DESIGN ISSUES
REAR MOUNT STATION FORCES
REAR MOUNT STATION FORCES -100/F15 150.43 VERTICAL
(FAN FRAME)
200.00 THRUST VERTICAL SIDE 100/F16 117.87 VERTICAL
(FRONT FRAME)
200.00 THRUST VERTICAL SIDE -400/F14 138.50 THRUST VERTICAL
SIDE(FANSTG3)
289.50 VERTICAL SIDE
Table 2.1 F110 Engine Model Mount Functions
STATIC STRUCTURES
Figure 2.29 F110 Mount Locations and Reactions
Casing (T16-4)
Upper link primary side load path (INC0 718)
In-plane load clevis Thrust socket
V-band flange
Sect F-F
Engine mount yoke (INC0 718) Note: 1718 Ti-6-4,
& rub mat'l all corrosion resistant
Cross-section of 360° ring stiffened
Sect B-B case
(INC0 718) Rub material (elastomer)
Figure 2.30 F110-400 Forward Mount System
2-24 STATIC STRUCTURES
Figure 2.31 F110-400 Engine
STATIC STRUCTURES 2-25
CF6-80A/A1 F w d E n g i n e Mount Platform Forged f t 6-4 Links Marage 300 Bolts INCO 718 - tensifized Sphr brgs 440C ball - CRM PUT 7-4 PH race - dry film Bushings INCO 718
-SO same except platform shorter
& (2) bolts to pylon
Figure 2.32 CF6-80A/AI Fwd Engine Mount
that permitted us to tighten the clearances in the forward compressor stages.
The aft mount that goes on the -80A turbine frame is shown in Figures 2.33 and 2.34. The mount clevises on the frame have moved to the ends of the struts, so that the loadpath from the rotor support consists of forces along the polygonal elements of the outer case and ten-sion or compresten-sion loads along the strut centerlines.
Bending in the frame elements due to thermal and mount loads has been significantly reduced or eliminated. The rear mount connection to the pylon consists of a two part assembly. The lower part is tied by means of the pin in a spherical bearing to the right frame clevis, so that both vertical and horizontal loads can be taken in any combi-nation. On the left side there is a pivoting link between the clevis and the lower mount fitting, so that it can ac-commodate differential thermal expansion of the frame and the mount. The upper mount fitting has a bearing in both the right and left sides so that the lower mount fit-ting can pivot relative to the upper, accommodafit-ting dif-ferential thermal expansion of the engine relative to the pylon.
Finally, let us look at the front thrust mount for the * 80C2 engine. Since this was a new engine, restrictions on the interface loads to the pylon were negotiable (as opposed to the -50 and -80A where the aircraft attach-ment already existed and was not capable of taking any moment). Figure 2.35 shows how the front mount is in-stalled on the engine behind the fan frame and over the compressor case. Figure 2.36 shows this mount in greater detail. Vertical load is transmitted by four bolts between the platform and the pylon foot and then to the mount yoke. In the mount yoke the vertical loads are carried down links on both sides to clevises on the fan frame. Side load is similarly carried from the platform to the yoke and out through the fixed link on the left side of the engine. Thrust load is carried from the platform through the platform links to clevises on the mount yoke and then forward by means of thrust links to clevises that are part of the fan frame at ± 45 ° from top center. The angle of the thrust links and the moment from the pylon makes this mount better man the -50 and -80A mounts in spreading the thrust load and reducing backbone bend-ing.
2-26 STATIC STRUCTURES
Vertical
pin load , , . . Link load w V |e w A-A
View B-B
— V N / Horizontal pm load
Pin or link load
Mount reaction
View A-A View B-B
Figure 2.33 TRF Multiple Load Paths
Installation interlace
Strut aft bulkhead
Upper mount fitting
Lower mount fitting
Turbine Frame
Figure 2.34 CF6-80A Rear Mount
STATIC STRUCTURES 2-27
Figure 2.35 CF6-80C Engine Mounts
Engine mount platform
Deflection limiter
Platform link
Engine mount yoke
Figure 2.36 CF6-80C2 Front Mount
2-28 STATIC STRUCTURES
CONTAINMENT
In an earlier section of this chapter, we discussed briefly the difference between the steel containment ring over the fan blades of the CF6-6 and -50 and the Kevlar cur-rently used in the new -80A and -80C engines. Figure 2.37 shows the CF6-50 fan assembly, with its steel con-tainment ring and stiffener. This steel ring was originally sized based on ballistic impact tests conducted at Water-town Arsenal with projectiles that struck a flat plate at various angles. The data from these tests is presented in Figure 2.38 and 2.39 in which the kinetic energy of the projectile is related to the square of the thickness of the
Figure 2.37 CF6-50 Fan Module
containment plate by the constant K, which is a function of the materials involved. When different containment material is used, this data can be scaled in an approxi-mate way, recognizing that the energy to rupture is pro-portional to the area under the stress-strain curve to ultimate failure. A very hard, strong material may have a high ultimate strength but relatively little deformation to failure. A softer, more ductile material may have a lower ultimate strength but very high elongation in which case the total energy required to rupture a unit
volume is much greater. It was this sort of reasoning that led to the design of the -50 containment ring. The ring uses a high strength and highly ductile 18-3 MN stainless steel for the forward section of the ring which is welded to 304 stainless steel in the aft sections. The capability of this ring to contain fragments of fan blades was demon-strated in spin pit tests. It also was observed that the shank and platform of the released blade was pushed aft by the following blade. So, a short extension was added to protect the bolted joint and the aluminum fan case from such shank fragments.
In an attempt at major weight savings the -80A engine whirligig tests were undertaken to determine the amount of Kevlar cloth required to contain a blade. While the first tests were successful in preventing penetration of me cloth by blade fragments, the tests were not success-ful as a complete containment system. Since the cloth deflected a great deal more than was expected, blade fragments escaped axially, going aft. It was determined that Kevlar fibers could be woven in a shaped strip, so that when wound in a circular containment ring, they would form a pocket which wouid retain the fragments by catching them very much like a ball player's mitt.
Since we needed to build a deep honeycomb sandwich on the outer ring to prevent resonance of ring modes and frequencies with the blade and disk, we had the Kevlar cloth woven to fit over the deep honeycomb. This proved to be totally successful in catching the first parti-cle of blade penetrating the honeycomb sandwich and striking the Kevlar cloth. However, the Kevlar is very elastic, and when the first particle was trapped, it stret-ched die cloth radially and the ends pulled in axially and uncovered significant areas of the containment system.
Subsequent particles were able to escape where the Kevlar cloth had moved axially. We solved this problem by bonding the layers of Kevlar together for about one inch on each edge with epoxy adhesive, forming a rim very much like the bead of an automobile tire. When the first fragment entered the Kevlar with this construction, the Kevlar still stretched in a radial direction, but the rigid ring at each edge formed by the epoxy bonded lay-ers of cloth did not climb up and over the honeycomb sandwich. The necessary layers of cloth remained in place to catch subsequent particles that would have oth-erwise escaped radially.
It was also necessary to determine the angle required for containment forward and aft of the plane of rotation.
Figure 2.40 presents this problem in a comparison of the -50, the -80A, and ultimately the -80C2 containment casings. The -80A is the same size as the -50, and the weight saving was achieved by reducing the steel shell of the container to very thin gauge in the prime contain-ment section and replacing the containcontain-ment capability
STATIC STRUCTURES 2-29
.500
.400 Armor thickness- .300
inches
(i) No perforation, r n 1/4"ofwwg in plate, slight bowing of plat*
(2) B t e c t e p w t a m w d . i l / r i r h o t * fliiekness - .300
inches
,200
.100
0
(1) Blade pertoraied. mao* 3 i / T * 3x1/2" square opening in pute
(2) Blade faded to perforate, but nr*
3 1/2" opening in plate
(3) No pertoraDon, slight bowing
(4) No perforation. tJigftt bowing
-(1) Blade pertoraied. mao* 3 i / T * 3x1/2" square opening in pute
(2) Blade faded to perforate, but nr*
3 1/2" opening in plate
(3) No pertoraDon, slight bowing
(4) No perforation. tJigftt bowing
* ( 4 )
Waiertown Arsenal Data - 321 S.S. - 60" obliquity - 70 gram blade
Figure 2.38 Ballistics Test Data
CF6-6 and -50 containment design line
1.0
Figure 2.39 Scaled Rupture Data
2-30 STATIC STRUCTURES
12.5
Figure 2.40 Kevlar Wrap
with the Kevlar belts over the honeycomb sandwich. To preserve the same containment capability forward and aft. the steel shell was thickened so thai it was identical to the -50 at the forward flange in front of the Kevlar system. When we observed that lhe-80 system was mar-ginal in containment in the aft direction, the steel shell also was thickened aft of the Kevlar. The Kevlar itself could not be extended any further aft because a mounting ring was needed to carry the fan mounted gearbox, which is a part of the -80A1 engines for the A310. This then established the criteria for the design of the -80C2.
With no fan mounted gearbox the Kevlar was extended aft to provide the same 18° angle of protection as the steel shell for the -80A. In the forward direction, how-ever, the design was considered to be inadequate because Kevlar did not extend to the same angle as had been cov-ered by the steel in the -50 and the -80A. The inner alu-minum shell and forward flange of the -80C2 is not considered to have any significant containment capabil-ity. The solution to this problem is shown in Figure 2.41 The forward flange of the -80C2 was moved forward by two inches and additional layers of Kevlar were carried forward with it. The lower sketch in the figure shows the final arrangement for the -80C2. The inner shell is a 2219 aluminum alloy, to which is bonded a 1/8 inch cell aluminum honeycomb covered with layers of graphite
epoxy to form the stiff sandwich. Cast titanium brackets are riveted and bonded to the inlet flange to reinforce it at the bolted connections to the inlet. Sixty-five layers of Kevlar cloth are used in the containment wraps. The fi-nal design on the -80C2 containment system is summa-rized in Figure 2.42.