Hardness Test on Cylindrical Shaft

 In the evaluation of a cylindrical shaft's material properties, a hardness test serves as a crucial investigative tool. By subjecting the material to indentation, commonly performed using methods such as Rockwell, Brinell, or Vickers hardness tests, engineers gain valuable insights into both the surface and internal characteristics of the shaft. This process involves applying a specific force to an indenter and measuring the resulting indentation size. The hardness value obtained is indicative of the material's resistance to plastic deformation, providing essential information about its mechanical strength. For a cylindrical shaft, this examination aids in comprehending not only the surface hardness, critical for wear resistance, but also the internal hardness, offering insights into the material's overall structural integrity and performance under various mechanical stresses. Through the analysis of hardness data, engineers can make informed decisions regarding material selection, heat treatment processes, and overall design considerations, contributing to the optimal performance and durability of the cylindrical shaft in diverse applications. In this experiment, we will use the Rockwell B indentation test on a cylindrical shaft to determine its properties.

Experiment Introduction

This experiment is designed to examine the physical properties of a cylindrical metal shaft. The process involves precision cutting of the shaft, followed by meticulous surface sanding and the implementation of four distinct hardness tests using the Rockwell B Method . Three of these tests are conducted on the surface at various positions, from the edge to the center, enabling a comprehensive analysis of the physical attributes across the shaft's cross-section. The fourth test, performed on the side of the shaft, scrutinizes its surface properties. The findings of these tests reveal the presence of a case-hardened shaft, and an approximation of the heat treatment depth is obtained. This investigation contributes crucial insights into the mechanical properties of the metal, offering valuable information for decision-making in engineering applications.

Analyzing the hardness test results, it is evident that the highest hardness is concentrated at the very edge of the sample. This characteristic can be attributed to the shaft undergoing a case-hardening treatment, with the material exhibiting a softer composition at the center to enhance toughness and a harder composition at the edges for increased durability. Scrutinizing the hardness scales, it becomes apparent that the material aligns with a softer type of steel. Analyzing the two different scales separately, the Rockwell B scale suggests that the material is easily machinable, while the Rockwell C scale indicates its proximity to nitrided steels. A rough estimate places the case treatment depth of the shaft between [4.3-6.3], signifying an approximate 2 mm hardening depth.

Hardness - Rockwell B indentations

Relating hardness to radius, we observe that the areas around the outer and inner circles correspond to where we expect the hardening to be at its highest