Windshield glass sandstone impact test device and method

Abstract

The invention provides a windshield glass sandstone impact test device and method. The windshield glass sandstone impact test device comprises a sandstone launching device (1), a test bed (2), a high-speed camera (18), a graduated scale (19) and a strain measurement system (4), the gravel launching device (1) comprises a gas storage bottle (6), a pressure regulating valve (7), a high-pressure-resistant dust blowing gun (8), a steel pipe (9) and a PU spring gas pipe (11); the strain measurement system comprises: a strain rosette (20); the strain rosette (20) is adhered to a position which is 30mm away from the geometric center of the impacted surface of the tested windshield glass test piece (5); the pressure of the high-pressure-resistant dust blowing gun (8) blown to the steel pipe (9) is adjusted through the pressure adjusting valve (7), and the strain rosette (20) measures stress values when sandstones at different speeds impact the tested windshield glass test piece (5). According to the method, sandstones of different sizes can be controlled to impact the windshield glass at different speeds, and a theoretical basis is provided for windshield glass damage tolerance design and the problem of damage cracking in the windshield glass service process.

Description

Technical Field

[0001] This invention belongs to the technical field of designing the impact strength of helicopter windshields against gravel, specifically relating to a windshield impact testing device and method. Background Technology

[0002] Helicopters typically need to meet the requirements of greater payload capacity, higher rotor speed, and operation in harsh environmental conditions. Safe and efficient helicopter operation necessitates a large transparent area in the cockpit, usually made of highly reinforced inorganic glass panels. During flight in near-ground gravel environments, helicopters create an environment where large components such as the windshield, rotor, and engine blades are subject to high-speed impacts from gravel, thus windshield design technology must keep pace with these increasingly demanding environmental requirements.

[0003] After detailed inspection of the windshields in field service and failure analysis of the cracked windshields, it was determined that the root cause of the helicopter windshield cracking was the high-speed impact of small-sized sand and gravel. During the helicopter's near-ground flight, the rotor downwash picks up sand and dust from the ground, forming a dust cloud around the rotor. As the particles recirculate downwards, the floating sand and gravel particles collide with the high-speed rotating rotor blades, gaining sufficient momentum to become projectiles. Some of these projectiles impact the windshield, causing it to crack.

[0004] Currently, there are no ground testing methods or devices for sand and gravel impact on windshields, so it is impossible to provide a theoretical basis for whether helicopter windshields can meet the sand and gravel impact environment in field service. Summary of the Invention

[0005] This invention provides a windshield impact testing device and method, which provides a theoretical basis for windshield damage tolerance design and solving damage and cracking during windshield service.

[0006] The first aspect of the present invention provides a windshield sand and gravel impact testing device, comprising: a sand and gravel launching device 1, a test bench 2, a high-speed camera 18, a scale 19, and a strain measurement system 4; The test bench 2 is an integral frame structure, on which are installed: steel pipe mounting frame 12, scale 19, glass mounting frame 13, push rod mounting frame 14, threaded push rod 17, push rod top 15, and push rod handle 16. The glass mounting stand 13 is used to fix the windshield glass test piece 5 to be tested; the threaded push rod 17 is threadedly connected to the push rod mounting stand 14, one end of which applies pressure to the windshield glass test piece 5 through the push rod top 15, and the other end is connected to the push rod handle 16. A scale 19 is set between the steel pipe mounting frame 12 and the glass mounting frame 13, and the high-speed camera 18 is arranged facing the scale 19. The sand and gravel launching device 1 includes: a gas cylinder 6, a pressure regulating valve 7, a high-pressure dust gun 8, a steel pipe 9, and a PU spring air tube 11; The steel pipe 9 is fixed on the steel pipe mounting frame 12. Sand and gravel are placed inside the pipe. The outlet faces the windshield test piece 5 to be tested. The inlet is connected in sequence to the high-pressure dust gun 8, the pressure regulating valve 7 and the gas cylinder 6. The gas cylinder 6 and the pressure regulating valve 7 and the high-pressure dust gun 8 are connected by a PU spring air tube 11. The strain measurement system includes: a strain rosette 20; the strain rosette 20 is bonded to the geometric center of the impact surface of the windshield test piece 5 30 mm above the surface. The pressure of the high-pressure dust gun 8 blowing onto the steel pipe 9 is adjusted by the pressure regulating valve 7, and the strain gauge 20 measures the stress value when sand and gravel at different speeds impact the windshield test piece 5.

[0007] Optionally, the pressure regulating valve 7 can operate within a pressure range of 0.1–1.5 MPa with an accuracy of 0.1 MPa.

[0008] Optionally, the inner diameter of the steel pipe 9 used is not less than 4mm. The outer surface of the steel pipe 9 is threaded within 80mm from the inlet and outlet, and two limit nuts 10 are installed at the front and back to fix the steel pipe 9 on the steel pipe mounting frame 12. The distance between the end face of the firing port of the steel pipe 9 and the impact surface of the windshield test piece 5 is 400mm-500mm. The diameter of the through hole in the steel pipe mounting frame 12 is 0.1 mm larger than the outer diameter of the steel pipe 9, and the coaxiality of the front and rear through holes is no greater than φ0.1 mm.

[0009] Optionally, the geometric center of the through hole of the steel pipe on the steel pipe mounting stand 12 is the same as the geometric center of the windshield test piece 5 under test. When the height of the windshield test piece 5 under test is 120mm, the distance between the glass mounting stand 13 and the through hole of the steel pipe in the height direction is 60±1mm.

[0010] Optionally, the threaded push rod on the push rod mounting frame 14 is threaded with an internal thread of the same diameter as the threaded push rod 17 through the hole, and the geometric center of the threaded push rod through the hole is the same as the geometric center of the glass. The threaded push rod 17 is welded to the push rod handle 15. The relative distance between the threaded push rod 17 and the windshield test piece 5 is adjusted by rotating the push rod handle 16, and the push rod top 15 is pressed onto the windshield test piece 5 to generate the required stress value on the windshield test piece 5. The vertical height of the push rod top 15 is the same as the vertical height of the windshield test piece 5 being tested.

[0011] Optionally, the minimum measuring size of the scale 19 is 1mm, and the scale range is not less than 400mm; The high-speed camera 18 has a frame rate of no less than 10,000 frames / s and a resolution of 1920×1080. A high-speed camera 18 is used to capture images during the sand and gravel impact test; the captured information is used to provide the sand and gravel impact velocity from 200 mm away from the impact surface of the windshield test piece 5 to the glass impact surface.

[0012] Optionally, the windshield test piece 5 includes: the glass under test 23, the push rod top buffer rubber plate 24, and two glass non-impact area protection rubber plates 25; The dimensions of the glass 23 being tested are 120mm × 250mm; The two non-impact area protection rubber plates 25 are bonded to the left and right sides of the glass 23 being tested, with a width of no more than 10mm in the middle position, to ensure that the impact position of sand and gravel is near the center line of the glass 23 being tested. The thickness of the push rod top buffer rubber plate 24 and the two glass non-impact area protection rubber plates 25 is not less than 2mm.

[0013] Optionally, the strain measurement system may also include: strain gauge cable 21 and dynamic resistance strain gauge 22; The strain gauge 20 is connected to the dynamic resistance strain gauge 22 via the strain gauge cable 21.

[0014] A second aspect of the present invention provides a method for testing windshield impact with gravel, employing the windshield impact testing apparatus as described in any one of the first aspects, the method comprising: Place the pre-sized sand and gravel into the steel pipe 9; Based on the real-time monitoring results of the strain gauge 20, the rotating push rod handle 16 applies a preset pressure to the windshield test piece 5 through the threaded push rod 17 and the push rod top 15; Adjust the pressure of the pressure regulating valve 7 to the pressure corresponding to the preset size of sand and gravel, turn on the high-pressure dust blower 8, and use the high-speed camera 18 to take pictures; The impact velocity of sand and gravel is obtained based on the shooting results of the high-speed camera 18. If the impact velocity of sand and gravel is within the preset range, the pressure of the pressure regulating valve 7 is adjusted if it is not satisfied.

[0015] Optional, the windshield gravel impact test method also includes: A bending strength test was performed on the uncracked windshield test specimen 5 to obtain the damage tolerance value of the windshield test specimen 5.

[0016] In summary, the beneficial effects of this invention are as follows: The windshield sand impact testing device and method proposed in this invention solve the problem of whether helicopter windshields can withstand impacts from sand of different sizes at different speeds, and provides a method for preparing specific damage to the glass under predetermined sand size and impact speed. Using the device designed in this patent, impact tests have been successfully completed with sand of 0.8mm, 1.6mm, and 3.2mm at speeds of 40m / s, 60m / s, and 80m / s, respectively. The glass damage morphology is the same as that of windshields during helicopter service. Bending strength tests were performed on the uncracked glass, and damage tolerance values ​​for the glass were given. This device provides theoretical support for solving the glass cracking problem. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a windshield impact testing device. Figure 2 This is a schematic diagram of a sand and gravel launching device; Figure 3 This is a schematic diagram of the test bench; Figure 4 This is a schematic diagram of a speed testing system; Figure 5 This is a schematic diagram of a strain measurement system; Figure 6 This is a schematic diagram of the windshield being tested; Explanation of reference numerals in the attached figures: 1-Sand and gravel launching device; 2-Test bench; 3-Velocity testing system; 4-Strain measurement system; 5-Windshield under test; 6-Gas cylinder; 7-Pressure regulating valve; 8-High-pressure dust blower; 9-Steel pipe; 10-Limit nut; 11-PU spring air hose; 12-Steel pipe mounting frame; 13-Glass mounting frame; 14-Push rod mounting frame; 15-Push rod top; 16-Push rod handle; 17-Threaded push rod; 18-High-speed camera; 19-Scale; 20-Strain rosette; 21-Strain rosette cable; 22-Dynamic resistance strain gauge; 23-Glass under test; 24-Push rod top buffer rubber plate; 25-Glass non-impact area protection rubber plate. Detailed Implementation

[0018] The windshield impact testing device and method provided by the present invention will be explained below with reference to the accompanying drawings.

[0019] like Figure 1-6 As shown, the present invention provides a windshield impact testing device and method.

[0020] The windshield impact testing device provided by the present invention includes: a sand and gravel launching device 1, a test bench 2, a velocity testing system 3, a strain measurement system 4, and a windshield test piece 5.

[0021] The sand and gravel launching device 1 comprises: a gas cylinder 6, a pressure regulating valve 7, a high-pressure dust gun 8, a steel pipe 9, a limit nut 10, and a PU spring air tube 11. The gas cylinder 6, the pressure regulating valve 7, and the high-pressure dust gun 8 are connected by the PU spring air tube 11.

[0022] The pressure regulating valve 7 has an operating pressure range of 0.1-1.5 MPa and an accuracy of 0.1 MPa. The inner diameter of the steel pipe 9 used is not less than 4 mm. The steel pipe 9 has threads tapped on its outer surface within 80 mm of the inlet and outlet, and two limit nuts 10 are installed at the front and rear to fix the steel pipe 9 on the test bench 2 and maintain the stability of the steel pipe 9 during launch. The distance between the launch port end face of the steel pipe 9 and the glass impact surface is 400 mm to 500 mm. The test bench 2 comprises a steel pipe mounting bench 12, a glass mounting bench 12, a push rod mounting bench 14, a threaded push rod 17, a push rod top 15, and a push rod handle 16; The diameter of the through hole in the steel pipe mounting frame 12 should be 0.1 mm larger than the outer diameter of the steel pipe, and the coaxiality of the front and rear through holes should not exceed φ0.1 mm. The height of the glass mounting platform 13 should be such that the geometric center of the steel pipe through hole on the steel pipe mounting platform 12 after the glass is installed is the same as the geometric center after the glass is installed. Since the height of the test piece is 120mm, the distance between the glass mounting platform 13 and the steel pipe through hole in the height direction is 60±1mm. The threaded push rod on the push rod mounting frame 14 has an internal thread of the same diameter as the threaded push rod 17 tapped in the hole, and the geometric center of the hole is the same as the geometric center of the glass. The distance between the axis of the threaded push rod 17 and the height direction of the glass mounting frame 13 is 60±1mm. The threaded push rod 17 is welded to the push rod handle 16. By rotating the push rod handle 16, the relative distance between the threaded push rod 17 and the glass can be adjusted, and the push rod top 15 can be pressed against the glass to generate the required stress value on the glass.

[0023] The vertical length of the push rod top 15 is 120mm, which is the same as the vertical width of the glass. The speed testing system 3 includes: a scale 19 and a high-speed camera 18; The minimum measuring size of the ruler 19 is 1mm, and the measuring range of the ruler is not less than 400mm; The high-speed camera 18 has a frame rate of no less than 10,000 frames / s and a resolution of 1920×1080 (1080p). Based on the information captured by the high-speed camera 18, the impact velocity of the sand and gravel from 200mm away from the glass impact surface to the glass impact surface is calculated. The strain measurement system 4 includes: a strain flower 20, a strain flower cable 21, and a dynamic resistance strain gauge 22; The strain gauge 20 is a three-directional strain gauge and is connected to the dynamic resistance strain gauge 22 via the strain gauge cable 21; the dynamic resistance strain gauge 22 can display the three-directional strain values ​​on the glass in real time. The strain gauge 20 should be bonded 30 mm above the geometric center of the glass surface being impacted.

[0024] The windshield 5 under test includes the glass under test 23, a push rod top buffer rubber plate 24, and two glass non-impact area protection rubber plates 25; The dimensions of the glass 23 being tested are 120mm × 250mm.

[0025] After the two non-impact area protective rubber plates 25 are bonded to the glass, the width of the middle position is no more than 10mm to ensure that the impact position of sand and gravel is near the center line of the glass. The thickness of the nitrile rubber sheet used for cushioning the push rod top and the nitrile rubber sheet used for protecting the non-impact areas of the two glass panels is no less than 2mm.

[0026] In a specific embodiment of the present invention, a pressure regulating valve with a pressure range of 0.1-1.5 MPa is connected to a gas cylinder and a high-pressure dust blowing gun via a PU spring tube, and the accuracy of the pressure regulating valve is 0.1 MPa. Insert a steel pipe with an inner diameter of 4mm into the steel pipe mounting frame, adjust the position of the steel pipe so that the distance between the end face of the steel pipe's firing port and the glass impact surface is 450mm, and tighten the two limit nuts at the front and back. A ruler with a measuring range of 500mm and a minimum measuring size of 1mm, and a high-speed camera with a maximum shooting speed of 10,000 frames / s were placed between the steel pipe's firing port and the glass that was being impacted.

[0027] Five gravel particles with a size between 1.6 mm and 1.8 mm were selected from the gravel using vernier calipers. Without installing the glass, the air pressure and the impact velocity of the gravel were adjusted. Finally, when the pressure regulating valve was stabilized at 0.4 MPa, the impact velocity of the gravel was stabilized at 60 ± 2 m / s.

[0028] Prepare an inorganic glass plate test specimen with dimensions of 120mm×250mm×3mm. Attach a 2mm thick protective nitrile rubber sheet to the impact surface of the test specimen, leaving a 10mm wide sand and gravel impact area in the middle. Place the specimen on a glass mounting stand.

[0029] Rotate the push rod handle to make the push rod tip gently contact the glass surface. A 2mm thick nitrile rubber sheet is bonded between the glass fish push rod tips.

[0030] Attach a three-directional strain gauge 30mm above the geometric center of the impacted surface of the glass. Continue to rotate the push rod handle to deform the glass. When the micro-strain displayed on the dynamic resistance strain gauge reaches 436.7με, the stress on the glass is 30.569MPa, which is the same as the operating condition. Stop rotating the handle to maintain the stress state of the glass at this time.

[0031] Place the selected gravel with a maximum size of 1.79mm into the front end of the steel pipe, connect the steel pipe to the high-pressure dust gun, and adjust the pressure of the pressure regulating valve to 0.4Mpa.

[0032] The high-pressure blower handle was operated, causing gravel to impact the surface of the glass being tested at high speed. At this point, a high-speed camera recorded the gravel velocity at a distance of 200mm from the impact surface as 61.3m / s. After the inorganic glass was impacted, a network of cracks appeared, and the crack pattern was basically consistent with the crack morphology of helicopter windshields.

Claims

1. A windshield impact testing device, characterized in that, include: Sand and gravel launching device (1), test bench (2), high-speed camera (18), scale (19), strain measurement system (4); The test bench (2) is an integral frame structure, on which are installed: steel pipe mounting bench (12), scale (19), glass mounting bench (13), push rod mounting bench (14), threaded push rod (17), push rod top (15), and push rod handle (16). The glass mounting stand (13) is used to fix the windshield glass test piece (5) to be tested; the threaded push rod (17) is threadedly connected to the push rod mounting stand (14), one end of which applies pressure to the windshield glass test piece (5) through the push rod top (15), and the other end is connected to the push rod handle (16). A scale (19) is set between the steel pipe mounting platform (12) and the glass mounting platform (13), and the high-speed camera (18) is positioned facing the scale (19); The sand and gravel launching device (1) includes: a gas cylinder (6), a pressure regulating valve (7), a high-pressure dust gun (8), a steel pipe (9), and a PU spring air tube (11); The steel pipe (9) is fixed on the steel pipe mounting frame (12), and sand and gravel are placed inside it. The outlet faces the windshield test piece (5) to be tested, and the inlet is connected in sequence to the high-pressure dust blower (8), the pressure regulating valve (7) and the gas cylinder (6); the gas cylinder (6), the pressure regulating valve (7) and the high-pressure dust blower (8) are connected by a PU spring air tube (11); The strain measurement system includes: a strain rosette (20); the strain rosette (20) is bonded to the geometric center of the impact surface of the windshield test piece (5) 30 mm above the surface; The pressure of the high-pressure dust gun (8) blown onto the steel pipe (9) is adjusted by the pressure regulating valve (7), and the stress value of the windshield test piece (5) is measured by the strain gauge (20) when sand and gravel at different speeds impact the test piece (5).

2. The windshield glass impact testing device according to claim 1, characterized in that, The pressure regulating valve (7) has a working pressure range of 0.1-1.5 MPa and an accuracy of 0.1 MPa.

3. The windshield glass impact testing device according to claim 1, characterized in that, The inner diameter of the steel pipe (9) used is not less than 4mm. The steel pipe (9) has threads tapped on its outer surface within 80mm from the inlet and outlet, and two limit nuts (10) are installed in front and behind to fix the steel pipe (9) on the steel pipe mounting frame (12). The distance between the end face of the firing port of the steel pipe (9) and the impact surface of the windshield test piece (5) is 400mm-500mm. The diameter of the through hole in the steel pipe mounting frame (12) is 0.1 mm larger than the outer diameter of the steel pipe (9), and the coaxiality of the through holes is no greater than φ0.1 mm.

4. The windshield glass impact testing device according to claim 1, characterized in that, The geometric center of the steel pipe through hole on the steel pipe mounting stand (12) is the same as the geometric center of the windshield glass test piece (5) under test. When the height of the windshield glass test piece (5) under test is 120mm, the distance between the glass mounting stand (13) and the steel pipe through hole in the height direction is 60±1mm.

5. The windshield glass impact testing device according to claim 1, characterized in that, The threaded push rod on the push rod mounting frame (14) has an internal thread of the same diameter as the threaded push rod (17) tapped in the hole, and the geometric center of the threaded push rod through the hole is the same as the geometric center of the glass. The threaded push rod (17) is welded to the push rod handle (15). The relative distance between the threaded push rod (17) and the windshield test piece (5) is adjusted by rotating the push rod handle (16), and the push rod top (15) is pressed onto the windshield test piece (5) to generate the required stress value on the windshield test piece (5). The vertical height of the push rod top is the same as the vertical height of the windshield test piece (5) being tested.

6. The windshield impact testing device according to claim 1, characterized in that, The minimum measuring size of the ruler (19) is 1 mm, and the measuring range of the ruler is not less than 400 mm; The high-speed camera (18) has a frame rate of no less than 10,000 frames / s and a resolution of 1920×1080. A high-speed camera (18) is used to take pictures during the sand and gravel impact test; the picture information is used to provide the sand and gravel impact velocity from 200 mm away from the impact surface of the windshield test piece (5) to the impact surface of the glass.

7. The windshield glass impact testing device according to claim 1, characterized in that, The windshield test piece (5) includes: the glass to be tested (23), the push rod top buffer rubber plate (24), and two glass non-impact area protection rubber plates (25). The dimensions of the glass (23) being tested are 120mm × 250mm; The two non-impact area protection rubber plates (25) are bonded to the left and right sides of the glass (23) being tested, with the width in the middle not exceeding 10mm, to ensure that the impact position of the sand and gravel is near the center line of the glass (23) being tested. The thickness of the push rod top buffer rubber plate (24) and the two glass non-impact area protection rubber plates (25) is not less than 2mm.

8. The windshield glass impact testing device according to claim 1, characterized in that, The strain measurement system also includes: strain gauge cable (21) and dynamic resistance strain gauge (22); The strain gauge (20) is connected to the dynamic resistance strain gauge (22) via the strain gauge cable (21).

9. A method for testing windshield glass against gravel impact, characterized in that, The method using the windshield sand and gravel impact testing apparatus as described in any one of claims 1-8 includes: Place the pre-sized sand and gravel into the steel pipe (9); Based on the real-time monitoring results of the strain gauge (20), the rotating push rod handle (16) applies a preset pressure to the windshield test piece (5) through the threaded push rod (17) and the push rod top (15); Adjust the pressure of the pressure regulating valve (7) to the pressure corresponding to the preset size of sand and gravel, turn on the high-pressure dust blower (8), and use a high-speed camera (18) to take pictures; The impact velocity of sand and gravel is obtained based on the shooting results of the high-speed camera (18). If the impact velocity of sand and gravel is within the preset range, the pressure of the pressure regulating valve (7) is adjusted.

10. The method for testing windshield glass impact with gravel according to claim 9, characterized in that, The method further includes: The flexural strength test was performed on the uncracked windshield test piece (5) to obtain the damage tolerance value of the windshield test piece (5).

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