X-ray Residual Stress Measurements Research Articles

X-ray residual stress measurement of several ceramic coated films.

X-ray residual stress measurement of several ceramic coated films.

Residual Stress State of Brazed Ceramic/Metal Compounds, Determined by Analytical Methods and X‐ray Residual Stress Measurements

The residual stress state of brazed ceramic/metal compounds is described by means of X‐ray residual stress determinations and analytical calculations using a model of three elastic infinite plates. It is shown that the residual stress state of the soldered compound depends on the materials combination and on the geometrical conditions. The combination of X‐ray residual stress measurements and analytical calculations allows decisions on whether the assumption of a linear elastic model, based on elementary bending theory, is valid for the particular compounds.

A contribution to the study of poisson's ratios and elasticconstants of TiN, ZrN and HfN

The elastic constants of the group IVB nitrides TiN, ZrN and HfN have beenstudied by X-ray residual stress measurements. Films of the nitrides were deposited onto stainless steel substrates by reactive sputtering and then vacuum annealed. They were studied using Cr Kα radiation and the five available diffraction peaks (111) to (222). Poisson's ratios for bulk material are 0.30, 0.19 and 0.35 for the three nitrides respectively, indicating that the first and last are nearly isotropic which requires ν to be ⅓. Values of the X-ray elastic constants and anisotropy factors were also derived.

X-ray Residual Stress Measurement of Ground Surface of Metal-Ceramic Composite

Machine parts made of ceramics are usually finished by grinding. Residual stresses as well as defects introduced by grinding will influence the fracture strength and the function of the ceramic parts. Although several investigators measured the grinding residual stresses by the X-ray diffraction method, their grinding conditions were rather limited.

Analysis of strengthening due to deformation-induced martensitic transformation in a Fe-Ni-C steel.

Strengthening of a Fe-27.59% Ni-0. 28%C (Wt%) steel in tension results from both the ordinary strain hardening in austenite and martensite which compose a dual-phase steel and the hardening due to martensite induced during straining of the steel. The volume fractions of martensite induced in the steel at 0°C, -19°C, -34°C and -49°C are measured by the X-ray diffraction method (Motarget, multi-peak method). The stress-strain relations of the steel at these temperatures are analyzed and expressed by the equations of a variable volume model (abbr. as VVM) previously proposed by us. The analytical relations of each strain, each stress, transformation strain, balanced bonding mechanism of two phases, contributions of strain and stress of each phase and so on are discussed in detail. These analytical curves show excellent agreement with the experimental data obtained from a study of the X-ray residual stress measurements on this steel, and the equations of the VVM model are shown to be successfully applied to the Fe-Ni-C steel which induces the lenticular martensite with different tensile properties from those of the lath martensite in SUS 304 stainless steel reported previously.

X-ray diffraction measurement of residual stress(strain): Energy dispersive X-ray residual stress measurement : Rosemeier, R.G. John Hopkins University, Baltimore, Maryland (United States), Ph.D. Thesis, 262 pp. (1981)

X-ray diffraction measurement of residual stress(strain): Energy dispersive X-ray residual stress measurement : Rosemeier, R.G. John Hopkins University, Baltimore, Maryland (United States), Ph.D. Thesis, 262 pp. (1981)

X-ray measurement of residual stresses induced by laser surface treatment

X-ray measurement of residual stresses induced by laser surface treatment

On X-ray measurements of residual stresses in materials with lattice strain gradient

The non-linear distribution of lattice straine310vs sin2Ω observed on the surface of a polished steel specimen can be interpreted by tri-axial stress state with surface components of stress tensorσ11(0)=σ22(0) and gradientsg11=∂σ11/∂T, g33=∂σ33/∂T. The distribution of experimental values\(\bar \varepsilon _\psi \) is duscussed from the viewpoint of various ways of calculatingσ11.

X-ray measurement of residual stress on bolt threads.

This study deals with X-ray measurement of residual stress at the local area around the thread root of a bolt. Residual stress in the 0.5 mm×5 mm area was measured using a method of stepped scanning and parabolic approximation. The conditions of measurement had been determined and evaluated through the preliminary measurement of compressive stress acting on the cylindrical surface. Furthermore, the fatigue strength estimated by applying the residual stress data to the previously presented hypothesis was compared with the experimental results. The main conclusions obtained were as follows: (1) The residual stress in a relatively small area on the cylindrdcal surface with large curvature can be measured by X-ray using a method of stepped scanning and parabolic approximation; (2) The compressive residual stress measured at the thread root was larger for the bolt manufactured by thread rolling after heat treatment than for one manufactured by thread rolling before heat treatment; (3) The distribution of residual stress along the axial direction from the thread root to the portion under crest did not represent remarkable change in its value; (4) The residual stress of a bolt was somewhat decreased by fatigue loading on the condition of low mean stress; (5) The fatigue strength estimated using residual stress data showed the tendency of experimental results well.

Analytical expression for the stress-strain curve of a dual phase material comprising two different strength level phases. Discussion of the results of the multiple X-ray peak method.

Equations expressing a tensile stress-strain relation of a dual phase material composed of a strong, brittle martensite and a weak, ductile austenite are proposed. This dual phase contains a constant volume of each phase and we call this the equation for a constant volume model (abbr. CVM). The experimental stress-strain data of the dual phase having various ratios of martensite to austenite are obtained and are analyzed by the equation using a computer with a multiregression program, and their best-fit flow curves are obtained. The above analysis of the co-operative deformation mechanism of two phases, which is balanced in stress and strain, shows that deformation starts with a bonding mechanism close to an equal strain chain and then gradually changes to one close to an equal stress chain as the plastic strain increases. The analysis of the plastic stress and strain concentrations in each phase is given in detail. These results are shown to agree excellently with the experimental data obtained from the X-ray residual stress measurements. The strain hardening exponent and the ultimate tensile strain of the dual phase decrease from the value of austenite to that of martensite as the volume of the latter increases.

X-ray Residual Stress Measurement on Fracture Surface of Stress Corrosion Cracking

X-ray fractography is a new method utilizing the X-ray diffraction technique to observe the fracture surface for the analysis of the micromechanisms and mechanics of fracture. The X-ray residual stress has been confirmed to be a particularly useful parameter when studying the fracture surfaces of high strength steels. The method has been applied to the fracture surface of fracture toughness and fatigue specimens.

X-ray residual stress measurement of yttria-partially stabilized zirconia.

The X-ray elastic constants and the stress constant for the X-ray stress measumement of partially stabilized tetragonal zirconia with 2.5 mol% and 3 mol% yttria were determined for diffractions from plane (0 2 6) by Cu-Kα radiation and from plane (1 3 3) by Cr-Kα radiation. The X-ray value of E/(1+ v) (E=Young's modulus, v=Poisson's ratio) was rather insensitive to the conditions of sintering and surface finishing. The measured value for plane (1 3 3) was lower than that for plane (0 2 6). The accuracy of the X-ray stress measurement was found to be higher for the case of plane (1 3 3). The residual stresses measured on the ground, lapped and polished surfaces were all compressive. The Ψ splitting of the sin2 Ψ diagram was observed for the cases of heavy grinding. The magnitude of the compressive residual stress became larger with increasing the diamond grain size of a cutting wheel, while it was insensitive to the cutting depth. The full width at the half maximum of the X-ray diffraction profiles and the amount of transformation from the tetragonal phase to the monoclinic phase also increased with increasing the diamond grain size of a cutting wheel.

X-ray residual stress measurement of silicon nitride by gaussian curve method.

Residual stress induced by sintering or machining has a large effect on the strength of ceramics. The X-ray technique can measure residual stress nondestructively. To determine accurately the stress by X-ray method, it is necessary to obtain experimentally the X-ray stress constant. By using the Gaussian curve methodν, the X-ray elastic constants E and ν, and stress constant K of a silicon nitride were determined together with their standard deviations representing the size of the variability caused by counting statistics. The planes of (323) and (212) were measured with CuKα and CrK α radiations, respectively. The 95% confidence limits of the stress constant were -779 ± 21 and -1027 ± 83 (MPa/deg) for (323) and (212) planes, respectively. The relative errors (standard deviation /measured value) of the X-ray elastic constants and stress constant for the (323) plane having a sharp and symmetrical Kα1 single diffraction profile were 1.4 %, whereas they were 3.4 to 4.3 % for the (212) plane having a Kα doublet.

X-Ray Residual Stress Measurements in Notched Test Specimens

Abstract X-ray residual stress measurements were made in notched test specimens of 7475-T651 aluminum and annealed Ti-6Al-4V in a configuration designed to simulate fatigue testing in a tensile testing machine. An automated and portable X-ray stress analysis system with a position-sensitive proportional counter was used for making the measurements. Sources of error in the measurements resulted from counting statistics, grain size, and preferred orientation in the specimen, and the radius of curvature of the notch. The feasibility of in situ residual stress measurements during brief pauses in fatigue testing is demonstrated.

The use of oscillation on PSD-based instruments for X-ray measurement of residual stress

Measurements of surface residual stress by X-ray diffraction can be accomplished very rapidly using a position-sensitive detector (PSD) to record the diffraction profile. It is shown that when the sample and detector are fixed during data accumulation, the profile shape may be distorted by large grain size or preferred orientation, which results in substantial error in the calculation of residual stress. Sample oscillation decreases the sensitivity of the PSD system to such microstructural variables in many cases. Instruments employing a PSD to measure surface residual stress should be designed with the capability of oscillating either the sample or the measuring head (X-ray tube and detector).

Focusing Circle Errors in X-Ray Residual Stress Measurements of Nickel-Based Materials

An unexplained anomalous sin2ψ split in x-ray stress measurements has consistently resulted from the use of Cr Kα radiation with nickel and austenitic stainless steels. Both, materials have diffraction peaks at low back-reflection angles for this radiation (nickel: 20 ⋍ 134°, austenitic stainless steel: 20 ⋍ 128°). The anomalous split is not evident when the measurements are made using Cr Kβ radiation, In an attempt to explain the errors produced by the Cr Kα radiation, focusing circle effects were analyzed and compared to experimental measurements made with both Cr Kα and Cr Kβ radiation on nickel-based samples,

Quantitative relation of strengthening in SUS 304 steel due to deformation-induced transformation.

Volume fractions of α' and e' martensite phases induced in tensile deformation in SUS 304 steel at temperature ranges from 20°C to -196°C are investigated by X-ray using the multi-diffraction peak method with an Mo-target. The former is presented well with the relation by the shear-band intersection mechanism and the latter with an exponential function of total plastic strain. The experimental plastic strain and flow stress of a dual phase steel at those temperatures are expressed by the variable volume model equations proposed here. The equation of total plastic strain comprises both components of the austenite and martensite phases and the transformation strain which is larger the larger the total plastic strain and the volume fraction of transformation. The equation of total plastic stress comprises both components of the austenite and martensite phases and a small additive component of the e' martensite rate and a small stress relaxation due to transformation strain in the austenite phase. Experimental data of these strains obtained from the X-ray residual stress measurement at 20°C have shown that the predicted relations agree excellently with the data.

Theoretical and experimental study of stationary and progressive induction hardening

Theoretical models for stationary and progressive induction hardening are proposed and briefly described. The models, which are valid for cylindrical geometries, have been used for calculation of the power input into the workpiece, temperature fields, phase transformations during heating and cooling, hardness patterns, stress distributions, and the relationships among these different quantities. The input data needed and the influence on the results of variations in input data are discussed on the basis of calculations carried out. In addition, hardening experiments for two standard Swedish steels, SS 2244 (∼AISI 4142) and SS 2258 (∼AISI 52100), Xray measurements of residual stresses and retained austenite, and hardness measurements are described. The computer calculations and the experimental measurements were found to agree well.

The use of X-ray stress analysis for WC-base cermets

Implications of the shallow penetration of X-rays in WC-base cermets are discussed with regard to conventional X-ray residual stress measurements. The principal factors of concern are relaxation of the volumetric differential thermal residual stress state at the surface and residual stress due to surface preparation. Model calculations are made of versus d sin2 Ψ plots, showing the effects of both relaxation and surface preparation for molybdenum, copper, cobalt and chromium X-rays. The occurrence of d versus sin2 Ψ plots with negative slopes, and subsequent biaxial analysis, precludes study of the differential thermal stress state although surface grinding and polishing effects may still be investigated.

Confidence Limits of Stress Values Measured by X-Ray Diffraction

Abstract The confidence limits of stress values measured by X-ray diffraction are usually determined from the equation of the t distribution for the linear regression analysis. Experimentation has shown that not all of the four assumptions on which the equation is based hold for X-ray stress measurement. X-ray residual stress measurement on a quenched structural steel was repeated 65 times. A slight failure of the assumption of linearity of the sin2ψ diagram gives confidence limits of the stress determined from the equation 1.5 to 6 times larger than the actual values depending on the preset times used. However, the confidence limits of the stress determined from the equation derived analytically from X-ray counting statistics agree very closely with the actual values. The standard error of the confidence limits determined from this equation is much smaller than that determined from the equation of the t distribution by a factor of 1∕15 to 1∕67.