Abstract

Hardness is a powerful property to evaluate the deformation behavior of materials. It serves as confident quality control for several processes, especially in the heat treatment of metals. With the advent of depth-sensing indentation, this technique embraces the determination of other mechanical properties. As proof, recognized standards are available to guide the evaluation of Young’s modulus using instrumented indentation. However, there are continuous efforts to describe the strength using hardness apparatus. This critical review aims to compile all ways of correlation between hardness and uniaxial strength. This relationship is usually addressed by a single value, called constraint factor, vastly recognized in metals as approximately 3. From a theoretical point of view, this value works well for materials with rigid-plastic behavior, where hardening effects can be discharged. Divergent variations presented herein show difficulties in incorporating the effect of plastic properties on the constraint factor determination. In the same way, the empirical determinations did not consider the differences in hardening exponents, putting in the same statistical analysis diverse microstructures. A specific section discusses the constraint factor for nonmetallic materials. There are critical doubts for determining strength from hardness values in this case. The existence of several approaches to estimate the constraint factor in brittle materials did not assure yet a unique value for the same material, which put in evidence the lack of a robust physical basis to understand the plastic deformation under indentation. Future trends are indicated along with these observations to become practical the recent developments that have allied hardness and strength. The most important aspect is to combine adequately the experimental and simulation approaches, which can be supported by an analysis of residual imprints of hardness and finite element model.

摘要

硬度是评估材料变形行为的重要属性。它可以为多种工艺提供可靠的质量控制，特别是在金属的热处理中。随着深度传感压痕的出现，该技术涵盖了其他机械性能的测定。作为证据，公认的标准可用于指导使用仪器压痕评估杨氏模量。然而，人们不断努力使用硬度设备来描述强度。这篇批判性评论的目的是汇编硬度和单轴强度之间的所有相关性。这种关系通常通过一个值来解决，称为约束因子，在金属中广泛认为约为 3。从理论角度来看，该值适用于具有硬塑性行为的材料，可以释放硬化效果的地方。本文提出的不同变化显示了将塑性特性的影响纳入约束因子确定中的困难。同样，经验测定也没有考虑硬化指数的差异，而是对不同的微观结构进行相同的统计分析。一个特定的部分讨论了非金属材料的约束因素。在这种情况下，根据硬度值确定强度存在严重疑问。存在多种估计脆性材料约束因素的方法并不能保证同一材料的唯一值，这表明缺乏坚实的物理基础来理解压痕下的塑性变形。这些观察结果表明了未来的趋势，使具有硬度和强度的最新发展变得实用。最重要的方面是充分结合实验和模拟方法，这可以通过硬度残留印记分析和有限元模型来支持。