Compact Stress Waveguide Using Folded Bar Structure
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Solution Overview
Problem
Current mechanical testing equipment, such as the split Hopkinson pressure bar (SHPB) apparatus, is cumbersome and costly due to its large size, which restricts its ability to test materials in the low-to-intermediate strain-rate range of 10−1/s to 102/s, as it requires extensive floor space and capital investment.
Innovation Solution
A compact stress waveguide design utilizing a folded-bar structure with an acoustic length significantly greater than its physical length, allowing for strain rate adjustment through branching and momentum traps, enabling efficient testing in a smaller form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long rods are used in SHPB apparatus to achieve 1-D stress wave propagation and low strain rates, then measurement precision and reliability are improved, but device complexity and floor space requirements increase significantly
Solution Approach 1:
The waveguide is folded back on itself multiple times, nesting the rod structure within a compact footprint. The rod follows a serpentine path that fits within a small laboratory space while maintaining the required acoustic length for low strain rate testing.
Solution Approach 2:
The rod is arranged in a three-dimensional folded configuration rather than a straight line, utilizing vertical and lateral dimensions to achieve the required length within a compact horizontal footprint.
2Adaptability or versatility
If longer rods are used to accommodate longer duration stress waves for lower strain rates, then the strain rate range is improved, but capital cost and device complexity increase
Solution Approach 1:
The waveguide is divided into multiple straight segments connected at joints, allowing the rod to be constructed from manageable sections that can be assembled in a folded configuration rather than requiring a single long rod.
Solution Approach 2:
The waveguide includes adjustable elements such as movable joints or reconfigurable segments that allow the acoustic length to be modified to test different strain rates with a single compact device.
3Measurement precision
If traditional SHPB apparatus is used for high strain rate testing, then measurement precision is improved, but the device cannot test materials in the low-to-intermediate strain-rate range
Solution Approach 1:
The compact waveguide is designed to function across multiple strain rate ranges by adjusting the excitation parameters and utilizing the folded structure's variable acoustic length, allowing a single device to replace multiple specialized testing systems.
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 compact stress waveguide allows for testing across a wide range of strain rates without the need for extensive space or capital investment, providing a more adjustable and compact solution than traditional equipment.
Implementation Method 1
The impact generates a 1-D stress wave in the rods
Implementation Method 2
an impedance-matched series of secondary bars that is impedance-matched with the primary bar at a connection point
Data Source
AI summary
The present disclosure relates to compact waveguides. One example includes a primary bar, and an impedance-matched series of secondary bars that is impedance-matched with the primary bar at a connection point that joins at least one secondary bar of the impedance-matched series of secondary bars to the primary bar. The secondary bars are noncollinear and nonconcentric with the primary bar.