Method for detecting mechanoresponse of mechanical component by organic mechanoresponsive luminogen

Abstract

The present invention discloses a method for detecting the mechanical response of a mechanical component by an organic mechanoresponsive fluorescent material, comprising the following steps of: selecting an organic mechanoresponsive fluorescent material; preparing an organic mechanoresponsive fluorescent material solution; forming a film on a metal surface; calibrating fluorescence intensity and obtaining the fluorescence intensity and distribution in a crack tip area; observing the fluorescence signal generated at cracks to monitor the occurrence of fatigue cracks, and predict a propagation pathway of fatigue cracks by using the fluorescence intensity distribution in the crack tip area.

Claims

1. A method for detecting the mechanical response of a mechanical component by an organic mechanoresponsive fluorescent material, comprising the following steps of: (1) selecting an organic mechanoresponsive fluorescent material; (2) preparing an organic mechanoresponsive fluorescent material solution; (3) forming a film on a metal surface, that is uniformly coating the organic mechanoresponsive fluorescent material solution on a metal surface by a brush, and heating it by a heating tool to form a film; (4) calibrating fluorescence intensity: performing uniaxial tensile test on metal samples coated with the organic mechanoresponsive fluorescent material, irradiating coatings on the samples by using an UV light as an excitation light source, establishing a relationship between the fluorescence intensity and the stress/strain by a fluorescence intensity measurement system to serve as fluorescence intensity sample data; analyzing a gray scale of pixels, representing the fluorescence intensity by using the gray scale of the pixels; or, measuring the fluorescence intensity by a fluorescence spectrometer; (5) detecting a stress/strain distribution on an actual mechanical component, or monitoring fatigue crack propagation on the actual mechanical component, wherein a method for detecting the stress/strain distribution on the actual mechanical component in step (5) comprises: irradiating the organic mechanoresponsive fluorescent material film coated on the surface of the mechanical component to be detected by an UV light, and obtaining the stress/strain distribution on a part to be detected by using the fluorescence intensity obtained by the fluorescence intensity measurement system and comparing an actually measured fluorescence result with sample data of a fluorescence spectrum, and wherein a method for monitoring fatigue crack propagation on the actual mechanical component in step (5) comprises: irradiating the organic mechanoresponsive fluorescent material film coated on the surface of the mechanical component to be detected by an UV light, observing fluorescence signal generated at cracks to monitor the occurrence of fatigue cracks, and detecting the fluorescence intensity and distribution in a crack tip area; since high fluorescence intensity indicates high stress concentration, the fatigue crack is easy to propagate along the direction having high stress concentration, thus a propagation pathway of fatigue cracks is predicted.

2. The method according to claim 1, wherein the organic mechanoresponsive fluorescent material is tetranitro-tetraphenyl ethylene (TPE-4N).

3. The method according to claim 2, wherein the concentration of the prepared TPE-4N solution is in the range of 1.00 to 0.01 g/mL.

4. The method according to claim 1, wherein the heating tool is a heat gun, a heating furnace or a heating jacket, and the heating temperature is in the range of 80° C. to 300° C.

5. The method according to claim 1, wherein the organic mechanoresponsive fluorescent material solution can be prepared in advance and stored away from light, is capable of coating on-site, and heated to form a film by a heat gun or a heating jacket.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a flow diagram of a detection method;

(2) FIG. 2A shows a picture of the fluorescent surface of a 316L stainless steel;

(3) FIG. 2B shows a diagram of a fluorescence gray scale;

(4) FIG. 2C shows a tendency of the fluorescence intensity of 316L stainless steel with the change of stress/strain;

(5) FIG. 3A shows the comparison of the stress distribution of a unilaterally-notched sample with the result of finite element simulation;

(6) FIG. 3B shows the comparison of the stress distribution of a round hole sample with the result of finite element simulation;

(7) FIG. 3C shows the comparison of the local stress distribution of a round hole sample with the result of finite element simulation;

(8) FIG. 4A shows the result of initial samples of 316L fatigue crack propagation test;

(9) FIG. 4B shows the result of prefabricated cracks of 316L fatigue crack propagation test (F=300 N, 45000 circles));

(10) FIG. 4C shows the result of 316L fatigue crack propagation test (F=700 N, 1000 circles);

(11) FIG. 4D shows the result of 316L fatigue crack propagation test (F=700 N, 3000 circles);

(12) FIG. 4E shows the result of 316L fatigue crack propagation test (F=700 N, 5000 circles);

(13) FIG. 4F shows the result of 316L fatigue crack propagation test (F=700 N, 8000 circles);

(14) FIG. 5A shows the result of initial samples of 2024 aluminum alloy fatigue crack propagation test;

(15) FIG. 5B shows the result of 2024 aluminum alloy fatigue crack propagation test (F=700 N, 4500 circles);

(16) FIG. 5C shows the result of 2024 aluminum alloy fatigue crack propagation test (F=700 N, 5500 circles);

(17) FIG. 5D shows the result of 2024 aluminum alloy fatigue crack propagation test (F=700 N, 8500 circles);

(18) FIG. 5E shows the result of 2024 aluminum alloy fatigue crack propagation test (F=700 N, 11200 circles); and

(19) FIG. 5F shows the result of 2024 aluminum alloy fatigue crack propagation test (F=700 N, 13000 circles).

DETAILED DESCRIPTION OF THE EMBODIMENT

(20) The flow diagram of the specific detection method is shown in FIG. 1, and the methods comprise:

(21) (1) An organic mechanoresponsive luminescent material tetranitro-tetraphenyl ethylene (TPE-4N) is selected as a material, and synthesized by a chemical method. The synthesis method referred to the Chinese Invention Patent “PREPARATION OF MULTI-NITRO SUBSTITUTED TETRAPHENYLETHYLENE COMPOUNDS AND APPLICATION THEREOF” (Application No. CN 201310057959 and Publication No. CN104003886 A).

(22) (2) A TPE-4N solution is prepared, then coated onto a surface of a metal component and heated to form a film. In accordance with the present invention, the following solutions are selectively prepared.

(23) Embodiment 1: TPE-4N is dissolved in chloroform to obtain a TPE-4N solution having a concentration of 0.01 g/mL, and the solution is coated onto the metal surface by a brush and then heated at 80° C. for 20 min by a heat gun to form a film.

(24) Embodiment 2: TPE-4N is dissolved in chloroform to obtain a TPE-4N solution having a concentration of 0.3 g/mL, and the solution is coated onto the metal surface by a brush and then heated at 150° C. for 1 min by a heat gun to form a film.

(25) Embodiment 3: TPE-4N is dissolved in chloroform to obtain a TPE-4N solution having a concentration of 1 g/mL, and the solution is coated onto the metal surface by a brush and then heated at 300° C. for 30s by a heat gun to form a film. The heating tool could be a heat gun, a heating furnace, a heating jacket or the like, with the same effects.

(26) The effects of the TPE-4N film formed by coating any one of the solutions prepared in Embodiments 1, 2 and 3 on the metal surface are the same, and the TPE-4N solution is stored away from light at a low temperature.

(27) (4) Calibration of fluorescence intensity: as shown in FIG. 2, an uniaxial tensile test is performed on the 316L stainless steel metal samples coated with TEP-4N, coatings on the samples are irradiated by using an UV light as an excitation light source, fluorescence pictures (FIG. 2A) on the samples are acquired and recorded by a CCD photographic system in different stress/strain response stages, gray scales at sample gauge sections in the pictures are extracted, the average gray scale (FIG. 2B) of this area is analyzed, and the fluorescence intensity is represented by the gray scale. According to the test results, a curve of the fluorescence intensity and the size of stress/strain is established as the fluorescence intensity sample data (FIG. 2C).

(28) Detection of the stress/strain distribution on an actual mechanical component: the stress/strain distribution is analyzed by taking a single edge notched tensile sample (FIG. 3A) and a round hole sample (FIGS. 3B and 3C) as examples. After the samples are subjected to tensile deformation, the pixel gray scale distribution on the surfaces of the samples is recorded by the CCD photographic system. The recorded gray scale is compared with the sample data in the curve of FIG. 2C to determine the size of stress corresponding to each pixel point. The results indicate that the maximum stress suffered by the deformed sample is about 430 MPa, and the minimum stress is about 10 MPa. The stress distribution is shown in FIG. 3. The result of fluorescence test provided by the present invention is basically consistent with the result of ANSYS finite element simulation, so that the effectiveness of this method is verified.

(29) More importantly, the stress/strain detection method of the present invention can observe details that cannot be achieved by the theoretical simulation. For the ANSYS finite element simulation, calculation can only perform on an ideal model, and the defects of mechanical components during the actual machining process cannot be predicted. However, the unpredictable defects will cause local stress concentration in the actual samples, thus resulting in failure and damage. The present invention provides an experimental method, so the actual stress distribution of the samples can be reflected accurately in real time. As shown in FIG. 3C, when there is an unexpected small defect on an edge of the round hole in the sample during the machining process, this defect caused by machining cannot be predicted by the ANSYS finite element simulation, but the stress concentration near the defect can be clearly visualized by the method of the present invention. Therefore, the accuracy of measurement of the stress/strain distribution in the actual mechanical component in the present invention is reflected.

(30) Monitoring of fatigue crack propagation on the actual mechanical component, the details are as follows: the TPE-4N film on the mechanical component to be monitored is irradiated by an UV light, and strong fluorescent signal at cracks are observed to monitor the occurrence of fatigue cracks. Meanwhile, the fluorescence intensity and distribution in a crack tip area can be detected. The fatigue cracks are easy to propagate along the direction having high stress concentration, thus a propagation pathway of fatigue cracks is predicted.

(31) Taking a single edge notched tensile sample of 316L stainless steel as an example, as shown in FIG. 4A, when no force is applied to the sample, there are no fatigue cracks and fluorescence signal. Firstly, cracks are prefabricated by a small repeative cyclic force (F=300 N) in 45000 cycles. At this time, since the loading force is small, the plastic area at the tip of the crack is small, and the fluorescence signal is not obvious (FIG. 4B). Then, a larger tensile force (F=700 N) is applied in 1000 cycles (FIG. 4C), there are fluorescence signals on edges of the prefabricated cracks. When the force is continuously applied to 3000 cycles, there are fluorescence signals at the tip and on two sides of the crack (FIG. D) along with the downward movement of the tip of the crack. As shown in FIG. 4E, when the force is applied to 5000 cycles, the fluorescence signals are more concentrated on the right side of the crack, indicating that the stress concentration point is on the right side of the crack, as indicated by the white arrow. Therefore, in the subsequent cycles, the crack begins to propagate to the right side, as shown in FIG. 4F.

(32) This method has been verified on other metal components (e.g., aluminum alloy A2024 (as shown in FIG. 5)). As shown in FIG. 5A, when no force is applied to the sample, there is no fluorescence response. When the force (F=700 N) is cyclically applied to 4500 cycles, there are fluorescence signals on the edge of the notch, indicating that stress concentration occurs at this position and fatigue crack generation is induced (FIG. 5B). When the force is cycled to 5500 cycles, the fatigue crack propagates, and there are fluorescence signals at the tip and on two sides of the crack (FIG. 5C). As shown in FIGS. 5E and 5F, fluorescence occurs in the front of the tip of the crack. It indicates that the stress concentration in this area is clearly visualized, which further predict the pathway of fatigue crack propagation in advance. This embodiment indicates a great potential of TPE-4N for mechanical analysis on various metals and different application scenarios.

(33) The present invention provides a method for detecting the mechanical response of a mechanical component by an organic fluorescent material, including: selecting an organic mechanoresponsive fluorescent material, and preparing an organic mechanoresponsive fluorescent material solution; coating the organic mechanoresponsive fluorescent material solution on a surface of a metal sample, and heating to form a film; calibrating fluorescence intensity: irradiating the organic mechanoresponsive fluorescent material film on the surface of a scale distance section of the metal tensile sample by using ultraviolet light as an excitation light source, acquiring fluorescence intensity data on the organic mechanoresponsive fluorescent material film by a detection device, and establishing association data of the fluorescence intensity and the stress/strain intensity; detecting an actual mechanical component: irradiating the organic mechanoresponsive fluorescent material film on the surface of the metal tensile sample by using UV light as an excitation light source, and acquiring fluorescence intensity data on the organic mechanoresponsive fluorescent material film by a detection device; comparatively analyzing the acquired fluorescence intensity of the organic mechanoresponsive fluorescent material film on the surface of the mechanical component with the fluorescence intensity sample data, and determining the size and distribution of the stress/strain suffered by the component according to the fluorescence intensity; by observing fluorescence signal at a crack on the organic mechanoresponsive fluorescent material, monitoring whether a fatigue crack occurs at a part to be detected; and, predicting a crack propagation direction by using the fluorescence intensity distribution near the tip of the crack.

(34) The method for detecting the mechanical response of a mechanical component by an organic mechanoresponsive fluorescent material disclosed and provided by the present invention can be implemented by those skilled in the art by referring to the contents in this article and appropriately changing conditions, routes or other links. Although the method and preparation technology of the present invention have been described by preferred embodiments, it is obvious for those skilled in the related art that the methods and technological route described herein can be modified or recombined to realize the final preparation technology without departing from the content, spirit and scope of the present invention. Particularly, it is to be pointed out that all similar substitutions and modifications are apparent for those skilled in the art and shall fall into the spirit, scope and content of the present invention.