Award Date

1-1-1996

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

Number of Pages

557

Abstract

This dissertation presents results from research in experimental and numerical studies related to deep denting of mild steel pipes. Two sets of large scale steel pipes having similar aspect ratios, diameter to thickness (D/t) of 64 and length to diameter (L/D) of 4.5 to 5 were tested in the laboratory and analyzed by nonlinear finite element method (FEA). The experiments were performed on a set of 12 inch diameter, 0.1875 inch thick, 60 inch long, and a set of 8 inch diameter, 0.125 inch thick, 36 inch long pipes using an MTS axial torsional testing equipment and Tinius Olsen universal testing machine. Strain gages were installed at selected locations on the pipes in each experiment. In some cases, preliminary finite element analysis was performed prior to the experimental procedure which helped in the selection of critical locations for strain gage installation. Preliminary FEA also helped in the selection of the maximum size of the pipes that could be dented without exceeding the capacities of the equipment. Pipes were tested with and without 0.5 inch thick welded end plates to study the influence of the addition of end plates on the stress and strain behavior. Pipes were dented in two modes; transverse and longitudinal modes up to dent depths equal to the radius of the pipe in the 12 inch diameter pipes, and equal to 1.5 times the radius in the 8 inch diameter pipes. Such large scale deep denting, equal or larger than the radii of the pipe have not been reported in the literature. The transverse denting mode was performed at the center points and quarter points of the pipes with end plates and only at center points for the pipes without end plates. A wedge shaped indenter 14 inches wide having a tip radius of 0.3125 inch is used to perform denting of the steel pipes; Material characterizations, up to failure in the neck region, were performed on steel specimen cut longitudinally from the pipes. Successive cycles of loading and unloading were used to characterize the behavior of the mild steel pipes. Strain gages capable of 20% strain were placed in the neck region at each loading cycle until the ultimate tensile strain was reached and the tensile strength for the specimen was measured. This technique was used to obtain an accurate description of the localized behavior of the mild steel specimen in the neck region; All experiments were duplicated by finite element analysis using shell elements. Large geometrical and material nonlinearities were included in FEA and gap elements were used to model the contact between the indenter and the pipes. Comparisons are shown between the experimental and the FEA results at various locations on the pipes and end plates during all stages of denting. (Abstract shortened by UMI.).

Keywords

Analysis; Cylindrical; Deep; Denting; Element; Experimental; Finite; Pipes; Shells; Steel; Steel Pipes; Strain; Stress; Stress-strain; Verification

Controlled Subject

Civil engineering; Mechanical engineering; Mechanics

File Format

pdf

File Size

11110.4 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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