Georgia State Legislative Update: End of Session 2022

An update on relevant bills relevant to Georgia librarians that were passed in the 2022 Georgia legislative session

Experimental and numerical investigation of small punch creep test

The small punch creep testing (SPCT) technique has received much attention because it can provide information on the creep behaviour of materials with a very small specimen being tested. However, the nature of the test is complex and several aspects of the behaviour of the specimen, characterised by various non-linear concurrent processes, still need investigation. This thesis reports the findings of experimental investigations and numerical analyses of SPCT carried out with the aim of improving the understanding of various features which characterise the behaviour of the specimen and to develop a novel technique to correlate the SPCT experimental output with the corresponding uniaxial creep test data, which is also presented. The experimental programme consisted of SPCTs and pre-strained uniaxial creep tests, all performed at 600°C on the same batch of P91 steel. The pre-strained uniaxial creep tests have been used to evaluate the effects of large initial plasticity on the subsequent creep behaviour of P91 steel. For different stress levels, the results of the experiments have shown that creep was resisted for low pre-strain levels and enhanced for high pre-strains. The SPCT specimens have been investigated by use of scanning electron microscopy (SEM) to identify the effects of the punch load on the fracture surface of the failed specimens and the evolution of microstructural features in the material during the test. When the punch load was increased, the failure mechanism changed from creep-governed to plasticity-governed, as the presence of fresh dimples in the fracture surface increased. For the low-load tests, a macro crack was found to nucleate on the bottom surface of the specimen at approximately 20% of the failure life, and it subsequently propagated along the circumferential direction and through the thickness of the specimen. A modified creep constitutive model has been developed based on the results of the pre-strained uniaxial creep tests and it has been implemented in a FE model of a SPCT capable to take into account the effects of the large initial plasticity, generated by the load application, on the creep response of the SPCT specimen. A global creep resistance in the SPCT specimen, due to the combination of localised different effects in various regions of the sample, was observed when these effects were included. FE calculations have also been performed to investigate the effects of the eccentricity and the misalignment of the punch loading conditions on the punch minimum displacement rate (MDR) and on the time to failure. A correlation equation for these effects has also been reported. When the punch load was eccentric and misaligned, the MDR decreased and the time to rupture increased. Further numerical analyses have been carried out to evaluate the effects of the friction coefficient modelling procedure on the behaviour of the specimen. The results obtained using the classical Coulomb friction theory are compared with those obtained by a more modern friction formulation, which takes into account the dependency of the friction coefficient on the contact pressure. Finally, a nobel interpretation technique for SPCT data has been developed using the results of experimental tests and numerical analyses. The interpretation technique takes into account the effects of the initial, large plasticity on the behaviour of the SPCT specimen, in order to correlate the SPCT results with the corresponding uniaxial data. A significant improvement in the accuracy of the correlation for rupture SPCT data with the corresponding uniaxial test results has been obtained

A study on the evolution of the contact angle of small punch creep test of Ductile materials

The work discussed in the present paper reports a novel investigation of the applicability of Chakrabarty's theory, for membrane stretching of a circular blank over a rigid punch, to small punch creep test (SPCT). The Chakrabarty solution was compared with corresponding results obtained by numerical finite element (FE) analyses and experimental tests. The Liu and Murakami creep damage model was used in the FE analyses. The aim of the work is also to improve the understanding of the mechanism governing the deformation and the failure of the specimen and to verify the range of applicability of the CEN Code of Practice CWA 15627, which is based on Chakrabarty's theory. The effects of various parameters, such as the initial thickness of the specimen, the radius of the punch, the load magnitude, the friction coefficient and different plasticity constitutive models, on the variation of the contact angle, θ0, and the central displacement of the punch, Δ, were identified and correlated by fitting equations. The variation of θ0 with Δ, obtained from Chakrabarty's solution was compared with that obtained by FE analyses of the SPCT. When the initial thickness of the specimen increased and the radius of the punch decreased, the FE results, in terms of the variation of θ0 versus Δ, showed to differ from Chakrabarty's solution, therefore new ranges of applicability of the CEN Code of Practice CWA 15627 were determined

Experimental and numerical investigation of small punch creep test

The small punch creep testing (SPCT) technique has received much attention because it can provide information on the creep behaviour of materials with a very small specimen being tested. However, the nature of the test is complex and several aspects of the behaviour of the specimen, characterised by various non-linear concurrent processes, still need investigation. This thesis reports the findings of experimental investigations and numerical analyses of SPCT carried out with the aim of improving the understanding of various features which characterise the behaviour of the specimen and to develop a novel technique to correlate the SPCT experimental output with the corresponding uniaxial creep test data, which is also presented. The experimental programme consisted of SPCTs and pre-strained uniaxial creep tests, all performed at 600°C on the same batch of P91 steel. The pre-strained uniaxial creep tests have been used to evaluate the effects of large initial plasticity on the subsequent creep behaviour of P91 steel. For different stress levels, the results of the experiments have shown that creep was resisted for low pre-strain levels and enhanced for high pre-strains. The SPCT specimens have been investigated by use of scanning electron microscopy (SEM) to identify the effects of the punch load on the fracture surface of the failed specimens and the evolution of microstructural features in the material during the test. When the punch load was increased, the failure mechanism changed from creep-governed to plasticity-governed, as the presence of fresh dimples in the fracture surface increased. For the low-load tests, a macro crack was found to nucleate on the bottom surface of the specimen at approximately 20% of the failure life, and it subsequently propagated along the circumferential direction and through the thickness of the specimen. A modified creep constitutive model has been developed based on the results of the pre-strained uniaxial creep tests and it has been implemented in a FE model of a SPCT capable to take into account the effects of the large initial plasticity, generated by the load application, on the creep response of the SPCT specimen. A global creep resistance in the SPCT specimen, due to the combination of localised different effects in various regions of the sample, was observed when these effects were included. FE calculations have also been performed to investigate the effects of the eccentricity and the misalignment of the punch loading conditions on the punch minimum displacement rate (MDR) and on the time to failure. A correlation equation for these effects has also been reported. When the punch load was eccentric and misaligned, the MDR decreased and the time to rupture increased. Further numerical analyses have been carried out to evaluate the effects of the friction coefficient modelling procedure on the behaviour of the specimen. The results obtained using the classical Coulomb friction theory are compared with those obtained by a more modern friction formulation, which takes into account the dependency of the friction coefficient on the contact pressure. Finally, a nobel interpretation technique for SPCT data has been developed using the results of experimental tests and numerical analyses. The interpretation technique takes into account the effects of the initial, large plasticity on the behaviour of the SPCT specimen, in order to correlate the SPCT results with the corresponding uniaxial data. A significant improvement in the accuracy of the correlation for rupture SPCT data with the corresponding uniaxial test results has been obtained

Quality characteristics of air-dried apple rings: Influence of storage time and fruit maturity measured by time-resolved reflectance spectroscopy

AbstractWith the aim of studying the influence of maturity and of cold storage time on the quality characteristics of air-dried apple rings, 60 apples (cv Pink Lady®) were measured at harvest by time-resolved reflectance spectroscopy (TRS) at 670nm, ranked on the basis of decreasing absorption coefficient at 670nm (μa670, increasing maturity) and hence classified based on the ranking order as less mature (LeM), medium mature (MeM,) and more mature (MoM). The sixty fruit were, then, randomized into 3 batches corresponding to 3 storage times (0, 3 and 5 months in normal atmosphere at +1°C), and, at each storage time, 3 rings/fruit were air-dried at 80°C up to a constant weight using a pilot air circulated drier. Quality characteristics of fresh fruit and of air-dried rings were analysed by ANOVA and PCA statistical analyses. Stored fruit compared to fruit at 0m were softer, had lower stiffness and energy-to-rupture, and higher soluble solids content (SSC), relative intercellular space volume (RISV) and L*f. LeM class had lower SSC and dry matter, and the MoM class higher a*f and lower b*f than the other two classes. 3m-Apples showed the highest differences with respect to fresh ring in browning index (BI), total colour, chroma and hue, compared to fruit processed at 0m and 5m. Air-dried rings from less mature apples (i.e. those processed at 0m and of LeM class) had higher Fmax, Emod, E and BI than those from more mature fruits (i.e. those processed after storage and of MoM class). PCA underlined the positive relationship between mechanical characteristics of fresh fruit with those of dried rings and ring shrinkage, which were opposite to RISV, SSC and weight loss

On the effects of friction modelling on small punch creep test responses: a numerical investigation

This paper shows the results of finite element (FE) analyses of Small Punch Creep Testing (SPCT) of a P91 steel at 600°C using two different approaches to model the friction between the specimen and the punch. The numerical results obtained by using the “classical” Coulomb friction model (i.e. constant friction coefficient) have been compared with those obtained by a more modern formulation, which takes into account the effects of local loading conditions, i.e. the contact pressure, between the contacting bodies (the small disc specimen and the punch) on the coefficient of friction. The aim of the work is to investigate the effects of the friction formulation used for the calculations on the numerical results representing the output of the test, i.e. the variation of the punch displacement versus time and the time to rupture. The calculations, carried out for various load levels, showed that the friction coefficient is not constant at all positions on the contacting surface between the punch and the specimen during the deformation process. The maximum value for the coefficient of friction is reached at the contact edge, which is a very important region in the specimen, because this is the position at which most of the creep deformation occurs. As expected, the displacement versus time curve (that is usually the only output obtained from experimental SPCTs) is affected by friction formulation which is used, as this directly influences the stress and strain fields in the specimen

Characterizing the tissue of apple air-dried and osmo-air-dried rings by X-CT and OCT and relationship with ring crispness and fruit maturity at harvest measured by TRS

Air-dried apple rings were prepared from ‘Golden Delicious’ apples selected at harvest as less mature and more mature according to the absorption coefficient measured at 670 nm by time-resolved reflectance spectroscopy (TRS), stored in air for 5 months, and subjected to air-drying with (OSMO) and without (noOSMO) osmodehydration pre-treatment (60% sucrose syrup). Selected rings were submitted to microstructural analysis by X-ray computed tomography (X-CT), to subsurface structure analysis by optical coherence tomography (OCT) and to texture and sound emission analysis by bending–snapping test. Higher crispness index, higher number of sound events and higher average sound pressure level (SPL) characterized the OSMO rings. Total porosity was related to SPLav 60, pore fragmentation index to fracturability and specific surface area to the work required to snap the ring. A differentiation of the drying treatments, as well as of the products according to the TRS maturity class at harvest was obtained analyzing by principal component analysis (PCA) microstructure parameters and texture and acoustic parameters. The differences in mechanical and acoustic characteristics between OSMO and noOSMO rings were due to the different subsurface structure as found with OCT analysis

Mechanical Processing of Hermetia illucens Larvae and Bombyx mori Pupae Produces Oils with Antimicrobial Activity

The aim of this work was to develop processing methods that safeguard the quality and antimicrobial properties of H. illucens and B. mori oils. We adopted a vegetable diet for both insects: leftover vegetables and fruit for H. illucens and mulberry leaves for B. mori. First, alternative techniques to obtain a good oil extraction yield from the dried biomass of H. illucens larvae were tested. Traditional pressing resulted to be the best system to maximize the oil yield and it was successfully applied to B. mori pupae. Oil quality resulted comparable to that obtained with other extraction methods described in the literature. In the case of B. mori pupae, different treatments and preservation periods were investigated to evaluate their influence on the oil composition and quality. Interestingly, agar diffusion assays demonstrated the sensitivity of Gram-positive Bacillus subtilis and Staphylococcus aureus to H. illucens and B. mori derived oils, whereas the growth of Gram-negative Pseudomonas aeruginosa and Escherichia coli was not affected. This study confirms that fat and other active compounds of the oil extracted by hot pressing could represent effective antimicrobials against bacteria, a relevant result if we consider that they are by-products of the protein extraction process in the feed industry

Experimental and numerical analysis of initial plasticity in P91 steel small punch creep samples

To date, the complex behaviour of small punch creep test (SPCT) specimens has not been completely understood, making the test hard to numerically model and the data difficult to interpret. This paper presents a novel numerical model able to generate results that match the experimental findings. For the first time, pre-strained uniaxial creep test data of a P91 steel at 600 °C have been implemented in a conveniently modified Liu and Murakami creep damage model in order to simulate the effects of the initial localised plasticity on the subsequent creep response of a small punch creep test specimen. Finite element (FE) results, in terms of creep displacement rate and time to failure, obtained by the modified Liu and Murakami model are in good agreement with experimental small punch creep test data. The rupture times obtained by the FE calculations which make use of the non-modified creep damage model are one order of magnitude shorter than those obtained by using the modified constitutive model. Although further investigation is needed, this novel approach has confirmed that the effects of initial localised plasticity, taking place in the early stages of small punch creep test, cannot be neglected. The new results, obtained by using the modified constitutive model, show a significant improvement with respect to those obtained by a state of the art creep damage constitutive model (the Liu and Murakami constitutive model) both in terms of minimum load-line displacement rate and time to rupture. The new modelling method will potentially lead to improved capability for SPCT data interpretatio