Residual Stress Detection Research Articles

Detection of residual stresses with impedance spectroscopy: A novel approach

Detection of residual stresses with impedance spectroscopy: A novel approach

Non-Destructive Hardness Indentation Measurement of Residual Stress on Large Aerospace Forged Components at the Engineering Site Based on Impact Hardness Tester.

Large forgings are crucial in aerospace applications; however, the residual stresses generated during their forming and heat treatment seriously affect their serviceability. Therefore, the non-destructive detection of residual stresses in large forgings is of far-reaching significance for ensuring the quality of forgings and realising precision machining. Although a variety of detection methods are available, there is still a lack of a programme that can comprehensively, accurately and non-destructively measure the residual stresses in large forgings. This study is dedicated to exploring the application of the bouncing impact indentation method in the non-destructive testing of residual stresses in large forgings. Through in-depth finite element simulations and orthogonal scheme analyses, we found that the elastic modulus, yield strength and work hardening indexes have significant effects on the impact indentation process. Further, we establish the dimensionless function of residual stress and indentation parameters, and successfully obtain the inversion algorithm of residual stress. The relative error of the calculated values of the indentation curves hm and hr in the simulation with reference values is not more than 3%, and the relative error of the corrected Pm inversion values for most virtual materials is not more than 5%. The folding elastic modulus and apparent elastic modulus obtained by inversion are controlled within 10%, which demonstrates a high value for engineering applications. In addition, we innovatively express the research results in the form of 3D stress diagrams, realising the digital expression of 3D residual stresses in large forgings based on feature point measurements and contour surface configurations, which provides intuitive and comprehensive data support for engineering practice.

Electromagnetic Acoustic Transducer and Method for Residual Stress Detection in Conducting Materials

Electromagnetic Acoustic Transducer and Method for Residual Stress Detection in Conducting Materials

Simulation and experiment of complex residual stress detection of metal plate based on critical refracted longitudinal wave (LCR) method

This study is based on the principles of acoustoelasticity, analyzing the variation in sound wave time-of-flight(TOF) under different conditions using the critical refracted longitudinal(LCR) wave method. A simulation model was developed using the COMSOL finite element simulation software to mimic the propagation of LCR wave in a stress-free plate. The model was then subjected to uniaxial loading, and the change in wave TOF was observed by varying the angle between the stress direction and the sound wave propagation direction under constant load. The results were compared with theoretical calculations, showing a high degree of agreement, validating the accuracy of the designed model. Subsequently, during the tensile testing, the influence of different uniaxial loads and angle variations on the TOF of LCR wave was observed. Upon comparing the experiment data with theoretical calculations, a high degree of consistency in the trend of variation is observed, this demonstrates that the detection platform established in this study is feasible for the assessment of residual stresses in practice.

Ultrasonic Non-Destructive Detection Method for Residual Stress in Rotary Forging Aluminum Alloy Plates.

Aluminum alloy plates are widely used to manufacture large-scale integral structure parts in the field of aerospace. During the forming and processing of aluminum alloy plates, different degrees of residual stress are inevitably produced. Fast and accurate detection of residual stress is very essential to ensuring the quality of these plates. In this work, the longitudinal critically refracted (LCR) wave detection method based on a one-transmitter and double-receiver (OTDR) transducer and the finite element simulation were employed to obtain the residual stress. Aluminum alloy plates with different deformation amounts were fabricated by rotary forging to obtain different residual stress states. Results reveal that the plate formed by rotary forging is in a stress state of central tension and edge compression. As the deformation increases from 20% to 60%, the peak residual tensile stress increases from 156 MPa to 262 MPa, and there is no significant difference in the peak compressive stress. When the deformation reaches 60%, the difference in the residual stresses at different depths is less than 13%, which indicates that the plastic deformation zone basically penetrates the entire longitudinal cross-section of the plate. The maximum deviation between measurement and FE is 61 MPa, which means the experimental data are in good agreement with the FE results.

Effect of laser shock peening on wear resistance of M50 steel

The effects of laser shock peening (LSP) on the surface state and wear resistance of M50 steel are studied by microstructure observation, hardness, and residual stress detection. Results show that after LSP, the carbides on the surface of steel are broken and micro-pits appear. After removing the surface carbide damage by electrolytic polishing, the number of sub-surface carbides increases, and the maximum content is 26.1%. After LSP, the wear resistance of the steel is improved because LSP causes a large residual compressive stress on the surface. The wear performance of the sample after removing the surface damage becomes better, which is related to the elimination of many crack sources and the larger residual compressive stress.

Near surface residual stress detection of metallic materials using the high order ultrasonic nonlinear coefficient

Because residual stress seriously affects the mechanical properties of metallic components, in the study the nonlinear property of LCR wave is studied and the near surface residual stress within a certain depth beneath the component surface is nondestructively detected for the safe service of metal components. The stress detection system based on LCR wave is constructed using the oblique incident method with one-in-one-out mode. The high order relative nonlinear coefficients, β′ and δ′, during 45 steel tensile process are measured to investigate the correlation between nonlinear property of ultrasonic and stress. Two pairs of relative nonlinear coefficients monotonically increase and the stress sensitivity of δ′ is better than β′. In order to eliminate the sensitivity difference, the comprehensive nonlinear parameter is proposed. Three stress detection models based on experimental data are established and the error of residual stress evaluation are all below 4%, this indicates the nonlinear characteristics of LCR wave can be used to detect the stress level within a certain depth beneath the component surface. So the high-order ultrasonic nonlinear coefficients of LCR wave provides an effective method of rapid non-destructive detection the near surface residual stress of metallic material.

Surface residual stress detection method for aero-engine blades based on active thermal deformation excitation

ABSTRACT Surface residual stress is made on the aero-engine blades by shot peening to improve the fatigue life of the blades. As the service time increases, the surface residual stress is decreasing due to thermomechanical relaxation and the centrifugal load caused by high-speed rotation. Therefore, the surface residual stress detection is of great importance for predicting the remaining life of aero-engine blades. Up to now, efficient and non-contact detection of surface residual stress is still a challenge. In this paper, an active thermal deformation excitation (ATDE) method for surface residual stress is proposed. According to the thermal deformation theory, the thermal deformation of the material is positively correlated with the surface residual stress, and by measuring the thermal deformation the surface residual stress can be detected and evaluated. The theoretical deformation model was established, and simulation models with different surface residual stresses were constructed. A detection system was proposed to detect the blade deformation with different surface residual stresses. Results show that there was a linear relationship between the blade deformation and the surface residual stress from −636 Mpa to −1403 Mpa.

Online detection of residual stress near the gate using cavity pressure for injection molding

Abstract Residual stress negatively affects the quality of optical products and is a difficult problem to solve. Regulating process parameters is a critical element in quality control. Therefore, the online monitoring of critical process variables is necessary for stabilizing product quality and reducing manufacturing cost. This study proposes a method for the online monitoring of residual stress near the gate of a mold using multiple pressure sensors to measure process variables and verifies the feasibility of online monitoring. The study found that residual stress near the gate could not be accurately measured with only a single sensor because measurements were susceptible to interference with process parameters. When a single sensor was used to measure process variables, correlation coefficients of between 0.48 and 0.59 were obtained, and when multiple sensors were used, correlation coefficients of between 0.80 and 0.92 were obtained, which indicated strong correlation. Therefore, the online monitoring of residual stress near the gate is feasible. This monitoring method can provide a new concept of online monitoring technology for the injection molding of optical products.

Research on an Ultrasonic Longitudinal Critically Refracted Wave Detection Method for the Depth Distribution of Stress

Aluminum alloy components typically have structural characteristics such as large size and complex shape, making the in situ non-destructive detection of internal residual stress in these structures a challenge that the manufacturing sector has tried to solve. Ultrasonic longitudinal critically refracted (LCR) waves have shown good sensitivity to normal stress in the horizontal direction and could be used to detect the distribution of internal residual stress in components, offering an advantage not shared by other detection methods. In this study, we investigated the propagation mode of LCR waves in a 2A14 aluminum alloy component and established the characterization model of the average normal stress of LCR waves in different depth ranges. The blocking effect of LCR waves by a groove with a depth equal to twice the wavelength was analyzed and experimentally verified using a machined aluminum alloy test specimen. Then, the propagation depths of LCR waves in the aluminum alloy at different frequencies were determined. A load test on a cantilever beam based on the stress depth distribution model was designed, and the stress characterization model and LCR waves’ propagation depth were further verified by the self-developed LCR wave stress detection system. The test results showed that the LCR wave could accurately detect the depth distribution of stress and could serve as a useful tool for evaluating the depth distribution of normal stress inside aluminum alloy components.

Multi-channel non-destructive testing of steel strip stress based on magneto-elastic effect

ABSTRACT Internal stress is an important factor that affects the quality of strip products. Most online detection methods for internal strip stress have been realised by contact sensors. However, contact sensors are expensive to manufacture and tend to scratch the strip surface. The purpose of this study was to develop a multi-channel non-contact stress detection system that can reflect the longitudinal stress inhomogeneity of the strip in the width direction. First, a finite element model of residual stress detection based on the magneto-elastic effect was established in COMSOL, and it was calculated that the detection sensitivity was optimal when the sensor was arranged at 45°. Magnetic shielding technology effectively reduces the minimum interference-free distance of the sensor. A prototype of the detection system was built, the accuracy of the simulation model and the feasibility of the online detection of common steel grades are proved by experiments. The simulation model can directly solve issues related to the sensor’s induced voltage and the minimum interference-free distance, thereby reducing the design cycle and trial production cost of the sensor and providing new ideas for the development of magnetic shielding technology. The experimental results demonstrated that the detection method was feasible, reliable, and displayed high detection precision.

An Initial Residual Stress Inference Method by Incorporating Monitoring Data and Mechanism Model

Initial residual stress is the main reason causing machining deformation of the workpiece, which has been deemed as one of the most important aspects of machining quality issues. The inference of the distribution of initial residual stress inside the blank has significant meaning for machining deformation control. Due to the principle error of existing residual stress detection methods, there are still challenges in practical applications. Aiming at the detection problem of the initial residual stress field, an initial residual stress inference method by incorporating monitoring data and mechanism model is proposed in this paper. Monitoring data during machining process is used to represent the macroscopic characterization of the unbalanced residual stress, and the finite element numerical model is used as the mechanism model so as to solve the problem that the analytic mechanism model is difficult to establish; the policy gradient approach is introduced to solve the gradient descent problem of the combination of learning model and mechanism model. Finally, the initial residual stress field is obtained through iterative calculation based on the fusing method of monitoring data and mechanism model. Verification results show that the proposed inference method of initial residual stress field can accurately and effectively reflect the machining deformation in the actual machining process.

Numerical simulation and Experimental Verification of Heat Treatment of ISO-CC8X Rivet Nut

In this paper, the method of finite element analysis is used to study and Simufact.forming software is used to simulate the cold forming process and heat treatment process of ISO-CC8X riveting nut. The changes of equivalent stress of the riveting nut after cold forming process and heat treatment process are obtained. Then, residual stress detection and metallographic experiments were carried out to verify the reliability of the numerical simulation. This method is of guiding significance to the design and optimization of heat treatment process of metal parts in practical production.

Fundamental aspects of processing multi-metallic components using additive manufacturing technologies

Additive Manufacturing (AM) has triggered development of advanced materials and supply chain strategies. Almost all newly launched metallurgical processing routes had initial technical limitations arising from the fact that their process-property-performance relationship is not well-explored. In the same context, understanding the ramifications of the transition from “conventional” to “additive” manufacturing, requires knowledge of the physical mechanisms associated with technical challenges. The latter becomes bolder when processing of multi-metallic components is addressed. The first half of the article is devoted to the status and recent progress in AM processing practices. We emphasize on the role of processing parameters and instrumentation-material interaction in various AM methods with focus on multi-metallic materials. The second half addresses material development and performance perspectives with emphasis on multi-metallic configurations. Crucial factors for structural integrity are introduced and specific technical challenges are demonstrated, considering engineering materials for multi-metallic components. It is also demonstrated how various cooling rates measurement techniques can be utilised for assessing the cooling rates in AM. Post processing challenges associated with the corrosion performance of bimetallic components and the effect of heat treatment on AM components are also included. Finally, the role, origin and detection of residual stresses in AM components are addressed.

An approach for obtaining surface residual stress based on indentation test and strain measurement

Abstract During the welding process of welded joints in nuclear power plants, uneven deformation caused by temperature changes will lead to the generation of residual stress. Aiming at the problem that the demarcate experiment is easy to cause errors when the traditional indentation strain method is used to measure the residual stress. Using 316L austenitic stainless steel as an example, ABAQUS finite element simulation is combined with physical experiments to study the effects of different indentation depths on the strain increment after unloading under a state of residual stress. The results show that the indentation depth and strain increment are linearly related. Based on the linear relationship, an independent parameter that characterizes the residual stress is obtained and a model between the parameter and residual stress established. It provides a certain basis for the convenience and precise detection of residual stress in nuclear power plants machinery structures in service.

Analysis of torsion bar failure occurring during the pre-strained manufacturing for heavy off-road tracked vehicles

The torsion bar used in the suspension system of the heavy off-road tracked vehicle was broken during the pre-strained manufacturing. A series of investigations were conducted including chemical composition analysis, metallographic examination, residual stress detection, hardness evaluation, and fractographic analysis. The anomalous phenomena were analyzed comprehensively under the condition that the fracture features could not conclude directly. The results showed that the low tempering temperature of the torsion bar was the root cause of fracture, which resulted in excessive residual stress. The hardness is higher than the standard 14 HBW. The maximum difference of residual stress was 278 MPa. They reduced the torsional resistance. Consequently, the fracture occurred during pre-strained. The excessive residual stress triggered the advent of cracks and intergranular fracture. The possibility of failure caused by chemical composition and inclusions was excluded. Due to the results and the related research, changing the tempering temperature to 290-310℃ (holding for 2 h) may avoid failure. The analysis procedure in this work provides a means to determine failure cause under the difficulty of fracture analysis, and it offers possible routes to improve the performance of the torsion bar.

Design of sweep frequency signal source in residual stress detection platform based on Zynq

The signal generator based on DDS technology has high frequency and resolution, and is widely used in many fields such as instrument technology, radar, satellite timing, remote control and telemetry, and is one of the important directions of current signal generator research. In order to achieve a cost-effective, high frequency resolution signal source to stimulate the sensors in the residual stress detection system, this paper selects the Zynq-7020 on-chip system to control the 14-bit direct digital frequency synthesis chip AD9954 to obtain a 40Hz~1MHz sinusoidal signal output. Finally, the performance and technical parameters of the system are tested experimentally. The output signal of the signal source is stable, the signal-to-noise ratio is high, and the frequency error is within 0.1%.

Investigation of electromechanical impedance and residual stress relation for samples machined by hot ultrasonic-assisted turning

Electromechanical impedance (EMI) method has been widely used in recent years to evaluate the condition of structures. In this method, piezoelectric sensors are added to the structure to examine material properties. The impedance/admittance signals are recorded with the aid of the impedance analyzer without any conversion. When there is any change in structures, differences occur in these signals. Thus, changes in structures can be easily determined. It is known that residual stress plays a vital role in materials in terms of crack initiation, breakage, fatigue life, etc. In contrast, the detection of residual stress is time-consuming and it requires experience. This study reveals the effect of cutting parameters on residual stress and electromechanical impedance/admittance values. Firstly, hot ultrasonic-assisted turning was performed for Ti6Al4V material. A parametric study was carried out with different cutting depth, feed rate, and cutting speed. In the second stage, residual stress values measured by X-Ray diffraction (XRD) method and impedance/admittance values measured by an impedance analyzer were compared. In this context, empirical equations with their values between stress/impedance–admittance values have been derived. In general, it has been observed that stress values are significantly associated with impedance/admittance values and the highest correlation was obtained with the reactance values.

Molecular dynamics study of tensile-compressive behavior of silicon steel single crystal

In this paper, molecular dynamics was used to model and simulate the silicon steel single crystal. The stress-strain curve of silicon steel single crystal in the process of tension and compression and the evolution law of single crystal structure defects in the process of tension and compression were studied. The results show that the tensile strength and compressive strength of the silicon steel model are not similar, the compressive strength is significantly higher than the tensile strength. The compressive strength is about 2 times of the tensile strength. This conclusion is qualitatively verified through macro experiments. The cluster defects and stress show a positive correlation. The number of dislocations in the compression process is more than that in the tension process, but the dislocation size is smaller than that in the tension process. The research in this paper will provide theoretical support for residual stress detection and reduction.

Detection of residual stress in friction stir welding of heterogeneous aluminum/copper sheets—ultrasonic method

Detection of residual stress in friction stir welding of heterogeneous aluminum/copper sheets—ultrasonic method