CN-121475880-B - Multi-scale in-situ monitoring equipment applied to crack propagation of material and test method thereof

CN121475880BCN 121475880 BCN121475880 BCN 121475880BCN-121475880-B

Abstract

The invention relates to the technical field of mechanical test devices, and particularly discloses multi-scale in-situ monitoring equipment applied to crack propagation of materials and a test method thereof. The device comprises a DCPD test part, a DIC test part and an electric control cabinet, wherein the DCPD test part comprises a fixed frame, a room temperature clamping device, a force loading system and a data acquisition system, and the DIC test part comprises a DIC camera. Through the cooperative combination of DCPD and DIC, the real-time monitoring of the macrocrack expansion rate and the in-situ analysis of the microcosmic rack tip stress strain field distribution are realized, so that the trans-scale material damage evolution information is obtained. The device has the advantages of full digital control of a computer, high measurement precision, multi-dimensional synchronous acquisition of data and the like, and is particularly suitable for high-precision multi-scale material damage detection and failure mechanism research in an air environment.

Inventors

CHEN KAI
ZHAO YIHAN
ZHOU YUHAO
WANG JIAMEI
ZHANG LEFU

Assignees

上海交通大学

Dates

Publication Date: 20260508
Application Date: 20251204

Claims (6)

1. A multi-scale in situ monitoring device for crack propagation of a material, comprising: the DCPD test part comprises a fixed frame, a room temperature clamping device, a force loading system and a data acquisition system; A DIC testing section comprising a DIC camera; The electric control cabinet is electrically connected with the force loading system, the data acquisition system and the DIC camera respectively; the DIC camera is used for collecting the strain of the sample clamped by the room temperature clamping device through the observation window; the room temperature clamping device comprises a sample clamp, an insulating ceramic gasket and an insulating ceramic tube, wherein the sample clamp is arranged on the fixed frame, and the insulating ceramic gasket and the insulating ceramic tube are used for isolating current between a sample and the sample clamp; The force loading system comprises a stretcher and a stretcher controller, the stretcher is electrically connected with the stretcher controller, and the stretcher is in driving connection with the room temperature clamping device; The data acquisition system comprises a current wire, a main voltage drop wire, a reference voltage drop wire, a constant current source and a nano-volt meter, wherein a sample is connected with the constant current source through the current wire, the sample is respectively connected with different nano-volt meters through the main voltage drop wire and the reference voltage drop wire, and the main voltage drop wire is distributed on two sides of a crack of the sample; the fixing frame comprises an upper surface, a lower surface and four fixing support columns arranged between the upper surface and the lower surface, a fixing bolt extends out of the center of the lower surface, and the sample clamp is connected with the stretcher through the fixing bolt; The room temperature clamping device comprises a room temperature upper clamp and a room temperature lower clamp which are detachably installed, wherein the room temperature upper clamp and the room temperature lower clamp are respectively provided with a first fastening bolt nut and a second fastening bolt nut, and the room temperature upper clamp and the room temperature lower clamp adjust the verticality and the tightness of a sample through the first fastening bolt nut and the second fastening bolt nut; The current wire, the main voltage drop wire and the reference voltage drop wire in the data acquisition system all comprise a platinum wire and an insulating PTFE heat shrinkage tube sleeved outside the platinum wire; the constant current source is used for providing stable current output, the nano-voltmeter is used for measuring the current voltage drop in each wire, and the reference voltage drop wire is used for correcting the main voltage drop so as to improve the test accuracy.
2. The multi-scale in-situ monitoring device for crack propagation of materials according to claim 1, wherein the upper surface of the fixed frame is provided with a bolt and nut, the room temperature upper clamp is connected with the upper surface of the fixed frame through the bolt and nut, and the room temperature lower clamp is connected with the stretcher through the fixed bolt, so that the room temperature lower clamp can move up and down to apply load.
3. The multi-scale in-situ monitoring device for crack growth of materials of claim 1, wherein the force loading system is connected to a computer through the electronic control cabinet, and parameters of the force loading system are controlled through a control program of the computer, wherein the parameters comprise constant stress intensity factors, load ratios, frequency and waveform of waves.
4. A test method of a multi-scale in-situ monitoring device for crack propagation of a material, characterized in that the multi-scale in-situ monitoring device for crack propagation of a material according to any one of claims 1-3 is used, comprising the steps of: Step 1, placing a DIC camera at the side of the DCPD test part, and collecting the strain of a sample through an observation window; Step 2, preparing a sample, including grinding, polishing and spraying speckles on the side surface; Step 3, clamping the sample by using a clamp at room temperature and a clamp at room temperature, and isolating the current between the sample and the clamp at room temperature and between the sample and the clamp at room temperature by using an insulating ceramic tube; step 4, welding the current line, the main voltage drop line and the reference voltage drop line with the sample; Step 5, opening a force maintaining function of the electric control cabinet and screwing the clamp; Step 6, setting parameters in a control program, introducing current and checking voltage drop errors; and 7, adjusting the DIC camera, shooting a reference image, shooting a speckle image after applying a load, and calculating stress-strain field distribution.
5. The method of claim 4, wherein the step of preparing the sample comprises sanding the surface of the sample and mechanically polishing the sample to free of significant scratches, and then electropolishing or vibratory polishing the sample to remove the stress layer.
6. The method of claim 4, wherein the parameters set in the control program include a constant stress intensity factor, a load ratio, a frequency and a waveform of the wave, and the protection parameters are set to avoid damage to the device and the sample due to excessive load or excessive displacement.

Description

Multi-scale in-situ monitoring equipment applied to crack propagation of material and test method thereof Technical Field The invention relates to the technical field of mechanical test devices, in particular to multi-scale in-situ monitoring equipment applied to crack propagation of materials and a test method thereof. Background The method has important engineering and scientific significance for effectively detecting the crack damage of the material. Cracks are one of main forms of material and structural failure, and in the fields of aerospace, energy power and the like, structural parts often run for a long time under complex loads and severe environments, so that the development of a high-precision crack detection technology is a core link for realizing structural health diagnosis, preventing sudden damage and guaranteeing life and property safety. From the point of material research and development, the microscopic mechanism of crack propagation is well understood, and in-situ and accurate experimental data are not available. The microscopic information such as strain field distribution and plastic region evolution of crack tips is a key for revealing material fracture mechanism, evaluating material performance and guiding the design of novel anti-fatigue and high-toughness materials. Direct current voltage drop (DCPD) is an advanced detection technique that reflects crack growth behavior of materials by monitoring voltage changes. The technique is based on applying a constant direct current to the specimen, inverting the crack length in real time by accurately measuring the voltage drop change between preset locations and calculating the Crack Growth Rate (CGR). Compared with other damage detection methods, the DCPD technology has excellent accuracy and repeatability, and still has good stability under high temperature, corrosion and other complex environments, so the DCPD technology is widely considered as one of the mainstream technologies for quantitative characterization and life assessment of future material damage. Digital Image Correlation (DIC) is a non-contact optical measurement method based on high resolution image processing and digital algorithms. The method realizes the accurate quantification of the deformation field and the strain field on the surface of the material on a microscopic scale (from millimeter scale to nanometer scale) by tracking the change of the speckle field on the surface of the material before and after deformation. The technology is widely applied to microscopic mechanism research of material surface damage behaviors, can reveal local strain concentration and evolution rules in crack initiation, expansion and fracture processes, and provides a key experimental basis for understanding material failure mechanisms. The DCPD and DIC technologies are combined, so that real-time monitoring of crack growth rate on a macroscopic scale can be realized, strain distribution and evolution behavior of a crack tip region can be captured on a microscopic scale, and therefore a trans-scale material damage evolution correlation is established, and a powerful experimental means is provided for deep research on a damage mechanism of a material in a complex load environment. There are some limitations in the prior art. For example, chinese patent publication No. CN115046872a discloses a real-time measurement method for fatigue crack based on DCPD, but the obtained data is concentrated on the rate of macrocrack propagation, lacking capture of microscopic mechanical information such as microscopic plastic region of crack tip, strain field distribution, etc. The Chinese patent application with publication number of CN105842062A discloses a device and a method for monitoring crack growth in real time, but strain information of a micro-area where a local crack is located is only relied on to represent failure trend of a main crack, so that macroscopic crack growth rate cannot be estimated and predicted. Accordingly, it is desirable to provide a monitoring apparatus capable of acquiring macroscopic and microscopic crack growth information simultaneously, and a test method thereof. Disclosure of Invention The invention aims to provide multi-scale in-situ monitoring equipment applied to crack propagation of materials and a test method thereof, so as to solve the problems in the prior art. To achieve the above object, the present invention provides a multi-scale in-situ monitoring apparatus for crack propagation of a material, comprising: the DCPD test part comprises a fixed frame, a room temperature clamping device, a force loading system and a data acquisition system; A DIC testing section comprising a DIC camera; The electric control cabinet is electrically connected with the force loading system, the data acquisition system and the DIC camera respectively; the DIC camera is used for collecting the strain of the sample clamped by the room temperature clamping device through the observation