![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
Key words: hysteresis characteristic, stiffness coefficient, Young's modulus, classification, number, document identification code, introduction, introduction, university, physical experiment, tensile method, measurement of Young's modulus of steel wire, generally using thin steel wire for experiment, The theoretical basis is Hooke's Law - K which shows that within the elastic limit, the tensile force of an object such as a spring is linear with the amount of elongation.
In the experiment, we increase the hysteresis characteristic of the steel wire during the process of reducing the weight and the weight reduction process. When the steel wire corresponds to the same tensile force, the corresponding elongation is negligible, although within the elastic limit of the steel wire, the weight is increased and the 祛 is reduced. The elongation corresponding to the code process can basically maintain a good linear relationship, but completely ignoring the hysteresis characteristics of the steel wire obviously increases the experimental error.
The experimental method is used to verify the hysteresis characteristics of the steel wire.
When the experimental design experimental device is installed on the Young's modulus measuring instrument, the wire to be measured is installed. If the spring is to be measured, the spring length experiment is used to measure the small length of the variable using the optical lever mirror method to ensure the accuracy of the experimental measurement data.
As a result of the experiment, the steel wire generally exhibits a natural curl, and a weight is added to the lower end of the weight plate to make the steel wire in a straight state, and then an experimental measurement is performed.
First, the weight of the lever is gradually increased in the weight plate to make the wire stretch continuously, and the weight of the weight and the corresponding elongation of the wire are recorded one by one. The number of changes in the length of l is gradually reduced by the pound code in the weight plate, so that the wire is continuously retracted, and the weight of the recorded weight and the elongation of the wire are recorded in the table. 2 The table is reduced by the number, the number of changes of the tensile force and the elongation l after the steady change of the steel wire is plotted according to the table and the table data, and the hysteresis curve as shown in the figure can be expressed as the elongation period corresponding to the increase of the tensile force. Tomb Gold Project Anhui Province Basic Course Experimental Teaching Demonstration Center Construction Fund Funding Project Authors Li Shigang, a male, led Yang Teachers College Physics to teachers, studying master students.
Research direction molecular dynamics.
The experimental analysis of the hysteresis characteristics of the Li Shigang wire in the first phase shows that the curve of the elongation corresponding to the reduction of the tensile force is 匡 刃 å¢.
Lu Yin.
Shanghai.
Fig. 50 shows the experimental hysteresis curve of Yinmao wire, which shows that the steel wire has obvious hysteresis characteristics, and the same tensile force corresponds to an elongation.
The area enclosed by the curve in the figure represents the energy lost during the period of addition and subtraction of the weight. During the stretching of the steel wire, the internal friction of the internal structure is displaced and converted into heat energy and is lost in the air. There are hysteresis and microscopic irreversibility for many materials with internal friction, and irreversible changes occur in the internal tension of steel wire.
It can also be seen that in the process of increasing and decreasing the weight, although the unit elongation is not completely the same, there are slight differences, but each has a good linear relationship.
This shows that the steel wire changes within the elastic limit during the experiment, which can ensure the accuracy of the experiment.
This also provides a basis for judging whether the tension applied during the experiment is too large.
Discussion In the experiment of Young's modulus, since the hysteresis characteristics of the steel wire are not considered, the experimental error will inevitably increase. In the experiment, we take the elongation at the time of increasing the weight and the corresponding elongation corresponding to the weight reduction. The average is taken as a measurement, of course this is just a very rough way.
What measures can be taken to minimize the error caused by the hysteresis characteristics of the steel wire, which inevitably improves the accuracy of the experiment.
In many physical experiments, springs are often used, such as the verification of the law of conservation of momentum kinetic energy, the measurement of the surface tension of liquids, and so on.
During the experimental operation, it is easy to overload the spring, that is, exceed its elastic limit.
Sometimes, individual students will intentionally or unintentionally stretch the twisted spring, so that the local damage of the spring can not be restored, so that the spring changes from the original following Hooke's law to the elongation does not change linearly with the tensile force, so that the stiffness coefficient of the spring changes. .
Experimenting with such a spring results in a relatively large error in the experimental data.
Therefore, students can first test the quality of the spring by the above experimental method, which not only reduces the systematic error caused by the improper selection of the spring, but also enriches the content of the experimental teaching and enhances the students' ability to use the experiment to solve practical problems. It all makes a lot of sense.
References] 裴文养殖.
Concise tutorial of physics experiment Xuzhou China University of Mining and Technology Press, a [Fantasy Wang Zhicheng.
Thermodynamics Statistical Mechanics Beijing Higher Education Press, a knives
Sungless Eva Cases,Eva Sunglasses Box,Compression Eva Sunglasses Case,Eva Hard Shell Sunglasses Case
Dongguan C.Y. RedApple Industrial Limited , https://www.redapplebags.com