New Four Points Initialization for Digital Image Correlation in Metal-Sheet Strain Measurements

Abstract

Nowadays, the deformation measurement in metal sheets is important for industries such as the automotive and aerospace industries during its mechanical stamping processes. In this sense, Digital Image Correlation (DIC) has become the most relevant measurement technique in the field of experimental mechanics. This is mainly due to its versatility and low-cost compared with other techniques. However, traditionally, DIC global image registration implemented in software, such as MATLAB 2018, did not find the complete perspective transformation needed successfully and with high precision, because those algorithms use an image registration of the type “afine” or “similarity”, based on a 2D information. Therefore, in this paper, a DIC initialization method is presented to estimate the surface deformation of metal sheets used in the bodywork automotive industry. The method starts with the 3D points reconstruction from a stereoscopic digital camera system. Due to the problem complexity, it is first proposed that the user indicates four points, belonging to reference marks of a “Circle grid”. Following this, an automatic search is performed among the nearby marks, as far as one desires to reconstruct it. After this, the local DIC is used to verify that those are the correct marks. The results show reliability by reason of the high coincidence of marks in experimental cases. We also consider that the quality of mark stamping, lighting, and the initial conditions also contribute to trustworthy effects.

Deformation measurement system for UAV components to improve their safe operation

“…7. The forces are generated using rotary servos (3). Servos generating a load of 35 kg/cm were used for forces acting in the vertical direction, while 25 kg/cm was used for forces acting horizontally.…”

“…The intrinsic and extrinsic parameters matrix consists of the properties of the cameras used and the image acquired by them i.e. the focal length, pixel size, distortion coefficients, cameras convergence angle and position [3]. On the basis of 𝐾and 𝐾 ′ , the position of certain 2D points 𝑚 and 𝑚' combined in 3D, point 𝑀, is determined (Eq.…”

Accurate Measurement of Strain in Noncontact Surface Deformation Using Subset-Based Digital Image Correlation

“…Hence, a DIC introduction technique is introduced to assess the surface mishappening of metal sheets utilized in automobile manufacturing. Because of the difficult multifaceted nature, the technique begins with the 3D focuses on recreation [ 13 ] to show the four focuses. Consequently, a programmed search is carried out among the close marks to recreate it.…”

Special Issue on Advances in Digital Image Correlation (DIC)

“…The above-mentioned question of large deformations implies, in addition to experimental constraints, particular complexities from an algorithmic point of view. Initialization in the large deformations framework of the correlation algorithm is also a topical issue [16].…”