Determination Of Residual Stresses Research Articles

Residual stress in fiber reinforced thermosetting composites: A review of measurement techniques

AbstractResidual stress is inherent in any fiber reinforced composite, created by the laminates processing route and high levels of anisotropy. The aim of this article is to provide an up to date review of the current state of the art in experimental techniques for the determination of residual stress in thermosetting fiber reinforced composites. Residual stress is considered at a micro‐mechanical, macro‐mechanical, and global scale as each require specific techniques to investigate and offer their own unique challenges to the designer. Many advances have been made in the experimental determination of residual stress in fiber reinforced composites since the last comprehensive review of the topic by Shokrieh in 2014. However, more work still needs to be done to develop a method that is applicable to all cases and can be applied as a universal standard. It remains a significant challenge to experimentally determine residual stress in thermosetting composites.

РАЗРУШАЮЩИЕ МЕТОДЫ ОПРЕДЕЛЕНИЯ ОСТАТОЧНЫХ НАПРЯЖЕНИЙ (обзор)

The paper presents an overview of methods for determining residual stresses. Methods such as splitting and segmentation, layer-by-layer removal, slitting (cutting, pliability), profiling, drilling holes (including a «deep» hole) are considered. The description of the methods for mea-suring the deformation used in the determination of residual stresses is given. The most common contact method using strain gauges, as well as non-contact methods: polarization-optical (photo-elasticity), optical speckle interferometry, digital image correlation.

Residual stresses determination by neutron diffraction in a 100Cr6 chromium steel bearing ring

Residual stresses determination by neutron diffraction in a 100Cr6 chromium steel bearing ring

Residual stress determination by neutron diffraction in a car gear-shaft made of 20NiCrMo2 alloyed case hardening steel

Residual stress determination by neutron diffraction in a car gear-shaft made of 20NiCrMo2 alloyed case hardening steel

Finite Element Simulation of Residual Stress Determination Based on Spherical Indentation Accumulation Morphology

The introduction of residual stress during the processing of materials has an important impact on the properties of the materials, so it is important to accurately measure the residual stress of the material. This paper established a finite element model of spherical indentation under the action of non-equivalent biaxial residual stress. Then we extracted the full-field accumulation state near the indentation under different stress states from the simulation results and summarized the pile height distribution near the indentation under different stress states. From the simulation, we found that the maximum pile-up height near the indentation point presented a regular trend.

Residual stress states in cementite and ferrite in a combined cold drawing process of AISI 1045 steel using neutron diffraction and synchrotron radiation

The evaluation and control of residual stress states in manufacturing processes such as cold drawing can be difficult, especially in multi-phase materials. Diffraction methods are ideal for characterizing residual stresses in individual phases provided these phases scatter neutrons or X-rays well enough to obtain a good signal. Residual stresses determination problems in drawn components have been reported. Main constraints are measurements in the primary ferrite phase only. The presence of cementite in carbon steel is often neglected. A problem that has not yet been extensively investigated is how residual stresses in the ferrite and cementite phases develop in subsequent steps of material processing such as cold drawing. In this work a combined straightening and bar drawing process of AISI 1045 round bars from coils of a hot-rolled material was investigated. A careful characterization of the material, including residual stress states in the ferrite (α−Fe) and cementite (Fe3 C) phases, using neutron diffraction and synchrotron diffraction was performed for each of the different manufacturing steps. The drawing and polishing and straightening (P.S.) parameters by crossed rolls were changed to evaluate their influence on the α−Fe and Fe3 C residual stress distributions. After the drawing process, residual stresses in the cementite phase are highly tensile, as already reported, however it can be shown that after polishing and straightening steps residual stresses in the cementite phase decrease and residual stress distributions also depend on the tool angle used.

Substantiation of the parameters of the process of plasma-mechanical milling of titanium alloys and alloyed steels

The article is devoted to the development and scientific substantiation of the method of processing high-strength materials using surface plasma heating. A method for determining the parameters of the plasma-mechanical milling process has been formed, which includes: thermal calculations of the plasma arc power; thermal field characteristics in the part material; determination of residual stresses and hardness of the surface layer of the part. The choice of technological parameters of a plasma heating source is grounded. Criteria are formulated to which the source of plasma heating must correspond. Calculations are performed to determine the dependence of the performance of the milling process on titanium alloy Ti-6Al-4V with the achievement of a certain microstructure of the part being cut off under the influence of plasma heating. A new scheme of plasma-mechanical milling is proposed, which provides for arc scanning in a magnetic field in the direction of the minute vector filing cutters and additional cyclical movement across the plasma torch feed vector with an amplitude of approximately equal to width milling. The proposed method of plasma heating a cut off layer allows lowering costs of processing time, and solve the problem of shortening ships' construction time.

Residual stress determination in thin films by X-ray diffraction and the widespread analytical practice applying a biaxial stress model: An outdated oversimplification?

Compressive stresses are commonly desired in thin films and the stress state in layers and coatings is in general evaluated assuming a biaxial nature of stress. But how thin is thick enough, or how many atom layers are necessary until this model assumption fails and a hydrostatic term joins in? In order to provide an answer molybdenum has been magnetron sputtered on display glass in layer thicknesses from 100 nm up to 2000 nm and afterwards investigated by X-ray diffraction to determine the residual stress state in the [110] fiber-textured sputtered films. It will be demonstrated that the use of a biaxial stress model might only be justified for thin layers if at all.

Determination of residual stresses in thermal barrier coating due to the amount of CMAS infiltration

In this work, we present the effect of the amount of CMAS infiltration into YSZ of Thermal barrier coatings (TBC) on the magnitude of residual stresses. The (TBC) were deposited by thermal spraying of CoNiCrAlY (Bond Coat-BC) and YSZ (Top Coat-TC) powders. The deposition of the BC was through the high velocity oxygen fuel (HVOF) system. The TC was deposited via an atmospheric plasma-spraying gun (APS). The TBCs were heat treated at 1250 °C, with a CMAS attack at a concentration of 10 mg/cm².The attack exposure was for 2 and 4 hours respectively. In this evaluation, the measured parameter was the magnitude of the residual stress state in Yttria Stabilized Zirconia (YSZ). The residual stress profiles were obtained using the Modified Layer Removal Method for Duplex Coatings (MRCMRB) and the Noda equations. An increase of 26.446 MPa was determined for 2 hours of thermal treatment and 30.743 MPa for 4 hours.

Determination of residual stresses during flaring of heat exchange tubes

The calculation of residual stresses in the attachment points of heat-exchange tubes in tube sheets during flaring is proposed, taking into account the peculiarities of axial movement of the spindle and local deformation of the tube under the influence of rollers. The calculation was based on the theory of continuity of a continuous medium and experimental data. Keywords: flaring, pipe, tube sheet, stress, deformation, torque. mironova_lub@mail.ru

Investigation of residual stress in composites produced by explosion welding with ultrasound

The paper presents the results of experimental studies of residual stress in homogeneous steel samples obtained by explosion welding with simultaneous exposure to ultrasound. For experimental determination of residual stress in composites, a method based on sequential removal of thin metal layers from the sample surface and measurement of deformations of the sample from the opposite side using strain gages was chosen. It is shown that the introduction of ultrasound in the process of explosion welding leads to both a redistribution of residual stress and a significant decrease in their maximum values measured in the immediate vicinity of the junction zone of steel samples.

Parameter Development via In Situ Residual Stress Measurement and Post-deposition Analysis of Cold Spray CuNi Coatings

Developing dense, well-adhered coatings with minimal heterogeneity via cold spray deposition has been a challenge because in-flight and layer-by-layer diagnostics has not yet been adequately adapted to complement existing post-deposition analyses and parameter process mapping. This study presents an empirical and analytical approach for development and optimization of requisite spray parameters via the cold spray solid-state consolidation process using the in situ beam curvature technique to assess particle dynamics during deposition, in conjunction with post-deposition analyses. Here, CuNi (62/38) powder was deposited onto CuNi (70/30) substrates and monitored with an in situ beam curvature sensor to provide real-time feedback of the coating’s evolving stress states during the deposition process and subsequent residual stress determination immediately after deposition. The resulting beam curvature compressive and tensile stress amplitudes detected layer-by-layer coating variations during deposition resulting from adjusted carrier gas flow rates, substrate surface preparations, nozzle deposition angle, robot raster speeds, powder feed rate, substrate preheat, as well as identifying nozzle clogging. The acquired stress-state data enhanced post-deposition analyses that directed and accelerated the downselection process to define and optimize cold spray parameters, as it pertained to coating adhesion, cohesion, and the corresponding microstructure.

Characterization and Evaluation of Mechanical Properties and Residual Stress in Aluminum-Magnesium Alloys Welded by the FSW Process

The demand for lighter materials with suitable mechanical properties and a high resistance to corrosion has been increasing in the industries. Therefore, aluminum appears as an alternative due to its set of properties. The aim of this work was to evaluate residual stress levels and mechanical properties of welded joints of Aluminum-Magnesium alloy AA 5083-O using the Friction Stir Welding process. For mechanical characterization were performed a uniaxial tensile test, Vickers hardness, bending test and, finally, the determination of residual stresses. It was concluded that welding by FSW process with an angle of inclination of the tool at 3o, established better results due to better mixing of materials. The best results of tensile strength and a lower level of residual stresses were obtained using a tool rotation speed of 340 RPM with welding advance speed of 180 mm/min and 70 mm/min.

Determination of the macroscopic residual stress: Modeling and experimental evaluation of texture and local grain-interaction

When the texture is present in the sheet, it is extremely difficult to test the residual stress based on the X-ray diffraction method. Based on the two extreme traditional Voigt and Reuss models, this paper proposes two specific corresponding local models (local Voigt and local Reuss) for the measurement of the plane residual stress of cold rolled sheet texture materials. The residual stress test results of CuNiSi specimen using these two local models show that the proposed local models are credible and can accurately characterize the residual stress in the specimen. In addition, based on the X-ray diffraction sin2ψ method of the classic residual stress test, a weighted average residual stress calculation method is proposed for cold-rolled texture materials. The dψ-sin2ψ method was used to analyze the effect of texture on residual stress. The results show that the copper texture C{211}〈111〉 in CuNiSi specimen has the effect of concentrating the residual compressive stress in the region. The stress increased by about 50 MPa. However, the effect of brass texture B{011} 〈211〉 and R texture R{011} 〈211〉 on residual stress was not obvious.

Determination and Validation of Residual Stresses in CFRP/Metal Hybrid Components Using the Incremental Hole Drilling Method

Lightweight materials contribute to an efficient decrease in fuel consumption in the automotive and aircraft industries. Hybrid components made of metal and carbon fiber-reinforced plastics (CFRP) have a high potential in lightweight applications due to their high strength-to-weight ratio. For cost-effective processing of hybrid materials, advanced manufacturing processes such as the prepreg-press-technology have been developed, in which the bonding between a metallic component and a fiber compound is exclusively realized in the forming process. However, upon processing of these hybrid components at elevated temperature, the difference in thermal expansion coefficients of the two materials leads to the formation of tensile residual stresses upon cooling. It is well known that these tensile residual stresses can be detrimentally effective with respect to the durability of a hybrid component. The objective of this work is to accurately measure and analyze residual stresses in hybrid components made of unidirectional CFRP and steel through the incremental hole drilling method. Within this study, the evaluation formalism for orthotropic materials is employed for measuring non-uniform residual stresses in hybrid materials. In order to improve the measurement accuracy, a customized strain gauge with eight grids is employed and a drilling increment size of only 20 µm is utilized. The influence of the angle between the strain gauge rosette and the fiber direction on the evaluation of the residual stresses is investigated. In order to evaluate the reliability of the results determined, a bending test applying a well-defined load is carried out. By direct comparison of the experimentally determined stresses and stress values calculated by the finite element method, the applicability of the hole drilling method for robust determination of residual stresses in CFRP/metal hybrid components is finally validated.

Discrete Element Framework for Determination of Sintering and Postsintering Residual Stresses of Particle Reinforced Composites.

In this paper, the discrete element method framework is employed to determine and analyze the stresses induced during and after the powder metallurgy process of particle-reinforced composite. Applied mechanical loading and the differences in the thermal expansion coefficients of metal/intermetallic matrix and ceramic reinforcing particles during cooling produce the complex state of stresses in and between the particles, leading to the occurrence of material defects, such as cracks, and in consequence the composite degradation. Therefore, the viscoelastic model of pressure-assisted sintering of a two-phase powder mixture is applied in order to study the stress field of particle assembly of intermetallic-ceramic composite NiAl/AlO. The stress evaluation is performed at two levels: macroscopic and microscopic. Macroscopic averaged stress is determined using the homogenization method using the representative volume element. Microscopic stresses are calculated both in the body of particles and in the contact interface (necks) between particles. Obtained results are in line with the cooling mechanism of the two-phase materials.

Determination of Optimum Process Parameters and Residual Stress in Friction Welding of Thixocast A356 Aluminum Alloy

The quest of automobile industries for weight reduction and enhancement of the mechanical strength of components has been a major incentive for new manufacturing technologies such as thixocasting. It is therefore important that the welded joints of such components exhibit adequate strength and formability. The present investigation is on optimization of process parameters to achieve better weld quality obtained in friction-welded joints of thixocast A356 aluminum alloy. The optimum combination of welding parameters is obtained by using the analysis of the signal-to-noise (S/N) ratio based on the Taguchi method. Joint strength higher than the parent material strength is achieved with an optimum set of friction-welding parameters. In addition, residual stress analysis is carried out both experimentally and numerically. Comparisons between the experimental and numerical residual stresses are in good agreement with each other. The residual stress obtained is of low magnitude and compressive in nature.

A Study on Determination of Residual Stresses by Hole Drilling Method in Welded Tubular K Joints

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Use of Power Series Expansion for Residual Stress Determination by the Incremental Hole-Drilling Technique

The integral method of incremental hole-drilling is used extensively to determine the residual stress distribution in isotropic materials. When used with Tikhonov regularization, the method is robust and produces accurate results with minimal uncertainty. Alternatively, an optimal hole depth distribution can be found using the method of Zuccarello to improve the conditioning of the calibration matrices. If substantial measurement noise or a steep variation in stress exists, however, considerable uncertainty in, or distortion of, the calculated residual stress distribution can occur. Series expansion offers an alternative solution, but it has been reported to become unstable before meaningful accuracy can be achieved. Investigate the use of series expansion to determine a rapidly changing throughthickness residual stress distribution in an aluminium alloy 7075 plate subjected to laser shock peening treatment. Power series expansion of eigenstrains is used in finite element modelling to calculate the calibration coefficients. Monte Carlo simulation is used to determine robust uncertainties in the residual stress distributions. This allows the series order with the lowest RMS uncertainty in stress to be selected from those series orders that have converged. The best estimate of the residual stress distribution is thereby obtained. Series expansion is shown to be stable up to 8th order and convergence to a stress solution can be found before instability dominates. The method is insensitive to measurement errors due to the least-squares approach employed by the inverse solution. The use of series expansion reduces the RMS uncertainty in stress when compared to the regularized integral and Zuccarello methods.

Experimental determination of the interface residual stresses of carbon-fiber-reinforced polymers

Combining the matrix crack method with the geometric phase analysis (GPA) method, the interface residual stresses in carbon-fiber-reinforced polymers were measured at nanoscale. A cross-grating with a pitch of 138 nm was fabricated on the surface of composite material by electron beam lithography. The residual stresses around fibers located in the 90°, 45°, and 0° fiber layers were released through the matrix crack method using a Berkovich nanoindenter. The released residual stresses led to a change in the pitch of the grating and the corresponding residual strains were obtained by the GPA method. The Hooke’s law was employed to calculate the interfacial residual stress in the 90° fiber layers (−6.7 ± 1.3 MPa) in a range of 13.8 nm around the fiber, which agreed well with the result calculated by the Bright’s equation, and then, the interfacial residual stresses in the 45° fiber layers and residual stress along the fiber axial direction were obtained. The effect range of the radial residual stresses was equal to about one fiber radius.