Repositori Digital KPT Kementerian Pengajian Tinggi
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WAHDAT AL-ADYAN MENURUT HAMZAH FANSURI
No full textDalam menanggapi kepelbagaian agama, tokoh-tokoh tasawuf ialah satu-satunya kelompok dalam dan luar kalangan umat Islam yang menekuni secara mapan menerusi gagasan istimewa wahdat al-adyan atau kesatuan antara agama yang wajar
diketengahkan sebagai pendekatan tersendiri dalam pengkajian agama. Meskipun gagasan ini menimbulkan perselisihan kalangan sarjana, ia telah mendorong pewacanaan keberagaman agama pada masa kini sekaligus menarik perhatian masyarakat khususnya di Alarn Melayu. Gagasan unik ini berupaya menjadi rumus manjur dalam menangani pertelingkahan agama, justeru berdaya untuk menyubur
ketenteraman hidup dan kemesraan bergaul dalam kemajmukan. Shaykh Hamzah Fansuri yang hidup di Acheh sekitar abad ke-15 dan 16 Masihi ialah sosok paling cocok
bagi mewakili kearifan tempatan dalam cetusan pengujarannya. Justeru, kajian ini dilakukan dengan mencerakinkan kandungan karya-karyanya bagi meneliti wahdat al-adyan menurut Hamzah Fansuri dari sudut pandangan, asas, dan pendekatan dalam
menghadapi kesan pertentangannya dengan pegangan agama, di samping disokong dengan analisis konsep, sejarah, retorik, dan perbandingan. Penelitian ini menemukan bahawa Hamzah Fansuri menggagaskan dua sudut pandang meliputi kesatuan dan kepelbagaian agama. Kesatuan tersebut merangkumi makrifat bahawa Allah ialah Pencipta serta Yang Disembah oleh semua agarna dan Allah ialah Tuhan semua agama. Kepelbagaian pula mencangkumi hakikat bahawa kepelbagaian agama ialah suatu fitrah dan suatu kesempumaan. Manakala asas penggagasan ini ialah tauhid yang melingkupi keesaan Allah sebagai Ilah yakni Yang Hanya Disembah serta Yang Sentiasa Bersama makhluk-Nya dan sebagai Rabb yakni Yang Maha Penentu serta Yang Maha Bijaksana terhadap makhluk-Nya. Pendekatan beliau dalam menghadapi pertentangan antara wahdat al-adyan dan pegangan agama mencakupi sudut akidah dan syariat. Kewaspadaan terhadap ittihad dan hulul memenuhi perbincangan akidah. Sementara ikutan terhadap Sunnah Nabi Muhammad SAW dan keteguhan terhadap ajaran Islam menempati perbahasan syariat. Kajian ini menyumbang ke arah pemahaman lebih mendalam mengenai wahdat al-adyan yang dapat dijadikan kaedah khusus dalam perbandingan agama di samping mengangkat ketokohan Hamzah Fansuri dalam bidang ini sekaligus merintis penerokaan lebih jauh mengenainya
ASSESSING COMPETENCY NEEDS AMONG SOCIAL WORK EDUCATORS IN MALAYSIAN PUBLIC UNIVERSITIES
No full textSocial work educators’ competency is pivotal in promoting professional social work practice. The performance of the students reflects the capability of social work educators in delivering knowledge through the learning sessions. The main aim of this study is to critically examine the competency needs in academics, skills, and training among social work educators in Malaysian public universities. The study attempts to get the insights on the current development of social work education in Malaysia, skills needed among social work educators and intervention strategies that could enhance competencies among social work educators. This study employs a qualitative approach in gathering data. A semistructured interview protocol is used in conducting in-depth interview among twenty social work educators in seven public higher institutions in gathering extensive information on the academic, skills and training. There were also three key informants interviewed to get a view on the current social work practice in Malaysia. The findings indicated that there are seven main themes and twenty-two sub-themes emerged in this study. Among the main themes are training and development, academic qualifications, skills, knowledge, individual factors, structural factors and training intervention
strategies. This study assured that hands-on practice is one of the ultimate competency skills need to be acquired by social work educators in teaching social work programmes or subjects. The findings confirmed that the critical competency deficit among social work educators is in the training and development area. Hence, the results are valuable and significant in proposing for training and development intervention strategies that would better enhance the competency standard of social work educators in Malaysian public universities
Fabrikasi Dan Pencirian Filem Nipis Au-Terfungsi Struktur-Nano Zink Oksida Untuk Penghasilan Gas Hidrogen Melalui Reaksi Pemisahan Air
No full textHidrogen berpotensi baik sebagai pembawa tenaga alternatif dan telah dikenalpasti sebagai suatu pembawa tenaga yang selamat dan bersih. Oleh yang demikian, penyelidikan terhadap penghasilan gas hidrogen khususnya daripada sumber boleh diperbaharu mencerminkan potensi yang kuat sebagai suatu calon tenaga masa hadapan. Seiring dengan perspektif ini, proses pemisahan air pacuan suria merupakan kunci utama bagi pembangunan lestari ekonomi gas hidrogen untuk sistem tenaga masa hadapan. Mengumpul dan menyimpan tenaga suria di dalam bentuk bahan api kimia (gas hidrogen) melalui fotosintesis buatan adalah tidak mustahil dengan pemisahan air fotoelektrokimia (PEC), di mana kaedah ini telah dikenalpasti sebagai suatu cara yang bersih dan mampan bagi penghasilan gas hidrogen. Di dalam kerja semasa, kami mengkaji kesan emas (Au) sebagai lapisan sentuhan-belakang bagi pemendapan nanorod zink oksida (ZnO) dan menggunakannya sebagai fotoanod untuk proses PEC dimana dalam masa yang sama menghasilkan gas hidrogen dan fotoarus melalui reaksi pemisahan air. Untuk penyediaan sampel, lapisan Au telah dimendapkan ke atas suatu substrat indium timah oksida (ITO) dengan teknik percikan magnetron dan seterusnya lapisan Au ini dijangka untuk bertindak sebagai landasan plasmonik bagi pemendapan nanorod ZnO melalui kaedah hidroterma tanpa perlu pembenihan. Bagi memahami perubahan morfologi dan liputan kepadatan nanorod ZnO, tempoh rawatan hidroterma dipelbagaikan di dalam julat 15 minit hingga 255 minit. Keputusan FESEM menunjukkan liputan kepadatan nanorod boleh dipelbagaikan dengan merubah masa pemanasan, di mana purata ketebalan nanorod telah jatuh di dalam julat 200 nm – 253 nm. Hasil pembelauan XRD menunjukkan kewujudan-bersama puncak belauan ITO, Au dan ZnO tanpa sebarang kehadiran puncak asing, yang mana menunjukkan sampel-tersedia sememangnya asli. Analisis spektroskopi UV-Vis pantulan resap (DRS) menyatakan nanokomposit Au/ZnO menunjukkan peningkatan dalam serapan cahaya tampak di samping cahaya ultraungu (UV) berbanding dengan nanorod ZnO asli yang merupakan UV-aktif. Dari segi prestasi aktiviti fotoelektrokimia, hasil analisis voltammetri berkitar (LSV) menunjukkan bahawa sampel-135 mempunyai ketumpatan fotoarus yang paling tinggi, iaitu tiga kali lebih tinggi berbanding ZnO asli. Demikian juga dengan analisis kronoamperometri di mana keputusan menunjukkan sampel-135 memiliki nilai purata ketumpatan fotoarus yang paling tinggi iaitu 0.1349 mA cm-2. Seterusnya, plot Nyquist mendedahkan bahawa sampel yang sama mempunyai kadar pemindahan cas yang tinggi dengan nilai diameter separa bulatan yang paling kecil berbanding ZnO asli. Dari segi penghasilan gas hidrogen fotoelektrokimia, sampel-135 mampu untuk menghasilkan kuantiti gas hidrogen sebanyak 21.91 μL, iaitu tujuh kali ganda lebih banyak berbanding ZnO asli. Peningkatan prestasi fotoelektrokimia bagi sampel tersedia Au/ZnO boleh dikaitkan dengan nanopartikel emas, yang mana menunjukkan sifat resonan permukaan plasmoniknya adalah diperlukan bagi menambah baik penyerapan cahaya dan pemisahan cas. Kajian ini boleh dijadikan sebagai model pembelajaran fabrikasi fotoelektrod yang dinilai tambah sebagai keperluan pembangunan mampan
LONG TERM OUTCOME OF IMMUNOGLOBULIN A (IgA) NEPHROPATHY: A SINGLE CENTRE EXPERIENCE
No full textIntroduction
IgA Nephropathy (IgA N) has heterogenous presentation and progression to End Stage Renal Disease (ESRD) contributed by demographics, ethnicity, and treatment regimen. We investigated long term survival of IgA N patients in our centre and factors affecting it.
Methods
All biopsy proven IgA N patients with > 1year follow-up excluded patients with diabetes mellitus at diagnosis and secondary IgA N. Medical records were reviewed for demographics, presentation, blood pressure, 24-hour urine protein, serum creatinine, renal biopsy and treatment received. Primary outcome was defined as combined event of 50% estimated glomerular filtration rate (eGFR) reduction or ESRD.
Results
We included 130 (74 females; 56 male) patients with mean age 38.0 ± 14.0 years and median eGFR of 75.2 (IQR 49.3-101.4) ml/min/1.73m2. Eighty-four (64.6%) were hypertensive at presentation, 35 (26.9%) with nephrotic syndrome and 57 (43.8%) with nephrotic range proteinuria (NRP). Median follow-up was 7.5 (IQR 4.0-13.0) years with 18 (13.8%) developed ESRD and 34 (26.2%) reached primary outcome. Annual eGFR decline was -2.1 (IQR -5.3 to -0.1) ml/min/1.73m2/year, with median survival of 20 years. Renal survival at 10, 20 and 30 years was 80%, 53% and 25%, while survival against ESRD was 87%, 73% and 65% respectively. In the univariate analysis; time-average proteinuria (HR = 2.41, 95% CI 1.80-3.30), eGFR at biopsy (HR = 2.35, 95% CI 1.03-5.32), hypertension (HR = 2.81, 95% CI 1.16-6.80), mean arterial pressure (HR = 1.02, 95% CI 1.01-1.03), tubular atrophy/interstitial fibrosis score (HR = 3.765, 95% CI 1.84-7.73), and cellular/ fibrocellular crescent score, (HR = 2.44, 95% CI 1.19 -5.00), were found to be significant while only time-average proteinuria (TA-proteinuria) remained significant predictor at multivariate analysis (HR = 2.23, 95% CI 1.57-3.16).
Conclusion
TA-proteinuria was the most important predictor in progression of IgA N in our cohort irrespective of degree of proteinuria at presentation
QUARTIC EL-GAMAL ENCRYPTION SCHEME BASED ON LUCAS SEQUENCE
No full textThis study focuses on developing a secure and efficient method of encryption and decryption of plaintext. The El-Gamal cryptosystem scheme based on the fourth and sixth order Lucas sequence, known as LUC(4,6)ELG, is developed. Then, LUC(4,6) is incorporated into ciphertexts calculation (C1;C2;C3 and C4) with the given encryption keys, e. C2 and C4 are calculated using the fourth order Lucas sequence, and C3 is calculated using the sixth order Lucas sequence. A similar method is used in the decryption process by the receiver to retrieve the original plaintext. This newly developed system underwent security analysis; four types of attacks, including GCD, Lenstra’s, Wiener’s, and garbage-man-in-the-middle (II) attacks, were implemented
to the existing cryptosystem (LUCELG and LUC(3)ELG) and to LUC(4,6)ELG. The findings show that LUC(4,6)ELG is harder to break when attacked by GCD and Lenstra’s attack. However, for Wiener’s and Garbage-man-in-the-middle (II) attacks,
the security level is compromised. Efficiency analysis shows that LUC(4,6)ELG is more efficient than the methods. However, computationally, LUCELG and LUC(3)ELG are more efficient than LUC(4,6)ELG
PENCIRIAN RNA KECIL TERPELIHARA BAKTERIA DALAM Burkholderia pseudomallei
No full textTerdapat banyak RNA kecil (sRNA) yang sangat terpelihara di kalangan spesis bakteria. sRNA ini terlibat dalam pelbagai peranan dalam sel tetapi masih banyak lagi sRNA yang tidak dicirikan dan tidak dikaitkan fungsi. Andaian dibuat bahawa gen sRNA yang sangat terpelihara akan mengekodkan fungsi penting yang merentasi pelbagai takson dan berkemungkinan adalah keperluan bagi organisma yang memilikinya. Dalam kajian ini, jujukan gen sRNA putatif yang terpelihara merentasi
pelbagai takson dikenal pasti. Gen-gen ini diperincikan secara perkomputeran dan dirujuk-balas terhadap dataset sRNA Burkholderia pseudomallei yang merupakan bakteria tanah tetapi juga agen penyakit parah, melioidosis. Lapan gen sRNA
dijumpai terpelihara pada pelbagai tahap taksonomi dengan tiga daripadanya belum dikaitkan dengan sebarang fungsi. Ketiga-tiga sRNA ini mempunyai homolog diluar order Burkholderiales. Dua daripada sRNA tidak diketahui fungsi ini, 1_sRNA_0575 dan 1_sRNA_0826, terdapat pada kedudukan gen-gen terlibat dalam pengangkutan sel dan gen pengapitnya mengekodkan protein membran luar A (ompA) iaitu homolog gen bagi 1_1740 dan 1_2453 masing-masing. Satu lagi sRNA yang tidak diketahui fungsi adalah 1_sRNA_0952 yang gen pengapitnya mengekodkan protein induksi osmotik (osmC), 1_2830 yang terlibat dalam proses penyahtoksikan bakteria. Ketiga-tiga sRNA terpelihara ekspres secara signifikan pada rawatan kepekatan spesifik
melebihi nilai ambang tetrasiklin atau natrium klorida, dan mempunyai corak pengekspresan yang sama bagi gen pengapit masing-masing. Seterusnya, penyuntingan gen menggunakan kaedah CRISPRi yang menyasarkan sRNA secara berasingan menunjukkan penindasan sRNA dalam rawatan termasuk gen pengapitnya, telah menunjukkan mekanisme pengawalaturan positif secara cis. Malahan, susunan gen dan jujukan hadapan mRNA mencadangkan mekanisme anti antisense antara sRNA dan gen pengapitnya. Dalam rawatan tetrasiklin (0.49 dan 0.98 μg/mL), peningkatan pengekspresan 1_sRNA_0575 di bawah rawatan mencadangkan pembukaan tapak pengikatan ribosom (RBS) dan pengaktifkan gen 1_1740. Manakala jujukan hadapan 1_2453 dan 1_2830 mengandungi kawasan kaya AU yang
merupakan tapak lekat pembelahan RNase E. Pengekspresan sRNA mencadangkan pelekatannya pada jujukan hadapan, mengaruh pembelahan kepada pembentukan mRNA baharu yang stabil dan RBS yang boleh capai. Asai ke atas strain ketukan bawah mendapati 1_sRNA_0575 dan 1_sRNA_0826 mensasarkan gen pengapitnya bertindak secara khusus, tidak menunjukkan perubahan fenotip tetapi mempengaruhi
perubahan genotip dalam analisis pengekspresan gen. Bagi 1_sRNA_0952 yang mengawalatur 1_2830 respon dilihat terhadap tekanan osmotik dan oksidatif secara genotip, impak fenotip hanya dilihat dalam rawatan natrium klorida sahaja. Kajian ini memberi maklumat baharu berkenaan gen-gen yang terbabit dalam laluan sRNA terpelihara dan pengenalpastian sasaran yang dikawalatur. Kajian ini juga
mencadangkan maklumat tambahan bagi mekanisme interaksi antara sRNA-mRNA. Berdasarkan penemuan eksperimen, kami ingin mengandaikan 1_sRNA_0575 dan
1_sRNA_0826 mempengaruhi ompA dalam kerintangan bakteria tetapi kekurangan bukti fenotip. Sementara, bagi 1_sRNA_0952 yang mensasarkan osmC, bukti menunjukkan kemungkinan tinggi penglibatannya dalam pengawalaturan
keseimbangan sistem osmotik dalam bakteria
HEALTHCARE UTILISATION DEVELOPMENT AND EVALUATION OF PHYSIOTHERAPEUTIC SELF-MANAGEMENT EDUCATION PROGRAMME IN OLDER ADULTS WITH KNEE OSTEOATHRITIS
No full textSelf-management education programme (SMEP) is recommended as one of the management strategies for knee osteoarthritis (OA) as it assists individuals to be involved in their health management. While several studies have shown the benefits of SMEP, there continue to be knowledge gaps in terms of strategies to implement SMEP in older adults with knee OA. Therefore, through a multi-phase approach, the objectives of this study were to determine knee OA healthcare utilisation, explore knee OA knowledge and educational needs, develop and determine the outcomes of Physiotherapeutic SMEP (PSMEP) for this cohort. In phase I which was a retrospective study, 1073 cases from the Malaysian Elders Longitudinal Research (MELoR) study were analysed. In phase H which was a qualitative study, focus group discussions (FGDs) were conducted among 16 older adults with knee OA. In phase
III, PSMEP was developed and pre- and post- evaluation was conducted among 30 older adults with knee OA. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and physical performances were evaluated after six weeks from the baseline.
The results showed that the healthcare utilisation among older adults with knee OA was significantly higher compared to those without knee OA (p < 0.01). Being married and have an income were found to be associated with outpatient care services (OR:11.136, 95% CI: 1.893 - 65.517, p < 0.01) and medication (OR:10.439, 95% CI: 1.187 — 91.812, p < 0.05) respectively while women were less likely to utilise inpatient care services (OR: 0.126, 95% CI: 0.021- 0.746, p < 0.05). Knowledge about knee OA varied in older adults with knee OA and the information required for PSMEP was warranted. The outcomes of the PSMEP showed that there were significant differences in sit to stand (p < 0.05), time up and go (p < 0.001) and two-minute walk (p < 0.001) tests when compared from the baseline. These results suggest that there were improvements in lower limb muscle strength, functional mobility and cardiovascular endurance in older adults with knee OA after PSMEP. In conclusion, educational intervention is crucial to enhance self-management skills and a tailored PSMEP is feasible and beneficial to support older adults with knee OA
RESISTANCE TRAINING, INSULIN SENSITIVITY & METABOLIC HEALTH
No full textSkeletal muscle is the largest organ in the human body, comprising 40%-50% of total body weight and more than 600 skeletal muscles in a human body performing common functions such as body movements, maintaining posture, storing protein and glycogen and generating heat. Approximately 0.8% skeletal muscle mass declines per year a process known as sarcopenia. On top of that, ageing also results in a decrease in muscle strength, at a rate of approximately 1-3% per year (Keller & Engelhardt, 2013). Skeletal muscle is the major organ responsible for glucose uptake under insulin stimulated conditions, accounting for
~80% of total glucose disposal and low muscle strength and mass likely contribute to metabolic dysregulation seen in Type 2 diabetes. Research has shown that resistance exercise
training can increase strength, muscle size, fat-free mass, connective tissue thickness, decrease body fat, reduce blood pressure and improve insulin sensitivity and VO2max (Croymans et al., 2013; Ozaki et al., 2013; Abdul & Defronzo, 2010). In order to monitor efficacy of such resistance training interventions it is important to be able to accurately quantify skeletal muscle mass and several methods exist for this purpose, although many require expensive equipment making them not always possible to use. The aim of chapter 2 was to investigate the repeatability and validity of a relatively cheap and portable A-mode ultrasound device. This chapter has found that A mode ultrasound is a repeatable measure of muscle thickness (CV of 4.6%) and that both A and B mode ultrasound provide valid measures of muscle volume, as compared to the gold standard MRI (r=0.96). Following this, the aim of chapter 3 was to determine if this A-mode ultrasound device is able to detect changes in muscle thickness in response to resistance exercise training and to
determine its validity. Findings in this Chapter 3 have shown that the A-mode ultrasound can detect increases in muscle thickness of 6.2 ± 5.4%, alongside a 26 ± 7.3% increase in
1RM after 8 weeks of resistance exercise training. However, it was also shown that both A and B mode measures of ultrasound muscle thickness were not valid measures of the
resistance exercise induced changes in muscle volume (r=0.30 A-mode & r=0.04 B-mode) Resistance exercise is known as the most efficacious method to increase muscle strength and mass. It has been demonstrated recently that if exercise is performed to volitional failure then gains in muscle mass, and to a lesser extent strength, are similar regardless of the load at which exercise is performed. The aims of chapter 4, were to investigate the effects of 6 weeks of resistance exercise training, comprised of 1 set of each exercise to voluntary failure, on insulin sensitivity and the time-course of adaptations in muscle strength/mass, in
overweight men. Results of this chapter have demonstrated that six weeks of resistance exercise, volitional failure of nine exercises – taking 15-20 min per session – undertaken
three times per week resulted in a 16% improvement in insulin sensitivity (61.6 ± 18.0 to 71.3 ± 22.9 mg.l2.mmol-2.mU-1.min-1 after the intervention (P<0.05) in healthy overweight
men and increases in muscle strength, size and RTD (rate torque development) 50 and 100 were also observed.
Several studies have demonstrated that people from South Asia are up to 4-6 times more likely to develop type 2 diabetes than White Europeans. Furthermore, in a recent study from the UK Biobank, grip strength in South-Asian men and women was 5–6 kg lower than in the other ethnic groups and a greater contributor to diabetes prevalence. As resistance exercise is the most effective intervention for increasing muscle mass, strength, and can improve
insulin sensitivity, the aim of the Chapter 5 was to compare the effect of resistance exercise on muscle and metabolic health between South Asians and White Europeans. This chapter has shown that there were no differences in the effect of 12 weeks of resistance exercise training on the majority of the muscle and metabolic outcomes measured, however the increase muscle thickness, 1.2 (95% CI 0.8 to 1.7) mm in South Asians and 2.3 (95%CI 1.8 to 2.9) mm in White Europeans and decrease in systolic blood pressure, 5.1 (95%CI:-7.5 to -2.7) mmHg in White Europeans and a 0.7 (95%CI:-2.4 to 1.0) mmHg in South Asians were attenuated in South Asians. There was also a trend for an attenuated effect of resistance exercise training on VO2max, decrease of 0.7 (95%CI -2.0 to 0.6) ml.kg.min-1 in South Asians. In summary, this thesis has demonstrated that whilst ultrasound measure of muscle thickness is valid at a single time point, this is not the case when evaluating changes with resistance exercise training. Following this we have demonstrated that resistance exercise training, involving a single set of exercise to muscle failure, is effective in inducing short-term improvements in muscle size and strength and also insulin sensitivity in White Europeans, with broadly similar findings in South Asians
FACTORS INFLUENCING CHANGE READINESS: THE MODERATING ROLE OF STAGES OF CHANGE
No full textIn today’s competitive market and challenging business environment, organisational abilities to efficiently respond and manage both external and internal changes are the keys to survival. However, the failure rate of change implementation
and management has been found to be extremely high at 70% and this has become a major concern to both organisational experts and researchers. In relation to this, the present study sought to examine the effect of communication, workgroup and
organisational factors in influencing change readiness. Kurt Lewin’s Stages of Change Model was utilized as the main framework. Three stages of change which were derived from the framework, namely, unfreezing, moving and refreezing, were tested as the moderating variable of the study. Preliminary investigation using in-depth interview was first conducted to gain deeper understanding and to confirm the stages
of change experienced by organisations. A cross-sectional research design was adopted and self-administered survey questionnaires were distributed to collect data from 400 employees of three corporate organisations identified earlier during the preliminary investigation. Data analysis involved two stages: (1) descriptive analysis using SPSS, and (2) hypothesis testing using partial least squares structural equation
modelling (PLS-SEM). The findings showed different stages of change were experienced by the employees of the selected organisations. Results indicated that out of eight hypotheses tested, four hypotheses (i.e., the direct effects of frequency of
communication, programmatic communication approach, affective commitment and normative commitment in influencing change readiness) were supported. However, quality of information, change agent characteristics, workgroup climate and collective efficacy did not show significant effects on change readiness. Twenty-four hypotheses were further tested to examine the moderating effect of stages of change on the
relationship between the independent variables and the dependent variable (i.e., change readiness). Results indicated that five hypotheses were supported. Unfreezing stage of change was found to moderate the relationship between collective efficacy, affective commitment and nonnative commitment on change readiness. Meanwhile, moving stage of change was found to have moderately affected the influence of
collective efficacy on change readiness. In addition, refreezing stage was found to moderate the relationship of frequency of communication on change readiness. The findings of the study have extended the Change Readiness framework by integrating
Kurt Lewin’s Model of Stages of Change as the moderating variable of the study and incorporating more factors into the framework. The results of the present study would be useful in assisting employers in designing effective change management strategies and programs in organisations which could be well-received by employees in the organisation
OPTIMIZATION OF CUSTOMIZED TWIST DRILL GEOMETRY FOR SINGLE-SHOT DRILLING OF COMPOSITE-METAL STACK
No full textDrilling a composite-metal stack in a single shot is a challenging process, as the drill bit needs to pass through two different materials in a short time. Currently, twist drill bit is widely used in the field of drilling due to its economical state. However, the existing twist drill bits exhibits quick wear and tear upon drilling stacked up plates. This leads to frequent drill bit replacement and thus incurring additional costs to the company. This issue is further exacerbated by the lack of knowledge on suitable drilling speed and feed rate during the drilling of stacked up materials. This study focused specifically on the optimization of
customized twist drill bit geometry' for the production of good holes quality during a single shot drilling process of composite-metal stack materials. First of all, an initial study was performed to identify which geometries of the drill bit and drilling parameters influence the hole quality the most. This step involved drilling a stacked-up plate at different feed rates of
0.05 min/rev to 0.1 mm/rev and spindle speeds of 1500 rev/min to 2600 rev/min using customized twist drill bit of different geometries. The geometries of the drill bit were varied
based on its helix angle, primary clearance angle, point angle, and chisel edge angle. The performance of the twist drill bit was assessed based on the drilling thrust force, hole surface roughness, burr formation and hole integrity (delamination, diameter error and hole circularity). The results were subsequently evaluated using the analysis of variance (ANOVA)
to determine the influence of the drill geometiy and drilling parameters on the maximum thrust force and the quality of the drilled hole. The results from initial study indicated that the any
interaction of drill geometry parameters with the 2600 rev/min and 0.05 mm/rev produced a good drilled hole quality. For the drill geometiy parameter, the interaction with drilling at the
helix angle of 30° contributed to minimum drilling thrust force, hole surface roughness, burr formation and good hole integrity. For the point angle parameter, drilling with 130° was proven
to reduce the burr formation by 89%. Other parameters like primary clearance angle and chisel edge angle were further analysed in the extended study since both parameters have interaction with the other drilling parameters. Later on, an extended investigation was carried out to study the effect of drill geometry on thrust force and hole quality comprising of chisel edge angle, primary clearance angle, and point angle at helix angle of 30°, 2600 rev/min, and 0.05 mm/rev. Twenty different drill designs with varied chisel edge angle, primaiy clearance angle, and point angle were fabricated and tested on the drilling of stacked up materials. The range of point angle parameters was extended from 130° to 140° in order to observe the impact of hole integrity. From the extended study, the most significant parameter affecting the drilling thrust force and hole surface roughness is the primary clearance angle followed by the chisel edge angle. For burr formation, the most significant parameter is the chisel edge angle, followed by the point angle. Through statistical analysis, the selected optimum drill geometry angles that scored the highest desirability based on the helix angle of 30° and drilling at 2600 rev/min and 0.05 mm/rev were chisel edge angle of 45°, primary clearance angle of 6°, and point angle of 130°. The new optimum drill design was fabricated and followed by a set of validating experimental works that produced errors in range of 6.64% to 9.23% for maximum thrust force, hole surface roughness, and burr formation. This confirmed its validity. For the hole integrity,
the delamination factor for all trial was observed in range of 1.0038 and 1.0196 and the hole circularity achieved below 30 pm for all trials. The current study provides practical guidelines
for machinists in selecting the right geometry angles to achieve suitable design for customised twist drills which are not readily available from standard drill catalogue in the market