Automated Mixed-Mode Loading Test Device

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Solution Overview

Problem

Existing methods for generating mixed-mode loading states in test specimens on uniaxial testing machines are complex, require manual intervention, and limit the ability to change loading conditions dynamically, especially after the crack has aligned parallel to one axis, making it difficult to automate and continuously adjust mixed-mode loads.

Innovation Solution

A testing device with adjustable sample holders and load transfer devices that allow for continuous angular adjustment of the sample holders relative to the load transfer devices, enabled by arcuate guide rails, plain or roller bearings, and servomotors, allowing for automated and targeted setting of mixed-mode loading conditions without manual intervention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If manual adjustment methods are used to change loading angles, then device complexity is reduced, but automation capability and continuous adjustment ability deteriorate

Engineering Contradiction:
Improveautomation capabilityVSAvoiddevice complexity
Core Design Contradiction:
Extent of automationVSDevice complexity

Solution Approach 1:

The patent replaces manual mechanical adjustment with an automated actuating device that uses a drive mechanism (such as a motor) to rotate the specimen holder about the load application axis. This substitution enables continuous angular adjustment and full automation of the loading angle change process, directly resolving the contradiction between automation capability and device complexity by introducing a controlled mechanical system that eliminates manual intervention.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements dynamic adjustability by enabling continuous rotation of the specimen holder to any angular position during the testing process. The actuating device allows the loading angle to be changed dynamically without removing the specimen from the testing machine, transforming a static manual adjustment system into a dynamic automated one that can adapt loading conditions in real-time.

Inventive Principle:
Principle #15Dynamics

2Adaptability or versatility

If fixed angle holes are used in Arcan frame, then manufacturing precision is improved, but adaptability and continuous angle adjustment capability deteriorate

Engineering Contradiction:
Improveloading angle adjustabilityVSAvoidangle positioning precision
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent replaces fixed angular positions with continuous rotational capability. Instead of relying on pre-drilled holes at specific angles, the specimen holder can be rotated to any angular position along a continuous arc. This dynamic system maintains manufacturing precision through controlled actuation while dramatically improving adaptability by allowing any loading angle to be achieved, not just discrete predetermined angles.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent substitutes the mechanical fixed-hole positioning system with an automated rotational actuation system. The drive mechanism controls the angular position with precision, replacing the need for physically drilled holes while enabling continuous angle adjustment. This substitution maintains positioning accuracy through controlled motor operation while providing unlimited angular adaptability.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If specimen removal and repositioning is required, then adaptability to different loading angles is improved, but productivity and testing time deteriorate

Engineering Contradiction:
Improveloading angle variabilityVSAvoidtesting efficiency
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent enables dynamic angle adjustment while the specimen remains clamped in the testing machine. The actuating device rotates the specimen holder in-situ, allowing loading angles to be changed during the test without removing the specimen. This eliminates the time-consuming removal and repositioning process while maintaining full adaptability to different loading angles, directly resolving the contradiction between adaptability and productivity.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent ensures continuous testing capability by allowing angle adjustments without interrupting the test setup. The specimen remains continuously engaged with the loading system throughout the angle change process, maintaining load application and eliminating idle time associated with specimen removal and repositioning. This continuity preserves testing efficiency while providing full angular adaptability.

Inventive Principle:
Principle #20Continuity of useful action

4Adaptability or versatility

If uniaxial testing machine is used with fixed geometry, then device complexity is reduced, but capability to generate variable mixed-mode loads deteriorates

Engineering Contradiction:
Improvemixed-mode loading capabilityVSAvoidtesting system complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces dynamic geometry change capability to a uniaxial testing machine by enabling rotation of the specimen holder. This allows the same uniaxial machine to generate variable mixed-mode loading conditions by changing the angular orientation of the specimen relative to the load axis. The dynamic adjustability transforms a fixed-geometry system into a variable-geometry system without requiring a complex multi-axial testing machine.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent makes the uniaxial testing machine universal by enabling it to perform multiple mixed-mode loading configurations through angular adjustment. The same testing system can generate different modes of loading (Mode I, Mode II, and their combinations) simply by changing the specimen angle, eliminating the need for multiple specialized testing machines or complex interchangeable fixtures.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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

Enables flexible and automated generation of any desired mixed-mode loading state, allowing for continuous adjustment of loading conditions during testing using the same sample, reducing the need for manual intervention and sample repositioning, and facilitating the investigation of crack growth under varying mixed-mode loads.

Implementation Method 1

The guide element (61) of the load transmission device (6) forms with the guide rail (51) a bearing which is displaceable in the test plane and which transmits loads in the test direction

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP4421473A1Test device for the automatable generation of a mixed-mode load state
Publication Date: 2024.08.28 DEUTSCHES ZENTRUM FÜR LUFT UND RAUMFAHRT E V
  • EP4421473A1 patent drawingFigure 1
  • EP4421473A1 patent drawingFigure 2
  • EP4421473A1 patent drawing

AI summary

Test device for the automated generation of a mixed-mode loading condition on a uniaxial testing machine, the test device comprising a first and a second clamping device for clamping a test specimen in a test plane and an adjusting device, wherein the first and second clamping devices each comprise a specimen holder for clamping two opposite ends of the test specimen and each a load transfer device for load-bearing connection of the specimen holders along a test direction with the testing machine, wherein the respective specimen holder is designed to be displaceable relative to the respective load transfer device in the test plane in order to change an angular position of the specimen holders relative to the load transfer devices, and wherein the adjusting device is designed to adjust the angular position of the specimen holders relative to the respective load transfer device in the test plane.