Thermal fatigue is one typical failure mode for engine components involving cyclic thermal stresses/strains. However, the microstructure evolution and its microscopic interaction with thermal fatigue ...cracking in Ni-based superalloys featuring intragranular γ′ and intergranular carbides have yet to be clarified. In this study, cyclic temperature variations ranging from 25 °C to 700 °C were conducted on Waspaloy to unravel the synergistic damage mechanisms including stress distribution, plastic deformation, recrystallization, oxidation, and crack propagation. The thermal fatigue cracks are found to predominantly propagate along grain boundaries with a gradually descending rate from 3.5 μm/cycle to 1.5 μm/cycle. Compared with the macroscopic thermal stress up to ∼800 MPa, the local thermal stress induced by different sizes of M23C6 carbides marginally affects the crack propagation. Intensive slip bands and sparse deformation twins in the deformed matrix are observed, indicating the plastic deformation is mainly achieved by dislocation slipping and supplemented by twinning. Trans-granular cracks parallel to {111} planes form occasionally when the propagation directions of intergranular cracks are almost parallel to the {111} slip bands. Besides, dislocations promote the oxidation damage of the crack surface through pipe diffusion of solutes, and the γ′-precipitate free zones (PFZs) and recrystallized areas are produced accordingly. The quantitation analysis of the PFZ thickness provides a reference for predicting crack initiation time during thermal fatigue.
•Increasing M23C6 size does not foster the propagation of cracks.•The plastic deformation is mainly achieved by dislocation slipping and supplemented by twinning.•The formation kinetics of PFZ is established to provide a reference for predicting the crack initiation time.•The recrystallized grains are formed without the retarding of γ′ precipitates.
•A multi-scale modelling approach has been presented to investigate the underpinning mechanisms of microstructure-sensitive damage of single crystal Sn-3Ag-0.5Cu solder joints of a ball grid array ...board assembly subject to thermal cycling.•Systematic studies of β-Sn crystal orientation and its role in thermal fatigue damage development within solder joints have been shown and compared to experimental observations and analysis.•It provides evidence-based optimization for solder microstructural design under in-service thermomechanical fatigue.
This paper presents a multi-scale modelling approach to investigate the underpinning mechanisms of microstructure-sensitive damage of single crystal Sn-3Ag-0.5Cu (wt%, SAC305) solder joints of a Ball Grid Array (BGA) board assembly subject to thermal cycling. The multi-scale scheme couples board-scale modelling at the continuum macro-scale and individual solder modelling at the crystal micro-scale. Systematic studies of tin crystal orientation and its role in fatigue damage have been compared to experimental observations. Crystallographic orientation is examined with respect to damage development, providing evidence-based optimal solder microstructural design for in-service thermomechanical fatigue.
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•Hot spots inside brake disc were acquired using energy conversion method.•Thermal fatigue crack was modeled by XFEM and virtual-node polygonal FEM.•Damage tolerance method was used to evaluate the ...fatigue crack growth life.
Railway brake discs are the safety–critical components usually designed for up to ten years of operation. To guarantee the safety, fracture mechanics method was applied to perform the thermal fatigue crack growth simulation. Before that, thermo-physical mechanical and fracture parameters for brake discs made of an alloy forged steel were experimentally determined under different temperatures. By using novel extended finite element method (XFEM) and crack tip region meshing refinement based on virtual-node polygonal finite element method (VPM), a semi-elliptical surface crack was then inserted into a predicted macroscopic hot spot to carry out the thermal fatigue cracking analysis under consecutive emergency braking. Computational results were employed to evaluate the fatigue life and safety domain of in-service. Predicted peak temperature and calculated crack geometry were well in agreement with the experimental. Thermal fatigue crack propagation was acquired for evaluating the safety degree of the brake disc due to emergency braking mode. Finally, some remarks were provided for the design and regular maintenance of high-speed railway brake discs.
A new thermal fatigue rig using High Frequency induction heating is developed to test automotive Diesel engine pistons. An adapted test piston is internally cooled by permanent water flow while its ...bowl sensitive to thermo-mechanical fatigue is subjected to cyclic induction heating. The temperature is measured in depth by thermocouples and in surface by a thermal infrared camera or a pyrometer. The crack initiation and propagation and the local deformations are provided by optical means. Thermo-mechanical loadings are calibrated by thermal measurements on the piston during engine operation and the entire test is modelled by finite elements. A constitutive model and a fatigue criterion for aluminium alloys are proposed to estimate the piston lifetime under severe cyclic loading. The proposed fatigue bench allows loading the piston in thermal fatigue scheme very similar to that encountered in engine operation conditions. Crack detection is facilitated by numerical modelling that helps to detect the most critical areas and also to reliably estimate the number of cycles for initiate cracks.
Thermal fatigue failure is one of the main factors affecting the service life of hot work die steel. Achieving excellent thermal fatigue resistance for hot working die steels can benefit the industry ...economically. In this work, (TiC + TiB2)/Al master alloys were used to add TiC–TiB2 nanoparticles into high-Cr die steels, which achieves microstructure manipulation and obtains excellent thermal fatigue resistance and strength-plastic combination. The results showed that after being manipulated by 0.02 wt% TiC–TiB2 nanoparticles, the surface oxidation zone of the high-Cr die steel after different thermal fatigue cycles is reduced than high-Cr die steel without manipulation. TiC–TiB2 nanoparticles effectively refined the heat-treated microstructure of high-Cr die steel, promoting the Cr element and alloy carbides being more uniformly distributed in the matrix, which prevents the occurrence of oxidative pitting and conducive to the formation of a dense and uniform Cr2O3 oxide layer, and further preventing the initiation of thermal fatigue cracks. Moreover, these finer and more uniformly distributed precipitates in TiC–TiB2 nanoparticles manipulated high-Cr die steels will promote stress dispersion and hinder thermal fatigue crack propagation. This work provides a promising avenue for the design of low-cost, high-performance, and long-life die steels for industrial applications.
•The microstructure has been manipulated with traces TiC–TiB2.•Thermal fatigue cracks initiation are closely correlated to surface oxidative erosion.•Nanoparticle-reinforced steels have better thermal fatigue resistance.
A new fatigue life prediction criterion has been developed for die casting processes, correlating cyclic temperature differences with thermal fatigue cracking cycles. A simple plate sample was tested ...to fit this new criterion, and a complex miniature H13 steel insert sample was further tested to extend the application of the criterion.
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Thermally-induced fatigue cracking of steel dies is one of the most common failures in die casting industry. Based on a modified universal slopes equation, a new fatigue life prediction criterion has been developed for die casting processes, correlating the temperature differences during casting cycles and thermal fatigue crack cycles. A laboratory thermal fatigue experiment, undergoing cyclic heating and water cooling, was used to reproduce thermal fatigue cracking. A simple plate sample was tested to fit this new fatigue model criterion, where its heating was achieved by residing in a kiln chamber. Furthermore, a finite element analysis code ProCAST® was used to model the thermal loadings during the test. To further extend the application of this newly developed criterion, a miniature H13 steel insert sample was machined and tested. The sample was designed to be geometrically similar to an actual water jacket insert in an automotive engine block. In addition to the kiln chamber heating, the sample was tested by immersion in A380 melt, which is more characteristic to actual die casting conditions. Based on the test results, the fatigue life prediction model can be used as a practical and efficient tool to predict and improve hot-work tooling life in the die casting and other manufacturing industries.
•Thermal cycling effects on granite fracture characteristics were investigated.•The number of thermal cycle in the present study were 1, 5, 10, 15, and 20.•Crack characteristics in granite was ...quantitative discussed.•Thermal cycling decreases Keff, U, Pv, and increases K.•Thermal cycling has effect on the predictive accuracy of MMTS.
The fracture characteristics of fine-grained granite were examined for a potential geothermal-energy reservoir. The granite was thermally cycled in a furnace between 100 °C and 300 °C and its mechanical behavior and meso-crack characteristics were analyzed. The results indicate that thermal cycling leads to decreased fracture toughness (Keff), absorbed energy (U), longitudinal wave velocity (Pv), and increased permeability (K) in granite. These changes can be explained using the thermal fatigue accumulated damage. The ability of granite to resist fracturing is greatly reduced in the first five thermal cycles. Thermal cycling is more conducive to inducing intergranular cracks. The interconnection of intragranular and intergranular cracks causes the structure of granite to become fragmented and more likely to fail. Thus, thermal cycling deteriorates the mechanical stability of fine-grained dense granite, and allows crack networks to form more easily. The correction of crack propagation critical radius (rc) can improve the accuracy of the modified maximum tangential stress (MMTS) predictive fracture.
•A hyper-reduced-order method is introduced for the accelerated modeling of thermal cycling-induced plastic deformation.•A reproducing kernel particle method (RKPM) with a stabilized reduced-order ...integration is introduced for effective model order reduction.•A Gappy-POD hyper-reduction is further introduced to accelerate the nonlinear computation of plastic deformation.•Fatigue life prediction by the hyper-reduced-order model can achieve 1.4% error and consume only 4.6% CPU time when compared to the high-fidelity model.•The proposed hyper-reduced-order model has been applied to evaluate how thermal cycling parameters affect solder joint fatigue life.
For materials under cyclic thermal loadings, temperature and strain rate-dependent creep deformation can occur due to the thermal expansion mismatch near material interfaces, leading to deterioration of fatigue life. Simulation of the nonlinear mechanical deformation processes of materials subjected to thermal cycling with high-fidelity numerical models often consume high computational costs due to material nonlinearities and long thermal loading period. To accelerate such thermal cycling simulation, an efficient reduced-order modeling framework is proposed. We adopt the reproducing kernel particle method (RKPM) to generate offline high-fidelity model snapshots, which are utilized to create low-dimensional surrogate models based on the proper orthogonal decomposition under Galerkin projection. Based on the stabilized conforming nodal integration technique, gradient smoothing at single integration point per integration cell is employed in conjunction with a least-squares stabilization for high computational efficiency. To further speed up the simulation, a hyper-reduction method is introduced to avoid the full domain integration during the elastoplastic online simulation. Numerical examples on modeling of thermal cycling-induced plastic deformation and thermal fatigue life prediction of a flip chip assembly are analyzed to demonstrate the effectiveness of the present hyper-reduced-order model in significant reduction of computational time while preserving desired accuracy.
•Transient thermal fatigue crack propagation behaviors of a Ni-based SX were studied.•K and J-integral were calculated based on 3D transient thermo-mechanical theory.•Anisotropic transient thermal ...fatigue crack model was developed.•The effective crack ultimate length influence coefficient keff was introduced.•Three surface heat transfer stages were considered during water cooling process.
Thermal fatigue crack propagation behaviors of a V-notched Ni-based single-crystal superalloy DD6 were tested at 25 °C ↔ 760 °C/900 °C/1000 °C. The propagation directions of the two main cracks were approximately 45° with the dendrite orientation, and the {1 1 1} 〈1 1 0〉 slip family was mainly activated. Based on 3D transient thermo-mechanical coupling theory and rate-dependent crystal plasticity theory, the stress intensity factor and J-integral were calculated to predict the thermal fatigue crack propagation behavior. Three surface heat transfer stages were considered. The predicted crack propagation rates at three heating temperatures all showed good agreement with those obtained in the experiments.
A new cobalt-based coating, CoNiTi, was developed for brake disc applications. The effect of temperature on the tensile and thermal fatigue cracking properties of CoNiTi was evaluated between room ...temperature (RT) and 700 °C, and compared with those of the commercial CoCrMoW and Stellite 6 coatings. The strength of all coatings decreased with increasing test temperature, and the elongation to fracture of Stellite 6 increased with increasing test temperature. However, CoNiTi and CoCrMoW presented deterioration in elongation to fracture at 400–500 °C. In addition, the crack propagation rate of CoCrMoW and CoNiTi also presented a trend of accelerated increase under RT ∼700 °C thermal fatigue condition. By combining the finite element simulation of thermal fatigue and in-situ tensile test, the grain boundary weakness at middle temperature was revealed to clarify the reason for the deterioration of plasticity and crack growth resistance in CoCrMoW and CoNiTi. The microstructure evolution of γ-Co → ε-Co martensitic transformation during tests depended on the temperature and chemical composition associated with stacking fault energy (SFE). Increasing temperature and nickel content could improve SFE, stabilize γ-Co, and make dislocation glide in cross-slip mode, on the contrary, γ-Co tended to undergo martensitic transformation, and the dislocation was in planar-slip mode, when SFE was low.
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•The temperature effect on the tensile and thermal fatigue cracking properties of cobalt-based coatings was revealed.•PLC band and grain boundary weakening at medium temperature deteriorated plasticity and crack resistance of coatings.•γ-Co → ε-Co martensitic transformation depended on SFE, and presented preferred selection obeying Schmid's law.
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