Planar Multi-Axis Platforms

Standard uniaxial testing equipment provides only one-dimensional material properties, which is insufficient for predicting the failure or forming limits of sheet metals and composites that operate under multiaxial stress. These systems overcome this by accurately simulating plane stress conditions and generating the full multiaxial yield surface data required for accurate forming simulations.

Maintaining the fixed center point of the cruciform specimen during simultaneous orthogonal loading is a critical technical hurdle, as any translation or rotation introduces invalid shear and bending stresses. The system's control architecture uses active, real-time feedback loops from the central area to lock the specimen's center position precisely throughout the entire loading path.

Accurate measurement of planar strain components (E1, E2, E shear) is impossible with standard extensometers due to the complex strain field. The robust test space and control system facilitate the use of non-contact biaxial extensometry or DIC, ensuring precise, high-resolution strain mapping of the central gauge area.

Designing and manufacturing a cruciform specimen geometry that fails consistently in the center gauge section, without premature failure at the arms, is challenging. The system's application support often provides validated specimen geometry templates and loading protocols that ensure the failure initiates correctly under the required uniform biaxial stress state.

Researchers requiring non-proportional loading paths (where the stress ratio changes during the test) find standard controllers incapable of handling the transition smoothly and accurately. The advanced control software allows for complex, programmed paths and independent control of the X and Y axis actuators, enabling the simulation of realistic, complex forming or service histories.

Testing materials that exhibit significant anisotropic behavior often requires multiple, time-consuming uniaxial tests at various angles to characterize the direction dependency fully. The biaxial system allows for the direct measurement of properties under various stress ratios (e.g., balanced biaxial stress) in one highly controlled test, significantly accelerating the material characterization process.

Achieving and maintaining the target stress ratio (sigma_x\sigma_y) precisely over the course of a test is difficult due to material non-linearity and changing cross-sectional areas. The control system utilizes real-time force feedback from both axes to actively regulate the actuator demands, ensuring the desired stress ratio is strictly maintained from yield initiation to ultimate failure.

The high cost and space requirements of a single-purpose multiaxial frame can be prohibitive. The modular design, when applicable, allows the core components to be reconfigured or adapted for specialized uniaxial tests when biaxial capability is not needed, thereby maximizing the flexibility of the capital investment.

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