Distributed over the cross section if

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Unformatted text preview: quate moments Mx, My from axial force P with Mx, My obtained from ¯ x dA Py = ¯ y dA P x = distributed stresses Z Z Assume σ is uniformly distributed Py = ¯ y dA P x = ¯ x dA R R P y dA x (coordinates of the centroid of an area) dA Invoke stress definiIon = y = ¯ x = ¯ A A A (1-3 a,b) 1/7/13 M. Mello/Georgia Tech Aerospace 7 UNIAXIAL STRESS AND STRAIN •  DeformaIon of the bar is uniform throughout its volume •  The bar is prismaIc “PrismaIc bar” : straight member with same cross secIon throughout Its length •  Loads act through centroids of cross- secIons •  Material making up the bar is homogeneous 1/7/13 M. Mello/Georgia Tech Aerospace 8 MECHANICAL PROPERTIES OF MATERIALS (I) LOAD CELL MEASURES APPLIED FORCE DURING LOADING EXTENSOMETER MEASURES SPECIMEN ELONGATON DURING LOADING LINEAR VARIABLE DIFFERENTIAL TRANSFORME (LVDT) MONITORS ACTUATOR POSITION DURING LOADING 1/7/13 M. Mello/Georgia Tech Aerospace 9 MECHANICAL TEST STANDARDS ²་  THE ENDS OF THE TENSILE TEST SPECIMEN ARE ENLARGED WHERE THEY FIT INTO THE MECHANICAL GRIPS IN ORDER TO PREVENT FAILURE NEAR THE GRIPS ²་  IN PROPERLY DESIGNED TEST SPECIMENS, FAILURE WILL OCCUR IN THE PRISMATIC PORTION WHERE THE STRESS DISTRIBUTION IS UNIFORM and BAR IS SUBJECTED TO PURE TENSION ²་  MACHINE PROGRAMMED LOADS SPECIMEN AT CONSTANT DISPLACEMENT RATE (DISPLACEMENT CONTROL) OR CONSTANT FORCE RATE (LOAD CONTROL) ²་  EXTENSOMETER PROVIDES CONTINUOUS MEASUREMENT OF SPECIMEN ELONGATION DURING LOADING ²་  LOAD CELL PROVIDES CONTINUOUS MEASUREMENT OF FORCE DURING LOADING ²་  DIGITAL DATA- ROCESSING SYSTEMS RECORD AND GRAPH THE TEST RESULTS (GENERATE A REAL- TIME PLOT OF LOAD VERSUS ELONGATION (P vs. δ) or STRESS VERSUS STRAIN (σ vs. ε). 1/7/13 ²་  SPECIMEN DIMENSIONS AND TEST METHODS (e.g. LOADING RATE) ARE STANDARDIZED BY AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM), AMERICAN STANDARDS ASSOCIATION (ASA), AND NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY (NIST) M. Mello/Georgia Tech Aerospace 10 SERVO- HYDRAULIC MECHANICAL LOAD FRAMES 1/7/13 MTS 858 (25kN capacity) MTS 810 (100kN capacity) M. Mello/Georgia Tech Aerospace 11 CLIP ON MECHANICAL EXTENSOMETER l0 + l0 ²་  Voltage output is proporIonal to Δ...
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This note was uploaded on 09/19/2013 for the course CEE 3001 taught by Professor Zhu during the Spring '09 term at Georgia Institute of Technology.

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