Publications
183 results found
Ab Razak N, Davies CM, Nikbin KM, 2016, Creep-fatigue crack growth behaviour of P91 steels, 21st European Conference on Fracture (ECF), Publisher: ELSEVIER SCIENCE BV, Pages: 855-862, ISSN: 2452-3216
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- Citations: 9
Rocchini M, Davies CM, Dean DW, et al., 2016, Fatigue and Fracture Resistance of 316H Stainless Steel With Prior Creep Damage, 21st European Conference on Fracture (ECF), Publisher: ELSEVIER SCIENCE BV, Pages: 879-886, ISSN: 2452-3216
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- Citations: 3
Béreš M, Abreu HFG, Santos LPM, et al., 2015, Effect of variant transformations in fusion zones of gas metal arc welds, Science and Technology of Welding and Joining, Vol: 20, Pages: 353-360, ISSN: 1362-1718
The macro- and microtextures of gas metal arc welds fabricated using both conventional ferritic and low transformation temperature (LTT) filler metals were examined. Both welds were largely composed of acicular ferrite. The weld textures were found to be distinct, which is observed to be due to variant selection during the austenite to ferrite transformation. In situ electron backscatter diffraction performed during thermal cycling of the LTT fusion zone into the austenite phase field confirmed that these transformations satisfy the expected crystallographic relationships. Implications for welding consumable design and finite element process modelling are drawn.
Kim N-H, Kim Y-J, Dean DW, et al., 2015, Elastic and Inelastic Responses of <i>C</i>(<i>T</i>) Specimens With Discontinuous Cracks, JOURNAL OF PRESSURE VESSEL TECHNOLOGY-TRANSACTIONS OF THE ASME, Vol: 137, ISSN: 0094-9930
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- Citations: 1
Tarnowski KM, Davies CM, Dean DW, et al., 2015, The influence of plasticity on crack length measurements using the potential drop technique, Pages: 73-96, ISSN: 0066-0558
The potential drop (PD) technique is one of the most common methods for determining crack growth; however, other factors can also change the resistance of the specimen, which may erroneously be interpreted as crack extension. In tough, ductile materials, plastic strain can cause a significant change in PD. This paper presents an experimental investigation which quantifies the apparent crack extension due to strain prior to the onset of physical crack growth and considers ways to mitigate it. Compact tension, C(T), and single edge notch tension, SEN(T), specimen geometries are considered with a range of crack lengths. The influence of probe location is also considered. The results identify apparent crack extensions of up to 1.0 mm in the absence of any physical crack extension. This can be reduced through careful selection of probe locations. Appropriate locations are suggested for the geometries considered. It is also shown that high constraint geometry can significantly reduce the influence of plasticity on PD.
Davies CM, Ahn J, Tsunori M, et al., 2015, The Influence of Pre-existing Deformation on GMA Welding Distortion in Thin Steel Plates, JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE, Vol: 24, Pages: 261-273, ISSN: 1059-9495
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- Citations: 8
Corcoran J, Davies CM, Nagy PB, et al., 2015, Potential Drop Strain Measurement for Creep Monitoring, 41st Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: AMER INST PHYSICS, Pages: 917-925, ISSN: 0094-243X
Tarnowski KM, Davies CM, Nikbin KM, et al., 2015, THE INFLUENCE OF CREEP STRAIN ON CRACK LENGTH MEASUREMENTS USING THE POTENTIAL DROP, ASME Pressure Vessels and Piping Conference, PVP-2015, Publisher: AMER SOC MECHANICAL ENGINEERS
Kapadia P, Davies CM, Dean DW, et al., 2015, CREEP CRACK GROWTH TESTING UNDER SECONDARY AND COMBINED LOADING, ASME Pressure Vessels and Piping Conference, PVP-2015, Publisher: AMER SOC MECHANICAL ENGINEERS
Shi Z, Lam ACL, Yang H, et al., 2014, Creep-age forming AA2219 plates with different stiffener designs and pre-form age conditions: Experimental and finite element studies, Journal of Materials Processing Technology, Vol: 219, Pages: 155-163, ISSN: 1873-4774
Creep-age forming (CAF) is one of the relatively new forming techniques that has been proven viable for the production of extra-large integral airframe structures. However, experimental studies on forming stiffened structures under creep-ageing conditions remain scarce. In this work, 200 mm × 48 mm integrally stiffened plates of aluminium alloy 2219 have been formed on an end clamp device that has a bending radius of 156 mm and creep-aged at 175 °C for 18 h. Three different stiffener designs, namely the beam stiffened, waffle and isogrid plates, are tested alongside the flat plates. Utilisation of PTFE pocket fillers and intermediate sheets to reinforce and protect stiffeners during forming operation is found effective as demonstrated by the defect-free formed parts with smooth curvature. Springback of the plates ranged from 12.2 to 15.7% in the experimental studies for different stiffener designs. Using the CAF material constants determined for this alloy, corresponding finite element models have been developed and experimentally validated using the measured profiles of the creep-age formed plates. Up to 6.3% difference in springback is observed when forming workpieces with different pre-form age condition alone.
Mehmanparast A, Davies CM, Dean DW, et al., 2014, Plastic pre-compression and creep damage effects on the fracture toughness behaviour of Type 316H stainless steel, ENGINEERING FRACTURE MECHANICS, Vol: 131, Pages: 26-37, ISSN: 0013-7944
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- Citations: 11
Zhou H, Biglari F, Davies CM, et al., 2014, Evaluation of fracture mechanics parameters for a range of weldment geometries with different mismatch ratios, ENGINEERING FRACTURE MECHANICS, Vol: 124, Pages: 30-51, ISSN: 0013-7944
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- Citations: 9
Mehmanparast A, Davies CM, Webster GA, et al., 2014, Creep crack growth rate predictions in 316H steel using stress dependent creep ductility, Materials at High Temperatures, Vol: 31, Pages: 84-94, ISSN: 0960-3409
Short and long term trends in creep crack growth (CCG) rate data over test times of 500–30 000 h are available for Austenitic Type 316H stainless steel at 550°C using compact tension, C(T), specimens. The relationship between CCG rate and its dependence on creep ductility, strain rate and plastic strain levels has been examined. Uniaxial creep data from a number of batches of 316H stainless steel, over the temperature range 550–750°C, have been collected and analysed. Power-law correlations have been determined between the creep ductility, creep rupture times and average creep strain rate data with stress σ normalised by flow stress σ0·2 over the range 0·2<σ/σ0·2<3 for uniaxial creep tests times between 100 and 100 000 h. Creep ductility exhibits upper shelf and lower shelf values which are joined by a stress dependent transition region. The creep strain rate and creep rupture exponents have been correlated with stress using a two-stage power-law fit over the stress range 0·2<σ/σ0·2<3 for temperatures between 550 and 750°C, where it is known that power-law creep dominates. For temperature and stress ranges where no data are currently available, the data trend lines have been extrapolated to provide predictions over the full stress range. A stress dependent creep ductility and strain rate model has been implemented in a ductility exhaustion constraint based damage model using finite element (FE) analysis to predict CCG rates in 316H stainless steel at 550°C. The predicted CCG results are compared to analytical constant creep ductility CCG models (termed NSW models), assuming both plane stress and plane strain conditions, and validated against long and short term CCG test data at 550°C. Good agreement has been found between the FE predicted CCG trends and the available experimental data over a wide stress range although it has been shown tha
Mehmanparast A, Davies CM, Nikbin KM, 2014, Quantification and Prediction of Residual Stresses in Creep Crack Growth Specimens, Materials Science Forum, Vol: 777, Pages: 25-30
Politis NJ, Politis DJ, Davies CM, et al., 2014, An experimental and numerical investigation into forming force reduction in precision gear forging, Pages: 165-173, ISSN: 1013-9826
A significant factor in the cost of industrial machinery for precision forging is the maximum load required to fully forge the final shape of components. Typically in a precision forging process, the required load increases greatly towards the end of the stroke. This study focuses on reducing the final sharp increase in load encountered in a typical closed die forging setup. A technique of reducing the peak load in the forging of gears is proposed, named the Peripheral Relief (PR) method. A gear forging tool set has been designed and manufactured. A number of experimental trials have been performed using model materials to investigate the force reduction technique. An efficient and simplified FE model has been developed to evaluate the effects of the PR method. The experimental load characteristics are compared to the simulated results. The method has been found, both numerically and experimentally, to significantly reduce the peak load encountered at the end of the forging stroke compared to current closed die forging techniques.
Kapadia P, Zhou H, Davies CM, et al., 2014, Simulating Residual Stresses using a Modified Wedge-Loaded Compact Tension Specimen, ASME Pressure Vessels and Piping Conference (PVP-2013), Publisher: AMER SOC MECHANICAL ENGINEERS
Mehmanparast A, Davies CM, Nikbin KM, et al., 2014, CREEP CRACK GROWTH PREDICTIONS IN 316H STEEL OVER A WIDE RANGE OF STRESSES AND TEMPERATURES, ASME 2014 Pressure Vessels and Piping Conference (PVP-2014), Publisher: AMER SOC MECHANICAL ENGINEERS
Kapadia P, Davies CM, Pirling T, et al., 2014, Neutron Diffraction Residual Stress Measurements in Electron Beam Welded Compact Tension Specimens, MECHANICAL STRESS EVALUATION BY NEUTRONS AND SYNCHROTRON RADIATION VII, Vol: 777, Pages: 99-+, ISSN: 0255-5476
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- Citations: 1
Yang H, Davies CM, Hooper P, et al., 2014, A NOVEL IMAGE PROCESSING METHOD FOR ARCMAC POINT TO POINT OPTICAL STRAIN MEASUREMENT, ASME Pressure Vessels and Piping Conference (PVP-2013), Publisher: AMER SOC MECHANICAL ENGINEERS
Tarnowski KM, Davies CM, Webster GA, et al., 2014, PREDICTIONS OF CREEP CRACK INITIATION PERIODS IN PRE-COMPRESSED 316H STAINLESS STEEL, ASME Pressure Vessels and Piping Conference (PVP-2013), Publisher: AMER SOC MECHANICAL ENGINEERS
Narayanan A, Davies CM, Mahmoud YK, 2014, USE OF THE ALTERNATING CURRENT POTENTIAL DROP (ACPD) TECHNIQUE TO MONITOR CREEP BEHAVIOUR OF AUSTENITIC STEELS, ASME Pressure Vessels and Piping Conference (PVP-2013), Publisher: AMER SOC MECHANICAL ENGINEERS
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- Citations: 1
Corcoran J, Davies C, Nagy P, et al., 2014, POTENTIAL DROP STRAIN SENSOR FOR CREEP MONITORING, ASME 2014 Pressure Vessels and Piping Conference (PVP-2014), Publisher: AMER SOC MECHANICAL ENGINEERS
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- Citations: 1
Zhou H, Biglari F, Davies CM, et al., 2014, SIMULATING RESIDUAL STRESS PROFILES OF WELDS WITH RE-HEAT CRACKING IN AN EX-SERVICED AISI 316H WELD HEADER, PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE - 2013, VOL 6A: MATERIALS AND FABRICATION
Davies CM, Kasahara N, Nikbin K, et al., 2014, INTRODUCTION G, PROCEEDINGS OF THE ASME PRESSURE VESSELS AND PIPING CONFERENCE - 2013, VOL 1A: CODES AND STANDARDS
Kim NH, Kim YJ, Davies CM, et al., 2013, The Effect of Discontinuous Crack in Creep Crack Growth Tests, ASME Pressure Vessels and Piping Division Conference, AMER SOC MECHANICAL ENGINEERS
Mehmanparast A, Davies CM, Dean DW, et al., 2013, The Influence of Inelastic Damage on Tensile Deformation and Creep Crack Growth Behaviour of Type 316H Stainless Steel, ASME Pressure Vessels and Piping Division Conference, AMER SOC MECHANICAL ENGINEERS
Zhou H, Mehmanparast A, Davies C M, et al., 2013, Evaluation of fracture mechanics parameters for bimaterial compact tension specimens, Materials Research Innovations, Vol: 17, Pages: 318-322, ISSN: 1432-8917
The elastic‐plastic fracture mechanics parameter J and its analogous creep fracture parameter C* are widely used to measure the fracture resistance of a material. The non-linear component of the J and C* parameters can be evaluated experimentally using the η factor. For weldments, the η factor is dependent on the relative properties of the base (parent) and weld materials, particularly the mismatch in their yield strengths. In this work, the η factor has been evaluated using non-linear finite element analyses in a standard compact tension C(T) specimen for a power law material. A range of mismatches in base/weld material properties have been considered. A through thickness strip of weld material, of height 2h, has been modelled, which was positioned at the mid height of the specimen. The η factor has been evaluated for a range of crack lengths and power law hardening exponents under both plane stress and plane strain conditions and the results compared with literature where available. For a given crack length and weld width, the η solutions of the undermatched and overmatched conditions examined show a maximum variation of 12% from the mean value. A relationship has been proposed with respect to crack length for the C(T) specimen to describe the decrease in the η factor with an increase in mismatch ratio.
Mehmanparast A, Davies CM, Dean DW, et al., 2013, The influence of pre-compression on the creep deformation and failure behaviour of Type 316H stainless steel, Engineering Fracture Mechanics, Vol: 110, Pages: 52-67
Mehmanparast A, Davies CM, Dean DW, et al., 2013, Material pre-conditioning effects on the creep behaviour of 316H stainless steel, International Journal of Pressure Vessels and Piping, Vol: 108-109, Pages: 88-93, ISSN: 0308-0161
Yang H, Davies CM, Lin J, et al., 2013, Prediction and assessment of springback in typical creep age forming tools, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART B-JOURNAL OF ENGINEERING MANUFACTURE, Vol: 227, Pages: 1340-1348, ISSN: 0954-4054
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- Citations: 3
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