Forming and Springback Prediction of Strips Under Multi-square Punch Concave Forming Process Considering Partial-unloading Effects

To further investigate the forming mechanism and springback characteristics of strips under multi-square punch forming (MSPF) considering partial-unloading effects, a series of concave form ing tests of strips are conducted on the MSPF machine. This paper aims to reveal the physical mecha nism of the elastic-plastic deformation in the MSPF process considering the effect of the forming ap proaches, and derive appropriate mathematical interpretations. The theoretical model is firstly estab lished to analyse the concave forming mechanism and springback characteristics of the strip, and its accuracy is then validated by experimental data. The forming history and load evolutions are depicted to explore the required forming capacity through the proposed analytical method. Besides, the paramet ric studies are carried out to discuss their effects on the springback of the strip. The results suggest that the deformation paths of the strip are influenced by the forming approach, and the springback of the strip in convex forming is larger than that in concave forming.

Soft-punch Hydro-forming of 304 Stainless Steel Sheet

The process of soft-punch hydro-forming was use.d to form some workpieces. However, it has not been completely understood until now. In this paper, based on some primary experiments, in which cups have been tried under different working conditions with the soft-punch hydro-forming process, systematical know-how about why the LDR of a metal sheet is different, how working conditions influence qualities of a work-piece, and how the deformation takes place has been achieved when simulations are employed. All these results claim that the cup depth heavily weighs on the cup wall thinning rate, and a satisfied complex part can be achieved when the contacting time between the sheet and the female die is under our control well by a movable slider, which is fixed as the bottom of the female die.

Wrinkling prediction in rubber forming of Ti-15-3 alloy

Wrinkling is a common failure in the sheet metal forming of titanium owing to the relatively poor ability to shrink. It is important to predict wrinkling accurately in the sheet metal forming without costly trials. The ABAQUS/Explicit code was utilized to predict the wrinkling behavior in the sheet metal forming of Ti-15-3 alloy sheets. In terms of the comparison of wrinkling behavior between the simulation and experiment of the Fukui＇s conical cup tests at room temperature, the sensitivities of wrinkling simulation to various input parameters were evaluated comprehensively and quantitatively. Prediction of wrinkling and influence of rubber hardness on the winkling behavior in the rubber forming of convex flange were investigated quantitatively and validated by the rubber forming experiments. The excellent agreements between the simulations and the experiments conIirmed the accuracy of the prediction.

Friction coefficient in rubber forming process of Ti-15-3 alloy

The forming limit diagram of Ti-15-3 alloy sheet was constituted at room temperature. The effects of different punch and rubber hardness on the limit principal strain distributions were investigated experimentally. Finite element analysis models of the samples with dimensions of 180 mm×180 mm were established to analyze the friction coefficients of different interfaces. Effects of various friction coefficients on the strain distributions were studied in detail. Finally, the friction coefficients in the cold forming were determined by contrasting the strain results between the experimental data and the simulated ones.

Microstructure and properties of Al-0.70Fe-0.24Cu alloy conductor prepared by horizontal continuous casting and subsequent continuous extrusion forming

A novel process for manufacturing A1-0.70Fe-0.24Cu alloy conductor was proposed, which includes horizontal continuous casting and subsequent continuous extrusion forming （Conform）. The mechanical properties, electrical conductivity and the compressed creep behaviour of the alloy were studied. The results indicate that the Conform process induces obvious grain refinement, strain-induced precipitation of AI7CuzFe phase and the transformation of crystal orientation distribution. The processed alloy has good comprehensive mechanical properties and electrical conductivity. Moreover, a better creep resistance under the conditions of 90 ~C and 76 MPa is shown compared with pure A1 and annealed copper, and the relationship between primary creep strain and time may comply with the logarithmic law. The enhanced properties are attributed to the grain refinement as well as the fine and homogeneously distributed thermally stable A1Fe and A17Cu2Fe precipitation phases.

RESEARCH ON HOT FORMING PROCESS OF A RETAINING RING OF HIGH-NITROGEN STEEL

Mn18Cr18N, the high-nitrogen steel, is the 2nd generation material for manufacturing the retaining ring of firepower generators. In this paper, the hot deformation behavior of the material was investigated by thermo-mechanical modeling tests. And the flow stress curves of the steel were obtained for various combinations of the temperature and strain rate. Based on the results of the tests, the complex forming process of a retaining ring including punching, expanding and extrusion with an enclosure was put forward and simulated by means of numerical simulation method. The results indicate that the process is a novel and force-saved practical technology for manufacturing heavy retaining rings.

Dimpling Suppression by Chamfered Rotatable Cubic Punch in Reconfigurable Die Forming

The dimpling defects caused by conventional hemispherical punch in doubly curved sheet metal reconfigurable die forming process were considered.The rotatable cubic punch (RCP) was developed to suppress the dimpling defects more effectively and conveniently.The former punch contacts with the work-piece through a point-surface contact and the latter punch contacts with the work-piece through a surface-surface contact.A series of stamping experiments were carried out using three different punches (hemispherical punch,RCP,chamfered-RCP) with three different loads.Some finite element simulations about the stamping experiments were carried out.The dimple scales were evaluated through the dimple depths.The corresponding data were obtained by 3-D scanning and FE result analysis respectively.A 3-D plate forming machine was developed,in which chamfered-RCP was adopted.Plate forming experiments were carried out on this machine.The stamped samples show a clear basis for the performance of chamfered-RCP.The study provided a means to guide the design of punches for dimpling suppression used in reconfigurable die.

Superplastic Forming and Diffusion Bonding for Sandwich Structure of Ti-6Al-4V Alloy

Superplastic forming and diffusion bonding (SPF/DB) is a well-established process for the manufacture of components almost exclusively from Ti-6AI-4V sheet material. The sandwich structure of Ti-6AI-4V alloy is investigated. The effects of the microstructure on the SPF/DB process were discussed. The microstructure at the interfaces and the distribution of thickness were researched.

The Evolutionary History of Ore-forming Processes of Metallic Ore Deposits in Northern Guangxi

The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis shows features of polycyclic spiral evolution throughout the geological history. As far as various cycles are concerned, mantle-derived ore substances were reduced while crust-derived ore substances increased from early to late timesfin the whole geological evolutionary history, mantle-derived substances decreased gradually while crust-derived ones increased. Meanwhile ore element associations became more and more varied. In terms of space, mineralization migrated from the old basement outwards, i.e. from west to east during the Precambrian, and from north to south during the Phanerozoic, and again from east to west during the Yanshanian.

The Forming Conditions of and Ore-searching Direction for B, Mg,Pb, Zn and Au Deposits in the Liaoji Proterozoic Rift

The Liaoji Proterozoic rift is an inter-intracontinenatl rift developed from Archean granite-greenstone tectonic regime and contains many important mineral deposits of U, B, magnesite, Pb-Zn, Au, Ag, Co and P. These deposits were formed as the result of late mobilization, transportation and concentfation of the previously enriched ore-forming mate- rials in several ore-bearing formations formed during the rift stage. So the metallogeny of these deposits in the rift shows both inheritance and new generation of the ore-forming materials. In future ore-searching practice, attentions should be paid on the studies of the ore-bearing formations in the rift, on the multiple stages of metallogeny and and on multiple derivations of the ore-forming materials.

Theoretical prediction and experimental investigation on formability of tailor-welded blanks

Based on the elastoplastic mechanical properties of the weld and heat affected zone metals obtained by a nanoindentation test, a theoretical calculation model was established for the forming limit diagram（FLD） of tailor-welded blanks（TWBs） on the basis of plastic constitutive relations and Hosford yield criteria. Hemispherical punch bulging tests were performed to verify the FLD theoretical calculation results. The results demonstrated that not only the FLD theoretical calculation of base materials but also that of TWBs had a good agreement with their experiments. Besides, poorer formability of TWBs caused its FLD significantly lower than that of base materials. The theoretical calculation model offers a reliable approach to obtain the specific FLD of TWBs.

Hot shear deformation constitutive analysis of fine-grained ZK60 Mg alloy sheet fabricated via dual equal channel lateral extrusion and sheet extrusion

Dual equal channel lateral extrusion(DECLE)process with various passes followed by sheet extrusion process was performed to produce fine-grained ZK60 alloy sheets.The coarse grain structure of the annealed sample after applying sheet extrusion(size:68μm)changed to fine grains of 6.0 and 5.2μm after 3 and 5 passes of DECLE and following extrusion.The hot shear deformation behavior of samples was studied by developing constitutive equations based on shear punch test(SPT)results.SPT was carried out in the temperature range of 200−300℃ and strain rate range of 0.003−0.33 s^(–1).The activation energy of 125−139 kJ/mol and the stress exponent of 3.5−4.2 were calculated for all conditions,which indicated that dislocation creep,controlled by dislocation climb and solute drag mechanism,acted as the main hot deformation mechanism.It was concluded that material constants of n and Q are dependent on the microstructural factors such as grain size and second phase particle fraction,and the relationship of which was anticipated using a 3D surface curve.Moreover,the similar strong basal texture of extruded sheets gave rise to the same deformation mechanisms during SPT and similar n and Q values for ZK60 alloy.

Novel AC Servo Rotating and Linear Composite Driving Device for Plastic Forming Equipment

The existing plastic forming equipment are mostly driven by traditional AC motors with long trans- mission chains, low efficiency, large size, low precision and poor dynamic response are the common disadvantages. In order to realize high performance forming processes, the driving device should be improved, especially for com- plicated processing motions. Based on electric servo direct drive technology, a novel AC servo rotating and linear composite driving device is proposed, which features implementing both spindle rotation and feed motion with- out transmission, so that compact structure and precise control can be achieved. Flux switching topology is employed in the rotating drive component for strong robustness, and fractional slot is employed in the linear direct drive component for large force capability. Then the mechanical structure for compositing rotation and linear motion is designed. A device prototype is manufactured, machining of each component and the whole assembly are presented respectively. Commercial servo amplifiers are utilized to construct the control system of the proposed device. To validate the effectiveness of the proposed composite driving device, experimental study on thedynamic test benches are conducted. The results indicate that the output torque can attain to 420 N-m and the dynamic tracking errors are less than about 0.3 rad in the rotating drive, the dynamic tracking errors are less than about 1.6 mm in the linear feed. The proposed research provides a method to construct high efficiency and accu- racy direct driving device in plastic forming equipment.

Unveiling the planar deformation mechanisms for improved formability in pre-twinned AZ31 Mg alloy sheet at warm temperature

To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation,the stretch forming is conducted at 200℃.Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to 11.30 mm.The mechanisms for the improved formability and the deformation behaviors during the planar stretch forming are systematically investigated based on the planar stress states.The Schmid factor for deformation mechanisms are calculated,the results reveal that planar stress states extremely affect the Schmid factor for{10-12}twinning.The detwinning is activated and the prismatic slip is enhanced in the pre-twinned sheet,especially under the planar extension stress state in the outer region.Consequently,the thickness-direction strain is accommodated better.The dynamic recrystallization(DRX)type is continuous DRX(CDRX)regardless of the planar stress state.However,the CDRX degree is greater under the planar extension stress state.Some twin lattices deviate from the perfect{10-12}twinning relation due to the planar compression stress state and the CDRX.The basal texture is weakened when the planar stress state tends to change the texture components.

碳纤维复合材料编织-针刺预制体成形质量研究

编织-针刺复合成形技术可实现大厚度回转形复合材料预制体一体化成形。为研究编织-针刺复合材料预制体成形质量,试制了不同K数纱线、编织角度的编织-针刺预制体以及作为对照组的机织-针刺预制体。考虑背面针刺纤维束形貌以及基布损伤提出通过用预制体纤维束细长率χ_(f)定量表征针刺纤维束形貌。结合实际针刺预制体剥离曲线的变化特点,采用有效剥离曲线内所有波峰和波谷的平均值来对层间剥离强力进行描述。结果表明,试样纱线K数为6K时,编织-针刺预制体平均细长率相较机织-针刺预制体提升7.2%,编织-针刺预制体纤维束形貌更理想。当纱线K数由6增加至12时,机织-针刺预制体背面纤维束平均细长率提升了78.9%,编织-针刺预制体却减少了30.6%,其原因在于编织-针刺预制体刺针作用位置处纱线被挤开,增大了纤维束投影面积。编织-针刺预制体在层间剥离强力指标方面优势显著,各试样相较机织-针刺预制体提升38.0%以上,12K纱线编织-针刺预制体层间剥离强力比6K纱线大78.3%,且随着编织角由30°增加至60°,编织-针刺预制体平均剥离强力减少46.6%。

The Protective Effects of Flavonoids from Scutellaria Baicalensis Georgi Stems and Leaves on Oligodendrocyte Damage Induced by Aβ1-42

Aim: This study aimed to investigate the protective effects of flavonoids from the stem and leaves of Scutellaria baicalensis Georgi (SSFs) against Aβ1-42-induced oligodendrocytes (OL) damage. Methods: Immunofluorescence was used for the detection of myelin-associated glycoprotein (MAG), a characteristic protein of rat oligodendrocytes (OLN-93 cells). To evaluate the potential protective effects of SSFs on OLN-93 cells injured by Aβ1-42, an injury model was established by subjecting OLN-93 cells to Aβ1-42 exposed. Cell morphology was examined using an inverted microscope, while cell viability was assessed using the colorimetric method of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Additionally, lactate dehydrogenase (LDH) was measured using the pyruvic acid reduction assay. The Ginkgo biloba leaf extract (GBE) injection was used as a positive control. Results: A total of >95% of the MAG immunofluorescence-positive cells were identified as oligodendrocytes. Gradually increasing concentrations of SSFs impaired the cells, and the maximum nondetrimental dose for OLN-93 cells was 75 mg/L. This study assessed the effects of SSFs on OLN-93 cells damaged by Aβ1-42. The results indicated that SSFs significantly improved OLN-93 cell morphological abnormal changes, increased the OLN-93 cell survival rate, and reduced LDH release. Conclusion: SSFs can alleviate Aβ1-42-induced damage of OL.

基于DEFORM的黄铜阀体冲压成形过程数值模拟

运用DEFORM软件模拟黄铜阀体冲压成形过程,阐述了阀体冲压成形的变形特点,分析阀体在塑性变形过程中可能产生裂纹的部位及其原因。缺陷产品统计分析数据验证了结论的可靠性。

基于ANSYS/LS-DYNA的杯形件椭圆角凸模拉深模拟

杯形件底部形状一般都设计成圆角过渡,这从加工性方面或许是比较方便的。然而,在拉深过程中,抵抗产生拉深缺陷的能力却并非是最理想的。研究带凸缘的杯形件,建立凸模直边与底部相连为椭圆角的有限元模型,用ANSYS/LS-DYNA进行杯形件拉深模拟,模拟结果与凸模直边与底部相连为圆角的杯形件比较,椭圆角凸模比圆角凸模的板料拉深成形能力有一定的提高。

基于PSO-BP和灰色关联度分析的盒形件成形工艺参数反求

以非线性有限元分析软件Dynaform为平台,基于粒子群算法优化的BP神经网络和灰色关联度,对盒形件成形过程进行成形参数寻优并反求。先利用正交试验法获取不同组合下的减薄率数值;采用灰色关联度理论,找到对该盒形件最大减薄率起主要影响的两个因素即压边力和摩擦因数;运用拉丁超立方抽样对选出的两个主要因素进行随机抽样,通过Dynaform进行数值仿真以获得样本数据;基于PSO-BP模型,将压边力和摩擦因数作为两输入值,最大减薄率作为输出,建立压边力和摩擦因数与最大减薄率之间的非线性映射关系,其后,利用粒子群算法对其优化可获得最优工艺参数和对应输入值。对比优化前后的数值模拟结果可知,优化后的冲压参数可以有效提高板料成形性能。

Ni-W合金镀层在电池外壳成形模中的应用

介绍采用电镀法在不锈钢电池外壳成形凸模上沉积Ni-W合金镀层,并对成形凸模失效形式、镀层的表面形貌、组织结构、显微硬度、耐磨性能等进行了分析。结果表明,已镀凸模的使用寿命比未镀凸模使用寿命有较大提高。