牛皮质骨脆性评估的划痕试验
Summary
本研究通过显微划痕试验, 评估了亚细层的牛皮质骨断裂韧性。这是一个原始的, 客观的, 严谨的, 和可重现的方法来探测宏观尺度下的断裂韧性。潜在的应用是研究骨质脆性的变化, 由于疾病, 如骨骼。
Abstract
骨是一种复杂的分层材料, 具有五不同层次的组织。诸如衰老和骨质疏松等疾病等因素增加了骨骼的脆弱性, 使其容易骨折。由于社会经济对骨折的巨大影响, 我们需要有新的方法来评估每个等级的骨骼的力学性能。尽管在所有尺度下都可以探测到刚度和强度–纳米、微观、细观和宏观–断裂评估迄今仅限于宏观测试。这一局限性限制了我们对骨折的认识, 制约了实验室和临床研究的范围。在本研究中, 我们利用微划痕试验和非线性断裂力学相结合的方法, 从微观到细观长度尺度来考察骨的抗裂性。对牛皮质骨标本进行短纵向定位试验。建立了细致的实验方案, 并进行了大量 (102) 试验, 以评估皮质骨标本的断裂韧性, 同时核算与骨显微结构有关的异质性。
Introduction
在本研究中, 我们用一种新颖的微划痕技术 (1、2、3、4, 测量从中尺度 (骨) 到微型 (层状) 的牛骨的断裂韧性, 5。由于不同层次的结构成分和组织不同, 断裂过程包括裂纹萌生和裂纹扩展直接影响着骨的长度尺度。因此, 评估较小长度的骨骨折是至关重要的, 以产生对骨骼脆弱性的基本认识。一方面, 常规的测试, 如三点弯曲, 紧凑的张力, 和弯曲试验通常进行的牛股骨和胫骨骨折的表征在宏观尺度6,7, 8. 另一方面, 为了测量显微尺度下的断裂韧性, 提出了硬度的压痕断裂.9。利用硬度的压进行微压痕产生径向裂纹。此外, 奥利弗法尔压断裂韧性的方法是使用一个尖锐的立方体角压10。
在上述压基断裂韧性研究中, 用观测器测量了由此产生的裂纹长度, 并用半经验模型计算了断裂韧性。然而, 这些方法是不可的, 主观的, 结果是高度依赖于观察者的技能, 由于需要测量的裂纹长度使用光学显微镜或扫描电子显微镜。此外, 在纳米级进行了划痕测试, 但基础数学模型不是基于物理的, 因为它没有考虑到由于裂缝和缺陷而导致的强度下降11。因此, 存在一个知识缺口: 一种基于物理力学模型的微观层次断裂评价方法。这一知识的缺口, 通过先聚焦于猪标本5, 促使微划痕试验应用于致密骨。这项研究现已进一步扩展, 以了解牛皮质骨。
试样的两个不同方向是可能的: 纵向横向和短纵向。纵向横向对应于股骨纵轴线的断裂性质。而短的纵向对应于股骨纵轴的断裂特性5。在这项研究中, 我们对牛皮质骨进行了划痕测试, 以表征骨在短的纵向方向上的骨折阻力。
Protocol
注: 这里描述的协议, 遵循动物保育指南的伊利诺伊州机构动物护理和使用委员会。 1. 标本采购 收集新鲜收获的牛股骨从美国农业部 (USDA) 认证屠宰场和运输他们在塑料空气紧密袋在一个冷却器。注意: 在这里进行的研究中, 股骨是从 24-30 月大的动物那里采集的, 玉米喂养的, 体重约 1000-1100 磅。 将股骨冻结在-20 ° c, 直到试样准备过程开始。此温度保持…
Representative Results
用原子力显微镜测量抛光表面的粗糙度。作为一个经验法则, 如果表面粗糙度是一个数量级小于感兴趣的表面特征, 那么试样就有资格作为一个抛光的。在这种情况下, 测量的表面粗糙度 60 nm 超过40µm x 40 µm 区域显然属于这个标准。 图 4显示了在短的纵向牛皮质骨标本上进行的典型划痕试验的力与穿透深?…
Discussion
微划痕测试导致混合模式的断裂3。此外, 在短的纵向牛皮质骨标本, 骨折的过程是激活的探针挖更深。对于一个3毫米长的划痕, 探测到的棱柱体积大约是3600µm 长, 600 µm 宽, 480 µm 深。这一大体积有助于预测均匀反应。一个非线性断裂力学模型, 使我们能够提取的断裂阻力基于J-积分计算1,2,4。
<p class="…Disclosures
The authors have nothing to disclose.
Acknowledgements
这项工作得到了土木和环境工程部和伊利诺伊大学香槟分校工程学院的支持。我们承认答 Kinra 和 Kavita Kinra 奖学金, 以支持 Kavya Mendu 的研究生研究。扫描电子显微镜调查在弗雷德里克塞茨材料研究实验室和贝克曼研究所在伊利诺伊大学香槟分校的设施进行。
Materials
| Table Top Diamond Band Saw | McMaster Carr, Elmhurst, IL | Model C-40 | Blade speed of 40 mph; Blade dimensions: 37 inch in diameter, 0.02 inch wide and 0.14 inch deep |
| Buehler Isomet 5000 Precision Cutter | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 112780 | Blade speed in the range of 200-5000 rpm in 50 rpm incrments; 8 inch diamond wafering blade |
| Branson 5800 Ultrasonic Cleanser | (Through) Grainger, Peoria, Illinois | 39J365 | Bransonic CPXH ultrasonic bath has a tank capacity of 2.5 gal |
| Buehler Ecomet 250 Grinder – Polisher | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 497250 | 8 inch base plate with a speed range from 10-500 rpm |
| Anton Paar, CSM Instruments Micro scratch tester | Anton Paar Switzerland AG | 163251 | Compact Platform, Acoutstic Emission Sensor |
| JEOL 6060LV general purpose scanning electron microscope | JEOL USA, Inc., Peabody, MA | Environmental scanning electron microscope which enables imaging at low vacuum levels. | |
| Philips XL30 ESEM FEG | FEI Company | Wet mode working of the instrument enables imaging of non conductive samples without altering them | |
| Name | Company | Catalog Number | Comments |
| Consumables | |||
| Bovine Femur | L&M Slaughter house, Georgetown, IL | Corn fed, 24-30 month old mature bovine specimens. | |
| Alconox Powdered Precision Cleaner | Alconox, Inc., 30 Glenn St., Ste. 309, White Plains, NY, 10603 | 1104-1 | Biodegradable, Non caustic, Interfering-residue free |
| Acrylic Plastic Casting | Electron Microscopy Sciences | 24210-02 | Polymethyl Methacrylate |
| CarbiMet SiC Abrasive Paper 400 grit, 8 inch, PSA backed | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 36080400 | Grinding – Abrasive Papers |
| CarbiMet SiC Abrasive Paper 600 grit, 8 inch, PSA backed | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 36080600 | Grinding – Abrasive Papers |
| MicroCut Discs 800 grit, 8 inch, PSA backed | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 36080800 | Grinding – Abrasive Papers |
| MicroCut Discs 800 grit, 8 inch, PSA backed | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 16081200 | Grinding – Abrasive Papers |
| Texmet P For 8'' Wheel PSA | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 407638 | Polishing Cloth |
| 8'' Microcloth PSA | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 407518 | Polishing Cloth |
| Meta Di Supreme Polycrystalline Diamond Suspension, 3 µm | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 406631 | Polishing suspension |
| Meta Di Supreme Polycrystalline Diamond Suspension, 1 µm | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 406630 | Polishing suspension |
| Meta Di Supreme Polycrystalline Diamond Suspension, 0.25 µm | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 406629 | Polishing suspension |
| MasterPrep Polishing Suspension, 0.05µm | Buehler,41 Waukegan Rd, Lake Bluff, IL 60044 | 40-6377-032 | Polishing suspension |
| HBSS, calcium, magnesium, no phenol red | Thermo Fisher Scientific | 14025126 | Buffer Solution |
References
- Akono, A., Reis, P., Ulm, F. Scratching as a fracture process: From butter to steel. Phys Rev Lett. 106 (20), 204302-204304 (2011).
- Akono, A. T., Randall, N. X., Ulm, F. J. Experimental determination of the fracture toughness via microscratch tests: application to polymers, ceramics, and metals. J of Mat Res. 27 (02), 485-493 (2012).
- Akono, A. T., Ulm, F. J. An improved technique for characterizing the fracture toughness via scratch test experiments. Wear. 313 (1-2), (2014).
- Akono, A. T. Energetic size effect law at the microscopic scale: Application to progressive-load scratch testing. J of Nanomech and Micromech. 6 (2), (2016).
- Kataruka, A., Mendu, K., Okeoghene, O., Puthuvelil, J., Akono, A. -. T. Microscopic assessment of bone toughness using scratch tests. Bone Reports. 6, 17-25 (2017).
- Melvin, J. W., Evans, F. G. Crack propagation in bone. ASME Biomech Symp. , (1973).
- Norman, T. L., Vashishth, D., Burr, D. B. Effect of groove on bone fracture toughness. J of Biomech. 25 (12), 1489-1492 (1992).
- Behiri, J. C., Bonfield, W. Crack velocity dependence of longitudinal fracture in bone. J of Mat Sc. 15 (7), 1841-1849 (1980).
- Mullins, L. P., Bruzzi, M. S., McHugh, P. E. Measurement of the microstructural fracture toughness of cortical bone using indentation fracture. J of Biomech. 40 (14), 3285-3288 (2007).
- Harding, D. S., Oliver, W. C., Pharr, G. M. Cracking during nanoindentation and its use in the measurement of fracture toughness. MRS Proceedings. 356, 663-668 (1994).
- Islam, A., Dong, X. N., Wang, X. Mechanistic modeling of a nanoscratch test for determination of in situ toughness of bone. J of the Mech Bhvr of Biomed Mat. 5 (1), 156-164 (2012).
- McAlden, R. W., McGeogh, J. A., Barker, M. B., Court-Brown, C. M. Age-related changes in the tensile properties of cortical bone: the relative importance of changes in porosity, mineralization and microstructure. J. Bone Joint Surg. 75, 1193-1205 (1993).
- Zioupos, P., Gresle, M., Winwood, K. Fatigue strength of human cortical bone: age, physical, and material heterogeneity effects. J of Biomed Mat Res Part A. 86 (3), 627-636 (2008).
- Linde, F., Sørensen, H. C. F. The effect of different storage methods on the mechanical properties of trabecular bone. J of Biomech. 26 (10), 1249-1252 (1993).
- Zioupos, P. Accumulation of in-vivo fatigue microdamage and its relation to biomechanical properties in ageing human cortical bone. J of Microscopy. 201 (2), 270-278 (2001).
- Yan, J., Clifton, K. B., Mecholsky, J. J., Reep, R. L. Fracture toughness of manatee rib and bovine femur using a chevron-notched beam test. J of Biomech. 39 (6), 1066-1074 (2006).
- Xu, J., Rho, J. Y., Mishra, S. R., Fan, Z. Atomic force microscopy and nanoindentation characterization of human lamellar bone prepared by microtome sectioning and mechanical polishing technique. J of Biomed Mat ResPart A. 67 (3), 719-726 (2003).
- Yan, J., Mecholsky, J. J., Clifton, K. B. How tough is bone? Application of elastic–plastic fracture mechanics to bone. Bone. 40 (2), 479-484 (2007).
- Ritchie, R. O. The conflicts between strength and toughness. Nat Mater. 10 (11), 817-822 (2011).
- Kim, K. T., Bažant, Z. P., Yu, Q. Non-uniqueness of cohesive-crack stress-separation law of human and bovine bones and remedy by size effect tests. Intrnl J of Frac. 181 (1), 67-81 (2013).
- Bazant, Z. P., Planas, J. . Fracture and size effect in concrete and other quasibrittle materials. 16, (1997).
Cite This Article
Mendu, K., Kataruka, A., Puthuvelil, J., Akono, A. Fragility Assessment of Bovine Cortical Bone Using Scratch Tests. J. Vis. Exp. (129), e56488, doi:10.3791/56488 (2017).