Finite Element Analysis for Optimal Heating Condition in Thermal Stress Cleaving of Brittle Materials Using Laser Irradiation

An optimal condition of thermal stress cleaving was investigated by assuming the element-by-element temperature rise situation using finite element method. The obtained thermal stress cleaving condition is found to be optimal for the symmetrical cleaving of a rectangular plate.9th International Conference on Fracture and Damage Mechanics, FDM 2010; Nagasaki; 20 September 2009 through 22 September 200

Versatile analysis of limited plasticity by body force method

A problem of thermally induced residual stress under plane strain constraint is considered based on a body force method (BFM). As a numerical example, a simple problem of limited plasticity due to a uniform strength of transient line heat source of finite width, which is applied to a surface of a semi-infinite solid for a short duration of time, was considered. Although the out-of-plane component of normal stress (σzz) can be simply estimated from the in-plane normal stress components σxx, σyy and the Poisson\u27s ratio ν as σzz = ν(σxx + σyy) for elastic plane strain problems, this relation is violated when plasticity is considered. As a result, the residual stress in the direction of out-of-plane found to be a major component in the present problem

Fabrication of Chitin Nanofiber-Reinforced PLA Nanocomposites by an Environmentally Friendly Process

Polylactic acid (PLA) reinforced with chitin nanofibers was produced from a mixture of a colloidal suspension of PLA particles with chitin nanofiber suspension. The dispersion medium was solely water, which was removed by filtration and drying. Nanocomposites were obtained by compression molding of the filtrates. Static tensile test and dynamic mechanical analysis were performed to evaluate the reinforcement as a function of nanofiber content. Chitin nanofibers delivered reinforcement similar to cellulose nanofibers, being especially effective at up to 70 wt% fiber load. The ultimate tensile modulus and strength reached 7.7 GPa and 110 MPa, respectively, at a nanofiber content of 70 wt%

Preparation of chitin nanofibers by surface esterification of chitin with maleic anhydride and mechanical treatment

Esterification with maleic anhydride significantly improved the mechanical disintegration of chitin into uniform 10-nm nanofibers. Nanofibers with 0.25° of esterification were homogeneously dispersed in basic water due to the carboxylate salt on the surface. Esterification proceeded on the surface and did not affect the relative crystallinity. A cast film of the esterified chitin nanofibers was highly transparent, since the film was free from light scattering

Analysis of 3D Planar Crack Problems by Body Force Method

Derivation of the integral equation for general 3D crack problems was examined based on the theory of body force method. In the present analysis, stress intensity factors (SIFs) along a front of arbitrary shaped 3D planar crack are obtained directly only by solving simultaneous equations expressing a boundary condition. The crack surface is discretized using number of triangular elements and the variation of the force doublet embedded in each triangle is assumed at constant. The derived boundary integral equation was transformed into a set of simultaneous equations and was solved computationally. In order to improve the accuracy of the numerically examined boundary integral, a polar transformation scheme combined with Tayler expansion of the fundamental solutions is introduced. Not only a single crack problem but also an interference among coplanar cracks can be calculated using the unique program developed in this research. It was verified that as the number of triangular elements increases, the evaluated SIF converges to the reference solution.13th International Conference on Fracture and Damage Mechanics, FDM 2014; Hotel Marina AtlanticoRua Joao de Melo AbreuPonta Delgada, Azores; Portugal; 23 September 2014 through 25 September 201

Protein/CaCO3/Chitin Nanofiber Complex Prepared from Crab Shells by Simple Mechanical Treatment and Its Effect on Plant Growth

A protein/CaCO3/chitin nanofiber complex was prepared from crab shells by a simple mechanical treatment with a high-pressure water-jet (HPWJ) system. The preparation process did not involve chemical treatments, such as removal of protein and calcium carbonate with sodium hydroxide and hydrochloric acid, respectively. Thus, it was economically and environmentally friendly. The nanofibers obtained had uniform width and dispersed homogeneously in water. Nanofibers were characterized in morphology, transparency, and viscosity. Results indicated that the shell was mostly disintegrated into nanofibers at above five cycles of the HPWJ system. The chemical structure of the nanofiber was maintained even after extensive mechanical treatments. Subsequently, the nanofiber complex was found to improve the growth of tomatoes in a hydroponics system, suggesting the mechanical treatments efficiently released minerals into the system. The homogeneous dispersion of the nanofiber complex enabled easier application as a fertilizer compared to the crab shell flakes

Cycloadditionen des Triphenylallenyl-Kations mit Cyclopentadien. Studium des Reaktionsmechanismus unter stabilen Ionen-Bedingungen

Das Triphenylallenyl-Kation (5) geht mit Cyclopentadien eine konzertierte [4 + 2]- sowie eine stufenweise [2 + 2]-Cycloaddition ein. Die Reaktionsmechanismen werden durch NMR-spektro-skopische Beobachtung der intermediären Carbenium-Ionen aufgeklärt

Interference Analysis between Crack and General Inclusion in an Infinite Plate by Body Force Method

A continously embedded force doublet over the particular region can be regarded as the distributing eigen strain. This fact implies that many sorts of inelastic strain can be replaced by the force doublet. In the present paper, the force doublet is used to alter the local constitutive relationship. As a result, a method for analyzing the general inclusion problem in which the material properties of the inclusion are not only different from those of the matrix material but also can be even a function of spacial coordinate variables is proposed. The theoretical background of the present analysis is explained followed by some representative numerical results.12th International Conference on Fracture and Damage Mechanics, FDM 2013; Sardinia; Italy; 17 September 2013 through 19 September 201