Fracture Mechanics of Bone

1993 ◽  
Vol 115 (4B) ◽  
pp. 549-554 ◽  
Author(s):  
J. W. Melvin
Keyword(s):  
Fracture Mechanics ◽  
Bone Fracture ◽  
Longitudinal Crack ◽  
Compact Bone ◽  
Plastic Zone Size ◽  
Geometric Constraints ◽  
External Loading ◽  
Specimen Thickness ◽  
Critical Crack ◽  
Critical Crack Length

This paper reviews the progress that has been made in applying the principles of fracture mechanics to the topic of fracture of long bones. Prediction of loading conditions which result in the propagation of fractures in bones has been of interest to the field of trauma biomechanics and orthopedics for over one hundred years. Independent verifications, by various investigators, of bone fracture mechanics parameters are reviewed and investigations of the effects of bone density and specimen thickness on the critical fracture mechanics parameters and of other factors such as critical crack length and plastic zone size in bovine femoral bone, and the effects of crack velocity on fracture mechanics parameters in bovine tibial bone are discussed. It took over ten years for the techniques of bone fracture mechanics to be applied to human compact bone, due primarily to geometric constraints from the smaller size of human bones. That work will be reviewed along with other continuing work to define the orientation dependence of the fracture mechanics parameters in bone and to refine the experimental techniques needed to overcome the geometric constraints of specimen size. A discussion is included of work still needed to determine fracture mechanics parameters for transverse and longitudinal crack propagation in human bone and to establish the effects of age on those parameters. Finally, a discussion will be given of how this knowledge needs to be extended to allow prediction of whole bone fracture from external loading to aid in the design of protective systems.

Fracture toughness, critical crack length and plastic zone size in bone

1978 ◽  
Vol 11 (8-9) ◽  
pp. 359-364 ◽  
Author(s):  
Diane Margel Robertson ◽  
David Robertson ◽  
Craig R Barrett
Keyword(s):  
Fracture Toughness ◽  
Plastic Zone ◽  
Crack Length ◽  
Plastic Zone Size ◽  
Zone Size ◽  
Critical Crack ◽  
Critical Crack Length

Damage Tolerance Assessment of Multi-Hull Aluminum Vessels Using Global Finite Element Methods

2021 ◽  
Author(s):  
Spencer Johnson ◽  
Boyden Williams ◽  
Christopher Palm
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
High Speed ◽  
Damage Tolerance ◽  
Element Model ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Hull Structure ◽  
Class Dynamic ◽  
Critical Locations

As aluminum high-speed multi-hulls continue to grow in size, capacity and operational sea state, a need is growing to understand the damage tolerance of these structures. This paper presents a Linear Elastic Fracture Mechanics (LEFM) approach to performing damage tolerance assessments of aluminum hull structures using the hydrodynamic analysis and global finite element model developed as part of a class Dynamic Loading Approach (DLA) notation. The LEFM approach is used to calculate the stress intensity factor (K) and the critical crack length throughout the model to screen the entire hull structure and identify fracture critical locations. This paper also investigates the use of elastic-plastic fracture mechanics to predict potential critical crack growth locations, rates, and directions. Fracture critical locations identified and visualized through the analysis provide the ship designer with tools to develop damage tolerant structures. The results of the analysis can also assist owners and regulatory bodies in developing structural inspection and repair plans.

scholarly journals Snow fracture in relation to slab avalanche release: critical state for the onset of crack propagation

2017 ◽  
Vol 11 (1) ◽  
pp. 217-228 ◽  
Author(s):  
Johan Gaume ◽  
Alec van Herwijnen ◽  
Guillaume Chambon ◽  
Nander Wever ◽  
Jürg Schweizer
Keyword(s):  
Crack Propagation ◽  
Slope Angle ◽  
Critical Length ◽  
Snow Layer ◽  
Critical Crack ◽  
Critical Crack Length ◽  
New Model ◽  
Avalanche Forecasting ◽  
Weak Layer ◽  
Recent Developments

Abstract. The failure of a weak snow layer buried below cohesive slab layers is a necessary, but insufficient, condition for the release of a dry-snow slab avalanche. The size of the crack in the weak layer must also exceed a critical length to propagate across a slope. In contrast to pioneering shear-based approaches, recent developments account for weak layer collapse and allow for better explaining typical observations of remote triggering from low-angle terrain. However, these new models predict a critical length for crack propagation that is almost independent of slope angle, a rather surprising and counterintuitive result. Based on discrete element simulations we propose a new analytical expression for the critical crack length. This new model reconciles past approaches by considering for the first time the complex interplay between slab elasticity and the mechanical behavior of the weak layer including its structural collapse. The crack begins to propagate when the stress induced by slab loading and deformation at the crack tip exceeds the limit given by the failure envelope of the weak layer. The model can reproduce crack propagation on low-angle terrain and the decrease in critical length with increasing slope angle as modeled in numerical experiments. The good agreement of our new model with extensive field data and the ease of implementation in the snow cover model SNOWPACK opens a promising prospect for improving avalanche forecasting.

Determination of Critical Crack Size Utilizing a Fracture Mechanics Test in Equipment Under Fatigue

2009 ◽  
Author(s):  
Irene Garcia Garcia ◽  
Radoslav Stefanovic
Keyword(s):  
Heat Treatment ◽  
Fracture Mechanics ◽  
Crack Size ◽  
Operational Experience ◽  
Element Analysis ◽  
Critical Crack ◽  
Circumferential Welds ◽  
Fea Model ◽  
Critical Crack Size

Equipment that is exposed to severe operational pressure and thermal cycling, like coke drums, usually suffer fatigue. As a result, equipment of this sort develop defects such as cracking in the circumferential welds. Operating companies are faced with the challenges of deciding what is the best way to prevent these defects, as well as determining how long they could operate if a defect is discovered. This paper discusses a methodology for fracture mechanics testing of coke drum welds, and calculations of the critical crack size. Representative samples are taken from production materials, and are welded employing production welding procedures. The material of construction is 1.25Cr-0.5Mo low alloy steel conforming to ASME SA-387 Gr 11 Class 2 in the normalized and tempered condition (N&T). Samples from three welding procedures (WPS) are tested: one for production, one for a repair with heat treatment, and one for repair without heat treatment. The position and orientation of test specimen are chosen based on previous surveys and operational experience on similar vessels that exhibited cracks during service. Fracture mechanics toughness testing is performed. Crack finite element analysis (FEA) model is used to determine the path-independed JI-integral driving force. Methodology for the determination of critical crack size is developed.

Fracture mechanics study of a pipe bend with a longitudinal crack under static loading

1990 ◽  
Vol 119 (2-3) ◽  
pp. 347-360 ◽  
Author(s):  
Dietmar Uhlmann ◽  
Harald Diem ◽  
Stefan Brosi
Keyword(s):  
Fracture Mechanics ◽  
Static Loading ◽  
Longitudinal Crack ◽  
Pipe Bend

A LIFE PREDICTION MODEL OF THERMAL BARRIER COATINGS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 3161-3166 ◽  
Author(s):  
LIYONG NI ◽  
CHAO LIU ◽  
CHUNGEN ZHOU
Keyword(s):  
Crack Propagation ◽  
Prediction Model ◽  
Thermal Barrier Coatings ◽  
Life Prediction ◽  
Crack Propagation Rate ◽  
Thermal Barrier ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Barrier Coatings ◽  
Life Prediction Model

The durability and reliability of thermal barrier coatings(TBCs) have become a major concern of hot-section components due to lack of a reliable life prediction model. In this paper, it is found that the failure location of TBCs is at the TBC/TGO interface by a sequence of crack propagation and coalescence process. The critical crack length of failure samples is 8.8mm. The crack propagation rate is 3-10µm/cycle at the beginning and increases largely to 40µm/cycle near coating failure. A life prediction model based a simple fracture mechanics approach is proposed.

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