Browsing by Author "Ali, Zain"

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    A sustainability-based framework for predicting the remaining useful life of a complex engineering asset
    (Cranfield University, 2024-06-07) Venkata Subhadua, Vaishnav; Ali, Zain; Farsi, Maryam; Norton, Andy
    As climate change became recognised as a major global challenge, the ability to define and account for the environmental performance of an asset became an important attribute aiding the sustainable development strategies towards net-zero. Remaining Useful Life (RUL) indicator allows for optimised maintenance scheduling and the life extension of an asset. However, the existing RUL prediction methods do not fully consider the environmental performance (EP) of an asset. This paper aims to develop a sustainability-based framework for complex engineering assets’ RUL prediction based on a systematic review of key literature. The proposed framework introduces a new concept, so-called ‘sustainable-RUL’ (SRUL), which refers to the estimated remaining lifetime that an item is able to function reliably and be environmentally sustainable. The Scopus database is used to develop the PRISMA framework. Finally, a generic S-RUL framework is introduced which incorporates the environmental sustainability aspect into the RUL prediction. Hence, the decision-maker is provided with a single predictive indicator, that accounts for the asset reliability and EP at the same level of granularity, thus facilitating the selection of maintenance policies that establishes a condition for ecological and economic stability.
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    Effective thermal diffusivity measurement using through-transmission pulsed thermography: extending the current practice by incorporating multi-parameter optimisation
    (MDPI, 2025-02-13) Ali, Zain; Addepalli, Sri; Zhao, Yifan
    Through-transmission pulsed thermography (PT) is an effective non-destructive testing (NDT) technique for assessing material thermal diffusivity. However, the current literature indicates that the technique has lagged behind the reflection mode in terms of technique development despite it offering better defect resolution and the detection of deeper subsurface defects. Existing thermal diffusivity measurement systems require costly setups, including temperature-controlled chambers, multiple calibrations, and strict sample size requirements. This study presents a simple and repeatable methodology for determining thermal diffusivity in a laboratory setting using the through-transmission approach by incorporating both finite element analysis (FEA) and laboratory experiments. A full-factorial design of experiments (DOE) was implemented to determine the optimum flash energy and sample thickness for a reliable estimation of thermal diffusivity. The thermal diffusivity is estimated using the already established Parker’s half-rise equation and the recently developed new least squares fitting (NLSF) algorithm. The latter not only estimates thermal diffusivity but also provides estimates for the input flash energy, reflection coefficient, and the time delay in data capture following the flash event. The results show that the NLSF is less susceptible to noise and offers more repeatable values for thermal diffusivity measurements compared to Parker, thereby establishing it as a more efficient and reliable technique.
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    Infrared thermography- a study into its current capabilities and future prospects
    (Cranfield University, 2024-06-07) Ali, Zain; Peng, Shaoyang; Addepalli, Sri; Zhao, Yifan
    The fourth industrial revolution has brought forward a paradigm shift in the analyses and interpretation of data. Emerging technologies such as artificial intelligence, Internet of Things (IoT), and cyber physical systems have accelerated the process of concepts such as decentralised decision making, automation, and digitalisation. In the context of Non-destructive Evaluation (NDE), adopting these technologies has substantially improved the efficiency of existing techniques. Currently, Ultrasound Testing (UT) has been dubbed as the “gold standard” for Non-destructive Testing (NDT). However, a major drawback to this technique is its contact-based inspection. Infrared Thermography (IRT) on the other hand offers a non-contact non-intrusive inspection and is a growing area of interest to researchers. This paper explores the impact of infrared thermography within the maintenance industry. Firstly, the current state-of-the-art in IRT is presented followed by the limitations of the technique, the current research and knowledge gap that exists in thermographic testing. Potential solutions that can overcome the limitations are proposed. These cover specific aspects of the technique such as the working principle, mathematical modelling, data interpretation and processing, automation, and digitalisation. Finally, future prospects of the technique are briefly presented.
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    Thermal material property evaluation using through transmission thermography: a systematic review of the current state-of-the-art
    (MDPI, 2024-08-03) Ali, Zain; Addepalli, Sri; Zhao, Yifan
    Determining thermal material properties such as thermal diffusivity can provide valuable insights into a material’s thermal characteristics. A well-established method for this purpose is flash thermography using Parker’s half-rise equation. It assumes one-dimensional heat transfer for thermal diffusivity estimation through the thickness of the material. However, research evidence suggests that the technique has not developed as much as the reflection mode over the last decade. This systematic review explores the current state-of-the-art in through-transmission thermography. The methodology adopted for this review is the SALSA framework that seeks to Search, Appraise, Synthesise, and Analyse a selected list of papers. It covers the fundamental physics behind the technique, the advantages/limitations it has, and the current state-of-the-art. Additionally, based on the Population, Intervention, Comparison, Outcome, and Context (PICOC) framework, a specific set of inclusion and exclusion criteria was determined. This resulted in a final list of 81 journal/conference papers selected for this study. These papers were analysed both quantitatively and quantitatively to identify and address the current knowledge gap hindering the further development of through-transmission thermography. The findings from the review outline the current knowledge gap in through-transmission thermography and the challenges hindering the development of the technique, such as depth quantification in pulsed thermography and the lack of a standardised procedure for conducting measurements in the transmission mode. Overcoming some of these obstacles can pave the way for further development of this method to aid in material characterisation.
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    Through transmission thermography- A review of the state-of-the-art
    (Cranfield University, 08/11/2022) Ali, Zain; Addepalli, Yifan; Zhao, Yifan
    Nondestructive Testing (NDT) covers a wide range of testing methods in which a component can be inspected without affecting its functionality. Infrared thermography is an NDT technique that has gained rapid popularity in recent years for structural integrity assessment, especially in the aerospace and oil & gas industries. Pulsed thermography, a subset of IR thermography is one of the active thermography techniques that uses flash lamps to thermally excite the specimen under observation. Thermal measurements can be taken in the reflection, or the transmission mode based on the positioning of the IR Camera and the flash lamps with respect to the specimen. Currently, estimating the defect depth using IR thermography remains a challenge as the reflection mode cannot accurately characterise defects that are deeper than 3mm. A major advantage of the throughtransmission technique lies in its ability to detect defects that are deeper than the 3mm depth with higher levels of precision and accuracy. This makes through-transmission a suitable candidate for measuring defect depths using IR thermography. However, unlike the reflection mode, through-transmission has a limited number of image post-processing algorithms for defect detection and characterisation. This paper presents the state-of-the-art in the development of through-transmission thermography together with the technique’s know-how and limitations currently available in the scientific committee.