Hydrodynamic Lubrication in Simple Stretch Forming Processes

1984 ◽  
Vol 106 (1) ◽  
pp. 70-77 ◽  
Author(s):  
W. R. D. Wilson ◽  
J. J. Wang
Keyword(s):  
Plastic Deformation ◽  
Plane Strain ◽  
Sheet Metal ◽  
Hydrodynamic Lubrication ◽  
Theoretical Models ◽  
Newtonian Liquid ◽  
Stretch Forming ◽  
Exponential Variation ◽  
Plane Strain Case

Theoretical models for the hydrodynamic lubrication of plane strain and axisymmetric sheet metal stretch forming processes with cylindrical and spherical headed punches, respectively, are developed. The lubricant is treated as an isoviscous Newtonian liquid for both geometries. In addition, the influence of sheet heating due to plastic deformation with an exponential variation of viscosity with temperature is analyzed for the plane strain case.

Hydrodynamic Lubrication in Axisymmetric Stretch Forming—Part 1: Theoretical Analysis

1991 ◽  
Vol 113 (4) ◽  
pp. 659-666 ◽  
Author(s):  
W. R. D. Wilson ◽  
L. G. Hector
Keyword(s):  
Theoretical Model ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Sheet Metal ◽  
Newtonian Fluid ◽  
Hydrodynamic Lubrication ◽  
Lubricant Film ◽  
Previous Model ◽  
Stretch Forming ◽  
Lubricant Viscosity

An improved theoretical model for the hydrodynamic lubrication of axisymmetric, sheet metal stretch forming is presented. The infinite initial film thickness problem, encountered in a previous model, is removed by accounting for the squeeze action occurring during the initial stages of the process. Both isoviscous and thermoviscous theories are developed assuming that the lubricant is a Newtonian fluid. In the thermoviscous model, the lubricant viscosity is assumed to vary exponentially with temperature. The influence of plastic heating of the sheet on the entrainment and transport of the lubricant film is examined. The effects of variable punch speed are also investigated.

Hydrodynamic Lubrication in Hemispherical Punch Stretch Forming

1986 ◽  
Vol 53 (2) ◽  
pp. 440-449 ◽  
Author(s):  
Kuo-Kuang Chen ◽  
D. C. Sun
Keyword(s):  
Strain Hardening ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Model Problem ◽  
Hydrodynamic Lubrication ◽  
Sheet Material ◽  
Stretch Forming ◽  
Variable Friction ◽  
Hemispherical Punch

The existence and consequence of hydrodynamic lubrication in sheet metal forming is demonstrated using a model problem of hemispherical punch stretch forming. The problem is solved by incorporating a lubrication analysis into an incremental plasticity analysis. The sheet material is assumed to be elastic plastic with strain hardening, and the lubricant is assumed isoviscous. The study identifies two dimensionless parameters controlling the condition of lubrication. The resulting variable friction at the punch-sheet interface is found to affect significantly the distribution of strains in the sheet metal and its formability.

A New Stretch-Forming Process Based on Loading at Discrete Points and its Numerical Investigation

2013 ◽  
Vol 423-426 ◽  
pp. 737-740
Author(s):  
Zhong Yi Cai ◽  
Mi Wang ◽  
Chao Jie Che
Keyword(s):  
Sheet Metal ◽  
Three Dimensional ◽  
Discrete Point ◽  
Stretch Forming ◽  
Sheet Metal Part ◽  
Metal Part ◽  
Forming Process ◽  
Loading Trajectory ◽  
New Process ◽  
Forming Defects

A new stretch-forming process based on discretely loading for three-dimensional sheet metal part is proposed and numerically investigated. The gripping jaw in traditional stretch-forming process is replaced by the discrete array of loading units, and the stretching load is applied at discrete points on the two ends of sheet metal. By controlling the loading trajectory at the each discrete point, an optimal stretch-forming process can be realized. The numerical results on the new stretch-forming process of a saddle-shaped sheet metal part show that the distribution of the deformation on the formed surface of new process is more uniform than that of traditional stretch-forming, and the forming defects can be avoided and better forming quality will be obtained.

Flexible Stretch Forming Technology for Sheet Metal Based on Discrete-Gripper and Multi-Point Die

2014 ◽  
Vol 556-562 ◽  
pp. 460-463 ◽  
Author(s):  
Xue Chen ◽  
Ming Zhe Li ◽  
Wen Hua Liu ◽  
Zhi Qiang Hou
Keyword(s):  
Sheet Metal ◽  
Experimental Results ◽  
Shape Error ◽  
Stretch Forming ◽  
Forming Process ◽  
Structural Composition ◽  
Forming Technology ◽  
Working Principle ◽  
Material Utilization

To solve the problem of low material utilization in traditional stretch forming process, a flexible stretch forming method was proposed, which can be realized by interaction of the multi-point stretch forming die with discrete-gripper stretch forming machine. The principle and characteristics of sheet metal flexible stretch forming technology was introduced, structural composition and working principle of the multi-point stretch forming die and discrete-gripper stretch forming machine were expounded, and the technology experiments was carried out with a self-designed flexible stretch forming technology equipment for sheet metal. The experimental results indicate that structure of multi-point stretch forming die and discrete-gripper stretch forming machine are reasonable, and flexible stretch forming technology can be realized by above-mentioned die and machine, stretch forming parts has a good quality and its shape error can satisfy requirements of production.

Research of stamping of unequal channel bars. Part 4. Deformed state of the workpiece when extruding channels. 2. Deformations under the punch end

2021 ◽  
pp. 53-57
Author(s):  
A.L. Vorontsov
Keyword(s):  
Plastic Deformation ◽  
Plane Strain ◽  
Deformation Zone ◽  
Plastic Deformation Zone ◽  
Die Forging ◽  
Deformed State

Determination of the deformed state of the workpiece at free extrusion of channels is considered. Formulas are obtained for determining the accumulated deformations at a given point of the plastic deformation zone and extruded walls of the product for any punch working stroke. Keywords: die forging, extrusion, misalignment, punch, matrix, plane strain, accumulated deformations, hardening. [email protected]

Research on Cold Orbital Forming of Complex Sheet Metal of Aluminum Alloy

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Xinghui Han ◽  
Qiu Jin ◽  
Lin Hua
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
Aluminum Alloy ◽  
Mobile Phone ◽  
Sheet Metal ◽  
Experimental Results ◽  
Complex Motion ◽  
Flow Lines ◽  
Inner Surface ◽  
Orbital Forming

This study aims at exploring the potentialities of cold orbital forming in forming complex sheet metal. Aiming at a complex mobile phone shell component of aluminum alloy, two technical schemes for cold orbital forming are first presented. Then, the optimized one, i.e., the more complex inner surface of mobile phone shell is arranged to be formed by the rocking punch with a complex motion, is determined by analyzing the nonuniform plastic deformation laws and punch filling behaviors. On the basis of the optimized technical scheme, the blank geometry in cold orbital forming of mobile phone shell is also optimized based on the forming status of the most difficult forming zone. The consistent finite element (FE) simulated and experimental results indicate that under the optimized technical scheme, not only the bosses in the mobile phone shell are fully formed but also the obtained flow lines are reasonable, which proves that the technical scheme presented in this study is feasible and cold orbital forming exhibits huge potentialities in forming complex sheet metal.

scholarly journals The Effect of Swinging Ball Heads with Different Arrangements in Multi-Point Stretch-Forming Process

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 337 ◽  
Author(s):  
Jian Xing ◽  
Yan-yan Cheng ◽  
Zhuo Yi
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Sheet Metal ◽  
Strain Distribution ◽  
Finite Element Models ◽  
Stretch Forming ◽  
Forming Process ◽  
Forming Quality ◽  
Staggered Arrangement ◽  
Simulation Results

To improve the effect of multi-point stretch forming of sheet metal, it is proposed in this paper to replace a fixed ball head with a swinging ball head. According to the multi-point dies with different arrangements, this research establishes finite element models of the following stretch forming, i.e., fixed ball heads with conventional arrangement, swinging ball heads with conventional arrangement, swinging ball heads with declining staggered arrangement, and swinging ball heads with parallel staggered arrangement, and then numerical simulation is performed. The simulation results show that by replacing a fixed ball head with a swinging ball head, the surface indentation of the part formed was effectively suppressed, the stress and tension strain distribution of the part formed was improved, and the forming quality was improved; the thickness of the elastic pad was reduced, the springback was reduced and the forming accuracy was improved; and when the ball head was applied to a multi-point die with staggered arrangement, a better forming result was achieved, where the best forming result was achieved in combining the swinging ball heads with the multi-point die with a parallel staggered arrangement. Forming experiments were carried out, and the experimental results were consistent with the trend of numerical simulation results, which verified the correctness of the numerical simulation.

Sign in / Sign up

Export Citation Format

Share Document