Residual Thermal Stresses in Multilayered Functionally Graded Material Plates

Functionally Graded Material (FGM) is a heterogeneous composite material that consists of a gradient compositional variation of the constituent materials from one surface of the material to the other. These continuous changes result in gradient material properties. Since ceramic has good heat resistance and metal has high strength, FGM made by ceramic and metal can work at super high temperatures or under a high-temperature-difference field. It is a primary to reduce thermal stress by selection of different effective material properties for the intermediate composition of the EGM and to prevent destruction by thermal stress. FGM is manufactured at a high temperature and then residual thermal stresses are produced during cooling to room temperature. In this paper, the elastic-plastic thermal stresses induced in a ceramic-metal FGM plate (FGP) taking the fabrication process into consideration are discussed. The region near the heat resistant surface is produced by metal particle reinforced ceramic while the region near the cooling surface is vice versa. As the metal and the ceramic near the middle region of the FGM are perfectly mixed, it is impossible to consider the particle-reinforced material. In this study, the FGP is divided into three regions. First, the region near the cooling surface is metal rich and then the metal is considered as a matrix while the ceramic is considered as particles. Second, the region near the heat resistant surface is ceramic rich so that the ceramic is considered as a matrix while the metal is considered as particles. Third, in the middle part between the previous two regions the metal and ceramic are perfectly mixed. In the third region macroscopic analysis is considered because the difference between the volume fractions of the ceramic and the metal is small and it is difficult to consider one of them as a matrix or particles. The effects of the distribution parameter of the composition and the fabrication temperature on the thermal stress variations are discussed.

Study on thermal shock behavior of YSZ abradable sealing coating prepared by mixed solution precursor plasma spraying

The adhesive bonding technique is widely used for joining similar or dissimilar materials in various engineering areas. Mismatches in the thermal expansion coefficients of adhesive and adherend materials in the vicinity of bi-material interfaces result in incompatible thermal strains and discontinuous thermal stress distributions along the bi-material interfaces. During the adhesive curing process, thermal residual stresses are induced due to the chemical and physical changes in adhesive material. The expansion of the adhesive with changes in moisture and temperature levels is the reason for hygroscopic residual stresses. Non-uniform temperature or material composition distributions also result in non-uniform thermal strain and stress distributions. Loading with a relatively high frequency cyclic component may result in a temperature rise due to internal heat generation and consideration of viscoelastic time-temperature effects may become necessary in the stress analysis even at moderately low temperatures. The crack nucleation, initiation and propagation around bi-material notches, and the fatigue crack growth in adhesively bonded integrated structures are important design considerations under cycling thermal loads. Therefore, the thermal strain and stress states of the adhesive joints should be analysed in order to predict the joint strength accurately and to improve joint service life. This article reviews from simple to more complicated mathematical models to analyse the thermal stress and deformation states of various adhesive joints under both steady state and transient thermal conditions.

FEM analysis of the stress response and failure mechanism of SiC-coated Cf/SiC composites during thermal shock

Residual stresses in thermoplastic composites – a study of the literature. Part III: Effects of thermal residual stresses

Thermal stresses in porcelain veneered lithium disilicate and zirconia dental crowns: Comparative analysis using a validated viscoelastic finite element model.

In this paper, numerical study analysis of residual thermal stresses in aluminum matrix reinforced with silicon carbide particles with double-crack has been carried out. is studied in order to determine the thermo-mechanical behavior under the effect of different temperature gradients during cooling. For a more realistic simulation of the microstructure of these materials subjected to different loadings, a representative volume element may be used. In this paper, three different types of crack width a = 5 μm, 10 μm, 15 μm, has been carried. The thermal residual stresses are calculated by considering a wide range of cracks of different penetrations proximity to particle of 0.1, 0.2 and 0.5 μm. regarding the distribution of the stresses along the plane of the crack and in vicinity of the particle, results show that the penetration of the crack in the matrix causes an asymmetry. The inter-distance between crack and particle plays an important role regarding the generation of residual stresses. The lower the inter-distance, the higher the internal stresses of normal residual stresses of σzz .

Residual stress field and thermal relaxation behavior of shot-peened TC4-DT titanium alloy

Analysis of residual thermal stress for AlN crystal growth by PVT

Thermal residual stress analysis of epoxy bi-material laminates and bonded joints

The residual thermal stresses induced in high-porous fibrous silicon nitride ceramics with fine reinforcement inclusions have been computed within numerical experiment. The computations have been performed employing a coupled transient linear thermoelastic problem. The initial state characterized by zero internal stresses is observed when the material is synthesized at high temperatures. Three-dimensional representative fragments of fibrous structures generated with stochastic algorithms accounting for the set microstructural parameters have been used for the simulation. The effect of the volume content and size of reinforcement as silicon carbide spherical inclusions on residual thermal stresses has been demonstrated. The simulations show that the residual stresses are commonly higher than the ultimate strength of the porous materials under study.

Metal-ceramic composites by their nature have thermal residual stresses at the micro-level, which can compromise the integrity of structural elements made from these materials. The evaluation of thermal residual stresses is therefore of continuing research interest both experimentally and by modeling. In this study, two functionally graded aluminum alloy matrix composites, AlSi12/Al2O3 and AlSi12/SiC, each consisting of three composite layers with a stepwise gradient of ceramic content (10, 20, 30 vol%), were produced by powder metallurgy. Thermal residual stresses in the AlSi12 matrix and the ceramic reinforcement of the ungraded and graded composites were measured by neutron diffraction. Based on the X-ray micro-computed tomography (micro-XCT) images of the actual microstructure, a series of finite element models were developed to simulate the thermal residual stresses in the AlSi12 matrix and the reinforcing ceramics Al2O3 and SiC. The accuracy of the numerical predictions is high for all cases considered, with a difference of less than 5 % from the neutron diffraction measurements. It is shown numerically and validated by neutron diffraction data that the average residual stresses in the graded AlSi12/Al2O3 and AlSi12/SiC composites are lower than in the corresponding ungraded composites, which may be advantageous for engineering applications.

Power transmission shafts such as driving shafts or automotive propeller shafts should transmit static and dynamic torques with vibrational stability. Hybrid shafts made of unidirectional fiber-reinforced composite and metal have high fundamental bending natural frequency as well as high torque transmission capability: composite increases the fundamental bending natural frequency due to its high specific stiffness and metal such as aluminum or steel transmits the required torque. However, fabrication-induced thermal residual stresses due to the coefficient difference of thermal expansion of the composite and the metal are developed during manufacturing hybrid shafts so that the high residual stresses decrease fatigue resistance of the hybrid shafts, especially at low operating temperatures. In this paper, the torsional fatigue characteristics of aluminum–composite co-cure joined shafts with axial compressive preload were investigated. To change the thermal residual stresses, an axial compressive preload was given to the aluminum tube by a compressive jig during the co-cure bonding operation. In order to determine the thermal residual stresses with respect to the preload and temperature difference, stress analyses were performed by simple equations from mechanics of materials and finite element method. Then the static torque capacities and fatigue strengths of the hybrid shafts from static and fatigue torsional tests were correlated with the calculated thermal residual stresses. The fatigue strength of the hybrid shaft was much improved by the axial compressive preload, exceeding that of a pure aluminum shaft. Also, the degradation of the fatigue resistance of the hybrid shaft at subzero operating temperature was overcome by the axial compressive preload.

In the manufacturing process of solid oxide fuel cells (SOFCs), the residual stresses and curvature are developed in components due to the differences in material properties of cell layers. Residual stress may lead to the crack formation in the cell layers and facilitates cell fracture. In this work, the changes of the residual stress in the electrolyte layer of the anode-supported planar solid oxide fuel cells are experimentally determined at room temperature. The “sin2ψ” technique of X-ray diffraction method is employed to measure the residual stress in the half-cell samples. Investigation on the changes of the residual stress and curvature state in the scaling-up process of the cell is crucial for commercial use. Therefore, several cells with different sizes and shapes are investigated to evaluate the potential impact of cell size and cell shape on the residual thermal stress. Values of about −610 MPa are determined for the electrolyte layer on an oxidized ∼400 μm thick anode substrate. The results reveal that despite the effect of size and shape on the radius of curvature, these parameters have no significant impact on the residual stress level.

Thermomechanical analysis of residual stresses in brazed diamond metal joints using Raman spectroscopy and finite element simulation