共查询到20条相似文献,搜索用时 125 毫秒
1.
厚板冲孔模凸模作为易损件,发生断裂现象会对机床设备、操作工自身安全都有重要影响。从实际冲孔模使用过程中出现的凸模断裂现象,结合理论知识及现场情况对凸模断裂原因进行分析研究。提出了改进措施,提高凸模稳定性,降低凸模断裂概率。 相似文献
2.
3.
4.
通过断口分析、受力分析等方法,对Cr12MoV钢冷挤凸模的断裂性质和断裂原因进行了分析。判定其断裂属于过载正向脆性断裂,断裂主要原因是挤压变形度过大、凸模工作端形状不合理、凸模顶端直径过大、Cr12MoV钢带状碳化物的分布方向不合理及强度不足。建议采用两次挤压成形、改进凸模工作端的形状设计、减小凸模顶端直径和改用基体钢。 相似文献
5.
6.
针对花键套在冷挤压成形内花键时出现的凸模断裂问题,建立内花键成形的有限元模型并进行数值模拟。模拟结果表明,凸模导向区与齿形区截面变化大,圆角过渡处容易产生应力集中,从而导致在过渡处发生断裂。提出去掉凸模导向区、在凹模内增加浮动芯轴作为导向的解决措施。并对改进的工艺方案进行数值模拟分析,凸模无应力集中现象,花键套无成形缺陷。工艺实验结果表明,采用改进的工艺方案可以有效避免凸模反挤压成形内花键的断裂问题,延长模具使用寿命。 相似文献
7.
8.
9.
探索采用700L高强钢作为卡车纵梁材料来实现制件减重。为解决纵梁落料冲孔模生产时常见的冲孔凸模断裂问题,以现有某量产车型的纵梁落料冲孔模来进行700L高强钢的生产实验,记录生产过程的机床工作台震动量、冲裁力等数据,为落料冲孔方案确定提供研究方向。通过优化制件结构以及对纵梁落料冲孔凸模进行阶梯型布置,减少冲裁力,校核模具冲裁中心与机床中心,减少设备震动对凸模寿命的影响。最终解决了冲孔凸模断裂频发的问题。 相似文献
10.
11.
通过介绍冷挤压凸模易断裂的情况,分析了易断的主要原因。提出了在凸模与凸模固定套之间加一45钢圈,本文称之为缓冲圈,来改善凸模的受力状况,实现了保护冷挤压凸模,延长凸模寿命的目的,缓冲圈的使用效果显著。 相似文献
12.
Yaning Li Meng Luo Jörg Gerlach Tomasz Wierzbicki 《Journal of Materials Processing Technology》2010,210(14):1858-1869
Necking has been the dominant failure mode in sheet metal forming industry and several analytical and numerical tools were developed to predict the onset of necking. However, the introduction of Advanced High Strength Steels (AHSS) with reduced ductility brought up an issue of a shear fracture which could not be predicted using the concept of Forming Limit Curve (FLC). The Modified Mohr-Coulomb fracture criterion (MMC) was recently shown to be applicable to problems involving ductile fracture of materials and sheets. In the limiting case of plane stress, the fracture locus consists of four branches when represented on the plane of the equivalent strain to fracture and the stress triaxiality. A transformation of above 2D fracture locus to the space of principal strains was performed which revealed the existence of two new branches not extensively studied before. The existence of those branches explains the formation of shear-induced fracture. As an illustration of this new approach, initiation and propagation of cracks is predicted and compared with series of deep-drawing punch tests of ThyssenKrupp AHSS (grade RA-K 40/70, standard HCT690T) performed at ThyssenKrupp. It was shown that the location of fracture as well as the magnitude of punch travel corresponding to first fracture was correctly predicted by MMC fracture criterion for both circular and square punch. 相似文献
13.
采用温挤压成形工艺生产减速顶滑动油缸体时,冲头经常会出现磨损和断裂失效。本文采用基于ANSYS软件的二维弹塑性热力耦合数值模拟系统,对该工艺进行数据模拟,得到了变形过程中的金属流动、工件及模具的应力场、应变场和温度场的变化,并根据这些结果对冲头失效的原因进行了分析。 相似文献
14.
应用韧性断裂准则与有限元数值模拟相结合的方法预测了铝合金板料的胀形极限.将有限元模拟获得板材的应力、应变值代入考虑应力三轴度的Oyane韧性断裂准则进行断裂判断,预测出初始断裂点.准则中的材料常数通过单向拉伸和平面拉伸试验确定.计算了三种铝合金板的半球形凸模胀形极限,计算结果表明,应用Oyane韧性断裂准则能有效地预测铝合金板材的胀形极限. 相似文献
15.
H. Fathi E. Emadoddin H. R. Mohammadian Semnani B. Mohammad Sadeghi 《Metals and Materials International》2016,22(3):397-406
The aim of the present study is to investigate the effect of punch speed on forming limit diagram (FLD) and the formability of austenitic stainless steel type 304L. Effect of strain rate on the height of dome is studied using the hemispherical punch test. Results of this study show that strain rate has significant effect on FLD in this material and high formability obtains at low strain rate. The safe area of FLD between major and minor strains is extended under low strain rate. It is seen that at low punch speed, failure and fracture occur at the pole region (top of the dome), whereas at higher forming rates, failure occurs close to the flange region. Modeling studies are also carried out using Ls-Dyna to know the region of high stress concentration and to predict the location of fracture. There is good agreement between simulation and experimental results. 相似文献
16.
A gradually contacting punch for improving stretch flangeability of ultra-high strength steel sheets having small ductility was developed. In the gradually contacting punch, tensile stress around the corner edge of the sheet in stretch flanging is decreased by gradually pressing the edge of the sheet with the inclined bottom of the punch. The critical flange heights of bent 980 and 1180 MPa ultra-high strength steel sheets without fracture with the gradually contacting punch increased by 32% and 31%, respectively. In addition, the stroke limit of the press was avoided by 2-stage flanging consisting of peripheral bending and corner bending. 相似文献
17.
《金属学报(英文版)》2015,(12)
To clarify the effects of the vertical angle of a conical punch on stretch flangeability, hole expansion forming tests were conducted. Test results showed that the hole expansion ratio becomes larger as the vertical angle decreases.Results also showed that the fracture strain at the fracture location on the hole edge was constant and independent of the vertical angle. This is because the hole expansion ratio was controlled not only by the fracture strain, which is independent of the vertical angle, but also by deformation uniformity along the hole edge. From the result of numerical analyses, it was determined that deformation uniformity depends on the gradient of circumferential stress along the radius direction. When the vertical angle is sharp, the circumferential stress showed a steep decline and the deformation localization was suppressed. Consequently, the hole edge deformed more uniformly and the hole expansion ratio became larger. It is concluded that in order to improve stretch flangeability of high strength steel, it is important to uniformly deform the hole edge by applying a conical punch with a sharp vertical angle. 相似文献
18.
Yongchao Xu Feng Li Xin Liu Shijian Yuan 《JOM Journal of the Minerals, Metals and Materials Society》2011,63(5):39-41
To improve the poor plasticity of 2024 aluminum alloy sheet, which causes wrinkle and fracture in conventional deep drawing
of complexshaped components, hydromechanical deep drawing (HDD) with pre-bulging was investigated. The loading paths of chamber
pressure and pre-bulging pressure were designed and optimized by numerical simulations and experiments, and effects of loading
paths were obtained and analyzed for thickness, stress and defects. A reasonable loading path was determined. Thickness is
more uniform when pre-bulging pressure is 2 MPa and chamber pressure is 15 MPa. The suspending area of a blank wrinkles easily
between the punch and the die when pre-bulging pressure is smaller than 1.5 MPa; fracture occurs for the suspending area of
blank between the punch and the die when pre-bulging pressure is larger than 8 MPa. The results show that a helpful friction
can be generated, the stress state can be improved, and fracture and wrinkle can be avoided by a reasonable pre-bulging in
the suspending area of the blank for a complex-shaped component. The uniformity of thickness and forming limit can be enhanced. 相似文献
19.
A slight clearance punching process of ultra-high strength steel sheets using a punch having a small round edge was developed to improve the quality of the sheared edge. No crack from the edge of the punch was generated by relaxing concentration of deformation with the punch having a small round edge, and the fracture was delayed. A small edge radius of 0.13 mm was effective for improving the quality of the sheared edge of ultra-high strength steel sheets, the increase in shiny burnished surface. The delayed fracture was prevented by the increase in compressive residual stress for the punch having the small round edge. For 1000 strike punching of an ultra-high strength steel sheet having a tensile strength of 1200 MPa, a sheared edge of high quality was produced with a TiAlN-coated punch having the small round edge. In addition, the chipping of the punch edge was prevented even for a slight clearance by the small round edge. It was found that both small round edge and slight clearance are indispensable for high quality punching of ultra-high strength steel sheets having low ductility. 相似文献
20.
探明实心锭穿孔过程的材料流动和穿透断裂行为对高性能优质无缝管材的实心锭穿孔挤压推广应用具有重要意义。以直径200 mm实心锭为原料,穿孔挤压成直径80 mm、壁厚10 mm的钛合金管材为研究对象,基于DEFORM-2D软件环境,建立了能够描述材料流动和穿透断裂行为的实心锭穿孔挤压穿孔过程的热力耦合有限元模型。研究分析了2种形状穿孔冲头的穿孔过程。结果表明:穿孔初始阶段变形行为类似正挤压,随后材料反向流动,堵头去掉前都是反挤压变形;正挤压变形下穿孔力迅速上升,上升至稳定值后开始反挤变形,去掉堵头后的穿透断裂阶段穿孔力迅速下降;采用圆柱形穿孔冲头情况下反挤时穿孔力变化幅度不大,而采用瓶形穿孔冲头情况下的穿孔力稳定一段时间后再次显著增加,瓶形穿孔冲头的穿孔力远大于圆柱形穿孔冲头的穿孔力;穿透断裂阶段,圆柱形穿孔冲头下的断裂行为类似于冲裁断裂,而瓶形穿孔冲头下的约束增强,其断裂面近似呈L型。 相似文献