1

1. Introduction
Bending is the uniform straining of material, generally flat sheet or strip metal, around a straight axis, which lies in the neutral plane and normal to the sideways direction of the sheet or strip. Sheet metal bending is one of the most commonly applied sheet metal forming operations. The fabrication of sheet metal bending is generally used in automobile and aircraft industrial processes and being employed to bend the plate to the required angle. The accuracy and success of the bending process depends upon the operating factors as well as the material properties. In the bending processes, the elastic limit of material can be exceeded but yield stress limits cannot. For this reason the material keeps some of its original elasticity. At the end of the loading operation the part being formed follows closely the tool shape. When the load is removed from the material, it tries to get back to its original shape and bent material springs-back partially
Spring back can be defined as the elastic deformation of sheet metal parts after unloading due to the action of internal stresses. This elastic recovery is one of the main sources of geometrical inaccuracies in the products of sheet metal forming processes. Spring back introduces surface distortions and unexpected out of shape tolerances that not only cause deviations from the designed target shapes in the products but also can lead to the assembly problems.

2. Problem definition
Titanium is extensively used due to their high strength to density ratio, high corrosion resistance and ability to withstand moderately high temperatures. Titanium u bend parts are commonly used in chemical, oil and gas, food processing and petroleum industry and while performing bending, spring back are a common problem and little research has been to done to reduce spring back on titanium grade 2 materials
3. Objective
The objective of the project is to
measure the amount of spring back and compare the values found by experimental and numerical analysis
find optimal parameter for u bending of titanium grade 2 metal
4. Methodology
19234154326255Design of experiment
00Design of experiment
1941830154305Literature survey
00Literature survey
center571500000center4850130center396430519430993469005Finite element analysis
00Finite element analysis
19240502602230 Modelling finite element analysis
0 Modelling finite element analysis
center313563000center225742500center1449705center6210300019240501725930Raw material purchase and testing
Raw material purchase and testing

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192280527293Material selection
00Material selection

2007870247015Spring back measurement
00Spring back measurement

2050415149225Analysis of results
00Analysis of results

288988526924000
2011680294005Results and discussion
00Results and discussion

5. Material selection
In pure titanium there are 4 different types of grade
Grade 1
Grade 1 titanium is the first of four commercially pure titanium grades. It possesses the greatest formability, excellent corrosion resistance and high impact toughness. Because of all these qualities, Grade 1 is the material of choice for any application where ease of formability is required and is commonly available as titanium plate and tubing.

Grade 2
Grade 2 titanium is called the “workhorse” of the commercially pure titanium industry, thanks to its varied usability and wide availability. It shares many of the same qualities as Grade 1 titanium, but it is slightly stronger. Both are equally corrosion resistant. This grade possesses good weldability, strength, ductility and formability
Grade 3
This grade is least used of the commercially pure titanium grades, but that does not make it any less valuable. Grade 3 is stronger than Grades 1 and 2, similar in ductility and only slightly less formable – but it possesses higher mechanicals than its predecessors
Grade 4
Grade 4 is known as the strongest of the four grades of commercially pure titanium. It is also known for its excellent corrosion resistance, good formability and weldability.

Reason : Grade 2 and 5 are commercially used to produce u bend parts. The material should have good formability and considerable amount of strength for ease of bending. Also spring back measurement was not done in titanium pure grade metals
6. Scope
Titanium grade 2 may be considered in any application where formability and corrosion resistance are important, and strength requirements are moderate. Ti has also been broadly used in marine and chemical applications such as condensers, evaporators, reaction vessels for chemical processing, tubing and tube headers in desalinization plants, and cryogenic vessels. Other uses have included items such as jigs, baskets, cathodes and starter-sheet blanks for the electroplating industry, and a range of medical applications
7. Literature survey
S.NO JOURNEL NAME AUTHOUR NAME CONFERENCE COMMENTS
1 FE-analysis of channel width effects on spring-back characteristics in the U-bending process Wiriyakorn Phanitwonga ,Sutasn Thipprakmas17th International Conference on Sheet Metal, SHEMET17 In this journal the effects of channel width on spring-back characteristics in the U-bending process were examined using the finite element method (FEM) and laboratory experiment
2 Effect of punch speed on amount of springback in U-bending process of auto-body steel sheets Min Kuk Choi, Hoon Huh 11th International Conference on Technology of Plasticity, ICTP 2014, 19-24 October 2014, Nagoya Congress Center, Nagoya, Japan In this paper, U-bending tests and finite element analysis of SPCC and DP780 steel sheets were directed for springback evaluation at different punch speeds
3 Spring-back and spring-go behaviors in bending of thick plates of high-strength steel at elevated temperature Joonhang Lee, , Kwangmin Lee, Dongok Kim, Hongseok Choi , Byungmin Kim Computational Materials Science (2015) In this study, a numerical simulation was conceded out to find the process conditions which affect the product quality by examining the U-channel shape and the forming capabilities for thick high-strength steel plates
4 The study of spring-back of CK67 steel sheet in V-die and U-die bending processes M. Bakhshi-Jooybari, B. Rahmani, V. Daeezadeh, A. GorjiMaterials and Design 30 (2009) In this research, the effects of significant parameters on spring-back in U-die and V-die bending of CK67 anisotropic steel sheet were considered by experiments and numerical simulations. Evaluation between the experimental and the finite element simulation results were also performed
Material Testing
Titanium grade 2 material testing was done at SI’Tarc, Coimbatore. The Material testing was done for chemical analysis. The test method used for testing is OES (Optical Emission Spectrophotometer). The sample size given for testing is given as follows and the thickness of the material is 0.9mm

Material specification as per ASTM B265 – 15 Grade 2
This standard is used for Titanium and Titanium Alloy Strip, Sheet and Plate.

B265 – 15 indicates
B – Non Ferrous
265 – Assigned sequential number
15 – Year of adoption
S.NO Elements Maximum value (%)
1 Iron 0.30
2 Hydrogen 0.015
3 Oxygen 0.25
4 Carbon 0.08
5 Nitrogen 0.03
6 Other element (each) 0.10
7 Other Element 0.40
8 Titanium Balance
U bending dimensions

Figure 1: U bending die

Figure 2: Punch

Figure 3: Top Plate

Figure 4: Bottom Plate
References
Yixi Zhao , Linfa Peng, Xinmin Lai, Influence of the electric pulse on springback during stretch U-bending of Ti6Al4V titanium alloy sheets, Journal of Materials Processing Tech.

K. Matsushitaa , T. Furushimaa , K. Tadaa , K. Manabe, Spring-in Behavior of Crystalline CFRTP Sheet after Thermal U-bending, Advances in Material ; Processing Technologies Conference
Komgrit Lawanwomga,, Hiroshi Hamasakib ,Ryutaro Hinob , Fusahito Yoshidab, Nagoya Congress Center, Nagoya, Japan A novel technology to eliminate U-bending springback of high strength steel sheet by using additional bending with counter punch, 11th International Conference on Technology of Plasticity, ICTP 2014, 19-24 October 2014
Angela Quadfasela , Johannes Lohmara , Gerhard Hirta, Investigations on Springback in High Manganese TWIP-Steels using U-Profile Draw Bending International Conference on the Technology of Plasticity, ICTP 2017, 17-22 September 2017, Cambridge, United Kingdom
Daw-Kwei Leu , A simplified approach for distinguishing between spring-back and spring-go in free U-die bending process of SPFC 440 sheets, Materials and Design 94 (2016) 314–321
M. Bakhshi-Jooybari , B. Rahmani, V. Daeezadeh, A. Gorji , The study of spring-back of CK67 steel sheet in V-die and U-die bending processes
https://www.ulbich.com/resources/strip-datasheets/titanium-grade-2-uns-r50400/