Electrical properties of ZnS, GaP, and Zr have been measured up to 40GPa with a Drickamer-type apparatus equipped with sintered diamond anvils. Phase transition pressures of these materials were determined through simultaneous X-ray diffraction measurements, using sodium chloride and gold as pressure standards. Various problems of the pressure calibration technique based on the X-ray measurements under uniaxial compression are discussed.

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Clad steel pipe, which is metallurgically bonded composite material, has been recently standardized in API 5LD for line pipe and increasingly used in the flow line for sour gas services.
The Japan Steel Works Ltd. (JSW) manufactures the stainless steel and nickel alloy clad steel pipe by hot roll bonding process and has supplied a lot of clad steel pipes for sour gas services. So far, a lot of knowledges on the rolled clad steel pipe, have been obtained through the tests for new manufacturing procedures and evaluation of pipe performance and the application experiences of clad steel pipe. In this paper, the following test results are described.
(1) Austenitic stainless steel and nickel alloy seamless clad steel pipe can be satisfactorily manufactared by inclined rolling method of mandrel type. The larger minus convergent angle of roll and rolling reduction ratio more than 1.8 can contribute to the minimization of twisting and debonding of clad steel pipe.
(2) Ni layer between cladding alloy and backing steel, improves the service performance for sour gas environments, accompanied with easier metallurgical bonding of clad steel. The smaller rolling reduction gives the adverse effect on the bonding properties of nickel inserted clad steel mainly due to the generation of Kirkendall's voids. Ni insertion can prevent the bonding interface from the formation of hard martensitic structure which is susceptible to hydrogen embrittlement.
(3) The corrosion test in Cl^--K₂S₂O₃ solution can be the substitute for the evaluation of pitting corrosion resistance in Cl^--H₂S solution of sour gas condition.
Ferritic and duplex stainless steels shows the lower pitting corrosion resistance than austenitic stainless steel and nickel alloy in Cl^--H₂S solution on terms of same pitting index of alloys.
(4) The existences of misalignment and oxide film on internal surface of girth welds, cause the degradation of corrosion resistance. The degradation in corrosion resistance due to oxide film is thought to be caused by the generation of crevice corrosion between oxide film and cladding alloy surface.

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Softening and microstructural evolution of low alloy steels during aging under stress were investigated using creep ruptured specimens.
Screw portion of the specimens was assumed to be subjected to no stress.
Regression equations for the softening curves in screw portion were estimated with hyperbolic one.
ΔG, that is, difference in logarithm of Lanson Miller parameter for screw portion and that for parallel portion at a given hardness level was plotted against applied stress.
Relationship between them was linear.
Critical stresses which had no influence on softening behavior were about 98 and 49MPa for Cr-Mo steels and Mn-Ni-Mo steel respectively.
The critical stress decreased with increasing temper parameter of PWHT (post weld heat treatment) and also corresponded approximately to creep rupture stress at 20×10³ of Larson Miller parameter in creep rupture master curve.
It was found that microstructural evolution and coarsening of carbides during aging were accelerated with stress.

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The authors have carried out finite element analysis (FEA) to obtain burst strength well by bifurcation theory in the last paper. Since it can be considered that the burst strength is dependent on stress-strain characteristics (work hardening), sensitive analysis of the stress-strain characteristics has been performed to clarify its influence on burst strength in the present paper. In addition, eccentricity of wall thickness may also be another effective factor and FEA with varying eccentricity has been carried out and revealed its influence.
The numerical results suggest that burst strength is strongly dependent on only stress-strain characteristics and that influence of eccentricity can be ignored within the range of its value less than 15%. Furthermore, the effect of large eccentricity and the local wear of wall thickness on the burst strength is also discussed. The authors make an assumption on two criteria of burst strength. One is governed by entire plastic instability in less than 15% eccentricity, another is governed by partial (weakest) plastic instability in more than 30%. The assumption should be confirmed by further experimental and numerical researches.
An empirical formula of burst strength under internal pressure alone is finally proposed using proportional limit and yield strength and the formula is in good agreement with the FEM results by less than 3% error. The formula can be expanded to burst strength under axial load by considering Mises' yield criterion such as described in the last paper where burst strength under axial load was calculated based on yield onset pressure considering Mises' yield criterion.

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The optimum design analysis in engineering is generally formulated as a nonlinear programming problem that includes continuous variables only or as a nonlinear mixed integer programming problem that includes continuous variables and combination (integer) variables for the selection of the grade of steel, welding method, etc.
Many characteristic optimization procedures including nonlinear programming and linear mixed integer programming have been proposed for dealing with these problems. However, all working solvers presently available for linear mixed integer programming are confined essentially to linear problems and short of versatility. To overcome this situation, a new procedure for nonlinear integer programming with constraint functions was developed.
In this paper, descriptions of the algorithm of nonlinear mixed integer programming optimization procedure are presented and its usefulness is verified by solving a nonlinear mixed integer problem, converted from a continuous problem. Furthermore optimum designs of LPG double-layered low-temperature cylindrical tank are obtained by nonlinear programming termed SUMT and by the nonlinear mixed integer programming developed.
The optimal solutions for the cylindrical tank are the ones that can decrease the steel weight by 5% comparing with a conventional design procedure.

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Nowadays, oil refining processes such as heavy oil up-grading and hydrodesulphurization require higher temperature and pressures in order for hydrotreating reactors to operate efficiently.
To meet these demands, three types of high strength pressure vessel steel have been developed and certified in ASME Code. The newly developed materials of enhanced 21/4Cr-1Mo, V-modified 21/4Cr-1Mo and V-modified 3Cr-1Mo steel have higher design stress intensity values at elevated temperature applications, which results in reduction of wall thickness and total weight of reactor vessels. In the world wide R & D Projects for the advanced materials, extensive studies on material degradation problems during long term hydrogenation services have been carried out to evaluate the feasibility for higher temperature applications. The applicability of the advanced pressure vessel steels is reviewed in terms of toughness degradation by temper embrittlement, hydrogen attack, hydrogen embrittlement and creep embrittlement.
Improved resistance to temper embrittlement was confirmed in the enhanced 21/4Cr-1Mo steel with low J-factor value. And also, two types of V-modified Cr-Mo steel exhibited sufficiently lower susceptibility to toughness degradation due to temper embrittlement. The stable carbide formation of VC produced the excellent resistance to hydrogen attack damage in the V-modified steel. At the same time, fine precipitation of VC carbides contributed significant improvements in the hydrogen assisted crack growth and the hydrogen induced disbonding at the base steel/stainless steel weld overlay interfaces. These beneficial material properties were confirmed to be derived from hydrogen trapping effect of VC carbides in the V-modified steel. It is concluded that two types of V-modified steel are highly applicable to severe service conditions of coal liquefaction and heavy oil up-grading processes. Large size hydrocracking reactors with a weight of 1000 ton were completed using the advanced 3Cr-1Mo-1/4V-Ti-B steel in 1992.

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6th Japanese-German Joint Seminar on Strucural Strength and NDE Problems in Nuclear Engineering was held on August 11 and 12, 1993 at MPA of Stuttgart University, German. The series of joint seminars have been held once every few yaers since 1980 under cooperation among experts in the field of strucural mechanics, material engineering and non-destructive examination from university, research organization and industries in both Japan and German.
In the 6th seminar, 23 participants from Japan and 43 from German joined in and 19 papers from Japan and 20 from German were presented in the series of 10 sessions.
The field of each session was as follows;
Session 1: Overview on structural and material engineering and nondestructive evaluation
Session 2: Leak-before-break
Session 3: Nondestruvtive evaluation (1)
Session 4: Nondestruvtive evaluation (2)
Session 5: Material design and strength evaluation (1)
Session 6: Material design and strength evaluation (2)
Session 7: Lifetime extension
Session 8: High temperature problems
Session 9: Degradation
Session 10: Others

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