別紙4 (課程博士)
Date of submlssion

平成Depar紅11ent

28年9月20日

StudentlD Number

機械工学専攻Pplicant's name

学籍番号第 139104 号

N山 Liyana BintiT@jul LⅡe

氏名Supervisor8

Professor Ken・ichiro Mori

指導教員

ASSOC. prof. Tomoyoshi
八4aenoAbstMct

論文内容の要旨(博士)Successive Forging ofQuenchable steel, Aluminium atld stainless steel sheets Having

Title ofThesis

博士学位論文名

Thickless Distribution and lnclined cross・section(肉厚分布と傾斜断面を持っ焼入れ鋼,アルミニウム,ステンレス鋼板の逐次鍛造)(Approx.80o words)
子4ぎミ(要旨 1,200字程度)

The use oftailored blanks having a thickness distribution increases in automobile body parts,
because the tailored blanks offer substantial、入,eight reduction, crash resistance and protection. The
tailored blanks a110w the use of an optimum thickness distribution in parts, and thus material
UtHization is optimized and weight is reduced. Although the tailored blanks are genera11y produced
by welding, joining of multゆle sheets by 、Nelding is costly and the sharp change in thichless
induces stress concentration. Although stress concentration is reduced by gradual change of thethichless in the transient region for tailor・r011ed blanks, these blanks are expensive.
A successive forging process oftailored blanks having a thickness distribution supplied for
hot stamping was developed to overcome these problems、 1n this study, a blank having a uniform
thichless was successively compressed with upper and lower punches. since local deformation
Was repeated in successive forging, the forging load is comparatively sma11, and tailored blanks、vithout joining are produced as 、Ne11 as to the tailor r0Ⅱing process. The thichless 、Nas contr011ed
Only by the fヒed under a fixed stroke of the punch. As the feed decreases, the forging loaddecreases due to sma11 Contact area, and thus, the reduction in thichless ofthe blank becomes large
for sma11 elastic deformation ofthe press and tools.

During compression, the press ram is inclined by deaection ofthe press frame, and then to01
marks were observed on the surface ofthe tailored blank. Finite element simulation 、vas performed
to obtain the shape ofthe punch to preventthe tool marks on the surface ofthe tailored blank. A die

for correcting the upper punch inclination 、vas proposed to reduce the tool marks. By inseHing
Concave and convex plates into a c・丘'ame of a press, the inclination of the upper punch 、Nasreduced and the misaHgnment bet、刃een the upper and lower punches 、Nas decreased. uneven
Surface of the tailor blank was minimized by using comer radius punch and also concave andConvex plates.
Although aluminium a110ys are a加active to reduce the weight of a car, car parts produced
介om steel are e丘'ective due to high strength and l0圦ler cost. High strength steelsheets ho、Never, are
di缶Cult to form. Hot stamping reduces the aow stress, forming load and produces parts
Strengthened by martensitic transformation. A tailored blank having t、vo thicknesses wasSuccessively forged, and then hot・stamped into a roof rail miniature. The large cuNature of thetailor・forged blank by successive forging 、刃as eliminated a負er the hot stamping process. The
Strength ofthe hot・stamped roofrail miniature increase significantly A reduction ofweight by 20%丘)rthe tailor・forged roofrail miniature was measured.
For tailor・r011ed blanks, the thichless of the sheet is reduced and this portion isWork‑hardened. However, the strength required forthe thin portion is smaⅡ, whereas the strength isincreased by work・hardening. sheet forging having local thickening by beading and compression
圦las developed to produce sheet having a strength distribution. A uniform thichless sheet wasbeaded and the sheet was then compressed to form thickening. As the beading die heightincreases,

the degree ofthickening increases. The effect ofbeading die shape was analysed to prevent folding
for a large beading height. The produced tailored blank has high and l0圦, strengths for the thick andthin p0πions, respectively.

Sheet forging is widely used in metal forming industries to form sheets having a thin
ゞーCross・section into various shapes and thicknesses.1n this process, the forming load becomes highdue to the large fi'ictional restraint. For long parts,the forming load increases for large deformingarea. Long sheets having a uniform cross‑section are generaⅡy produced by r0Ⅱing, whereas itis

not easy to change tools and formed cross‑sectional shapes are Ⅱmited due to curvature andWrinkling. Long sheets are also produced by cU札ing, however this process results in a large
amount of scrap. The use of long paHs having an inclined cross‑section is important in thePrinting industry to ensure smooth and high qua1北y printing. These blades are used for cleaning
and regulating toners in printers.1n order to produce a long sheet having an inclined
Cross・section, a successive fbrging process was employed. since only a smaⅡ Portion ofthe sheet
Was deformed at a time, a smaⅡ 10ad is required. The used of a taper bottom inclined punch
minimized the formation of 、Naving and depression of the forged sheet. A side guide 、vas
introduced to reduce the curvature of the sheet. However for a very sma11 feeding, burr 、Nas
气、

formed on the side of the sheet due to a large curvature. The introduction of a grooved die
eliminates the curvature ofthe forged sheet having an inclined cross・section.