Evaluation on residual stresses of silicon-doped CVD diamond films using X-ray diffraction and Raman spectroscopy

The effect of silicon doping on the residual stress of CVD diamond films is examined using both X-ray diffraction (XRD) analysis and Raman spectroscopy measurements. The examined Si-doped diamond films are deposited on WC-Co substrates in a home-made bias-enhanced HFCVD apparatus. Ethyl silicate (Si(OC2H5)4) is dissolved in acetone to obtain various Si/C mole ratio ranging from 0.1% to 1.4% in the reaction gas. Characterizations with SEM and XRD indicate increasing silicon concentration may result in grain size decreasing and diamond [110] texture becoming dominant. The residual stress values of as-deposited Si-doped diamond films are evaluated by both sin2ψ method, which measures the (220) diamond Bragg diffraction peaks using XRD, with ψ-values ranging from 0° to 45°, and Raman spectroscopy, which detects the diamond Raman peak shift from the natural diamond line at 1332 cm-1. The residual stress evolution on the silicon doping level estimated from the above two methods presents rather good agreements, exhibiting that all deposited Si-doped diamond films present compressive stress and the sample with Si/C mole ratio of 0.1% possesses the largest residual stress of ~1.75 GPa (Raman) or ~2.3 GPa (XRD). As the silicon doping level is up further, the residual stress reduces to a relative stable value around 1.3 GPa.

X-Ray Measurement of Residual Stress in Plastic Bonded Explosives

The X-ray diffractive technology was adopted for tentative study of plastic bonded explosive.The datum of some new diffractive peaks in standard PDF cards were added.The effects of strain to interplanar distance and crystal size of the explosive were studied.The results show that grain size of plastic bonded explosive is decreasing with the increasing of the pressure,and the residual stress of the explosive is draw stress.

Residual stress measurement of coarse-grain aluminum alloy using X-ray diffraction method

When measuring residual stress of coarse-grain aluminum alloy using X-ray diffraction method, the diffraction profile shows two peaks and position of measured 20 will be changed, which lead to an inaccurate measurement result. Hence, in this paper, some methods were employed to improve the measurement accuracy. During the measuring process, different parameters （diameter of irradiated area, Ψ-oscillation range and exposure time） were selected and profile peak shift method was utilized. Moreover, when the 20 of profiles was determined, different calculation methods were used to calculate the residual stress. The results show that diameter of irradiated area and Ψ-oscillation range have significant influence on the measuring result. For stress value calculated directly from the test equipment, cross correlation method is more accurate than the absolute peak. Furthermore, another two calculation methods of slope with 2θ- sin^2Ψ and ε- sin^2Ψwere used to calculate the stress based on parameters （2θ, ε） obtained from cross correlation method. It is concluded that 2θ - sin^2Ψ method can further improve the measurement accuracy.

Determination of Residuals Stresses Induced by the Autofrettage Treatment by the X-Rays Diffraction Method

Some meaningful advances have been made these last years to value precise and reliable way the residual stresses experimentally created by the autofrettage. The autofrettage process is used widely to introduce residual stresses into thick walled tubes;traditionally residual stresses have been measured using the Sachs method destructive or non-destructive methods. In this paper we describe the application of the X-rays diffraction;this technique permits to justify the presence of the compressive tangential residual stresses, and to value their distribution after two different autofrettage internal pressures loading. The results show that there is a large difference in the residual stresses find in the different autofrettege pressure. One can see the influence of the autofrettage’s pressure quantity on residual stresses created in the thickness of the test tubes.

Characterization of residual stresses and microstructural features in an Inconel 718 forged compressor disc

Residual stress plays an important part in fabricating commercial aero engine Inconel 718 components for their fatigue properties, reliability and durability. Due to the limitation of Chinese neutron diffraction instrument and lack of test practice and specifications, there is little systematic research on the residual stress of forged compressor disc. X-ray diffraction and neutron diffraction methods were used to measure the residual stress of Inconel 718 forged discs at the surface and in the interior, respectively. Scanning electron microscope and transmission electron microscope were used to characterize the microstructural features. The residual stress state at the disc is in near-surface compression, balanced by tension within the disc core. However, the surface residual stress of disc depends more on the rough machining than on the forging process. Also, the dislocation densities increase with decreasing distance to the surfaces of disc, and the residual stress accelerates dislocation generation and dynamic recrystallization.

Method for Measuring Residual Stresses Induced by Boring in Internal Surface of Tube and Its Validation with XRD Method

Residual stresses can have a strong effect on the usability of machined parts,and the X-ray diffraction(XRD)measuring equipment,which is commonly used to measure residual stresses,is very expensive.This paper presents a method of measuring the residual stresses induced by boring in the internal surface of a tube with much cheaper equipment.The method,called the strain-based method is mainly based on the strains measured on the external surface of the tube.It is proposed on the basis of the very long tube assumption.The finite element method(FEM)analysis is thus used to validate the length of the tube.Guided by the FEM results,an appropriate length of the tube is chosen,and the residual stresses are obtained from both the strain-based method and the XRD method.Stress profiles obtained from both two methods are compared.The comparison result indicates that the profiles of the two methods agree well with each other.Therefore,it can be concluded that the accuracy of the strain-based method is high enough,and it can be applied to residual stress measurement in practice.

Effect of homogenization annealing on internal residual stress distribution and texture in ME21 magnesium alloy extruded plates

The distribution of residual stresses through thickness of 5 mm-thick ME21 magnesium alloy extruded plates was analyzed non-destructively using short-wavelength X-ray diffraction(SWXRD),and the effect of homogenization annealing before extrusion on the residual stress was discussed.The classic d 0 method with an annealed stress-free reference specimen was employed to determine the residual stress of the extruded plates.The residual stress results showed that the gradient of residual stress in the transverse direction was larger than that of the extrusion direction.The homogenization process prior to extrusion weaken the formed sample’s texture.The maximum residual stress of the as-extruded plate was reduced,and the residual stress distribution was homogenized.

Residual stress measurement and analysis of siliceous slate-containing quartz veins

Engineering geological disasters such as rockburst have always been a critical factor affecting the safety of coal mine production.Thus,residual stress is considered a feasible method to explain these geomechanical phenomena.In this study,electron backscatter diffraction(EBSD)and optical microscopy were used to characterize the rock microcosm.A measuring area that met the requirements of X-ray diffraction(XRD)residual stress measurement was determined to account for the mechanism of rock residual stress.Then,the residual stress of a siliceous slate-containing quartz vein was measured and calculated using the sin^(2) ϕ method equipped with an X-ray diffractometer.Analysis of microscopic test results showed homogeneous areas with small particles within the millimeter range,meeting the requirements of XRD stress measurement statistics.Quartz was determined as the calibration mineral for slate samples containing quartz veins.The diffraction patterns of the(324)crystal plane were obtained under different ϕ and φ.The deviation direction of the diffraction peaks was consistent,indicating that the sample tested had residual stress.In addition,the principal residual stress within the quartz vein measured by XRD was compressive,ranging from 10 to 33 MPa.The maximum principal stress was parallel to the vein trend,whereas the minimum principal stress was perpendicular to the vein trend.Furthermore,the content of the low-angle boundary and twin boundary in the quartz veins was relatively high,which enhances the resistance of the rock mass to deformation and promotes the easy formation of strain concentrations,thereby resulting in residual stress.The proposed method for measuring residual stress can serve as a reference for subsequent observation and related research on residual stress in different types of rocks.

Effect of Al_2O_3 Content on Residual Stress and Proper-ties of CAS Glass-ceramics

The structure and properties of the glass-ceramics were tested with X-ray diffraction testing instrument,correlative software,and other modern testing means.Then the effect of Al2O3 content on internal stresses in CaO-Al2O3-SiO2 glass-ceramics was studied deeply.In order to study the relationship of Al2O3 to the residual stress of CaO-Al2O3-SiO2 glass-ceramics,X-ray diffraction ＂sin2ψ＂ was used.The means utilized the x radial incidence produced from cathode radial tube,and took the space between crystals as measurement of strain.When the stresses produced,the space between crystals changed and the diffraction peak moved during Bragg diffraction.The magnitude of movement is related to the stresses.The experimental results show the residual stress is considerably high and Al2O3 can influence the mechanical properties of this material hugely.

Rolling Deformations and Residual Stresses of Large Circular Saw Body

Rolling path squeezes and rolling residual stresses of large diameter circular saw body for wood, generated by rolling pressure from 10 up to 120 bar were examined. X-ray diffraction, Barkhausen noise (BN) and Full Width of the peak at a Half Maximum (FWHM) (o) methods for evaluation of residual stresses were used. Dependencies of a tangential rolling residual stresses inside rolling paths upon rolling pressure p (bar) and rolling area A (mm2) were evaluated. The rolling pressure, as large as 60 bar, resulting in the rolling squeeze as high as 0.04 mm2, and, tangential residual compression stresses inside a rolling path, as large as ?TI = ?822 MPa, was considered to be the largest for the practical application.

Residual Stresses in Resistance Spot Welded AZ61 Mg Alloy

The use of magnesium alloys has been rapidly increased due to their ability to maintain high strengths at light weights.However weldability of steels and aluminum alloys by using resistance spot weld(RSW)process is a major issue,because it cannot be directly utilized for magnesium alloys.In this study,a structural-thermal-electrical finite element(FE)model has been developed to predict the distribution of residual stresses in RSW AZ61 magnesium alloy.Thermophysical and thermomechanical properties of AZ61 magnesium alloy have been experimentally determined,and have been used in FE model to increase the accuracy of the model.X-ray diffraction(XRD)technique has been utilized to measure the residual stresses in welded samples,and its results have been used to validate the FE model.Comparison study shows that the results obtained by using FE model have a good agreement with the experimental XRD data.In specific,the results show that the maximum tensile residual stress occurs at the weld center while decreases towards the nugget edge.In addition,the effects of welding parameters such as electrical current,welding time,and electrode force have been investigated on the maximum tensile residual stress.The results show that the tensile residual stress in welded joints rises by increasing the electrical current;however,it declines by prolonging the welding time as well as increasing the electrode force.

GRINDING RESIDUAL STRESS OF CEMENTED CARBIDE

Grinding residual stress in the surface layer of WC-6 Wt—％Co hard alloy was measured by means of X-ray diffraction. The effects of various grinding parameters and treatment processes on the stress were studied. By means of electrolytic etching, the stress distribution along the depths beneath the surface was measured. The relationship between the stress and the service life of the alloy is discussed.

Study on the distribution of residual stresses in linear friction welds of Ti6AI4V

The linear friction welding process of Ti6Al4 V was modeled and computed ,for obtaining the residual stresses. Temperature, stress and strain fields were simulated, based on which, the residual stresses were also cah＇ulated. Simulated resttlts showed that the longitudinal residual stresses were tensile stresses at the bonding interface, and decreased rapidly with the increase of the distance from the bonding interface until turned into compressive stresses. The compressive stresses decreased slowly as the distance increased, and approached to zero finally. The distribution of the transverse residual stresses was similar to that of the longitudinal residual stresses, but showed much smaller values. The residual stresses in one linear friction weld were measured by an X-ray diffrnctometer. The average valwe of errors between computed and measured results was 14. 5 %.

Evaluation of multiaxial stress in textured cubic films by x-ray diffraction

X-ray diffraction is used extensively to determine the residual stress in bulk or thin film materials on the as- sumptions that the material is composed of fine crystals with random orientation and the stress state is biaxial and homogeneous through the x-ray penetrating region. The stress is calculated from the gradient of ε ～ sin^2 φ linear relation. But the method cannot be used in textured films due to nonlinear relation. In this paper, a novel method is proposed for measuring the multiaxial stresses in cubic films with any [hkl] fibre texture. As an example, a detailed analysis is given for measuring three-dimensional stresses in FCC films with [111] fibre texture.

Effect of Microstructure of Cementite on Interphase Stress State in Carbon Steel

The experiments related to stress states of ferrite and cementite in carbon steels were carried out including in situ four-point bending and tensile test by X-ray diffraction technique. Stresses in the cementite phase can be measured by conventional X-ray diffraction instrument after a specific treatment on the specimen surface. In order to estimate the stress states in two phases, the X-ray elastic constants of two phases in single-phase state （PXEC） are determined by the experimental X-ray elastic constants of them in composite state （CXEC）. The effects of volume fraction and particle size of spheroidal cementite on the interphase stress state are estimated. The experimental results are in good agreement with the theoretical relationships reported in the previous studies.

Analysis of Quenching Stresses in 35CrMo Axle

By using the finite element method （FEM）, we comprehensively analyzed the fields of temperature, organization, and stress in 35CrMo train axles during the quenching process is conducted, and experimentally studied the formation and evolution of inner stresses in axles during the quenching process. The results show that in the quenching process, stresses on the axle surface change from tensile to compressive gradually, while stresses in the axle core change from compressive to tensile gradually. Heat stresses and the amount of martensitic transformation are all increased with the increase of cooling rate. As a result, the maximmn instantaneous stresses in the axle are increased greatly when the cooling rate is increased with brine quenching. Large instantaneous tensile stress in the axle core with brine quenching is very likely to cause quench cracking and should be avoided.

全因子试验设计在X射线衍射法测试高应力标样残余应力值中的应用

针对X射线法测试残余应力值的主要参数——准直器直径、曝光时间和β角数量,依据6σ的DMAIC流程和全因子试验设计,研究了标准高应力试样残余应力值的测试方法。结果表明:上述参数对探测器X光子接收数量、衍射峰强度和峰背比的大小有较大影响。为提高测试精确度和重复性,在满足检测效率的前提下,可选择较小的准直器直径、较长的曝光时间和较大的β角数量进行残余应力测试。对于标准高应力试样,选择2mm准直管、3s曝光时间和11个β角参数测定的残余应力值与标准值最为接近。

中子衍射应力测量试验中赝偏移现象的影响

主要介绍了中子衍射应力谱仪试验过程中,由非应力原因引起的衍射偏移的各种因素的影响。讨论了样品的定位与样品测量体积的选择对衍射峰赝偏移的影响,最后给出了赝偏移校正方法与试验过程中减小赝偏移的有效技术手段,使试验数据得到有效的处理,从而得到样品内部应力的真实信息。

Effect of Pre-loading on Short Fatigue Crack Growth at a Notch

Results indicate that under cyclic tension the growth rate of short fatigue crack from notch root will be lowered greatly by tensile pre-loading,but only a little change by compressive pre-loading. The effect of tensile pre-loading will decrease with the increase of stress ratio.The variation of short fatigue crack growth rate is related to the residual stress distribution around notch root.

Interfacial Bonding Strength of TiN Film Coated on Si_3N_4 Ceramic Substrate

The fraction of TiN/Si3N4 in the cross section was observed with scanning electric microscope （SEM）, and residual stresses of TiN coated on the surface of Si3N4 ceramic were measured with X-ray diffraction （XRD）.The hardness of TiN film was measured, and bonding strength of TiN film coated on Si3N4 substrate was measured by scratching method. The formed mechanism of residual stress and the failure mechanism of the bonding interface in the film were analyzed, and the adhesion mechanism of TiN film was investigated preliminarily. The results show that residual stresses of TiN film are all behaved as compressive stress, and TiN film is represented smoothly with brittle fracture, which is closely bonded with Si3N4 substrate. TiN film has high hardness and bonding strength of about 500 MPa, which could satisfy usage requests of the surface of cutting Si3N4 ceramic.