Deformation measurement around a high strain-gradient region using a digital image correlation method

Shao

Advances in Mechanical Engineering

et al. 2018

Marine power rear transmission system is a constant power system under specific working condition, which relies on alternating meshing gears to transfer the movement and torque. It is difficult to accurately determine the actual thermal stress and thermal deformation for time-varying distribution using the traditional methods. Elastic structural mechanics modeling and method details of thermal expansion deformation are presented and analyzed. Both the actual reflection thermoelastic contact condition for meshing gears and the coupling effect results of the practical loading process of marine power rear transmission system carried out on alternating meshing gear surfaces are also detailed. In this article, the changes in gear meshing angles of several key meshing positions are presented. The 16 meshing positions of contact stresses and loaded deformation approach are analytically evaluated in terms of the rotation range of driving spur gear (35°) and driving helical gear (36°). The purpose of this study is to confirm the significant stress concentration areas of gear meshing in and meshing out and to obtain that the deformation amounts of gear meshing impact positions within selected zones. The aim of this article is to reach gear deformation on the basis of theoretical conception.

Section: Introductionmentioning

confidence: 99%

Thermomechanical coupled contact analysis of alternating meshing gear teeth surfaces for marine power rear transmission system considering thermal expansion deformation

Shao

Advances in Mechanical Engineering

et al. 2018

“…The measurement accuracy of DIC in the local deformation has an important influence on quantifying the strain localization zone, the deformation near the crack, and the determination of the fracture parameters of the crack 27 – 30 . The calculation parameters affect the displacement measurement results because the shape function does not match the actual deformation.…”

Section: Principle Of Measurement Methodsmentioning

confidence: 99%

Improved virtual extensometer measurement method in complex multi-fracture situation

Chai

Ouyang

Liu

et al. 2022

Sci Rep

To overcome the limitation of the virtual extensometer method in measuring the crack opening displacement (COD) in the process of complex multi-crack propagation of rock, the measurement error of Digital Image Correlation (DIC) local deformation is theoretically analyzed. An improved virtual extensometer method for measuring the COD is proposed, which considers the temporal and spatial characteristics of crack development in the process of complex crack propagation. The accuracy of the proposed method is verified by the strain localization band numerical simulation test and indoor single crack simulation test. Furthermore, the method is applied to the two-dimensional similarity simulation test of simulating complex multi-fractures in rock stratum. The COD obtained by the traditional and improved methods is compared with the measured COD. The results show that in the case of multiple complex cracks, to obtain the COD accurately, the relative distance between the virtual extensometer measuring point and the crack should be greater than half of the sum of the width of the crack strain localization zone and the subset size. With the development of the crack, the relative distance between the virtual extensometer measuring point and the crack should increase with the increase of the width of the crack strain localization zone. The error of the COD measured by the traditional method increases with fracture development, and the maximum is 21.20%. The maximum relative error between the COD measured by the improved method and the measured crack opening is 3.61%. The research results improve the accuracy of the virtual extensometer in measuring the COD under complex multi-crack conditions.

“…The parameter d i is determined by searching for enough nodes for the matrix A in Eq. (12) to be regular. In order to prevent the singularity of the matrix A, the number of nodes in the influence domain should be kept larger than the order of polynomial basis used for approximations, i.e., n > m. In this study, because of the high density of SIFT points extracted from the images, the minimum number of nodes is set to be much larger than the minimum requirements (with neighborhoods not less than 100 nodes).…”

Section: Variable Domain Of Influencementioning

confidence: 99%

“…DIC has been improved since its invention in the early 1980s; many applications of this technique can be found in the literature for the determination of strain fields under different loading conditions [6][7][8][9], including those around notches [10][11][12]. However, reliable measurement values in the presence of high strain gradients near the edge of the notches may present some challenges to DIC techniques.…”

Section: Introductionmentioning

confidence: 99%

Strain field measurements around notches using SIFT features and meshless methods

Gonzáles

Meggiolaro

2015

Appl. Opt.

This work proposes a hybrid experimental-numerical technique with the aim to improve strain measurements at stress concentration regions. The novel technique is performed employing the computer vision scale invariant feature transform (SIFT) algorithm and meshless methods, here termed SIFT-meshless. The SIFT is applied to perform feature points matching in two images of the specimen surface at different stages of mechanical deformation. The output data are provided as a set of displacement measurements by tracking matched feature points. This information is then used to model displacement and strain field on the surface by means of a meshless formulation based on the moving least squares approximation. By applying the proposed SIFT-meshless method, the strain distribution around a semicircular notch in a plate under bending load was investigated. The experimental results were compared with those obtained by a digital image correlation technique based on a subset approach and to simulations from finite element analysis software. The experimental results demonstrated that the present method is capable of performing reliable strain measurements at distances close to the notch where the peak strain value is expected, even in the presence of high strain gradients.