Aluminum WrapUp
Volume 6, Issue 2
May/June 2018
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Secat Welcomes Jim Hands!
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Jim Hands joined Secat as Sales Manager in March 2018. Jim has a Bachelor of Science in Business from Miami University and an MBA from Xavier University. Jim has worked with both metal producing and metal distribution companies in positions including outside sales, marketing, management and commercial leadership. Jim spent the early part of his career developing large volume carbon flat rolled business for Coilplus Ohio in southwest Ohio and Kentucky. More recently, Jim led the US commercial team of marketing managers and outside sales representatives for stainless and nickel bar producer Valbruna Stainless. We are happy to have Jim as part of the Secat team!
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Secat Gets Great Feedback!
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Secat recently conducted a customer feedback survey to assess the experience of working with Secat. The response was overwhelmingly positive with customers giving mostly excellent ratings, great comments about the usefulness of result, and positive responses to turnaround time. Many customers mentioned Secat employees by name and spoke about the strong working relationship between Secat and their companies. Good job, Secat Team!!
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You can learn more about us on Secat’s website
here.
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Tech Talk: Forming Limit Diagrams
Influence of Tooling and Measurement Method
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Forming limit diagrams are a convenient means of determining and visualizing formability strain limits over a wide range of forming conditions – spanning pure tension to biaxial stretching in one diagram as shown in figure 1. Many variations of determining forming limits are used based on specifications of the supplier or the laboratory doing the testing. These variations may lead to different forming limit curves for the same sheet which poses two major issues: 1 – comparisons between laboratories such as in round robin testing may lead to different results or 2 – a supplied sheet is near to a limit strain for an application and may be erroneously discarded
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utilized in a part because variations were not accounted in the analysis. The most common modifications in measuring forming limits are the tooling geometry and the method of measurement (ASTM vs ISO).
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Figure 1: Example FLD and Types of Strain Conditions (from ASTM E2218-2015)
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To determine the influence of tooling geometry and measurement methods on forming limit curves, Secat performed a systematic study utilizing a single lot of AA5xxx sheet. The lot was used to assess the forming limit curves using three tool geometries and two measurement methodologies. In total, the study documented the effects of 60 mm vs 100 mm hemispherical punches, the effect of a hemispherical punch vs a flat top punch, and the effect of a user interactive measurement approach with high friction conditions vs an automated measurement approach with near frictionless conditions
Effect of Tooling
The tooling used in the study were two different diameters (60 mm, 100 mm) of Nakajima hemispherical domes and a 100 mm diameter flat top cylindrical punch of the Marciniak design. Both die designs and tooling is shown in figure 2.
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Figure 2: Nakajima and Marciniak Tooling
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The main differences between using the Nakajima tooling and the Marciniak tooling is in the method of handling friction and the effect of die curvature on the strain path. The Nakajima setup required a complex lubrication system to achieve a near frictionless forming with the lubrication comprised of 5 layers – lanolin grease, PVC sheet, lanolin grease, Teflon film, lanolin grease. The Marciniak tooling uses a carrier blank with a center hole formed above the flat top of the punch to minimize frictional effects. The carrier blank allows the sheet under test to deform without any surface to surface friction in the area of highest strain because that location is suspended above the carrier blank hole. Although friction is not expected to change the overall forming limit curve, the effect of tool geometry (hemispherical vs flat) is expected to be substantial.
In a hemispherical tool, the curvature imposed on the sheet during forming does three things
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: (1) – creates a nonlinear strain path to the failure point, (2) – causes a curvature induced pressure effect through the sheet thickness, and (3) – superimposes a contact pressure in addition to the planar straining that is occurring. The Marciniak tool with the flat top design minimizes these effects. Figure 3 below shows a comparison of the Nakajima and Marcianak tooling results. The use of the Marciniak tooling is expected to move the plane strain point closer to the zero minor strain axis and shift to lower major strains. The results of the study show the first point to be true but further investigation is ongoing as to why the second point is not showing as expected.
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Figure 3: Comparison of Nakajima and Marciniak Tooling
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The use of smaller tool radius further elucidates the expected differences between the Nakajima tooling and Marciniak tooling by accentuating the curvature effects on a smaller tool. In figure 4 below, a comparison is shown between a 60 mm and 100 mm Nakajima tool. For the 60 mm tool, there is an expectation of higher nonlinearity, higher curvature pressure, and higher contact pressure – all leading to a shift towards higher strain limits which is what was observed. The reason for the higher strain limits is that the condition of necking requires all layers through thickness to have failed. When superimposing the contact pressure and curvature pressure (bending) on the region of necking, the point of failure is shifted towards a higher strain limit. In essence the compressive stress imposed delays the onset of necking from occurring which is not present in the Marciniak setup.
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Figure 4: Comparison of 60 mm and 100 mm Nakajima Tooling
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Effect of Measurement Method
The main differences observed when comparing the ASTM E2218-2015 method and the ISO 12004-2:2008 method is in the treatment of friction, necking, and level of user interpretation and interaction. For the ASTM method, a frictional condition is desirable which is in stark contrast to the ISO method. By having a level of friction, the position of failure is moved from the apex of the Nakajima dome to the sides of the dome and generally there are two failures as opposed to one. As already stated, the general understanding is that friction does not change the overall forming limit curve but only moves to higher and lower minor strain along the same curve. In the ISO method, the measurement principle is based on refitting an inverse parabola in the area of failure which requires there to be a single failure at the apex of the dome whereas in the ASTM method, the judgment of necking or failure is visual and both can be observed because there is generally two regions produced on opposite sides of the dome. In one region, there is normally a crack/failure and the opposite side would show a neck.
For the ASTM method, the test is stopped when necking is first observed, usually, whereas in the ISO method, the test is stopped only after failure. For ISO necking strain is established based on refitting an assumed parabola curves to the failure region based on the major and minor strain of fitting sections. Figure 5 below compares the two methodologies in more detail.
In figure 5, the ASTM method example is shown on the top and the ISO method example is shown at the bottom. The ASTM method requires reconstruction of the deformed grid and identifying each grid point as failed, marginal, or okay. The identification is a purely subjective rating based on the user and a fitting line is drawn through the marginal or upper level of okay points to establish the forming limit curve (FLC)
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Figure 5: Comparison of ASTM (top) and ISO (bottom) Neck Determination for FLC’s
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In the case of the ISO method, three section lines are drawn perpendicular to the crack. For each section line, the major-minor strains are extracted and used to fit a parabola like curve to the fracture region. The fracture itself is excluded and the areas adjacent to the fracture is used to fit the missing area. In figure 5 (bottom), an example section line is shown with the major (blue) and minor (red) strains plotted. The fitted parabolas are shown in green with the X’s showing the points used for fitting. The apex of each parabola is then used as the major-minor strain point assumed to be just before necking occurs. This method is easily adapted to automation and does not require subjective judgment in identifying failed, marginal, and okay points.
Figure 6 below shows the comparison of 60 mm and 100 mm Nakajima tooling with both ASTM and ISO methods of measurement. For the ASTM method, there is no difference observed for the two tool sizes. However, for the ISO method, the difference between the tool geometries are observed. Based on the previous discussion, there should be an expected difference which the ASTM method does not show. The two possible reasons for the discrepancy is the subjective nature of identification of points and line fitting for the ASTM method as well as the grid size used in the ASTM method has a lower resolution in comparison to the resolution of a stochastic grid.
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Figure 6: ASTM (left) and ISO (right) Methods Utilized on 60 mm and 100 mm Tooling
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Summary
The study shows the effect of tooling geometry and measurement method on forming limit diagrams. When defining a procedure for establishing a forming limit diagram or when using the data in a finite element simulation of a stamping, both the method of how it was assessed and the tooling used should be defined. Misleading results could occur between labs or for lot evaluation if the factors are not taken into account. Higher curvature and smaller punch sizes lead the forming limit curves towards higher strain limits which could offset the safety margin used in design and field failure. Use of a lower resolution and higher subjectivity method may not elucidate lot to lot differences or production inconsistencies that may be present.
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J. Min, et.al., “Compensation for process-dependent effects in the determination of localized necking limits”, Int. J. of Mech. Sciences, 117 (2016) pp 115-134
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Scott Goodrich
Quality and Metallurgy Director
Constellium Rolled Products
Ravenswood, WV
After receiving B.S. degrees in Nuclear Engineering and Metals & Metallurgical Engineering in 1977 and his M.S. in Metallurgical Engineering in 1978 from the University of Michigan, Scott Goodrich went on to a successful career in the industry. Scott worked for Kaiser Aluminum, Century Aluminum, Pechiney Rolled Products and Alcan prior to his current position at Constellium.
In his 40 year career, Scott has spent time in Mississippi, West Virginia and France. He holds three U.S. Patents in the brazing sheet field and is a ASQC certified Quality Engineer, a member of ASM International and a member of the Society of Mechanical Engineers.
We asked Scott about his current job.
Give us a quick overview of your job.
Laboratory – main tasks are chemical analysis of cast ingots, management of the Hot Line coolant systems and lot release testing for our coil and plate products. The Lab has 50 employees, working 24 x 7, and conducts over 700 tests per day including tensile tests, fracture toughness, formability tests, surface characterizations, corrosion and dye penetrant inspections. The Lab also manages the outside testing contracts for tests that are not currently done at Ravenswood such as fatigue tests, stress corrosion and R-Curve. And from time to time the Lab gets involved in solving punctual quality issues in the plant.
Quality Systems – The main task of this function is to ensure that Ravenswood’s quality management systems meets all of the requirements of our customers as well as of certain outside certifications such as NADCAP, AS9100, IATF16949, ABS, TUV and ISO. The Quality Systems function will also issue and track corrective actions or 8Ds as necessitated by the customer or QMS.
Customer Technical Support and Claims Administration – This groups responds to customers when they have trouble using our product, either because the product may not meet their specification or because something in the customer’s process is not in control. When there is a material defect this group also enters and administers the claim resolutions.
Industrialization of new products – This group is responsible for the industrialization of new products and / or processes. This could be the implementation of a new alloy or temper, a new process in order to meet a new specification or to qualify new equipment through a formal management of change procedure. The industrialization group is also responsible for maintaining the plant metallurgical recipes, machine limitations and product availabilities.
What are some things that happen for you in a typical work day?
The typical work day starts out with a morning routine meeting with the Laboratory staff to review the performance from the previous 12 hours and then to schedule the day in terms of what tests to be perform, the manpower, SPCs, maintenance, audits, etc. There are then a series of management meetings to communicate the status of the business in terms of safety, quality, delivery performance, inventory, etc. and then we discuss countermeasure for those unexpected things that happen that are barriers to making the monthly plan. There are technical update meetings where the status of major development projects are discussed, and recent customer issues that need to be resolved quickly. We are constantly reviewing and resetting priorities.
How does your job impact the markets you serve?
Our role is first to deliver a quality product to the market, on time, that consistently meets the customer’s needs. The markets such as aerospace, automotive, heavy truck, vacuum chamber and defense are constantly looking for new solutions and my team’s role is to execute the industrialization plan after the appropriate R&D has been completed. We are on the phone daily with customers, discussing the performance of existing products and their needs for future alloys.
How do you interact with Secat, Inc. and how does that relationship benefit you?
The Ravenswood site has enjoyed a very good relationship with Secat since the beginning of Secat. We are currently collaborating on how to solve various surface defects on our sheet products and characterizing the formability of our new automotive products using the expertise and specialized equipment of Secat. We have also used Secat as a full partner in the research and development of new alloys.
Tell us something about yourself (outside of the industry) that people may not know.
I am from Hannibal Missouri, Mark Twain’s home town. I have two grown children, Mary and Andrew who both live in West Virginia. I am a distance runner, a bicycler, like to read history; and play rock & roll and blues guitar.
#ScottLovesAluminum
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Featured Capabilities
Imaging Software Update
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Secat has recently updated their imaging software to the Omnimet version 10.
OmniMet 10 by Buehler delivers powerful image analysis possibilities combined with flexible database functionality. The software has intuitive user-friendly point-and-click measurement possibilities, pre-programmed analysis Scripts and or capabilities for running user programmable analysis Scripts. The database utilizes a multi-tiered approach to logically organize numerous users and image data with unprecedented ease.
Larger images can be easily stitched together using the Montage application. If the single view images are calibrated then the larger stitched image will also be calibrated and suitable for quantitative image analysis.
The images can be analyzed using interactive point-and-click measurement modules. And the data can be burned in directly onto the image. OmniMet™ includes measurements of length, radius, angle, parallel lines, curve (freehand), object counts along with area and perimeter.
Objects can be measured by applying a threshold within a specified region of interest: entire image, rectangle, or freehand ROI (region of interest). Results can be shown by area fraction, area position, number of objects, perimeter, compactness, length, feret diameter, center of gravity, inclusion, and exclusion of objects by size.
Grain sizes can be easily estimated according to ASTM E112 using linear and circular intercept techniques. The linear intercept method is recommended for uniform grain sizes and the circle intercept method is recommended for measurement of non-symmetrical grain sizes.
The software also has a variety of image filters, thresholding, and allows for measurements to be performed on the image with the click of a button. Statistics and results are shown and can be easily exported to Microsoft® Excel® or Microsoft Word®.
Popular applications and associated routines are shown below. Scripts measurements easily follow industry standards such as ASTM E112 Grain Size or ASTM E1245 Inclusion Rating.
- Manual Interactive Thickness Measurements: line lengths with statistics for length and thickness measurements.
- Grain Size: Automated grain size measurements in accordance with ASTM E112. Average grain size by intercept methods and grain size distributions using areas are delivered. Additional processing identifies ALA grain size and duplex populations in accordance to ASTM E930 and ASTM E1181 where appropriate. ISO 643 compliant.
- Coating Layer Thickness: measures coating, plating or layer thickness of cross-sectioned samples in compliance with ASTM B487.
- Particle Sizing: measures particles in a field of view providing statistics on quantity and size distribution. Suitable for non-agglomerated particulates, precipitates, and powders.
- Porosity Assessment: provides automated measurements of fine holes or pores in a material.
- Dendritic Spacing: delivers measurements of lengths between dendrite arms in cast aluminum alloys.
- Phase Area Percent: determines phase area and percentage area of multiple phases in accordance with ASTM 562
- Intercept Grain Size: automated grain size determination delivering average grain size per field using straight line and circular intercept methods in accordance with ASTM E112.
- Determine depth of total or partial decarburization according to the relative amount of free ferrite present according to ASTM E1077.
- Determine the degree of micro structural banding in conformance with ASTM E1268.
- Inclusion Rating can be determined in terms of area percentage, and average numbers.
Grain Size:
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Applications:
The Omnimet system allows Secat to do comprehensive metallurgical evaluations of length, shape, size, area, and other measures of microstructural and macro characteristics. This can be done on images taken on different types of equipment including Optical and Scanning Electron Microscopes. For a billet caster, the area of interest may be in grain size and uniformity, segregation depth, particle count and shape. For rolled products as well, similar features of grain size, particle count and percent transformed may be of interest with the additional necessity of measuring sheet thickness and or coating thickness. For those that use reduced pressure testing or need to measure gas porosity, the Omnimet system allows for a measure of the size distribution, area percentage, shape, number per area, and spacing of pores for a sample. Weld analysis can be done for heat affected zone, grain size, particle counts in the area in and around the welds.
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Future Aeronautical Engineer Visits Secat
Kiera Fehr is focused. The 7th grader attends EJ Hayes Middle School in Lexington where she takes all AP classes, plays the violin, and desires to be an aeronautical engineer. With inspiration from the move
Star Wars, Kiera set out at an early age to learn about NASA and find a way to attend Space Camp. Asking for financial gifts for birth, and the support of her parents, Kiera has been able to fund her attendance to Space Camp every year beginning in the 3rd grade. Her hope is to complete NASA’s Space Camp program through high school.
Kiera won first place overall champion last year in the 6th grade and followed up this year as the 7th grade overall champion at the FCPS District Science Fair. Next, at the Central Kentucky Regional Science and Engineering Fair, she was awarded first place in Engineering Mechanics for the second time. She was also awarded second place overall middle school champion. In addition, en selected twice for the Broadcom Masters National Science Fair, hosted by Eastern Kentucky University, which included her latest accomplishment of winning first place in the Engineering Mechanics Division. She also won second place overall “Best in Fair” for the middle school division.
Kiera’s winning science fair project tested two types of 3D printed infill patterns of wrenches for strength and flexibility to be used on the International Space Station. To accomplish this, she built a homemade air piston to measure the force exerted on the wrench before fracturing.
Kiera felt she needed more accurate test results and a graphical analysis of her fractured wrenches to win the state science fair, a goal she set as her New Year’s resolution. That is when Secat came into the picture. Secat allowed Kiera to tour the facility and observe two tensile test machines in action, including testing some of her 3D printed dog bone samples. Kiera was excited that the Secat staff took her project seriously and became empowered by the fact that her experimental design and results were reinforced at their lab. Kiera says her project was a success because she was greatly assisted by industry professionals who mentored her and generously gave of their time.
Keep your eyes open for Kiera Fehr who has a bright future and continues to reach for the stars!
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Aluminum Art
Ultra Thin Aluminum Creates Unique Sculpture/Space
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Minima | Maxima was commissioned for World Expo 2017, an event with a history of architectural and engineering innovations. MARC FORNES/THEVERYMAN created the structure from 6 mm aluminum, (If an egg were scaled up to the same height Minima | Maxima, it would be much thicker.) The structure was situated prominently on the grounds in Astana, Kazakhstan, where it will continue to live as a permanent structure.
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At 43 feet, this tallest-ever construction from material as thin as a coin challenges how we understand structure and space.
Do you have a piece of Aluminum Art you’d like to share? Contact us at
info@secat.net
#WeLoveAluminumArt
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Don’t Forget to Connect with Secat on Social Media!
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