Compensating springback in the automotive practice\ud using MASHAL

New materials are used in the automotive industry to reduce weight and to improve crash performance. These\ud materials feature a higher ratio of yield stress to elastic modulus leading to increased springback after tool release. The resulting\ud shape deviations and their efficient reduction is of major interest for the automotive industry nowadays. The usual strategies for\ud springback reduction can diminish springback to a certain amount only. In order to reduce the remaining shape deviation a\ud mathematical compensation algorithm is presented. The objective is to obtain the tool geometry such that the part springs back\ud into the right shape after releasing the tools.\ud In practice the process of compensation involves different tasks beginning with CAD construction of the part, planning the\ud drawing method and tool construction, FE-simulation, deep drawing at try-out stage and measurement of the manufactured part.\ud Thus the compensation can not be treated as an isolated task but as a process with various restrictions and requirements of\ud today’s automotive practice. For this reason a software prototype for compensation methods MASHAL – meaning program to\ud maintain accuracy (MASsHALtigkeit) – was developed. The basic idea of compensation with MASHAL is the transfer and\ud application of shape deviations between two different geometries on a third one. The developed algorithm allows for an effective\ud processing of these data, an approximation of springback and shape deviations and for a smooth extrapolation onto the tool\ud geometry.\ud Following topics are addressed: positioning of parts, global compensation and restriction of compensation to local areas,\ud damping of the compensation function in the blank holder domain, simulation and validation of springback and compensation of\ud CAD-data. The complete compensation procedure is illustrated on an industrial part

The development of a finite elements based springback compensation tool for sheet metal products

Springback is a major problem in the deep drawing process. When the tools are released after the forming stage, the product springs back due to the action of internal stresses. In many cases the shape deviation is too large and springback compensation is needed: the tools of the deep drawing process are changed so, that the product becomes geometrically accurate after springback. In this paper, two different ways of geometric optimization are presented, the smooth displacement adjustment (SDA) method and the surface controlled overbending (SCO) method. Both methods use results from a finite elements deep drawing simulation for the optimization of the tool shape. The methods are demonstrated on an industrial product. The results are satisfactory, but it is shown that both methods still need to be improved and that the FE simulation needs to become more reliable to allow industrial application

Springback Compensation: Fundamental Topics and Practical Application

Now that the simulation of deep drawing processes has become more reliable the virtual\ud compensation of the forming tools has become reality. In literature, the Displacement Adjustment (DA)\ud algorithm has proved to be most effective. In this article it is shown how the compensation factor, required for\ud (one-step) DA depends on material, process and geometrical parameters. For this an analytical bar stretchbending\ud model was used. A compensation factor is not required when DA is applied iteratively and the\ud products geometrical accuracy is improved further. This was demonstrated on an industrial part. The\ud compensation varies over the product, leading to a reduction in shape deviation of 90% and more, a result that\ud could not have been achieved with one-step compensatio

Greenhouse and Field Evaluations of Entomopathogenic Nematodes (Nematode: Heterorhabditidae and Steinernematidae) for Control of Cabbage Maggot (Diopters: Anthomyiidae) on Cabbage

Entomb pathogenic nematodes-Heterorhabditis bacteriophora Poinar (Oswego strain), Steinenema carpocapsae (Weiser) (NY001 strain), Steinemema carpocapsae (25 strain), Steinemema feltiae Filipjev (=Neoaplectana carpocapsae Weiser) (369 strain), Steinernema feltiae (27 strain), and Steinernema riobravus Cabanillas and Poinar (355 strain)-were examined for pathogenicity against cabbage maggot, Delia radicum (L.), larvae in the greenhouse and field. Applications (per plant) of 3,000 and 4,000 infective juveniles of S. feltiae (369 strain), 30,000 infective juveniles of H. bacteriophora (Oswego strain), and 300 and 30,000 infective juveniles of S. feltiae (27 strain) reduced the number of D. radicum that developed to pupae on potted cabbage plants. H. bacteriophora (Oswego) at applications of 3,000 and 30,000 infective juveniles per plant and S. feltiae (27 strain) at applications of 30,000 (but not 3,000) infective juveniles per plant significantly reduced root damage caused by larvae of D. radicum. Logarithmically increased dosages between 100 and 100,000 infective juveniles per plant of S. feltiae (27 strain) linearly reduced the number of D. radicum pupae that developed on potted cabbage plants and the damage caused to the roots by D. radicullarvae. Root and stem dry weights of cabbage plants infested with D. radicum were significantly greater for plants inoculated with 100,000 infective juveniles of S. feltiae (27 strain) than for plants not inoculated with nematodes. Nematode inoculation did not prevent significant losses in root or stem dry weights at dosages less than 100,000 infective juveniles per plant. Soil surface applications of 100,000 and 200,000 infective juveniles per plant of S. feltiae (27 strain) were more effective than subsurface applications in preventing damage by natural or augmented populations of D. radicum larvae on cabbage in the field. However, mortality rates of wax moth larvae exposed to soil samples treated with S. feltiae (27 strain) suggested that this nematode showed greater persistence when applied beneath rather than on the soil surfac

Diffuse reflection of ultracold neutrons from low-roughness surfaces

We report a measurement of the reflection of ultracold neutrons from flat, large-area plates of different Fermi potential materials with low surface roughness. The results were used to test two diffuse reflection models, the well-known Lambert model and the micro-roughness model which is based on wave scattering. The Lambert model fails to reproduce the diffuse reflection data. The surface roughness b and correlation length w , obtained by fitting the micro-roughness model to the data are in the range 1$\le$ b $\le$3 nm and 10$\le$ w $\le$120 nm, in qualitative agreement with independent measurements using atomic force microscop

Testing isotropy of the universe using the Ramsey resonance technique on ultracold neutron spins

Physics at the Planck scale could be revealed by looking for tiny violations of fundamental symmetries in low energy experiments. In 2008, a sensitive test of the isotropy of the Universe using has been performed with stored ultracold neutrons (UCN), this is the first clock-comparison experiment performed with free neutrons. During several days we monitored the Larmor frequency of neutron spins in a weak magnetic field using the Ramsey resonance technique. An non-zero cosmic axial field, violating rotational symmetry, would induce a daily variation of the precession frequency. Our null result constitutes one of the most stringent tests of Lorentz invariance to date.Comment: proceedings of the PNCMI2010 conferenc