Desired Deformation Research Articles

An inversion procedure for determination of variable binder force in U-shaped forming

In this article, a neural network procedure is suggested to inversely determine the variable binder force in U-shaped forming from the deforming shape of the part. The finite element method (FEM) is used to simulate the forming process. The inputs of the neural network (NN) model come from the deformation shape of the part. The outputs of the NN are the stepped variable binder force parameters. To reach the desired deformation, the NN model will go through a progressive retraining process. A constant binder force simulation method is also recommended to obtain the desired deformation shape. The numerical result for model NUMISHEET’93 demonstrates the efficiency of the present procedure.

On a conjecture of Conrad, Diamond, and Taylor

We prove a conjecture of Conrad, Diamond, and Taylor on the size of certain deformation rings parametrizing potentially Barsotti-Tate Galois representations. To achieve this, we extend results of Breuil and Mézard (classifying Galois lattices in semistable representations in terms of "strongly divisible modules") to the potentially crystalline case in Hodge-Tate weights (0, 1). We then use these strongly divisible modules to compute the desired deformation rings. As a corollary, we obtain new results on the modularity of potentially Barsotti-Tate representations.

Optimal Operational Conditions during Production of Lead-Calcium-Tin Anodes for Improve Their Mechanical Properties

Previous works have shown that a minimum yield strength s0 of 58 MPa for leadcalcium- tin anodes of 6 mm thickness and a nominal composition of 0.7% Ca and 1.3% Sn are required to avoid early deformations and distortions during their operation in copper electrowinning cell. This s0 value for the anodes is associated with a terminal cold rolling process and a further precipitation hardening prior to their installation in the electrowinning cells. The objectives of the present work are to determine the alloy recrystallization temperature according to Ca and Sn contents, the maximum cold rolling temperature and the aging time required to obtain the desired mechanical quality. The results indicate that recrystallization temperature ranges between 120 and 150°C, according to the anode composition. To reach the desired deformation and precipitation hardening and consequently a yield strength of 58 MPa, the maximum cold rolling temperature is 45°C and the minimum aging time, 30 days.

Finite Element and Experimental Investigation of Piezoelectric Actuated Smart Shells

In the recent years, research on the use of piezoelectric actuators for shape and vibration control of structures has been gaining prominence. Analytical and finite element models have been developed to analyze structures under piezoelectric actuation, but experimental studies, particularly on curved structures, are limited. In the current study, a finite element model is developed for piezoelectric actuated shell structures, based on Ahmad’s reduced shell element. Experiments have been conducted on a number of structures like straight beams, curved beams, and shells. Finite element and experimental results have been shown to match well. Nonlinear behavior has been observed in the experiments, particularly at higher fields, and complete hysteresis loops have been presented. The finite element is then applied to the study of deformation of a typical paraboloid shell (representative antenna shell) under piezoelectric actuation. It has been shown that piezoelectric actuation can be used to induce desired deformation shapes in the antenna shell, which result in beam steering and shaping.

A Novel Compliant Mechanism for Converting Reciprocating Translation Into Enclosing Curved Paths

This paper introduces a novel contact-aided compliant mechanism that uses intermittent contacts to convert a single translatory reciprocating input into two output curves, which intersect to enclose a two dimensional region. Contact interactions endow contact-aided compliant mechanisms with enhanced kinematic and kinetostatic capabilities. The mechanism described in this paper is designed to undergo large deformations repeatedly, without yielding by avoiding flexural joints and by using contacts to obtain the desired deformation. A single-material, joint-free and planar design makes the mechanism easy and economical to fabricate at the macro or micro scales. The design is validated experimentally by manufacturing and testing macro scale prototypes. Two potential applications that motivated this mechanism are also noted.

Methods to increase sound fidelity and quality produced from piezoelectric devices

Methods to increase sound level, fidelity and quality produced from vibrating lamina such as piezoelectric actuators, vibrating plates or vibrating films are presented. Results of using the methods are shown for piezoelectric devices. Four methods are described: (1) tailoring the vibration response to develop desired deformation shapes and amplitudes, (2) mapping vibration out-of-plane deformation to ascertain locations on the surfaces of lamina suitable for stroke-like actuation, (3) coupling vibration to a collection of acoustic chambers and (4) increasing the vibration decay rate. The first two methods provide a single piezoelectric device with the functionality of numerous actuators combined. A piezoelectric actuator with numerous high-amplitude natural vibration responses has been produced using the aforementioned methods. Numerous high-amplitude vibrations increase the functionality of the devices. A collection of acoustic chambers were affixed to the piezoelectric actuator's surface. The addition of the chambers resulted in more efficient audio output. The result of using all of the aforementioned methods is a high fidelity, high-bandwidth, and high sound-quality audio device with a low physical profile. The use of the piezoelectric actuator effectively results in an audio driver with a thickness less than 1 mm. The piezoelectric audio device achieved a response of 93±4 dB measured at 1 cm in the frequency range (1–5 kHz) with very good audio output for frequencies less than 1 kHz. The methods can be used to design other devices using solid-state piezoelectric actuators or vibrating lamina (e.g., plates or films).

Nonlinear behaviour of interacting dielectric cracks in piezoelectric materials

Existing studies on the fracture of cracked piezoelectric materials have been limited mostly to the electrically impermeable and permeable crack models, which represent the limiting cases of the physical boundary condition along the crack surfaces. This paper presents a study on the electromechanical behaviour of interacting dielectric cracks in piezoelectric materials. The cracks are filled with dielectric media and, as the result, the electric boundary condition along the crack surfaces is governed by the opening displacement of the cracks. The formulation of this nonlinear problem is based on simulating the cracks using distributed dislocations and solving the resulting nonlinear singular integral equations. Multiple deformation modes are observed. A solution technique is developed to determine the desired deformation mode of the interacting cracks. Numerical results are given to show the effect of the interaction between parallel cracks. Attention is paid to the transition between permeable and impermeable models with increasing crack opening.

Seismic Retrofit of RC Columns with Continuous Carbon Fiber Jackets

The development, the validation, and the implementation of a new seismic retrofit system for reinforced concrete columns are described. The column jacketing system consists of continuous carbon fiber prepreg tows wound in an automated fashion onto existing circular or rectangular concrete columns, with variable jacket thickness along the column height based on experimentally validated design models. Jacket design criteria for various seismic column failure modes are described and detailed examples show their application to retrofits of columns with circular and rectangular column geometry, different reinforcement ratios, and detailing. The carbon jacket designs are validated through large-scale bridge column model tests and are found to be just as effective as steel shell jacketing in providing desired inelastic design deformation capacity levels. Furthermore, it is shown that the retrofit criteria and guidelines are also applicable to other advanced composite jacketing systems with appropriate considerat...

A simplified geometrically nonlinear approach to the analysis of the Moonie actuator

A simplified model for the analysis of ceramic-metal composite actuators has been developed. The model consists of two beams symmetrically arranged about the actuator neutral axis and attached to the actuator at the ends with an offset (Moonie shape). When an electrical field is applied such that the actuator will contract, a compressive force and a moment, due to the beams' eccentricity, are applied to the beams. This loading will produce the desired deformation of the beams. Using the beam-column theory and the appropriate boundary conditions, it is possible to derive a set of equations relating the free induced strain (/spl Lambda/) of the actuator to the midspan displacement of the beams. Nonlinear terms which allow for the interaction of the developed in-plane force with the out-of-plane displacements have been included in the equations. Applying these equations to a particular case, it is found that the offset distance of the beams has a large impact on the behavior of the system. An increase in the offset distance produces both a suitable augmentation of the moment applied to the beams and an undesirable diminution of the midspan displacement for a given free induced strain. From these two positive anti negative effects, an optimum value of the offset distance is found. Additionally, it is found that with a transverse load applied to the beams, the optimum offset distance is further increased. Furthermore, the nonlinear terms in the governing equations are found to have only a small impact on the system in the free induced strain range of typical actuator materials, i.e., /spl Lambda//spl les/1500 /spl mu/strain. Thus, in conclusion, the effect of the offset distance of the beams to the actuator is the primary design criteria when maximum displacement of the actuator is required.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microstructure and Slip Character in Titanium Alloys

Influence of microstructures in titanium alloys on the basic parameters of deformation behaviour such as slip character, slip length and slip intensity have been explored. Commercial titanium alloys contain the hexagonal close packed (alpha) and body centred cubic (bita) phases. Slip in these individual phases is shown to be dependent on the nature of alloying elements through their effect on phase stability as related to decomposition into ordered or w structures. When alpha and bita coexist, their relative crystallographic orientations, size, shape and volume fraction, control the nature of slip. For a given composition, structure may be manipulated through appropriate thermomechanical treatment to obtain the desired deformation behaviour and therefore fracture mode.

An upper bound model of the process of hydrostatic extrusion of implosively prewelded bimetallic arrays of rods

The salient technological aspects of the process have already been described in a companion paper by the present authors— “The Response of Implosively Prewelded Arrays of Rods to Processing by Hydrostatic Extrusion”, J. Mech. Work. Tech., 6 (1982) 291 – 302 — to which the reader is referred for full details. The presently reported study is concerned with establishing reasonably reliable means of predicting power requirements — expressed in terms of extrusion pressure — necessary to effect the desired deformation of an integrally-bonded bimetallic composite. It is demonstrated that the mathematical model adopted provides equations which are sufficiently accurate for practical purposes.

A Versatile Control System for Triaxial Testing of Soils

Abstract Specimens of sedimented kaolinite were subjected to consolidated-undrained triaxial compression by means of a new electropneumatic control system that will apply any desired loading path in the axisymmetric stress space or any desired deformation path. Specimens were tested under ramp loading, ramp deformation and combined ramp loading—ramp deformation with both constant cell pressure and constant first invariant of the applied stress tensor. To determine the entire stress-strain-pore pressure relationship, it was necessary to perform the combined load rate-deformation rate test. It was found that while a unique principal stress difference-major principal strain relationship exists, a unique pore pressure-major principal strain relationship does not exist.

The Rotary Forging Concept and Initial Work with an Experimental Machine

The rotary forging process is based on a recognition of the fact that the axial force required to effect a desired deformation during, for example, an upsetting operation may be reduced if the plastically deforming zone is confined throughout to a small region beneath the upper platen. The top portion of the workpiece is then rotated through this plastic zone thus resulting in a progressive deformation. An experimental rotary forging machine has been designed and constructed which incorporates a lower platen capable of axial movement only, whilst the upper conical platen is capable of rotation about the central axis of the machine and also about its own inclined axis. The principal design features of the experimental machine are described and the results of some preliminary experiments using the machine are presented. Operation of the experimental machine has demonstrated the feasibility of the process. The effect of the axial force on the rotary forging of cylindrical specimens having a height/diameter ( H/D) ratio of unity and for a fractional reduction of 0.5 is discussed. Pure lead at ambient temperature was used, as a model material, to simulate the rotary forging of steels in the approximate temperature range of 700-1400°C. A comparison is made between the axial force required to rotary forge and conventionally upset identical pure lead cylinders. It is shown that the optimum axial force required for slow rotary forging is a small fraction of that required for the conventional slow upsetting of circular cylinders having H/D ratios of less than unity.