advanced line-heating process for hull-steel assembly...journal of ship production, vol. 16, no. 2,...

Journal of Ship Production, Vol. 16, No. 2, May 2000, pp. 121-132

Advanced Line-Heating Process for Hull-Steel Assembly

Morinobu Ishiyama I (Member), and Yoshihiko Tango (Visitor)

lshikawajima-Harima Heavy Industries Co., Ltd. (IHI) has successfully employed the logic of the Finite Element Method on the principle of Thermal Forming or Line Heating, which facilitates use of computer aided, fully automated line heating machines for forming any curvature precisely and efficiently on a hull steel plate in the shipbuilding process.

It is undesirable for the future in line heating that only an experienced technician is able to be skilled in the use of existing line heating f l or steel plate forming. Accuracy of shape formed by existing line heating is not necessarily well controlled and work at succeeding stages is adversely affected by inaccurate interim products, though it is a ve~ useful method informing steel plates and all apparatus required for line heating is just light tools. The IHI-Advanced Line-heating Process for Hull-steel Assembly (IHI-ALPHA) has succeeded in solving these problems.

1. I N T R O D U C T I O N

Line heating is the term given to a method of bend processing of a steel plate to produce three-dimensional curvature from a flat plate by alternating heating and cooling using a manual gas burner and cooling water, often applied to the bending process of curved outer shell of a vessel. Since the method in- volves a minimum of equipment, it became popular in Japan and certain other areas as a highly flexible and efficient method. Its weakness, however, is that the judgment of "where and how much" to heat de- pends mainly on individual experience and intuition, causing inconsistency of precision and processing time as the operator varies. There is also some con- cem that with average aging of craftsmen, traditional experience and skills might not be preserved.

In the past 40 odd years in Japan, there have been numerous efforts to technically formulate the line heating to thereby automate the processl~-41, includ-

1. Ishikawajima-Harima Heavy Industries Co., Ltd., Kure, Japan.

Presented at the Ship Production Symposium, Arlington, Virginia, July 29-30, 1999.

ing such attempts to replace heating by cold work using universal press[51, and efforts to translate human expertise into artificial intelligence technology, or development of a simulator to expeditiously train skilled operators[6.Vl.Despite these efforts, however, a fully automatic system to replace the entire manual process has not been realized, because of the complexity of deformation mechanism and the faittlre to establish its quantitative definition in practical terms, except for some substitute performance of heating plan by an NC heating device which is still to be determined by experience and the skills of accomplished special- ists.

Our team realized full automation of the line heating process by applying a theory of elastic inherent strain, and in April 1998 successfully installed an automatic line heating steel plate bend processing system at Kure Ship Yard of IHI. At the moment, the system greatly contributes to the serial construction of a 280 000 MTDW VLCC by its bend processing of curved outer shell of the bow and the stem.

The characteristics of the system are as follows:

1. To benefit from the variation factors of inherent strain caused upon heating of steel plate, series of

MAY 2000 8756-141710011602-0121500.4910 JOURNAL OF SHIP PRODUCTION 121

systematic experiment and examination have been conducted to tentatively determine their function, to consider influence of said variation factors in calculation for heating plan. Through such effort and by means of practical elastic calculation, an automatic calculation of heating plan became possible.

2. It became possible also to consistently formulate the process from development of the objective curvature to the bend processing by use of inherent strain. As a result, calculation of developed shape with anticipation of the shrinkage upon heating is made feasible. This greatly contributes to improv- ing, along with the bending process, precision within the surface area which in turn affects precision of the ensuing steps (block assembly).

3. Using an NC machine with high frequency induction heating device as the heat source enables high speed bend processing with excellent reproducibility.

4. To accomplish a high precision bend processing, rich experience is not required.

2. STRUCTURE OF THE THEORY 2.1 Plate deformation mechanism upon line

heating Fig. 1 shows the qualitative mechanism of bend-

ing of steel plate upon line heating. Application of heat to a part of steel plate by gas burner will bring about rapid rise of temperature in the heated area, to soften and expand the area, which will be subjected to the tight constraint from the ambient area of nor- mal temperature, and therefore expansively deform toward the outside of the surface where constraint is absent. During the cooling process, on the other hand,

heated area and its periphery will be similar in temperature due to thermal conductivity of the material and will be subjected to even shrinkage. This will cause part of extra-surface expansion to remain as the plastic deformation. Line heating is the process to create the desired curved surface by arranging said particular deformation on the surface of steel plates.

2.2 Innate difficulty in line heating and measures to overcome

The major difficulty in automation of line heating may be derived from the complexity of the deformation mechanism upon line heating, the salient points of which are as described below.

1. There are numbers of nonlinear influencing factors to alter the interrelation between the heating and subsequent inherent strain (hereinafter called the variation factor).

2. Inherent strain caused by a single continuous line heating comprises four components, which are bend and inplane strain tangent to the heating line, and bend and inplane strain perpendicular to the heating line. at the same time.

3. Discontinuous strain caused by a heating line leaves in its periphery secondary elastic strain. Upon heating, such elastic strain also becomes an influencing factor on the generated curvature.

Measures to overcome these difficulties under a conventional process that relies on human skills and under our system are contrasted in Table 1.

Conventional craftsmen apply their individual and empirical memory of interrelation and assessment, as- sisted by bending templates, to gradually arrive at

Table 1 Difficulties of line heating and countermeasures

Phenomena Conventional measures IHI-c~

(a) Complex interrelation between heating and deformation (influence of variation factor).

Experience and empirical judgment.

Bending template.

STEP BY STEP.

Quantitative formulation.

Incorporation in database and arrangement calculation program.

(b) Multiple direction of strain (4 components).

Included in data base.

(c) Secondary elastic strain. Iterative calculation (optimization). J,

Final heating plan.

122 MAY 2000 JOURNAL OF SHIP PRODUCTION

the objective curved surface, whereas our system is applied as follows:

1. Influence of variation factor is quantitatively for- mulated and incorporated in the data base and a heating plan calculation program. It enables accu- rate estimation of complex deformation phenomena, in which heat conductivity and thermal elastic plastic phenomena are intertwined, through a practical elastic calculation.

2. The data base takes all of the four components of strain into consideration.

3. The final heating plan, taking elastic strain into account, is calculated by an optimization method using iterative calculation.

2.3 Review of effect of variation factors We have attempted to quantitatively formulate the

variation factors through systematic series of exper- iments on small sample pieces and FEM analysis of thermal-elastic-plastic. By our method, once the distance and other elements of preceding heating lines under a given heating condition are determined, subsequent deformation may be estimated by means of elastic calculation, the result of which is then fed to the data base and the heating plan calculation program.

To show an example of a review of the variation factors, a case of simple immobile heating to evaluate the effect of secondary elastic strain caused by preceding heating lines is illustrated in Fig. 2.

In this experiment, heating area Heat-1 had been heated a distance of 140 mm apart, then the middle of two lines was heated under the same condition.

Fig.3 shows the secondary elastic strain caused by heat 1 area and the results of elastic strain release calculation to determine the effect of such strain by means of elastic calculation (where the process of temperature rise during heat 2 was simulated by sub- stituting for heat 2 with sufficiently small Young's modulus by elastic strain from heat 1).

Table 2 Shrinkage obtained by parallel heating experimental

Experiment FEM Calculation

Single Parallel Elastic Thermal- heating heating elastic-plastic

-0.14 +0.26 +0.13 +0.12

This calculation represents that a heating in between two parallel heating lines would release elastic strain of heat 1 which will concentrate toward heat area 2. In the above condition elastic calculation substituted the inherent strain by heating area 2 indicates that the component at heat area 2 extends by 0.12 mm. To verify that the adopted sequence of influence corresponds to actual change, a two dimensional thermal-elastic-plastic calculation has been conducted, the result of which is shown in Fig. 4.

It suggests an elongation of 0.12 mm, which may be considered identical to our elastic calculation. A related experiment resulted in an elongation of 0.26 mm, and was deemed compatible with our explana- tion of phenomena. These results of experiment, thermal-elastic-plastic calculation, and elastic calculation are compared in Table 2.

2.4 Theory of heating plan calculation Automatic calculation of heating plan in our sys-

tem is based on the data base regarding interrela- tionship between heating and deformation, allowing selection of combination to yield the objective curvature. The calculation process may be divided into three major parts, namely, the process to calculate distribution of strain (hereinafter called the.,,required inherent strain) over the entire steel plate to the objective curvature; process to calculate a heating plan by means of a combination of heating conditions selected from the data base to produce a strain distribution subsequent to applied heating lines; and evaluation process to verify applicability of calculated heating plan (hereinafter called the deformation simulation). A brief description of each of them is as follows,

2.4.1 Calculation of required inherent strain To produce three-dimensional curved surface by

heating a flat steel plate, strength and size of strain as well as its positioning should first be determined. For the said purpose, objective curvature will be de- formed into a fiat plane by using elastic-large-flexion- analysis (hereinafter called the compulsive deformation calculation) to identify the required inherent strain distribution to result in objective curvature. The calculation also identifies the original fiat shape of the plate to be configured. This original fiat shape and the objective curvature correspond to a perfect mapping when translated by a relative set of strains. Such strain distribution which will translate the original fiat shape to the objective curvature is called the required in-

MAY 2000 JOURNAL OF SHIP PRODUCTION 123

S t r a t h e a t i n g

P l a s t i c d e f o r m a t i o n

A f t e r c o o l i n g

O n h e a t i n g

On cooling

Fig.1 Mechanism of deformation by line heating

Cram) 0.12

01 0.08 0.06 004 0.02

- 0 , 02

~--o.o~ ~ -006

-O.OR

-01

. . . . . . . _--_

. . . . . . . ~ . . . . . . ~ - - - i . . . . i . . . . ~ - I : : . . . .

-016 . . . . . . . . .

Fig 4 Calculated shrinkage by 2-D thermal-elastic-plastic FEM

6gO

Heatinl~ Coil; 20mmx2OOmm Oondlt lon : 39KW in 15sec.

- ~ X

H e a t - 1

H e a t - 2

Fig. 2 Condition of the parallel heating experimental

5 0 m m ~

---q/

Fig. 5 Objective saddle shape

- l q

! Released residual strain

After i "i: ~ heatinE-1 [ i:

,.=!

Heat-1 Heat-2

Fig3 Calculated residual strain(emx)

PRIN CI PAL ~RA I N ~ P~ ~ ELEM ENT IMAX E P~ 1 = 0 ~ 4 1 . EP~2 - -0 ~ 174~ )

so l e 0 .~4 BINDING ~RA IN

{ { [ { { [ [ [ ~ ] ] t ] 1 t } t t ] ~ { t { l { t t I ] ] ] } 1 t t } t { t ~ { f { [ { t t t j l ] } ] t t t t ~ i ~

Fig. 6 Distribution of required bending inherent strain to form saddle shape


herent strain. Bend strain and inplane strain within the required inherent strain may be treated inde- pendently.

As an example, the required inherent strain of the saddle shape curved surface as in Fig. 5 is separately shown as its bend strain and inplane strain in Fig.6 and Fig. 7 respectively.

2.4.2 Calculation for heating line arrangement In our method, after the required bending inher-

ent strain and the required inplane inherent strain are separated, heating lines for bend strain (hereinafter the bend heating lines) and heating lines for inplane strain (hereinafter the inplane heating lines) are in- dependently calculated.

2.4.1.1 Bend heating lines For actual vessels, curves on their outer shell are

mild, calling for little change in strength and direction of bend strain. Taking advantage of this feature and inspired by the contour lines of a topographical map, a contour heating method for bend strain has been developed. The outline of such a contour heating method is as follows.

Contour heating method As in Fig.8, if the height at a ground point x, y is

z, its contour will be the curved line which appears when specific height is assigned to z, such as z0, Z l . . . z~, as the set of (x ,y) which will be (x 0, Y0) - . . (xi, Yi ). If the same principle is applied to determine heating line arrangement, the calculated in- tegral value distribution of bend strain (curved surface) will be assigned to elevation level z on the map. Such a general concept as applied to a saddle shape which is represented as z = x 2 - y2 is shown in Fig. 9.

The subject curved surface (a) in this case will be determined relative to the x and y axies, therefore a curved surface with gradient distribution u, v, or (b), may be either obtained by integration of main curve (c) along main x, y axis, or as the distribution of dif- ferentiated (a) by x, y. If _u here is the degree of an- gle deformation caused by single heating line, by cal- culating in Fig. (b) the (xi, Yi) tO correspond to each u i, wherein

u = Uo, ui (= Uo + _ u ) . . . ui (= Uo + i x _u),

the necessary heating line arrangement to create bend inherent strain can be obtained.

In Fig.10, bend heating lines acquired by the con-

tour heating method for the aforesaid saddle shape is shown. The solid line represent is the surface heating line with travel speed of 2336mm/min., and the broken line represents the heating line on reverse side with travel speed of 935 mm/min.

2.4.1.2 Inplane heating lines Unlike bend strain, inplane strain is characterized

by violent changes in its strength and direction, for which reason by hinging on its strength alone, as is the case for contour heating method, the gap between the direction of heating lines and principal axis for inplane strain becomes too large to make resulting estimation inaccurate.

Furthermore, line heating does not consider shear strain and tensile strain. To overcome this, an itera- tire calculation is introduced to convert the orthogonal straintSl and tensile strain near zero, i.e., to Or- thogonal compressive inplane strain distribution before they are dispersed and gathered. The conversion algorithm into orthogonal compressive inplane strain is as described below.

Conversion algorithm to orthogonal compressive inherent strain

The required inherent strain acquired by giving the bend w of the objective curvature to a fiat plane is separated into inplane strain E m and bend strain eb through elastic large flexion calculation.

Focusing attention to inplane strain.

~* mx = En~, if Emx < 0 ~* mx = O, if amx > 0 E* my ---- Emy, if Emy < 0 E* my = O, if Emy > 0

'Y* mxy ---- 0

In the above equation, E*m~, E'my, '~*mxy are the primary approximate value of necessary required inherent strain.

Elastic strain eb(invariable) and E m at the time above inherent strain e*n~, E'my are given simultaneously to bend w to the flat plane are calculated.

Focusing attention to inplane strain:

~* = ~m~ if ~m~ < 0 - - m x ,

~* = O. if ~m~ > 0 - - m x •

--E* my ---- Emy, if Emy < 0

--~* my ---- O, if Emy > 0

-7* mxy = 0


P~IIN CIPAL ~'TRAIN i~ R . ,A~ EI.~M ENT ~ EP~- | . 0 00( ]~ lS4~, EPS-2 . -O 0C~4~ ! )

~CIII~ 01004 MIEM BRANE STP~IN

~ ~ 1 ~ 1 ~ 1 ~ 1 . 1 , I * [ * I - I - I - I * 1 , 1 ¢ [ 1 1 ~ 1 1 [ b l b

t I J - I - 1 - - I - - 1 - - 1 - - 1 ~ 1 ~ 1 - - 1 - - 4 - - 1 - - 1 - - 1 - - I - I - I t

~ I - I ~ I - - I - - I - - I - - I - - I - - I - - I - - I - - I - - I ~ l ~ 1 t I = I #

~ l l l l l # l , I - I , i - ] - I , I - I - I = 1 , 1 % 1 1 1 1 [ ~ 1 I

Fig. 7 Distribution of required inplane inherent strain to form saddle shape

I - I - / - - t ! I l l ._~.i LIY ~ I i l - - , . . :

Ilq- L-LF ,--, l--If- - ' r , ~-~ ~-~-~

L . . . . . . ~1 a . . . . . il-~i

I

• ~ . . . . . . 7 t . -

" " ' . . . . . , ' , 1 " ~ . - ~ . . ; ~- ..~ . . . . . !i-~

t i - - -

Fig. 10 Obtained Bend

] 3 ~13, .:~--vrk "l - -~l-~;~t,~ i - ' ~I-'.- . . . .

. . . . H ' ~ ' ! I " ' I -

7 - - ! t ~ t I_~..

-i

Ll 17 tL

-If

heat line arrangement

x Fig. 8 Topographical map and contour line

PRINCIPAL STRAI N o~ I:I..A'I~ ELEMENT (MAX E PE,- 1 . -O GOG66~ I~*. EPS-2 = -00(311,84101)

scale 0004 MEMBRANE STRAIN

÷ ÷

i

÷ ÷

Fig. 11 Distribution of orthogonal compressive inplane strain

Y

Fig. 9

,A, w u : -'A-'~

Y ~ "~ T ~ff-

A w

z ~ r

Gradient distribution of saddle shape and obtained heat lines for bending strain


Assuming the above, new inherent strain is calculated by

E* = E* mx + - E * mx m~

E* my ---- E* my + _ E * my

-7* mxy = 0

Above calculations are repeated until the volume of adjustment _e* mx and E ' m y becomes effectively negligible.

Converted inplane components of required inherent strain, i.e., the orthogonal compressive inplane strain distribution of the aforesaid saddle shape curvature are shown in Fig. 11, and that of inplane heating lines in Fig.12.

Continuous heating lines corresponding to the separately calculated bend strain and inplane strain of the required inherent strain would produce, as discussed earlier, four components of strain. In other words, bend heating lines and inplane heating lines respectively and simultaneously induce strain other than in- tended, such as bend strain perpendicular to bend heating lines and inplane strain perpendicular to inplane heating lines, which causes discrepancies between objective curvature and created curvature upon heat processing. To compensate for the deviation from the objective curvature, the effect of the unintended strain is rectified by the following procedure (also see Fig. 13).

a. Compulsive deformation calculation is made to convert open (fiat plane) configuration to objective curvature to determine the required inherent strain, which will be then separated between bend strain and inplane strain,

b. bend heating line is calculated by contour heating method on bend strain as a),

c. curvature caused by the heating line as b) is calculated by means of deformation simulation relative to the heating lines,

d. by a compulsive deformation calculation from the calculated curvature as c) and the objective curvature, thereby determining new required inherent strain,

e. inplane heating lines are calculated relative to the inplane strain as part of the required inherent strain as above d),

f. bend strain attributable to inplane heating lines as above e) is subtracted from the bend strain element

in a) above to determine new bend heating lines, and

g. above steps b) through f) are repeated until each heating line arrangement sufficiently converges. The principle is to discount unintended strain in

each of the heating lines through a repeated adjustment process of feeding back the deviation each time to recalculate a less extraneous heating plan.

2.4.1.3 Deformation simulation The deformation simulation program we have de-

veloped relies on elastic FEM deriving from strain in- put in the form of equivalent nodal point force of the heat condition at every FEM element grid point over which the heating line traverses. The deformation simulation program enables estimation of curvature upon heat processing and therefore is an essential subsys- tem with which to evaluate the appropriateness of the heating line arrangement plan. Our system is designed to repeat the optimizing calculation until the discrepancy between the estimate by the deformation simulation and the objective curvature falls within a satisfactory range. The system also includes an application program which may respond to hand drawn heating lines and display on screen the simulated deformation such heating lines would generate, thereby enabling on-screen comparison of the results of a set of calculations and any section of the resulting curvature. The application may serve as a training simulator to educate heating line arrangement special- ists quickly to replace empirical artisans.

The deformation simulation of the automatically calculated heating arrangement plan of the aforesaid saddle-shape configuration and the bend of objective curvature are compared in Fig.14.

When the discrepancy between the confirmed result of the calculation and targeted configuration (objective curvature) is found to be within the permissi- ble range, the heating plan is sent to the production line as the final one.

3. S Y S T E M S T R U C T U R E O F A C T U A L L I N E ( IHI-A)

The system of the actual production line (IHI-a) is illustrated in Fig. 15. The heating plan that has been discussed in the preceding section will be calculated on the designated EWS at the design office, then stored in the respective directory indexed for each ship


i _ l I !

' !

r i

Fig. 12 Obtained Inplane heating line arrangement

1 I Required inherent strain h

(bendinq ii,qredient ) I-

Calculate bend heating lines by Contour Heatin,q Method

t ] Deformation simulation]

(by bend heatin.q lines}

1 Compulsiv deformation calculation

(to calculate new required inherent strain}

Fig. 13

_1 Required inherent strain I ~ i -] (in°laneinlqredient)

Calculate the orthogonal compressive inplane inherent strain

I Calculate inplane heatin~ lines I

Bending strain ingredient of inplane heatinq lines I

Algorithm to reduce the unintended strain

.... targeted Oross section of center line calculated

J f

400 800 1200 1600

Fig 14

__, targetes Ve~dcal section o{ center line calculated ¥

200 500 1000 1500 2000

Comparison between calculated and targeted saddle shape

2500 3 0 0 0 3500 4001


f, F 77

S L S I L j /

~__-_ - ~ ~ , - _

Fig. 16 The sphere to bend by IHl-o(

Oooling Device

/

-lea# ing ca

' ' " I f f l Side d*okS~ 2lines (s-~oke-=3 O0 ram)

Induobon heating de¢ice

7 l 't I i",'leesurlng Inst~umer J by Laser

Center dack x7set:s (st~oke=l rn)

• Desisn Section

I Qelcu'ate the he~bn~ plan

Network(J_~. N)

pl eri ~3rm e~

Work Shop ~--

fight, ~sured dat~a Fig. 15 Composition of the actual system


280. 000 M T D t q D 1 E S E L T A N K I T R (ELS I L ~ A )

S M d l e

, ~ • : ~ ~ ' . • . 7 : - X ] - ; T Q" ~ - = @~'.~Sf ~ =; :~

" ";'4"-~"9000x'2000x20~ " ~ < - k .

Fig. 17 Target configuration of bow bottom shell in VLCC

(ro,..at• , _

(f~r beoa~g) (for b e l i e r )

Fig. 18 Calculated heating plan

Fig. 19 Cross section

Fig. 20

t ~ t e d - t ~ t e d

-- --~d SEC C- j

i r

i i

t ~ g e ~ e d - - - - ~ d S E C B

] . . ~ d SEC. D

, r a n ~ - r r m r n ~ n ~ m " n - n ~ m f

Comparison between measured and targeted configuration


number and block number. The EWS of the design office and terminal PCs at workshops are connected by LAN, and operators conduct all necessary data processing with their PCs. Furthermore, the heating plan may be approved, and any sectional bend condition upon such heat processing is compared with the objective curvature and rated on the PC screen.

A total of twenty-three hydraulic jacks are placed on the work table, the height of which is automatically adjusted in response to the selected objective curvature.

The heat source has excellent reproducibility compared to gas heaters, and the selection of a high frequency induction heater (50 kW, 20 kHz) made precision evaluation and control easy. Since the device produce heat within the steel plate, it eliminated problems associated with heat conduction, at the same time achieving a few times quicker processing speed and improved productivity in comparison with conventional gas heating.

A 100 mm-diameter heating coil is designed to track the surface of the plate as the heating progresses; this is connected to a ball-spline by a universal joint and is driven by an NC travel device along x and y axies while the distance between the heating coil and processed steel plate is kept constant by gravitational support.

The coil is surrounded by a ring to spray cooling water and air, to lower the temperature of the steel plate automatically after heating. When the cooling is complete, a laser gauge travelling on an NC stand will automatically measure the bend of the after heating configuration.

This mechanism sequence makes bend processing available to less experienced operators, who may per- form the entire process by setting the plate on the work table and leaving it there while automatic heating, cooling and measuring are being conducted.

4. P R O C E S S I N G R E C O R D S 4.1 Targeted configuration of bend processing

and the heating plan Since the introduction of the actual equipment, ac-

tual ship components have been bend processed by the system in Fig. 16.

From among those, an example of bow shell plate processing for an ongoing VLCC construction is introduced. As shown in Fig.17, the objective curvature for the bend has an approximate length and width

of 9 m and 2 m respectively while the plate thickness is 20 mm, requiring an S curve mixed saddle and cup shape, which is usually considered a fairly diffi- cult curvature for bend processing. The heating plan for the curvature which has been automatically calculated is shown in Fig.18.

Black numbers on white indicate heating on the upper surface, and white on black numbers indicate heating on the opposite surface, to be performed in numerical order. Fine lines represent bend heating lines, which heating will be conducted at relatively high speed, resulting in a sideways bend as an effect of heat gradient along the plate thickness. Thick lines represent the inplane heating lines; this heating will be conducted at slower speed compared to bend heat lines, cased inplane shrinkage by the heat reaching the opposite surface.

The entire heating process begins with ten heating lines on the upper surface at a speed of 1000 mm/min to produce a sideways bend; then in order to induce a cup shape by shrinkage of the edge of the plate, five heating lines are used at the speed of 315 mm/min. Nine heating lines at 2000 ram/rain are used on the opposite surface after reversing its position to produce further bend, whereupon the center of the plate is contracted to create a saddle shape by six heating lines travelling at a speed of 300 mm/min. The net processing time for the plate, excluding the time required to reverse the plate position, was 1 h 40 rain. for the upper side of the plate, and 50 min for the opposite side, making a total of 2.5 hours.

4.2 Measured configuration after the heat processing

Fig. 20 shows actual measurement of the configuration after applying the above heating plan. Each section of the graph corresponds to data in Fig.19.

The broken line shows the objective curvature and the solid line shows actual measurement of the configuration after the heat processing. The vertical axis indicates the extent of the bend in millimeters. Every section will be recognized as having satisfied the stan- dard process of JSQS, which qualifies the bend processing for any practical fabrication.

5. C O N C L U S I O N

We have successfully automated the full steel plate bending process by means of line heating, and applied


the system to production at IHI's Kure ship yard. The system enabled high speed and high precision bend processing of a vessel's outer shell.

The system comprises an automatic calculation heating plan program, based on any information re- lating to the objective curvature, and a high frequency induction heating device as a stable heat-volume heat source which is mounted on an NC travel device. Such a combination insures automation of the entire process of steel plate bending by line heat processing (from the plate development of the objective curvature to selection of heating line arrangement, and actual bend processing), which heretofore has been dependent on intricate skills. It may be termed a total automatic system to eliminate most difficulties associated with steel plate bend processing.

As a secondary effect of the system, improved bend processing precision will contribute to higher effi- ciency in subsequent assembly work within the yard, a feature that derivesd from the high level of consis- tency between the developed shape and the objective curvature of the processing piece, which in turn is the product of coordination between the development of an objective curved surface, calculation of the heating plan, and quantitative simulation of anticipated configuration upon application of the said arrangement plan.

References Ueda, Y., Murakawa, H., Rashwan, A. M., Oku-

moto, Y. and Kamichika, R.. "Development of Com- puter Aided Process Planning System for Plate Bend- ing by Line-Heating," Naval Architecture and Ocean Engineering, Vol. 3, 1993, pp. 99-112.

Ueda, Y., Murakawa, H., Rashwan, A. M., Oku- moto. Y. and Kamichika. R., "Development of Com- puter Aided Process Planning System for Plate Bend-

ing by Line-Heating (Report 2)--Practice for Plate Bending in Shipyard Viewed from Aspect of Inher- ent Strain," Naval Architecture and Ocean Engineer- ing, Vol. 10, No. 4, 1994, pp. 239-247.

Ueda, Y., Murakawa, H., Rashwan, A. M., Neki, I., Kamichika, R.. Ishiyama, M., and Ogawa, J., "De- velopment of Computer Aided Process Planning System for Plate Bending by Line-Heating (Report 3)--Relation Between Heating Condition and Defor- mation," Naval Architecture and Ocean Engineering, Vol. 10, No. 4, 1994, pp. 248-257.

Ishiyama, M.. Gu, S., Ogawa, J. and Takakura, D., "Numerical Processing for Precision Plate Bending by Computer Aided Line-heating System." Journal of The Societa, of Naval Architects of Japan, Vol. 180, 1996, pp. 731-738 (in Japan).

Nomoto, T., Ohtsuka, M. and Yokoyama, T., "Fun- damental Studies on the bending work using multiple- piston-pressing method for outside plate of ship?' Journal of the Societ3' of Naval Architects ~?f Japan, Vol. 170, 1991, pp. 599-607 (in Japan).

Nomoto,T., Ohmori.T., Sutoh.T., Enosawa. M., Aoyama, K., and Saitoh, M.. "Development of Sim- ulator for Plate Bending by Line-Heating?' Journal of the Societa, of Naval Architects of Japan. Vol. 168, 1990, pp. 527-535(in Japan)

Nomoto, T., et al., "Development of Simulator for Plate Bending by Line-Heating Considering lnplane Shrinkage," Journal of The Societa' of Naval Archi- tects of Japan. Vol. 170, 1991, pp. 599-607(in Japan).

Ueda, Y.. Murakawa. H., Rashwan, A. M.. Kami- tika, R., Ishiyama. M. and Ogawa. J.. "Development of Computer Aided Process Planning System for Plate Bending by Line-heating (4th Report)." Journal of The Society of Naval Architects of Japan, Vol. 174, 1993, pp. 683-695 (in Japan).


advanced line-heating process for hull-steel assembly...journal of ship production, vol. 16, no. 2,...

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