Electromagnetic Hopkinson Bar Loading Device
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Solution Overview
Problem
Existing split Hopkinson pressure and tension bar technologies face challenges in accurately controlling incident wave amplitude, achieving a wide range of strain rates, and integrating tension and compression loading systems, limiting their experimental capabilities and standardization.
Innovation Solution
An electromagnetic induction type Hopkinson pressure/tension bar loading device and method using a power supply, capacitor charger, and loading gun with a primary coil, secondary coil, and amplifier to generate stress waves, allowing for controlled pulse width and amplitude, and enabling both compression and tension testing on the same apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an air gun and impact bar are used to generate incident waves in Hopkinson pressure bar, then the incident waves can be generated, but the amplitude of incident waves cannot be accurately controlled and many experiments are required to obtain desired strain rate
Solution Approach 1:
The patent replaces the mechanical air gun and impact bar system with an electromagnetic loading system consisting of a loading gun, primary coil, and secondary coil. The electromagnetic system generates stress waves through electromagnetic repulsion force between the coils, allowing precise control of incident wave amplitude through electrical parameters (voltage, current, pulse width) rather than mechanical parameters, thereby eliminating the need for multiple trial experiments.
Solution Approach 2:
The patent changes the control parameters from mechanical (air pressure, impact bar position) to electrical (voltage, current, pulse width). By adjusting the voltage and pulse width of the power supply to the primary coil, the amplitude and duration of incident waves can be precisely controlled without requiring multiple experimental trials, directly improving measurement precision and reducing time loss.
2Adaptability or versatility
If the impact bar length is changed to obtain different strain rates, then the range of strain rates can be expanded, but the experiment becomes complex and the wavelength is limited
Solution Approach 1:
The patent uses electrical parameters (voltage, pulse width) to control strain rate instead of changing the physical dimensions of the impact bar. By adjusting the pulse width of the electromagnetic loading, different strain rates can be achieved without modifying the apparatus, thereby expanding the adaptable range while reducing experimental complexity.
Solution Approach 2:
The electromagnetic loading system serves multiple functions: it can generate different strain rates, control wave amplitude, and adjust pulse width all through a single unified system controlled by electrical parameters. This eliminates the need for multiple impact bars of different lengths and simplifies the overall experimental setup while maintaining versatility.
3Adaptability or versatility
If a hollow impact tube is used in Hopkinson tension bar, then tension loading can be achieved, but the incident bar is easy to bend and the wavelength is limited to about 0.2 ms
Solution Approach 1:
The patent replaces the hollow impact tube mechanical system with an electromagnetic loading system. The loading gun with primary and secondary coils generates electromagnetic repulsion force that applies tension loading to the incident bar without requiring a hollow tube structure. This eliminates the bending instability issue while maintaining tension loading capability.
Solution Approach 2:
The electromagnetic field acts as an intermediary between the power supply and the incident bar. The primary coil generates a magnetic field that induces current in the secondary coil, creating repulsion force that loads the incident bar. This intermediary electromagnetic mechanism provides stable and controllable tension loading without the structural weaknesses of hollow impact tubes.
4Use of energy by stationary object
If the impact tube wall thickness is increased, then the air pressure requirement can be reduced, but the generated stress wave amplitude is limited
Solution Approach 1:
The patent replaces the pneumatic system with an electromagnetic system. The electromagnetic repulsion force between the primary and secondary coils directly generates stress waves in the incident bar, eliminating the need for high air pressure to accelerate thick-walled impact tubes. The stress wave amplitude is controlled by electrical parameters rather than being limited by wall thickness constraints.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides accurate control over stress wave amplitude and pulse width, expands the range of achievable strain rates, and integrates tension and compression testing, enhancing experimental repeatability and reducing apparatus complexity.
Implementation Method 1
the primary coil and the secondary coil are used to generate electromagnetic repulsion force to accelerate the compression head or flange
Implementation Method 2
generate electromagnetic repulsion force between the primary coil and the secondary coil
Data Source
Figure 1~2
Figure 3~5b
Figure 6~9
AI summary
An electromagnetic induction type Hopkinson pressure/tension bar loading device and experiment method therefor. A positive electrode output line of the output of a capacitive charger is connected with a positive electrode line of a loading gun, and a negative electrode output line of the output of a capacitive charger is connected with a negative electrode line of the loading gun. The present invention not only can generate compression stress waves but also can generate tension stress waves through the electromagnetic induction principle, and is applied to the loading of a Hopkinson tension bar and a pressure bar. Thus, the loading systems for a Hopkinson tension bar and a pressure bar can simultaneously achieve the strain rate and strain range, which the traditional split Hopkinson bar experiment cannot reach, on the same device, so that the Hopkinson bar experiment technology is standardized, and the experiment devices for a tension bar and a pressure bar are integrated, thereby reducing complexity and floor space of equipment.