Constructive and biomechanical properties of material of decalcified bone matrix impregnated with bone cement

AIM:To analyze constructive and biomechanical properties of different quality ratio material impregnated decalcified bone matrix (DBM) with bone cement (BC).M ETHODS:The DBM particles and the materials impregnated 0 mg/g, 300 mg/g and 400 mg/g mass ratio DBM particles with BC were made according to the methods of Uris t et al.The compound material constructions were observed by scanning electron m icroscope and the biomechanical properties were measured by Instron mechanics te sting-machine.RESULTS:The DBM particles with irregular gaps existing within int erspace were connected with BC by the multipoint mode in the compound material. The ultimate compressive strength were 0 mg/g DBM in (59.3±2.2) MPa, 300 mg/g i n (27.1±1.8) MPa, 400 mg/g in (19.3±1.6) MPa.The ultimate bending strength wer e 0 mg/g in (54.3±3.7) MPa, 300 mg/g in (18.5±1.1) MPa, 400 mg/g in (13.3±1.4 ) MPa.CONCLUSION:The materials of DBM impregnated with BC had perfect plastic pr operty with much more irregular gaps existing within interspace.The materials co uld provide abundant biomechanical support.

Effect of Pre-loading on Short Fatigue Crack Growth at a Notch

Results indicate that under cyclic tension the growth rate of short fatigue crack from notch root will be lowered greatly by tensile pre-loading,but only a little change by compressive pre-loading. The effect of tensile pre-loading will decrease with the increase of stress ratio.The variation of short fatigue crack growth rate is related to the residual stress distribution around notch root.

Theoretical Study of Fatigue Limit for Crack

The material parameter ρ*=4c/σ-13 is put forward, which represents the crack tip radius independent of crack length under the action of the fatigue limit stress. According to the fatigue notch factor of the crack propagation, Kt=Kt1/（3+n）=（4d/ρ*）1/3, the fatigue limits of sharp notch, long crack and short crack are calculated, which are very close to the measurements. The calculated results make it clear that for surface crack the transition point from long crack to short crack is a*=(ΔKth3/12.8c)2, the range of physical short crack （as） is ρ*/4≤as≤a*, the threshold of the fatigue crack initiation is ΔKth（i）=0.66 Δσ-1 （πρ*/4）1/2, the material parameter that indicates the fatigue crack sensitivity is ρ*/a*, which represents the blunting condition of crack tip under the action of the fatigue limit stress.

Prediction of Fatigue Notch Factor for Metallic Materials

The fatigue notch factors （Kf） of metallic materials with high and low notch sensitivities, which have been derived in theory, are Kt1/（1+n） and Kt2/（3+n） respectively. The diagram of Kf vs. Kt is obtained by means of comprehensive analysis of alarge number of data, and the applicable range of the above two Kc relations is given. The calculation results for steel and aluminum alloy agree with the measured values very well.The fatigue limit of smooth specimens are also derived in this paper, i. e. σtheory=（K/En）1/（1+n）. The calculation results are σtheory=σcy （cyclic yield strength）.