The controllable horizontal impact test is suitable for evaluating the horizontal impact force that the transport package can withstand and the protection ability of the package for the contents when simulating vehicle braking, train hanging operation and other conditions. The sample is impacted at a certain speed according to the predetermined state, and the required impact pulse is controlled by the pulse program controller.
①Controllable horizontal impact testing machine
The test equipment used in the controllable horizontal impact test is a controllable horizontal impact Tester, and a modified inclined plane impact Tester or pendulum impact Tester equipped with a pulse program can also be used. Figure 6-8 is the principle of the controllable horizontal impact testing machine, which is composed of impact surface, trolley, guide rail, bearing, braking system, program controller and control cabinet. The trolley is supported by ball bearings installed on its two sides, the guide rail is connected to the guide rail support with bolts, and the ball bearing is between the trolley and the guide rail. The front edge of the trolley is provided with a baffle. Both the baffles and the countertops have a plywood face to simulate actual train transport conditions. A program controller is installed on the impact surface of the baffle, and it collides with another program controller installed on the shock-absorbing base to generate the required shock pulse. The shock-absorbing base consists of a welded support frame, steel blocks and an energy-absorbing cylinder installed between the steel block and the support frame in the impact plane. Another program controller is mounted on the front face of the steel block. The acceleration and positioning system is implemented by a long-stroke cylinder, which itself is bolted to a special concrete foundation. The brake system is composed of brakes, which have two functions, one is to start the trolley as a release device; the other is to brake the trolley after rebounding to prevent multiple impacts. The program controller can generate the required shock waveforms, such as trapezoidal wave and half sine wave. All operations of the horizontal impact testing machine are carried out on the control cabinet, through which the various states and impact speeds of the vehicle can be controlled, and the waveform of the impact pulse can be recorded. The non-return load device is a simulation device that is the same as or similar to the sample. When impacting, the non-return load device provides extrusion force to the sample to simulate the load on the rear of the package in the transport vehicle.
The weight of the non-return load device is determined by the performance of the vehicle and the transportation environment. Under the condition of no special requirements, the empirical formula for calculating the weight of the non-return load device is:
W=W P F/l
In the formula, W——the weight of the non-return load device, kg;
W P - sample weight, kg;
F - proportional factor, take F=0.89, m;
l - the length of the sample in the horizontal impact direction, m.
If the inclined plane impact testing machine is used for the test, the weight of the non-return load device can be appropriately reduced in order to adapt to the non-horizontal plane.
②Test parameters
The test parameters include impact velocity, impact number, impact waveform and impact acceleration. Unless otherwise specified, the selection of test parameters such as the number of samples, test sequence, number of tests and impact velocity is the same as that of the horizontal impact test.
In addition, there is another way to select the experimental parameters. The impact velocity change is selected within the range of 0.5~5.0m/s, and the selection of the change range is determined by the transportation conditions, quality, and product characteristics of the package. During road transportation, the basic value of the impact velocity is 1.5m/s, and the variation range is 1.5~2.7m/s; the impact acceleration generally varies within the range of 0.1~15g (g is the acceleration of gravity), and the pulse duration is within the range of 40~800ms Change, sometimes up to 1s. During railway transportation, the basic value of the impact velocity is 1.8m/s, and the variation range is 1.8~4.0m/s; the impact acceleration generally varies within the range of 0.1~6.0g, up to 18g, and the pulse duration ranges from a few milliseconds to 300ms. When the pallet package is loaded and unloaded by a forklift, the pallet package will be subjected to horizontal impact force, and the maximum horizontal impact strength is 10g, 50ms and 40g, 10ms pulse.
Shock waveforms generally take half sine waves or trapezoidal waves, but in actual shocks, due to the influence of many factors, half sine waves are often accompanied by high-order harmonics and noise. The number of impacts is generally 2 to 15 times. Table 6-6 is the main technical parameters of the horizontal impact testing machine.
Table 6-6 Main parameters of horizontal impact testing machine
③Test method
The number of samples in each group is generally not less than 3 pieces. Before the test, each part of the sample should be numbered according to GB 4857.1, and a condition should be selected according to GB 4857.2 to adjust the temperature and humidity of the sample. According to product characteristics and transportation conditions, determine the impact surface (or edge), and the number of tests for each impact surface (or edge) is 1 to 4 times, generally 2 times. The test sequence generally refers to the sequence specified in Table 6-4.
Test according to the national standard GB 4857.15 "Packaging, Transport Packages, Controlled Level Impact Test Method". The specific test steps are as follows.
a. Place the sample on the axial center position of the trolley (horizontal impact testing machine, inclined plane impact testing machine) or platen (pendulum impact testing machine), and the surface ( or edge) receiving the impact is stably leaning against the partition plate. The non-return load device is placed at the rear of the specimen, next to the specimen. If the samples are packed in pallets, no additional non-return load device is required.
b. Select the appropriate pulse program controller according to the required impact acceleration, impact waveform and impact duration, and perform impact at the specified impact speed. The impact velocity error should not be greater than ±5% of the predetermined horizontal impact velocity.
c. After the test, check the damage of the packaging and contents according to the relevant product standards, and analyze the test results.
