Incremental Bending of Three-Dimensional Free Form Metal Plates Using Minimum Energy Principle and Model-Less Control

Author(s):  
Xiaobing Dang ◽  
Kai He ◽  
Wei Li ◽  
Qiyang Zuo ◽  
Ruxu Du

Bending 3D free form metal plates is a common process used in many heavy industries such as shipbuilding. The traditional method is the so-called line heating method, which is not only labor intensive but also inefficient and error-prone. This paper presents a new incremental bending method based on minimum energy principle and model-less control. First, the sheet metal is discretized into a number of strips connected through virtual springs. Next, by applying the minimum energy principle, the punching and supporting points are calculated for the strip. Then, the bended shape of the strip is computed based on the beam bending theory. This process is continued until the final shape is reached. To compensate the bending error, the computer vision-based model-less control is applied. The computer vision detects the bending error based on which additional bending steps are calculated. The new method is tested in a custom build incremental bending machine. Different metal plates are formed. For a metal plate of 1000 × 800 × 5 mm3, the average bending error is less than 3 mm. In comparison with the existing methods, the new method has a number of advantages, including simple, fast, and highly energy efficient.

Author(s):  
Toru Yamada ◽  
Anurag Kumar ◽  
Yutaka Asako ◽  
Mohammad Faghri

A three-dimensional computational model using dissipative particle dynamics (DPD) is developed to simulate dynamics and deformation of red cells (RBC) in capillaries. DPD is able to produce correct hydrodynamics of the flow and incorporate microscopic detail of various segments of the cell. RBC is constructed using DPD particles, which are connected by a spring network to represent the membrane. The total energy of the RBC is associated with the bending energy, in-plane shear energy and the constraints of fixed area and volume. Shape optimization of swollen RBC due to continuous deflation based on the minimum energy principle is conducted to obtain the biconcave shape in equilibrium. Then, an external force is applied to the cell to study the large deformation in axial and lateral direction and compared with the experimental results. Also, RBC is placed inside a 10 μm capillary flow to study the dynamics and deformation of the cell. The cell undergoes steady deformation and acquires parachute type shape as observed in experiments.


Author(s):  
Eiji Shamoto ◽  
Masahiro Kato ◽  
Norikazu Suzuki ◽  
Rei Hino

A new and basic analytical model of three-dimensional cutting is proposed by assuming multiple thin shear planes with either the maximum shear stress or minimum energy principle. The three-dimensional cutting process with an arbitrarily shaped cutting edge in a flat rake face is formulated with simple vector equations in order to understand and quickly simulate the process. The cutting edge and workpiece profile are discretized and expressed by their position vectors. Two equations among three unknown vectors, which show the directions of shear, chip flow, and resultant cutting force, are derived from the geometric relations of velocities and forces. The last vector equation required to solve the three unknown vectors is obtained by applying either the maximum shear stress or minimum energy principle. It is confirmed that the directions and the cutting forces simulated by solving the proposed vector equations agree with experimentally measured data. Furthermore, the developed model is applied to consider the three-dimensional cutting mechanics, i.e., how the chip is formed in the three-dimensional cutting with compressive stress acting between the discrete chips, as an example.


2021 ◽  
Vol 502 (3) ◽  
pp. 4064-4073
Author(s):  
Y Ellinger ◽  
M Lattelais ◽  
F Pauzat ◽  
J-C Guillemin ◽  
B Zanda

ABSTRACT The analysis of the organic matter of meteorites made it possible to identify over 70 amino acids (AA), including 8 of those found in living organisms. However, their relative abundances vary drastically with the type of the carbonaceous chondrite, even for isomers of same chemical formula. In this report, we address the question whether this difference may have its origin in the relative stability of these isomers according to the conditions they experienced when they were formed and after. To this end, we rely on the fact that for most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle, MEP). Using quantum density functional theory (DFT) simulations, we investigate the relative stability of the lowest energy isomers of alanine (Ala) and amino butyric acid (ABA) in the neutral, protonated, and zwitterionic structures together with corresponding nitrile precursors. It is shown that β-alanine and γ-ABA are the most stable in a protonated form, whereas α-AA are the most stable in the zwitterionic and nitrile structures. The different composition of the carbonaceous chondrites CIs and CMs could be linked to the chemical context of the aqueous alterations of the parent bodies.


1992 ◽  
Vol 32 (3) ◽  
pp. 97-116 ◽  
Author(s):  
Ikuo Towhata ◽  
Yasushi Sasaki ◽  
Ken-Ichi Tokida ◽  
Hideo Matsumoto ◽  
Yukio Tamar ◽  
...  

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