Strength of Materials (Mechanics of Materials) (SI Units) Dr. Ashraf Alfeehan

Transcription

1 Strength of aterials (ehanis of aterials) (SI Units) Dr. Ashraf Alfeehan

2 ehanis of aterial I Tet Books ehanis of aterials, 1th edition (SI version), b: R. C. Hibbeler, 217 ehanis of aterials, 2nd edition (SI version), b:. Popov, 199 Referenes Strength of aterials, fifth edition,(si units), Shaum s outlines, b: W. ash and. Potter, 1977 ehanis of aterials, eighth edition,(si units), b: James. Gere, and Barr J. Goodno, 213. Strength of aterials Letures, Civil ngineering Department, ault of ng., UO, b: Dr Ali Al- Ghalib, 214. Sllabus of ehanis of aterial I Course o. (56122): Ch1. Stress, Aial Loads The onept of the stress, General stresses in a spae element, Tpes of stresses, Riveted (Bolted) Joints, Allowable stresses; ator of Safet, Ch2. Strain, Hooke s Law, Aial Load Problems True Stress- strain diagram, Dutile and Brittle aterials, Defletion of Aiall Loaded Rods (applied within elasti range onl), Statiall indeterminate members (aiall loaded onl), Problems Involving Temperature Changes (Thermal hanges), Poisson s Ratio, Generalized Hooke s Law, Shear Strain, Hooke s Law in Shear, Ch3. Aial ore, Shear and Bending moment Tpes of supports, Tpes of loadings, Classifiation of beams aording to their supporting sstem, Classifiation of beams aording to their analsis proedure, Calulations of beams reations, Internal fores and moments in beams, Shear and moment diagrams b equations, Shear and moment diagrams b summation approah, Ch4. Torsion Torsion formula of irular setions, Polar moment of inertia, Hollow irular setions, Statiall Indeterminate Problems, Torsion of onirular embers, Thin-walled members with open ross setions Thin-walled members with open ross setions Ch5. Pure Bending of Beams Curvature of a beam, Bending formula, lasti setion modulus, Beams of Two aterials, Stress Distribution in Composite Setions (ethod of Transformed setion). 2

3 COURS OBJCTIVS (Learning Outomes): Analze and design strutural members subjeted to tension, ompression, torsion, bending and ombined stresses using the fundamental onepts of stress, strain and elasti behavior of materials. Utilize appropriate materials in design onsidering engineering properties, sustainabilit, ost and weight. Perform engineering work in aordane with ethial and eonomi onstraints related to the design of strutures and mahine parts. ITRODUCTIO Strength of materials is a branh of applied mehanis that deals with the behavior of solid bodies subjeted to various tpes of loading. Other names for this field of stud are mehanis of materials and solid mehanis. The solid bodies onsidered in this book inlude bars with aial loads, shafts in torsion, beams in bending, and olumns in ompression. The prinipal objetive of mehanis of materials is to determine the stresses, strains, and displaements in strutures and their omponents due to the loads ating on them. If we an find these quantities for all values of the loads up to the loads that ause failure, we will have a omplete piture of the mehanial behavior of these strutures 3

4 SYBOLS AD SI UITS 4

5 CHAPR O STRSS, AXIAL LOADS Stati Review: Sine statis has an important role in both the development and appliation of mehanis of materials, it is ver important to have a good grasp of its fundamentals. or this reason we will review some of the main priniples of statis that will be used throughout the tet. ternal Loads: A bod is subjeted to onl two tpes of eternal loads; namel, surfae fores or bod fores. Surfae ores: Surfae fores are aused b the diret ontat of one bod with the surfae of another. In all ases these fores are distributed over the area of ontat between the bodies. If this area is small in omparison with the total surfae area of the bod, then the surfae fore an be idealized as a single onentrated fore, whih is applied to a point on the bod. If the surfae loading is applied along a narrow strip of area, the loading an be idealized as a linear distributed load, w(s). Here the loading is measured as having an intensit of fore/length along the strip and is represented graphiall b a series of arrows along the lines. The resultant fore of w(s) is equivalent to the area under the distributed loading urve, and this resultant ats through the entroid C or geometri enter of this area. Bod ores: A bod fore is developed when one bod eerts a fore on another bod without diret phsial ontat between the bodies. amples inlude the effets aused b the earth s gravitation or its eletromagneti field. In the ase of gravitation, this fore is alled the weight of the bod and ats through the bod s enter of gravit. 5

6 Support Reations: The general rule is: if the support prevents translation in a given diretion, then a fore must be developed on the member in that diretion. Likewise, if rotation is prevented, a ouple moment must be eerted on the member. or eample, the roller support onl prevents translation perpendiular or normal to the surfae. Hene, the roller eerts a normal fore on the member at its point of ontat. Sine the member an freel rotate about the roller, a ouple moment annot be developed on the member. 6

7 quations of quilibrium: quilibrium of a bod requires both a balane of fores, to prevent the bod from translating or having aelerated motion along a straight or urved path, and a balane of moments, to prevent the bod from rotating. Internal Resultant Loadings and free bod diagram ormal fore,. This fore ats perpendiular to the area. It is developed whenever the eternal loads tend to push or pull on the two segments of the bod. Shear fore, V. The shear fore lies in the plane of the area and it is developed when the eternal loads tend to ause the two segments of the bod to slide over one another. Torsional moment or torque, T. This effet is developed when the eternal loads tend to twist one segment of the bod with respet to the other about an ais perpendiular to the area. Bending moment,. The bending moment is aused b the eternal loads that tend to bend the bod about an ais ling within the plane of the area. 7

8 Coplanar Loadings: If the bod is subjeted to a oplanar sstem of fores, then onl normal fore, shear fore, and bending moment omponents will eist at the setion. 8

9 XAPL 1-1 Determine the resultant internal loadings ating on the ross setion at C of the antilevered beam shown in the igure. The negative sign indiates that ats in the opposite diretion to that shown on the free-bod diagram. H.W. Tr solving this problem using segment AC, b first obtaining the support reations at A. m V V m w w ) ( ) ( ) ( /

10 XAPL 1-2 Determine the resultant internal loadings ating on the ross setion at C of the mahine shaft shown in the igure. The shaft is supported b support bearings at A and B, whih onl give vertial fores on the shaft. ( ) A V ( ) ( ) ( ) 58.8 B A m V H.W. Calulate the reation at B and tr to obtain the same results using segment CBD of the shaft. 1

11 XAPL 1-3 The 5-kg engine is suspended from the rane boom in the igure. Determine the resultant internal loadings ating on the ross setion of the boom at point. ( ) A A V CD ( ) ( ) ( ) ( ) A A 9.81k V 2.54k CD A m 2.45k. m 3 2 (5 9.81) 3 5 ( ( ) 5 3 ) (5 9.81) 11