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9 years ago

SUMMER 2011

  • Text
  • Fastener
  • Fasteners
  • Products
  • Threaded
  • Metric
  • Screws
  • Association
  • Plastics
  • Bolt
  • Industrial
Distributor's Link Magazine Summer Issue 2011 / VOL 34 / NO.3

96 THE DISTRIBUTOR’S

96 THE DISTRIBUTOR’S LINK SEFA - PO Box 448, Elba, AL 36323 • Email: sefa@thesefa.com • www.thesefa.com SOUTHEASTERN FASTENER ASSOCIATION SCHOLARSHIP AWARDED IN PRESIDENT’S MEMORY Em Datwyler-Webb passed away this past fall at age 84. Em Webb was the first woman President of the Southeastern Fastener Association and presided in 1991-1992. She was known for her work on building the SEFA Scholarship program, which began in 1989. Members have made contributions in Em’s memory since her passing and the board of directors have since passed the motion to offer one scholarship per year in Em Webb’s name. The first annual Em Webb Memorial Scholarship was awarded this spring to Ashley Nichole Setser of King, North Carolina. Ashley is the child of Keith E. Setser, employee of Southern Fasteners and Supply in Winston-Salem, NC who sponsored her application. Ashley received 00 toward her college education. If you would like to make a donation to the Em Datwyler-Webb Memorial Scholarship fund, please send your check in care of SEFA, P.O. Box 448, Elba, AL 36323. For more info, email sefa@thesefa.com. The annual Gilchrist Foundation Scholarship was A SYSTEMATIC APPROACH TO BOLTED/SCREWED JOINT DESIGN continued from page 8 The failure of not seriously basing our joint design on some real and reasonably well established load data is not uncommon. As a consultant, I often find that joint failures are consequences of hasty and shady guess work in this area. 2. Define the joint area(s) If a part of a machine is to be attached to the main frame it may require a number of fasteners. The “bolting pattern” may be uniform like in a circular flange, or the fasteners may be located differently due to a nonuniform shape of the part. Each individual joint location must contribute some amount of clamping force to keep the whole part fixed in place. The pressure areas under heads and nuts must be low enough to prevent embedment. If the relative pressure is too high, the head and/or nut will produce a coining of the substrate which will also result in a loss of preload. If gaskets are used, the pressure must be well controlled to prevent crushing of the gasket also awarded this past spring to Andrew Vu of Lawrenceville, GA. Andrew is the child of Lam Vu, employee of Brighton Best International in Duluth, GA. Robbie and Gina Gilchrist have awarded 00 to a worthy scholarship applicant for the past six years. Many thanks to them! The 2012 Scholarship application is online and available for download from the SEFA website. It can be found at www.thesefa.com and click on the scholarship link. It is never too early to start planning for scholarships. The deadline is February 1, 2012 but will be here before we know it. Scholarships are available to employees and employee’s spouse or children of members of the Southeastern Fastener Association. Please share this information with the rest of the employees at your company so that all can have the opportunity to apply for scholarship funds. and subsequent leaks. 3. Define the joint volume The amount of compressed material in a joint will determine the spring rate/ elasticity of the joint. Typically, the more joint material being compressed by the preload force of the tightened fastener, the higher stiffness is the Due to the many variables associated with bolted/screwed joints the design work must be done right. result (use Hooke’s Law). If the joint is stiff and the fastener springy by comparison, we will have a joint able to take a lot of abuse. Our joint calculations should, once we have a handle on the external loads, always begin with giving consideration to the geometry of the joint. In fact, I would simply state that a successful joint is based on the three most important items – Geometry, geometry and geometry! If we can find a good balance between the “tension spring” (the fastener) and the “compressive spring” (the joint parts) we will end up with a good, reliable joint. please turn to page 107

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