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SUMMER 2020

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Distributor's Link Magazine Summer 2020 / Vol 43 No3

32 THE DISTRIBUTOR’S

32 THE DISTRIBUTOR’S LINK Del Williams Del Williams is a technical writer based in Torrance, California. He writes about health, business, technology, and educational issues, and has an M.A. in English from C.S.U. Dominguez Hills. NEW APPROACH TO FASTENER DESIGN PREVENTS LOOSENING IN VEHICLES In any type of vehicle – whether car, motorcycle, airplane, military tank, farming machine or construction equipment, there can be severe consequences if critical fasteners loosen or fail during operation. If this occurs, it not only affects the function of the equipment and causes substantial downtime and costs for repair, but for the operator and any passengers it can be potentially life threatening. Yet this is exactly what happens to vehicles when subjected to vibration, shock, dynamic loading or thermal stress. The most frequent cause of self-loosening is the side sliding of the nut or bolt head relative to the joint, resulting in related motion occurring in the threads. The gradual rotation causes a bolted joint to lose its preload (the initial fastener tension when tightened) and subsequently lead to fatigue failure. Although many OEMs view fasteners as commodity items, in vehicles the conditions demand superior solutions to prevent fasteners from loosening. In vehicle assembly alone, approximately two-thirds of the parts and half the labor are related to fastening in one way or another. So, applying the wrong type of fastener can have a negative impact on assembly costs, warranties, sales, liability and even the overall brand image. Fortunately, a new approach to fastener design is promising to resolve issues of loosening due to vibration TECHNICAL ARTICLE using a smaller, lighter and more compact fastener, without the use of adhesives. Solutions for Preventing Loosening OEMs have long used a variety of fastener designs that attempt to stop bolted joint loosening through the use of adhesives or added components that physically restrain the bolt or nut from loosening. However, these methods have significant drawbacks. Locking adhesives attempt to hold fasteners in place once tightened, yet the adhesives progressively lose effectiveness as temperature rises. Bolts secured with a single use, dry patch adhesive that is activated when the bolts are tightened also add to assembly costs. With both options, if the item is to be removed and re-used the threads must be cleaned first at great cost in time and labor. With mechanical locking approaches, the goal is to physically prevent loosening. However, this often means adding components that increase the size of the fastener and add weight and complexity to component design. For land or air vehicles, “smaller and lighter” affects fuel efficiency, so heavier fasteners are a drawback. Now, however, an original, innovative approach physically prevents vehicular bolt loosening without the traditional limitations of excess weight, complexity and length. CONTINUED ON PAGE 112

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