Additive Manufacturing Proof Load Testing for Internal Flaw Detection
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Solution Overview
Problem
Additive manufactured metal parts often contain internal flaws that are difficult to detect, especially with radiographic inspection, due to their rough surface finish, which can lead to fatigue failure over their service life, and there is a lack of specifications for qualifying these parts for fatigue strength.
Innovation Solution
A method and system for calculating a proof load that will cause a part to fracture if an internal flaw of a certain size exists, using stress intensity data and operational load, and applying this load during a compliance test to ensure the part can withstand operational loads without cracking, based on geometry and static strength data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radiographic inspection is used to detect internal flaws, then defects can be detected volumetrically, but the rough as-printed surface finish obscures internal flaws making inspection difficult
Solution Approach 1:
The method applies preliminary computational analysis to determine the critical flaw size and proof load requirements before performing the compliance test. This preliminary calculation of the threshold stress-intensity factor and critical fracture toughness allows the inspection process to be targeted and efficient, overcoming the obscuration problem by focusing on specific critical parameters rather than attempting general visual inspection of the rough surface
Solution Approach 2:
The patent replaces traditional mechanical/visual inspection methods with a computational mechanics approach. By using stress intensity data, operational load analysis, and fracture mechanics calculations, the system substitutes direct visual/radiographic inspection with a mathematical model that predicts flaw detectability and part reliability based on material properties and loading conditions
2Ease of manufacture
If additive manufacturing is used to produce parts, then complex geometries can be manufactured directly, but internal flaws are hard to detect and parts may contain undetected defects
Solution Approach 1:
The compliance test with proof load application is performed as a preliminary action before the part enters service. By calculating the critical fracture toughness based on print direction and applying a predetermined proof load, the method proactively identifies parts with critical flaws before they can cause failures, thus ensuring reliability while maintaining the manufacturing advantages of additive technology
Solution Approach 2:
The patent changes the approach from attempting to detect all possible flaws to focusing on critical parameters: the threshold stress-intensity factor, critical fracture toughness, and proof load magnitude. By changing the inspection paradigm to focus on these specific parameters rather than all potential defects, the system maintains reliability while accommodating the unique characteristics of additive manufactured parts
3Reliability
If a proof load test is applied to ensure part safety, then critical flaws can be identified, but the part may fracture during testing reducing productivity
Solution Approach 1:
The critical flaw size and proof load are calculated in advance using stress intensity data and material properties before the compliance test is performed. This preliminary computational work enables the test to be conducted efficiently with a predetermined load level, reducing the time required for testing while maintaining high reliability standards
Solution Approach 2:
The patent changes the test parameter from arbitrary overload to a precisely calculated proof load based on critical fracture toughness and operational requirements. By optimizing the proof load magnitude to exactly what is needed to detect critical flaws, the method minimizes unnecessary test failures while ensuring safety, thus improving productivity without compromising reliability
Data Source
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AI summary
An example method for identifying an internal flaw in a part produced using additive manufacturing includes calculating a proof load of a part, in which the proof load is a load that when applied to the part will cause the part to fail based on presence of an internal flaw in the part, determining whether the part can withstand the proof load based on a geometry of the part and static strength data, and based on a determination that the part can withstand the proof load, applying the proof load to the part during a compliance test of the part. The proof load causes the part to fracture, when applied to the part, based on presence of the internal flaw in the part that is of a threshold size at which the internal flaw would cause cracking and potential part failure when the part is placed under the operational load.