Reliability Analytics Corporation
Previous | Next      Search Home

First 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 Last

First 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 Last

Previous | Next      Search Home

Just as failure modes are dependent on the application of the equipment, so must the failure rate be adjusted per the individual machine design and the number of bolts being used. For a complex machine design where weight or potential deformation becomes a factor, a finite element or stress analysis is usually performed. Detailed procedures for evaluating a bolt or other threaded fastener for reliability are contained in Chapter 16. 23.4 BUSHING A mechanical bushing is a type of vibration isolator providing an interface between two parts, dampening transmitted energy from one part to the other. A bushing is also used as a bearing that is inserted into a housing to provide a bearing surface for rotary applications. This is the simplest type of bearing, comprising just a bearing surface and no rolling elements. The shaft in contact with the bearing slides over the bearing surface. There are many different bushing designs for particular applications. Sleeve bushings or journal bearings are used to protect steel shafts from wear due to a combination of pressure and rotating motion. Slide bushings are used where accurate linear movement of a large object is required. A ball bushing permits rotation, sliding motion or both. A bushing blank is used as an insert in a hole to reduce the inside diameter of the hole and protect the surrounding body structure from damage resulting from vibrational and loading stress. Many bushings are press fit into structures and can be replaced after wear without requiring replacement of the entire structure. Chapter 7 contains the procedures for evaluating a plain bearing for reliability including the failure modes to be considered. These same procedures can be used for determining the failure rate of a bushing. 23.4.1 Bushing Failure Modes Failure modes of a bushing depend on the application of the bushing. Mechanical bushings may be a fixed or removable cylinder metal lining used to constrain, guide, or reduce friction, or they may be a threaded adapter to permit joining of pipes with different diameters. In some applications leakage past the bushing can be a potential failure mode. Some leakage can be expected since by design there is a gap between the bushing and shaft. Bushings are also used in chain drives providing separation between lubrication and contaminants. Chapter 21 contains failure mode information on these types of bushings. Table 23-4 provides typical failure modes for bushings to be considered in a reliability analysis. Miscellaneous Parts 23-5 Revision B

Toolkit Home

Reliability Analytics Corporation
reliabilityanalytics.com