RU2733106C2 - Methods for evaluation of operational efficiency of profiled sheet from polymer composite materials - Google Patents

Abstract

FIELD: testing technology; production of composite materials.

SUBSTANCE: invention relates to investigation of strength properties of articles based on profiled sheet (PS) for various purposes from polymer composite materials (PCM). Method comprises testing for three-point bending of sheet specimen by load to close to destructive values of load and deflection and comparing said values with corresponding design values. At the first stage of the test, the submarine sample mounted on the support locating blocks of the test rig is loaded with a linearly distributed load of the specified value, transmitted through loading beam and simulating operating load for specified distance between supports, and for specified time check sheet state and its deflection. At that, it is considered that the sample has passed check under condition of absence of visually observed signs of destruction, and its maximum deformation/deflection under action of rated load during 5 minutes is not higher than allowable design values. At the second stage, the sample is further loaded with a linearly distributed load of a given nominal value, transmitted through loading beam and imitating maximum design value, under conditions of PS control and deflection. At the same time it is considered that the sample has passed the test provided that without the visually observed signs of destruction it has sustained maximum load during 60 minutes. At the third stage, loaded shaped sheet is unloaded and residual deflection state is controlled, wherein it is considered that the sample has passed the test provided that its residual deformations/deflection do not exceed allowable design values. Based on the results of tests carried out at three stages, conclusion is made on workability of the profiled sheet and articles based on it under bending in conditions of use for the intended purpose. Summary: sheet specimen is subjected to bending test to load close to destructive values of load and deflection and comparing said values with corresponding design values, however, the sample of the submarine installed on the supporting locating blocks of the test rig is loaded with a linearly distributed load of the press type, which imitates the operational load for a given distance between the supports, until preset deformations are achieved under conditions of monitoring its state. Sample is considered to have passed the test provided that without the visually observed signs of failure it has withheld maximum deformation/deflection during 60 minutes. Based on the results of the test, a conclusion is made on operational performance of the profiled sheet and articles based on it under bending in conditions of use for the intended purpose.

EFFECT: high accuracy and efficiency of determining mechanical characteristics of profiled sheet products from PCM based on a technique which is easy to implement in practice.

2 cl, 16 dwg

Description

The invention relates to the field of studying the strength properties of solid materials and products based on them, specifically, profiled sheet (profiled sheet or PL) for various purposes made of polymer composite materials (PCM). The invention can be used to determine the operational characteristics and issue recommendations for the use of products from submarines based on tested materials operating under static loading.

Known methods of testing with mechanical loading, providing the creation of tensile-compressive stresses in samples made in the form of a strip or rod in the direction of their longitudinal axis. The combined action of normal and tangential stresses is investigated during transverse bending of a sample in the form of a bar. According to the proposed three-point loading scheme, the sample is installed on two supports located along its edges, and loaded with a transverse force applied in the middle between the supports [Tarnopolsky Yu.M. and other Methods of static testing of reinforced plastics. M .: Chemistry, 1981, p. 272].

The known method of continuous mechanical testing of long specimens for transverse bending [RF Patent No. 2006022]. During the test, the sample is rolled between two pairs of rollers that support it, and one of the rollers ensures its movement. The transverse force acting on the sample is created by means of an additional roller located between the supporting pairs of rollers. The loading parameters are controlled by means of a loading roller. All rollers have a cylindrical shape with a straight generatrix and provide uniform pressure across the width of a long specimen. Thus, a three-point loading scheme and the study of samples from isotropic materials are realized.

Known standard for testing metallic materials [GOST R 52752-2007 (Formwork. Test methods. Date of introduction 2008-06-01], according to which the strength and stiffness of formwork elements is assessed based on the results of their control static loading tests by comparing the values of the actual bearing capacity and stiffness element and the corresponding values of the actual breaking load and the deflection of the element, determined from the test results, with the corresponding calculated values established in the design documentation, standards and (or) technical specifications for the formwork and its elements.

Compared to metal, profiled sheet made of PCM has a lower modulus of elasticity, which leads to deflections and requires special control for use in each of the areas of application (roofing, decking, fences, supporting structures, etc.). At the same time, PL products do not require high strength and stiffness requirements as for formwork.

There are known types of loads acting on profiled sheets used in construction, for example, as a roof, and their calculated values, for example, snow or wind loads (Methodological manual on the use of profiled steel decks in construction http://profnastilspb.ru/gost_pdf/ ).

A known method for determining the mechanical characteristics, in particular, the modulus of elasticity, ultimate strength, ultimate deformation, rods made of PCM [RF Patent No. 2451281]. The invention provides for loading a horizontally installed sample with an increasing load, recording the magnitude of the load and the corresponding deformation of the sample and the subsequent calculation of the values of mechanical characteristics, while the sample in the form of a rod of constant cross section with hinged ends is subjected to buckling by longitudinal loading, the value of the longitudinal load and the corresponding values of the boom are recorded deflection and radius of curvature in the zone of greatest deflection, longitudinal loading is continued until the beginning of the destruction of the sample, stress σ, deformation ε and elastic modulus E are determined by the formulas.

Known standardized methods of testing for bending samples of metallic and non-metallic sheet or having a rectangular cross-section of materials [GOST 25.604, 4648, 9454, 9550, 14019, 18228, 27208], for which standard devices (equipment) are used in the form of two supports and a loading device. According to GOST 25.604-82, the bending test method for composite material specimens consists of determining, inter alia, the dependence of the deflection on the load when the specimen is loaded up to failure.

As a result of the proposed tests, the parameters of loading-forces and the displacements caused by them or the deformation of the sample and the value of the mechanical load providing it are determined.

The closest in terms of test methodology and determination of strength characteristics of materials under deformations arising under bending loads is GOST R 56810-2015 [Polymer composites. Bending test method for flat specimens. Date of introduction 2017-01-01]. This standard applies to unreinforced and reinforced materials, including laminated polymer composite materials reinforced with continuous fibers. The standard specifies a method for testing materials for three-point bending. The essence of the method lies in the bending of a flat specimen of constant rectangular cross section, which is freely lying on two supports, with a constant loading rate until the moment of specimen failure or until the tensile strain on the outer surface of the specimen reaches a predetermined value. The critical (ultimate) load is determined from the deformation diagram, including as a load equal to the load of the beginning of the deviation of the diagram from a linear one, or as a load equal to the load of destruction of the sample (the moment of destruction of the sample is determined visually). The flexural strength is calculated using the formula presented, taking into account the width and thickness of the specimen, the span between the supports, and the maximum load preceding the failure of the specimen.

However, the presented test method is rather complicated and laborious, requires equipment such as a testing machine with a loading punch, and, most importantly, is not adapted for prompt issuance of recommendations on the use of tested materials based on refined test data and their comparison with theoretical ones. Specifically, it has not been developed to assess the possibility of safe operation of profiled sheets made of polymer composite materials, including unidirectionally reinforced ones, widely used in various fields of economic activity.

The technical objective of the invention is to assess the performance and quality control of products from a profiled sheet based on PCM by testing sheet samples and monitoring their operational parameters.

The technical result of the proposed invention is to improve the accuracy of determining the mechanical characteristics of profiled sheet products from PCM, which is necessary, in particular, when releasing a new range of products and its safe operation, on the basis of an easily implemented methodology. This result is achieved by comparing test data with theoretical data obtained from analytical calculations and / or using software products.

The posed technical problem is solved by the selected author's program for testing sheet samples made of PCM at three-point bending under the action of a linearly distributed load of a given nominal value or a given deformation, in stages with the definition of indicators, the accuracy of their measurement, and tracking the measurement results:

The essence of the claimed technical solution consists in loading the profiled sheet installed on the support cradles of the test equipment with a linearly distributed load of a given nominal value (according to test stages 1-3) or a given deformation (stage 4 of testing), simulating operational (for example, snow load) in a three-point bending and comparison of the measured values with the corresponding theoretical and / or normative design values, incl. established in the design and construction documentation, standards, technical conditions (TU), reference materials.

At all stages, the test equipment plays the role of fixed elements of the building structure, on which the profiled sheet is installed during operation, ensures safety when installing a load simulator, and ensures convenience and accuracy of measurements.

The essence of the claimed technical solution is illustrated by pictorial elements:

Figure 1. Rigging before load application.

Figure 2. Measurement of baseline distance.

Figure 3. Test object under load.

Figure 4. Measurement of deflection.

Figure 5. Test object before loading.

Figure 6. Measurement of baseline distance.

Figure 7. Measurement of current values of deformation.

Figure 8. Load test object.

Figure 9. Displacements under the design load according to example No. 1.

Figure 10. Displacements at 150% design load according to example No. 1.

Figure 11. 1st form of buckling at 150% design load according to example No. 1.

Figure 12. Material safety factor at 150% design load according to example No. 1.

Figure 13. Displacements under the design load according to example No. 2.

Figure 14. The safety factor at the design load according to example No. 2.

Figure 15. Displacement at 150% design load according to example No. 2.

Figure 16. Safety factor at 150% design load according to example No. 2.

Stage 1 of the test program is carried out as follows (by sub-stages):

1.1. The test fixture is assembled in such a way that the profile of the support cradles corresponds to the profile of the test object, and the distance between the supports is closest to the specified value L ₂ .

1.2. Measure the actual distance between the supports with a tape measure between the inner edges of the support cradles on both sides of the test rig, record its arithmetic mean in the protocol.

1.3. The test object is placed on top of the test fixture support cradles so that its center is approximately midway between the test fixture support cradles. The free ends of the test object must protrude beyond the support cradles by at least 100 mm.

1.4. The loading beam is installed on the guide pins of the rig with the cradle down.

1.5. Measuring nuts and washers are installed on the ends of the studs. The appearance of the test equipment at this stage of testing is shown in figure 1.

1.6. Using a vernier caliper, the distance H _{0_1} and H _{0_2} from the top surface of the washers to the top surface of the loading beam is measured. The measurement is shown in Figure 2.

1.7. At the ends of the loading beam, weights are fixed, the total mass M _{1 of} which is determined by the formula:

where g = 9.81 m / s ² is the acceleration of gravity.

The actual weight of the goods is measured by means of scales and recorded in the protocol. The difference in the mass of weights installed at the ends of the loading beam should not exceed 5% of their total mass.

1.8. The stopwatch measures the shutter speed. The appearance of the rig at this stage is shown in figure 3.

1.9. Using a vernier caliper or a metal ruler, the current distances H _{1_1} and H _{1_2} from the top surface of the washers to the top surface of the loading beam are measured. The measurement is shown in Figure 4.

Measurements are taken at both ends of the loading beam.

The actual value of the deflection under load D ₁ is determined by the formula:

1.10. The actual deflection value is recorded in the protocol.

The test object is considered to have passed the test if it meets the requirements specified at the (Error! Reference source not found) stage of the test program: without visually observed signs of destruction, it withstood the rated load for 5 minutes (maximum deformations are not higher than permissible).

The essence of stage No. 2 of the test program consists in loading the profiled sheet installed on the supporting cradles of the test equipment with a linearly distributed load of a given nominal value, monitoring its condition and deflection.

The tests are carried out immediately after the end of the tests according to stage 1.

Stage No. 2 of the test program is carried out as follows (by sub-stages)

2.1. At the ends of the loading beam, weights are additionally fixed, the total mass M _{2 of} which is determined by the formula:

where g = 9.81 m / s ² is the acceleration of gravity.

The actual weight of the goods is measured by means of scales and recorded in the protocol. The difference in the mass of weights installed at the ends of the loading beam should not exceed 5% of their total mass.

2.2. The stopwatch measures the shutter speed. During holding, every 10 minutes, the presence of a gap between the test object and the support bed of the loading beam and the absence of visible signs of destruction of the test object are monitored.

The test object is considered to have passed the test if it meets the requirements given for stage 2 of the test program: without visually observed signs of destruction, it withstood the maximum specified load for 60 minutes.

The essence of stage No. 3 of the test program consists in unloading a pre-loaded profiled sheet installed on the support cradles of the test rig and monitoring its residual deflection.

The tests are carried out immediately after the end of the tests according to stage 2.

Stage 3 of the test program is carried out as follows (by sub-stages):

3.1. The load simulator is removed from the test object. By rotating the support nuts, the loading beam is raised until it touches the test object with the support cradle.

3.2. Using a vernier caliper, the current distances H _{2_1} and H _{2_2} from the top surface of the washers to the top surface of the loading beam are measured. Measurements are taken at both ends of the loading beam. The actual value of the residual deflection D ₂ is determined by the formula:

The actual value of the residual deflection is recorded in the protocol.

The test object is considered to have passed the test if it meets the requirements given for stage 3 of the test program: permanent deformations do not exceed permissible.

The essence of stage 4 of testing consists in loading the profiled sheet installed on the support cradles of the test equipment with a linearly distributed press-type load until the specified deformations are achieved and its condition is monitored.

Stage 4 of the test program is methodologically related to stages 1–3; it is performed after stages 1–3 independently as follows (by sub-stages):

4.1. The test fixture is assembled in such a way that the profile of the support cradles corresponds to the profile of the test object, and the distance between the supports is closest to the specified value L ₃ .

4.2. Measure the actual distance between the supports with a tape measure between the inner edges of the support cradles on both sides of the test rig, record its arithmetic mean in the protocol.

4.3. Nuts and washers are installed on the guide pins, at a distance from the end, approximately 100 mm higher than the assumed value of the maximum deflection D _max3 .

4.4. The test object is placed on top of the test fixture support cradles so that its center is approximately midway between the test fixture support cradles. The free ends of the test object must protrude beyond the support cradles by at least 100 mm.

4.5. The loading beam is installed on the guide pins of the rig with the cradle down. Loading nuts are installed on the ends of the studs.

The appearance of the test fixture with the test object is shown in figure 5.

4.6. Using a caliper, the distance H _{0_1} and H _{0_2} is measured from the top surface of the washers to the bottom surface of the loading beam. The measurement is shown in Figure 6.

4.7. Synchronous rotation of the loading nuts gives the test object a given level of deformation. At the same time, the current values of H _{1_1} and H _{2_2} are periodically measured from the upper surface of the washers to the lower surface of the loading beam. The measurement is shown in Figure 7.

4.8. The current value of the deflection D ₃ is determined by the formula:

By adjusting the position of the loading nuts, the test object is provided with a given level of deformations.

4.9. The stopwatch measures the shutter speed. During holding, every 10 minutes, the presence of a gap between the test object and the support bed of the loading beam and the absence of visible signs of destruction of the test object are monitored.

The appearance of the test fixture during loading is shown in FIG. 8.

The test object is considered to have passed the test if it meets the requirements given for stage 4 of the test program: without visually observed signs of destruction, it withstood maximum deformation for 60 minutes.

Based on the results of the tests carried out at stages 1-3 and stage 4 of the test program, a conclusion is made about the serviceability of the profiled sheet and products based on it in the conditions of use for the intended purpose, for example, for a roof or a fence.

EXAMPLES OF IMPLEMENTATION OF A TECHNICAL SOLUTION

Example # 1

Profiled sheet made of PCM with a profile pitch of 250, the size of the lower flange 183, the upper flange 25 and the height of the profile 32, made of fiberglass based on plain weaving fabric made of E-glass with a thickness of 0.25 mm with laying layers (0 ° / 90 °, ± 45 °, ± 45 °, 0 ° / 90 °) and polyester binder, with a fabric content of 70%, the calculated modulus of elasticity of the material E = 22 MPa, composite thickness 1 mm, mounted on linear supports with a distance between the supports of 800 mm. The total sheet width is 1.076 m, the total length is 2 m. The vertical load transmitted to the sheet through the loading beam is 200 kg.

1.1 Preliminary calculation.

The calculation of the stress-strain state of the structure by the finite element method is performed. FIG. 9 shows the displacement field of the structure. The maximum calculated displacements in the area between the supports are 7 mm.

For a load increased by 50% of 300 kgf, the deflection in the central zone is 10.5 mm (Fig. 10).

The design margin for the stability of the wall at such a load is 21% (Fig. 11).

The safety margin of the material at 150% of the design load in the most loaded area is 38% (Fig. 12).

Thus, the calculation performed shows that the type of profiled sheet under consideration is suitable for use in structures with a pitch between supporting surfaces of no more than 800 mm, with an effective bending load of no more than 1962 N (200 kgf) and maximum displacements of no more than 1/100 span ( 8 mm) with a load margin of 1.5. A typical application of this profiled sheet can be the coating of enclosing structures with a step of reinforcing elements (frame racks) of no more than 800 mm, with a calculated value of a linearly applied load no more than 1962 N (200 kgf).

1.2 Testing.

Testing of this profiled sheet for bending under the action of a distributed load using the proposed equipment in stages No. 1-3 (load application by installing weights on the loading beam) is performed as follows.

1. The test equipment is assembled in such a way that the profile of the supporting cradles corresponds to the profile with a profile pitch of 250, the size of the lower flange 183, the upper flange 25 and the height of the profile 32, the distance between the supports is 800 mm.

2. The test object is placed on top of the test fixture support cradles so that its center is approximately halfway between the test fixture support cradles. In this case, the free ends of the test object protrude beyond the support cradles by approximately 600 mm.

3. The loading beam is installed on the guide pins of the rig with the cradle down.

4. Measuring nuts and washers are installed on the ends of the studs. Using a vernier caliper, the distance H _{0_1} and H _{0_2} from the top surface of the washers to the top surface of the loading beam is measured. The following values were measured: Н0_1 = 50 mm, Н0_2 = 45.5 mm.

5. The calculated total weight of the load is determined M1 = P _n2 / g = 1962 / 9.81 = 200 kg. A load simulator in the form of weights is attached to the ends of the loading beam. The actual measured weights are 99.5 and 100.2 kg. The total actual weight of the load simulator is 199.7 kg.

6. The stopwatch measures the exposure interval of 5 minutes.

7. Using a vernier caliper, the current distances H _{1_1} = 57.3 and H _{1_2} = 52 from the top surface of the washers to the top surface of the loading beam were measured.

8. The actual value of the maximum deflection under load was calculated by the formula: D ₁ = (H _{1_1} + H _{1_2} -H _{0_1} -H _{0_2} ) / 2 = (57.3 + 52-50-45.5) / 2 = 6.9 mm. The resulting value does not exceed 8 mm. Thus, the tested profiled sheet meets the requirements of stage 1 of the test program.

9. The total weight of the additional load is calculated by the formula M ₂ = 0.5 × P _n2 / g = 0.5 × 1962 / 9.81 = 100 kg. An additional load simulator in the form of weights is attached to the ends of the loading beam. The actual measured additional weights are 50.1 and 50.0 kg. The total actual weight of the additional load simulator is 100.1 kg. The total actual mass of the total load is thus 299.8 kg.

10. The stopwatch measures a shutter speed of 60 minutes.

11. There are no visually controlled signs of destruction of the profiled sheet. Thus, the tested profiled sheet meets the requirements of stage 2 of the test program.

12. The load simulator is removed from the test object.

13. Using a vernier caliper, the current distances H _{2_1} = 50.1 mm and H _{2_2} = 45.7 mm are measured from the upper surface of the washers to the upper surface of the loading beam.

14. The actual value of the residual deflection D ₂ is determined by the formula D ₂ = (H2_1 + H2_2-H0_1-H0_2) / 2 = (50.1 + 45.7-50.0-45.5) / 2 = 0.15 mm ...

15. The actual value of the residual deflection does not exceed 10% of the maximum allowable deflection. Thus, the profiled sheet is considered to have passed the test according to stage No. 3.

16. Since the tested profiled sheet meets the requirements of all 3 stages of the test program, it is recognized as suitable for use as a roof covering with a step of reinforcing elements (lathing) of no more than 1000 mm, with a calculated value of snow load of no more than 192 kg / m ² .

1.3. Testing of this profiled sheet for bending under the action of a distributed load using the proposed equipment according to stage 4 (application of a press load through a loading beam) is performed as follows.

1. The test fixture is assembled in such a way that the profile of the support cradles corresponds to the profile of the type with a profile pitch of 250, the size of the lower flange 183, the upper flange 25 and the height of the profile 32, the distance between the supports is 800 mm.

2. Install nuts and washers on the guide pins approximately 110 mm from the end.

3. The test object is placed on top of the test fixture support cradles so that its center is approximately halfway between the test fixture support cradles. The free ends of the test object protrude about 600 mm beyond the support cradles.

4. The loading beam is installed on the guide pins of the rig with the cradle down. Loading nuts are installed on the ends of the studs.

5. Using a vernier caliper, measure the distance H _{0_1} = 90.2 and H _{0_2} = 89.7 from the upper surface of the washers to the lower surface of the loading beam.

6. Synchronous rotation of the loading nuts gives the test object a given level of deformations. Upon reaching it, the measured values of the distances H _{1_1} and H _{2_2} from the upper surface of the washers to the lower surface of the loading beam are 82.5 and 81.6 mm, respectively.

7. The current value of the deflection D ₃ is determined by the formula D ₃ = (H _{0_1} + H _{0_2} -H _{1_1} -H _{1_2} ) / 2 = (90.2 + 89.7-82.5-81.6) / 2 = 7 , 9 mm.

8. The stopwatch measures a shutter speed of 60 minutes. There are no visual signs of destruction of the profiled sheet.

9. Thus, the tested sample of profiled sheet is suitable for use in structures, the calculated values of deformations in which with a span length of 800 mm correspond to the value of 1/100 span (no more than 8 mm).

Example No. 2

Profiled sheet with a profile pitch of 250, the size of the lower flange 183, the upper flange 25 and the height of the profile 32, is made of fiberglass on the basis of a chaotically reinforced glass mat made of E-glass with a thickness of 0.4 mm with layers laid in the 0 ° direction and a polyester binder containing fabric 60%, design modulus of elasticity of the material E = 22 MPa, composite thickness 1.6 mm, mounted on linear supports with a distance between supports 800 mm. The total width of the sheet is 1.076 m, the total length is 2 m. The calculated linearly distributed load on the sheet in the area between the supports is 4415 N (450 kgf).

2.1. Advance paynemt.

The calculation of the stress-strain state of the structure by the finite element method is performed. FIG. 13 shows the displacement field of the structure. The maximum calculated displacements in the area between the supports are 20.5 mm.

The safety margin of the material at the design load is 1.53 (Fig. 14).

For a load increased by another 50%, amounting to 6620 N (675 kgf), the maximum calculated displacements are 31.6 mm (Fig. 15). The design safety margin of the material at 150% design load is 2% (Fig. 16).

Thus, the calculation performed shows that the type of profiled sheet under consideration is suitable for use in structures with a step between the supporting surfaces of no more than 800 mm, with acting loads of no more than 450 kgf with unregulated maximum displacements with a safety factor of 1.5. A typical application of this profiled sheet can be a load-bearing wall with a step of reinforcing elements (struts) of no more than 800 mm, with a calculated value of a linearly applied load in the structure of no more than 450 kgf.

2.2. Testing.

Testing of this profiled sheet for bending under the action of a distributed load using the proposed equipment is performed as follows.

1. The test equipment is assembled in such a way that the profile of the supporting cradles corresponds to the profile with a profile pitch of 250, the size of the lower flange 183, the upper flange 25 and the height of the profile 32, the distance between the supports is 800 mm.

2. The test object is placed on top of the test fixture support cradles so that its center is approximately halfway between the test fixture support cradles. In this case, the free ends of the test object protrude beyond the support cradles by approximately 600 mm.

3. The loading beam is installed on the guide pins of the rig with the cradle down.

4. Measuring nuts and washers are installed on the ends of the studs. Using a vernier caliper, the distance H _{0_1} and H _{0_2} from the top surface of the washers to the top surface of the loading beam is measured. The following values were _measured : H _{0_1} = 50 mm, H0_2 = 45.5 mm.

5. The estimated total weight of the load is determined M ₁ = P _n2 / g = 4415 / 9.81 = 450 kg. A load simulator in the form of weights is attached to the ends of the loading beam. The actual measured weights are 223.5 and 227 kg. The total actual weight of the load simulator is 450.5 kg.

6. The stopwatch measures the exposure interval of 5 minutes.

7. Using a vernier caliper, the current distances H _{1_1} = 70.2 and H _{1_2} = 65.8 from the top surface of the washers to the top surface of the loading beam were measured.

8. The actual value of the maximum deflection under load was calculated according to the formula: D ₁ = (H _{1_1} + H _{1_2} -H _{0_1} -H _{0_2} ) / 2 = (70.2 + 65.8-50-45.5) / 2 = 20 , 25 mm. The resulting value does not exceed the calculated one. Thus, the tested professional sheet meets the requirements of stage 1 of the test program.

9. The total weight of the additional load is calculated according to the formula M ₂ = 0.5 × P _n2 / g = 0.5 × 4415 / 9.81 = 225 kg. An additional load simulator in the form of weights is attached to the ends of the loading beam. The actual measured weights of the additional weights are 112.7 and 113.0 kg. The total actual weight of the load simulator is 225.7 kg. The total actual mass of the total load is thus 676.2 kg.

10. The stopwatch measures a shutter speed of 60 minutes.

11. There are no visually controlled signs of destruction of the profiled sheet. Thus, the tested profiled sheet meets the requirements of stage 2 of the test program.

12. The load simulator is removed from the test object.

13. Using a vernier caliper, the current distances H _{2_1} = 51.3 mm and H _{2_2} = 46.2 mm are measured from the upper surface of the washers to the upper surface of the loading beam.

14. The actual value of the residual deflection D ₂ is determined by the formula D ₂ = (H _{2_1} + H _{2_2} -H _{0_1} -H _{0_2} ) / 2 = (51.3 + 46.2-50.0-45.5) / 2 = 1 mm.

15. The actual value of the residual deflection does not exceed 10% of the maximum calculated deflection. Thus, the profiled sheet is considered to have passed the test according to stage 3 of the test program.

16. Since the tested profiled sheet meets the requirements of all 3 stages of the test program, it is recognized as suitable for use as a load-bearing wall panel with a step of reinforcing elements (posts) of no more than 800 mm, with a calculated linear load of no more than 450 kgf.

2.3 Bending tests of this profiled sheet under the action of a distributed load using the proposed equipment according to stage 4 (application of a press load through the loading beam) is performed as follows.

1. The test equipment is assembled in such a way that the profile of the supporting cradles corresponds to the profile with a profile pitch of 250, the size of the lower flange 183, the upper flange 25 and the height of the profile 32, the distance between the supports is 800 mm.

2. Install nuts and washers on the guide pins approximately 110 mm from the end.

3. The test object is placed on top of the test fixture support cradles so that its center is approximately halfway between the test fixture support cradles. The free ends of the test object protrude about 600 mm beyond the support cradles.

4. The loading beam is installed on the guide pins of the rig with the cradle down. Loading nuts are installed on the ends of the studs.

5. Using a vernier caliper, measure the distance H _{0_1} = 90.2 and H _{0_2} = 89.7 from the upper surface of the washers to the lower surface of the loading beam.

6. Synchronous rotation of the loading nuts gives the test object a given level of deformations. Upon reaching its measured distance values H _{1_1} and _{2_2} H from the top surface to the bottom surface of washers urging beams are respectively 69.5 and 68.9 mm.

7. The current value of the deflection D ₃ is determined by the formula D ₃ = (H _{0_1} + H _{0_2} -H _{1_1} -H _{1_2} ) / 2 = (90.2 + 89.7-69.5-69.9) /2=20.25 mm.

8. The stopwatch measures a shutter speed of 60 minutes. There are no visual signs of destruction of the profiled sheet.

9. Thus, the tested sample of the profiled sheet is suitable for use in structures, the calculated values of deformations in which at a span length of 800 mm do not exceed 20 mm (1/40 span).

Claims (4)

1. A method for assessing the operational efficiency of a profiled sheet made of polymer composite materials, consisting in carrying out tests for three-point bending of a sheet sample with a load up to close to breaking load and deflection values and comparing these indicators with the corresponding calculated values, characterized in that the profiled sheet sample installed on support cradles of the test equipment, at the first stage of testing, load with a linearly distributed load of a given rating, transmitted through a loading beam and simulating an operational load for a given distance between the supports, and for a given time, the state of the sheet and its deflection are monitored, while it is considered that the sample has withstood check provided that there are no visually observed signs of destruction, and its maximum deformations / deflection under the action of the rated load for 5 minutes is not higher than the permissible design values, then at the second stage, the sample is additionally loaded with a linearly distributed load of a given rating, transmitted through the loading beam and simulating the maximum design value, under conditions of monitoring the condition of the profiled sheet and its deflection, while it is considered that the sample has passed the test provided that it has no visually observed signs of destruction withstood the maximum load for 60 minutes, then at the third stage, the loaded profiled sheet is unloaded and the state of its residual deflection is monitored, while it is considered that the sample has passed the test provided that its residual deformation / deflection does not exceed the permissible design values, based on the results of the tests carried out at three stages, it is concluded that the workability of the profiled sheet and products based on it during bending under the conditions of use for the intended purpose. 2. A method for assessing the performance of a profiled sheet made of polymer composite materials by determining the specified performance characteristics, which consists in carrying out bending tests of a sheet sample with a load up to close to breaking load and deflection values and comparing these indicators with the corresponding calculated values, characterized in that the profiled sheet sample , installed on the supporting cradles of the test equipment, is loaded with a linearly distributed press-type load simulating the operating load for a given distance between the supports until the specified deformations are achieved under conditions of monitoring its condition, while it is considered that the sample has passed the test provided that it is not visually of the observed signs of destruction withstood the maximum deformation / deflection for 60 minutes, according to the results of the test, it is concluded that the profiled sheet and products based on it are serviceable in bending under conditions of use according to intended purpose.

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