“+ Machine Design: Machine design isthe process of Selection of the materia, shapes, sizes ang arrangements of mechanical elements so that the resultant machine wll perform the prescribed tare Machine design deals with the design of machines and thelr elemen’. The concept of machine design feilusratedin Fig 1.1.1. Fig, 1.11: Concept of Machine Design Erample of machine design : The process of | 2 $0 of » bet drve is an example of machine ‘sign Iconsetsof: 0 sa {arrangement of mechanical plo, ek shat, bearings, Shapes of these mechanical { materials for these mechanical $85 of these mechanical Definition of Problem Synthesis Analysis and Optimtzation Evaluation Presentation Recognition of Need : Recognition of need isthe outcome o the requirement or the discontentme the existing gy Is highly a crea and most ofthe times comes out of imovative minds. ‘© For example, the need to do something about Definition of +The difference between the ta And the definition of problem {seals on option = § Presentation 1 defined, the next the process of method of jm has beer is symtests echanism of the syt™ shapes ofthe component sred output with the even number of iterations very sntesis must be flowed BY analy natal ove proces of rica examin ng traiready existing or propased design in order tojudge ts sulablity forthe task, anal cmplies with the requirements, All possible mines whether the performance ys are analysed and optimum one is a Atthls stage, sometimes, it may be neces to modify the problem definition, ifno fea aon : Evaluation involves of prototype {nthe laboratory or testing by creating the ‘model on computer. Evaluation verifies the the inal proof ofa successful design ing the design to others is the P in the design process. The design an be presented with the help of writen ocuments, including drawings or with the help ofsoid modeling on the computers “Te me design procs pay You may proceed trey one pane then ay hae 0 cin age at ase, eine iP a4, Fig. 12:1: Phases of Design 1.3 DESIGN PROCEDURE ‘The general procedure tit strated in Fig 13ig, 13.1: Design Process ‘tp 1: Defintion of robiem: Define the design problem giving aees cup parameter Step 2: Sythe; beeen chal lets ss to ays ii ven input. itgram of each element of Find out the loads (forces, ue) acting on exch clement by Bi ral orcad tment. ut to be conside Seba Sesto eect = : re een Seen ae x ermine the permis ite or desen Convenience ofassemby; and Convenience of manufacturing Step 9: Preparation of Drawings: Propare working drawing of each element of component with minimum two views showing folowing details Dimensional tolerances Surface ish; lv) Geomecrical tolerances and (9) Special production requirements ke heat treatment. ‘Prepare assembly drawing giving par numbers, overall mensions and pa ‘The component drawing is 20 the shop oor for manufscturing purpose, while assembly drawing is supplied to the assembly shop. | company standards = oranda are defined o stb a ompeny or ae companies for their use. » -tnese standards ate define or set by a national apex boul the country ‘standards prepared by (Bureau of indian Standards (85) (i) American Society of Mechanical Engineers iy and are normaly folowed througout “The examples of mation] standards are mechanical i aansartevset z= eas: es and shapes of COmPONETS ards ord bolts, bearings: Keys. neat ru he: elem in presi vesels ore Morances ond surticc ectric motors, nal apex body and are normally fl (sand the word, The examples of Intern fish ofcomvonent presentation of | __ standards ae standards prepared DJ; oe rae ee 5 ean | ore design nebo testing, and manufacturing component ayer or prodict 144 Advantages of Standardization : Some ofthe advantages of standardization are as tows (),lerchangeablty ofthe components possible. (@ eretuces the inventory ofcomponents required. {a ensires certain minimum spected quality. (w Easy and quick replacement ofthe components Is posible cies censure the safety sults in overall ost eduction 142 Types (Categories) of Standards : Measures (1BWM) Some of the standards are ad fare used as guldeline, whereas by. the national brganizations, are obligatory enforced by law. Based on the defining body or organization, the andards can be divided into following three types | 4 (categories):Example of brit brittle material, Malleability ; ° Mall feability : The property of a material which enables itto be malleability. drawn into sheet called {ttle material : Cast iron is a . 4 malleable material should possess a good asticity. This property is i i ee ty is important in press (9) Resilience : + Resilience : The capacity of a material to absorb energy (elastic strain energy) within the elastic range is called resilience. + Modulus of resilience : The standard measure of resilience is modulus of resilience ‘R,’, and is defined as the energy absorbed per unit volume of material when loaded to its elastic limit. o oo ‘Modulus of Reslience (Rn) Stiess,¢ = ee Svaine—~ Fig. 1.15.5: Modulus of Resilience ae .(115:3) or Re Where, S, = elastic limit ofthe material, N/mm = strain at elastic limit, ee E = modulus of elasticity of the material, N/mm* § R, ( Sy=S.) (0.15.4) 2E sty is desirable in materials for fa © This proper springs. , Creep: | ‘rain, fig. 1.15.6 : Modulus of Toughness a A 9 3 ‘Toughness : The cotal pacity Ce, to absorb energy without racire ‘toughness. a Modulus of toughness: Gee sure of roughness meatitses Tq) and is aefined as the oa a sorbed per unit volume of MALTS when loaded till Is fracture. 1, = Jode 115.5) 0 (1.15.6) ‘The components subjected to impact loads are normally designed for toughness. Hardness : The property of a material which enables it to resist penetration, abrasion, indentation, or plastic deformation is called Hardness. Measure of hardness : The hardness is normally measured by Brinell hardness number (HB) and Rockwell hardness number (Ry Ros Re). This property is very important for the components subjected to surface stresses. ‘When a machine component is subjected to a constant stress at high temperature, it deforms slowly but progressively over a long period oftime. Creep : The progressive deformation of ‘machine component under the load at high temperature is called ereep.1g. is a deformation process ir ae ‘ fl is forced under ¢ us. ini{Machine Design (MU-6% Sem=Mech) = controls in Motorcycle : Control Controlled by [clutch lever: Left hand [Accelerator control _| Right hand Front brakelever __|Right hand Head lamp switches ieee | Lefthand thumb {indicator switch Lefthand thumb Left foot Gear shifter Rear brake pedal 9, |Kickstartlever 40. _ [ignition switch Right hand + Displays in Motorcycle: 4, Speedometer Gear indicator Headlamp indicator. 2 3, Turn indicator 4 Aesthetics and 410.6 Ergonomics, Performance : ie is compromi © petomance ar aestti. ExPain. ‘aesthetics and Performance Fig, 1.10.4 : Ergonomics, and performance are + Ergonomics, aesthetics always inter-related. + The basic principle 0! comfort. The ergonomic P applied to create more environment to the Use? * The aesthetic and positive env ergonomics is a human rinciples or designs are ‘esthetic and positive jronment adds to ‘ovement in the human comfort and Jeads to impr productivity or performance of the uStF solidification, change in CF st the boss, ‘avoid thin sections and make provisfon for easy 7 ould. tension = srefcas ton is much stronger PRCEREN ST than design the parts such that in tension. Hence, om as of the parts are under compression stressed jevahownyin Fig, 1 11.4(2)) rather than under tension, as shown in Fig. 1.11.1(b) F (@) Good (Part Under Compression)2.1 TYPES OF LOADS ¥ Machine Design (MU-6% Sem: The machine elements sleee to various external loads which ending moments, and torsional momen basically classified into three types as shown 7 Fig. 2.1.1: Types of Loads 1, Static Load : © Agradually applied load which do* direction, or point of application in magnitude, with respect to cime is known as steady load. 2 Exam] member, load due to deai 2. Fluctuating Load : «A load which direction and/or ples of static load : tension In 2 vai respect to time is alternating load. Example: engine valve springs, rotating shafts, 3, Impact Load : © Aload which issu wn as Impact OF ‘of impact toad : pact during punching 0Pe iskno Examples hammer, im .5 of fluctuating load etc. fos of fares In the components: eo diferort modes of (ales OF nent 2 ries in magnitude and/or point of application with cddenly applied with a velocity Mech. oe or components ae h include forces) ts, The loads are Fig. 24-4 es not change static load or truss d weight, tc known as fluctuating 0” force in LC. ‘ending moment on shock load. blows of a rations, wechanical 1. 3. 1 component, made of dict iding or plastic deformation mes to an end and it j jonent. Such failure en a mechanical dergoes ve 1 utility ¢0! 7 ftlure of te com atic failure ora breakage ofa mate long the cross-section normal to th piesa ese) eae fracture pmriicelisis\sudden late without plasti deformation. ‘The failure of compone to fracture. Fracture * \ suaden separation nts made of brittle material is due Elastic Deflection : ke : columns, beams, shafts, et tion, in a elastic range is termed as failure ol tn. components Il the lateral or torsion deflec ejond a permissible limit thecomponent. . . 2.3 TYPES OF STRESSES types of stresses induced in ts The various jined below: ‘mechanical components are expla 4, Direct Shear Stress 5, Torsional Shear Stress 6. Bearing Pressure 7. Crushing Stress (Bearing Stress) 8. Contact StressWH _Machine Design (MU-6% Sem-Mech,) 29 ‘Theories of Failures ‘Sr.No. | Fig. 2.3.13 Fig. 2.3.14 Jas, the transverse shear stress inarod is given by, i T surface and minimum at the inner surface. (iv), Shafts, torsion bars, shear stress 2.4 PRINCIPAL STRESSES AND MAXIMUM SHEAR STRESS @. Explain the principal stresses, * Consider a member subj g, anda shear stress ty 9 ‘as shown in Fig. 2.4.1 oo Fig. 2.4.1 : Biaxial Stress System Fig. 2.4.2: Stresses on Oblique Plane Examples of components subjected to to From Fig, 2.3.13, the torsional shear stress induced The torsional shear stress is maximum at the outer yrsional helical 2.4. jected to biaxial stresses Oy | , From Fig. Induced in a beam is given DY. rAd bl she wanverse | nore ofthe beam The examples of comp The grse shear stre5s ans ee principal (Normal) Stresses : ne and principal stress : The Ftique plane on which the shear stress 1s ero Is falled principal plane and the normal stress on the principal plane fs called principal stress. ‘Two principal stresses : These are two principal planes and correspondingly the two principal stresses (0; and 02) © ‘ear stress is maximum at the id minimum at the extreme jonents subjected Different types of 4 principal pla Maximum principal stress : oO + Oy o=—37° 244) (i) Minimum principal stress: ote. [=e ee jee 42) The shear stress ‘t’ is zero on both the principal planes. 2.4.2 Maximum Shear Stress : ‘These are two planes on which the shear stress is maximum. Maximum shear stress : (he4 ae (243) G1-% br ee ae wri