Doctor of Philosophy, The Ohio State University, 2005, Materials Science and Engineering

Electromagnetic forming can lead to better formability along with additional benefits. The spatial distribution of forming pressure in electromagnetic forming can be controlled by the configuration of the actuator. A new type of actuator is discussed which gives a uniform pressure distribution in forming. It also provides a mechanically robust design and has a high efficiency for flat sheet forming. An analysis of the coil is presented that allows a systematic design process. Examples of uses of the coil are then presented, specifically with regards to forming a depression, embossing and cutting. Some practical challenges in the design of the coil are also addressed. This work emphasizes the approaches and engineering calculations required to effectively use this actuator.

Committee: Glenn Daehn (Advisor) Subjects:

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Business Administration, The Ohio State University, 1963, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2007, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2023, Mechanical Engineering

Conventional sheet metal forming tooling in the automotive industry is made up of hardened steel and used for mass-production. Prototype tooling made of metal is durable, but it is only used for a small number of parts despite its high cost, contributing heavily to the vehicle development cost. Additive manufacturing (AM) offers a cost-effective and rapid tooling option for prototyping, and low cost, low volume sheet metal forming applications. Due to the high anisotropy in mechanical properties of 3D printed composites, accurate characterization, and finite element modeling of the material becomes paramount for successful design and application of these forming tools. This study investigates the feasibility of using AM polymer composite tooling for the stamping of HSS 590 steel sheets through a two-pronged approach – experimental and numerical analysis. Experimental characterization of 3D printed fiber–reinforced polymer composite material was performed at various strain rates. A homogenized material model with orthotropic elasticity and the Hill 1948 anisotropic yield criterion was then calibrated based on these experimental data. Sheet metal stamping experiments were conducted with AM polymer tooling and their performance was evaluated based on various metrics such as tool deformation and part accuracy. Finite element simulations of the stamping of high strength steel sheets using composite tooling were performed and tool deformation were predicted and compared with experimental measurements. FE simulation results were in good agreement with stamping experiments performed with polymer tooling. It was found that the anisotropy and strain rate sensitivity of 3D printed polymer composites play a significant role in their performance as tooling materials. The effective use of simulations in optimizing process parameters to achieve the desired final part geometry is also demonstrated. Fiber reinforced FDM and BAAM produced polymer composite tooling was found to b (open full item for complete abstract)

Committee: Farhang Pourboghrat (Advisor); Jose Castro (Committee Member); Marcelo Dapino (Committee Member); Noriko Katsube (Committee Member) Subjects: Mechanical Engineering; Mechanics

Master of Science, The Ohio State University, 2022, Mechanical Engineering

Flexible sheet metal assemblies, such as those seen in automotive bodies, encounter sources of manufacturing variation during their production such as material anisotropy from cold rolling processes, springback behavior following stamping, and distortion after clamping and spot welding due to residual stresses. Designing a product and corresponding manufacturing process which minimizes these variations requires significant iteration of design and analysis, performed by individuals with expert knowledge of complex, multi-stage nonlinear finite element analysis (FEA). The over-arching goal of this research is to investigate the use of machine learning (ML) for predicting manufacturing variations in flexible assemblies, which would significantly reduce these development times. To accomplish this, an automated, multi-stage, explicit FEA workflow for producing a large, balanced, and validated dataset of formed sheet metal components and assemblies has been constructed as a preliminary case study for a larger NSF project. The corresponding dataset has also been used to demonstrate its compatibility for training a machine learning algorithm – namely a fully connected neural network (FCNN) – for use in tooling and process design. To construct the workflow, first a simulation procedure for component forming/springback was set up and verified with the NUMISHEET 1993 U-draw/bending benchmark using implicit FEA. Next, the verified forming/springback simulation was used to investigate whether implicit or explicit FEA would be more appropriate for automated simulations. Following this, methods for transfer of relevant results to succeeding simulation stages were developed. Using these methods, simulations of clamping components and joining with simplified (adiabatic) spot welds were then set up using explicit FEA. Additionally, both variety and balance were introduced to key workflow inputs through parameterization and design of experiments methodologies. The finite element (F (open full item for complete abstract)

Committee: Jami Shah (Advisor); Farhang Pourboghrat (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2020, Mechanical Engineering

Sheet metal forming or stamping is the process of plastically deforming sheet blanks into a complex-shaped part, usually without significant change in sheet thickness and surface characteristics. As the problem of climate change is becoming more prominent, the emission standards are becoming more stringent for automobiles. This has driven automotive companies towards light weighting while maintaining the structural integrity of the vehicle. Tailor Welded Blanks (TWBs) have been introduced in the automotive industry to aid in reducing the weight while maintaining the structural performance of stamped parts. Laser welding is the most conventional method for developing TWB. The mechanical behavior of tailor-welded blanks differs from the base materials (materials being welded together) due to the welding. Therefore, comprehensive understanding of deformation behavior and formability of TWBs is essential. The objective of this study is to develop a practical methodology for evaluating the formability of TWBs. This study focuses on TWBs with sheets of same thickness on both sides of weld. In this study, same thickness welded blank (1.2 mm to 1.2 mm) of Galvannealed Draw Quality Aluminium Killed (GNDQAK) steel is evaluated using the tensile test, limiting dome height test, viscous pressure bulge test and plane strain loading condition. Mechanical properties of the material is obtained through the tensile test. The hardening curve for the weld zone and heat affected zone (HAZ) is approximated by comparing the hardness of these zones compared to the base material. Numerical models are developed to simulate material behavior in each of these tests. To improve the simulation accuracy, various material models for the base material, the HAZ, and the weld zone are considered. The most accurate model has been used for simulating the behavior of the welded blank in the hat bending and square cup drawing process. Tensile test experiments of the monolithic and welded coupons are c (open full item for complete abstract)

Committee: Taylan Altan (Advisor); Yannis Korkolis (Committee Member) Subjects: Aerospace Engineering; Industrial Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2017, Industrial and Systems Engineering

Sheet Metal forming is facing many difficult problems such as forming of hard formable materials with high strength and low ductility, high precision forming and improvement of productivity. Due to the recent development, there has been increase in the use of servo presses and servo cushions. The use of servo press is expected to improve tool-life, increase productivity, improve processing accuracy, reduce noise and vibration, develop complex processes and shorten forming processes. New forming techniques have been developed utilizing the characteristics of servo press and servo cushions. This thesis studies whether the drawability of the part can be improved by using (a) Servo Press and Servo Cushion characteristics such as Attach – Detach, variable blank holder force and Pulsating blank holder force and (b) optimum slide velocity and forming conditions (lubrication, blank holder force and blank size). Two forming examples have been studied. FE simulations using PAMSTAMP 3D and experimental tryouts using Servo Press and Servo Cushions have been carried out and formed samples have been evaluated to determine whether drawability can be improved by using servo press and servo cushion characteristics. The overall conclusions on the study are: Attach –Detach: Ram Motion can influence the drawability of the material. Results show that for some material and tool geometry, Attach – Detach may improve drawability. However, additional studies are needed to understand this observation. Cushion Pulsation: Cushion Pulsation improve the drawability by improving the lubrication condition and by reducing friction in the flange. However, the applicability of cushion pulsation maybe be limited to small tool geometries and the long range dependability should be considered. Ram Speed: For certain tool geometry and material, using fast ram speed improve the drawability by improving the lubrication conditions (Certain additives in the lubricant can perform better at hig (open full item for complete abstract)

Committee: Taylan Altan (Advisor) Subjects: Industrial Engineering

Master of Science, The Ohio State University, 2016, Industrial and Systems Engineering

Lubrication is one of the process variables that affects the quality of the stamping part. With an appropriate lubrication, quality of the formed part can be improved, and scrap rate can be reduced. The objective of this study is to provide detailed information about Cup Drawing Test (CDT) and Twist Compression Test (TCT) as two common methods to evaluate lubricants performance. In this study, different types of lubricants were evaluated for different sheet materials using CDT and TCT. In CDT, the perimeters of the drawn cups were used to evaluate lubricants' performance. TCT factors were used in TCT to compare the performance of the lubricants. Finite element (FE) simulations were used to predict the temperature distribution in the sheet during both CDT and TCT. According to simulation results, temperature generated at the tool-sheet interface in TCT do not reflect the conditions exists in practical stamping operations. Additionally, TCT results show larger scatter. However, easiness in the application and short process time, make TCT useful to compare the performance of various lubricant additives.

Committee: Taylan Altan (Advisor); Jerald Brevick (Committee Member) Subjects: Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2014, Industrial and Systems Engineering

Stamping of Advanced High Strength Steel (AHSS) alloys poses several challenges due to the material's higher strength and low formability compared to conventional steels and other problems such as (a) inconsistency of incoming material properties, (b) ductile fracture during forming, (c) higher contact pressure and temperature rise during forming, (d) higher die wear leading to reduced tool life, (e) higher forming load/press capacity, and (f) large springback leading to dimensional inaccuracy in the formed part. [Palaniswamy et. al., 2007] The use of AHSS has been increasing steadily in automotive stamping. New AHSS alloys (TRIP, TWIP) may replace some of the Hot Stamping applications. Stamping of AHSS alloys, especially higher strength materials, 780 MPa and higher, present new challenges in obtaining good part definition (corner and fillet radii), formability (fracture and resulting scrap) and in reducing springback. Servo-drive presses, having the capability to have infinitely variable and adjustable ram speed and dwell at BDC, offer a potential improvement in quality, part definition, and springback reduction especially when the infinitely adjustable slide motion is used in combination with a CNC hydraulic cushion. Thus, it is desirable to establish a scientific/ engineering basis for improving the stamping conditions in forming AHSS using a servo-drive press. The overall objectives of the study are to determine the optimum slide velocity and forming conditions in stamping of selected AHSS (DP600, DP780, DP980 and DP1200) sheet materials in a servo press. The specific outcomes include: 1. Material property: material properties results (flow stress, yield, ultimate tensile, elongation, anisotropy) for selected AHSS alloy (DP590, CP800, DP980, TWIP900, TWIP980, and TRIP1180). 2. Lubrication condition: identified the best lubricants for forming DP590 and DP980 with the cup draw test. Determined the maximum value of coefficient of friction (COF) for forming (open full item for complete abstract)

Committee: Jerald Brevick Ph.D. (Advisor); Taylan Altan Ph.D. (Advisor); Rajiv Shivpuri Ph.D. (Committee Member) Subjects: Industrial Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2014, Mechanical Engineering

The dissertation focuses on fracture induced formability in advanced metal forming techniques. The purpose of this study is to fundamentally understand the fracture mechanics in metal forming processes and propose innovative alternative/optimized solutions to produce high quality part without fracture. The dissertation is divided into two major parts: bulk forging and sheet metal forming In bulk forging part, three case studies were presented: 1. Precision forging of engine valves: the complete valve forging process (extrusion and coining) was investigated and the cracking at the “blade” area of the valve was predicted by Finite Element Simulations. Modified tooling design was proposed to reduce the cracking in forging. 2. Open die forging: comprehensive literature survey was conducted to explore the forming conditions that could influence part quality in open die forging. 3D FE simulation was conducted in order to emulate the actual forging process. Initial billet temperature was concluded to be the major factor to cause fracture. Adjustment of the initial temperature is one of the solutions to avoid fracture. 3. Bi-metal forging: an innovative gear forging concept for lightweight vehicle design was proposed and the forging process was validated by Finite Element simulations. Bi-metallic billet was designed and manufactured for test purpose. A new approach of utilizing induction heating method was studied and adopted to heat up the billet to achieve the required temperature gradients. Closed forging die design with special modification to prevent cracking was developed in the actual forging experiment to forge “pancake” shape parts. In sheet metal forming, the results of investigation on blanking and hole flanging of Advanced High Strength Steel (AHSS) were presented: 1. Blanking: the physical nature of blanking operation and the characters of a blanked edge were thoroughly investigated, using FEM and comparison of results with published data. The factors th (open full item for complete abstract)

Committee: Taylan Altan (Advisor); Blaine Lilly (Committee Co-Chair); Jerald Brevick (Committee Member); Allen Yi (Committee Member) Subjects: Mechanical Engineering

MS, University of Cincinnati, 2003, Engineering : Mechanical Engineering

The design of sheet metal parts and the dies used to manufacture them is an art perfected through decades of experience. Reduction of costs is also increasingly important and lack of this experience is a handicap in designing a part with the lowest achievable cost. Parts are frequently redesigned after being deemed as expensive or infeasible to manufacture. Products can be brought to market faster if the designer follows certain recommended guidelines without violating any design rules. The present work aims at developing a feature extraction module and intra-feature design advisor for reducing infeasible designs, costs and production cycle times. The proposed design advisory system will aid the designer right at the design stage with useful design and manufacturability recommendations that have been gathered through decades of experience. These rules are incorporated here and implemented for SolidWorks 2000, which has a separate sheet metal modeling module. The implementation has been done in Visual Basic using the OLE Interface provided by SolidWorks API.

Committee: Dr. Sam Anand (Advisor) Subjects: Engineering, Mechanical

MS, University of Cincinnati, 2003, Engineering : Industrial Engineering

Sheet metal part design relies heavily on manufacturing experience, which is not very easily available to the designer. The manufacturing experience has to be documented and incorporated in the design process. This would eliminate frequent redesign of parts, after being assessed as infeasible or costly for manufacture in the design stage. Such a DFM analysis would reduce product time to market and reduce overall product costs. The present work aims at compiling a comprehensive set of design rules for sheet metal part design and a methodology for implementing inter-feature design rule checking for reducing infeasible designs, costs and production cycle times. The inter-feature module is part of a Design Advisory and Feature Extraction system that aims at checking the CAD model for various design rules. These rules are incorporated here and implemented for SolidWorks 2000, which has a separate sheet metal modeling module. The implementation has been done in Visual Basic using the OLE Interface provided by SolidWorks API.

Committee: Dr. Sam Anand (Advisor) Subjects: Engineering, Industrial

Master of Science, The Ohio State University, 2011, Materials Science and Engineering

Impulse forming techniques are used to produce high strain rates to improve the formability of sheet metal. While these techniques are not commonly used in industry at the present time, research and testing has demonstrated enormous potential for new manufacturing processes incorporating these methods. The objective of this paper is to discuss the feasibility of the use of disposable actuators to eliminate springback in sheet metal components. Two impulse forming methods were investigated, electromagnetic forming and forming using an electrically driven expanding plasma, while three parts of increasing complexity were tested: a simple curved aluminum part, an aluminum aerospace part with a convex flange, and a high-strength steel structural u-channel part. The parts were pre-formed to a rough shape using traditional forming methods and then calibrated to the final desired shape using the impulse forming techniques. These processes work by transferring a large current through a thin aluminum actuator, generating a large controlled electromagnetic impulse in the case of electromagnetic forming or a high-pressure shockwave due to foil vaporization in the case of forming using electrically driven expanding plasma (fugitive foil forming). The test setup was optimized according to parameters such as actuator design, tool material, part stand-off distance, and capacitor discharge energy. In each case, the use of impulse forming methods resulted in significant springback reduction so that the parts were at or very near the desired specifications, demonstrating that these techniques can be used to improve current sheet metal production processes.

Committee: Glenn Daehn PhD (Advisor); Suresh Babu PhD (Committee Member) Subjects: Electromagnetics; Materials Science; Mechanical Engineering

Master of Science, The Ohio State University, 2010, Materials Science and Engineering

Traditional stamping technologies that sandwich sheet metal between a die and punch have several inherent limitations such as the use of heavy tools, localized deformation that damage the parts and inhibit consistency. High speed forming is a light weight tooling assembly that forms the part without using any punch. Electromagnetic forming (EMF) is one among the gamut of high speed forming technologies that is used for embossing fine surface features onto sheet metals. This work investigates the dynamics of sheet metal impact through a simulation study. The primary objective of this work is to develop a modelling facility that guides experimental design of flat ridged parts. Critical factors that influence the product quality are investigated. The high impact energy translates into an appreciable rebound that affects the product shape. Interface conditions play a critical role in influencing the shape of the final part. Contrary to intuition, friction is beneficial in high speed forming unlike traditional stamping where friction leads to tearing of sheet metal. Shape fidelity is investigated through a prototypical study of the expansion of a round tube into a square hole. Traditional modelling techniques solve a coupled system of equations with spatially varying electromagnetic fluxes controlling the dynamics of the plastic deformation. Because the magnetic pressure is spatially uniform, the flux equations are obviated from the coupled system rendering them computationally efficient. The calibration of contact mechanics that influence the rebound behaviour of the sheet metal remains as a difficult issue. The interfaces between various sheet metals and the metal die play a critical role in controlling the shape of the final product. The characterization of such an interface using appropriate calibrated friction coefficients is assessed. The role of magnetic pressure in reducing the sheet metal rebound is demonstrated via a comparison between results from mechanical (open full item for complete abstract)

Committee: Shekhar Daehn (Advisor); Suresh Babu (Committee Member) Subjects: Materials Science; Mechanical Engineering; Mechanics

Doctor of Philosophy, The Ohio State University, 2008, Industrial and Systems Engineering

This thesis presents initial attempts to simulate the sheet hydroforming process using Finite Element (FE) methods. Sheet hydroforming with punch (SHF-P) process offers great potential for low and medium volume production, especially for forming (a) lightweight materials such as Al- and Mg- alloys and (b) thin gage high strength steels (HSS). Sheet hydroforming has found limited applications and is thus still a relatively new forming process. Therefore, there is very little experience-based knowledge of process parameters (namely forming pressure, blank holder tonnage) and tool design in sheet hydroforming. For wide application of this technology, a design methodology to implement a robust SHF-P process needs to be developed. There is a need for a fundamental understanding of the influence of process and tool design variables on hydroformed part quality. This thesis addresses issues unique to sheet hydroforming technology, namely, (a) selection of forming (pot) pressure, (b) excessive sheet bulging and tearing at large forming pressures, and (c) methods to avoid leaking of pressurizing medium during forming. Through process simulation and collaborative efforts with an industrial sponsor, the influence of process and tool design variables on part quality in SHF-P of axisymmetric punch shapes (cylindrical and conical punch) is investigated.In stamping and sheet hydroforming, variation in incoming sheet coil properties is a common problem for stamping plants, especially with (a) newer light weight materials for automotive applications (aluminum-, magnesium- alloys) and (b) thin gage high strength steels. Even though incoming sheet coil may meet tensile test specifications, high scrap rate is often observed in production due to inconsistent material behavior. Thus, tensile test specifications may not be adequate to characterize sheet material behavior in production stamping/hydroforming operations. There is a strong need for a discriminating method for testing incoming (open full item for complete abstract)

Committee: Taylan Altan PhD (Advisor); Gary L. Kinzel PhD (Committee Member); Jerald R. Brevick PhD (Committee Member); Donald M. Terndrup PhD (Committee Member) Subjects: Automotive Materials; Industrial Engineering; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2006, Materials Science and Engineering

Sheet metal stamping is an important manufacturing process because of its high production rate and low cost. It is a fundamental technology in automotive, heavy vehicle and aerospace manufacture. A successful sheet metal stamping is to convert an initially flat metal sheet into a useful part with the desired shape. Stamping failures consist of either tearing (excessive tension) or wrinkling (excessive compression). A new technology, hybrid electromagnetically assisted sheet metal stamping, was developed to control the strain distribution in a stamping operation to avoid failures. By embedding electromagnetic coils in conventional forming tools, controlling of the strain distribution of parts is enabled. Different applications of this new technology to sheet metal stamping are presented. And to better understand and utilize the new technology, analytical analyses for some application are also presented. This work focuses on the practical applications of this new technology.

Committee: Glenn Daehn (Advisor) Subjects: Engineering, Mechanical

Master of Science, The Ohio State University, 1995, Mechanical Engineering

Committee: Gary Kinzel (Advisor) Subjects:

Master of Science (MS), Ohio University, 1990, Mechanical Engineering (Engineering)

Investigation of hydroforming sheet metal with varying blankholding loads

Committee: M. Dehghani (Advisor) Subjects: Engineering, Mechanical