CN107014688B - A Method for In Situ Observation of Fracture Behavior of Materials - Google Patents

Abstract

The present invention relates to a kind of methods of home position observation material fracture behaviour, it is by pedestal that this method, which is related to device, mechanical drum, lower wedge block, upper wedge block, push cylinder, tested sample, upper pressure cylinder, upper pressure cylindrical holder, locking knob and fastening screw composition, it is converted by regulating device horizontal direction machinery drum and by wedge block, so that tested sample obtains plus load in the vertical direction and deformation occurs, and then micro-crack is generated in sample interior, observing tested specimen material in conjunction with scanning electron microscope, underbead crack generates under that loading condition, the information such as extension, and the deformation quantity of tested sample can convert to obtain by the step-wise displacement of mechanical drum.The device can be used cooperatively with the scanning electron microscope of different model.The method through the invention, can directviewing description be tested specimen material microstructure in loading process situation of change, to disclose material deformation mechanism, fracture behaviour and failure mode on micro-nano-scale, foundation is provided for the design, application and life prediction of material.

Description

A Method for In Situ Observation of Fracture Behavior of Materials

technical field

The invention relates to a method for observing material fracture behavior in situ.

Background technique

The mechanical properties of materials are very important for the design of materials, evaluation of service safety and life prediction. Generally, parameters such as modulus, strength, hardness, and toughness of materials can be obtained by different testing methods, so as to evaluate the mechanical properties of materials. However, the above-mentioned evaluation test methods and parameters all reflect the mechanical properties of materials on a macro scale. Since the properties of materials are closely related to their microstructure, clarifying the corresponding relationship between the mechanical behavior of materials and the corresponding microstructure morphology can reveal the deformation and damage rules of materials under external loads and some new Phenomena and mechanisms, such as the reinforcement and toughening of the matrix by nanoparticles in the nanocomposite system. In-situ micro-nano mechanical testing is an important means to achieve this goal: by combining scanning electron microscopy (SEM) and micro-mechanical testing instruments, the mechanical properties of materials and the corresponding changes in microstructure on the micro-nano scale can be realized. It will help researchers to truly understand the mechanism behind the mechanical behavior of materials at a deep level, and provide a powerful reference for the design and application of materials.

At present, the methods and technologies to characterize the mechanical properties of materials and the corresponding morphology characteristics on the microscopic scale mainly include nano-indentation, atomic force microscopy, scanning electron microscopy/transmission electron microscopy, etc. Among them, the nanoindentation instrument and the atomic force microscope mostly focus on the surface properties of the material, while the in-situ mechanical testing instrument used in the electron microscope is closer to the macroscopic mechanical tensile test behavior. However, the above methods only study the surface properties and morphology of the material, and it is difficult to obtain the microstructure and information in the bulk phase of the material, especially the information on the generation and propagation of internal cracks before the material is destroyed. In addition, the in-situ mechanical testing instruments used in electron microscopes are generally expensive, difficult to operate in the narrow electron microscope sample cavity, and can only be used in certain electron microscopes. For example, the Chinese invention patent CN203405477U discloses an in-situ mechanical tester that can realize multiple load modes including tension, shear, and torsion, but its size is 250mm*150mm*80mm, which exceeds the existing market The range of operating space available for the internal cavity of the sold SEM. The micro-mechanical behavior of materials under load can be studied through in-situ mechanical tension or compression experiments, such as the in-situ micro-mechanical testing devices under the scanning electron microscope described in Chinese invention patents CN102359912A and CN105388327A, which are used to study materials under load The microscopic deformation and damage process of the surface cannot observe and detect the internal behavior of the material. The mechanical behavior inside the bulk phase can provide more abundant information, which is extremely critical for a comprehensive and true evaluation of the mechanical characteristics of the material during the loading process.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a method for observing the fracture behavior of materials in situ. The method involves a device consisting of a base, a mechanical drum, a lower wedge-shaped slider, an upper wedge-shaped slider, a lower pressure cylinder, a tested Composed of the sample, the upper pressing cylinder, the upper pressing cylinder support, the locking knob and the fastening screw, the mechanical drum in the horizontal direction of the adjustment device is converted by a wedge-shaped slider, so that the tested sample obtains an applied load in the vertical direction and undergoes deformation , and then produce microcracks inside the sample, combined with scanning electron microscopy (SEM) to observe the internal crack generation and expansion of the tested sample material under load conditions, and the deformation of the tested sample can be transformed by the step displacement of the mechanical drum get. In order to ensure that the device does not deform during the sample loading process, the materials used in the device are all high-strength metals or alloys; through the locking function in the device, the stability of the deformation of the tested sample under certain load conditions is ensured. The device is exquisite in design, simple in structure and small in size, and can be used in conjunction with different types of scanning electron microscopes (SEM). The method of the present invention can intuitively describe the change of the microstructure of the tested sample material during the stress process, thereby revealing the deformation mechanism, fracture behavior and failure mode of the material at the micro-nano scale, which provides a basis for the design, application and life prediction of the material. Provide evidence.

A method for observing the fracture behavior of materials in situ according to the present invention, the method involves a device consisting of a base, a mechanical drum, a lower wedge-shaped slider, an upper wedge-shaped slider, a lower-pressing cylinder, a sample to be tested, an upper-pressing cylinder, It consists of a cylinder support for pressing up, a locking knob and a fastening screw. A mechanical drum (2) with a scale is fixed on one side of the base (1), and a locking knob (9) is fixed on the other side of the base (1). The lower wedge-shaped slider (3) is connected with the mechanical drum (2), and the upper wedge-shaped slider (4) is placed on the lower wedge-shaped slider (3), and the lower wedge-shaped slider (3) is in contact with the upper wedge-shaped slider (4) surface sliding, a groove is provided at the center of the upper wedge-shaped slider (4), the pressing cylinder (5) is placed in the groove of the upper wedge-shaped slider (4), and the tested cylinder is placed on the pressing cylinder (5). Sample (6), the two ends of the tested sample (6) are in contact with the upper pressure cylinder (7), the center of the tested sample (6) has a V-shaped opening, and the upper pressure cylinder (7) is fixed on the upper pressure cylinder bracket (8), press the cylindrical support (8) and the base (1) to be fixed, respectively fix the fastening screws (10) symmetrically on the base (1), the specific operation is carried out according to the following steps:

a. Place the tested sample (6) on the pressing cylinder (5), turn the fine-tuning mechanical drum (2) to keep the tested sample (6) stable, and record the scale indication of the mechanical drum (2) at this time , recorded as zero point;

b. Fix the device with the tested sample (6) on the scanning electron microscope sample stage through the fastening screw (10), and observe the shape of the V-shaped notch in the center of the tested sample (6) through the scanning electron microscope. That is, the morphology at the zero point position;

c. After the observation is completed, take the device out of the scanning electron microscope, and then adjust the mechanical drum (2) so that the upper wedge-shaped slider (4) moves upward, and apply displacement to the tested sample (6) by pressing down the cylinder (5) , and then lock the locking knob (9) to ensure stable deformation, record the scale indication of the mechanical drum (2) at this time, which is the strain s1;

d. Place the device with the tested sample (6) in the scanning electron microscope, and observe the shape of the V-shaped notch in the center of the tested sample (6), which is the shape of the notch when the strain is s1;

e. Take the device out, loosen the locking knob (9), and then adjust the mechanical drum (2) to make the upper wedge-shaped slider (4) move upwards, press the cylinder (5) to the tested sample (6) Apply displacement, then lock the locking knob (9) to ensure stable deformation, record the scale indication of the mechanical drum (2) at this time, which is the strain s2;

f. Place the device with the tested sample (6) in the scanning electron microscope, and observe the shape of the V-shaped notch in the center of the tested sample (6), which is the shape of the notch when the strain is s2;

g. According to the strain interval required by the experiment, repeat step e and step f in sequence until the material breaks, and obtain a series of V-shaped notches in the center of the tested sample (6) corresponding to different strains, so as to understand the fracture of the sample process.

A method for observing the fracture behavior of materials in situ according to the present invention, the device involved in the method is exquisite in design, simple in structure, and the size is as small as 100mm*90mm*35mm, and the size of test sample 6 is 70mm*14mm*10mm. Each surface needs to be polished and polished to eliminate the influence of scratches on the experimental results, and a 1-3mm deep V-shaped notch is prefabricated in the height direction as the observation area. The device has the advantages of small size, strong compatibility with SEM, real-time observation of material fracture process, etc., and can be used to study the deformation and destruction of materials under external loads. At the same time, using the method provided by the present invention can pre-set the magnitude of the strain suffered by the material, thereby establishing the corresponding relationship between the mechanical behavior of the material and the microscopic appearance, in order to reveal the mechanical behavior of the material at the micro-nano scale, such as inside the material The formation mechanism of cracks and the strengthening effect of micro-nano particles provide a test path, and provide a micro-mechanism explanation at the micro-nano scale for the macroscopic mechanical properties and behavior of materials.

Description of drawings

Fig. 1 is the structural representation of the device related to the present invention;

Fig. 2 is the top view of the structure of the device involved in the present invention;

Fig. 3 is the bridging phenomenon figure of whisker when no load is applied in the present invention;

Fig. 4 is a fracture diagram of bridging whiskers when a displacement of 0.9 mm is applied in the present invention.

Detailed ways

Example

A method for observing the fracture behavior of materials in situ according to the present invention, the method involves a device consisting of a base, a mechanical drum, a lower wedge-shaped slider, an upper wedge-shaped slider, a lower-pressing cylinder, a sample to be tested, an upper-pressing cylinder, Composed of an upper pressing cylindrical bracket, a locking knob and a fastening screw, a mechanical drum 2 with a scale is fixed on one side of the base 1, a locking knob 9 is fixed on the other side of the base 1, and the lower wedge-shaped slider 3 is connected to the mechanical drum. The wheel 2 is connected, the upper wedge slider 4 is placed on the lower wedge slider 3, the lower wedge slider 3 and the upper wedge slider 4 slide along the contact surface, and a groove is provided at the center of the upper wedge slider 4, and the lower wedge slider 4 is pressed down. The cylinder 5 is placed in the groove of the upper wedge-shaped slider 4, and the tested sample 6 is placed on the lower pressure cylinder 5. The two ends of the tested sample 6 are in contact with the upper pressure cylinder 7, and the center of the tested sample 6 has a V-shaped The upper pressure cylinder 7 is fixed on the upper pressure cylinder support 8, the upper pressure cylinder support 8 is fixed to the base 1, and the fastening screws 10 are symmetrically fixed on the base 1 respectively. The specific operation is carried out according to the following steps:

a. The tested sample 6 is a whisker-reinforced epoxy resin material, the size is 70mm*14mm*10mm, the vertical depth of the V-shaped notch is 2mm, and the whisker-reinforced epoxy resin material of the tested sample 6 is placed on the pressing cylinder 5 , rotate the fine-tuning mechanical drum 2 so that the whisker-reinforced epoxy resin material of the tested sample 6 remains stable, record the scale indication of the mechanical drum 2 at this time, and record it as zero;

b. The device with the tested sample 6 whiskers reinforced epoxy resin material is fixed on the scanning electron microscope sample stage by the fastening screw 10, and the central part of the tested sample 6 whiskers reinforced epoxy resin material is passed through the scanning electron microscope The shape of the V-shaped notch is observed. When no force is applied, the position of the mechanical drum 2 is set to zero. At this time, the internal morphology of the material is shown in Figure 3. It can be observed that the whiskers can play a bridging role at the V-shaped notch, that is The morphology at the zero position;

c. After the observation is completed, take the device out of the scanning electron microscope, and then adjust the mechanical drum 2 so that the upper wedge-shaped slider 4 moves upward, and moves upward by pressing down the cylinder 5, applying a mechanical displacement of 0.3mm to the tested sample 6, Apply deformation to the whisker-reinforced epoxy resin material of the tested sample 6 containing a V-shaped notch, lock the lower wedge-shaped slider 3 with the locking knob 9 to ensure stable deformation, and record the scale of the mechanical drum 2 at this time The indication is the strain s1;

d. Place the device with the tested sample 6 whisker-enhanced epoxy resin material in the scanning electron microscope, and observe the appearance of the V-shaped notch in the center of the tested sample 6 whisker-enhanced epoxy resin material, namely is the shape of the notch at the strain s1;

e. Take out the device, loosen the locking knob 9, and then adjust the mechanical drum 2 to move the upper wedge-shaped slider 4 upwards, apply a mechanical displacement of 0.3mm to the tested sample 6 by pressing down the cylinder 5, and then lock the Tighten the knob 9 to ensure stable deformation, and record the scale indication of the mechanical drum 2 at this time, which is the strain s2;

f. Place the device with the tested sample 6 whisker-reinforced epoxy resin material in the scanning electron microscope, and observe the shape of the V-shaped notch in the center of the tested sample 6 whisker-reinforced epoxy resin material, which is Morphology of the notch at strain s2;

g. According to the strain interval required by the experiment, step e and step f were repeated successively, and several observations were carried out, and it was found that when the mechanical displacement imposed by the mechanical drum 2 reached 1.5mm, the "bridge" produced by the whiskers had broken (see Fig. 4) Obtain a series of morphology of the V-shaped notch in the center of the whisker-reinforced epoxy resin material of the tested sample 6 corresponding to different strains, so as to understand the fracture process of the sample.

Claims (1)

1. a kind of method of home position observation material fracture behaviour, it is characterised in that it is by pedestal, machinery drum that this method, which is related to device, Wheel, lower wedge block, upper wedge block, push cylinder, tested sample, upper pressure cylinder, upper pressure cylindrical holder, locking knob and Fastening screw composition, the graduated mechanical drum (2) of fixing belt in pedestal (1) side, the other side of pedestal (1) is fixed with locking Knob (9), lower wedge block (3) are connected with mechanical drum (2), place on lower wedge block (3) upper wedge block (4), under Wedge block (3) and upper wedge block (4) are slided along contact surface, are equipped with groove in the centre of upper wedge block (4), will under Pressure cylinder (5) is placed in the groove of wedge block (4), and tested sample (6) are placed above pushing cylinder (5), are tested The both ends of test agent (6) are contacted with upper pressure cylinder (7), and the centre of tested sample (6) is provided with V-shaped part, upper pressure cylinder (7) It is fixed in pressure cylindrical holder (8), upper pressure cylindrical holder (8) and pedestal (1) are fixed, respectively symmetrically fix on pedestal (1) Fastening screw (10), concrete operations follow these steps to carry out:

A, tested sample (6) is placed on and is pushed on cylinder (5), rotation finely tunes mechanical drum (2) and makes tested sample (6) It keeps stablizing, writes down the scale registration of mechanical drum (2) at this time, be denoted as zero point；

B, the device for being placed with tested sample (6) is fixed on sample platform of scanning electronic microscope by fastening screw (10), is passed through Scanning electron microscope carries out pattern when morphology observation, as dead-center position to the centre v-notch of tested sample (6)；

C, after observation, device is taken out from scanning electron microscope, then adjusts mechanical drum (2) so that upper wedge block (4) to Upper movement applies displacement to tested sample (6) by pushing cylinder (5), then locks locking knob (9), it is ensured that deformation Stablize, write down the scale registration of mechanical drum (2) at this time, to strain s1；

D, the device for being placed with tested sample (6) is placed in scanning electron microscope again, to the centre V-type of tested sample (6) Notch carry out morphology observation, as when straining s1 notch pattern；

E, device is taken out, is unclamped locking knob (9), then by adjusting mechanical drum (2) so that upper wedge block (4) to Upper movement applies displacement to tested sample (6) by pushing cylinder (5), then locks locking knob (9), it is ensured that deformation Stablize, write down the scale registration of mechanical drum (2) at this time, to strain s2；

F, the device for being placed with tested sample (6) is placed in scanning electron microscope again, to the centre V-type of tested sample (6) Notch carry out morphology observation, as when straining s2 notch pattern；

G, changing distance is answered according to requirement of experiment, is repeated in step e and step f, until material fracture, obtained a series of not With the pattern for the centre v-notch for straining corresponding tested sample (6), to understand the process of sample fracture.