Thermal-mechanical Coupling Effect Research Articles

Study on fatigue damage characteristics of deformable mirrors under thermal-mechanical coupling effect.

In a wavefront correction process, both the mechanical effect and the irradiation of a high-power continuous-wave laser distort the deformable mirror (DM) surface, which inevitably speeds up the fatigue damage of the DM. By utilizing the stress analysis model for the fatigue damage of the DM, the fatigue damage effects are analyzed quantitatively on the consideration of thermal-mechanical coupling effects, and the fatigue life prediction model has further been proposed based on the S-N curve and Miner cumulative damage theory. On this basis, thermal-mechanical conditions have been analyzed, and the influence of laser parameters on the fatigue life of the DM has also been discussed in detail. The results indicate that the increasing of maximum temperature rise of the DM leads to the increasing of stress, and further brings about the decreasing of the fatigue life. Meanwhile, the position at the rear surface of the DM subjected to the maximum stress always presents the minimum fatigue life. Furthermore, the laser irradiation makes the DM more easily damaged when the DM is correcting a distorted wavefront, and the fatigue life decreases with the increasing of irradiation time and power density for a given peak and valley (PV) value of the corrected wavefront. Additionally, the fatigue life also decreases with the increasing of power density and the decreasing of spot radius for a certain total irradiation. On the other hand, for the given laser parameters, the influence of the mechanical effect on fatigue life is gradually apparent with increasing PV value of the corrected wavefront, and when the PV value is more than 2λ, the mechanical effect instead of the thermal effect becomes the key factor for fatigue damage of the DM.

Dynamic modeling and experimental verification for the feeding system of a gantry machine tool based on thermal-mechanical coupling

In order to study the dynamic performance of the feeding system of a gantry machine tool in its working process, a thermal-mechanical coupling dynamic modeling method was put forward. The structural performance analysis of the feeding system of a gantry machine tool shows that its dynamic performance is affected by combined action of heat and force in the working process. Based on exploring the thermal-mechanical coupling mechanism and effect, a dynamic model was established for the feeding system of the gantry machine tool, and the central difference method was applied to solve this model. The axis feeding system of a gantry machine tool was taken as research object; the correctness and feasibility of its thermal-mechanical coupling dynamic model was verified by comparing its solved results with that of vibration experiments, which provides a theoretical basis for the thermal-mechanical coupling dynamic analysis and optimization design subsequently.

Trans-scale modeling framework for failure analysis of cryogenic composite tanks

The mechanical performances of cryogenic composite tanks need strict evaluation due to its extreme temperature condition of service. In this paper, a trans-scale modeling strategy is developed for the failure analysis of cryogenic composite structures, which is based on theories from micromechanics to continuum mechanics. Micromechanical model of representative volume element is developed to obtain the thermo-mechanical coupling properties of materials in the composite structure. Continuum mechanics model is sub-sequentially developed to predict the fields of physical properties in the composite structures. The predictions of performances of composite structures at cryogenic and different temperatures are of good agreement with conventional theoretical solutions. Numerical examples of cryogenic composite tanks indicate that the large temperature change can directly cause the fracture of matrix that can result in the overall failure of composite tanks. In addition, the thermal–mechanical coupling effect can reduce the prediction of critical thermal loads in the failure analysis of cryogenic composite tanks, which is more favorable for engineering designs due to the strict requirements of safety.

A Novel Constitutive Formulation for Rubberlike Materials in Thermoelasticity

The objective of this paper is to present a new framework to formulate thermoelastic constitutive relations for initially isotropic rubberlike materials undergoing finite deformations. The strain-energy function for incompressible materials is extended to include the effects of compressibility and temperature changes. The novelty of this framework is that only a few material functions and material parameters to be fitted with the experimental data are required, and these functions and parameters have clear physical meaning. In order to validate the proposed formulation, the Gent–Gent model for incompressible rubbers is chosen as an illustrative example. A new expression of the Helmholtz free energy of rubberlike materials, which takes into account the material compressibility and thermal effect, is then derived. In this generalized Gent–Gent model, only one material function and six material parameters are introduced. It is shown that the generalized Gent–Gent model can be used to predict the stress-strain behavior over the entire range of deformation. Even for incompressible materials, the strain-energy function in this paper is different from that given by Gent himself. The generalized Gent–Gent model can also adequately describe the thermal-mechanical coupling effect, in which thermoelastic inversion phenomena occur.

Effects of cutting parameters on surface residual stress and its mechanism in high-speed milling of TB6

Formation mechanism and influence of cutting parameters on residual stress in flank milling of TB6 are investigated through orthogonal experiments. The thermal–mechanical coupling effect on forming residual stress is studied by analyzing the microstructure of metamorphic layer. Experiment results show that cutting temperature varies between 300 °C and 518 °C under experiment conditions, while residual compressive stress on machined surface is −199.8 to −41.7 MPa. Tensile residual stress occurs on subsurface when increasing milling parameters excessively. When cutting TB6 with parameters of fz = 0.02 mm/z, vc = 60 m/min, ae = 0.2 mm and ap = 10 mm, only the compressive residual stress can be detected, which is good for its fatigue life. The depth of compressive residual stress layer is 10–20 µm.

Investigation on Laser Etch-Machining Underwater Based on Thermal-Mechanical Effect

The method of high-energy short pulse laser etching underwater based on thermal - mechanical effect was put forward. In the experiment system with mask and salt solution , heat affected zone was visible decrease and the image of mask was micro-copied at the workpiece surface. Owing to the photochemical reaction and thermal-mechanical coupling effect, uniform line width of 120μm can be obtained.

Numerical simulation on the damage of buried thermal-pipeline under seismic loading based on thermal-mechanical coupling

The thermal-mechanical coupling effect is one of important factors in construction engineering, which will cause the buried thermal-pipeline to damage. So a three-dimensional finite element model is established based on ADINA-TMC, which considers thermal-mechanical coupling and seismic loading simultaneously. In this model, seismic loads and faults movement are defined. According to the numerical results, stresses and strains under gravity, seismic loading, and temperature load are compared, which provides theoretical method for failure analysis of buried thermal-pipeline.

Variational Principle of Carbon Nanotubes with Temperature Changes Based on Nonlocal Euler-Bernoulli Beam Model

In this paper, the CNTS are considered as the Euler-Bernoulli beams which have been used in many references about the CNTS. Taken the thermal-mechanical coupling and small scale effect into account, the variational principle for the CNTS is presented by the variational integral method. With the derivation of the varitional principle, the vibration governing equation is illustrated, which will be benefit for the numerical simulation with finite element method in further investigations. From the stationary value conditions deduced by the variational principle, the influences of the temperature changes and the thermal expansion coefficients based on nonlocal Euler-Bernoulli beam model are presented.