Oshida Y. Bioscience and Bioengineering of Titanium Materials

Подождите немного. Документ загружается.

[4-17] Albrektsson T, Brånemark PI, Hansson HA, Kasemo B, Larsson K,

Lundstroem I, McQueen DH, Skalak R. The interface zone of inorganic

implants in vivo: titanium implants in bone. Ann Biomed Eng 1983;11:1–27.

[4-18] Lausmaa J, Kasemo B, Hansson S. Accelerated oxide growth on titanium

implants during autoclaving caused by fluorine contamination. Bio-

materials 1985;6:23–27.

[4-19] Weast RC. CRC handbook of chemistry and physics. The 47th edition.

Cleveland, OH: The Chemical Rubber Co. 1966. p. E-58.

[4-20]

http://en.wikipedia.org/wiki/Titanium.

[4-21] Fraker AC, Ruff AW. Corrosion of titanium alloys in physiological solu-

tions. In: Titanium science and technology. Vol. 4 New York: Plenum

Press. 1973. pp. 2447–2457.

[4-22] Sittig C, Textor M, Spencer ND, Wieland M, Vallotton P-H. Surface char-

acterization of implant materials c.p. Ti, Ti-6Al-7Nb and Ti-6Al-4V with

different pretreatments. J Mater Sci: Mater Med 1999;10:35–46.

[4-23] Mazhar AA, Heakal FEl-T, Gad-Allah AG. Anodic behavior of titanium

in aqueous media. Corrosion 1988;44:705–710.

[4-24] Metikoš-Hukovic´ M, Ceraj-Ceric´ M. Anodic oxidation of titanium:

mechanism of non-stoichiomeric oxide formation. Surf Technol 1985;24:

273–283.

[4-25] Hanawa T, Asami K, Asaoka K. Repassivation of titanium and surface

oxide film regenerated in stimulated bioliquid. J Biomed Mater Res

1998;40:530–538.

[4-26] Gilbert JL, Buckley CA, Lautenschlager EP. Electrochemical reaction to

mechanical disruption of titanium oxide films. J Dent Res. Special Issue

1995;74:92 (Abstract No. 645).

[4-27] Hruska AR, Borelli P. Quality criteria for pure titanium casting, labora-

tory soldering, intraoral welding, and a device to aid in making unconta-

minated castings. J Prosthet Dent 1999;66:561–565.

[4-28] Adachi M, Mackert JR Jr, Parry EE, Fairhurst CW. Oxide adherence and

porcelain bonding to titanium and Ti-6Al-4V alloy. J Dent Res 1990;69:

1230–1235.

[4-29] Kimura H, Horng CJ, Okazaki M, Takahashi J. Oxidation effects on

porcelain-titanium interface reactions and bond strength. Dent Mater

J 1990;9:91–99.

[4-30] Hautaniemi JA, Herø H. Porcelain bonding on Ti: its dependence on sur-

face roughness, firing and vacuum level. Surf Interface Anal

1993;20:421–436.

[4-31] Atsü S, Berksun B. Bond strength of three porcelain to two forms of tita-

nium using two firing atmospheres. J Prosthet Dent 2000;84:567–574.

[4-32] Oshida Y, Hashem A. Titanium–porcelain system. Part I: oxidation kinet-

ics of nitrided pure titanium, simulated to porcelain firing process.

J Biomed Mater Eng 1993;3:185–198.

[4-33] Wang RR, Fung KK. Oxidation behavior of surface-modified titanium

for titanium–ceramic restorations. J Prosthet Dent 1997;77:423–434.

98 Bioscience and Bioengineering of Titanium Materials

Else_BBTM-OSHIDA_ch004.qxd 9/15/2006 8:41 AM Page 98

[4-34] Wang RR, Welsch G, Monteiro O. Silicon nitride coating on titanium

to enable titanium–ceramic bonding. J Biomed Mater Res 1999;46:

262–270.

[4-35] Sundgren J-E, Bodö P, Lundström I. Auger electron spectroscopic stud-

ies of the interface between human tissue and implants of titanium and

stainless steel. J Colloid Interf Sci 1986;110:9–20.

[4-36] McQueen D, Sundgren JE, Ivarsson B, Lundstrom I, af Ekenstam CB,

Svensson A, Brånemark PI, Albrektsson T. Auger electron spectroscopic

studies of titanium implants. In: Lee AJC, editor. Clinical applications of

biomaterials. New York: Wiley. 1982. pp. 179–185.

[4-37] Liedberg B, Ivarsson B, Lundstrom I. Fourier transform infrared reflection

absorption spectroscopy (FTIR-RAS) of fibrinogen adsorbed on metal

and metal oxide surfaces. J Biochem Biophys Method 1984;9:233–243.

[4-38] Hanawa T. Titanium and its oxide film: a substrate for formation of

apatite. In: The bone-biomaterial interface. Davies JE, editor. Toronto:

University of Toronto Press. 1991. pp. 49–61.

[4-39] Healy KE, Ducheyne P. Hydration and preferential molecular adsorption

on titanium in vitro. Biomaterials 1992;13:553–561.

[4-40] Healy KE, Ducheyne P. The mechanisms of passive dissolution of tita-

nium in a model physiological environment. J Biomed Mater Res

1992;26:319–338.

[4-41] Brånemark PI. Introduction to osseointegration. In: Tissue-integrated

protheses. Brånemark PI, editor. Chicago: Quintessence Publishers. 1985.

pp. 63–70.

[4-42] Kasemo B, Lausmaa J. Metal selection and surface characteristics. In:

Tissue-integrated protheses. Brånemark PI, editor. Chicago: Quintessence

Publishers. 1985. pp. 108–115.

[4-43] Meachim G, Williams DF. Changes in non-osseous tissue adjacent to tita-

nium implants. J Biomed Mater Res 1973;7:555–572.

[4-44] Ferguson AB, Akahoshi Y, Laing PG, Hodge ES. Characteristics of trace

ions released from embedded metal implants in the rabbit. J Bone Joint

Surg 1962;44-A:323–336.

[4-45] Ducheyne P, Williams G, Martens M, Helsen J. In vivo metal-ion release from

porous titanium-silver material. J Biomed Mater Res 1984;18:293–308.

[4-46] Ducheyne P, Healy KE. Surface spectroscopy of calcium phosphate

ceramic and titanium implant materials. In: Surface characterization of

biomaterials. Ratner BD, editor. Amsterdam: Elsevier Science. 1988.

pp. 175–192.

[4-47] Albreksson T, Hansson HA. An ultrastructural characterization of the

interface between bone and sputtered titanium or stainless steel surfaces.

Biomaterials 1986;7:201–205.

[4-48] Wyckoff RWG. The structure of crystals. New York: Chemical Catalog

Co. 1931. pp. 134, 239.

[4-49] Tang H, Prasad K, Sanjinès R, Schmid PE, Lévy F. Electrical and optical

properties of TiO

anatase thin films. J Appl Phys 1994;75:2042–2047.

Oxidation and Oxides 99

Else_BBTM-OSHIDA_ch004.qxd 9/15/2006 8:41 AM Page 99

[4-50] Douglass DL, van Landuyt J. The structure and morphology of oxide films

during the initial stages of titanium oxidation. Acta Met 1966;14: 491–503.

[4-51] Nakayama T, Oshida Y. Effects of surface working on the structure of

opxide films by wet oxidation in austentic stainless steels. Trans Jpn Inst

Metals 1971;12:214–217.

[4-52] Mahla EM, Nielsen NA. A study of films isolated from passive stainless

steels. Trans Elctrochem Soc 1948;81:913–916.

[4-53] Nakayama T, Oshida Y. Identification of the initial oxide films on 18-8

stainless steel in high temperature water. Corrosion 1968;24:336–337.

[4-54] Kuphasuk C, Oshida Y, Andres CJ, Hovijitra ST, Barco MT, Brown DT.

Electro-chemical corrosion of titaniuim and titanium-based alloys.

J Prosthet Dent 2001;85:195–202.

[4-55] Lim YJ, Oshida Y, Andres CJ, Barco MT. Surface chacterization of variously

treated titanium materials. Int J Oral Maxillofac Implants 2002;16:333–342.

[4-56] Cullity BD. Elements of X-ray diffraction. Reading, MA: Addison-

Wesley. 1978. pp. 86–89.

[4-57] Schwartz LH, Cohen JB. Diffraction from materials. Heidelberg:

Springer, 1987. pp. 46–49.

[4-58] American Society for Testing and Materials. X-ray powder data file.

Philadelphia: American Society for Testing and Materials. 1960.

[4-59] GAuszek J, Masalski J, Furman P, Nitsch K. Structural and electrochemi-

cal examinations of PACVD TiO

films in Ringer solution. Biomaterials

1997;18:789–794.

[4-60] Liu X, Ding C. Plasma sprayed wollastonite/TiO

composite coatings on

titanium alloys. Biomaterials 2002;23:4065–4077.

[4-61] Browne M, Gregson PJ. Surface modification of titanium alloy implants.

Biomaterials 1994;15:894–898.

[4-62] Takemoto S, Yamamoto T, Tsuru K, Hayakawa S, Osaka A, Takashima S.

Platelet adhesion on titanium oxide gels: effect of surface oxidation.

Biomaterials 2004;25:3845–3892.

[4-63] Allen KW, Alsalim HS. Titanium and alloy surfaces for adhesive bond-

ing. J. Adhesion 1974;6:229–237.

[4-64] Felske A, Plieth WJ. Raman spectrcoscopy of titanium dioxide layers.

Electrochim Acta 1989;34:75–77.

[4-65] Matthews A. The crystallization of anatase and rutile from amorphous

titanium dioxide under hydrothermal conditions. Am Miner

1976;61:419–424.

[4-66] Yahalom J, Zahavi J. Electrolytic breakdown crystallization of anodic

oxide films on Al, Ta and Ti. Electrochem Acta 1970;15:1429–1435.

[4-67] Ohtsuka T. Structure of anodic oxide films on titanium. Surface Sci

1998;12:799–804.

[4-68] Liang B, Fujibayashi S, Neo M, Tamura J, Kim H-M, Uchida M, Kikubo T,

Nakamura T. Histological and mechanical investigation of the bone-bond-

ing ability of anodically oxidized titanium in rabbits. Biomaterials 2003;24:

4959–4966.

100 Bioscience and Bioengineering of Titanium Materials

Else_BBTM-OSHIDA_ch004.qxd 9/15/2006 8:41 AM Page 100

[4-69] Koizumi T, Nakayama T. Structure of oxide films formed on Ti in boiling

dilute H

and HCl. Corr Sci 1968;8:195–199.

[4-70] Ask M, Lausmaa J, Kasemo B. Preparation and surface spectroscopic

characterization of oxide films on Ti6Al4V. Appl Surf Sci 1988/1989;35:

283–301.

[4-71] Lausmaa J, Kasemo B, Mattsson H, Odelius H. Multiple-technique sur-

face characterization of oxide films on electropolished and anodically

oxidized titanium. Appl Surf Sci 1990;45:189–200.

[4-72] Michaelis A, Schultze JW. Effect of anisotropy on microellipsometry in

the Ti/TiO

system. Thin Solid Films 1993;233:86–90.

[4-73] Tomkiewicz M. Relaxation spectrum analysis of semiconductor-elec-

trolyte interface-TiO

J Electrochem Soc 1979;126:2220–2225.

[4-74] Dolata M, Kedzierzawski P, Augustynski J. Comparative impedance spec-

troscopy study of rutile and anatase TiO

film electrodes. Electrochim

Acta 1996;41:1287–1293.

[4-75] http://www.highbeam.com/doc./1G1:102604482/Photocatalyst.

[4-76] Sutherland DS, Forshaw PD, Allen GC, Brown IT, Williams KR. Surface

analsyis of titanium implants. Biomaterials 1993;14:893–899.

[4-77] Lausmaa GJ, Kasemo B. Surface spectroscopic characterization of tita-

nium implant materials. Appl Surf Sci 1990;44:133–146.

[4-78] Kubaschewski O, Hopkins BE. Oxidation of metals and alloys. London:

Butterworths. 1962. p. 24.

[4-79] Tummler H, Thull R. Model of the metal/tissue connection of implants

made of titanium or tantalum. Biological and biochemical performance

of biomaterials. Netherlands: Elsevier. 1986. pp. 403–408.

[4-80] Eliades T. Passive film growth on titanium alloys: physiochemical and

biologic considerations. Int J Oral Maxillofac Implant 1997;12:

621–627.

[4-81] Drath DB, Karnovsky ML, Superoxide production by phagocytic leuko-

cytes. J Exp Med 1975;144:257–261.

[4-82] Root BK, Metcalf JA. H

release from human granulocytes during

phagocytosis: Relationship to superoxide anion formation and cellular

catabolism of H

. Studies with normal and cytochalasin B-treated

cells. J Clin Invest 1977;60:1266–1279.

[4-83] DeChatelet LR. Oxide bactericidal mechanisms of PMN. J Infect Dis

1975;131:295–303.

[4-84] Milošev I, Metikoš-Hukovic´ M, Strehblow H-H. Passive film on

orthopaedic TiAlV alloy formed in physiological solution investigated by

X-ray photoelectron spectroscopy. Biomaterials 2000;21:2103–2113.

[4-85] Kovacs, P. Electrochemical techniques for studying the corrosion behav-

iour of metallic implant materials. Corrosion ’92, NACE Conference

Proceedings 1992;214:1–214.

[4-86] Sundararajan T, Kamachi MU, Mair KGM, Rajeswari S, Subbiyan M.

Surface characterization of electrochemically for passive film on nitrogen

implanted Ti6Al4V alloy. Mater Trans JIM 1998;39:756–761.

Oxidation and Oxides 101

Else_BBTM-OSHIDA_ch004.qxd 9/15/2006 8:41 AM Page 101

[4-87] Okazaki Y, Tateishi T, Ito Y, Corrosion resistance of implant alloys in

pseudo physiological solution and role of alloying elements in passive

films. Mater Trans JIM 1998;38:78–84.

[4-88] Hernardez de Gatica NL, Jones GL, Gardella JA Jr. Surface characteri-

zation of titanium alloys sterilized for biomedical applications. Appl Surf

Sci 1993;68:107–121.

[4-89] Pham MT, Zyganow I, Matz W. Corrosion behaviour and microstructure

of titanium implanted with  and  stabilizing elements. Thin Solid Films

1997; 310:251–259.

[4-90] Sodhi RNS, Weninger A, Davis JE, Sreenivas K. X-ray photoelectron

spectroscopic comparison of sputtered Ti, Ti6Al4V, and passivated bulk

metals for use in cell culture techniques. J Vac Sci Technol A 1991;A9:

1329–1333.

[4-91] Maeusli P-A, Bloch PR, Geret V. Steinmann SG. In: Biological and bio-

mechanical performance of biomaterials. Christel P, Meunier A, editors.

Amsderdam: Elsevier. 1986. p. 57.

[4-92] O’Brien B, Carroll WM, Kelly MJ. Passivation of nitinol wire for vascular

implants – a demonstration of the benefits. Biomaterials 2002;23:

1739–1748.

[4-93] Metikoš-Hukovic´ M, Kwokal A, Piljac J. The influence of niobium and

vanadium on passivity of titanium-based implants in physiological solu-

tion. Biomaterials 2003;24:3765–3775.

[4-94] Ohtsuka T, Masuda M, Sato N. Cathodic reduction of anodic oxide films

formed on titanium. J Electrochem Soc 1987;134:2406–2410.

[4-95] Heusler KE. The influence of electrolyte composition on the formation

and dissolution of passivating films. Corr Sci 1989;29:131–147.

[4-96] Arsov Lj D. Dissolution electrochimique des films anodiques du titane

dans l’acide sulfurique. Electrochim Acta 1985;12:1645–1657.

[4-97] Sul Y-T, Johansson CB, Petronis S, Krozer A, Jeong Y, Wennerberg A,

Albrektsson T. Charactristics of the surface oxides on turned and elec-

trochemically oxidized pure titanium implants up to dielectric break-

down: the oxide thickness, micropore configuration, surface roughness,

crystal structure and chemical composition. Biomaterials 2002;23:

491–501.

[4-98] Shibata T, Zhu Y-C. The effect of film formation potential on the sto-

chastic processes of pit generation on anodized titanium. Corr Sci

1994;36:153–163.

[4-99] Tengvall P, Elwing H, Sjöqvist L, Lundström I. Interaction between

hydrogen peroxide and titanium: a possible role in the biocompatibility of

titanium. Biomaterials 1989;10:118–120.

[4-100] Jacob HS, Craddock PR, Hammerschmidt DE, Moldow CF. Induced

granulocyte aggregation – unsuspected mechanism of disease. New Engl

J Med 1980;302:789–794.

[4-101] Del Masestro RF, An approach to free radicals in medicine and biology.

Acta Physiol Scand (Suppl) 1980;492:153–168.

102 Bioscience and Bioengineering of Titanium Materials

Else_BBTM-OSHIDA_ch004.qxd 9/15/2006 8:41 AM Page 102

[4-102] Sundgren J-E, Bodö P, Lundström I, Berggren A, Hellem S. Auger elect-

ron spectroscopic studies of stainless steel implants. J Biomed Mater Res

1985;19:663–671.

[4-103] Tengvall P, Bjursten LM, Elwing H, Lunström I, Free radicals oxidation

of metal implants and biocompatibility. 2nd International conference of

biointercations ’87. London. 1987.

[4-104] Jaeger CD, Bard AJ. Spin-trapping and electron spin resonance detection

of radical intermediates in the photodecompositions of water at TiO

par-

ticulate systems. J Phys Chem 1979;83:3146–3151.

[4-105] Barb WG, Baxendale JH, George P, Hargrave KR. Recations of ferrous and

ferric ions with hydrogen peroxide. Trans Farady Soc 1951;47:462–500.

[4-106] Bielski BHJ. Fast kinetic studies of dioxygen-derived species and their

metal-complexes. Phil Trans R Soc Lond B 1985;311:473–482.

[4-107] Armstrong D. Free radicals in molecular biology, aging and disease. New

York: Raven Press. 1984.

[4-108] Janzén EG, Wang YY, Shetty RW. Spin-trapping with -(4-pyridyl-

1-oxide)-N-tert-nutylnitrone in aqueous solutions: a unique electron spin

resonance spectrum for the hydroxyl radical adduct. J Am Chem Soc

1978;100: 2923–2925.

[4-109] Tengvall P, Lundström I, Sjöqvist L, Elwing H, Bjursten LM. Titanium-

hydrogen peroxide interaction: model studies of the influence of the inflam-

matory response on titanium implants. Biomaterials 1989;10:166–175.

[4-110] Pan J, Thierry D, Leygraf C. Electrochemical and XPS studies of titanium

for biomaterial applications with respect to the effect of hydrogen perox-

ide. J Biomed Mater Res 1994;28:113–122.

[4-111] Bianchi G, Malaguzzi S. Cathodic reduction of oxygen and hydrogen per-

oxide on titanium. Proceedings of 1st international congress of metallic

corrosion London, April 10–15. 1961. pp. 78–83.

[4-112] Pan J, Thierry D, Leygraf C. Hydrogen peroxide toward enhanced oxide

growth on titanium in PBS solution: blue coloration and clinical rele-

vance. J Biomed Mater Res 1996;30:393–402.

[4-113] Pan J, Liao H, Leygraf C, Thierry D, Li J. Variation of oxide films on tita-

nium induced by osteoblast-like cell culture and the influence of an H

pretreatment. J Biomed Mater Res 1998;40:244–256.

[4-114] Albrektsson T. The response of bone to titanium implants. CRC Crit Rev

Bicompat 1984;1:53–84.

[4-115] Bearinger JP, Orme CA, Gilbert JL. Effect of hydrogen peroxide on tita-

nium surfaces: in situ imaging and step-polarization impedance spec-

troscopy of commercially pure titanium and titanium, 6-aluminum,

4-vanadium. J Biomed Mater Res 2003;67A:702–712.

Oxidation and Oxides 103

Else_BBTM-OSHIDA_ch004.qxd 9/15/2006 8:41 AM Page 103

Chapter 5

Mechanical and Tribological Behaviors

5.1. Fatigue 107

5.2. Fracture and Fracture Toughness 111

5.3. Biotribological Actions 113

5.3.1 General 113

5.3.2 Friction 114

5.3.3 Wear and Wear Debris Toxicity 116

References 120

Else_BBTM-OSHIDA_ch005.qxd 9/16/2006 11:23 AM Page 105

Else_BBTM-OSHIDA_ch005.qxd 9/16/2006 11:23 AM Page 106

107

Chapter 5

Mechanical and Tribological Behaviors

Biomechanics includes all facets of musculoskeletal, cardiovascular, respiratory,

implant–tissue interface, mechanics of prostheses, and mechanisms of chewing.

Given such a wide range of coverage, the area of interest becomes much narrower

when considering titanium applications only. Simultaneously, however, biome-

chanics is a multidisciplinary field, requiring various basic knowledge including

statics and dynamics, elasticity and plasticity, fatigue, fracture mechanics and

toughness, and tribological actions. Materials in bioengineering, in a broad sense,

range widely from very small units, such as a virus or bacteria, to very large and

complex, such as a healthy human body. They also cover the various products

manufactured by using the methodologies in connection with biological disci-

plines.

Based on the above argument, in this chapter, fatigue, fracture, and biotribolog-

ical actions, such as friction and wear as well as wear debris toxicity, will be dis-

cussed.

5.1. FATIGUE

Fatigue is the loss of strength and other important properties as a result of stress-

ing over a quite long period of time. Fatigue is very important, as it is the single

largest cause of failures in metals, estimated as about 90% of metallic failures,

polymers and ceramics are also susceptible to this type of failure. Fatigue is a very

general phenomenon in most materials and even living organisms. The ‘Fatigue’ is

originally from Latin ‘Fatigare’. The term itself is derived from fatigue meaning

‘to tire’. The root ‘fati’ refers literally to an opening or yawning phenomenon

vividly descriptive of fatigue in people, and especially, in view of ubiquity of craz-

ing and cavitation, in materials as well [5-1].

Fatigue has often been observed in Ti and Ti alloys, and is considered as an

important cause to the failure of the materials. For example, fatigue failure has

been reported in dental implants [5-2], removable partial denture (RPD) frame-

work [5-3], clasps [5-4, 5-5], plates, pedicle screws and cables [5-6–5-9]. The

cyclic loading applied to orthopedic implants during body motion results in an

alternating localized plastic deformation of microscopically small zones of stress

concentration produced by notches or microstructural inhomogeneities [5-9].

Mechanical environments related to fatigue may be divided into two distinct

Else_BBTM-OSHIDA_ch005.qxd 9/16/2006 11:23 AM Page 107

groups: strain-controlled and stress-controlled. Although practically most fatigue

environments in human body are a combination of the two, the highly compliant

nature of biological materials tends to place them toward the direction of strain-

controlled fatigue [5-10]. Examples for strain-controlled application include pace-

maker leads, which require a conductive metal that can survive very high numbers

of flexing motions without breaking, and clasps of RPD, which require adequate

retention for insertion and removal of the device [5-11]. Lin et al. [5-12] employed

the tension-to-tension stress mode for fatigue tests on titanium materials (CpTi, Ti-

13Nb-13Zr, Ti-6Al-4V, and Ti-7.5Mo) in air under R (stress ratio ⫽ 

min

/

max

) of

0.1, with frequency of 10 Hz. It was found that (i) Ti-6Al-4V and CpTi have higher

stress-controlled fatigue

resistance, but lower strain-controlled fatigue (see foot-

note 1) resistance than Ti-7.5Mo and Ti-13Nb-13Zr, (ii) Ti-7.5Mo demonstrates

the best strain-controlled fatigue performance, and (iii) the fatigue cracks almost

always initiate from casting-induced surface/subsurface pores [5-12].

Clasps undergo permanent deformation to cause fatigue fracture under repeated

flexures during denture insertion and removal, and masticatory actions [5-13–5-

16]. The fatigue life of cast clasps made of CpTi was reported to be shorter than

that of Co-Cr and gold alloy clasps [5-11]. However, the fatigue fracture and per-

manent deformation of cast claps made of Ti-based alloy has not been sufficiently

assessed in relation to stress distribution, and little is known about how these

clasps would function in long-term clinical use. Permanent deformation and

fatigue fracture are caused by the stress created in the clasp [5-17, 5-18]. The stress

distribution may depend on the elastic modulus of the alloy, dimensions and cur-

vature of the clasp [5-19, 5-20], and amount and direction of deflection in relation

to the abutment undercut [5-21]. Mahmoud et al. [5-22] investigated the gold alloy

and Ti-6Al-7Nb, which were subjected to cyclic deflection of pre-set values of

0.25, 0.50, and 0.75 mm for 10

cycles. It was concluded that the gold alloy

(70Au-4.4Pt-13.5Ag-8.8Cu-2Pd-0.1Ir) clasps exhibited significantly longer

fatigue lives, while the Ti-6Al-7Nb clasps showed significantly greater resistance

to permanent deformation under cyclic deflection [5-22].

108 Bioscience and Bioengineering of Titanium Materials

Stress-controlled fatigue test is conducted in such a way that repeated load is controlled between

pre-determined upper and lower stress levels. If the tested material is fully annealed to start with and

a work-hardening type, the material’s strength increases by repeated stressing. Hence, the severity of

fatigue process is getting milder. On the other hand, if the starting material’s condition is a work-soft-

ening type, its original strength decreases by cycles, resulting in shortening fatigue life. On the con-

trary, by the strain-controlled fatigue testing, each cycle is controlled between pre-set upper and

lower strain. If the fully annealed and work-hardening material is tested under the strain-controlled

fatigue mode, because the material strength increases by cyclic loading, the applied stress needs to

increase to maintain the pre-set level of upper strain. On the other, by the work-softening type mate-

rials, applied stress level decreases.

Else_BBTM-OSHIDA_ch005.qxd 9/16/2006 11:23 AM Page 108