Feliks Stachowicz

Warm forming of stainless steel sheet

The aim of warm sheet metal forming processes is to improve plastic flow of material, as well as to decrease the springback effect. This investigation deals with the effect of temperature in the range from 20 °C to 700 °C on basic material parameters of stainless steel sheet metal such as yield stress, ultimate strength, total and uniform elongation, strain hardening parameters and plastic anisotropy factor. The results of carried out investigations will be useful for deep drawing processes preparation and modification, especially considering proper forming temperature. It was determined that the most suitable temperature of warm forming of the AMS 5604 stainless steel sheet is 500 °C. Examination of the influence of the temperature, sheet thickness and material heating method (only sheet heating, sheet and forming die heating, isothermal conditions) on springback quantity was performed in air bending test. The MSC Marc Mentat commercial computer code was used for numerical simulation of analyzed forming processes.

Estimation of hole-flange ability for deep drawing steel sheets

Hole-flanging is a common sheet forming operation to produce structural sheet metal components. Flanges are used for appearance, rigidity, hidden joints, and strengthening of the edge of sheet metal parts. Trial-end-error is the most common approach for tooling and process design in flanging operations. This paper presents some experimental results of hole-flanging process performed on flat deep drawing steel sheets with circular hole drilled in the centre. Three punches of different geometry i.e. cylindrical, hemispherical and conical were used in this experiment. The effect of both the punch geometry and material mechanical parameters (especially strain hardening and plastic anisotropy) on the limit expansion of the hole was determined.

On Finite Element Computations of Contact Problems in Micropolar Elasticity

Within the linear micropolar elasticity we discuss the development of new finite element and its implementation in commercial software. Here we implement the developed 8-node hybrid isoparametric element into ABAQUS and perform solutions of contact problems. We consider the contact of polymeric stamp modelled within the micropolar elasticity with an elastic substrate. The peculiarities of modelling of contact problems with a user defined finite element in ABAQUS are discussed. The provided comparison of solutions obtained within the micropolar and classical elasticity shows the influence of micropolar properties on stress concentration in the vicinity of contact area.

On Computational Evaluation of Stress Concentration Using Micropolar Elasticity

We discuss the implementation the finite element approach to the linear micropolar elasticity in order to perform the analysis of the stress concentration near holes and notches. Within the micropolar elasticity we analyze the behaviour of such microstructured solids as foams and bones. With developed new finite element few problems are analyzed where the influence of the microstructure may be important. The provided comparison of solutions obtained within the micropolar and classical elasticity show the influence of micropolar properties on stress concentration near notches and contact areas.

The effect of technological parameters on intensity of shot peening process of 51CrV4 steel

Abstract In the paper the effect of selected technological parameters of shot peening on process intensity of 51CrV4 steel was presented. The experiments were conducted according to statistical 3-level completed plan PS/DC 32. Technological parameters were changed in the range: shot peening time t = 1-3 min and pressure p = 0.2-0.4 MPa. In the article the analysis of experiment reproducibility, impact parameters significance and adequacy of equation were done. As the result of investigations the adequate equation was obtained describing the effect of technological parameters. Significant influence on process intensity was found in case of pressure and interaction of both analyzed technological parameters. The biggest energy of stream shots was gained at the maximum pressure of 0.4 MPa and the shot peening time of 3 minutes. As the result of analysis according to design of experiment (DOE) the adequate equation describing the dependencies between technological parameters and process intensity was found.

METHOD OF FERTILIZATION OF ENERGY WILLOW PLANTATION USING SEWAGE SLUDGE

Sewage sludge deriving from biofiltration of municipal waste abound in soil processed organic substances and mineral fertilization components which may be used for fertilization of energy willow plantations. In the article the potential of natural utilization of sewage sludge and the patented device for injection dosage of sludge has been presented. The device enables putting into soil mineral and organic fertilizers with loose consistency and their immediate covering by soil in order to reduce unpleasant smell and limit loss of volatile components of fertilizer.

Fracture Prediction of Piezoelectric Ceramic by the 2-D Boundary Element Analysis

Piezoelectric ceramics are widely used as sensors and multilayer actuators in many areas of industry [1], despite the absence of a fundamental understanding of their fracture behaviour [2]. Piezoelectricity is a linear effect that is related to the microscopic structure of the solid. Among piezoelectric materials, barium titanate is the most often used as a ceramic material. Barium titanate is a ferroelectric classic perovskite structure with wide-ranging material properties that depend on its composition [3, 4]. The perovskite structure ABO3 (Fig. 1) is the arrangement where the corner-sharing oxygen octahedra are linked together in a regular cubic array with smaller cations (Ti, Zr, Sn, Nb, etc.) occupying the central octahedral B-site, and larger cations (Pb, Ba, Sr, Ca, Na, etc.) filling the interstices between octahedra in the larger A-site [5]. Several studies have been carry out in order to study the influence of compositionally modified ceramic bodies and the sintering conditions on the properties of ceramic [6]. The ceramic material which is composed of the random orientation of these piezoelectric crystallites, is inactive, i.e., the effects from the individual crystals cancel each other and no discernable piezoelectricity is present [5]. The domains are the regions of equally oriented polarization vectors. To orient the domains the pooling method can be used. This technique consist in polarizing the ceramic through the application of a static electric field. Open image in new window Fig. 1 Perovskite structure

Linear Micropolar Elasticity Analysis of Stresses in Bones Under Static Loads

We discuss the finite element modeling of porous materials such as bones using the linear micropolar elasticity. In order to solve static boundary-value problems, we developed new finite elements, which capture the micropolar behavior of the material. Developed elements were implemented in the commercial software ABAQUS. The modeling of a femur bone with and without implant under various stages of healing is discussed in details.

Application of the grain boundary formulation and image processing-based algorithm in micro-mechanical analysis of piezoelectric ceramic

The main subject of this paper is the micro-mechanical analysis of a piezoelectric ceramic. In micro-mechanical analyses, it is very important to have knowledge about the real and natural micro-structure of materials. Therefore, the barium titanate powder was prepared using the solid-state technique, and pellets and beams were manufactured by uniaxial and isostatic pressing. The boundary element method (BEM) is used in order to be combined with three different grain boundary formulations for investigation of micro-mechanics and crack nucleation and evaluation in piezoelectric ceramic. In order to develop a numerical programming algorithm, suitable models of polycrystalline aggregate have to be discretised for the BEM analysis. Hence, original comprehensive algorithms are designed on the basis of image processing methods. Several assumptions are made to model the grain boundary in micro-scale. In the first step, before having any cracks, the traction equilibrium and displacement compatibility are governing equations. When the onset micro-crack starts to initiate, one mixed-mode potential based cohesive law is applied to model grain boundaries and investigate the intergranular crack nucleation and evolution. Upon interface failure, a frictional law is utilised in order to study separation, sliding or sticking between micro-crack surfaces. Several numerical experiments on barium titanate polycrystalline aggregate are presented to show the effectiveness of image processing-based discretisation algorithms and grain boundary formulation in micro-mechanical analysis.

Application of BaTiO3 Perovskite Material for Piezoelectric Multilayer Actuators

In this paper, the results of the manufacturing of BaTiO3 material destined for use in stacked-disk multilayer actuator production are presented. SEM microstructures and electric properties of the fabricated pellets are presented and discussed. The dilatometric curve was executed using the high temperature dilatometer in order to determine at which temperature barium titanate pellets and beams should be sintered to receive full dense sinters. Finally, the problem of metal layer deposition on barium titanate ceramics during actuator fabrication is considered.