Coupled explicit-damping simulation of laser shock peening on x12Cr steam turbine blades

Timeous prevention of, and recovery from, downtimes due to in-service failure of crucial power plant components, like turbine blades, portends huge consequences in the form of operational and financial viability concerns. Intensive research and development in manufacturing, re-manufacturing and condition-based maintenance of these components have birthed a novel technique, which deploys high intensity lasers to induce compressive residual stresses to the surface of the blades. This paper presents the application of an alternate computational modelling technique in simulating this surface treatment technique on X12Cr steel, an exotic steam turbine blades material, while also investigating the economic parameters of the induced residual stresses. A numerical model is developed in this work using the commercial finite elements software ABAQUS©. The results show this computational modelling technique as being time efficient. The parametric outcomes of the simulation agreed with experimental results, lending credence to its validity. Induced compressive stresses as high as 700 MPa and depths close to 1 mm from the surface of the blade were obtained. This by indication can prospectively quell crack initiation, growth and unplanned failure of the blade while in service, with the introduced simulation technique offering a solution for timely, non-destructive mechanical integrity enhancement of engineered components.The National Research Foundation, ESKOM, Tshwane University of Technology (TUT), National Laser Centre (NLC-CSIR) and the Department of Science and Technology (DST), Republic of South Africa.http://iopscience.iop.org1742-6596am2022Mechanical and Aeronautical Engineerin

Residual Stress Enhancement by Laser Shock Treatment in Chromium-Alloyed Steam Turbine Blades

In-service turbine blade failures remain a source of concern and research interest for engineers and industry professionals with attendant safety and economic implications. Very high-pressure shock impacts from laser shots represent an evolving technique currently gaining traction for surface improvement and failure mitigation in engineering components. However, the physical characteristics and effects of parameter variations on a wide range of materials are still not fully understood and adequately researched, especially from a computational point of view. Using the commercial finite element code ABAQUS©, this paper explores the application of laser shock peening (LSP) in the enhancement of residual stresses in Chromium-based steel alloyed turbine blade material. Results of the numerically developed and experimentally validated LSP model show that peak compressive residual stresses (CRS) of up to 700 MPa can be induced on the surface and sub-surface layers, while the informed varying of input parameters can be used to achieve an increase in the magnitude of CRS imparted in the peened material. Analysis of the hierarchy of influence of the five input parameters under investigation on residual stress enhancement reveals the laser shock intensity as the most influential, followed in descending order of influence by the exposure time, shot size, degree of overlaps, and the angle of shot impact

Simulation of laser shock peening on X12Cr steel using an alternate computational mechanical threshold stress plasticity model

The ever-increasing relationship between energy consumption and economic growth continues to reinforce functional power generation infrastructure as the centerpiece of development. However, downtimes from in-service failure of power plant components, such as turbine blades, portend dire consequences in the form of huge financial and safety concerns. This challenge is now being progressively overcome through intensive research in the development of laser shock peening (LSP) models, which simulate the induction of compressive layers around and beneath the surface of the blades. This paper presents an alternate experimentally validated computational modelling approach of the LSP process, grounded on a physics-based plasticity model which describes a mechanical threshold for compressive residual stress induction irrespective of increasing laser shock intensities. This is a phenomenon which hitherto has previously been overlooked by many researches. The results of this work show considerable promise when compared to experimental results.The National Research Foundation, Eskom, the National Laser Centre, Centre for Scientific and Industrial Research, Pretoria, Tshwane University of Technology and the Department of Science and Technology, Republic of South Africa.http://link.springer.com/journal/1702021-09-23hj2021Mechanical and Aeronautical Engineerin