ASTM D4728 Test

Standard Test Method for Random Vibration Testing of ASTM D4728 Shipping Containers

The scope of ASTM D4728 includes random vibration testing of filled shipping units. It can be used to test how a container performs in two ways.

• Robustness - the test evaluates the inner packaging and closing means
• Protection- assesses whether the container provides adequate protection to its load when exposed to random vibrations

ASTM D4728 is important because shipping containers are often exposed to many stresses during the distribution process. This test will mimic some of these stresses. After passing the random vibration test, the container can be evaluated for damage or lack.

Random vibration testing has advantages over sinusoidal resonance sitting or screening tests. For example, resonance buildups that occur during random vibration tests are not that dense. As a result, unrealistic fatigue damage is minimized, unlike other types of tests, during the non-random vibration test.

Random vibration tests should be done based on field data so that they are an accurate representation of transport stresses. Test labs can use real field shipping effects to increase confidence levels for simulated testing. Vibrations will affect the shipping container itself, its inner packaging, closure means, and content. The test will allow analysis of each component.

If any element is lacking performance, design changes can be made. The changes will ensure that all components of the shipping container perform well during random vibrations. The test can be carried out in any axis or direction. However, different test levels can be used for other axes or directions to accurately simulate field conditions of that container position.

ASTM D4728 requires four test apparatus;

• Vibration Test System - The vibration test system, also known as a shaker, will have a table that can support the entire test sample (shipping container). The table should also be able to distribute vibrations evenly across the entire test surface.
• Electronic Controls - The controls will generate vibrations. They should be able to produce the desired power spectral density on the table surface supporting the sample.
• Closed Loop-Auto Balancing- Closed loop controller is required for this type of tests. This means that the controller automatically generates synchronized drive signals. The operator will enter the desired PSD data and the synchronized vibrations will reach the desired PSD, which will maintain closed loop control.
• instrumentation - Instrumentation devices such as accelerometers, signal conditioners, analyzers, data display, storage devices and control techniques are required to measure the PSD on the table surface. Instrumentation can also be useful in measuring the response of the test sample throughout the test. Any instrument used must be +/- 5% accurate in the specified frequency range.

The ASTM D4728 procedure starts with conditioning if necessary. Conditioning will be done according to the requirements of the relevant specification. In the absence of conditioning requirements, it should be conditioned whether the container materials are climate sensitive.

To start the test, the sample is placed on the vibration table in the normal shipping direction. The sample must be fixed to the table or have holding devices to prevent the container from coming off the table. The sample should be able to move approximately 10 mm (0,4 inch) in any direction when held. It is important that the vibration levels do not exceed the PSD profile initially, as random vibrations produce large but low frequency displacements in an unpredictable order.

The test should be started below the desired PSD and increased by a specified increase until the desired test level is reached. When the desired level is reached, the test time begins. The start / build time is not included in the test time. The duration should be based on either the requirement of test specifications or a predetermined amount of time / observable damage.

Finally, after the test is completed, the test lab will compile a comprehensive report based on the instructions of ASTM D4728.