X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 01 Jun 2013 17:40:03 -0400 Message-ID: X-Original-Return-Path: Received: from mail-ob0-f175.google.com ([209.85.214.175] verified) by logan.com (CommuniGate Pro SMTP 6.0.5) with ESMTPS id 6301927 for lml@lancaironline.net; Sat, 01 Jun 2013 11:25:19 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.214.175; envelope-from=pjdmiller@gmail.com Received: by mail-ob0-f175.google.com with SMTP id xn12so4837040obc.20 for ; Sat, 01 Jun 2013 08:24:43 -0700 (PDT) X-Received: by 10.60.92.41 with SMTP id cj9mr7487344oeb.31.1370100283426; Sat, 01 Jun 2013 08:24:43 -0700 (PDT) X-Original-Return-Path: Received: from [10.4.103.38] ([205.150.123.10]) by mx.google.com with ESMTPSA id lz18sm5020022oeb.7.2013.06.01.08.24.42 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 01 Jun 2013 08:24:42 -0700 (PDT) Subject: Re: [LML] Temperature effect on aluminum References: From: Paul Miller Content-Type: multipart/alternative; boundary=Apple-Mail-4C7A0299-DA4C-4D1F-AF47-984FCB237782 X-Mailer: iPad Mail (10B146) In-Reply-To: X-Original-Message-Id: <9BBBC4A0-1334-46CC-B50B-A7314CF6F254@gmail.com> X-Original-Date: Sat, 1 Jun 2013 09:24:40 -0600 X-Original-To: Lancair Mailing List Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) --Apple-Mail-4C7A0299-DA4C-4D1F-AF47-984FCB237782 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Very interesting graph but duration at temp is the problem. I will make a f= ew assumptions from this graph and toss them out: 1. Minor time excursions into the higher temps will not affect strength. O= perating at 425 through TBO would affect strength appreciably but 15 minutes= is not going to make any difference. 2. We must have safety margins built in even at max operating temp for thes= e engines so we must be operating way down on that graph. 3. Fatigue strength is probably far less than tensile stress in the graph so= we must have even a larger safety margin for fatigue protection and be furt= her down the graph in normal ops. 4. Cylinder heads likely have both tensile and compressive loads. Tensile l= oads may be an issue or maybe high temps near the exhaust valve is the limit= ing issue with temps. 5. Rebuilding with previously flown cylinder heads could leave you with dimi= nished protection in strength unless you know the temp history. Thanks for that graph Fred. Paul On 2013-05-31, at 23:04, "Frederick Moreno" wr= ote: >=20 > > Paul wrote: > =20 > "Colyn: I just re-read that article, Busch states: >=20 > (The head's tensile strength is reduced to 50% of its room-temperature va= lue at a CHT of 400F, and to about 33% at 500F.) >=20 > I don't see that supported in any literature studying the properties of st= eel versus temperature." > =20 > The cylinder heads are ALUMINUM and the cylinders are steel. Attached cha= rt shows that the 1000 hour strength of 356 aluminum alloy heads south rapid= ly as exposure temperature exceeds 300F.=20 > =20 > Fred > > -- > For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.htm= l --Apple-Mail-4C7A0299-DA4C-4D1F-AF47-984FCB237782 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Very interesting graph but duration at= temp is the problem.   I will make a few assumptions from this graph a= nd toss them out:
1. Minor time excursions into the higher temps w= ill not affect strength.   Operating at 425 through TBO would affect st= rength appreciably but 15 minutes is not going to make any difference.
=
2.  We must have safety margins built in even at max operating tem= p for these engines so we must be operating way down on that graph.
3. Fatigue strength is probably far less than tensile stress in the graph s= o we must have even a larger safety margin for fatigue protection and be fur= ther down the graph in normal ops.
4. Cylinder heads likely have b= oth tensile and compressive loads.  Tensile loads may be an issue or ma= ybe high temps near the exhaust valve is the limiting issue with temps.
5. Rebuilding with previously flown cylinder heads could leave you wit= h diminished protection in strength unless you know the temp history.
<= div>
Thanks for that graph Fred.

Paul
=
On 2013-05-31, at 23:04, "Frederick Moreno" <frederickmoreno@bigpond.com> wrote:

<SENDER_EMAILfrederickmoreno@bigpond@@com.png>
Paul wrote:
 
"Colyn: I just re-read that article, Busch states:=20

 (The head's tensile strength is reduced to 50% of= its room-temperature value at a CHT of 400F, and to about 33% at 500F.)

I don't s= ee that supported in any literature studying the properties of steel versus t= emperature."
 
The cylin= der heads are ALUMINUM and the cylinders are steel.  Attached chart sho= ws that the 1000 hour strength of 356 aluminum alloy heads south rapidly as e= xposure temperature exceeds 300F. 
 
Fred
<cz_Heat_Effect_on_Aluminum.JPG>
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