Evaluation Of Residual Strains Research Articles

A Study on the Mechanical Properties of Glass-Fiber-Reinforced Defective Gypsum Boards

As a waste derivative, glass fiber has drawn a lot of interest from the engineering community. The purpose of this study was to use glass fiber to improve the performance of defective gypsum boards. Single compression experiments, repeated loading experiments, and scanning electron microscopy (SEM) testing were performed on defective gypsum boards. The results showed that the addition of glass fiber can improve the compressive strength of defective gypsum boards. When the fiber concentration is 1.5%, the strength of single-hole gypsum boards increases by 77.1%. Energy evolution and residual strain evaluation after repeated loading showed the significant reinforcement of the dual-hole gypsum board samples with the addition of glass fiber, improving the stress distribution and elasticity, which was confirmed using damage factor analysis. Glass fibers reduce stress concentrations, improve integrity, and prevent brittle failure, especially at high stress levels. The microstructural analysis showed that the addition of glass fiber improves adhesion and prevents microcracking while acting as a stress transfer bridge, enhancing the behavior of the specimen under cyclic loading. Based on the experimental results and cost, 1.5% glass fiber is the optimal concentration. The research results provide new ideas for the application of glass fiber in defective and brittle materials and contribute toward the sustainable development of the construction industry.

Small-diameter optical fibre sensor embedment for ambient temperature cure monitoring and residual strain evaluation of CFRP composite laminates produced by vacuum-assisted resin infusion

Out of autoclave (OoA) processing techniques, such as liquid composite moulding techniques (LCM) and, particularly, the vacuum-assisted resin infusion (VARI) technique, are being used, with increasing success, in replacement of prepreg/autoclave technologies to produce structural aircraft/aerospace polymer composite parts, due to its better cost effectiveness and competitiveness. This work aims to embed Fibre Bragg grating (FBG) sensors to monitor the VARI manufacturing of carbon fibre reinforced polymer (CFRP) composites and evaluate the associated phenomena: ambient curing and post curing reactions and resulting residual strains. The curing kinetics of the epoxy resin system alone was initially studied through isothermal differential scanning calorimetry (DSC) tests and applying the isoconversional Friedman method, and further studied by strain monitoring during ambient curing and post curing resorting to FBG sensors. The FBG sensors in the CFRP laminates were able to detect a subtle increase of strain as infusion of the CFRP started and to measure decreasing strain as resin filled in the dry fabric layers. Subtle strain decrease revealed forming crosslink bonds. Compressive strains measured by the FBG sensors during post curing show that further crosslink takes place. A comparison of resultant residual strains was made between specimens with embedded FBG sensors on small-diameter optical fibres (SDOF) and on large-diameter optical fibres (LDOF).

Investigation of electromagnetic nondestructive evaluation of residual strain in low carbon steels using the eddy current magnetic signature (EC-MS) method

Abstract A novel magnetic nondestructive testing method, that is named eddy current magnetic signature (EC-MS) method, is proposed to evaluate the residual strain in low carbon steels. This method relies on characterization of eddy current signals in the impedance plane if low frequency major magnetization is superimposed. To investigate the mechanism of the proposed method, the eddy current magnetic signatures of a set of tensile test specimens are measured, and their relationship to the residual strain is surveyed. The trajectories of the eddy current signals show significant dependences on the residual strain; the EC-MS changes depending on the three residual strain stages, the region just after elastic limit before yield point, the Luders-strain region, and the region after start of work hardening. The EC-MS under elastic strain/stress is measured to investigate the influence of stress on the EC-MS. Numerical calculation is performed considering micro-eddy current field associated with moving domain walls and compared with experimental results to interpret the EC-MS phenomena.

Cure Monitoring and Evaluation of Residual Strains for GFRP Laminates

Cure Monitoring and Evaluation of Residual Strains for GFRP Laminates

Eigenstrain reconstruction of residual strains in an additively manufactured and shot peened nickel superalloy compressor blade

Numerical modelling of the residual stresses and strains within mechanical components is of great importance for improving the quality and reliability of design for structural integrity. A particularly versatile and powerful approach is offered by direct and inverse eigenstrain modelling. The nature of the eigenstrain modelling approach is that it not only generates an efficient parametric representation of the residual stress field, but also ensures consistency by enforcing stress equilibrium and strain compatibility. In the present study we propose a particular way of prescribing the eigenstrain field due to surface treatment such as shot peening. Eigenstrain variation is described by a continuous function of the distance from the boundary of the object in a two-dimensional model of its cross-section. The procedure is compatible with the use of commercial numerical simulation software, and allows correct assignment of all eigenstrain components. We apply the technique to the evaluation of residual strain within an additively manufactured nickel superalloy compressor blade that was subsequently subjected to shot peening treatment. Two experimental techniques are used to validate the model, namely, Focused Ion Beam ring core milling (FIB-DIC) and synchrotron X-ray Powder Diffraction (SXRPD). Consistency between model prediction and experimental measurements provides verification of the suitability of eigenstrain modelling as consistent basis for the incorporation of residual stress effects on the deformation behaviour of manufactured components.

Understanding nature’s residual strain engineering at the human dentine–enamel junction interface

Human dental tissue is a hydrated biological mineral composite. In terms of volume and mass, a human tooth mainly consists of dentine and enamel. Human dental tissues have a hierarchical structure and versatile mechanical properties. The dentine enamel junction (DEJ) is an important biological interface that provides a durable bond between enamel and dentine that is a life-long success story: while intact and free from disease, this interface does not fail despite the harsh thermo-mechanical loading in the oral cavity. The underlying reasons for such remarkable strength and durability are still not fully clear from the structural and mechanical perspectives. One possibility is that, in an example of residual stress engineering, evolution has led to the formation of a layer of inelastic strain adjacent to the DEJ during odontogenesis (tooth formation). However, due to significant experimental and interpretational challenges, no meaningful quantification of residual stress in the vicinity of the DEJ at the appropriate spatial resolution has been reported to date. In this study, we applied a recently developed flexible and versatile method for measuring the residual elastic strain at (sub)micron-scale utilising focused ion beam (FIB) milling with digital image correlation (DIC). We report the results that span the transition from human dentine to enamel, and incorporate the material lying at and in the vicinity of the DEJ. The capability of observing the association between internal architecture and the residual elastic strain state at the micrometre scale is useful for understanding the remarkable performance of the DEJ and may help the creation of improved biomimetic materials for clinical and engineering applications. Statement of SignificanceWe studied the micron-scale residual stresses that exist within human teeth, between enamel (outer tooth shell, hardest substance in the human body) and dentine (soft bone-like vascularised tooth core). The dentine–enamel junction (DEJ) is an extremely interesting example of nature’s design in terms of hierarchical structuring and residual stress management. Key developments reported are systematic focused ion beam (FIB) milling and digital image correlation (DIC) micrometre scale residual strain evaluation, and the determination of principal strain direction near DEJ, correlated with internal architecture responsible for remarkable strength. This work helps understanding DEJ performance and improving biomimetic materials design for clinical and engineering applications.

Internal Residual Strain Evaluation in Dissimilar Welding Using White X-rays

Internal Residual Strain Evaluation in Dissimilar Welding Using White X-rays

159 増分透磁率法による炭素鋼に生じた残留ひずみの定量的評価

159 増分透磁率法による炭素鋼に生じた残留ひずみの定量的評価

Neutron Residual Strain Surface Scans - Experimental Results and Monte Carlo Simulations

Precise determination of diffraction peak positions is of particular importance for the evaluation of residual strains. Neutrons are commonly used to probe residual strains from material volumes in depths of several millimetres under the sample surface. However, neutron strain analyses are critical for the near surface region. When scanning close to a sample surface, aberration peak shifts arise, which can be of the same order as the peak shifts related to residual strains [1]. Series of Monte Carlo (M.C.) simulations using the software package RESTRAX/SIMRES [2] were carried out to simulate the peak shift as a function of gauge volume depth, monochromator curvature and other instrumental parameters, which can be used to quickly optimise the experimental setup for direct measuring residual strains near the sample surface at an arbitrary surface orientation. The M.C. simulations were compared and agree very well with the experimental data, not only for a stress free steel sample but as well for a deep rolled steel sample, measured at the STRESS-SPEC diffractometer at the research reactor FRM II, Garching (Germany).

111 繊維基材を用いた複合材料の硬化に伴う残留ひずみの評価

111 繊維基材を用いた複合材料の硬化に伴う残留ひずみの評価

Evaluation of residual strain in directional solidified mono‐Si ingots

AbstractCast‐grown mono‐like Si ingots for photovoltaic application are getting increasing attention due to the possibility of obtaining highly efficient solar cells at a low‐cost production process. The reduction of crystallographic defects is essential to reach that potential. In this study, the residual strain and dislocation distribution in monolike ingots grown by directional solidification was experimentally determined. It was found that both strain and dislocations are mainly concentrated in the periphery of the ingots (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Circular polariscopic analysis of a ZnO wafer for highly sensitive and speedy evaluation of residual strains: Its relation with X‐ray diffraction pattern and topography

AbstractWe have explored the effectiveness of applying the circular polariscopic measurement to the mapping of the strains in a ZnO wafer. Initially, monochromatic X‐ray topography, which is regarded as a fundamental evaluation technique for wafers, is applied. The measured monochromatic X‐ray topograph shows that the image contrast is remarkably inhomogeneous; namely, the bark patterns exist in various regions. In order to clarify the origin of the above‐mentioned dark patterns, we apply the circular polariscopic measurement, which is sensitive to strains through the photoelastic effect. The brightness of the circular polariscopic wafer map reveals that the dark pattern in the monochromatic X‐ray topograph results from the strain. Thus, we conclude that the circular polariscopic analysis has the ability to compliment the information obtained by the monochromatic X‐ray topographic measurement. The presence of the relatively large strains is confirmed from the fact that the forbidden reflection lines are observed in the θ ‐2θ X‐ray diffraction pattern. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

132 ECT-EMAT 複合プローブによる構造材料の残留歪みの評価(材料力学IV/情報・知能・精密機器/機械力学・計測制御,一般講演)

The experiments of residual strain testing with an EMAT and ECT dual probe showed that the birefringence coefficient of shear waves can generally evaluate the residual strain. In addition, since the residual strain can be tested with ECT method as a supplemental result, the dual probe is meaningful in residual strain evaluation.

Residual strain evaluation of curved surface by grating-transferring technique and GPA

This paper investigates an advanced grating-transferring technique combined with geometric phase analysis (GPA) for residual strain evaluation of curved surface. A standard holographic grating is first transferred to a pre-produced epoxy resin film and then consolidated to a test region of curved surface. With a rubber mold and silicone rubber the deformed grating is replicated to a sheet metal after hole-drilling for release of residual stress. After that the grating is transferred from the sheet metal to the glass plate, which would be served as an analyzer grating (specimen grating). By GPA the local strain distributions related to the phase difference between the reference grating and analyzer grating for the released stress can be evaluated. A validation test has been conducted on the weld joint of a stainless steel tube and the obtained results demonstrate the ability of the method in measuring the residual strain of curved surface.

A non-destructive method for the measurement of residual strains in semi-crystalline polymer components

A new non-destructive tool is presented, enabling the measurement of locked-in residual strains in semi-crystalline polymer-based components. The technique employs high-energy synchrotron X-rays to probe the variation of diffraction angle within a well-defined ‘gauge volume’ with a spatial resolution of the order of 1 mm. Lattice strain is calculated from the diffraction angles. An overview of the experimental methodology and underlying principles involved in the non-destructive evaluation of residual strain in polymer-based components is given. Preliminary results show that synchrotron X-rays can be used successfully to measure the internal elastic residual strain field in polymer components, being potentially applicable to other materials. The method was used successfully to measure residual strains in a commercial high density polyethylene gas pipeline sample.

Evaluation of residual strains in epoxy with different nano/micro-fillers using embedded fiber Bragg grating sensor

The influence of SiO 2 nanoparticles and rubber micro-fillers on the mechanical and thermal responses of an epoxy based composite is investigated using classical quantitative thermo-mechanical testing (tensile tests, DMTA, TMA), microstructural analysis (Micro-CT, TEM, SEM microscopy) as well as distributed optical sensing in order to determine different residual strain fields generated during processing. The results show that the tensile modulus of the compounds increases with the addition of SiO 2 and decreases with the rubber content, following estimates of the Hashin–Shtrikman model. The coefficient of thermal expansion appears to be insensitive to the particles’ content in the temperature range investigated. The residual strains generated during processing are influenced by the rubber content that introduces a strong relief, with respect to the one generated by the neat resin, whereas the silica content tends to increase their level.

Evaluation of Residual Strain and Oxygen Vacancy in Multilayer Ceramic Capacitor Using Laser Raman Spectroscopy

Micro-Raman spectroscopy was employed to investigate the residual strain and oxygen vacancies of BaTiO3-based multilayer ceramic capacitors (MLCCs) with a Ni internal electrode. Strain was found to accumulate around the internal Ni electrodes layers than at other parts of the MLCCs. In addition, the number of oxygen vacancies near the internal Ni electrode was larger than that at any other parts of the MLCCs. These observations clearly show that Raman spectroscopy is extremely useful for evaluating the residual strain and oxygen vacancies in MLCC devices.

Oxford HEXameter: Laboratory High Energy X-Ray Diffractometer for Bulk Residual Stress Analysis

Diffraction of penetrating radiation such as neutrons or high energy X-rays provides a powerful non-destructive method for the evaluation of residual stresses in engineering components. In particular, strain scanning using synchrotron energy-dispersive X-ray diffraction has been shown to offer a fast and highly spatially resolving measurement technique. Synchrotron beamlines provide best available instruments in terms of flux and low beam divergence, and hence spatial and measurement resolution and data collection rate. However, despite the rapidly growing number of facilities becoming available in Europe and across the world, access to synchrotron beamlines for routine industrial and research use remains regulated, comparatively slow and expensive. A laboratory high energy X-ray diffractometer for bulk residual strain evaluation (HEXameter) has been developed and built at Oxford University. It uses a twin-detector setup first proposed by one of the authors in the energy dispersive X-ray diffraction mode and allows simultaneous determination of macroscopic and microscopic strains in two mutually orthogonal directions that lie approximately within the plane normal to the incident beam. A careful procedure for detector response calibration is used in order to facilitate accurate determination of lattice parameters by pattern refinement. The results of HEXameter measurements are compared with synchrotron X-ray data for several samples e.g. made from a titanium alloy and a particulate composite with an aluminium alloy matrix. Experimental results are found to be consistent with synchrotron measurements and strain resolution close to 2×10-4 is routinely achieved by the new instrument.

Evaluation of Residual Stress in Thin Ferroelectric Films Using Grazing Incident X-Ray Diffraction

A comparative study of three methods for thin film, in-plane residual strain evaluation is presented. Thin films of SrTiO3 and BaxSr(1 - x)TiO3 deposited using pulsed laser deposition on LaAlO3 and MgO substrates were investigated. It is shown that the most precise way to evaluate thin film, in-plane residual strain is by using Grazing Incidence X-ray diffraction.

IMAGE-BASED EVALUATION OF VASCULAR RESIDUAL STRAIN

We propose a method that aids in the evaluation of residual strain in blood vessels. Strain measurement is important in stress analysis of cardiovascular tissues. Since its introduction in 1983, arterial residual strain is evaluated manually which is a lengthy process. This involved photography, film development, printing of large photographs, and finally digitization of the edges of the vascular rings before and after cut using a flatbed digitizing tablet. These processes are highly labor intensive and time consuming, in the order of days. In this paper we introduce an image analysis and processing technique in which arterial residual strain can be evaluated efficiently and reliably. To insure portability, a JAVA-based application is developed which is designed for a semi-automatic operation in evaluating residual strain values. The use of the image-based evaluation technique is validated by comparison of arterial residual strain evaluated using photographs and digitizing tablet.