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1、TOPICSchool of Engineering Mechanical EngineeringME 462Design of Mechanical Systems Tulong Zhu, All rights reserved. 06 Bolted and Riveted Joints Loaded in ShearEscBolted and Riveted Joints in ShearJoint in ShearNotes Riveted and bolted joints loaded in shear are treated exactly alike in design and
2、analysis.FF The information presented here is for reference only. The design of bolted and riveted connections for boilers, buildings, bridges, autos, aircraft, and other structures in which danger to human life is involved is STRICTLY governed by various construction codes/standards.American Instit
3、ute of Steel Construction Handbook The American Railways Eng. Association Specifications. Boiler Construction Code of ASME. Mil Handbook. 2EscFailure ModesFailure Modes (a) Shear Loading(b) Bending of rivet(c) Shear of rivet(d) Tensile Failure of members(e) Bearing Failure(f) Edge Shear Tear- out(g)
4、 Edge Tensile Tear-out3EscAnalysis: Bending of RivetsBending of RivetNotes This is approximate. The actual stress distribution is unknown , and the stress concentration is not included M: Bending moment f: Shear Force of one rivet t: Total thickness of of the joined components I/c: Section modulus f
5、or the weakest member of for the rivets. This approach is seldom used in design; instead the bending effect is compensated for by an increase of the safety factor (generally an additional 1.15 SF is used.) 4EscAnalysis: Shear of RivetsShear of rivet F: Total shear Force A: Cross-sectional area of al
6、l the rivets (bolts) in the group.Notes Shear stress distribution is assumed to be uniform. This is acceptable for static loading and ductile materials. FF For fatigue loads, shear stress distribution must be considered for both brittle and ductile materials. 5EscFFAnalysis: Tensile Failure of Membe
7、rsTensile failure of membersNotes For static loads, stress concentration is not considered for ductile materials, but must be included for brittle materials. For fatigue loads, stress concentration must be included for both brittle and ductile materials. F: Total shear force A: Net area of the plate
8、. Use of a bolt with initial preload and, sometimes, a rivet will place the area around the hole in compression and thus tend to nullify the effects of stress concentration.6EscAnalysis: BearingBearingNotes The bearing strength (yield and ultimate) of metals are generally higher than the tensile str
9、ength. f: Shear force on ONE rivet (bolt) A=td: Project area of a single rivet t : The thickness of the thinnest plate, and d : The rivet or bolt diameter. Bearing is the failure caused by crushing of the rivet or plate.Bearing StressSafety Factor Sb: The bearing strength of the material. If no data
10、 is available, the bearing strength is about twice the tensile strength. 7EscAnalysis: Edge Shear Tear-out (I)Shear Tear- outNotes In most codes, this failure is not checked; instead it is avoided by recommending a minimum edge distance, e: 2d for protruding head rivets 2.5d for countersunk flush ri
11、vets. See the next slide for details. f: Shear force on ONE rivet (bolt) t:The thickness of the thinnest plate, and e: The edge distance.e8EscAnalysis: Edge Shear Tear-out (II)Shear Tear- out In most codes, using e 2d (for protruding head rivets) to preventing this failure. An approximate proof is g
12、iven below.e If we use e 2d , then from the above Eq., we have i.e., as long as the bearing strength is satisfied and e 2d the shear tear-out will not occur. In joint design, the bearing strength must be satisfied, i.e where, Sb, Sult, and Ss are the bearing, ultimate tensile and ultimate shearing s
13、trength of the metal.(For most metals, Sult 2Ss)9EscAnalysis: Edge Tensile Tear-outShear Tear- outNotes In most codes, this failure is also not checked; instead it is avoided by recommending a minimum edge distance, e and minimum and maximum pitch, p. f: Shear force on ONE rivet (bolt) t:The thickness of the thinnest plate e: The edge distance p: pitch The edge tensile tear-out is from the bending stress of ABCD, modeled as a centered loaded fixed-fixed beam. ABC DA BCDfpe10
