Master of Science / Department of Grain Science and Industry / Sajid Alavi / Extrusion is a popular technology for production of expanded products. However, variability in multiple input parameters can lead to significant variations in the end product which becomes a concern for process control and efficiency in industries. This study was focused on understanding the uncertainty in input parameters during extrusion and their impact on variability in output. A mechanistic model was developed for bubble growth dynamics in starch based melts at microscopic and macroscopic levels using heat, mass and momentum transfer equations. This model was used for uncertainty simulations using the Monte-Carlo method by integrating it with a stochastic interface for input of randomly generated process data based on experimentally obtained distributions and output of simulated distributions of end-product properties such as expansion ratio (ER). A pilot-scale twin screw extruder was used for processing of corn-based expanded products, which was used as a model system for experimental validation of the mathematical model. A 4x2 factorial design was used with different in-barrel moisture contents (19, 23, 28 and 33% dry basis) and extruder screw speeds (250 and 350 rpm) to measure process data (such as moisture injection rate and T[subscript]d[subscript]i[subscript]e) and product characteristics (such as ER). Average experimental ER ranged from 2.33-10.88 and simulated ER ranged from 1.16-12.86, where both had similar trends with respect to in-barrel moisture (MC) and die temperature (T[subscript]d[subscript]i[subscript]e = 108.8-145.4˚C) although conditions for optimum expansion differed possibly due to non-correspondence of material properties. Experimental coefficient of variation (CV) for MC (0.6-1.6%) and T[subscript]d[subscript]i[subscript]e (0.29-0.91%) and an assumed CV of 2% for a material constant (k[subscript]f) that controls the consistency index of starch-based melt were used for simulations. The stochastic model was used to carry out sensitivity analysis for CV of ER with respect to CV of MC, T[subscript]d[subscript]i[subscript]e and k[subscript]f. Variability in ER was impacted the most by variation in T[subscript]d[subscript]i[subscript]e, followed by MC with k[subscript]f having relatively lower impact on it. Since there are fundamental flaws in modeling approach as reflected by the thermodynamically infeasible parameter dynamics, the results from these mechanistic or stochastic simulations cannot be used as a basis for scientific analysis.

Master of Science / Department of Grain Science and Industry / Greg Aldrich / Novel ingredients fuel growth in the pet food market. Sorghum grain is a promising ingredient source. It grows in semi-arid regions and the pericarp is rich in phenolic compounds that are well-known antioxidants. The objectives were to determine the impact of milling sorghum on yield and composition of the various fractions, their impact on diet extrusion, and nutrient utilization when fed to dogs. Sorghum milling yields were 68.3% flour, 27.2% mill-feed, and 1.25% germ. Four nutritionally similar dog diets were extruded containing whole sorghum (WSD), sorghum flour (FLD), sorghum mill-feed (MFD), or a control diet (CON) with an equal proportion of corn, wheat and rice. The MFD had the highest (P < 0.05) bulk density and was 1.37-fold heavier than FLD. The FLD had a sectional expansion index (SEI) of 1.92 and 1.35-fold more than MFD and WSD. The FLD and MFD had the hardest kibbles (P < 0.05). Twelve Beagle dogs were fed the experimental diets in a 4 period replicated Latin square design with 9 d adaptation and 5 d total fecal collection (TFC). Fecal output was also estimated using acid insoluble ash (AIA), Cr₂O₃ and TiO₂. Plasma antioxidant activity was measured by oxygen radical absorbance capacity (ORAC) method. Fecal scores were highest (P < 0.05) for MFD treatment and lowest for CON, with FLD and WSD similar to both extremes. Dogs fed the MFD had the largest quantity (P < 0.05) of feces excreted and FLD the least. Dogs fed the FLD had highest (P < 0.05) overall nutrient digestibility values; whereas, MFD had the lowest values. TiO₂ estimates of fecal output correlated best to all other markers. The MFD had more than 2-fold (P < 0.05) the antioxidant value by ORAC versus the other treatments (20,482 vs average 8,923 μM Trolox Equivalent/L). This study suggests that sorghum flour would benefit easy-to-digest foods and the sorghum mill-feed could benefit foods needing indigestible fiber and antioxidants. Titanium dioxide may be a better marker for fecal output than Cr₂O₃ or TFC. Future work should determine the optimal mill-feed level to provide health benefits without affecting nutrient digestibility.

Introdução - Devido ao perfil de mortalidade e de danos patológicos associados, as doenças cardiovasculares são consideradas um sério problema de saúde pública. Níveis de colesterol plasmático elevados fazem parte dos fatores de risco mais importantes para o desenvolvimento dessas doenças. Pesquisas recentes demostraram que a proteína do feijão caupi promove a redução dos níveis de colesterol em hamsters e em seres humanos, possivelmente pela ação de peptídeos bioativos advindos da dieta. Entretanto, a via pela qual o colesterol é inibido por esses peptídeos, assim como os efeitos do processamento na ação biológica ainda são desconhecidos. Objetivo - Verificar a via de ação hipocolesterolêmica dos hidrolisados do feijão caupi e o efeito do processamento térmico nesta propriedade. Métodos - Parte da farinha integral foi submetida ao isolamento de proteína e o restante dos grãos foi submetido à cocção em autoclave e à extrusão. Após ser cozido em autoclave, o feijão cozido também teve sua proteína isolada. Posteriormente, a proteína isolada do feijão integral e do feijão cozido foi submetida à hidrólise in vitro. O processo de extrusão foi modelado em função da expansão dos extrusados segundo a metodologia de superfície de resposta. A farinha do feijão extrusado foi submetida à hidrólise enzimática in vitro sem isolamento prévio da proteína. Os três hidrolisados foram submetidos à ultrafiltração e a fração menor que 3 kDa foi utilizada nos ensaios de inibição da enzima 3-hidroxi-3-metilglutaril coenzima A redutase (HMGR) e no ensaio de inibição da solubilização micelar do colesterol para avaliar a ação dos hidrolisados na via hepática e na via entérica do metabolismo do colesterol respectivamente. Resultados - Os hidrolisados provenientes dos isolados proteicos apresentaram comportamentos semelhantes. Em doses mais elevadas de proteína (acima de 70 µg/mL), a inibição apresentou-se estável, por volta dos 75 por cento. Em relação ao hidrolisado da farinha de feijão extrusado, à medida que se aumenta a quantidade de proteína a capacidade inibitória diminui. Os hidrolisados foram capazes de inibir a solubilização micelar do colesterol de 5 a 39 por cento. O processamento térmico foi fator determinante para diminuir a solubilização do colesterol in vitro. Conclusão Os hidrolisados do feijão caupi são capazes de inibir a enzima HMGR e reduzir a solubilização micelar do colesterol in vitro, mesmo após o feijão ser processado termicamente. A capacidade dos hidrolisados de insolubilizar o colesterol foi melhorada pelo cozimento em autoclave e pela extrusão / Introduction- The cardiovascular diseases, due to mortality and associated pathological damage, are considered a serious public health problem. Elevated plasma cholesterol levels are part of the most important risk factors for the development of these diseases. Recent research indicated that Cowpea protein promotes the reduction of cholesterol levels in hamsters and humans, possibly by the action of bioactive peptides from the diet. However, the route by which cholesterol is inhibited by peptides, as well as the processing effects on biological action are still unknown. Objective - To verify the hypocholesterolemic pathway of hydrolyzed cowpea and the effect of thermal processing on this property. Methods - Part of wholemeal flour was subjected to isolation of protein, and the remaining of the grains was subjected to retort and extrusion cooking processes. After autoclaving the grain, protein was also isolated from the flour. Subsequently, the isolated protein from wholemeal and cooked flour was subjected to in vitro hydrolysis. The extrusion process was optimized according to response surface methodology using the expansion ratio of extrudates as the dependent variable. The extruded bean flour was subjected to in vitro enzymatic hydrolysis without the isolation of the protein. The three hydrolysates were subjected to ultrafiltration and and fractions smaller than 3 kDa was used for inhibition assays of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) and for inhibition assay of micellar solubilization of cholesterol to evaluate their effect on the liver and enteral cholesterol metabolism respectively. Results - The hydrolysates from the protein isolates showed similar. At higher doses of protein (above 70 mg/mL), the inhibition was stable at around 75 per cent. Regarding the hydrolyzate of bean flour extruded as it increases the amount of protein inhibitory capacity decreases. The hydrolysates were able to inhibit the micellar solubilization of cholesterol between 5 and 39 per cent. The thermal processing was the determining factor to decrease the solubility of cholesterol in vitro. Conclusion The hydrolysates of cowpea are able to inhibit the enzyme HMGR micellar solubilization and reducing cholesterol in vitro, even after being thermally processed beans. The ability of hydrolysates insolubilize cholesterol was improved by cooking in an autoclave and by extrusion

Este trabalho propõe contribuir no desenvolvimento do processo de extrusão para a produção de compósitos cimentícios, mediante metodologia que possibilite a obtenção de formulações extrudáveis utilizando cimento Portland de alta resistência inicial, sílica ativa, calcário, polpa de celulose de eucalipto, fibras de polipropileno e aditivos. Para isso, foram caracterizadas as matérias-primas como subsidio para as discussões. O efeito dos diferentes componentes da formulação no comportamento reológico da mistura foi avaliado utilizando reômetro extrusor. As propriedades físicas e mecânicas dos compósitos elaborados com combinações de calcário, sílica ativa e cimento foram modeladas estatisticamente com o propósito de estimar o comportamento das matrizes. A demanda de água dos sistemas cimentícios foi determinada experimentalmente e utilizada na extrusão das matrizes. Selecionada uma matriz, suas propriedades mecânicas e físicas foram modeladas, estatisticamente, com diferentes teores de polpa celulósica de eucalipto e fibras de polipropileno. As formulações com características desejadas foram avaliadas ao envelhecimento acelerado por 200 ciclos de imersão-secagem. Finalmente foi analisada a reprodutibilidade utilizando o módulo de Weibull para as formulações selecionadas. O estudo reológico constatou que as fibras de polipropileno apresentam os maiores aumentos nos valores dos parâmetros reológicos se comparados com os efeitos do calcário, sílica ou celulose de eucalipto, repercutindo em maiores pressões de extrusão. O incremento do modificador reológico hidroxipropilmetilcelulose reduz no compósito cimentício o módulo de ruptura mesmo que durante o processamento, promova o incremento da pressão de extrusão. Os modelos estatísticos empregados para modelar a matriz reforçada foram de maior complexidade e com menor coeficiente de determinação se comparados com os utilizados na modelagem das matrizes. O preço de mercado do fibrocimento é aproximadamente 64% menor do que os determinados utilizando unicamente os valores das matérias-primas e aditivos do fibrocimento extrudado no presente estudo. / This work intends to contribute in the development of the extrusion process for the production of cementitious composites, through methodology that makes it possible to obtain formulas using high resistance Portland cement, silica fume, limestone, eucalyptus pulp, polypropylene fibers and admixtures. With this intention, the raw materials were characterized as a support for the discussions. The effects of the different components of the formula on the rheological behavior of the mixture were evaluated using an extrusion rheometer. The physical and mechanical properties of the composites elaborated with the combinations of limestone, silica fume and cement were modeled statistically with the purpose of estimating the behavior of the matrix. The water demand of the cementitious systems was determined experimentally and used in the matrixes extrusion. After the Matrix Selection, their mechanical and physical properties were modeled statistically, with different pulp eucalyptus and polypropylene fibers quantities. The formulas with the expected characteristics were evaluated to the accelerated aging for 200 wet-drying cycles. Finally the reproducibility was analyzed using the Weibull module for the selected formulas. The rheological studies verified that the polypropylene fibers demonstrate the largest increase in the values of the rheological parameters when compared with the effects of the limestone, silica fume or eucalyptus pulp, inducing larger extrusion pressures. The increment of the rheological modifier hydroxypropyl methylcellulose decreases the module of rupture in the cementitious composite, and simultaneously during the process it promotes the increment of the extrusion pressure. The statistical models used to reinforce the matrix modeling were of large complexity and with smaller coefficient determination when compared to matrixes used for modeling. The fiber cement market price is approximately 64% smaller than the raw materials and admixtures used in extruded fiber cement in this study.

L’amélioration de la solubilité des principes actifs peu solubles est devenue l’un des principaux challenges de l’industrie pharmaceutique. Bien que présentant une structure chimique potentiellement idéale pour interagir avec la cible, elles échouent dans l’efficacité in vivo : après administration, elles ne peuvent se dissoudre dans les milieux aqueux biologiques et par conséquent ne peuvent être transportées sur leur site d’action pour atteindre la concentration efficace, amenant à un échec thérapeutique. De nombreuses stratégies très intéressantes ont été proposées pour surmonter ce sérieux obstacle.Les dispersions solides sont étudiées depuis plus de 40 ans et ont conduit à de très nombreuses publications mais jusqu’à aujourd’hui peu de produits ont été commercialisés principalement pour des raisons de stabilité physico-chimique. Celles-ci ont pour but de présenter le principe actif sous sa forme amorphe : cette dernière présentant un état d’énergie plus élevé et par conséquent une solubilisation facilitée. Dans le même temps, le système doit rester stable durant le stockage, ainsi la recristallisation ou tout autre changement entraînant une modification du profil de libération doivent être évités. Différentes techniques de production peuvent être utilisées pour préparer ce genre de systèmes polymériques tels que l’extrusion en phase chauffante ou l’atomisation-séchage. Le principal objectif de ce travail a été d’améliorer la solubilité des principes actifs peu solubles par formation de dispersions solides utilisant les deux techniques les plus utilisées : l’extrusion en phase chauffante et l’atomisation-séchage. Dans cette étude, le kétoprofène a été incorporé dans des matrices polymériques hydrophiles pour augmenter sa solubilité apparente. Les deux techniques ont été employées et l’Eudragit® E a été considéré comme une matrice intéressante pour plusieurs raisons : c’est un polymère thermoplastique, offrant une stabilité thermique suffisante pour l’extrusion en phase chauffante, il se dissout rapidement en milieu acide et peut interagir avec les groupements acides de par ses nombreux azotes ternaires. Des mélanges binaires « principe actif – Eudragit®E » ainsi que des mélanges ternaires « principe actif – Eudragit®E - PVP », « principe actif – Eudragit®E - PVPVA », « principe actif – Eudragit®E - HPMC » ont été étudiés et caractérisés Les systèmes obtenus ont été caractérisés par macro/microscopie optique, microscopie électronique à balayage, diffraction laser, analyse calorimétrique différentielle modulée, diffraction des rayons X et l’étude du profil de libération in vitro en milieu acide (HCl 0.1M). Les libérations ont été intentionnellement réalisées en condition « non sink » afin d'évaluer le potentiel des formulations à produire des solutions sur-saturées et la durée de ces dernières. Tous les systèmes présentent un profil de libération du kétoprofène beaucoup plus rapide comparé au produit commercial et à la dissolution du principe actif pur. De plus, des solutions sur-saturées peuvent être obtenues et restent stables au moins 2 h. Cependant, en fonction des polymères utilisés, différents profils de libération ont été obtenus indiquant que l’utilisation de matrices polymériques pour l’accélération de la libération de principes actifs peu solubles peut être très complexe puisqu’elle n’est pas seulement influencée par la composition du système mais aussi potentiellement par leur structure interne et notamment par l’homogénéité/hétérogénéité de la distribution des excipients.[...]. / Poor aqueous solubility has become a property of numerous new drug candidates causing major concern. Despite a potentially ideal chemical structure allowing for interaction with the target, these substances fail to be effective in vivo: upon administration, they cannot dissolve sufficiently in the aqueous fluids of the body and, thus, cannot be transported to their site of action to reach therapeutically effective concentrations. Various interesting strategies have been proposed to overcome this crucial hurdle.Solid dispersions have been studied for more than 40 years and lead to numerous interesting research articles. However, today, only a few products have reached the market principally due to problems with the physico-chemical stability. The idea is to transform the crystalline raw material into a physical state having a greater energy in order to increase the driving force for drug dissolution. At the same time, the system should be stable during long term storage, thus, re-crystallization or other system changes, resulting in altered drug release rates, must be avoided. Different manufacturing techniques can be used to prepare such polymeric drug delivery systems, including hot-melt extrusion and spray-drying.The main objective of this work has been to improve drug solubility by forming solid dispersions using the two most employed techniques: hot-melt extrusion and spray-drying. In this study ketoprofen has been incorporated into hydrophilic polymeric matrices to increase its apparent aqueous solubility. Both techniques have been applied and Eudragit® E has been considered to be an interesting matrix former in this case, as it is thermoplastic, provides sufficient thermal stability for hot-melt extrusion, rapidly dissolves at acidic pH and can interact with acidic drugs due to its multiple tertiary ammonium groups. Binary “drug-Eudragit®E” as well as ternary “drug-Eudragit®E-PVP”, “drug-Eudragit®E-PVPVA”, “drug-Eudragit®E-HPMC” combinations were investigated and characterized using X-ray diffraction, mDSC, SEM, optical macro/microscopy, and drug release measurements in 0.1 M HCl before and after storage. Drug release has been intentionally monitored under non-sink conditions, in order to evaluate the potential of the formulations to provide super-saturated solutions and the life-time of the latter. In all cases ketoprofen release was much faster compared to a commercially available product and the dissolution of the drug powder (as received). More important, super-saturated solutions could have been obtained, which were stable for at least 2 h. [...]

Currently, extensive research in using bio‐derived polymers is being done, highlighting the importance of sustainable, green polymeric materials. Some sustainable alternatives to synthetic polymers include lignin, starch, cellulose or blends of these with petroleum‐based polymers. In New Zealand, large quantities of animal derived proteins are available at very low cost, making it ideal as a sustainable alternative to petroleum‐derived polymers. However, the processability of most proteins is very difficult, but can be improved by blending with synthetic polymers, such as polyolefins. To improve, the compatibility between these substances, a functional monomer could be grafted onto the polyolefin chain. Using an appropriate functional group, the polyolefin could then react with certain amino acids residues in the protein. Lysine and cystein are the two most appropriate amino acid residues because of their reactivity and stability at a wide pH range. In this study, free radical grafting of itaconic anhydride (IA) onto polyethylene was investigated. IA was selected because it is capable of reacting with polyethylene and amino acid residues, such as lysine. The objective of the research was to identify and investigate the effect of reaction parameters on grafting. These were: residence time, temperature, initial monomer concentration as well as peroxide concentration and type. Grafting was characterized in terms of the degree of grafting (DOG), percentage reacted and the extent of side reactions. The reaction temperature was taken above the melting point of the polyethylene, monomer and decomposition temperature of the initiator. It was found that above 160 C polymer degradation occurred, evident from sample discolouration. A higher degree of grafting can be achieved by increasing the initial monomer concentration up to a limiting concentration. The highest DOG achieved was about 1.2 mol IA per mol PE, using 2 wt% DCP. When using 2 wt % peroxide, the limiting concentration was found to be 6 wt% IA, above which no improvement in DOG was achieved. It was found that DCP is much more effective at grafting, compared to DTBP because DTBP is more prone to lead to side reactions than DCP. iv It was found that a residence time of 168 seconds resulted in the highest DOG, corresponding to 4 extrusions in series. However, it was also found that an increase in residence time resulted in an increase in polymer degradation. The tensile strength of PE decreased after two extrusions when using DTBP, and three extrusions, when using DCP. Young's modulus decreased only slightly, while all samples showed a dramatic decrease in ductility, even after one extrusion. It was concluded that degradation had a more pronounced effect on mechanical properties than cross‐linking, and residence time should therefore not exceed three extrusions in series, which corresponded to about 126 seconds. It can be concluded that a high reaction temperature and high initiator concentration lead to a low degree of grafting, accompanied by high cross‐linking and increased degradation. On the other hand, high monomer concentration and high residence time lead to a high degree of grafting. Optimising grafting is therefore a trade off between maximal DOG and minimising side reactions such as cross‐linking and degradation and optimal conditions do not necessarily correspond to a maximum DOG. Other factors, such as the use of additives to prevent degradation should also be investigated and may lead to different optimum conditions.

Whole sorghum kernels were directly processed into whole grain snacks with acceptable texture. Extrudates made from whole sorghum had a harder gritty texture than those made from decorticated materials. Extrusion of whole sorghum provides significant savings in processing: there are no dry matter losses; no equipment or energy is required for decortication or milling; the extruder consumes less power and processes more material per time unit. In addition, the extruder utilized is a simple adiabiatic, friction extruder of relatively low cost. Grinding whole sorghum and removing fines did not improve product expansion during extrusion but altered the gritty pieces in the extrudates. The best products were obtained when whole sorghum (ground or un-ground) was extruded at 14% moisture. The whole sorghum extrudates had larger bubbles with thick cell walls, which made extrudates more crunchy. Decortication of sorghum improved extrusion performance and products by allowing adequate formation and retention of air cells. Decortication to remove 20% of the original sorghum weight was enough to produce extrudates with characteristics comparable to those made from commercial yellow corn meal. Sorghum milled fractions with composition and particle size distribution similar to corn meal produced extrudates with higher expansion, lower bulk density and similar texture. In addition, sorghum extrudates were rated equal to corn meal extrudates by a taste panel for appearance, flavor, texture and overall characteristics. Extrudates made from polished rice were less expanded and whiter than extrudates made from sorghum. When processed under similar conditions, sorghum extrusion required more energy than corn meal extrusion. However, whole sorghum extrusion required less energy than corn meal extrusion. Unground sorghum samples (decorticated or non-decorticated) produced harder extrudates compared to those made from ground raw material. White sorghum is a feasible option for snack extrusion because of its versatility, product characteristics, cost and processing properties.

Wood Plastic Composites (WPCs) have experienced a healthy growth during the last decade. However, improvement in properties is necessary to increase their utility for structural applications. The toughness of WPCs can be improved by creating a fine cellular structure while reducing the density. Extrusion processing is one of the most economical methods for profile formation. For our study, rectangular profiles were extruded using a twin-screw extrusion system with different grades of HDPE and with varying wood fibre and lubricant contents together with maleated polyethylene (MAPE) coupling agent to investigate their effects on WPC processing and mechanical properties. Work has been done to redesign the extrusion system setup to achieve smoother and stronger profiles. A guiding shaper, submerged in the water, has been designed to guide the material directly through water immediately after exiting the die; instead of passing it through a water cooled vacuum calibrator and then through water. In this way a skin was formed quickly that facilitated the production of smoother profiles. Later on chemical blowing agent (CBA) was used to generate cellular structure in the profile by the same extrusion system. CBA contents die temperatures, drawdown ratios (DDR) and wood fibre contents (WF) were varied for optimization of mechanical properties and morphology. Cell morphology and fibre alignment was characterized by a scanning electron microscope (SEM). A new compression molding system was developed to help in quick evaluation of different material formulations. This system forces the materials to flow in one direction to achieve higher net alignment of fibres during sample preparation, which is the case during profile extrusion. Operation parameters were optimized and improvements in WPC properties were observed compared to samples prepared by conventional hot press and profile extrusion. / UOIT

The demand for lightweight materials in automobiles has been motivated by two factors: fuel economy and air pollution reduction. One of the first steps taken in automotive vehicle weight reduction was the use of aluminum alloys for both structural and non-structural parts. Although magnesium alloys, that have one fourth the density of steel and one third that of aluminum, have also been used in automobiles, however, their applications were limited to non-structural parts. Recently, interest has been focused on using magnesium alloys as structural materials for automotive load-bearing components. Load-bearing components in automobiles are usually subjected to multiaxial cyclic loading. Fatigue is considered to be a significant cause of ground vehicle component failure. Therefore, for magnesium alloys to be used for these components, an understanding of their fatigue behaviour is necessary. In this study, series of monotonic and cyclic tests were conducted on smooth specimens machined from AZ31B magnesium extrusion section. Two loading modes were considered in this investigation, axial and torsional. Monotonic tensile and compressive tests were performed at three different orientations, longitudinal (LD), i.e., parallel to the extrusion direction, 45° and transverse (TD) directions. Monotonic torsion tests were performed on specimens that were machined along the LD. Similarly, cyclic axial and torsional as well as multiaxial axial-torsional tests were performed on specimens that that were machined along the LD. Three different phase angles were considered for multiaxial tests: in-phase, and 45° and 90° out-of-phase. It was found that monotonic axial stress-strain behaviour is direction dependent due to the different deformation mechanisms involved. Significant yield anisotropy and sigmoidal-type hardening were observed. Twinning-detwinning deformation was considered as the major cause of these behaviours. On the other hand, monotonic torsional stress-strain curve had a linear hardening behaviour. Cyclic axial behaviour was found to be affected by twinning-detwinning deformation. Its most significant characteristics are: yield asymmetry, power-like hardening in compressive reversal and sigmoidal-type hardening in tensile reversal. This unusual behaviour was attributed to the contribution of three different deformation mechanisms: slip, twinning and detwinning. Due to yield asymmetry, significant positive mean stress was observed especially at LCF. Cyclic hardening was also observed and it was found to be associated with a substantial decrease in plastic strain energy density. Cyclic shear behaviour was symmetric and did not exhibit any of the aforementioned behaviours in cyclic axial loading. Two major observations were made from multiaxial tests. First, additional hardening due to nonproportionality was observed. Second, phase angle has no effect on fatigue life. Three fatigue life models were considered for multiaxial fatigue life prediction: Smith-Watson-Topper, Fatemi-Socie and Jahed-Varvani. The first two models are based on strain and are evaluated on specific critical planes. The third model is based on energy densities calculated from hysteresis loops. Strain- and energy-life curves had knees and pronounced plateaus. Therefore, it was not possible to model the entire fatigue life using Coffin-Manson-Type equations. Low cycle fatigue lives were predicted within ۬x scatter bounds using the Fatemi-Socie and the Jahed-Varvani models for all loading conditions which was not the case with Smith-Watson-Topper model. Total energy, the sum of plastic and positive elastic strain energy densities, was found to correlate fatigue lives for several wrought Mg-alloys under different loading conditions.

The object of this study is to explore the deformation pattern of axisymmetric clad materials composed of the single-core and the sleeve during hydrostatic extrusion, and discuss the relations between processing condition factors and extrusion pressure in hydrostatic extrusion of axisymmetric clad materials. In the FEM simulation of composite materials during hydrostatic extrusion, this paper describes a technique that can be used for predicting whether core bursting of composite materials occurs or not. The effect of several extrusion parameters on the damage value of the core is examined: extrusion ratio(R), die semicone angle(£\¢X), bonding friction factor(mi), material strength ratio. By performing FEM simulations and discussing the effect of parameters on distribution of damage value obtained, it is possible to establish a data base for prevention of fracture of the core. The paper has designed and constructed an experimental receiver pressure of hydrostatic apparatus with a maximum working pressure of 7000 kgf/cm2. In experiment, extrusion of Cu-Al composite rods with different of core radius ratio was carried out. It has been found that uniform deformation always occurs under the combination of hard sleeve and soft core and the core layer usually fails due to the tension under the combination of hard core and soft sleeve.