新FM法拔长的临界砧宽比、临界料宽比及工艺参数研究

通过有限元模拟新FM法锻造,分析了锻件心部一定区域内的应力场分布规律,得出：对于不同压下率,在不同料宽比条件下,都存在着使轴向应力由拉应力转变为压应力的临界砧宽比l1cr;在不同砧宽比条件下,都存在着使横向应力由拉应力转变为压应力的临界料宽比l1cr。合理的工艺参数应由砧宽比、料宽比及压下率三者匹配确定。数值分析结论,是新FM法工艺参数的精细化。     

平砧拔长矩形截面毛坯的新理论

在拔长工艺理论方面,论证了只有砧宽比ω/h一个工艺参数的不足,而应增加一个工艺参数料宽比b/h,才能正确描述拔长毛坯中心区域的应力状态与有效控制锻件质量。该论述已被实验验证。同时用料宽比和砧宽比这二个工艺参数控制锻件内部质量的拔长工艺,简称为LZ工艺。     

芯轴拔长接砧区域工艺参数的研究

基于DEFORM-3 D数值模拟软件,针对芯轴拔长的工艺特点,利用数值模拟的方法,分析了锻件在切向和轴向接砧位置的金属变形状态,研究了不同的工艺参数对锻造接砧区域的应力场、应变场的影响。模拟结果表明,合理的接砧角度和接砧量能够使得接砧区域具有良好的应力状态,改善应变的均匀性。研究结果可为核反应堆主管道接管锻造工艺的制定提供理论依据。     

水平V型砧连续拔长工艺的数值模拟

对水平V型砧锻造法进行了连续拔长过程的数值模拟.以前的研究仅仅给出了单次压下拔长模拟结果,忽略了上一次压下所产生的变形对后续压下的影响,采用ANSYS有限元分析软件对水平V型砧锻造法实现了矩形截面毛坯连续拔长过程的数值模拟,分析了锻件横截面上的中心轴线横向应力分布.     

阶梯轴改锻中台阶变形规律及拔长工艺探讨

带有台阶的大型轴类锻件在改锻过程中,难度最大的是对台阶区域的拔长,尤其是当台阶直径落差较大时,往往会在台阶根部小圆造成径缩形成的折叠缺陷。而通过改变布砧方式可以改变台阶与坯料轴线的垂直状态,减小拔长过程中台阶端部金属的轴向伸长,消除折叠缺陷。通过数值模拟的方法对不同布砧方式的拔长过程进行分析,可以找到最佳布砧方式。     

发动机与液力变矩器的合理匹配研究

通过对液力变矩器和发动机之间的合理匹配,能够进一步提升石油机械的燃油的燃烧效率,在提升动力的同时也减少了尾气的排放。因为液力传动有着操作便捷和适应能力强等特点,所以得到了十分广泛的应用。但液力传动的研究内容中,实现液力变矩器和发动机之间的合理匹配是其中的关键性问题,不但要考虑到两者一起工作时的情况,同时也要研究出怎样进行两者之间的配合才能够获得更好的性能。为了能够将液力变矩器和发动机的特点充分的发挥,需要对两者进行有效的匹配,从而提升石油机械工作的环保型和经济性。因此,对于发动机与液力变矩器的合理匹配进行研究是非常有意义的。     

平砧连续拔长矩形截面毛坯的数值模拟

对平砧锻造法进行了连续拔长过程的数值模拟.以前的研究仅仅给出了单次压下拔长模拟结果,忽略了上一次压下所产生的变形对后续压下的影响,这里采用ANSYS有限元分析软件对该锻造法实现了拔长一趟过程的数值模拟,并分析了锻件横截面上的中心轴线横向应力分布.分析结果表明:在使用普通平砧拔长时,在砧宽比为1.0和料宽比为0.5的条件下,坯料横截面上的其横向应力都是拉应力状态.并且随着拔长的进行,横向拉应力越来越大.这一点吻合了平砧拔长矩形截面毛坯的新理论,也表明了应用普通平砧锻造法时要注意控制横向拉应力.     

试论小方坯连铸与炼钢和轧钢的匹配

对国内小方坯连铸的现状和与国外先进水平差距进行对比,指出我国小方坯连铸水平不高的主要原因是工艺问题。可以通过炼钢与轧钢的合理匹配,提高技术水平。     

试论小方坯连铸与炼钢和轧钢的匹配

对国内小方坯连铸的现状和与国外先进水平差距进行对比,指出我国小方坯连铸水平不高的主要系因是工艺问题.可以通过炼钢与轧钢的合理匹配,提高技术水平.     

神经网络在振动攻丝工艺参数匹配中的应用

介绍了神经网络基本原理及建模方法。利用MATLAB神经网络模块对振动攻丝试验数据进行训练 ,获得了振动攻丝工艺参数与攻丝扭矩之间的多因素关系模型及关系曲线 ,为振动攻丝的工艺参数匹配和攻丝扭矩预测提供了依据。     

THREE-DIMENSIONAL FINITE-ELEMENT SIMULATION OF STRETCHING TECHNOLOGICAL PARAMETERS bt/h AND bb/h OF HEAVY FORGINGS

0 INTRODUCTIONHeaVy fOrgings are made by fOrging ingOtsdirectly.Owing to the inevitable existence Ofmetallurgical defects such as POrosities, shrinkagecavities and cracks, we have tO utilize an effectivefOrging technology to eliminate these defects in order to Obtain high quality forgings. Stretching betweenflat tools is a mainly applied operation in free fotgingprocess of heavy forgings. How to design stretchingtechnolOgical parameters to create a favorable tri-axialcompressive st…     

ENVELOPING THEORY BASED METHOD FOR THE DETERMINATION OF PATH INTERVAL AND TOOL PATH OPTIMIZATION FOR SURFACE MACHINING

An enveloping theory based method for the determination of path interval in three-axis NC machining of free form surface is presented, and a practical algorithm and the measures for improving the calculating efficiency of the algorithm are given. Not only the given algorithm can be used for ball end cutter, flat end cutter, torus cutter and drum cutter, but also the proposed method can be extended to arbitrary milling cutters. Thus, the problem how to strictly calculate path interval in the occasion of three-axis NC machining of free form surfaces with non-ball end cutters has been resolved effectively. On this basis, the factors that affect path interval are analyzed, and the methods for optimizing tool path are explored.     

ENVELOPING THEORY BASED METHOD FOR THE DETERMINATION OF PATH INTERVAL AND TOOL PATH OPTIMIZATION FOR SURFACE MACHINING

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应变疲劳可靠性理论与方法的新进展

介绍概率应变疲劳试验法、评价模型和损伤随机演化机制方面的新进展。突破经典极大似然法在参考试验载荷之外的单试样限制，提出新的广义极大似然疲劳试验法。新发现随机循环应力—应变响应现象并建立其概率模型。新发展概率疲劳应变一寿命模型。概率模型参数由称为广义极大似然法的方法确定，在整体数据层面综合考虑数据分散性规律与样本量对概率评价的影响。考虑随机应力—应变关系反映“随机应变载荷”、随机应变—寿命关系揭示材料的“应变强度”，提出随机应变载荷—强度干涉恒幅可靠性模型，与Keciguliu的递推法结合可进行变幅和应变载荷谱下的可靠性分析，形成了应变疲劳可靠性理论和方法的新体系。进一步根据有效短裂纹准则，揭示疲劳性能随机及演化性的本质原因源于主导有效短裂纹萌生区域及其裂尖区域微观结构扩展条件的差异及演化性；随机疲劳裂纹扩展、应变—寿命和应力—应变关系是3个关联的随机疲劳关系；疲劳损伤是一个由初始混沌状态，到独立无关的随机状态，然后到史相关随机状态的演化过程。     

EFFECT OF SOME MODIFICATIONS TO OXLEY'S MACHINING THEORY AND THE APPLICABILITY OF DIFFERENT MATERIAL MODELS

Oxley's machining theory has recently been extended[1] to accept material property inputs in the form of widely used constitutive models such as the Johnson-Cook and MTS material models. In the process, additional modifications have been made to the model to improve its self-consistency. For instance, the shear force is obtained from the total work of deformation, thereby eliminating the unknown parameter η, and the hydrostatic pressure at the tool-chip interface is calculated considering the gradient in temperature in addition to the gradient in strain. This study is aimed at understanding the effect of these modifications separate from the changes due to the introduction of the new material models by comparing results obtained using Oxley's original model to that obtained with the above modifications. We also compare results obtained using different constitutive models for AISI 1045 to the experimental results of the “Assessment of Machining Models” effort.     

EFFECT OF SOME MODIFICATIONS TO OXLEY'S MACHINING THEORY AND THE APPLICABILITY OF DIFFERENT MATERIAL MODELS

Oxley's machining theory has recently been extended[1] Adibi-Sedeh, A. H., Madhavan, V. and Bahr, B. 2002. Extension of Oxley's analysis of machining to use different material models. Submitted to ASME Journal of Manufacturing Science and Engineering [Google Scholar] to accept material property inputs in the form of widely used constitutive models such as the Johnson–Cook and MTS material models. In the process, additional modifications have been made to the model to improve its self-consistency. For instance, the shear force is obtained from the total work of deformation, thereby eliminating the unknown parameter η, and the hydrostatic pressure at the tool-chip interface is calculated considering the gradient in temperature in addition to the gradient in strain. This study is aimed at understanding the effect of these modifications separate from the changes due to the introduction of the new material models by comparing results obtained using Oxley's original model to that obtained with the above modifications. We also compare results obtained using different constitutive models for AISI 1045 to the experimental results of the “Assessment of Machining Models” effort.