Stress Control Method Research Articles

The Generation, Measurement, Prediction, and Prevention of Residual Stress in Nickel-Based Superalloys: A Review

As a crucial high-performance material, nickel-based superalloys inevitably generate residual stresses during processing, manufacturing, and usage. The mechanical properties of nickel-based superalloys are significantly reduced by residual stress, which becomes one of the important factors restricting material reliability. The systematic analysis of residual stresses in nickel-based superalloys throughout the entire manufacturing and usage processes is insufficient. The residual stress generation factors, measurement methods, prediction models, and control methods in nickel-based superalloys in recent years are summarized in this paper. The current challenge and future development trends in the research process of nickel-based superalloy residual stress are also presented. A theoretical reference for further research on residual stresses in nickel-based superalloys can be provided in this review.

Microstructure and cyclic hardening/softening behavior of laser welded high strength steel joints under asymmetrical cyclic loading

The cyclic behavior of materials under load and its influence on the mechanical properties of materials have always been the focus of engineering research. In this study, high strength steel was successfully welded by laser welding. The microstructure of each region of the high strength steel DP590 post-welding was meticulously analyzed. Additionally, 500 cycles of low-cycle fatigue tests of laser welded high strength steel were carried out by using asymmetric stress control method. After fatigue test, tensile test shall be carried out on some samples. Under the specific combination of mean stress and stress amplitude, compare the specimens that have not been fatigue tested with those that have been fatigue tested, the change of properties of laser welded high strength steel joint under asymmetric cyclic load was analyzed. The results showed that, due to cyclic hardening, the tensile strength of the sample increased to 601 MPa and the yield strength to 325 MPa. Compared with the original sample, the tensile strength and yield strength of the sample after asymmetric cycling had increased by 8.65% and 31.3%, respectively.

Key principles of stress control method

Underground excavation would cause two main excavation effects: (1) stress redistribution, including radial stress decrease and tangential stress concentration; and (2) surrounding rock degradation. Comprehensive consideration of excavation effects is crucial to prevent underground engineering disasters. However, the two excavation effects are not considered in the predominantly used Platts pressure arch theory, whereas the New Austrian tunneling method is focused on the full utilization of the strength of the surrounding rock. Construction designing using these methods could lead to disaster deep underground. Thus, in this study, the stress control method (SCM) was proposed to comprehensively consider the two excavation effects. The following two key SCM principles were introduced in this study: (1) adopt the largest possible prestressing force to increase the low radial stress caused by excavation; (2) timing of support should be as early as possible to minimize surrounding rock deterioration. The application principles of SCM in hard rock tunnels and soft rock tunnels are explained

Epitaxial Lateral Overgrowth of Wafer‐Scale Heteroepitaxial Diamond for Quantum Applications

Wafer‐scale heteroepitaxial diamond thin films demonstrate multiple advantages for a further development of integrated optical and quantum devices based on impurity–vacancy color centers. The main obstacle here is a high structural defect density characteristic for heteroepitaxial epilayers. In this work, technological methods of stress control, NV formation, and defect density reduction in diamond epilayers, which are based on principles of epitaxial lateral overgrowth (ELO) are reported on. Herein, material and quantum properties of NV‐doped diamond thin films obtained by patterned nucleation growth and by ELO of microstructured epilayers, are compared. It is demonstrated that a combination of both methods might have a significant potential for the wafer‐scale production of heteroepitaxial diamond for quantum devices.

Laboratory investigation on early-age shrinkage cracking behavior of partially continuous reinforced concrete pavement

As a form of durable pavement structure commonly used in the world, continuously reinforced concrete pavement (CRCP) has prominent problems caused by irregular crack distribution in the early stage. According to the characteristics of the discontinuous distribution of CRCP longitudinal steel bar stress and active crack control method, a rigid pavement structure called partially continuous reinforced concrete pavement (PCRCP) was proposed to simultaneously optimize the crack distribution pattern and reduce the longitudinal steel ratio in this paper. Since early-age shrinkage cracking behavior is a key factor affecting its durability. This paper purposes to assess the early-age shrinkage cracking behavior of PCRCP by comparing different reinforcement methods in laboratory experiments. Research results indicated that the early-age shrinkage behavior of PCRCP is basically the same as that of CRCP. The early-age shrinkage behavior of PCRCP is significantly improved than the advanced reinforced concrete pavement (ARCP). Restricted by the boundary and longitudinal steel bars system, the concrete beam produces a top-down nonlinear temperature and humidity gradient, resulting in various degrees of shrinkage deformation at different depths inside. The active crack control method can control the early-age concrete slab to form uniform crack pattern with straight lines or fewer bending cracks, which improves early-age cracking behavior significantly. This paper is to further deepen and develop the theory of CRCP early-age cracking behavior and provide basic theory support for the subsequent experimental section studies of PCRCP.

Research on Residual Stresses and Microstructures of Selective Laser Melted Ti6Al4V Treated by Thermal Vibration Stress Relief

The efficient and cost-effective residual stress control method is of great significance for the application of additive manufacturing (AM) technology. In this work, thermal-vibration stress relief (TVSR) with different temperatures and dynamic stresses was performed on Ti6Al4V samples prepared by selective laser melting (SLM), the stress relief effects of TVSR and its influence on phase and microstructure were investigated and compared with thermal stress relief (TSR) and vibration stress relief (VSR), and the stress relief mechanisms of these methods are discussed. It was found that the residual stress relief rate can reach 86.76% after TVSR treatment at a temperature of 380 °C and a dynamic stress of 400 MPa, which increased by 63.63% compared with VSR under the same dynamic stress. The efficiency is increased by 76% compared with TSR at 580 °C and the residual stress relief rate is almost the same. After TVSR, VSR and TSR treatments, the grain morphology, size and phase content of samples were basically unchanged, and low-angle grain boundaries (LAGBs) were increased after TVSR and VSR treatments and decreased after TSR treatment. The results confirm that the TVSR method has the ability to control the residual stress of selective laser melted Ti6Al4V with low time and cost consumption, and are helpful for engineering applications of TVSR.

Residual stress control of hot-rolled strips during run-out table cooling

The strips with good flatness after finish rolling will have flatness defects such as edge wave after run-out table cooling. These defects are caused by the residual stress due to inhomogeneous thermal and microstructural behaviors during the cooling stage. The traditional residual stress control methods rely too much on experience, resulting in poor control effect and poor universality. Therefore, this study proposed two residual stress control methods based on model calculation: water flow central crown and center wave compensation control. The former is mainly based on controlling the uniformity of strip transverse temperature and microstructure. The latter is mainly controlled by mutual compensation of internal stresses. In this paper, the mathematical models of water flow central crown cooling and critical center wave compensation stress were established, respectively. Meanwhile, a post-buckling model of hot-rolled strip was established to calculate the aim flatness value at exit of finishing mill under critical compensation stress. Furthermore, a fully coupled finite element model based on temperature, phase transitions, and stress was developed and it was verified using experimental data. Finally, the above two residual stress control methods were realized in the finite element model. The results showed that the two methods can reduce the residual stress and improve the flatness, and the application of center wave compensation control is more effective.

Stress control as a method to reduce perceived pain in oral lichen planus.

Oral lichen planus (OLP) is a common chronic, T-cell-mediated, inflammatory and non-infectious mucodermatosis. Patients diagnosed with oral lichen planus are more prone to depression, anxiety and higher perceived mental stress than the rest of the population. This study investigated stress control methods as a means of reducing pain levels in patients with oral lichen planus. The study involved 62 adult oral lichen planus patients who have never received any OLP treatment before. Patients with a high level of perceived mental stress received, in addition to standard pharmacological treatment, herbal sedative medication or Jacobson's Progressive Muscle Relaxation guidance (JPMR), and the patients without a high level of perceived mental stress level did not receive any additional stress control methods. The research tool was the PSS questionnaire and NRS pain level scale. Before the treatment, the level of perceived pain did not differ in any of analysed groups. After the treatment, in the group not using any stress control methods, the mean NRS level was significantly higher than in the group performing Jacobson's Progressive Muscle Relaxation (2.79 ±1.76 vs. 1.08 ±1.29), and also significantly higher than in the group receiving the herbal sedative (2.79 ±1.76 vs. 1.41 ±2.06). The use of mental stress control methods as an additional element of therapy has a positive effect on the success of oral lichen planus treatment since it helps to reduce the perceived pain level in the oral mucosa better than a standard pharmacological therapy alone.

Study on the influence of ultrasonic impact treatment (UIT) on stress evaluation of laser cladding coating by using metal magnetic memory technology

The effect of ultrasonic impact treatment (UIT) on stress of laser cladding coating evaluated with metal magnetic memory technology (MMMT) was discussed, so a stress control method was proposed. In this paper, a metal magnetic memory testing device of EMS-2003, a two-channel pen metal magnetic memory probe and a non-ferromagnetic three-dimensional electronically controlled displacement plat form were employed to collect Hp(y) signal defined as the normal component of MMM signal, and tensile test was carried out on LC-50 testing machine. To prove the theoretical analysis, the microstructure and three dimensional surface topography of coating under different repetition rates of UIT were observed by using optical microscope and laser scanning confocal microscopy. The results show that the influence of detection line on Hp(y) signal can be ignored, and the distribution of Hp(y) signals under different tensile loads are all approximately an oblique line, which can be explained by the magnetic dipole model. As tensile load increases, the magnetic field intensity gradient of Hp(y) signal (K) becomes higher, and after coating is in the plastic deformation state, the value of K becomes lower gradually as tensile load increases further. When tensile loads are the same, the value of K becomes higher gradually as the repetition rate of UIT increases. But as repetition rate of UIT increases, the slope of K becomes lower gradually, and the changes on microstructure and deformation caused by UIT are seen as main reasons. At last, the experimental results were theoretically discussed based on the magnetostriction effect, and it was thought that the change on orientation of magnetic domain was the main reason.

Three-dimensional stress rotation and control mechanism of deep tunneling incorporating generalized Zhang–Zhu strength-based forward analysis

Deep rock tunneling exhibits a significant three-dimensional (3D) space effect. The complex stress path and extrusion deformation during excavation are the most significant and decisive factors in the stability and construction safety of a deep tunnel. 3D and forward numerical analyses based on generalized Zhang–Zhu (GZZ) strength criterion are performed to investigate the principal stress rotation behavior and active control mechanism during deep tunneling. The surrounding rock element experiences significant stress rotations because of the sharply increased shear stress (τry) near the tunnel face. A dimensionless stress index (τry/I1) is proposed to quantitatively evaluate the principal stress rotation during excavation. τry/I1 increases with increasing buried depth, and the deep tunnel presents significant principal stress rotation that reaches a large τry/I1 value. The mechanical behavior of the advanced core rock is primarily affected by the strengthening parameter, geological strength index (GSI). Strengthening of the core rock can greatly improve the stress conditions and mechanical behavior, increase the strength of the rock mass, and reduce the stress rotation. The pre-extrusion deformation of the core rock and pre-convergence of the surrounding rock are discovered to follow a consistency law, which suggests that the pre-convergence deformation and surrounding rock stability near the tunnel face depend on the extrusion deformation of the tunnel face. The GZZ strength-based 3D forward analysis and stress control method proposed in this study can enhance the design and construction of deep and ultra-deep tunnels by weakening the 3D space effect (e.g., tunnel face extrusion and stress rotation) and exerting the strength potential (self-bearing capacity) of a rock mass.

Lab-scale simulation of hydraulic fracturing: some outcomes

The paper describes the lab-scale physical simulation of hydraulic fracturing in measurement holes. The tests were carried out using cubical polymethyl methacrylate specimens with faces of 200 mm. The open-end or dead-end holes with diameter of 12 mm were made in the test specimens. In the preset intervals in the holes, the longitudinal or latitudinal (ring-wise) slots with depths up to 3 mm were precut to initiate and orient created fractures. Hydrofracturing was carried out using prototype tools for sealing a test interval in a hole (packer-to-packer spacing) and to feed it with power fluid under pressure. The model specimens were tested under different triaxial loading conditions on a special testing machine. The representative cases of the created fracture growth in the model specimens were analyzed. The physical simulation outcomes can be used in formulation and solution of analytical problems on HF stress measurement, as well as to improve procedures and equipment involved in this method of stress control in underground mines.

Prediction study on in-situ reduction of thermal stress using combined laser beams in laser powder bed fusion

High thermal stress induced by extremely high temperature gradient significantly hinders the development of the laser powder bed fusion (LPBF). In this study, an in-situ stress control method based on the combined laser beams was proposed, in which a second laser beam was added to release the thermal stress during the process. The effect of the combined laser beams on the temperature distribution and thermal stress in LPBF was studied. A definition of the equivalent scan length was adopted to simulate the effect of the scan length. It was found that when the second beam was used, the post-heating strategy can reduce the residual stress better than the pre-heating strategy. The stress relief effect was close to the scan direction of the second beam and the vertical post-heating pattern was recommended to in-situ reduce the thermal stress. More obvious thermal stress cycles and the thermal stress peaks appeared in the long scan length. The stress release effect caused by the second beam decreased with the increase of the scan length, indicating that the scan length should be also reduced even if the second beam was used. The simulated results were indirectly verified by the experimental data with different re-scanning strategies and scan lengths. The purpose of this paper is expected to significantly in-situ reduce the thermal stress during the process without increasing the manufacturing time.

Perilaku Penderita Hipertensi di Rumah Sakit X

The prevalence of hypertension is still high, despite various treatments have been done. The success of hypertension treatment depends on the behavior of people with hypertension during treatment. This study aimed to understand the behavior of hypertensive sufferers at X Hospital which supported or unsupported the health. The qualitative study with phenomenology method was involved six informants. Data collection was done by in-depth interviews, observation, and analysis based on Miles Huberman principals. This research found the behaviors that support the health of hypertension sufferer's are the application of a low salt diet, cessation of cigarette and alcohol consumption, increase in activity and exercise, regulation of sleep and rest needs, application of stress control methods, and hypertension treatment and care. Overall, the informants have implementesd that six behaviors, but in the aspects of treatment and care of hypertension it has not been implemented properly. It is hoped that the nurses in the hospital need to provide education about healthy lifestyle independently that able to lower hypertension and emphasize on the importance of undergoing regular treatment and care to health services

Determination of the steel axial stresses in memory mode by the exponential law of magnetoelastic demagnetization

Magnetic and magnetoelastic methods of stress control are based on changes in the magnetic parameters of steel upon deformation. However, the magnetic properties of different steel grades, and even of the same grade in different heats may differ noticeably. The inhomogeneity of the magnetic and magnetoelastic properties of steel attributed to variations in the chemical composition, as well as in the modes of rolling and heating during manufacture affects the accuracy of stress control being a common disadvantage of magnetoelastic methods used for monitoring the stress-strain state of steel structures. The goal of the study is to consider the possibility of monitoring uniaxial mechanical stresses in steel structures in the «magnetoelastic memory» mode, based on H(σ) dependence of the strength of magnetic field of scattering local remanent magnetization of steel on the uniaxial stresses. The exponential function is shown to provide a satisfactory description of the experimental dependence of the strength of the magnetic field of scattering of the permanently magnetized 17G1S and 15KhSND steels on the stresses induced in steels by tension, compression, and impact. To improve the accuracy of the control, we propose to introduce the magnetoelastic sensitivity of steel (MSS) into the accepted form of the exponential dependence H(σ). A way to MSS determination not only on laboratory samples under ideal conditions, but directly on the construction under control (which reduces the errors of the control attributed to variations in the magnetic and magnetoelastic properties of steels) is considered. To implement the proposed procedure, prototypes of the devices for static and dynamic local loading of metal structure elements have been developed and manufactured. The devices have undergone a pilot test when monitoring the stress-strain state of the load-bearing beams of an automobile overpass. Using the developed devices, a local dosed loading with a hemispherical indenter was carried out through shock or static loading of a pre-magnetized region of the structure resulted in a decrease in the intensity of the magnetic field of scattering. A procedure for monitoring uniaxial stresses in steel structure elements by the method of magnetoelastic «memory» is proposed taking into account the measured magnetoelastic sensitivity of their material.

Влияние функциональных добавок к корму на иммунный ответ и здоровье рыб

In aquaculture, one of the most promising methods of disease and stress control is considered to be strengthening the defense mechanism through prophylactic administration of immunostimulants, which are seen as a reassuring alternative to chemotherapy and vaccines. All these preventive measures are aimed at strengthening the innate and/or adaptive immune system. New immunostimulants, prebiotics, and probiotics are increasingly being discussed in scientific journals. As a multifunctional complex structure, the gut has a key immunological role in homeostasis and the maintenance of fish health, in addition to food digestion and nutrient absorption. The review article presents new studies on the effect of prebiotics and/or probiotics as functional feed additives on immune and physiological responses in the fish intestine and its microbiota.

Effects of the specimen form on high cycle fatigue properties of 7050-T7451 and 2524-T3 aluminum alloys

High cycle fatigue properties of 7050-T7451 and 2524-T3 aluminum alloys at three stress ratios R=-1, 0.06, and 0.5 were experimentally studied, in which the axial stress control method was used to measure the funnel-shaped and iso-section specimens, with a MTS electro-hydraulic test system. Stress-life data were obtained and equivalant stress-life curves were plotted based on the equivalent stress model. Results showed that as for 7050-T7451 and 2524-T3 aluminum alloys, stress-life curves obtained with two kinds of specimens basically agreed, and effects of the specimen form on high cycle fatigue properties of these two aluminum alloys can be neglected.

(Invited) Atomic Layer Deposition Coatings for Medical Devices

Implantable medical devices must withstand the corrosive environment inside the human body for prolonged periods of time. Hermetic sealing of the device to protect it from the corrosive environment of human body and vice versa is a key step to enable long life time for the smart medical devices. Atomic layer deposition (ALD) is an advanced deposition technique belonging to the family of chemical vapor deposition (CVD) techniques. In ALD the substrate to be coated is exposed sequentially to precursor chemicals that react with the reactive surface sites on the substrate and form a chemically bonded adsorption layer. This growth mode of the film enables extremely conformal and uniform films to be coated on three-dimensional objects having any shape. Even the smallest, nanometer sized features on the objects can be coated with ease, making the technique extremely useful when hermetic sealing of complex shaped objects are required. The advantages of ALD over other deposition techniques makes it powerful method for applications where sensitive substrate materials combine with extreme demands on coating quality and temperature/chemical resistance, such as those often seen in the medical applications. In order to make a robust protective sealing for the medical device, the film properties must fulfill certain key criteria. First and foremost, the film material needs to be non-toxic for human cells in order to be biocompatible. Secondly, the film needs to function as an highly efficient diffusion barrier against the ions and molecules present in body fluids. In addition, the adhesion of the film with the device surface needs to be strong enough to prevent the delamination of the film. In our recent work [1] we have shown that SiO2-HfO2 coated sub-millimeter-sized microelectronic chiplets for wireless body implants can last without degradation and electronic failure in accelerated aging tests in saline at T = 87 °C for more than 180 days. This corresponds an equivalent lifetime of more than 10 years at human body equivalent temperature of 37 °C. Latest results on ALD films (deposited with Picosun® R-200 Advanced ALD reactor) for medical applications will also be discussed. Biocompatibility tests for Al2O3, TiO2, HfO2, SiO2, Ta2O5 films using the ISO standard Cytotoxicity of Medical Device (ISO 10993-5) procedure will be presented. In addition, we will show results of corrosion tests in PBS solution at elevated temperature (87 °C) for a number of ALD oxides and their nanolaminates, highlighting a stress control method that can improve the long-term delamination resistance of the coatings. Furthermore, we will show some results on the diffusion barrier properties of Al2O3, TiO2, HfO2, SiO2, Ta2O5 and their nanolaminates on different electrode materials (Al, Au, Pt, TiN) when exposed to PBS solution. [1] Conformal Hermetic Sealing of Wireless Microelectronic Implantable Chiplets by Multilayered Atomic Layer Deposition (ALD) by J. Jeong, F. Laiwalla, J. Lee, R. Ritasalo, M. Pudas, L. Larson, V. Leung, and A. Nurmikko, https://doi.org/10.1002/adfm.201806440. Acknowledgements: This work is part of the ULIMPIA project funded by PENTA under grant number PENTA-2017-Call2-16101-ULIMPIA

Fatigue Life Improvement for Aeroengine Disks Based on Active Thermal Management

Fatigue life is closely associated with stress level for aeroengine disks. A stress control method using active thermal management has been proposed and may benefit fatigue life. This study numerically investigates the effect of active thermal management on fatigue life of disks and explores possible methods for fatigue life improvement. In this numerical modeling investigation, a disk of uniform thickness containing a preset initial crack subjected to simplified loads is considered. Active thermal management is conducted by transferring parts of the rim’s heat flow to actively heat the hub, and this process is represented by energy transfer coefficient . A numerical simulation is used to compute the temperature and stress distributions of the disk, and the fatigue life is analyzed using universal weight function expressions. The results show that the fatigue life under an actively managed thermal load () increases by 26.1% compared with that of the conventional load (). Thus, active thermal management can be used to increase the fatigue life of a disk. The reason for this improvement in fatigue life is studied numerically and theoretically. The temperature becomes a V-shaped distribution as the hub is heated, and the thermal stresses that are induced by reverse temperature gradients counteract parts of the centrifugal stresses; the reduced stress enhances fatigue life.

Microstructure and ratcheting behavior of 6061 aluminum alloy laser-MIG hybrid welding joint

In this paper, 6061-T6 aluminum alloy was welded by laser-MIG hybrid welding. The microstructures of the upper part of the weld center, the lower part and the edge of the weld near the fusion line in the welded joint were analyzed. The hardness and mechanical properties of welded joints were analyzed in detail. The ratchet strain of 6061 aluminum alloy welded joints was tested, and the asymmetric stress control method was used to test the ratchet strain of 6061 aluminum alloy welded joints. The results show that ratcheting strain increases with the increase of average stress and stress amplitude, and has the characteristics of cyclic softening first and then hardening. The degree of hardening increases with the increase of the maximum cyclic stress. Cyclic hardening is mainly caused by the uninterrupted dislocations in the process of cycling. The accumulation of ratchet strain results in plastic damage of materials. Pre-ratcheting can improve the tensile properties of welded joints by 6.49% and 97.7% yield strength, which is mainly attributed to cyclic hardening caused by ratcheting strain.

Residual Stress in Metal Additive Manufacturing

Additive manufacturing (AM) has been widely used to fabricate functional metal parts in automobile, aerospace, energy, and medical device industries due to its flexible process capacity including complex geometry, functional graded materials, and free usage of tool. For the two major categories of metal additive manufacturing processes include powder bed fusion (PBF) and directed energy deposition (DED), parts are fabricated through melting of feed stock materials in the form of either powders or wires directly from a CAD model. The unique thermal cycle of metal additive manufacturing is characterized by: (1) rapid heating rate due to high energy intensity with steep temperature gradients; (2) rapid solidification with high cooling rates due to the small volume of melt pool; and (3) melt-back involving simultaneous melting of the top powder layer and re-melting of underlying previously solidified layers. Residual stress caused by the unique thermal cycle in AM is the critical issue for the fabricated metal parts since the steep residual stress gradients generate part distortion which dramatically deteriorate functionality of the end-use parts. This paper comprehensively assessed the current research status on residual stress sources, characteristics, and mitigation. First, the relationship between residual stress and microstructure is highlighted in AM metal parts. Then, the measurement methods and characteristics of residual stress in both as-build metal parts and post-processed ones were summarized. Third, residual stress mitigation and control methods including in-situ and post-process control methods were thoroughly discussed. Furthermore, future work directions are provided in this work.