Young modulus measuring device

Abstract

The utility model provides a Young modulus measuring device which comprises a base provided with a fixed support and a movable support which are vertically arranged on the base. The measuring mechanism comprises an upper chuck, a lower chuck, a working platform and a weight adjusting assembly; the light-emitting mechanism comprises a laser, a first plane mirror, a second plane mirror and a third plane mirror, the laser is arranged on a movable support, and the third plane mirror is arranged on the working platform and located on the same horizontal line with the laser; and the scale is arranged right above the laser and is perpendicular to the working platform, and the light beams emitted by the laser are projected to the scale after being reflected. The low-power laser is adopted, the optical path of the low-power laser is visible in real time, visual observation with naked eyes is achieved, and the low-power laser can also be used for detecting whether the optical lever device is horizontal or not; the utility model also provides a multi-stage optical lever amplification system to improve the maximum amplification factor of the optical lever system.

Description

Technical Field

[0001] The utility model belongs to the technical field of measuring tools and relates to a device for measuring Young's modulus. Background Art

[0002] Young's modulus is a physical quantity that characterizes the tensile or compressive properties of a material within the elastic limit. It is the elastic modulus along the longitudinal direction and is also a term in material mechanics. It is a physical quantity that characterizes the properties of a material and depends only on the physical properties of the material itself. The magnitude of Young's modulus indicates the rigidity of the material. The larger the Young's modulus, the less likely the material is to deform. Taking a metal wire with a length of L and a cross-sectional area of S as an example, when the metal wire is stretched by ΔL under the action of a force F, the force F / S per unit cross-sectional area is called stress, and the elongation ΔL / L corresponding to the unit length is called strain. According to Hooke's law, within the elastic deformation range, the stress is proportional to the strain, and we can obtain:

[0003] #timg# （1）

[0004] Substitute the cross-sectional area calculation formula of the material into formula (1) to obtain:

[0005] #timg# （2）

[0006] Y in formulas (1) and (2) is Young's modulus.

[0007] In the experimental teaching of measuring Young's modulus, the optical lever amplification method is generally used. The optical lever amplification method is an experimental method based on the principle of optical path reflection to amplify small deformation quantities. Its principle is simple and easy to operate, and the effect is clear and easy to observe. Therefore, it is widely used in experiments that require measuring small deformation quantities. The experimental device for measuring Young's modulus by the optical lever amplification method is as Figure 1 shown. Generally, it can be divided into two parts: a stretching device and an optical lever device. Among them, in the stretching device part, a metal wire to be measured is fixed by two chucks. A weight carrier is connected below the metal wire. Loading weights on the weight carrier can apply a certain tensile force to the metal wire, causing corresponding small deformations of the metal wire. The experiment of measuring Young's modulus by the optical lever method has been included in teaching for decades. However, the experimental device and experimental reference content of the traditional optical lever method for measuring Young's modulus have not changed for many years. Therefore, some problems have gradually emerged, such as:

[0008] 1. It is difficult to read the scale of the ruler with a telescope. When looking for the image of the ruler on the plane mirror in the telescope, the movement of the field of view is opposite to the habit in direction. When the telescope is adjusted upward, the image of the ruler moves downward, and when the telescope is adjusted downward, the image of the ruler moves upward. If the image of the ruler does not appear in the field of view at the beginning, it usually takes a lot of time to find the image of the ruler.

[0009] 2. The experimental device occupies a large space. In the traditional optical lever method, in order to obtain a large magnification, the distance between the plane mirror and the scale needs to be as large as possible, which makes the floor area of a single set of experimental devices too large, and the number of experimental devices that can be placed in a standard experimental classroom is relatively small, reducing the students' practical operation opportunities to a certain extent.

[0010] 3. The magnification cannot be adjusted flexibly, and the measurement range of Young's modulus is small. The maximum magnification of the traditional optical lever method is relatively low, and the measurement range is limited by the experimental environment, and materials with a large Young's modulus cannot be measured. Summary of the Utility Model

[0011] The purpose of the present utility model is to provide a new type of Young's modulus measuring device in view of the deficiencies of the existing Young's modulus measuring devices, cancel the setting of the telescope, and add a multi-stage optical lever amplification system to effectively solve the deficiencies of the existing technology.

[0012] The present utility model adopts the following technical solutions:

[0013] A Young's modulus measuring device, comprising:

[0014] A base, on which a fixed bracket and a movable bracket perpendicular to the base are provided;

[0015] A measuring mechanism, including an upper chuck, a lower chuck, a working platform and a weight adjusting component, wherein the upper chuck is fixedly arranged on the fixed bracket, the working platform is arranged below the upper chuck, the lower chuck is arranged on the working platform, the upper chuck and the lower chuck are used for clamping the ends of the metal wire to be measured, and the lower chuck is connected to the weight adjusting component;

[0016] A light emitting mechanism, including a laser and a third plane mirror, wherein the laser is arranged on the movable bracket, and the third plane mirror is arranged on the working platform and is on the same horizontal line as the laser;

[0017] A scale, which is arranged directly above the laser and is perpendicular to the working platform in direction, and the light beam emitted by the laser is reflected by the third plane mirror and then projected onto the scale.

[0018] Further, the light emitting mechanism further includes a first plane mirror and a second plane mirror, the first plane mirror is arranged directly above the laser, and the second plane mirror is arranged directly above the third plane mirror.

[0019] Further, both the first plane mirror and the scale are detachably connected to the movable bracket, and the second plane mirror is detachably connected to the fixed bracket.

[0020] Further, the laser, the first plane mirror, the second plane mirror, and the third plane mirror constitute a multi-stage optical lever amplification system.

[0021] Further, the weight adjustment assembly includes a weight tray and weights placed in the weight tray.

[0022] Further, a plurality of feet are provided below the base, and the height of the feet is adjusted by screws.

[0023] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0024] The present utility model does not use a telescope in the traditional experimental device, but uses a low-power laser. The laser can be observed by the naked eye, and its optical path is also visible in real time. Therefore, it is very easy to adjust the process of the laser of the laser passing through the plane mirror of the optical lever and being reflected onto the scale. In addition, the laser can also be used to detect whether the optical lever device is level. Remove the laser and place it flat on the base, measure the distance from the light spot irradiated on the third plane mirror in the distance to the tabletop, change the orientation of the laser and repeat the above process until it is equal in all directions. At this time, it can be considered that the instrument is in a relatively ideal horizontal state.

[0025] The present utility model also sets up a multi-stage optical lever amplification system, that is, a detachable plane mirror and a detachable scale are provided on the bracket. By combining the positions of the plane mirror and the scale, a multi-stage optical lever amplification system can be built according to the experimental needs, which can not only increase the maximum amplification factor of the optical lever system, but also reduce the floor area of the experimental instrument to a certain extent. Description of the Drawings

[0026] Figure 1 It is an experimental device for measuring Young's modulus by the traditional optical lever amplification method.

[0027] Figure 2 It is a schematic structural diagram of the Young's modulus measuring device of the present utility model.

[0028] Figure 3 It is a schematic principle diagram of the adjustable multi-stage amplification system in the present utility model, where A is the optical path diagram and B is the equivalent optical path diagram.

[0029] Markings in the figure: 1. Base; 1-1. Fixed bracket; 1-2. Movable bracket; 2. Measuring mechanism; 2-1. Upper chuck; 2-2. Lower chuck; 2-3. Working platform; 2-4. Weight adjustment assembly; 3. Light-emitting mechanism; 3-1. Laser; 3-2. First plane mirror; 3-3. Second plane mirror; 3-4. Third plane mirror; 4. Scale. Detailed Embodiment

[0030] The following further describes the present utility model with reference to the accompanying drawings.

[0031] As Figure 2 shown, the present utility model provides a device for measuring Young's modulus, including a base 1. A fixed bracket 1-1 and a movable bracket 1-2 perpendicular to the base 1 are provided on the base 1. A plurality of feet are provided under the base 1, and the height of the feet is adjusted by screws. The number of feet is 3 in this embodiment;

[0032] A measuring mechanism 2, including an upper chuck 2-1, a lower chuck 2-2, a working platform 2-3 and a weight adjustment component 2-4. The upper chuck 2-1 is fixedly arranged on the fixed bracket 1-1. The working platform 2-3 is arranged below the upper chuck 2-1. The lower chuck 2-2 is arranged on the working platform 2-3. The upper chuck 2-1 and the lower chuck 2-2 are used to clamp the ends of the metal wire to be measured. The lower chuck 2-2 is connected to the weight adjustment component 2-4, specifically including a weight tray and weights placed in the weight tray;

[0033] A light emitting mechanism 3, including a low-power laser 3-1, a first plane mirror 3-2, a second plane mirror 3-3 and a third plane mirror 3-4. The laser 3-1 is arranged on the movable bracket 1-2. The third plane mirror 3-4 is arranged on the working platform 2-3 and is on the same horizontal line as the laser 3-1. The first plane mirror 3-2 is arranged directly above the laser 3-1 and is detachably connected to the movable bracket 1-2. The second plane mirror 3-3 is arranged directly above the third plane mirror 3-4 and is detachably connected to the fixed bracket 1-1;

[0034] A scale 4, the scale 4 is arranged directly above the first plane mirror 3-2 and the direction is perpendicular to the working platform 2-3. The light beam emitted by the laser 3-1 is projected onto the scale 4;

[0035] The laser 3-1, the first plane mirror 3-2, the second plane mirror 3-3 and the third plane mirror 3-4 constitute a multi-stage optical lever amplification system. As Figure 3 shown in A, after geometric analysis of the multi-stage optical lever amplification system (three stages in this embodiment), its optical path diagram is drawn. The distance D between the two brackets and the length b of the optical lever arm are measured. When the metal wire is stretched by force, the distance that the foot tip of the optical lever moves down is ΔL, and the angle that the normal line of the center of the optical lever plane mirror moves up is θ. The angles that the laser is deflected on the optical lever plane mirror and on the two vertical plane mirrors are 2θ and 4θ respectively. When both θ and 2θ are very small, it can be approximately considered that θ = tanθ and 2θ = tan(2θ). From this, it can be obtained that:

[0036] #timg# （3）

[0037] The optical path with three horizontal distances of D after two reflections is equivalent to an optical path with a horizontal distance of 3D, as shown in Figure 3 Figure B; from Figure 3 Figure B, we can obtain

[0038] #timg# （4）

[0039] By combining Equation (3) and Equation (4), we have

[0040] #timg# （5）

[0041] In Equation (5), 6D / b is the magnification of the three-stage optical lever. By measuring the distance Δx that the laser moves on the scale before and after adding the weights, the small deformation amount ΔL generated by the metal wire under force can be obtained. Compared with the traditional optical lever method, when D remains unchanged, its magnification is 3 times that of the traditional optical lever method. To obtain the same magnification as the traditional optical lever method, the floor area of the experimental instrument can be reduced by more than half. According to different experimental requirements, such as measuring the Young's modulus of different metal wires, one, two, three, or even more stages of optical levers can be freely built by increasing or decreasing the number of plane mirrors and adjusting the bracket spacing to obtain a more appropriate magnification. In this embodiment, the three-stage is only an illustrative example.

[0042] When the utility model is in use, it includes the following steps:

[0043] Coarse adjustment of the instrument: After fixing the metal wire to be measured with the upper chuck 2-1 and the lower chuck 2-2, use the laser 3-1 for adjustment to ensure that the Young's modulus measuring device is horizontal. Use the laser 3-1 for adjustment. Place the laser 3-1 flat on the working platform 2-3 and turn on the switch. Place a light blocking plate at a certain distance from the base 1, measure the distance from the light spot irradiated on the light blocking plate to the horizontal plane where the instrument is placed, change the orientation of the laser 3-1 and repeat the above process, and adjust the screws on the three feet of the base 1 until they are equal in all directions to ensure the horizontal of the experimental device.

[0044] Build an optical lever amplification system: Adjust the relative positions of the laser 3-1, the third plane mirror 3-4, and the scale 4. Clamp the laser 3-1 onto the movable vertical rod, turn on the switch of the laser 3-1 so that the laser can irradiate on the third plane mirror 3-4, and then clamp the first plane mirror 3-2, the second plane mirror 3-3, and the scale 4 onto the movable bracket 1-2 and the fixed bracket 1-1 respectively, so that the laser can irradiate on the scale 4 after two-stage reflection.

[0045] Record the initial reading: After the laser 3-1, the plane mirror, and the scale 4 are adjusted in place, record the initial position of the laser on the scale 4.

[0046] Loading weights: Gradually add weights of the same mass to the weight tray. After each addition, record the new position of the laser on scale 4. If the laser shines outside the plane mirror, adjust the position of the plane mirror and continue the measurement.

[0047] Recording the readings after adding weights: After all the weights are placed, record the final position of the laser on scale 4.

[0048] Unloading weights: After all the weights are placed on the weight tray, remove the weights one by one and record the position of the laser on scale 4 each time. Calculate the average value of the same set of data when adding and unloading weights, and take the average value as the measured value of the reading of scale 4.

[0049] Measuring physical quantities: Use a steel tape measure to measure the length L of the metal wire, the distance D between the movable vertical rod and the fixed vertical rod, and the optical lever arm length b three times. Use a micrometer to measure the diameter d of the metal wire at three different positions, and take the average value of each set of data as the measured value.

[0050] Data analysis and processing: Analyze the experimental data using the least squares method and the graphical method, calculate the Young's modulus of the metal wire, analyze the possible errors in the experiment and calculate the uncertainty value.

Claims

1. A Young's modulus measuring device, characterized in that: include: A base (1), wherein the base (1) is provided with a fixed bracket (1-1) and a movable bracket (1-2) vertically standing on the base (1); The measuring mechanism (2) comprises an upper clamp (2-1), a lower clamp (2-2), a working platform (2-3) and a weight adjustment component (2-4), wherein the upper clamp (2-1) is fixedly arranged on a fixed bracket (1-1), the working platform (2-3) is arranged below the upper clamp (2-1), and the lower clamp (2-2) is arranged on the working platform (2-3); the upper clamp (2-1) and the lower clamp (2-2) are used to clamp the end of the metal wire to be measured, and the lower clamp (2-2) is connected to the weight adjustment component (2-4); A light emitting mechanism (3) comprising a laser (3-1) and a third plane mirror (3-4), wherein the laser (3-1) is arranged on a movable support (1-2), and the third plane mirror (3-4) is arranged on the working platform (2-3) and is on the same horizontal line as the laser (3-1); A ruler (4) is arranged directly above the laser (3-1) and in a direction perpendicular to the working platform (2-3); a light beam emitted by the laser (3-1) is reflected by a third plane mirror (3-4) and then projected onto the ruler (4).

2. The Young's modulus measuring device according to claim 1, characterized in that: The light-emitting mechanism (3) further comprises a first plane mirror (3-2) and a second plane mirror (3-3), wherein the first plane mirror (3-2) is arranged directly above the laser (3-1), and the second plane mirror (3-3) is arranged directly above the third plane mirror (3-4).

3. The Young's modulus measuring device according to claim 2, characterized in that: The first plane mirror (3-2) and the scale (4) are both detachably connected to the movable bracket (1-2).

4. The Young's modulus measuring device according to claim 2, characterized in that: The second plane mirror (3-3) is detachably connected to the fixing bracket (1-1).

5. The Young's modulus measuring device according to claim 2, characterized in that: The laser (3-1), the first plane mirror (3-2), the second plane mirror (3-3) and the third plane mirror (3-4) constitute a multi-stage optical lever amplification system.

6. The Young's modulus measuring device according to claim 1, characterized in that: The weight adjustment component (2-4) comprises a weight holder and a weight placed in the weight holder.

7. The Young's modulus measuring device according to claim 1, characterized in that: A plurality of feet are arranged below the base (1), and the height of the feet can be adjusted by screws.

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