CN117740492A - Sample preparation method for testing parameters of heterogeneous and anisotropic materials of long bones - Google Patents

Abstract

The invention relates to the technical field of orthopedic biomechanics, in particular to a sample preparation method for testing long bone non-uniform and anisotropic material parameters. The method includes: positioning marking, bone ring cutting, quadrant marking and division, specimen area cutting and specimen processing. Determine the position of the middle bone ring on the long bone diaphysis and mark it through the positioning marking step. Then, according to the length of the long bone diaphysis, determine and mark the position of each bone ring in percentage, and cut the bone ring along the marked line. Then, mark the four quadrants A/P/L/M on each bone ring, and divide the transverse sample area and the longitudinal sample area. Afterwards, the sample blocks were cut along the divided sample area lines and prepared. Finally, the specimen block was roughed and finished. The method of the invention can effectively prepare axial, circumferential and transverse anisotropic samples, provides a tool for testing non-uniform and anisotropic material parameters of long bones, and can more comprehensively reveal the position and different directions of long bones. material properties.

Description

Specimen preparation method for non-uniform and anisotropic material parameter testing of long bones

Technical field

The invention relates to the technical field of orthopedic biomechanics, in particular to a sample preparation method for testing long bone non-uniform and anisotropic material parameters.

Background technique

As a heterogeneous and anisotropic composite material, the material properties of long bones show significant differences at different locations, especially along the axial and circumferential gradients. This anisotropy is mainly reflected in the biomechanical response of the loading axis and bone unit orientation to the specimen, which includes different responses in the axial, tangential and transverse directions. By obtaining specimens from multiple sites and orientations of the long bones, the mechanical properties of lower extremity long bones can be more accurately characterized, which is critical to providing more precise bone material parameters. These precise parameters are key to building finite element models, which are the cornerstone of future digital developments. Accurate numerical models are crucial for in-depth study of lower limb injury mechanisms and for the development of research and treatment strategies for bone diseases.

It is difficult to prepare bone specimens. In the existing long bone biomechanical testing technology, non-standardized specimens such as whole bones or partial bone segments are usually used for testing, which is inevitably affected by factors such as geometry and structure. The microstructure and composition of long bones may vary at different locations and orientations, resulting in non-uniform distribution of their mechanical properties. At the same time, the stiffness, strength and toughness of long bones may also be different in different directions, showing obvious anisotropy. The existing technology is relatively single in terms of characterization of the mechanical properties of long bones, and it is usually impossible to clearly distinguish the material properties of long bones in different directions and different parts. Therefore, specimens need to be obtained from multiple locations and orientations of long bones to fully characterize their mechanical properties.

Contents of the invention

The purpose of the present invention is to provide a sample preparation method for long bone non-uniform and anisotropic material parameter testing, which can provide more detailed mechanical property information, reflect the differences in mechanical behavior in different parts of the long bone and in different directions, and more comprehensively reveal Material properties of long bones in position and in different orientations.

The basic solution provided by the invention: a sample preparation method for long bone non-uniform and anisotropic material parameter testing, including: positioning marking step, bone ring cutting step, quadrant marking and dividing step, quadrant block cutting step, and sample processing Steps; the positioning and marking step is used to determine and mark the position of the middle bone ring on the long bone backbone; the bone ring cutting step is to cut the bone ring along the marked ring line according to the length of the long bone backbone; the quadrant marking and dividing step is used to Mark the quadrant lines on the outer surface of the bone ring, and divide the transverse sample area and the longitudinal sample area in each quadrant; the quadrant block cutting step is based on the method used to cut the quadrant; the sample processing step includes cutting the sample block roughing and finishing.

Implementation principles and beneficial effects of the present invention: By determining and marking the position of the middle bone ring on the long bone backbone, the precise positioning of the bone center is achieved. According to the length of the long bone diaphysis, the positions of other bone rings are determined and marked, and the bone rings are cut along the marked lines, which allows specimens to be obtained at specific axial positions, which can reflect the differences in mechanical behavior of long bones at different parts. Quadrants were marked on each bone ring and transverse and longitudinal specimen areas were divided, allowing the mechanical properties of the bone in different directions (anterior, posterior, medial, and lateral) to be studied. By cutting and preparing sample blocks in the divided sample areas, and roughing and finishing the sample blocks, samples with specific directions (axial, circumferential and transverse) can be obtained, while ensuring the integrity of the sample. Quality and precision.

Further, the step of positioning and marking includes marking the midpoint position of the long bone backbone with a ring line, the ring line being perpendicular to the backbone axis; and further including establishing a position offset by a specific distance from the determined midpoint position along the backbone axis to the proximal end and distal end respectively. Middle bone ring.

Further, the step of cutting the bone ring includes determining the middle ring line of each bone ring by sequentially offset from the middle position to the proximal end and the distal end by a specific distance; and also includes starting from the center ring line of each bone ring along the backbone axis to the proximal center respectively. The end and the distal end are offset by a certain distance to determine the marked ring line of each bone ring; the specific distance is determined according to the length of the backbone and a specific percentage spacing.

Further, the specific offset distance is 12.5mm.

Beneficial effects of this solution: Marking the midpoint of the long bone diaphysis perpendicular to the axis of the bone can accurately determine the center of the bone, thereby achieving precise positioning of the center of the bone; from the midpoint along the axis of the bone to the proximal and distal ends Each is offset by 12.5mm to establish the middle bone ring, and the position of the remaining bone rings is determined according to a specific percentage along the position of this middle bone ring, and the cutting line is marked. Samples at different positions can be obtained to fully consider the non-uniformity of the long bone. sex.

Further, the quadrant block cutting step includes determining the quadrant cutting line according to the division of the transverse sample area and the longitudinal sample area, and cutting the bone ring into four separate quadrant blocks according to the quadrant cutting line.

Further, the quadrant block cutting step also includes cutting each quadrant block into transverse sample blocks and longitudinal sample blocks; and marking each surface of the sample block; the marks include the marks of adjacent quadrants ( A/P/L/M), markings on the proximal and distal ends, markings on the outer and inner circumferential surfaces, and markings to distinguish the transverse and longitudinal properties of the specimen.

Beneficial effects of this solution: By marking the transverse and longitudinal sample areas inside each quadrant of the long bone, and accurately cutting and preparing the sample blocks along the boundary lines of these areas, sampling of different positions and directions of the long bone is achieved. Detailed labeling of each specimen block ensures that the specific origin and orientation attributes of each specimen are accurately identified during subsequent testing and analysis, improving the accuracy and consistency of specimen preparation.

Further, the rough processing in the sample processing step includes processing the sample block using a metallographic grinder and P1000 roughness silicon carbide sandpaper under water cooling conditions to obtain a transverse rough sample and a longitudinal rough sample.

Further, the finishing process in the sample processing step includes milling machine processing; it also includes using P1500 roughness silicon carbide sandpaper to edge polish the sample block processed by the milling machine; the sample block processed by the milling machine includes The circumferential specimens and transverse specimens obtained after fine milling of rough transverse specimens, and the longitudinal specimens obtained after fine milling of rough longitudinal specimens.

Beneficial effects of this solution: In the rough processing stage, using a metallographic grinder and silicon carbide sandpaper with P1000 roughness, combined with operation under water cooling conditions, can effectively form the basic shape and smooth surface of the sample, while reducing the number of steps in the processing process. Possible thermal damage. In the subsequent finishing stage, finer P1500 roughness silicon carbide sandpaper was used to polish the edges of all sample blocks to further remove burrs and ensure the smoothness and consistency of the sample surface.

Description of drawings

Figure 1 is a sample preparation flow chart of the sample preparation method for long bone non-uniform and anisotropic material parameter testing in the present invention;

Figure 2 is a schematic diagram of the sample preparation method used for long bone non-uniform and anisotropic material parameter testing in the present invention;

Figure 3 is a schematic diagram of the CNC milling machine fixture used in the sample preparation method for long bone non-uniform and anisotropic material parameter testing in the present invention;

Figure 4 is a schematic diagram of the CNC milling machine processing path of the sample preparation method for long bone non-uniform and anisotropic material parameter testing in the present invention.

Detailed ways

The following is further detailed through specific implementation methods:

As a composite material with significant heterogeneity and anisotropy, long bones have different material properties in different parts and directions. In order to accurately characterize the mechanical properties of long bones and provide accurate bone material parameters for related research, the method of the present invention includes measurement of dimensions, division and cutting of two-way multi-gradient (axial and circumferential) specimen blocks, three-way rough testing cutting and grinding, and finally CNC fine milling.

First, a complete long bone is obtained, then the standardized sampling position along the axial direction is determined, and equal-thickness bone rings at different axial positions are obtained by cutting. Next, these bone rings were cut into four parts: anterior, posterior, inner, and outer parts along the circumferential direction, thereby obtaining a bidirectional multi-gradient (axial and circumferential) sample block. Then, a rough cortical bone sample with regular shape and smooth surface was obtained by grinding with two levels of roughness using a metallographic grinder.

This embodiment also includes the use of a high-precision automated CNC milling machine and customized fixtures to precisely control the cutting position and sample shape by optimizing the processing sequence, cutting path, and sample layout. The rough specimen will undergo rough and fine milling steps to ultimately produce smaller bidirectional multi-gradient (axial and circumferential) and three-dimensional (axial, circumferential and transverse) specimens. In addition, every time a preparation step is completed, it needs to be marked, checked with number and location to ensure the standardization and traceability of the operation. The entire sample preparation process is carried out under water-cooling conditions. After completion, the samples will be frozen and stored in an environment of minus 20 degrees Celsius.

The following is a detailed description of a sample preparation method for long bone non-uniform and anisotropic material parameter testing in the present invention. As shown in Figure 1, the method includes the following steps: positioning marking, bone ring cutting, quadrant marking and Division, quadrant block cutting, and specimen processing.

After obtaining the entire long bone, you first need to determine the length of the long bone's backbone, use a measuring tool to determine the midpoint of the backbone, and use a marker to mark a loop line at that location. This loop must be perpendicular to the axis of the long bone to ensure accuracy and consistency of the sample. Subsequently, along the axis of the backbone, offset 12.5 mm toward the proximal and distal ends respectively to establish an intermediate bone ring, and mark the corresponding cutting lines at these positions with a marker pen. Using the middle bone ring as a reference point, use a uniform percentage to determine the position of other bone rings in the axial direction of the long bone based on the total length of the diaphysis, and mark the center ring lines of other bone rings along the diaphyseal axis. In this embodiment, the percentage pitch is 7%.

As shown in Figure 2, according to the above markings, use an appropriate cutting tool (such as a wire saw) to precisely cut along the marked lines to obtain bone rings at different axial positions. During cutting, ensure alignment of the tool with the marked lines to maintain an even thickness of the bone ring. The cutting ring line of each bone ring is determined according to the mark in the previous step, that is, offset from the central ring line of each bone ring along the axis of the bone to the proximal end and distal end by 12.5 mm.

Before more detailed cutting, each bone ring needs to be divided into four quadrants along the circumferential direction: anterior (A), posterior (P), medial (L), and external (M). First, draw the dividing lines of the four quadrants on the outer surface of the bone ring. These lines should be evenly distributed along the circumference of the bone ring to ensure that each quadrant occupies an equal circumferential length. After marking these dividing lines, use a marker to write the corresponding quadrant marks on the surface of each quadrant, namely A (front), P (back), L (inner), M (outer). Next, draw the boundaries of the four quadrants on the cross-section of the bone ring based on the dividing lines of the four quadrants on the outer surface of each bone ring. This step is further preparation for specimen preparation within each quadrant. In each quadrant, further divide the transverse sample area (use a marker pen to mark a 12×4 area on the upper surface, try to mark from the edge) and the longitudinal sample area (try to be centered, mark 6×4 on the upper surface) 4), determine the final quadrant cutting line based on the division of the sample area.

According to the division of the sample area, the final quadrant cutting line is determined. Then, cut the bone ring into four separate quadrant pieces. On the cutting surface of each quadrant block, mark the name of the adjacent quadrant to facilitate subsequent identification and processing. Next, each quadrant block was further cut into transverse specimen blocks and longitudinal specimen blocks. On the six faces of each specimen block, the adjacent quadrants (A/P/L/M), proximal end (P), distal end (D), and outer circle need to be clearly marked. Marking of surface (O) and inner circular surface (I). At the same time, for the longitudinal specimen block, mark the longitudinal specimen (L), and on the transverse specimen block, mark the transverse specimen (T). These detailed markings help accurately track and identify the specific origin and location of each specimen during subsequent processing and analysis.

Sample processing includes sample rough processing and sample finishing.

Remove the marked transverse and longitudinal specimen blocks from each quadrant block. Use a metallographic grinder and silicon carbide sandpaper with a roughness of P1000 to polish the sample at a speed of 450 rpm under water cooling conditions. The grinding process aims to transform the irregular three-point bending specimen into a roughly regular shape, such as a rough transverse specimen of 20 mm × 12 mm × 4 mm and a rough longitudinal specimen of 20 mm × 6 mm × 4 mm. These dimensions can be appropriately adjusted based on actual cortical bone thickness. During the preparation process, the orientation of each side and the characters that should be marked need to be carefully recorded and marked immediately after the preparation is completed.

For the three-point bending rough specimen after cutting and grinding, if the accuracy does not meet the test requirements, a milling machine needs to be used for further finishing. According to the characteristics of the bone material and the size of the specimen, select a milling cutter with an appropriate diameter and a corresponding low rotational speed for operation. All milling processes were performed under water cooling conditions in a water tank to prevent specimen deformation due to high temperatures. Since milling machine processing may cause burrs on the edges of the specimen, silicon carbide sandpaper with a roughness of 1500 must be used to grind the four long edges of the specimen very lightly. In addition, if necessary, the surfaces of the specimen in contact with the two support axes and one loading axis should be lightly polished to ensure smooth and resistance-free deformation of the specimen. After polishing is completed, use a low-magnification microscope to carefully inspect the surface of the specimen to ensure that there are no remaining burrs. At the same time, in order to prevent the sample from overheating during processing, physiological saline with a concentration of 0.9% was continuously sprayed for cooling throughout the process. During the entire specimen preparation process, transverse specimens need to be marked as specimens No. 0 to No. 3 from the proximal end to the distal end. These markers help accurately track the origin and orientation of each specimen during subsequent testing and data analysis.

In addition, the invention also discloses a fixture and processing path of a CNC milling machine for manufacturing samples. As shown in Figure 3, the fixture can be fixedly installed on the operating table of a CNC milling machine. The fixture has eight grooves, and each groove can place a sample block. The fixture can be fixedly installed on the operating table of a CNC milling machine. Each recess is designed to accommodate a specific specimen block. When installing the sample block, one end face of the sample block is close to the corresponding end face of the groove, thereby ensuring that the sample block is placed accurately and avoiding deflection during processing.

The two ends of the sample block are tightened and fixed with two screws. Sample blocks of different thicknesses can be clamped according to the screwing depth. Each groove has six bolt holes. By changing the bolt holes into which the screws are screwed, a variety of (five) different lengths of specimen blocks can be fixed, providing flexibility in handling specimen blocks of different sizes.

The design of the fixture also takes into account the orientation of the specimen block. The fixture is divided into four quadrants A/M/P/L. The left side is dedicated to mounting longitudinal specimen blocks, while the right side is used to mount transverse and circumferential specimen blocks. This design allows each CNC milling machine operation to complete the processing of a complete long bone ring, and the placement position and direction of the specimen are fixed, effectively preventing confusion about the specimen and its direction.

In the embodiment of the present invention, it also includes using a special fixture designed according to Figure 3 to plan the processing paths of the two processes of rough milling and fine milling in a targeted manner. First, use a milling cutter with a diameter of 2mm for rough milling to create two large parallel flat upper and lower surfaces, ensuring that the distance between the two surfaces is approximately 2mm. Subsequently, fine milling is performed using a milling cutter with a diameter of 0.5 mm. Finally, 3-4 circumferential specimens (9mm×1.2mm×0.4mm) and 4-5 transverse specimens (9mm×1.2mm×0.4mm) were obtained from the transverse rough specimen, and the longitudinal specimen block was Then 2-4 longitudinal specimens (12mm×2mm×0.5mm) are obtained. Details are as follows:

At the beginning of processing, first use a milling cutter with a diameter of 2mm and operate in the order of A/M/P/L. At this stage, priority is given to processing the four longitudinal specimen blocks on the left side of the fixture, and immediately upon completion, the process moves to the circumferential and transverse specimen blocks on the right side. In order to ensure the efficiency and accuracy of the machining process, a down milling priority strategy and a method of pursuing the shortest machining path are adopted. During the rough milling process, the milling depth of each layer is set to 0.2mm, but in the last two layers of processing, the depth is adjusted to 0.1mm. The purpose of this is to reduce the number of tool lifts and ensure that each layer is milled to the specified thickness. The flat surface is shown in Figure 4(a). In addition, in order to further optimize the processing process, the path spacing is set to 1.8mm and the overlap rate is 10%.

The fine milling stage is shown in Figure 4(b). Continue processing in the same sequence using a milling cutter with a diameter of 0.5mm. At this stage, the grooves of the four longitudinal specimen blocks on the left are processed first, followed by the grooves of the circumferential and transverse specimen blocks on the right. During the fine milling process, a layered processing method was used to process the groove part of each sample block. The processing depth of each layer was controlled at 0.05mm, while the path spacing was set to 0.25mm, and the overlap rate was 50%. . This strategy of layering and fine control is designed to minimize deviations in specimen dimensions. At the same time, in order to improve processing efficiency and reduce idle stroke, after each sample block is processed, it is immediately moved to the next sample block for processing. Through this processing process, 8 sample blocks can be efficiently processed at one time, significantly improving the batch processing efficiency of samples while ensuring high precision and good quality of the samples.

In general, this embodiment provides a comprehensive and accurate process for the preparation of long bone cortical bone samples, including sample length normalization, definition and cutting of the long bone axial bone ring, and four circumferential quadrants of the long bone ring. Division and cutting, cutting and grinding of three-dimensional rough specimens for each quadrant, and CNC fine milling and storage of the final specimen. It not only ensures the standardization and accuracy of sample preparation, but also provides the ability to prepare bidirectional multi-gradient (axial, circumferential) and three-dimensional (axial, circumferential, transverse) anisotropic samples. Through such specimens, the mechanical behavior and material properties of long bones in different positions and directions can be more comprehensively revealed.

In addition, advanced processing technology and precise and efficient sample preparation methods are used to ensure the consistency of sample size and shape and the efficiency of the preparation process. An electric saw and fixed fixture are used to cut bone rings and sample blocks under water-cooling circulation conditions to ensure processing accuracy and improve work efficiency. During the grinding process of the rough sample block, use a metallographic grinder and silicon carbide sandpaper with a roughness of P600 and P1200 to grind at a speed of 450 rpm under water cooling conditions to ensure that the rough sample has a regular shape and a smooth surface. smooth. By using an automated CNC milling machine and a self-designed fixture, through two processes of rough milling and fine milling, the cutting position and sample shape can be accurately controlled, and the final sample can be processed in batches. At the same time, by optimizing the processing sequence, cutting path, and specimen layout, processing efficiency and consistency can be further improved. Make sure to obtain a sufficiently small and regularly shaped three-dimensional specimen. During the preparation process, a detailed and complete error-proofing mechanism was also designed, such as detailed labeling and recording of samples at each step, the use of specially designed fixtures and positioning devices, and the use of automated equipment to reduce human errors. By adjusting the processing path and parameters, the processing progress is monitored in real time, and adjustments and corrections are made in a timely manner during the processing to ensure the accuracy and consistency of the preparation.

The above are only embodiments of the present invention. Common knowledge such as the specific structures and characteristics that are known in the scheme are not described in detail here. Those of ordinary skill in the art know all the common technical knowledge in the technical field to which the invention belongs before the filing date or priority date. , be able to know all the existing technologies in this field, and have the ability to apply conventional experimental methods before this date. Persons of ordinary skill in the field can, under the inspiration given by this application, improve and implement this solution based on their own abilities. Some typical The well-known structures or well-known methods should not hinder those of ordinary skill in the art from implementing the present application. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These should also be regarded as the protection scope of the present invention and will not affect the implementation of the present invention. effectiveness and patented practicality. The scope of protection claimed in this application shall be based on the content of the claims, and the specific implementation modes and other records in the description may be used to interpret the content of the claims.

Claims (8)

1. A method of preparing a sample for testing parameters of a non-uniform and anisotropic material of a long bone, comprising: positioning and marking, bone ring cutting, quadrant marking and dividing, quadrant block cutting and sample processing; the positioning and marking step is used for determining the position of the middle bone ring on the diaphysis of the long bone and marking; the bone ring cutting step is used for cutting the bone ring along the marked ring line according to the length of the diaphysis of the long bone; the quadrant marking and dividing step is used for marking quadrant lines on the outer circular surface of the bone ring and dividing a transverse sample area and a longitudinal sample area in each quadrant; the quadrant block cutting step is used for cutting quadrants; the sample processing step includes rough processing and finish processing of the sample block.

2. The method of preparing a sample for testing parameters of heterogeneous and anisotropic materials of a long bone according to claim 1, wherein the positioning and marking step comprises marking a ring line at a midpoint of the diaphysis of the long bone, the ring line being perpendicular to the diaphysis axis; further comprising establishing an intermediate bone ring offset from the determined midpoint location a specific distance along the diaphyseal axis toward the proximal and distal ends, respectively.

3. The method for preparing a sample for testing parameters of heterogeneous and anisotropic materials of long bones according to claim 2, wherein the bone ring cutting step comprises sequentially biasing a specific distance from the middle position to the proximal end and the distal end respectively to determine the middle loop line of each bone ring; the method also comprises the steps of respectively biasing a certain distance from the central loop line of each bone loop to the proximal end and the distal end along the diaphysis axis to determine the marking loop line of each bone loop; the specific distance is determined according to the backbone length and the specific percentage spacing.

4. A method of preparing a sample for testing parameters of non-uniform and anisotropic materials for long bones according to claim 2 or 3, wherein said offset specific distance is 12.5mm.

5. A method of preparing a sample for testing parameters of non-uniform and anisotropic materials for long bones according to claim 3, wherein the quadrant block cutting step comprises determining quadrant cut lines from the division of the transverse sample areas and the longitudinal sample areas, and cutting the bone ring into four separate quadrant blocks according to the quadrant cut lines.

6. The method of preparing a sample for testing parameters of non-uniform and anisotropic materials for long bones according to claim 5, wherein the quadrant block cutting step further comprises cutting each quadrant block into a transverse coupon and a longitudinal coupon; marking each surface of the sample block; the marks include marks for adjacent quadrants, marks for proximal and distal ends, marks for outer and inner circular surfaces, and marks for distinguishing transverse and longitudinal properties of the sample.

7. The method for preparing a test specimen for heterogeneous and anisotropic material parameters testing of long bones according to claim 1, wherein the rough machining in the specimen processing step comprises processing the test specimen block under water-cooling condition using a metallographic grinder and silicon carbide sandpaper with P1000 roughness to obtain a lateral rough specimen and a longitudinal rough specimen.

8. The method of preparing a sample for testing parameters of non-uniform and anisotropic materials for long bones according to claim 7, wherein the finishing in the sample processing step comprises milling machine processing; the method further comprises the step of edge polishing of the sample block processed by the milling machine by using silicon carbide abrasive paper with P1500 roughness; the sample block after milling machine processing comprises a circumferential sample and a transverse sample which are obtained after finish milling of a transverse rough sample, and a longitudinal sample which is obtained after finish milling of a longitudinal rough sample.