INFLUENCE OF TOP TEMPERATURE OF THERMAL CYCLE ON THERMAL STRESS/STRAIN AND THERMAL FATIGUE BEHAVIOR OF PURE IRON

１．ＩｎｔｒｏｄｕｃｔｉｏｎＦｉｇ．１　ＴｈｅｒｍａｌｆａｔｉｇｕｅｔｅｓｔｍａｃｈｉｎｅｗｉｔｈＯｕｔｅｒｃｉｎｓｔｒａｉｎｔＴｈｅｄａｍａｇｅｃａｕｓｅｄｂｙｔｈｅｒｍａｌｆａｔｉｇｕｅｉｓｏｎｅｏｆｔｈｅｍａｉｎｆａｉｌｕｒｅｆｏｒｍｓｏｆｍｅｔａｌｗｏｒｋｉｎｇｐｉｅｃｅｓｕｎｄｅｒｔｈｅｔｅｍｐｅｒａｔｕｒｅｖａｒｉａｔｉｏｎｃｏｎｄｉｔｉｏｎｓ．Ａｌｏｔｏｆｔｈｅｒｍａｌｆａｔｉｇｕｅｔｅｓｔｓｃｏｎｃｅｒｎｉｎｇｔｈｅｆａｉｌｕｒｅｗｅｒｅｃｏｎｄｕｃｔｅｄｏｎｔｈｅｖａｒｉｏｕ…     

纯铜动态再结晶的Monte Carlo法模拟

本文建立了一种基于能量判据的确定动态再结晶各个阶段临界应变的方法，并基于此种方法Monte Carlo(MC)法进行了纯铜动态再结晶的二维模拟，定量计算了变形引起的存储能与变形之间的关系，计算出了发生动态再结晶的临界应变。模拟结果表明，采用MC法可以揭示动态再结晶的形核生长过程与应变历史之间的关系。结合本文所建立的基于能量判据的确定动态再结晶各个阶段临界应变的方法，可以预测开始发生动态再结晶的临界变形条件。     

应用最大熵三维取向分布函数法测算深冲IF钢板的塑性应变比

采用最大熵三维取向分布函数（MEMODF）和简ODF法，按照织构多晶体连续力学法（CTMP法），遵循Konchendoerfer模型，选择非二次型函数来多晶体（深冲IF钢板）的塑性应变比R值，预估结果表明，MEMODF法测算值与实测值符合更好。     

A microstructural investigation of the surface of a drilled hole in carbon steels

The microstructure of the surface of drilled holes generated under different drilling conditions in carbon steels has been investigated. It is found that the surface microstructure depends strongly on the drilling parameters and the hardness of the matrix. White etching layers, composed of an equiaxed nanocrystalline structure layer with an average grain size of the order of several 10 nm and a submicron grained layer containing fresh martensite along the depth, formed on the hole surfaces during drilling at moderate to high cutting speed in carbon steels with high matrix hardness. The existence of a high content of austenite at the hole surface suggests that dynamic phase transformation (DPT) from body-centered cubic to face-centered cubic occurred during high-speed drilling. It is proposed that the ultrafine structure layer on the surface of a drilled hole is produced by severe plastic deformation-induced DPT together with a large strain gradient and high strain rate.     

EXPERIMENTAL INVESTIGATION ON HISTORY-DEPENDENCE OF PLASTIC BEHAVIOR OF TYPE 302 STAINLESS STEEL UNDER COMBINED AXIAL-TORSIONAL LOADS

1.IntroductionTheexperimentalinvestigation0fmaterialbehavi0rundercomplexloadinghasat-tractedmuchattentioninrecentyears,sinceuniaxialexperimentshavebeenfoundin-capable0frevealingmaterialbehavi0rundernonproporti0nall0adingconditi0ns.Conse-quentlymanyexperimentshavebeencarried0ut[1-3],iIlwhichthin-walledtubularspec-imensofbrassandmildsteelweresubjectedtoaxialandtorsi0nall0adsalongbilinearstrainpaths-Thevariati0nofthedirection0fstressvectorwithrespecttothat0fthepath,andtherelationbetweenthemagnitu…     

POSITRON ANNIHILATION STUDY ON THE DISTRIBUTION OF DEFECTS IN THE PLASTIC ZoNE A-T CRACK TIP

用楔形加载试样测定了裂纹顶端区正电子湮没多普勒加宽谱的S参数,并确定了试样充氢以后S参数的变化。经过标定,定出塑性区内的等应变曲线。充氢以后,使塑性内的等应变曲线向外扩展,在最大切应力方向发展最快。作者认为氢使塑性区内的位错增殖或可动位错滑移,同时产生空位。     

Theoretical and experimental plastic strain ratios in planar isotropic textures

The plastic strain ratios of planar isotropic sheet specimens were studied by using unidirectionally solidified commercial Al. Sn and Al-Cu alloy sheets and Cu sheets electrodeposited under the various electrolysis conditions. The measured plastic strain ratios of [100] planar isotropic sheets by using unidirectionally solidified Al and Al-Cu alloy are about 0.17–0.52, that of [110] planar isotropic sheets using unidirectionally solidified Sn(BCT) are about 2.5, that of [110] planar isotropic sheets using electrodeposited Cu are 1.38–2.05 and that of [111] planar isotropic sheets using electrodeposited Cu are 2.61–2.85. There is a substantial discrepancy between the experimental plastic strain ratios which are measured from planar isotropic sheets and theoretical plastic strain ratios which are calculated by Backofen method and Bunge method, but the measured plastic strain ratio of [100] planar isotropic sheet using unidirectionally solidified Al and Al-Cu alloy is in good agreement with Bunge method and the measured plastic strain ratio of [110] and [111] planar isotropic sheets using electrodeposited Cu are in good agreement with Backofen method.     

搅拌摩擦焊接过程中搅拌头转速对材料流动的影响

使用有限元方法模拟了不同搅拌头转速下,搅拌摩擦焊接过程中Al6061～T6材料的三维流动,以及材料流动与搅拌头转速的关系,结果表明,在搅拌摩擦焊接过程中,后退侧的材料流动较前进侧更为剧烈,并且随着搅拌头转速的增加,材料流动也会得到不同程度增强,搅拌头前方的材料在搅拌头的推动作用下向上涌起,被旋推到搅拌头后方并向下运动,该过程的周而复始是促使搅拌摩擦焊接顺利完成的主要原因,等效塑性应变等值线的形状与材料热影响区,热力影响区以及搅拌区的边界形状具有较好的对应关系,随着搅拌头转速的增加,等效塑性应变随之增加。     

MICROMECHANICS OF THE DAMAGE-INDUCED CELLULAR MICROSTRUCTURE IN SINGLE CRYSTAL Ni-BASED SUPERALLOYS

An analytical method to investigate the morphological evolution of the cellular microstructure is explored and proposed. The method is essentially based on the Eshelby‘s micromechanics theory, and it is extended so as to be applied for a material system containing inclusions with high volume fraction, by employing the average stress field approximation by Mori and Tanaka. The proposed method enables us to discuss a stable shape of precipitate in the material system, which must be influenced by many factors: e.g., volume fraction of precipitate; Young‘s modulus ratio and lattice misfit between matrix and precipitate; external stress field in multiaxial state; and heterogeneity of plastic strain between matrix and precipitate. A series of numerical calculations were summarized on stable shape maps. The application of the method to predict the γ‘ rafting in superaUoys during creep showed that the heterogeneity of plastic strain between matrix and precipitates may play a significant role in the shape stability of the precipitate. Furthermore, it was shown that the method was successfully applied to estimate the morphology of the cellular microstructure formed in CMSX-4 single crystal Ni-based superaUoy.     

氢在面心立方金属裂纹尖端变形过程中的作用SCIEI

选用高纯度Ni单晶体,利用扫描电镜原位拉伸,观察了充氢后Ni单晶裂纹尖端的变形过程。发现氢的存在不改变在混合型载荷作用下,裂纹尖端的塑性变形特征。用网格法加计算机处理系统,测出氢显著促进裂纹尖端区域内的局部塑性变形。