Young-Chan Kim
,
Chang-Seog Kang
,
Jae-Ik Cho
,
Chang-Yeol Jeong
,
Se-Weon Choi
,
Sung-Kil Hong
材料科学技术（英文）
Recently, demand for the lightweight alloy in electric/electronic housings has been greatly increased. However, among the lightweight alloys, aluminum alloy thin-walled die casting is problematic because it is quite difficult to achieve sufficient fluidity and feedability to fill the thin cavity as the wall thickness becomes less than 1 mm. Therefore, in this study, thin-walled die casting of aluminum (Al-Si-Cu alloy: ALDC 12) in size of notebook computer housing and thickness of 0.8 mm was investigated by solidification simulation (MAGMA soft) and actual casting experiment (Buhler Evolution B 53D). Three different types of gating design, finger, tangential and split type with 6 vertical runners, were simulated and the results showed that sound thin-walled die casting was possible with tangential and split type gating design because those gates allowed aluminum melt to flow into the thin cavity uniformly and split type gating system was preferable gating design comparing to tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. Also, the solidification simulation agreed well with the actual die-casting and the casting showed no casting defects and distortion.
关键词:
Aluminum casting alloy
,
null
,
null
Chang-Seog Kang
,
Jae-Ik Cho
,
Chang-Yeol Jeong
,
Se-Weon Choi
,
Young-Chan Kim
材料科学技术（英文）
Silicon-based aluminum casting alloys are known to be one of the most widely used alloy systems mainly due to their superior casting characteristics and unique combination of mechanical and physical properties. However, manufacturing of thin-walled aluminum die-casting components, less than 1.0 mm in thickness, is generally known to be very difficult task to achieve aluminum casting alloys with high fluidity. Therefore, in this study, the optimal die-casting conditions for producing 297 mm×210 mm×0.7 mm thin-walled aluminum component was examined experimentally by using 2 different gating systems, tangential and split type, and vent design. Furthermore, computational solidification simulation was also conducted. The results showed that split type gating system was preferable gating design than tangential type gating system at the point of view of soundness of casting and distortion generated after solidification. It was also found that proper vent design was one of the most important factors for producing thin-wall casting components because it was important for the fulfillment of the thin-wall cavity and the minimization of the casting distortion.
关键词:
Aluminum
,
null
,
null
,
null
张莉
,
马敬红
,
梁伯润
,
余亦华
高分子材料科学与工程
在氮气氛中采用热重分析的方法对热致液晶共聚酯60PHB/PEN的热降解动力学进行了研究.采用Friedman和Chang两种单一加热速率方法对活化能Ea、反应级数n和频率因子Z等降解反应动力学参数进行了分析.讨论了加热速率和计算方法对热稳定性及降解动力学参数的影响.
关键词:
热致液晶共聚酯
,
热降解
,
动力学
,
热稳定性
金属学报
Volu扣ne 27SeriesB1991AUTHOR INDEX CCAO Guanghan(曹光旱)············……6一B科6CAo weijie(曹卫恋)..················……5一B32oCAO Yilin(曹益林)··················……6一B443CHANG Xin(常听)···············……1一B48CHE Guang邻n(车广灿)·············一6一B科0CHEN Erbao(陈二保)···············……6一B410CHEN Jia....
关键词:
徐颖
,
温卫东
,
崔海坡
材料科学与工程学报
doi:10.3969/j.issn.1673-2812.2006.01.020
针对复合材料层板在冲击载荷下,各种损伤的产生和扩展是一个随载荷、时间和空间而演变的过程,发展了复合材料层合板低速冲击逐渐累积损伤预测方法.采用刚度退化技术和改进的Chang-Chang失效准则、显式有限元法来模拟复合材料层合板受到低速冲击下逐渐损伤过程.使用所发展的方法分析了[0m/90n/0m]铺层的复合材料层合板在低速冲击过程中的逐渐损伤扩展,结果表明本文的方法能较好地模拟复合材料层板在低速冲击下的损伤扩展及变形过程,计算结果与实验结果吻合较好;对不同冲击能量下层合板损伤扩展研究表明,冲击能量与分层损伤面积成线性关系.
关键词:
复合材料层合板
,
冲击
,
逐渐累积损伤
,
破坏机理
,
数值模拟
张鹏飞
,
金海波
复合材料学报
建立了有效的复合材料层合板结构冲击损伤分析方法,层合板面内损伤采用改进的Chang/Chang失效准则做判据,得到面内各类损伤形式.层间损伤采用与Mixed-Mode粘接元等效的TIEBREAK接触模拟.利用此分析方法,从复合材料薄壁结构设计需要出发,研究了在低能量冲击下,铺层的层间角度、铺层方向、铺层重叠对层合板结构冲击损伤阻抗的影响规律,并对它们的综合影响进行了总体分析,得到了能提高层合板结构损伤阻抗的铺层顺序设计指导.最后用该设计指导对某种铺层结构进行了重新设计和有限元模拟,验证了该设计指导的可行性和有效性.
关键词:
冲击损伤
,
分层损伤
,
TIEBREAK接触
,
铺层顺序
,
损伤阻抗
LIU Yongning
,
ZHU Jinhua
,
ZHOU Huijiu Xi'an Jiaotong University
,
Xi'an
,
China A.Kildegaard
,
J.A.Kristensen Department of Mechanical Engineering
,
Aalborg University
,
Denmark Dept.of Materials Science and Engineering Xi'an Jiaotong University
,
Xi'an 710049
,
China
金属学报(英文版)
The dynamic fracture toughness of a mild steel has been studied at different loading rates and temperatures.The material exhibits a transition from tough to brittle fracture with the chang- ing loading rate alone.Analysis of the fracture process by the theory of thermal activation suggests that the fracture activation energy approximates to the bond energy of the{100}of a unit cell.The toughness can be resolved into two parts,J-(fd)=J_a+J_l,where J_a is the athermal part,being independent on temperature and loading rate,while J_l=(K/K_o)~(1/n)exp(Q_f/nkT),which controls the fracture process is temperature and load- ing rate dependent.The transition of fracture mechanism caused by both temperature and loading rate is associated with the thermal movement of atoms.
关键词:
mild steel
,
null
,
null
,
null
王艳龙
,
蔡敬标
,
陆晓峰
,
朱晓磊
复合材料学报
doi:10.13801/j.cnki.fhclxb.20160328.005
针对含孔复合材料点阵夹层结构在面内压缩载荷作用下的失效模式及其影响因素问题，通过实验对含孔复合材料点阵夹层结构失效模式进行了研究；基于3D Hashin准则和Chang-Chang刚度退化准则建立了含孔复合材料点阵夹层结构有限元渐进损伤失效分析模型，并将计算结果与实验结果进行了对比；基于有限元分析方法探讨了开孔形状、开孔率以及开孔位置对其极限承载力的影响。结果表明：当点阵夹层结构面板厚度较大时，含孔复合材料点阵夹层结构的主要失效模式为面板圧溃；通过对比有限元计算结果和实验结果，极限承载力的最大误差约为12%，失效位置与实验结果一致；当点阵夹层结构的对称面与载荷方向平行且孔的中心在对称面上时，面内压缩强度与开孔位置无关，主要受到开孔形状和开孔率的影响；当点阵夹层结构对称面与载荷方向垂直且孔的中心在对称面上时，边距大于一个胞元，面内压缩强度基本不变，边距小于一个胞元，面内压缩强度下降。
关键词:
点阵夹层结构
,
开孔率
,
开孔位置
,
开孔形状
,
压缩强度
方王平
,
杨胜林
,
李光
,
江建明
高分子材料科学与工程
由TGA测定了通过先酯化、再缩聚方法合成的PET-PTT共聚酯(以PET,PTT作对照)在一定升温速率下氮气及空气气氛中的热失重行为.采用Friedman和Chang方法研究了样品的降解动力学.研究表明,在氮气和空气气氛中PET-PTT共聚酯的热稳定性都介于PET和PTT之间,且随着PET链段单元含量的增加,共聚酯的热稳定性提高.气氛对聚合物降解行为的影响很大,在空气中PET-PTT共聚酯的起始分解温度下降了近50℃,且在空气气氛中存在两个降解阶段,空气中的氧在降解的第一阶段起了催化剂的作用.
关键词:
PET-PTT共聚酯
,
热稳定性
,
热氧稳定性
张莉
,
隋坤艳
,
杨明
,
马敬红
,
梁伯润
高分子材料科学与工程
在氮气氛中采用热重分析的方法对聚萘二甲酸乙二酯(PEN)的热降解动力学进行了研究.采用Friedman和Chang两种单一加热速率方法对活化能Ea反应级数n和频率因子Z等降解反应动力学参数进行了分析.讨论了降解机理以及加热速率和计算方法对降解温度和降解动力学参数的影响.由单一加热速率法得到的丁Td、Tdm和(dа/dt)m,以及Ea和In(Z)值均随加热速率的增加而增加,n值则随加热速率略有变化.随加热速率的提高,聚合物的降解由分解控制转变为扩散控制过程.
关键词:
聚萘二甲酸乙二酯
,
热降解
,
热重分析
,
动力学
,
热稳定性
