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The growing use of carbon-fibre-reinforced polymer (CFRP) composites as high-performance lightweight materials in aerospace and automotive industries demands efficient and low-cost machining technologies. The use of laser machining for cutting and drilling composites is attractive owing to its high speed, flexibility, and ease of automation. However, the anisotropic material properties of composites, and issues related to the heat-affected zone (HAZ), charring, and potential delamination during laser processing, are major obstacles in its industrial applications. In order to improve the quality and dimensional accuracy of CFRP laser machining, it is important to understand the mechanism of the transient thermal behaviour and its effect on material removal. Based on the ‘element death’ technique of the finite element (FE) method, a three-dimensional model for simulating the transient temperature field and subsequent material removal has been developed, for the first time, on a heterogeneous fibre—matrix mesh. In addition to the transient temperature field, the model also predicts the dimensions of the HAZ during the laser machining process. Experimental results obtained with same process variables using a 355 nm DPSS Nd:YVO4 laser were used to validate the model. Based on the investigation, the mechanism of material removal in laser composite machining is proposed. The results suggest that the employed FE approach can be used to simulate pulsed laser cutting of fibre-reinforced polymer composites.

In manufacturing by machining, thermal loads on cutting tools can have a major influence on tool wear and hence process cost, especially at higher cutting speeds. An investigation has been undertaken to determine heat partition into the cutting tool for high-speed machining of AISI/SAE 4140 high-strength alloy steel with uncoated and TiN-coated tools. The cutting tests have been performed at cutting speeds ranging between 100 and 880 m/min with a feed rate of 0.1 mm/rev and a constant depth of cut of 2.5 mm. Cutting temperatures are measured experimentally using an infrared thermal imaging camera. The sticking and sliding regions are investigated from an examination of the tool-chip contact region using a scanning electron microscope (SEM). In addition, non-uniform heat intensity is modelled according to the contact phenomena. In this work, evaluation of the fraction of heat flowing into the cutting tool is carried out by iteratively reducing the available heat flux until the finite element method (FEM) temperatures are simultaneously matched at multiple points with the experimentally measured temperatures. This paper elucidates on the differences in thermal shielding for uncoated and TiN-coated tools. It is found that heat partition into the cutting tool decreases from a fraction of 0.41 to 0.17 for conventional cutting speeds and increases from 0.19 to 0.24 for high-speed machining when using uncoated carbide cutting tools. On the other hand, with TiN-coated tools, heat partition varies from 0.35 down to 0.095 for the whole range of cutting speeds. These results clearly show that the use of TiN-coated tools generally reduces heat partition into the cutting tool, but does so more significantly in high-speed machining (HSM) as compared with conventional machining speeds. The driver behind this study on heat partition in machining with TiN coatings is the design of coatings with enhanced thermal shielding properties.

Abstract. Avian pneumovirus (APV) infection of turkeys in Minnesota was first confirmed in March 1997. Serum samples (n ϭ 5,194) from 539 submissions to Minnesota Veterinary Diagnostic Laboratory were tested by a modified enzyme-linked immunosorbent assay (ELISA). Of these, 2,528 (48.7%) samples from 269 submissions were positive and 2,666 (51.3%) samples from 270 submissions were negative for APV antibodies. Most positive samples were from Kandiyohi, Stearns, Morrison, and Meeker counties in Minnesota. In addition, 10 samples from South Dakota were positive. The sensitivity and specificity of the ELISA test with anti-chicken and anti-turkey conjugates were compared by testing field and experimental sera. The ELISA test with antiturkey conjugate was more sensitive than that with anti-chicken conjugate. The ELISA tests with antigens prepared with APV strains isolated from Colorado and Minnesota were also compared. No difference was detectable. Currently, the Minnesota Veterinary Diagnostic Laboratory uses an antigen prepared from the Colorado isolate of APV and a goat anti-turkey conjugate in the ELISA test.Turkey rhinotracheitis, caused by turkey rhinotracheitis virus (TRTV), was first detected in South Africa in the late 1970s 2 and was subsequently reported from Great Britain, South Africa, France, Israel, Spain, Germany, Italy, and The Netherlands. 1,15 The TRTV is an avian pneumovirus that belongs to family Paramyxoviridae, subfamily Pneumovirinae. It is an enveloped virus that lacks hemagglutination and neuraminidase activities and contains a nonsegmented, negative-sense, single-stranded RNA. The virus has been separated into 2 subgroups, the subgroup A being formed by the early British and French isolates and the subgroup B, by the other continental European strains. 4,5,13 The diagnosis of TRTV infection is based on the isolation and identification of the virus and/or serology. Because of the fastidious nature of the virus, the isolation of TRTV is very difficult and time consuming. The detection of TRTV antibodies, on the other hand, may be more rapid and economical when compared with virus isolation and reverse transcriptase-polymerase chain reaction. 6,12 Serum antibodies to TRTV have been detected by indirect immunofluorescence assay (IFA), virus neutralization, and enzyme-linked immunosorbent assay (ELISA). 3,7,9,10,16,118 Outbreaks of avian pneumovirus (APV) infection were reported in Minnesota turkeys for the first time in March 1997. The clinical signs consisted of depression, coughing, sinusitis, airsacculitis, and mortality. Several isolates of APV were isolated from infected turkey flocks. 8 Earlier, an APV was isolated from infected turkey flocks in Colorado.