علم المواد و اختبار الشد

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علم المواد

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  دا   و   دشا   ةوق ( Tensile Strength وا   دا   و   أ   و  ) (UTS) (Ultimate Tensile Strength)   ـ      زرو UTS σ وأ m R       و   ا   صاو (  د      أ   ودا   دا  ) و   دا   لاأ   ا      د   ل   أ   ىووا   را   طا         وب   دا   و   سو  . وم / م 2    / نو   وأ 2   و / لطر   وأ  ) ل   نو  =( 2   و / لطر   و   وأ 2  . m R = max P /  A 0         أ   أ   تاذ      اوا      أ   إ   دا   را   ئ   ن   ل   ا   نﻷا   مظ      ا      دا   و   زا      نأ   ن   ىذا   ﻷا   ل   ً   دا   و   ر   نأ      طا   تاز     . زا   و   د   فورظ   لظ      ز   ةدا   و         تاذ   ا   هذ   نأ   حو  . روا   ىدأ   ل   دا   ةد   ردَُ   نا   دا   ن   ن   ةدد   تاو  . اوا   دا   تا      ةد   اَوُ   ا   ًد   رأ   دا   فورظ   لظ      ا   دا   و   سأ      ازﻷا   ورأ      و   ا   هاو  . نأ   ل   ماد   ب   ل   ت      وط   را   بو   كذ   و  . و   و      طا   تاز   ا   لﻷا   ىذ   ما   دإ         اذ   و   اد   و      تأ   د   داوا   و   دد   دا   و   ماداداوا   دد   اد   ةد      وا   و   دا   و   دد   لا   ن   ﻷ   كذ  . ا   وأ   زا   دد   ئا   برا      ل   ىذا   موا   س   ر   تطرا   كو  . تا   ةدو   ارو   تاوا   ضارغﻷ   ةد      سا   ةد   ً      د   ا   داو     .    ةد   نو      غ   لا   وو   ةدا   ل   صئو   دا   و   ن   قطا   او . م   م   ر      دا   و   أ   رظا  وا  ا   صاو  ا   را   خ   دولاق ذه   حت   يف   ي ر   كشب   مهاس   ا   و   دا     ا   تارا  اوا   صاو   ئ     را    )  سدنه ( عوضخ   عوضخا   ةوق ( Yield Strength   ) ةر      ثاد   مزا   دا   سا   أ   ةرا   ندا   هوا         ا و   ندا   هوا   ن   ةدد   و   و   عو   نر   وأ   نو      إد   عو   ووإ   دد   د   عو   و  . ا   صاوب   عوا   و   س   وم / م 2  / نو   وأ 2 وأ  ) ل   نو  =( و / لطر 2 و / لطر   و   وأ 2.  فر   . ددا   رغ   كئ   طا   عوا   كو 1: True elastic limit 2: Proportionality limit 3: Elastic limit 4: Offset yield strength It is often difficult to precisely define yielding due to the wide variety of stress  – strain curvesexhibited by real materials. In addition, there are several possible ways to define ldingyie [1] : True elastic limit The lowest stress at whichdislocationsmove. This definition is rarely used, since dislocations move at very low stresses, and detecting such movement is very difficult . Proportionality limit The point at which the stress  – strain curve deviates fromHooke's law ; i.e., becomes nonlinear  . Elastic limit   خ   دولقا   اذه   ررح   يف   يسئر   لكشب   مهس  Beyond the elastic limit, permanent deformation will occur. The lowest stress at which permanent deformation can be measured. This requires a manual load-unload procedure, and the accuracy is critically dependent on equipment and operator skill. For elastomers , such asrubber  , the elastic limit is much larger than the proportionality limit . ( دوا   دجإ   وأ   عوضخا   ةوق yield strength or proof stress ) This is the most widely used strength measure of metals, and is found from the stress-strain curve as shown in the figure to the right. A plastic strain of 0.2% is usually used to define the offset yield stress, although other values may be used depending on the material and the application. The offset value p0.2 en as a subscript, e.g. Ris giv =310 MPa. In some materials there is essentially no linear region and so a certain value of strain is defined instead.  Although somewhat arbitrary, this method does allow for a consistent comparison of materials . ا   عوضخا   ةطقنسا   عوضخا   ةطقنو    Some metals, such as mild steel, reaches an upper yield point before it drops rapidly to a lower yield point. The material response is linear up until the upper yield point, but the lower yield point is used in structural engineering as a conservative value .  ةَ دْ ح   عوضخ   ةوق ( Offset Yield Strength    ن  ) ا   و   دا   زاو   م   ط      كذ   و   راد   غ      د   و   ا   ن   ما   ز 0,002 وأ 0,2 از   يرأ   م   مد   د ( لا   رو     %  ل   تاوا   ض      لا   رو    0,001 وأ 0,1    و  )% ىذا   دا      ا   هذ      عوا   و      ثاد   مزا   دا      عوا   و   نأ      و   لا   و   دا         طا      ط 0,2% ندا   لا         دا   و   و   رطا   هذ   ز   و  .    و   رأ      و   سا   رارا   ود   عوإ   دد / م   ب   عوا   و   سو  .2  / نو   وأ 2 و / لطر   وأ  ) ل   نو  =(2 و / لطر   و   وأ 2.  ردا  J.R. Davis (Edit.) , Tensile Testing, 2nd edition, ASM International, 2004 . 1 . ^ G. Dieter  , Mechanical Metallurgy  , McGraw-Hill, 1986   Avallone, Eugene A & ;. Baumeister III, Theodore (1996.) Mark's Standard Handbook for Mechanical Engineers . New York: McGraw-Hill. ISBN 0-07-004997-1 .  Young, Warren C & ;. Budynas, Richard G ( .2002.) Roark's Formulas for Stress and Strain, 7th edition . New York: McGraw-Hill. ISBN 0-07-072542-X .  Engineer's Handbook  Boresi, A. P., Schmidt, R. J., and Sidebottom, O. M ( .1993.)  Advanced Mechanics of Materials ,5 th edition. John Wiley & Sons. ISBN 0-471-55157-0  Oberg, E., Jones, F. D., and Horton, H. L ( .1984.) Machinery's Handbook  ,22 nd edition. Industrial Press. ISBN 0-8311-1155-0   Shigley, J. E., and Mischke, C. R ( .1989.) Mechnical Engineering Design ,5 th edition. McGraw Hill. ISBN 0-07-056899-5 دشل ص وخ   دشا   صاوخ ( Tensile Properties   ) ا   صاوا   ةاا   را   و (1) ا   وا   و   دا         د      أ    . ل (2) وا   وإ      ود   عو   وأإ   دد   د   عو   و . بوطا   عوا   ر   ب (3) طا   وطا   أا   ضا    . ردا (1) J.R. Davis (Edit.) , Tensile Testing, 2nd edition, ASM International, 2004 .(2) J. Dieter, Mechanical Metallurgy, 3rd edition, McGraw Hill, 1986 .   دا   را   دشا   ربخا ( Tensile Test أ   دأ   و  ) ا   تاراىر   ااوا : ا   ب   هؤارإ   م   و   ا  ã دا   صاواوا   ردا   تط   ا  ã وأ   ةدد      بأ   روط   ما   أ   ا   ا   فورظ   وأ   ا   داوا   ن      را   ئ   مدةدد   داو  ã او   مدوا   ىدأ   دارو      و   روا   دأ   رغ   لأ   ر   ت   تو   اذإ   داوا   كو   ؤماارد   رأ  ã    اردإ   مئادا   صاوا   مأ   ن   دا   صاواو   ا   تاواهذ   ط   ئار   د   داوا   ر      واوا   تسرف   ]  إ [  1 ا   را   ن   ةا   توا  2 ا   را   ارإ     3 دا  4 أ   رظا دا   را   ن   ةا   توا ا   صاو :    و  ã    ةدد      ثاد   مزا   دا      تأ   او  : ةدا   ودا   هوا ( وا   ووأ  ) أا (     ةد   نا   ودا   ما      ةر   تط      نرا   نذ      ةدا   و  )   خ   دولاق ذه   حت   يف   ي ر   كشب   مهاس
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