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Effect of Material Properties on Design
Published in Mahmoud M. Farag, Materials and Process Selection for Engineering Design, 2020
Elastic instability becomes an important design criterion in the case of columns, struts, and thin-wall cylinders subjected to compressive axial loading where failure can take place by buckling. Buckling takes place if the applied axial compressive load exceeds a certain critical value, Pcr. The Euler column formula is usually used to calculate the value of Pcr, which is a function of the elastic modulus of the material, geometry of the column, and restraint at the ends. For the fundamental case of a pin-ended column, that is, ends are free to rotate around frictionless pins, Pcr is given as Pcr=π2EIL2
Three-dimensional second order analysis of scaffolds with semi-rigid connections
Published in J.A. Packer, S. Willibald, Tubular Structures XI, 2017
U. Prabhakaran, M.H.R. Godley, R.G. Beale
Steel scaffolds are extensively used to provide access and support to permanent works during different stages of their construction. These structures are generally slender and prone to fail by elastic instability. The elastic buckling load of a scaffold is strongly influenced by the stiffness of the connections, which exhibits semi-rigid deformation behaviour that can contribute substantially to the stability of the structure as well as to the distribution of member force.
Columns
Published in Robert L. Mott, Joseph A. Untener, Applied Strength of Materials, 2016
Robert L. Mott, Joseph A. Untener
After completing this chapter, you should be able to do the following: Define column.Differentiate between a column and a short compression member.Describe the phenomenon of buckling, also called elastic instability.Define radius of gyration for the cross section of a column and be able to compute its magnitude.Understand that a column is expected to buckle about the axis for which the radius of gyration is the minimum.Define end-fixity factor, K, and specify the appropriate value depending on the manner of supporting the ends of a column.Define effective length, Le, slenderness ratio, and transition slenderness ratio (also called the column constant, Cc), and compute their values.Use the values for the slenderness ratio and the column constant to determine when a column is long or short.Use the Euler formula for computing the critical buckling load for long columns and the J.B. Johnson formula for short columns.Apply a design factor to the critical buckling load to determine the allowable load on a column.Recognize efficient shapes for column cross sections.Design columns to safely carry given axial compression loads.Apply the specifications of the American Institute of Steel Construction (AISC) and the Aluminum Association to the analysis of columns.Analyze columns that are initially crooked to determine their critical buckling load.Analyze columns for which the applied load acts eccentric to the axis of the column.
Mechanical properties characterization and zero Poisson’s ratio design for perforated auxetic metamaterial by computational homogenized method
Published in Mechanics of Advanced Materials and Structures, 2022
Feng Hou, Sihang Xiao, Hui Wang
The realization of desired auxetic properties of mechanical metamaterials mainly depends on the elaborated design of microstructure so that the global deformation behavior of auxetic structures is governed by local mechanism. In general, there are several mechanisms leading to auxetic deformation [6], mainly including rigid rotation, beam bending, elastic instability, etc. The rigid rotation mechanism can be used to design kirigami-like auxetic structures, in which the rigid cells connected with rigid nodes are allowed to rotate [7–11]. The beam bending mechanism uses the bending deformation of beams to produce the beam-dominated auxetic structures, such as the classic reentrant structures [12–14] and the chiral structures [15–17]. Different to the rigid rotation and beam bending mechanisms, the elastic instability mechanism typically refers to the deformation of perforated solid structures with elliptical cuts, which can be regarded as a consequence of elastic buckling of circular hole under uniaxial compression [18,19]. Due to the attractive characteristics of relatively simple topology and ease to be produced, the perforated structures have formed one of the most important classes of auxetic materials and the concepts have been successfully extended to include various shaped cuts, for example, rectangular cuts [20,21] or slits [22,23], elliptical or peanut-shaped cuts [24–26], star-shaped or triangular cuts [27,28]. All these practices demonstrated that the architected perforations offer opportunity to design functionalized auxetic materials and structures. Among these proposed perforated auxetic structures, the elliptical perforation is of particular interest due to the extra-simple mathematical depiction of its smooth profile which can make it easier to be manufactured, and the tunable static and dynamic mechanical properties [29,30]. Therefore, the auxetic metamaterial perforated with elliptical cuts is studied in this work.