CN116086935A - Temperature shrinkage fracture strength testing method and device - Google Patents
Temperature shrinkage fracture strength testing method and device Download PDFInfo
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- CN116086935A CN116086935A CN202310371776.3A CN202310371776A CN116086935A CN 116086935 A CN116086935 A CN 116086935A CN 202310371776 A CN202310371776 A CN 202310371776A CN 116086935 A CN116086935 A CN 116086935A
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Abstract
The invention discloses a temperature shrinkage fracture strength testing method and a temperature shrinkage fracture strength testing device. Belongs to the technical field of material temperature shrinkage cracking performance test, and solves the problems of the defects and limitations of the traditional temperature stress test. The method comprises the following steps: s1, installing and debugging a test piece forming device, and preparing a material to be tested; s2, loading the prepared material to be tested into a test piece forming device for repeated rolling and flattening treatment; s3, demolding and curing to obtain a test piece; s4, sticking strain gauges on the outer sides of the limiting blocks on the two sides of the test piece; s5, connecting the strain gauge with a data acquisition system to obtain the micro-strain of the limiting block
And calculating the thermal shrinkage stress and the thermal shrinkage fracture strength. The invention can be used for testing the thermal shrinkage breaking strength of cement concrete, asphalt concrete and inorganic binder stable materials, and makes up for the stateBlank of internal experiment test method and test device; the test device is simple, the test piece is easy to form, and popularization and application are facilitated.
Description
Technical Field
The invention relates to the technical field of material thermal shrinkage cracking performance test, in particular to a thermal shrinkage breaking strength test method and a thermal shrinkage breaking strength test device.
Background
Thermal shrinkage cracking is one of the main damage causes of cement concrete, asphalt concrete and inorganic binder-stabilized materials in low-temperature areas. There is no standardized quantitative test and evaluation method in China, and the cracking temperature is usually calculated indirectly by adopting the temperature coefficient and the strength characteristic of the material.
At present, two methods for testing the thermal shrinkage cracking strength of cement concrete, asphalt concrete and inorganic binder stable materials exist abroad: constrained test piece temperature stress test (TSRST) and tube cracking test (ASTM C1581). The tubular cracking can be applied to the thermal shrinkage cracking test of cement concrete, but the problem of test piece molding is not applicable to asphalt concrete and inorganic binder stable materials; the temperature stress test of the constraint test piece can be applied to columnar test pieces formed by various materials, but the test piece is difficult to form, has very high requirements on test equipment, and mainly depends on import equipment at present.
The test device is simple, the test piece is easy to form, the test device and the test method are favorable for popularization, and the test method and the test device are used for testing the thermal shrinkage breaking strength of the stable materials of cement concrete, asphalt concrete and inorganic binders and improve the material performance evaluation.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a temperature shrinkage fracture strength testing method and a temperature shrinkage fracture strength testing device, and aims at: the method and the device for testing the temperature shrinkage breaking strength of the stable materials can be used for cement concrete, asphalt concrete and inorganic binder.
The technical scheme adopted by the invention is as follows:
a temperature shrinkage fracture strength testing method comprises the following steps:
s1, installing and debugging a testing device for a temperature stress constraint test and a matched test piece forming device, and preparing a material to be tested;
s2, loading the prepared material to be tested into a test piece forming device, enabling the height of the loaded material to be tested to be slightly higher than the height of a fence of the forming device, and after loading is completed, placing the whole test piece forming device under a rut wheel rolling machine for repeated rolling and flattening treatment;
s3, after the material to be tested in the test piece forming device reaches the demolding strength, demolding, curing to obtain a test piece required by a test, wherein the test piece is formed by embedding limiting blocks on two sides of the test piece;
s4, sticking strain gages on the outer sides of the limiting blocks on the two sides of the test piece, wherein in the process of sticking the strain gages, the strain gages are completely attached to the limiting blocks, and no gap is reserved between the strain gages and the limiting blocks;
s5, placing the test piece with the strain gauge adhered into a temperature control box, connecting the strain gauge with a data acquisition system through a data acquisition line, starting the temperature control box, controlling temperature change, setting target temperature, adjusting temperature rise and fall speed, and reading data on the data acquisition system to obtain micro-strain of the limiting block
And calculates thermal shrinkage stress +.>
When the test piece is damaged, that is, the thermal shrinkage stress reaches the maximum value, the stress is the thermal shrinkage fracture strength of the material to be tested>
。
Preferably, in the temperature change process, the limiting block restrains the thermal shrinkage deformation of the material to be measured and generates a stress concentration effect; the deformation of the limiting block in the temperature change process is collected through a data collection system; providing a temperature shrinkage stress calculation formula of the material to be tested corresponding to the testing device and the testing method, and taking the maximum stress value obtained according to the temperature-temperature shrinkage stress curve in the testing process as the temperature shrinkage breaking strength of the material to be tested; and designing a test piece forming device matched with the experimental method according to the temperature shrinkage fracture strength of the material to be tested.
Preferably, the limiting block adopts a temperature shrinkage coefficient lower than
The cross section of the limiting block is trapezoid, and the lower base angle of the trapezoid is a round angle; the thermal expansion coefficient of the limiting block is smaller than that of the material to be tested; embedding and extruding limiting blocks on two sides of a material to be tested in the molding process of a cement concrete, asphalt concrete or inorganic binder stable material test piece; in the cooling process, the temperature shrinkage deformation of the material to be detected is limited and the stress concentration effect is generated.
Preferably, after the material to be tested is molded and demoulded, the test piece is placed in a temperature control box; the temperature control box is internally provided with a ventilation loop which is used for keeping the temperature inside the temperature control box uniform, wherein the stable high temperature which can be achieved in the temperature control box is higher than 50 ℃, the stable low temperature which can be achieved is lower than-20 ℃, the cooling rate in the temperature control box is controllable; the strain gauges on two sides of the limiting block are connected to a data acquisition system, and the data acquisition system acquires the deformation of the limiting block and the temperature in the temperature control box in the cooling process; according to the formula (1), the thermal shrinkage stress of the material to be tested is calculated, a temperature-thermal shrinkage stress curve is displayed and recorded on a display screen of the testing device, and the maximum stress value is used as the thermal shrinkage breaking strength of the material.
Wherein:
representing the thermal shrinkage stress of the material to be measured; />
Representing the lateral microstrain of the confinement block, taking a negative value due to the compression of the material; />
Representing the Young's modulus of the limiting block; />
Representing the coefficient of thermal expansion of the confinement block; />
Representing the temperature difference; A. b, C the shape factor.
A thermal shrinkage fracture strength testing device, comprising: the strain gauge is used for collecting strain data of a material to be tested, the temperature control box is used for simulating an environment temperature state, the data collection system is used for reading the collected strain data, the strain gauge is adhered to limiting blocks on two sides of a test piece, the strain gauge is electrically connected with the data collection system through a wire, and the test piece is placed in the temperature control box.
A test piece forming device comprising: left side board, posterior lateral plate, intermediate barrier, restriction piece, bottom plate, right side board, preceding curb plate, left side board, posterior lateral plate, right side board, preceding curb plate are vertical to be installed on the bottom plate, left side board, posterior lateral plate, right side board, preceding curb plate connect gradually and form closed rail, the intermediate barrier is installed at the rail middle part, the intermediate barrier is parallel with left side board, right side board, the restriction piece with left side board, right side board, intermediate barrier can dismantle and be connected.
Preferably, grooves are formed in the inner sides of the left side plate and the right side plate, grooves are formed in two sides of the middle partition plate, and the limiting blocks are arranged in the grooves.
Preferably, the grooves on the inner sides of the left side plate and the right side plate and the grooves on the two sides of the middle partition plate are respectively positioned in the middle of the left side plate, the right side plate and the middle partition plate.
Preferably, the grooves on the inner sides of the left side plate and the right side plate and the grooves on the two sides of the middle partition plate are symmetrically arranged by the central axis of the middle partition plate.
Preferably, the groove is in a trapezoid table shape, the limiting block is in a trapezoid table shape, and the top shape of the limiting block is matched with the shape of the groove.
In summary, the beneficial effects of the invention are as follows:
the temperature shrinkage breaking strength testing method and the temperature shrinkage breaking strength testing device can be used for testing the temperature shrinkage breaking strength of cement concrete, asphalt concrete and inorganic binder stable materials, and make up for the blank of the domestic experimental testing method and the testing device; compared with the foreign testing method, the testing device is simple, the test piece is easy to mold, and popularization and application are facilitated.
Drawings
The invention will now be described by way of example and with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram of a molding situation of a test piece molding device according to the present invention;
FIG. 2 is a schematic diagram of a limiting block structure in a second embodiment of the present invention;
FIG. 3 is a schematic view of a test piece with strain gauge attached;
FIG. 4 is a schematic diagram of the overall structure of the testing device of the present invention;
FIG. 5 is a schematic diagram of a control system of the testing device according to the present invention
FIG. 6 is a graph of temperature versus thermal shrinkage stress for the test procedure;
FIG. 7 is a schematic view showing the overall structure of a test piece molding device according to the present invention;
FIG. 8 is a schematic view showing the structure of the specimen molding device of the present invention after the restriction block is removed;
FIG. 9 is a schematic view of the structure of the specimen molding device of the present invention with the restriction block and the middle partition removed;
FIG. 10 is a schematic view showing the structure of the specimen molding device of the present invention after the limiting block and the front side plate are removed;
FIG. 11 is a diagram showing stress distribution of a finite element test material according to the present invention;
FIG. 12 is a schematic diagram of a finite element analysis confinement block side strain distribution according to the present invention;
icon: 1-left side plate, 2-rear side plate, 3-test piece, 4-middle partition plate, 5-limiting block, 6-bottom plate, 7-right side plate, 8-front side plate, 9-connecting component, 10-bottom plate mounting hole, 11-strain gauge, 12-temperature control box and 13-data acquisition system.
Description of the embodiments
For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to be within the scope of the present application.
In the description of the embodiments of the present application, it should be noted that, directions or positional relationships indicated by terms such as "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., are directions or positional relationships based on those shown in the drawings, or those that are conventionally put in use of the inventive product, are merely for convenience of description and simplicity of description, and are not indicative or implying that the apparatus or element to be referred to must have a specific direction, be configured and operated in a specific direction, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
The present invention is described in detail below with reference to fig. 1-12.
Example 1
A temperature shrinkage fracture strength testing method comprises the following steps:
s1, installing and debugging a testing device for a temperature stress constraint test and a matched test piece forming device, and preparing a material to be tested;
s2, loading the prepared material to be tested into a test piece forming device, enabling the height of the loaded material to be tested to be slightly higher than the height of a fence of the forming device, and after loading is completed, placing the whole test piece forming device under a rut wheel rolling machine for repeated rolling and flattening treatment;
s3, after the material to be tested in the test piece forming device reaches the demolding strength, demolding, curing to obtain a test piece 3 required by a test, wherein the test piece 3 is formed to be tested material with two sides embedded with limiting blocks 5;
s4, sticking strain gauges 11 on the outer sides of the limiting blocks 5 on the two sides of the test piece 3, wherein in the process of sticking the strain gauges 11, the strain gauges 11 are completely attached to the limiting blocks 5, and no gap is reserved between the strain gauges 11 and the limiting blocks 5;
s5, placing the test piece 3 with the attached strain gauge 11 into a temperature control box 12, connecting the strain gauge 11 with a data acquisition system 13 through a data acquisition line, starting the temperature control box 12, controlling temperature change, setting target temperature, adjusting temperature rise and fall speed, and reading data on the data acquisition system 13 to obtain the micro strain of the limiting block 5
And calculates thermal shrinkage stress +.>
When the test piece 3 breaks due to temperature reduction, namely, when the thermal shrinkage stress reaches the maximum value, the stress is the thermal shrinkage breaking strength +.>
。
In the temperature change process, the limiting block 5 restrains the thermal shrinkage deformation of the material to be tested and generates a stress concentration effect; the deformation of the limiting block 5 in the temperature change process is acquired through the data acquisition system 13; providing a temperature shrinkage stress calculation formula of the material to be tested corresponding to the testing device and the testing method, and taking the maximum stress value obtained according to the temperature-temperature shrinkage stress curve in the testing process as the temperature shrinkage breaking strength of the material to be tested; and designing a test piece forming device matched with the experimental method according to the temperature shrinkage fracture strength of the material to be tested.
The limiting block 5 adopts a temperature shrinkage coefficient lower than
The cross section of the limiting block 5 is trapezoid, and the lower bottom corner of the trapezoid is a round corner; the thermal expansion coefficient of the limiting block 5 is smaller than that of the material to be tested; in the process of molding a cement concrete, asphalt concrete or inorganic binder stable material test piece, embedding and extruding limiting blocks 5 on two sides of a material to be tested; in the cooling process, the limiting speed 5 restrains the thermal shrinkage deformation of the material to be tested and generates a stress concentration effect.
After the material to be tested is molded and demoulded, placing the test piece 3 into a temperature control box 12; the stable high temperature which can be achieved in the temperature control box 12 is higher than 50 ℃, the stable low temperature which can be achieved is lower than-20 ℃, the cooling rate in the temperature control box 12 is controllable, a ventilation loop is arranged in the temperature control box 12, and the ventilation loop is used for keeping the temperature in the temperature control box 12 uniform; the strain gauges 11 on two sides of the limiting block 5 are connected to a data acquisition system 13, and the data acquisition system 13 acquires the deformation of the limiting block 5 and the temperature in the temperature control box 12 in the cooling process at the same time; according to formula (1), calculating the thermal shrinkage stress of the material to be measured
Displaying and recording a temperature-thermal shrinkage stress curve on a display screen of the testing device, wherein the maximum value of the thermal shrinkage stress of the material to be tested is taken as the thermal shrinkage breaking strength of the material to be tested>
Calculating the thermal shrinkage fracture strength of the material to be tested according to the formula (2)>
The formulas (1), (2) are as follows:
wherein:
a, B, C-shape factor.
A thermal shrinkage fracture strength testing device, comprising: the strain gauge 11 is used for collecting strain data of a material to be tested, the temperature control box 12 is used for simulating an environment temperature state, the data collection system 13 is used for reading the collected strain data, the strain gauge 11 is adhered to the limiting blocks 5 on two sides of the test piece 3, the strain gauge 11 is electrically connected with the data collection system 13 through a wire, and the test piece 3 is placed in the temperature control box 12.
The test piece forming device includes: left side board 1, posterior lateral plate 2, intermediate baffle 4, restriction piece 5, bottom plate 6, right side board 7, preceding curb plate 8, left side board 1, posterior lateral plate 2, right side board 7, preceding curb plate 8 are vertical to be installed on bottom plate 6, left side board 1, posterior lateral plate 2, right side board 7, preceding curb plate 8 connect gradually and form closed rail, intermediate baffle 4 installs at the rail middle part, intermediate baffle 4 is parallel with left side board 1, right side board 7, restriction piece 5 with left side board 1, right side board 7, intermediate baffle 4 can dismantle the connection. The inner sides of the left side plate 1 and the right side plate 7 are provided with grooves, the two sides of the middle partition plate 4 are provided with grooves, and the limiting blocks 5 are arranged in the grooves. Grooves on the inner sides of the left side plate 1 and the right side plate 7 and grooves on the two sides of the middle partition plate 4 are respectively positioned in the middle of the left side plate 1, the right side plate 7 and the middle partition plate 4. Grooves on the inner sides of the left side plate 1 and the right side plate 7 and grooves on two sides of the middle partition plate 4 are symmetrically arranged on the central axis of the middle partition plate 4.
Referring to fig. 7, 8, 9, 10, the test piece forming device of the present invention is installed as follows:
the bottom plate 6 is horizontally placed, the left baffle plate 1, the middle baffle plate 4 and the right baffle plate 7 with grooves are respectively fixed on the bottom plate 6 by three screws penetrating through the bottom plate mounting holes 10, the screws are not required to be screwed, and a small-amplitude adjustment margin is reserved; the front baffle plate 8 and the rear baffle plate 2 are respectively fixed on the bottom plate 6 by three screws penetrating through corresponding bottom plate mounting holes 10, at the moment, the screws are not required to be screwed, the relative positions of the panels are slightly adjusted, the front baffle plate 8 is respectively connected with the three left baffle plates 1, the middle baffle plates 4 and the right baffle plates 7 with grooves by two connecting components 9, and the connecting components 9 can be screws; the tailgate 2 is also mounted on the floor 6 in the same manner; all screws are screwed, and limiting blocks 5 corresponding to the grooves of the left baffle plate 1, the middle baffle plate 4 and the right baffle plate 7 are arranged on the side surfaces of the left baffle plate and the right baffle plate, and the limiting blocks 5 are preferably invar steel blocks.
As shown in fig. 1, the mixed material to be tested is put into the whole device, is put under a rut wheel mill for rolling and flattening, and is demoulded after the material to be tested in the test piece forming device reaches the demoulding strength, so as to obtain two test pieces 3 with the same size and embedded with a limiting block 5.
As shown in fig. 3, one strain gage 11 is attached to each of the outer sides of the left and right side restriction blocks 5 of the obtained test piece 3.
As shown in fig. 4, the test piece 3 with the strain gauge 11 attached thereto is placed in a temperature control box 12, and a data acquisition system 13 is connected thereto. The test piece is placed in the temperature control box 12, the target temperature is set, the temperature change is controlled, the temperature control box 12 is started, and the real-time strain data is read through the data acquisition system 13.
As shown in fig. 11 and 12, when the temperature decreases, the material to be measured and the limiting block 5 shrink simultaneously, but since the thermal shrinkage coefficient of the limiting block 5 is lower than that of the material to be measured, the thermal shrinkage deformation of the limiting block 5 is smaller than that of the material to be measured, thereby playing a role in limiting the thermal shrinkage deformation of the material to be measured, and since the shape of the limiting block 5 is specially designed, the stress concentration effect is induced, the stress distribution on the side surface of the limiting block 5 is uniform, and through simulation calculation and experimental verification, the functional relationship of the temperature stress along with the micro strain on the side surface of the limiting block, the young modulus of the limiting block, the thermal expansion coefficient of the limiting block and the temperature difference is obtained, and the functional relationship is shown in formula (1).
As shown in FIG. 5, by sticking strain gauges 11 on the outer sides of two limiting blocks 5 of a test piece 3, placing the strain gauges 11 in an environment box 12, connecting the strain gauges 11 to a data acquisition system 13, starting the environment box 12, setting a target temperature, adjusting a temperature change rate, performing a temperature stress constraint test, and obtaining micro-strain on the side surfaces of the limiting blocks 5 in real time according to the test
And maximum microstrain->
Calculating the corresponding temperature stress in real time>
And the thermal shrinkage breaking strength when the material to be tested is broken>
。
And (3) rolling and flattening the mixed test materials loaded into the matched test piece forming device through a rut wheel rolling instrument, and demolding after the strength is formed, so as to prepare the test piece 3 required by the temperature stress constraint test.
In order to coordinate the non-parallel two sides of the test piece 3 caused by errors in the manufacturing process of the test piece 3, each baffle of the test piece forming device can be adjusted in a small amplitude in the mounting process. Three baffles with trapezoidal grooves are respectively connected with the bottom plate 6 through three screws and are respectively connected with the front baffle 8 and the rear baffle 2 through two screws.
Example two
A temperature shrinkage fracture strength testing method comprises the following steps:
s1, assembling a test piece forming device matched with a temperature stress constraint test device, and preparing a material to be tested;
s2, loading the prepared material to be tested into a test piece forming device, enabling the height of the loaded material to be tested to be slightly higher than the height of a fence of the forming device, and after loading is completed, placing the whole test piece forming device under a rut wheel rolling machine for repeated rolling and flattening treatment;
s3, after the material to be tested in the test piece forming device reaches the demolding strength, demolding, curing to obtain a test piece 3 required by a test, wherein the test piece 3 is a formed material to be tested, the two sides of which are embedded with limiting blocks 5, and the formed material to be tested has the following size: 300mm×140mm×50mm, wherein the shape of the limiting block 5 is a test piece 3 of a trapezoid limiting block 5;
s4, embedding limiting blocks 5 on two sides of the test piece 3 after demolding in S3, adhering strain gauges 11 on the outer sides of the limiting blocks 5, and enabling the strain gauges 11 to be completely adhered to the limiting blocks 5 in the process of adhering the strain gauges 11, wherein gaps cannot be left between the strain gauges 11 and the limiting blocks 5;
s5, placing the test piece 3 with the strain gauge 11 adhered in a temperature control box 12, connecting the strain gauge 11 to a data acquisition system 13, starting the temperature control box 12, controlling temperature change, setting target temperature, adjusting temperature rise and fall rate, and reading data on the data acquisition system 13 to obtain the micro strain of the limiting block 5
And calculates thermal shrinkage stress +.>
When the test piece 3 breaks, i.e. the thermal shrinkage stress reaches the maximum value, the stress is the thermal shrinkage breaking strength +.>
。
In the temperature change process, the limiting block 5 restrains the thermal shrinkage deformation of the material to be tested and generates a stress concentration effect; the deformation of the limiting block 5 in the temperature change process is acquired through the data acquisition system 13; providing a temperature shrinkage stress calculation formula of the material to be tested corresponding to the testing device and the testing method, and taking the maximum stress value obtained according to the temperature-temperature shrinkage stress curve in the testing process as the temperature shrinkage breaking strength of the material to be tested; and designing a test piece forming device matched with the experimental method according to the temperature shrinkage fracture strength of the material to be tested.
The limiting block 5 adopts a temperature shrinkage coefficient lower than
The cross section of the limiting block 5 is trapezoid, and the lower bottom corner of the trapezoid is a round corner; the thermal expansion coefficient of the limiting block 5 is smaller than that of the material to be tested; the preparation material of the limiting block 5 in the embodiment adopts invar, and the limiting block 5 is embedded and extruded on two sides of the material to be tested in the molding process of the cement concrete, asphalt concrete or inorganic binder stable material test piece; in the cooling process, the limiting speed 5 restrains the thermal shrinkage deformation of the material to be tested and generates a stress concentration effect.
After the material to be tested is molded and demoulded, placing the test piece 3 into a temperature control box 12; the stable high temperature which can be achieved in the temperature control box 12 is higher than 50 ℃, the stable low temperature which can be achieved is lower than-20 ℃, the cooling rate in the temperature control box 12 is controllable, a ventilation loop is arranged in the temperature control box 12, and the ventilation loop is used for keeping the temperature in the temperature control box 12 uniform; the strain gauges 11 on two sides of the limiting block 5 are connected to a data acquisition system 13, and the data acquisition system 13 acquires the deformation of the limiting block 5 and the temperature in the temperature control box 12 in the cooling process at the same time; according to formula (1), calculating the thermal shrinkage stress of the material to be measured
Displaying and recording a temperature-thermal shrinkage stress curve on a display screen of the testing device, wherein the maximum value of the thermal shrinkage stress of the material to be tested is used as the material to be testedMeasuring the thermal shrinkage breaking strength of the material>
Calculating the thermal shrinkage fracture strength of the material to be tested according to the formula (2)>
The formulas (1), (2) are as follows:
wherein:
a, B, C-form factor, when the size and shape of the molding material to be measured and the restriction block 5 are set as in the present embodiment, i.e., the size of the molding material to be measured is: 300mm×140mm×50mm, and the shape of the molded material to be measured is shown in fig. 1 and 3, and when the size and shape of the limiting block 5 are shown in fig. 2, the values of the shape coefficients a, B, and C are a= 0.007943, respectively; b= -0.00791; c= 0.051058.
A thermal shrinkage fracture strength testing device, comprising: the strain gauge 11 is used for collecting strain data of a material to be tested, the temperature control box 12 is used for simulating an environment temperature state, the data collection system 13 is used for reading the collected strain data, the strain gauge 11 is adhered to the limiting blocks 5 on two sides of the test piece 3, the strain gauge 11 is electrically connected with the data collection system 13 through a wire, and the test piece 3 is placed in the temperature control box 12.
The test piece forming device includes: left side board 1, posterior lateral plate 2, intermediate baffle 4, restriction piece 5, bottom plate 6, right side board 7, preceding curb plate 8, left side board 1, posterior lateral plate 2, right side board 7, preceding curb plate 8 are vertical to be installed on bottom plate 6, left side board 1, posterior lateral plate 2, right side board 7, preceding curb plate 8 connect gradually and form closed rail, intermediate baffle 4 installs at the rail middle part, intermediate baffle 4 is parallel with left side board 1, right side board 7, restriction piece 5 with left side board 1, right side board 7, intermediate baffle 4 can dismantle the connection. The inner sides of the left side plate 1 and the right side plate 7 are provided with grooves, the two sides of the middle partition plate 4 are provided with grooves, and the limiting blocks 5 are arranged in the grooves. Grooves on the inner sides of the left side plate 1 and the right side plate 7 and grooves on the two sides of the middle partition plate 4 are respectively positioned in the middle of the left side plate 1, the right side plate 7 and the middle partition plate 4. Grooves on the inner sides of the left side plate 1 and the right side plate 7 and grooves on two sides of the middle partition plate 4 are symmetrically arranged on the central axis of the middle partition plate 4. The recess is trapezoidal form, restriction piece 5 is trapezoidal form, the top shape of restriction piece 5 with recess shape adaptation installation.
Referring to fig. 7, 8, 9, 10, the test piece forming device of the present invention is installed as follows:
the bottom plate 6 is horizontally placed, the left baffle plate 1, the middle baffle plate 4 and the right baffle plate 7 with the trapezoid grooves are respectively fixed on the bottom plate 6 by three screws penetrating through the bottom plate mounting holes 10, the screws are not required to be screwed, and a small-amplitude adjustment margin is reserved; the front baffle plate 8 and the rear baffle plate 2 are respectively fixed on the bottom plate 6 by three screws penetrating through corresponding bottom plate mounting holes 10, at the moment, the screws are not required to be screwed, the relative positions of the panels are slightly adjusted, the front baffle plate 8 is respectively connected with the three left baffle plates 1, the middle baffle plates 4 and the right baffle plates 7 with trapezoid grooves by two connecting components 9, and the connecting components 9 can be screws; the tailgate 2 is also mounted on the floor 6 in the same manner; all screws are screwed, and limiting blocks 5 corresponding to the grooves of the left baffle plate 1, the middle baffle plate 4 and the right baffle plate 7 are arranged on the side surfaces of the left baffle plate and the right baffle plate, and the limiting blocks 5 are preferably invar steel blocks.
As shown in fig. 1, the mixed material to be tested is put into the whole device, is put under a rut wheel mill for rolling and flattening, and is demoulded after the material to be tested in the test piece forming device reaches the demoulding strength, so as to obtain two test pieces 3 with the same size and embedded with a limiting block 5.
As shown in fig. 3, one strain gage 11 is attached to each of the outer sides of the left and right side restriction blocks 5 of the obtained test piece 3.
As shown in fig. 4, the test piece 3 with the strain gauge 11 attached thereto is placed in a temperature control box 12, and a data acquisition system 13 is connected thereto. The test piece is placed in the temperature control box 12, the target temperature is set, the temperature change is controlled, the temperature control box 12 is started, and the real-time strain data is read through the data acquisition system 13.
As shown in fig. 11 and 12, when the temperature decreases, the material to be measured and the limiting block 5 shrink simultaneously, but since the thermal shrinkage coefficient of the limiting block 5 is lower than that of the material to be measured, the thermal shrinkage deformation of the limiting block 5 is smaller than that of the material to be measured, thereby playing a role in limiting the thermal shrinkage deformation of the material to be measured, and since the shape of the limiting block 5 is specially designed, the stress concentration effect is induced, the stress distribution on the side surface of the limiting block 5 is uniform, and through simulation calculation and experimental verification, the functional relationship of the temperature stress along with the micro strain on the side surface of the limiting block, the young modulus of the limiting block, the thermal expansion coefficient of the limiting block and the temperature difference is obtained, and the functional relationship is shown in formula (1).
As shown in FIG. 5, by sticking strain gauges 11 on the outer sides of two limiting blocks 5 of a test piece 3, placing the strain gauges 11 in an environment box 12, connecting the strain gauges 11 to a data acquisition system 13, starting the environment box 12, setting a target temperature, adjusting a temperature change rate, performing a temperature stress constraint test, and obtaining micro-strain on the side surfaces of the limiting blocks 5 in real time according to the test
And maximum microstrain->
Calculating the corresponding temperature stress in real time>
And the thermal shrinkage breaking strength when the material to be tested is broken>
。
And (3) rolling and flattening the mixed test materials loaded into the matched test piece forming device through a rut wheel rolling instrument, and demolding after the strength is formed, so as to prepare the test piece 3 required by the temperature stress constraint test.
In order to coordinate the non-parallel two sides of the test piece 3 caused by errors in the manufacturing process of the test piece 3, each baffle of the test piece forming device can be adjusted in a small amplitude in the mounting process. Three baffles with trapezoidal grooves are respectively connected with the bottom plate 6 through three screws and are respectively connected with the front baffle 8 and the rear baffle 2 through two screws.
The foregoing examples merely represent specific embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that, for those skilled in the art, several variations and modifications can be made without departing from the technical solution of the present application, which fall within the protection scope of the present application.
Claims (10)
1. The temperature shrinkage fracture strength testing method is characterized by comprising the following steps of:
s1, installing and debugging a testing device for a temperature stress constraint test and a matched test piece forming device, and preparing a material to be tested;
s2, loading the prepared material to be tested into a test piece forming device, enabling the height of the loaded material to be tested to be slightly higher than the height of a fence of the forming device, and after loading is completed, placing the whole test piece forming device under a rut wheel rolling machine for repeated rolling and flattening treatment;
s3, after the material to be tested in the test piece forming device reaches the demolding strength, demolding, curing to obtain a test piece (3) required by a test, wherein the test piece (3) is formed by embedding limiting blocks (5) on two sides;
s4, sticking strain gauges (11) on the outer sides of the limiting blocks (5) on the two sides of the test piece (3), and enabling the strain gauges (11) to be completely attached to the limiting blocks (5) in the process of sticking the strain gauges (11), wherein gaps are not reserved between the strain gauges (11) and the limiting blocks (5);
s5, placing the test piece (3) with the strain gauge (11) adhered into a temperature control box (12), connecting the strain gauge (11) with a data acquisition system (13) through a data acquisition line, starting the temperature control box (12), controlling temperature change, setting target temperature, adjusting temperature rise and fall rate, and reading data on the data acquisition system (13) to obtain the micro strain of the limiting block (5)
And calculates thermal shrinkage stress +.>
When the test piece (3) is broken due to temperature reduction, namely, the thermal shrinkage stress reaches the maximum value, the stress is the thermal shrinkage breaking strength of the material to be tested>
。
2. The method for testing the thermal shrinkage fracture strength according to claim 1, wherein the method comprises the following steps: in the temperature change process, the limiting block (5) is used for limiting the thermal shrinkage deformation of the material to be tested and generating a stress concentration effect; the deformation of the limiting block (5) in the temperature change process is collected through a data collection system (13); providing a temperature shrinkage stress calculation formula of the material to be tested corresponding to the testing device and the testing method, and taking the maximum stress value obtained according to the temperature-temperature shrinkage stress curve in the testing process as the temperature shrinkage breaking strength of the material to be tested; and designing a test piece forming device matched with the experimental method according to the temperature shrinkage fracture strength of the material to be tested.
3. A method for testing thermal shrinkage fracture strength according to claim 1, wherein the limiting block (5) has a thermal shrinkage coefficient lower than that of
The cross section of the limiting block (5) is trapezoid, and the lower bottom corner of the trapezoid is a round corner; the thermal expansion coefficient of the limiting block (5) is smaller than that of the material to be tested; in the process of molding a cement concrete, asphalt concrete or inorganic binder stable material test piece, embedding and extruding limiting blocks (5) on two sides of a material to be tested; in the cooling process, the fast limiting (5) restricts the thermal shrinkage deformation of the material to be measured and generates a stress concentration effect.
4. The method for testing the thermal shrinkage fracture strength according to claim 1, wherein after the material to be tested is molded and demolded, the test piece (3) is placed in a temperature control box (12); the stable high temperature which can be achieved in the temperature control box (12) is higher than 50 ℃, the stable low temperature which can be achieved is lower than-20 ℃, the cooling rate in the temperature control box (12) is controllable, a ventilation loop is arranged in the temperature control box (12), and the ventilation loop is used for keeping the temperature in the temperature control box (12) uniform; the strain gauges (11) on two sides of the limiting block (5) are connected to a data acquisition system (13), and the data acquisition system (13) acquires the deformation of the limiting block (5) and the temperature in a temperature control box (12) in the cooling process at the same time; calculating the thermal shrinkage stress of the material to be tested according to a formula (1), displaying and recording a temperature-thermal shrinkage stress curve on a display screen of a testing device, and taking the maximum value of the thermal shrinkage stress of the material to be tested as the thermal shrinkage breaking strength of the material to be tested, wherein the formula (1) is as follows:
wherein:
representing the thermal shrinkage stress of the material to be measured; />
Representing lateral microstrain of the confinement block (5), taking a negative value due to the compression of the material; />
Represents the Young's modulus of the limiting block (5); />
Representing the coefficient of thermal expansion of the confinement block (5); />
Representing the temperature difference; A. b, C the shape factor. />
5. A thermal shrinkage fracture strength testing device, comprising: strain gauge (11), control by temperature change case (12), data acquisition system (13), strain gauge (11) are used for gathering the strain data of material that awaits measuring, control by temperature change case (12) are used for simulating ambient temperature state, data acquisition system (13) are used for reading the strain data of gathering, strain gauge (11) paste on limiting block (5) of test piece (3) both sides, strain gauge (11) are connected with data acquisition system (13) electricity through the wire, and test piece (3) are placed in control by temperature change case (12).
6. A test piece forming device, comprising: left side board (1), posterior lateral plate (2), intermediate baffle (4), restriction piece (5), bottom plate (6), right side board (7), preceding curb plate (8), left side board (1), posterior lateral plate (2), right side board (7), preceding curb plate (8) are vertical to be installed on bottom plate (6), left side board (1), posterior lateral plate (2), right side board (7), preceding curb plate (8) connect gradually and form closed rail, intermediate baffle (4) are installed at the rail middle part, intermediate baffle (4) are parallel with left side board (1), right side board (7), restriction piece (5) with left side board (1), right side board (7), intermediate baffle (4) can dismantle and be connected.
7. The test piece forming device according to claim 6, wherein grooves are formed in the inner sides of the left side plate (1) and the right side plate (7), grooves are formed in both sides of the middle partition plate (4), and the limiting blocks (5) are installed in the grooves.
8. The test piece forming device according to claim 7, wherein the grooves on the inner sides of the left side plate (1) and the right side plate (7) and the grooves on the two sides of the middle partition plate (4) are respectively positioned in the middle of the left side plate (1), the right side plate (7) and the middle partition plate (4).
9. The test piece forming device according to claim 7, wherein grooves on the inner sides of the left side plate (1) and the right side plate (7) and grooves on the two sides of the middle partition plate (4) are symmetrically arranged with the central axis of the middle partition plate (4).
10. A test piece forming device according to any one of claims 6-9, wherein the recess is in the shape of a trapezoidal table, the restriction block (5) is in the shape of a trapezoidal table, and the top shape of the restriction block (5) is fitted to the shape of the recess.
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