Sheet Metal Strip Research Articles

Subfoil Stiffness Effects in Gas-Lubricated Foil Journal Bearings

A gas-lubricated foil journal bearing consists of a compliant foil structure that supports a rigid journal by means of a gas film. The foil structure consists of a top foil and a subfoil. The subfoil, which is constructed of one or more corrugated strips of sheet metal, supports the top foil and provides the primary resistance to radial deflection. As such, the radial stiffness of the subfoil has a direct influence on the gas film thickness and pressure distributions in the bearing. A finite element model incorporating the gas film and the foil structure will be used to investigate the effects of axial variations in the stiffness of the subfoil.

Dimensional errors of rollers in the stream of variation modeling in cold roll forming process of quadrate steel tube

In the cold roll forming process, the sheet metal strip is gradually bent into a desired profile by successive roller stations. During this process the roller locating errors of each roller station are introduced, transformed and accumulated until the sheet metal is bent into the final desired profile, which does influence the product’s dimension quality, affect the end-welding of quadrate steel tube, and elongate the costly error-and-trial phase in ramp-up. This paper introduces procedures for expressing the influence of roller locating errors in the forming process of quadrate steel tube, which is based on the formulation of the stream of variation (SOV) model of roller dimensional errors using the CAD/CAPP parameters of the cold roll forming process. The SOV model is utilized to reveal the variation propagation in the manufacturing process. The modeling process is experimentally validated in a two-station forming process.

On the modeling and simulation of induced anisotropy in polycrystalline metals with application to springback

The presence of initial, and the development of induced, anisotropic elastic and inelastic material behavior in polycrystalline metals, can be traced back to the influence of texture and dislocation substructural development on this behavior. As it turns out, via homogenization or other means, one can formulate effective models for such structure and its effect on the macroscopic material behavior with the help of the concept of evolving structure tensors. From the constitutive point of view, these quantities determine the material symmetry properties. Most importantly, all dependent constitutive fields (e.g., stress) are by definition isotropic functions of the independent constitutive variables, which include these evolving structure tensors. The evolution of these tensors during loading results in an evolution of the anisotropy of the material. From an algorithmic point of view, the current approach leads to constitutive models which are quite amenable to numerical implementation. To demonstrate the applicability of the resulting constitutive formulation, we apply it to the case of metal plasticity with combined hardening involving both deformation- and permanently induced anisotropy. Comparison of simulation results based on this model for the bending tension of aluminum-alloy sheet-metal strips with corresponding experimental ones show good agreement.

A study of the microscopic deformation behavior of an phosphor bronze plate during arbitrary holes piercing process

In order to obtain competitiveness in the field of industrial manufacturing, a reduction in the development period for the small batch manufacturing of products is required. However, metal forming tools cause multiple cracking on sheet metal strips during piercing process due to clearance between punch and die. Such a cracking eventually causes severe degradation of the critical current density. Therefore, it is very important to understand the microscopic deformation behavior of CuSn9 alloy under mechanical loading. A method of evaluating the strain over the deformed surface of stamping is described. Measurements of the deformation width of the edges of arbitrary holes on the sheet metal were analyzed to determine the strain and the stress distributions which were displayed in the form of contours. For an arbitrary hole piercing process, FEM simulation with ANSYS/LS-DYNA Test of Edbound with Eroding Contact was used and as the first step, strip process layout was designed. After that, the process of die development was studied according to the sequence of die components, i.e., die structure, machining condition for die making, die materials, heat treatment of partially die components, and so on. In this study, modeling of strip layout and die components with the Mechanical Desktop commercial program, standard components selection and strip process layout drawing with the Auto-LISP, CAD/CAM application, ordinary machine tool operating, and measurement microscopic cracking deformation is done.

An effect of feeding system on the scratches of sheet metal strips

Over the years, significant improvements have been made in the area of press feeding system. As feeds become more accurate, faster, and varied in their use, the entire system must also be more capable to accommodate these new requirements. Generally, mechanical feeders used for thin sheet metal strips are adjusted to press eccentric shafts. Pneumatic feeders are installed to an air pressure system. Both mechanical and pneumatic feeders have been used in industry. These systems had many overlapping applications. Therefore, it is important for the industry to understand both processes, in order to optimize the process. The comprehensive knowledge on usefulness, deformation and damage scratches would help the users to judge which feeder is more appropriate for each type of application. This paper presents how to select a useful feeder according to deformation and damage scratches of both mechanical and pneumatic system. Case on feeding dead-soft material, cold-rolled material and hot-rolled material of different thicknesses are also discussed in a comparison study.

Rotary Blanking ‐ a New Manufacturing Process

Rotary blanking is a method of blanking and punching with rotating tools whereby the cutting tools are fixed to a pair of rollers performing a continuous blanking operation on a strip of sheet metal. The purpose of this paper is to outline the determining conditions under which the rotary blanking process takes place and to discuss advantages, restrictions, applications and optimization of this technology.

Influence of pitch and cross-sectional ratio of strip of sheet metal on incremental in-plane bending

Incremental in-plane bending which has been invented by authors is a new and flexible manufacturing technology for short production runs in a variety of sizes and shapes. The strip of sheet metal is bent incrementally by an inclined punch beating according to the control program. The prototype incremental bending machine, which has been invented and produced, uses the numerical control technology and bends the strip of sheet metal flexibly. The cross-sectional ratio of width to thickness of sheet metal and the pitch are important for in-plane bending conditions. The bending experiment is carried out and some experimental results such as beating force, bending radius and strain distribution are experimentally examined. The forming properties of in-plane bending are clarified in this study.

Damage Identification for Anisotropic Sheet-Metals Using a Non-Local Damage Model

A new damage model which takes account of void shape effect and anisotropy of the matrix material is integrated into the explicit finite element framework to predict the damage evolution which occurs under crash or stamping process. The void coalescence failure mechanism by internal necking is also considered by using a modified Thomason’s plastic limit-load model. An inverse method is developed to identify the material parameters by correlating experimental and numerical measurements with tensile tests on sheet-metal strips. The pathological mesh dependence has been overcome by a non-local approach where the evolution equation for the porosity is modified by an additional term containing a characteristic internal length. In this paper the evaluation of the Laplacian is based on a least square approximation of the internal state variable around each integration points. The presented formulation is applied to an Ni-based sheet-metal (INCO 718) and an aluminium alloy (AA 5182). The effectiveness of the numerical predictions is verified carrying out a set of experimental tests with a flat-headed punch.

Experimental investigation and theoretical analysis of roll forming of electrical resistance welded pipes

Roll forming is a general term used to describe a large class of continuous manufacturing processes where a long strip of sheet metal is deformed into products with desired geometry by passing through a series of rotating rolls arranged in tandem. Electrical resistance welded (ERW) pipe can be manufactured by roll forming. Based on the updated-Lagrange method in deformation mechanics, an elastic–plastic large deformation spline finite strip method is developed to analyze roll-forming ERW pipe. The longitudinal strains, the opening values, and the springback of the skelp are obtained. Simulated results are compared with the results obtained. They agree well with each other.

유한요소법을 이용한 롤포밍 공정에서의 버클링 해석

In code roll forming processes, the sheet metal strip is gradually and successively bent into a desired profile.Occurrence of buckling is one of the major defects. Buckling may occur due to longitudinal stress and it is difficult to predict buckling behavior. In this study an analytical method for buckling behavior during roll forming is proposed. All numerical simulations are performed by finite element analysis. The behavior of buckling can be predicted with the simulation modeling of the finite element method.

Rotary Blanking

Rotary blanking is a method of blanking and punching with rotating tools whereby the cutting tools are fixed to a pair of rollers performing a continuous blanking operation on a strip of sheet metal. The purpose of this paper is to outline the determining conditions under which the rotary blanking process takes place and to discuss advantages, restrictions, applications and optimization of this technology.

Analysis Tool for Roll Forming of Sheet Metal Strips by the Finite Element Method

A computational method based on the three-dimensional finite element method is developed for the deformation analysis of roll forming process. The method approximates the process as a kinematically steady state deformation of strip. For industrial usefulness of the simulation method, several rolls with arbitrary shapes in one stand can be considered. The shapes and the thickness distributions of strip after roll forming were examined by comparing computation results with experiments. It is concluded that the tool is useful enough to predict the process. The overall simulation method was integrated into a software package to help the industrial roll-pass design.

Development of a Die Shoulder Force Transducer for Sheet Metal Forming Research

A force transducer has been developed for measuring the tension in a strip of sheet metal as it passes over a die shoulder. This transducer is primarily a research tool. The die shoulder portion of the transducer can be selectively fixed or permitted to roll by contact with the moving strip. Applications of this force transducer are to measure pull force, drawbead restraining force, calculate the average coefficient of friction over the die shoulder, and quantify bending effects. Described in this paper is the development of the force transducer. It is a design based on four webs with strain gages as the transduction elements. It has been built, calibrated, and shown to accurately measure sheet tension in a strip test apparatus before and after the portion simulating the die shoulder. Friction and bending effects are studied from the sheet tensions.

Sash sheet metal development and the application of a back-propagation neural network in the calculation of the developed length

All of the sides constituting a sash sheet metal are most squares or rectangles, only the sections of sheet metal needing to be designed. The rest of the entire sash sheet metal product can be generated from the width of the sash sheet metal entered by the user, and the section shape of the sheet metal designed by the user. Before a sheet metal product is developed, the developed length needs to be calculated. The calculation of the developed length requires the curve data for the ‘relative curve drawing of the bending radius, the sheet metal strip thickness and the correction factor’. This paper uses a back-propagation neural network to search for the relationship between the two coordinate axis data of the curve. This relationship is stored in the connected weight amongst neurons. Therefore, it is possible to simply run the attribute value data to be inferred through the weight matrix calculation to quickly obtain the network inference results, which also possess the capability of uncertainty inference. By means of the weight matrix, the correction factor can be obtained from the ‘bending radius, sheet metal strip thickness and correction factor relative curve drawing’ to calculate the developed length.

Model experiment on noise barriers having a random edge

A preliminary model experiment showed that the insertion loss for a random edge barrier exceeded that of a straight edge barrier of the same average height [J. Acoust. Soc. Am. 97, 3392(A) (1995)]. Based on this promising result, a three-level full factorial model experiment has been conducted on random edge barriers. The top of the barrier is a strip of sheet metal of fixed average height but made randomly triangular by straight line cuts. A random number generator was used to specify the height variations Δy (scaled to a prescribed maximum value) at fixed intervals Δx along the barrier. Nine different random edges provide a range of 9–37 mm in Δx and 5–18 mm in Δy. An electric spark was the sound source, a 1/8-in. B&K condenser microphone the receiver. The frequency range of the measurements is 5–21 kHz, the Fresnel number range 2–20. In most of the measurements the random edge barriers showed 3–8 dB more insertion loss than the straight barrier. For several cases, however, the straight barrier was better. [Work supported by TxDOT.]

Tenlined June Beetle Control, 1993

Abstract The experiment was performed in two commercial orchards. Trees in Orchard #1 were in the second leaf, while those in Orchard #2 varied between second and fourth leaf. Both orchards were planted on sandy soil. Trees used in the experiment showed visible signs of stress (abnormally small leaves, reduced terminal growth, water stress) associated with grub damage to the root sytem. Each treatment was replicated ten times, with a replicate consisting of a single tree. All treatments were applied 10-11 Jun. A second application to the Diazinon plot was made 25 Jun. A strip of sheet metal ca. 15 cm wide was formed into a circle 39 cm in diameter and centered around the trunk of the tree. The bottom edge was worked into the soil to form a seal such that the drench solution could not escape. Two gallons of test insecticide mixtures were poured around the base of test tree, and allowed to soak into the soil before the metal strip was removed. Trees and the surrounding soil (39 cm diameter × 46 cm deep) were excavated 22-30 Jul about six weeks after the first application date. Live and dead grubs were recorded.

Development of a Computer-Controlled Drawbead Simulator for Sheet Metal Forming

A multiple-action hydraulic sheet metal strip drawing test device has been constructed for the purpose of studying the effectiveness of feedback controls in sheet metal forming. The apparatus simulates the flow of sheet metal in the blankholder and over the die shoulder during the stamping of sheet metal panels. Its special features consist of the ability to adjust both blankholder force and drawbead penetration while the strip is being drawn. A force transducer was developed to measure the forces in the sheet on either side of the die shoulder. Measurements from this unique transducer determine both the drawbead restraining force in the simulator and friction between the sheet and the die shoulder. Data demonstrating the capabilities of the equipment are presented.

Free rigid/plastic plane bending of a slender beam

Large rigid/plastic plane bending of a slender structural element as e.g., a beam or a sheet metal strip is examined, in view of its applications to metal forming. Loads, i.e. forces and moments, are admitted only at the ends of the element; the loads or the corresponding displacements and rotations may be prescribed. Using the normal force, the transversal force and the bending moment as generalized stresses acting at the cross sections the differential equations of the problem are set up for an arbitrary, strain-hardening and/or rate-sensitive material. As an example a homogeneous, ideally plastic beam is considered to be plastified by means of the bending moment only. It is shown that it can be brought into any shape provided the end conditions are adequately controlled. Circular bending as a special case becomes possible in two different ways i.e., by pure bending (without end forces) or by localized bending (generated by a moving yield hinge).

Crested Wheatgrass Vigor as Affected by Black Grass Bug and Cattle Grazing

Crested Wheatgrass Vigor as Affected by Black Grass Bug and Cattle Grazing

Improvement of Sheet Metal Strength by Localized Thermal Shocks

Abstract In two previous papers, the authors presented results of a new process of introducing beneficial residual stresses in a sheet metal strip containing a small circular hole by a single thermal shock applied over an annular region concentric with the hole. In this paper, it is shown that multiple thermal shocks over separate annular regions are considerably more advantageous in introducing such beneficial residual stresses in the same sheet metal and in permitting wider tolerances for such variables as locations, sizes of shock zones, and strengths of the shocks for desired degree of benefit.