Week Six

Testing New Materials

This week we finished the grid analyzing of the DP-980 samples.  We are now starting to work on studying the stretchability as a function of cutting clearance for two new types of high strength steel; HSLA-350 and BH-210.  Similar to how we previously prepared the dual-phase steel samples, the specimens of these metals had to be polished, etched, measured, painted, and finally tested using the tensile test apparatus.  As seen in the graph below, HSLA and BH steels have lower tensile strengths than the DP steels but have higher ductility.  It will be interesting to see how these properties affect the results obtained from this week's testing.

Week Five

Grid Analysis

This week we examined the strain on the fractured DP-980 samples with a Grid Analyzer. Seen in the image to the left, this instrument locates the grid squares on each sample and calculates the major and minor strains of that particular square. To properly analyze each specimen, we analyzed the grid squares near the area of fracture as well as outside the necking region. This allows for measurement of localized and global strain. Pictured below is the specimen with the etched grid.

Last Week

Fiat Chrysler Wind Tunnel Tour

                                            On Friday we were able to tour the FCA wind tunnel.  There, an aerospace engineer explained the details behind the design that allows for very accurate testing results. They test both full scale and 3/8th scale models.  In the early stages of design, the testing is performed with vehicles made of clay to allow easier adjustment of features on site.

Week Four

We have been working on testing the stretchability of our DP980 specimens. To do this we have to prepare the samples by:

• Polishing the scrap edge (helps ensure that the crack propagates from sheared edge) 
• Etching a 1mm grid 
• Measuring the width and thickness 
• Painting a black and white speckle on the non etched side  

Next we preform the stretchability test using a tensile testing machine equipped with DIC technology that is used to track the painted speckles.

Week Three

Chrysler Pacifica Vehicle Event

This week we went to an SAE vehicle event for the 2017 Chrysler Pacifica. Speakers spoke about the design and architecture of the minivan as well as how it compares to competitors' models and previous designs. We had the chance to see a few of these vehicles and test out some of the new features. The event also featured many of the suppliers that contributed to the production of the Pacifica. We really enjoyed attending this vehicle showcase and the closer look at the engineering behind this new product. 

Week Two

Burnished Area and Burr Depth

The image on the left shows us taking pictures using a microscope to measure the burnished area and burr depth of a specimen. We used a program called SPOT to capture an image from the microscope and draw 20 vertical lines which are measured in pixels. The first 10 lines (green) are from the top edge to the bottom of the burnished area, and the next 10 lines (red) are from the top edge to the bottom edge. We have been using this method during our first week to take measurements of the sheared edge of steel samples cut by a specific tool. These samples are organized by how many cuts a machine has made up to that point. The samples that we were testing were taken every 50,000 cuts made by the machine with the initial batch taken from zero cuts. Figuring out how to obtain the highest quality image took some patience since the glare from the burnished area would distort the image, but after                                                                                 some time we got the hang of it.   

Week One

Introduction 

Contributors:

Erika Rugh – Undergraduate senior at Sweet Briar College majoring in engineering

Collin Malek – Undergraduate senior at Oakland University majoring in mechanical engineering

Project Description:

This project aims to better implement high and ultra-high strength steels in the automotive industry which allows for an improved fuel economy. Specifically, this program addresses the problem of splitting from the sheared edge that occurs when tension is applied along the sheared surface.  Presented by Dr. Golovashchenko, the following are the goals of this assignment.

1. Study sheared surface parameters (burr height, burnished area - indentation of the tool before initiation of fracture, height of the brittle zone and rollover zone) for the range of cutting clearances by: a) observing the sheared surface under the microscope and b) preparing crosssections for several steels employed in automotive industry, such as Interstitial Free steel, Bake Hardenable steel, High Strength Low Alloy Steel and Dual Phase Steel DP980.
2. Understand the effects of tool wear during trimming process on sheared edge parameters by: a) comparing the burnished areas of trimmed samples selected after specified number of cuts and b) performing stretchability experiments of these selected samples.
3. Analyze the mechanism of fracture of sheared samples as a function of cutting clearance and cutting edge condition and locate initiation of fracture during stretching of sheared edge of sheet metal samples.
4. Compare sheared edge stretchability for sheared surfaces fabricated by piercing 10mm in diameter holes and trimmed along the straight line by measuring the strains along the perimeter of stretched sheared edge.