ASTM B820 - Bend Test for Determining the Formability of Copper and Copper Alloy Strip
Standard Test Method for Bend Test: Evaluating Formability of Copper and Copper Alloy Strip
Introduction
Copper and copper alloy strips are widely used in various industries, from electronics to automotive applications. One crucial aspect of these materials is their ability to be formed into specific shapes without cracking. The bend test is a fundamental evaluation method used to assess the formability and resistance to cracking of copper and copper alloy strips when subjected to bending processes. This article outlines the test procedure and its significance in quality control, research, development, and manufacturing.
Significance and Use
The bend test serves several important purposes:
1. Assessing Formability and Crack Resistance
The primary significance of the bend test is to provide essential information about the formability of copper and copper alloy strips. Formability refers to the material's capacity to undergo plastic deformation without cracking or failure. By subjecting the strip to bending forces, this test determines whether the material can be shaped without developing cracks.
2. Quality Control Tool
As a quality control tool, the bend test helps manufacturers ensure that the materials they use will form to a given radius without issues. This is crucial for maintaining consistent product quality and avoiding defects that may arise during forming processes.
3. Research and Development
In research and development, the bend test provides valuable data for selecting suitable spring materials. By understanding the strip's behavior during bending, engineers can choose materials that will safely and effectively form to the required geometry of a specific part.
4. Application in Design and Manufacturing
The results obtained from the bend test are directly applicable in design and manufacturing processes. However, for the results to be reliable, it is crucial to consider other factors such as part geometry, punch and die design, lubrication, stamping speed, and additional material properties.
Test Procedure
1. Scope
The bend test method described here focuses on evaluating the formability of copper and copper alloy strips by subjecting them to bending forces. The criterion for failure in this test is the appearance of cracks on the outer (convex) radius of curvature.
2. Sample Preparation
Prepare samples of copper and copper alloy strips with a thickness ranging from 0.003 to 0.031 inches (0.076 to 0.79 mm). The size and shape of the sample should comply with industry standards and agreed upon specifications.
3. Determining the Bend Radius
The forming or punch radius for the bend test should be determined through mutual agreement between the strip's producer and the customer. The chosen radius will depend on the intended application and the strip's properties.
4. Test Apparatus
Use a suitable testing machine equipped with appropriate bending tools. The machine should be capable of applying controlled bending forces to the strip.
5. Conducting the Bend Test
Place the prepared sample on the bending apparatus, ensuring it aligns with the bending tools.
Gradually apply bending forces to the strip until it reaches the agreed-upon bend radius.
Observe the strip's behavior during bending, paying close attention to any signs of cracking or failure.
If cracks appear on the outer radius of curvature, the strip has failed the test, indicating poor formability.
6. Reporting the Results
Record the observations and outcomes of the bend test. Document any cracks or failures that occurred during the test. These results will provide valuable insights into the material's formability and its ability to withstand bending processes.
Conclusion
The bend test for evaluating the formability of copper and copper alloy strips is a vital tool in ensuring product quality, research and development, and successful manufacturing. By understanding how these materials respond to bending forces, manufacturers and engineers can select appropriate materials and optimize forming processes to achieve desired shapes without compromising product integrity. Conducting this test with adherence to the specified procedure and considering other relevant factors will yield reliable results for material selection and process optimization.