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Stacking takes place in the storage process and requires inspection of the packages that are placed on the lowest level. The stacking strength depends on the product packaging, the product itself, the stacking method, and the stacking environment. To integrate all factors, it is necessary to reproduce the test method of the storage process. This test method can evaluate the compressive strength of the transport package at the time of stacking. And the ability to protect the contents, to study the impact of pressure on the package, such as the deformation of the outer packaging, packaging materials, creep, cracking, crushed inner products and so on.
We usually use static load stacking test method and pressure testing machine stacking test method, according to different needs, choose one. The static load stacking test maintains the load for a predetermined duration or until the package is crushed. The method is convenient in form, long in cycle, can match a certain temperature and humidity environment, and reproduce the real environment in which the package is located. The pressure stacking test utilizes a pressure testing machine that can move the platen uniformly and apply a predetermined pressure. The load increases step by step. If the predetermined value is not reached and the package under pressure has been deformed or crushed, the test is terminated. It is also possible to press down at a predetermined value or until it is destroyed. When the load reaches a predetermined value, it is continued until a predetermined time and the change is observed. This method has high test accuracy. The test cycle is short. It simulates the effect of stacking on packages. Can refer to GB4857.3_1992, GB4857.16-1992 separately. Taking into account the actual situation, stacking is often not a single stack of similar goods, mixed goods occupy a considerable proportion. Under the premise of obtaining the average density of mixed goods, we must also consider the choice of storage stacking height and the coefficient of deterioration of stacking transportation to obtain the corresponding stacking strength. For example, ISTA 3C 2001 is for dynamic pressure testing. The packaging is classified in terms of volume and quality into packages of <0.06 m3 or <14 kg and packages of> 0.06 m3 or> 14 kg.
In short, we should select the most appropriate test program based on the actual logistics environment requirements so that packaging products can get the most reasonable packaging.
Vibration test method Packages will vibrate during transportation regardless of the transportation tools used, due to the road surface and transportation tools. In the actual process, the vibration of the package is very complicated, because the general package is transported under the condition of stacking, so we must consider the stacking vibration; In addition, if the package is not fixed during transportation, in addition to vibration, Continuous impact may also occur. Vibration will cause loosening of screws, deformation of parts, and cracking due to repeated application of force. The surface of the product may be scratched or peeled off due to the movement of the package or the product, especially when resonance occurs. Large; vibration will also affect the packaging material, change the package's resistance to pressure, impact and cushioning properties. The vibration test is to examine the vibration resistance of the package.
The vibration test can be used as a stand-alone test to examine the vibration resistance of the package. It can also be used as part of the entire test. After the vibration test, the physical and mechanical properties of the package and the product will be reduced. After checking the vibration of the package, whether it can resist Damage caused by other factors such as impact, fall, etc.
The vibration test wave type includes sine wave, triangle wave and square wave, and has several different vibration directions such as vertical, horizontal, elliptical and oblique lines. The vibration modes include fixed frequency test, sweep frequency test and random test.
The fixed-frequency vibration is to make the package vibrate at a certain fixed frequency. The test intensity values ​​include the vibration frequency, vibration acceleration or displacement, and the vibration duration. The vibration frequency is generally selected from the main vibration frequency or the resonant frequency of the package during the transportation process, and the vibration resistance of the package at a specific frequency is examined.
The vehicle vibration test is a kind of special constant-frequency vibration test. The United States uses more of this kind of test. The test method is to place the package on the vibration table according to the normal state of transportation, ensure the vibration peak value is constant, and adjust the vibration frequency to make the package Jump up and reach the required height, vibrate at the vibration frequency, and stop the test after the number of times the package jumps up to the specified requirement. This test method examines the impact of continuous impact on the package.
Sweep frequency vibration test is a variable frequency vibration, and the vibration frequency is constantly changing at a fixed frequency sweep rate within a certain frequency range. There are two methods for frequency sweeping the package. One method is to find the resonance point. After the frequency sweeping, resonance is usually required at the resonant frequency. This test method is commonly used in China; the other test method is to use The high vibration acceleration oscillates back and forth several times within a certain frequency range. Its purpose is to examine the vibration resistance of the package in a certain frequency range.
In the actual process, the vibration of the vehicle is determined by the mode of transportation, road surface conditions, operating speed, and the characteristics of the vehicle itself. The vibration source is irregular and random, and it is impossible to accurately describe the specific vibration process with the formula; The transmission performance of vibration is also very different, and the structure of the vehicle and the buffer method, the weight of the load and the position of the center of gravity, the condition of the tire, and the position of the package on the vehicle are all greatly related. Obviously, the fixed frequency test and the sweep frequency test are different from the actual situation. To simulate the actual vibration better, a random vibration test is needed.
Random vibration is the regularity of the particle motion cycle during vibration, and the process never repeats exactly. In order to describe random vibration characteristics, statistical mechanics and information theory must be used. In the random vibration test, the power spectrum density is usually used to describe the random vibration characteristics, abbreviated as PSD, which reflects the energy distribution of the vibration process in different frequency bands.
The power spectral density curves of random vibrations of road, railway, air and sea transportation are different. Even in a mode of transportation, the power spectral density curve is different. Taking road transport as an example, the factors such as road class, vehicle type, and load will affect the shape and acceleration RMS of the power spectral density curve. During the test, the power spectral density should be selected according to the actual transportation process of the package, and at the same time, the insurance level should be selected according to the value and nature of the package, and the power spectral density curve should be finally determined after comprehensive consideration of the above factors.
In the random vibration test, the code should be simulated as much as possible to the actual situation, including the sample placement direction, stacking layer number, etc. The fixture should be able to ensure that the sample moves freely in the direction of vibration. If it is not possible to determine the orientation of the package during transport, it is necessary to perform a vibration test in any of the possible directions. (Finish)
The test of the transport package can only examine whether the package can protect the product and does not prove that the package is reasonable. For this purpose, we must understand how much impact the product itself can withstand. That is, we often say the impact brittle value. High impact brittleness, strong impact resistance of the product, we can moderately reduce the strength of the package; impact brittle value is low, the impact resistance of the product is weak, we need to increase the strength of the packaging. Two different experimental methods were included in the test of product impact brittleness. One is to test the fragility of the product through the drop test of the package, and the other is to test it through a vertical impact tester. At present, the vertical impact test of products is commonly used at home and abroad to test the fragility of products. The standards that can be used include: GB/T15009-94, GB/T8171-87, ASTM D3332-99 and so on. Stacking test method The stacking test is the degree of influence of the inspection time on the packaging material. From an experience point of view, as the loading of packages increases, the holding time of the pressure applied to the package decreases.