Cold Assessment Research Articles

Stress distribution in laser metal deposited multi-layer thick-walled parts of Ti-6Al-4V

The laser metal deposition is an additive manufacturing technology enabling the production of large scale complex parts without additional treatment like welding or machining. The study of the origin of the stress field during laser metal deposition is essential for solving a number of problems, including: the assessment of cold and hot cracking; prediction of the fatigue resistance, and the stress corrosion cracking. The quantitative study of transient and residual stresses in build parts is necessary for optimising the parameters of processing and post-production stress relieving heat treatment. Residual stress field in laser metal deposited 50-layer (4-pass per layer) wall of Ti-6Al-4V was analysed experimentally using neutron diffraction and numerically using finite element simulation. Long dwell time between passes and a rigid substrate was used in order to simulate conditions of large scale parts fabrication. An analysis of the calculated and experimentally measured residual stress field showed that near the edges of the buildup there is a region where all three components of stress field are tensile, and normal stress exceeds the yield stress by more than 25%. Moreover, normal plastic strain in this area are also tensile and reaches 2.5-3%. The longitudinal tensile stress closes to yield stress on almost the entire length of the several last layers near the top of the buildup. Residual stress field calculated using neutron diffraction data according to interplanar lattice distance obtained assuming plane stress approach has a satisfactory agreement with FE simulated results.

Safety Assessment of Cold Welding Defect in Electro-Fusion Joint of Polyethylene Pipe

Cold welding defect is the most common defect in electro-fusion (EF) joint for connecting polyethylene (PE) pipe. In our previous study [1], the cold welding defect is successfully inspected by an eigen-line method based on phased array ultrasonic testing technology. However, limited research has been reported on the acceptance criterion of cold welding defect in EF joint. In this paper, the bonding strength of EF joint is measured using a peeling test. The bonding energy of welding interface is calculated both by phenomenological model and deformation energy analysis method. EF joints with different degrees of cold welding are made and used for peeling tests. The results show that the bonding energy of fused interface rises rapidly after bonding and then goes through a plateau region. The starting point of the plateau region in the bonding energy versus welding time curve is regarded as the minimum required welding time of EF joint. Based on bilinear fitting, the acceptance criterion of cold welding defect is proposed.

North hardship conditions rating in research works and regional policy (on examples of the regions related to resources)

The influence of peculiar features of the North and the Arctic on formation of scope of research works and the directions of regional policy is shown. The assessment of cold (climatic discomfort, permafrost, etc.), periferieness, high natural and resource potential, ethnicity is directed on the studying of traditional problems of demography, the organization of the relations between corporations and territories, the tax and budgetary providing. The problem of choice of measurement techniques of level of economic and social condition is especially allocated. The attempt to coordinate raw specialization of the northern and the arctic regions with the solution of strategic problems of their sustainable development is made.

Assessment of Cold Induced Alterations in Catecholamine Turnover of Lean and Glutamate-treated Obese Rats

Excretion of norepinephrine (NE) and vanillylmandelic acid (VMA) in urine as well as NE-turnover in tissues from lean and glutamate-treated obese rats were determined in warm and cold environment. NE-and VMA-excretion in urine was elevated by cold exposure, indicating an activation of the sympathetic nervous system in animals of both groups. Organspecific NE-turnover responds with higher sensitivity to cold in obese rats but without complete compensation in brown adipose tissue. Urinary NE- and VMA- excretion as well as NE-turnover in organs confirmed that cold exposure activates the sympathetic nervous system. Measurement of NE-turnover in tissues gives organspecific information regarding alterations in sympathetic activity during cold exposure, whereas excretion of NE and VMA in urine is a summarizing measure for the whole body turnover only.

Assessment of Cold and Heat Tolerance of Winter‐grown Canola (Brassica napus L.) Cultivars by Pollen‐based Parameters

AbstractWinter‐grown canola (Brassica napus L.) production is limited mostly by frost and winter kill in the southern canola‐growing regions of the United States. Tolerance to cold and heat were assessed by studying percentage of pollen viability (PV), in vitro pollen germination (PG) and pollen tube length (PTL) for 12 field‐grown cultivars. Freshly collected pollen from all cultivars were incubated on artificial solid growth media at a constant temperature ranging from 10 to 35 °C at 5 °C interval for 30 h to determine PG and PTL. A modified bilinear model best described the temperature response functions of PG and PTL. Canola cultivars showed significant variability (P < 0.001) for PV (61.3 % to 89.7 %), PG (29.0 % to 48.2 %) and PTL (463 to 931 μm). The average cardinal temperatures, Tmin, Topt and Tmax, for PG and PTL were 6.4, 24.3 and 33.7 °C, respectively. Principal component analysis revealed that maximum PG, PTL, Tmin and Topt of both PG and PTL were the most important factors in determining cold tolerance, whereas Tmax of PG and PTL, and maximum PG and PTL were more responsible in separating the cultivars for heat tolerance. The canola cultivar, KS3077, was the most cold tolerant with the lowest Tmin and the widest temperature adaptability range, and the cultivar Kadore was the most heat tolerant with the highest Tmax for the PG. The identified cold‐ and heat‐tolerant cultivars may be useful in canola‐breeding programmes to develop cultivars suitable for a niche environment.

Hobson's Choice

Enemy forces should not be able to pursue their way either by land, sea or air to the United States across Canadian territory. William Lyon Mackenzie King, 20 August 1938 [W]hat we have to fear is more a lack of confidence in the United States as to our security, rather than enemy action... If we do enough to assure the United States we shall have done a good deal more than a cold assessment of the risk would indicate to be necessary. Maurice Pope, April 1944THE CANADA-UNITED STATES DEFENCE RELATIONSHIP has been a real bargain for the Canadian government, allowing it to enjoy a level of security it could never have reached with its own resources. In return, Ottawa must make sure that its territory will not be used as a forward base or a port of entry for eventual enemies of the United States. The problem is that Canadians do not necessarily share either American perceptions of what constitutes a threat or their view of how a perceived threat should be countered. Consequently, the government of Canada often adopts defensive measures that it does not always consider necessary. Thus, according to Paul Letourneau and Michel Fortmann, when faced with a Pentagon 'which almost unilaterally defines the nature of the threat, Canada essentially tries to limit American ambitions, whilst preserving the friendly character of their exchanges.'(1) This was certainly an apt description of the situation that prevailed during the Second World War and the cold war. It is our contention that little has changed in the dynamics of the United States-Canadian defence and security relationship since the cold war ended. The risks of diverging in any meaningful way from what the United States expects of Canada are still considered far too great for any Canadian government to contemplate seriously.Since 1993, when the Liberal government came to power in Ottawa, bilateral relations between Canada and the United States have seemed to be nothing less than agreement and harmony, especially over questions of defence and security. Despite its rhetoric, which is full of references to the need for greater independence vis-a-vis the United States, the government of Jean Chretien has developed a good relationship with the administration of Bill Clinton in the United States.(2) Nevertheless, changes in United States threat perceptions and defence doctrines could force Canada to adopt measures that do not necessarily correspond to its priorities and might even conflict with some of its policies, notably in the areas of the fight against non-military threats and the defence of North American aerospace. Unfortunately, Canada has little choice. Refusal could endanger the very foundations of the American pillar of Canada's defence policy.DIFFERING PRECEPTIONS AND PRIORITIESThe different views of the two governments on what constitutes a threat and how to deal with it affect the grand orientations of Canadian and American security policies. United States strategic priorities have evolved over the last few years. The American government can hardly escape its 'international responsibilities,' that is, putting American interests first and protecting the country's dominant position, any more than it could during the cold war. Washington has no qualms about using force against perceived 'trouble-makers' such as Serbia, Iraq, or North Korea. But what changes the defence equation in the United States is the increasing number of insidious and unpredictable threats against its territory. Terrorism, drug trafficking, attacks against cyberspace, proliferation of missile technology, and sophisticated industrial spying have all become objects of increasing concern.Nobody should be surprised that more and more Americans worry just as much, if not more so, about the security of the territory of the United States itself as about protecting their international interests, or that an important segment of the political elite is turning toward isolationism and defence of the homeland. …