Shell Fracture Research Articles

Finite strain fracture of plates and shells with configurational forces and edge rotations

SUMMARYWe propose a simple and efficient algorithm for FEM‐based computational fracture of plates and shells with both brittle and ductile materials on the basis of edge rotation and load control. Rotation axes are the crack front nodes, and each crack front edge in surface discretizations affects the position of only one or two nodes. Modified positions of the entities maximize the modified mesh quality complying with the predicted crack path (which depends on the specific propagation theory in use). Compared with extended FEM or with classical tip remeshing, the proposed solution has algorithmic and generality advantages. The propagation algorithm is simpler than the aforementioned alternatives, and the approach is independent of the underlying element used for discretization. For history‐dependent materials, there are still some transfer of relevant quantities between elements. However, diffusion of results is more limited than with tip or full remeshing. To illustrate the advantages of our approach, three prototype models are used: tip energy dissipation linear elastic fracture mechanics (LEFM), cohesive‐zone approaches, and ductile fracture. Both the Sutton crack path criterion and the path estimated by the Eshelby tensor are employed. Traditional fracture benchmarks, including one with plastic hinges, and newly proposed verification tests are solved. These were found to be very good in terms of crack path and load ∕ deflection accuracy. Copyright © 2013 John Wiley & Sons, Ltd.

A hail damaged Eastern Long-neck turtle: a case study

Veterinary practices may be presented with both captive and wild turtles that have sustained shell fractures caused by such things as road trauma and dog attacks. With the appropriate care these animals can be successfully treated. The initial nursing care provided to these patients can greatly affect their long-term survivability. This case report details the treatment of an Eastern Long-neck Turtle (Chelodina longicollis) that sustained a shell fracture after being struck by a large hail stone. It highlights the treatment required to initially stabilise the turtle, the options available to repair the shell fracture and the post-operative care needed for a successful outcome.

Preparation of fracture-free, uniform, crystallized titania hollow nanospheres by spray pyrolyzing core–shell seeds

Crystalline hollow nanospheres that are potentially applicable for optical, catalytic, and electronic devices have been generally synthesized by wet chemical approaches with multiple steps. Colloidal aerosol pyrolysis is a valuable approach producing crystallized hollow nanospheres with mass-production, minimum manufacturing steps, and less chemical usage than conventional wet chemical methods. However, conventional gas phase pyrolysis strategy has unsolved critical issues when synthesizing uniform shell-type nanoparticles including uncontrollable fracturing by sharp thermal shocks and material shrinking during crystallization. In this manuscript, the shell fracture in the gas phase continuous process is eliminated utilizing two stage pyrolysis which removes significant stresses from thermal treatment and gas emission. Advantages of solution chemistry and gas phase continuous process are combined by exploiting colloidal spray pyrolysis with two stages, therefore enabling continuous synthesis of uniform hollow spheres accompanying with organic core burning and nanoshell crystallization without fracture.

Sulphur–TiO2 yolk–shell nanoarchitecture with internal void space for long-cycle lithium–sulphur batteries

Sulphur is an attractive cathode material with a high specific capacity of 1,673 mAh g(-1), but its rapid capacity decay owing to polysulphide dissolution presents a significant technical challenge. Despite much efforts in encapsulating sulphur particles with conducting materials to limit polysulphide dissolution, relatively little emphasis has been placed on dealing with the volumetric expansion of sulphur during lithiation, which will lead to cracking and fracture of the protective shell. Here, we demonstrate the design of a sulphur-TiO(2) yolk-shell nanoarchitecture with internal void space to accommodate the volume expansion of sulphur, resulting in an intact TiO(2) shell to minimize polysulphide dissolution. An initial specific capacity of 1,030 mAh g(-1) at 0.5 C and Coulombic efficiency of 98.4% over 1,000 cycles are achieved. Most importantly, the capacity decay after 1,000 cycles is as small as 0.033% per cycle, which represents the best performance for long-cycle lithium-sulphur batteries so far.

Mechanisms of structural bearing capacity exhaustion of large-sized pressure shells made of polymeric composite materials

In this paper, the mechanisms of structural bearing capacity exhaustion of large-sized pressure shells made of polymeric composite materials are considered. These mechanisms include strength reduction of layers within one or more elements of the pressure shell, general buckling of the pressure shell, local buckling, and specific fracture mechanisms of a composite material that take place in particular cases depending on material reinforcement.

Accurate in vitro identification of fracture onset in bones: Failure mechanism of the proximal human femur

Bone fractures have extensively been investigated, especially for the proximal femur. While failure load can easily be recorded, and the fracture surface is readily accessible, identification of the point of fracture initiation is difficult. Accurate location of fracture initiation is extremely important to understand the multi-scale determinants of bone fracture. In this study, a recently developed technique based on electro-conductive lines was applied to the proximal femoral metaphysis to elucidate the fracture mechanism. Eight cadaveric femurs were prepared with 15–20 electro-conductive lines (crack-grid) covering the proximal region. The crack-grid was connected to a dedicated data-logger that monitored electrical continuity of each line at 700kHz. High-speed videos (12,000 frames/s, 0.1–0.2mm pixel size) of the destructive tests were acquired. Most crack-grid-lines failed in a time-span of 0.08–0.50ms, which was comparable to that identified in the high-speed videos, and consistent with previous video recordings. However, on all specimens 1–3 crack-grid-lines failed significantly earlier (2–200ms) than the majority of the crack-grid-lines. The first crack-grid-line to fail was always the closest one to the point of fracture initiation identified in the high-speed videos (superior–lateral neck region). Then the crack propagated simultaneously, at comparable velocity on the anterior and posterior sides of the neck. Such a failure pattern has never been observed before, as spatial resolution of the high-speed videos prevented from observing the initial opening of a crack. This mechanism (fracture onset, time-lag, followed by catastrophic failure) can be explained with a transfer of load to the internal trabecular structure caused by the initial fracture of the thin cortical shell. This study proves the suitability of the crack-grid method to investigate bone fractures associated to tensile stress. The crack-grid method enables significantly faster sampling than high-speed cameras. The present findings elucidate some aspects of the failure mechanism of the proximal human femoral metaphysis.

Effect of chemical and structural nonuniformity of vver vessel steel on the critical brittleness temperature under irradiation

More accurate modeling of the radiation embrittlement of a calibration metal on the basis of the shift criteria and envelopes of the dose–time dependences experimentally confirms that the modeling error corresponds to the variance band limits of the results of tests performed in control samples and reflects the structural nonuniformity of the metal of large-size blanks. It is recommended that high-quality VVER-1000 vessel steel with critical brittleness temperature from –44 to –78°C and from –78 to –121°C be used to eliminate the risk of brittle fracture of the core shells of GEN-IV VVER vessels.

Numerical simulation of fracture in experiments with compressed shells

The acceleration dynamics and fracture of 12Kh18N10T steel shells loaded by the detonation of a spherical explosive layer are numerically simulated. NAG-type and some other fracture calculation techniques are shown to correctly describe the experimental results obtained in this work.

FRACTURE OF THIN PIPES WITH SPH SHELL FORMULATION

We study the dynamic fracture of thin-walled structure mainly due to impact and explosive loading. Therefore, we make use of a meshless smoothed particle hydrodynamics (SPH) shell formulation based on Mindlin–Reissner's theory. The formulation is an extension of the continuum-corrected and stabilized SPH method, so that thin structure can be modeled using only one particle characterizing mean position of shell surface. Fracture is based on separation of particles. We study tearing of pre-notched plates, fracture due to impact loading and dynamic fracture of cylindrical shells.

Fracture of Ensis siliqua mollusk shell reveals multiple delaminations as a potential defence and toughening mechanism

Fracture of Ensis siliqua mollusk shell reveals multiple delaminations as a potential defence and toughening mechanism

Influence of Baking Temperature on Shell Fracture Using Photo-solidified Polymer as Model Material

Influence of Baking Temperature on Shell Fracture Using Photo-solidified Polymer as Model Material

Prediction of Shell Fracture in Shell Manufacturing Using Photo-solidified Polymer as Model Material

Prediction of Shell Fracture in Shell Manufacturing Using Photo-solidified Polymer as Model Material

Meshless study of dynamic failure in shells

The dynamic fracture of a thin-walled structure that is mainly due to impact and explosive loading is studied. Use is made of a meshless SPH shell formulation based on Mindlin–Reissner’s theory. The formulation is an extension of the continuum-corrected and stabilized SPH method allowing a thin structure to be modelled using only one particle characterizing the mean position of the shell surface. Fracture is based on an effective criterion similar to that of the visibility method. Four numerical examples are studied among which tearing of pre-notched plates, fracture due to impact loading and dynamic fracture of cylindrical shells.

PROCESSING, MICROSTRUCTURE AND MECHANICAL PROPERTIES OF LARGE DIRECTIONALLY SOLIDIFIED CASTINGS FOR INDUSTRIAL GAS TURBINE APPLICATIONS

Contamination of low melting point metal and distortion and fracture of ceramic shell during directional solidification assisted by liquid metal cooling(LMC) were discussed.Large DS castings with 430 mm in length were produced by optimizing the processing parameters.The microstructure,heat treatment response and typical creep rupture properties of the large casting were analyzed.Results of the preliminary casting trials of large blades were also reported.

TEM observations of buckling and fracture modes for compressed thick multiwall carbon nanotubes

The buckling and fracture modes of thick (diameter >20 nm) multiwall carbon nanotubes (MWCNTs) under compressive stress were examined using in situ transmission electron microscopy. The overall dynamic deformation processes of the MWCNTs as well as the force/distance curves can be obtained. The buckling behavior of MWCNTs under compression falls into two categories, the first is non-axial buckling and subsequently complex Yoshimura patterns can be induced on the compressive side of the MWCNTs. The second is axial buckling followed by catastrophic failure. We find the buckling mode of thick MWCNTs is highly dependent on the diameter and length of the MWCNTs. A continuum mechanics model is employed to determine the buckling mode criterion for the MWCNTs. Moreover, the shell by shell fracture mode and planar fracture mode of MWCNTs are directly observed in our experiments.

Infection in revised total knee arthroplasty due to Candida krusei. Successful treatment with voriconazole and staged reimplantation

Fungal infections of total knee arthroplasty are extremely rare. Only a few cases have been reported in the literature. To our knowledge, this is the first case of infection caused by Candida krusei. The occurrence of C. krusei infection has increased since the early 1990s probably owing to the use of fluconazole, especially for fungal infection prophylaxis. The patient was successfully treated by two-stage revision and parenteral administration of voriconazole with a dosage of 6 mg/kg body weight (400 mg) two times in the first 24 h followed by 4 mg/kg body weight (200 mg) every 12 h for 6 weeks. At the time of second-stage surgical procedure, a distal femoral allograft was used in combination with a rotating hinge prosthesis due to a massive femoral bone defect. A collapse of the allograft and a fracture of the host cortical shell occurred 4 months after the operation necessitating a third revision with a megaprosthesis. At the latest follow-up 65 months after the infection, she had no sign of recurrence with a good functional result.

Dynamic Fracture of Shells Subjected to Impulsive Loads

A finite element method for the simulation of dynamic cracks in thin shells and its applications to quasibrittle fracture problem are presented. Discontinuities in the translational and angular velocity fields are introduced to model cracks by the extended finite element method. The proposed method is implemented for the Belytschko–Lin–Tsay shell element, which has high computational efficiency because of its use of a one-point integration scheme. Comparisons with elastoplastic crack propagation experiments involving quasibrittle fracture show that the method is able to reproduce experimental fracture patterns quite well.

Explosive projection of liquid from a thick-walled cylindrical container

The process of projection of a layer of an ideal liquid enclosed into a cylindrical elastoplastic shell by products of instantaneous detonation of a high explosive charge is studied numerically in a two-dimensional plane formulation. The processes of shell fracture and liquid exhaustion through the resultant slots are considered. Numerical results are analyzed, and analytical relations for angular distributions of radial velocity and mass of the liquid escaping through the slots are derived.

Complete polyethylene wear-through and secondary breakage of the expansion cup in a ceramic-polyethylene total hip arthroplasty

Catastrophic polyethylene failure is an uncommon complication of ceramic-on-polyethylene total hip arthroplasty (THA) because of the favourable tribological characteristics of these implants. We present a case of a 50-year-old woman who formerly underwent bilateral ceramic-on-polyethylene THA with expansion acetabular cups and eleven years later presented with unilateral THA dislocation, secondary to catastrophic polyethylene failure and metal shell fracture. The patient came to our hospital for worsening pain in her left hip and an acute incapacity to bear weight on her left lower limb. Twelve and eleven years earlier she had undergone bilateral ceramic-on-polyethylene THA with acetabular expansion components of identical size on both sides. Radiographically, the left femoral head appeared superiorly dislocated and severe polyethylene wear was detected. The inclination angles of the left and right cups were 60° and 44°, respectively. The patient underwent left acetabular revision, and complete polyethylene wear-through with fracture of a cranial lobe of the expansion metal shell was noted at surgery. One large osteolytic lesion in the roof of the acetabulum and diffuse periarticular metallosis were also present. These findings required the use of a Burch–Schneider reinforcement cage. Two years later the patient is functioning well and has full autonomy in her activities of daily living. The correct inclination of the acetabular component is necessary to prevent accelerated polyethylene wear in THA, even though favourable articular bearing surfaces have been used (e.g., ceramic-on-polyethylene coupling). Should the cup appear well fixed and fairly oriented on follow-up radiographies, the early detection of severe polyethylene wear may permit a revision of only the femoral head and acetabular liner.

Patterns of failure of ceramic liner in total hip replacement: report of two cases

We report two cases of ceramic liner fracture that occurred 8 months and 12 years after uncemented total hip arthroplasty (one JRI and the other one was Mittelmaier ceramic-on-ceramic prostheses). There was history of fall in one case. The ceramic liner was found within the metal shell in many large pieces and small fragments in one case and with a missing superior sector and titanium shell wear and fracture in the other. Both prostheses were revised with satisfactory outcome. The patterns of the failure of the ceramic liner seem to be acute and multifragmented following a fall and a missing sector of the line following repeated episodes of impingement between the prosthetic neck and the edge of the ceramic liner. This report highlights the fact that there are limitations of ceramic articulation in hip arthroplasty, which both the surgeon and the patient have to be aware of.