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The crystal plastic theory was used to examine the effect of film-cooling hole arrangements on mechanical properties of cooled turbine blade. The finite element method was used to analyze the maximum von Mises stress and resolved shear stress of an octahedral slip system considering the number of rows, diameter, spacing, and tangential-to-longitudinal hole spacing (h/l) ratio. The different arrangements were found to have a significant influence on the maximum von Mises stress and resolved shear stress. For the triangular arrangement, the von Mises stress and resolved shear stress were highest with double rows, followed by a single row and then triple rows. For the quadrilateral arrangement, the stresses were highest with double rows, followed by triple rows and then a single row. Increasing the spacing or decreasing the diameter reduced the maximum von Mises stress and weakened the multi-hole interference effect. Both the maximum von Mises stress and resolved shear stress decreased with the h/l ratio.

Nickel-based superalloys are widely used in key hot-end components such as aero engines and industrial gas turbines due to their excellent comprehensive properties. Real-time monitoring of engine blades and other structures in high-temperature environments can promptly discover possible internal damage to the structure. Optical fiber sensing technology has unique advantages that traditional electrical sensors do not have, such as anti-electromagnetic interference, small size, light weight, and corrosion resistance. The technology is gradually replacing traditional methods and becoming an important means of structural health monitoring. We propose an optical fiber sensor and assembly method that can be used to measure the strain of a nickel-based directionally solidified superalloy in a high-temperature environment more accurately. The proposed technology is simple to manufacture and also has low cost and a high survival rate, which is of great significance for high-temperature strain measurements in aerospace and other fields.

According to the installation environment of the pre-swirl nozzle in the aero-engine, the equivalent constraint fixture is designed, which is the special fixture for vibration test. The equivalent constraint fixture has been checked in three aspects: stiffness simulation ring stiffness check, modal matching check and equivalent constraint fixture strength check. The modal characteristics of the pre-swirl are tested by hammering modal test method, and the natural frequency, mode shape and damping ratio are obtained within 2200Hz. By comparing the modal test results with the simulation results, the mode shapes are consistent. The maximum error of natural frequency is the 1st order 6 pitch diameter, , and the minimum error of the natural frequency is the 1st order 2 pitch diameter. The main frequency of the pre-swirl nozzle is determined to be 665.029Hz by frequency sweep test. The error of the result compared with the modal test result is 3.30%, and the error compared with the simulation result is only 1.59%. The excitation mode of pre-swirl nozzle formal durability test is determined by the pre-test. Finally, it is concluded that the vibration fatigue life of the pre-swirl nozzle can reach 5×10 7 times under a given stress level (120MPa).

Withdrawal rate is a critical parameter that affects the microstructure during single-crystal growth. In the present work, the effect of the withdrawal rate (3, 4.5, 6, and 9 mm/min) on the microstructure and mechanical properties of a novel CoNi-based single-crystal alloy in the as-cast and heat-treated states was investigated in detail. As the solidification distance decreased with increasing withdrawal rate, the dendritic structures and γ′ phase in as-cast microstructures were significantly refined, the element (e.g. W, Al, Ta, Ti, etc.) segregation aggravated, and the volume fraction of the intercrystalline phase increased from 11.9% to 25.2%, which led to a decrease in the creep rupture life (from 90.4 h to 57.8 h) of the as-cast alloy at 1000 °C/150 MPa. By contrast, the withdrawal rate had no significant effect on the size and fraction of the γ′ precipitates in the heat-treated microstructures. The tensile and creep rupture properties of the heat-treated alloy, which were probably caused by the full heat treatment, may have eliminated the effects of the withdrawal rate and uniformed the composition and γ′ size and morphology of the precipitates from the microstructure. This investigation provides theoretical support and a practical basis for the growth of large-scale single crystals from CoNi-based superalloys.

Nickel-based single crystal superalloys reveal obvious anisotropy and orientation correlation. Choosing the orientation with the best mechanical properties is beneficial to prolong its service life. In this paper, the effects of crystal orientation on the plastic deformation and mechanical properties of the nickel-based single crystal two-phase model under uniaxial tension/compression were simulated by molecular dynamics. The microstructure evolution and dislocation movement are studied through stress-strain response and structural changes of the two phases with different crystal orientations. In addition, the typical dislocation structures are analyzed, it is found that the yield stress of different orientation models is: [111] > [001] > [011]. Different orientation models all show tension/compression asymmetry and the [001] orientation is the most obvious. The results showed that the evolution of dislocation and stacking faults is one of the reasons which causes the crystal anisotropy.

In this work, the anisotropic tensile properties of laser additive manufactured (LAMed) GH4169 in as deposited and different heat-treated conditions are presented and the underlying mechanisms are analyzed in detail. Vertical and horizontal specimens for tensile tests were taken from as deposited (AD) and heat-treated blocks. Two heat treatment conditions with solution temperature of 980 °C and 1050 °C were considered. The tensile test results indicate different tensile properties of the vertical and horizontal samples, and such anisotropy is related to heat treatment conditions. The vertical AD sample has higher tensile strength than its horizontal counterpart, while after heat treatment, the horizontal direction shows higher tensile strength. Microstructure characterization, texture and grain morphology analyses were conducted through SEM with EBSD, XRD and TEM observations in order to figure out the main influential factors of the anisotropic tensile properties. Besides, fracture surfaces of the tensile specimens were observed to study the role of precipitates. In addition, the residual stresses in the LAMed samples in AD and heat-treated conditions were measured, and their effects on the anisotropic tensile strength were clarified by correlating the residual stress levels with the recrystallization fractions extracted from EBSD data. The obtained results show that a large number of brittle Laves phases growing along the vertical direction are distributed in the AD samples, which leads to different separation manners of Laves phase/γ matrix interfaces under different loading directions. Besides, the residuals stress level is high direction dependent in the AD samples. After heat treatment, most of the Laves phases are dissolved, and the residual stress experiences a significant variation. On the whole, the anisotropic tensile strength is mainly influenced by the residual stress level before and after heat treatment, and slightly influenced by the dissolution of the Laves phase. The present study provides a deeper understanding of the anisotropic tensile properties of LAMed GH4169, which may contribute to future engineering applications of Ni-based superalloys.

Recent investigations suggest that the addition of trace Re element has a significant influence (the so-called Re-effect) on the mechanical properties of Ni-based single crystal superalloys. Nevertheless, the mechanisms for this Re-effect at different service temperatures are still unclear. The present work studied the elastoplastic deformation behavior of the γ phase in Ni-based single crystal superalloys by molecular dynamics, with the emphasis on Re-associated mechanisms at a wide range of Re contents (from 0 at.% to 9 at.%) and temperatures (from 300 K to 1100 K). The results indicate that the Re content and temperature have an obvious effect on the elastic modulus of the γ phase, the higher the Re content and temperature, the lower the elastic modulus. The yield stress and strain decrease with the increase of Re content and temperature. Both the temperature and Re content affect the formation and propagation of dislocations, which further leads to a correlation between the evolution of dislocations and stress-strain. In addition, the effects of size and strain rate on elastoplastic behavior are also studied.

Molecular dynamics has been widely used to study the fundamental mechanism of Ni-based superalloys. However, the effect of the potential function and strain rate on mechanical behavior has rarely been mentioned in the previous molecular dynamics studies. In the present work, we show that the potential function of molecular dynamics can dramatically influence the simulation results of single crystal Ni-based superalloys. The microstructure and mechanical behavior of single crystal Ni-based superalloys under four commonly used potential functions are systematically compared. A most suitable potential function for the mechanical deformation is critically selected, and based on it, the role of strain rate on the mechanical deformation is investigated.

A normalized equivalent initial flaw size method is proposed based on the updated Kitagawa–Takahashi diagram considering the small crack growth behavior, which is essential to accurately predict the fatigue crack initiation and propagation. Meanwhile, the updated Kitagawa–Takahashi diagram indicates that small cracks can propagate even with an applied stress below the fatigue limit, which is consistent to the experimental observations. A new fatigue life prediction model is proposed by considering the fatigue crack growth from the normalized equivalent initial flaw size to normalized final crack length when the failure occurs. The parameters of the proposed model have clear physical meaning and can be determined from experiments. Experimental data for aluminum alloys and steels under different test conditions are adopted to verify the proposed model, the theoretical predictions show good agreement compared with the experimental results.

Structure optimization seeks to achieve the best performance for a structure while satisfying various constrains such as a given probability. In the traditional mathematical model of structure optimization, the goal and the restraint functions are given without considering the randomness of the structural system. In this paper, the random loads and strength are described by probability method, the structure reliability is considered as objective function. Using the genetic algorithm, the mega-sub controlled structural systems is multi-objective optimization designed based on the structure reliability under random excitation, combined with the probability density evolution method for evaluation of extreme value distribution. A low-cost and high-performance structure is getting.

It is still a serious challenge for structural engineers to effectively reduce the seismic responses of tall and super tall buildings to further improve these structural safeties. In order to solve this problem, in this article a new kind of structural configuration, named passive mega-sub controlled structure (PMSCS), is presented, which is constructed by applying the structural control principle into structural configuration itself, to form a new structure with obvious response self-control ability, instead of employing the conventional method. In the analysis of PMSCS the equations of motion of the seismically excited system are developed, based on a realistic analytical model of the complete mega-structural system. Expressions of the displacement and acceleration response of the structure, resulting from simulated earthquake ground motions represented by stationary and nonstationary random processes, are derived. These responses are then determined for both the PMSCS and its conventional mega-sub stru...