CN108806422A - A kind of statics synthesis experiment platform and experimental method - Google Patents

Abstract

A statics comprehensive experimental platform and an experimental method, the experimental platform includes a bench with a chute, a plane frame structure and a plane three-hinge arch structure installed at the front and rear ends of the bench, and a loading column with an adjustable position in the middle of the bench , a horizontal bar with adjustable position and capable of moving up and down is set on the loading column, and a pulley is set at the end of the horizontal bar; the connection between the plane frame structure and the bench can be fixed and hinged at both ends or fixed at one end and hinged at the other. In the way of movable hinge at one end, the rod materials of the planar frame structure and the planar three-hinge arch structure can be made of materials with different elastic moduli. The influence of the transmissibility on the restraint force and internal force in different structures, the loading device with adjustable position, height and orientation can not only conveniently load the plane frame and three-hinged arch, but also independently complete the friction coefficient measurement experiment.

Description

A kind of statics comprehensive experiment platform and experiment method

technical field

The invention relates to the field of mechanics experiments, in particular to a statics comprehensive experiment platform and an experiment method.

Background technique

Most of the existing experimental platforms for basic mechanics are aimed at the knowledge points in the course of material mechanics. The experimental platforms for the relevant knowledge points in the course of theoretical mechanics are limited, and the experimental items are outdated. There is a lack of a comprehensive experimental platform to support students to combine the knowledge points in the theoretical mechanics and mechanics of materials courses, carry out comprehensive experiments, and further understand the applicability of mechanical models and related principles.

Contents of the invention

In order to overcome the above-mentioned problems, the object of the present invention is to propose a statics comprehensive experiment platform and experimental method to realize plane static indeterminate, hyperstatically indeterminate structural constraint force, internal force measurement and friction coefficient measurement. Experiments include statically indeterminate and hyperstatically indeterminate mechanical models composed of rods with different elastic moduli, and are loaded at different points to compare the influence of force transferability on statically indeterminate and hyperstatically indeterminate structural constraints and internal forces. The application conditions and influence laws of force transferability, the loading device can independently measure the friction coefficient, and verify the Euler friction formula. This comprehensive experiment has positive and important significance for strengthening the cultivation of students' comprehensive practical ability, stimulating students' in-depth understanding of the transferable nature, the difference between statically determinate and hyperstatically indeterminate models, and static sliding friction.

In order to achieve the above object, the technical solution of the present invention is achieved in that:

A statics comprehensive experiment platform, comprising a bench 1 with a chute, a planar three-hinge arch structure 2 and a planar frame structure 3 are respectively installed at the front and rear ends of the bench 1, and a position-adjustable loading device is installed in the middle of the bench 1. Column 4, the loading column 4 is provided with an adjustable horizontal bar 5 that can move up and down on the loading column 4, and the end of the horizontal bar 5 is provided with a pulley 6; the plane three-hinge arch structure 2 and the plane frame structure 3 are both There are two loading points, preferably both loading points are on the vertical bars of the plane three-hinge arch structure 2 and the plane frame structure 3, and must be located on the same horizontal line; the plane three-hinge arch structure 2 and the plane frame structure 3 are also provided with There are strain gauges attached to the strain gauge to measure the strain in the member when loaded at two loading points.

The rods of the planar frame structure 3 and the planar three-hinged arch structure 2 can be replaced with rods with the same cross-sectional shape and size and different elastic modulus.

The pulley 6 uses a movable pulley in the plane frame and three-hinge arch loading tests, and uses a static pulley in the friction test.

The plane frame structure 3 is connected to the platform 1 by fixed hinges at both ends to form a statically indeterminate structure, or one end is fixedly hinged and the other end is movable to form a statically indeterminate structure. The shape and size of the structures are exactly the same under the two connection methods.

The planar three-hinge arch structure 2 is a statically determinate three-hinge arch formed by two right-angled rods hinged through hinges 11 .

The experimental method of described statics comprehensive experiment platform,

Connect the two ends of the planar frame structure 3 to the stand 1 through fixed hinge supports to form a statically indeterminate structure, adjust the orientation of the pulley 6 so that the plane where the radius of the pulley is located is coplanar with the planar frame structure 3, and one end of the cable is tied to the planar frame On the loading point of structure 3, the other end straddles the pulley 6 to hang the weight, respectively loads in the horizontal direction on the two loading points on the vertical rod of the plane frame structure 3, and measures the strain of the rod at different loading positions through the strain gauge , the signal of the strain gauge is connected to the strain tester placed next to the experimental device, and the wiring is based on the output characteristics of the Wheatstone bridge and the internal force test principle to test the axial force and bending moment of the rod. The test results reflect the force in the statically indeterminate structure The effect of translation along its line of action on the constraint force and internal force; replace the fixed hinge support at one end of the planar frame structure 3 with a movable hinge support, and the planar frame structure 3 becomes a statically determinate structure. Load, measure strain, and calculate constraint force and internal force; the measurement results reflect the influence of force translation along the line of action on the statically determinate structure on the constraint force and internal force.

For the plane three-hinge arch structure 2, the fixed hinge support is used to install it on the platform 1 to form a plane statically indeterminate structure. The planes of the arch structure 2 are coplanar, and the weights are suspended by flexible cables across the pulleys. Loads of the same magnitude are sequentially loaded horizontally on the two loading points on the vertical rods of the planar three-hinge arch structure 2, and different loads are measured by strain gauges. The strain at the loading position, the signal of the strain gauge is connected to the strain gauge placed next to the experimental device, the wiring is based on the output characteristics of the Wheatstone bridge and the internal force test principle, and the axial force and bending moment of the rod are tested. The measurement results reflect the force along the The influence of the line of action on the binding force at 11 hinges and the internal force at the location of the strain gauge before and after the sliding of the line of action; change the material of the two right-angle rods, measure the binding force and internal force under the same loading conditions, and compare the statically determinate three-hinge arch of different materials Constraint force and internal force under the same external load;

In the plane frame and three-hinge arch loading experiments, the pulley 6 uses a movable pulley, and the weight of the weight suspended by the flexible cable is the size of the horizontal load. In addition to horizontal loading, the pulley is replaced with a static pulley, and a flexible cable is straddled on the pulley. A weight is hung on one end of the flexible cable, and the other end is pulled by a force-measuring spring. By comparing the weight of the weight with the tension measured by the force-measuring spring, the friction coefficient between the flexible cable and the static pulley is calculated according to the Euler friction formula.

The statics comprehensive experiment platform of the present invention can carry out the constraint force measurement and internal force measurement experiments of plane statically indeterminate structures and hyperstatically indeterminate structures of different constraints and different materials, and the friction coefficient measurement experiment can be set up by using static pulleys on the loading device. During the experiment, the students independently design the experiment according to the experiment task book, which can measure the change of the constraint force before and after the force slides along the line of action and the change of the internal force of the rod, observe the effect of the force before and after the slide, and also change the constraint type for comparison. The effect of the same force on the statically determinate structure and the super-statically indeterminate structure, replace the static pulley with different roughness, measure the coefficient of static sliding friction, and verify the Euler friction formula. The invention has the advantages of replaceable rod material, replaceable restraint type, replaceable loading position, simple and compact structure, convenient operation and the like. The experimental projects that can be set up are positive and important for strengthening the cultivation of students' comprehensive practical ability, stimulating students' in-depth understanding of transmissible inferences, understanding the impact of loads on statically determinate and hyperstatically indeterminate structures, static sliding friction and friction coefficient measurement methods, etc. meaning.

Description of drawings

Fig. 1 is a front view of the present invention.

Figure 2 is a front view of the frame structure.

Figure 3 is a front view of the three-hinged arch.

Detailed ways

The structural principle and working principle of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Fig. 1, Fig. 2 and Fig. 3, a kind of static comprehensive experiment platform comprises a bench 1 with a chute, a plane three-hinge arch structure 2 is installed in the front of the bench 1, and a plane frame structure 3 is installed in the back. The loading column 4 is installed in the middle part of the frame 1, and the horizontal bar 5 that can move up and down on the loading column 4 is installed on the loading column 4. The end of the horizontal bar 5 is equipped with a pulley 6, and the horizontal bar 5 is adjustable in position. Adjust the orientation of the pulley 6, so that The plane where the radius of the pulley is located is coplanar with the plane frame structure 3, one end of the flexible cable is tied to the loading point of the plane frame structure 3, and the other end straddles the pulley 6 to hang the weight, and the plane frame structure 3D point is pasted with a plane frame strain gauge 14, the plane There are two loading points on the frame structure 3, and the sliding loading column 4 is loaded sequentially on the two loading points 7 and 8 on the vertical bar of the plane frame structure 3 respectively, and the loading points 7 and 8 are on the same horizontal line, changing the level The orientation of the bar 5 is such that the plane where the radius of the pulley is located is coplanar with the plane where the plane three-hinge arch structure 2 is located, and the weight is suspended across the pulley by flexible cables, and two loading points 9 and 9 are placed on the vertical bar of the plane three-hinge arch structure 2 10 is loaded sequentially, the loading points 9 and 10 are on the same horizontal line, the plane three-hinge arch strain gauge 15 is pasted on point E of the right bar of the plane three-hinge arch structure 2, and the pulley 6 in the loading device can be a movable pulley or a static pulley. The movable pulley is used in the three-hinge arch and plane frame loading experiments, and the static pulley is used in the friction coefficient measurement experiment.

The planar frame structure 3 and the platform 1 can be connected by a fixed hinge support and a movable hinge support, and can also be connected by two fixed hinge supports, so as to realize two structures of static determination and ultra-static indetermination. The planar frame structure 3 and the The materials of the planar three-hinge arch structure 2 can be replaced. Materials with different elastic moduli are used to compare the influence of the elastic modulus of the materials on the experimental results. The pulley 6 can use static pulleys with different surface roughness. By hanging weights, different materials can be measured. coefficient of static sliding friction.

The experimental method of statics comprehensive experiment platform of the present invention is:

According to the self-designed and confirmed plan, the two ends of the plane frame structure 3 are connected to the stand 1 through fixed hinge supports to form a super static structure, and the orientation of the pulley 6 is adjusted so that the plane where the radius of the pulley is located is the same as that of the plane frame structure 3. On the surface, one end of the flexible cable is tied to the loading point of the plane frame structure 3, and the other end straddles the pulley 6 to hang the weight, respectively loads in the horizontal direction on the two loading points 7 and 8, and measures the different loads through the plane frame strain gauge 14 The strain of the rod at point D, the signal of the plane frame strain gauge 14 at point D is connected to the strain tester placed next to the experimental device, and is connected according to the output characteristics of the Wheatstone bridge and the internal force test principle, and the axis of the rod is tested. Force and bending moment, the test results reflect the influence of force translation along its line of action on the restraint force and internal force in the statically indeterminate structure; the fixed hinge support at one end of the planar frame structure 3 is replaced with a movable hinge support, and the planar The frame structure 3 becomes a statically indeterminate structure, which is loaded horizontally at two loading points 7 and 8 respectively, and the strain at point D is measured to calculate the restraint force and internal force. and internal influence.

For the plane three-hinge arch structure 2, the fixed hinge support is used to install it on the platform 1 to form a plane statically indeterminate structure. The planes of the arch structure 2 are in the same plane, and the weights are suspended by flexible cables across the pulleys, and the two loading points 9 and 10 on the vertical rods of the planar three-hinge arch structure 2 are sequentially loaded with the same magnitude of load along the horizontal direction. The three-hinge arch strain gauge 15 measures the strain at point E at different loading positions, and the signal of the plane three-hinge arch strain gauge 15 at point E is connected to the strain gauge placed next to the experimental device, and the wiring is based on the output characteristics of the Wheatstone bridge and the internal force test principle , to test the axial force and bending moment of the rod, and the measurement results reflect the influence of the force on the constraint force at hinge 11 and the internal force at E before and after the force slides along the line of action. The material of the two right-angled rods was replaced, and the binding force and internal force were measured under the same loading conditions, and the binding force and internal force of the statically determinate three-hinged arch of different materials were compared under the same external load.

The loading device used in this test bench, in the plane frame and three-hinge arch loading experiments, the pulley 6 uses a movable pulley, and the weight of the weight suspended by the flexible cable is the size of the horizontal load. In addition to horizontal loading, the pulley is replaced with a static pulley. A flexible cable is straddled on the static pulley, and a weight is hung on one end of the flexible cable. The weight is G, and the other end is pulled by a force-measuring spring. The obtained pulling force is F, the wrapping angle of the cable on the pulley is β, and the weight G, the reading F of the force-measuring spring, and the wrapping angle β of the cable on the pulley are brought into the Euler friction formula F=Ge ^uβ , the static sliding friction coefficient u between the cable and the static pulley is calculated.

Claims (6)

1. a statics comprehensive experiment platform, is characterized in that, comprises the bench (1) of band chute, and planar three-hinge arch structure (2) and plane frame structure (3) are respectively installed at the front and rear ends of bench (1) ), the middle part of the stand (1) is equipped with a position-adjustable loading column (4), and the loading column (4) is provided with an adjustable horizontal rod (5) that can move up and down on the loading column (4), The end of the horizontal bar (5) is provided with a pulley (6); the plane three-hinge arch structure (2) and the plane frame structure (3) both have two loading points, and when the two loading points are in the plane three-hinge arch structure (2) and the vertical bar of the plane frame structure (3), must be located on the same horizontal line; Strain gauges for the member strain when loaded at a loading point. 2. A static comprehensive experiment platform according to claim 1, characterized in that: the rods of the plane frame structure (3) and the plane three-hinge arch structure (2) can be replaced by materials with the same cross-sectional shape and size Members with different moduli of elasticity. 3. A static comprehensive experiment platform according to claim 1, characterized in that: the pulley (6) adopts a movable pulley in the plane frame and three-hinge arch loading experiments, and adopts a static pulley in the friction experiment. 4. A kind of static comprehensive experiment platform according to claim 1, it is characterized in that: the connection mode of described plane frame structure (3) and stand (1) adopts two ends to be fixedly hinged to form super statically indeterminate structure, or One end is fixedly hinged and the other end is movable hinged to form a statically determinate structure. The shape and size of the structure are exactly the same under the two connection methods. 5. A kind of static comprehensive experiment platform according to claim 1, characterized in that: the plane three-hinge arch structure (2) is a statically definite three-hinge formed by two right-angled rods hinged by hinges (11) arch. 6. the experimental method of the statics comprehensive experiment platform described in any one of claim 1 to 5, it is characterized in that: Connect the two ends of the planar frame structure (3) to the stand (1) through fixed hinge supports to form a statically indeterminate structure, adjust the orientation of the pulley (6) so that the plane where the radius of the pulley is located is coplanar with the planar frame structure (3) , one end of the flexible cable is tied to the loading point of the plane frame structure (3), and the other end straddles the pulley (6) to hang the weight, respectively, on the two loading points on the vertical rod of the plane frame structure (3) along the horizontal direction Loading, measure the strain of the rod at different loading positions through the strain gauge, the signal of the strain gauge is connected to the strain tester placed next to the experimental device, and the connection is made according to the output characteristics of the Wheatstone bridge and the internal force test principle to test the axial force of the rod and bending moment, the test results reflect the influence of force translation along its line of action on the constraint force and internal force in the statically indeterminate structure; the fixed hinge support at one end of the planar frame structure (3) is replaced with a movable hinge support, The planar frame structure (3) becomes a statically indeterminate structure, and the two loading points are loaded horizontally, the strain is measured, and the restraint force and internal force are calculated. The measurement results reflect the influence of force translation along the action line on the statically indeterminate structure on the restraint force and internal force. For the plane three-hinge arch structure (2), a fixed hinge support is used to install it on the platform (1) to form a plane statically indeterminate structure. Two right-angle bars are hinged together to change the orientation of the horizontal bar (5), so that the radius The plane where it is located is coplanar with the plane where the planar three-hinge arch structure (2) is located, and the weight is suspended by flexible cables across the pulleys, and the two loading points on the vertical rod of the planar three-hinge arch structure (2) are sequentially loaded along the horizontal direction For the same load, measure the strain at different loading positions through the strain gauge. The signal of the strain gauge is connected to the strain gauge placed next to the experimental device, and the connection is made according to the output characteristics of the Wheatstone bridge and the internal force test principle to test the axial force of the rod. and bending moment, the measurement results reflect the influence of the force on the restraint force at the hinge (11) before and after sliding along the action line and the influence of the internal force at the strain gauge; Internal force measurement, comparing the restraining force and internal force of statically determinate three-hinged arches of different materials under the same external load; In the plane frame and three-hinge arch loading experiments, the pulley (6) uses a movable pulley, and the weight of the weight suspended by the flexible cable is the size of the horizontal load. In addition to horizontal loading, the pulley is replaced with a static pulley, and a flexible A weight is hung on one end of the flexible cable, and the other end is pulled by a force-measuring spring. Comparing the weight of the weight with the tension measured by the force-measuring spring, the coefficient of friction between the flexible cable and the static pulley is calculated.