A method for testing the accuracy of an accelerated polishing machine

Abstract

A method for testing the accuracy of an accelerated polishing machine belongs to the field of testing the accuracy of an accelerated polishing machine. Sand blockage and sand breakage phenomena generally occur during the operation of the equipment. They are highly concealed and difficult to detect. Some sand blockage and sand breakage phenomena cannot even be identified by the naked eye. How to prevent the occurrence of such phenomena from the source is a problem that every engineering and technical personnel involved in this field must face. The present invention improves the existing method and refines the order, mode of action, and position of action of water and coarse and fine sand on the test piece to solve or partially solve the coarse and fine sand blockage and sand breakage phenomena currently existing in the test piece polishing process. In addition, the coarse and fine sand conveying devices are improved. The present invention solves the above problems.

Description

Technical Field

[0001] The invention belongs to the field of accuracy testing of accelerated polishing machines. Background Art

[0002] Accelerated Grinding Machine: This test equipment uses water and corundum to polish specimens made of aggregate particles indoors, simulating the polishing effect of automobile tires on road surfaces. Its operating principle follows the method specified in JTG E42-2005: the specimen is mounted on the road wheel of the grinder, which is then pressed forward against the rubber wheel. Water and coarse and fine corundum are added, and the specimen is rotated and polished at a specific load and time, simulating the polishing effect of coarse aggregate used in asphalt pavement during wheel operation.

[0003] The basic structure of the accelerated grinding machine is as follows: Figure 1 It is divided into nine parts: load adjustment assembly, adjusting arm (counterweight), road wheel, rubber wheel, fine sand storage hopper, coarse sand storage hopper, water supply device, machine body, and test piece.

[0004] Accelerated polishing machines are a key device used for indoor simulation of pavement aggregate polishing properties. They are widely used in domestic aggregate performance research, with several thousand units in service. They are crucial for research on aggregate anti-skid properties and have garnered significant attention from industry regulators and engineers. Highway anti-skid performance is directly related to vehicle safety. Aggregate is the primary component of pavement, and material selection and structural characteristics are among the most important factors influencing pavement anti-skid performance. Therefore, research on the anti-skid performance of aggregates used in highway construction has long been a focus of engineering and scientific research, culminating in the publication of numerous specifications, standards, and methods to guide construction and testing.

[0005] As the primary instrument for studying the anti-skid properties of aggregates, the accelerated grinding machine fully complies with the test parameters for the polishing value of coarse aggregates (JTG E42-2005, Test Method for Aggregates in Highway Engineering) and T0321-2005. These parameters integrate relevant parameters such as wheel, road, vehicle speed, vehicle load, and environment. Their output data represents the anti-skid properties of aggregates under specific conditions and serves as a guide for construction. Therefore, ensuring that key parameters of the accelerated grinding machine conform to the T0321-2005 Test Method for Polishing Value of Coarse Aggregates is crucial for metrological verification. In accordance with the requirements of JJG (Traffic) 054-2009, the metrological verification procedures for accelerated grinding machines require verification and standardization of the road wheel, rubber wheel, sand and water feeding devices, the positive pressure of the rubber wheel on the road wheel, and overall accuracy. This ensures the uniformity of the test apparatus and the credibility of the accelerated grinding machine's output values, providing technical support for the assessment of aggregate anti-skid properties.

[0006] The majority of highways in my country are asphalt pavements, with aggregates comprising approximately 95% of the pavement. Aggregate properties have a significant impact on the pavement's performance. Repeated wear and tear from vehicle tires gradually reduces the surface texture and roughness of the aggregate in the surface layer of an asphalt pavement, leading to a gradual smoothing of the aggregate, significantly reducing the pavement's skid resistance. Therefore, accurately evaluating the polishing and wear resistance of coarse aggregates and selecting aggregates with good wear resistance for the surface layer of asphalt pavement ensures excellent skid resistance.

[0007] Accelerated polishing machines are specialized equipment used to evaluate the polishing value of stone. The conformity of each component, along with the scientific nature and stability of its operation, are crucial to its suitability for stone evaluation. Under normal conditions, the conformity of each functional component in static conditions is readily assessed and easily assessed. However, stone polishing occurs under dynamic conditions. Therefore, the performance changes of each component under both dynamic and static conditions, as well as the ability of the components to meet process requirements, are even more crucial for the equipment.

[0008] The accuracy of the whole machine is the only indicator for the dynamic evaluation of the accelerated grinder and the key to evaluating the quality of the accelerated grinder. In a large number of engineering practices, we found that the following problems exist in the stone grinding process of the accelerated grinder:

[0009] 1. The results of evaluating the same batch of stones by different qualified accelerated grinding machines are not exactly the same, and even completely opposite results appear;

[0010] 2. For the accelerated polishing machine with obviously unqualified test results, after polishing the standard test piece (the test piece is made of epidote petrified andesite), the polishing value is within the standard range;

[0011] 3. Install 14 standard stones from the same batch on a qualified accelerated grinding machine. After polishing with the qualified accelerated grinding machine, the polishing values of most of the stones are not within the standard range (such as 46 to 52 PSV).

[0012] The aforementioned issues with accelerated polishing machines have long been a high priority for road management authorities. For years, researchers and engineers within the transportation industry have conducted multifaceted research to identify the root causes of these issues and develop solutions to keep the polishing value of stone within a manageable range.

[0013] The National Metrology Station for Road and Bridge Engineering Testing Equipment is the highest metrology verification agency in the road and bridge engineering field within China's transportation industry. Since its establishment in 2010, it has been dedicated to researching the measurement values of engineering testing equipment. In recent years, the station has conducted comprehensive research on the measurement formation mechanisms of accelerated grinding machines, focusing on traceability. They have identified sand blockage and breakage as significant contributors to deviations in the accuracy evaluation of accelerated grinding machines. Sand blockage and breakage typically occur during equipment operation and are highly concealed, making them difficult to detect. Some instances are even impossible to detect visually. Preventing these blockages and breakages at the source is a crucial challenge for every engineer involved in this field.

[0014] The polishing forming mechanism of the specimen is that during the high-speed operation of the rubber wheel and the specimen, a certain amount of abrasive (coarse sand, fine sand) and a certain amount of water are evenly added between the rubber wheel and the specimen to act on the specimen.

[0015] JTG E42-2005 Highway Engineering Aggregate Test Procedure T0321-2005 Coarse Aggregate Polishing Value Test Method, the polishing value operation process is as follows:

[0016] 1. Install the coarse sand rubber wheel on the adjusting arm, cover it with the road wheel cover, place a sand accumulation tray underneath, fill the water tank on the water storage bracket with water, and adjust the flow valve to temporarily interrupt the water flow.

[0017] 2. Prepare No. 30 corundum coarse sand and place it in a dedicated sand storage hopper. Install the hopper above the rubber wheel and connect it to the micromotor power supply. Turn the load adjustment handwheel to rotate the cam and lower the rubber wheel. Press the rubber wheel's spokes completely against the surface of the aggregate specimen on the road wheel.

[0018] 3. Adjust the amount of sand flowing: Use a special hopper to catch the diamond sand flowing out at the discharge port, start timing at the same time, remove the hopper after 1 minute, and use a balance to weigh the amount of sand flowing to make the flow rate 27g / min±7g / min. If it does not meet the requirements, use the speed control button or adjust the storage hopper control gate to adjust it.

[0019] 4. Set the speed to 57,600 on the control panel, press the power switch to start the grinder, and simultaneously press the coarse sand speed control button. Open the sand storage hopper control gate to control the diamond sand flow rate to 27g / min±7g / min. Immediately adjust the flow meter to a water flow rate of 60mL / min.

[0020] 5. The grinder will automatically stop after 1 hour and 2 hours of the test (be careful not to press the reset button and power switch on the panel). Use a brush and a small shovel to remove the emery on the box and the sand tray at the bottom of the machine. Check and tighten any nuts on the road wheel that may be loose. Then start the grinder. The grinder will automatically stop when the speed display shows 57,600 rpm. The required grinding time is about 3 hours.

[0021] 6. Remove the coarse sand rubber wheel and replace it with a fine sand rubber wheel and install it according to the method in step 1.

[0022] 7. Prepare No. 280 corundum fine sand and put it into the special sand storage hopper according to the method in step 2.

[0023] 8. Repeat step 3 and adjust the fine sand flow rate to 3g / min±1g / min.

[0024] 9. Follow step 4, set the speed to 57600 rpm, start the polishing operation, control the diamond sand flow rate to 3g / min±1g / min, and the water flow rate to a maximum of 60mL / min.

[0025] 10. After grinding the specimen for 2 hours, stop the machine for proper cleaning. Follow step 5 to check and tighten the road wheel nuts. Then start the grinder again and stop automatically when it reaches 57,600 rpm. Summary of the Invention

[0026] This invention improves the T0321-2005 coarse aggregate polishing value test method by refining the sequence, method, and location of water and coarse and fine sand application to the specimen. This approach addresses or partially resolves the current problems of coarse and fine sand blockage and breakage during specimen polishing. Furthermore, improvements are made to the coarse and fine sand delivery devices.

[0027] The patent accelerates the grinding machine test piece to add water, add sand, and grind the process flow. The distribution of the water adding station and the water spraying area, the coarse aggregate station and the coarse aggregate area, and the fine aggregate station and the fine aggregate area is as follows: Figure 2 shown.

[0028] 1. Install the coarse sand rubber wheel on the adjusting arm, cover it with the road wheel cover, place a sand accumulation tray underneath, fill the water tank on the water storage bracket with water, and adjust the flow valve to temporarily interrupt the water flow.

[0029] 2. Prepare No. 30 corundum coarse sand and place it in a dedicated sand storage hopper. Install the hopper above the rubber wheel and connect it to the micromotor power supply. Turn the load adjustment handwheel to rotate the cam and lower the rubber wheel. Press the rubber wheel's spokes completely against the surface of the aggregate specimen on the road wheel.

[0030] 3. Adjust the amount of sand flowing: Use a special hopper to catch the diamond sand flowing out at the discharge port, start timing at the same time, remove the hopper after 1 minute, and use a balance to weigh the amount of sand flowing to make the flow rate 27g / min±7g / min. If it does not meet the requirements, use the speed control button or adjust the storage hopper control gate to adjust it.

[0031] 4. Set the speed to 57,600 on the control panel, press the power switch to start the grinder counterclockwise, and simultaneously press the coarse sand speed control button and open the sand storage hopper control gate to control the diamond sand flow rate to 27g / min±7g / min. Immediately adjust the flow meter to a water flow rate of 60mL / min.

[0032] 4.5. The specimen first passes through the water spraying area of the water adding station, where a layer of water film is evenly distributed on the surface. Then it enters the coarse aggregate area of the coarse aggregate station. The coarse aggregate is evenly sprayed on the water film of the specimen and adsorbed on the surface of the specimen. Finally, it enters the junction of the rubber wheel and the road wheel. The fine aggregate begins to polish the specimen under the action of the rubber wheel.

[0033] 5. The grinder will automatically stop after 1 hour and 2 hours of the test (be careful not to press the reset button and power switch on the panel). Use a brush and a small shovel to remove the emery on the box and the sand tray at the bottom of the machine. Check and tighten any nuts on the road wheel that may be loose. Then start the grinder. The grinder will automatically stop when the speed display shows 57,600 rpm. The required grinding time is about 3 hours.

[0034] 6. Remove the coarse sand rubber wheel and replace it with a fine sand rubber wheel and install it according to the method in step 1.

[0035] 7. Prepare No. 280 corundum fine sand and put it into the special sand storage hopper according to the method in step 2.

[0036] 8. Repeat step 3 and adjust the fine sand flow rate to 3g / min±1g / min.

[0037] 9. Follow step 4, set the speed to 57600 rpm, start the polishing operation, control the diamond sand flow rate to 3g / min±1g / min, and the water flow rate to a maximum of 60mL / min.

[0038] The specimen first passes through the water spraying area of the water adding station, where a layer of water film will be evenly distributed on the surface. Then it enters the coarse aggregate area of the fine aggregate station, where the fine aggregate is evenly sprayed on the water film of the specimen and adsorbed on the surface of the specimen. Finally, it enters the junction of the rubber wheel and the road wheel, where the fine aggregate begins to polish the specimen under the action of the rubber wheel.

[0039] 10. After grinding the specimen for 2 hours, stop the machine for cleaning. Follow step 5 to check and tighten the road wheel nuts. Then start the grinder again and it will automatically stop when it reaches 57,600 rpm. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the basic structure of the accelerated grinder

[0041] Figure 2 This is a schematic diagram of the present invention

[0042] Figure 3 Polishing water and sand delivery diagram of test piece

[0043] Figure 4 Specimen water spraying process

[0044] Figure 5 The water spout is in the shape of a duckbill

[0045] Figure 6 Schematic diagram of sand conveying device

[0046] Figure 7 Schematic diagram of sand outlet structure

[0047] Among them: 1 - road wheel; 2 - adjustment arm; 3 - adjustment assembly; 4 - lever; 5 - rubber wheel; 6 - fine sand storage hopper; 7 - water supply device; 8 - coarse sand storage hopper; 9 - machine body; 10 - test piece; 11 - baffle; 12 - flow valve; 13 - fine sand material area; 14 - coarse sand material area; 15 - water outlet; 16 - water spray area; 17 - water channel; 18 - water film; 19 - conveyor belt; 20 - vibrator; 21 - mixer; 22 - mixer regulator DETAILED DESCRIPTION

[0048] The water spraying process of the specimen is as follows Figure 3 As shown in the figure, the road wheel of the loaded specimen rotates counterclockwise at a speed of v1 = 320r / min, and the water spraying system sprays water evenly on the surface of the specimen at a speed of v2 = 60ml / min = 1ml / min. The calculation is performed with the road wheel running one circle as the unit. The model is as follows Figure 4 shown.

[0049] S - the distance that the road wheel (test piece) runs for one circle;

[0050] L - width of test piece (water spray width), the specification stipulates (45±1) mm.

[0051] 1) Road wheel: The distance traveled in one circle is S = π × D ≈ 1275.5 mm, where D is the diameter of the road wheel after it is filled with the specimen (based on the arc of the stone specimen), which is 406 mm. The running time

[0052]

[0053] 2) Water spray system flow rate v 水=60ml / min=1ml / s=1000mm 3 / s;

[0054] 3) The volume of water required for each revolution of the road wheel

[0055] 4) Water film thickness

[0056] 5) Sprinkling width: 14 specimens are distributed on the 406 diameter road wheel, and the arc length of each specimen is To ensure uniform water volume, the nozzle length is designed to be 45mm and the width is designed to be 0.2mm.

[0057] In order to ensure that the amount of water (V) required for each polishing of the road wheel specimen is uniformly sprayed on the specimen surface with a water film thickness of h1, the water spray system is controlled by a precision flow valve to ensure uniform water flow at all times; the water spray nozzle adopts a duckbill shape, as shown below Figure 5 As shown, the internal dimensions of the water nozzle are 45mm in length and 0.2mm in width, and the interior is treated to be non-hydrophilic.

[0058] Sand transport method design process

[0059] The sand conveying device is similar to the water spraying system. It is designed to ensure the uniformity of sand flow during the sand conveying process and prevent the occurrence of sand and gravel piling and sand breakage.

[0060] The surface of the sand conveyor belt must have a certain degree of roughness, such as a finish of no less than 1.6μm, and the inner wall of the storage hopper must have a finish of no more than 0.4μm. A mixer is installed inside the storage hopper, and a vibrator is installed outside to prevent sand and gravel from being cut off. The sand outlet below the storage hopper is designed to be flat, and the sand discharge pipe is slightly angled to ensure that the sand flows out of the outlet evenly. To ensure that the discharge speed of the outlet matches the speed of the feed belt, the rotation speed of the storage hopper mixer and the oscillation frequency of the vibrator can be externally unlimited.

[0061] Sand outlet structure Figure 7 As shown, the sand outlet is flat, 45 mm long and 3 mm wide. The vertical sand delivery channel is inclined at about 3 degrees. The interior is smooth and has no dead angles, which prevents the loss of sand energy and affects the sand delivery effect on the specimen surface.

[0062] Features of the present invention:

[0063] 1. The grinding process of the test piece adopts the process of adding water first, then adding materials and finally grinding;

[0064] 2. The water inlet adopts a duckbill structure to spray water evenly on the surface of the specimen;

[0065] 3. The injection port adopts duckbill type and direct injection structure to ensure that the abrasive is sprayed continuously and evenly onto the surface of the test piece;

[0066] 4. Designed with abrasive feeding plate.

Claims

1. A method for testing the accuracy of an accelerated polishing machine, wherein the accelerated polishing machine comprises: a load adjustment assembly, an adjustment arm, a road wheel, a rubber wheel, a fine sand storage hopper, a coarse sand storage hopper, a water supply device, a machine body, and a test piece, wherein the rubber wheel is divided into a coarse sand rubber wheel and a fine sand rubber wheel; characterized in that: 1) Install the coarse sand rubber wheel on the adjusting arm, cover it with the road wheel cover, place a sand accumulation tray underneath, fill the water tank on the water storage bracket with water, and adjust the flow valve to temporarily interrupt the water flow; 2) Prepare No. 30 corundum coarse sand and load it into the coarse sand storage hopper. Install the coarse sand storage hopper above the coarse sand rubber wheel and connect the micro motor power supply. Turn the load adjustment hand wheel to rotate the cam to lower the coarse sand rubber wheel. Press the wheel of the coarse sand rubber wheel completely against the surface of the test piece sprayed with coarse aggregate on the road wheel. 3) Adjust the sand flow rate: catch the diamond sand flowing out at the discharge port and start timing at the same time. After 1 minute, remove the hopper and weigh the sand flow rate with a balance to make the flow rate 27g / min±7g / min. If the flow rate requirement is not met, adjust it by using the speed control button or adjusting the gate of the sand storage hopper. 4) Set the speed to 57600 on the control panel, press the power switch, and the grinder starts to run counterclockwise; at the same time, press the coarse sand speed control button, open the sand storage hopper control gate, and control the diamond sand flow rate to 27g / min±7g / min; at this time, immediately adjust the flow meter to make the water flow reach 60mL / min; the specimen first passes through the water spraying area of the water adding station, and a layer of water film will be evenly distributed on the surface. Then it enters the coarse aggregate area of the coarse aggregate station. The coarse aggregate is evenly sprayed on the water film of the specimen and adsorbed on the surface of the specimen. Finally, it enters the junction of the coarse sand rubber wheel and the road wheel. The coarse aggregate begins to polish the specimen under the action of the coarse sand rubber wheel; 5) The grinder will automatically stop after 1 hour and 2 hours of the test. Use a brush and a small shovel to clean the diamond sand on the box and the sand tray at the bottom of the machine. Check and tighten the nuts on the road wheel that may be loose. Then start the grinder. When the speed display shows 57,600, the grinder will automatically stop. 6) Remove the coarse sand rubber wheel, replace it with a fine sand rubber wheel, and install it according to the method in step 1); 7) Prepare 280# corundum fine sand and put it into the fine sand storage hopper according to the method in step 2); 8) Repeat step 3) and adjust the fine sand flow rate to make the flow rate 3g / min±1g / min; 9) According to step 4), set the speed to 57600 rpm and start the polishing operation. Control the diamond sand flow rate to 3g / min+1g / min and the water flow rate to 60mL / min. The specimen first passes through the water spraying area of the water adding station, where a layer of water film is evenly distributed on the surface. Then it enters the coarse aggregate area of the fine aggregate station, where the fine aggregate is evenly sprayed on the water film of the specimen and adsorbed on the surface of the specimen. Finally, it enters the junction of the fine sand rubber wheel and the road wheel, where the fine aggregate begins to polish the specimen under the action of the fine sand rubber wheel. 10) After grinding the specimen for 2 hours, stop the machine for cleaning, check and tighten the road wheel nuts according to step 5), and then start the grinder again until it automatically stops at 57,600 rpm.

2. The method according to claim 1, wherein: The road wheel rotates counterclockwise at a speed of v1 = 320r / min.

3. The method according to claim 1, wherein: The internal dimensions of the water nozzle are 45mm in length and 0.2mm in width, and the interior is treated to be non-hydrophilic.

4. The method according to claim 1, wherein: The surface finish of the sand conveying belt shall not be less than 1.6μm, the inner wall finish of the storage hopper shall not be greater than 0.4μm, a mixer shall be installed in the storage hopper, and a vibrator shall be installed outside.

5. The method according to claim 1, wherein: The length of the sand outlet is 45mm and the width is 3mm, and the vertical sand transport channel is inclined at 3 degrees.

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