scholarly journals What is the influence of two strain rates on the relationship between human cortical bone toughness and micro-structure?

2019 ◽  
Vol 234 (3) ◽  
pp. 247-254 ◽  
Author(s):  
Rémy Gauthier ◽  
Hélène Follet ◽  
Max Langer ◽  
Françoise Peyrin ◽  
David Mitton
Keyword(s):  
Crack Propagation ◽  
Strain Rate ◽  
Cortical Bone ◽  
Static Loading ◽  
Fracture Mechanisms ◽  
Strain Rates ◽  
Micro Structure ◽  
Human Cortical Bone ◽  
Cross Links ◽  
Haversian System

Cortical bone fracture mechanisms are well studied under quasi-static loading. The influence of strain rate on crack propagation mechanisms needs to be better understood, however. We have previously shown that several aspects of the bone micro-structure are involved in crack propagation, such as the complete porosity network, including the Haversian system and the lacunar network, as well as biochemical aspects, such as the maturity of collagen cross-links. The aim of this study is to investigate the influence of strain rate on the toughness of human cortical bone with respect to its microstructure and organic non-collagenous composition. Two strain rates will be considered: quasi-static loading (10−4 s−1), a standard condition, and a higher loading rate (10−1 s−1), representative of a fall. Cortical bone samples were extracted from eight female donors (age 50–91 years). Three-point bending tests were performed until failure. Synchrotron radiation micro-computed tomography imaging was performed to assess bone microstructure including the Haversian system and the lacunar system. Collagen enzymatic cross-link maturation was measured using a high performance liquid chromatography column. Results showed that that under quasi-static loading, the elastic contribution of the fracture process is correlated to both the collagen cross-links maturation and the microstructure, while the plastic contribution is correlated only to the porosity network. Under fall-like loading, bone organization appears to be less linked to crack propagation.

Fracture resistance of human cortical bone across multiple length-scales at physiological strain rates

Biomaterials ◽  
2014 ◽  
Vol 35 (21) ◽  
pp. 5472-5481 ◽  
Author(s):  
Elizabeth A. Zimmermann ◽  
Bernd Gludovatz ◽  
Eric Schaible ◽  
Björn Busse ◽  
Robert O. Ritchie
Keyword(s):  
Cortical Bone ◽  
Fracture Resistance ◽  
Strain Rates ◽  
Physiological Strain ◽  
Length Scales ◽  
Human Cortical Bone ◽  
Multiple Length Scales

Strain Rate Sensitivity of Mixed SAC-SnBi Solder Joints

2019 ◽  
Vol 2019 (1) ◽  
pp. 000480-000487
Author(s):  
Luke A. Wentlent ◽  
James Wilcox ◽  
Xuanyi Ding
Keyword(s):  
Melting Point ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Solder Joints ◽  
Volume Ratio ◽  
Rate Sensitivity ◽  
Thermal Exposure ◽  
Fracture Mechanisms ◽  
Eutectic System ◽  
Strain Rates

Abstract As the electronics industry continues to evolve a concerted effort has developed to implement lower melting point solders. The ability to minimize the thermal exposure that an assembly is subjected to affords significant benefits with respect to both the reliability and the materials that can be used. One of the most popular low melt solder alloys currently being investigated by the industry is the Bi-Sn eutectic system, which has a melting point of 139°C. The BiSn system itself is not particularly novel as it was posited as a SAC alternative during the initial shift from Pb based solders. While a body of knowledge currently exists regarding this system, and the near eutectic variant BiSnAg, there are still concerns regarding its ductility, especially as a function of thermal exposure and strain rate. Bismuth is widely acknowledged as a brittle element and its presence in such quantities raises concerns of not just Cu6Sn5 embrittlement but also solder fragility in high strain rate types of environments. A challenge with regards to near term implementation is that most packages are not available with BiSn solder bumps. Therefore, it will be necessary to use components already balled with SAC 305 solder. This means that the resulting solder interconnect, reflowed below conventional SAC reflow temperatures, will form a type of mixed hybrid microstructure. This non-equilibrium microstructure will be composed of two regions, one Bi-rich region which is well past saturation and a second region which is Bi-deficient. It is of specific industrial interest then to not just investigate the BiSn solder system but also within the context of a realistic mixed interconnect. Recent work by several researchers has shown that this hybrid microstructure is unstable and quite active with respect to the movement and localized concentration of the Bismuth. The degree of mixing of these two regions has been shown to be highly dependent upon reflow temperature and the paste to ball volume ratio. Mixed SAC-BiSn solder joints were formed by placing SAC 305 spheres on BiSn paste deposits for a paste to ball volume ratio of .18. These samples were then reflowed at either 175°C or 200°C. SAC 305 control samples were also made using a conventional Pb-free reflow profile with a peak temperature of 247°C. A 22 mil Cu-OSP pad on a 1.0 mm thick FR4 substrate was used for all samples. A selection of the solder joints were then isothermally aged at 90°C for 200 hours. Using a joint level micromechanical tester, ball shear tests were conducted at a range of strain rates for samples in the as-reflowed and aged state. Using this information, the strain rate sensitivity of the interconnects was mapped and correlated with the observed failure modes. Investigations into the fracture mechanisms were conducted by examining the shear fracture surface with optical and scanning electron microscopy. Additionally, the evolution of the microstructure was characterized. Results showed a clear transition from ductile solder failure to a brittle separation failure at the higher strain rates.

scholarly journals A multispecies investigation of the strain rate sensitivity of the modulus of cortical bone

2021 ◽  
Vol 250 ◽  
pp. 06003
Author(s):  
Claire Victoria Rampersadh ◽  
Lee-Anne Welgemoed ◽  
Trevor John Cloete
Keyword(s):  
Strain Rate ◽  
Cortical Bone ◽  
Rate Sensitivity ◽  
Species Variation ◽  
Strain Rates ◽  
Intermediate Strain Rate ◽  
Inherent Feature ◽  
Rate Effects ◽  
Static Regime ◽  
Testing Protocols

The stiffness of cortical bone shows both inter- and intra-species variation. Currently, it is unclear whether this variation is due to differing testing protocols or an inherent feature of the material. Additionally, there is a lack of literature dealing with species other than human and bovine, particularly in the intermediate strain rate regime. In this study, cortical bone specimens were machined from the femurs of four species: baboon, crocodile, sheep and ostrich. Specimens were tested in the quasi-static and intermediate strain rate regimes using consistent testing protocols implemented by a single researcher. The results show a similar strain rate dependence for all species, i.e. the modulus shows negligible rate effects in the quasi-static regime, but a significant increase when moving to intermediate strain rates. This suggests that while the stiffness of the bone is species dependent, the effect of strain rate may be species independent. The observed intra- and inter-species variation is less than that reported in literature, highlighting the importance of a consistent testing protocol in multi-species studies.

Experimental Study on Mechanism of Crack Coalescence between Two Pre-Existing Flaws under Dynamic Loading

2006 ◽  
Vol 324-325 ◽  
pp. 117-120 ◽  
Author(s):  
Ping Zhang ◽  
Ning Li ◽  
Ruo Lan He
Keyword(s):  
Crack Propagation ◽  
Dynamic Loading ◽  
Static Loading ◽  
Crack Coalescence ◽  
Engineering Practice ◽  
Strength Increase ◽  
Strain Rates ◽  
Inertia Effect ◽  
Coalescence Pattern ◽  
Static And Dynamic Loading

More and more engineering practice indicates rock mass is prone to lose its stability through crack coalescence under dynamic loading, such as blasting and earthquake. However, the crack coalescence pattern of rock specimens containing two or more flaws has not been studied comprehensively under dynamic loading. In this paper, the mechanism of the crack coalescence and peak strength of sandstone-like materials containing two parallel flaws are studied under uniaxial static and dynamic loading with strain rates 1.7×10-5 s-1 and 1.7×10-1 s-1. Through the comparisons of the propagation length, coalescence pattern of the cracks and strength increase of the pre-cracked specimens under static and dynamic loading, the dynamic response of the crack coalescence is found different from static loading under different geometric setting of the flaws. The inertia effect of the crack propagation is revealed under dynamic loading, that is to say, the growth of the secondary cracks tends to the original propagation direction, and the direct and immediate coalescence is taken place easily between two pre-existing flaws, which is different from the kinking coalescence under static loading. So, the inertia effect of the crack propagation is regarded as the main cause of the strength increase of the brittle material under dynamic loading for medium strain rates. In virtue of the explanation, another cause of the mode II shear fracture occurred under earthquake is opened out.

Dynamic Tensile Characteristics of DP600 Steel Sheets for Automotive Applications

2012 ◽  
Vol 509 ◽  
pp. 40-45
Author(s):  
Dan Yang Dong ◽  
Yang Liu ◽  
Lei Wang ◽  
Chang Sheng Liu
Keyword(s):  
Strain Rate ◽  
Tensile Testing ◽  
High Speed ◽  
Greenhouse Gas Emission ◽  
Testing Machine ◽  
Fracture Mechanisms ◽  
Strain Rates ◽  
Automotive Applications ◽  
Tensile Testing Machine ◽  
Steel Sheets

To reduce fuel consumption and greenhouse gas emission, dual phase (DP) steels have been considered for automotive applications due to their higher tensile strength, better initial work hardening along with larger elongation compared to conventional grade of steels. In such applications, which would create potential safety and reliability issues under dynamic loading, the mechanical behavior of DP steel considering the strain rate must be examined. In the present study, the dynamic tensile behavior of DP600 steel sheets was investigated using a high-speed tensile testing machine at various strain rates. And the quasi-static tensile testing was also conducted on the steel to understand the effect of the strain rate on the tensile property. The fracture mechanisms of the steel were also analyzed. The results show that the mechanical properties of DP600 steel are noticeably influenced by the strain rates. As the strain rate increases, the strength of the steel increases and the obvious yield phenomenon can be observed when the strain rate is above 0.01 s-1. The fracture elongation of DP600 steels decreases with increasing strain rate from 0.001 to 1 s-1, then increases up to the strain rate of 100 s-1 and reaches the lowest value at the strain rate of 1000 s-1. DP600 steel sheet exhibit typical ductile fracture characteristics with dimples morphology of the facture surface when tensile deformed at various strain rates.

The Effect of Strain Rate on the Mechanical Properties of Human Cortical Bone

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Ulrich Hansen ◽  
Peter Zioupos ◽  
Rebecca Simpson ◽  
John D. Currey ◽  
David Hynd
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Cortical Bone ◽  
Maximum Load ◽  
Strain Rate Range ◽  
Stress And Strain ◽  
Tension Stress ◽  
Strain Rates ◽  
Tension And Compression ◽  
Ductile To Brittle Transition

Bone mechanical properties are typically evaluated at relatively low strain rates. However, the strain rate related to traumatic failure is likely to be orders of magnitude higher and this higher strain rate is likely to affect the mechanical properties. Previous work reporting on the effect of strain rate on the mechanical properties of bone predominantly used nonhuman bone. In the work reported here, the effect of strain rate on the tensile and compressive properties of human bone was investigated. Human femoral cortical bone was tested longitudinally at strain rates ranging between 0.14–29.1s−1 in compression and 0.08–17 s−1 in tension. Young’s modulus generally increased, across this strain rate range, for both tension and compression. Strength and strain (at maximum load) increased slightly in compression and decreased (for strain rates beyond 1 s−1) in tension. Stress and strain at yield decreased (for strain rates beyond 1 s−1) for both tension and compression. In general, there seemed to be a relatively simple linear relationship between yield properties and strain rate, but the relationships between postyield properties and strain rate were more complicated and indicated that strain rate has a stronger effect on postyield deformation than on initiation of yielding. The behavior seen in compression is broadly in agreement with past literature, while the behavior observed in tension may be explained by a ductile to brittle transition of bone at moderate to high strain rates.

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