scholarly journals Determination of the strain rate dependent thermal softening behavior of thermoplastic materials for crash simulations

2016 ◽  
Author(s):  
Christian Hopmann ◽  
Jan Klein ◽  
Maximilian Schöngart
Keyword(s):  
Strain Rate ◽  
Thermal Softening ◽  
Softening Behavior ◽  
Rate Dependent

Determination of Strain Rate Depended Stress and Strain Fields in PVD Coatings on Cemented Carbide Inserts during the Repetitive Impact Test

2020 ◽  
Vol 404 ◽  
pp. 45-52
Author(s):  
Antonios Bouzakis ◽  
Georgios Skordaris ◽  
Konstantinos Dionysios Bouzakis ◽  
Mehmet Gökhan Gökcen ◽  
Apostolos Boumpakis ◽  
...  
Keyword(s):  
Strain Rate ◽  
Cemented Carbide ◽  
Stress And Strain ◽  
Strain Fields ◽  
Rate Dependent ◽  
Impact Forces ◽  
Repetitive Impact ◽  
Carbide Inserts ◽  
Fatigue Endurance

Recently, stress, strain, strain-rate dependent curves for cemented carbide have become an established tool for evaluating the mechanical properties. In this paper, related strain-rate dependent data of a K05 insert were employed to define the developed stress and strain fields occurring in the compound coating-substrate at impact forces of various durations. In this way, the occurring maximum strains at various impact loads and times were analytically calculated. These maximum values and related fatigue endurance coating strain-rate dependent limits were consequently used to validate published coating fatigue critical impact forces associated with certain impact times.

Velocity of Torsional Waves in Metals Stressed Statically into the Plastic Range

1968 ◽  
Vol 10 (2) ◽  
pp. 153-164 ◽  
Author(s):  
E. Convery ◽  
H. LI. D. Pugh
Keyword(s):  
Strain Rate ◽  
Strain Curve ◽  
Plastic Range ◽  
Stress Strain Curve ◽  
Rate Dependent ◽  
Torsional Waves ◽  
Dependent Theory ◽  
Velocity Of Propagation ◽  
Elastic Shear

This paper is concerned with the determination of the velocity of propagation of torsional plastic waves in metals stressed statically into the plastic range. A new method was developed in which a tubular test specimen together with a concentric bar of a brittle material was twisted slowly such that when the specimen was stressed beyond its yield the brittle bar broke suddenly and transmitted a plastic torsional stress increment along the specimen. It was found that the velocity of propagation both in copper and mild steel was the same as the elastic shear wave velocity. Although consistent with the strain-rate dependent theory, the result can be explained in terms of the strain-rate independent theory provided the stress-strain curve for the appropiate strain rate is used.

scholarly journals A Combined Experimental and Numerical Approach That Eliminates the Non-uniqueness Associated With the Johnson-cook Parameters Obtained Using Inverse Methods

2021 ◽  
Author(s):  
Nishant Ojal ◽  
Harish P. Cherukuri ◽  
Tony L. Schmitz ◽  
Kyle T. Devlugt ◽  
Adam W. Jaycox
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Cutting Forces ◽  
Inverse Method ◽  
Material Model ◽  
Numerical Approach ◽  
Thermal Softening ◽  
Analytical Models ◽  
Initial Yield Stress ◽  
Softening Behavior

Abstract Johnson-Cook constitutive model is a commonly used material model for machining simulations. The model includes five parameters that capture the initial yield stress, strain-hardening, strain-rate hardening, and thermal softening behavior of the material. These parameters are difficult to determine using experiments since the conditions observed during machining (such as high strain-rates of the order of 10 5 /sec - 10 6 /sec) are challenging to recreate in the laboratory. To address this problem, several researchers have recently proposed inverse approaches where a combination of experiments and analytical models are used to predict the Johnson-Cook parameters. The errors between the measured cutting forces, chip thicknesses and temperatures and those predicted by analytical models are minimized and the parameters are determined. In this work, it is shown that only two of the five Johnson-Cook parameters can be determined uniquely using inverse approaches. Two different algorithms, namely, Adaptive Memory Programming for Global Optimization (AMPGO) and Particle Swarm Optimization (PSO), are used for this purpose. The extended Oxley’s model is used as the analytical tool for optimization. For determining a parameter’s value, a large range for each parameter is provided as an input to the algorithms. The algorithms converge to several different sets of values for the five Johnson-Cook parameters when all the five parameters are considered as unknown in the optimization algorithm. All of these sets, however, yield the same chip shape and cutting forces in FEM simulations. Further analyses show that only the strain-rate and thermal softening parameters can be determined uniquely and the three parameters present in the strain-hardening term of the Johnson-Cook model cannot be determined uniquely using the inverse method. A combined experimental and numerical approach is proposed to eliminate this determine all parameters uniquely.

Modeling Temperature and Strain Rate Dependent Large Deformations of Metals

1990 ◽  
Vol 43 (5S) ◽  
pp. S312-S319 ◽  
Author(s):  
Douglas J. Bammann
Keyword(s):  
Strain Rate ◽  
Large Deformations ◽  
Uniaxial Stress ◽  
Thermal Softening ◽  
Plasticity Model ◽  
Anisotropic Hardening ◽  
Temperature Dependent ◽  
History Effects ◽  
Rate Dependent ◽  
Comparison With Experimental Data

We review the development of a strain rate and temperature dependent plasticity model for finite deformation. In particular we address both the method of determining the parameters of the model and the engineering meaning of the parameters in terms of uniaxial stress-strain curves. The ability of the model to predict some aspects of anisotropic hardening, strain rate history effects, and thermal softening are then illustrated by comparison with experimental data.

DETERMINATION OF THE BEHAVIOR OF 6063 ALUMINUM IN THE FRICTION WELDING PROCESS USING MATHEMATICAL MODELS

2012 ◽  
Vol 1381 ◽  
Author(s):  
F. García ◽  
P. del C. Zambrano Robledo ◽  
M.P. Guerrero ◽  
F. García-Vazquez
Keyword(s):  
Mechanical Strength ◽  
Mathematical Models ◽  
Strain Rate ◽  
Friction Welding ◽  
Welded Joint ◽  
Welding Process ◽  
Plastic Model ◽  
Rate Dependent ◽  
Ideal Process

AbstractIn this work, it was used a Johnson-Cook elastic-plastic model to represent the behavior in the friction welding process of 6063 aluminum. Temperature and strain rate dependent laws were used to determine the behavior of the material. The results determined that the amount of heat transferred into the material dictates the quality and the microstructure of the welding and the mechanical strength of the welded joint in an ideal process.

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