Wear mode map evaluation of induction hardened 4140 and carburised 8617H steels on 1040 steel

This study was undertaken to evaluate the likely effect on the wear rate of changing the pinion material in a rack and pinion steering box from carburised SAE-AISI grade 8617 H steel to induction hardened SAE-AISI grade 4140 steel. Accordingly, pin-on-disc unlubricated wear tests were conducted using carburised 8617 H pins and through hardened 4140 pins. The surface hardness of the pins was approximately 60 HRC for both materials. The discs were made of SAE-AISI grade 1040 steel through hardened to a hardness of 45 HRC. The tests were conducted using a load of 2.2 kg and a rotational speed of 60 rpm and also under a load of 28.5 kg and a speed of 99 rpm. The results showed that both the pins and the discs wore more rapidly when the tests were carried out with 4140 pins. The data was evaluated using a wear mode map developed by Lim, Ashby and Brunton. This indicated that the wear mode was mild delamination wear at the lower load and speed but severe oxidational wear for higher load and higher speed

A study wear behaviour of induction hardened 4140 and carburised 8617H steels on 1040 steel

This study was undertaken to evaluate the likely effect on the wear rate of changing the pinion material in a rack and pinion steering box from carburised SAE-AISI grade 8617 H steel to induction hardened SAE-AISI grade 4140 steel of the same hardness. Accordingly, pin on disc wear tests were conducted using carburised 8617 H pins and through hardened 4140 pins. The surface hardness of the pins was approximately 60 HRC for both materials. The discs were made of SAEAISI grade 1040 steel through hardened to a hardness of 45 HRC. The results showed that both the pins and the discs wore more rapidly when the tests were carried out with 4140 pins. The study indicates that the wear rate would be increased on both the rack and the pinion if the pinion material were changed from case hardened 8617 H to induction hardened 4140

Comparison of Experimental and Calculated Tensile Properties of Flax Fibres

The tensile properties of natural plant fibres are commonly determined by single fibre testing. The cross-sectional area used to determine the modulus and strength is usually obtained by measuring the fibre width and using this as the fibre diameter on the assumption that the fibres are circular in section. The assumption of circularity is reasonably true for synthetic fibres but is not correct for natural fibres, and this can lead to a substantial error when determining the tensile properties of the fibres. The incorporation of a fibre area correction factor, which takes into account the non-circularity of natural fibres, has been proposed by earlier workers, who used it successfully to predict the mechanical properties of jute fibre composites. The aim of the present study was to evaluate the wider applicability of this methodology by applying it to flax fibre composites. The work involved determination of the tensile properties of 113 flax technical fibres using an experimentally determined fibre area correction factor to account for the non-circularity of the fibres. The data were then compared with those obtained from back-calculation of the results obtained from longitudinal tensile testing of flax/vinyl ester unidirectional composites manufactured utilising identical fibres to those used in the single fibre tests. Account was taken of the effect of fibre length on strength. The experimentally determined fibre area correction factor was found to be 2.70. Taking this into account for the single fibre tests, the back-calculated modulus of the flax fibres was within 6% of that obtained from the single fibre tests, while the strength was within 7%

Effect of the addition of multi-walled carbon nanotubes on the thermomechanical properties of epoxy resin

The influence of multi-walled carbon nanotubes (MWCNTs) on thermosetting epoxy is examined using dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry (DSC). Specimens are prepared with loadings of 0.1 and 1 wt% MWCNTs which are dispersed in the resin using two different dispersion methods. While the storage modulus of the specimens is improved, both the glass transition temperature and the thermal stability are reduced by the addition of MWCNTs with both effects being greater for the higher MWCNT loading, for both dispersion systems. The DSC results additionally indicate that the level of residual unreacted epoxy increases progressively with the addition of the nanotubes. This finding is considered as confirmation that the MWCNTs obstruct crosslinking of the epoxy resin

Experimental protocol for stress corrosion cracking of rockbolts

A new laboratory facility designed and constructed at the University of New South Wales, aims to continue and offer a new approach to researching the phenomenon of the stress corrosion cracking. This new approach includes the use of full sized specimens, a specially designed frame, as well as a new loading regime, known as the Periodically Increasing Stress Test, to closely simulate the loading encountered by bolts in service. Coupled with a detailed water testing program to be undertaken at a number of partner sites, this new approach hopes to further increase understanding of stress corrosion cracking and its causes

A blended approach to collaborative learning: Can it make large group teaching more student-centred

Current educational thinking promotes a student-centred approach to teaching as more engaging and challenging for students, leading to improved learning outcomes. But what is ‘student-centred ’ learning, and how can it be achieved in a higher education setting with very large classes and content-rich courses? In a materials engineering course for 300 firstyear engineers, an online group project was introduced to add authenticity and collaborative activity into the course, and to improve student engagement. We explore the design, development and implementation of the project, and see if the intended outcomes were achieved

Effect of the addition of multi-walled carbon nanotubes on the thermomechanical properties of epoxy resin

The influence of multi‐walled carbon nanotubes (MWCNTs) on thermosetting epoxy is examined using dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry (DSC). Specimens are prepared with loadings of 0.1 and 1 wt% MWCNTs which are dispersed in the resin using two different dispersion methods. While the storage modulus of the specimens is improved, both the glass transition temperature and the thermal stability are reduced by the addition of MWCNTs with both effects being greater for the higher MWCNT loading, for both dispersion systems. The DSC results additionally indicate that the level of residual unreacted epoxy increases progressively with the addition of the nanotubes. This finding is considered as confirmation that the MWCNTs obstruct crosslinking of the epoxy resin