Table 1. STAGE 1 Tooling, Drawbead and Processing Parameters in Figures 2 and 3.

Table 1.1 Binder Gap and Drawbead Depth for the Standard Benchmark. The additional drawbead depths are used in the Extended Benchmark study as described in the footnote. The bead depths are nominally set at 25, 50, 75, and 100% penetration.

 STAGE 1. Springback and Blank Trimming for Stage 2.

Following Stage 1 forming, the side view of the sheet after springback has the nominal shape shown in Figure 5. Profiles of the sheet will be measured and the radius of curvature (R-curl) in the sidewall will be determined as shown in the figure.

Two trimmed blanks are cut from separate specimens of the Stage 1 channel draw test after springback in preparation for Stage 2 forming. The trim lines are at arc length distances DA and DB from the centerline of the Stage 1 process (), as shown in Figure 5 for Specimens A and B, respectively. Specimen A is cut from the side wall as illustrated in RED with the longer dimension (LA) out of the plane of the page in this figure. Point 1, located at one end of the RED line, forms one edge of the width of Specimen A at a arc length distance (DA) from the centerline. Point 2 is located at an arc length distance (DA+WA) from the centerline to form the opposite edge of the specimen width. The length of the blank (LA) is nominally 254 mm, but is in fact determined by the STAGE 1 forming process, which is not precisely in a plane-strain condition. Specimen B is cut from the sidewall as illustrated in BLUE in Figure 5 with the longer dimension (LB) along the arc length of the sidewall curl of the STAGE 1 forming process. Point 2 along the BLUE line is located at a distance (DB) from the centerline. Point 1 of this specimen is located at an arc length distance (DB+LB) from the centerline.

Since the metal near edge 2 is in the punch radius contact area, it has a much higher curvature than the majority of the specimen, which is also curved in the opposite direction. For practical reasons, the curvature of this edge is reduced to nearly a flat condition using a manual 3 ton Arbor press as illustrated in Figure 7 using wood tools to avoid marring the sheet surface. This procedure is necessary to ensure proper control of the blank location and bead setting during binder closure of Stage 2. The flattening process may be simulated as illustrated, but since all the metal that is affected in this process remains outside the drawbead/lockstep of the Stage 2 process, it is not considered to be necessary.

Since all the metal for Specimen A and all the metal that ends up inside the drawbead/lockstep after binder closure in Stage 2 is nearly uniformly prestrained from Stage 1, the precise location of trimming for both Specimen A and B is not considered to be critical to the Stage 2 forming process.

 Table 2. STAGE 1 to STAGE 2 trimming dimensions referenced in Figures 5 and 6.

 Table 3. Blank holding forces are the same for Specimens A and B.

Binder Travel:

 Table 4. Final Punch Depths for the Standard Benchmark in Stage 2 forming.

The punch depths listed in Table 4 are for the Standard Benchmark specification. As discussed in the footnote on page 4, tests will be done and reported at the conference using the additional bead depths listed in Table 4.1 Furthermore, flat, non-prestrained samples of all four metals in the as-received condition will be tested in Stage 2 forming with the longer dimension of Specimen A cut along the rolling direction of the sheet and Specimen B cut along the transverse direction. Each prestrained Stage 1 test and as-received condition is taken to a different punch depth in Stage 2 as listed in Table 4.1. The punch depths used for these different conditions are empirically selected to maximize the amount of plastic deformation during Stage 2 without exceeding the forming limits of the materials. The same washer material and material axis orientation is used for all tests.

 Table 4.1 Final Punch Depths for the Expanded Benchmark in Stage 2 forming. Only the 6.85 mm Stage 1 drawbead depth tests are to be reported to the Benchmark Analysis Committee.

The additional tests in Table 4.1 are not included in the Standard Benchmark due to the large amount of data, which would likely inhibit completion of all test conditions by the benchmark participants. Such a result would interfere with a meaningful comparison and reduce the value of the Standard Benchmark for the Numisheet Conference. However, experimental results for the Extended Benchmark may be of considerable interest from a theoretical and practical standpoint, and that is why they will also be reported at the conference.

Initial blank setup position: see Figures 12-16. The net result is that the blank is aligned with and lays flat against the washer at the end of binder closure and both are centered in the tooling.

 Table 5. STAGE 2 Parameters identified in Figures 10, 11 and 13.

Files for simulation

All geometry data is defined parametrically in the above description. The tooling for Stage 1 has a uniform section along the y-axis as defined in Figures 2 and 3. The tooling for Stage 2 is axisymmetric with a section through its axis of symmetry defined in Figures 10 and 11. No IGES surface geometry or NASTRAN mesh files are provided for this benchmark.

Material Property Files:

Standard properties are listed in the following worksheet and additional information is provided from auxiliary downloads in case participants want to use more sophisticated material models. Data for this benchmark are in the following 4 Excel spreadsheets.

                                   BM3_AKDQ.xls                                             BM3_DP600.xls        

                                   BM3_HSLA50.xls                                          BM3_AL6022-T43.xls

BENCHMARK REPORT

The due date for benchmark submission is listed on the website. All results are to be reported using the benchmark report template that is included in the download (BM1_Report_TMP.xls). Instructions for participating in the benchmark are provided in the file General_Benchmark_Instructions.pdf.  A total of 20 distributions and 44 data values are required for completion of Benchmark 3. Note that results for each of the four materials are to be reported in a separate worksheet within the same spreadsheet, each containing 5 distributions and 11 data values. The following information is requested for each material on the appropriate worksheet:

1. Load1 (displacement). Distribution of punch load vs. punch displacement (100 points or less) during Stage 1 Forming. Distributions: 1.

2. Rcurl. Sidewall curl (Rcurl in Figure 5) after Stage 1 springback. Data values: 1.

3. Epsilon1 and Epsilon2. Major and minor strain components at Point 3 in Figure 6 after Stage 1 springback and blank trimming on the convex (Stage 1 punch) side. Strains must be dimensionless, not in units of percent. Data values: 2.

4. SigmaXX (thickness) and SigmaYY (thickness). Distribution of major and minor residual stress components through the sheet thickness at Point 3 in Figure 6 after Stage 1 springback and blank trimming. Distributions: 2.

5. Load2A (displacement). Distribution of punch load vs. punch displacement (100 points or less) during Stage 2 Forming for Test Specimen A. Distributions: 1.

6. SigmaXXA and SigmaYYA. In-situ stress components on the upper surface at Point 4 in Figure 14 at maximum punch depth at the end of Stage 2 Forming (Table 4) for Specimen A. Data values: 2.

7. EpsilonXXA and EpsilonYYA. Net major and minor strain components on the upper surface at Point 4 in Figure 14 after Stage 2 unloading for Specimen A. Strains must be dimensionless, not in units of percent. Data values: 2.

8. Load2B (time), SigmaXXB, SigmaYYB, Epsilon1B and Epsilon2B. Repeat items 5-7 for Test Specimen B. Distributions: 1. Data values: 4.

It is critical to update the number of points used in each of the distributions in ROW 10 of the appropriate columns and worksheets.