Zirconia-toughened alumina (ZTA) currently represents the bioceramic gold standard for load-bearing components in artificial hip joints. ZTA is long known for its high flexural strength and fracture ...toughness, both properties arising from a microscopic crack-tip shielding mechanism due to the stress-induced tetragonal-to-monoclinic (t→m) polymorphic transformation of zirconia. However, there have been concerns over the years regarding the long-term structural performance of ZTA since the t→m transformation also spontaneously occurs at the material's surface under low-temperature environmental conditions with a concomitant degradation of mechanical properties. Spontaneous surface degradation has been extensively studied in vitro, but predictive algorithms have underestimated the extent of in vivo degradation observed in retrievals. The present research focused on burst-strength assessments of Ø28 mm ZTA femoral before and after long-term in vitro hydrothermal ageing according to ISO 7206-10. An average burst strength of 52 kN was measured for pristine femoral heads. This value was ~36% lower than results obtained under the same standard conditions by other authors. A further loss of burst strength (~13% in ultimate load) was observed after hydrothermal ageing, with increased surface monoclinic content ranging from ~6% to >50%. Nevertheless, the repetitively stressed and hydrothermally treated ZTA heads exceeded the minimum burst strength stipulated by the US Food and Drug Administration (FDA) despite severe test conditions. Lastly, Raman spectroscopic assessments of phase transformation and residual stresses on the fracture surface of the femoral heads were used to clarify burst-strength fluctuations and the effect of hydrothermal ageing on the material's overall strength degradation.
Xenogeneic extracellular matrix (ECM) can be harvested and configured to function as a bioscaffold for tissue and organ reconstruction. The mechanical properties of the ECM vary depending upon the ...tissue from which it is harvested. Likewise, the manufacturing steps required to develop ECMs into medical grade devices will affect the surface morphology and the mechanical properties of the bioscaffold; important properties for constructive tissue remodeling. The present study compared the ball-burst strength of five different ECM scaffolds before and after treatment with peracetic acid (PAA): porcine small intestinal submucosa (SIS), porcine urinary bladder submucosa (UBS), porcine urinary bladder matrix (UBM), a composite of UBS+UBM, and canine stomach submucosa (SS). This study also compared the mechanical properties of 2- and 4-layer ECM scaffolds. Results showed 2-layer SS devices had the highest ball-burst value of all 2-layer ECM devices. Moreover, all 4-layer ECM devices had similar ball-burst strength except for 4-layer UBM devices which was the weakest. PAA-treatment decreased the ball-burst strength of SS and increased the ball-burst strength of UBS 2-layer devices. This study showed the material properties of the ECM scaffolds could be engineered to mimic those of native soft tissues (i.e. vascular, musculotendinous, etc) by varying the number of layers and modifying the disinfection/sterilization treatments used for manufacturing.
In an effort to make laparoscopic suturing more efficient, the V-Loc advanced wound closure device (Covidien, Mansfield, MA) has been produced. This device is a self-anchoring barbed suture that ...obviates the need for knot tying. The goal of this initial feasibility study was to investigate the use of the barbed suture in gastrointestinal enterotomy closure. A randomized study of 12 pigs comparing enterotomy closure with barbed versus a nonbarbed suture of similar tensile strength was performed. To this end, 25 mm enterotomies were made in the stomach (1 control, 1 treatment), jejunum (2 controls, 2 treatments), and descending colon (1 control, 1 treatment). Animals were killed at 3, 7, and 14 days postoperatively (4 each group) and their gastrointestinal tracts harvested; 6 of the 8 enterotomies from each pig underwent burst strength testing. The remaining 2 were fixed in formalin and sent for histological examination. All 12 pigs survived until they were killed without any major complications. Enterotomy closure with barbed suture revealed adhesion scores, burst strength pressures, and histology scores that were similar to those for the control. Jejunal closures resulted in 6 failures at 7 days (3 control, 3 barbed) and 4 failures at 14 days (2 control, 2 barbed). The barbed suture significantly reduced suturing time in the stomach, jejunum, and colon. The V-Loc wound closure device appears to offer comparable gastrointestinal closure to 3-0 Maxon while being significantly faster. Further studies with V-Loc are required to assess its use in laparoscopic surgery.
Oil and gas pipelines are susceptible to various forms of damage where repair mechanisms have since been developed for rehabilitation. Once installed, structural health monitoring often incurs ...excessive costs and defects rectification of the repaired pipeline becomes a major challenge. Finite element analysis (FEA) provides a rapid route to predict the behaviour of the rehabilitated pipelines under prescribed in-service conditions. In this paper, burst strength of a commercially available composite sleeve repair system, Helicoid Epoxy Sleeve (HES)™, which combines the use of carbon fibre strip and epoxy grout as reinforcement to damaged pipe, was investigated through experimental and numerical approaches. Design standards for subsea pipelines are used in the calculation of design pressure and burst pressure. In the experimental setup, API 5L X52 steel pipe was machined with 50% metal loss defect in wall thickness to simulate external corrosion. Results from design calculations, experimental and FEA showed good correlation with margin less than 10%.
One of the topics for the phase 2 of GTR13(HFCV) activity is the study of an appropriate burst pressure of tanks. For this study, we evaluated any degradation and variability of the burst pressure ...due to hydraulic sequential tests on 70MPa compressed-hydrogen tanks. When the burst pressure after the hydraulic sequential testing was compared with the initial burst pressure, the pressure proved to have dropped by a few percent while the variation increased, and the main factor for the increase in the burst pressure variation was considered to be the drop test comprising the sequential tests.
This study conducts failure analysis of filament wound glass reinforced plastic (GRP) pipes made of E-glass/epoxy with an inclined surface crack under open-ended internal pressure. Test specimens are ...composed of six antisymmetric layers with (±55°)
3 winding angles. Tests have been performed at seven different crack angles:
0
°
,
15
°
,
30
°
,
60
°
,
45
°
,
75
°
, and
90
°
, with crack-to-thickness ratio of
a
/
t
=
0.50
. The burst strengths of the specimens were determined, and the dependence of the burst strength on the crack angle was examined.
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