Residual Stress Measurement and Control Applications of Micro-Indentation Testing in Advanced Manufacturing

Residual stress can initiate cracks, shorten service life, or cause deformation, but engineering practice does not always aim to eliminate it completely. The appropriate treatment depends on the type and location of the stress.

In fact, residual stress cannot be completely eliminated. In the vast majority of industrial scenarios, our goal is to significantly reduce harmful high-magnitude tensile stresses and homogenize the internal stress field of the entire component through processes such as heat treatment and vibratory stress relief, thereby bringing it within a controllable and acceptable range.

Evaluating the treatment requires reliable measurements of stress magnitude and distribution.

Micro-indentation testing provides one way to obtain these data.

I. Different Effects of Tensile and Compressive Stress

Residual tensile stress reduces fatigue strength and induces stress corrosion cracking; while residual compressive stress can effectively inhibit crack initiation and propagation, significantly improving the fatigue life and corrosion resistance of components.

Therefore, all engineering practices of residual stress management are essentially redistributing the stress field — reducing harmful high-magnitude tensile stresses, homogenizing the overall stress level, while in specific working conditions, actively introducing a controllable residual compressive stress field on the component surface through surface strengthening processes such as shot peening and roller burnishing, to offset the tensile stresses generated by external loads during service, thereby achieving performance enhancement.

However, in the vast majority of industrial scenarios, especially for large pressure equipment and welded components, the core means of stress management is heat treatment. Through post-weld heat treatment (PWHT), the peak residual stress of welded joints can be effectively reduced while the stress distribution is homogenized. This is a mainstream engineering method that has been verified by long-term industrial practice, with mature and reliable processes. Surface strengthening methods such as shot peening and roller burnishing are more commonly applied to components or specific surface conditions.

II. From Basic Compliance to Precise Stress Control

Ordinary manufacturing's understanding of residual stress often stays at the level of "it is a defect, to be eliminated as much as possible." The mindset of high-end manufacturing is completely different: treating residual stress as a controllable process parameter, pursuing controllability and homogenization of the stress field.

The three levels to judge a manufacturing enterprise's stress management capability are:

Level 1: Can it measure — can it accurately identify stress distribution and magnitude

Level 2: Can it eliminate — can it reduce harmful stress below the safety threshold

Level 3: Can it utilize — can it actively regulate the stress field to enhance product competitiveness

The first two levels are the threshold of "qualified," and the third level is the watershed of "excellent."

And "being able to measure" is the prerequisite for everything — without seeing the stress, one cannot judge whether to eliminate or utilize it, let alone verify the effectiveness of the process.

III. Measurement Features of the Micro-Indentation Tester

Residual-stress methods such as X-ray diffraction and the hole-drilling method have specific requirements for the test environment, operator, or component. Micro-indentation testing offers another option for field measurement.

Wuxi Zhanghua's Deep-Sensing Micro-Indentation Residual Stress Tester uses the Indentation Energy Difference Method to measure residual stress through indentations only a few micrometers in diameter. Its main features include:

1. Non-Destructive, Portable, On-Site Testing

The unit weighs only a few kilograms and can be taken to the worksite. It measures pressure vessels, pipelines, and large structures directly without sampling, which is useful for stress measurement and life assessment of in-service equipment.

2. Precise Micro-Area Measurement

Traditional methods can often only obtain macroscopic average stress and cannot distinguish micro-area stress distributions such as weld zones and heat-affected zones. The indentation size of the micro-indentation testing technology is extremely small, enabling precise positioning of weld zones, heat-affected zones, stress concentration zones, and other key micro-areas, providing micro-scale stress data for welding procedure qualification and failure analysis.

3. Aligned with International Standards

This technical method has been officially included in Appendix G of GB/T 30583-2026 "Code for Post-Weld Heat Treatment of Pressure Equipment," marking that the Indentation Energy Difference Method has been officially incorporated into the national pressure equipment standard system for evaluating the effectiveness of heat treatment processes in eliminating or reducing harmful residual stress. Meanwhile, the Micro-Indentation Tester won the Gold Medal at the 48th International Exhibition of Inventions of Geneva in 2023, representing high recognition by international authoritative judges of its practicality and technological advancement.

IV. Using Measurement Results for Process Control

Connecting stress measurement with stress regulation forms a complete stress management view:

· To be eliminated: High-magnitude tensile stress in the weld heat-affected zone, tensile residual stress on the machined surface — mainly achieved through post-weld heat treatment for effective reduction and homogenization

· To be utilized: Surface compressive stress introduced through shot peening and roller burnishing under specific working conditions (applicable to local surface strengthening scenarios)

Post-weld heat treatment is widely used to manage stress in large pressure equipment and welded components. Its effectiveness depends on parameters such as temperature, holding time, and heating and cooling rates. Micro-indentation measurements can compare stress before and after treatment to verify the process.

Quantitative residual-stress measurements give manufacturers a clearer basis for adjusting heat-treatment and surface-strengthening processes.

Wuxi Zhanghua Pharm & Chem Equipment Co., Ltd.

Deep-Sensing Micro-Indentation Residual Stress Tester

— Gold Medal Technology at the International Exhibition of Inventions of Geneva · Measurement Method Included in GB/T 30583-2026 National Standard

Contact us for technical documentation and on-site demonstration.

Contact: Manager Zhang

Tel: 13961802200 (same number on WeChat)

Email: zqz008@126.com

Website: www.jszhanghua.com