CN104975157A - Newly developed technology application for stainless steel for biomedical implants - Google Patents

Abstract

The invention relates to a method for using surface mechanical attrition treatment (SMAT) of a plurality of spheres to treat the surface of metal alloy under a set of conditions to obtain a metal base which is suitable for medical implants and has high yield strength and hardness, low cytotoxicity, high cell compatibility and high blood compatibility. The plurality of spheres comprise 316L stainless steel spheres or zirconia (ZrO2) spheres.

Description

For the technology application stainless newly developed of biomedical implant

The cross reference of related application

The application is the application number submitted on August 1st, 2014 is the part continuation application of 14/449, No. 158 non-provisional, the content of this application is all herein incorporated by way of reference.

Technical field

The present invention relates to the method for the grid (lattice) of nanostructure and the grid for the manufacture of this nanostructure, more specifically, relate to the grid of the nanostructure manufactured by surface mechanical attrition (attrition) treatment process specially.

Background technology

Grid, due to its intrinsic porous character, is applied to light structures usually, the frame roof in such as truss-type bridges, stadium and telescope holder.In simple two dimension (2D) space, common periodicity grid is by the geometric configuration of the regular polygon as equilateral triangle, square and regular hexagon.See Fig. 1 (Ashby and Gibson, 1997; Fleck etc., 2010).

But in some cases, the mechanical property of grid, as tensile strength, hardness or ductility, can not meet the needs of some application scenario completely.

Stainless steel 316 L combines because of the excellence of mechanical property, erosion resistance and biocompatibility, is the traditional material that can be used in manufacturing angiocarpy bracket.But, with some other metallic biomaterials for support (such as, cochrome, Co-Cr) compare, 316L SS is still poor in yield strength and hardness, therefore for meeting mechanicalness requirement, the strut thickness (~ 150 μm) of 316L SS support should be much thicker than the strut thickness of Co-Cr support (~ 90 μm).Through metal is foreign matter concerning human body, its get involved after target blood because of the harmful structure easily causing such as inflammation and immunological rejection react often cause blood vessel intervene for a long time after may again narrow.Confirmed by patient treatment outcome, the support with thicker pole more easily causes the restenosis of sufferer blood vessel compared with having the support of thinner pole.And the pole of support is too thick will reduce its snappiness, and therefore it becomes more difficult by guide catheter and by crooked position coronarius.Also there are some other problems in the through metal used clinically at present, the release of such as potential toxicity Ni, relatively high cytotoxicity, for the low cell compatibility of specific cells kind (such as, endotheliocyte) and low blood compatibility.

CN101899554A discloses a kind of Ni-Ti alloy, and this Ni-Ti alloy uses plasma nitridation process after surface mechanical attrition treatment (SMAT), to improve the hardness of Ni-Ti alloy.Although illustrated that in CN101899554A plasma nitridation process is to improve the hardness of Ni-Ti alloy, but the plasma nitrided effect to other metal alloy may not be desirable, especially stainless steel, this is because the high content iron in stainless steel becomes unstable after plasma nitridation.Plasma nitrided also making discharges increase from those metal alloys Ni, and the release of high-content Ni is unfavorable for Growth of Cells, is thus unfavorable for the tissue regeneration of the frame peripheral made by those metal alloys.

Therefore, need a kind of like this 316L SS alloy as the biomaterial for the manufacture of implanted medical devices: this 316L SS alloy has higher yield strength and hardness, Ni release reduces, cytotoxicity is relatively low, Human Umbilical Vein Endothelial Cells has higher cell compatibility, and blood compatibility also increases.

Summary of the invention

Therefore, main aspect of the present invention is to provide a kind of method that surface mechanical attrition treatment (SMAT) that application has multiple spheroids of desired size and weight under one group of operational condition processes the metal substrate surface for Medical implant.These conditions include but not limited to vibrational frequency, amplitude and treatment time.In the exemplary embodiment, the spheroid for the treatment of metal substrate surface can be the 316L stainless steel spheroid or the zirconium white (ZrO that are of a size of about φ 3.0mm ₂) spheroid.It is (bright finished) 316L stainless steel plate by the metal base by the SMAT process with spheroid.In another embodiment, in order to process the metal base being of a size of 100mm x 50mm x 0.9mm, the gross weight of spheroid is approximately 20g.There is provided the enclosing with chamber, this enclosing support metal substrate and spheroid of the present invention, to perform SMAT to metal base.Chamber is also constructed to support vibrating device on the opposite side of metal base, to produce the vibrational frequency of about 20,000Hz, thus spheroid is moved towards metal base along chamber, processes the surface of metal base.In another embodiment, the working amplitude of vibrating device is approximately 80%.Treatment time on every side of metal base is approximately 15 minutes; Therefore 30 minutes are approximately total time for the treatment of the both sides of metal base.Total time for the treatment of the both sides of metal base can be divided into four time periods: (i) was from the 0th minute to the 1st minute; (ii) from the 1st minute to the 5th minute; (iii) from the 5th minute to the 29th minute; And (iv) was from the 29th minute to the 30th minute.In each time period, in order to perform SMAT to every side of metal base, utilize the average duration of at every turn knocking of spheroid of the present invention for knock 5 seconds to 15 seconds at every turn.Should avoid in the present invention carrying out plasma nitridation process before SMAT.

Accompanying drawing explanation

Below with reference to the accompanying drawings, each embodiment of the present invention is described in more detail, wherein:

Fig. 1 shows difform grid of the prior art;

Fig. 2 shows in prior art, for producing the schematic diagram of the device of nanostructure in SMAT process;

Fig. 3 A-3D shows the grid of the nanostructure of the Four types according to different embodiments of the invention;

(A) in Fig. 4-(C) shows the SMAT process carried out according to employing scheme (strategy) AI, option A II and the option A III3 each unit cell to square grid of the embodiment of the present invention;

(A) and (B) in Fig. 5 respectively illustrates the geometry with the empirically sample of 0/90 ° of square grid and having ± 45 ° of square grids according to the embodiment of the present invention;

(A) and (B) in Fig. 6 respectively illustrates two the 0/90 ° of square grids using SMAT-option A II according to whole use SMAT-option A I of the embodiment of the present invention and part;

(C) and (D) in Fig. 6 respectively illustrates two ± 45 ° square grids using SMAT-option A III according to whole use SMAT-option A I of the embodiment of the present invention and part;

Fig. 7 A-7B respectively illustrates the result of the square grid of 0/90 ° of square grid and ± 45 ° measured for the square grid in (A) in Fig. 6-(D);

(A) in Fig. 8-(C) respectively illustrates the 0/90 ° of square grid sample not using SMAT-scheme N, part use SMAT-option A II and all fractures of use SMAT-option A I according to the embodiment of the present invention;

(D) in Fig. 8-(F) respectively illustrate according to the embodiment of the present invention do not use SMAT-scheme N, part uses SMAT-option A III and all use SMAT-option A I distortion ± 45 ° of square grid samples;

(A) in Fig. 9-(C) shows the SMAT process adopting option b I, option b II and option b III to carry out each elementary cell in Kagome shape grid;

(A) and (B) in Figure 10 respectively illustrates the geometry of the horizontal Kagome shape grid sample according to the embodiment of the present invention and vertical Kagome shape grid sample;

(A) and (B) in Figure 11 respectively illustrates two the horizontal Kagome shape grids using SMAT-option b II according to whole use SMAT-option b I of the embodiment of the present invention and part;

(C) and (D) in Figure 11 respectively illustrates whole use SMAT-option b I according to the present invention and two the vertical Kagome shape grids partly using SMAT-option b III;

Figure 12 A-12B respectively illustrates the result of horizontal Kagome shape grid sample and the vertical Kagome shape grid sample measured about the Kagome shape grid in Figure 11 A-D;

(A) in Figure 13-(C) respectively illustrates and does not use SMAT-scheme according to the embodiment of the present invention , part uses SMAT-option b II and all uses the horizontal Kagome shape grid sample of fracture of SMAT-option b I;

(D) in Figure 13-(F) respectively illustrates and does not use SMAT-scheme according to the embodiment of the present invention , part uses SMAT-option b III and all uses the vertical Kagome shape grid sample of fracture of SMAT-option b I;

(A) in Figure 14-(C) respectively illustrates the uniaxial extension of the bending and stage that is dominant that the stretches ± 45 ° of square grids according to the having of the embodiment of the present invention initial bending be dominant the stage (regime), half beam element;

Figure 15 shows the schematic diagram how SMAT and spheroid being applied to the experimental installation of the metal base of Medical implant according to the embodiment of the present invention;

Figure 16 shows by SMAT and by the tensile strength test result of the metal base sample handled by different spheroid of the present invention;

Figure 17 illustrates by SMAT and with the hardness test result of the metal base sample handled by different spheroid of the present invention;

Figure 18 shows the shape characteristic of the different metal substrate by optical profile assay method: (A) is untreated; (B) 316L SS spheroid SMATization; (C) ZrO ₂spheroid SMATization;

Figure 19 shows by the time dependent viability test result of metal base sample handled by the SMAT with different spheroid of the present invention, this test is for endotheliocyte EA.hy926 cell: utilize One-way ANOVA to determine significance level, * the highest OD value (the best viability of endotheliocyte on sample); P<0.05;

Figure 20 shows the erythrocytic SEM photo be attached to by the metal base sample handled by the SMAT with different spheroid of the present invention: enlargement ratio x 500 (left column) and x 1000 (right row);

Figure 21 shows the change of erythrocytic prothrombin time (PT), thrombin time (TT) and activated partial thromboplastin time (APTT), and this red corpuscle is from the platelet poor plasma (PPP) by the metal base sample handled by the SMAT with different spheroid of the present invention is planted;

Figure 22 shows when carrying out/when not carrying out plasma nitridation process, by the Ni release profiles of the metal base sample handled by the SMAT with different spheroid of the present invention; And

Figure 23 shows when carrying out/when not carrying out plasma nitridation process, and by the Ni rate of release of the metal base sample handled by the SMAT with different spheroid of the present invention.

Embodiment

In the following description, set forth the grid of nanostructure and the corresponding embodiment of manufacture method thereof in the mode of preferred exemplary, in first US non-transitory patent application the 14/449th, in No. 158, disclosed this preferred exemplary.

This invention is the combination of the nano structural material that dot matrix topology (lattice topologies) is prepared with SMAT process.On the one hand, SMAT method significantly increases the intensity of metallic substance.On the other hand, dot matrix topology is designing these structures volume and geometrical aspects possess diversity.If both combine, SMAT-lattice work can be stronger, and can provide various geometrical dimension and moulding.

This invention relates to and carrys out Design and manufacture grid framework by the nano structural material by SMAT manufacture technics.Prior art US7,691, outline the method being produced solid nanostructure material by SMAT process in 211.This method has been proved to be able to the intensity significantly improving metallic substance (as stainless steel plate), see (2010) and Chen etc. (2011) such as document Chan.

Effectively prepare nano structural material by surface mechanical attrition treatment method can realize, see document Lu Ke and Lv Jian (1999 and 2004) and US7,691,211.As shown in Fig. 2 schematic diagram, in SMAT process, drive a large amount of cannonball by vibration machine, clash into material surface from different perspectives to make these bullets, cause grain-size on this surface by refinement, thus form the nanostructured layers with tens nano particle size sizes.Finally, the macro-mechanical property of this material, as intensity and hardness, be significantly improved (reference, Chan etc., 2010; Chen etc., 2011).

Fig. 2 shows prior art US7, and 691, the schematic diagram of the SMAT device of the ultrasonic generation nanostructure of the use in 211, is applied to implement this invention.In this embodiment of prior art, SMAT device comprises sound insulation chamber 25.Ultrasonic generator 24 is connected with bowl 20, and device 21 covers the open top of bowl 20, and device 21 is used for placing the sample 10 that will carry out under stress processing.Device 21 is arranged on relative to bowl 20 on the device of the distance between surface and the bottom surface of bowl 20 making it possible to adjust and be exposed to shock, and the bottom surface of bowl 20 forms the emitting surface of spheroid 22.Can in device to be processed or installation space 27 between its upholder and bowl 20.Ultrasonic principle spheroid being set to kinestate is used to be that by the ultrasonic generator 24 run with CF, spheroid 22 is kept in motion, it transmits the motion of particular amplitude and speed to bowl 20.The vibration amplitude of ultrasonic generator can be selected between several microns to hundreds of micron.Spheroid 22 obtains energy and with the surface of the multiple input angle a large amount of number of times impact sample 10 of change from the motion of bowl, and the shock gone up in any direction each time all causes the crystal grain generation viscous deformation be made up of the molecular grouping of alloy or material.Degradedness after spheroid and device contacts, from the surface rebound of bowl, and then obtain new speed on a new direction, this direction looks like random from the angle of sample, but it is determined by physical laws.In the sound insulation chamber 25 of sealing, arrange diffusion or evaporation unit 26, just can realize one or more chemistry as described below or thermochemical treatment, this may be relevant to needing the device in heating work chamber or sample.

In the invention, in order to reduce total mass and produce light structures, the hole of regular polygon (trilateral, square or hexagon) embeds in solid nanostructure material with uniform periodicity pattern.Fig. 3 A to 3D illustrates four kinds of lattice design.These design respectively: hexagonal grid (Fig. 3 A), triangular lattice (Fig. 3 B), square grid (Fig. 3 C) and Kagome shape grid (Fig. 3 D).

Fig. 3 A shows the design of hexagonal honeycomb shape grid.This grid only has the hole of identical regular hexagon shape.This some holes is arranged with periodicity pattern, so that this grid can along two of a two-dimensional space major axis X ₁and X ₂extend equably.

Fig. 3 B shows the design of triangular lattice.This grid only has the hole of identical equilateral triangular shape.This some holes is also with two major axis X of periodicity pattern along plane space ₁and X ₂arrangement.

Fig. 3 C shows the design of square grid.This grid only has the hole of identical square shape.This some holes is along two major axis X of plane space ₁and X ₂periodically arrange.

Fig. 3 D represents the design of Kagome shape grid.This grid has identical regular hexagon and the hole of equilateral triangular shape.This some holes arranges with periodicity pattern, so that this grid can along two of a two-dimensional space major axis X ₁and X ₂extend equably.

For the grid of every type, the feature of remaining solid bar framework is all that three geometric parameter (t, l, r): l are centerline length of the design of each bar part in grid; T is the thickness of the design of each bar part in grid; R is the radius of the design of the fillet of each node corner in grid.The object designing this arc reduces the stress concentration at node location place in grid.

The quality of each grid depends primarily on t and l, can change by changing these two parameter values.Such as, if ratio l/t >=30, then can think that this grid is thin (lightweight), and if 4≤l/t≤10, then can think thick (the heavy amount) of this grid.The design ratio of t/r is between 1 to 2.

According to embodiments of the invention, the grid manufacture method of nanostructure is as follows.First, initial solid material, through the process of SMAT process, is made as prior art US 7, and 691, the nano structural material in 211.Secondly, select the type of grid, and design the value of three parameters (l, t, r), to determine the size in the hole cut out from solid SMAT material.The accompanying drawing of grid is built when the value of (l, t, the r) of three designs also for programming in nc wire-cutting.Finally, cut out the hole of design from solid nanostructure material center line, thus obtain the grid of nanostructure.

In the invention, especially for two kinds of periodic lattice topological frameworks: square and Kagome shape, make nano structural material by the method for surface mechanical attrition treatment and measure.The SMAT scheme selected is applied to the bar part in the unit cell of considered each topological framework.Maximum axial stress in these bars calculates as the function of principle stress in macroscopical face.Determine the elastic limit of the grid using often kind of SMAT scheme with simple yield criteria, and the yield strength just improved and SMAT efficiency discuss the relative merits of these selection schemes.The experiment of the SMAT scheme selected by implementing the square be made up of stainless steel plate and Kagome shape grid, to assess for the analyses and prediction under the load condition of uniaxial extension.

As described below to the uniaxial tensile test of the square and Kagome shape grid that use SMAT.

Tentative test is carried out, to study the strengthening effect of SMAT method to these two kinds of grids considered.Manufacture and the sample of the square arranged in the selected direction by SMAT process and Kagome shape lattice work.Successively uniaxial tensile test is carried out to these grid samples, and for each trellis topology structural appraisal SMAT effect.

Square grid: 0/90 ° contrasts with ± 45 °, tests and study as follows.

The a series of SMAT schemes applied each unit cell of square grid are as described below.

(i) scheme N: do not carry out SMAT; For reference contrast.

(ii) option A I: SMAT is carried out to bar part whole in grid, sees (A) in Fig. 4.This scheme for be the situation of any loads in plane.

(iii) option A II: only carry out SMAT to two horizon bar a and a ', is shown in (B) in Fig. 4.This scheme for be X along square grid ₁the load condition of axle uniaxial extension.In this case, two bar a and a ' directly bear applied load, and the power that two other bar b and b ' bears can be ignored.

(iv) option A III: in the circle around the radius of each node being R=(1-1/k) l/2, SMAT is applied to the end of bar, sees (C) in Fig. 4.This scheme for the situation of carrying out uniaxial extension on ° direction, square grid ± 45.Under such load, all bars all bear bending, and maximum stress appears near boom end.Therefore, SMAT is applied to these regions the most effective.

(A) and (B) in Fig. 5 respectively illustrates the geometry of the stretchable dog bone type sample of 0/90 ° of square grid and ± 45 ° of square grids.The length l=9mm of each bar part in square grid, width t=1.6mm, relative density

Manufacture three identical 0/90 ° of square grid flat boards, the situation for three kinds are considered: do not carry out SMAT-scheme N, all carries out SMAT-option A I, and part carries out SMAT-option A II.Operational version AI and AII carries out the surf zone of SMAT process respectively as shown in (A) (B) in Fig. 6.Similarly, manufacture identical ± 45 ° square grid sample, for three kinds of situations: do not carry out SMAT-scheme N, all carry out SMAT-option A I, part carries out SMAT-option A III.(C) in Fig. 6 shows the SMAT region of option A I, and (D) in Fig. 6 shows the SMAT region of option A III.

All samples is all formed by the 304 stainless steel plates cutting of the thickness d=1mm meeting AISI (AISIA) standard.Manufacture path is as described below: first, is three identical dog bone type tension specimens by steel plate Linear cut, for 0/90 ° of square grid, and cuts out three identical tension specimens, for ± 45 ° of square grids.For the sample not carrying out SMAT, be the pattern of design by the central zone Linear cut of these plates, review (A) (B) in Fig. 5.For the sample all carrying out SMAT, first carry out SMAT process 3 minutes to central zone, then Linear cut is the geometry of design.With the sample of same steps fabrication portion SMAT; But carrying out in SMAT process, using the region of cloth covering protection non-process.

Utilize servo-hydraulic tensile testing machine, with strain rate quasi-static tensile test is carried out successively (along the X shown in Fig. 5 to the sample obtained ₁axle).In process of the test, the load cell record load of test machine, the nominal axial stress on the net section determining sample.Be the axial elongation of the extensometer measure sample of 50mm by gauge length, thus determine nominal axial strain.As shown in figs. 7 a-b, and the photo of fracture specimens as shown in Figure 8 for the stress and strain curve measured.

First, the result of 0/90 ° of square grid is considered.This grid has pole-stretching (strut-stretching) effect to uniaxial extension, and all samples presents initial linear elasticity behavior, follows by hardening phase, sees Fig. 7 A.The yielding stress that the part measured carries out the sample of SMAT (option A II) approximates the yielding stress of the sample all carrying out SMAT (option A I), and exceeds the yielding stress three times of the sample not carrying out SMAT (scheme N).On the contrary, the unit elongation carrying out the sample of SMAT is less than the sample not carrying out SMAT.All carry out SMAT, the breaking strain of sample that part is carried out SMAT and do not carried out SMAT is respectively about 11%, about 22% and about 41%.

The stress strain relationship of following analytical calculation 0/90 ° of square grid when uniaxial extension.Horizon bar a and a ' directly resists along X ₁the stretching, extension load that axle applies, and the power that vertical rod b and b ' bears can be ignored, and sees (A) and (B) in Fig. 6.Horizon bar is applied to the bilinear model of the parent material carrying out SMAT and do not carry out SMAT, so that the nominal axial stress of computation grid and strain.These analytical calculations are comprised in Fig. 7 A.It is clear that at linear elastic stage, quite consistent with measuring result with the analyses and prediction of yield strength to Young's modulus.Similarly, the option A II that part carries out SMAT is same with the option A I all carrying out SMAT effectively, the value k of strengthening factor _s=3.5 is applicable.In the plastic stage, utilize and infinitely small calculate that the analysis carried out is moderately too low predicts measurement curve.Strain concentrating can be there is in this owing to the low approximation of double-line railway tunnel model and grid interior joint position.As shown in (A) in Fig. 8, the fracture position not carrying out the sample of SMAT is three horizon bars of turbogrid plates central authorities.On the contrary, all carry out the sample that SMAT or part carry out SMAT and rupture in the horizon bar position of turbogrid plates corner, see (B) and (C) in Fig. 8.

Present consideration ± 45 ° square grid.Along X ₁under the uniaxial load of axle ((B) in Fig. 5), grid presents initial pole-flexural deformation pattern, comprises linear elasticity behavior, follows by hardening phase, sees Fig. 7 B.In the middle strain stage, such as grid starts to be converted to pole-tensile deformation pattern, in this pattern, and the stress measured along with strain increase significantly improve.It is evident that, to be bendingly dominant the stage initial, the sample (option A III) that part carries out SMAT has almost identical stress-strain curve with the sample (option A I) all carrying out SMAT.Therefore, which demonstrate analyses and prediction, namely option A III is equally effective with option A I.For the bending specific strain value be dominant in the stage the corresponding stress measured in option A I or AIII is approximately the twice of scheme N (not carrying out SMAT).

Fig. 7 B also comprise utilize infinitely small method of calculation right ± 45 ° of square grids bending be dominant the deformation analysis in stage and the stage that is dominant that stretches.After a while by the more details that descriptive analysis calculates, now main result is summarized in this.In initial pole-bending stage, be bear bending beam by each bar part modeling, and bilinear description followed by the material of this beam.For the sample not carrying out SMAT, the relationship description of the stress-strain of material is E _s=200GPa, ε _y=0.001 and E _t=2GPa.For the sample all carrying out SMAT, the relation of the stress-strain of material follows parameter: E _s=200GPa, ε _y=0.001, k=k _b=2 Hes here, utilize take off data to carry out curve fitting to analytical model and obtain k _bwith value.Therefore, the SMAT strengthening factor k of ± 45 ° of square grids _bthe SMAT strengthening factor k of=2 to 0/90 ° of square grids _s=3.5 is much smaller.

The stretching final at ± 45 ° of square grid samples is dominant the stage, and the material property in analytical model adopts the material property of 0/90 ° of square grid sample.Fig. 7 B shows the stress strain relationship not carrying out the sample of SMAT that calculates lower than measuring result.On the contrary, to all carrying out the analyses and prediction of sample of SMAT higher than measuring result.These differences can be owing to, and it is high-caliber non-linear that the simple hypothesis in analysis have ignored that the material in gross distortion stage and geometry cause.But this analysis gives rational estimation at right ± 45 ° square grid from the conversion of the deformation pattern bending to stretching to a certain extent.

Kagome shape grid: the test in horizontal and vertical direction and research as follows:

The various SMAT schemes applying to select to each unit cell of Kagome shape grid are as follows.

(i) scheme : do not carry out SMAT; For reference contrast.

(ii) option b I: SMAT is carried out to bar part whole in grid, sees (A) in Fig. 9.

(iii) option b II: only carry out SMAT to two horizon bar a and a ', is shown in (B) in Fig. 9.This scheme for be along grid X ₁the load condition of axle uniaxial extension.In this case, two horizon bar a and a ' directly bear maximum axial stress.

(iv) option b III: only to four braces b, b ', c and c ' carry out SMAT, see (C) in Fig. 9.This scheme for be X along grid ₂the situation of axle uniaxial extension.Under this load condition, four braces have maximum axial stress.

(A) and (B) in Figure 10 respectively illustrates the geometry of horizontal Kagome shape grid sample and vertical Kagome shape grid sample.For square grid, each bar part in Kagome shape grid is designed to length l=9mm, the relative density of width t=1.6mm, horizontal and vertical Kagome shape grid sample

Manufacture three identical horizontal Kagome shape grid samples, the situation for three kinds are considered: do not carry out SMAT-scheme , all carry out SMAT-option b I, part carries out SMAT-option b II.The SMAT region of option b I is as shown in (A) in Figure 11, and the SMAT region of option b II is as shown in (B) in Figure 11.Similarly, manufacture vertical Kagome sample, for three kinds of situations: do not carry out SMAT-scheme , all carry out SMAT-option b I, part carries out SMAT-option b III.(C) and (D) in Figure 11 respectively illustrates the surf zone being carried out SMAT process by option b I and option b III.

All Kagome shape grid samples are repeated to the Computer-Assisted Design, Manufacture And Test process of 0/90 ° of square grid sample.These Kagome shape turbogrid plates are also by AISI 304 stainless steel cut of thickness d=1mm.Concerning all samples, the time length of SMAT is 3 minutes, and the non-process surf zone that part carries out the sample of SMAT protects with cloth in treating processes.Servo-hydraulic test machine and gauge length are that the extensometer of 50mm is for measuring nominal stress and the nominal strain of Kagome shape grid sample.As shown in Figures 12 A and 12 B, Figure 13 shows the photo of fracture specimens to measuring result.

Kagome shape grid is the leading structure that stretches, so the Kagome sample of horizontal and vertical all presents initial linear behavior, is then sclerization, sees Figure 12 A and 12B.The sample stress-strain curve in the two directions that part carries out SMAT is almost identical with the sample all carrying out SMAT.For the Kagome shape grid of horizontal and vertical, part is approximately 2/3rds of the sample not carrying out SMAT with the breaking strain of the sample all carrying out SMAT.Therefore, this demonstrate that the minimizing of the material ductility caused due to SMAT process.

Figure 12 A and 12B also comprises and utilizes infinitely small method of calculation to carry out analyses and prediction.First, horizontal Kagome is considered in more detail.This analysis shows, along X in (A) and (B) in fig. 11 ₁the tension load of axle is born by the elongation effect of horizon bar (a and a '), and the power that brace (b, b ', c and c ') bears can be ignored.This is confirmed by test, and as shown in (A) in Figure 13, (B) and (C), the horizon bar of horizontal Kagome sample ruptures at different positions.Therefore, in order to nominal axial stress and the strain of computation grid, double-line railway tunnel is described and is applied to horizon bar, and ignore the little impact on brace.As illustrated in fig. 12, this simple method gives good prediction to the sample all carrying out SMAT and do not carry out SMAT in linear elastic range.Similarly, the value k of the strengthening factor caused by SMAT process _s=3.5 is applicable.For plastic zone, analytical calculation is too low predicts the result measured in all cases.This can be interpreted as, by the strain concentrating around grid interior joint position and the double-line railway tunnel model that is significantly underestimated cause high-caliber non-linear.

Finally, the analysis to vertical Kagome shape grid is considered.According to analysis, the elongation of brace (b, b ', c and c ') is along to the X shown in (C) and (D) in such as Figure 11 ₁the dominant result of tension load of axle.This is confirmed by test, and all vertical Kagome sample all ruptures at the brace place of grid mid range, sees (D), (E) and (F) in Figure 13.Therefore, to brace application double-line railway tunnel model, with the stress strain relationship of computation grid, and ignore the little impact of vertical rod (a and a ').For the sample carrying out SMAT, (use strengthening factor k _s=3.5) a little higher than observed value of the yielding stress predicted, and the breaking strain of prediction is approximately 2 times of measuring result, sees Figure 12 B.For the sample not carrying out SMAT, analytical calculation is quite consistent with measuring result at elastic stage, but the too low result measured predicted in the plastic stage.With 0/90 ° of square grid and horizontal Kagome shape lattices seemingly, can owing to the strain concentrating around the low approximation of double-line railway tunnel model and grid interior joint in the too low prediction of the plastic zone inner analysis of vertical Kagome shape grid.

In the invention, the grid for two types passes through analysis and the test determination strengthening effect of SMAT method: square and Kagome shape grid, find the most effective when SMAT method being applied to the position of high stress concentrations.The structure that is dominant for bending (under uniaxial extension ± 45 ° of square grids), applies SMAT near the end by the most concentrated bar of counter stress and obtains maximum stiffening effect.In this case, by the SMAT technique used in current research, the yield strength of the grid sample be made up of 304 stainless steel plates is increased to coefficient k _b=2.For the structure (0/90 ° of square grid under axial deformation and the Kagome shape grid under any macroscopical load) be dominant that stretches, when exceeding the whole bar certain applications SMAT of elastic limit of parent material to axial stress, reinforced effects is maximum.In this case, based on this yielding stress, the SMAT strengthening factor of the steel grid sample of all tests is k _s=3.5.

For a long time, for material supply section scholar, can produce the structural material having high yield strength and high ductility concurrently is a dream.Show the research of the mechanical property using the surface nano-structure material of SMAT, the mechanical property of the nano structure superficial layer of differing materials significantly improves.

Under uniaxial extension ± deformation stage of 45 ° of square grids is as described below.

± 45 ° of square grids have two dominant deformation stages: (i) initial pole-bending, pole-stretching that (ii) is final.Infinitely small method of calculation are used to carry out stress-strain analysis at this for each deformation pattern.

Stage I: the deformation pattern of pole-bending

(A) in Figure 14 show ± and 45 ° of square grids are to the initial bar-bending response of uniaxial tensile load.The stress strain relationship of grid is determined, as shown in (B) in Figure 14 by analyzing representational the bending of half bar part.The nominal stress of this grid relevant to transverse load P:

${\mathrm{\&sigma;}}_1^{*}=\frac{2P}{\mathrm{dl}}---(A.1)$

Wherein, d is the degree of depth of grid, and l is the length of each bar part.The nominal strain of grid relevant to tip offset δ:

${\mathrm{\&epsiv;}}_1^{*}=\frac{2\mathrm{\&delta;}}{l}---(A.2)$

Retrospective test, d=1mm is the thickness of 304 stainless steel plates, t=1.6mm and l=9mm is width and the length of each bar part in designed grid sample.Because bar part is short and thick, in our calculating, that the length of bar adopts is l'=l-t=7.4mm.

Elizabeth Ferris (Fertis) (1999) use the inelastic bending of method to the socle girder be made up of double-line railway tunnel of equivalent system to analyze.Have ignored process tediously long in this approximation method, relevant detailed content, reader can with reference to Fertis (1999).At this, beam is not being carried out to SMAT process and under SMAT process both of these case is all carried out to beam, applying their method to determine relation between load p and tip offset δ.Again, these the two kinds situation application double-line railway tunnel considered are similar to.For the grid not carrying out SMAT, material property is the material property of original steel plate: E _s=200GPa, ε _y=0.001 and E _t=2GPa.For the grid all carrying out SMAT, initial Young's modulus and yield strain constant: E _s=200GPa and ε _y=0.001.Two SMAT parameter: k=k are obtained by carrying out curve fitting by take off data _b=2 Hes for not carrying out the sample of SMAT and all carrying out the sample of SMAT, the nominal stress of the grid of derivation and nominal strain as shown in Figure 7 B, they and measuring result are very consistent.

Stage II: the deformation pattern of pole-stretching

Suppose ± 45 ° of square grids in all nodes be all pivot joint.Under infinitesimal drawing force, due to the collapse mechanism (collapse mechanism) of grid, bar part is drawn as straight structure from initial rhombus, sees (C) in Figure 14.In this stage, all bars are all along X ₁the direction of pull of axle aligns.Because each bar starts to stretch along with the increase of the power applied, be locked stage (locking stage) by this stage definitions.The locked lengths h of half unit cell _lbe:

$h_L=h_0+\mathrm{\&Delta;}{h}_L=h_0(1+{\mathrm{\&epsiv;}}_L^{*})---(A.3)$

Wherein, locking strain is:

${\mathrm{\&epsiv;}}_L^{*}=\frac{\mathrm{\&Delta;}{h}_L}{h_0}---(A.4)$

The nominal strain of grid is defined as:

${\mathrm{\&epsiv;}}_1^{*}=\frac{\mathrm{\&Delta;}{h}_L+\mathrm{\&Delta;h}}{h_0}={\mathrm{\&epsiv;}}_L^{*}+\mathrm{\&epsiv;}\left(\frac{h_L}{h_0}\right)---(A.5)$

Wherein, ε=Δ h/h _lit is the nominal strain of bar part.The nominal stress of grid relevant with the stretching, extension stress σ of bar part:

${\mathrm{\&sigma;}}_1^{*}=\frac{\sqrt{2}t}{l}\mathrm{\&sigma;}---(A.6)$

± 45 ⁰the elemental height of square grid sample is bar part is relatively short and thick, so locked lengths adopts h _l=l-t/2=8.2mm, causes locking strain for the sample not carrying out SMAT, the material property of sample adopts given parameter: E _s=200GPa, ε _y=0.001 and E _t=2GPa; For the sample all carrying out SMAT, adopt E _s=200GPa, ε _y=0.001, k _s=3.5 Hes for not carrying out the sample of SMAT and all carrying out the sample of SMAT, derive the stress strain relationship of grid as shown in Figure 7 B.

Example below or embodiment intention illustrate to produce the alloy material with high-yield strength and hardness, low cytotoxicity, high cell compatibility and high blood compatibility being suitable for manufacturing Medical implant (such as when it needs for the support of cardiovascular patient) better, and use 316L SS spheroid or ZrO in the treat surface of the metal base of Medical implant (such as, support) ₂the application of the SMAT of spheroid.It is evident that for a person skilled in the art, when do not depart from the scope of the present invention and can make when aim comprise add or replace amendment.Can omit concrete details in order to avoid make the present invention unclear, but to write out disclosed content be in order to those skilled in the art can be made when without the need to putting into practice content of the present invention when undo experimentation:

Example 1

Figure 15 shows device and under certain condition with the schematic diagram of the metal base (1501) of the SMAT process Medical implant of spheroid of the present invention.Method of the present invention comprises the 316L stainless steel spheroid or zirconium white (ZrO that size are approximately φ 3.0mm ₂) spheroid (1502) is applied to metal base.The physical and mechanical property produced due to Medical implant and its be conducive to Growth of Cells and the tissue regeneration of surrounding, being therefore preferably used in SMAT process for the spheroid of the metal base of Medical implant is ZrO ₂spheroid.Metal base 1501 by SMAT and spheroid process is 316L stainless steel plate (minute surface cuts open light) and is of a size of 100mm x 50mm x 0.9mm.The gross weight processing the spheroid 1502 of metal base both sides for this example is approximately 20g.The SMAT of this spheroid comprised being applied to metal base is performed in the enclosing (1500) with chamber (1504).On the side of chamber 1504, by processed metal substrate support in the position almost relative with the vibrating device (1503) on the opposite side being positioned at chamber 1504.By the vibratory drive of vibrating device, spheroid 1502 is moved around in the inside of chamber.20,000Hz is approximately for making the vibrational frequency of spheroid vibrating device of movement in the chamber of enclosing.The working amplitude of vibrating device 1503 is approximately 80%.Treatment time on every side of metal base is most important for the character of metal base.Treatment time on every side of preferable alloy substrate is approximately 15 minutes.Mean like this and be approximately 30 minutes total time for the treatment of the both sides of metal base.Four sections are divided into: (i) was from the 0th minute to the 1st minute by 30 minutes processes of the both sides of the SMAT process metal base with this spheroid; (ii) from the 1st minute to the 5th minute; (iii) from the 5th minute to the 29th minute; And (iv) was from the 29th minute to the 30th minute.In each time period, perform SMAT on every side of metal base, utilize the average duration of at every turn knocking of this spheroid for knock 5 seconds to 15 seconds at every turn.In order to realize the various durations of knocking at every turn, be provided with and start/stop button for what control spheroid vibration, and after a keystroke terminates, usually overturn plaques.Use treatment schedule below in this example:

From the 0th minute to the 1st minute: knock 5 seconds in every side of metal base at every turn;

From the 1st minute to the 5th minute: knock 10 seconds in every side of metal base at every turn;

From the 5th minute to the 29th minute: knock 15 seconds in every side of metal base at every turn;

From the 29th minute to the 30th minute: after every side of metal base is knocked and knocked 10 seconds for four times, knock four times in every side of metal base and knock 5 seconds at every turn at every turn.

Because 316L plate thickness is only 0.9mm, the side therefore constantly processing this plate for a long time by SMAT may make substrate bend, and causes this plate to be difficult to recover.The timetable in treatment time can avoid this problem to produce above.

In first time period (from the 0th minute to the 1st minute), knock six times to process every side of metal base in the mode of knocking 5 seconds at every turn by this spheroid.In the second time period (from the 1st minute to the 5th minute), knock 12 times to process every side of metal base in the mode of knocking 10 seconds at every turn by this spheroid.In the 3rd time period, knock 48 times to process every side of metal base in the mode of knocking 15 seconds at every turn by this spheroid.In the 4th time period (from the 29th minute to the 30th minute), to be knocked after twice in the mode of knocking 10 seconds at every turn by this spheroid and knock in the mode of knocking 5 seconds at every turn the every side processing metal base for twice again.

Example 2

To passing through with 316L SS spheroid or ZrO according to example 1 ₂yield strength and the hardness of the metal base (having the 316L SS plate of polishing minute surface) handled by the SMAT of spheroid are tested.In order to test in this example, the metal base obtained is cut into the less sheet of every sheet 10x 10x 0.9mm by the method described in example 1.With 316L SS spheroid (316L SMATization) process and the ZrO with process ₂spheroid (ZrO ₂sMATization) the metal base sample that processes all significantly improves, but strains impaired (Figure 16) in yielding stress; 316L SMATization and ZrO ₂metal base sample (the especially ZrO of SMATization ₂the metal base of SMATization) show the improvement (Figure 17) of hardness aspect.

Example 3

As shown in Figure 18, untreated metal base (blank group) has greatest differences with the pattern of the metal base (SMATization) of SMAT process.Specifically, blank group sample (Figure 18 A) relatively flat and the sample of SMATization has some obvious grinding marks.Interestingly, the sample morphology (Figure 18 B) caused by 316L SS ball lapping with by ZrO ₂the sample morphology (Figure 18 C) that ball lapping causes is different.The sample of 316L SMATization has some cuts and hole and ZrO ₂on the sample of SMATization, some shadow regions are significant.This difference is considered to because of 316L SS and ZrO ₂mechanical differences different between spheroid causes.Led to the same conclusion by the further feature of the sample topography of optical profile assay method, and disclosed surfaceness (Ra=2.08 μm) and the ZrO of the sample of 316LSMATization by optical profile assay method ₂the surfaceness (Ra=2.85 μm) of the sample of SMATization is all higher than surfaceness (Ra=0.038 μm) 2 orders of magnitude of blank group sample.

example 4

By plant on metal base sample endotheliocyte (EA.hy926, cRL-2922TM) determine the cell compatibility of different sample (metal base of untreated metal base and SMATization) and cultivate these cells in different time scope.As shown in figure 19, among them, ZrO ₂cytoactive on the sample of SMATization is best.This may be due to ZrO ₂be a kind of biocompatible pottery and with ZrO ₂some ZrO after the SMAT of spheroid ₂composition is introduced in metal base.

example 5

By by the metal base sample of untreated and SMATization from contacting blood to evaluate the blood compatibility of different sample.Be attached to red corpuscle on the sample of SMATization (Figure 20, second and the micro-image of the third line) obviously to reduce than the red corpuscle be attached in untreated samples (Figure 20, the micro-image of the first row).As shown in Figure 21, the prothrombin time (PT) of different sample does not have difference.But, the thrombin time (TT) in metal base all can be improved by two kinds of SMAT techniques, and in activated partial thromboplastin time (APTT), ZrO ₂the sample of SMATization is better than the sample of blank group sample and 316L SMATization.

example 6

In order to show the negative impact of pecvd nitride in the cell compatibility of metal base (especially iron containing alloy), determine the Ni burst size of various sample (after SMAT technique, the sample of the sample of plasma nitridation process contrast non-plasma nitriding treatment) and result as shown in figure 22.For the sample of pecvd nitride SMATization, pecvd nitride is the operation after SMAT process.Result shows, relatively higher than the Ni burst size of the metal base of not carrying out plasma nitridation process by the Ni burst size of all metal base (comprising the sample of blank group sample and SMATization) of plasma nitridation process.What is interesting is, at these three kinds of samples (sample of blank group sample, 316L SMATization and ZrO ₂the sample of SMATization) between, do not carry out the ZrO of plasma nitridation process ₂the sample of SMATization with in Ni burst size, there is the most significant difference by the same sample of plasma nitridation process.As shown in Figure 23, nitriding treatment and ZrO ₂the sample of SMATization has the highest Ni rate of release and only ZrO ₂the sample of SMATization has minimum Ni rate of release.Although pecvd nitride can improve the mechanical property (such as, hardness) of metal base further.But, from test result above, because plasma nitridation process will cause a large amount of release of poisonous Ni and then remarkable cell compatibility and the blood consistency (nitrided iron is very unstable in human physiological environment) reducing sample.By in the sample of plasma nitridation process (especially at the ZrO of nitrogenize ₂the sample of SMATization) high Ni release show nitriding treatment and be unfavorable for the stability of the metal base of SMATization in physiological environment, therefore pass through with the SMAT of spheroid of the present invention to carry out in the surface treatment of the metal base of Medical implant not recommendation.We provide the above-mentioned description of this invention, its intention just in order to the object illustrated and set forth, instead of in order to exhaustive or limit the invention to disclosed accurate form.To those skilled in the art, a lot of improvement and change is obviously admitted of.

In order to explain principle of the present invention and practical application thereof well, selecting and describing above embodiment, thus enabling other those skilled in the art for being suitable for the various embodiment of desired specific end use and various improvement to understand the present invention.Scope of the present invention is by following claim and equivalents thereof.

By reference to the mode quoted, the reference of following discloses is integrated in this:

Reference:

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Claims (12)

1., for the treatment of a method for the stainless steel-like substrate as Medical implant material, described method comprises:

On the surface of described substrate, application uses the surface mechanical attrition treatment (SMAT) of multiple spheroid; And

There is provided the enclosing with chamber, the described substrate on the side being supported on chamber and the vibrating device on the opposite side for described substrate;

Wherein, described vibrating device is constructed to make described multiple spheroid along chamber towards the frequency of described substrate movement and amplitude vibration, thus makes the multiple spheroids moved forward and backward in chamber interior can according to treatment schedule to process the surface of described metal base; And

Wherein, avoid processing described substrate by pecvd nitride.

2. method according to claim 1, wherein, described multiple spheroid is selected from stainless steel spheroid or zirconium white (ZrO ₂) spheroid.

3. method according to claim 2, wherein, described stainless steel spheroid comprises 316L stainless steel.

4. method according to claim 2, wherein, the diameter of each spheroid in described multiple spheroid is about 3mm.

5. method according to claim 1, wherein, described substrate comprises 316L stainless steel.

6. method according to claim 1, wherein, when metal base is of a size of 100mm x50mm x 0.9mm, the gross weight of described multiple spheroid is 20g.

7. method according to claim 1, wherein, described vibrating device runs with the frequency of about 20,000Hz.

8. method according to claim 1, wherein, described vibrating device produces the working amplitude of about 80%.

9. method according to claim 1, wherein, the treatment time for the treatment of each surface of metal base is about 15 minutes.

10. method according to claim 1, wherein, treatment schedule comprised for the treatment of two of the metal base surperficial overall treatment times of about 30 minutes, was divided into four time periods described overall treatment time, comprised:

A () was from the 0th minute to the 1st minute: knock 5 seconds on the surface in each of metal base at every turn;

B () was from the 1st minute to the 5th minute: knock 10 seconds on the surface in each of metal base at every turn;

C () was from the 5th minute to the 29th minute: knock 15 seconds on the surface in each of metal base at every turn;

D () was from the 29th minute to the 30th minute: after each of metal base is knocked twice each 10 seconds on the surface, knock on each surface twice each 5 seconds.

11. 1 kinds are carried out surface-treated metal base by method according to claim 1.

12. 1 kinds of Medical implants, described Medical implant comprises and carries out surface-treated metal base by method according to claim 1.