Hi,
I am looking for a text book or paper that can take me through the stress
analysis of the loads a mult-engine turbo-prop and or radial engine will put
into the wing supporting structure. I am sure thirty or fourty years ago
such references were commonly available, but they sure are hard to find now.
Can anybody help me out?
Regards,
Steve
__________________________________________________________________ Stephen
Hall Celeris Aerospace Canada Inc. ICQ#: 9011995 Current ICQ status: ( Work
Tel#: (613) 837-1161 7 Fax#: (613) 834-6420 + More ways to contact me i See
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Stephen,
Some of the "old" guys all used an old book written in the 50's but I
cannot recall the title nor the author. However, I would advise to have
a look at the FAA certification rules first which require that your
structure must survive a, I think, 10G vertical load and a 3-4G
longitudinal load. There were also angular velocity such as 1 rad/s
too. I bet that these are the largest loads that the mounts will have
to survive to. These are the modern requirements but I don't know the
50's or 60's requirements.
Hope this help.
Gilles Carrier
Stephen Hall wrote:
Gilles,
If you could locate a reference to the book sometime it would be
appreciated. My problem is not so much that of meeting the FAA requirements
but rather that of assessing the reasonableness of the data I am obtaining
from a strain gauge rosettete attached to the lower spar cap of an
operational aircraft. In particular I am trying to estimate the sort of
contributions I can expect from reacting the engine loads
Thanks for your help.
Regards,
Steve
They are evidently lower than you expected. I still recall a Rolls
development engineer telling me that one of their
(earlier) jet engines was hung on a single quarter inch bolt.
Brian W
wrote:
That sounds a bit small on CSA but I believe that engines are weak mounted
to break away in the case of a crash. The weak axis is probably in a
longitudinal direction though rather than vertical.
John
The very first RR turbojet was, I think, the Welland, which produced
1700 lbf of thrust, and probably had a thrust to weight ratio of 1.3
If you want to hang that off a 1/4 inch bolt, fair enough. Strictly
speaking you can hang any weight off a single bolt in shear, if you
think about it.
As to the original question - if you know the max torque of the engine,
and the reduction box ratio, then the overall torque exerted on the
airframe can be worked out. If you know how far the mounting bolts are
apart this will give you a good idea of the loads in the airframe.
Other loads will be the inertial loads due to maneuvers, and the higher
frequency (crankshaft speed and above) vibrations due to the internals
of the engine. I doubt you are interested in the latter, the former will
be roughly engine mass* g rating of the aircraft.
Cheers
Greg Locock
///
weight 1308 lb
thrust 1700 lb
vectored: 1 ton
Load factor 4 (about right for commercial jet structure)
Stress from 4 tons on 1/4 in bolt: 82 tons.
So a 1/4 in bolt in 100 ton steel is slightly over specified.
But that WAS Rolls-Royce!
:-)
Brian W
Ah yes: you too. This is a happy moment. No wars blowing up too badly.
A chance at health care for the needy. A chance at a yacht for the not
so needy. Merry Christmas - and may your equable nature be matched by
your plush lined wallet next year.
Brian W
Let's see where I went wrong, shall we?.....
On Thu, 25 Dec 2003 17:25:27 GMT, "Don Phillips"
///
[Don Phillips]
Hmmm... let's see where I went wrong, then.
you multiplied 82 tons by 2000 to preoduce a stress of 164,000 psi
Then you divided this stress by the area of the bolt to calculate the
limit load:
Area of 1/4 in diam bolt = 0.049 square inch
Let's call it 1/20 sq in.
So you concluded that if one square inch of steel can handle 100 tons
1/20 square inch should be able to take a 1671 ton load.
I don't think so. Do you?
I'll leave you to work out this correction on your factor of safety
calculations.
(Remember that in those far off days, by the way, the British used a
ton of 2200 pounds. Their hundredweight (cwt) was 112 pounds.
Their quarter was 28 pounds
their stone was 14 pounds)
Good riddance to Imperial units!
Don,
you are embarrassing youself now.
Just sit back, relax, and realise that you are wrong, and I will
explain again why you are wrong.
A load of 1 British ton is applied to a 1/4 inch diameter bolt by an
early Rolls-Royce engine.
Suppose the bolt is made of a 100 ton steel - that is to say a
steel with a yield strength of 100 British tons per square inch.
1/4 inch diameter is about 1/20 of one square inch in cross-section.
So the maximum force allowable on that bolt is
1/20th of 100 tons.
1/20th of 100 tons is 5 tons.
But the load is one ton.
And a relevant design factor is X4 or 4 tons.
So the factored load is four tons and the max allowable is 5 tons, so
the bolt is overspecified by about 1/5th.
NOW do you get it?
Brian Whatcott Altus OK
p.s. In case that doesn't get through, I annotated your
calculations below.
On Sat, 27 Dec 2003 00:59:47 GMT, "Don Phillips"
Perhaps so: but its one ton on a 1/4 inch bolt!
Good! You understood that I meant the term "100 ton steel" to imply
that number is specifying its maximal stress. And calling 100
tons/sq in = 200 kips is OK in an American context.
So far, so good..
Although your units looked a little messy, you are saying the maximum
allowable force on a quarter inch diameter bolt in this material is
10,000 pounds.
That *IS* what you wrote, isn't it?
Now this is where you go off the track.
Remind yourself: the actual load is about 1 ton, and the allowable
load is 10,000 pounds or 5 tons.
I'll write that again:
the actual load on the bolt is about 1 ton, and the allowable load on
that bolt is 10,000 pounds or 5 tons.
No,no,no,no!
allowable load 10000 lb
actual load 2100 lb
Factor of Safety about 5
An engineer cannot allow the actual stress to exceed the allowable
stress
Allowable stress 100 ton /sq in
Actual stress is about 1 ton on 1/20 sq in or 20 ton/sq inch.
NO again! You worked out the actual load yourself, in an earlier
post. You made it 2100 lbs. Remember?
Actual load X 4 = 8400 pounds.....
Wrong yet again.
Actual load = 2100 lb allowable stress (say ) 200,000 psi
Required area is 2100/200000 = 0.01 sq inch
So you concluded after being told of an error, that the required
number of bolts is now sixty-seven!
Good grief!
Alright, I am not going to be snide, or personal: but I should ask one
question: what specialty of engineering did you pass the P.E in, and
in which state?
Does it even make sense to you (or any engineer) that you would hold
up a load of one ton with sixty seven quarter inch bolts?
Brian Whatcott Altus OK
I hate to butt in to a good argument...
If Brian will agree that a load of 84 tonnes would need about 20 1/4 "
bolts, and Don will agree that a 1 tonne load can be held by a single 1/4"
bolt then all that remains is to specify the engine force.
At one point the stress from a 1 ton load was calculated to be 84 ton /
in^2, but was noted as 84 tons.
I think Don took this to be the force of the engine...........
I still find it surprising that a ton load can be supported safely on a
single 1/4 inch bolt, but then I mainly use stainless bolts, with a UST of
45 ton / in^2, and a yield of about 15.
Is a 100 ton bolt able to take this stress without yielding ??
--
Jonathan
Barnes's theorem; for every foolproof device
there is a fool greater than the proof.
To reply remove AT
wrote:
produced
1.3
steel
typically
definition,
kips).
lbf
Ah, the voice of reason appears....
On Sat, 27 Dec 2003 11:51:43 -0000, "Jonathan Barnes"
Yep, I can easily agree that 20 1/4 bolts of 100 ton steel can hold
a load of 84 tons. Or you could use one bolt of just over 1 inch
diameter: say 1 1/16 diam - for this unfactored load.
But I would expect a P.E to note that a one tonne load could be held
by a 1/8th in diameter bolt (one eighth inch) in 100 ton material.
Actually, aircraft designers take a bare load, and multiply it by an
expected g loading which varies for different classes of aircraft then
apply a factor to reflect the uncertainties of production,
installation and maintenance.
So the actual stress on a 1/4 inch bolt from a 1 ton (say 2000 lb)
load is really only about 20 X 2000 = 40,000 psi but it needs to be
factored. I factored with X4 to put the upper working stress at
about 160,000 psi. This is nicely contained by a 200,000 psi yield
material
His working was frankly, too muddled for me to be sure.
I will ignore the implication that I would talk about unobtainium,
and simply list some of the commonly obtainable 100 ton metals:
Of those listed, 31 materials have tensile strength to yield of
250,000 psi or greater. These include "120 ton steels" and copper
alloy(!), stainless alloy, beryllium nickel alloy (!), cobalt alloy,
titanium alloy in appropriate heat treat conditions.
[ The results of a matweb search at <http://www.matweb.com ]
1 AISI Grade 18Ni (200) Maraging Steel, Aged, 16 mm round bar,
tested in longitudinal direction
[various other heat treats and sheet sizes excluded]
39 AISI Grade 18Ni (350) Maraging Steel, Aged, at RT, tested
longitudinal, round bar 16 mm
[various other heat treats and sizes excluded]
47 AISI 4140 Steel, oil quenched, 205°C (400°F) temper, 25 mm
(1 in.) round
[various tempers and variants excluded]
56 AISI 4340 Steel, oil quenched 845°C, 650°C (1200°F) temper,
tested at -195°C (-320°F)
[various tempers and variants excluded]
74 Beryllium Copper, UNS C17200, TH04 Temper
75 Beryllium Copper, UNS C17300, TH04 Temper
76 Copper, UNS C71700
77 ASTM 897 Grade 5 (230-185-00), Austempered Ductile Iron
78 79Pt-15Rh-6Ru; Alloy 851
79 ASTM A228
80 AISI Type H11 Hot Work Tool Steel, air or oil quenched from
995-1025°C
81 AISI Type H13 Hot Work Tool Steel, air or oil quenched from
995-1025°C
82 AISI Type S1 Tool Steel, quenched 955°C (1750°F), tempered
150°C (300°F)
83 AISI Type S1 Tool Steel, quenched 955°C (1750°F), tempered
250°C (500°F)
84 AISI Type S2 Tool Steel, austenitized 845°C (1550°F), brine
quenched to 55 HRC
85 AISI Type S5 Tool Steel, austenitized 855-870°C (1575-1600°F),
oil quenched to 55 HRC
86 AISI Type W1 Tool Steel, water quenched at 775°C (1425°F),
tempered 350°C (660°F)
87 AISI Type W2 Tool Steel, water quenched at 775°C (1425°F), and
tempered
88 Titanium Beta C ST 815°C, Aged 425°C
89 Titanium Beta-CEZ ST 830°C (1525°F), Aged 550°C
90 Titanium Beta-CEZ ST 860°C (1580°F), Aged 550°C
91 Titanium Ti-6Al-2Sn-4Zr-6Mo STA-2
92 AISI A6, Type Tool Steel, austenitized 830-870°C (1525-1600°F)
93 AISI A9, Type Tool Steel, tempered at 500°C
94 Vasco® 4340 Specialty Steel, Heat Treatment: 899°C (1650°F) Q+T
95 Vasco® D6AC Specialty Steel, Heat Treatment: 913°C (1675°F) Q+T
96 Vasco® 9-4-30 Specialty Steel,
Heat Treatment: 899°C (1650°F) + Age
97 VascoMax® C-250 Specialty Steel,
Heat Treatment: 927°C (1700°F) + Age
98 VascoMax® C-300 Specialty Steel,
Heat Treatment: 927°C (1700°F) + Age
99 VascoMax® C-350 Specialty Steel,
Heat Treatment: 927°C (1700°F) + Age
100 VascoMax® T-250 Specialty Steel,
Heat Treatment: 816°C (1500°F) + Age
101 Vasco® 13-8Mo Precipitation Hardening Steel,
Heat Treatment: 927°C (1700°F) + Age
102 Vasco® 455 Specialty Steel, Heat Treatment:
829°C (1525°F) + Age
103 Vasco® 440 C UNS S44004 Specialty Steel
104 Nickelvac® 43-40 UNS G43400, UNS H43400 Specialty Steel
105 Nickelvac® D6AC UNS K24728 Specialty Steel
106 VascoMax® T-200 Specialty Steel
107 Brush Wellman Beryllium Nickel Strip - Alloy 360
1/2 Hard, 1.5 hr at 950°F
113 Brush Wellman Beryllium Copper Alloy 25 Plate & Rolled Bar;
HT (TH04) Temper; over 9.5 to 25 mm Thickness (UNS C17200)
115 Brush Wellman Beryllium Copper Alloy 25 Wire; 1/2HT (TH02)
Temper; 1.3-12.7 mm Diameter (UNS C17200)
123 Carpenter Custom 455® Stainless Steel, Condition H900
(Age Hardened 482°C)
125 Carpenter Custom 450® Stainless Steel, Condition H900
(Age Hardened 482°C); Tensile/Impact Properties at -196°C
129 Carpenter MP35N* Ni-Co-Cr-Mo Alloy, 55% Cold Reduction
141 Carpenter Custom 630 (17-Cr-4Ni) Precipitation Hardening
Stainless Steel, Condition H 1100
(Heated 593°C); Tensile Properties at -196°C
142 Carpenter AerMet®-for-Tooling Tool Steel, Double Aged 468°C
144 Carpenter Extendo-Die® Hot Work Die Steel, Tempered 560°C
147 Carpenter Pyrotough® 78 Hot Work Die Steel
148 Carpenter R.D.S.® Alloy Tool Steel (Oil-Hard) (AISI L6)
149 Carpenter No. 484® Alloy Tool Steel
(Carpenter Air-Hard) (AISI A2)
150 Carpenter Vega® Alloy Tool Steel (Air-Tough) (AISI A6)
151 Carpenter No. 883® Hot Work Die Steel (Red-Tough) (AISI H13)
152 Carpenter S7 Alloy Tool Steel (AISI S7)
159 Elgiloy® Co-Cr-Ni Alloy, Wire, 40% Cold Reduction,
Heat Treated
167 Special Metals INCONEL® 718SPF™ Nickel Superalloy,
Annealed + Aged
168 Special Metals UDIMET® Alloy 250 Maraging Steel
169 Allegheny Ludlum Stainless Steel Type 201, 60% Cold Work
(UNS S20100)
173 Allegheny Ludlum Martensitic Stainless Steel Type 425 Mod,
Hardened + 204°C Temper
180 Alloy C-22, 60% Cold Worked
188 Alloy 718, 50% Cold Worked, Aged
191 AISI Type 308 Stainless steel, cold drawn wire,
full hardened, 0.53-3.18 mm diameter
195 AISI Type 347 Stainless Steel, cold drawn wire,
full hard, 0.53-3.18 mm diameter
197 AISI Type 348 Stainless Steel, cold drawn wire,
75% hard, 0.53-3.18 mm diameter
200 AISI Type 420 Stainless Steel, hardened and tempered bar
AISI Type 660 Stainless Steel (A286) room temperature,
cold drawn wire diameter of 2.84 mm,
aged at 480°C (900°F)
204 AISI Type S13800 Stainless Steel (PH 13-8 Mo)
longitudinal properties, condition RH950
207 AISI Type S14800 Stainless Steel condition SRH950,
tested at -73°C (-100°F)
208 AISI Type S14800 Stainless Steel condition SRH950,
tested at 27°C
220 AISI Type S15500 (15Cr-5Ni) Precipitation Hardening
Stainless Steel tested at 425°C (800°F),
condition H925
223 17-7 PH Stainless Steel, CH900, plate, sheet, and strip
224 AISI Type S20910 Stainless Steel, 6.4 mm diameter rod,
annealed at 1120°C, 60% cold reduction
226 AISI Type S21800 Stainless Steel tested at RT,
70% cold reduction
227 AISI Type S24100 Stainless Steel 6.4 mm diameter
annealed rod, 50% cold reduction
229 AISI Type S45000 Stainless Steel, 25 mm diameter bar,
tested at -195°C (-320°F), aged at 480°C (900°F)
230 AISI Type S45000 Stainless Steel, 25 mm diameter bar,
tested at -195°C (-320°F), aged at 565°C (1050°F)
232 AISI Type S45500 Stainless Steel, hardened at
480°C (900°F) for 4 hours, air cooled,
25 mm (1 in.) round
242 AISI Type O1, Oil-hardening Tool Steel,
oil quenched at 800°C, tempered at 425°C
243 AISI Type O2, Oil-hardening Tool Steel, oil quenched
at 800°C, tempered at 260°C
[end]
I emphasise that from my reading of both your calculations Don is working on
an engine force of 84 tons.
I'm sorry to have given the impression that I thought 100 ton steel was not
obtainable.
My work is in the area of bottling equipment, in the drinks industry.
weight is never important, but the machinery is maintained by gorillas
equipped with worn adjustable spanners....
It's not unusual for me to use 2 x M6 ( approx. 1/4" ) stainless grade A2
bolts simply to hold a limit switch bracket in position.
I am constantly amazed by what can be done with materials.
Most people will not believe a perfectly ordinary piece of paper rolled to
give a long cylinder, held with a couple of elastic bands will support a
full 2 l drinks bottle.
I digress... :-)
To return to my original question, is the 100 tons a yield, UTS, or working
load ?
Jonathan
Barnes's theorem; for every foolproof device
there is a fool greater than the proof.
To reply remove AT
On Sat, 27 Dec 2003 18:24:59 -0000, "Jonathan Barnes"
The hundred thirty plus materials I excerpted in a post earlier today
were selected for tensile strength at yield point of at least 200,000
psi. I mentioned that more than 30 of these, would not yield until
stressed to 250,000 psi or more.
I urge you to register with the material properties site I mentioned
earlier - it is a useful resource. You have no need to take my word
for such things as yield strengths.....
It is typical of high performance materials in this class that the
yield point is not far below the ultimate, however.
It is also true that aluminum alloys in aerospace service often do not
have a well defined knee at yield. For these, it is customary to
specify the 0.1% yield stress.
Ultimate Tensile Strengths of engineering materials are all but unused
in aerospace applications. Yield point is never intentionally
exceeded. (This contrasts with some other structural design fields
where the ductile nature of lower performance steels allows some load
sharing in less than perfectly built structures as bolts etc. stretch)
Did this response answer your question understandably?
Brian Whatcott
mounted
Fuse pins react a shear load which in a crash would tend to be upwards
and rearwards. On Boeing commercial widebody airplanes, the engine
struts are held on by four fuse pins. One in the front spar pitch load
fitting, two in the midspar fittings on the lower wing and one in the
aft drag brace fitting also on the lower wing. There is another fitting
on the lower front spar/wing surface that reacts side load and prevents
fitting flange bending loads on the other fittings as well as acting as
a fail-safe for failure of one of the fuse pins. Development of loads is
achieved by consideration of engine weight and thrust and inertia loads
from operation of the aircraft and is not any easy thing. Fatigue
spectrum loads being one consideration and protection of the wing
structure under ultimate conditions (fuse load) being the other.
Phil Holman
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