Littérature scientifique sur le sujet « SPECIFIC WEAR RATE (K) »

Dental decay still presents a major health problem among children. Its treatment usually requires the use of stainless steel crowns. This study compares the wear behavior of 316 L stainless steel and polyetheretherketone (PEEK) composite under identical test conditions. The wear tests were conducted in a reciprocating ball-on-plate tribometer (Plint TE67/R) using alumina balls as a counterface and artificial saliva as a lubricant at 37 °C to faithfully mimic oral conditions. The coefficient of friction (COF) and specific wear rate (k) values were determined and SEM/EDS examinations were performed to identify the predominant wear mechanisms. Results showed that PEEK exhibited a significantly lower coefficient of friction (COF = 0.094 ± 0.004) and thus lower wear volume (ΔV = 0.0078 ± 0.0125 mm3) and higher wear resistance, with an average value of specific wear rate of k = 9.07 × 10−6 mm3N−1m−1 when compared to stainless steel (COF = 0.32 ± 0.03, ΔV = 0.0125 ± 0.0029 mm3, k = 1.45 × 10−5 mm3N−1m−1). PEEK was revealed to be a potential material for use in pediatric crowns due to its high wear resistance while overcoming the disadvantages associated with steel at both an aesthetic and biological level.

Plastic recycling in the automotive industry is a priority. In this study, the effect of adding recycled polyvinyl butyral (rPVB) from automotive windshields on the coefficient of friction (CoF) and specific wear rate (k) of a glass–fiber reinforced polyamide (PAGF) is investigated. It was found that, at 15 and 20 wt.% of rPVB, it acts as a solid lubricant, reducing CoF and k up to 27% and 70%, respectively. Microscopical analysis of the wear tracks showed that rPVB spreads over the worn tracks, forming a lubricant layer, which protects the fibers from damage. However, at lower rPVB content, fiber damage cannot be prevented as the protective lubricant layer is not formed.

Purpose Lithium disilicate glass-ceramics (LS2 GC) are widely used as dental prosthetics and dental restorations. Based LS2 GC have hardness and translucency similar to that of natural teeth. This study aims to investigate the tribological features of LS2 GC with crystalline volume fraction of 64% and different crystal sizes from 8 µm to 34 µm for different counterparts. Design/methodology/approach The tribological behavior was investigated using a pin-on-disc tribometer with alumina and tungsten carbide (WC) spheres, applied load of 5 N and sliding speed of 5 cm/s at normal conditions. The coefficient of friction was measured continuously up to 10,000 sliding cycles. The specific wear rate was calculated from tribological and profile measurements. The wear mechanism was investigated by surface morphology analysis. Findings The coefficient of friction during running-in varied from 0.8 to 1.0 for the alumina counterpart, because of severe wear. Afterwards, it reduced and reached a stationary regime, characterized by a mild wear regime and the formation of a tribolayer formed by the debris. For the WC counterpart, the coefficient of friction curves increased initially with sliding cycles up to a stationary regime. The samples tested against WC presented the lowest specific wear rate (k), and no variation of wear rate with crystal size was observed. For samples tested against the alumina, crystallization and crystal size increased the wear resistance. Originality/value This study evaluated the effect of different counterfaces on the tribological properties of the LS2 GC, an important glass-ceramic base for many dental prosthetics and dental restorations, discussing results in light of the contact mechanics. Different specific wear rates, wear regimes and dependence on the glass-ceramic microstructure were observed depending on the counterpart. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0352/

AbstractTwo copper based composites: an experimental Cu-Al2O3 and commercial GlidCop AL-60 grade (with 1.1 wt.% Al2O3) with grains size approximately 1–2 µm were treated by Equal Channel Angular Pressure (ECAP) technique in order to induce severe plastic deformation and to reduce the grain size by about an order of magnitude. Microstructure of the as-received and ECAPed states of both systems were observed. Hardness of the experimental materials was measured by instrumented indentation. Tribological properties were studied by pin-on-disk technique in dry sliding against a steel ball at a various temperatures from room temperature up to 873 K. For all systems the coefficient of friction and specific wear rates were evaluated. Worn surfaces were studied by scanning electron microscopy and level of oxidation was measured using EDX spectrometry. It was found that between 473 K and 673 K the coefficient of friction decreased significantly. At lower temperatures the finer grained systems were more wear resistant than the as-received ones. The wear rate of all systems decreased down to zero at 673 K due to formation of hard oxide rich layers. Damage mechanisms were identified and their relationship with structural characteristics was inferred.

Different techniques have been developed in the area of bearing wear monitoring. This paper proposes a different experimental study on bearing wear monitoring by using an airborne technique. The data captured in the airborne technique will be analyzed by using I-kazTM Multi Level (7Z) coefficient and then will be correlated with the conventional specific wear rates, K. The wear tests were carried out by using a pin-on-disc configuration at a sliding speed of 7.85 m/s. A set of sliding distance ranging from 20 160 km at a fixed load of 200 N was utilized and the K value was measured at every interval of 20 km for the speed. SAE40 type lubricant was used in the test to simulate the actual operation of the connecting rod bearing. The audio range frequency below 20 kHz in the airborne technique was obtained through a microphone 40SC type which was placed 10 mm from the pin-disc contact. The analysis result showed that the wear rate, K increased from 1.82 to 6.70x10-8 mm3/Nm as the sliding distance increased, indicating that a mild-abrasion wear regime had occurred. The curve fitting of K as a function of I-kazTM Multi Level coefficient showed a similarity to an established of Taylor Tool Life curve. Thus, it was possible to correlate the Taylor curve and worn bearing, mainly in monitoring and identifying the bearing condition with respect to the sliding distance. The trend of I-kazTM Multi Level coefficient was found to be consistent with the increase of sliding distance which indicates that the I-kazTM Multi Level value can positively be used as wear response indicator for bearing.

Using the Taguchi’s robust design of experiments methodology, this article presents the systematic identification and optimization of most influential parameters of deep cryogenic treatment process to minimize the specific wear rate of UNS R56700 (Ti6Al7Nb). In addition to the different soaking durations (0–96 h) at 77 K and different tempering temperatures (room temperature, 403–523 K), three commonly used variables of pin-on-disk test, namely, sliding speed (1.047–2.723 ms−1), contact pressure (0.641–1.282 MPa), and sliding time (600–2280 s) were chosen to conduct the tests. During dry sliding conditions, pin-on-disk tribo-tests were performed to slide Ti6Al7Nb on the surface of UNS 52986 (En31) material as per standardized ASTM G99 guidelines. Experimentally measured wear rate values were converted to signal–noise ratio to statistically analyze the influence of five control variables using pooled analysis of variance and F-test. Statistically found influential control variables are confirmed experimentally. The results show that sliding speed, contact pressure and soaking duration are the most significant factors influencing the wear rate. In contrast, the parameters, that is, tempering temperature and sliding time, exhibit a lower level of influence. Microstructural characterizations done using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques suggested that deep cryogenic treatment favors the refinement of grain size of present phases with reduction in β-stabilization (β-phase) in Ti6Al7Nb. The possible reasons for the improvement in wear rate of Ti6Al7Nb underlying the morphological alterations have been explained.

Technological progress in hybrid bearings developed high wear and abrasion resistant materials for rolling elements. The manufacturing process of bearing balls presents new challenges, as nowadays, it requires time-consuming and costly processes. In this frame, the bearing manufacturing industry is demanding improvements in materials, geometry, and processes. This work aims to investigate new abrasive coatings for grinding wheels for Si3N4 ball manufacturing. Tribological pin on disk tests are performed on samples of grinding materials (disk) versus a Si3N4 ball (pin). Two samples of specimens coated with an electrodeposited diamond and diamond-reinforced metal matrix composite are examined to measure the abrasion rate and the wear resistance of Silicon Nitride Si3N4 balls, considering the influence of sliding speed and the effect of coating deposition on diamond particle density and granulometry. The measurements estimated the specific wear coefficient k, the height wear surface h, and the wear rate u of the Si3N4 balls. The results pointed out that by increasing the sliding speed, the abraded volume increases for both the coatings. The parameters affecting the abrasion effectiveness of both the coatings are the surface roughness, the abrasive particle dimension, and the sliding speed.

This work aims to explore the impact of side loads, drill-pipe tool-joint (DP-TJ) speed (rpm), and mud type on the austenitic stainless steel SM2535-110 casing wear characteristics. Actual field drill pipe tool joints, casings, and drilling muds are used in this study. The results of the study show that under both types of lubrication, the wear volume increased with radial load and DP-TJ speed. SM2535-110 casing specimens tested under oil-based mud (OBM) lubrication had higher casing wear volumes than those obtained under water-based mud (WBM) lubrication. This unexpected behavior is mainly due to the increase in the surface hardness of the casing specimens tested under WBM. The results also show that the specific wear rate or wear factor (K) (which is defined as the volume loss per unit load per unit distance sliding) values of specimens tested under WBM are in general two to four times higher than those obtained under OBM. While K values under WBM increase with both the side load and rpm, those under OBM show a sharp decrease with rpm. This behavior under OBM is due to this lubricant’s higher viscosity and the change of lubrication regime from thin film to thick film lubrication at higher rpm. Scanning electron microscopy (SEM) and the digital microscopic imaging (DMI) of SM235-110 casing specimens show that an aggressive combination of adhesive, abrasive, and plastic deformation was observed under WBM, while the dominant wear mechanism under OBM is abrasive wear.

ABSTRACTAISI 4140 steel is a popular low alloy steel due to its wide applications as workpiece in the metal-mechanic industry; there are extensive research about surface modification to enhance its properties for specific applications. The focus of this study was to investigate the influence of the nature of lubricants, mineral and vegetable oils, on the tribological performance of the hardened and tempered AISI 4140 steel against alumina (Al2O3). For this purpose, friction tests were conducted in a pin on disc tribometer according to ASTM standard G 99-05, at room temperature of 25 °C and in air with about 30% relative humidity. Lubricants were selected to be commercial Holifa B22/2 oil as mineral oil and Castor Oil as bio-lubricant, with kinematic viscosity at 25 °C of 667 and 662 cSt respectively. The following conditions were settled for all the experiments: relative sliding speed of 0.05 ms-1, sliding distance of 1000 m and wear track radius of 2 mm. Friction behaviour was reported as the average kinetic friction coefficient (µK) while wear performance was evaluated as wear rate (K). In order to identify and determine wear mechanisms, worn surfaces were analyzed by optical microscopy and profilometry. It was found that, for these tribosystems, hardened and tempered AISI 4140 steel had the best friction and wear performance under lubrication with Castor Oil. The lowest µK achieved was 0.035, whereas the lowest K was 1.02x10-8 mm3/Nm. With this bio-lubricant, there were reductions in friction and wear up to 72% compared with those under mineral oil lubrication.

The goal of this study was to improve the mechanical and thermal properties of PolyMethyl Meth Acrylate (PMMA) by adding Zirconia nanoparticles in various weight fraction percentages (0, 1, 1.5, 2, 2.5, 3)%. The cast technique was utilized of to prepare the (PMMA/zirconia) nanocomposites. The thermal and mechanical characterized of (PMMA/zirconia) nanocomposites were studied. Increased zirconia percentages in (PMMA/zirconia) nanocomposites lead to increase thermal conductivity (K), glass transition temperature, specific heat capacity (Cp), effusivity, impact strength, hardness, flexural strength, compressive strength and reduced wear rate, enhancing the thermal and mechanical properties of Poly-Methyl Meth Acrylate (PMMA).

Automotive companies are actively pursuing to increase the use of high-strength-lightweight alloys such as aluminum, magnesium, and advanced/ultra high-strength steels (A/UHSS) in body panel and structural part applications to achieve fuel efficiency while satisfying several environmental and safety concerns. A/UHSS sheet materials with higher strength and crashworthiness capabilities, in comparison to mild steel alloys, are considered as a near-term (i.e., ~5 years) choice of material for body and structural components due to their relatively low cost when compared with other lightweight materials such as aluminum and magnesium. However, A/UHSS materials present an increased level of die wear and springback in stamping operations when compared to the currently used mild steel alloys due to their higher surface hardness and high yield strength levels. In order to prevent the excessive wear effect in stamping dies, various countermeasures have been proposed such as alternative coatings, modified surface enhancements in addition to the use of newer die materials including cast, cold work tool, and powder metallurgical tool steels. In this study, a new die wear test method was developed and tested to provide a cost-effective solution for evaluating various combinations of newly developed die materials, coatings and surfaces accurately and rapidly. A new slider type of test system was developed to replicate the actual stamping conditions including the contact pressure state, sliding velocity level and continuous and fresh contact pairs (blank-die surfaces). Several alternative die materials in coated or uncoated conditions were tested against different AHSS sheet blanks under varying load, sliding velocity circumstances. Prior to and after wear tests, several measurements and tribological examinations were performed to obtain a quantified performance evaluation using commonly adapted wear models. Analyses showed that (1) the rapid wear method is feasible and results in reasonable wear assessments, (2) uncoated die materials are prone to expose severe form wear (galling, scoring, etc.) problems; (3) coated samples are unlikely to experience such excessive wear problems, as expected; (4) almost all of the the recently developed die materials (DC 53, Vancron 40, Vanadis 4) performed better when compared to conventional tool steel material AISI D2, and (5) in terms of coating type, die materials coated with thermal diffusion (TD) and chemical vapor deposition (CVD) coatings performed relatively better compared to other tested coating types; (6) It was seen that wear resistance correlated with substrate hardness.

No
Optimisation of the drilling operations is becoming increasingly important as it can significantly reduce the oil well development cost. One of the major objectives in oil well drilling is to increase the penetration rate by selecting the optimum drilling bit based on offset wells data, and adjust the drilling factors to keep the bit in good condition during the operation. At the same time, it is important to predict the bit wear and the time to pull out the bit out of hole to prevent fishing jobs. Numerous models have been suggested in the literature for predicting the time to pull the bit out to surface rather than predict or estimate the bit wear rate. Majority of the available models are largely empirical and can be applied for limited conditions, and do not include all the drilling parameters such as the formation abrasiveness and bit hydraulic. In this paper, a new approach is presented to improve the drill bit wear estimation that consists of a combination of both Bourgoyne and Young (BY) drilling rate model and theory of empirical relation for the effects of rotary speed (RPM), and weight on bit (WOB) on drilling arte (ROP) and rate of tooth wear. In addition to the drilling parameters, the formation abrasiveness and the effect of the jet impact force of the mud have also been accounted to estimate the bit wear. The proposed model enables estimation of the rock abrasiveness, and that lead to calculate the dynamic dulling rate of the bit while drilling that used in more accurate to assess the bit tooth wear compared with the mechanical specific energy (MSE). Then the estimated dulling rate at the depth of pulling out is used to determine the dull grade of the bit. The technique is validated in five wells located in two different oil fields in Libya. All studied wells in this showed a good agreement between the actual bit tooth wear and the estimated bit tooth wear.

The recent past has seen a rise in litigation seeking to hold specific private and public actors liable for their contribution to and impacts of climate change, with a relatively low success rate. This highlights the need for further research into the reasonable and just distribution of responsibility for mitigation and adaptation. This book unites renowned researchers from various disciplines to explore the challenges and opportunities of assigning responsibility and liability for climate change to specific actors. Thereby, the importance of interdisciplinary scientific dialogue on climate change is strengthened, and a new generation of jurists is to be provided with novel arguments for protecting our climate system. With contributions by Christoph Bezemek, Wei Cao, Marcelo de Araujo, Oliver Dörr, Mastawesha M. Engdaw, Daniel Ennöckl, Judith Fitz, Michael Hanemann, Monika Hinteregger, Birgit Hollaus, Gottfried Kirchengast, Verena Madner, Lukas Meyer, Lydia A. Omuko-Jung, Julia Pleiel, Mareike Rumpf, Oliver Ruppel, Kirsten Schmalenbach, Gerhard Schnedl, Eva Schulev-Steindl, Jaap Spier, Andrea K. Steiner, Karl Steininger, Erika Wagner, Julia Wallner and Ke Zhou.

Bones are multifunctional passive organs of movement that supports soft tissue and directly attached muscles. They also protect internal organs and are a reserve of calcium, phosphorus and magnesium. Each bone is covered with periosteum, and the adjacent bone surfaces are covered by articular cartilage. Histologically, the bone is an organ composed of many different tissues. The main component is bone tissue (cortical and spongy) composed of a set of bone cells and intercellular substance (mineral and organic), it also contains fat, hematopoietic (bone marrow) and cartilaginous tissue. Bones are a tissue that even in adult life retains the ability to change shape and structure depending on changes in their mechanical and hormonal environment, as well as self-renewal and repair capabilities. This process is called bone turnover. The basic processes of bone turnover are: • bone modeling (incessantly changes in bone shape during individual growth) following resorption and tissue formation at various locations (e.g. bone marrow formation) to increase mass and skeletal morphology. This process occurs in the bones of growing individuals and stops after reaching puberty • bone remodeling (processes involve in maintaining bone tissue by resorbing and replacing old bone tissue with new tissue in the same place, e.g. repairing micro fractures). It is a process involving the removal and internal remodeling of existing bone and is responsible for maintaining tissue mass and architecture of mature bones. Bone turnover is regulated by two types of transformation: • osteoclastogenesis, i.e. formation of cells responsible for bone resorption • osteoblastogenesis, i.e. formation of cells responsible for bone formation (bone matrix synthesis and mineralization) Bone maturity can be defined as the completion of basic structural development and mineralization leading to maximum mass and optimal mechanical strength. The highest rate of increase in pig bone mass is observed in the first twelve weeks after birth. This period of growth is considered crucial for optimizing the growth of the skeleton of pigs, because the degree of bone mineralization in later life stages (adulthood) depends largely on the amount of bone minerals accumulated in the early stages of their growth. The development of the technique allows to determine the condition of the skeletal system (or individual bones) in living animals by methods used in human medicine, or after their slaughter. For in vivo determination of bone properties, Abstract 10 double energy X-ray absorptiometry or computed tomography scanning techniques are used. Both methods allow the quantification of mineral content and bone mineral density. The most important property from a practical point of view is the bone’s bending strength, which is directly determined by the maximum bending force. The most important factors affecting bone strength are: • age (growth period), • gender and the associated hormonal balance, • genotype and modification of genes responsible for bone growth • chemical composition of the body (protein and fat content, and the proportion between these components), • physical activity and related bone load, • nutritional factors: – protein intake influencing synthesis of organic matrix of bone, – content of minerals in the feed (CA, P, Zn, Ca/P, Mg, Mn, Na, Cl, K, Cu ratio) influencing synthesis of the inorganic matrix of bone, – mineral/protein ratio in the diet (Ca/protein, P/protein, Zn/protein) – feed energy concentration, – energy source (content of saturated fatty acids - SFA, content of polyun saturated fatty acids - PUFA, in particular ALA, EPA, DPA, DHA), – feed additives, in particular: enzymes (e.g. phytase releasing of minerals bounded in phytin complexes), probiotics and prebiotics (e.g. inulin improving the function of the digestive tract by increasing absorption of nutrients), – vitamin content that regulate metabolism and biochemical changes occurring in bone tissue (e.g. vitamin D3, B6, C and K). This study was based on the results of research experiments from available literature, and studies on growing pigs carried out at the Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences. The tests were performed in total on 300 pigs of Duroc, Pietrain, Puławska breeds, line 990 and hybrids (Great White × Duroc, Great White × Landrace), PIC pigs, slaughtered at different body weight during the growth period from 15 to 130 kg. Bones for biomechanical tests were collected after slaughter from each pig. Their length, mass and volume were determined. Based on these measurements, the specific weight (density, g/cm3) was calculated. Then each bone was cut in the middle of the shaft and the outer and inner diameters were measured both horizontally and vertically. Based on these measurements, the following indicators were calculated: • cortical thickness, • cortical surface, • cortical index. Abstract 11 Bone strength was tested by a three-point bending test. The obtained data enabled the determination of: • bending force (the magnitude of the maximum force at which disintegration and disruption of bone structure occurs), • strength (the amount of maximum force needed to break/crack of bone), • stiffness (quotient of the force acting on the bone and the amount of displacement occurring under the influence of this force). Investigation of changes in physical and biomechanical features of bones during growth was performed on pigs of the synthetic 990 line growing from 15 to 130 kg body weight. The animals were slaughtered successively at a body weight of 15, 30, 40, 50, 70, 90, 110 and 130 kg. After slaughter, the following bones were separated from the right half-carcass: humerus, 3rd and 4th metatarsal bone, femur, tibia and fibula as well as 3rd and 4th metatarsal bone. The features of bones were determined using methods described in the methodology. Describing bone growth with the Gompertz equation, it was found that the earliest slowdown of bone growth curve was observed for metacarpal and metatarsal bones. This means that these bones matured the most quickly. The established data also indicate that the rib is the slowest maturing bone. The femur, humerus, tibia and fibula were between the values of these features for the metatarsal, metacarpal and rib bones. The rate of increase in bone mass and length differed significantly between the examined bones, but in all cases it was lower (coefficient b <1) than the growth rate of the whole body of the animal. The fastest growth rate was estimated for the rib mass (coefficient b = 0.93). Among the long bones, the humerus (coefficient b = 0.81) was characterized by the fastest rate of weight gain, however femur the smallest (coefficient b = 0.71). The lowest rate of bone mass increase was observed in the foot bones, with the metacarpal bones having a slightly higher value of coefficient b than the metatarsal bones (0.67 vs 0.62). The third bone had a lower growth rate than the fourth bone, regardless of whether they were metatarsal or metacarpal. The value of the bending force increased as the animals grew. Regardless of the growth point tested, the highest values were observed for the humerus, tibia and femur, smaller for the metatarsal and metacarpal bone, and the lowest for the fibula and rib. The rate of change in the value of this indicator increased at a similar rate as the body weight changes of the animals in the case of the fibula and the fourth metacarpal bone (b value = 0.98), and more slowly in the case of the metatarsal bone, the third metacarpal bone, and the tibia bone (values of the b ratio 0.81–0.85), and the slowest femur, humerus and rib (value of b = 0.60–0.66). Bone stiffness increased as animals grew. Regardless of the growth point tested, the highest values were observed for the humerus, tibia and femur, smaller for the metatarsal and metacarpal bone, and the lowest for the fibula and rib. Abstract 12 The rate of change in the value of this indicator changed at a faster rate than the increase in weight of pigs in the case of metacarpal and metatarsal bones (coefficient b = 1.01–1.22), slightly slower in the case of fibula (coefficient b = 0.92), definitely slower in the case of the tibia (b = 0.73), ribs (b = 0.66), femur (b = 0.59) and humerus (b = 0.50). Bone strength increased as animals grew. Regardless of the growth point tested, bone strength was as follows femur > tibia > humerus > 4 metacarpal> 3 metacarpal> 3 metatarsal > 4 metatarsal > rib> fibula. The rate of increase in strength of all examined bones was greater than the rate of weight gain of pigs (value of the coefficient b = 2.04–3.26). As the animals grew, the bone density increased. However, the growth rate of this indicator for the majority of bones was slower than the rate of weight gain (the value of the coefficient b ranged from 0.37 – humerus to 0.84 – fibula). The exception was the rib, whose density increased at a similar pace increasing the body weight of animals (value of the coefficient b = 0.97). The study on the influence of the breed and the feeding intensity on bone characteristics (physical and biomechanical) was performed on pigs of the breeds Duroc, Pietrain, and synthetic 990 during a growth period of 15 to 70 kg body weight. Animals were fed ad libitum or dosed system. After slaughter at a body weight of 70 kg, three bones were taken from the right half-carcass: femur, three metatarsal, and three metacarpal and subjected to the determinations described in the methodology. The weight of bones of animals fed aa libitum was significantly lower than in pigs fed restrictively All bones of Duroc breed were significantly heavier and longer than Pietrain and 990 pig bones. The average values of bending force for the examined bones took the following order: III metatarsal bone (63.5 kg) <III metacarpal bone (77.9 kg) <femur (271.5 kg). The feeding system and breed of pigs had no significant effect on the value of this indicator. The average values of the bones strength took the following order: III metatarsal bone (92.6 kg) <III metacarpal (107.2 kg) <femur (353.1 kg). Feeding intensity and breed of animals had no significant effect on the value of this feature of the bones tested. The average bone density took the following order: femur (1.23 g/cm3) <III metatarsal bone (1.26 g/cm3) <III metacarpal bone (1.34 g / cm3). The density of bones of animals fed aa libitum was higher (P<0.01) than in animals fed with a dosing system. The density of examined bones within the breeds took the following order: Pietrain race> line 990> Duroc race. The differences between the “extreme” breeds were: 7.2% (III metatarsal bone), 8.3% (III metacarpal bone), 8.4% (femur). Abstract 13 The average bone stiffness took the following order: III metatarsal bone (35.1 kg/mm) <III metacarpus (41.5 kg/mm) <femur (60.5 kg/mm). This indicator did not differ between the groups of pigs fed at different intensity, except for the metacarpal bone, which was more stiffer in pigs fed aa libitum (P<0.05). The femur of animals fed ad libitum showed a tendency (P<0.09) to be more stiffer and a force of 4.5 kg required for its displacement by 1 mm. Breed differences in stiffness were found for the femur (P <0.05) and III metacarpal bone (P <0.05). For femur, the highest value of this indicator was found in Pietrain pigs (64.5 kg/mm), lower in pigs of 990 line (61.6 kg/mm) and the lowest in Duroc pigs (55.3 kg/mm). In turn, the 3rd metacarpal bone of Duroc and Pietrain pigs had similar stiffness (39.0 and 40.0 kg/mm respectively) and was smaller than that of line 990 pigs (45.4 kg/mm). The thickness of the cortical bone layer took the following order: III metatarsal bone (2.25 mm) <III metacarpal bone (2.41 mm) <femur (5.12 mm). The feeding system did not affect this indicator. Breed differences (P <0.05) for this trait were found only for the femur bone: Duroc (5.42 mm)> line 990 (5.13 mm)> Pietrain (4.81 mm). The cross sectional area of the examined bones was arranged in the following order: III metatarsal bone (84 mm2) <III metacarpal bone (90 mm2) <femur (286 mm2). The feeding system had no effect on the value of this bone trait, with the exception of the femur, which in animals fed the dosing system was 4.7% higher (P<0.05) than in pigs fed ad libitum. Breed differences (P<0.01) in the coross sectional area were found only in femur and III metatarsal bone. The value of this indicator was the highest in Duroc pigs, lower in 990 animals and the lowest in Pietrain pigs. The cortical index of individual bones was in the following order: III metatarsal bone (31.86) <III metacarpal bone (33.86) <femur (44.75). However, its value did not significantly depend on the intensity of feeding or the breed of pigs.

AbstractCurrently, the safety assessment of radio-frequency (RF) heating using computational modeling is limited by the available numerical models which are not patient specific. However, RF-induced heating depends on the physical characteristics of the patient. The numerical model generation is difficult due to the highly time-consuming segmentation process. Therefore, having fewer types of segmented structures simplifies the generation of numerical models and reduces computational burden as a result. In this study, we used the k-means clustering method to reduce the number of dielectric properties of an existing numerical model and investigated the resulting difference in specific absorption rate (SAR) with respect to the number of clusters.

AbstractAustenitic stainless steels have been widely used for fabricating reactor core-internal components in PWRs due to its high strength, ductility and fracture toughness. The accelerated failure or degradation of austenitic stainless steel represented by IASCC has become one of the key problems affecting the safe and efficient operation of reaction core-internal in PWR nuclear power plants. IASCC is generally divided into three stages: crack initiation, crack propagation and instable fracture. Among the three stages, the crack initiation stage would occupy the major service time, the crack growth stage is featured by quasi-steady crack propagation at a certain rate, and the instable fracture stage should be avoided. Stress intensity factor K at the crack tip is often used to represent the mechanical driving force for SCC as well as IASCC.In this paper, SCC crack growth rate (CGR) data of austenitic stainless steels irradiated in high temperature water were compiled and reanalyzed to evaluate the influence of key parameters such as radiation dose and mechanical properties on IASCC sensitivity and crack growth rate of these materials in PWR nuclear power plant environment. The CGR-K curves of the irradiated materials were also analyzed. The effects of low, medium and high doses of neutron irradiation are compared, and the analysis process is illustrated with examples. In the research process, abnormal CGR and K of materials under a specific irradiation dose was found, so this phenomenon was analyzed. The CGR data and irradiation dose of austenitic stainless steel in different K range were analyzed. And proposed a way to judge the type of change:type I, type II and type III. Finally, the yield strength of the material under the same irradiation dose was found, and combined with other research data, it was further demonstrated that the neutron irradiation dose had a significant effect on the crack growth rate.

Bonded MoS2 film lubricants are widely used in industry as solid lubricants. It has excellent lubrication properties, but it also has characteristics that require careful consideration. As is well known, its friction and wear are greatly affected by the environmental atmosphere and its wear life depends on the pre-treatment of the substrate. It was found that in many cases the wear life could not be correctly estimated by a specific wear rate and could be explained by the fatigue life, especially under high loading conditions. The atmosphere dependent wear life can also be explained by the fatigue life.

This chapter starts with the importance of composite materials over single-phase materials and further explores the importance of natural fiber reinforced composites over synthetic fiber reinforced composites followed by chemical and physical modifications of the fiber surface to enhance the adhesion between the fiber and the matrix. The chapter also focuses on the different types of wear mechanisms that lead to shutting down the industries and types of different wear test rings to measure the wear rate of a material. Current work also represents a comprehensive literature study on tribological characterisation of composite materials. In addition, it focuses composites as TRIBO material in engineering systems. The effect of tribological operating parameters like load, sliding velocity, sliding distance, temperature, and other influential parameters like fiber length, fiber volume fraction, fiber orientation, and surface treatment on friction and wear rate of composites are also described. Over the past few years composites have been dominant in the emerging materials. The applications areas of composite materials have grown steadily in the various systems of Mechanical Engineering, Civil Engineering, Electrical Engineering, Medical Engineering, and Automobile Engineering. In engineering systems, failure of parts may occur due to different types of wear mechanisms. The availability of a range of fiber reinforcements, fillers, matrices, and processing techniques offers ample scope for tailoring properties in composites as required for specific applications.

In this Chapter, a severely adhesive wear on a rough aluminum (Al) substrate is simulated by molecular dynamics (MD) under a high velocity impact of a hard-asperity (a hard-tip) with the Al-asperity. Multiple simulations include effects of four factors: the inter-asperity bonding, the geometry overlap between two asperities, the impact velocity between two asperities and the starting temperature of the Al-substrate. It is observed that the deformation mechanism on the Al-substrate would involve a local melting (from 1200 to 2500 K) which forms liquid type layers (amorphous textures) in the contact area between two asperities. Also, temperature profiles on the hard-tip and the Al-substrate is depicted. Moreover, a method in the Design of Experiments (DOE) is employed to interpret above all simulations. The DOE results indicate that the inter-asperity bonding and the geometry overlap between two asperities would substantially increase the wear rate (for about 53.56% and 67.29% contributions), while the starting temperature of the Al-substrate and the impact velocity between two asperities would play less important roles (about 10.30% and 6.61%) in raising the wear rate.

Lately, artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) models have been recognized as potential and good tools for mathematical modeling of complex and nonlinear behavior of specific wear rate (SWR) of composite materials. In this study, modeling and prediction of specific wear rate of polytetraflouroethylene (PTFE) composites using FFNN and ANFIS models were examined. The performances of the models were compared with conventional multilinear regression (MLR) model. To establish the proper choice of input variables, a sensitivity analysis was performed to determine the most influential parameter on the SWR. The modeling and prediction performance results showed that FFNN and ANFIS models outperformed that of the MLR model by 45.36% and 45.80%, respectively. The sensitivity analysis findings revealed that the volume fraction of reinforcement and density of the composites and sliding distance were the most and more influential parameters, respectively. The goodness of fit of the ANN and ANFIS models was further checked using t-test at 5% level of significance and the results proved that ANN and ANFIS models are powerful and efficient tools in dealing with complex and nonlinear behavior of SWR of the PTFE composites.

Corrosive behavior of austenitic chromium-nickel steels from the magnetic state (parameter χ0) of austenite, pre-formed to interact with aggressive media are research. Correlation between the rate K of pitting corrosion and the specific magnetic susceptibility χ0 of austenite was experimentally established. It is experimentally established that the corrosion resistance of austenitic steels AISI304, 08Cr18Ni10, AISI 321, 08Cr18Ni10Тi (containing a low amount of δ-ferrite ∼0.005…0.5%) depends on the magnetic state of austenite: the corrosion rate of steel decreases with increases χ0 austenite. The tendency of change in the corrosion rate of austenitic alloy with a high nickel content 06Crh28NiMoCuTi (not contain δ-ferrite) has the opposite character: with increasing χ0, the corrosion rate of the alloy increases is revealed. For austenitic chromium-nickel steels, the corrosion rates of the individual (austenite (A), δ-ferrite (F), strain-induced α′-martensite (M)) and total (A + F, A + M and A + F + M) phases are determined. It is proposed to predict corrosion according to the specific magnetic susceptibility χ0 of austenite and the amount δ-ferrite.

In this digital age, science teachers are continuously confronted with new emerging opportunities and challenges as a result of the rapid rate of discoveries in science and technology and information technology as well. Science educators, therefore, emphasize restructuring the education system to prepare 21st century learners to face complex challenges and prepare them to avail the opportunities at their fullest. This present study aimed to identify in-service science teachers' perceptions of developing 21st century skills through science education by employing an updated TPACK-21 framework. A mixed-methods study, using a survey-based questionnaire and focus group interviews with selected teachers, was undertaken to collect teachers' perspectives. The study revealed that when technology is used by teachers, it is often paired with specific content and pedagogically very different from what teachers are used to performing. The results highlight the need to use technology for innovation and to renovate contemporary teaching practices for 21st century learning.

This chapter considers the application of alkaline (NaOH) based catalyzed methanolysis of seed oil from Chrysophyllum albidum (African star apple) as a viable route for synthesis of methyl esters (biodiesel). Specific consideration was given to the chemical kinetics and thermodynamics of the irreversible consecutive mechanism of the process on the basis of higher application of methanol/molar ratio (>3:1) as a feasible approach for generating required data for commercial scale-up of the process. The application of power rate law revealed that second order model was the best fitted model on the 328 K, 333 K and 338 K temperature and 0–100 min ranges studied. Rate constants of the glyceride hydrolysis were 0.00710, 0.00870 and 0.00910 wt% min−1 for the triglyceride (TG), 0.02390, 0.03040 and 0.03210 wt% min−1 for the diglycerides (DG) and 0.01600, 0.03710 and 0.04090 wt% min−1 for the monoglycerides (MG) at the above respective temperatures. The activation energies were 2.707, 7.30 and 23.33 kcal/mol respectively. TG hydrolysis to DG was the rate determining step. Rates of reactions were found to increase with increase temperature and mixing rate (200, 400 and 800 rpm). No optimal mixing rate was detected and the highest mixing rate of 800 rpm was the most favorable in the mixing range under investigation. The possible reason for the absence of lag period is formation of methyl esters, which acted as a solvent for the reactants, and consequently, made the reaction mixture a homogeneous single phase. The quality of the produced methyl esters were found to compare with international standards. All the results lead to more diverse and novel applications of the seed oil in biodiesel productions.

ABSTRACT Improving drilling efficiency is crucial in reducing drilling costs, and monitoring drill bit wear provides an intuitive reflection of drilling efficiency. However, collecting on-site parameters that directly reflect drill bit wear is challenging, and few monitoring methods are available for assessing the degree of wear. Thus, quantitatively evaluating the wear of PDC drill bits has been a persistent research challenge. Evaluating drill bit wear status mainly relies on rock breaking efficiency and mechanical specific energy. In this study, a physical model was used to calculate mechanical specific energy, while wavelet analysis and clustering algorithms were used to characterize the wear process of drill bits. A GRU neural network was established to map drilling parameters to drill bit wear levels, achieving an accuracy of 95%. The model was tested using data from well A in China's Xinjiang oilfield, demonstrating its ability to predict the current drill bit wear level accurately. This model provides a solution for monitoring drill bit wear, assisting on-site personnel in making decisions on when to stop drilling, and enhancing the level of intelligence at drilling sites. BACKGROUND The drilling operation in the oil industry is a complex engineering process, and the drill bit is a critical component. The drill bit not only has to endure immense pressure but also fend off the effects of wear, heat, impact, corrosion, and other factors (Weeden, R, et al. 2011)1. If the wear on the drill bit reaches a certain level, it not only lowers drilling efficiency but also increases the safety risks associated with drilling (Wilson, A, et al. 2018)2. Therefore, monitoring the wear condition of the drill bit is highly important. The current technology for determining when to replace worn drill bits is based on the inferred dullness of the drill bit, derived from the trend of drilling parameters, rather than a reliable engineering method (Waughman, R, et al. 2003)3. Most scholars primarily characterize the trend of drill bit wear failure through changes in mechanical rate of penetration (ROP) (SONG Xianzhi., et al. 2022)12 and drill bit rock mechanical specific energy (MSE) to determine the appropriate time to remove the drill bit (Dupriest, F. E., et al. 2005)4. Quantitatively monitoring the degree of drill bit wear remains a challenging issue. This is primarily due to the influence of complex drilling conditions on subsurface information, (Abbas, R. K., et al. 2014)5 which leads to unavoidable deviations and noise in the recorded well data when reflected to the surface, and the limited number of factors considered in the drill bit wear models obtained from laboratory experiments, resulting in poor model performance in field applications (Rashidi, B., et al. 2014)6. On the other hand, the nature of subsurface operations is characterized by its concealment, making it difficult to quantitatively characterize the drill bit wear process. In recent years, with the development of digital and intelligent technologies, (XIAO Hua., et al. 2018)11 experts both domestically and abroad have conducted extensive research on the intelligent recognition of drill bit efficiency, (LI Hongbo., et al. 2022)13 significantly improving the accuracy of drill bit efficiency and rock breaking condition recognition. However, stability still needs to be improved (Chen, X., et al. 2018)7.

Flow Accelerated Corrosion (FAC) is very effective for nuclear power plant. This generalized corrosion can lead to the rupture of pipe and in some dramatic cases to casualties. During the last 20 years Electricité de France (EDF) has developed software called BRT-CICERO™ for the surveillance of the carbon steel piping system of its Nuclear Power Plants (NPPs). This software enables the operator to calculate the FAC wear rates by taking into account all the influencing parameters such as pipe isometrics, alloy content, chemical conditioning, design and operating parameters of the steam water circuit (temperature, pressure, etc…). This is a major tool to help operators organize their maintenance and inspections plan. The algorithms implemented in BRT-CICERO™ are based on tests conducted by EDF R&D, empirical results (national and international feedback), literature reviews and on permanent adjustments based on the operating feedback, via statistical studies. However, for some piping components, from the turbine’s hall, flow dynamics are not optimized and calculated FAC kinetics may be too conservative. EDF is committed for optimizing and increasing reliability of its maintenance programs to prevent the risk of pipe rupture due to FAC. As in consequence EDF is leading continuous improvement in parameters and calculation algorithms for BRT-CICERO™. Furthermore studies on the geometric characteristics of the pipes were conducted. In BRT-CICERO™ geometric effect of a pipe component (elbow reduction, tees …) is taken into account by considering a factor called “Geo” in the calculation to tune the thickness loss rate according the component type, its characteristics and specific effect on flow mass transfer. EDF implements finite element analysis software to compute the mass transfer coefficient k and so ascertain the “Geo” coefficient. These computed “Geo” coefficients are compared to those used in BRT-CICERO™. If necessary, current “Geo” coefficients used in BRT-CICERO™ will be adjusted and optimized to improve maintenance programs issued from the software. The presentation deals with the calculation method used for these studies and some results will be shown on tube and elbows.

Abstract This paper introduces an empirical Wear Projection Technology (WPT) which relies solely on data from two (or more) time-independent wear related measurements at a wear site. The development and application of this WPT insures that it is completely general in nature. Thus, WPT is potentially useful for all wear experiences where measurements and related extrapolations and interpolations can be made before a “failure” occurs. When applied to nuclear plant steam generator tubes using non-destructive examination measurements (obtained during in-service inspections) as input, WPT enables mechanism (typically turbulence and / or fluid-elastic induced vibration) independent and motion-type (sliding-only, impact-sliding or impacting) independent projections for each site with an ongoing wear process. A single application, or successive applications in a monitoring mode, provides the basis for proactive planning of inspections as well as for required decisions regarding the short and long term maintenance of that specific tube, of that specific steam generator, and finally, of that entire plant. Appropriate timing and number of applications provides plant operators with the basis to assure safe (and commercially optimum) continued operation under either constant or changing operating conditions. This paper presents the development of WPT along with example results from steam generator tube straight-leg and U-bend applications. These applications include an input data error assessment and a qualification. Views on how WPT relates to the Proposed US-NRC Steam Generator Rule for the tube wear degradation mode, and how it can be used to implement an Alternate Plugging Criteria, are provided. Ideas relative to the implementation of the original wear process model and numerical methods to compute tube vibration and related wear are also presented.

The aim of the research article is to study the mechanical and abrasive wear behaviour of carbon and glass fabric reinforced vinyl ester composites. The measured wear volume loss increases with increasing load/abrading distance. However, the specific wear rate decreases with increase in abrading distance and load. The results showed that the highest specific wear rate is for glass fabric reinforced vinyl ester composite with a value of 8.96 × 10−11 m3/Nm and the lowest wear rate is for carbon fabric reinforced vinyl ester composite with a value of 5.84 × 10−11 m3/Nm. Mechanical properties were evaluated and obtained values compared with the wear behaviour. The worn surfaces were examined using scanning electron microscopy (SEM).

Fiber-reinforced polymer (FRP) piping has been recognized for excellent corrosion resistance and high specific properties such as its strength-to-weight ratio. Despite the positive characteristics, FRP piping has limited, albeit growing utilization in industrial service. This is in part due to initial cost when compared to conventional metallic pipe. Reduced life cycle expenditures in conjunction with operational advantages may foster an increased implementation of FRP piping. This may be achieved through installation procedures, longevity and operational capabilities that are superior to those related to metallic piping. The present article reviews recent technological advances relating to these attributes, namely improved joining methods; enhanced wear, corrosion and damage resistance; and embedded monitoring systems for wear and other parameters.

The friction and wear properties of polymer were investigated under a hydrogen atmosphere, by using PTFE (polytetrafluoroethylene) and two kinds of PTFE composites. Experiments were also conducted in air, nitrogen, and vacuum environment. The experiment carried out by pin-on-disk friction and wears apparatus in the vacuum chamber. Pin specimens are no filling PTFE, Gr-filled PTFE (Gr filled with 25 wt%) and MoS2–filled PTFE (MoS2 filled with 25 wt%). Friction disk is aluminum alloy 6061-T6 with 0.02μm surface roughness. Aluminum alloy 6061-T6 is able to use for apparatus for hydrogen. After experiments, specific wear rate was calculated, specimen surface, wear track and wear debris were observed, surface profile of the wear track were measured. The specific wear rate of unfilled PTFE and PTFE/MoS2 of in air was lower than the other atmospheres. The A6061-T6 disk was worn by PTFE pin specimens and in the case of wear track was much rougher, the specific wear rate of pin specimens tended to increase without unfilled PTFE in air and PTFE/Gr.

Wear behavior of polymeric sealing material sliding against austenitic stainless steel was evaluated within gaseous hydrogen atmosphere to ensure the durability and longevity of polymeric seals used in fuel cell vehicles and related hydrogen infrastructures. In this study, unfilled polytetrafluoroethylene (PTFE) was considered as a representative polymeric material for seals and its wear behavior was evaluated by using 3pin-on-disk wear tester coupled with the environmental test chamber. Results indicated that the specific wear rate of unfilled PTFE became significantly smaller in gaseous hydrogen compared with that in air. However, the specific wear rate further decreased in argon gas. Optical microscopy and XPS analysis of the disk specimen surface indicated that the wear behavior of PTFE highly depended on the transfer film formation on the sliding counterface. Notable influences of gaseous hydrogen on the formation process of PTFE transfer film and subsequent wear behavior could be postulated from XPS spectra.

In this study, the effect of different counterparts on the wear resistance of AA6082 aluminum alloy was investigated. In tests using pin-on-disk method, 6 mm diameter Al2O3, 100Cr6 and WC-6Co balls were used as counterparts. The tests were carried out using 500 m sliding distance and 5N load. The lowest specific wear rate was measured as 7.58x10-4 mm3/Nm in WC-6Co / AA6082 couple, and the highest value was measured as 9.71x10-4 mm3/Nm in 100Cr6/AA6082 couple. In the Al2O3/AA6082 couple, the specific wear rate of the AA6082-T6 sample was determined as 8.23x10-4 mm3/Nm.While it was observed that the dominant wear type in the 100Cr6/AA6082 pair was abrasive wear, oxidation wear and oxide tribofilm were detected in the WC-6Co/AA6082 and Al2O3/AA6082 couple besides the abrasive wear.

In this study the effects of silica size (or specific surface area), mechanical properties and crosslink density on the wear of silica-filled SBRs (styrene butadiene rubbers) were examined. The modulus of each silica-filled SBR examined was proportional to crosslink density. The wear rate of silica-filled SBRs was reduced as the modulus and crosslink density increased. The wear rates increased as the specific surface area of the silica fill particles decreased, when the content of silane coupling agent was constant. As a result, the wear rate was shown to be lower as the modulus and crosslink density increased.

Abstract. Current approaches to maintenance of rolling stock bogies are focused on compliance to wear limits as stipulated by OEM specifications. OEM recommendations are critical to providing an industry wide approach to safety and compliance. These are not operation specific and are often not the most cost-effective solutions. A system approach to reliability is an established approach that is applied in less complex systems where the relationships between components are well defined with historical data and predictable conditions. Extending this approach to more complex multi-variate systems where many relationships are not intuitively obvious or mathematically defined presents a challenge. Machine learning techniques have been applied to address such problems with examples in image recognition, tool wear prediction using multiple sensory inputs and estimating railway bogie wear using vibration inputs. [8,9,10] The aim of the study is to extend and adapt machine-learning techniques to the area of developing maintenance strategies for optimal business benefit with a specific focus on railway bogie maintenance. This study aims to present an insight into the variables, which includes bogie tracking condition affecting track side wear rate. A finding is that an in-depth study of each independent variable’s individual impact is a necessary step to efficient modelling. These include track geometry, operating and bogie component wear variables. Track side wear, curve radius, superelevation and track top variance have been found to be significant predictors of track side wear rate. These impact predictions are not consistent between the different rail tracks and are not exhaustive. Specifically, the impact of bogie performance requires inclusion. Combining these variables mathematically using statistical inference and convolutional theory with maximum likelihood estimators would establish a predictor for side wear rate for the specific operation. The paper finally discusses the relationship of area wear rate to side wear rate and the influences of grinding frequency and rail material type.

The overall objective of the current proposal is to develop procedures to improve the pregnancy rate achieved following transfer of fresh or cryopreserved embryos produced in the laboratory into heat-stress recipients. The overall hypothesis is that pregnancy rate in heat-stressed lactating cows can be improved by use of embryo transfer and that additional gains in pregnancy rate can be achieved through development of procedures to cryopreserve embryos, select embryos most likely to establish and maintain pregnancy after transfer, and to enhance embryo competence for post-transfer survival through manipulation of culture conditions. The original specific objectives were to 1) optimize procedures for cryopreservation (Israel/US), 2) develop procedures for identifying embryos with the greatest potential for development and survival using the remote monitoring system called EmbryoGuard (Israel), 3) perform field trials to test the efficacy of cryopreservation and the EmbryoGuard selection system for improving pregnancy rates in heat-stressed, lactating cows (US/Israel), 4) test whether selection of fresh or frozen-thawed blastocysts based on measurement of group II caspase activity is an effective means of increasing survival after cryopreservation and post-transfer pregnancy rate (US), and 5) identify genes in blastocysts induced by insulin-like growth factor-1 (IGF-1) (US). In addition to these objectives, additional work was carried out to determine additional cellular determinants of embryonic resistance to heat shock. There were several major achievements. Results of one experiment indicated that survival of embryos to freezing could be improved by treating embryos with cytochalasin B to disrupt the cytoskeleton. An additional improvement in the efficacy of embryo transfer for achieving pregnancy in heat-stressed cows follows from the finding that IGF-1 can improve post-transfer survival of in vitro produced embryos in the summer but not winter. Expression of several genes in the blastocyst was regulated by IGF-1 including IGF binding protein-3, desmocollin II, Na/K ATPase, Bax, heat shock protein 70 and IGF-1 receptor. These genes are likely candidates 1) for developing assays for selection of embryos for transfer and 2) as marker genes for improving culture conditions for embryo production. The fact that IGF-1 improved survival of embryos in heat-stressed recipients only is consistent with the hypothesis that IGF-1 confers cellular thermotolerance to bovine embryos. Other experiments confirmed this action of IGF-1. One action of IGF-1, the ability to block heat-shock induced apoptosis, was shown to be mediated through activation of the phosphatidylinositol 3-kinase pathway. Other cellular determinants of resistance of embryos to elevated temperature were identified including redox status of the embryo and the ceramide signaling pathway. Developmental changes in embryonic apoptosis responses in response to heat shock were described and found to include alterations in the capacity of the embryo to undergo caspase-9 and caspase-3 activation as well as events downstream from caspase-3 activation. With the exception of IGF-1, other possible treatments to improve pregnancy rate to embryo transfer were not effective including selection of embryos for caspase activity, treatment of recipients with GnRH.and bilateral transfer of twin embryos. In conclusion, accomplishments achieved during the grant period have resulted in methods for improving post-transfer survival of in vitro produced embryos transferred into heat-stressed cows and have lead to additional avenues for research to increase embryo resistance to elevated temperature and improve survival to cryopreservation. In addition, embryo transfer of vitrified IVF embryos increased significantly the pregnancy rate in repeated breeder cows.