Analysis of Repetitive Anomalies and Common Errors in Testing Machine Tests

Original author: Tai'an City Tiancheng detection Ltd.

Universal material testing machine and pressure testing machine are the main equipments for building engineering materials inspection. Due to the characteristics of the construction industry, the testing machine often moves with the project, and its use environment is relatively poor, so it is easy to produce errors and abnormalities. Therefore, in addition to the metrological verification after each relocation, the testing machine must also be verified on a periodic basis. When the error and the repeatability of the indication are abnormal during the verification process, it is necessary to gradually find the cause, eliminate the error, and eliminate the abnormality.

1 Analysis and treatment of indication repeatability abnormalities 1.1 Repetitiveness caused by loosening of the active needle fixing screw Such problems are generally not easy to find, but it does occur from time to time. During the handling and use of the test machine, the active needle fixing screw may loosen due to insufficient vibration and tightening, so that the position of the active needle changes at any time during use, resulting in the test machine being adjusted to zero position and the indication value fluctuating greatly.

The problem is as follows: When using the progressive zeroing method, it is always inaccurate and cannot be strictly aligned to the zero position. In actual work, it can be confirmed by the following method: fix the screw with the right hand, and use the left hand to move the needle in the center of the dial glass, so that the follower pin gently hits the active needle. If the active needle moves, it can be concluded. The fixing screws are loose. Retighten the screws.

1.2 Repeatability of the main pendulum bearing problem of the test machine Because the main pendulum bearing is in a relatively sealed environment, external dust and impurities are not easy to enter. The biggest problem may be: 1) the bearing is rusted, when rotating Friction increases. This is because the test machine is used in a humid environment, and there is no control over the relative humidity of the use environment. 2) The test machine has a long service life or its own quality problems, resulting in fatigue shedding and sticking. The influence of such problems on the small force value is extremely obvious, which not only causes the relative error of the indication value to be excessive, but also can cause the variability of the indication value to increase.

Since such problems cannot be directly observed and found, it is often necessary to rely on experience to judge that it is not easy to disassemble the main pendulum without much confidence, because it is troublesome to disassemble and install the pendulum. After determining that there is a problem with the main pendulum bearing and disassembling it, it is often found that the bearing has rust stains and is accompanied by a stuck phenomenon. For the handling of such problems, we generally advocate direct replacement of new bearings. Be careful when installing and do not take any damage to it. In order to reduce friction and prevent rust, a few drops of watch oil or transformer oil can be dropped into the bearing, and the problem can be solved after re-assembly. : A 2 common error causes and elimination methods 21 incorrect installation of the test machine error test machine installation is not level, will increase the friction between the moving parts, affecting the vertical installation, resulting in error to the test machine.

1) The host part is not installed horizontally. Friction will be generated between the working piston and the working cylinder, and the friction wheel between the working platform of the testing machine and the side column will also generate friction, which will cause errors, generally showing positive difference, and the error increases with the load. And decrease. 2) The dynamometer part is not installed horizontally. If the dynamometer is not installed horizontally before and after, it will cause friction between the pendulum shaft and the bearing, and the error is generally negative.

The combination of the above two factors produces a large error, which has a large impact on small loads and a small impact on large loads.

2.2 Error caused by friction resistance 1) Frictional resistance of the main part. The frictional resistance of the test machine mainly occurs between the working cylinder and the working piston. In addition to the installation is not level, there is dirt in the cylinder, the viscosity of the oil is too large, it will also increase the frictional resistance. In addition, the improper position of the guide wheel of the working platform will also increase the friction with the one side column. 2) Part of the frictional resistance of the dynamometer. There are many reasons for the frictional resistance of the dynamometer. For example, the viscosity of the dirty oil between the force measuring cylinder and the force measuring piston is too large, the friction of the driven needle on the indicating device is large, and there is oil and dirt on the gear toothed rod. Or the upper limit of the rack is too tight, and the force measuring piston belt is worn and broken. 2.3 Elimination method For the above error, first check whether the test machine is installed horizontally, and level the horizontal level of the mainframe with the frame level in the two directions perpendicular to each other outside the working cylinder. For the dynamometer, adjust the front and rear level of the dynamometer on the front of the pendulum, align the edge of the pendulum with the inner scribe line, and adjust the left and right horizontal level of the body with the horizontal ruler on the side of the oscillating bar. The oil in the cylinder can be drained and replaced with oil of suitable viscosity. The dynamometer indicating device has excessive friction of the moving needle, the gear rack is dirty, can be cleaned with gasoline, and the pressing screw and the upper limit plate of the rack are replaced, and the belt on the force measuring piston is replaced, which can eliminate the error. The purpose is to make the testing machine reach the qualified state of use.

  Taian Tiancheng Testing Equipment Co., Ltd. was established in 2009. It is a new-type technology enterprise integrating design, research and development, production and sales, after-sales maintenance, import and export trade. The company is located in the west of Tai'an, 5 kilometers west of Tai'an Station.

 Since the establishment of our company, we have continuously innovated and researched R&D, and have passed the EU CE certification and ISO9001 quality system certification. Our products cover all parts of the country and are exported to Korea, Japan, Malaysia, Vietnam, Philippines, Myanmar, Thailand, Indonesia, Angola and Saudi Arabia. , Congo, Spain, Germany, Austria, Peru, the United States and other countries.

  Based on the enterprise spirit of “Quality creates brand, service seeks development”, the company constantly innovates and strives to build a after-sales team with exquisite technology and high quality service to spare customers from worries. We sincerely hope to cooperate with colleagues from all walks of life to create brilliant future. !