Introduction.

Sheet rolling bend equipment has to bear big load, consequently requirements on its parts force are quite rigorous. Offering sheet rollers at reduced costs will push a way in market competitiveness for manufacturers, meanwhile the equipment should be of an accurate and reliable design. For this load analysis is the primary requirement, which allows the equipment design to have proper parameters.

Driven power estimate is compulsory to devise major driving systems and to select a proper engine. Thus, analyzing load and drive power of sheet roller equipment is mandatory for designing roll bend equipment. Calculating load capacities of symmetric three-rolled bend machine provides a method for other sheet roller types as well.

2. Analysis of Load.

2.1 Utmost torque needed for cylindrical roll.

Steel sheets are turned into steel pipes while processing them by roller equipment. Plate pressure reaches its yielding limits. Bend stress delivery over pipe area is depicted in the figure (b), the bend point M of the area is:

In the given formula:

B, δ is the utmost breadth and thickness of processed plate (m).

σs is the plate yielding limit (kN x m-2)

Figure 1. Stress delivery of roll bend.

Considering plate deformity reinforcement exists, reinforce factor K is input to define this statement:

In given equation:

K is the reinforcement factor. Its value equals 1.10~1.25. If results for ð/R are bigger, decide on the biggest one.

R is neutral layer semi diameter of rolling sheet (m).

2.2 Strength conditions.

Strength state while rolling steel plates can be seen in the given figure. In accordance with strength balancing, supportive strength F2 over rolling sheet is gained through this equation.

In given equation:

θ is the angle in the midst of defile 001 and 002 lines.

In given equation:

a is the bottom roll center length (m).

dmin is the bottom roll caliber (m).

Figure 2. Roll bending load analysis.

Taking into consideration that sheet δ is much smaller compared to the least caliber of the roll tube, semi diameter R of neutral level is about 0.5dmin. For simplifying calculation the formula mentioned above may be modified like this:

In accordance with strength balancing, pressure strength F1, produced by the top roll, upon the roll sheet becomes:

3. Estimate of driven power

3.1 Bottom roller driving point.

The bottom roller of sheet roller equipment is the drive roll. Driven torque over the bottom roller usually overcomes deformity torque Tn1 as well as frictional torque Tn2.

During steel sheet roll procedure deformity capacities saved at AB sectional part of the sheet (Figures 1a, 2) is 2Mθ, spent period is 2θR/V, where V indicates roll speed. Correlation equals deformity torque Tn1 strength:

Frictional torque involves roll frictional torque in the middle of top and bottom rollers and steel sheet, as well as the slide frictional torque in the midst of roll nozzle and roll hub. It is estimated like this:

In this given equation:

f is the roll frictional factor

μ is the slide frictional factor, take μ equals 0.05-0.1d1

d2 is the top and bottom roll caliber (m)

D1, D2 are the top and bottom roll nozzle caliber (m).

Sizes are still not precise in designing step, the value may equal Di=0.5di(i=1.2). Bottom roll driving torque is equal the deformity torque Tn1 and frictional torque Tn2 amount.

3.2 Bottom roller drive power.

Bottom roller drive power equation is as the following:

In this given equation:

P is the drive power(m.KW)

T is the drive strength point(KN.m)

n2 is the bottom roll rotating rate (r x min-1), n2=2V/d2, where V indicates roll speed

η is the transmitting performance, which equals 0.65-0.8

The major engine power is gained via P value.

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