Lizeng Ling Shiguo Long Zengsheng Ma Xu Liang
材料科学技术（英文）
In this paper, mechanical properties of Nickel film under residual stress have been systematically examined by finite element method in nanoindentation. It was found that load-displacement curves shifted under elastic residual stress and residual stress exceeded the yield stress for fixed indentation depth. Indentation profiles changed monotonously with compressive and tensile stresses at peak force which determinates contact area observed directly by finite element modeling (FEM). The elastic residual stress has an effect slightly on the hardness but residual stress exceeded the yield stress shows a remarkable effect in nickel film. The hardness increased when residual stress exceeded the yield stress increased under tensile and compressive stress applied to specimen. The relationship between residual stress and hardness was linear. It was found that residual stresses didn0t affect elastic modulus whether elastic residual stress or plastic stress was applied to specimen.
关键词:
Residual stress
,
Hardness
,
Elastic Modulus
,
Indentation profile
,
Finite element method
C.M.Cheng
材料科学技术（英文）
This study, taking three types of aluminum alloys 2024-T351, 6061-T6 and 7075-T6 as experimental materials, conducted single V-groove GTAW (gas tungsten arc welding) butt-welding to analyze and compare the magnitude and differences of residual stress in the three aluminum alloys at different single V-groove angles and in restrained or unrestrained conditions. The results show that the larger the grooving angle of butt joint, the higher the residual tensile stress. Too small grooving angle will lead to dramatic differences due to the amount of welding bead filler metal and pre-set joint geometry. Therefore, only an appropriate grooving angle can reduce residual stress. While welding, weldment in restrained condition will lead to a larger residual stress. Also, a residual stress will arise from the restraint position. The ultimate residual stress of weldment is determined by material yield strength at equilibrium temperature. The higher the yield strength at equilibrium temperature, the higher the material residual stress. Because of its larger thermal conductivity, aluminum alloy test specimens have small temperature differential. Therefore, the residual tensile stress of all materials is lower than their yield strength.
关键词:
Residual stress
,
null
,
null
,
null
Wu TANG
,
Kewei XU
材料科学技术（英文）
Au/NiCr/Ta multilayered metallic films deposited on Al2O3 substrate by magnetron sputtering have been used in microwave integrated circuits (MIC). The residual stress and scratch resistance were investigated at different deposition temperature. The residual stress in as-deposited films was of tension with 155 MPa～400 MPa and changed to compression after samples annealing. It was found that both friction and acoustic emission modes can eventually be used for conventionally critical load determination, the critical characteristic load at each point corresponding to abrupt change of the friction coefficient was not sensitive to deposition temperature, but sensitive to the film thickness. Critical load is less sensitive to the change of residual stress by microscratch method.
关键词:
Residual stress
,
null
,
null
X.C. Zhao
,
Y.D. Zhang
,
H.W.Zhang
金属学报(英文版)
A finite element model is developed for the
simulation of vibration stress relief (VSR) after welding. For the
nonresonant vibration, the reduction in stress strongly depends on
the amplitude of vibration. For the resonant vibration, the
vibration frequency is the key for stress relief. The vibration
frequency should be close to the structure natural frequency for the
desired vibration mode. Only small vibration amplitude is required,
which will be amplified during vibration. Vibration time does not
have a major impact on vibration stress relief. When the amplitude
of vibration stress relief is large, the treatment will be more
effective.
关键词:
Residual stress
,
null
,
null
Liping SHI
,
Yao LI
,
Xiaodong HE
材料科学技术（英文）
The preparation technology of microlayer composite material by the electron beam physical vapor deposition (EBPVD) technique was briefly introduced. Taking the advantage of the large-scale commercial software of finite element analysis, a reasonable physical model was built up during the deposition processing and the distribution of residual stress was analyzed between substrate and deposition layer or among deposition layers. The results show that: with the increasing substrate preheating temperature, the interlaminar shear stress increases but the axial residual stress decreases. The probability of curling up after de-bonding tends to enhance as the thickness of deposition film increases.
关键词:
Microlayer composite material
,
null
,
null
,
null
Y.X. Hu
,
Z.Q. Yao
金属学报(英文版)
Finite element method is presented to attain the numerical simulation of residual stresses field in the material treated by laser shock processing. The distribution of residual stresses generated by single laser shock with square and round laser spot is predicted and validated by experimental results. With the FEM model, effects of different overlapping rates and impact sequences on the residual stresses distribution are simulated. And the results indicate that: (1) Overlapping laser shock can increase the compressive residual stresses. But it is not effective on the growth of plastically affected depth; (2) Overlapping rate should be optimized and selected carefully for the large area treatment. Appropriate overlapping rate is beneficial to obtain a homogeneous residual stress field; (3) Impact sequence has a great effect on the residual stress field. It can greatly attenuate the phenomenon of “residual stress hole” to obtain a homogeneous residual stress field.
关键词:
Laser shock processing
,
null
,
null
,
null
G.Montay
,
A.Cherouat
,
A.Nussair
,
J.Lu
材料科学技术（英文）
Residual stress in coatings is the result of individual particle stress. Their effects may be either beneficial or detrimental, depending upon the magnitude, sign and distribution of the stresses with respect to the external load. Tensile stress which exceeds the elastic limit causes cracking in surface coatings or at the interface between the substrate and the coat. Compressive stress, in general, has a beneficial effect on the fatigue life, crack propagation, coating adhesion and on the durability of the top coat during service. Compressive residual stresses can increase the number of cycles before crack initiation begins through a mean stress effect. Temperature gradients which occur during solidification and subsequent cooling are the principal mode of internal stresses generation. Some parameters influence the residual stress field of both the coating and the substrate. Substrate nature, spraying temperature, thickness of the coat layer, substrate preparation (grit blasting conditions), and velocity of the splats are in the relation with the quality of the coating. In this work, we will describe the role playing by the ceramics coating elaboration on the residual stress gradient in depth of the component. The incremental hole drilling technique has been developed to determine the residual stress gradient in depth of the coat and substrate which must be used with particularly conditions. This new technology has been employed on zirconia, alumina and tungsten carbide plasma sprayed coating.
关键词:
Coating
,
null
,
null
,
null
Xiancheng ZHANG
,
Jianming GONG
,
Sh
,
ong TU
材料科学技术（英文）
The thermomechanical behavior and the distribution of residual stresses due to thermal spraying of NiCoCrAlY coating were studied by thermomechanical finite element analysis. The effects of phase transformation due to solidifying process of coating particles, thickness and material properties of coating on the residual stresses were discussed. Results showed that residual stress decreases little with the stress relaxation due to the phase transformation. For the substrates with the same thickness, the residual stress increases with the increase in coating thickness. The state of
residual stresses relates to the material properties of coating and substrate closely. The stress-induced failure model of coating is also discussed.
关键词:
Coating
,
null
,
null
,
null
Changzhong WU
,
Huaining CHEN
,
Jing CHEN
,
Quanhong LIN
材料科学技术（英文）
The explosion treatment technique has been used in the relief of residual stresses in 800 MPa grade high strength steel manual welded joints. The residual stresses on surface and through thickness of the weldment were measured for both as-welded and explosion-treated sample, the mechanical properties of welded joints under different conditions were also tested. The effect of explosion treatment on the fracture toughness of materials with a residual defect was investigated by crack opening displacement (COD) test. The results show that explosion treatment can reduce not only the surface residual stress but also the residual stress through thickness in the welded joints. The effect of explosion treatment on the mechanical properties and a residual defect in welded joint were inconspicuous.
关键词:
High strength steel
,
爆炸处理
,
残余应力
,
接头力学性能
,
CO
Katsuji Tosha
,
Jian Lu
,
Bruno Guelorget
材料科学技术（英文）
The effect of shot peening on surface integrity was described. After shot peening was performed for carbon steel under several conditions with steel shot, peened materials were heat-treated at various temperatures and times (100~600℃, 15~240 min), and then hardness, half width and surface residual stress were measured. The following results are obtained: (1) non-affected layer induces compressive residual stresses on the peened surface and surface layer, (2) hardness increases after heating at 200~400℃, but decreases in case of 600℃, (3) compressive residual stresses decrease after all heat treatments, (4) microstructure may be recovered by heat treatment at low temperature
关键词:
Shotpeening
,
null
,
null
,
null
