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Numerical and experimental investigation of the formation mechanism and the distribution of the welding residual stress induced by the hybrid laser arc welding of AH36 steel in a butt joint configuration
摘要： Formation mechanism of the welding residual stress (WRS) is a key part of welding research. However, there is a lack of meaningful numerical models of the WRS. In this work, a thermal-metallurgical-mechanical (TMM) model was developed using SYSWELD to investigate the distribution and the formation mechanism of WRS during the hybrid laser arc welding of AH36 steel. A series of simulations were conducted to explore the effects of various factors on the WRS. The numerical results matched well with the experimental data. The computational accuracy was improved by considering the typical “wine glass” weld profile and the dilution rate during simulation. The evolution of the WRS is strongly affected by the interaction of phase transformation and strain hardening. The austenite-martensite transformation has a great potential to reduce the WRS whereas the austenite-bainite transformation produces high levels of WRS. The phase transformation temperature has a great influence on WRS.
关键词： Hybrid laser arc welding,Welding residual stress,Phase transformation,Numerical modeling
更新于2025-09-19 17:13:59
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Degradation mechanisms of bias stress on nitride-based near-ultraviolet light-emitting diodes in salt water vapor ambient
摘要： Degradation mechanisms of nitride-based near-ultraviolet (near-UV) light-emitting diodes (LEDs) were systematically analyzed by applying forward- and reverse-bias stresses to them in a salt water vapor ambient. The surface temperature of the forward-bias stress sample was higher than that of the reverse-bias stress sample. The high temperature of the forward-bias stress sample accelerated the chemical reaction of the device structure with salt water vapors and led to faster degradation. Composition analyses of the sample surface and cross-section were conducted to investigate the failure mechanism. The analyses results indicated that the erosion of the indium–tin–oxide layer enhanced the diffusion of the conducting metal into the LED crystal. The proposed method can effectively characterize the quality of near-UV LEDs in a short duration.
关键词： failure mechanisms,bias stress,reliability,near-UV LEDs
更新于2025-09-19 17:13:59
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Photovoltaic Module Reliability || What does the Future Hold for PV and a Brief Summary
摘要： The discussions in the previous chapters looked at both the history and present‐day status of photovoltaics (PV) module reliability and the accelerated stress testing associated with it. In this final chapter, the focus will shift to the future. PV is a dynamic industry so the technology and the testing standards are constantly evolving. The first section in this chapter will provide an update on the changes already in progress for some of the more important module qualification and safety standards. The second section will switch to a longer‐range view, discussing how PV module reliability is likely to change in the future and what sort of accelerated stress testing will be necessary to validate the quality of the huge volume of modules produced. The book will end with a brief summary of the status of PV module reliability today.
关键词： accelerated stress testing,flexible modules,IEC 61215,IEC 61730,bifacial modules,module lifetime,degradation rates,PV module reliability,photovoltaics
更新于2025-09-19 17:13:59
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Photovoltaic Module Reliability || Module Failure Modes
摘要： Initial product reliability assessments are based on the environment in which the product is going to be exposed, the outdoor terrestrial environment in the case of photovoltaic (PV) modules. Such an analysis can provide some clues as to the level of stresses to be encountered. The earliest module manufacturers understood that the modules would be required to endure exposure to the weather (rain, hail, and snow), high temperatures, UV, humidity, and thermal cycling. However, in most cases, the stresses were underestimated. The first generation of terrestrial PV modules was not very reliable nor did the modules survive for very long in the field. However, this first generation of product served an important function in that they failed in the field (often very quickly) allowing for subsequent analysis and development of accelerated stress tests to be described in Chapter 3. It wasn’t until the product designs could be tested using the accelerated stress tests that reliability was significantly improved.
关键词： failure modes,field failures,photovoltaic modules,reliability,accelerated stress tests
更新于2025-09-19 17:13:59
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Photovoltaic Module Reliability || Development of Accelerated Stress Tests
摘要： The chapter discusses the development of accelerated stress tests (ASTs) for photovoltaic (PV) modules to identify and mitigate field failure modes. It outlines various ASTs such as Thermal Cycling, Damp Heat, Humidity Freeze, UV Light Exposure, Static Mechanical Load, Cyclic (Dynamic) Mechanical Load, Reverse Bias Hot Spot Test, Bypass Diode Thermal Test, and Hail Test, detailing their parameters and the failure modes they address. The importance of ASTs in improving module reliability and lifetime is emphasized, along with the challenges in accelerating certain processes without altering the failure mechanisms.
关键词： Reverse Bias Hot Spot Test,UV Light Exposure,Damp Heat,Static Mechanical Load,Hail Test,Thermal Cycling,Photovoltaic Module Reliability,Accelerated Stress Tests,Humidity Freeze,Bypass Diode Thermal Test,Cyclic (Dynamic) Mechanical Load
更新于2025-09-19 17:13:59
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Photovoltaic Module Reliability || Predicting PV Module Service Life
摘要： What the PV industry would like is one set of accelerated stress tests that when successfully passed would ensure that a particular module type could survive in the field for 25 years. Implicit in that statement is the assumption that the test sequence is reasonably short. Most people asking for such a test sequence are probably thinking in terms of a few months of testing with an answer that spans a reasonable range of years (something like 25–35 years). This is not likely to happen because not all modules are designed and made the same way, nor are they deployed in the same geographic locations, so they are likely to degrade or fail via different mechanisms at different rates. McMahon et al. [1] came to this same conclusion as early as 2000.
关键词： PV module,degradation,service life,failure modes,accelerated stress tests
更新于2025-09-19 17:13:59
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Quality and Reliability of Publicly Accessible Information on Laser Treatments for Urinary Incontinence: What Is Available to Our Patients?
摘要： Study Objective: To determine the quality and reliability of the top 20 internet search results for laser treatment of stress urinary incontinence (SUI). Design: Review of 20 websites. Setting: N/A. Patients: None. Interventions: An internet search with the most popular search engine, Google, was undertaken to identify the top 20 websites for laser treatment of SUI. The DISCERN instrument, Journal of the American Medical Association (JAMA) benchmarks, and Health on the Net Foundation Code of Conduct certification, which are standardized, validated tools for the analysis of website quality, credibility, and transparency, were used independently by 7 healthcare workers. The readability of the information was assessed by a single reviewer using the Flesch-Kincaid Grade Level and Automated Readability Index. The intraclass correlation coefficient was calculated to document the reliability among website assessors. Measurements and Main Results: Of the 20 websites reviewed, 15 were created by private clinics, 2 by online newspaper or newsletter sites, and 3 by laser medical device manufacturers. None of the websites met all of the JAMA criteria: 1 had attained authorship, 1 had clear attribution, none had adequate disclosure, and 2 achieved currency. None of the websites took part in the Health on the Net Foundation Code of Conduct certification program. The mean DISCERN score (to determine the quality of websites) was 40 (out of 80), with the lowest average scores within the DISCERN tool primarily associated with clarity around sources of information, website bias, posting dates, risks of treatment, and shared treatment decision-making. The intraclass correlation coefficient was calculated for the DISCERN tool (0.72; 95% confidence interval, 0.48?0.87) and JAMA benchmarks (0.85; 95% confidence interval, 0.73?0.93). The mean Flesch-Kincaid Grade Level was 13.2 (§3.1) and the Automated Readability Index scores ranged from 7.6 to 22.8 (mean 13.5 § 3.5). Conclusion: There is a lack of good quality, reliable, and unbiased information available to patients on laser treatment of SUI on the most commonly searched websites. Information is presented at a reading level that is above that of the average reader, which may indicate that patients will have trouble comprehending the information. Journal of Minimally Invasive Gynecology (2020) 00, 1?7. ? 2020 AAGL. All rights reserved.
关键词： Website review,Stress urinary incontinence,Laser vaginal treatment
更新于2025-09-19 17:13:59
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The Influence of Selected Selective Laser Sintering Technology Process Parameters on Stress Relaxation, Mass of Models, and Their Surface Texture Quality
摘要： The article presents the results of research on the impact of basic process parameters of selective laser sintering technology on the mass of the produced models (density of the sintered material—polyamide PA 2200), stress relaxation during compression determined in accordance with the ISO 3384 standard, and geometric surface structure parameters (SGPs). During the tests, the influence of process parameters such as the location of the models on the virtual construction platform (printing direction), the density of the energy supplied to the sintered layer of powder, and the layer thickness of the manufactured material layer was taken into account. The test results confirmed that the process parameters have a significant impact on the density of the model material (in the sintered state), the mechanical properties (stress relaxation during compression), and the quality of the surface texture (SGPs). The most favorable positioning variants of the models on the construction platform were determined. The most favorable thickness variants of the combined layers and the density value of the energy supplied to the sintered powder layer were selected, depending on the expected mass, strength, and SGP quality. In addition, it has been shown that it is possible to build models with reduced mass (>20%), while maintaining satisfactory mechanical and qualitative properties of the surface texture.
关键词： additive manufacturing technologies,GPS,rapid prototyping,SLS,3D printing,stress relaxation
更新于2025-09-19 17:13:59
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Is there enough evidence to justify the use of laser and other thermal therapies in female lower urinary tract dysfunction? Report from the ICIa??RS 2019
摘要： Aims: There is increasing evidence to suggest that thermomodulation may have a role in the management of women with lower urinary tract dysfunction (LUTD) and there has been widespread adoption of laser and radiofrequency (RF) therapies within clinical practice. However, in many areas of LUTD, the data are still limited and there remains a need for further evaluation of the safety and efficacy of thermal therapy. The aim of this study proposal is to report the findings of the International Consultation on Incontinence Research Society to clarify our current knowledge regarding the evidence for thermal therapy in LUTD and to set research priorities for the future. Methods: Literature review based on the search terms: "laser," "radiofrequency," "genitourinary syndrome of the menopause" or "urogenital atrophy," "stress urinary incontinence (SUI)," "pelvic organ prolapse," "OAB" or "overactive bladder," and "urinary tract infection." Results: The current available evidence, though of low or very low quality, appears promising for the use of laser therapy in the management of genitourinary syndrome of the menopause, there are some data to suggest a possible role in SUI although very little evidence for urogenital prolapse. At present, the evidence supporting the use of laser in OAB and recurrent urinary tract infection is limited or lacking, while the available evidence for RF in the management of all forms of LUTD is much less robust. Conclusions: Laser and RF are being introduced clinically as a minimally invasive, low‐risk interventions for women with LUTD although at present, the evidence supporting usage is limited. Consequently, there is an urgent need to demonstrate the safety and efficacy with prospective long‐term studies including sham studies and comparative studies with current standard therapy.
关键词： lower urinary tract dysfunction,laser,radiofrequency,female,atrophy,stress urinary incontinence
更新于2025-09-19 17:13:59
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Local deformation and macro distortion of TC4 titanium alloy during laser shock processing
摘要： Experimental investigation has been carried out to understand the local deformation, macro distortion, and residual stress distribution of TC4 titanium alloy thin plate with different thickness during laser peening processing. The results show that the geometry distortions generate different profile directions depending on the laser shock processing condition. The deformation coefficient λ based on laser power density and sheet thickness is used to predict the macro deformation mode. When λ < 0.212, no macro distortion is produced; when 0.212 < λ < 0.58, volume is transferred along the top surface, the geometric distortion direction is away the laser beam, compressive residual stress is induced on the surface, and convex deformation is produced; when 0.65 < λ, volume is transferred along the bottom surface, the macro distortion direction is toward the laser beam, tensile residual stress is induced on the surface, and concave deformation is produced; the threshold of concave and convex deformation is about 0.62. The deformation coefficient λ and the threshold of concave and convex deformation can be adopted to predict and control the geometry distortion of TC4 titanium alloy thin plate during laser shock processing.
关键词： Thin plate,Residual stress,Geometry distortion,Laser shock peening
更新于2025-09-19 17:13:59