Shock test is a type of environmental and reliability testing that aims to determine the suitability of a product to withstand non-repetitive mechanical shocks during use and transport, the integrity of its structure, and the reliability of its ability to withstand shock loads.
Shock can be regarded as a special case of vibration environment and is divided into simple shock and complex shock. Simple shock has a time-varying curve of shock amplitude, which can be approximately represented by simple geometric shapes according to international standards, such as half-sine, trapezoidal, and post-peak sawtooth waves. Complex shock has a complex attenuation oscillation curve of shock amplitude over time.
Shock stresses often cause equipment to elicit forced vibration and natural frequency response, causing varying degrees of damage or even failure to the product's performance and structural strength. Rockets, airplanes, ships, vehicles, and various types of engineering machinery are often subjected to shock loads during their operation, which will have harmful effects on their structure, performance, and installation equipment. For example, spacecraft undergo various shocks during the completion of their missions. When subjected to shock loading, the external energy is transmitted to the spacecraft structure and components in an instant, and sudden changes in displacement, velocity, and acceleration may cause damage or malfunction to the spacecraft structure and instruments, so it is necessary to perform ground shock simulation tests to expose design or manufacturing defects as soon as possible.
The simplest traditional shock test equipment in the early days was divided into two types: a free-fall shock machine with variable buffering stiffness and dropping height that can produce simple shock waveforms, mainly half-sine waveforms; and a hammer shock machine with adjustable mass and angle of the hammer. These traditional types of shock machines have simple structures but significant limitations, with only a single waveform and mechanical limitations, and difficulties in controlling and adjusting, with poor reproducibility.
With the development of computer technology, digital signal processing technology, and test control equipment, electric test systems have been used to implement shock testing, which has the advantages of accurate test parameters, ease of control and adjustment, high precision, the ability to simulate and control shock, and the ability to use the vibration table for multiple purposes. However, electric vibration tables are limited by the acceleration amplitude they can produce, and can generally only achieve vibration of 100g and force of 10T. In situations where high acceleration is required for shock testing, traditional test equipment still needs to be used.
With the development of shock response spectrum time-domain matching control technology, these limitations are being broken, and large shock force, high acceleration shock testing machines on electric vibration tables are becoming possible.