Punch Speed Research Articles

Finite element and metallurgical study of properties of deformed pure copper by ECAE at various strain rates

In this work, annealed pure copper is deformed by equal channel angular extrusion (ECAE) for a maximum of eight passes. Mechanical properties of the extruded material are obtained at tension velocities of 0.5 mm/min, 200 mm/min and 8 m/s. It is found that the maximum increase of ultimate strength occurs after the second pass for the V = 200 mm/min. The total increase of ultimate strength after eight passes is around 100%. Hardness increases to a maximum of 36% after eight passes. The elongation decreases for the second and fourth passes but increases after sixth and eighth passes. The reason is believed to be due to the formation of equiaxed grains and gradual decrease in dislocation density at the same time after the sixth pass. As the number of equiaxed grains increases, a high rate of dynamic recovery gives rise to further decrease in dislocation density or in other word to decrease in strain hardening. Therefore, after the sixth pass, elongation continues to increase. At the same time, tensile strength also keeps increasing but at a slower rate. Fracture mechanism of extruded specimens was studied at strain rates to a maximum of 4 × 103 s−1. Fractography of specimens shows that fracture mechanism is strain rate independent. ECAE process is simulated using the DEFORM-3D software through a three-dimensional analysis. Grain refinement is simulated by forcing the element size to zero. It is found that for a very fine mesh, the PEEQ converges to 1.51. The value of predicted PEEQs is not rate sensitive and is almost the same for all punch speeds considered in the simulations.

Finite element analysis for temperature distributions in a cold forging

In this research, the finite element method is utilized to predict the temperature distributions in a cold-forging process for a cambolt. The cambolt is mainly used as a part of a suspension system of a vehicle. The cambolt has an off-centered lobe that manipulates the vertical position of the knuckle and wheel to a slight degree. The cambolt requires certain mechanical properties, such as strength and endurance limits. Moreover, temperature is also an important factor to realize mass production and improve efficiency. However, direct measurement of temperature in a forging process is infeasible with existing technology; therefore, there is a critical need for a new technique. Accordingly, in this study, a thermo-coupled finite element method is developed for predicting the temperature distribution. The rate of energy conversion to heat for the workpiece material is determined, and the temperature distribution is analyzed throughout the forging process for a cambolt. The temperatures associated with different punch speeds are also studied, as well as the relationships between load, temperature, and punch speed. Experimental verification of the technique is presented.

Finite Element Simulation and Experimental Study on Isothermal Forging Technology for a Complex-Shaped Titanium Alloy Wing

A closed isothermal forging process was adopted for precision forming of the Ti-6Al-4V wing with a variable cross-section asymmetric structure. Firstly, simulations under different process parameters, such as the deformation temperature, punchs velocity et al. were analyzed with DEFORM-3D software to eliminate the defects in the isothermal forming process. The simulation results demonstrated that the loads during isothermal deformation were determined not just by the forging temperature but the punchs velocity, the less velocity of punch, the better filling ability, and yet temperatures from 900 to 950°C had less influence on filling ability. To verify the validity of simulation results, the isothermal forging experiment was carried out on an isothermal forging hydraulic press (THP10-630). It is demonstrated that the optimized billet dimension can ensure the quality of forging part and the titanium alloy wing component with complex shape was successfully forged with the punch speed of 0.1mm/s at 950°C and its mechanical performances were improved.

Push‐out bond strength of MTA with antiwashout gel or resins

Assessment of the push-out bond strength of four MTA-based formulations for use as root-end filling materials. MTA Plus mixed with (i) water ('MTA-W'); (ii) a proprietary water-based antiwashout gel ('MTA-AW'); (iii) Superbond C&B chemically curing resin ('MTA-Chem'); and (iv) Heliobond light-curing resin ('MTA-Light') was tested. Root slices 3 mm thick human had a 1.5 mm diameter hole drilled centrally and were treated with 17% EDTA for 60s. Forty specimens divided into groups 1-4 were prepared and filled with MTA-W, MTA-AW, MTA-Chem and MTA-Light, respectively. Groups 3 and 4 were etched with 37% phosphoric acid for 60s, and bonding agent was applied to the dentine surface. Specimens were stored for 28 days in Hanks' Balanced Salt Solution at 37 °C. Push-out strength was tested with a punch and die (punch diameter 1.3 mm, die diameter 2.0 mm, punch speed 1 mm min(-1)). Stereomicroscopy was used to classify failure mode (adhesive, cohesive or mixed type). The resulting push-out strengths were 5.1 MPa (MTA-W), 4.3 MPa (MTA-AW), 4.7 MPa (MTA-Chem) and 11.0 MPa (MTA-Light). MTA-W had higher push-out strength than MTA-AW (P = 0.022). The same was noted for MTA-Light relative to the other materials (P < 0.05). All materials exhibited adequate push-out strengths compared with MTA-W. Failure was predominantly mixed, except for MTA-Chem (predominantly adhesive). All materials exhibited adequate push-out strength. Previous studies have shown the new formulations have additional advantages including increased washout resistance and faster setting time, making them promising for future dental applications.

Study on Microstructure of a Gear Shaft during Hot Forging Process

The microstructure revolution of a spur gear shaft during hot forging was numerically simulated with FEM using Yada Model. The grain size distribution of the gear shaft after hot forged using initial billets with different dimensions was obtained through microstructure simulation and relative metallographic experiment show a good agreement with the simulation result. Effect laws of different forging parameters including the initial forging temperature and the punch speed, on grain size of the gear shaft after forged were given. A preforming process was proposed and the microstructure simulation shows that the preforming process can significantly improve the grain size refinement and distribution uniformity of the gear shaft by hot forging.

Study the Optimization Parameters for Spring Back Phenomena in U-Die Bending

The main objective of the research is to find the optimum parameters that reduce the springback by using the commercially [SPSS] program to analysis data and find the best parameters which given lowest springback in the U-die bending. A commercial aluminum alloy [AL-1050] sheet (0.9 mm) thickness that founded when punch speed increase the springback increase, when rolling direction angle is 90 Lower springback, and when increase the dwell time decrease the springback, and the value of parameters predicted from [SPSS] have lower springback and obtain a goal dimension for the products. And predict the springback value by especial equations which given correlation coefficient 95.4% between the observed value of the dependent variable and the predicted value.

Microstructural Evolution in Multiway Loading-Forming Process of AISI 5140 Steel Triple Valve Body

The microstructural evolution and distribution rules, such as dynamic recrystallization (DRX) volume fraction, dynamically recrystallized grain size, and average grain size, in multiway loading-forming process of AISI 5140 steel triple valve body have been investigated using numerical simulation, combined with the analytic method by considering the influences of process parameters including loading speed of punch, initial temperature of billet, and friction. The results show that the DRX volume fraction increased, and its distribution became more uniform with the increases of punch loading speed and billet initial temperature, or the decrease of friction factor; the dynamically recrystallized grain size decreased, and its distribution was more uniform, with the increases of punch loading speed and friction factor, or the decrease of billet initial temperature; the average grain size decreased, and its distribution became more uniform with the increases of punch loading speed and billet initial temperature, or decrease of friction factor.

Blank Shape Optimization in Sheet Hydroforming Process

Blank shape is one of the most important parameters of sheet metal stamping. In fact it can directly affect the forming quality of parts and it has to be taken in account in sheet hydroforming design. Reasonable blank shape not only can reduce materials and production cost but, also, it can improve the strain distribution of the material and product quality in the hydroforming process. However, it is not easy to find an optimal blank shape because of complexity of deformation behavior and presence of many process parameters like die radius, punch radius, punch speed, blank holder force and friction. In fact, they affect the result of the process i.e. tearing, wrinkling, springback and surface conditions such as earing. Even a slight variation in one of these parameters can result in defects. This paper reports numerical and experimental correlation for axis symmetrical hydroformed component using initial blank with different shape and size. Experimental tests have been carried out through the hydroforming cell tooling, designed by the authors thanks to a research project, characterized by a variable upper blankholder load of eight different hydraulic actuators. Two different initial blank shapes, square and circular, of same material and thickness have been used.

The Effect of the Imposed Boundary Rate on the Formability of Strain Rate Sensitive Sheets Using the M-K Method

In spite of the fact that the experimental results indicate the significant effect of strain rate on forming limits of sheets, this effect is neglected in all theoretical methods of prediction of Forming Limit Diagrams (FLDs). The purpose of this paper is to modify the most renowned theoretical method of determination of FLDs (e.g., M-K model) so as to enable it to take into account the effect of strain rate. To achieve this aim, the traditional assumption of preexistence of an initial geometrical inhomogeneity in the sheet has been replaced with the assumption of a preexisting “material” inhomogeneity. It has been shown that using this assumption, the strain rate would not be omitted from equations; thus, it is possible to demonstrate its effect on FLDs. To validate the results, they are compared with some published experimental data. The good agreement between the theoretical and experimental results shows capabilities of the proposed method in predicting the effect of the imposed rate at the boundary (which is physically the effect of the punch speed difference in sheet forming) on FLDs.

High Speed Blanking: An Experimental Method to Measure Induced Cutting Forces

A new blanking process that involves punch speed up to 10 ms −1 has obvious advantages in increased productivity. However, the inherent dynamics of such a process makes it difficult to develop a practical high speed punch press. The fracture phenomenon governing the blanking process has to be well understood to correctly design the machine support and the tooling. To observe this phenomenon at various controlled blanking speeds a specific experimental device has been developed. The goal is to measure accurately the shear blanking forces imposed on the specimen during blanking. In this paper a new method allowing the blanking forces to be measured and taking into account the proposed test configuration is explained. This technique has been used to determine the blanking forces experienced when forming C40 steel and quantifies the effect of process parameters such as punch die clearance, punch speed, and sheet metal thickness on the blanking force evolution.

Coupled finite element simulation and optimization of single- and multi-stage sheet-forming processes

This article presents the development and application of a coupled finite element simulation and optimization framework that can be used for design and analysis of sheet-forming processes of varying complexity. The entire forming process from blank gripping and deep drawing to tool release and springback is modelled. The dies, holders, punch and workpiece are modelled with friction, temperature, holder force and punch speed controlled in the process simulation. Both single- and multi-stage sheet-forming processes are investigated. Process simulation is coupled with a nonlinear gradient-based optimization approach for optimizing single or multiple design objectives with imposed sheet-forming response constraints. A MATLAB program is developed and used for data-flow management between process simulation and optimization codes. Thinning, springback, damage and forming limit diagram are used to define failure in the forming process design optimization. Design sensitivity analysis and optimization results of the example problems are presented and discussed.

Experimental studies of deep drawing of AZ31B magnesium alloy sheet under various thermal conditions

The effect of temperature and temperature gradient within the blank on formability of AZ31B-O magnesium alloy is investigated. The effect of blank size on the success of isothermal deep drawing is studied. As blank size increases, forming under isothermal conditions becomes more difficult. To address this issue, non-isothermal forming is investigated and a formability window is identified in which the temperature at the punch nose must lie below the flange temperature to promote enhanced drawability, but above the temperature for activation of non-basal slip systems (to avoid low temperature fracture). The effect of punch speed on the forming forces, thickness and strain distribution within the formed cup is also investigated. At higher punch speeds, small cracks initiate at the punch radius region which increases the possibility of failure. Finally, the fracture surfaces from each thermal condition are observed using scanning electron microscopy. It is demonstrated that the fracture mechanism during deep drawing of magnesium alloy AZ31B is dependent on the forming temperature which controls the active deformation mechanisms.

The Limiting Dome Height Tests and Formability of Magnesium Alloy Sheet AZ31B

The assembly of the limiting dome height tests is developed to evaluate the formability of the magnesium alloy sheet AZ31B. The influence of forming conditions on the formability of AZ31B sheet is investigated by limiting dome height tests. The limiting bulging coefficient is used to represent the formability of AZ31B sheet in the tests. The sheet thickness, forming temperature, punch speed and lubrication are taken as influence factors in the tests. The experimental results show that the sheet of thickness 0.6mm has better formability and the proper forming temperature is about 200~250°C for AZ31B sheet. The low punch speed and good lubrication can also improve the formability of AZ31B sheet.

Taguchi Method and Genetic Algorithm Neural Networks Analysis of Forging Process of Bicycle Chain Wheel

Recent years due to the rise of awareness of environmental protection and energy conservation are attention. Which is the most representative of the bike. Many processing factors must be controlled in the bicycle chain wheel. This study employed the rigid-plastic finite element (FE) DEFORMTM 3D software to investigate the plastic deformation behavior of an aluminum alloy workpiece as it is forged for bicycle chain wheels. Factors include the temperature of the forging billet, shear friction factor, temperature of die and punch speed control all parameters. Moreover, this study used the Taguchi method and Genetic algorithm neural networks to determine the most favorable optimization parameters. Finally, our results confirmed the suitability of the proposed design, which enabled a bicycle chain wheel die to achieve perfect forging during finite element testing.

Blunt Liver Injury with Intact Ribs under Impacts on the Abdomen: A Biomechanical Investigation

Abdominal trauma accounts for nearly 20% of all severe traffic injuries and can often result from intentional physical violence, from which blunt liver injury is regarded as the most common result and is associated with a high mortality rate. Liver injury may be caused by a direct impact with a certain velocity and energy on the abdomen, which may result in a lacerated liver by penetration of fractured ribs. However, liver ruptures without rib cage fractures were found in autopsies in a series of cases. All the victims sustained punches on the abdomen by fist. Many studies have been dedicated to determining the mechanism underlying hepatic injury following abdominal trauma, but most have been empirical. The actual process and biomechanism of liver injury induced by blunt impact on the abdomen, especially with intact ribs remained, are still inexhaustive. In order to investigate this, finite element methods and numerical simulation technology were used. A finite element human torso model was developed from high resolution CT data. The model consists of geometrically-detailed liver and rib cage models and simplified models of soft tissues, thoracic and abdominal organs. Then, the torso model was used in simulations in which the right hypochondrium was punched by a fist from the frontal, lateral, and rear directions, and in each direction with several impact velocities. Overall, the results showed that liver rupture was primarily caused by a direct strike of the ribs induced by blunt impact to the abdomen. Among three impact directions, a lateral impact was most likely to cause liver injury with a minimum punch speed of 5 m/s (the momentum was about 2.447 kg.m/s). Liver injuries could occur in isolation and were not accompanied by rib fractures due to different material characteristics and injury tolerance.

ハイテン材の平滑・高精度切り口面を得る方法

Methods by which smooth and high-precision cut surfaces of high strength steel sheets with strength of up to 980MPa class have been investigated using a servo press in which the average punching speed can be varied from 2 to 140mm·s-1. A method called finish blanking has been performed, and the other method called press shaving has also been conducted to obtain either smooth cut surfaces or highly precise product shapes and dimensional sizes. The results show that both methods can yield good cut surfaces if appropriate working parameters including punch/die clearance, edge radius and punching speed are used. However, as regards shape and dimensional accuracies, the press shaving method yielded the most satisfactory results.

J121022 スプリングゴー/バック抑制のための最適モーション設定([J121-02]解析・設計の高度化・最適化(2))

Spring-go/back is one of the factors influencing product quality in sheet metal forming. Blank holder force (BHF) and punch speed (SPD) are considered as important factors for spring-go/back reduction. In many papers on the springback reduction, the BHF and the SPD are not handled as the design variables. In this paper, the BHF and the SPD are simultaneously controlled for the spring-go/back reduction by using sequential approximate optimization with radial basis function network. To reduce the spring-go/back, bending moment of blank is minimized under tearing constraint. In order to examine the validity of the proposed approach, U-shape forming provided in NUMISHEET'93 is adopted. Numerical result shows that the proposed approach is effective to the spring-go/back reduction.

Numerical Simulation for Microstructure Evolution in In718 Alloy During Cylindrical Cup Backward Extrusion

A coupled numerical simulation between thermal-mechanical and microstructure evolution was realized through embedding the developed user subroutines into the FEM software DEFORM-3D system. Then the dynamic recrystallization fraction and average grain size of In718 alloy in cylindrical cup backward extrusion with different parameters was solved and analyzed. The complete dynamic recrystallization occurs in the middle of cylinder wall and the grain size is the finest. However, the grain size of top of cylinder wall changes less because of the less plastic deformation. Furthermore, higher speed of punch is useful to the DRX but it is not enough time to occur dynamic recrystallization completely with much higher speed of punch. In spite of more recrystallization occurring in the bottom, the grains grow in the cylinder wall so that much higher temperature goes against improving finer and uniform of grain size. Therefore, it is better for obtaining finer and uniform grain size with 1000(°C)-1050(°C) and 5(mm/s) in In718 alloy cylindrical cup backward extrusion according to the research.

Effect of tool temperature and punch speed on hot stamping of ultra high strength steel

The hot stamping process of ultra high strength (UHS) sheet metal is an innovative way which is used in automobile increasingly for the manufacturing of components with a ultra high ultimate tensile strength (UTS). Due to the high nonlinear elastoplastic and thermo-mechanical responses of material during the hot forming process, practically it is difficult to investigate such hot forming presses only via experiments. Therefore, it is necessary to develop a 3D elastoplastic coupled thermo-mechanical finite element model (FEM) of UHS sheet metal hot forming. Meanwhile, the mechanical properties of UHS steel at elevated temperatures were characterized and the corresponding material constitutive, which is strain, strain rate and temperature dependent, is developed on the basis of unaxial tensile test at elevated temperatures. In addition, hot stamping experiments were conducted and combined with the simulation to investigate the effect of tool temperature and punch speed on the hot stamping of UHS sheet metal for the square-box-shaped (SBS) component. Considering the UTS of hot formed component, the optimum tool temperature and the punch speed are achieved.

Predicting the density and tensile strength of viscoelastic soy powder compacts

The key physical property of compact density is important for scale up and influences the mechanical properties such as tensile strength. Hence, the objective of this research was to develop semi-mechanistic models for density of Soy Flour (SF) and Soy Protein Concentrate (SPC) powder compacts as a function of viscoelastic properties and process variables. Each of the powders was compacted at a punch speed of 5mm/min to final compaction pressures in the range of 26–230MPa, in a 13mm diameter cylindrical die. Pressure–time profile during compaction, compact height and force relaxation during the dwell time were also recorded. Compact density was measured under maximum pressure and 24h post ejection. The force relaxation data was fit to linear Maxwell model for a viscoelastic solid (R2>0.99) and the viscoelastic properties of the pure solid material were estimated by extrapolating to zero compact porosity. Although density of compacts from either powder was found to be comparable, SPC produced much stronger compacts compared to SF due to higher bonding. The estimated compact density under pressure was found to be much higher than the pycnometer measured true densities. The contact area between two particles was estimated using Lum and Duncan-Hewitt (1999) using median particle size, pressure–time during compaction and material viscoelastic properties. Power law and logarithmic models that express the compact density and tensile strength respectively as a function of total viscoelastic contact area in a compact were successfully developed (R2>0.95–0.99). Thus, viscoelastic properties were found to influence compact density and tensile strength through their influence on the contact area.