implications and serves as an application reference for the development of high-performance electrical contact materials.

Effects of TVSR process on the dimensional stability and residual stress of 7075 aluminum alloy parts

Abstract Residual stress generated during the blank forming and machining process significantly influences the dimensional stability of the mechanical parts. The equivalent bending stiffness and thermal vibration stress relief (TVSR) are two factors that affect the deformation of thin-walled workpiece. To increase the machining accuracy, on the one hand, increase the equivalent bending stiffness in manufacturing, and on the other hand, usually conduct the stress relief process to reduce the residual stress in manufacturing. In the present study, morphology optimization and TVSR process are conducted on a thin-walled part Specimen B of 7075 aluminum alloy to control the residual stress and machining deformation before finish machining. As a contrast, Specimen A is machined in one step. The deformations vary with time of Specimen A and B are measured. The corresponding finite element model is built to further study the stress and distortion during the machining process. Results showed that (1) deformation decreased with the increase of equivalent bending stiffness, compared with Specimen A, the maximum deformation of Specimen B decreased by 58.28%. (2) The final maximum deformation of Specimen B can be reduced by 38.33% by topology reinforcement to improve the equivalent stiffness and TVSR to reduce the residual stress.

Effects of segmented thermal-vibration stress relief process on residual stresses, mechanical properties and microstructures of large 2219 Al alloy rings

Large 2219 Al-Cu alloy transition rings are extensively employed in propellant tanks of heavy launch vehicles. These rings have a diameter exceeding 5 m or even reaching 10 m, with a less than 2% thickness-to-radius ratio, and low stiffness which can cause machining deformation due to the residual stress. Thus, residual stress relief of these rings is necessary in their extreme manufacture. A novel effective method is thermal-vibration stress relief (TVSR), which integrates the conventional thermal stress relief (TSR) and vibratory stress relief (VSR); however, the existing TVSR equipment cannot meet the requirements of large rings, and the underlying mechanisms of TVSR remain unclear and a quantitative interpretation is still lacking. Therefore, a segmented TVSR (STVSR) process suitable for large rings was proposed and the corresponding experiment was carried out with a self-made STVSR experiment platform. Then this study investigated the evolution and distribution laws of the residual stresses, tensile properties, Vickers hardness, dislocations, precipitated phases and metallography during STVSR. Based on the experimental results, multi-scale mechanics theory and strengthening mechanisms were applied to quantitatively reveal the underlying mechanisms of residual stress relief by STVSR. The results showed that the circumferential and axial residual stress relief rates can reach 44.43% and 45.14% after STVSR, respectively. The residual stress relief after STVSR is attributed to the dynamic evolution of dislocations and precipitated phases in the material. The improvement of mechanical properties mainly depends on the precipitated phases and is also affected by the residual stress. The findings confirm the significant effects of STVSR on metal plasticity and provide valuable insight into the underlying mechanisms of TVSR.