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利用Gleeble-1500热力模拟试验机,获得了20 vol%TiC-弥散铜复合材料在温度450~850℃、应变速率0.001~1 s-1的真应力-应变数据。采用非线性拟合法建立了真应力-应变曲线的非线性方程,求得加工硬化率;研究了该材料的动态再结晶,并采用Zener-Homon参数建立了临界应变模型。结果表明,非线性方程能精确表征真应力-应变曲线,该材料的真应力-应变曲线主要以动态再结晶软化机制为特征;该材料的lnθ-ε曲线出现拐点,-(lnθ)/ε-ε曲线出现极小值说明材料发生了动态再结晶;临界应变均随应变速率的增加及变形温度的降低而增大,且临界应变与峰值应变之间具有相关性,即εc=0.5276εp;临界应变与Z参数之间的函数关系为εc=7.91×10-3Z0.0736。 相似文献
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设计了成分与SAF2205双相不锈钢中奥氏体相和铁素体相成分相近的单相奥氏体不锈钢和铁索体不锈钢,根据其应力.应变曲线,采用有限元方法,计算了双相不锈钢的应力.应变曲线,并与实测值进行对比,同时对奥氏体的体积分数和双相不锈钢中两相屈服强度之比(C^*)等影响双相不锈钢力学性能的因素进行了讨论。由单相奥氏体和铁素体不锈钢的应力-应变曲线计算的双相不锈钢的应力.应变曲线和实测的双相不锈钢应力-应变曲线吻合很好,说明本文所建立的有限元模型正确。计算表明奥氏体体积分数对应力.应变曲线的弹性部分没有影响,而对塑性部分影响较大。在外应力作用下,随着奥氏体体积分数的增加,应变增加;不同奥氏体与铁素体屈服强度之比(C^*)对应力-应变曲线弹性部分没有影响,而对塑性部分略有影响,在外加应力作用下,随着C^*增加,应变增加。 相似文献
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《锻压技术》2015,(10)
三销架是球销式等速万向节的重要部件。通过Solidworks对三销架冷锻成形模具及工件进行三维建模,采用大型有限元软件Deform 3D研究了顶杆圆角半径对三销架成形缺陷的影响规律,及其对等效应力、等效应变分布和载荷-位移曲线的影响。结果表明,当顶杆上凸台直径D1为Ф24 mm、下凸台直径D2为Ф22 mm、顶杆速度为10 mm·s-1时,顶杆下圆角半径R2的增大可以减小甚至消除三销架销轴根部的成形缺陷,顶杆上圆角半径R1对三销架成形无影响,三销架的中间孔处及销轴根部的应力应变最大。提出了适用于三销架冷锻成形的顶杆圆角半径R1为2 mm,R2为10 mm,并通过实际生产进行了实验验证。 相似文献
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讨论了金属材料受载时弹——塑性非线性变形理论和曲线,将材料的真实应力——应变曲线简化为双线性强化弹塑性曲线,并对曲线参数进行了计算。以压缩机底座为例,提出非线性材料零件的建模、分析、设计的方法,并对此模型的压缩机底座结构参数进行设计。 相似文献
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利用液压试验机对金属钛、镁和钴进行循环加载-卸载压缩试验,利用引伸计测量应变,获得样品的应力-应变曲线.钛、镁和钴因为六方密堆积晶体结构,具有塑性各向异性,导致一定的非线性弹性.这些非线性弹性在循环加载应力-应变曲线中表现为滞后环.研究表明,适当的预变形可以增大这些材料的非线性弹性.粗晶样品一般比细晶样品具有较大的非线性弹性.一种源于三元碳化物Ti3SiC2的初始弯折带(Incipient kink bands)理论可以解释这些材料的非线性弹性以及与非线性弹性相联系的微屈服、阻尼减震.一种经典滞后模型Preisach-Mayergoyz模型,可以用来计算这些材料的非线性变形量. 相似文献
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M. Plancak A. N. Bramley F. H. Osman 《Journal of Materials Processing Technology》1996,60(1-4):339-342
The information on the intensity and distribution of the contact stresses in bulk metal forming operations is essential both for the die design and for the process analyst. As the theoretical and numerical methods for the contact stress determination have some analytical constraints a number of experimental methods have been developed. One of them is the pin load cell technique which has been applied in different metal forming operations. In this paper some problems related to the measurement of normal contact stress are presented. The focus is placed on the problem of initial pin position relative to the die surface. Experimental investigations were carried out in order to determine the influence of the axial pin position on the measured contact stress values. The process studied was that of simple upsetting of cylindrical specimens. It has been shown that the axial pin position 0.15mm above the die surface prior to the defonnation gives the most realistic results. 相似文献
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销轴连接是液压支架结构件的主要连接形式,其可靠性对液压支架的正常使用具有重要影响。基于赫兹接触理论,建立销孔处接触应力理论模型;采用ADAMS对液压支架各结构件受力分析,得到销孔受力情况;基于有限元法分析销孔处接触应力、变形及塑性应变。结果表明:在顶梁扭转、底座扭转工况下,销轴连接接触应力超过材料的屈服极限,其接触应力分布结果具有较强的非线性;销孔应力主要集中在销孔前端接触部位,销孔塑性应变集中在销孔前端接触部位,表现为挤堆效应,在正拉力下销孔两侧塑性应变更为明显。 相似文献
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在型腔模设计中 ,推杆直径大小的确定一般是根据经验或依据类比法确定 ,这样确定的推杆往往与生产实际有一定的差距 ,通过对推杆的受力状况进行分析 ,从理论计算角度对推杆直径进行确定。 相似文献
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Influences of tool pin profile and welding speed on the formation of friction stir processing zone in AA2219 aluminium alloy 总被引:1,自引:0,他引:1
AA2219 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio. Compared to the fusion welding processes that are routinely used for joining structural aluminium alloys, friction stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. This process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters and tool pin profile play major roles in deciding the weld quality. In this investigation, an attempt has been made to understand the effect of welding speed and tool pin profile on FSP zone formation in AA2219 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular and square) have been used to fabricate the joints at three different welding speeds. The formation of FSP zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the FSP zone formation. From this investigation it is found that the square pin profiled tool produces mechanically sound and metallurgically defect free welds compared to other tool pin profiles. 相似文献
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某工程机械用销轴的制备工艺为调质处理+表面镀硬铬,其工作时需承受较高的载荷及一定的冲击,实际使用中约300 h发生了磨损失效。通过金相观察、硬度测试、扫描电镜表面形貌分析及能谱成分分析等检测方法对失效销轴的磨损原因进行分析。结果表明,该销轴磨损失效的主要原因是其表面镀铬层与基体的硬度差异较大,在高应力与冲击荷载的作用下,镀铬层发生了脆性剥落。可选用表面淬火、表面渗碳等工艺代替表面镀硬铬,提高销轴表面硬度的同时消除其径向性能的突变,提升销轴的使用寿命。 相似文献
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根据工业纯钛的室温蠕变等时应力-应变曲线,应用有限元方法研究了钛制压力容器的蠕变极限载荷。结果发现,随着室温蠕变时间的增加,压力容器蠕变极限载荷由快速下降趋于缓慢下降。以圆筒型压力容器为例,详细分析了径比K对极限载荷的影响规律,给出了室温蠕变极限载荷的预测公式。该公式能够体现蠕变时间对极限载荷的劣化作用,以及许用应变和径比K对极限载荷的影响。 相似文献
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抽芯距离长、包紧力大的侧向抽芯机构是压铸模设计的难点之一,采用斜销-齿条-齿轮二次抽芯机构解决了这一问题。该机构先用刚性较强的斜销抽拔型芯去除包紧力,开模至一定距离,固定在定模上的齿条开始与齿轮啮合,齿轮转动带动齿条的滑块,使滑块带动型芯完成抽芯。设计了模具结构,论述了模具工作原理,给出了压铸工艺参数,并说明了模具在具体使用中应该注意的问题。 相似文献
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The residual stress of a landing gear part of a fighter jet that has a frequent practice of takeoff and landing was evaluated for the safety. The sample was a cylindrical steel bar with a 22.2 mm diameter and 55 mm length used to fix the main landing gear to the aircraft body. For a deep measurement up to 6 mm, we used a neutron beam. From the measurements, the tensile and compressive strain in the axial direction were observed around one side of the pin hole which was across the steel bar vertically with an 8 mm diameter. The strain distribution along the length of the bar presented a similar tendency through the thickness and a larger value on the surface. The maximum value of the residual stress around the pin hole was about 100 MPa. However, there was no strain on the opposite side of the pin hole. From the results, it may be surmised that the steel bar received a steady force in one direction around the pin hole, however the force was weak and affected a small limited area and thus not influence on the steel bar on the whole. 相似文献
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分析电潜螺杆泵举升过程传动轴断轴部位应力分布及疲劳寿命对提高传动机构可靠性和保障电潜螺杆泵连续稳定运行具有重要意义。针对传动轴断轴部位,提出传动轴多载荷作用力学特性分析和疲劳寿命预测方法。数值仿真和现场测试分析结果表明:各载荷单独作用时,销孔应力较大区域沿径向条状分布且应力分布较均匀,内螺纹应力较大区域沿径向自上向下逐渐减弱,且最大应力受扭矩作用最大而受狗腿度产生的弯矩作用最小;各载荷组合作用时,轴向力对销孔和内螺纹应力分布影响最大,且最大应力均小于许用应力而推断两处断轴原因不是超载导致的脆性断裂;内螺纹处疲劳寿命明显小于销孔处疲劳寿命,为传动轴优化设计提供依据。 相似文献