Crosshead-Position Force Limiting in Material Testing Machines
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Solution Overview
Problem
Conventional material testing machines are limited by physical constraints that restrict load string height, leading to reduced testing force capabilities when extended height testing is required, which can cause damage due to buckling of machine components.
Innovation Solution
The system employs a control circuitry that adjusts the upper testing force limit based on the distance or position of the crosshead relative to the base, allowing extended height testing while preventing buckling by reducing the force limit when the crosshead exceeds a threshold distance or position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the crosshead is positioned at extended height to test longer specimens, then the testing range is extended, but the machine components are subject to buckling due to high compressive forces
Solution Approach 1:
The patent implements dynamic adjustment of the upper testing force limit based on the crosshead position. The control circuitry continuously monitors the distance between the crosshead and base, and automatically reduces the maximum allowable testing force when the crosshead exceeds a threshold position, preventing buckling while enabling extended height testing
Solution Approach 2:
The system changes the operational parameters (testing force limit) based on the system state (crosshead position). By dynamically modifying the force parameter according to position, the system adapts to prevent component failure while maximizing testing capability across different specimen lengths
2Reliability
If the upper testing force limit is reduced to prevent buckling at extended heights, then component safety is improved, but the testing force capability is limited
Solution Approach 1:
The system dynamically adjusts the testing force limit based on real-time crosshead position monitoring. When the crosshead is within the safe operating range, the full testing force capability is available. When the crosshead exceeds the threshold position, the system automatically reduces the force limit to prevent buckling, creating an adaptive safety mechanism
Solution Approach 2:
The control circuitry continuously monitors the crosshead position and uses this feedback to adjust the upper testing force limit. This closed-loop control ensures that the system operates within safe parameters while maximizing testing capability, automatically reducing force when position indicates risk of buckling
3Reliability
If conventional machines operate along the entire range using reduced testing force, then component damage is prevented, but testing efficiency is reduced
Solution Approach 1:
Instead of using a static reduced force limit across the entire operating range, the system dynamically adjusts the force limit based on crosshead position. This allows the machine to operate at full testing force capability when the crosshead is within the safe range, and only reduces force when necessary to prevent buckling at extended heights
Solution Approach 2:
The system changes the testing force parameter based on the operational conditions (crosshead position). By modifying the force parameter only when the crosshead exceeds the threshold position, the system maintains high testing efficiency for normal operations while providing protection when needed
Data Source
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AI summary
Disclosed example material testing systems include: a test frame; a base configured to grip a first position on a test specimen; a crosshead configured to be coupled to a second position on the test specimen, and to be actuated to transfer testing force to the test specimen during a material test; an actuator configured to actuate the crosshead along the test frame and to apply the testing force to the crosshead; and control circuitry configured to: control the actuator to apply the testing force to a specimen via the crosshead, such that the testing force does not exceed an upper limit; and while a distance between the crosshead and the base is at least a threshold distance, reduce the upper limit on the testing force from a value of the upper limit while the distance between the crosshead and the base is less than the threshold distance.