Wechselverfestigung beim Fräsen von Stahl/Kinematic hardening in steel 42CrMo4

Bei der spanenden Endbearbeitung treten an der Oberfläche zyklische Belastungen in wechselnden Richtungen auf. Isotrope Verfestigungsmodelle wie das Johnson-Cook-Modell berücksichtigen dies nicht. In diesem Beitrag wird eine Erweiterung des JC-Modells um einen kinematischen Verfestigungsanteil untersucht, um genauere Vorhersagen zu ermöglichen. In zyklischen Biegetests wurden für 42CrMo4 die Parameter für einen Armstrong-Frederick-Ansatz ermittelt, der im FE-System „Abaqus“ implementiert wurde.   During the finishing of components, cyclic loads occur on the surface in alternating directions. Isotropic hardening models do not take this into account. Here, an addition of kinematic hardening to the Johnson-Cook model is investigated. In cyclic bending tests, a Bauschinger effect was observed on 42CrMo4. This can be simulated by supplementing the JC model with the Armstrong-Frederick approach with a Vumat in the FE-System „Abaqus“.

Comparison between XY Spin Chains with Spin 1/2 or 1 Interacting with Quantized Electromagnetic Field by One and Two Photon Jaynes-Cummings Model

This paper describes two cases of interaction between a quantized electromagnetic field and two different XY spin molecules; one with spins ½, and the other with spins 1. Both interact with a quantized electromagnetic field, with one of the spins in the chain interacting with the electromagnetic field. The interaction between the field mode and the spin chain with spins 1 is described by the one- and two-photon Jaynes-Cummings model (JC model). On the other hand, the interaction between the spins ½ and the electromagnetic field is described only by the one-photon Jaynes-Cummings model. Analytical and numerical calculations were made for the case of a different number of photons in the field mode, a different number of spins, and a different position of spin, interacting with the electromagnetic field. The invariant and block structures of such a chain are shown with a comparison made between the evolution of the magnetic moment and the number of photons in both cases.

Constitutive Modeling of the Flow Stress Behavior for the Hot Deformation of Cu-15Ni-8Sn Alloys

Three constitutive models, strain-compensated Arrhenius model, modified Johnson–Cook (JC) model, and modified Zerilli–Armstrong (ZA) model, were established for the hot-deformed Cu-15Ni-8Sn alloy based on hot compression tests. By introducing average absolute relative error (AARE), correlation coefficient (R), and relative error, the prediction accuracy of these three models was assessed. The results indicate that strain-compensated Arrhenius model has the highest accuracy at describing the flow stress behavior of the studied alloy, followed by modified JC model and modified ZA model. Moreover, the strain-compensated Arrhenius model established in this work has a great practicability in the hot-extrusion simulation of Cu-15Ni-8Sn alloys. This article provides a theoretical basis for optimizing hot deformation parameters in industrial production of the Cu-15Ni-8Sn alloys.

NIMG-29. DEVELOPING AUTOMATIC SEGMENTATION METHOD FOR BRAIN TUMOR MR IMAGES THAT CAN BE USED AT MULTIPLE FACILITIES

BACKGROUND Manual segmentation of brain tumor images from a large volume of MR images generated in clinical routines is difficult and time-consuming. Hence, it is imperative to develop a machine learning model for automated segmentation of brain tumor images. PURPOSE Machine learning models for automated MR image segmentation of gliomas may be useful. However, the image differences among facilities cause performance degradation and impede successful automatic segmentation. In this study, we proposed a method to solve this issue. METHODS We used the data from the Multimodal Brain Tumor Image Segmentation Benchmark (BraTS) and the Japanese cohort (JC) datasets collected from 10 facilities. Three models for tumor segmentation were developed. The BraTS model was trained on the BraTS dataset, and the JC model was trained on the JC dataset; whereas, the Fine-tuning model was a fine-tuned BraTS model using the JC dataset. RESULTS MR images of 544 patients were obtained for the JC dataset. Half of the JC dataset was used for independent testing. The Dice coefficient score of the JC model for the JC dataset was 0.779± 0.137, whereas that of the BraTS model was remarkably lower (0.717 ± 0.207). The mean of the Fine-tuning models for the JC dataset was 0.769 ± 0.138. There was a significant difference between the BraTS and JC models (P < 0.0001) and the BraTS and Fine-tuning models (P = 0.002); however, no significant difference was observed between the JC and Fine-tuning models (P = 0.673). CONCLUSIONS Application of the BraTS model to heterogeneous datasets can significantly reduce its performance; however, fine-tuning can solve this issue. Since our fine-tuning method only requires less than 20 cases, this methodology is particularly useful for a facility where there are a few glioma cases.

Two Methods for the Constitutive Modeling of TiB2/7050 Al Composites

In this paper, the Johnson-Cook constitutive model of in situ TiB2/7050 Al metal matrix composites determined by two different methods are compared. The commonly used quasi-static and dynamic compressive experiments are firstly conducted under the strain rate range of 10−3∼5000s−1 and temperature range of 20∼200 °C. The orthogonal cutting experiments are also used to calculate the JC model. The description ability of two models are evaluated by two statistical parameters: correlation coefficient and average absolute error. The results show that the JC model determined by the compression experiments performs better to describe the stress-strain behavior of in situ TiB2/7050 Al composites. Although the JC model from orthogonal cutting experiments can be used to simulate the cutting process, it cannot describe the flow stress behavior exactly during material deformation processes. For an accurate constitutive model of a material, the basic tensile or compression test is deemed necessary.

Numerical Simulation of Damage on Warm Deep Drawing of Al 6061-T6 Aluminium Alloy

This work focuses on the numerical simulation of warm deep drawing operation of car sump oil made with Al 6061-T6 aluminum alloy for the purpose of process optimization. The thermo visco-plastic behavior with damage effect of the material is described by the Johnson-Cook (JC) model. The JC model parameters for the Al 6061-T6 Aluminum alloy were exploited. Numerical simulation of the deep drawing operation was performed with the use of the ABAQUS FE software thanks to the dynamic Explicit Temperature-Displacement algorithm. The design of the different tools is obtained on the basis of the geometry of the finished product. Designing of punch, die and blank holder is performed using CATIA 3D CAD software. The warm forming method involves the heating of the blank holder and the die to a certain temperature, whereas, the punch is kept at room temperature. In this study, predefined temperatures of the die and blank holder and punch speed will be investigated among other stamping parameters. The computed damage evolution curves for a given set of the process parameters are retrieved at the end of the simulation to determine suitable forming conditions. It can be noted that the slower the damage evolution achieved within the blank, the more appropriate the process parameters. Thus, by increasing strain rate, main cracks change location.

A Comparative Study on Johnson–Cook, Modified Johnson–Cook, Modified Zerilli–Armstrong and Arrhenius-Type Constitutive Models to Predict Hot Deformation Behavior of TA2

The true strain data and true stress data are obtained from the isothermal compression tests under a wide range of strain rates (0.1–20 s−1) and temperatures (933–1,133 K) over the Gleeble-3500 thermomechanical simulator. The data are employed to generate the constitutive equations according to four constitutive models, respectively, the strain-compensated Arrhenius-type model, the modified Zerilli–Armstrong (ZA) model, the modified Johnson–Cook (JC) model and the JC model. In the meanwhile, a comparative research was made over the capacities of these four models and hence to represent the elevated temperature flow behavior of TA2. Besides, a comparison of the accuracy of the predictions of average absolute relative error, correlation coefficient (R) and the deformation behavior was made to test the sustainability level of these four models. It is shown from these results that the JC model is not suitable for the description of flow behavior of TA2 alloy in α+β phase domain, while the predicted values of modified JC model, modified ZA model and the strain-compensated Arrhenius-type model could be consistent well with the experimental values except under some deformation conditions. Moreover, the strain-compensated Arrhenius-type model can be also used to track the deformation behavior more precisely in comparison with other models.

A Modified Johnson Cook Constitutive Model for Aermet 100 at Elevated Temperatures

The predicted flow behaviors of Aermet 100 steel were analyzed within a wide range of temperatures of 1,073 K–1,473 K and strain rates of 0.01 s–1–50 s–1 based on isothermal compression tests. Using the original Johnson Cook (JC) model and a modified Johnson Cook (MJC) model, the constitutive equations were constructed in the case of elevated temperatures. For both the JC and MJC, and the previously studied (Arrhenius-type model and double-multivariate nonlinear regression (DMNR)) models, their respective predictability levels were evaluated by contrasting both the correlation coefficient R and the average absolute relative error (AARE). The results showed that the prediction from the three models meet the accuracy requirement based on the experimental data, the only exception being the JC model. By comparing the predictability and numbers of material constants involved, the modified Johnson Cook model is regarded as an excellent choice for predicting the flow behaviors of Aermet 100 steel within the range being studied.

Full spectrum of nonlinear Jaynes–Cummings and anti-Jaynes–Cummings models

The unitary transformation method is utilized for the closed form solution of the nonlinear generalization of the Jaynes–Cummings (JC) model, which includes arbitrary multiphoton and intensity-dependent interactions between radiation and matter. Specifically, the unitary transformation leading to the diagonalization of the relevant Hamiltonian is established and energy levels and eigenstates are derived. It is also shown that the results for the JC model can be extended to the anti-Jaynes–Cummings (AJC) model through the map between the two models.