The invention relates to a concrete surface non-uniform strain measurement system and method. The system comprises a sample positioning system, a 3D digital image acquisition system and a digital image storage and calculating system. By collecting specklegrams of a concrete surface in real time before and after deformation through a binocular and high-resolution industrial camera, and then, matching the digital images collected by the industrial camera and matching the digital images obtained before and after deformation, a non-uniform strain distribution diagram of concrete surface deformation is obtained. The system can determine the position of the sample accurately, can adjust the measurement area according to research needs to obtain overall or local non-uniform strain of the sample and can realize batch measurement of the samples. The concrete surface non-uniform strain measurement system and method have the advantages of non-contact, high spatial resolution, high precision and full-field measurement and the like. The method can measure non-uniform strain on the surface of different sizes of concrete samples under different environment conditions.

Concrete surface non-uniform strain measurement system and method

The invention discloses a composite rock stratum rock briquette casting mold, a preparation method thereof and a composite rock stratum sample processing tool and method, and relates to the field of composite rock stratum rock sample casting and processing. Specific to the situation of difficulty in obtaining a natural layered composite rock stratum sample, a rock-like briquette casting mold and asample processing method are provided. The mold is easy to make, and is low in cost. The method is easy to operate, and intervals between casting layers can be adjusted conveniently. Meanwhile, briquette layers are bonded firmly, are clear in interface. The test sample processing tool can be adjusted freely at the angle of 0 to 45 degrees, can be used for drilling test samples of any rock stratumdip angle between 0 and 90 degrees according to the test demand, and meets different test demands.

Composite rock stratum rock briquette casting mold, preparation method thereof and composite rock stratum sample processing tool and method

The invention provides a non-contact displacement and strain measuring method based on image feature recognition and matching. Experimental equipment and process required by the method are relativelysimple, and in the experimental process, one camera only needs to be used to shoot digital images of a tested material before and after deformation. Natural textures on the surface of the tested material can serve as mark speckles, and if the surface of the tested material is very balanced, the mark speckles can be obtained through a manual speckle making technology. Relatively speaking, a displacement and strain measuring technology based on image processing is simple in calculation and high in feasibility. For the non-contact loss-free measuring method, the textures and characteristics of the material are not lost, obtained data is more accurate, automatic data processing is realized, the change values of a full-field displacement, the width of a material structural member and the like can be obtained, and the environmental requirements are relatively low.

Non-contact displacement and strain measuring method based on image feature recognition technology

The invention discloses a determination method and a test device for bending springback parameters of a high-strength aluminum alloy plate. The determination method comprises the steps of acquiring parameters of an elastic-plastic hardening material model of the high-strength aluminum alloy plate by adopting a unidirectional tensile test; carrying out a three-point bending test on a strip-shaped high-strength aluminum alloy plate sample to obtain a circumferential strain parameter of the sample; according to the parameters of the elastic-plastic hardening material model, specification parameters of the sample, test parameters of the three-point bending test and the circumferential strain parameter of the sample, and in combination with a bending moment balance equation of the sample, a geometric relation equation of the sample and a volume equation of the sample, carrying out solving to obtain a bending angle of the sample, the curvature radius and the wall thickness of a stress neutral layer; according to the bending angle of the sample and the curvature radius and the wall thickness of the stress neutral layer, obtaining a circumferential stress of an outermost layer; and according to the circumferential stress of the outermost layer and the circumferential strain parameter of the sample, determining an elastic modulus of the high-strength aluminum alloy plate. According to the determination method and the test device, the calculation accuracy of the bending springback parameters can be improved.

Determination method and test device for bending springback parameters of high-strength aluminum alloy plate

The invention discloses a strain measuring method based on an SEM in-situ imaging system The method comprises the following steps: generating a series of randomly distributed points by using computersoftware, and simulating a speckle pattern; machining a sample, sanding the cut sample, polishing and washing; performing speckle preparation: based on the generated simulation speckle pattern, preparing micro-nano speckles on the surface of the sample by using a photoetch technology; finding out a speckle area by using the SEM in-situ imaging system, and shooting an image of the undeformed sample; performing a tensile test on the sample in a testing machine; finding out the speckle area by using the SEM in-situ imaging system, and shooting an image of the deformed sample; and performing digital image correlation analysis on the images before and after the sample deformation in combination with the computer software, to obtain a strain field of a sample shooting area The method is high in precision, convenient to operate, and capable of realizing the non-contact measurement and the full-field measurement, wherein the dimension is calculated in nanometer level

Strain measuring method based on SEM in-situ imaging system

The invention discloses a concrete working stress measuring method. The concrete working stress measuring method comprises the following steps: first, manufacturing an artificial speckle field on the surface of a concrete structure, cutting a circular hole, obtaining concrete surface digital images before and after cutting the circular hole, and matching the concrete surface digital images with corresponding image sub areas to obtain in-plane displacements of the surface; then, conducting least square fit on the in-plane displacements of the surface to obtain a local area displacement distribution field function; finally, calculating a partial derivative of the displacement to obtain strain field distribution; calculating a mean strain within a certain diameter range of the center of the cut circular hole and calculating the working stress of the concrete. As the concrete working stress measuring method uses a non-contact full-field strain method digital image measuring technology during measuring concrete surface strain, the interference between concrete cutting and strain measurement is reduced to the full extent and the operation difficulty and measuring error are reduced. Through full-field strain measurement, the measuring error caused by concrete surface heterogeneity is reduced. Meanwhile, the cutting size and depth of the traditional stress release are reduced, the damage to the concrete is small and the operation is simple.

Deng Shiqin

Papers

Concrete working stress measuring method