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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 03-10-08, 11:00 PM   #1
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carbon fiber components with steel frames

CARBON FIBERS

Updated: April, 2004 - Raghavendra R. Hegde, Atul Dahiya, M. G. Kamath
(Monika Kannadaguli & Haoming Rong)
1. INTRODUCTION

Carbon fibers are a new breed of high-strength materials. Carbon fiber has been described as a fiber containing at least 90% carbon obtained by the controlled pyrolysis of appropriate fibers. The existence of carbon fiber came into being in 1879 when Edison took out a patent for the manufacture of carbon filaments suitable for use in electric lamps. However, it was in the early 1960s when successful commercial production was started, as the requirements of the aerospace industry - especially for military aircraft - for better and lightweight materials became of paramount importance. In recent decades, carbon fibers have found wide application in commercial and civilian aircraft, recreational, industrial, and transportation markets. Carbon fibers are used in composites with a lightweight matrix. Carbon fiber composites are ideally suited to applications where strength, stiffness, lower weight, and outstanding fatigue characteristics are critical requirements. They also can be used in the occasion where high temperature, chemical inertness and high damping are important. The suppliers of Advanced Composites Materials Association released 1997 industry statistics on worldwide shipments of carbon fibers for composites [1,2] (Table 1). However, from 1997 to 1999 there was a global slowing of carbon fiber demand [3]. According to Mitsubishi Rayon Co. Ltd. (Tokyo, Japan), a carbon fiber producer, worldwide consumption for sporting goods is nearly 11 million lb of carbon fiber

Table 1: Worldwide shipment of carbon fibers for composites

YEAR
POUNDS
1992
13,000,812
1993
14,598,544
1994
17,425,452
1995
19,714,671
1996
20,672,741
1997
25,900,000



Currently, the United States of America uses nearly 60% of the world production of carbon fibers and the Japanese account for almost 50% of the world capacity for production. The largest producer of this fiber is Toray Industries of Japan. The world production capacity of pitch-based carbon fiber is almost totally based in Japan [4].

Table 2: Us composite Shipment in 1998

MARKET
PERCENT OF TOTAL VOLUME
Transportation
31.6
Construction
20.8
Corrosion- resistant
11.8
Marine
10.1
Electrical/Electronics
10.0
Consumers
6.3
Appliances/Business equipment
5.5
Aircraft
0.6
Others
3.3


2. CLASSIFICATION AND TYPES:

Based on modulus, strength, and final heat treatment temperature, carbon fibers can be classified into the following categories:

2.1 BASED ON CARBON FIBER PROPERTIES, CARBON FIBERS CAN BE GROUPED INTO:

Ultra-high-modulus, type UHM (modulus >450Gpa)

High-modulus, type HM (modulus between 350-450Gpa)
Intermediate-modulus, type IM (modulus between 200-350Gpa)
Low modulus and high-tensile, type HT (modulus < 100Gpa, tensile strength > 3.0Gpa)
Super high-tensile, type SHT (tensile strength > 4.5Gpa)
2.2 BASED ON PRECURSOR FIBER MATERIALS, CARBON FIBERS ARE CLASSIFIED INTO;

PAN-based carbon fibers

Pitch-based carbon fibers
Mesophase pitch-based carbon fibers
Isotropic pitch-based carbon fibers
Rayon-based carbon fibers
Gas-phase-grown carbon fibers
2.3 BASED ON FINAL HEAT TREATMENT TEMPERATURE, CARBON FIBERS ARE CLASSIFIED INTO:

Type-I, high-heat-treatment carbon fibers (HTT), where final heat treatment temperature should be above 2000C and can be associated with high-modulus type fiber.

Type-II, intermediate-heat-treatment carbon fibers (IHT), where final heat treatment temperature should be around or above 1500C and can be associated with high-strength type fiber.
Type-III, low-heat-treatment carbon fibers, where final heat treatment temperatures not greater than 1000C. These are low modulus and low strength materials.
3. MANUFACTURE

In Textile Terms and Definitions, carbon fiber has been described as a fiber containing at least 90% carbon obtained by the controlled pyrolysis of appropriate fibers. The term "graphite fiber" is used to describe fibers that have carbon in excess of 99%. Large varieties of fibers called precursors are used to produce carbon fibers of different morphologies and different specific characteristics. The most prevalent precursors are polyacrylonitrile (PAN), cellulosic fibers (viscose rayon, cotton), petroleum or coal tar pitch and certain phenolic fibers.

Carbon fibers are manufactured by the controlled pyrolysis of organic precursors in fibrous form. It is a heat treatment of the precursor that removes the oxygen, nitrogen and hydrogen to form carbon fibers. It is well established in carbon fiber literature that the mechanical properties of the carbon fibers are improved by increasing the crystallinity and orientation, and by reducing defects in the fiber. The best way to achieve this is to start with a highly oriented precursor and then maintain the initial high orientation during the process of stabilization and carbonization through tension.

4. CARBON FIBERS FROM POLYACRYLONITRILE (PAN):

There are three successive stages in the conversion of PAN precursor into high-performance carbon fibers. Oxidative stabilization: The polyacrylonitrile precursor is first stretched and simultaneously oxidized in a temperature range of 200-300C. This treatment converts thermoplastic PAN to a non-plastic cyclic or ladder compound. $Carbonization: After oxidation, the fibers are carbonized at about 1000C without tension in an inert atmosphere (normally nitrogen) for a few hours. During this process the non-carbon elements are removed as volatiles to give carbon fibers with a yield of about 50% of the mass of the original PAN. Graphitization: Depending on the type of fiber required, the fibers are treated at temperatures between 1500-3000C, which improves the ordering, and orientation of the crystallites in the direction of the fiber axis.


Fig. 1: Schematic representation of carbon fiber preparation from PAN fibers.

4.1. CARBON FIBERS FROM RAYON:

4.1.1 THE CONVERSION OF RAYON FIBERS INTO CARBON FIBERS IS THREE PHASE PROCESS

Stabilization: Stabilization is an oxidative process that occurs through steps. In the first step, between 25-150C, there is physical desorption of water. The next step is a dehydration of the cellulosic unit between 150-240C. Finally, thermal cleavage of the cyclosidic linkage and scission of ether bonds and some C-C bonds via free radical reaction (240-400 C) and, thereafter, aromatization takes place.

Carbonization: Between 400 and 700C, the carbonaceous residue is converted into a graphite-like layer.

Graphitization: Graphitization is carried out under strain at 700-2700C to obtain high modulus fiber through longitudinal orientation of the planes.

Fig. 2: Reactions involved in the conversion of cellulose into carbon fibers

4.1.2. The carbon fiber fabrication from pitch generally consists of the following four steps:

Pitch preparation: It is an adjustment in the molecular weight, viscosity, and crystal orientation for spinning and further heating.

Spinning and drawing: In this stage, pitch is converted into filaments, with some alignment in the crystallites to achieve the directional characteristics.

Stabilization: In this step, some kind of thermosetting to maintain the filament shape during pyrolysis. The stabilization temperature is between 250 and 400 C.

Carbonization: The carbonization temperature is between 1000-1500C.


Fig. 3: Manufacturing process schematic for pitch-based carbon fibers





5. CARBON FIBERS IN MELTBLOWN NONWOVENS

Carbon fibers made from the spinning of molten pitches are of interest because of the high carbon yield from the precursors and the relatively low cost of the starting materials. Stabilization in air and carbonization in nitrogen can follow the formation of melt-blown pitch webs. Processes have been developed with isotropic pitches and with anisotropic mesophase pitches. The mesophase pitch based and melt blown discontinuous carbon fibers have a peculiar structure. These fibers are characterized in that a large number of small domains, each domain having an average equivalent diameter from 0.03mm to 1mm and a nearly unidirectional orientation of folded carbon layers, assemble to form a mosaic structure on the cross-section of the carbon fibers. The folded carbon layers of each domain are oriented at an angle to the direction of the folded carbon layers of the neighboring domains on the boundary [5].

6. CARBON FIBERS FROM ISOTROPIC PITCH:

The isotropic pitch or pitch-like material, i.e., molten polyvinyl chloride, is melt spun at high strain rates to align the molecules parallel to the fiber axis. The thermoplastic fiber is then rapidly cooled and carefully oxidized at a low temperature (<100C). The oxidation process is rather slow, to ensure stabilization of the fiber by cross-linking and rendering it infusible. However, upon carbonization, relaxation of the molecules takes place, producing fibers with no significant preferred orientation. This process is not industrially attractive due to the lengthy oxidation step, and only low-quality carbon fibers with no graphitization are produced. These are used as fillers with various plastics as thermal insulation materials.

7. CARBON FIBERS FROM ANISOTROPIC MESOPHASE PITCH:

High molecular weight aromatic pitches, mainly anisotropic in nature, are referred to as mesophase pitches. The pitch precursor is thermally treated above 350C to convert it to mesophase pitch, which contains both isotropic and anisotropic phases. Due to the shear stress occurring during spinning, the mesophase molecules orient parallel to the fiber axis. After spinning, the isotropic part of the pitch is made infusible by thermosetting in air at a temperature below it's softening point. The fiber is then carbonized at temperatures up to 1000C. The main advantage of this process is that no tension is required during the stabilization or the graphitization, unlike the case of rayon or PAN precursors.

8. STRUCTURE

The characterization of carbon fiber microstructure has been mainly been performed by x-ray scattering and electron microscopy techniques. In contrast to graphite, the structure of carbon fiber lacks any three dimensional order. In PAN-based fibers, the linear chain structure is transformed to a planar structure during oxidative stabilization and subsequent carbonization. Basal planes oriented along the fiber axis are formed during the carbonization stage. Wide-angle x-ray data suggests an increase in stack height and orientation of basal planes with an increase in heat treatment temperature. A difference in structure between the sheath and the core was noticed in a fully stabilized fiber. The skin has a high axial preferred orientation and thick crystallite stacking. However, the core shows a lower preferred orientation and a lower crystallite height.

9. PROPERTIES

In general, it is seen that the higher the tensile strength of the precursor the higher is the tenacity of the carbon fiber. Tensile strength and modulus are significantly improved by carbonization under strain when moderate stabilization is used. X-ray and electron diffraction studies have shown that in high modulus type fibers, the crystallites are arranged around the longitudinal axis of the fiber with layer planes highly oriented parallel to the axis. Overall, the strength of a carbon fiber depends on the type of precursor, the processing conditions, heat treatment temperature and the presence of flaws and defects. With PAN based carbon fibers, the strength increases up to a maximum of 1300oC and then gradually decreases. The modulus has been shown to increase with increasing temperature. PAN based fibers typically buckle on compression and form kink bands at the innermost surface of the fiber. However, similar high modulus type pitch-based fibers deform by a shear mechanism with kink bands formed at 45 to the fiber axis. Carbon fibers are very brittle. The layers in the fibers are formed by strong covalent bonds. The sheet-like aggregations allow easy crack propagation. On bending, the fiber fails at very low strain.

10. APPLICATIONS

The two main applications of carbon fibers are in specialized technology, which includes aerospace and nuclear engineering, and in general engineering and transportation, which includes engineering components such as bearings, gears, cams, fan blades and automobile bodies. Recently, some new applications of carbon fibers have been found. Such as rehabilitation of a bridge [6] in building and construction industry. Others include: decoration in automotive, marine, general aviation interiors, general entertainment and musical instruments and after-market transportation products [7]. Conductivity in electronics technology provides additional new application. Table 2 illustrates some of the characteristics and applications of carbon fibers[8] .

Table 3: Characteristics and Applications of Carbon Fibers

1. Physical strength, specific toughness, light weight
Aerospace, road and marine transport, sporting goods
2. High dimensional stability, low coefficient of thermal expansion, and low abrasion
Missiles, aircraft brakes, aerospace antenna and support structure, large telescopes, optical benches, waveguides for stable high-frequency (GHz) precision measurement frames
3. Good vibration damping, strength, and toughness
Audio equipment, loudspeakers for Hi-fi equipment, pickup arms, robot arms
4. Electrical conductivity
Automobile hoods, novel tooling, casings and bases for electronic equipments, EMI and RF shielding, brushes
5. Biological inertness and x-ray permeability
Medical applications in prostheses, surgery and x-ray equipment, implants, tendon/ligament repair
6. Fatigue resistance, self-lubrication, high damping
Textile machinery, genera engineering
7. Chemical inertness, high corrosion resistance
Chemical industry; nuclear field; valves, seals, and pump components in process plants
8. Electromagnetic properties
Large generator retaining rings, radiological equipment
The production of highly effective fibrous carbon adsorbents with low diameter, excluding or minimizing external and intra-diffusion resistance to mass transfer, and therefore, exhibiting high sorption rates is a challenging task. These carbon adsorbents can be converted into a wide variety of textile forms and nonwoven materials [9]. Cheaper and newer versions of carbon fibers are being produced from new raw materials. Newer applications are also being developed for protective clothing (used in various chemical industries for work in extremely hostile environments), electromagnetic shielding and various other novel applications. The use of carbon fibers in Nonwovens is in a new possible application for high temperature fire-retardant insulation (eg: furnace material.)

..............





You have discovered the secret thread, congratulations. Now that you are here, however, you must swear not to tell anyone. The secret thread is serious business. The secret thread is holy. No mod's allowed. No admin's allowed. No women allowed.

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Old 03-10-08, 11:03 PM   #2
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thoughts on steel italian bikes? which one is bestest?
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Old 03-10-08, 11:06 PM   #3
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thoughts on steel italian bikes? which one is bestest?

3Rensho


That was easy.
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Old 03-10-08, 11:07 PM   #4
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thoughts on steel italian bikes? which one is bestest?
I've heard this one is nice.
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Old 03-10-08, 11:09 PM   #5
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ah!

that's a lot to read at 1am. i gotta remember this thread tomorrow morning though. what's your source? ...or is it somewhere in all that stuff i gotta read through? ...maybe i'll ask questions after i read it.



also, best italian steel is Gabbledobie. know about it.
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Old 03-10-08, 11:10 PM   #6
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I've heard this one is nice.



Not a predictible response whatsoever. You are so clever. Ask me out, and I'll say "yes". You did not fail.



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Old 03-10-08, 11:12 PM   #7
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ah!

that's a lot to read at 1am. i gotta remember this thread tomorrow morning though. what's your source? ...or is it somewhere in all that stuff i gotta read through? ...maybe i'll ask questions after i read it.
It's a clever ploy to disguise the thread as useful information, when later on it will be derailed into chaotic babble. It's a ruse. A charade. A plot against the man.



Quote:
Originally Posted by naive guy
also, best italian steel is Gabbledobie. know about it.

See above.
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Old 03-10-08, 11:15 PM   #8
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god damn italians with their ini's and their iti's and their oily skin i hate them i hate them so much
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Old 03-10-08, 11:16 PM   #9
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god damn italians with their ini's and their iti's and their oily skin i hate them i hate them so much

I LOVE that movie.No idea how long I've wanted to use that quote. Kudos!
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Old 03-10-08, 11:22 PM   #10
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bike movies in order of worthmoneyness

-breaking away
-quicksilver
-american flyers

to be fair, american flyers has brief toplessness
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Old 03-10-08, 11:32 PM   #11
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I had a carbon fork break at the steertube on Sunday sending me into a cartwheel on GG bridge. If I hadn't been going 5mph, my trip to the doctor would have been to the morgue. I'm sure it was a fluke HOWEVER I won't be using an all carbon fork anytime in the near future.

Steel... it's sexy and it's safe.
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Old 03-10-08, 11:35 PM   #12
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I had a carbon fork break at the steertube on Sunday sending me into a cartwheel on GG bridge. If I hadn't been going 5mph, my trip to the doctor would have been to the morgue. I'm sure it was a fluke HOWEVER I won't be using an all carbon fork anytime in the near future.

Steel... it's sexy and it's safe.


*whistles*
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Old 03-10-08, 11:49 PM   #13
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thanks for the info.

It would be cool to see another decade of statistics on production and more info about the latest technology in CF.

It would also be cool to get some info about the fatigue characteristics of CF. It's fairly well known how metals fatigue, but i've never heard any solid details about CF. The stuff certainly doesn't last forever, but i've even asked some of my mechanical engineering profs and they all just seem to shrug at the question.
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Old 03-10-08, 11:58 PM   #14
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you spelled "road" wrong in your custom title.

there's a weird creaking coming from my fork when i climb or sprint. hopefully the front wheel just needs to be tightened (spokes/qr) or something with the shim (nitto bars + slightly too big stem + shim).

if the fork collapses i'll let you know
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Old 03-10-08, 11:59 PM   #15
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thanks for the info.

It would be cool to see another decade of statistics on production and more info about the latest technology in CF.

It would also be cool to get some info about the fatigue characteristics of CF. It's fairly well known how metals fatigue, but i've never heard any solid details about CF. The stuff certainly doesn't last forever, but i've even asked some of my mechanical engineering profs and they all just seem to shrug at the question.
My fork lasted eleven months. I did have a seat post last nine years before I retired it.
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Old 03-11-08, 12:06 AM   #16
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My fork lasted eleven months. I did have a seat post last nine years before I retired it.
yeah. Its not uncommon to hear of seat posts and forks failing. But how do you know when the CF is about to give up the ghost? At least with AL you can look for cracks.
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Old 03-11-08, 01:57 AM   #17
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yeah. Its not uncommon to hear of seat posts and forks failing. But how do you know when the CF is about to give up the ghost? At least with AL you can look for cracks.
A friend of mine had a CF skimboard, I think they employ some heavy duty multidirectional weave CF as it has to deal with high stresses and impacts, and he had been using it for a month in moderate surf. One day it just up and split in half on a small wave with no prior signs of delamination or fatigue. It scared me enough to never really trust CF in high stress/ high impact applications like for a fork in s***ty streets. Of course it was just an isolated incident and my fear is baseless as boeing is sucking up most of the CF on the market with their "dreamliner" and it seems fatigue strength and stress resistance is heavily scrutinized in that industry.

Then again the application of CF is different in aerospace, cycling, and skimboarding so I don't know.
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Old 03-11-08, 03:47 AM   #18
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bike movies in order of worthmoneyness

-breaking away
-quicksilver
-american flyers

to be fair, american flyers has brief toplessness
i bought american flyers for $5 used, and was still pissed at that purchase. they just kept showing that guys butt, and he never had a shirt on, and he wore a ****ing cowboy hat. it was like the beginning to a gay bike-themed porno.
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Old 03-11-08, 04:02 AM   #19
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I had a carbon fork break at the steertube on Sunday sending me into a cartwheel on GG bridge. If I hadn't been going 5mph, my trip to the doctor would have been to the morgue. I'm sure it was a fluke HOWEVER I won't be using an all carbon fork anytime in the near future.

Steel... it's sexy and it's safe.
+1
steel is real.
I liked the pista concept fork I rode for like, a week, but I just like the feel of a steel fork better.
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Old 03-11-08, 10:40 AM   #20
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bike movies in order of worthmoneyness

-breaking away
-quicksilver
-american flyers

to be fair, american flyers has brief toplessness
I'd throw 2 seconds and The Flying Scotsman in there.
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Old 03-11-08, 05:18 PM   #21
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can someone sum that up for me?
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Old 03-11-08, 05:30 PM   #22
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Originally Posted by letsthrowfries View Post
A friend ave CF as it has to deal with high stresses and impacts, and he had been using it for a month in moderate surf. One day it just up and split in half on a small wave with no prior signs of delami...blah blah blah...
Then again the application of CF is different in aerospace, cycling, and skimboarding so I don't know.
Time to get this **** back off track

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Old 03-11-08, 05:38 PM   #23
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Tomasini frames are better than carbon fibre
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Old 03-11-08, 06:12 PM   #24
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specifically the gorilla ones.
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Old 03-11-08, 06:16 PM   #25
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correct
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