Rectangular Punch Research Articles

Strain analysis of a bonded, dissimilar, composite material T-joint using moiré interferometry

High-sensitivity moiré interferometry and finite-element analysis are used to analyze the state of deformation and stress in the region of contact between a plane orthotropic rectangular punch bonded to a foundation with dissimilar elastic properties which models a highly loaded region of a composite material rocket motor casing. Stress distributions are presented for the contact region and an estimate of the maximum shear stress in the foundation is given. The displacement components show good qualitative agreement between analysis and experiment. The lack of quantitative agreement between the experimental and the finite-element analysis is attributed to uncertainty of the material properties.

Analysis of Stretch Forming Process — Simulation and Experiment

Summary In the present work a computer aided calculation for determine the forming depth, punch load and strain distribution during punch stretching is proposed. The results predicted by the program were compared and agree well with experimental results. Stretch forming of steel and aluminium blanks using hemispherical and rectangular punches was analysed. The influence of sheet thickness, variations in mechanical properties, friction conditions and die geometry were investigated. The formability of low-carbon steels, high-strength steels and Aluminium alloys are discussed and a new criteria to predict the stretchability of sheet metal is pointed out.

Plane contact problems for a periodic two-layered elastic composite

This paper deals with the two-dimensional static punch problems in the presence of friction for a periodically layered half-space. Within the framework of the homogenized model of linear elasticity with microlocal parameters [8–11] the exact solutions of the considered problems are obtained. The case of the indentation of the composite body by a rigid rectangular punch has been discussed in detail.

Plane contact problem for an elastic rectangular punch and a half-plane with initial stresses

Plane contact problem for an elastic rectangular punch and a half-plane with initial stresses

Creation of Stable Cracks in Hardmetals Using ‘Bridge’ Indentation

Bridge indentation involves the initiation of a precrack at thq centre of the top surface of the sample by meajns of diamond indentation (i.e. a Palmqvist crack). Growth of this crack is then induced by pressing either side of it with rectangular punches having their edges parallel with the crack direction. With I increasing load, the crack grows outwards and downwards, and eventually forms a straight-through crack. The present authors have made a study of the effect of experimental variables such as punch spacing, punch contact area, and diamond indentation load on the crack growth. Specimens of a WC–6Co alloy cracked in this way were subsequently used for K 1C measurement. An important result was that the cracks grew to a stable depth, the value of which could be determined by suitable choice of indentation parameters. Numerical analysis using a boundary element method (BEM) was used to explore the stress situation in bridge indentation and provided a qualitative prediction of the experimental results. The K 1C measurements, using four point bending, indicated that plastic deformation associated with the hardness indentation causes an underestimate of the K 1C value, and should therefore be removed by polishing. However, the effect is relatively small if the ratio of crack depth to indentation size is large. PM/0285

Limit Analysis of Ice Sheet Indentation

The methods of plastic limit analysis are used to determine the indentation pressures of a flat rectangular punch on an ice sheet. The ice sheet is idealized as a semi-infinite layer of elastic-perfectly plastic material. Lower bounds are computed by application of the lower bound limit theorem. The suitability of basic yield functions are assessed based on their ability to predict failure at demonstrated ice failure stress ratios. The particular yield functions that are employed include the generalized Mohr-Coulomb (or Drucker-Prager) criterion, a modified Drucker-Prager criterion, as well as a parabolic yield criterion used previously in literature on this topic. A study of the effects on indentation pressure of varying ice strength parameters is presented. Limit analysis solutions are obtained for plane stress conditions, and thus the applicability of a particular yield function can be evaluated for a range of ice strengths for indentation problems involving high aspect ratios.

On the Solution of Three-Dimensional Metal-Forming Processes

The use of “dual-stream functions” in analyzing some three-dimensional metal-forming processes is demonstrated in this paper. The problems discussed are open-die forging of blocks, rolling of a rectangular bar with spread, piercing by elliptic and rectangular punches, and extrusion of a rectangular shape. For these forming processes, kinematically admissible velocity fields are selected using characteristics of the two stream functions. Approximate upper-bound solutions of the forming processes can be obtained from the proposed velocity fields.

A solution for the narrow rectangular punch

This paper considers the problem of a rectangular flat ended punch acting on an elastic half-space. An approximate solution is generated through application of the elastic line integral equations. The results produced by this method are then compared with another approximate solution already available.

Uniform indentation of the elastic half-space by a rigid rectangular punch

The problem considered is that of a rigid flat-ended punch with rectangular contact area pressed into a linear elastic half-space to a uniform depth. Both the lubricated and adhesive cases are treated. The problem reduces to solving an integral equation (or equations) for the contact stresses. These stresses have a singular nature which is dealt with explicitly by a singularity-incorporating finite-element method. Values for the stiffness of the lubricated punch and the adhesive punch are determined: the effect of adhesion on the stiffness is found to be small, producing an increase of the order of 3%.

METHOD FOR OBTAINING COMPRESSION AND SHEAR COEFFICIENTS OF FOODS USING CYLINDRICAL PUNCHES

AbstractThe force required to puncture a food has been described previously as F=Ka?A+Kp? P++C where A and P are, respectively, the area and perimeter of the punch, C is a constant and Ka and Kp are two coefficients that are properties of the food. This paper describes how the equation can be rearranged for circular punches in a manner that allows the numerical values of the coefficients to be evaluated by a graphical method. A comparison of the numerical values obtained with the new method and those obtained with the older method using rectangular punches showed good agreement when carrots, two varieties of apples, agar gel, margarine, and polystyrene board were used as test materials. The method of deriving coefficients Ka and Kp is relatively easy and the coefficients may be more meaningful than the raw puncture data.

Textural Changes in Ripening Peaches

Clingstone and freestone peaches of varying degrees of ripeness were subjected to a puncture test, a modified G. F. Texture Profile, and a set of rectangular punches that enable a compression coefficient (Kc), and a shear coefficient (Ks), to be evaluated. Adhesiveness and viscosity were absent in the G. F. Texture Profile. Cohesiveness was constant for clingstone peaches although the two areas whose ratio is the cohesiveness parameter decreased at the same rate as the puncture test. The other textural properties: fracturability, hardness, elasticity, chewiness, Kc, and Ks decreased at about the same rate as the puncture test. Correlation coefficients between these textural parameters and the puncture test were all significant. This leads to the conclusion that almost any kind of textural property can be used successfully as an index of textural quality of fresh freestone or clingstone peaches because the various textural parameters change in the same direction and at approximately the same rate as the fruit rlpens. The results also indicate that compression (Kc), is the major contributor to the puncture reading and that shear is a minor contributor.

The Plane Strain Indentation of Anisotropic Aluminium Using a Frictionless Flat Rectangular Punch

In Part 1, the slip-line field solutions and the associated load requirements necessary for the indentation of anisotropic solids are presented. The analysis is based on Hill's approach to the analysis of anisotropic material. All results are recorded in terms of a lumped anisotropic parameter, c. In Part 2, the results of an investigation to determine the anisotropic parameters of a commercially available aluminium are reported. Specimens machined from the aluminium at selected orientations to the anisotropic axes were indented using a nominally frictionless flat rectangular punch. A comparison between the theoretical and experimental indentation loads is given.

A rectangular punch for removing uniform samples of tissue from blood vessels postmortem.

A rectangular punch for removing uniform samples of tissue from blood vessels postmortem.

The Application of Limit Analysis to Punch-Indentation Problems

Abstract Limit analysis is applied to obtain upper and lower bounds for the punch pressure in the indentation of the plane surface of an elastic-perfectly plastic material by a flat rigid punch. The two-dimensional flat punch and the three-dimensional flat square and rectangular punch problems are considered. The analysis assumes Tresca’s yield criterion of constant maximum shearing stress k, during plastic deformation. It is shown that the pressure required to produce indentation in the two-dimensional problem lies between 5k and (2 + π)k. The lower bound obtained for any rectangular punch is again 5k while the upper bound for a smooth punch lies between 5.71k for a square and (2 + π)k for a very long rectangle. A value of 5.36k is found for a ratio of length to breadth of 3. The limit pressure for a uniformly loaded area, as distinguished from an area loaded by a punch, is bracketed by 5k and (2 + π)k when the area is convex.

INSTRUMENTS FOR USE IN LARYNGOFISSURE

The instruments presented have proved of value in simplifying the operation of laryngofissure for cancer of the larynx. They are as follows: A special rotary saw blade. A special elevator. A pair of three-pronged sharp retractors. A pair of double-ended blunt retractors. A heavy rectangular punch. A straight and a right-angled hemostat. A pair of curved, angular cutting scissors. An angular knife for cutting through cartilage. The saw blade is approximately 6 mm. in diameter. It is designed for use with a special hand motor and is employed for cutting through the center of the thyroid cartilage with facility and precision. When used, the blade penetrates the cartilage but does not cut through the internal perichondrium and soft tissues. The elevator is used for two purposes, to ascertain whether the cartilage is completely severed and to elevate the internal or the external perichondrium. The three-pronged sharp retractors are insinuated