FALL 2024

26 THE DISTRIBUTOR’S

26 THE DISTRIBUTOR’S LINK Guy Avellon Guy Avellon has been in MRO and Fastener Distribution for over 30 years, in such positions Sales Engineer, Chief Engineer, Manager of Product Marketing, Product Engineering & Quality and Director of Quality & Engineering. He founded GT Technical Consultants where he performs failure analysis, lectures on fastener safety, works for law firms and designs/audits Quality systems. He is a member of SAE, is Vice Chairman of the ASTM F16 Fastener Committee, Chairman of the F16.01 Test Methods Committee and received the ASTM Award of Merit in 2005. Guy can be contacted at 847- 477-5057, Email: ExpertBoltGuy@gmail.com or visit www.BoltFailure.com. WHAT FASTENER DISTRIBUTORS NEED TO KNOW ABOUT HOW TO INVESTIGATE FASTENER FAILURES When a fastener fails, it is important to gather as much information about the application and details of the installation as possible as this will not only help determine the root cause of the failure but how further failures may be prevented. Basic Questions [Q] What type and grade strength of fastener was used? ¤ Did the grade of the nut match the strength of the fastener? [Q] Was the fastener strength compatible with the service loads? [Q] How was the fastener used? ¤ Was it a static load? ¤ Was it subject to extreme environmental conditions? ¤ Was it in a dynamically loaded joint? ¤ Were there alternating loads? ¤ Were the loads transverse or axial? ¤ Was the joint subject to vibration or impact loads? [Q] Ancillary components used: ¤ Flat washer; type, size, coating. ¤ Nut; standard, locking, grade, coating. [Q] Were there multiple fasteners in the joint? ¤ Were the failures adjacent to each other? [Q] How were the fasteners installed? ¤ By hand wrench ¤ Pneumatic tool ¤ Torque wrench [Q] Where were the fasteners tightened? ¤ Bolt head CONTRIBUTOR ARTICLE ¤ Nut ¤ Both [Q] What is the condition of the joint surfaces? ¤ Rusty or rough ¤ Painted or smooth [Q] What is the condition of the failed parts? [Q] Where is the location of the fracture? ¤ At the head? ¤ The thread run-out? ¤ First thread outside of the nut? [Q] What is the condition of the fracture surface? ¤ Smooth, dull, bright, rusty? Investigation This is the time we categorize the data we collected. Sometimes we can tell by the appearance of the samples and fracture surface what may have happened. This will narrow the questions and failure possibilities. For instance, a ductile fracture will exhibit dimples with an inclusion, or a cups and cones appearance with a dull colored surface. It will also show some type of distortion, as the material will deform plastically before ultimate failure. However, if the load is applied very rapidly, as in a shock or impact load even while tightening, a ductile material may have the appearance of a brittle fracture. This can happen when using unregulated pneumatic installation tools. Check the threads of the bolt to determine if there is a change in thread pitch. This will indicate if the bolt was stretched into yield either by service loads or during installation. CONTINUED ON PAGE 96