Portable simple photoelastic mechanics instrument for teaching

Abstract

The invention belongs to the technical field of mechanics teaching aids, and particularly discloses a portable simple photoelastic mechanics instrument for teaching, which comprises a photoelastic sample, and also comprises a sample mounting bracket, the upper end of the photoelastic sample is connected with the sample mounting bracket, and the front end and the rear end of the sample mounting bracket are through; the lever loading assembly is connected with the lower end of the photoelastic sample and is used for applying a load to the photoelastic sample; the polaroid assemblies are arranged on the front side and the rear side of the sample mounting bracket; the light source assembly is arranged on the outer side of the polaroid assembly and provides a light source. The white light source is used, so that the weight and the size of the instrument can be effectively reduced, the instrument is convenient to carry, lever loading is applied, loading visualization and visualization are achieved, light and dark stripes on the photoelastic sample are alternately arranged, small elastic deformation can be visually displayed, elastic deformation display visualization is achieved, cost is low, operation is easy and convenient, and popularization is facilitated.

Description

Technical Field

[0001] This invention relates to the field of teaching aids for mechanics, and in particular to a portable and simple photoelasticity mechanics instrument for teaching. Background Technology

[0002] In the teaching of "Mechanics of Materials", photoelasticity apparatus is often used to demonstrate the elastic deformation of structural components. Although existing photoelasticity apparatus can accurately demonstrate the elastic deformation of elastic components such as plexiglass and show the stress distribution inside the component, there are still certain limitations when applying photoelasticity apparatus to the teaching of courses such as mechanics of materials. The specific limitations are as follows: (1) Traditional photoelasticity instruments are large in size, inconvenient to carry, and cumbersome to operate. Traditional photoelasticity instruments mostly use a combination of point light source + lens group + polarization and analysis module, which is large in size and inconvenient to carry; and in actual use, the lens group is cumbersome to operate, and it is very easy to cause lens defocus due to improper operation, which makes it impossible to obtain a high-quality parallel white light source, thus affecting the imaging quality.

[0003] (2) The loading method of traditional photoelasticity apparatus is not intuitive. In terms of loading, traditional photoelasticity apparatus often uses a combination of screw and nut to load structural components. When using this loading mode in the teaching process, its intuitiveness is poor, and it is difficult for students to establish an intuitive impression of mechanical loading in the experiment.

[0004] (3) Traditional photoelasticity instruments are expensive. The point light source and lens group in traditional photoelasticity instruments are difficult to process and have high costs, which is not conducive to their promotion. Summary of the Invention

[0005] In view of this, in order to solve the problems of the large size and cumbersome operation of existing traditional photoelasticity instruments, and to meet the requirements of being portable, easy to operate, and suitable for classroom teaching, the present invention proposes a portable and simple photoelasticity instrument for teaching.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A portable, simple photoelasticity apparatus for teaching purposes includes a photoelastic sample and further includes: A sample mounting bracket is provided, wherein the upper end of the photoelastic sample is connected to the sample mounting bracket, and the sample mounting bracket is through-type at both ends. A lever loading assembly is connected to the lower end of the photoelastic sample to apply a load to the photoelastic sample. A polarizer assembly is disposed on both the front and rear sides of the sample mounting bracket; A light source assembly is disposed outside the polarizer assembly to provide a light source.

[0007] As a further improvement to the above technical solution: An optimized version of the above technical solution is that the polarizer assembly includes a vertical linear polarizer disposed at the front end of the sample mounting bracket and a horizontal linear polarizer disposed at the rear end of the sample mounting bracket.

[0008] An optimized version of the above technical solution is that the light source assembly is located outside the horizontal linear polarizer.

[0009] An optimized version of the above technical solution is that the light source component is an LED flat panel lamp.

[0010] An optimized version of the above technical solution is that the photoelastic sample is L-shaped.

[0011] An optimized version of the above technical solution is that the photoelastic sample is made of transparent plexiglass.

[0012] An optimized version of the above technical solution is that the upper end of the photoelastic sample is suspended from the sample mounting bracket by a traction rope, and the lower end of the photoelastic sample is fixedly connected to the lever loading assembly by a traction rope.

[0013] An optimized version of the above technical solution is that the lever loading assembly includes a loading lever and a loading weight. One end of the loading lever passes through the sample mounting bracket from left to right and is rotatably mounted on the sample mounting bracket. The other end of the loading lever is provided with a loading weight at its lower end. The middle of the loading lever is connected to the photoelastic sample.

[0014] Compared with existing technologies, the beneficial effects of this invention are: This invention uses an LED flat panel lamp as a white light source, which can effectively reduce the weight and size of the instrument, making it easy to carry. By using lever loading, the loading is made intuitive and visual. The alternating light and dark stripes on the photoelastic sample can intuitively show the small elastic deformation of the structural components, thus making the elastic deformation display more intuitive. The overall processing is simple, the cost is low, and the operation is easy, which is conducive to its promotion. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the overall exploded structure of the present invention; Figure 3 Bright and dark fringe patterns under a photoelastic apparatus when a sample mounting bracket is subjected to tensile load; Figure 4 A schematic diagram of the bright and dark fringes under a photoelastic apparatus when a specimen mounting bracket (L-shaped specimen) is subjected to tensile load; Figure 5A schematic diagram of the bright and dark fringes under a photoelastic apparatus when a specimen mounting bracket (an L-shaped specimen with a 45° filler angle) is subjected to tensile load. Figure 6 A schematic diagram of the bright and dark fringes under a photoelastic apparatus when a support (L-shaped specimen with rounded chamfers) is subjected to tensile load.

[0016] In the figure: 1. Sample mounting bracket; 2. Vertical linear polarizer; 3. Horizontal linear polarizer; 4. LED plane lamp; 5. Photoelastic sample; 6. Traction rope; 7. Loading lever; 8. Loading weight. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] This technical solution optimizes the force loading method and simplifies the light source while ensuring the most basic imaging function of the photoelasticity instrument, so as to make the loading more intuitive and the instrument more portable. By utilizing mature commercial flat panel lights instead of the point light source + lens combination, the instrument achieves miniaturization, lightweighting, portability, and low cost. The lever principle is applied to load the structural specimen, making the loading process more intuitive. The specific technical solution is as follows: As attached Figure 1 With appendix Figure 2 As shown, it mainly consists of three parts, as detailed below: The first part is the sample mounting bracket 1, which is mainly used to fix the photoelastic sample 5 and observe it. The sample mounting bracket 1 is through the front, back, left and right sides. The upper end of the photoelastic sample 5 is suspended from the upper end of the sample mounting bracket 1 by the traction rope 6. The second part is the light source assembly and the polarizer assembly. Specifically, the polarizer assembly is as follows: a vertical linear polarizer 2 is installed at the front end of the sample mounting bracket 1 and a horizontal linear polarizer 3 is installed at the rear end. During installation, the vertical linear polarizer 2 and the horizontal linear polarizer 3 should be installed at perpendicular angles.

[0021] Meanwhile, a light source assembly is installed on the outside of the horizontal linear polarizer 3. The light source assembly uses an LED flat panel lamp. This operation helps to reduce the weight and size of the entire instrument, making it easier to carry.

[0022] The third part is the lever loading part. One end of the loading lever 7 passes horizontally through the lower end of the sample mounting bracket 1 to one side and is rotatably connected to the inner wall of the sample mounting bracket 1. At the same time, the other end passes through the other side of the sample mounting bracket 1, and a loading weight 8 is provided at the lower end of the end. The lever 7 is fixedly connected to the lower end of the photoelastic sample 5 at the middle position by the traction rope 6.

[0023] The working principle of this technical solution is as follows: The photoelastic sample 5 is made of transparent plexiglass (i.e., polymethyl methacrylate, PMMA), with its upper end suspended on the sample mounting bracket 1 and its lower end suspended on the loading lever 7.

[0024] When the weight is suspended on the right side of the loading lever 7, the photoelastic plexiglass specimen 5 is mechanically loaded, and elastic deformation occurs inside the photoelastic specimen 5.

[0025] When the LED planar light 4 is powered on, it emits white natural light, which is then converted into linearly polarized light by the horizontal linear polarizer 3. After the linearly polarized light passes through the photoelastic sample 5, it undergoes birefringence inside the plexiglass sample, generating a pair of mutually perpendicular polarized lights in the direction of principal stress. Subsequently, this pair of mutually perpendicular polarized lights passes through the vertical linear polarizer 2, and under the polarization effect of the vertical linear polarizer 2, interference occurs, forming a series of fringes, which can intuitively show the small elastic deformation of the elastic component and the distribution direction of the principal stress. Specific implementation examples: Figure 3 These are the alternating bright and dark optical stripes produced by the L-shaped photoelastic specimen 5 when subjected to tensile load. By observing the stripes, the elastic deformation inside the structure and the distribution of strain inside the structure can be observed intuitively.

[0027] In addition to directly observing the elastic deformation and strain distribution of the photoelastic specimen 5, the stripe distribution of different photoelastic specimens 5 can also be compared to observe the influence of structural parameters on the internal stress distribution of the structure.

[0028] For example, for Figure 4 L-shaped photoelastic sample 5 Figure 5 5. L-shaped photoelastic specimen with a 45° filler angle. Figure 6 The L-shaped photoelastic specimen 5 with rounded chamfers in the sample allows for a direct observation of the influence of different structural parameters on the internal stress distribution of the structure under the same load conditions by comparing the stripe distribution of the three specimens. This is beneficial for explaining the concept of "stress concentration" in teaching practice.

[0029] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A portable, simple photoelasticity apparatus for teaching, comprising a photoelastic sample (5), characterized in that, Also includes: The upper end of the photoelastic sample (5) is connected to the sample mounting bracket (1), and the sample mounting bracket (1) is through at both ends. A lever loading assembly is connected to the lower end of the photoelastic specimen (5) to apply a load to the photoelastic specimen (5); Polarizing film assembly, wherein the polarizing film assembly is disposed on the front and rear sides of the sample mounting bracket (1); A light source assembly is disposed outside the polarizer assembly to provide a light source.

2. The portable, simple photoelasticity apparatus for teaching according to claim 1, characterized in that, The polarizer assembly includes a vertical linear polarizer (2) disposed at the front end of the sample mounting bracket (1) and a horizontal linear polarizer (3) disposed at the rear end of the sample mounting bracket (1).

3. The portable, simple photoelasticity apparatus for teaching according to claim 2, characterized in that, The light source assembly is located outside the horizontal linear polarizer (3).

4. The portable, simple photoelasticity apparatus for teaching according to claim 1, characterized in that, The light source component is an LED flat lamp (4).

5. The portable, simple photoelasticity apparatus for teaching according to claim 1, characterized in that, The photoelastic sample (5) is L-shaped.

6. The portable, simple photoelasticity apparatus for teaching according to claim 1 or 5, characterized in that, The photoelastic sample (5) is made of transparent plexiglass.

7. The portable, simple photoelasticity apparatus for teaching according to claim 1 or 5, characterized in that, The upper end of the photoelastic specimen (5) is suspended on the specimen mounting bracket (1) by a traction rope (6), and the lower end of the photoelastic specimen (5) is fixedly connected to the lever loading assembly by a traction rope (6).

8. The portable, simple photoelasticity apparatus for teaching according to claim 1, characterized in that, The lever loading assembly includes a loading lever (7) and a loading weight (8). One end of the loading lever (7) passes through the sample mounting bracket (1) and is rotatably mounted on the sample mounting bracket (1). The other end of the loading lever (7) is provided with a loading weight (8). The middle of the loading lever (7) is connected to the photoelastic sample (5).

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