Brittle Plate Research Articles

An experimental study on Kca value to arrest a running brittle crack in structural model specimens with steel plate of 100 mm thickness for container ships

With demand for ultra-large container ships, high-strength steel plates with extremely large thicknesses are applied to the structural elements around hatch side structures. The two longitudinal plates of the upper deck and hatch side coaming are the main structural elements that support bending stress during hogging of the ship structure, and brittle crack arrest toughness as well as crack initiation toughness are required in these steel plates to avoid the catastrophic ship damage. Although the International Association of Classification Societies prescribes a unified requirement for brittle crack arrest steel plates providing the value of brittle crack arrest toughness Kca at − 10 °C for plate thicknesses of 80 mm or less, ultra-large container ships using steel plates with thicknesses exceeding 80 mm are continuously required and built. In the present work, brittle crack arrest tests with large scale structural model specimens which simulate the structural element of the hatch side structure were performed to investigate the Kca value required to arrest a running brittle crack for steel plates with the thickness of 100 mm. The present investigation suggested that the test plate simulating upper deck could arrest a running brittle crack at the plate Kca of 6000 N/mm3/2, nevertheless the Kca value of 8000 N/mm3/2 was needed in the test plate simulating hatch side coaming. The different Kca values required to arrest a running crack between the test plates simulating the upper deck and the hatch side coaming are also discussed from the viewpoint of the arrested crack size and shape.

Analysis on the influence of Poisson’s ratio on brittle fracture by applying uni-bond dual-parameter peridynamic model

Poisson’s ratio is a crucial mechanical parameter of materials, but its significance is normally underrated in practical application. Aiming at investigating how Poisson’s ratio influences the fracture of brittle materials by using peridynamic (PD) method, a uni-bond dual-parameter peridynamic (UDPD) model is proposed. The expressions of normal stiffness and tangential stiffness by elastic modulus and Poisson’s ratio are derived. The two-parameter characteristic makes UDPD break the limitation of the specific Poisson's ratio of bond-based peridynamics, thus the modeling of the mechanical behavior of materials with various Poisson's ratio can be achieved. With single-bond property, UDPD inherits the simplicity and stability of the traditional bond-based peridynamics. In addition, the critical value of micro strain energy density for UDPD model is given to judge the damage. The validity and accuracy of UDPD model are illustrated by three numerical examples: the plate deformation subject to static load, the Kalthoff-Winkler experiment and the brittle plate fracture subject to biaxial loads. Ultimately, by simulating and comparing the damage of brittle plates under tension of different Poisson’s ratio, it is concluded that Poisson’s ratio has substantial effect on fracture initiation time and crack propagation path. The larger Poisson’s ratio has the plate, the earlier the fracture initiates. The cut-through locations and crack propagation paths in plates of different Poisson’s ratio are significantly different.

Redundancy and robustness of brittle laminated plates. Overlooked aspects in structural glass

It is a consolidated belief that the reliability of brittle plates is increased using laminated layers instead of a monolith: redundancy permits stress redistribution after partial breakage. To quantify this effect, the retro-cumulative function of plate strength is calculated for inflected laminates with a variable number of plies using the failure modes approach. The material is elastic perfectly-brittle and its strength may be characterized by different statistics, implying either volume-size-effect, area-size-effect, or no-size-effect. The plate is analysed in limit conditions for what concerns the capability of the adhesive layers to transfer shear stresses. Robustness is discussed by assuming that an accidental event may break one of the plies.The type of size-effect plays a decisive role. Under the same maximum tensile stress in the sound state, lamination is always beneficial only for volume-size-effect. For area-size-effect, the negative effect of the new surface from lamination is counterbalanced by stress redistribution only for the lower quantiles of the strength distribution. The same is true under an accidental event. With no-size-effect, the gain from lamination is again appreciable only at low failure probabilities. These findings raise questions about the positive effects of lamination for structural glass, strongly characterized by an area size effect.

Формирование дефектного слоя при лезвийной обработке хрупких материалов

Parts made of modern brittle materials with high quality finish are widely used in manufacturing of optical and electronic devices as well as crucial assemblies in mechanical engineering products. Diamond machining enables generation of geometry without affecting the functional surface layers by heat. At the same time, brittle material cutting is accompanied by the formation of a defective layer on the machined surface due to the structural disturbances in the material caused by the applied cutting force. The paper discusses causes and the mechanism of the defective layer formation on the machined surface during non-free cutting of brittle materials and examines ways of reducing the size of the defective layer. Theoretical and computer-aided analysis is performed to determine the impact of the local stresses field in the zone of concentrated pressing force acting on the brittle plate surface. Using experimental methods, a defective layer formed after cutting notches on a silicon plate by a diamond tool is studied.

Developement of Composite Armors Using Natural Rubber Reinforced with Steel Wire Mesh for Ballistic Resistance

A protective ballistic armor used for military buildings, that will meet the anti-terrorism and force protection demands, are increasingly needed, particularly in Thailand's southernmost provinces. A new type of ballistic armor system has been developed, composing of composite layers, using natural rubber reinforced with steel wire mesh, and Al plate. The composite layers were used as front material while the Al plate was used as backing plate. The armors were tested against NIJ-Type III threats using NIJ 0108.01 ballistic test standard. The armor, with 12 mm Al backing plate, can successfully resist the NIJ-Type III treat with only combination of two composite layers. Different than hard and brittle plate, such as ceramic, the use of composite layer at the front did not blunt and erode the projectile, due to its ductile property. However, the composite layer effectively reduces the velocity of projectile, due to high fracture toughness, as a result of reinforcing steel wire mesh layers in the composites. The projectile was finally stopped by the Al backing plate.

Влияние неравномерного трещиноватого слоя поверхности обработанных пластин хрупких материалов на качество готовых изделий

Влияние неравномерного трещиноватого слоя поверхности обработанных пластин хрупких материалов на качество готовых изделий

Application of the incubation time criterion for dynamic brittle fracture

The complex issue of penetration and perforation of brittle plates subjected to normal impact is addressed. Fracture and fragmentation are simulated numerically by using simultaneously two failure criteria: ductile and brittle failure. A new brittle failure criterion, which is based on incubation time, is proposed. The criterion, inspired from the Tuler–Butcher criterion, is implemented in a commercial finite element code by means of a user subroutine. It is validated by comparing numerical predictions to experimental ballistic results of normal impact on polymethylmethacrylate plates. It is shown that the projectile's exit velocity and the timing of the penetration are faithfully reproduced. It is also verified visually that the experimental damage/fracture pattern, namely radial cracking and dishing, are both well captured by the proposed criterion.

Large-scale 3D modeling of projectile impact damage in brittle plates

The damage and failure of brittle plates subjected to projectile impact is investigated through large-scale three-dimensional simulation using the DG/CZM approach introduced by Radovitzky et al. [Comput. Methods Appl. Mech. Eng. 2011; 200(1–4), 326–344]. Two standard experimental setups are considered: first, we simulate edge-on impact experiments on Al2O3 tiles by Strassburger and Senf [Technical Report ARL-CR-214, Army Research Laboratory, 1995]. Qualitative and quantitative validation of the simulation results is pursued by direct comparison of simulations with experiments at different loading rates and good agreement is obtained. In the second example considered, we investigate the fracture patterns in normal impact of spheres on thin, unconfined ceramic plates over a wide range of loading rates. For both the edge-on and normal impact configurations, the full field description provided by the simulations is used to interpret the mechanisms underlying the crack propagation patterns and their strong dependence on loading rate.

An extended peridynamic approach for deformation and fracture analysis

An extended bond-based peridynamic approach is proposed for quantitative analysis of elastic deformation and simulation of both quasi-static and dynamic crack propagation. A continuous function is uniquely introduced in the commonly used peridynamic constitutive model by considering the internal length effect of long-range forces. Moreover, a local damping is incorporated into the peridynamic equations of motion, and the step-by-step loading algorithms and non-equilibrium criterion for particle systems are developed specifically for quasi-static problems. The effective calculation field of material points in the numerical peridynamic discretization is discussed as well. Analysis of quantitative elastic deformation and quasi-static fracture behavior of the model is verified through simulating the uniaxial tension and compression of a slab, bending and failure of a cantilever beam, and quasi-static propagation of mode I and mode II cracks in a plate. The numerical examples show that the present approach is capable of quantitatively calculating the elastic deformation and accurately predicting the critical failure load and crack propagation paths. To further demonstrate the capabilities of the proposed model, dynamic fracture of a brittle plate under high-rate loading is simulated, in which the experimentally-observed phenomena, such as successive branching, are captured naturally as a consequence of the solution.

A prediction method of fracture probability for lapped brittle plate

Fracture of lapped brittle plate exhibits a random and uncertain property. In this study, based on a finite element division and the fracture mechanics of micro surface cracks, a numerical prediction approach for fracture cumulative distribution function (CDF) for lapped brittle plate under non-uniform stress field is proposed. Applications under different conditions are carried out, and influences of abrasive size and crack density on the proposed prediction method are discussed. The predicted Weibull parameters are in good agreement with experimental results, which establishes validation and potential engineering value of the proposed prediction method.

Utilization of En Ac-42100 Cast Aluminum Alloy for Casting of Critical Components. I. Preparation and Mechanical Properties

Abstract Requirement on the minimum value of elongation for critical components is about 15 %. The research deals with the possibility of replacing the dendritic morphology of primary solid solution and brittle eutectic silicon plates with finer particles with a more suitable morphology and size, and the possibility of increasing the mechanical properties. Introduced first part is focused on the process of preparation of experimental material and mechanical properties.

Fragmentation of brittle plates by localized impact

We address the fragmentation of thin, brittle layers due to the impact of high-velocity projectiles. Our approach is a geometric statistical one, with lines and circles playing the role of cracks randomly located over the surface and following distributions that come from an analysis of how the energy input propagates and dissipates over the material. The cumulative mass distributions F(m) we obtain are in excellent agreement with the data produced by Kadono [Phys. Rev. Lett. 78, 1444 (1997)]. In the small mass regime we get F(m) ∼ m−α, with 0.1 < α < 0.3 for a broad range of dissipation strengths and total number of fragments. In addition we obtain the fractal dimension of the set of cracks and its correlation to the exponent α that account for the experimental results given by Kadono and Arakawa [Phys. Rev. E 65, 035107(R) (2002)].

A two-dimensional peridynamic model for thin plates

A general plate model based on the peridynamic theory of solid mechanics is presented. The model is derived as a two-dimensional approximation of the three-dimensional bond-based theory of peridynamics via an asymptotic analysis. The resulting plate theory is demonstrated using a specially designed peridynamics code to simulate the fracture of a brittle plate with a central crack under tensile loading.

The role of lithospheric processes on the development of linear volcanic ridges in the Azores

Linear volcanic ridges (LVRs) are widespread along the Azores plateau and are often used as a tectonic marker of the surface stress field. Nevertheless, the mechanisms that drive the emplacement and development of these structures are not well established and they have been attributed to the plateau diffuse deformation, off-rift extension or the result of the interaction between a hotspot and the brittle lithosphere. This study hypothesizes that linear volcanic ridges are the result of magma emplacement into pre-existing damaged lithosphere, using a 3D finite-element representation of the brittle lithosphere and underlying ductile mantle, and assuming that the deformation is driven by plate boundary forces applied at the edges, as describe by global plate kinematic models. The brittle layer is described by an elastoplastic rheology with progressive damage, where fractures are assumed to be analogous to localized shear bands. The ductile mantle underneath is modeled as a viscoelastic layer that exerts a shear drag at the base of the brittle layer. The modeling shows that lithospheric processes alone can justify the spatial distribution of linear volcanic ridges, and even the development of the Faial Ridge. The factors controlling the fracturing pattern are the plate geometry and velocity boundary conditions, the shearing introduced at the East Azores Fracture Zone/Gloria fault limit and the interaction between the viscous mantle and the spatially varying brittle plate thickness. Along the Terceira Rift the predicted fractures match the orientation of the LVRs in the second (~ N135°–N140°) and third (N150° to N–S) sectors and provide an explanation for the arcuate shape of the rift itself. The brittle plate thickness variations are crucial for the development of the more recent LVRs, which are predicted to occur along the Faial Ridge. In the best fit model the top mantle viscosity is 1 × 1022 Pa s at 5–15 km depth, and the present-day fracture network takes ~ 3 Ma to develop.

Star-Shaped Crack Pattern of Broken Windows

Broken thin brittle plates like windows and windshields are ubiquitous in our environment. When impacted locally, they typically present a pattern of cracks extending radially outward from the impact point. We study the variation of the pattern of cracks by performing controlled transverse impacts on brittle plates over a broad range of impact speed, plate thickness, and material properties, and we establish from experiments a global scaling law for the number of radial cracks incorporating all these parameters. A model based on Griffith's theory of fracture combining bending elastic energy and fracture energy accounts for our observations. These findings indicate how the postmortem shape of broken samples are related to material properties and impact parameters, a procedure relevant to forensic science, archaeology, or astrophysics.

Dynamic fragmentation of a brittle plate under biaxial loading: strength or toughness controlled?

The fragmentation of a brittle plate subjected to dynamic biaxial loading is investigated via numerical simulations. The aim is to extend our understanding of the dynamic processes affecting fragment size distributions. A scalable computational framework based on a hybrid cohesive zone model description of fracture and a discontinuous Galerkin formulation is employed. This enables large-scale simulations and, thus, the consideration of rich distributions of defects, as well as an accurate account of the role of stress waves. We study the dependence of the fragmentation response on defect distribution, material properties, and strain rate. A scaling law describing the dependence of fragment size on the parameters is proposed. It is found that fragmentation exhibits two distinct regimes depending on the loading rate and material defect distribution: one controlled by material strength and the other one by material toughness. At low strain rates, fragmentation is controlled by defects, whereas at high strain rates energy balance arguments dominate the fragmentation response.

Comparison of Characteristics of Fluorine Doped Zinc and Gallium Tin Oxide Composite Thin Films Deposited on Stainless Steel 316 Bipolar Plate by Electron Cyclotron Resonance-Metal Organic Chemical Vapor Deposition for Proton Exchange Membrane Fuel Cells

In order to replace the brittle graphite bipolar plates currently used for the PEMFC stack, coated SUS 316 was employed. As a metallic bipolar plate, coated SUS 316 can provide higher mechanical strength, better durability to shocks and vibration, less permeability, improved thermal and bulk electrical conductivity, as well as being thinner and lighter. To enhance the interfacial contact resistance and corrosion resistance of SUS 316, the deposition of GTO:F and ZTO:F composite films was carried out by ECR-MOCVD. The surface morphology of the films consisted of tiny elliptically shaped grains with a thickness of 1 microm. The corrosion current for GTO:F was 0.13 Acm(-2) which was much lower than that of bare SUS 316 (50.16 Acm(-2)). The GTO:F coated film had the smallest corrosion current due to the formation of a tight surface morphology with very few pin-holes. The GTO:F coated film exhibited the highest cell voltage and power density due to its lower ICR values.

A numerical approach to the analysis of failure modes in anisotropic plates

This study is motivated by the attempt to characterize failure modes of silicon chips commonly used in electronic industries. Previous experimental investigations provided the failure probability of dies made of a single-crystal and produced a large variety of crack patterns, but were not able to elucidate the link between defect distributions and crack initiation and propagation. To get some insight in the fracture activation and propagation mechanisms, we resort to finite element analyses and adopt an explicit methodology for crack tracking, based on the self-adaptive insertion of cohesive elements into a coherent mesh of solid elements. Finite kinematics material models with anisotropic features for both bulk and cohesive surfaces are employed to describe the behavior of single-crystal silicon plates undergoing a particular bending test up to failure. The cohesive model adopted in the calculation is fully anisotropic and newly formulated to accomplish the present study. Numerical simulations considering different material properties were able to ascertain the effects of particular flaws on failure modes of brittle silicon plates.

Elasticity with energy limiters for modeling dynamic failure propagation

Separation of two particles is characterized by a magnitude of the bond energy, which limits the accumulated energy of the particle interaction. In the case of a solid composed of many particles a magnitude of the average bond energy – the failure energy – exists, which limits the energy that can be accumulated in an infinitesimal material volume under strain. The energy limiter controls material softening, which indicates failure. Thus, by limiting the stored energy density it is possible to include a description of material failure in the constitutive model. When the failure energy, i.e. the energy limiter, is introduced in the constitutive model it can be calibrated in macroscopic experiments. Traditional elasticity models do not have energy limiters and they allow for the unlimited energy accumulation under the strain increase, which is physically meaningless because no material can sustain large enough strains without failure. We use elasticity with energy limiters for modeling dynamic failure propagation in brittle solids. Two models of isotropic Hookean solids with energy limiters are introduced and examined in simulations of the penetration of a projectile into a brittle plate in the present work. The first model uses the energy limiter with the overall energy term while the second model has separate energy limiters for the volumetric and deviatoric components. The results of the penetration simulation obtained by using both models are similar qualitatively. It is remarkable that the penetration depth is mesh-independent for fine meshes even without the special regularization procedures. This is the first work where the methods of elasticity with energy limiters are used in dynamic analysis of brittle failure.

Fractal design for efficient brittle plates under gentle pressure loading

We consider a plate made from an isotropic but brittle elastic material, which is used to span a rigid aperture, across which a small pressure difference is applied. The problem we address is to find the structure which uses the least amount of material without breaking. Under a simple set of physical approximations and for a certain region of the pressure-brittleness parameter space, we find that a fractal structure in which the plate consists of thicker spars supporting thinner spars in an hierarchical arrangement gives a design of high mechanical efficiency.