X. Lei

Pennsylvania State University, University Park, MD, United States

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Publications (2)2.35 Total impact

  • C. J. Lissenden · X. Lei
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    ABSTRACT: Conventional methods for constructing yield loci rely on the assumption that nonlinear strains are permanent strains, which is not always the case. A nickel-base alloy, SiC fiber-reinforced titanium, an aluminum alloy, and particlereinforced aluminum have been observed to violate this assumption. We present a method for constructing yield loci using a proof strain criterion for the permanent strain that relies on cyclic, proportional, probes of the yield surface. Two criteria are implemented: one for stress reversal and one for yielding. The method is demonstrated by the construction of initial and subsequent yield loci in the axial-shear stress plane using thin-walled tubular specimens. Results are presented for 6061-T6 aluminum as well as for 6092/SiC/17.5p-T6, which is 6092 aluminum reinforced with 17.5 volume percent silicon carbide particulate. The centers of the initial yield loci for the composite are eccentric to the origin of the stress plane most likely because of the residual stresses induced during processing. Material hardening due to multiaxial stress states can be described by tracking evolution of the subsequent yield surfaces and here hardening of the particulate composite was primarily kinematic
    Experimental Mechanics 02/2004; 44(1):10-20. DOI:10.1007/BF02427970 · 1.57 Impact Factor
  • X. Lei · C. J. Lissenden
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    ABSTRACT: The mechanical properties of ductile iron can be improved by ausforming, that is, applying work during austempering. The resulting yield strength and ductility are comparable to those of SAE 4140 steel, while the density is approximately 10 percent less. The viability of manufacturing components by casting a preform, austenitizing it, quenching it to the austempering temperature, forging it, austempering it, and finally, quenching it to the net shape is investigated by simulating the forging operation with finite element analysis. The preform geometry and die set geometry are determined such that the forging operation imparts a reasonably uniform equivalent plastic strain of 20 percent to the workpiece and the prescribed final component geometry is obtained. Forging of two components of varying geometric complexity is simulated using a commercial software package. The results indicate that the geometry of the final part is reasonably close to the goal and that the equivalent plastic strain distribution is reasonably uniform-over 80 percent of the material was plastically deformed 15-25 percent. The design of the preform and die sets appears to be an excellent application for an optimization algorithm.
    Journal of Manufacturing Science and Engineering 08/2001; 123(3). DOI:10.1115/1.1380383 · 0.78 Impact Factor

Publication Stats

18 Citations
2.35 Total Impact Points

Institutions

  • 2004
    • Pennsylvania State University
      • Department of Engineering Science and Mechanics
      University Park, MD, United States
  • 2001
    • William Penn University
      Worcester, Massachusetts, United States