Modelling ductile fracture behaviour from deformation parameters in HSLA steels

In this work, an attempt is made to model the ductile fracture behaviour of two Cu‐strengthened high strength low alloy (HSLA) steels through the understanding of their deformation behaviour. The variations in deformation behaviour are imparted by prior deformation of steels to various predetermined strains. The variations in parameters such as yield strength and true uniform elongation with prior deformation is studied and was found to be analogous to that of initiation fracture toughness determined by independent method. A unique method is used to measure the crack tip deformation characterized by stretch zone depth that also depicted a similar trend. Fracture toughness values derived from the stretch zone depth measurements were found to vary in the same fashion as the experimental values. A semiempirical relationship for obtaining ductile fracture toughness from basic deformation parameters is derived and model is demonstrated to estimate initiation ductile fracture toughness accurately.     

温度对金刚石刀具影响的理论模型和实验分析

为减小大型金属反射镜在金刚石车削中,刀具的热变形对加工精度的影响,研究了金刚石刀具在温度影响下的热变形规律,结合俄罗斯在热力学方面的研究成果,根据金刚石晶体和刀体的热膨胀系数和导温系数的不同,建立了刀具变形量随温度变化的理论计算模型,并采用高精度的热像仪和电感测微仪记录刀具的温度变化和变形量,发现当温度从23．4℃升高到32．1℃时,刀具变形量达到1．48μm．     

Combined effect of shear and large deformation on stress intensity factors

An attempt has been made to study the influence of large deformation on the stress intensity factor in a cracked plate subjected to bending including shear deformation. It is assumed that singular terms for stress resultants and strains in the case of large deformation have the same angular distribution and order of singularity as in the case of a linear problem. With this in view the small deformation singular element has been used at the crack tip region surrounded by large deformation plate bending elements. The finite element analysis, based on total Lagrangian formulation combined with the modified Newton–Raphson technique, has been used to get numerical results. Several examples connected with large deformation of cracked plates subjected to bending are studied. Using the above technique stress intensity factors for linear and non-linear cases have been compared.     

冰箱压缩机电路控制保护器之关键技术“记忆金属元件设计应用”

通过探讨电冰箱压缩机电路控制保护器的工作机理,通过结合实践探讨关键记忆金属元件双金属片材料基础理论,包括双金属片的基本特性,如何工作,规格品种,标准试验方法,主要指标（曲率半径、挠性、热变形、弹性模量、机械力、温度力）,应力与温度关系,物理和机械性能（电阻率和电阻、硬度）,稳化热处理,耐腐蚀性及保护,特别是蠕变式园盘的热变形与温度力的组合、＂热变形与温度力＂和温度、直径、厚度的关系等规律,从而初步掌握电冰箱压缩机保护器设计与工艺编制中所需双金属片应用知识。     

钢板卷制汽封圈变形原因分析

钢板卷制汽封圈在切割成弧段时发生不同程度的收缩变形。采用X射线法对汽封圈的制造过程进行了跟踪测试。通过分析，确认校圆后的回火质量是钢板卷制汽封圈产生变形的主要原因。严格控制第二次回火的保温时间和降温速度可提高回火质量，从而使变形得到了控制。     

聚脲弹性体夹芯防爆罐抗爆性能研究

应用ANSYS/LS-DYNA有限元软件对三种防爆罐在1.2kgTNT爆炸载荷作用下的动态响应过程进行数值模拟。研究了无夹层、聚脲弹性体夹层和橡胶夹层防爆罐的抗爆性能。分析了不同夹层对防爆罐整体变形的影响,并分析了聚脲弹性体和橡胶夹层的吸能特性。通过聚脲弹性体夹层防爆罐在爆炸载荷作用下的变形试验研究,验证了数值计算结论的可靠性。结果表明,在相同爆炸载荷作用下,无论是在变形还是在能量吸收方面,聚脲弹性体夹层防爆罐都要优于无夹层防爆罐和橡胶夹层防爆罐;冲击波在聚脲弹性体传播过程中衰减幅度最大。     

超高层结构施工竖向变形规律及预变形控制研究

为了掌握超高层结构施工竖向变形累积规律,提出合适的施工预变形分析方法。该文对国内3个400m以上典型超高层结构进行施工全过程仿真研究,开发标准化施工仿真建模方法,综合时变结构离散分析法、龄期调整有效模量法、单元生死、位型控制、分步加荷等关键技术对材料时变,几何时变、边界条件时变进行模拟,形成完整的超高层结构施工全过程仿真技术,得到了不同工况下超高层结构施工竖向变形规律。在此基础上,采用阶段位移补偿法,以竖向位移、框筒内外相对变形为控制目标,建立超高层预变形分析方法,得到了结构施工过程中各层标高预调值,为该类结构的施工变形控制提供了理论依据。     

TC4钛合金激光焊接/超塑成形组合工艺研究

本文将超塑成形(SPF)和激光焊接技术(LW)相结合,开发激光焊接/超塑成形组合工艺(LW/SPF),研究TC4钛合金激光叠焊接头的超塑性变形行为,并对超塑性变形前后的显微组织进行分析.结果表明,TC4钛合金激光叠焊接头能够承受焊板的变形,试样在母材断裂,并通过四层板的模拟件研制验证了超塑成形/激光焊组合工艺工业应用的可行性.     

The identification of dynamic recrystallization and constitutive modeling during hot deformation of Ti55511 titanium alloy

In the present paper, an internal-variable identification approach has been proposed to investigate the dynamic recrystallization (DRX) behavior during hot deformation and corresponding constitutive model has been constructed. Isothermal compression experiments of Ti55511 titanium alloy were conducted for verification. Plastic behavior is determined by dislocation evolution in many cases while deforming. The comparison between saturated and DRX critical dislocation density was made to distinguish the occurrence of dynamic recrystallization/recovery (DRV) during hot deformation. The influence of deformation parameters on DRX behavior was illustrated by dislocation evolution map, validated by the power dissipation efficiency distribution. DRX process during hot deformation of Ti55511 alloy tends to occur under moderate temperatures and low strain rates. In addition, a physical-based Arrhenius constitutive formula has been derived for DRX criticality. The strain-rate sensitivity coefficients during hot deformation were fixed as a constant equal to 1/6 and the deformation activation energy was related to the material's self-diffusion activation.     

Experimental investigation of inertia effects in one-dimensional metal ring systems subjected to end impact — I. Fixed-ended systems

Arising from an interest in the use of laterally compressed metal tubes and rings as impact energy absorbing components, the role played by inertia in the deformation of systems of such components is examined experimentally. Crossed-layered systems of metal tubes undergoing low speed impact in a drop hammer are considered briefly. The paper is principally concerned with the response of one-dimensional ring systems tested in a simple high speed impact apparatus over a range of conditions. An account is given of various features of the modes of deformation which occur and an explanation is offered which highlights the mechanisms controlling the deformation process. Reference is made to a structural shock wave theory which is suggested by the results of the tests.     

复合材料大变形任意加筋壳单元

构造了用于复合材料偏心加筋壳形结构大变形分析的任意加筋壳单元。在此模型中,肋骨连同壳的整体被视为一个单元偏心加筋壳单元。肋骨可放在壳单元内的任意位置和任意方向。所构造单元的特点是在网格划分时,可不必考虑肋骨的位置,这就给网格划分带来了很大的灵活性。在壳和肋骨的方程中,引用Von-Karman大变形理论计及几何非线性的影响,按照Mindlin-Reissner一阶剪切变形理论考虑横向剪切变形。     

大口径反射镜轻量化结构比较及面形分析

根据某空间光学系统的SiC反射镜的设计指标要求,对比分析了各种轻量化结构(包括三角形、正方形、六边形和各种扇形轻量化结构)的力学(自重变形)、热学性能(温度应力变形).综合比较这些轻量化结构的轻量化率,比刚度和热稳定性能,最终确定采用一种扇形轻量化结构.在轻量化率达到75%的情况下,镜体的自重变形和热变形均满足要求:采用Zemike多项式拟合去除刚体位移后得出,在周边支撑情况下镜面由于自重引起的表面畸变量的RMS值为0.010 μm,约为2/60(2=0.632 8μm).     

Increasing the endurance limit by broaching the hole

The authors propose a model of static deformation of the material at the tip of a notch with a formation of residual stresses, the variation of the coordinates of the deformation diagram in accordance with the Mazing principle, with an allowance made for the parameters of broaching the hole and a correction for structural changes in the material as a result of plastic deformation. The proposed model is verified by experiment and the broaching parameters are optimized.Translated from Problemy Prochnosti, No. 7, pp. 22–33, July, 1994.     

Some studies of deformation processes in fully-spherulitic polypropylene

The deformation of isotactic polypropylene has been studied by optical microscopy of thin sections cut from bulk tensile specimens. An attempt has been made to relate the three different deformation zones within a spherulite to the cross-hatched structure peculiar to polypropylene.     

对铝合金内胆碳纤维全缠绕复合气瓶的水压试验结果分析

根据制造厂实际试验数据和气瓶容积变形的统计分析,对同一时期10批次近1600只复合气瓶的水压试验结果进行了比较,结果表明,复合气瓶通过自紧压力后可有效提升产品容积变形同一性。水压试验后复合气瓶的容积残余变形值分散率大大降低。     

Tensile elongation of lean-alloy austenitic stainless steels: transformation-induced plasticity versus planar glide

An Fe–13Cr–3.4Mn–0.47C lean-alloy stainless steel was made austenitic by solution annealing at 1250°C. Tensile tests between 20 and 200°C indicated enhancement of ductility at higher temperatures. At 200°C where planar glide, manifested as deformation twinning, was the dominant deformation mechanism, a uniform tensile elongation of 102% was achieved. At 20°C where deformation-induced α′-martensitic transformation replaced deformation twinning as the dominant deformation mechanism, tensile elongation was significantly impaired. The tensile elongation contribution by the planar glide was estimated to be at least four times that of the α′-TRIP (transformation-induced plasticity) mechanism. The results indicate that inexpensive lean-alloy austenitic stainless steels exhibiting pronounced α′-formation at room temperature could become highly formable at higher temperatures.     

熔纺氨纶的动态力学性能分析

应用动态力学分析，研究了两种自制的熔纺氨纶样品的动态模量、力学损耗、蠕变行为的温度依赖性，并与杜邦的干纺氨纶(Lycra)和日清纺的熔纺氨纶(Mobilon)产品的动态力学性能进行比较，从硬段微区结构、物理交联密度、软段玻璃化转变温度、蠕变-温度曲线等方面，探讨了熔纺和干纺氨纶在热变形性能上的差别．     

塑性加工对Csf/Al复合材料组织与性能的影响

短碳纤维增强铝基复合材料可以经塑性变形加工成各种形状的零件。但塑性变形过程对材料的组织与性能有着重要影响。本工作用挤压浸渗法获得的Caf/Al复合材料为毛坯。通过挤压的方法。研究了变形温度、变形量等对材料组织与性能的影响。结果表明，一定量的塑性变形可以弥合浸渗不完全留下的微小空隙，并使纤维成方向性排列，复合材料的性能得到提高。但大变形会使纤维断裂，影响增强效果。变形温度越高，对复合材料性能越有利。     

In situ characterization of the deformation and failure behavior of non-stochastic porous structures processed by selective laser melting

Cellular materials are promising candidates for load adapted light-weight structures. Direct manufacturing (DM) tools are effective methods to produce non-stochastic structures. Many DM studies currently focus on optimization of the geometric nature of the structures obtained. The literature available so far reports on the mechanical properties but local deformation mechanisms are not taken into account. In order to fill this gap, the current study addresses the deformation behavior of a lattice structure produced by selective laser melting (SLM) on the local scale by means of a comprehensive experimental in situ approach, including electron backscatter diffraction, scanning electron microscopy and digital image correlation. SLM-processed as well as heat treated lattice structures made from TiAl6V4 alloy were employed for mechanical testing. It is demonstrated that the current approach provides means to understand the microstructure-mechanical property-local deformation relationship to allow for optimization of load adapted lattice structures.     

粘弹塑性理论在混凝土变形中的应用

首先文章介绍了粘弹塑性统一本构模型的基本方程,根据混凝土的特点对统一本构模型进行了简化,简化后的模型对混凝土的无损伤段的变形模拟,取得了满意的结果。之后应用粘弹塑性统一本构模型对混凝土进行跳跃实验预测,同样获得了预期效果,证明粘弹塑性统一本构模型在混凝土的变形预测中的应用是成功的。