THERMAL CONSOLIDATION OF LAYERED POROUS HALF-SPACE TO VARIABLE THERMAL LOADING

An analytical method was derived for the thermal consolidation of layered, saturated porous half-space to variable thermal loading with time. In the coupled governing equations of linear thermoelastic media, the influences of thermo-osmosis effect and thermal filtration effect were introduced. Solutions in Laplace transform space were first obtained and then numerically inverted. The responses of a double-layered porous space subjected to exponential decaying thermal loading were studied. The influences of the differences between the properties of the two layers （e.g., the coefficient of thermal consolidation, elastic modulus） on thermal consolidation were discussed. The studies show that the coupling effects of displacement and stress fields on temperature field can be completely neglected, however, the the thermal responses. effect has an obvious influence on

A Theoretical Analysis of Functionally Graded Beam under Thermal Loading

Modeling of the behavior for Functionally Graded Beam (FGB) under thermal loading is introduced in the present work. The material properties are assumed to vary according to power function along the thickness of the beam. The effects of several parameters such as thermal expansion parameter, thermal conductivity and modulus of elasticity on the resultant axial stress of the FG beam have been studied. For thermal loading the steady state of heat conduction with power and exponentially variations through the thickness of FGB, is considered. The results obtained show that temperature distribution plays very important parameter controlling thermal resultant distribution of stresses and strains.

Stability and local bifurcation of parameter-excited vibration of pipes conveying pulsating fluid under thermal loading

The parametric excited vibration of a pipe under thermal loading may occur because the fluid is often transported heatedly. The effects of thermal loading on the pipe stability and local bifurcations have rarely been studied. The stability and the local bifurcations of the lateral parametric resonance of the pipe induced by the pulsating fluid velocity and the thermal loading are studied. A mathematical model for a simply supported pipe is developed according to the Hamilton principle. Two partial differential equations describing the lateral and longitudinal vibration are obtained. The singularity theory is utilized to anMyze the stability and the bifurcation of the system solutions. The transition sets and the bifurcation diagrams are obtained both in the unfolding parameter space and the physical parameter space, which can reveal the relationship between the thermal field parameter and the dynamic behaviors of the pipe. The frequency response and the relationship between the critical thermal rate and the pulsating fluid velocity are obtained. The numerical results demonstrate the accuracy of the single-mode expansion of the solution and the stability and local bifurcation analyses. It also confirms the existence of the chaos. The presented work can provide valuable information for the design of the pipeline and the controllers to prevent the structural instability.

Analysis of energy pile groups subjected to non-uniform thermal loadings

Sequentially coupled thermal-stress finite element analyses were performed to investigate the mechanical behaviors of an energy pile group subjected to non-uniform thermal loadings.The group effect was highlighted by comparing the thermo-mechanical responses with those of the single pile case.Due to the thermal interactions between piles,the group piles’temperatures were higher than that of the isolated single pile.If only part of the piles served as heat exchangers,i.e.,the pile group was thermal loaded unevenly,there were dif-ferential deformations between the heated and the non-heated piles.Due to the pile-raft-pile interaction,the axial forces of the piles chan-ged significantly.The location of the heated pile had an important influence on the thermally induced axial force,while the effect of the soil’s coefficient of thermal expansion was not significant.Inspired by the numerical result,a simplified method was proposed to capture the main characteristics of energy pile groups and to facilitate the design.The proposed method was developed in the framework of the traditional load transfer approach,and the pile-raft-pile interaction was included.By applying different temperature increments to dif-ferent piles,the non-uniform thermal loading was modeled.The proposed method was verified by comparing with the finite element anal-ysis results and the data collected from the literature.

INFLUENCE OF TEMPERATURE-DEPENDENT PROPERTIES ON THERMAL STRESSES RESPONSE AND OPTIMUM DESIGN OF C/M FGMS UNDER THERMAL CYCLIC LOADING

The influence of temperature-dependent properties on thermal stresses response and optimum design of newly developed ceramic-metal functionally graded materials under cyclic thermal loaning and high temperature gradient environment is studied. The thermal conductivity of material is considered to be dependent on the temperature. In this paper, the thermal stresses response of the material is calculated rising a nonlinear finite element method. Emphasis is placed on the influence of temperature-dependent properties on the thermal stresses response characteristics, the thermal stresses relaxation property and the thermal stresses history under the different graded compositional distributions and different heat flux magnitudes. Through tile analysis. it is suggested that the influence of temperature-dependent properties can not be neglected In the thermal stresses response analysis and the optimum design process of the material must be based on the temperature-dependent thermo-elastic-plastic theory.

Experimental Measurements of the Sensitivity of Fiber-optic Bragg Grating Sensors with a Soft Polymeric Coating under Mechanical Loading,Thermal and Magnetic under Cryogenic Conditions

The strain and temperature sensing performance of fiber-optic Bragg gratings （FBGs） with soft polymeric coating, which can be used to sense internal strain in superconducting coils, are evaluated under variable cryogenic field and magnetic field. The response to a temperature and strain change of coated-soft polymeric FBGs is tested by comparing with those of coated-metal FBGs. The results indicate that the coated-soft polymeric FBGs can freely detect temperature and thermal strain, their At variable magnetic field, the tested results indicate accuracy and repeatability are also discussed in detail. that the cross-coupling effects of FBGs with different matrixes are not negligible to measure electromagnetic strain during fast excitation. The present results are expected to be able to provide basis measurements on the strain of pulsed superconducting magnet/cable （cable- around-conduit conductors, cable-in-conduit conductors）, independently or utilized together with other strain measurement methods.

INFLUENCE OF TEMPERATURE-DEPENDENT PROPERTIES ON TEMPERATURE RESPONSE AND OPTIMUM DESIGN OF C/M FGMS UNDER THERMAL CYCLIC LOADING

The influence of temperature-dependent properties on temperature response and optimum design of newly developed ceramic-metal functionally graded materials under cyclic thermal loading and high temperature gradient environment is studied. The thermal conductivity of the material is considered to be dependent on the temperature. In this paper, the temperature response of the material is calculated using a nonlinear finite element method. Emphasis is placed on the influence of temperatue-dependent properties on the thermal response and insulation property of the material render the different graded compositional distributions and different heat flux magnitudes. Through the analysis, it is suggested that the influence of temperature-dependent properties can not be neglected in the temperature response analysis and the optimum design process of the material must be based on the temperature-dependent temperature analysis theory.

The thermal effect in diode-end-pumped continuous-wave 914-nm Nd:YVO_4 laser

The thermal effect and the heat generation in diode-end-pumped continuous-wave 914-nm Nd：YVO4 lasers are investigated in detail. A theoretical model of a diode end-pumped solid-state laser is constructed to analyse the influence of fractional thermal loading on the thermal effect in the Nd：YVO4 laser based on finite element analysis. The thermal focal lengths and the end-surface deformations of laser rods in Nd：YVO4 quasi-three-level and four-level lasers are measured and compared with the results obtained by ordinary interferometry for the demonstration of higher thermal loading in 914-nm laser. Finally the fractional thermal loading in the Nd：YVO4 quasi-three-level laser is calculated by matching the experimental and the simulated end deformations.

NON-LINEAR DYNAMIC BEHAVIOR OF THERMOELASTIC CIRCULAR PLATE WITH VARYING THICKNESS SUBJECTED TO NONCONSERVATIVE LOADING

The non-linear dynamic behaviors of thermoelastic circular plate with varying thickness subjected to radially uniformly distributed follower forces are considered. Two coupled non-linear differential equations of motion for this problem are derived in terms of the transverse deflection and radial displacement component of the mid-plane of the plate. Using the Kantorovich averaging method, the differential equation of mode shape of the plate is derived, and the eigenvalue problem is solved by using shooting method. The eigencurves for frequencies and critical loads of the circular plate with unmovable simply supported edge and clamped edge are obtained. The effects of the variation of thickness and temperature on the frequencies and critical loads of the thermoelastic circular plate subjected to radially uniformly distributed follower forces are then discussed.

THERMO-ELASTIC-PLASTIC RESPONSE AND OPTIMUM DESIGN OF CERAMIC-METAL FGMS-CYCLIC THERML LOADING PROBLEM

The materials are made with a graded composition and microstructure in the thickness direction from the ceramic side to the metal side. The cyclic thermal loading and high temperasure gradient environment are simulated by heating the ceramic surface with a cyclic hear flux input and cooling the metal surface with a flowing liquid niterogen. The thermal and themo-elastic-plastic response of the materials is calculated using the isotropic hardening model and kinetic hardening model. Emphasis is placed on the response analysis under the different graded compositional distributions. Through the response analysis, the optimum design process of the graded composition under the dynamic case is established, which is bused on a unified viewpoint of the heat insulation property, thermal stress relaxation property and stress history feature.

Numerical modeling of thermally-induced fractures in a large rock salt mass

Numerical modeling of thermally-induced fractures is a concern for many geo-structures including deep underground energy storage caverns. In this paper, we present the numerical simulation of a large-scale cooling experiment performed in an underground rock salt mine. The theory of fracture mechanics was embedded in the extended finite element code used. The results provide reliable information on fracture location and fracture geometry. Moreover, the timing of the fracture onset, as well as the stress redis- tribution due to fracture propagation, is highlighted. The conclusions of this numerical approach can be used to improve the design of rock salt caverns in order to guarantee their integrity in terms of both their tightness and stability.

Thermal Analysis of a Novel Oil Cooled Piston Using a Fluid-Solid Interaction Method

Thermal load has a vital influence on the normal operation and service life of diesel engines.In this study,the thermal load and oil-cooling effect on diesel engine pistons were investigated by means of computational fluid dynamics.In particular,the flow and heat transfer characteristics of the cooling gallery were determined during the oscillation of the piston.Moreover,the temperature field distribution of the piston with and without the cooling gallery were compared.The results revealed that the cooling gallery has a prominent effect on reducing the thermal load on the piston crown and piston lands.To fully understand the oscillating heat transfer effect related to the cooling gallery and verify the accuracy of the calculation,the numerical results were also compared with temperature values experimentally measured at key positions of the piston.The measurements were found to be consistent with the calculation results within an acceptable error range,which proves the rationality and accuracy of the mathematical and numerical models used.

Influence of Thermal Load on Mechanical Property of Cemented Carbide Material and Heavy Cemented Carbide Inserts Life

A large amount of cutting heat is produced during the heavy cutting process,and insert life is restricted by the effect of thermal load. The thermal load experiment of cemented carbide SCS,WF and YT15 is carried out,and the results show that the bending strength and fracture toughness of cemented carbide material decrease obviously under cyclic thermal load,while in the cooling process,the material mechanical property changes worse suddenly. The high-temperature mechanical property of SCS is the most stable,and that of YT15is the worst. Further,a relation model among cutting temperature,cutting parameters and insert life is established. Finally,the measures to improve heavy cemented carbide inserts life are summarized from the aspects of cutting parameters selection,insert optimization design and TiCN,A12O3,TiN complex insert coating. The research results are expected to provide support and reference for heavy cutting technology and insert technology.

Thermal-induced snap-through buckling of simply-supported functionally graded beams

The instability of functionally graded material(FGM)structures is one of the major threats to their service safety in engineering applications.This paper aims to clarify a long-standing controversy on the thermal instability type of simply-supported FGM beams.First,based on the Euler-Bernoulli beam theory and von K′arm′an geometric nonlinearity,a nonlinear governing equation of simply-supported FGM beams under uniform thermal loads by Zhang’s two-variable method is formulated.Second,an approximate analytic solution to the nonlinear integro-differential boundary value problem under a thermal-induced inhomogeneous force boundary condition is obtained by using a semiinverse method when the coordinate axis is relocated to the bending axis(physical neutral plane),and then the analytical predictions are verified by the differential quadrature method(DQM).Finally,based on the free energy theorem,it is revealed that the symmetry breaking caused by the material inhomogeneity can make the simply-supported FGM beam under uniform thermal loads occur snap-through postbuckling only in odd modes;furthermore,the nonlinear critical load of thermal buckling varies non-monotonically with the functional gradient index due to the stretching-bending coupling effect.These results are expected to provide new ideas and references for the design and regulation of FGM structures.

Transverse Vibration and Stability Analysis of Circular Plate Subjected to Follower Force and Thermal Load

Transverse vibration and stability analysis of circular plate subjected to follower force and thermal load are analyzed.Based on the thin plate theory in involving the variable temperature,the differential equation of transverse vibration for the axisymmetric circular plate subjected to follower force and thermal load is established.Then,the differential equation of vibration and corresponding boundary conditions are discretized by the differential quadrature method.Meanwhile,the generalized eigenvalue under three different boundary conditions are calculated.In this case,the change curve of the first order dimensionless complex frequency of the circular plate subjected to the follower force in the different conditions with the variable temperature coefficient and temperature load is analyzed.The stability and corresponding critical loads of the circular plate subjected to follower force and thermal load with simply supported edge,clamped edge and free edge are discussed.The results provide theoretical basis for improving the dynamic stability of the circular plate.

A Study on the Relationship between Anodic Oxidation and the Thermal Load on the Aluminum Alloy Piston of a Gasoline Engine

In order to analyze the influence of the anodizing process on the thermal load of an aluminum alloy piston,dedicated temperature tests have been carried out using the Hardness Plug method and the results for the anodized piston have been compared with those obtained separately for an original aluminum piston.In addition,numerical simulations have been conducted to analyze the temperature field and thermal stress distribution.Simulations and experiments show that the maximum temperature of the anodized piston is 16.36%and 5.4%smaller than that of the original piston under the condition of maximum torque and maximum power,respectively.The thermal stress of the temperature field of both pistons is within 50 Mpa,which meets the strength requirements of the material at high temperature.However,the area with significant thermal stress of the anodized piston is significantly smaller than that of the original piston.Combined with the fatigue analysis data,it can be seen that the safety factor of the anodized piston greater than 1.8 is 99.13%.Therefore,adopting the anodizing process not only reduces the piston thermal load,but also helps to extend its life and improve its reliability.

Effect of Thermal Cycling under Load on Martensite Transformation and Two-way Shape Memory Effect in a TiNi Alloy

The effect of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at. pci Ni alloy. It is shown that Ms and Mf temperature increase with increasing the number of cycles, while As and Af temperature decrease during thermal cycling. The total strain et and permanent strain ep increase with increasing applied stress and number of cycles. The two-way shape memory effect can be improved by proper thermal cycling training under loading, while excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and two-way shape memory effect during thermal cycling under loading is discussed based on the analysis of microstructure by TEM observations.

Non-uniform thermal behavior of single-layer spherical reticulated shell structures considering time-variant environmental factors: analysis and design

Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.

Efficient 2D Analysis of Interfacial Thermoelastic Stresses in Multiply Bonded Anisotropic Composites with Thin Adhesives

In engineering practice,analysis of interfacial thermal stresses in composites is a crucial task for assuring structural integrity when sever environmental temperature changes under operations.In this article,the directly transformed boundary integrals presented previously for treating generally anisotropic thermoelasticity in two-dimension are fully regularized by a semi-analytical approach for modeling thin multi-layers of anisotropic/isotropic composites,subjected to general thermal loads with boundary conditions prescribed.In this process,an additional difficulty,not reported in the literature,arises due to rapid fluctuation of an integrand in the directly transformed boundary integral equation.In conventional analysis,thin adhesives are usually neglected due to modeling difficulties.A major concern arises regarding the modeling error caused by such negligence of the thin adhesives.For investigating the effect of the thin adhesives considered,the regularized integral equation is applied for analyzing interfacial stresses in multiply bonded composites when thin adhesives are considered.Since all integrals are completely regularized,very accurate integration values can be still obtained no matter how the source point is close to the integration element.Comparisons are made for some examples when the thin adhesives are considered or neglected.Truly,this regularization task has laid sound fundamentals for the boundary element method to efficiently analyze the interfacial thermal stresses in 2D thin multiply bonded anisotropic composites.