The Merlin Titanium Primer Glossary

3-2.5
a titanium alloy of 3% aluminum, 2.5% vanadium, and 94.5% titanium, valued for its high strength and excellent ductility
4130
a steel alloy classified as a carbon steel, consisting of 0.95% chromium, 0.5% manganese, 0.3% carbon, 0.25% silicon, and 0.2% molybdenum. 4130 is the most common steel used in high-quality bicycle frames due to its high strength, acceptable formability, and low cost
6061
an aluminum alloy of 1.0% magnesium, 0.6% silicon, 0.28% copper, and 0.2% chromium. It is often tempered to T6 condition, which includes solution heat treatment and artificial aging. 6061 is the most common aluminum alloy for bicycle frames due to its reasonable strength, good formability, low cost, and good weldability
6-4
a high-strength titanium alloy of 6% aluminum, 4% vanadium, and 90% titanium
Alloy
a mixture of two or more metals, or a metal and other materials; 3-2.5 titanium is an alloy of 94.5% titanium, 3% aluminum and 2% vanadium
AMS
aerospace materials specifications, a standard classification system issued by the Society of Automotive Engineers (SAE)
Anneal
to heat and cool at a controlled rate. Annealing is used for many purposes, such as to remove work-hardening and embrittlement. The term is often used to signify a reduction in strength of a material due to heating; a more precise term for this is -full annealing+
Butt
a thickened section of a tube that reinforces the tube in that area
Butting
a process that varies the wall thickness of a tube, either internally or externally, to provide local reinforcement
CP
commercially pure; a designation for pure, unalloyed titanium
Cro-Mo (chrome-molybdenum steel)
a high-strength steel with alloying elements almost identical to 4130 alloy
CSR
contractile strain ratio; a numerical index of crystallographic texture (see "texture") determined by the ratio of diametral strain to radial strain in a titanium tube
CWSR
cold-worked, stress-relieved; said of tubing that has been pressed to its final shape without the use of heat (while "cold"), and then annealed to relieve internal stresses from the forming processes
Delaminate
in a fiber composite structure, such as carbon fiber or fiberglass, the separation of the fiber from the epoxy resin that holds the fiber strands together; caused by stress, fatigue, or impact
Density
the ratio of mass to volume
Double butting
a tube that has two internal or external butts, or reinforcements, usually one at each end
Ductility
percent elongation of a material in a tensile test to failure. Ductile metals are pliable and easily worked, and can be drawn, shaped and formed without cracking or breaking
Elastic Modulus
(Young's modulus) ratio of stress to strain within the elastic region of a material in tension or compression. High-modulus materials deflect less (exhibit less strain) under a given load (or stress) than low-modulus materials. Modulus is not affected by strength (i.e., a low-strength 4130 tube effectively has the same modulus as a heat-treated high-strength 4130 tube)
Elongation
the length change found in a tensile test specimen from its initial length to its length at failure
Endurance
see fatigue endurance
Fatigue endurance
the stress level at which the number of cycles to failure is infinite. Aluminum has no fatigue endurance; steel and titanium do. Also called -fatigue strength+
Flaring
enlarging the diameter of a tube through mechanical action; a process that is the opposite of tapering, although the final shape may be the same. In titanium, flaring alters texture
HAZ
heat-affected zone; the area around a miter or other frame joint that is potentially weaker due to the heat of welding or brazing
MMC
metal-matrix composite; a material made of a base metal and other metallic or non-metallic inclusions that improve the properties of the base metal
Modulus
see elastic modulus
MTS325
(Merlin Tube Specification for 3-2.5 tubing) Merlin's additional specification for AMS 105 tubing; it calls for better straightness, a smoother surface finish, and higher minimums for ultimate tensile strength and yield strength
Pilgering
a reduction process used to create the final inside and outside diameters of a tube by rolling grooved dies back and forth (rocking) along the outside diameter of the tube while the inside is supported by a mandrel
Purity
measure of contaminants in a given material, as compared against the material's specification index
Resiliency
the energy per unit volume that a material can absorb without yielding
Rocking
see pilgering
Swaging
the forced reshaping of a material through the use of a die or stamp, called a swage
Tapering
the process of shaping a tube into a conical section. Tapered tubing can be formed by swaging, or by rolling a conical section of sheet metal into a tube and welding the seam
Texture
in titanium, the orientation of the hexagonally shaped molecules of titanium in a tube. Crystallographic texture affects yield strength, tensile elongation, ductility and fatigue strength; it can be controlled during pilgering. Texture is measured by comparing the deformation of the tube under tensile strain in the radial direction to the deformation in the circumferential direction (contractile strain ratio)
UTS
ultimate tensile strength; the maximum load a material can withstand before breaking
Work Hardening
the increase in hardness and strength exhibited when a material is formed or worked. Some materials exhibit extreme work hardening, titanium among them
YS
yield strength; generally considered to be a point 0.2% beyond the material's upper limit of elastic deformation, where an applied load causes a permanent deformation
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