Effect of Variable Blank Holder Force on Rectangular Box Drawing Process of Hot-galvanized Sheet Steel

At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force （VBHF） was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.

Effect of Friction on the Drawing Process of Hot-Galvanized Sheet Steel

A probe test method was employed to detect the friction condition of the interfaces between tools and blank. At the same time a self-developed measurement apparatus to realize the probe test method was also presented. Based on the analysis of force, a correlative friction model was also given. With the self-developed measurement apparatus,the effects of three kinds of lubricating oils which were in common use during the process of sheet steel drawing were studied. By probing the friction coefficient values of different lubricating oils during the drawing process of the hot-galvanized sheet steel （steel brand： ST07Zn）, we can see that the friction caused by PK oil was the lowest, so the effect of PK oil was the best. Then PK oil was used as the base lubricating oil and some solid additive powers was added into it to make a new type lubrication （named as L oil）.The result of test proved that the new lubricating oil had remarkable effect on the drawing process of hot-galvanized sheet steel.

FRACTURE LIMIT LOAD OF CONE SHAPE PART IN DRAWING PROCESS

The deformation characters and load status of the blank＇s potential fracture zone are analyzed at the moment when blank is approaching to punch comer in drawing process of cone shape part. Based on tension instability theory, the formula for calculating fracture limit load of cone shape part in drawing process is derived. Also, the formula is analyzed and verified by experiment.

Influence of process parameters on deep drawing of AA6111 aluminum alloy at elevated temperatures

To gain a deep insight into the hot drawing process of aluminum alloy sheet, simulations of cylindrical cup drawing at elevated temperatures were carried out with experimental validation. The influence of four important process parameters, namely,punch velocity, blank holder force(BHF), friction coefficient and initial forming temperature of blank on drawing characteristics(i.e.minimum thickness and thickness deviation) was investigated with the help of design of experiments(DOE), analysis of variance(ANOVA) and analysis of mean(ANOM). Based on the results of ANOVA, it is shown that the blank holder force has the greatest influence on minimum thickness. The importance of punch velocity for thickness deviation is 44.35% followed by BHF of 24.88%,friction coefficient of 15.77% and initial forming temperature of blank of 14.995%. After determining the significance of each factor on forming characteristics, how the individual parameter affects characteristics was further analyzed by ANOM.

Software Development for the Management of CAD Drawings

A software for the management of computer aided design（CAD） drawings was developed. It can be used to classify and register information including geometric features of the drawings, and to search appropriate reference drawings matching the given conditions of a new design. The thumbnails of the drawings can be displayed in an order of preference and can be used to zoom and access the PDF file or CAD data of a selected drawing. The thumbnails and the data structure are two key elements of the software.

Thermally Drawn Multi‑material Fibers Based on Polymer Nanocomposite for Continuous Temperature Sensing

With increasing personalized healthcare,fiber-based wearable temperature sensors that can be incorporated into textiles have attracted more attention in the field of wearable electronics.Here,we present a flexible,well-passivated,polymer–nanocomposite–based fiber temperature sensor fabricated by a thermal drawing process of multiple materials.We engineered a preform to optimize material processability and sensor performance by considering the rheological and functional properties of the preform materials.The fiber temperature sensor consisted of a temperature-sensing core made from a conductive polymer composite of thermoplastic polylactic acid,a conductive carbon filler,reduced graphene oxide,and a highly flexible linear low-density polyethylene passivation layer.Our fiber temperature sensor exhibited adequate sensitivity(−0.285%/℃)within a temperature range of 25–45℃with rapid response and recovery times of 11.6 and 14.8 s,respectively.In addition,it demonstrated a consistent and reliable temperature response under repeated mechanical and chemical stresses,which satisfied the requirements for the long-term application of wearable fiber sensors.Furthermore,the fiber temperature sensor sewn onto a daily cloth and hand glove exhibited a highly stable performance in response to body temperature changes and temperature detection by touch.These results indicate the great potential of this sensor for applications in wearable,electronic skin,and other biomedical devices.

Efects of Die Corner Radius and Temperature on the Formability of AA7075-T6 Alloy

This study focused on the formability of aluminium alloy（7075-T6） sheets through hydroforming route. Formability of these sheets was tested using a warm forming setup at three diferent temperatures and four diferent die corner radii. Forming limit diagrams（FLD） were generated by measuring the grids of the sheet formed. The results show that the forming limit of AA7075-T6 can be significantly improved when the blank was heated to 140–250℃. It was also observed that as the temperature increases above 140℃, dome height began to decrease. Also the results indicated that both the die corner radius and temperature have a significant efect on the stress-strain curve and warm forming of AA7075-T6 sheets. Thus, with the temperature increased from room temperature（RT） to 140℃, the flow stress decreased and the strain increased, hence, the formability is enhanced. However, further increase in temperature causes decreases the flow stress and strain. Similar changes of the flow curve were seen in die corner radius. Decreasing the die corner radius decreases the flow stress and increase the strain. Moreover, an equation was obtained by establishing correlations between the experimental parameters and their results. In this way, it became possible to make predictions.

Determination of continuous constitutive relationship of weld zone of high-strength steel rectangular welded tube

For QSTE700 high-strength steel rectangular welded tube,the mechanical properties of the weld zone vary with the distancefrom the centerline of the weld.Therefore,the accurate description of constitutive relationship of the weld zone is of greatsignificance for the study of formability of QSTE700 rectangular welded tube.Firstly,the mechanical properties of parentand mixed specimens containing weld zone and parent zone were obtained by uniaxial tensile test.And based on the micro-hardness test,the width and the microhardness distribution of the weld zone were determined.Secondly,by subdividingthe weld zone into several small areas,and combining with the rule of mixtures and nanoindentation test,the continuous functional relationships of strength coefficient K,hardening coeffecient n and elastic modulus E were obtained,and then,the continuous constitutive relationship of QSTE700 rectangular welded tube was established.Finally,the validity and reliability of the continuous constitutive relationship of welded tube were verified by nanoindentation fest and rotary drawbending of rectangular welded tubc.Besides,it was found that the finite element model of rotary draw bending of QSTE700 rectangular welded tube established by using the continuous constitutive relationship can well simulate the cross sectiondeformation and wall thickness variation.