Proposal of New Upper Limit of Hydrostatic Test Pressure in KT-3 of ASME Section VIII Division 3

The current upper limit of hydrostatic test pressure in KT-3 of ASME Sec. VIII Division 3 is determined by general yielding through the thickness obtained by Nadai’s equation with a design factor of 0.866 (= 1.732/2). On the other hand, the upper limit of hydrostatic test pressure in 4.1.6 of the ASME Sec. VIII Division 2 is determined by general yielding through the thickness with a design factor of 0.95. In cases where a ratio of hydrostatic test pressure to design pressure of 1.43 similar to PED (Pressure Equipment Directive) is requested, the upper limit of hydrostatic test pressure may be critical for vessel design when material with a ratio of yield strength to tensile strength less than 0.7 is used. In order to satisfy the requirements in KT-3, it is necessary to decrease design pressure or increase wall thickness. Therefore, it is proposed to change the design factor of intermediate strength materials to obtain the upper limit of hydrostatic test pressure. In this paper, a new design factor to obtain the upper limit of hydrostatic test pressure is proposed and the validity of this proposal was investigated by burst test results and elastic-plastic analysis.

Impact Toughness of Titanium Alloys with Different Strengthening Methods

In present paper effect of alloying elements and strengthening particle on the impact toughness were investigated. Load and energy in the impact tests were also discussed in detail for Ti-2Al, Ti-2Sn,Ti-2Zr, Ti-1Mo and Ti/TiC. Impact tests were carried out at room temperature (293K) and low temperature (83K) using a 300J capacity impact machine. Ti-1Mo, Ti-2Zr,Ti-2Sn alloys exhibit high impact toughness even at low temperature, while Ti-2Al and Ti/TiC only have high toughness at room temperature. At room temperature, general yielding occurred in all the materials, but it occurred only in Ti-1Mo, Ti-2Zr and Ti-2Sn at low temperature. It seemed that strengthening titanium couldn’t affect the elastic energy (Ei) effectively, but bring about more changes to Ep (propagation energy of crack) than to Ei (initiation energy of crack). As for the effect of alloying elements on the impact toughness, it seems to be related to the comprehensive result of the concentration and electronegative property of alloying elements. The interface between the TiC particles and matrix resulted in low toughness, especially at cryogenic temperature.

Strain-concentration factor of plane-strain notched rectangular bars under pure bending

A new strain-concentration factor (SNCF) has been defined for plane-strain notched rectangular bars under pure bending. The nominal strain for this new SNCF is obtained from an assumed linear distribution of the longitudinal strain on the net section. This nominal strain is defined under the triaxial stress state at the net section. The new SNCF provides reasonable values for the non-linear distributions of the longitudinal strain, while the conventional SNCF provides unreasonable values. The new SNCF increases from its elastic value to a peak value with plastic deformation. On further deformation it gradually decreases and then increases up to the value at the general yielding. The relation between the new SNCF and M/MY, the ratio of the applied bending moment to the bending moment at yielding at the notch root, is independent of the stress- strain curve up to general yielding.

Analysis of Small Edge Cracks and Its Implications to Multiaxial Fatigue Theories

The near-tip fields of small edge (Case B) cracks in power-law hardening materials are investigated under generalized plane strain, mixed mode, and general yielding conditions by finite element analyses. The results of the J integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trend of constant J contours on the Γ-plane is compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate under multiaxial loading conditions.

A Plastic Fracture Mechanics Analysis of Small Case B Fatigue Cracks Under Multiaxial Loading Conditions

The near-tip fields of small Case B cracks in power law, hardening materials are investigated under generalized plane-strain and general yielding conditions by finite element analyses. The results for two different crack orientations are examined and compared. The results indicate that the plastic deformation patterns near the tips of the cracks of two different orientations are remarkably similar in terms of the global coordinates. The results of the J-integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trends of constant ΔJ-contours on the Γ-plane for two cracks of different orientations are virtually the same. Further, the trends are compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate.

A Plastic Fracture Mechanics Analysis of Small Case B Fatigue Cracks Under Multiaxial Loading Conditions

The near-tip fields of small Case B cracks in power-law hardening materials are investigated under generalized plane-strain and general yielding conditions by finite element analyses. The results for two different crack orientations are examined and compared. The results indicate that the plastic deformation patterns near the tips of the cracks of two different orientations are remarkably similar in terms of the global coordinates. The results of the J integral from the finite element analyses are used to correlate to a fatigue crack growth criterion for Case B cracks. The trends of constant ΔJ contours on the Γ-plane for two cracks of different orientations are virtually the same. Further, the trends are compared reasonably well with those of the experimental results of constant fatigue life and constant fatigue crack growth rate.