S.R. Mannava, Sagar Bhamare, Vibhor Chaswal, Leonora Felon, David Kirschman, David Lahrman, Richard Tenaglia, Dong Qian and Vijay Vasudevan
The current industry standard rigid spinal implants suffer fatigue failures due to bending and torsion loads. The purpose of this program was to design novel prototype flexible…
Abstract
Purpose
The current industry standard rigid spinal implants suffer fatigue failures due to bending and torsion loads. The purpose of this program was to design novel prototype flexible titanium alloy spinal implant rod with machined features, and then apply the laser shock peening (LSP) process to restore the fatigue strength debit due to these features.
Design/methodology/approach
A flexible prototype rod was designed with flat section at the center of the rod. The flat section was laser shock peened. Static compression tests were conducted as per American Society of Testing Materials standards for three‐ and four‐point bending tests and “vertebrectomy” constructs. Finite element models were developed to aid in the design of LSP and also to guide the experiments.
Findings
The test results indicated a ∼3X improvement in flexibility and a reduction in fatigue load ratio, defined as applied load divided by the yield load; from 72 to 68 percent. This rod was LSP's on the flat sections, and tested again. The results indicated an increase in the fatigue load ratio from 68 to 75 percent without any further change in flexibility.
Originality/value
It has been demonstrated successfully that the current industry rigid spinal implant rod can be modified for flexibility and laser shock peened to increase fatigue strength. This enhancement will enable the use of the implant for longer periods and higher loads; and for surgical processes with and without fusion. This technology can be readily applied to all metals that are certified for human implant applications; thus can be implemented with minimal clinical trials.
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Anoop Vasu and Ramana V. Grandhi
The impact of laser peening on curved geometries is not fully comprehended. The purpose of this paper is to explain the action of laser peening on curved components (concave and…
Abstract
Purpose
The impact of laser peening on curved geometries is not fully comprehended. The purpose of this paper is to explain the action of laser peening on curved components (concave and convex shapes for cylindrical and spherical geometries) by means of shock wave mechanics.
Design/methodology/approach
An analytical formulation is derived based on the plasticity incurred inside the material and the results are compared with the prediction by numerical simulation.
Findings
A near-linear relationship is observed between curvature and compressive residual stress; an increasing trend was observed for concave models and a decreasing trend was observed for convex models. The consistency in the analytical formulation with the simulation model indicates the behavior of laser peening for curved geometries.
Originality/value
The differences observed in the residual stresses for spherical and cylindrical geometries are primarily due to the effect of Rayleigh waves. This paper illustrates the importance of understanding the physics behind laser peening of curved geometries.
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Susheel Pandey, Rajeev Srivastava, Christ Prakash Paul, Arun Kumar Rai and Rakesh Narain
The aim of this paper is to study the effect of laser shock peening (LSP) on mechanical behaviour of the laser-directed energy deposition (LDED)-based printed 15-5 PH stainless…
Abstract
Purpose
The aim of this paper is to study the effect of laser shock peening (LSP) on mechanical behaviour of the laser-directed energy deposition (LDED)-based printed 15-5 PH stainless steel with U and V notches. The study specifically concentrates on the evaluation of effect of scan strategy, machining and LSP processing on microstructural, texture evolution and fatigue behaviour of LDED-printed 15-5 PH steel.
Design/methodology/approach
For LSP treatment, 15-5 PH steel was printed using LDED process with bidirectional scanning strategy (XX [θ = 0°) and XY [θ = 90°]) at optimised laser power of 600 W with a scanning speed of 300 mm/min and a powder feed rate of 3 g/min. Furthermore, LSP treatment was conducted on the V- and U-notched fatigue specimens extracted from LDED-built samples at laser energy of 3.5 J with a pulse width of 10 ns using laser spot diameter of 3 mm. Post to the LSP treatment, the surface roughness, fatigue life assessment and microstructural evolution analysis is performed. For this, different advanced characterisation techniques are used, such as scanning electron microscopy attached with electron backscatter diffraction for microstructure and texture, X-ray diffraction for residual stress (RS) and structure information, Vicker’s hardness tester for microhardness and universal testing machine for low-cycle fatigue.
Findings
It is observed that both scanning strategies during the LDED printing of 15-5 PH steel and laser peening have played significant role in fatigue life. Specimens with the XY printing strategy shows higher fatigue life as compared to XX with both U- and V-notched conditions. Furthermore, machining and LSP treatment led to a significant improvement of fatigue life for both scanning strategies with U and V notches. The extent of increase in fatigue life for both XX and XY scanning strategy with V notch is found to be higher than U notch after LSP treatment, though without LSP samples with U notch have a higher fatigue life. As fabricated sample is found to have the lowest fatigue life as compared to machines and laser peened with both scan strategies.
Originality/value
This study presents an innovative method to improve the fatigue life of 15-5 PH stainless steel by changing the microstructure, texture and RS with the adoption of a suitable scanning strategy, machining and LSP treatment as post-processing. The combination of preferred microstructure and compressive RS in LDED-printed 15-5 PH stainless steel achieved with a synergy between microstructure and RS, which is responsible to improve the fatigue life. This can be adopted for the futuristic application of LDED-printed 15-5 PH stainless steel for different applications in aerospace and other industries.
Graphical abstract
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Yongxiang Hu, Mengqi Lai, Zonghao Hu and Zhenqiang Yao
Laser additive manufacturing is widely utilized to fabricate the Ti6Al4V alloy, but it requires post-processing to improve its performance. This paper aims to propose laser…
Abstract
Purpose
Laser additive manufacturing is widely utilized to fabricate the Ti6Al4V alloy, but it requires post-processing to improve its performance. This paper aims to propose laser peening (LP) as an effective way to improve the surface characteristics of the Ti6Al4V alloy fabricated by direct laser deposition (DLD).
Design/methodology/approach
Surface integrity including surface roughness, porosity, residual stress and microhardness are investigated in detail before and after LP treatment. Microstructure evolution is characterized by the electron backscatter diffraction (EBSD) to analyze crystal phase, grain boundary misorientation and texture.
Findings
Multiple overlapping layers of LP treatment result in slight influence on the polished surface of DLD-built samples. Porosity measured by the Archimedes test is found to be greatly decreased after LP treatment. Compressive residual stresses are significantly induced, the magnitude of which is greatly increased by increasing layers of LP treatment. And, local weakening or enhancement of residual stress in depth is observed because of pore and inclusion defects in the DLD-built Ti6Al4V alloy. Favorable hardness property can be obtained after multiple overlapping layers of LP treatment. EBSD analysis shows that LP treatment with multiple layers can introduce a large amount of lower-angle boundaries, indicating that dislocations beneath the top surface could induce a strain-hardened layer. The microtexture of the DLD-built Ti6Al4V alloy cannot be eliminated to decrease the anisotropy of the mechanical property.
Research limitations/implications
The variation of porosity observed after LP inside the DLD-built Ti-Al-4V is attractive but requires more detailed work to analyze the evolution of pore geometry.
Practical implications
Surface treatment of an additive manufactured titanium alloy was carried out to improve its fatigue resistance.
Originality/value
This work is original in proposing LP as an effective post process for the surface treatment of an additive manufactured titanium alloy through analyzing the surface integrity and microstructure evolution.
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Augustine Adomah-Afari, Doris Doris Darkoa Mantey and Kwasi Awuah-Werekoh
The purpose of this paper is to determine the factors that influence patients’ long-term relationship with healthcare providers in healthcare delivery at hospitals.
Abstract
Purpose
The purpose of this paper is to determine the factors that influence patients’ long-term relationship with healthcare providers in healthcare delivery at hospitals.
Design/methodology/approach
Data were gathered using 170 patients in a cross-sectional survey with quantitative research methods at a public regional hospital. Results were obtained using descriptive analysis and regression analysis.
Findings
Generally, the study found that the health-related factors (the reception of staff, providers’ attitude, waiting time, competence and expertise and the hospital environment) that influence patients’ long-term relationship with the healthcare providers/hospital were statistically significant (p < 0.001). The findings showed that overall 90.0 per cent of the patients were very satisfied with the overall healthcare services at the hospital.
Research limitations/implications
Limited sample size, lack of examination of healthcare providers’ perspectives and non-application of qualitative methods make it difficult to give a true picture of how these can enhance patients’ intent to keep a long-term relationship with the healthcare providers/hospital.
Practical implications
The paper suggests that health policymakers and practitioners need to enhance measures that will make patients satisfied leading to their long-term commitment and cordial relationship with the healthcare providers/hospital.
Social implications
The study demonstrated how health-related factors will be associated with the patients’ agreement/intent to keep a long-term relationship with their service providers at hospitals. Thus, the overall hypothesis was true that there is a relationship between patients’ satisfaction with the healthcare experienced and their long-term relationship with healthcare providers/hospital.
Originality/value
This is one of the few studies conducted on the topic in the context of Ghana’s health sector. It recommends that there should be a good interpersonal relationship between healthcare providers and patients, as patients’ satisfaction is not based on only receiving treatment at the health facility.
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Walter Leal Filho, Murukesan Krishnapillai, Aprajita Minhas, Sannia Ali, Gabriela Nagle Alverio, Medhat Sayed Hendy Ahmed, Roselyn Naidu, Ravinesh R. Prasad, Navjot Bhullar, Ayyoob Sharifi, Gustavo J. Nagy and Marina Kovaleva
This paper aims to address a gap in investigating specific impacts of climate change on mental health in the Pacific region, a region prone to extreme events. This paper reports…
Abstract
Purpose
This paper aims to address a gap in investigating specific impacts of climate change on mental health in the Pacific region, a region prone to extreme events. This paper reports on a study on the connections between climate change, public health, extreme weather and climate events (EWEs), livelihoods and mental health, focusing on the Pacific region Islands countries.
Design/methodology/approach
This paper deploys two main methods. The first is a bibliometric analysis to understand the state of the literature. For example, the input data for term co-occurrence analysis using VOSviewer is bibliometric data of publications downloaded from Scopus. The second method describes case studies, which outline some of the EWEs the region has faced, which have also impacted mental health.
Findings
The results suggest that the increased frequency of EWEs in the region contributes to a greater incidence of mental health problems. These, in turn, are associated with a relatively low level of resilience and greater vulnerability. The findings illustrate the need for improvements in the public health systems of Pacific nations so that they are in a better position to cope with the pressures posed by a changing environment.
Originality/value
This paper contributes to the current literature by identifying the links between climate change, extreme events, environmental health and mental health consequences in the Pacific Region. It calls for greater awareness of the subject matter of mental health among public health professionals so that they may be better able to recognise the symptoms and relate them to their climate-related causes and co-determinant factors.
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Yuting Lv, Xing Ouyang, Yaojie Liu, Ying Tian, Rui Wang and Guijiang Wei
This paper aims to investigate the differences in hot corrosion behavior of the GTD222 superalloy and TiC/GTD222 composite in a mixed salt of 75% Na2SO4 and 25% K2SO4 at 900°C.
Abstract
Purpose
This paper aims to investigate the differences in hot corrosion behavior of the GTD222 superalloy and TiC/GTD222 composite in a mixed salt of 75% Na2SO4 and 25% K2SO4 at 900°C.
Design/methodology/approach
The GTD222 superalloy and TiC/GTD222 nickel-based composite were prepared using selective laser melting (SLM). Subsequently, the hot corrosion behavior of the two alloys was systematically investigated in a salt mixture consisting of 75% Na2SO4 and 25% K2SO4 (Wt.%) at 900°C.
Findings
The TiC/GTD222 composite exhibited better hot corrosion resistance compared to the GTD222 superalloy. First, the addition of alloying elements led to the formation of a protective oxide film on the TiC/GTD222 composites 20 h before hot corrosion. Second, TiC/GTD222 composite corrosion surface has a higher Ti content, after 100 h of hot corrosion, the composite corrosion surface Ti content of 10.8% is more than two times the GTD222 alloy 4% Ti. The Ti and Cr oxides are tightly bonded, effectively resisting the erosion of corrosive elements.
Originality/value
The hot corrosion behavior of GTD222 superalloy and TiC/GTD222 composites prepared by SLM in a mixed salt of 75% Na2SO4 and 25% K2SO4 was studied for the first time. This study provides insights into the design of high-temperature alloys resistant to hot corrosion.
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Gulshan Singh, Miguel Cortina, Harry Millwater and Allan Clauer
The purpose of this paper is to estimate probabilistic and regional importance sensitivities of fatigue life, with respect to the laser peening (LP) parameters applied to a…
Abstract
Purpose
The purpose of this paper is to estimate probabilistic and regional importance sensitivities of fatigue life, with respect to the laser peening (LP) parameters applied to a Titanium turbine disk.
Design/methodology/approach
The sensitivities were calculated from Monte Carlo (MC) analysis of 21,000 simulations and probabilistic sensitivity methods.
Findings
The probabilistic sensitivity results indicate that the peak pressure and the mid‐span are the most important variables. The regional importance sensitivity results indicate that probability of failure is the most sensitive to the left tail of peak pressure and middle region of mid‐span and the fatigue life mean is the most sensitive to the left tails of the peak pressure and the mid‐span.
Practical implications
The sensitivity results of this research indicate that more time and energy should be focused on managing peak pressure and mid‐span, as compared to the remaining variables, to design and improve the laser peening process.
Originality/value
The paper presents four sensitivity analysis approaches which were formulated and employed to estimate fatigue life sensitivities with respect to the LP variables.
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To identify the factors that need to be addressed by Indian industry to steeply ramp up its production and productivity in the coming years, so as to achieve the goal of the…
Abstract
Purpose
To identify the factors that need to be addressed by Indian industry to steeply ramp up its production and productivity in the coming years, so as to achieve the goal of the country becoming a 5 trillion dollar economy by 2025.
Design/methodology/approach
Lean Management Leaders in Indian Industry (LMLII), i.e. those companies in India who are well known for having adopted TQM, BE and Lean methods for many years, and achieved success in their business) in Indian industry were selected and surveys were done between 2013 and 2017, to assess the status of LM adoption, by using the LESAT (version 2.0) survey tool. A longitudinal empirical study has been done, over a period of five years, so that the identification of factors is based on a few years’ data rather than a one year, spot-check or snapshot view. A new method, titled the ‘Three Step Reverse Exploratory Factor Analysis Procedure (TSREP)’, has been attempted to identify the ‘root causes’.
Findings
LMLII's have improved in their adoption of LM over these years by about 10%. The root causes that can help in further advancement in adoption have been identified and classified under six component factors.
Research limitations/implications
The identification of LMLII's has been done based on the experience and views of experts in TQM/ BE/ Lean in India. Since this is a first of such study (viz., the term LMLII is being defined and used for the first time), this methodology has been adopted. However, in future, a systematic way to assess the criteria for LMLII's could be designed. Secondly, the sample size of LMLII's needs to be fully representative of the industry.
Practical implications
By using the results of this study, Indian companies can accelerate their LM adoption programmes, leading to quantum jumps in production and productivity, so as to achieve the 5 trillion USD economy by 2025. The practical implications are immense.
Social implications
Since LM is a bundle of Lean, TQM and BE, companies adopting LM will, due to the inclusion of waste reduction through 5S, JIT, kaizens and continuous improvement, address the Triple Bottom Line (TBL) protocol of the UN. TBL has comprehensive implications on society and environment, climate change and sustainability of business.
Originality/value
This work is original, at least in three ways. First, in the use of the concept of ‘LML’. Second, there is no previous longitudinal study done on Indian industry in LM. Third, the TSREP is being used for the first time. The value of this research is in its findings, in the identification of key factors for future growth and the use of a novel technique for improving upon the accuracy, analytical rigour and legitimacy of the results.