DENG Rongying ZHOU Aihua JIANG Huaiqing LI Chunxiu Institute of Mechanics,Academia Sinica,Beijing,ChinaZHANG Liqing,SUN Yutian Beijing Institute of Engineering,Beijing,China [Originally published in ACTA METALL SIN(CHINESE EDN)25(3)1989 pp A219—A225, Associate Profes sor,Institute of Mechanics,Academia Sinica,Beijing,China