CN103234823B - Artificial heart valve pyrolytic carbon and testing method for fracture toughness of pyrolytic carbon composite material - Google Patents
Artificial heart valve pyrolytic carbon and testing method for fracture toughness of pyrolytic carbon composite material Download PDFInfo
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- CN103234823B CN103234823B CN201310115477.XA CN201310115477A CN103234823B CN 103234823 B CN103234823 B CN 103234823B CN 201310115477 A CN201310115477 A CN 201310115477A CN 103234823 B CN103234823 B CN 103234823B
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Abstract
The invention relates to an artificial heart valve pyrolytic carbon and a testing method for the fracture toughness of a pyrolytic carbon composite material. A testing method for the fracture toughness of the pyrolytic carbon composite material has not been brought forward yet. The testing method provided by the invention comprises the following steps: preparing a plurality of compact tension C(T) specimens from heart valve pyrolytic carbon or a composite material thereof and prefabricating sharp cracks on each specimen, wherein the specimen is of a specification as recommended by American ASTM standard E399, a gap is processed at the central part of the specimen, and upper and lower ends of the gap are respectively provided with a loading hole; then respectively clamping the two loading holes of the gap by using clamps and erecting an extensometer on an open end of the gap; and starting a loading platform to apply an upward load increasing at a uniform speed until the specimens fracture, determining critical load and effective crack length of each specimen, calculating fracture toughness according to the critical load and the effective crack length and taking a mean value as a fracture toughness test value of the heart valve pyrolytic carbon or the composite material thereof. The method provided by the invention can accurately determine fracture toughness of pure pyrolytic carbon and a pyrolytic carbon composite material.
Description
Technical field
The present invention relates to a kind of Carbon Materials mechanic property test method, be specifically related to a kind of heart valve pyrolytic carbon and fracture of composite materials toughness test method thereof.
Background technology
Heart valve is the substitute of people body-centered lobe, for cardiac valves patient replacing, its limb often adopts pure pyrolytic carbon or Carbon coating graphite composite material, and lobe ring often adopts pure pyrolytic carbon or titanium alloy to make.Heart valve runs on decades in physiological environment complicated in human body, and need very high permanance and structural reliability, the pyrolyzed carbon materials therefore as its surface coating needs to have good fracture property.
Plane strain fracture toughness is the important parameter of pyrolyzed carbon materials fracture property, and the ability of exosyndrome material opposing Crack Extension and brittle fracture, generally uses K
iCrepresent.Accurate test material Fracture Toughness, research affect the factor of material fracture toughness, can clearly with improve pyrolytic carbon fracture property, to heart valve assembly damage tolerance and life prediction program also significant.
Pyrolyzed carbon materials adopts chemical vapor deposition method preparation, is a kind of typical hard brittle material.Due to its preparation technology's singularity, sample size is little, thickness is thin, and many traditional fracture toughness method of testings is inapplicable to it, therefore for the test of heart valve pyrolytic carbon fracture toughness, domesticly there is no this type of report.The people such as external Ritchie, Cao Hengchu, Glipin had once carried out certain research to heart valve pyrolytic carbon fracture toughness, but did not propose a set of method of testing for heart valve pyrolytic carbon fracture toughness.
Summary of the invention
The inventive method, for the deficiencies in the prior art, provides a kind of heart valve pyrolytic carbon and fracture of composite materials toughness test method thereof.The method can the fracture toughness of the pure pyrolytic carbon of Accurate Measurement and pyrolytic carbon compound substance.
The concrete steps of the inventive method are:
Step (1). heart valve pyrolytic carbon to be tested or its compound substance are prepared into the individual compact tension specimen C(T of n (n >=3)) sample, then at each compact tension specimen C(T) prefabricated sharp crack on sample;
Described compact tension specimen C(T) sample is according to U.S. ASTM standard E399 recommendation specification, and sample is cube, middle section mechanism machining gap, loading hole is offered respectively in the upper and lower two ends of breach, described breach is straight-through v notch v, and one end is opened in the side of sample, and the other end is most advanced and sophisticated; Effect of stress effective width is W, and described effect of stress effective width is the center of loading hole sample being positioned at same surface and the distance of the non-gap end side surface of sample; The width of sample is D, and length is L, and thickness is B, and gap width is d, and the aperture of loading hole is Φ, and the vertical center line of loading hole and the distance at breach tip are a
0; W=18.8mm, a
0=4.8mm, D=1.25W, L=1.2W, B=0.5W, d=0.5W, Φ=0.25W;
The through sample front and rear surfaces of described sharp crack, its starting point is positioned at breach tip, and sharp crack length is 1.5 ~ 2.5mm; Described sharp crack length is two end points projector distance in the horizontal plane of sharp crack; The method of described precrack adopts cyclic fatigue precrack method, and the method is ripe prior art.
Step (2). each sample two U-shaped fixtures clamp the two ends of two loading hole respectively, and two bearing pins are each passed through two sides of two U-shaped fixtures and corresponding loading hole, are fixedly connected with by U-shaped fixture with sample; Extensometer is erected at breach and is positioned on the open end of sample sidewall, and two pins of extensometer are separately fixed at the upper and lower knife-edge part of breach; Described extensometer adopts electronic extensometer, in order to detect the joint open of sample mechanism machining gap leading edge;
The end face center vertical of the U-shaped fixture on sample top is fixedly installed load bar, and weighted platform is connected with load bar; Described weighted platform can to load bar applying load upwards;
The bottom center of the U-shaped fixture of sample bottom is vertically fixedly installed fixed bar, and stationary platform offers through hole, and fixed bar is arranged through through hole activity, and the bottom of fixed bar is provided with spacer pin, and the size of spacer pin is greater than the aperture of through hole.
Step (3). start-up loading platform, weighted platform applies the upwards load at the uniform velocity increased, and upwards the rate of loading of load is 0.6 ~ 0.8 N/S, until sample breakage; Critical load P when determining each sample breakage
qwith effective crack length a;
Record each sample not size of imposed load in the same time and gap opened amount, until sample breakage; According to the not size of imposed load and gap opened amount in the same time, with 0 be initial point, imposed load P is ordinate, gap opened amount is for horizontal ordinate curve plotting figure; This curve comprises linear segment straight line and non-linear component curve, and the intersection of linear segment straight line and non-linear component curve is some A, draws the straight line by initial point with the slope of 0.95 times of OA, and the intersection point of this straight line and non-linear component curve is some B; The imposed load getting the A point point maximum with ordinate in the non-linear component curve before B point corresponding is the critical load P of this sample
q;
The mean value of sharp crack length when described effective crack length a is each sample breakage, specifically on sample breakage face, section is divided into m (m >=3) decile along thickness, gets the mean value of the sharp crack length of m-1 division surface and two end faces.
Step (4). calculate fracture toughness K
iC:
If P
max/ P
qbe less than or equal to 1.1, be calculated as follows the material fracture toughness K of each sample
iC, P
maxfor the maximum imposed load in curve map
, in formula
；
Calculate the material fracture toughness K of n sample
iCmean value, as the fracture toughness test value of heart valve pyrolytic carbon or its compound substance;
If P
max/ P
qbe greater than 1.1, then retest.
The inventive method has fully taken into account the factor such as hard fragility and preparation size limitation of pyrolyzed carbon materials, all adjusts and improves, ensure that test procedure feasibility and test result reliability in extensometer, U-shaped fixture, precrack method etc.
Accompanying drawing explanation
Fig. 1 is compact tension specimen C(T in the present invention) structural representation of sample;
Fig. 2 is proving installation structural representation.
Embodiment
Below in conjunction with accompanying drawing and example, the concrete implementation step of the present invention is described further.
Heart valve pyrolytic carbon and fracture of composite materials toughness test method thereof, concrete steps are:
Step (1). heart valve pyrolytic carbon to be tested or its compound substance are prepared into the individual compact tension specimen C(T of n (n >=3)) sample, then at each compact tension specimen C(T) prefabricated sharp crack on sample;
As shown in Figure 1, compact tension specimen C(T) sample is according to U.S. ASTM standard E399 recommendation specification, and sample 1 is cube, and middle section mechanism machining gap 1-1, breach 1-1 offer loading hole 1-2 in upper and lower two ends respectively.Breach 1-1 is straight-through v notch v, and one end is opened in the side of sample 1, and the other end is most advanced and sophisticated; Effect of stress effective width W is the center of loading hole 1-2 sample 1 being positioned at same surface and the distance of the non-gap end side surface of sample 1, W=18.8mm; Aperture Φ=the 0.25W of width D=1.25W, the length L=1.2W of sample 1, thickness B=0.5W, gap width d=0.5W, loading hole, the vertical center line of loading hole and the distance a at breach tip
0=4.8mm, above size is accurate to 0.1 ﹪.
Sharp crack 1-3 through sample 1 front and rear surfaces, it is most advanced and sophisticated that its starting point is positioned at breach 1-1, and sharp crack length a is 1.5 ~ 2.5mm.Sharp crack length is two end points projector distance in the horizontal plane of sharp crack 1-3.The method of precrack adopts cyclic fatigue precrack method.
Step (2). as shown in Figure 2, each sample 1 two U-shaped fixtures 4 clamp the two ends of two loading hole 1-2 respectively, two bearing pins 5 are each passed through two sides of two U-shaped fixtures 4 and corresponding loading hole 1-2, are fixedly connected with by U-shaped fixture 4 with sample 1; Extensometer 6 is erected at breach 1-1 and is positioned on the open end of sample sidewall, and two pins of extensometer 6 are separately fixed at the breach upper and lower edge of a knife 7 place (in figure enlarged fragmentary portion), and extensometer 6 adopts electronic extensometer.
The end face center vertical of the U-shaped fixture on sample 1 top is fixedly installed load bar 3, and weighted platform 2 is connected with load bar 3, the load that weighted platform 2 can apply upwards to load bar 2.
The bottom center of the U-shaped fixture of sample 1 bottom is vertically fixedly installed fixed bar 8, and stationary platform 9 offers through hole, and fixed bar 8 is arranged through through hole activity, and the bottom of fixed bar 8 is provided with spacer pin 10, and the size of spacer pin 10 is greater than the aperture of through hole.
Step (3). start-up loading platform 2, weighted platform 2 applies the upwards load (in figure the direction of arrow) at the uniform velocity increased, and upwards the rate of loading of load is 0.6 ~ 0.8 N/S, until sample breakage; Critical load P when determining each sample breakage
qwith effective crack length a;
Record each sample not size of imposed load in the same time and gap opened amount, until sample breakage; According to the not size of imposed load and gap opened amount (being detected the joint open of breach leading edge by extensometer 6) in the same time, with 0 be initial point, imposed load P is ordinate, gap opened amount is for horizontal ordinate curve plotting figure; This curve comprises linear segment straight line and non-linear component curve, and the intersection of linear segment straight line and non-linear component curve is some A, draws the straight line by initial point with the slope of 0.95 times of OA, and the intersection point of this straight line and non-linear component curve is some B; The imposed load getting the A point point maximum with ordinate in the non-linear component curve before B point corresponding is the critical load P of this sample
q;
The mean value of sharp crack length when effective crack length a is each sample breakage, is specifically divided into m (m >=3) decile by section along thickness on sample breakage face, gets the mean value of the sharp crack length of m-1 division surface and two end faces.
Step (4). calculate fracture toughness K
iC:
If P
max/ P
qbe less than or equal to 1.1, be calculated as follows the material fracture toughness K of each sample
iC, P
maxfor the maximum imposed load in curve map
, in formula
；
Calculate the material fracture toughness K of n sample
iCmean value, as the fracture toughness test value of heart valve pyrolytic carbon or its compound substance;
If P
max/ P
qbe greater than 1.1, then retest.
Although the present invention discloses as above with preferred embodiments and result; so itself and be not used to limit the present invention; any person of ordinary skill in the field; without departing from the spirit and scope of the invention; can do a little variation and improvement, the protection domain of therefore the present invention is when being as the criterion depending on the claim person of defining.
Claims (3)
1. heart valve pyrolytic carbon and fracture of composite materials toughness test method thereof, is characterized in that the concrete steps of the method are:
Step (1), heart valve pyrolytic carbon to be tested or its compound substance are prepared into n compact tension specimen C (T) sample, then prefabricated sharp crack on each compact tension specimen C (T) sample, n >=3;
Described compact tension specimen C (T) sample is according to U.S. ASTM standard E399 specification, and sample is cube, middle section mechanism machining gap, loading hole is offered respectively in the upper and lower two ends of breach, described breach is straight-through v notch v, and one end is opened in the side of sample, and the other end is most advanced and sophisticated; Effect of stress effective width is W, and described effect of stress effective width is the center of loading hole sample being positioned at same surface and the distance of the non-gap end side surface of sample; The width of sample is D, and length is L, and thickness is B, and gap width is d, and the aperture of loading hole is Φ, and the vertical center line of loading hole and the distance at breach tip are a
0; W=18.8mm, a
0=4.8mm, D=1.25W, L=1.2W, B=0.5W, d=0.5W, Φ=0.25W;
The through sample front and rear surfaces of described sharp crack, its starting point is positioned at breach tip, and sharp crack length is 1.5 ~ 2.5mm; Described sharp crack length is two end points projector distance in the horizontal plane of sharp crack;
Step (2), each sample two U-shaped fixtures clamp the two ends of two loading hole respectively, and two bearing pins are each passed through two sides of two U-shaped fixtures and corresponding loading hole, are fixedly connected with by U-shaped fixture with sample; Extensometer is erected at breach and is positioned on the open end of sample sidewall, and two pins of extensometer are separately fixed at the upper and lower knife-edge part of breach;
The end face center vertical of the U-shaped fixture on sample top is fixedly installed load bar, and weighted platform is connected with load bar; Described weighted platform can to load bar applying load upwards;
The bottom center of the U-shaped fixture of sample bottom is vertically fixedly installed fixed bar, and stationary platform offers through hole, and fixed bar is arranged through through hole activity, and the bottom of fixed bar is provided with spacer pin, and the size of spacer pin is greater than the aperture of through hole;
Step (3), start-up loading platform, weighted platform applies the upwards load at the uniform velocity increased, and upwards the rate of loading of load is 0.6 ~ 0.8N/S, until sample breakage; Critical load P when determining each sample breakage
qwith effective crack length a;
Record each sample not size of imposed load in the same time and gap opened amount, until sample breakage; According to the not size of imposed load and gap opened amount in the same time, with 0 be initial point, imposed load P is ordinate, gap opened amount is for horizontal ordinate curve plotting figure; This curve comprises linear segment straight line and non-linear component curve, and the intersection of linear segment straight line and non-linear component curve is some A, draws the straight line by initial point with the slope of 0.95 times of OA, and the intersection point of this straight line and non-linear component curve is some B; The imposed load getting the A point point maximum with ordinate in the non-linear component curve before B point corresponding is the critical load P of this sample
q;
When described effective crack length a is each sample breakage, the mean value of sharp crack length, is specifically divided into m decile by section along thickness on sample breakage face, gets the mean value of the sharp crack length of m-1 division surface and two end faces, m >=3;
Step (4), calculating fracture toughness K
iC:
If P
max/ P
qbe less than or equal to 1.1, be calculated as follows the material fracture toughness K of each sample
iC, P
maxfor the maximum imposed load in curve map;
Calculate the material fracture toughness K of n sample
iCmean value, as the fracture toughness test value of heart valve pyrolytic carbon or its compound substance;
If P
max/ P
qbe greater than 1.1, then retest.
2. heart valve pyrolytic carbon as claimed in claim 1 and fracture of composite materials toughness test method thereof, is characterized in that the method for precrack in step (1) adopts cyclic fatigue precrack method.
3. heart valve pyrolytic carbon as claimed in claim 1 and fracture of composite materials toughness test method thereof, is characterized in that the extensometer described in step (2) adopts electronic extensometer, in order to detect the joint open of sample mechanism machining gap leading edge.
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| CN112748002A (en) * | 2020-12-17 | 2021-05-04 | 杭州电子科技大学 | Method for measuring notch opening amount in measurement of fracture toughness of pyrolytic carbon for artificial heart valve |
| CN113466038B (en) * | 2021-06-21 | 2022-05-20 | 长江存储科技有限责任公司 | Detection sample for fracture toughness and detection method thereof |
| CN113834730B (en) * | 2021-07-14 | 2023-07-21 | 滁州职业技术学院 | Mechanical property experimental device and experimental method based on hydraulic component |
| CN115014986A (en) * | 2022-06-23 | 2022-09-06 | 西安热工研究院有限公司 | Fracture toughness K for CB2 high-temperature cast steel IC Method of measurement of |
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