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塑性条件是研究金属从弹性变形过渡到塑性变形的应力状态条件,表达这个条件的数学方程式称为塑性方程式。确定出这个方程式之后,就可求出金属塑性变形所需之外力。单向拉伸时,可以通过实验建立塑性方程式: 相似文献
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为研究地震工况下边坡的稳定响应,基于强度折减法,利用三维有限元模型对边坡进行静力分析和动力时程分析,对比不同工况条件下边坡失稳特征和边坡稳定安全系数。结果表明:高达98. 6 m的水库软岩边坡开挖,通过喷砼、系统锚杆和局部预应力锚索等支护后,受地震工况影响,边坡整体位移量和特征断面位移量增加显著,最大位移增加量达到7. 6倍;边坡塑性区深度增加明显,最大塑性区深度增加了1. 5倍; 坡体主应力值的变化量较小,且均为受压状态;在静力、动力工况条件下,边坡总体稳定,边坡安全系数降低约25%;静力、动力工况所对应有限元强度折减法安全系数均满足规范要求。 相似文献
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本文详细论述了Al·Zn-Mg-RE超塑性合金的制备过程和超塑性拉伸特性。初步分析了稀土元纱在超塑性变形中的作用。适量RE加入Al-Zn-Mg合金中可加宽超塑性变形的温度范围,降低变形抗力,大幅度提高合金的超塑性变形速度,对合金的超塑性效应有显著的影响。 相似文献
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纳米晶合金-掺硼Ni3Al金属间化合物和Al合金1420(Al-5.5%Mg-2.2%Li-0.12%Zr),以及亚微米晶铝合金1420经过了两种急剧塑性变形法的处理,即通过施加大压力状态下的扭曲应变的加工和等路径斜向挤压加工(ECAP)。这样加工的超细晶粒(UFG)合金表现出了在相对低的温度和/或高应变速度条件下增强超塑性。本文根据透射电子显微镜/高分辨率电子显微镜(TEM/HREM)的分析结果讨论了超细晶粒合金超塑性行为的特点以及获得增强超塑性的条件。 相似文献
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过去认为轧辊咬入轧件的条件是其最大咬入角的正切小于或等于摩擦系数,用式子表示即 tgα最大≤f。本文认为这个条件只是轧辊咬入轧件的必要条件,并不是充分条件,满足这个条件不一定就能实现咬入。因为咬入过程的实质是轧件在外力作用下产生塑性变形的过程,故咬入首先必须满足塑性条件才行,即轧件与轧辊的接触应力σ_K 应大于或等于金属的变形抗力 K;用式子表示σ_K≥K,它是实现咬入过程的充分条件。而α≤β是自然条件下轧辊咬住轧件的条件,而满足咬住条件不一定就能满足产生塑性变形的咬入条件。本文推导出轧件在有外力 Q 作用下考虑塑性变形条件时的咬入角公式:tgα咬入≤Q/2·K·F-QF。这个α咬入角才是实现轧制时的真实咬入角,而不是接触角α接和咬住角α咬住。同时也应把轧制角α轧和最大咬入角α最大区别开来,因为在大多数情况下α轧角不是在α最大角的条件实现的,显然α接角也经常不是α咬入角。 相似文献
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用示波冲击方法研究了不同冶炼方法对10CrSiNiCu钢低温脆性的影响。研究发现,硫含量对裂纹塑性形核功的影响最显著。随实验温度的降低,裂纹扩展功迅速下降、形核功降低较慢,同时钢的屈服载荷、断裂载荷上升,并逐渐接近或达到最大载荷。从室温至-80℃,10CrSiNiCu钢的断裂方式依次经历完全塑性断裂、弹塑性断裂和完全脆性断裂。当发生弹塑性断裂时,10CrSiNiCu钢的冲击功、扩展功与断口纤维量呈较好的线性关系。 相似文献
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We discuss the effect of porosity on the plastic deformation work density for compression of a high-porosity material. We show that the strain hardening curve in the low hardening stage can be described on the basis of the principle of similarity. The dependence of the plastic deformation work density on the initial porosity in the low hardening stage is characterized by the presence of a maximum whose magnitude and position are determined by the strain hardening parameters of the solid phase and the type of pore space. We use our analysis to propose a procedure for selecting the optimum material capable of absorbing the maximum energy of plastic deformation under compressive loads. 相似文献
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G. Gershteyn F. Nürnberger F. Cianciosi N. Shevchenko M. Schaper Fr.‐W. Bach 《国际钢铁研究》2011,82(12):1368-1374
In this work was studied the influence of the plastic deformation's intensity under deep drawing on microstructures of a pearlitic steel containing 0.8% C. Varying the levels of deformation causes diverse dislocation movements as well as modified structural states in the individual phases of the pearlitic eutectoid steel. It is shown that in the course of plastic deformation there is a reduction of interlamellar distance in a pearlite and increase in dislocation density. In some parts partial spheroidisation cementite plates is observed. The bands formed in dislocation structure are found out. The analysis of failure mechanisms of steel with pearlite structure after plastic deformation is carried out. During the deformation of pearlite, the increase in stress at the phase boundary, owing to the elastic strain incompatibility between the ferrite and cementite phases, resembles the stress concentration at grain boundaries. Pores form at the interface between the surface of the ferritic matrix and the spheroidised carbide particles. Such micro pores occur by means of plastic deformation of the ferrite's interstices around the stronger cementite owing to the reduction of the ferritic interstices and their subsequent cracking. 相似文献
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为定量研究砂岩中矿物颗粒在载荷作用下的塑性应变和应力,揭示岩石内部赤铁矿颗粒的变形行为,基于弹塑性力学理论和张量分析,采用X射线CT对砂岩三维结构进行扫描(空间分辨率为4.6 μm),分析岩石内部矿物颗粒的运移规律,并提出了岩石矿物颗粒变形梯度张量计算的方法研究其塑性应变。首先对砂岩矿物颗粒位移进行提取,并采用Non Local Means滤波算法对砂岩三维数字图像去噪;然后基于砂岩三维结构,对不同矿物组分进行分割,通过构造主轴应变的变形张量,计算砂岩矿物颗粒的变形梯度和应力、应变分量。结果表明:该滤波算法对砂岩CT图像和射束硬化现象具有显著改善效果。此外,基于X射线CT的砂岩原位测试结果显示,砂岩内部存在较复杂的变形行为和应力响应,且在断裂带和非断裂区域变形行为有着显著差异;岩石内部颗粒在Z轴方向受到压应力,而在XY平面受到拉伸应力的作用,同时矿物颗粒内部存在较大的塑性应变,且试样内部颗粒的应变和应力要远远大于试样宏观应变和应力。该方法对于揭示岩体内部结构和应力、应变状态演化过程具有重要作用。 相似文献
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The multi-roller straightening process of section steel is analyzed by the springback theory of small curva- ture plane bending. The theoretical analysis results prove the curvature unification in straightening process and clear- ly reveal the principle of the multi-roller straightening process. The principle can be described as~ the initial curva- tures are reduced by several times anti-bendingl meanwhile the initial curvature differences are diminished and the residual curvatures are unified~ finally, the member after curvature unification is straightened by the last anti-ben- ding. With the plastic region ratios becoming larger, the initial curvatures are more easily unified in straightening process. Based on the plastic region ratios and the required number of roller systems for unifying the initial curva- tures, the large deformation straightening strategy and the small deformation straightening strategy are redefined. The new definition provides an important theoretical basis for setting reliable reduction rules. Through the theoretical analysis results, a new straightener design philosophy is proposed to improve the straightening quality and further increase the adjustment precision as well as the flexibility of the last roller system. The adjustable end roller emerges as the times required, achieving a good effect in practical application. 相似文献
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碳锰钢压缩过程中非均匀应变与再结晶之间关系的研究 总被引:1,自引:1,他引:1
采用有限元方法模拟了热模拟试验的变形过程,分析了热模拟变形过程中的非均匀应变对奥氏体动态再结晶及晶粒尺寸的影响.结果表明,在等效应变最大的区域,奥氏体动态再结晶并非最完全,而剪应变对动态再结晶的影响则较大,在剪应变最大的区域,再结晶最完全,晶粒最细小.在试验所设定的最大变形量为62%的变形条件下,等效应变对晶粒细化的影响存在一个临界值,当等效应变大于0.96时,不完全动态再结晶区域的奥氏体晶粒得不到进一步细化,而随着剪应变的增加,奥氏体晶粒不断细化,可见剪应变对奥氏体晶粒尺寸的影响更大.因此,用等效应变等于实际应变处的晶粒尺寸来考察实际晶粒尺寸的方法,存在着不合理性. 相似文献