Recent advances in modelling of metal machining processes

A study of process-induced stress and deformation in thick-section thermosetting composite laminates is presented. A methodology is proposed for predict ing the evolution of residual stress develop...

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Process-Induced Stress and Deformation in Thick-Section Thermoset Composite Laminates:

An explanation of the different regimes of friction and wear using asperity deformation models

After a brief historical introduction, recent achievements in the theory of plasticity are surveyed with emphasis on applications in mechanical engineering.Kinematic models are presented that indicate the complexities of mechanical behaviour in the plastic range. The fundamental theorems of limit analysis are discussed, and their application to two- and three-dimensional problems is illustrated by examples. Shakedown analysis and limit design are defined. Problems involving large plastic deformations are discussed with special reference to metal forming processes. Applications of the theory of plasticity to impact testing and blast damage are reviewed. Recent changes in the theory of structural stability in the plastic range are mentioned. Throughout the lecture, impending developments of the theory of plasticity are indicated.

The Theory of Plasticity: A Survey of Recent Achievements

Present Situation and Future Trends in Modelling of Machining Operations Progress Report of the CIRP Working Group ‘Modelling of Machining Operations’

The Theory of Plasticity Applied to a Problem of Machining

W recent years, considerable interest has developed in filament-reinforced plastics This new, composite material possesses many advantageous material properties including a high strength-to-weight ratio, which compares favorably with homogeneous metallic materials At one time, the fabrication of filament reinforced plastic pressme vessels presented itself as a formidable problem, but the difficulties have since been overcome There still remain some problems of analysis, but these too are being solved Conventional elasticity formulas are not applicable for use in analyzing filament-reinforced plastics because some of the material property assumptions of classical elasticity are invalid Instead, it is necessary to derive new relations based on suitable simplifying assumptions In recognition of this fact, Kitzmiller, DeHaven, and Young assumed in their analysis of a filament reinforced plastic pressure vessel that the resin is used as a binder with no force carrying capacity Their approach, commonly referred to as the netting analysis, was subsequently extended by Zickel and Read 3 In a later analysis of the problem Hoffman included the force carrying capacit}^ of the resin and derived formulas which contain orthotropic material constants The material constants of the composite material depend upon the properties and distribution of the filament and the resin Changes in its composition will affect the material constants in a way that may be studied experimentally, analytically, or by a combination of the two The analytic point of view will be developed in the present paper Bell, Brown, Ekvall, and Cutwater, to name a few, were motivated toward similar objectives All but one confined his analytical work to materials loaded in the direction of the reinforcing filaments They found relations similar to those presented at the beginning of the present paper Ekvall, on the other hand, also considered the complementary problem in which an external force was applied normal to the direction of the reinforcing filaments It is the purpose of the present paper to analyze the behavior of filament reinforced plastics from a solid mechanics point of view The study is directed toward an evaluation of the stress strain relations in the direction of and normal to the internal filaments Each analysis will be conducted with the aid of an equivalent model Unlike the work of the previous investigators, the present study will not be confined to the elastic range, but will include the elastic-plastic range as well To the best of the author's knowledge, HofTman is the only other investigator who has heretofore used a plastic yield condition in his analysis of a reinforced plastic

Stress-strain relations of reinforced plastics parallel and normal to their internal filaments

The Elastic-Plastic Stress Distribution Within a Wide Curved Bar Subjected to Pure Bending

Expressions are developed for the residual thermal stresses in a solid sphere cast from a chemically hardening thermosetting material in a rigid spherical mold. The description of the heat generation rate and temperature variation is derived from a first-order chemical reaction. Solidification is described by the continuous transformation of the material from an inviscid liquidlike state into an elastic solid, with intermediate properties determined by the degree of chemical reaction. Residual stress components are obtained as functions of the parameters of the hardening process and the properties of the hardening material. Variation of the residual stresses with a nondimensionalized reaction rate parameter and the relative compressibility of the hardened material is discussed in detail.

Residual Thermal Stresses in a Solid Sphere Cast From a Thermosetting Material

Two sets of equations have been derived which describe the internal stress distribution within reinforced plastics subjected to a force normal to the direction of its internal filaments. One set of equations is applicable to reinforced plastics with less than 68% filament by volume and the other to reinforced plastics with more than 68% filament. Each set is applicable over a complete range of loading which includes both elastic and plastic stresses. It is found that when reinforced plastics have less than 68% filament by volume only one plastic zone develops in a generic section before the cross section becomes entirely plastic. Additional plastic zones develop when reinforced plastics have more than 68% filament by volume. A simple expression for the elastic stress concentration factor was also found.

Bernard W. Shaffer

Papers

The Theory of Plasticity Applied to a Problem of Machining

Stress-strain relations of reinforced plastics parallel and normal to their internal filaments

The Elastic-Plastic Stress Distribution Within a Wide Curved Bar Subjected to Pure Bending

Residual Thermal Stresses in a Solid Sphere Cast From a Thermosetting Material

Elastic-plastic stress distribution within reinforced plastics loaded normal to its internal filaments.