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通常组合凹模的设计是根据经验公式确定直径及过盈量,往往不是最优值.本文根据工作状态的内压力及模具的材料屈服强度,用弹塑性理论及热的传导理论及多元函数偏微分求极值的方法得出组合凹模各直径及过盈量的最优设计值,最大地增加模具承受的内压力,从而提高模具寿命.用此方法进行设计,已在我厂生产实践中收到良好效果. 相似文献
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无铆连接模具参数对异种金属板料接头成形的影响 总被引:2,自引:0,他引:2
为了研究无铆连接模具参数对 304 不锈钢和 AL6061 板料接头成形的影响,基于 DEFORM-2D 建立了有限元模型,分析了凹模深度、凹槽深度和凸模直径三个主要模具参数对接头成形的影响.研究结果表明,凹模深度越大,越有利于下板料变形,反之,则有利于上板料变形.当凹模直径一定时,凹槽深度和凸模直径过小不利于形成互锁,而凹槽深度不宜过大,避免出现充不满现象,凸模直径过大导致接头颈厚值过小.通过正交试验发现,对接头成形的影响程度从大到小依次为凸模直径、凹槽深度和凹模深度,确定了最优模具参数,并通过无铆连接实验验证了正交试验的可靠性.此外,通过剪切实验获得了接头最大剪切失效载荷为 1.8 kN. 相似文献
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凸模是冷挤压模具中重要的工件,其强度计算是模具设计的一个主要课题。本文用有限单元法对不同尺寸比的凸模进行计算,求出应力集中系数。此外,对于四种不同上端形状的凸模进行了比较,分析凸模安装部分的不同形状对应力集中的影响。并用夹片光弹法(三维)测试了部分凸模的应力集中系数。以上计算结果与三维光弹性应力分析的试验数据相比较,证实是可靠的。 相似文献
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基于内时大变形弹塑性本构模型的回弹和二次屈服分析 总被引:1,自引:0,他引:1
采用了一个由简单机构建立的材料热力学一致性弹塑性大变形本构模型,该模型满足热力学基本的不可逆约束条件,并考虑到了储存在残余微应力场中的能量,用相应的算法,编制了一个用户子程序UMAT,并将其嵌入到商用软件ABAQUS中,对圆柱形工件在弹性工具中镦粗和闭合模镦粗时的回弹和二次屈服进行了分析。比较模拟和实验所测得的载荷一位移关系,可以看出在镦粗的第一阶段发生塑性变形,工件在轴向加载过程中产生的横向变形受到了由于模具的弹性变形引起的径向约束,载荷迅速增加;第二阶段轴向压力减少,模具回弹使得工件的径向变形得以恢复,但随着塑性应变的增加,发生工作强化;第三阶段模具约束解除,工作的径向尺寸增加。用该本构模型对闭合模镦粗过程的计算,表明计算结果与实验结果是一致的。 相似文献
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针对采用整模结构的冷镦模具疲劳寿命极低的现状,提出以三层圆筒组合模具结构
替代整体模具, 改变模具受力方式, 使冷镦件模具达到较高寿命的设计方法. 以螺栓
圆头的冷镦试验结果为依据,以力学的应力分析方法为基础,应用力学理论,导出了生产实
践中实用的组合模具设计原理与经验公式,并举例说明了该方法的应用. 相似文献
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零能模式超材料指弹性矩阵的特征值中有若干为零的弹性材料,根据零特征值的个数可将其分类为一模至五模材料。当前,针对五模材料已有较深入研究,并在水声和弹性波调控方面获得重要应用,而对其他类型零能模式材料的研究尚未展开。本文对扭曲Kagome周期桁架这样一类欠约束点阵材料的有效弹性性质进行了研究,结果表明通过调节点阵材料的微观几何构型和杆件刚度,该类结构能够涵盖一系列一模材料谱系。针对给定一模弹性张量,发展了软-硬模式分离的微结构逆向优化设计策略。通过特定一模材料中的波传播现象对有效性质预测和微结构设计进行了数值验证。 相似文献
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LI Shaojie 《力学与实践》2014,36(6):774
采用线弹性平板理论,对均匀、连续、各向同性材料制成的变横截面为直角梯形的圆孔凹模板刚度计算理论进行了研究. 首先建立力学和数学计算模型,其次,针对承受垂直冲裁力的圆形孔凹模板,建立了用挠度表示的三阶变系数常微分方程,并给出了新的边界条件,然后采用半逆解法求解,进行弯曲问题的挠度计算,进而确定刚度计算理论,最后进行实例分析. 相似文献
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Yoshio Ohashi 《Experimental Mechanics》1968,8(4):182-187
The stress state in the V-shaped die for plastic compression was investigated by using a photoelastic stress analysis in which an Araldite in a glassy elastic state and a softened celluloid were used as model materials for the die and work specimen, respectively. It was found that the direction of the frictional shear stress is reversed at a certain point on the die surface. Because the frictional shear stress of the die mainly depends on the flow speed of the work material, the popular assumption that the coefficient of friction is a constant over the die surface such as in the case of Coulomb friction appears unrealistic. 相似文献
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Reflection type photoelastic experiment can be used more effectively than a transmission type photoelastic experiment especially
in industrial fields. Moreover, composite materials have been widely used in engineering applications and structures because
of their outstanding advantages which individual isotropic components do not have. The development of these materials requires
a promising technique such as reflection photoelasticity to analyze their behaviors in service. Unfortunately, there are few
experimental studies based on this technique. Therefore, a hybrid method based on this technique was developed in this research
to analyze the fracture behavior of opaque anisotropic materials. The application of this method will help to understand the
fracture behaviors of anisotropic materials used in engineering components and structures. The validity of this method was
verified by comparison of the results obtained from this method with ones obtained from the hybrid methods for isotropic material
on the same isotropic specimen. The reflection type photoelastic experiment for orthotropic materials was then applied to
orthotropic plates with a central crack of various inclination angles. Using this hybrid method for anisotropic materials,
stress intensity factors and separated stress components were obtained at the vicinity of the crack-tip in orthotropic plates
from only the isochromatic fringe patterns of the isotropic coating material. 相似文献
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The present paper is addressed to the finite element method combined with dynamic photoelastic analysis of propagating cracks, that is, on the basis of [1] by Chien Wei-zang, finite elements which incorporate the propagating crack-tip singularity intrinsic to two-dimensional elasticity are employed. The relation between crack opening length and time step obtained from dynamic photoelastic analysis is used as a definite condition for solving the dynamic equations and simulating the crack propagations as well. As an example, the impact response of dynamic-bending-test specimen is investigated and the dynamic stressintensity factor obtained from the mentioned finite element analysis and dynamic photoelasticity is in reasonable agreement with each other.Finally, my special thanks go to Prof. Chien Wei-zang for his kind guidance and I would like to express my thanks to Mr. Pang Jin-xiang for conducting the successful experiment. 相似文献
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Transmission photoelastic patterns for generally and specially orthotropic beams and an isotropic beam are presented. Theoretical
isochromatic and isoclinic results for these beams, calculated from classical elasticity stress equations and stress-optic
laws, are also presented and compared with experiment. The agreement between the theory and experiment is excellent. For the
orthotropic beams, a stressoptic law which accounts for the effects of residual birefringence was used. The residual birefringence
observed for the composite used in this study is greater than one fringe order and results from a matrix residual tension
which is about one fourth of the resin's ultimate tensile strength. Finally, the influence of such a large residual birefringence
on beam and calibration photoelastic data is discussed in detail.
Paper was presented at the 1986 SEM Spring Conference on Experimental Mechanics, held in New Orleans, LA on June 8–13. 相似文献
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Scattered photoelastic techniques would gain considerable momentum through better understanding of the nature and response
of the available photoelastic materials. The influence of the prevailing birefringent effect in the state of load-free polymers
on the radiated scattered light energy is investigated. Six different photoelastic materials are considered.
The impact of material birefringences on the quality of reading the fringe orders of the scattered radiation in a stressed
photoelastic medium is explored. Spectral dependence of the modulation of light vectors in acrylic materials (Plexiglas) is
illustrated. The advantage of this characteristic as a convenient means of compensation in scattered photoelasticity is pointed
out. Acrylic sheets, a relatively cheap transparent polymer, seem to be suitable for scattered photoelastic analysis. The
moiré technique might find application in determining fringe orders in a material such as Homalite-100. Replacing the primary
beam by a primary sheet saves the cost and effort consumed in the scanning process.
Paper was presented at the 1988 SEM Spring Conference on Experimental Mechanics held in Portland, OR on June 5–10. 相似文献
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A tomographic method for identification of stress fields based on 3D photoelasticity has been developed. A second order tensor field tomographic method based on the general inverse problem of 3D photoelasticity, previously developed by the authors, is found to be highly sensitive to errors in photoelastic observations. In this study a new tomographic method for stress field with fairly high robustness to errors in photoelastic observations has been developed by introducing both equilibrium condition and linear elasticity to the previously developed general tensor field tomographic method. This new stress field tomographic method expands unknown 3D stress distributions as a linear combination of independent set of basis functions and a new inverse problem is posed: identify the amplitudes of basis functions based on photoelastic observations. Just as the inverse problem of 3D photoelasticity, this newly posed inverse problem is also nonlinear and ill posed. Unlike conventional approaches to 3D photoelasticity, both these nonlinearity and ill-posedness are properly treated using a load incremental approach. Load incremental approach chops the nonlinear solution space into segments with unique solutions by conducting photoelastic observations at sufficiently small increments in external load. Validating both numerically and experimentally, it is shown that this new stress field tomographic method has sufficient robustness against errors in photoelastic observations and is applicable to experimental stress measurements. 相似文献
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复合材料光弹性分析的工程方法 总被引:1,自引:0,他引:1
本文在推导均衡光弹性复合材料应力(应变)—光定律的基础上,导出了均衡光弹性复合材料的近似应变—光定律。然后加以推广,提出适用于一般光弹性复合材料的近似应变—光定律.精度分析及实验验证表明:作为工程计算,在采用本文推荐的参数时,光弹性复合材料可视作各向同性材料进行光弹性分析。 相似文献
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本文介绍了变弹模成层岩基受预锚荷载作用的三维光弹性实验过程。求出了岩基在锚固应力作用下锚根附近的应力场,并和电测成果、理论计算成果进行了比较,结果非常相近.为进一步探讨这些问题提供了可靠的依据. 相似文献