High precision measuring method for stretching displacement

Abstract

The invention discloses a kind of high accuracy method to measure pull and stretch displacement. It adopts two digital vidicons to shoot, establish two markings in the work segment of the test piece, and make these two digital vidicons' imaging targets form in one plane. The vidicons locate in front of the markings and their imaging targets' on-line runs parallel with two markings' on-line. The vidicons respectively collect the two light signals which are in response to the changed markings after movement. At last, by inputting these signals which are converted into numerical picture signals into a computer to process, output the measure result. Because the invention adopts two vidicons to observe two markings staying on the work segment respectively, it can remove the measure error margin produced by the test piece's displacement when the piece is in the pull and stretch process; The method also has the advantage of high accuracy, no contact and precise real time, so it can be applied vastly in future.

Description

technical field [0001] The invention relates to a method for measuring the length variation and strain of a test piece under heat or stress, in particular to a non-contact, high-sensitivity method for measuring tensile displacement using optical technology. Background technique [0002] The strength and deformation characteristics of materials under the action of external force are called the mechanical properties of materials. Tensile test is the main test to determine the mechanical properties of materials. When doing the tensile test, the material is made into a standard sample so that its geometric shape and stress conditions can meet the requirements of axial tension. When the specimen is stretched, the tensile displacement of the specimen is measured by the displacement sensor installed at the moving end of the testing machine. The strain is calculated by the ratio of the tensile displacement value measured by the displacement sensor to the o...

AI Technical Summary

Problems solved by technology

On the existing extensometer, the following problems exist in the measurement of tension and compression displacement by the displacement sensor: 1. The elongation measured by the displacement sensor is the displacement of the gripper at the end of the displacement sensor installed during tension and compression, rather than the elongation of the working section. The end is a non-uniform strain area, and the middle working area is a uniform strain area, so a large error will be introduced

2. The test piece may slip during the stretching process, and in this case, the existing displacement sensor also includes this displacement into the deformation and elongation of the test piece, which brings a large error to the calculation of the elongation

3. The displacement measurement accuracy of the existing displacement sensor is not high, and the accurate value of the strain during the stretching process of the material cannot be given

At present, there is no ideal method for measuring the tensile displacement of flexible materials

Images