Study on Spinning Process Parameters of the Copper Bushing by Tribological Properties and Physical Testing

The bushing is a kind of ring sleeve which acts as a liner outside the mechanical parts, which needs good strength, hardness and fatigue resistance. In this paper, the copper bushing was prepared by spinning forming method, and the process parameters of spinning were explored. According to the results of material thermal simulation and test, the conclusion is that the spinning process of copper bushing needs to be carried out in two passes by reverse spinning method. The thinning rate is 30% and 25% respectively. The gap between the mandrel and the roller is 10mm, the feed ratio is 1mm/r, and the spinning temperature is 250°C.

Brief communication: Thwaites Glacier cavity evolution

Between 2014 and 2017, ocean melt eroded a large cavity beneath and along the western margin of the fast-flowing core of Thwaites Glacier. Here we show that from 2017 to the end of 2020 the cavity persisted but did not expand. This behaviour, of melt concentrated at the grounding line within confined sub-shelf cavities, fits with prior observations and modelling studies. We also show that acceleration and thinning of Thwaites Glacier grounded ice continued, with an increase in speed of 400 m a−1 and a thinning rate of at least 1.5 m a−1, between 2012 and 2020.

Research on Ultimate Thinning Rate of Superalloy Spinning

Spinning forming is an effective method for processing thin-walled rotating body parts. The influence of process parameters on the spinning forming limit of materials was studied for the four high-temperature alloys of GH3044, GH3625, GH3536 and GH4169 used in aero-engines. The results can be used as aero-engine high-temperature alloy parts spinning process and provides experimental basis and process guidance. The research results showed that the forming temperature had a significant effect on the spinning forming performance of superalloy materials. When the temperature increased to 800°C and above, the ultimate thinning rate raised 70%. The ultimate thinning rate of GH4169 was higher than the other three materials and GH3044 and GH3536 was at the middle level, GH3625 was relatively low. At the same time, the feed ratio and the corner radius of the rotary wheel had a certain influence on the ultimate thinning rate of different superalloys. The spinning process needs to select reasonable process parameters according to the actual situation when the spinning is applied to manufacture parts.

Spinning Process of D406A Ultra-High Strength Steel

D406A steel is a medium-carbon low-alloy steel, which has excellent comprehensive mechanical properties. It is widely used in the production of missiles and rocket barrels. In this paper, the spinning forming limit test and the intermediate heat treatment process of ultra-high-strength steel were used to explore the effect of spinning process and heat treatment on the properties of spinning parts. The research results showed that the reduction amount of the material made the material thinning rate approach the limit thinning rate. The final blank wall thickness was reduced from 15 mm to 3.0 mm when the cracking occurred. It was calculated that the material's power spinning limit thinning rate was 80%. The ferrite matrix after spinning showed a streamline distribution characteristic perpendicular to the thinning direction, and the precipitated carbides were uniformly distributed on the surface of the matrix, which had the characteristics of deformation and extension along the streamline. After the heat treatment, the structure of the spinning parts changed continuously. When the structure was quenched and tempered, the martensitic structure can be obtained, and the tempered martensitic structure was smaller. Furthermore a test piece for ultra-high-strength steel spinning technology has been developed, and the solutions discussed for flanging defects in the actual spinning process, and test data for the actual production of ultra-high-strength steel spinning parts accumulated.

Numerical simulation for expansion of preform and optimization of preform in thermoset composites

The expansion of preform and the optimization of preform have become important steps in the molding process. At present, there are some questions in the expansion of thermoset composite material preform and precompression, for example, the inaccurate dimensions, cracks, and wrinkles. For the expansion of preform, the finite element inverse algorithm is used as the expansion algorithm, and then the initial solution is optimized by the arc length mapping method, the expansion of preform is realized by the iterative equation which is solved by the ABAQUS solver. The effectiveness of the expansion of preform is verified through the comparison between the finite element inverse algorithm with DYNAFORM. The optimization of the precompression process is researched in order to solved the problems of cracks and wrinkles in the integral precompression method of preform. Firstly, the precompression sequence is adjusted by the precompression method, and then the precompression direction is optimized by the genetic algorithm. Through numerical simulation, the maximum thinning rate is reduced to 13%, and the maximum thickening rate is reduced to 6%, which improve the problems of cracks and wrinkles of preform, and the effectiveness of the optimization method is verified.

Numerical Simulation and Experimental Research on Rubber Flexible-Die Forming Limitation with New Position-Limited Back Pressure Mechanism

The forming limitation and the wall thickness distribution are two main parameters for estimating the forming quality of T-shaped tube. In this paper, the effects of three key factors on the forming limitation and the wall thickness distribution are investigated, which are punch front distance l1, reverse height h1 and matching relationship between rubber hardness and axial feed Δl. A new position-limited back pressure mechanism is proposed which is made up of rigid position-limited lever, flexible back pressure medium and rigid spacer. The simulations and experiments are carried out. Both results show the thinning rate of the wall thickness decreases first and then increases and the thickening rate decreases gradually with the increase of l1. The branch reaches the highest with the l1 of 5mm under the requirements of thinning rate and thickening rate. With the increase of reverse height h1, the bigger h1 is beneficial to the wall thickness thinning suppress at the top of branch, the highest branch was formed when h1 is 7mm. When Δl is fixed, the rubber hardness has a great influence on the forming defects, higher rubber hardness causes the top of branch to rupture and lower causes the wall to wrinkle. When rubber hardness is fixed, the thickening rate decreases with the increase of Δl. The best forming limitation and thickness distribution are achieved with the punch front distance l1 of 5mm, the reverse height h1 of 7mm, the rubber hardness of 70HA and the axial feed Δl of 24mm.

Brief Communication: Thwaites Glacier cavity evolution

Between 2014 and 2017, ocean melt eroded a large cavity beneath and along the western margin of the fast-flowing core of Thwaites Glacier. Here we show that from 2017 to the end of 2020 the cavity persisted but did not expand. This behaviour, of melt concentrated at the grounding line within confined sub-shelf cavities, fits with prior observations and modelling studies. We also show that acceleration and thinning of Thwaites Glacier grounded ice continue, with an increase in speed of 400 ma−1 and a thinning rate of 1.5 ma−1, between 2012 and 2020.

Tracking the thickness of the A68 Iceberg using CryoSat-2 and ICESat-2

<p>The A68 iceberg calved from the Larsen C ice shelf on the Antarctic Peninsula in July 2017 and has since been drifting northwards towards South Georgia. Originally covering an area of 5664 sq km, A68A's extent has been reduced to 2606 sq km (as of 23 December 2020) following the detachment of multiple smaller bergs. Using Satellite Altimetry data from CryoSat-2 and ICESat-2, we measure the thickness of the A68 iceberg. We use CryoSat-2 data acquired in the year before A68's calving from the Larsen C Ice Shelf in 2017 to create an initial thickness map. Following its calving, both CryoSat-2 and ICESat-2 tracks are geocoded onto the iceberg using imagery from MODIS and Sentinel-1. Comparing these measurements to the initial thickness allows us to track changes in A68's thickness. The thickness map reveals the presence of multiple 30m deep channels oriented along its narrow side, forming lines of weakness along which the iceberg shattered into multiple large fragments in December 2020. At the time of calving, its average thickness was 232m with a maximum thickness of 285m. Repeated measurements from satellite altimetry show the iceberg has thinned by an average of 32m, a thinning rate of 2.5cm per day. Combined with changes in area, we estimate that the iceberg has lost 64% of its original volume, or 941 cubic kilometres, representing a significant input of freshwater to the surrounding ocean. </p>