Thermal Residual Stress Distribution Research Articles

Stress distribution around Fe5Si3 and its effect on interface status and mechanical properties of Si3N4 ceramics

AbstractSi3N4 ceramics with different amount of Fe5Si3 were prepared by adding FeSi2. Residual thermal stress distribution and elastic energy around Fe5Si3 particles in various depths were calculated. The interface status between second phase particles and matrix was analyzed in terms of stress and energy. High tangential compressive stresses and low radial tensile stresses were generated along the surface of the ceramics. Elastic strain energy caused by unit interface was high around big particles in deep area of the ceramics. Microcracks are observed around the big Fe5Si3 particles. Furthermore, accord to our calculation, microcracks are easily generated around particles in superficial layer of matrix when second phase particles have lower thermal expansion coefficient than the matrix, while microcracks tend to be generated in deep layer of matrix preferentially when the thermal expansion coefficient of second phase particles is higher than matrix. Residual stresses and microcracks around Fe5Si3 particles greatly influenced mechanical properties. Fracture toughness of Si3N4 ceramics with similar Si3N4 particle size distribution increased with the amount of Fe5Si3, and fine Fe5Si3 particles could enhance the strength of Si3N4 ceramics. Si3N4 ceramics exceeding 1.2 GPa strength were prepared.

Experimental and numerical investigation into effect of weld configuration geometry on distribution of residual stress and temperature in the welded parts of stainless steel

In multi-pass grooved welding, residual stress and corresponding distortion are highly affected by welding process parameters, material properties, and fixture design. Therefore, having knowledge about value of the residual stress and transient temperature yields long life joints with high dimensional accuracy. In the present study, three joints with different T-joint configurations made of 316 stainless steel were fabricated through gas tungsten arc welding process. The first configuration includes single bevel without root face and gap, the second includes single bevel with root face and 1 mm gap, and the third includes double bevels with root face and 1 mm gap. In order to evaluate temperature and residual stress distribution, finite element simulation of aforementioned process using SIMUFACT WELDING software along with hole-drilling method (as semi-destructive evaluation) and ultrasonic method (as non-destructive evaluation) were performed. Also, thermal history of welding process was recorded by K-type thermocouple. Research findings showed that the thermal history and residual stress distribution which were obtained through FE simulation are in high agreement with those derived from both ultrasonic and hole-drilling methods. Furthermore, the change in joint configuration significantly affects transverse residual stress but it has not great impact on longitudinal residual stress. Also, the highest and lowest residual stress and corresponding distortion are for the first and third configurations, respectively.

Mechanical properties and residual stresses in ZrB2–SiC spark plasma sintered ceramic composites

ZrB2-17vol% SiC, ZrB2-32vol% SiC, and ZrB2-45vol% SiC ultra-high temperature particulate ceramic composites were sintered using Spark Plasma Sintering (SPS). The mechanical performance of the ZrB2–SiC composites was investigated using 4-point bending to determine their instantaneous flexural strength and fracture toughness. Resonant Ultrasound Spectroscopy was used to determine the Young’s, shear, and bulk moduli as well as Poisson’s ratio of all examined composites. The distribution of thermal residual stresses and the effect of applied external load on their re-distribution was studied using micro-Raman spectroscopy. Piezospectroscopic coefficients were determined for all three ZrB2–SiC ceramic composites and their experimentally obtained values were compared with the piezospectroscopic coefficients both published in the literature and calculated theoretically. Finally an attempt was made to evaluate the redistribution of thermal residual stresses under external applied stress in order to estimate their contribution to the mechanical behavior of the material.

Finite element analysis of the residual thermal stresses on functionally gradated dental restorations

The aim of this work was to study, using the finite element method (FEM), the distribution of thermal residual stresses arising in metal–ceramic dental restorations after cooling from the processing temperature. Three different interface configurations were studied: with conventional sharp transition; one with a 50% metal–50% ceramic interlayer; and one with a compositionally functionally gradated material (FGM) interlayer. The FE analysis was performed based on experimental data obtained from Dynamic Mechanical Analysis (DMA) and Dilatometry (DIL) studies of the monolithic materials and metal/ceramic composites.Results have shown significant benefits of using the 50% metal–50% ceramic interlayer and the FGM interlayer over the conventional sharp transition interface configuration in reduction of the thermal residual stress and improvement of stress profiles. Maximum stresses magnitudes were reduced by 10% for the crowns with 50% metal–50% ceramic interlayer and by 20% with FGM interlayer. The reduction in stress magnitude and smoothness of the stress distribution profile due to the gradated architectures might explain the improved behavior of these novel dental restorative systems relative to the conventional one, demonstrated by in-vitro studies already reported in literature.

Damage evolution and multi-scale analysis of carbon fiber-reinforced cross-ply laminate with thermal residual stress

In order to study the mechanical and thermal properties of carbon fiber-reinforced cross-ply laminate, a macroscopic [90/0]8S cross-ply laminate model and a unit cell of fiber regular distribution near the [90/0]8S laminate interlaminar zone with plastic matrix and interface were created. Then the damage initiation discipline details of [90/0]8S cross-ply laminate are researched, and the effects of interfacial coefficient of thermal expansion on thermal residual stress distribution and damage initiation are researched in detail both based on the macroscopic and microscopic models. It shows that the initial damage of interlaminar interface occurs in macroscopic model and the initial damage in microscopic model occurs both at intralaminar interface and interlaminar cohesive zone. No matter in macroscopic or microscopic model, the residual stress of 6.27 × 10−6/°C interfacial coefficient of thermal expansion is larger than that of 6.27 × 10−7/°C interfacial coefficient of thermal expansion. And the initial damage expands more widely in the first one.

Analysis on the Welding Thermal Field and Residual Stress of Thick Plate

A 60mm Q345 rigid thick plate with V groove welding connection was modeled in order to simulate the welding residual stress by finite element method. Both element birth and death technique and double ellipse heat source model were introduced to simulate the welding process. The welding thermal field and residual stress of thick steel plate were analyzed by finite element simulation software ANSYS.Then the thermal field and residual stress distribution were visually demonstrated. The result shows that the thermal field shaped like a spindle during welding period and the residual stress at the mid-section in lateral, longitudinal and thickness direction of the welding joint is lower than the stress at the surface of the welding connection.

Residual thermal stresses in carbon/carbon–Zr–Ti–C composites and their effects on the fracture behavior of composites with different preforms

Carbon/carbon(C/C)–Zr–Ti–C composites were fabricated using chemical vapor infiltration and liquid metal infiltration processes. The residual thermal stress (RTS) distribution in the C/C–Zr–Ti–C composites was analyzed by Raman spectroscopy and finite element (FE) calculation. The mechanical behaviors of C/C–Zr–Ti–C composites with three types of carbon fiber preforms were tested. The results showed that there was very high compressive RTS in the fibers and high tensile RTS in the pyrocarbon (PyC) in the marginal region near the carbide. However, in the central region away from the carbide, relatively low compressive stress and tensile RTS were found in the fibers and PyC, respectively. The FE analysis showed that the introduction of carbide into the C/C composites caused a significant increase of the RTS in the PyC near the carbide, indicating that the carbide could change the RTS distribution in C/C composites. Moreover, the distribution of the RTS and its release combined with the carbide distribution and fiber architecture led to variations in the mechanical performance of composites with different preforms.

Effect of Thermal Residual Stresses on Bonded Structures Containing Cold Expanded and Bolted Holes

The primary focus of this investigation is to determine the distribution of thermal residual stresses that result during composite bonding processes, and the effect on stresses generated during the subsequent cold expansion of holes. Residual stress measurements were carried out using neutron diffraction techniques. Results show that the cold expansion process resulted in radial compressive stresses 3-4 mm from the edge of the hole and there was no significant effect of thermal residual stresses from the bonding process on the cold expansion and bolted stresses.

Multi-Scale Modeling and Damage Analysis of Composite with Thermal Residual Stress

In order to analysis thermal residual stress and its influence on the strength of composite, the hierarchical multi scale simulation method is applied. A microscopic computational model of single fiber composite with thermal residual stress is built to research the stress distribution. Then the damage initiation discipline details of unidirectional composite are researched, and the effects of different fiber arrangements on thermal residual stress distribution, damage initiation and the different final failure behaviors of fiber regular distribution and random distribution under tension and compression are researched in details. It shows that in fiber regular arrangement, damage initiation in interface appears evenly and in matrix it appears at somewhere randomly. But in fiber random arrangement, initial damage focuses at the resin pockets between closely packed fibers with both interface and matrix damage. The maximal thermal residual stress in fiber random arrangement model is larger than that in fiber regular arrangement model. And it reaches the normal strength of the interface and thus causing the initiation of interface damage. Also the failure modes of composites under transverse tension and compression with and without residual stress are quite different from each other. The strength and failure path of different RVE and loading are showing respectively in this paper.

Thermal stress analysis on chemical vapor deposition tungsten coating as plasma facing material for EAST

Chemical vapor deposition-tungsten (CVD-W) coating on CuCrZr surface forming a flat-type structure is likely to be used as the vacuum wall materials except the divertor areas in EAST during its up-grade phase. This paper describes the residual thermal stress distribution in CVD-W coating substrate system using finite element analysis method (ANSYS code). Especially, the influence of interlayers, i.e. oxygen-free Cu (OFC) and W/Cu functionally gradient materials (FGMs) interlayer have been investigated in view of stress alleviation. Both the OFC and W/Cu FGMs interlayer can reduce the residual thermal stress, in which the OFC shows better interface and surface stress distribution than W/Cu FGMs, and is a preferred interlayer for CVD-W coating processing.

Evolution of residual stress during fatigue crack growth in an aluminium specimen with a bonded crack retarder

The application of bonded crack retarders in critical aircraft integral structures has been of great interest recently for the improvement of damage tolerance. One potential disadvantage of bonded crack retarders is that the thermal residual stresses which are developed during the strap bonding process are detrimental to the performance of the structure. This investigation explores the distribution of thermal residual stresses developed in an aluminium substrate reinforced with GLARE (glass-fibre-reinforced epoxy) straps and the evolution of stresses during fatigue crack growth. Residual stress measurements were performed using neutron diffraction. The results show that tensile residual stresses are developed in the aluminium substrate as a consequence of the strap bonding process. In situ residual stress measurements during constant amplitude fatigue crack growth were performed and it was observed that the growth of the fatigue crack altered the initial residual stress.

Thermal Residual Stresses in W Fibers/Zr-based Metallic Glass Composites by High-energy Synchrotron X-ray Diffraction

Thermal residual stresses in W fibers/Zr-based metallic glass composites were measured by in situ high energy synchrotron X-ray diffraction (HEXRD). The W fibers for the composites were 300, 500, and 700 μm in diameter, respectively. Coaxial cylinder model (CCM) and finite element model (FEM) were employed to simulate the distribution of thermal residual stress, respectively. HEXRD results showed that the selected diameters of W fiber had little influence on the value of thermal residual stresses in the present composites. Thermal residual stresses simulated by CCM and FEM were in good agreement with HEXRD measured results. In addition, FEM results exhibited that thermal residual stress concentrated on interface between the two phases and area where the two W fibers were the closest ones to each other.

Residual stress modeling of narrow gap welded joint of aluminum alloy by cold metal transferring procedure

Research on FE method simulation of CMT+P MIX welding process has been suspended because of the absence of qualified model for characterizing cooperation between wire feeding and heat input. A novel 3D FE thermo-mechanical model was established, in which impulse input of weld wire and weld heat was simplified by decreasing the impulse frequency. Materials were modeled as elastic-perfectly-plastic with composite heat sources utilized. Numerically simulated results were validated by thermal cycle curves and residual stress distribution obtained with infrared photography instrument and X-ray diffraction tester, respectively. The numerical residual stress distribution also got well supported by the tested results obtained by the blind-hole method. Residual stress evolution was analyzed, whereas special attention was paid to the influences on residual stress distribution by the subsequent weld passes. Based upon this was the vulnerable area of the joint identified under the conduction of different strength theories. The global stress distribution was found to be dominated by the first weld pass while more residual stress in the re-melted zone than that in the HAZ could be released by the last two welding passes. The mechanism was studied through the yielding process of residual strain which was divided into two steps.

An Educational Platform in Structural Mechanics

Thermal residual stresses often arise due to a manufacturing process, involving localised thermal induction, or to the existence of structural components with different thermal expansion coefficients. The existence of thermal residual stresses within a structural member is usually undesired, as it decreases the mechanical resistance of structures. Hence, it is desirable to obtain both a minimum level of residual stresses and smoother stresses transitions in the materials interfaces. Regarding the mitigation of thermal residual stress concentration, the use of materials which properties can vary along the component directions has great interest. This work addresses the use of dual-phase functionally graded materials, which microstructure varies gradually from a material to another according to a given gradation function. On the order hand, it is also addressed the use of a population based optimization algorithm in order to attain the referred minimum stress level. Summarizing, the current work presents an educational platform directed to structural mechanics students, which aims to give the tools to understand both the influence of design parameters in the thermal residual stress level and distribution along the material and the advantages of using a structural optimization technique in order to minimize the drawback thermal residual stresses effects.

Analysis of Thermal Residual Stresses Distribution in Circular and Elliptical Bonded Composite Repair of Metallic Cracked Structures

In this study, the distribution of the thermal residual stresses due to the adhesive curing in elliptical and circular bonded composite repairs is analyzed using the finite element method. The computation of these stresses comprises all components of the structures: cracked plate, composite patch and adhesive layer. In addition, the influence of these residual stresses on the repair performance is highlighted by analyzing their effect on the stress intensity factor at the crack tip. The obtained results show that the normal thermal stresses in the plate and the patch are significant.. The presence of the thermal stresses increases the stress intensity factor at the crack tip which reduce the repair efficiency.

Residual thermal stress analysis of SiC joint by polysiloxane silicon resin YR3187

Reaction-bonded silicon carbide was joined using a polysiloxane silicon resin YR3187. Residual thermal stress distribution in joint structure was calculated by finite element analysis method. Factors influencing the distribution of residual thermal stress, including joining temperature, thickness of join layer, and presence of crack in join layer, were studied. The simulated results were compared with actual joint strength. It is showed that in determining the joining temperature, the pyrolysis procedure of silicon resin should be taken into consideration; in addition, the reasonable thickness of the join layer and the reduction of cracks in join layer are important to obtain higher joint strength.

Finite Element Analysis for the Influence of Nanoparticles on the Thermal Resudual Stressinfiber Reinforced Composite

In the present work, the finite element analysis was employed to study the distribution and level of thermal residual stress generated in matrix reinforced with SO2 nanoparticles. Using Cohesive Element as the bonding of the interface between fiber and matrix, three–dimensional finite element models of periodic cells were established. The results of the models with and without nanoparticles were compared. The residual thermal stressdue to the mismatch of the thermal expansion coefficients between matrix and fibers, especially theshear stress in the interface, decreased with nanoparticles, which could explain the reinforcing mechanism of nanoparticles. Our numerical study can be of great significance in designing new composites with high performance

Finite Element Analysis of Thermal Residual Stress in Unidirectional Fiber Reinforced Composite

During the cooling process of composites after curing, thermal residual stress will be produced due to mismatch of the coefficients of thermal expansion between matrix and reinforcement phases. Thermal residual stress is one of the most important factors that affect the mechanical properties of composite materials. The effect of fiber volume fraction on the distribution of thermal residual stress in unidirectional fiber reinforced composite has been investigated with finite element analysis. The results show an inhomogeneous distribution of thermal residual stress in different regions of composites. The longitudinal stress on the interface between matrix and fiber is the main factor resulting in debonding failure of composites. This numerical study can be of great significance in designing new composites with high performance.

An investigation on thermal residual stresses in a cylindrical functionally graded WC–Co component

The thermal residual stress distribution in a functionally graded cemented tungsten carbide (FG WC–Co) hollow cylinder was examined with an emphasis on the effects of key variables, such as gradient profile and gradient thickness on the magnitude and distribution of the stress field. An analytical direct solution based on solving the governing equations of a cylinder composed of a uniform inner core and a functionally graded outer shell was developed, considering the cylindrical compound as two separate elements: a homogeneous cylinder and a functionally graded shell. Through the graded shell, material properties such as the modulus of elasticity and the coefficient of thermal expansion (CTE), except Poisson's ratio, were considered to vary as a power function of the radius, and proper mechanical boundary conditions were imposed at the interface of the two cylinders. Practical values for the two variables, gradient profile and gradient thickness, were evaluated in the mathematical solution for the FG WC–Co compound, and their effects on the stress distribution were studied. An examination of different gradient profiles showed that with excess Co content in the graded region, compressive radial stresses were created, while with decreasing Co content through the graded region tensile stresses were generated at the interface. The effect of gradient thickness was shown to have a greater effect on radial stress, compared to hoop stress, and increasing the gradient thickness significantly increased the radial stress magnitude.

Minimization of the Local Residual Stress in 3D Flip Chip Structures by Optimizing the Mechanical Properties of Electroplated Materials and the Alignment Structure of TSVs and Fine Bumps

Since the thickness of stacked silicon chips in 3D integration has been thinned to less than 100 μm, the local thermal deformation of the chips has increased drastically because of the decrease of the flexural rigidity of the thinned chips. The clear periodic thermal deformation and thus, the local distribution of thermal residual stress appears in the stacked chips due to the periodic alignment of metallic bumps, and they sometimes deteriorate mechanical and electrical reliability of electronic products. In this paper, the dominant structural factors of the local residual stress in a silicon chip are investigated quantitatively based on the results of a three-dimensional finite element analysis and the measurement of the local residual stress in a chip using stress sensor chips. The piezoresistive strain gauges were embedded in the sensor chips. The length of each gauge was 2 μm, and an unit cell consisted of four gauges with different crystallographic directions. This alignment of the strain gauges enables us to measure the tensor component of three-dimensional stress fields separately. Test flip chip substrates were made of silicon chip on which the area-arrayed tin/copper bumps were electroplated. The width of a bump was fixed at 200 μm, and the bump pitch was varied from 400 μm to 1000 μm. The thickness of the copper bump was about 40 μm and that of tin layer was about 10 μm. This tin layer was used for the formation of rigid joint by alloying it with copper interconnection formed on a stress sensing chip. The measured amplitude of the residual stress increased from about 30 MPa to 250 MPa depending on the combination of materials such as bump, underfill, and interconnections. It was confirmed that both the material constant of underfill and the alignment structure of fine bumps are the dominant factors of the local deformation and stress of a silicon chip mounted on area-arrayed metallic bumps. It was also confirmed that not only the control of mechanical properties of electroplated copper thin films, but also the hound’s-tooth alignment of a through silicon via and a bump are indispensable for minimizing the packaging-induced stress in the three-dimensionally mounted chips. This test chip is very effective for evaluating the packaging-process-induced stress in 3D stacked chips quantitatively.