The laser-based interferometric strain—slope rosette (ISSR) has been used to measure principal strains and stresses on material surfaces. In this paper, optical theory models and computer programs ...are developed to simulate the optical diffraction and interference of the ISSR. The simulation results compare with the experimental results. Then the feasibility of extending the ISSR into a nanoscale rosette is studied. The indentation size is selected on a nanometre scale and other parameters in the nanoscale ISSR design are studied. A virtual optical experiment is conducted to use the designed nanoscale ISSR to measure virtual strains. The simulations show that the ISSR can be potentially extended to nanometre-scale measurement of material deformations.
A novel Fiber Bragg Grating sensor with temperature compensation function was designed which can be used for structure health monitoring in harsh environment. The sensor achieved temperature ...compensation with a reference Fiber Bragg Grating. From the strain experiment and temperature experiment, it showed that the linear fitting degree of the strain curve and temperature curve were above 99%. And the temperature sensitivities of strain Grating and reference Grating were 11.2 pm/ C and 4.3 pm/ C, respectively. Two kinds of Fiber Bragg Grating rosettes based on the designed sensor were introduced which applied the multiplexing ability of FBG and could be used in practice.
Optical Methods Nelson, Drew V
Practical Residual Stress Measurement Methods,
2013, 2013-08-30
Book Chapter
Basic principles of holographic and electronic (digital) speckle pattern interferometry, Moire interferometry and digital image correlation are reviewed. Determination of residual stresses by hole ...drilling utilizing each of those methods is described and examples given, ranging from “in the field” to within the chamber of a scanning electron microscope. Performance characteristics and limitations of hole drilling implemented with those four optical methods are suggested. The use of shearography and interferometric strain rosettes with hole drilling is summarized. Other optically‐based approaches for finding residual stresses, such as photoelasticity and optical measurement of deflections accompanying material removal or deposition, are also summarized.
3D Image correlation technology has been widely used for the analysis of a broad range of materials ranging from biomechanics measurements of tissues, organs, ligaments and bones to microelectronics, ...automotive and aerospace applications. Manufacturing optical measurement systems for digitizing, forming analysis and materials analysis has become a part of advanced process chains for the development of products and production processes allowing data to be linked and automatically uploaded to quality control systems for precision lean operations.
ExxonMobil was an early adopter of the 3D Image Correlation technology for full-field deformation and strain studies of their piping systems and pipeline welding. This same technology has been widely used for the analysis of a broad range of materials ranging from biomechanics measurements of tissues, organs, ligaments and bones to microelectronics, automotive and aerospace applications. Because of its accurate and full-field nature, it is the best tool for computer model validation and iteration. As an example, the high speed ARAMIS 3D Image Correlation system was chosen by NASA for the Return-to-Flight of the Space Shuttle LS-DYNA model validations (Tyson et al. Performance verification of 3D image correlation using digital high-speed cameras. Proceedings of 2005 SEM Annual Conference and Exposition; 2005 June 7–9, Portland, OR, 2005). A related system monitors quality at Ford stamping plants and automatically downloads comparisons to finite element model (FEM) data of real line parts directly into the Ford Quality Control System (Tyson and Psilopoulos, Automated quality control of stamping with optical methods. International auto body congress, Troy, MI, 2009).
Image Correlation (DIC) has greatly benefited from the explosive growth of computer power and digital camera technology. We used to perform full-field optical measurements with laser holography (ESPI). ARAMIS has replaced most of this technology with its simple method of stereo imaging, which uses a pair of video cameras, like our eyes, to measure materials and structures in 3D space, but quantitatively down to the micron-scale world (Tyson et al. 3D Image correlation for dynamic and extreme environment materials measurements holistic structure measurements from the laboratory to the field. SEM 2005 Conference Proceedings, Portland, OR, 2005). The materials that this measures are any solid materials. Deformation and strain are material independent, so it works well for ceramics to thin films. Fields-of-view are solely optics dependant, so the technology is capable of performing measurements from 100 m (wind turbines & bridges) (Schmidt Paulsen et al. 2009) to sub-micron volumes (crystalline structures) (Kang J. 2007 Microscopic strain mapping based on digital image correlation). Since ARAMIS measures with 10,000 measurement points, it’s like having a finite element program for real testing, which compares directly to finite element analysis (FEA) models. Advances in high-speed cameras have allowed the technology to measure high-speed events from impact, ballistic and blast to split-Hopkinson bar and shock, up to 1 M frames/s (fps) (Tyson et al. 3D image correlation studies of geometry and material property effects during split hopkinson bar experiments. SEM 2008 Conference, 2008).
•Multiaxial non-proportional fatigue life evaluation using strain rosette data.•Multiaxial non-proportional evaluation of a complex gussetless bridge connection.•Complex connections experience ...multiaxial non-proportional stresses.•Multiaxial non-proportional stresses cause a decrease in fatigue life.•Uniaxial based procedures are insufficient for complex connections.
Civil engineering structures grow more complex as engineers push innovation boundaries. Load complexity, costs, construction and maintenance efficiency, among other things, can lead to unique designs that are often excluded in current design codes and evaluation standards. Fatigue-induced damage is currently one of the most common damage types experienced by ordinary and complex civil engineering structures subjected to cyclic loading such as bridges. However, current fatigue evaluation and design standards provide limited guidance on how to approach complex welded connections. Uniaxial and multiaxial methods for the evaluation of fatigue life using strains histories are compared for the assessment of a welded gussetless truss connection of the Memorial Bridge, a vertical-lift bridge connecting Portsmouth, NH and Kittery, ME. As expected, using both approaches result in sufficient remaining fatigue life. However, it is demonstrated that commonly used uniaxial fatigue analysis methods can be insufficient in complex structures that experience variable amplitude, multiaxial, and non-proportional loading. Multiaxial non-proportional stresses experienced by a complex connection can cause a decrease in remaining fatigue life estimates. This paper presents assessment tools and a method for the evaluation of fatigue life of complex welded connections using strain time histories.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
: The strain tensor, principal strains and precision of the estimates of these values are derived for a range of different layouts of three‐dimensional strain rosettes. These values are based on the ...Monte Carlo technique applied to experimental work which was carried out on transducers tested in different laboratories. The estimates of precision are determined theoretically and compared with results based on experimental findings. A new design of a miniature tri‐rectangular tetrahedral rosette was manufactured and tested. Results suggest that this transducer does not perform as well as the rectangular patterns.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
This chapter contains sections titled:
Introduction
Transformation of Stress in Two Dimensions
Principal Axes and Principal Stresses in Two Dimensions
Transformation of Strain in Two Dimensions
...Strain Rosettes
Stress Transformation and Principal Stresses in Three Dimensions
Allowable and Ultimate Stress, and Factors of Safety
Fatigue
Creep
Orthotropic Materials—Composites
Summary and Conclusions
Prepared in collaboration with the Naval Surface Warfare Center West Bethesda, MD. The original document contains color images.
This document summarizes the recent deployment of a fiber optic strain ...sensing (FOSS) system to monitor loads on a Navy Vessel, as requested and authorized by Commander Naval Surface Force, Atlantic. The objectives were to (1) conduct an in-service validation of the technology onboard a U.S. Navy ship and (2) determine contributing influences to recurring cracking of new deckplate, as described by the Southeast Regional Maintenance Center (SERMC) Port Engineer. Previous NAVSEA investigations discuss sensitization of the aluminum and onset of stress corrosion cracking (SCC), although the source of the SCC stresses have never been characterized. This effort attempts to quantify performance of the FOSS technology as a tool to provide such characterization. Covered in this document are the instrumentation, data collection and subsequent analysis.
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