Trinity Centre for Bioengineering, Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland.
J Mech Behav Biomed Mater. 2018 Jan;77:776-782. doi: 10.1016/j.jmbbm.2017.07.007. Epub 2017 Jul 5.
Many biological materials fail by cracking. Examples are bone fractures, contact damage in eggs, splits in bamboo culm and defects in cartilage. The mechanical property that best describes failure by cracking is fracture toughness, which quantifies the ease with which cracks propagate and defines a material's tolerance for pre-existing cracks and other stress concentrating features. The measurement of fracture toughness presents some challenges, especially for biological materials. To obtain valid results requires care and, in many cases, considerable ingenuity to design an appropriate specimen and test protocol. Common mistakes include incorrect interpretation of the mechanics of loading in unusual specimen designs, and failures occurring at the material's ultimate tensile strength as a result of specimens or cracks being too small. Interpretation of the resulting toughness data may also present challenges, for example when R-curve behaviour is present. In this article, examples of good and bad practice are described, and some recommendations made.
许多生物材料会因开裂而失效。例如，骨骼断裂、鸡蛋的接触损伤、竹秆的裂缝和软骨缺陷。最能描述开裂失效的力学性能是断裂韧性，它量化了裂纹扩展的容易程度，并定义了材料对预先存在的裂纹和其他应力集中特征的容忍度。断裂韧性的测量存在一些挑战，特别是对于生物材料。要获得有效的结果，需要小心谨慎，并且在许多情况下，需要相当的创造力来设计合适的试样和测试方案。常见的错误包括对不寻常试样设计中加载力学的不正确解释，以及由于试样或裂纹太小而导致在材料的极限拉伸强度处发生失效。韧性数据的解释也可能存在挑战，例如当存在 R 曲线行为时。本文描述了良好和不良实践的例子，并提出了一些建议。
