Papers by Keyword: Strain Measurement

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Authors: Matthias Reihle, Michael Hofmann, Uwe Wasmuth, Wolfram Volk, Hartmut Hoffmann, Winfried Petry
Abstract: Composite castings exhibit high residual stresses, mainly because of different thermal expansion of the used materials. Similar to the in-cast cylinder liners in a motor block, a composite specimen, consisting of a steel insert and an aluminum cast surrounding, was analyzed by neutron diffraction. The temperature- and time-dependent change of lattice spacing and thus the strain evolution was investigated by in-situ experiments directly after casting and during the cooling of the part. Different cooling conditions were investigated using two different molds, namely a sand and a permanent (steel) mold, optimized for in-situ neutron diffraction.
Authors: Tomoyuki Fujishiro, Takahisa Shobu, Koji Kiriyama, Atsushi Yamamoto
Abstract: In-situ diffraction measurements were carried out on a tensile specimen of SUS304 stainless steel using a small autoclave at BL22XU at SPring-8. The temperature of circulating water in the autoclave was changed from room temperature to 561 K under ambient pressure and also under a pressure of 8.8 MPa. Tensile stress of 260 MPa was applied to the specimen at 561 K under 8.8 MPa, and a two dimensional strain distribution was obtained by calculation based on measured lattice spacings of the γ-Fe311 plane under various conditions. The interior region of the specimen showed higher strain compared with that on the surface region. After the tensile deformation in the autoclave, CT images of cross sections of the specimen were taken. Void-like images with about 50 μm in size were observed.
Authors: Peter Stanley
Abstract: The paper provides a picture of the changes and advances in the field of strain measurement, as represented by the contents of the journal “strain”, from its inception in 1965 to the present day.
Authors: M. Karadge, Benedict M.B. Grant, Giovanni Bruno, Javier R. Santisteban, Philip J. Withers, Michael Preuss
Abstract: In this study we present a direct comparison between residual strain measurements carried out on the same inertia friction weld using ENGIN-X at ISIS, UK and the new strain scanner SALSA at ILL, France. ENGIN-X is a time of flight (TOF) instrument, which receives neutrons from a neutron spallation source, while the SALSA Strain-Imager, a high resolution diffractometer, is based at a research reactor source with a continuous neutron flux and is operated with a constant wavelength. The purpose of this study was to demonstrate a confidence in crosscomparing future strain measurements to be performed at ENGIN-X and SALSA. Measurements were carried out on medium size inertia friction welded nickel superalloy test-piece, which show no significant crystallographic texture across the weld line. The results demonstrate that, even though residual stresses determined on SALSA only rely on a single peak analysis (in this case the (111) reflection), the results show excellent agreement with the measurements carried out on ENGIN-X, where strain is determined from multi-peak Rietveld analysis.
Authors: Jun Cao, Na Zhang, Jia Wei Zhang, Ming Bao Li, Xiu Mei Zhang
Abstract: To improve the accuracy of strain, the design method and technology based on the theory of double-channel parametric measurement is proposed. At last, the measuring circuit with linear conversion function is designed. Based on the theory, a measuring system is developed. The practical experimentation indicates that the theory and technology are right, and the accuracy, stability, anti-interference and reliability are excellent.
Authors: Wieslaw Jerzy Staszewski, Ruztamreen bin Jenal, Andrzej Klepka, Mariusz Szwedo, Tadeusz Uhl
Abstract: Non-contact optical/laser measuring techniques are very attractive in many engineering applications. The paper demonstrates examples related to structural health monitoring. Various methods based on strain, vibration and ultrasound measurements are presented together with relevant references. Applications examples utilise in-plane and out-of-plane measurements taken by 1-D and 3-D laser Doppler vibrometers.
Authors: Xiao Peng Zhang, Yan Qiang Chen, Huai Nian Xing, Li Qiang Jin, Da Li
Abstract: In fatigue crack growth experiment and fracture toughness test, the crack length measurement is very important. Here, this paper proposes a new method for measuring crack length, namely in the case of a known load, according to the strain on the front end face of the three point bending specimen would be to get crack length.
Authors: Zi Hui Xia, Jie Chen
Abstract: For strain-controlled fatigue tests, especially at elevated temperature, implementation of knife-edges and punching dimples within gauge length of specimen may cause premature failure on the test section. In this paper, an alternative approach is introduced to control and measure the strains in fatigue tests. Two dimples outside the gauge length section are punched and used to mount the extensometer. The correlation between the controlled (measured) strain and the strain within the gauge length section is established. By comparing the hysteresis loops obtained through the correlation and the one directly measured within the gauge length, it is found that the established correlations are in good agreement with the latter result.
Authors: Jin Liang Gu, Hong E Luo, Ke Jie Qiang, Bao Ming Li
Abstract: Strain measurement in electromagnetic rail launching processes is of significant importance to studies on rail life, wrap material selection, and initial armature disturbance. Based on a discussion about the principle of fiber-optic differential strain measurement, the constitution of a rail strain measurement device based on fiber-optic differential interference was introduced, and its data processing method and system calibration method were discussed. With this measurement method, electromagnetic rail strain measurement was completed, and experimental results indicate that the differential strain measurement device is able to operate reliably and stably under an intense electromagnetic interference environment in an electromagnetic railgun launching process and can be applied to strain measurement and in-bore projectile motion velocity measurement of gun barrel weapons.
Authors: Peng Hui Li, Yin Ping Wen, Wen Guang Zhao, Hong Ping Zhu
Abstract: The realization of strain measurement based on digital image processing technique is discussed. Combined with the strain measurement principle and the optical imaging feature, considered the axisymmetrical and non-axisymmetrical distortion, the automatic surface-fitting calibration method based on region growing is adopted. Cubic polynomial is applied to establish the relationship between the object space and pixel coordinate system. The expectations based on wavelet coefficients are used for sub-pixel edge detection, measurement accuracy can reach 0.02 pixels. Accuracy of displacement for strain measurement achieves micrometer-level. The theoretic validity and practical feasibility of the system are proved by the strain measurement of a cantilever steel beam.
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