Lesson #5 Sheet Metal Processes PDF

EG 4391 A Manufacturing Processes Fall 2024 Lesson # 5 - Sheet Metal Processes Chapter 7 Sheet Metal Processes Copyright © 2017, 2008 Pearson Education, Inc. All Rights Reserved  Lesson # 5- Sheet Metal Processes...

EG 4391 A Manufacturing Processes Fall 2024 Lesson # 5 - Sheet Metal Processes Chapter 7 Sheet Metal Processes Copyright © 2017, 2008 Pearson Education, Inc. All Rights Reserved  Lesson # 5- Sheet Metal Processes Sheet Metal Forming: Beverage cans, kitchen utensils, metal furniture Synonyms: pressworking, press forming, stamping Started as early as 5000 B.C. Image Courtesy: https://www.britannica.com/topic/metalwork/American-Indian-peoples Lesson # 5- Sheet Metal Processes Lesson # 5- Sheet Metal Processes  Lesson # 5- Sheet Metal Processes Sheet Metal; Charcteristics (Stretching, necking, and failure) Uniform to non-uniform elongation True Stress Strain Curve Where sigma is normal stress, K is the strength coefficient, epsilon is true strain, and n is the strain-hardening exponent Necking begins at instability (where material follows the true stress strain curve)  Lesson # 5- Sheet Metal Processes Sheet Metal; Characteristics (Stretching, necking, and failure) Isotropic vs. Anistropic Mohr's Circle:  Lesson # 5- Sheet Metal Processes Sheet Metal; Characteristics (Stretching, necking, and failure) Mohr's Circle For Isotropic materials 2 phi = 110 degrees. This doesn't hold true for anistropic materials  Lesson # 5- Sheet Metal Processes Sheet Metal; Characteristics (Stretching, necking, and failure) Strain-rate sensitivity determines localized or diffuse necking Where sigma is normal stress epsilon (dot) is true strain rate, and m is strain rate sensitivity Higher m values mean more diffuse necking  Lesson # 5- Sheet Metal Processes Sheet Metal; Characteristics (Stretching, necking, and failure) Low carbon steel may exhibit Lüders bands (stretcher strain marks) (Not seen in Aluminum alloys due to their lack fo yield point elongation) Anistropy (preferred grain orientation) vs. Mechanical fibering (alignment of impurities) Grain Size (ASTM grain size no. 7 or finer preferred fro general sheet metal forming operations) Residual Streses, Stress-corrosion cracking Springback  Lesson # 5- Sheet Metal Processes Sheet Metal; Characteristics (Stretching, necking, and failure) Wrinkling Coated Sheet  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Image Courtesy: Image Courtesy: https://vanderzielmachinery.com/wp-content/uploads/2019/09/Cincinnati-12- https://benoitsheetmetal.com/wp-content/uploads/2024/03/202 Hydraulic-Shear-b-scaled.jpg 209_103449-1030x1030.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Punches , and dies Image Courtesy: https://vanderzielmachinery.com/wp-content/uploads/2019/09/Cincinnati-12- Hydraulic-Shear-b-scaled.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Punches , and dies (C values typically 2-8% of sheet thickness, 1% in fine blanking)  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Punches and dies  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Punches and dies  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Punches and dies  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Punches and dies  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Punches and dies Punch Force Where: Fmax is maximum punch force S_ut is the ultimate tensile strenght t is the thickness L is the total length of the sheared edge  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Die Cutting  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Fine blanking  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Slitting  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Steel rules Image Courtesy: https://www.bohlerstrip.com/img/va-8-897-127_764.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Nibbling Image Courtesy: https://motionconstrained.com/wp-content/uploads/2020/07/BCT1.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Scrap in shearing operations reduced by: -Proper arrangement of the shapes on the sheet to be cut (layout and nesting) -Appropriate starting material size selection  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Shearing Dies (shaving)  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Shearing Dies Punch and die shapes  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Compound dies Image Courtesy: https://www.northernindmfg.com/wp-content/uploads/2021/10/s-compound-tooling- 1.png  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Progressive dies  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Transfer die Image Courtesy: https://upload.wikimedia.org/wikipedia/en/9/92/Sequence_of_dies_in_a_transfer_press%2C_Draw %2C_trim%2C_flange%2C_KamConsultant.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Shearing Tool and die materials -Tool Steel -Carbides (High production rates) Lubrication key to wear reduction and edge quality  Lesson # 5- Sheet Metal Processes Sheet Metal; Steel Cutting Band Saws Image Courtesy: https://cdn2.grizzly.com/pics/jpeg1000/g/g0926- e78b19f36fd9e0b5515958b4e941cb76.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Steel Cutting Oxyfuel-gas cutting (typical for plate) Image Courtesy: https://meritusgas.com/wp-content/uploads/2023/09/cutting-torch-safety-1024x576- 1.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Steel Cutting Plasma Cutting Image Courtesy: https://weld-ready.com/cdn/shop/files/Crossfire-Invercut-105HD- Cutting_941x630.jpg?v=1682605784  Lesson # 5- Sheet Metal Processes Sheet Metal; Steel Cutting Friction sawing Image Courtesy: https://ronixtools.com/img/media/products/5901/modeling- Image Courtesy: https://encrypted-tbn0.gstatic.com/images? 638029189701018606.webp q=tbn:ANd9GcTF6rymXeZBUVR80mqdG4Ayk2sKCLVjywvYcw&s  Lesson # 5- Sheet Metal Processes Sheet Metal; Steel Cutting Water-jet cutting/Abrasive water jet cutting Image Courtesy: https://swaterjet.com/wp-content/uploads/2020/12/waterjet4.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Steel Cutting Laser-beam cutting Image Courtesy: https://esab.com/sites/nam_en/cache/file/72AFC016-6D96-4CD4-85A218CE7CEFFC42.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Tailor-Welded Blanks Two pieces of sheet metal of differing thicknesses and shapes laser butt welded together, then formed to its final shape  Lesson # 5- Sheet Metal Processes Sheet Metal; Tailor-Welded Blanks  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Bend Allowance Where L_b is bend allowance Alpha is the bend angle R is the bend radius Kappa is the constant (0.33 for R < 2t, 0.5 for R > 2t) t is the sheet thickness  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Bend Allowance  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius Strains at the fibers Where e_i is engineering strain  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius: Where cracks first begin to appear on the outer surface of the bend - True Strain at fracture Where e_f is engineering strain at fracture A_o is original cross-sectional area A_f is final cross-sectional area r is the reduction in area  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius:  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius: -Note as R/t approaches zero (complete bendability) at a tensile reduction of area 50%  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius: Sample Problem Calculate the minimum tensile true fracture strain that a sheet metal should have in order to be bent to the following R/t ratios: (a) 0.25, (b) 1, and (c) 2.  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius: Factors affecting bendability Bendability may be increased by increasing its tensile reduction of area (e.g. using heating, hydrostatic pressure) As bend length (L) increases up to 10t stress in the sheet outer fibers goes from uni to biaxial (with a decreasing R/t ration narrow sheets crack at the edges and wider sheets at the center) Surface roughness (stress risers) Cold working undergone during shearing Inclusions (in the form of stringers)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius: Factors affecting bendability - length of bend and edge condition for 7075-T aluminum sheet  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius: Factors affecting bendability Surface roughness (stress risers) Cold working undergone during shearing Inclusions (in the form of stringers)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Minimum Bend Radius:  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Springback - the elastic recovery following plastic deformation  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Springback factor (Ks) Where: K_s is springback factor Alphaf is final bend angle Alphai is initial bend angle Ri is the initial bend radius Rf is the final bend radius  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Estimated Springback - When Ks = 1 - no springback Ks = 0 – complete elastic recovery Where R is the initial bend radius i R is the final bend radius f Sy is yield strength E is the elastic modulus t is the thickness  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Springback - Negative springback  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Compensation for springback Overbending Coining – fig b, uses localized compressive stress between the punch and die Stretch bending – subjects the part to tension Bending at elevated temperatures  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Compensation for springback Overbending  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Bending force (Simple bending of a rectangular beam) Where: F_max is maximum bending force k is constant that includes various factors and ranges for different dies S_ut is the ultimate tensile strength L is length t is thickness  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Press-brake forming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Press-brake forming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Other bending operations Air/Free bending 4-slide machine Roll Bending  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Other bending operations Air/Free bending 4-slide machine Roll Bending  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Beading: Edge of the sheet bent into the cavity of a die  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Flanging  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Dimpling (hole punched then expanded to the shape of a flange)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Hemming (flattening), Seaming Image Courtesy: https://www.dsource.in/sites/default/files/course/sheet-metal/sheet-metal-joinery/hemming-and-seaming/images/ 67_joinery_hemming_seaming.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Common Bending Operations Roll forming (contour roll forming, cold roll forming)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Tube bending  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Tube bending (sharp bends)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Stretch forming (blanks stretched lengthwise)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Bulging  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Embossing Image Courtesy: https://media-upload-craft.s3.amazonaws.com/wp-content/uploads/2022/07/18124340/IMG_0121-scaled.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Embossing Image Courtesy: https://media-upload-craft.s3.amazonaws.com/wp-content/uploads/2022/07/18124340/IMG_0121-scaled.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Rubber-pad forming and hydroforming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Rubber-pad forming and hydroforming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Tube hydroforming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Spinning (axisymmetric parts formed over a rotating mandrel) Conventional spinning:  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Spinning (axisymmetric parts formed over a rotating mandrel) Conventional spinning:  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Spinning (axisymmetric parts formed over a rotating mandrel) Conventional spinning:  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Spinning (axisymmetric parts formed over a rotating mandrel) Shear Spinning (power spinning, flow turning, hydrospinning, spin forging): Part diameter remains constant during forming Images Courtesy: https://www.metalformingmagazine.com/article/?/other-processes/spinning/metal-spinning-technology https://autoformcc.co.za/wp-content/uploads/2020/02/shearformpagetop.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Spinning (axisymmetric parts formed over a rotating mandrel) Tube spinnning  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Spinning (axisymmetric parts formed over a rotating mandrel) Incremental forming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Spinning (axisymmetric parts formed over a rotating mandrel) Incremental forming Images Courtesy: https://www.ammarkalo.com/Research-Projects/filter/digital-fabrication/Incremental-Sheet-Metal-Forming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate High Energy Rate Forming Explosive forming  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate High Energy Rate Forming Explosive forming Where: p is peak pressure K is a constant that depens on the type of explosive (51.3 for TNT) W is the mass of the explosive R is the distance of the explosive form the workpiece in meters a is a constant, generally taken as 1.15  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate High Energy Rate Forming Electrohydraulic forming (underwater-spark or electric-discharge forming) Similar to explosive forming A spark from two electrodes connected to a bank of charged condensers used to generate a shock wave  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate High Energy Rate Forming Magnetic pulse forming Energy stored in a capacitor bank is discharged rapidly through a magnetic coil The transient magnetic field generates eddy currents in the tube, these two magnetic fields oppose eachother and collapse over the plug (b)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate High Energy Rate Forming Superplastic forming Superplastic behavior – some very fine grained alloys (< 10 to 15 micrometers) can have elongations up to 2000% at certain temps and low strain rates. E.G. Zn-Al, Ti Complex shapes can be made through traditional metalworking or polymer-processing techniques (e.g. thermoforming, vacuum forming, and blow molding)  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate High Energy Rate Forming Superplastic forming Advantages: Complex, fine detail parts, with close tolerances and no need for secondary operations can be made. Weight and material savings, little to no residual stress, and lower strength tooling. Disadvantages: Material must not be superplastic at service temps, low rate of forming due to strain-rate sensivity, long forming times in some cases  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate High Energy Rate Forming Superplastic forming Images Courtesy: https://www.shapesbyhydro.com/en/manufacturing/how-you-can-lightweight-cars-with-superplastic-forming/  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Misc. Forming Operations Peen forming: Used on thin sheet metals. Images Courtesy: https://ars.els-cdn.com/content/image/3-s2.0- B9780128035818091979-f09197-02-9780128035818.jpghttps://ars.els-cdn.com/ content/image/3-s2.0-B9780128035818091979-f09197-02-9780128035818.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Misc. Forming Operations Thermal forming: localized heating used to induce thermal-stress gradients through the sheet thickness. Usually by way of a laser or plasma torch. Creep Age Forming (CAF) (age forming): Combines artificial aging and forming of aluminum (2024-T351, and 2022-T8) sheets. Used on top wing-skin panels of commercial aircraft. Microforming: (covered in Chapter 13) the production of small metallic parts and components (submilillimeter range) Straightening: the straightening of produced sheet, plate, tube through various methods. E.g. shot peening.  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Misc. Forming Operations Manufacturing honeycomb structures: Expansion process: Corrugation process:  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Misc. Forming Operations Manufacturing honeycomb structures: Expansion process: Corrugation process:  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Hot Stamping: Used on high-strength steels in the automotive industry for weight reduction Material is heated up to the austnization temp and allowed to soak so that it will be quenched when it contacts the die Cooling avoided by transferring the blank to forming dies quickly Part then quenched with the dies closed  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Hot Stamping: Images Courtesy: https://ars.els-cdn.com/content/image/1-s2.0-S2588840423000690-gr3.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Electrically Assisted Forming (EAF) High current used to increase the formability of materials Images Courtesy: https://ars.els-cdn.com/content/image/1-s2.0-S2588840423000690-gr3.jpg  Lesson # 5- Sheet Metal Processes Sheet Metal; Bending of sheet and plate Deep Drawing: Flat sheet metal blank formed into cylindrical or box shaped parts by way of a punch and die