Notched stress-strain behavior of a conventional and a sequentially annealed highly crosslinked UHMWPE.
Contemporary total joint replacement designs contain stress-risers such as fillets, grooves, and undercuts; therefore, it is of interest to analyze the behavior of UHMWPEs in the presence of such design-related stress-risers. This study examined the engineering and true axial stress-strain behavior of smooth cylindrical and notched cylindrical test specimens, under applied axial tensile loading (2 displacement rates, 37 degrees C) for a conventional and a highly crosslinked second generation UHMWPE. Both materials were prepared from ram extruded GUR 1050. The conventional material (30 kGy) was gamma sterilized at 30 kGy in an inert N(2) environment. The sequentially annealed material (SA) was gamma irradiated at 30 kGy and annealed for 8h at 130 degrees C. The irradiation-annealing process was repeated two more times for an overall irradiation dose of 90 kGy. Differential scanning calorimetry (DSC) was utilized to investigate changes in crystallinity and lamellar thickness distributions upon loading. Fractographic analysis of scanning electron microscope (SEM) images of fracture surfaces was performed to investigate changes in fracture micromechanism with notching. Both the 30 kGy and SA materials, in the smooth condition, demonstrated substantial ductility and orientation hardening. With the introduction of a notch, both materials demonstrated an elevation in the yield stress (notch strengthening) and a reduction in the ultimate stress and ultimate strain at both displacement rates. Additionally, it was found that the uniaxial stress-state (smooth condition) allowed for greater changes in crystallinity and the lamellar thickness distributions, when compared to the untested materials, than the triaxial stress-state induced by the notched geometry.
Sobieraj
Michael C
MC
Musculoskeletal Mechanics and Materials Laboratories, Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, USA.
Kurtz
Steven M
SM
Wang
A
A
Manley
Michael M
MM
Rimnac
Clare M
CM
D001672:Biocompatible Materials / Q000737:chemistry; D001729:Bismuth; D019245:Compressive Strength; D003432:Cross-Linking Reagents / Q000737:chemistry; D008422:Materials Testing; D009942:Organometallic Compounds; D011095:Polyethylenes / Q000737:chemistry; D019736:Prostheses and Implants; D012459:Salicylates; D013718:Tensile Strength
D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D009942:Organometallic Compounds; D011095:Polyethylenes; D012459:Salicylates; C111601:ultra-high molecular weight polyethylene; C015715:bismuth subsalicylate; D001729:Bismuth
J Bone Joint Surg Am. 2000 Dec;82-A(12):1708-25
11130644
Biomaterials. 2002 Sep;23(17):3681-97
12109694
J Biomed Mater Res. 2002 Sep 5;61(3):430-9
12115468
Biomaterials. 2003 Oct;24(22):3947-54
12834590
Biomaterials. 2004 Jan;25(1):9-21
14580904
Clin Orthop Relat Res. 2006 Dec;453:265-71
17016228
Biomaterials. 2005 Apr;26(11):1271-86
15475057
J Biomed Mater Res. 1982 Jul;16(4):399-405
7107657
J Orthop Res. 1999 Mar;17(2):157-67
10221831
Biomaterials. 2005 Jun;26(17):3411-26
15621230
Biomaterials. 2005 Nov;26(33):6430-9
15935468
Biomaterials. 2005 Mar;26(8):905-15
15353202