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MECHANICS OF MATERIALS - I

MECHANICS OF MATERIALS - I. INTRODUCTION TO STUDY OF MECHANICS OF MATERIALS. MATTER, MATERIALS & ELEMENTS. MATTER IS SOMETHING WHICH HAS MASS AND OCCUPIES VOLUME. MATERIAL IS THE REFINED TYPE OF MATTER DIVIDED INTO DIFFERENT CATEGORIES.

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MECHANICS OF MATERIALS - I

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  1. MECHANICS OF MATERIALS - I

  2. INTRODUCTION TO STUDY OF MECHANICS OF MATERIALS

  3. MATTER, MATERIALS & ELEMENTS • MATTER IS SOMETHING WHICH HAS MASS AND OCCUPIES VOLUME. • MATERIAL IS THE REFINED TYPE OF MATTER DIVIDED INTO DIFFERENT CATEGORIES. • DIFFERENT MATERIALS CATEGORIZED INTO DIFFERENT TYPES ON THE BASIS OF THEIR PROPERTIES, PHYSICAL, MECHANICAL, CHEMICAL, ELECTRICAL ETC.

  4. BACKGROUND OF MATTER & MATERIALS UNIVERSE MATTER MATERIAL (ELEMENTS) ORGANIC INORGANIC METALS, CERAMICS, COMPOSITES, GLASSES, STONE, WATER, ACIDS, BASES, ARGON, HELIUM LIVING ORGANISMS, POLYMERS, SOILS, FOOD CHEMICALS, CARBON OXIDE

  5. DIFFERENT STATES OF MATTER • SOLID • LIQUID • GAS • PLASMA • IN PHYSICS AND CHEMISTRY MATTER EXHIBITS BOTH AS WAVE-TYPE AND PARTICLE-TYPE BEHAVIOUR AND IS CALLED WAVE-PARTICLE DUALITY

  6. PERIODIC TABLE • THE PERIODIC TABLE OF THE ELEMENTS IS A TABULAR DISPLAY OF THE SO FAR IDENTIFIED CHEMICAL ELEMENTS. THE LAYOUT OF THE PERIODIC TABLE DEMONSTRATES RECURRING ("PERIODIC") CHEMICAL PROPERTIES. • ELEMENTS ARE LISTED IN ORDER OF INCREASING ATOMIC NUMBER. ROWS (PERIODS) ARE ARRANGED SO THAT ELEMENTS WITH SIMILAR PROPERTIES FALL INTO THE SAME COLUMNS (GROUPS OR FAMILIES).

  7. AS OF 2010, THE TABLE CONTAINS 118 CHEMICAL ELEMENTS WHOSE DISCOVERIES HAVE BEEN CONFIRMED. • NINETY-FOUR ARE FOUND NATURALLY ON EARTH, AND THE REST ARE SYNTHETIC ELEMENTS THAT HAVE BEEN PRODUCED ARTIFICIALLY IN PARTICLE ACCELERATORS. • THE MAIN VALUE OF THE PERIODIC TABLE IS THE ABILITY TO PREDICT THE CHEMICAL PROPERTIES OF AN ELEMENT BASED ON ITS LOCATION ON THE TABLE. • IT SHOULD BE NOTED THAT THE PROPERTIES VARY DIFFERENTLY WHEN MOVING VERTICALLY ALONG THE COLUMNS OF THE TABLE THAN WHEN MOVING HORIZONTALLY ALONG THE ROWS.

  8. TYPES OF MATERIALS MATERIALS CAN BE DIVIDED INTO DIFFERENTTYPOLOGIES IN RELATION TO THEIR COMPOSITION AND PROPERTIES. SUCH AS • METALS • CERAMICS • POLYMERS • COMPOSITES • SEMICONDUCTORS • BIOMATERIALS • SMART MATERIALS • NANOMATERIALS

  9. SELECTION OF MATERIALS • ALL TYPES OF MATERIALS EXHIBIT MANY DIFFERENT PROPERTIES WHICH CAN BE CLASSIFIED AS PHYSICAL, MECHANICAL, CHEMICAL, ELECTRICAL, MAGNETIC AND SO ON. • QUITE MANY PROPERTIES OR QUALITIES OF MATERIALS NEED TO BE CONSIDERED WHEN CHOOSING A MATERIAL TO MEET DESIGN INPUT REQUIREMENTS. • THESE MAY BE SUCH AS PHYSICAL, CHEMICAL & MECHANICAL PROPERTIES, MANUFACTURING CHARACTERISTICS, AVAILABILITY, RAW MATERIALS AND MANUFACTURING COSTS.

  10. SELECTION OF MATERIALS • ALSO NEEDED AESTHETIC QUALITIES SUCH AS APPEARANCE, COLOR, SHAPE, TEXTURE. • SOME OF THE IMPORTANT CHARACTERISTICS AND PROPERTIES OF MATERIALS ARE SHOWN BELOW TO HAVE AN IDEA ABOUT WIDE RANGE OF SELECTION OF CRITERIA.

  11. MATERIAL PROPERTIES AND QUALITIES • PHYSICAL PROPERTIES: DENSITY, MELTING POINT, HARNESS, ELASTIC MODULI, DAMPING CAPACITY • MECHANICAL PROPERTIES YIELD, TENSILE, COMPRESSIVE & TORSIONAL STRENGTHS, DUCTILITY, FATIGUE STRENGTH, CREEP STRENGTH, FRACTURE TOUGHNESS • CHEMICAL PROPERTIES RESISTANCE TO OXIDATION, CORROSION, SOLVENTS & ENVIRONMENTAL FACTORS

  12. MORE PROPERTIES • OTHER NON-MECHANICAL PROPERTIES ELECTRICAL, MAGNETIC, OPTICAL AND THERMAL PROPERTIES • MANUFACTURING PROPERTIES ABILITY TO BE SHAPED BY MOULDING, CASTING, PLASTIC DEFORMATION, POWDER PROCESSING, MACHINING, ABILITY TO BE JOINED BY ADHESIVES, WELDING AND OTHER PROCESSES • AESTHETIC PROPERTIES APPEARANCE, TEXTURE AND ABILITY TO ACCEPT SPECIAL FINISHES • ECONOMIC PROPERTIES RAW MATERIAL AND PROCESSING COSTS, AVAILABILITY

  13. CASE STUDY DRINK CONTAINER • WHAT ARE THE REQUIREMENTS?

  14. CASE STUDY - DRINK CONTAINER • PROVIDE LEAK FREE ENVIRONMENT FOR STORING LIQUID. • COMPLY WITH FOOD STANDARDS & PROTECT LIQUID FROM HEALTH HAZARDS. • FOR FIZZY DRINKS, WITHSTAND PRESSURE. • BRAND IMAGE & IDENTITY • EASY TO OPEN • EASY TO STORE & TRANSPORT • CHEAP FOR HIGH VOLUMES

  15. POSSIBLE MATERIALS • Steel • Aluminium • Glass • Plastic • Paper

  16. MATERIAL PROPERTIES TESTING TESTING OF MATERIALS IS IS AN ESSENTIAL PART OF ANY ENGINEERING ACTIVITY. TESTING AND INSPECTION MUST TAKE PLACE AT MANY STAGES IN THE COMPLEX PROCESS OF PRODUCING ENGINEERING MATERIALS WHETHER THESE ARE METALS, POLYMERS, CERAMICS AND COMPOSITES AND THEIR ALLOYS. TESTING AND INSPECTION IS ALSO IMPORTANT DURING THE FORMING OF THESE MATERIALS INTO COMPONENTS AND ASSEMBLING THE COMPONENTS TO CREATE AN ENGINEERING PRODUCT TO SATISFY SOME SPECIFIC REQUIREMENTS. THE NEED OF TESTING AND INSPECTION DOES NOT CEASE ONCE THE PRODUCT HAS BEEN MANUFACTURED AND PUT INTO SERVICE. IT IS FREQUENTLY NECESSARY TO CHECK AND TEST THE PRODUCT EVEN DURING THE SERVICE LIFE OF PRODUCTS TO MONITOR CHANGES SUCH AS THE POSSIBILITY OF DEVELOPMENT OF FATIGUE OR CORROSION DAMAGE.

  17. THEREFORE THE TYPES OF TEST USED CAN BROADLY BE CLASSIFIED INTO FOLLOWING TWO CATEGORIES: TESTS TO DETERMINE THE PROPERTIES OF MATERIALS TESTS TO DETERMINE THE INTEGRITY OF THE MATERIALS, COMPONENTS OR STRUCTURES TESTS IN THE FIRST CATEGORY ARE GENERALLY OF A DESTRUCTIVE NATURE. THESE ARE PERFORMED ON SAMPLE OF A MATERIAL AND THE TEST PIECE IS DAMAGED OR BROKEN IN THE PROCESS. TESTS IN THE SECOND CATEGORY ARE OF NON-DESTRUCTIVE NATURE AND ARE USED TO DETECT THE PRESENCE OF INTERNAL OR SURFACE FLAWS IN A MATERIAL, COMPONENT OR FINISHED PRODUCT. IN THIS CATEGORY PARTS ARE NOT BROKEN FOR TESTING.

  18. TEST PROCEDURES HAVE BEEN DEVELOPED FOR DETERMINATION OF PROPERTIES OF MATERIALS SUCH AS HARDNESS TESTING, IMPACT TESTING, TENSILE TESTING. COMPRESSIVE TESTING SHEAR / TORSION TESTING FATIGUE TESTING CREEP TESTING FATIGUE-CREEP TESTING TESTS HAVE TO BE PERFORMED ACCORDING TO PROCEDURES PUBLISHED BY ANSI, ASTM, BSI AND OTHER STANDARD ORGANIZATIONS.

  19. WHAT IS MECHANICS OF MATERIALS? • WE HAVE DISCUSSED A LOT ABOUT MATERIALS OR ENGINEERING MATERIALS. • WE HAVE WITH US REQUIRED INFORMATION ABOUT THE PRODUCT WE ARE GOING TO MANUFACTURE. • PRODUCT WOULD BE UNDER DIFFERENT TYPES OF LOADING DURING SERVICE LIFE. • SO WE MUST KNOW HOW WOULD BEHAVE THE MATERIAL UNDER SUCH TYPE OF LOADINGS………….. THIS IS MECHANICS OF MATERIALS.

  20. Machine / Mechanics • MACHINE • MECHANIC • MECHANICS • MECHANICAL ENGINEERING • MECHANISM

  21. WHAT IS MECHANICS? • IN VERY SIMPLE WORDS MECHANICS IS THE SCIENCE OF FORCE AND MOTION AND HENCE SCIENCE OF MACHINERY. • IF IT IS FURTHER ELABORATED, THEN MECHANICS IS THE PHYSICAL SCIENCE THAT IS CONCERNED WITH THE CONDITION OF REST OR MOTION OF BODIES ACTED ON BY FORCES OR BY THERMAL DISTURBANCES.

  22. WHAT IS MECHANICS? • IT CAN FURTHER BE EXPLAINED AS MECHANICS IS THE BRANCH OF PHYSICS CONCERNED WITH THE BEHAVIOR OF BODIES WHEN SUBJECTED TO FORCES OR DISPLACEMENTS, AND THE SUBSEQUENT EFFECTS OF THE BODIES ON THEIR ENVIRONMENT. • THE DISCIPLINE HAS ITS ROOTS IN SEVERAL ANCIENT CIVILIZATIONS. DURING THE EARLY MODERN PERIOD, SCIENTISTS SUCH AS GALILEO, KEPLER, AND ESPECIALLY NEWTON, LAID THE FOUNDATION OF MECHANICS AND WHAT IS NOW KNOWN AS CLASSICAL MECHANICS.

  23. TYPES OF MECHANICS OF MATERIALS • THE STUDY OF BODIES AT REST IS KNOWN AS STATICS • THE STUDY OF BODIES WHILE THESE ARE MOTION IS CALLED DYNAMICS • THE PRACTICAL APPLICATION OF SCIENCE OF MECHANICS IS KNOWN AS APPLIED MECHANICS. APPLIED MECHANICS EXAMINES THE RESPONSE OF BODIES (SOLIDS AND FLUIDS) OR SYSTEMS OF BODIES TO EXTERNAL FORCES. • SOME EXAMPLES OF MECHANICAL SYSTEMS INCLUDE THE FLOW OF A LIQUID UNDER PRESSURE, AND THE FRACTURE OF A SOLID FROM AN APPLIED FORCE.

  24. TYPES OF MECHANICS OF MATERIALS • THEREFORE, THERE ARE TWO MAJOR TYPES OF APPLIED MECHANICS, MECHANICS OF SOLIDSAND MECHANICS OF FLUIDSRESPECTIVELY. • THE BASIC PRINCIPLES OF STATICS AND DYNAMICS ARE FUNDAMENTAL TO MECHANICS OF SOLIDS AND MECHANICS OF FLUIDS. • MECHANICS OF SOLIDS IS THE SUBJECT TO BE DISCUSSED IN THIS SEMESTER. THIS IS ALSO KNOWN AS MECHANICS OF MATERIALS, STRENGTH OF MATERIALSAND ALSO MECHANICS OF DEFORMABLE BODIES.

  25. CLASSICAL MECHANICS • CLASSICAL MECHANICS IS A BRANCH OF CLASSICAL PHYSICS WHICH IS CONCERNED WITH THE SET OF PHYSICAL LAWS DESCRIBING THE MOTION OF BODIES UNDER THE ACTION OF A SYSTEM OF FORCES. • THIS IS ONE OF THE OLDEST AND LARGEST SUBJECTS IN SCIENCE, ENGINEERING AND TECHNOLOGY. • CLASSICAL MECHANICS DESCRIBES THE MOTION OF MACROSCOPIC OBJECTS, FROM PROJECTILES TO PARTS OF MACHINERY, AS WELL AS ASTRONOMICAL OBJECTS SUCH AS SPACECRAFT, PLANET, STARS AND GALAXIES.

  26. CLASSICAL MECHANICS • BESIDES THIS, MANY SPECIALIZATIONS WITHIN THE SUBJECT DEAL WITH GASES, LIQUIDS, SOLIDS, AND OTHER SPECIFIC SUB-TOPICS. • CLASSICAL MECHANICS PROVIDES EXTREMELY ACCURATE RESULTS AS LONG AS THE DOMAIN OF STUDY IS RESTRICTED TO LARGE OBJECTS AND THE SPEEDS INVOLVED DO NOT APPROACH THE SPEED OF LIGHT.

  27. QUANTUM MECHANICS • QUANTUM MECHANICS IS A BRANCH OF PHYSICS PROVIDING A MATHEMATICAL DESCRIPTION OF THE WAVE-PARTICLE DUALITY OF MATTER AND ENERGY. • QUANTUM MECHANICS DESCRIBES THE TIME EVOLUTION OF PHYSICAL SYSTEMS VIA A MATHEMATICAL STRUCTURE CALLED THE WAVE FUNCTION. • QUANTUM MECHANICS DIFFERS SIGNIFICANTLY FROM CLASSICAL MECHANICS IN ITS PREDICTIONS WHEN THE SCALE OF OBSERVATIONS BECOMES COMPARABLE TO THE ATOMIC AND SUB-ATOMIC SCALE.

  28. QUANTUM MECHANICS • HOWEVER, MANY MACROSCOPIC PROPERTIES OF SYSTEMS CAN ONLY BE FULLY UNDERSTOOD AND EXPLAINED WITH THE USE OF QUANTUM MECHANICS. • PHENOMENA SUCH AS SUPERCONDUCTIVITY, THE PROPERTIES OF MATERIALS SUCH AS SEMICONDUCTORS AND NUCLEAR REACTION MECHANISMS OBSERVED AS MACROSCOPIC BEHAVIOUR, CANNOT BE EXPLAINED USING CLASSICAL MECHANICS.

  29. BOOKS ON MECHANICS OF MATERIALS • MECHANICS OF MATERIALS BY BEER & DEWOLF MCGRAW-HILL • MECHANICS OF MATERIALS BY R. CRAIG JOHN WILEY • MECHANICS OF MATERIALS BY JAMES GERE BROOKS • MECHANICS OF MATERIALS BY R. C. HIBBLELER PEARSON/PRENTICE HALL

  30. APPLICATION OF MECHANICS OF MATERIALS • APPLICATION OF MECHANICS OF MATERIALS IS ENDLESS AND CAN BE FOUND IN EVERY DISCIPLINE OF ENGINEERING. FOR EXAMPLE, BUILDINGS AND BRIDGES, MACHINES AND MOTORS, SUBMARINES AND SHIPS, OR AEORPLANES AND ANTENNAS. • THE SUBJECTS OF STATICS AND DYNAMICS ARE ALSO IMPORTANT, BUT THESE DEAL WITH PRIMARILY WITH THE FORCES AND MOTIONS ASSOCIATED WITH PARTICLES AND RIGID BODIES. • HOWEVER, MECHANICS OF MATERIALS GO A STEP FURTHER TO EXAMINE THE STRESSES AND STRAINS THAT OCCUR INSIDE REAL BODIES THAT DEFORM UNDER LOADS.

  31. APPLICATION OF MECHANICS OF MATERIALS • AS WE HAVE DISCUSSED THAT MECHANICS OF MATERIALS DEALS WITH RESPONSE OF SOLID BODIES SUBJECTED TO DIFFERENT TYPES OF LOADING CONDITIONS. • THE SOLID BODIES FROM ENGINEERING POINT OF VIEW ARE AXIALLY LOADED MEMBERS, SHAFTS IN TORSION, THIN SHELLS, BEAMS AND COLUMNS, STRUCTURES WHICH ARE SUB-ASSEMBLIES AND ASSEMBLIES OF THESE COMPONENTS.

  32. APPLICATION OF MECHANICS OF MATERIALS • AIM OF MECHANICS OF MATERIALS WOULD, THEREFORE, BE THE DETERMINATION OF THE STRESSES, STRAINS, AND DEFLECTIONS PRODUCED BY THE LOADS. • A COMPLETE PICTURE OF THE MECHANICAL BEHAVIOUR OF THE BODY CAN EASILY BE DETERMINED IF STRESS, STRAIN AND DEFLECTIONS ARE KNOWN FOR ALL VALUES OF LOAD UP TO THE FAILURE LOAD.

  33. BOTH THEORETICAL ANALYSES AND EXPERIMENTAL RESULTS HAVE EQUALLY IMPORTANT ROLES IN THE STUDY OF MECHANICS OF MATERIALS. • HOWEVER, IT MUST BE NOTED THAT THEORETICAL DERIVATIONS AND FORMULAS CANNOT BE USED IN A REALISTIC WAY UNLESS CERTAIN PROPERTIES OF THE MATERIALS ARE NOT DETERMINED. • THE SPECIFIC PROPERTIES OF MATERIALS ARE AVAILABLE ONLY AFTER CONDUCTING SUITABLE EXPERIMENTS IN THE LABORATORIES AND EXTRACTING RESULTS. • FURTHERMORE, MANY PRACTICAL ENGINEERING PROBLEMS OF GREAT IMPORTANCE CANNOT BE HANDLED EFFICIENTLY BY THEORETICAL MEANS, AND HENCE EXPERIMENTAL RESULTS ARE QUITE ESSENTIAL.

  34. SYSTEM OF UNITS • DISCUSSION ABOUT SYSTEMS OF UNITS IS ALSO VERY IMPORTANT. IF IT IS NOT VERY CLEARLY UNDERSTOOD ACCURATE RESULTS CAN BE OBTAINED. • ALL SYSTEMS ARE SAME, IT ALL DEPENDS UPON YOUR CHOICE. HOWEVER, UNDERSTANDING MUST BE QUITE CLEAR. • MANY SYSTEMS OF MEASUREMENTS HAVE BEEN DEVISED OVER THE CENTURIES, BUT TODAY THERE ARE TWO BASIC SYSTEMS OF MEASUREMENTS USE IN ENGINEERING AND SCIENTIFIC WORK.

  35. BASIC SYSTEMS OF UNITS • INTERNATIONAL SYSTEM OF UNITS (SI) • U.S. CUSTOMARY SYSTEM (USCS), IMPERIAL SYSTEM (IS) OR BRITISH SYSTEM (BS)

  36. SYSTEM OF UNITS • THE INTERNATIONAL SYSTEM (SI) IS BASED UPON MASS (KG), LENGTH (METER) AND TIME (SECONDS). THESE THREE QUANTITIES ARE INDEPENDENT OF THE LOCATION AND HENCE THIS SYSTEM IS KNOWN AS ABSOLUTE SYSTEM. • THE U.S. CUSTOMARY SYSTEM (USCS) IS BASED UPON FORCE (POUND), LENGTH (FOOT) AND TIME (SECONDS). THIS SYSTEM IS NOT INDEPENDENT AS UNIT OF FORCE DEPENDS UPON GRAVITATIONAL ATTRACTION AND HENCE IS ALSO CALLED GRAVITATIONAL SYSTEM. • THE SI SYSTEM IS AN IMPROVED AND MODERNIZED VERSION OF WELL KNOWN METRIC SYSTEM AS SI SYSTEM HAS IMPORTANT NEW FEATURES NOT PREVIOUSLY PART OF METRIC SYSTEM.

  37. SYSTEM OF UNITS • STRESS IS DEFINED AS FORCE PER UNIT AREA. IN SI SYSTEM THE UNIT OF FORCE IS NEWTON (N) AND THE UNIT OF AREA IS SQUARE METERS. HENCE UNIT OF STRESS IS NEWTONS PER SQUARE METER (N/M²). THIS IS ALSO KNOWN AS PASCAL (PA). • IN USCS SYSTEM THE UNIT OF FORCE IS POUND AND HENCE UNIT OF STRESS WOULD BE POUNDS (P) PER SQUARE FOOT (LB/FT²). COMMONLY STRESS IS MEASURED AS POUNDS PER SQURE INCHES (PSI). • AS PASCAL IS A VERY SMALL VALUE IN SI UNITS, IT IS TAKEN AS MEGA PASCALS (MPA) OR GIGA PASCALS (GPA). IN USCS SYSTEM LARGER VALUES OF STRESSES ARE ALSO MEASURED AS KSI.

  38. CONVERSION OF UNITS POUND = 4.45 NEWTONS KIP = 4.45 KILONEWTONS PSI = 6890 PASCALS KSI = 1000 PSI KSI = 6.890 PASCALS PSF = 47.9 PASCALS KSF = 47.9 KILOPASCALS

  39. QUESTIONS AND QUERIES IF ANY! IF NOT THEN GOOD BYE SEE ALL OF YOU IN NEXT LECTURE ON STRESS AND STRAIN, allowable stresses & FACTOR OF SAFETY

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