CN107607372B - Brittle material fatigue crack prefabrication testing machine - Google Patents
Brittle material fatigue crack prefabrication testing machine Download PDFInfo
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- CN107607372B CN107607372B CN201710722274.5A CN201710722274A CN107607372B CN 107607372 B CN107607372 B CN 107607372B CN 201710722274 A CN201710722274 A CN 201710722274A CN 107607372 B CN107607372 B CN 107607372B
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Abstract
The invention provides a brittle material fatigue crack prefabrication testing machine which comprises a base, a motor, a transmission shaft, an impact ball, a pressure head, a supporting frame, a supporting plate, a laser counter, a pressure sensor, a laser signal controller, an alarm, a PLC (programmable logic controller) control system, a compression spring, a limiting barrel, a clamp and the like. The loading of different size loads is realized through the position of pressure sensor, adjustment impact ball connecting rod and spacing section of thick bamboo, and prefabricated crack length reaches the required size, and PLC control system can cut off the power of motor according to the signal information of laser probe feedback, and the alarm can send out the police dispatch newspaper simultaneously, and the fatigue crack of suggestion this test piece has prefabricated the completion. And unattended operation in the whole crack prefabricating process is realized. The fatigue crack of the prefabricated brittle material can save manpower and material resources to a great extent and improve the crack preparation precision.
Description
Technical Field
The invention relates to the field of testing of material fracture toughness, in particular to a brittle material fatigue crack prefabrication testing machine.
Technical Field
The fatigue theory research has great engineering practical value. Its first role is to solve the problem of life determination, i.e. to accurately estimate or predict the fatigue life of a component, to prevent catastrophic failure of the structure, and to avoid significant loss of life and property. The second function is to solve the problem of prolonging the service life, namely optimizing the material and the process, prolonging the fatigue life of the component and providing a basis for developing a new anti-fatigue material. As is well known, the fatigue performance of materials is measured by experiments, and a large amount of manpower, material resources and financial resources are consumed; in particular, fatigue testing of components and even full-scale structures under service load is more costly. Therefore, the third important function of the fatigue theory research is to estimate the fatigue performance of the material by using simple mechanical performance parameters, such as tensile performance, and simplify or replace the fatigue test; especially, the period of the fatigue test of the component or the full-size structure is shortened, so that the manpower, material resources and financial resources are saved. Excessive deformation, cracking, and interlaminar cracking of composite materials are the primary failure modes of mechanical parts and engineering components. Among them, cracking, which results in the fracture of the component, is the most hazardous failure mode. Due to the sudden nature of the fracture, not only can significant economic losses be incurred, but catastrophic accidents often result. Conventional classical strength theory holds that fracture occurs instantaneously, and fracture is controlled by nominal fracture stress and fracture strain calculated from the section dimensions. However, for practical components, the interior of the material is non-uniform and non-continuous, and micro-and macro-cracks or crack-like defects may be present, which have a significant effect on the service properties of the material and the component. As early as the 15 th century, people measured the strength of iron wires and found that when the diameter of the iron wire was the same, the tensile strength was inversely proportional to the length of the iron wire, and thus presumably the strength was controlled by the defects in the iron wire, the longer the iron wire, the larger the volume, the greater the possibility of having larger defects, and the lower the strength. Cracks or crack-like defects in materials and components may be initiated in service under the combined action of an applied load and an environmental medium, and may also be generated in the process of manufacturing materials, such as various metallurgical defects in castings, forgings and welded structures. It is not uncommon for a real defective component to break upon initial normal working loading, since the defects that result in a one-time fracture of the component are generally large and such large defects are easily discovered upon non-destructive inspection. Small defects or cracks, which are not detected by non-destructive inspection, existing in the actual component material, may propagate during long-term service due to fatigue, stress corrosion, creep, and the like, and eventually suddenly fracture at normal operating stresses, which are generally below yield stress. Since plastic deformation does not occur before fracture, no sign is visible, and fracture is abrupt. This very dangerous fracture is therefore referred to as low stress brittle fracture.
The fracture toughness is an important mechanical property index of the material, the test of the fracture toughness of the material usually needs to be tested to contain prefabricated cracks, the prefabrication of the prefabricated cracks of non-brittle materials such as metal and the like usually needs to be preformed through a fatigue tester, the fatigue tester usually needs to watch the prefabricated cracks in the prefabrication process, whether the prefabricated cracks meet the requirements or not is observed through visual inspection, and the precision control is low. For brittle materials, however, the pre-crack is typically pre-formed in two ways: one method is that a sample is caused to generate fatigue cracks by manual knocking through a sharp blade and a small hammer, but the manual knocking can not ensure that the same force is applied to each knocking, the direction of the prepared prefabricated crack has larger deviation, and the sample is extremely easy to damage and scrap in the knocking process; the other method is to perform crack prefabrication by using a fatigue testing machine through alternating load of a fatigue laboratory, but the vibration of a clamp of the fatigue testing machine is easier to cause the sample to be damaged and failed in the crack prefabrication process, in addition, in the crack prefabrication process, people need to keep watch all the time, the prefabricated crack is easy to be overlong due to negligence of an operator, and the test piece becomes an invalid test piece.
Disclosure of Invention
Based on the problems in the technical background, the invention provides a brittle material fatigue crack prefabrication testing machine.
The tester provided by the invention is mainly used for prefabricating the fatigue cracks of the brittle material, utilizes the motor, the laser counter, the pressure sensor and the laser signal controller, has simple integral structure and easy assembly realization, the PLC can realize small change of load and low vibration of the base in the crack prefabrication process, reduce the probability of failure of the brittle material in the fatigue crack prefabrication process, and after the corresponding load is set, without the need of operator's guard, when the crack is extended to the designated length, the laser signal controller can transmit signals to the PLC, the console can automatically turn off the motor, send out an alarm and prompt an operator that the preparation of the fatigue crack of the test piece is finished, the fatigue prefabricated crack preparation precision of the brittle material and the success rate of qualified samples are improved while the energy input of operators in the crack prefabrication process is reduced.
A brittle material fatigue crack prefabrication testing machine comprises a base, a supporting system, a power output system, a control system, a limiting protection system and a sample clamp system; all equipment is fixed on a base, a motor is fixed on a support frame connected with the base and is connected to a transmission shaft through threads, the transmission shaft is fixed on a bearing at the top end of the support frame, and a threaded connecting rod with an impact ball is welded in the middle of the transmission shaft; the control system comprises a motor switch, a pressure sensor, a laser counter, a PLC (programmable logic controller) and a PLC terminal, and equipment except the PLC terminal is fixed on the same support rod with the motor in an up-down horizontal mode in the same fixing mode as the motor; the impact ball is fixed on the rotating shaft through a threaded connecting rod and is vertical to the limiting cylinder; the laser counter control terminal is fixed on an aluminum alloy panel which is connected with the support frame and contains an insulating layer, the motor switch, the pressure sensor control terminal and the laser counter control terminal are connected to the PLC terminal through the PLC, and meanwhile, the PLC is connected with the laser signal probe and the alarm for monitoring crack propagation.
The base and the support system specifically include:
the transmission shaft is fixed on the upper part of the support frame through a bearing, a threaded connecting rod with variable length is welded in the middle of the transmission shaft, and a nitrile rubber impact ball is connected to the threaded connecting rod through threads; the motor fixing base is made of alloy steel plates and is connected through bolts; the two laser probes and the PLC are connected to the support frame through bolts, an insulating rubber pad is arranged between the support frames, and the two laser probes with different functions are respectively connected to the specified positions on the steel frame through bolts and can be adjusted in the vertical direction; the supporting plate is connected with the supporting frame through a flange, and the motor is connected with the supporting plate through a bolt.
The control system specifically comprises:
a manual switch of the motor controls a control terminal of the pressure sensor; when the crack length of the sample reaches the specified length, the crack length monitoring laser probe feeds back a signal to the PLC controller, the PLC controller cuts off the power supply of the motor, and simultaneously controls the pressure sensor to output load-time data in the single-period loading process, and the counter stops counting.
The limiting protection system specifically comprises:
the limiting cylinder can be adjusted horizontally and vertically, the impact ball impact plate, the pressure spring, the fixed support, the pressure sensor and the pressure head are all required to be arranged in the limiting cylinder, and the inner surface of the limiting cylinder is required to be coated with lubricating oil; the pressure sensor is bonded between the pressure head and the fixed support by strong glue; the pressure head is made of light alloy steel with high rigidity.
The sample holder system specifically comprises:
the sample span support rod is fixed on the sample base, and two ends of the sample span support rod are provided with movable limit bolts; the support frame welds at the testing machine base, and the sample base passes through the bolt fastening on the testing machine base.
The application of the fatigue loads with different sizes is realized by adjusting the length of the rod connected with the impact ball and the position of the limiting barrel.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, an operator does not need to watch for a long time in the brittle material fatigue crack prefabrication process, when the prefabricated crack reaches the specified length, the test machine can automatically stop and give an alarm, so that a great deal of energy of the operator can be saved, and the experiment operation cost can be saved.
2. The method can effectively improve the preparation precision of the prefabricated cracks of the brittle material and the success rate of the prefabricated cracks, improve the effectiveness of the fracture experiment result of the brittle material and effectively save the preparation cost of the sample.
3. The experiment mechanism is simple, the assembly cost is lower, and the experiment mechanism has wider application prospect.
Drawings
FIG. 1 is a schematic diagram of the structure of the practice of the present invention.
Detailed Description
The following detailed description is to be read with reference to the drawings and the accompanying detailed description.
On the striking ball struck the steel sheet that compression spring connects, steel sheet downstream made the spring take place to warp, and pressure sensor control terminal can demonstrate corresponding pressure value, and the pressure head can transmit this pressure to brittle material simultaneously, makes brittle material be in the state of three-point bending, realizes the fatigue loading of different loads through the length of the threaded connection pole 11 of adjusting striking ball 14 and the height of spacing section of thick bamboo.
The limiting cylinder is fixed on the support frame through a bolt, and the limiting cylinder can prevent overload in the loading process from causing damage to the sample in the crack prefabricating process.
The sample span support rod 23 is fixed on the sample base 24 to realize loading of brittle material samples with different spans, and the two ends of the sample base are provided with movable limit bolts to prevent the samples from moving in the loading process.
The support frame welds at the testing machine base, and the sample base passes through the bolt fastening on the testing machine base, and two laser probe, PLC controller all place insulating rubber pad on the support frame and between the support frame through bolted connection.
Example (b):
the overall structure schematic diagram of the brittle material crack prefabrication testing machine is shown in figure 1, and the whole machine comprises a base 26, a supporting system, a power output system, a control system, a limiting protection system and a sample clamp system. The support frame adopts high strength steel, and bearing 9 and transmission shaft 10 are fixed on the top of support frame 12, and after the bearing both ends keep the level, are connected the transmission shaft of left end bearing with motor 8, and the motor is fixed on the backup pad 7 that the support frame is connected. The supporting plate is connected with the supporting frame through a flange, and the motor is connected with the supporting plate through a bolt. The first laser probe 13 and the second laser probe 25 with two different functions are respectively connected to the designated positions on the support frame through bolts, and the vertical position can be adjusted.
The limiting cylinder 18 is connected to the supporting frame by a bolt which can be adjusted up and down. The position limiting cylinder 18 is connected with the bracket by a threaded connecting rod capable of adjusting the position left and right. The steel block 15, the compression spring 16, the pressure head-spring fixing support 19 are connected through welding, and the pressure sensor 17 is connected between the pressure head 20 and the spring fixing support by high-strength glue. After a certain amount of lubricating oil is coated on the periphery of the limiting cylinder, the steel block 15, the compression spring 16, the pressure sensor 17, the pressure head-spring fixing support 19 and the pressure head 20 are placed into the limiting cylinder, and the limiting cylinder is adjusted to a specified position and fixed.
The motor manual switch 1, the pressure sensor terminal 2 and the laser counter terminal 3 are connected to the fixing plate through bolts and then fixed to the support frame, the alarm 6 and the second laser probe 25 are respectively connected to the PLC 4, and the motor rotates normally, and the PLC works normally to perform a brittle material prefabricated crack preparation experiment.
Before the experiment began, place the steel block sample on anchor clamps, adjust earlier spacing section of thick bamboo and connect the height of impact ball threaded connection pole, manual rotatory threaded connection pole observes the size of pressure sensor terminal pressure value, selects the impact ball of different masses according to the size of the experimental required pressure value of actual material, adjusts the height of threaded connection pole and spacing section of thick bamboo, and the pressure value satisfies the experimental requirement and can carry out on next step.
The brittle material sample 22 is placed on a supporting clamp, the sample is limited through the sample limiting bolt 21, the sample is prevented from sliding left and right and back and forth in the crack prefabricating process, and the pressure head is adjusted to the middle position of the sample.
And adjusting the position of the second laser probe 25, enabling the laser to reach the maximum position of the prefabricated length of the crack, and when the crack expands to the required size, enabling the PLC to close the motor according to the change of the laser signal intensity.
The position of the first laser probe 13 is adjusted, and the threaded connecting rod containing the impact ball is manually rotated, so that the laser counter can be ensured to have the change of the number when the impact ball rotates to the specified position.
And (3) turning on a power supply main switch of the PLC terminal 5, turning on a pressure sensor 17 and a first laser probe 13 switch, and turning on a motor switch when the PLC terminal works normally, so that the fatigue prefabricated cracks of the brittle material are prepared by adjusting the rotating speed of a motor through the PLC terminal.
When the crack is expanded to a designated length, the intensity of the laser signal of the second laser probe 25 changes, the PLC automatically cuts off the power supply of the motor, and the alarm 6 gives an alarm to prompt an operator that the preparation of the prefabricated crack of the sample is finished.
The operator records the fatigue times of the laser counter terminal, and the change data of fatigue load along with time in one fatigue period is output through the pressure sensor. And replacing the sample, and performing the prefabricating process of the fatigue crack of the next sample.
Claims (1)
1. The utility model provides a brittle material fatigue crack prefabrication testing machine which characterized in that: the testing machine comprises a base (26), a supporting system, a power output system, a control system, a limiting protection system and a sample clamp system; all equipment is fixed on a base, a motor is fixed on a support frame connected with the base and is connected to a transmission shaft through threads, the transmission shaft is fixed on a bearing at the top end of the support frame, and a threaded connecting rod with an impact ball is welded in the middle of the transmission shaft; the control system comprises a motor switch, a pressure sensor, a laser counter, a PLC (programmable logic controller) and a PLC terminal, and equipment except the PLC terminal is fixed on a support rod of the same support frame in a vertical horizontal mode with the motor in the same fixing mode with the motor; the impact ball is fixed on the rotating shaft through a threaded connecting rod and is vertical to the limiting cylinder; the laser counter control terminal is fixed on an aluminum alloy panel which is connected with the support frame and contains an insulating layer, the motor switch, the pressure sensor control terminal and the laser counter control terminal are connected to the PLC terminal through a PLC controller, and meanwhile, the PLC controller is connected with a laser signal probe and an alarm for monitoring crack propagation;
the base and the support system specifically include:
the transmission shaft is fixed on the upper part of the support frame through a bearing, a threaded connecting rod with variable length is welded in the middle of the transmission shaft, and a nitrile rubber impact ball is connected to the threaded connecting rod through threads; the motor fixing base is made of alloy steel plates and is connected through bolts; the two laser probes and the PLC are connected to the support frame through bolts, an insulating rubber pad is arranged between the support frames, and the two laser probes with different functions are respectively connected to the support frame through bolts and can be adjusted in the vertical position; the supporting plate is connected with the supporting frame through a flange, and the motor is connected with the supporting plate through a bolt;
the control system specifically comprises:
the manual switch of the motor controls the control terminal of the pressure sensor; when the crack length of the sample reaches a specified length, the crack length monitoring laser probe feeds back a signal to the PLC controller, the PLC controller cuts off a power supply of the motor, and simultaneously controls the pressure sensor to output load-time data in the single-period loading process, and the counter stops counting;
the limiting protection system specifically comprises:
the limiting cylinder can be adjusted horizontally and vertically, the impact ball impact plate, the pressure spring, the fixed support, the pressure sensor and the pressure head are all required to be arranged in the limiting cylinder, and the inner surface of the limiting cylinder is required to be coated with lubricating oil; the pressure sensor is bonded between the pressure head and the fixed support by strong glue; the pressure head is made of light alloy steel;
the sample holder system specifically comprises:
the sample span support rod is fixed on the sample base (24), and two ends of the sample span support rod are provided with movable limit bolts; the support frame is welded on the testing machine base, and the sample base is fixed on the testing machine base through bolts;
the application of different size fatigue loads is realized through the length of the length that the adjustment striking ball is connected and the position of spacing section of thick bamboo.
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| WO2019208651A1 (en) * | 2018-04-25 | 2019-10-31 | 日立金属株式会社 | Amorphous metal ribbon, method for processing same, and method for producing laminate |
| CN112604994A (en) * | 2020-12-23 | 2021-04-06 | 宋莹莹 | Sorting device for waterproof roll sticks and working method of sorting device |
| CN116152216B (en) * | 2023-03-03 | 2023-08-25 | 北京理工大学 | Preparation method and equipment for fatigue sample of protective material based on neural network |
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