Page 78 - 《橡塑技术与装备》英文版2026年3期

HINA R&P TECHNOLOGY AND EQUIPMENT

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P D =S x σ x +ΣF d σ b （4) values reaching over 610 MPa and 2,200 MPa respectively,
P D — Nominal breaking force of the bead wire, N; are set at lower values here, which has a certain impact on the
S x — cross-sectional area of the bead wire core, mm2; calculation results.
σ x — Nominal tensile strength of the bead wire core, with （3)The total breaking force borne by the bead wire core
a value of 600 MPa here; generally does not exceed 5%. Its joint adopts the current butt
F d —sum of the cross-sectional wire areas of the welding process, and the tensile strength performance of the
2
externally wrapped steel wires, mm ; joint decreases by about 10%. Each layer of bead wire has a
σ b — the nominal tensile strength of the externally copper-sheathed joint, which has little impact on the overall
wrapped steel wire, with a value of 2100 MPa here. performance of the bead wire, but the manufacturing process
determines its objective performance impact.
5 ≤ N S = P D ≤ 6.5 （5)
T Z （4)The circular steel bead wire, with its outer surface
N S —static safety margin
wrapped in steel wire and plated with tin bronze, enhances its
The upper limit imposed on the static safety factor is due
adhesion to the rubber material during the tire vulcanization
to the selection of a lighter-weight wire ring. The value of P D in
formula (4) is a theoretical value, and the actual fracture load process. From the vulcanized product, it can be observed that
the rubber material has penetrated into the outer layer and even
of a circular wire ring is influenced by various factors. The
deeper, which optimizes the overall mechanical properties of
fracture load calculated according to formula (4) is typically
the steel bead wire to a certain extent.
0% to 12% higher than the minimum theoretical fracture load
The static safety multiple design only calculates the
listed in Table 1, taking into account the following influencing
strength of the circular bead wire using internal pressure
factors:
tension. In use, aircraft tires are not only subjected to
（1)The outer wrapped steel wires of the circular steel
internal pressure, but also to tension generated by torque and
wire ring form a spiral trajectory in space, with each layer of
centrifugal force under high-speed conditions, which falls
steel wires forming a spatial mesh structure between them.
within the scope of dynamic load-bearing safety multiple.
Radial force is transmitted in the form of compression between
the same layers, while the force between steel wires in adjacent Using ND to represent the dynamic load-bearing safety
multiple of radial aircraft tires, for heavy-duty and demanding
layers is transmitted in the form of a spatial grid. For steel wire
(high torque) automobile tires, the design dynamic load-
rings made of the same material, the winding lead directly
bearing safety multiple of the bead wire is greater than 2.3.
affects the mechanical properties of the steel wire ring. The
There is no literature discussing this aspect for aircraft tires,
greater the lead number, the more uneven and higher the stress
and it requires our continuous exploration.
distribution of the steel wire ring, while the smaller the lead
(the larger the lay length), the better the mechanical properties N D = P D （5)
T Z
of the steel wire ring. in figure 2, the angle λ between the N D — Dynamic load safety factor;
projection of the winding direction of the steel wire at point A P D — the combined force generated by the actual load
onto the center plane of the steel wire ring core and the tangent inflation pressure, torsional moment, and centrifugal force in
to the central axis of the steel wire ring core at this point is aviation tires.
determined by the lead number. The greater the lead number, Due to the complex structural characteristics of circular
the larger the angle λ, and the uneven stress distribution of the steel wire rings, accurately determining their breaking force
steel wire affects the breaking force of the entire steel wire requires testing on a specially designed steel wire ring breaking
ring. test machine, which is only a single test using the tension
（2)In formula (4), the nominal tensile strength of the extension method. In China, most circular steel wire ring
bead core σx and the nominal tensile strength of the externally manufacturers perform theoretical calculations of breaking
wound wire σb, with the manufacturer's average supply force based on a single steel wire, while some manufacturers

·32· Vol.52，No.3