REG NASA-LLIS-1426-1998 Lessons Learned Cadmium-plated High-Strength Bolts Used in High Temperature Applications (1998).pdf

1、Lessons Learned Entry: 1426Lesson Info:a71 Lesson Number: 1426a71 Lesson Date: 1998-07-06a71 Submitting Organization: LARCa71 Submitted by: Grant WatsonSubject: Cadmium-plated High-Strength Bolts Used in High Temperature Applications (1998) Abstract: Potential bolt failure where high-strength cadmiu

2、m-plated bolts are used in high-temperature applications.Description of Driving Event: During the re-installation of a piece of hardware at the 8-Foot High Temperature Tunnel (8HTT), several grade 8 high-strength cadmium-plated hex head bolts failed as technicians were tightening the bolts with a to

3、rque wrench. The failed bolts used for the re-installation of the hardware had been through numerous thermal cycles during testing at the 8HTT. Analysis of the failed bolts indicated that the bolts met all metallurgical specifications. Failure patterns suggested a fatigue fracture where the head of

4、the bolt meets the body.Lesson(s) Learned: Research has found that high-strength cadmium-plated bolts should never be used in applications where the temperature will exceed 450 F. If the temperature exceeds this recommendation, liquid metal embrittlement can occur that adversely affects the mechanic

5、al properties of the bolts and leads to failure. The bolts at the 8HTT had been exposed to temperatures well in excess of 450 F.Recommendation(s): Examine all equipment (in use or under design) that could be exposed to temperatures in excess of 450 F for cadmium-plated bolts. Any cadmium-plated bolt

6、s found in such applications should be removed and replaced with bolts having an acceptable coating, such as black oxide. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/

7、AMission Directorate(s): a71 Exploration Systemsa71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Accident Investigationa71 Facilitiesa71 Hardwarea71 Human Factorsa71 Mishap Reportinga71 Safety & Mission AssuranceAdditional Info: Approval Info: a71 Approval Date: 2004-06-04a71 Approval Name: Leslie Johnsona71 Approval Organization: LARCa71 Approval Phone Number: 757-864-9409Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-